[RFC PATCH v6 0/8] vfs/xfs/ext4: GETFSMAP support

[RFC PATCH v6 0/8] vfs/xfs/ext4: GETFSMAP support

[Darrick J. Wong]

Hi all,

This is an RFC patchset implementing the GETFSMAP ioctl that we
discussed at LSFMM 2016[1].  GETFSMAP takes two search keys, which are
defined as a tuple of (device, physical block, owner, file offset), and
returns all known space mapping information for the given filesystem.

The XFS implementation is fully complete for filesystems having the new
reverse-mapping feature introduced in 4.8.  For legacy XFS filesystems
and ext4, there is no reverse-mapping data and the returned extent
information is restricted to listing "free", "unknown", or "metadata"
owners.

Space mapping information can be dumped via the xfs_io 'fsmap' command,
and the upcoming xfs_spaceman utility analyzes the free extent data to
produce free space fragmentations reports.  Further in the future, the
xfs_scrub utility will use GETFSMAP to assist in data block read
verification.

Kernel source can be found in the git repo [2] and userspace utilities
in the git repo[3].  The XFS patches have been hanging around in my
repos for months accumulating fixes; the ext4 patches are newish.

Note: This patchset is headed for 4.12 at the earliest.

Questions?  Comments?

--D

[1] https://lwn.net/Articles/685978/
[2] https://git.kernel.org/cgit/linux/kernel/git/djwong/xfs-linux.git/log/?h=djwong-devel
[3] https://git.kernel.org/cgit/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=djwong-devel

[PATCH 1/8] vfs: add common GETFSMAP ioctl definitions

[Darrick J. Wong]

From: Darrick J. Wong <darrick.wong@oracle.com>

Add the GETFSMAP headers to the VFS kernel headers

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 include/uapi/linux/fsmap.h |  110 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 include/uapi/linux/fsmap.h


diff --git a/include/uapi/linux/fsmap.h b/include/uapi/linux/fsmap.h
new file mode 100644
index 0000000..1e94856
--- /dev/null
+++ b/include/uapi/linux/fsmap.h
@@ -0,0 +1,110 @@
+/*
+ * FS_IOC_GETFSMAP ioctl infrastructure.
+ *
+ * Copyright (C) 2017 Oracle.  All Rights Reserved.
+ *
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ */
+#ifndef _LINUX_FSMAP_H
+#define _LINUX_FSMAP_H
+
+#include <linux/types.h>
+
+/*
+ *	Structure for FS_IOC_GETFSMAP.
+ *
+ *	The memory layout for this call are the scalar values defined in
+ *	struct fsmap_head, followed by two struct fsmap that describe
+ *	the lower and upper bound of mappings to return, followed by an
+ *	array of struct fsmap mappings.
+ *
+ *	fmh_iflags control the output of the call, whereas fmh_oflags report
+ *	on the overall record output.  fmh_count should be set to the
+ *	length of the fmh_recs array, and fmh_entries will be set to the
+ *	number of entries filled out during each call.  If fmh_count is
+ *	zero, the number of reverse mappings will be returned in
+ *	fmh_entries, though no mappings will be returned.  fmh_reserved
+ *	must be set to zero.
+ *
+ *	The two elements in the fmh_keys array are used to constrain the
+ *	output.  The first element in the array should represent the
+ *	lowest disk mapping ("low key") that the user wants to learn
+ *	about.  If this value is all zeroes, the filesystem will return
+ *	the first entry it knows about.  For a subsequent call, the
+ *	contents of fsmap_head.fmh_recs[fsmap_head.fmh_count - 1] should be
+ *	copied into fmh_keys[0] to have the kernel start where it left off.
+ *
+ *	The second element in the fmh_keys array should represent the
+ *	highest disk mapping ("high key") that the user wants to learn
+ *	about.  If this value is all ones, the filesystem will not stop
+ *	until it runs out of mapping to return or runs out of space in
+ *	fmh_recs.
+ *
+ *	fmr_device can be either a 32-bit cookie representing a device, or
+ *	a 32-bit dev_t if the FMH_OF_DEV_T flag is set.  fmr_physical,
+ *	fmr_offset, and fmr_length are expressed in units of bytes.
+ *	fmr_owner is either an inode number, or a special value if
+ *	FMR_OF_SPECIAL_OWNER is set in fmr_flags.
+ */
+struct fsmap {
+	__u32		fmr_device;	/* device id */
+	__u32		fmr_flags;	/* mapping flags */
+	__u64		fmr_physical;	/* device offset of segment */
+	__u64		fmr_owner;	/* owner id */
+	__u64		fmr_offset;	/* file offset of segment */
+	__u64		fmr_length;	/* length of segment */
+	__u64		fmr_reserved[3];	/* must be zero */
+};
+
+struct fsmap_head {
+	__u32		fmh_iflags;	/* control flags */
+	__u32		fmh_oflags;	/* output flags */
+	__u32		fmh_count;	/* # of entries in array incl. input */
+	__u32		fmh_entries;	/* # of entries filled in (output). */
+	__u64		fmh_reserved[6];	/* must be zero */
+
+	struct fsmap	fmh_keys[2];	/* low and high keys for the mapping search */
+	struct fsmap	fmh_recs[];	/* returned records */
+};
+
+/* Size of an fsmap_head with room for nr records. */
+static inline size_t
+fsmap_sizeof(
+	unsigned int	nr)
+{
+	return sizeof(struct fsmap_head) + nr * sizeof(struct fsmap);
+}
+
+/* Start the next fsmap query at the end of the current query results. */
+static inline void
+fsmap_advance(
+	struct fsmap_head	*head)
+{
+	head->fmh_keys[0] = head->fmh_recs[head->fmh_entries - 1];
+}
+
+/*	fmh_iflags values - set by FS_IOC_GETFSMAP caller in the header. */
+/* no flags defined yet */
+#define FMH_IF_VALID		0
+
+/*	fmh_oflags values - returned in the header segment only. */
+#define FMH_OF_DEV_T		0x1	/* fmr_device values will be dev_t */
+
+/*	fmr_flags values - returned for each non-header segment */
+#define FMR_OF_PREALLOC		0x1	/* segment = unwritten pre-allocation */
+#define FMR_OF_ATTR_FORK	0x2	/* segment = attribute fork */
+#define FMR_OF_EXTENT_MAP	0x4	/* segment = extent map */
+#define FMR_OF_SHARED		0x8	/* segment = shared with another file */
+#define FMR_OF_SPECIAL_OWNER	0x10	/* owner is a special value */
+#define FMR_OF_LAST		0x20	/* segment is the last in the FS */
+
+/* Each FS gets to define its own special owner codes. */
+#define FMR_OWNER(type, code)	(((__u64)type << 32) | \
+				 ((__u64)code & 0xFFFFFFFFULL))
+#define FMR_OWN_FREE		FMR_OWNER(0, 1) /* free space */
+#define FMR_OWN_UNKNOWN		FMR_OWNER(0, 2) /* unknown owner */
+#define FMR_OWN_METADATA	FMR_OWNER(0, 3) /* metadata */
+
+#define FS_IOC_GETFSMAP		_IOWR('X', 59, struct fsmap_head)
+
+#endif /* _LINUX_FSMAP_H */

[PATCH 2/8] xfs: plumb in needed functions for range querying of the freespace btrees

[Darrick J. Wong]

From: Darrick J. Wong <darrick.wong@oracle.com>

Plumb in the pieces (init_high_key, diff_two_keys) necessary to call
query_range on the free space btrees.  Remove the debugging asserts
so that we can make queries starting from block 0.

While we're at it, merge the redundant "if (btnum ==" hunks.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/libxfs/xfs_alloc_btree.c |  162 +++++++++++++++++++++++++++++----------
 1 file changed, 119 insertions(+), 43 deletions(-)


diff --git a/fs/xfs/libxfs/xfs_alloc_btree.c b/fs/xfs/libxfs/xfs_alloc_btree.c
index efb467b..ba3ec9c 100644
--- a/fs/xfs/libxfs/xfs_alloc_btree.c
+++ b/fs/xfs/libxfs/xfs_alloc_btree.c
@@ -205,19 +205,28 @@ xfs_allocbt_init_key_from_rec(
 	union xfs_btree_key	*key,
 	union xfs_btree_rec	*rec)
 {
-	ASSERT(rec->alloc.ar_startblock != 0);
-
 	key->alloc.ar_startblock = rec->alloc.ar_startblock;
 	key->alloc.ar_blockcount = rec->alloc.ar_blockcount;
 }
 
 STATIC void
+xfs_bnobt_init_high_key_from_rec(
+	union xfs_btree_key	*key,
+	union xfs_btree_rec	*rec)
+{
+	__u32			x;
+
+	x = be32_to_cpu(rec->alloc.ar_startblock);
+	x += be32_to_cpu(rec->alloc.ar_blockcount) - 1;
+	key->alloc.ar_startblock = cpu_to_be32(x);
+	key->alloc.ar_blockcount = 0;
+}
+
+STATIC void
 xfs_allocbt_init_rec_from_cur(
 	struct xfs_btree_cur	*cur,
 	union xfs_btree_rec	*rec)
 {
-	ASSERT(cur->bc_rec.a.ar_startblock != 0);
-
 	rec->alloc.ar_startblock = cpu_to_be32(cur->bc_rec.a.ar_startblock);
 	rec->alloc.ar_blockcount = cpu_to_be32(cur->bc_rec.a.ar_blockcount);
 }
@@ -236,18 +245,24 @@ xfs_allocbt_init_ptr_from_cur(
 }
 
 STATIC __int64_t
-xfs_allocbt_key_diff(
+xfs_bnobt_key_diff(
 	struct xfs_btree_cur	*cur,
 	union xfs_btree_key	*key)
 {
 	xfs_alloc_rec_incore_t	*rec = &cur->bc_rec.a;
 	xfs_alloc_key_t		*kp = &key->alloc;
-	__int64_t		diff;
 
-	if (cur->bc_btnum == XFS_BTNUM_BNO) {
-		return (__int64_t)be32_to_cpu(kp->ar_startblock) -
-				rec->ar_startblock;
-	}
+	return (__int64_t)be32_to_cpu(kp->ar_startblock) - rec->ar_startblock;
+}
+
+STATIC __int64_t
+xfs_cntbt_key_diff(
+	struct xfs_btree_cur	*cur,
+	union xfs_btree_key	*key)
+{
+	xfs_alloc_rec_incore_t	*rec = &cur->bc_rec.a;
+	xfs_alloc_key_t		*kp = &key->alloc;
+	__int64_t		diff;
 
 	diff = (__int64_t)be32_to_cpu(kp->ar_blockcount) - rec->ar_blockcount;
 	if (diff)
@@ -256,6 +271,33 @@ xfs_allocbt_key_diff(
 	return (__int64_t)be32_to_cpu(kp->ar_startblock) - rec->ar_startblock;
 }
 
+STATIC __int64_t
+xfs_bnobt_diff_two_keys(
+	struct xfs_btree_cur	*cur,
+	union xfs_btree_key	*k1,
+	union xfs_btree_key	*k2)
+{
+	return (__int64_t)be32_to_cpu(k1->alloc.ar_startblock) -
+			  be32_to_cpu(k2->alloc.ar_startblock);
+}
+
+STATIC __int64_t
+xfs_cntbt_diff_two_keys(
+	struct xfs_btree_cur	*cur,
+	union xfs_btree_key	*k1,
+	union xfs_btree_key	*k2)
+{
+	__int64_t		diff;
+
+	diff =  be32_to_cpu(k1->alloc.ar_blockcount) -
+		be32_to_cpu(k2->alloc.ar_blockcount);
+	if (diff)
+		return diff;
+
+	return  be32_to_cpu(k1->alloc.ar_startblock) -
+		be32_to_cpu(k2->alloc.ar_startblock);
+}
+
 static bool
 xfs_allocbt_verify(
 	struct xfs_buf		*bp)
@@ -346,44 +388,78 @@ const struct xfs_buf_ops xfs_allocbt_buf_ops = {
 
 #if defined(DEBUG) || defined(XFS_WARN)
 STATIC int
-xfs_allocbt_keys_inorder(
+xfs_bnobt_keys_inorder(
 	struct xfs_btree_cur	*cur,
 	union xfs_btree_key	*k1,
 	union xfs_btree_key	*k2)
 {
-	if (cur->bc_btnum == XFS_BTNUM_BNO) {
-		return be32_to_cpu(k1->alloc.ar_startblock) <
-		       be32_to_cpu(k2->alloc.ar_startblock);
-	} else {
-		return be32_to_cpu(k1->alloc.ar_blockcount) <
-			be32_to_cpu(k2->alloc.ar_blockcount) ||
-			(k1->alloc.ar_blockcount == k2->alloc.ar_blockcount &&
-			 be32_to_cpu(k1->alloc.ar_startblock) <
-			 be32_to_cpu(k2->alloc.ar_startblock));
-	}
+	return be32_to_cpu(k1->alloc.ar_startblock) <
+	       be32_to_cpu(k2->alloc.ar_startblock);
 }
 
 STATIC int
-xfs_allocbt_recs_inorder(
+xfs_bnobt_recs_inorder(
 	struct xfs_btree_cur	*cur,
 	union xfs_btree_rec	*r1,
 	union xfs_btree_rec	*r2)
 {
-	if (cur->bc_btnum == XFS_BTNUM_BNO) {
-		return be32_to_cpu(r1->alloc.ar_startblock) +
-			be32_to_cpu(r1->alloc.ar_blockcount) <=
-			be32_to_cpu(r2->alloc.ar_startblock);
-	} else {
-		return be32_to_cpu(r1->alloc.ar_blockcount) <
-			be32_to_cpu(r2->alloc.ar_blockcount) ||
-			(r1->alloc.ar_blockcount == r2->alloc.ar_blockcount &&
-			 be32_to_cpu(r1->alloc.ar_startblock) <
-			 be32_to_cpu(r2->alloc.ar_startblock));
-	}
+	return be32_to_cpu(r1->alloc.ar_startblock) +
+		be32_to_cpu(r1->alloc.ar_blockcount) <=
+		be32_to_cpu(r2->alloc.ar_startblock);
+}
+
+STATIC int
+xfs_cntbt_keys_inorder(
+	struct xfs_btree_cur	*cur,
+	union xfs_btree_key	*k1,
+	union xfs_btree_key	*k2)
+{
+	return be32_to_cpu(k1->alloc.ar_blockcount) <
+		be32_to_cpu(k2->alloc.ar_blockcount) ||
+		(k1->alloc.ar_blockcount == k2->alloc.ar_blockcount &&
+		 be32_to_cpu(k1->alloc.ar_startblock) <
+		 be32_to_cpu(k2->alloc.ar_startblock));
+}
+
+STATIC int
+xfs_cntbt_recs_inorder(
+	struct xfs_btree_cur	*cur,
+	union xfs_btree_rec	*r1,
+	union xfs_btree_rec	*r2)
+{
+	return be32_to_cpu(r1->alloc.ar_blockcount) <
+		be32_to_cpu(r2->alloc.ar_blockcount) ||
+		(r1->alloc.ar_blockcount == r2->alloc.ar_blockcount &&
+		 be32_to_cpu(r1->alloc.ar_startblock) <
+		 be32_to_cpu(r2->alloc.ar_startblock));
 }
-#endif	/* DEBUG */
+#endif /* DEBUG */
+
+static const struct xfs_btree_ops xfs_bnobt_ops = {
+	.rec_len		= sizeof(xfs_alloc_rec_t),
+	.key_len		= sizeof(xfs_alloc_key_t),
+
+	.dup_cursor		= xfs_allocbt_dup_cursor,
+	.set_root		= xfs_allocbt_set_root,
+	.alloc_block		= xfs_allocbt_alloc_block,
+	.free_block		= xfs_allocbt_free_block,
+	.update_lastrec		= xfs_allocbt_update_lastrec,
+	.get_minrecs		= xfs_allocbt_get_minrecs,
+	.get_maxrecs		= xfs_allocbt_get_maxrecs,
+	.init_key_from_rec	= xfs_allocbt_init_key_from_rec,
+	.init_high_key_from_rec	= xfs_bnobt_init_high_key_from_rec,
+	.init_rec_from_cur	= xfs_allocbt_init_rec_from_cur,
+	.init_ptr_from_cur	= xfs_allocbt_init_ptr_from_cur,
+	.key_diff		= xfs_bnobt_key_diff,
+	.buf_ops		= &xfs_allocbt_buf_ops,
+	.diff_two_keys		= xfs_bnobt_diff_two_keys,
+#if defined(DEBUG) || defined(XFS_WARN)
+	.keys_inorder		= xfs_bnobt_keys_inorder,
+	.recs_inorder		= xfs_bnobt_recs_inorder,
+#endif
+};
 
-static const struct xfs_btree_ops xfs_allocbt_ops = {
+static const struct xfs_btree_ops xfs_cntbt_ops = {
 	.rec_len		= sizeof(xfs_alloc_rec_t),
 	.key_len		= sizeof(xfs_alloc_key_t),
 
@@ -397,11 +473,12 @@ static const struct xfs_btree_ops xfs_allocbt_ops = {
 	.init_key_from_rec	= xfs_allocbt_init_key_from_rec,
 	.init_rec_from_cur	= xfs_allocbt_init_rec_from_cur,
 	.init_ptr_from_cur	= xfs_allocbt_init_ptr_from_cur,
-	.key_diff		= xfs_allocbt_key_diff,
+	.key_diff		= xfs_cntbt_key_diff,
 	.buf_ops		= &xfs_allocbt_buf_ops,
+	.diff_two_keys		= xfs_cntbt_diff_two_keys,
 #if defined(DEBUG) || defined(XFS_WARN)
-	.keys_inorder		= xfs_allocbt_keys_inorder,
-	.recs_inorder		= xfs_allocbt_recs_inorder,
+	.keys_inorder		= xfs_cntbt_keys_inorder,
+	.recs_inorder		= xfs_cntbt_recs_inorder,
 #endif
 };
 
@@ -427,16 +504,15 @@ xfs_allocbt_init_cursor(
 	cur->bc_mp = mp;
 	cur->bc_btnum = btnum;
 	cur->bc_blocklog = mp->m_sb.sb_blocklog;
-	cur->bc_ops = &xfs_allocbt_ops;
-	if (btnum == XFS_BTNUM_BNO)
-		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtb_2);
-	else
-		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtc_2);
 
 	if (btnum == XFS_BTNUM_CNT) {
+		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtc_2);
+		cur->bc_ops = &xfs_cntbt_ops;
 		cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]);
 		cur->bc_flags = XFS_BTREE_LASTREC_UPDATE;
 	} else {
+		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtb_2);
+		cur->bc_ops = &xfs_bnobt_ops;
 		cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]);
 	}
 

Re: [PATCH 2/8] xfs: plumb in needed functions for range querying of the freespace btrees

[Brian Foster]

On Fri, Feb 17, 2017 at 05:17:30PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Plumb in the pieces (init_high_key, diff_two_keys) necessary to call
> query_range on the free space btrees.  Remove the debugging asserts
> so that we can make queries starting from block 0.
> 
> While we're at it, merge the redundant "if (btnum ==" hunks.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/xfs/libxfs/xfs_alloc_btree.c |  162 +++++++++++++++++++++++++++++----------
>  1 file changed, 119 insertions(+), 43 deletions(-)
> 
> 
> diff --git a/fs/xfs/libxfs/xfs_alloc_btree.c b/fs/xfs/libxfs/xfs_alloc_btree.c
> index efb467b..ba3ec9c 100644
> --- a/fs/xfs/libxfs/xfs_alloc_btree.c
> +++ b/fs/xfs/libxfs/xfs_alloc_btree.c
...
> @@ -346,44 +388,78 @@ const struct xfs_buf_ops xfs_allocbt_buf_ops = {
...
> -static const struct xfs_btree_ops xfs_allocbt_ops = {
> +static const struct xfs_btree_ops xfs_cntbt_ops = {
>  	.rec_len		= sizeof(xfs_alloc_rec_t),
>  	.key_len		= sizeof(xfs_alloc_key_t),
>  
> @@ -397,11 +473,12 @@ static const struct xfs_btree_ops xfs_allocbt_ops = {
>  	.init_key_from_rec	= xfs_allocbt_init_key_from_rec,
>  	.init_rec_from_cur	= xfs_allocbt_init_rec_from_cur,
>  	.init_ptr_from_cur	= xfs_allocbt_init_ptr_from_cur,
> -	.key_diff		= xfs_allocbt_key_diff,
> +	.key_diff		= xfs_cntbt_key_diff,
>  	.buf_ops		= &xfs_allocbt_buf_ops,
> +	.diff_two_keys		= xfs_cntbt_diff_two_keys,

Any reason we add diff_two_keys() but not init_high_key_from_rec() for
the cntbt? If so.. could you note the different requirements in the
commit log?

Brian

>  #if defined(DEBUG) || defined(XFS_WARN)
> -	.keys_inorder		= xfs_allocbt_keys_inorder,
> -	.recs_inorder		= xfs_allocbt_recs_inorder,
> +	.keys_inorder		= xfs_cntbt_keys_inorder,
> +	.recs_inorder		= xfs_cntbt_recs_inorder,
>  #endif
>  };
>  
> @@ -427,16 +504,15 @@ xfs_allocbt_init_cursor(
>  	cur->bc_mp = mp;
>  	cur->bc_btnum = btnum;
>  	cur->bc_blocklog = mp->m_sb.sb_blocklog;
> -	cur->bc_ops = &xfs_allocbt_ops;
> -	if (btnum == XFS_BTNUM_BNO)
> -		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtb_2);
> -	else
> -		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtc_2);
>  
>  	if (btnum == XFS_BTNUM_CNT) {
> +		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtc_2);
> +		cur->bc_ops = &xfs_cntbt_ops;
>  		cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]);
>  		cur->bc_flags = XFS_BTREE_LASTREC_UPDATE;
>  	} else {
> +		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtb_2);
> +		cur->bc_ops = &xfs_bnobt_ops;
>  		cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]);
>  	}
>  
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 2/8] xfs: plumb in needed functions for range querying of the freespace btrees

[Darrick J. Wong]

On Tue, Feb 21, 2017 at 09:35:04AM -0500, Brian Foster wrote:
> On Fri, Feb 17, 2017 at 05:17:30PM -0800, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Plumb in the pieces (init_high_key, diff_two_keys) necessary to call
> > query_range on the free space btrees.  Remove the debugging asserts
> > so that we can make queries starting from block 0.
> > 
> > While we're at it, merge the redundant "if (btnum ==" hunks.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  fs/xfs/libxfs/xfs_alloc_btree.c |  162 +++++++++++++++++++++++++++++----------
> >  1 file changed, 119 insertions(+), 43 deletions(-)
> > 
> > 
> > diff --git a/fs/xfs/libxfs/xfs_alloc_btree.c b/fs/xfs/libxfs/xfs_alloc_btree.c
> > index efb467b..ba3ec9c 100644
> > --- a/fs/xfs/libxfs/xfs_alloc_btree.c
> > +++ b/fs/xfs/libxfs/xfs_alloc_btree.c
> ...
> > @@ -346,44 +388,78 @@ const struct xfs_buf_ops xfs_allocbt_buf_ops = {
> ...
> > -static const struct xfs_btree_ops xfs_allocbt_ops = {
> > +static const struct xfs_btree_ops xfs_cntbt_ops = {
> >  	.rec_len		= sizeof(xfs_alloc_rec_t),
> >  	.key_len		= sizeof(xfs_alloc_key_t),
> >  
> > @@ -397,11 +473,12 @@ static const struct xfs_btree_ops xfs_allocbt_ops = {
> >  	.init_key_from_rec	= xfs_allocbt_init_key_from_rec,
> >  	.init_rec_from_cur	= xfs_allocbt_init_rec_from_cur,
> >  	.init_ptr_from_cur	= xfs_allocbt_init_ptr_from_cur,
> > -	.key_diff		= xfs_allocbt_key_diff,
> > +	.key_diff		= xfs_cntbt_key_diff,
> >  	.buf_ops		= &xfs_allocbt_buf_ops,
> > +	.diff_two_keys		= xfs_cntbt_diff_two_keys,
> 
> Any reason we add diff_two_keys() but not init_high_key_from_rec() for
> the cntbt? If so.. could you note the different requirements in the
> commit log?

Come to think of it, the cntbt isn't overlapped and nothing ever calls
query_range on it, so we don't need xfs_cntbt_diff_two_keys at all.

That said, between getfsmap and the scrub patches we eventually make all
the other btree types query_range-able, so there's no reason to leave
this subtle logic bomb in libxfs for someone else to trip over later.

Thanks for the review!

--D

> 
> Brian
> 
> >  #if defined(DEBUG) || defined(XFS_WARN)
> > -	.keys_inorder		= xfs_allocbt_keys_inorder,
> > -	.recs_inorder		= xfs_allocbt_recs_inorder,
> > +	.keys_inorder		= xfs_cntbt_keys_inorder,
> > +	.recs_inorder		= xfs_cntbt_recs_inorder,
> >  #endif
> >  };
> >  
> > @@ -427,16 +504,15 @@ xfs_allocbt_init_cursor(
> >  	cur->bc_mp = mp;
> >  	cur->bc_btnum = btnum;
> >  	cur->bc_blocklog = mp->m_sb.sb_blocklog;
> > -	cur->bc_ops = &xfs_allocbt_ops;
> > -	if (btnum == XFS_BTNUM_BNO)
> > -		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtb_2);
> > -	else
> > -		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtc_2);
> >  
> >  	if (btnum == XFS_BTNUM_CNT) {
> > +		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtc_2);
> > +		cur->bc_ops = &xfs_cntbt_ops;
> >  		cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]);
> >  		cur->bc_flags = XFS_BTREE_LASTREC_UPDATE;
> >  	} else {
> > +		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtb_2);
> > +		cur->bc_ops = &xfs_bnobt_ops;
> >  		cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]);
> >  	}
> >  
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

[PATCH v2 2/8] xfs: plumb in needed functions for range querying of the freespace btrees

[Darrick J. Wong]

Plumb in the pieces (init_high_key, diff_two_keys) necessary to call
query_range on the free space btrees.  Remove the debugging asserts
so that we can make queries starting from block 0.

While we're at it, merge the redundant "if (btnum ==" hunks.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
v2: Add forgotten cntbt high key function.
---
 fs/xfs/libxfs/xfs_alloc_btree.c |  172 +++++++++++++++++++++++++++++----------
 1 file changed, 129 insertions(+), 43 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_alloc_btree.c b/fs/xfs/libxfs/xfs_alloc_btree.c
index efb467b..e1fcfe7 100644
--- a/fs/xfs/libxfs/xfs_alloc_btree.c
+++ b/fs/xfs/libxfs/xfs_alloc_btree.c
@@ -205,19 +205,37 @@ xfs_allocbt_init_key_from_rec(
 	union xfs_btree_key	*key,
 	union xfs_btree_rec	*rec)
 {
-	ASSERT(rec->alloc.ar_startblock != 0);
-
 	key->alloc.ar_startblock = rec->alloc.ar_startblock;
 	key->alloc.ar_blockcount = rec->alloc.ar_blockcount;
 }
 
 STATIC void
+xfs_bnobt_init_high_key_from_rec(
+	union xfs_btree_key	*key,
+	union xfs_btree_rec	*rec)
+{
+	__u32			x;
+
+	x = be32_to_cpu(rec->alloc.ar_startblock);
+	x += be32_to_cpu(rec->alloc.ar_blockcount) - 1;
+	key->alloc.ar_startblock = cpu_to_be32(x);
+	key->alloc.ar_blockcount = 0;
+}
+
+STATIC void
+xfs_cntbt_init_high_key_from_rec(
+	union xfs_btree_key	*key,
+	union xfs_btree_rec	*rec)
+{
+	key->alloc.ar_blockcount = rec->alloc.ar_blockcount;
+	key->alloc.ar_startblock = 0;
+}
+
+STATIC void
 xfs_allocbt_init_rec_from_cur(
 	struct xfs_btree_cur	*cur,
 	union xfs_btree_rec	*rec)
 {
-	ASSERT(cur->bc_rec.a.ar_startblock != 0);
-
 	rec->alloc.ar_startblock = cpu_to_be32(cur->bc_rec.a.ar_startblock);
 	rec->alloc.ar_blockcount = cpu_to_be32(cur->bc_rec.a.ar_blockcount);
 }
@@ -236,18 +254,24 @@ xfs_allocbt_init_ptr_from_cur(
 }
 
 STATIC __int64_t
-xfs_allocbt_key_diff(
+xfs_bnobt_key_diff(
 	struct xfs_btree_cur	*cur,
 	union xfs_btree_key	*key)
 {
 	xfs_alloc_rec_incore_t	*rec = &cur->bc_rec.a;
 	xfs_alloc_key_t		*kp = &key->alloc;
-	__int64_t		diff;
 
-	if (cur->bc_btnum == XFS_BTNUM_BNO) {
-		return (__int64_t)be32_to_cpu(kp->ar_startblock) -
-				rec->ar_startblock;
-	}
+	return (__int64_t)be32_to_cpu(kp->ar_startblock) - rec->ar_startblock;
+}
+
+STATIC __int64_t
+xfs_cntbt_key_diff(
+	struct xfs_btree_cur	*cur,
+	union xfs_btree_key	*key)
+{
+	xfs_alloc_rec_incore_t	*rec = &cur->bc_rec.a;
+	xfs_alloc_key_t		*kp = &key->alloc;
+	__int64_t		diff;
 
 	diff = (__int64_t)be32_to_cpu(kp->ar_blockcount) - rec->ar_blockcount;
 	if (diff)
@@ -256,6 +280,33 @@ xfs_allocbt_key_diff(
 	return (__int64_t)be32_to_cpu(kp->ar_startblock) - rec->ar_startblock;
 }
 
+STATIC __int64_t
+xfs_bnobt_diff_two_keys(
+	struct xfs_btree_cur	*cur,
+	union xfs_btree_key	*k1,
+	union xfs_btree_key	*k2)
+{
+	return (__int64_t)be32_to_cpu(k1->alloc.ar_startblock) -
+			  be32_to_cpu(k2->alloc.ar_startblock);
+}
+
+STATIC __int64_t
+xfs_cntbt_diff_two_keys(
+	struct xfs_btree_cur	*cur,
+	union xfs_btree_key	*k1,
+	union xfs_btree_key	*k2)
+{
+	__int64_t		diff;
+
+	diff =  be32_to_cpu(k1->alloc.ar_blockcount) -
+		be32_to_cpu(k2->alloc.ar_blockcount);
+	if (diff)
+		return diff;
+
+	return  be32_to_cpu(k1->alloc.ar_startblock) -
+		be32_to_cpu(k2->alloc.ar_startblock);
+}
+
 static bool
 xfs_allocbt_verify(
 	struct xfs_buf		*bp)
@@ -346,44 +397,54 @@ const struct xfs_buf_ops xfs_allocbt_buf_ops = {
 
 #if defined(DEBUG) || defined(XFS_WARN)
 STATIC int
-xfs_allocbt_keys_inorder(
+xfs_bnobt_keys_inorder(
 	struct xfs_btree_cur	*cur,
 	union xfs_btree_key	*k1,
 	union xfs_btree_key	*k2)
 {
-	if (cur->bc_btnum == XFS_BTNUM_BNO) {
-		return be32_to_cpu(k1->alloc.ar_startblock) <
-		       be32_to_cpu(k2->alloc.ar_startblock);
-	} else {
-		return be32_to_cpu(k1->alloc.ar_blockcount) <
-			be32_to_cpu(k2->alloc.ar_blockcount) ||
-			(k1->alloc.ar_blockcount == k2->alloc.ar_blockcount &&
-			 be32_to_cpu(k1->alloc.ar_startblock) <
-			 be32_to_cpu(k2->alloc.ar_startblock));
-	}
+	return be32_to_cpu(k1->alloc.ar_startblock) <
+	       be32_to_cpu(k2->alloc.ar_startblock);
 }
 
 STATIC int
-xfs_allocbt_recs_inorder(
+xfs_bnobt_recs_inorder(
 	struct xfs_btree_cur	*cur,
 	union xfs_btree_rec	*r1,
 	union xfs_btree_rec	*r2)
 {
-	if (cur->bc_btnum == XFS_BTNUM_BNO) {
-		return be32_to_cpu(r1->alloc.ar_startblock) +
-			be32_to_cpu(r1->alloc.ar_blockcount) <=
-			be32_to_cpu(r2->alloc.ar_startblock);
-	} else {
-		return be32_to_cpu(r1->alloc.ar_blockcount) <
-			be32_to_cpu(r2->alloc.ar_blockcount) ||
-			(r1->alloc.ar_blockcount == r2->alloc.ar_blockcount &&
-			 be32_to_cpu(r1->alloc.ar_startblock) <
-			 be32_to_cpu(r2->alloc.ar_startblock));
-	}
+	return be32_to_cpu(r1->alloc.ar_startblock) +
+		be32_to_cpu(r1->alloc.ar_blockcount) <=
+		be32_to_cpu(r2->alloc.ar_startblock);
+}
+
+STATIC int
+xfs_cntbt_keys_inorder(
+	struct xfs_btree_cur	*cur,
+	union xfs_btree_key	*k1,
+	union xfs_btree_key	*k2)
+{
+	return be32_to_cpu(k1->alloc.ar_blockcount) <
+		be32_to_cpu(k2->alloc.ar_blockcount) ||
+		(k1->alloc.ar_blockcount == k2->alloc.ar_blockcount &&
+		 be32_to_cpu(k1->alloc.ar_startblock) <
+		 be32_to_cpu(k2->alloc.ar_startblock));
 }
-#endif	/* DEBUG */
 
-static const struct xfs_btree_ops xfs_allocbt_ops = {
+STATIC int
+xfs_cntbt_recs_inorder(
+	struct xfs_btree_cur	*cur,
+	union xfs_btree_rec	*r1,
+	union xfs_btree_rec	*r2)
+{
+	return be32_to_cpu(r1->alloc.ar_blockcount) <
+		be32_to_cpu(r2->alloc.ar_blockcount) ||
+		(r1->alloc.ar_blockcount == r2->alloc.ar_blockcount &&
+		 be32_to_cpu(r1->alloc.ar_startblock) <
+		 be32_to_cpu(r2->alloc.ar_startblock));
+}
+#endif /* DEBUG */
+
+static const struct xfs_btree_ops xfs_bnobt_ops = {
 	.rec_len		= sizeof(xfs_alloc_rec_t),
 	.key_len		= sizeof(xfs_alloc_key_t),
 
@@ -395,13 +456,39 @@ static const struct xfs_btree_ops xfs_allocbt_ops = {
 	.get_minrecs		= xfs_allocbt_get_minrecs,
 	.get_maxrecs		= xfs_allocbt_get_maxrecs,
 	.init_key_from_rec	= xfs_allocbt_init_key_from_rec,
+	.init_high_key_from_rec	= xfs_bnobt_init_high_key_from_rec,
 	.init_rec_from_cur	= xfs_allocbt_init_rec_from_cur,
 	.init_ptr_from_cur	= xfs_allocbt_init_ptr_from_cur,
-	.key_diff		= xfs_allocbt_key_diff,
+	.key_diff		= xfs_bnobt_key_diff,
 	.buf_ops		= &xfs_allocbt_buf_ops,
+	.diff_two_keys		= xfs_bnobt_diff_two_keys,
 #if defined(DEBUG) || defined(XFS_WARN)
-	.keys_inorder		= xfs_allocbt_keys_inorder,
-	.recs_inorder		= xfs_allocbt_recs_inorder,
+	.keys_inorder		= xfs_bnobt_keys_inorder,
+	.recs_inorder		= xfs_bnobt_recs_inorder,
+#endif
+};
+
+static const struct xfs_btree_ops xfs_cntbt_ops = {
+	.rec_len		= sizeof(xfs_alloc_rec_t),
+	.key_len		= sizeof(xfs_alloc_key_t),
+
+	.dup_cursor		= xfs_allocbt_dup_cursor,
+	.set_root		= xfs_allocbt_set_root,
+	.alloc_block		= xfs_allocbt_alloc_block,
+	.free_block		= xfs_allocbt_free_block,
+	.update_lastrec		= xfs_allocbt_update_lastrec,
+	.get_minrecs		= xfs_allocbt_get_minrecs,
+	.get_maxrecs		= xfs_allocbt_get_maxrecs,
+	.init_key_from_rec	= xfs_allocbt_init_key_from_rec,
+	.init_high_key_from_rec	= xfs_cntbt_init_high_key_from_rec,
+	.init_rec_from_cur	= xfs_allocbt_init_rec_from_cur,
+	.init_ptr_from_cur	= xfs_allocbt_init_ptr_from_cur,
+	.key_diff		= xfs_cntbt_key_diff,
+	.buf_ops		= &xfs_allocbt_buf_ops,
+	.diff_two_keys		= xfs_cntbt_diff_two_keys,
+#if defined(DEBUG) || defined(XFS_WARN)
+	.keys_inorder		= xfs_cntbt_keys_inorder,
+	.recs_inorder		= xfs_cntbt_recs_inorder,
 #endif
 };
 
@@ -427,16 +514,15 @@ xfs_allocbt_init_cursor(
 	cur->bc_mp = mp;
 	cur->bc_btnum = btnum;
 	cur->bc_blocklog = mp->m_sb.sb_blocklog;
-	cur->bc_ops = &xfs_allocbt_ops;
-	if (btnum == XFS_BTNUM_BNO)
-		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtb_2);
-	else
-		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtc_2);
 
 	if (btnum == XFS_BTNUM_CNT) {
+		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtc_2);
+		cur->bc_ops = &xfs_cntbt_ops;
 		cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]);
 		cur->bc_flags = XFS_BTREE_LASTREC_UPDATE;
 	} else {
+		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtb_2);
+		cur->bc_ops = &xfs_bnobt_ops;
 		cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]);
 	}
 

Re: [PATCH v2 2/8] xfs: plumb in needed functions for range querying of the freespace btrees

[Brian Foster]

On Tue, Feb 21, 2017 at 09:34:10AM -0800, Darrick J. Wong wrote:
> Plumb in the pieces (init_high_key, diff_two_keys) necessary to call
> query_range on the free space btrees.  Remove the debugging asserts
> so that we can make queries starting from block 0.
> 
> While we're at it, merge the redundant "if (btnum ==" hunks.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

> v2: Add forgotten cntbt high key function.
> ---
>  fs/xfs/libxfs/xfs_alloc_btree.c |  172 +++++++++++++++++++++++++++++----------
>  1 file changed, 129 insertions(+), 43 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_alloc_btree.c b/fs/xfs/libxfs/xfs_alloc_btree.c
> index efb467b..e1fcfe7 100644
> --- a/fs/xfs/libxfs/xfs_alloc_btree.c
> +++ b/fs/xfs/libxfs/xfs_alloc_btree.c
> @@ -205,19 +205,37 @@ xfs_allocbt_init_key_from_rec(
>  	union xfs_btree_key	*key,
>  	union xfs_btree_rec	*rec)
>  {
> -	ASSERT(rec->alloc.ar_startblock != 0);
> -
>  	key->alloc.ar_startblock = rec->alloc.ar_startblock;
>  	key->alloc.ar_blockcount = rec->alloc.ar_blockcount;
>  }
>  
>  STATIC void
> +xfs_bnobt_init_high_key_from_rec(
> +	union xfs_btree_key	*key,
> +	union xfs_btree_rec	*rec)
> +{
> +	__u32			x;
> +
> +	x = be32_to_cpu(rec->alloc.ar_startblock);
> +	x += be32_to_cpu(rec->alloc.ar_blockcount) - 1;
> +	key->alloc.ar_startblock = cpu_to_be32(x);
> +	key->alloc.ar_blockcount = 0;
> +}
> +
> +STATIC void
> +xfs_cntbt_init_high_key_from_rec(
> +	union xfs_btree_key	*key,
> +	union xfs_btree_rec	*rec)
> +{
> +	key->alloc.ar_blockcount = rec->alloc.ar_blockcount;
> +	key->alloc.ar_startblock = 0;
> +}
> +
> +STATIC void
>  xfs_allocbt_init_rec_from_cur(
>  	struct xfs_btree_cur	*cur,
>  	union xfs_btree_rec	*rec)
>  {
> -	ASSERT(cur->bc_rec.a.ar_startblock != 0);
> -
>  	rec->alloc.ar_startblock = cpu_to_be32(cur->bc_rec.a.ar_startblock);
>  	rec->alloc.ar_blockcount = cpu_to_be32(cur->bc_rec.a.ar_blockcount);
>  }
> @@ -236,18 +254,24 @@ xfs_allocbt_init_ptr_from_cur(
>  }
>  
>  STATIC __int64_t
> -xfs_allocbt_key_diff(
> +xfs_bnobt_key_diff(
>  	struct xfs_btree_cur	*cur,
>  	union xfs_btree_key	*key)
>  {
>  	xfs_alloc_rec_incore_t	*rec = &cur->bc_rec.a;
>  	xfs_alloc_key_t		*kp = &key->alloc;
> -	__int64_t		diff;
>  
> -	if (cur->bc_btnum == XFS_BTNUM_BNO) {
> -		return (__int64_t)be32_to_cpu(kp->ar_startblock) -
> -				rec->ar_startblock;
> -	}
> +	return (__int64_t)be32_to_cpu(kp->ar_startblock) - rec->ar_startblock;
> +}
> +
> +STATIC __int64_t
> +xfs_cntbt_key_diff(
> +	struct xfs_btree_cur	*cur,
> +	union xfs_btree_key	*key)
> +{
> +	xfs_alloc_rec_incore_t	*rec = &cur->bc_rec.a;
> +	xfs_alloc_key_t		*kp = &key->alloc;
> +	__int64_t		diff;
>  
>  	diff = (__int64_t)be32_to_cpu(kp->ar_blockcount) - rec->ar_blockcount;
>  	if (diff)
> @@ -256,6 +280,33 @@ xfs_allocbt_key_diff(
>  	return (__int64_t)be32_to_cpu(kp->ar_startblock) - rec->ar_startblock;
>  }
>  
> +STATIC __int64_t
> +xfs_bnobt_diff_two_keys(
> +	struct xfs_btree_cur	*cur,
> +	union xfs_btree_key	*k1,
> +	union xfs_btree_key	*k2)
> +{
> +	return (__int64_t)be32_to_cpu(k1->alloc.ar_startblock) -
> +			  be32_to_cpu(k2->alloc.ar_startblock);
> +}
> +
> +STATIC __int64_t
> +xfs_cntbt_diff_two_keys(
> +	struct xfs_btree_cur	*cur,
> +	union xfs_btree_key	*k1,
> +	union xfs_btree_key	*k2)
> +{
> +	__int64_t		diff;
> +
> +	diff =  be32_to_cpu(k1->alloc.ar_blockcount) -
> +		be32_to_cpu(k2->alloc.ar_blockcount);
> +	if (diff)
> +		return diff;
> +
> +	return  be32_to_cpu(k1->alloc.ar_startblock) -
> +		be32_to_cpu(k2->alloc.ar_startblock);
> +}
> +
>  static bool
>  xfs_allocbt_verify(
>  	struct xfs_buf		*bp)
> @@ -346,44 +397,54 @@ const struct xfs_buf_ops xfs_allocbt_buf_ops = {
>  
>  #if defined(DEBUG) || defined(XFS_WARN)
>  STATIC int
> -xfs_allocbt_keys_inorder(
> +xfs_bnobt_keys_inorder(
>  	struct xfs_btree_cur	*cur,
>  	union xfs_btree_key	*k1,
>  	union xfs_btree_key	*k2)
>  {
> -	if (cur->bc_btnum == XFS_BTNUM_BNO) {
> -		return be32_to_cpu(k1->alloc.ar_startblock) <
> -		       be32_to_cpu(k2->alloc.ar_startblock);
> -	} else {
> -		return be32_to_cpu(k1->alloc.ar_blockcount) <
> -			be32_to_cpu(k2->alloc.ar_blockcount) ||
> -			(k1->alloc.ar_blockcount == k2->alloc.ar_blockcount &&
> -			 be32_to_cpu(k1->alloc.ar_startblock) <
> -			 be32_to_cpu(k2->alloc.ar_startblock));
> -	}
> +	return be32_to_cpu(k1->alloc.ar_startblock) <
> +	       be32_to_cpu(k2->alloc.ar_startblock);
>  }
>  
>  STATIC int
> -xfs_allocbt_recs_inorder(
> +xfs_bnobt_recs_inorder(
>  	struct xfs_btree_cur	*cur,
>  	union xfs_btree_rec	*r1,
>  	union xfs_btree_rec	*r2)
>  {
> -	if (cur->bc_btnum == XFS_BTNUM_BNO) {
> -		return be32_to_cpu(r1->alloc.ar_startblock) +
> -			be32_to_cpu(r1->alloc.ar_blockcount) <=
> -			be32_to_cpu(r2->alloc.ar_startblock);
> -	} else {
> -		return be32_to_cpu(r1->alloc.ar_blockcount) <
> -			be32_to_cpu(r2->alloc.ar_blockcount) ||
> -			(r1->alloc.ar_blockcount == r2->alloc.ar_blockcount &&
> -			 be32_to_cpu(r1->alloc.ar_startblock) <
> -			 be32_to_cpu(r2->alloc.ar_startblock));
> -	}
> +	return be32_to_cpu(r1->alloc.ar_startblock) +
> +		be32_to_cpu(r1->alloc.ar_blockcount) <=
> +		be32_to_cpu(r2->alloc.ar_startblock);
> +}
> +
> +STATIC int
> +xfs_cntbt_keys_inorder(
> +	struct xfs_btree_cur	*cur,
> +	union xfs_btree_key	*k1,
> +	union xfs_btree_key	*k2)
> +{
> +	return be32_to_cpu(k1->alloc.ar_blockcount) <
> +		be32_to_cpu(k2->alloc.ar_blockcount) ||
> +		(k1->alloc.ar_blockcount == k2->alloc.ar_blockcount &&
> +		 be32_to_cpu(k1->alloc.ar_startblock) <
> +		 be32_to_cpu(k2->alloc.ar_startblock));
>  }
> -#endif	/* DEBUG */
>  
> -static const struct xfs_btree_ops xfs_allocbt_ops = {
> +STATIC int
> +xfs_cntbt_recs_inorder(
> +	struct xfs_btree_cur	*cur,
> +	union xfs_btree_rec	*r1,
> +	union xfs_btree_rec	*r2)
> +{
> +	return be32_to_cpu(r1->alloc.ar_blockcount) <
> +		be32_to_cpu(r2->alloc.ar_blockcount) ||
> +		(r1->alloc.ar_blockcount == r2->alloc.ar_blockcount &&
> +		 be32_to_cpu(r1->alloc.ar_startblock) <
> +		 be32_to_cpu(r2->alloc.ar_startblock));
> +}
> +#endif /* DEBUG */
> +
> +static const struct xfs_btree_ops xfs_bnobt_ops = {
>  	.rec_len		= sizeof(xfs_alloc_rec_t),
>  	.key_len		= sizeof(xfs_alloc_key_t),
>  
> @@ -395,13 +456,39 @@ static const struct xfs_btree_ops xfs_allocbt_ops = {
>  	.get_minrecs		= xfs_allocbt_get_minrecs,
>  	.get_maxrecs		= xfs_allocbt_get_maxrecs,
>  	.init_key_from_rec	= xfs_allocbt_init_key_from_rec,
> +	.init_high_key_from_rec	= xfs_bnobt_init_high_key_from_rec,
>  	.init_rec_from_cur	= xfs_allocbt_init_rec_from_cur,
>  	.init_ptr_from_cur	= xfs_allocbt_init_ptr_from_cur,
> -	.key_diff		= xfs_allocbt_key_diff,
> +	.key_diff		= xfs_bnobt_key_diff,
>  	.buf_ops		= &xfs_allocbt_buf_ops,
> +	.diff_two_keys		= xfs_bnobt_diff_two_keys,
>  #if defined(DEBUG) || defined(XFS_WARN)
> -	.keys_inorder		= xfs_allocbt_keys_inorder,
> -	.recs_inorder		= xfs_allocbt_recs_inorder,
> +	.keys_inorder		= xfs_bnobt_keys_inorder,
> +	.recs_inorder		= xfs_bnobt_recs_inorder,
> +#endif
> +};
> +
> +static const struct xfs_btree_ops xfs_cntbt_ops = {
> +	.rec_len		= sizeof(xfs_alloc_rec_t),
> +	.key_len		= sizeof(xfs_alloc_key_t),
> +
> +	.dup_cursor		= xfs_allocbt_dup_cursor,
> +	.set_root		= xfs_allocbt_set_root,
> +	.alloc_block		= xfs_allocbt_alloc_block,
> +	.free_block		= xfs_allocbt_free_block,
> +	.update_lastrec		= xfs_allocbt_update_lastrec,
> +	.get_minrecs		= xfs_allocbt_get_minrecs,
> +	.get_maxrecs		= xfs_allocbt_get_maxrecs,
> +	.init_key_from_rec	= xfs_allocbt_init_key_from_rec,
> +	.init_high_key_from_rec	= xfs_cntbt_init_high_key_from_rec,
> +	.init_rec_from_cur	= xfs_allocbt_init_rec_from_cur,
> +	.init_ptr_from_cur	= xfs_allocbt_init_ptr_from_cur,
> +	.key_diff		= xfs_cntbt_key_diff,
> +	.buf_ops		= &xfs_allocbt_buf_ops,
> +	.diff_two_keys		= xfs_cntbt_diff_two_keys,
> +#if defined(DEBUG) || defined(XFS_WARN)
> +	.keys_inorder		= xfs_cntbt_keys_inorder,
> +	.recs_inorder		= xfs_cntbt_recs_inorder,
>  #endif
>  };
>  
> @@ -427,16 +514,15 @@ xfs_allocbt_init_cursor(
>  	cur->bc_mp = mp;
>  	cur->bc_btnum = btnum;
>  	cur->bc_blocklog = mp->m_sb.sb_blocklog;
> -	cur->bc_ops = &xfs_allocbt_ops;
> -	if (btnum == XFS_BTNUM_BNO)
> -		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtb_2);
> -	else
> -		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtc_2);
>  
>  	if (btnum == XFS_BTNUM_CNT) {
> +		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtc_2);
> +		cur->bc_ops = &xfs_cntbt_ops;
>  		cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]);
>  		cur->bc_flags = XFS_BTREE_LASTREC_UPDATE;
>  	} else {
> +		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtb_2);
> +		cur->bc_ops = &xfs_bnobt_ops;
>  		cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]);
>  	}
>  
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

[PATCH 3/8] xfs: provide a query_range function for freespace btrees

[Darrick J. Wong]

From: Darrick J. Wong <darrick.wong@oracle.com>

Implement a query_range function for the bnobt and cntbt.  This will
be used for getfsmap fallback if there is no rmapbt and by the online
scrub and repair code.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/libxfs/xfs_alloc.c |   42 ++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/libxfs/xfs_alloc.h |   10 ++++++++++
 2 files changed, 52 insertions(+)


diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index 9f06a21..526df17 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -2875,3 +2875,45 @@ xfs_free_extent(
 	xfs_trans_brelse(tp, agbp);
 	return error;
 }
+
+struct xfs_alloc_query_range_info {
+	xfs_alloc_query_range_fn	fn;
+	void				*priv;
+};
+
+/* Format btree record and pass to our callback. */
+STATIC int
+xfs_alloc_query_range_helper(
+	struct xfs_btree_cur		*cur,
+	union xfs_btree_rec		*rec,
+	void				*priv)
+{
+	struct xfs_alloc_query_range_info	*query = priv;
+	struct xfs_alloc_rec_incore		irec;
+
+	irec.ar_startblock = be32_to_cpu(rec->alloc.ar_startblock);
+	irec.ar_blockcount = be32_to_cpu(rec->alloc.ar_blockcount);
+	return query->fn(cur, &irec, query->priv);
+}
+
+/* Find all free space within a given range of blocks. */
+int
+xfs_alloc_query_range(
+	struct xfs_btree_cur			*cur,
+	struct xfs_alloc_rec_incore		*low_rec,
+	struct xfs_alloc_rec_incore		*high_rec,
+	xfs_alloc_query_range_fn		fn,
+	void					*priv)
+{
+	union xfs_btree_irec			low_brec;
+	union xfs_btree_irec			high_brec;
+	struct xfs_alloc_query_range_info	query;
+
+	ASSERT(cur->bc_btnum == XFS_BTNUM_BNO);
+	low_brec.a = *low_rec;
+	high_brec.a = *high_rec;
+	query.priv = priv;
+	query.fn = fn;
+	return xfs_btree_query_range(cur, &low_brec, &high_brec,
+			xfs_alloc_query_range_helper, &query);
+}
diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h
index 1d0f48a..f534998 100644
--- a/fs/xfs/libxfs/xfs_alloc.h
+++ b/fs/xfs/libxfs/xfs_alloc.h
@@ -223,4 +223,14 @@ int xfs_free_extent_fix_freelist(struct xfs_trans *tp, xfs_agnumber_t agno,
 
 xfs_extlen_t xfs_prealloc_blocks(struct xfs_mount *mp);
 
+typedef int (*xfs_alloc_query_range_fn)(
+	struct xfs_btree_cur		*cur,
+	struct xfs_alloc_rec_incore	*rec,
+	void				*priv);
+
+int xfs_alloc_query_range(struct xfs_btree_cur *cur,
+		struct xfs_alloc_rec_incore *low_rec,
+		struct xfs_alloc_rec_incore *high_rec,
+		xfs_alloc_query_range_fn fn, void *priv);
+
 #endif	/* __XFS_ALLOC_H__ */

Re: [PATCH 3/8] xfs: provide a query_range function for freespace btrees

[Brian Foster]

On Fri, Feb 17, 2017 at 05:17:36PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Implement a query_range function for the bnobt and cntbt.  This will
> be used for getfsmap fallback if there is no rmapbt and by the online
> scrub and repair code.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

>  fs/xfs/libxfs/xfs_alloc.c |   42 ++++++++++++++++++++++++++++++++++++++++++
>  fs/xfs/libxfs/xfs_alloc.h |   10 ++++++++++
>  2 files changed, 52 insertions(+)
> 
> 
> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> index 9f06a21..526df17 100644
> --- a/fs/xfs/libxfs/xfs_alloc.c
> +++ b/fs/xfs/libxfs/xfs_alloc.c
> @@ -2875,3 +2875,45 @@ xfs_free_extent(
>  	xfs_trans_brelse(tp, agbp);
>  	return error;
>  }
> +
> +struct xfs_alloc_query_range_info {
> +	xfs_alloc_query_range_fn	fn;
> +	void				*priv;
> +};
> +
> +/* Format btree record and pass to our callback. */
> +STATIC int
> +xfs_alloc_query_range_helper(
> +	struct xfs_btree_cur		*cur,
> +	union xfs_btree_rec		*rec,
> +	void				*priv)
> +{
> +	struct xfs_alloc_query_range_info	*query = priv;
> +	struct xfs_alloc_rec_incore		irec;
> +
> +	irec.ar_startblock = be32_to_cpu(rec->alloc.ar_startblock);
> +	irec.ar_blockcount = be32_to_cpu(rec->alloc.ar_blockcount);
> +	return query->fn(cur, &irec, query->priv);
> +}
> +
> +/* Find all free space within a given range of blocks. */
> +int
> +xfs_alloc_query_range(
> +	struct xfs_btree_cur			*cur,
> +	struct xfs_alloc_rec_incore		*low_rec,
> +	struct xfs_alloc_rec_incore		*high_rec,
> +	xfs_alloc_query_range_fn		fn,
> +	void					*priv)
> +{
> +	union xfs_btree_irec			low_brec;
> +	union xfs_btree_irec			high_brec;
> +	struct xfs_alloc_query_range_info	query;
> +
> +	ASSERT(cur->bc_btnum == XFS_BTNUM_BNO);
> +	low_brec.a = *low_rec;
> +	high_brec.a = *high_rec;
> +	query.priv = priv;
> +	query.fn = fn;
> +	return xfs_btree_query_range(cur, &low_brec, &high_brec,
> +			xfs_alloc_query_range_helper, &query);
> +}
> diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h
> index 1d0f48a..f534998 100644
> --- a/fs/xfs/libxfs/xfs_alloc.h
> +++ b/fs/xfs/libxfs/xfs_alloc.h
> @@ -223,4 +223,14 @@ int xfs_free_extent_fix_freelist(struct xfs_trans *tp, xfs_agnumber_t agno,
>  
>  xfs_extlen_t xfs_prealloc_blocks(struct xfs_mount *mp);
>  
> +typedef int (*xfs_alloc_query_range_fn)(
> +	struct xfs_btree_cur		*cur,
> +	struct xfs_alloc_rec_incore	*rec,
> +	void				*priv);
> +
> +int xfs_alloc_query_range(struct xfs_btree_cur *cur,
> +		struct xfs_alloc_rec_incore *low_rec,
> +		struct xfs_alloc_rec_incore *high_rec,
> +		xfs_alloc_query_range_fn fn, void *priv);
> +
>  #endif	/* __XFS_ALLOC_H__ */
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

[PATCH 4/8] xfs: create a function to query all records in a btree

[Darrick J. Wong]

From: Darrick J. Wong <darrick.wong@oracle.com>

Create a helper function that will query all records in a btree.
This will be used by the online repair functions to examine every
record in a btree to rebuild a second btree.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/libxfs/xfs_alloc.c |   15 +++++++++++++++
 fs/xfs/libxfs/xfs_alloc.h |    2 ++
 fs/xfs/libxfs/xfs_btree.c |   15 +++++++++++++++
 fs/xfs/libxfs/xfs_btree.h |    2 ++
 fs/xfs/libxfs/xfs_rmap.c  |   28 +++++++++++++++++++++-------
 fs/xfs/libxfs/xfs_rmap.h  |    2 ++
 6 files changed, 57 insertions(+), 7 deletions(-)


diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index 526df17..ba15f30 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -2917,3 +2917,18 @@ xfs_alloc_query_range(
 	return xfs_btree_query_range(cur, &low_brec, &high_brec,
 			xfs_alloc_query_range_helper, &query);
 }
+
+/* Find all free space records. */
+int
+xfs_alloc_query_all(
+	struct xfs_btree_cur			*cur,
+	xfs_alloc_query_range_fn		fn,
+	void					*priv)
+{
+	struct xfs_alloc_query_range_info	query;
+
+	ASSERT(cur->bc_btnum == XFS_BTNUM_BNO);
+	query.priv = priv;
+	query.fn = fn;
+	return xfs_btree_query_all(cur, xfs_alloc_query_range_helper, &query);
+}
diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h
index f534998..a2101de 100644
--- a/fs/xfs/libxfs/xfs_alloc.h
+++ b/fs/xfs/libxfs/xfs_alloc.h
@@ -232,5 +232,7 @@ int xfs_alloc_query_range(struct xfs_btree_cur *cur,
 		struct xfs_alloc_rec_incore *low_rec,
 		struct xfs_alloc_rec_incore *high_rec,
 		xfs_alloc_query_range_fn fn, void *priv);
+int xfs_alloc_query_all(struct xfs_btree_cur *cur, xfs_alloc_query_range_fn fn,
+		void *priv);
 
 #endif	/* __XFS_ALLOC_H__ */
diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index 2849d3f..ca94b87 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -4823,6 +4823,21 @@ xfs_btree_query_range(
 			fn, priv);
 }
 
+/* Query a btree for all records. */
+int
+xfs_btree_query_all(
+	struct xfs_btree_cur		*cur,
+	xfs_btree_query_range_fn	fn,
+	void				*priv)
+{
+	union xfs_btree_irec		low_rec;
+	union xfs_btree_irec		high_rec;
+
+	memset(&low_rec, 0, sizeof(low_rec));
+	memset(&high_rec, 0xFF, sizeof(high_rec));
+	return xfs_btree_query_range(cur, &low_rec, &high_rec, fn, priv);
+}
+
 /*
  * Calculate the number of blocks needed to store a given number of records
  * in a short-format (per-AG metadata) btree.
diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
index 33a8f86..5114055 100644
--- a/fs/xfs/libxfs/xfs_btree.h
+++ b/fs/xfs/libxfs/xfs_btree.h
@@ -494,6 +494,8 @@ typedef int (*xfs_btree_query_range_fn)(struct xfs_btree_cur *cur,
 int xfs_btree_query_range(struct xfs_btree_cur *cur,
 		union xfs_btree_irec *low_rec, union xfs_btree_irec *high_rec,
 		xfs_btree_query_range_fn fn, void *priv);
+int xfs_btree_query_all(struct xfs_btree_cur *cur, xfs_btree_query_range_fn fn,
+		void *priv);
 
 typedef int (*xfs_btree_visit_blocks_fn)(struct xfs_btree_cur *cur, int level,
 		void *data);
diff --git a/fs/xfs/libxfs/xfs_rmap.c b/fs/xfs/libxfs/xfs_rmap.c
index 3a8cc71..3840556 100644
--- a/fs/xfs/libxfs/xfs_rmap.c
+++ b/fs/xfs/libxfs/xfs_rmap.c
@@ -2001,14 +2001,14 @@ xfs_rmap_query_range_helper(
 /* Find all rmaps between two keys. */
 int
 xfs_rmap_query_range(
-	struct xfs_btree_cur		*cur,
-	struct xfs_rmap_irec		*low_rec,
-	struct xfs_rmap_irec		*high_rec,
-	xfs_rmap_query_range_fn	fn,
-	void				*priv)
+	struct xfs_btree_cur			*cur,
+	struct xfs_rmap_irec			*low_rec,
+	struct xfs_rmap_irec			*high_rec,
+	xfs_rmap_query_range_fn			fn,
+	void					*priv)
 {
-	union xfs_btree_irec		low_brec;
-	union xfs_btree_irec		high_brec;
+	union xfs_btree_irec			low_brec;
+	union xfs_btree_irec			high_brec;
 	struct xfs_rmap_query_range_info	query;
 
 	low_brec.r = *low_rec;
@@ -2019,6 +2019,20 @@ xfs_rmap_query_range(
 			xfs_rmap_query_range_helper, &query);
 }
 
+/* Find all rmaps. */
+int
+xfs_rmap_query_all(
+	struct xfs_btree_cur			*cur,
+	xfs_rmap_query_range_fn			fn,
+	void					*priv)
+{
+	struct xfs_rmap_query_range_info	query;
+
+	query.priv = priv;
+	query.fn = fn;
+	return xfs_btree_query_all(cur, xfs_rmap_query_range_helper, &query);
+}
+
 /* Clean up after calling xfs_rmap_finish_one. */
 void
 xfs_rmap_finish_one_cleanup(
diff --git a/fs/xfs/libxfs/xfs_rmap.h b/fs/xfs/libxfs/xfs_rmap.h
index 7899305..faf2c1a 100644
--- a/fs/xfs/libxfs/xfs_rmap.h
+++ b/fs/xfs/libxfs/xfs_rmap.h
@@ -162,6 +162,8 @@ typedef int (*xfs_rmap_query_range_fn)(
 int xfs_rmap_query_range(struct xfs_btree_cur *cur,
 		struct xfs_rmap_irec *low_rec, struct xfs_rmap_irec *high_rec,
 		xfs_rmap_query_range_fn fn, void *priv);
+int xfs_rmap_query_all(struct xfs_btree_cur *cur, xfs_rmap_query_range_fn fn,
+		void *priv);
 
 enum xfs_rmap_intent_type {
 	XFS_RMAP_MAP,

Re: [PATCH 4/8] xfs: create a function to query all records in a btree

[Brian Foster]

On Fri, Feb 17, 2017 at 05:17:42PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Create a helper function that will query all records in a btree.
> This will be used by the online repair functions to examine every
> record in a btree to rebuild a second btree.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

>  fs/xfs/libxfs/xfs_alloc.c |   15 +++++++++++++++
>  fs/xfs/libxfs/xfs_alloc.h |    2 ++
>  fs/xfs/libxfs/xfs_btree.c |   15 +++++++++++++++
>  fs/xfs/libxfs/xfs_btree.h |    2 ++
>  fs/xfs/libxfs/xfs_rmap.c  |   28 +++++++++++++++++++++-------
>  fs/xfs/libxfs/xfs_rmap.h  |    2 ++
>  6 files changed, 57 insertions(+), 7 deletions(-)
> 
> 
> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> index 526df17..ba15f30 100644
> --- a/fs/xfs/libxfs/xfs_alloc.c
> +++ b/fs/xfs/libxfs/xfs_alloc.c
> @@ -2917,3 +2917,18 @@ xfs_alloc_query_range(
>  	return xfs_btree_query_range(cur, &low_brec, &high_brec,
>  			xfs_alloc_query_range_helper, &query);
>  }
> +
> +/* Find all free space records. */
> +int
> +xfs_alloc_query_all(
> +	struct xfs_btree_cur			*cur,
> +	xfs_alloc_query_range_fn		fn,
> +	void					*priv)
> +{
> +	struct xfs_alloc_query_range_info	query;
> +
> +	ASSERT(cur->bc_btnum == XFS_BTNUM_BNO);
> +	query.priv = priv;
> +	query.fn = fn;
> +	return xfs_btree_query_all(cur, xfs_alloc_query_range_helper, &query);
> +}
> diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h
> index f534998..a2101de 100644
> --- a/fs/xfs/libxfs/xfs_alloc.h
> +++ b/fs/xfs/libxfs/xfs_alloc.h
> @@ -232,5 +232,7 @@ int xfs_alloc_query_range(struct xfs_btree_cur *cur,
>  		struct xfs_alloc_rec_incore *low_rec,
>  		struct xfs_alloc_rec_incore *high_rec,
>  		xfs_alloc_query_range_fn fn, void *priv);
> +int xfs_alloc_query_all(struct xfs_btree_cur *cur, xfs_alloc_query_range_fn fn,
> +		void *priv);
>  
>  #endif	/* __XFS_ALLOC_H__ */
> diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
> index 2849d3f..ca94b87 100644
> --- a/fs/xfs/libxfs/xfs_btree.c
> +++ b/fs/xfs/libxfs/xfs_btree.c
> @@ -4823,6 +4823,21 @@ xfs_btree_query_range(
>  			fn, priv);
>  }
>  
> +/* Query a btree for all records. */
> +int
> +xfs_btree_query_all(
> +	struct xfs_btree_cur		*cur,
> +	xfs_btree_query_range_fn	fn,
> +	void				*priv)
> +{
> +	union xfs_btree_irec		low_rec;
> +	union xfs_btree_irec		high_rec;
> +
> +	memset(&low_rec, 0, sizeof(low_rec));
> +	memset(&high_rec, 0xFF, sizeof(high_rec));
> +	return xfs_btree_query_range(cur, &low_rec, &high_rec, fn, priv);
> +}
> +
>  /*
>   * Calculate the number of blocks needed to store a given number of records
>   * in a short-format (per-AG metadata) btree.
> diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
> index 33a8f86..5114055 100644
> --- a/fs/xfs/libxfs/xfs_btree.h
> +++ b/fs/xfs/libxfs/xfs_btree.h
> @@ -494,6 +494,8 @@ typedef int (*xfs_btree_query_range_fn)(struct xfs_btree_cur *cur,
>  int xfs_btree_query_range(struct xfs_btree_cur *cur,
>  		union xfs_btree_irec *low_rec, union xfs_btree_irec *high_rec,
>  		xfs_btree_query_range_fn fn, void *priv);
> +int xfs_btree_query_all(struct xfs_btree_cur *cur, xfs_btree_query_range_fn fn,
> +		void *priv);
>  
>  typedef int (*xfs_btree_visit_blocks_fn)(struct xfs_btree_cur *cur, int level,
>  		void *data);
> diff --git a/fs/xfs/libxfs/xfs_rmap.c b/fs/xfs/libxfs/xfs_rmap.c
> index 3a8cc71..3840556 100644
> --- a/fs/xfs/libxfs/xfs_rmap.c
> +++ b/fs/xfs/libxfs/xfs_rmap.c
> @@ -2001,14 +2001,14 @@ xfs_rmap_query_range_helper(
>  /* Find all rmaps between two keys. */
>  int
>  xfs_rmap_query_range(
> -	struct xfs_btree_cur		*cur,
> -	struct xfs_rmap_irec		*low_rec,
> -	struct xfs_rmap_irec		*high_rec,
> -	xfs_rmap_query_range_fn	fn,
> -	void				*priv)
> +	struct xfs_btree_cur			*cur,
> +	struct xfs_rmap_irec			*low_rec,
> +	struct xfs_rmap_irec			*high_rec,
> +	xfs_rmap_query_range_fn			fn,
> +	void					*priv)
>  {
> -	union xfs_btree_irec		low_brec;
> -	union xfs_btree_irec		high_brec;
> +	union xfs_btree_irec			low_brec;
> +	union xfs_btree_irec			high_brec;
>  	struct xfs_rmap_query_range_info	query;
>  
>  	low_brec.r = *low_rec;
> @@ -2019,6 +2019,20 @@ xfs_rmap_query_range(
>  			xfs_rmap_query_range_helper, &query);
>  }
>  
> +/* Find all rmaps. */
> +int
> +xfs_rmap_query_all(
> +	struct xfs_btree_cur			*cur,
> +	xfs_rmap_query_range_fn			fn,
> +	void					*priv)
> +{
> +	struct xfs_rmap_query_range_info	query;
> +
> +	query.priv = priv;
> +	query.fn = fn;
> +	return xfs_btree_query_all(cur, xfs_rmap_query_range_helper, &query);
> +}
> +
>  /* Clean up after calling xfs_rmap_finish_one. */
>  void
>  xfs_rmap_finish_one_cleanup(
> diff --git a/fs/xfs/libxfs/xfs_rmap.h b/fs/xfs/libxfs/xfs_rmap.h
> index 7899305..faf2c1a 100644
> --- a/fs/xfs/libxfs/xfs_rmap.h
> +++ b/fs/xfs/libxfs/xfs_rmap.h
> @@ -162,6 +162,8 @@ typedef int (*xfs_rmap_query_range_fn)(
>  int xfs_rmap_query_range(struct xfs_btree_cur *cur,
>  		struct xfs_rmap_irec *low_rec, struct xfs_rmap_irec *high_rec,
>  		xfs_rmap_query_range_fn fn, void *priv);
> +int xfs_rmap_query_all(struct xfs_btree_cur *cur, xfs_rmap_query_range_fn fn,
> +		void *priv);
>  
>  enum xfs_rmap_intent_type {
>  	XFS_RMAP_MAP,
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

[PATCH 5/8] xfs: introduce the XFS_IOC_GETFSMAP ioctl

[Darrick J. Wong]

From: Darrick J. Wong <darrick.wong@oracle.com>

Introduce a new ioctl that uses the reverse mapping btree to return
information about the physical layout of the filesystem.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/Makefile        |    1 
 fs/xfs/libxfs/xfs_fs.h |   13 +
 fs/xfs/xfs_fsmap.c     |  782 ++++++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_fsmap.h     |   51 +++
 fs/xfs/xfs_ioctl.c     |  103 ++++++
 fs/xfs/xfs_ioctl32.c   |    2 
 fs/xfs/xfs_trace.h     |   85 +++++
 fs/xfs/xfs_trans.c     |   22 +
 fs/xfs/xfs_trans.h     |    2 
 9 files changed, 1061 insertions(+)
 create mode 100644 fs/xfs/xfs_fsmap.c
 create mode 100644 fs/xfs/xfs_fsmap.h


diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile
index c7515d4..0e7ee30 100644
--- a/fs/xfs/Makefile
+++ b/fs/xfs/Makefile
@@ -80,6 +80,7 @@ xfs-y				+= xfs_aops.o \
 				   xfs_extent_busy.o \
 				   xfs_file.o \
 				   xfs_filestream.o \
+				   xfs_fsmap.o \
 				   xfs_fsops.o \
 				   xfs_globals.o \
 				   xfs_icache.o \
diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
index b72dc82..095bdf0 100644
--- a/fs/xfs/libxfs/xfs_fs.h
+++ b/fs/xfs/libxfs/xfs_fs.h
@@ -92,6 +92,18 @@ struct getbmapx {
 #define BMV_OF_LAST		0x4	/* segment is the last in the file */
 #define BMV_OF_SHARED		0x8	/* segment shared with another file */
 
+/*	fmr_owner special values for FS_IOC_GETFSMAP */
+#define XFS_FMR_OWN_FREE	FMR_OWN_FREE      /* free space */
+#define XFS_FMR_OWN_UNKNOWN	FMR_OWN_UNKNOWN   /* unknown owner */
+#define XFS_FMR_OWN_FS		FMR_OWNER('X', 1) /* static fs metadata */
+#define XFS_FMR_OWN_LOG		FMR_OWNER('X', 2) /* journalling log */
+#define XFS_FMR_OWN_AG		FMR_OWNER('X', 3) /* per-AG metadata */
+#define XFS_FMR_OWN_INOBT	FMR_OWNER('X', 4) /* inode btree blocks */
+#define XFS_FMR_OWN_INODES	FMR_OWNER('X', 5) /* inodes */
+#define XFS_FMR_OWN_REFC	FMR_OWNER('X', 6) /* refcount tree */
+#define XFS_FMR_OWN_COW		FMR_OWNER('X', 7) /* cow staging */
+#define XFS_FMR_OWN_DEFECTIVE	FMR_OWNER('X', 8) /* bad blocks */
+
 /*
  * Structure for XFS_IOC_FSSETDM.
  * For use by backup and restore programs to set the XFS on-disk inode
@@ -502,6 +514,7 @@ typedef struct xfs_swapext
 #define XFS_IOC_GETBMAPX	_IOWR('X', 56, struct getbmap)
 #define XFS_IOC_ZERO_RANGE	_IOW ('X', 57, struct xfs_flock64)
 #define XFS_IOC_FREE_EOFBLOCKS	_IOR ('X', 58, struct xfs_fs_eofblocks)
+/*	XFS_IOC_GETFSMAP ------ hoisted 59         */
 
 /*
  * ioctl commands that replace IRIX syssgi()'s
diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
new file mode 100644
index 0000000..09d6b92
--- /dev/null
+++ b/fs/xfs/xfs_fsmap.c
@@ -0,0 +1,782 @@
+/*
+ * Copyright (C) 2017 Oracle.  All Rights Reserved.
+ *
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+#include "xfs.h"
+#include "xfs_fs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_log_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_sb.h"
+#include "xfs_mount.h"
+#include "xfs_defer.h"
+#include "xfs_inode.h"
+#include "xfs_trans.h"
+#include "xfs_error.h"
+#include "xfs_btree.h"
+#include "xfs_rmap_btree.h"
+#include "xfs_trace.h"
+#include "xfs_log.h"
+#include "xfs_rmap.h"
+#include "xfs_alloc.h"
+#include "xfs_bit.h"
+#include <linux/fsmap.h>
+#include "xfs_fsmap.h"
+#include "xfs_refcount.h"
+#include "xfs_refcount_btree.h"
+
+/* Convert an xfs_fsmap to an fsmap. */
+void
+xfs_fsmap_from_internal(
+	struct fsmap		*dest,
+	struct xfs_fsmap	*src)
+{
+	dest->fmr_device = src->fmr_device;
+	dest->fmr_flags = src->fmr_flags;
+	dest->fmr_physical = BBTOB(src->fmr_physical);
+	dest->fmr_owner = src->fmr_owner;
+	dest->fmr_offset = BBTOB(src->fmr_offset);
+	dest->fmr_length = BBTOB(src->fmr_length);
+	dest->fmr_reserved[0] = 0;
+	dest->fmr_reserved[1] = 0;
+	dest->fmr_reserved[2] = 0;
+}
+
+/* Convert an fsmap to an xfs_fsmap. */
+void
+xfs_fsmap_to_internal(
+	struct xfs_fsmap	*dest,
+	struct fsmap		*src)
+{
+	dest->fmr_device = src->fmr_device;
+	dest->fmr_flags = src->fmr_flags;
+	dest->fmr_physical = BTOBBT(src->fmr_physical);
+	dest->fmr_owner = src->fmr_owner;
+	dest->fmr_offset = BTOBBT(src->fmr_offset);
+	dest->fmr_length = BTOBBT(src->fmr_length);
+}
+
+/* Convert an fsmap owner into an rmapbt owner. */
+static int
+xfs_fsmap_owner_to_rmap(
+	struct xfs_fsmap	*fmr,
+	struct xfs_rmap_irec	*rm)
+{
+	if (!(fmr->fmr_flags & FMR_OF_SPECIAL_OWNER)) {
+		rm->rm_owner = fmr->fmr_owner;
+		return 0;
+	}
+
+	switch (fmr->fmr_owner) {
+	case 0:			/* "lowest owner id possible" */
+	case -1ULL:		/* "highest owner id possible" */
+		rm->rm_owner = 0;
+		break;
+	case XFS_FMR_OWN_FREE:
+		rm->rm_owner = XFS_RMAP_OWN_NULL;
+		break;
+	case XFS_FMR_OWN_UNKNOWN:
+		rm->rm_owner = XFS_RMAP_OWN_UNKNOWN;
+		break;
+	case XFS_FMR_OWN_FS:
+		rm->rm_owner = XFS_RMAP_OWN_FS;
+		break;
+	case XFS_FMR_OWN_LOG:
+		rm->rm_owner = XFS_RMAP_OWN_LOG;
+		break;
+	case XFS_FMR_OWN_AG:
+		rm->rm_owner = XFS_RMAP_OWN_AG;
+		break;
+	case XFS_FMR_OWN_INOBT:
+		rm->rm_owner = XFS_RMAP_OWN_INOBT;
+		break;
+	case XFS_FMR_OWN_INODES:
+		rm->rm_owner = XFS_RMAP_OWN_INODES;
+		break;
+	case XFS_FMR_OWN_REFC:
+		rm->rm_owner = XFS_RMAP_OWN_REFC;
+		break;
+	case XFS_FMR_OWN_COW:
+		rm->rm_owner = XFS_RMAP_OWN_COW;
+		break;
+	case XFS_FMR_OWN_DEFECTIVE:	/* not implemented */
+		/* fall through */
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+/* Convert an rmapbt owner into an fsmap owner. */
+static int
+xfs_fsmap_owner_from_rmap(
+	struct xfs_rmap_irec	*rm,
+	struct xfs_fsmap	*fmr)
+{
+	fmr->fmr_flags = 0;
+	if (!XFS_RMAP_NON_INODE_OWNER(rm->rm_owner)) {
+		fmr->fmr_owner = rm->rm_owner;
+		return 0;
+	}
+	fmr->fmr_flags |= FMR_OF_SPECIAL_OWNER;
+
+	switch (rm->rm_owner) {
+	case XFS_RMAP_OWN_FS:
+		fmr->fmr_owner = XFS_FMR_OWN_FS;
+		break;
+	case XFS_RMAP_OWN_LOG:
+		fmr->fmr_owner = XFS_FMR_OWN_LOG;
+		break;
+	case XFS_RMAP_OWN_AG:
+		fmr->fmr_owner = XFS_FMR_OWN_AG;
+		break;
+	case XFS_RMAP_OWN_INOBT:
+		fmr->fmr_owner = XFS_FMR_OWN_INOBT;
+		break;
+	case XFS_RMAP_OWN_INODES:
+		fmr->fmr_owner = XFS_FMR_OWN_INODES;
+		break;
+	case XFS_RMAP_OWN_REFC:
+		fmr->fmr_owner = XFS_FMR_OWN_REFC;
+		break;
+	case XFS_RMAP_OWN_COW:
+		fmr->fmr_owner = XFS_FMR_OWN_COW;
+		break;
+	default:
+		return -EFSCORRUPTED;
+	}
+	return 0;
+}
+
+/* getfsmap query state */
+struct xfs_getfsmap_info {
+	struct xfs_fsmap_head	*head;
+	struct xfs_fsmap	*rkey_low;	/* lowest key */
+	xfs_fsmap_format_t	formatter;	/* formatting fn */
+	void			*format_arg;	/* format buffer */
+	bool			last;		/* last extent? */
+	xfs_daddr_t		next_daddr;	/* next daddr we expect */
+	u32			dev;		/* device id */
+	u64			missing_owner;	/* owner of holes */
+
+	xfs_agnumber_t		agno;		/* AG number, if applicable */
+	struct xfs_buf		*agf_bp;	/* AGF, for refcount queries */
+	struct xfs_rmap_irec	low;		/* low rmap key */
+	struct xfs_rmap_irec	high;		/* high rmap key */
+};
+
+/* Associate a device with a getfsmap handler. */
+struct xfs_getfsmap_dev {
+	u32			dev;
+	int			(*fn)(struct xfs_trans *tp,
+				      struct xfs_fsmap *keys,
+				      struct xfs_getfsmap_info *info);
+};
+
+/* Compare two getfsmap device handlers. */
+static int
+xfs_getfsmap_dev_compare(
+	const void			*p1,
+	const void			*p2)
+{
+	const struct xfs_getfsmap_dev	*d1 = p1;
+	const struct xfs_getfsmap_dev	*d2 = p2;
+
+	return d1->dev - d2->dev;
+}
+
+/* Compare a record against our starting point */
+static bool
+xfs_getfsmap_rec_before_low_key(
+	struct xfs_getfsmap_info	*info,
+	struct xfs_rmap_irec		*rec)
+{
+	uint64_t			x, y;
+
+	if (rec->rm_startblock < info->low.rm_startblock)
+		return true;
+	if (rec->rm_startblock > info->low.rm_startblock)
+		return false;
+
+	if (rec->rm_owner < info->low.rm_owner)
+		return true;
+	if (rec->rm_owner > info->low.rm_owner)
+		return false;
+
+	x = xfs_rmap_irec_offset_pack(rec);
+	y = xfs_rmap_irec_offset_pack(&info->low);
+	if (x < y)
+		return true;
+	return false;
+}
+
+/* Decide if this mapping is shared. */
+STATIC int
+xfs_getfsmap_is_shared(
+	struct xfs_trans		*tp,
+	struct xfs_getfsmap_info	*info,
+	struct xfs_rmap_irec		*rec,
+	bool				*stat)
+{
+	struct xfs_mount		*mp = tp->t_mountp;
+	struct xfs_btree_cur		*cur;
+	xfs_agblock_t			fbno;
+	xfs_extlen_t			flen;
+	int				error;
+
+	*stat = false;
+	if (!xfs_sb_version_hasreflink(&mp->m_sb))
+		return 0;
+	/* rt files will have agno set to NULLAGNUMBER */
+	if (info->agno == NULLAGNUMBER)
+		return 0;
+
+	/* Are there any shared blocks here? */
+	flen = 0;
+	cur = xfs_refcountbt_init_cursor(mp, tp, info->agf_bp,
+			info->agno, NULL);
+
+	error = xfs_refcount_find_shared(cur, rec->rm_startblock,
+			rec->rm_blockcount, &fbno, &flen, false);
+
+	xfs_btree_del_cursor(cur, error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
+	if (error)
+		return error;
+
+	*stat = flen > 0;
+	return 0;
+}
+
+/*
+ * Format a reverse mapping for getfsmap, having translated rm_startblock
+ * into the appropriate daddr units.
+ */
+STATIC int
+xfs_getfsmap_helper(
+	struct xfs_trans		*tp,
+	struct xfs_getfsmap_info	*info,
+	struct xfs_rmap_irec		*rec,
+	xfs_daddr_t			rec_daddr)
+{
+	struct xfs_fsmap		fmr;
+	struct xfs_mount		*mp = tp->t_mountp;
+	xfs_daddr_t			key_end;
+	bool				shared;
+	int				error;
+
+	if (fatal_signal_pending(current))
+		return -EAGAIN;
+
+	/*
+	 * Filter out records that start before our startpoint, if the
+	 * caller requested that.
+	 */
+	if (xfs_getfsmap_rec_before_low_key(info, rec)) {
+		rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
+		if (info->next_daddr < rec_daddr)
+			info->next_daddr = rec_daddr;
+		return XFS_BTREE_QUERY_RANGE_CONTINUE;
+	}
+
+	/*
+	 * If the caller passed in a length with the low record and
+	 * the record represents a file data extent, we incremented
+	 * the offset in the low key by the length in the hopes of
+	 * finding reverse mappings for the physical blocks we just
+	 * saw.  We did /not/ increment next_daddr by the length
+	 * because the range query would not be able to find shared
+	 * extents within the same physical block range.
+	 *
+	 * However, the extent we've been fed could have a startblock
+	 * past the passed-in low record.  If this is the case,
+	 * advance next_daddr to the end of the passed-in low record
+	 * so we don't report the extent prior to this extent as
+	 * free.
+	 */
+	key_end = info->rkey_low->fmr_physical + info->rkey_low->fmr_length;
+	if (info->dev == info->rkey_low->fmr_device &&
+	    info->next_daddr < key_end && rec_daddr >= key_end)
+		info->next_daddr = key_end;
+
+	/* Are we just counting mappings? */
+	if (info->head->fmh_count == 0) {
+		if (rec_daddr > info->next_daddr)
+			info->head->fmh_entries++;
+
+		if (info->last)
+			return XFS_BTREE_QUERY_RANGE_CONTINUE;
+
+		info->head->fmh_entries++;
+
+		rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
+		if (info->next_daddr < rec_daddr)
+			info->next_daddr = rec_daddr;
+		return XFS_BTREE_QUERY_RANGE_CONTINUE;
+	}
+
+	/*
+	 * If the record starts past the last physical block we saw,
+	 * then we've found some free space.  Report that too.
+	 */
+	if (rec_daddr > info->next_daddr) {
+		if (info->head->fmh_entries >= info->head->fmh_count)
+			return XFS_BTREE_QUERY_RANGE_ABORT;
+
+		trace_xfs_fsmap_mapping(mp, info->dev, info->agno,
+				XFS_DADDR_TO_FSB(mp, info->next_daddr),
+				XFS_DADDR_TO_FSB(mp, rec_daddr -
+						info->next_daddr),
+				info->missing_owner, 0);
+
+		fmr.fmr_device = info->dev;
+		fmr.fmr_physical = info->next_daddr;
+		fmr.fmr_owner = info->missing_owner;
+		fmr.fmr_offset = 0;
+		fmr.fmr_length = rec_daddr - info->next_daddr;
+		fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
+		error = info->formatter(&fmr, info->format_arg);
+		if (error)
+			return error;
+		info->head->fmh_entries++;
+	}
+
+	if (info->last)
+		goto out;
+
+	/* Fill out the extent we found */
+	if (info->head->fmh_entries >= info->head->fmh_count)
+		return XFS_BTREE_QUERY_RANGE_ABORT;
+
+	trace_xfs_fsmap_mapping(mp, info->dev, info->agno,
+			rec->rm_startblock, rec->rm_blockcount, rec->rm_owner,
+			rec->rm_offset);
+
+	fmr.fmr_device = info->dev;
+	fmr.fmr_physical = rec_daddr;
+	error = xfs_fsmap_owner_from_rmap(rec, &fmr);
+	if (error)
+		return error;
+	fmr.fmr_offset = XFS_FSB_TO_BB(mp, rec->rm_offset);
+	fmr.fmr_length = XFS_FSB_TO_BB(mp, rec->rm_blockcount);
+	if (rec->rm_flags & XFS_RMAP_UNWRITTEN)
+		fmr.fmr_flags |= FMR_OF_PREALLOC;
+	if (rec->rm_flags & XFS_RMAP_ATTR_FORK)
+		fmr.fmr_flags |= FMR_OF_ATTR_FORK;
+	if (rec->rm_flags & XFS_RMAP_BMBT_BLOCK)
+		fmr.fmr_flags |= FMR_OF_EXTENT_MAP;
+	if (fmr.fmr_flags == 0) {
+		error = xfs_getfsmap_is_shared(tp, info, rec, &shared);
+		if (error)
+			return error;
+		if (shared)
+			fmr.fmr_flags |= FMR_OF_SHARED;
+	}
+	error = info->formatter(&fmr, info->format_arg);
+	if (error)
+		return error;
+	info->head->fmh_entries++;
+
+out:
+	rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
+	if (info->next_daddr < rec_daddr)
+		info->next_daddr = rec_daddr;
+	return XFS_BTREE_QUERY_RANGE_CONTINUE;
+}
+
+/* Transform a rmapbt irec into a fsmap */
+STATIC int
+xfs_getfsmap_datadev_helper(
+	struct xfs_btree_cur		*cur,
+	struct xfs_rmap_irec		*rec,
+	void				*priv)
+{
+	struct xfs_mount		*mp = cur->bc_mp;
+	struct xfs_getfsmap_info	*info = priv;
+	xfs_fsblock_t			fsb;
+	xfs_daddr_t			rec_daddr;
+
+	fsb = XFS_AGB_TO_FSB(mp, cur->bc_private.a.agno, rec->rm_startblock);
+	rec_daddr = XFS_FSB_TO_DADDR(mp, fsb);
+
+	return xfs_getfsmap_helper(cur->bc_tp, info, rec, rec_daddr);
+}
+
+/* Transform a absolute-startblock rmap (rtdev, logdev) into a fsmap */
+STATIC int
+xfs_getfsmap_rtdev_helper(
+	struct xfs_btree_cur		*cur,
+	struct xfs_rmap_irec		*rec,
+	void				*priv)
+{
+	struct xfs_mount		*mp = cur->bc_mp;
+	struct xfs_getfsmap_info	*info = priv;
+	xfs_daddr_t			rec_daddr;
+
+	rec_daddr = XFS_FSB_TO_BB(mp, rec->rm_startblock);
+
+	return xfs_getfsmap_helper(cur->bc_tp, info, rec, rec_daddr);
+}
+
+/* Set rmap flags based on the getfsmap flags */
+static void
+xfs_getfsmap_set_irec_flags(
+	struct xfs_rmap_irec	*irec,
+	struct xfs_fsmap	*fmr)
+{
+	irec->rm_flags = 0;
+	if (fmr->fmr_flags & FMR_OF_ATTR_FORK)
+		irec->rm_flags |= XFS_RMAP_ATTR_FORK;
+	if (fmr->fmr_flags & FMR_OF_EXTENT_MAP)
+		irec->rm_flags |= XFS_RMAP_BMBT_BLOCK;
+	if (fmr->fmr_flags & FMR_OF_PREALLOC)
+		irec->rm_flags |= XFS_RMAP_UNWRITTEN;
+}
+
+/* Execute a getfsmap query against the log device. */
+STATIC int
+xfs_getfsmap_logdev(
+	struct xfs_trans		*tp,
+	struct xfs_fsmap		*keys,
+	struct xfs_getfsmap_info	*info)
+{
+	struct xfs_mount		*mp = tp->t_mountp;
+	struct xfs_fsmap		*dkey_low = keys;
+	struct xfs_btree_cur		cur;
+	struct xfs_rmap_irec		rmap;
+	int				error;
+
+	/* Set up search keys */
+	info->low.rm_startblock = XFS_BB_TO_FSBT(mp, dkey_low->fmr_physical);
+	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
+	error = xfs_fsmap_owner_to_rmap(keys, &info->low);
+	if (error)
+		return error;
+	info->low.rm_blockcount = 0;
+	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
+
+	error = xfs_fsmap_owner_to_rmap(keys + 1, &info->high);
+	if (error)
+		return error;
+	info->high.rm_startblock = -1U;
+	info->high.rm_owner = ULLONG_MAX;
+	info->high.rm_offset = ULLONG_MAX;
+	info->high.rm_blockcount = 0;
+	info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;
+	info->missing_owner = XFS_FMR_OWN_FREE;
+
+	trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
+			info->low.rm_startblock,
+			info->low.rm_blockcount,
+			info->low.rm_owner,
+			info->low.rm_offset);
+
+	trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
+			info->high.rm_startblock,
+			info->high.rm_blockcount,
+			info->high.rm_owner,
+			info->high.rm_offset);
+
+
+	if (dkey_low->fmr_physical > 0)
+		return 0;
+
+	rmap.rm_startblock = 0;
+	rmap.rm_blockcount = mp->m_sb.sb_logblocks;
+	rmap.rm_owner = XFS_RMAP_OWN_LOG;
+	rmap.rm_offset = 0;
+	rmap.rm_flags = 0;
+
+	cur.bc_mp = mp;
+	cur.bc_tp = tp;
+	return xfs_getfsmap_rtdev_helper(&cur, &rmap, info);
+}
+
+/* Execute a getfsmap query against the regular data device. */
+STATIC int
+xfs_getfsmap_datadev(
+	struct xfs_trans		*tp,
+	struct xfs_fsmap		*keys,
+	struct xfs_getfsmap_info	*info)
+{
+	struct xfs_mount		*mp = tp->t_mountp;
+	struct xfs_btree_cur		*bt_cur = NULL;
+	struct xfs_fsmap		*dkey_low;
+	struct xfs_fsmap		*dkey_high;
+	xfs_fsblock_t			start_fsb;
+	xfs_fsblock_t			end_fsb;
+	xfs_agnumber_t			start_ag;
+	xfs_agnumber_t			end_ag;
+	xfs_daddr_t			eofs;
+	int				error = 0;
+
+	dkey_low = keys;
+	dkey_high = keys + 1;
+	eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks);
+	if (dkey_low->fmr_physical >= eofs)
+		return 0;
+	if (dkey_high->fmr_physical >= eofs)
+		dkey_high->fmr_physical = eofs - 1;
+	start_fsb = XFS_DADDR_TO_FSB(mp, dkey_low->fmr_physical);
+	end_fsb = XFS_DADDR_TO_FSB(mp, dkey_high->fmr_physical);
+
+	/* Set up search keys */
+	info->low.rm_startblock = XFS_FSB_TO_AGBNO(mp, start_fsb);
+	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
+	error = xfs_fsmap_owner_to_rmap(dkey_low, &info->low);
+	if (error)
+		return error;
+	info->low.rm_blockcount = 0;
+	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
+
+	info->high.rm_startblock = -1U;
+	info->high.rm_owner = ULLONG_MAX;
+	info->high.rm_offset = ULLONG_MAX;
+	info->high.rm_blockcount = 0;
+	info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;
+	info->missing_owner = XFS_FMR_OWN_FREE;
+
+	start_ag = XFS_FSB_TO_AGNO(mp, start_fsb);
+	end_ag = XFS_FSB_TO_AGNO(mp, end_fsb);
+
+	/* Query each AG */
+	for (info->agno = start_ag; info->agno <= end_ag; info->agno++) {
+		if (info->agno == end_ag) {
+			info->high.rm_startblock = XFS_FSB_TO_AGBNO(mp,
+					end_fsb);
+			info->high.rm_offset = XFS_BB_TO_FSBT(mp,
+					dkey_high->fmr_offset);
+			error = xfs_fsmap_owner_to_rmap(dkey_high, &info->high);
+			if (error)
+				goto err;
+			xfs_getfsmap_set_irec_flags(&info->high, dkey_high);
+		}
+
+		if (bt_cur) {
+			xfs_btree_del_cursor(bt_cur, XFS_BTREE_NOERROR);
+			bt_cur = NULL;
+			info->agf_bp = NULL;
+		}
+
+		error = xfs_alloc_read_agf(mp, tp, info->agno, 0,
+				&info->agf_bp);
+		if (error)
+			goto err;
+
+		trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
+				info->low.rm_startblock,
+				info->low.rm_blockcount,
+				info->low.rm_owner,
+				info->low.rm_offset);
+
+		trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
+				info->high.rm_startblock,
+				info->high.rm_blockcount,
+				info->high.rm_owner,
+				info->high.rm_offset);
+
+		bt_cur = xfs_rmapbt_init_cursor(mp, tp, info->agf_bp,
+				info->agno);
+		error = xfs_rmap_query_range(bt_cur, &info->low, &info->high,
+				xfs_getfsmap_datadev_helper, info);
+		if (error)
+			goto err;
+
+		if (info->agno == start_ag) {
+			info->low.rm_startblock = 0;
+			info->low.rm_owner = 0;
+			info->low.rm_offset = 0;
+			info->low.rm_flags = 0;
+		}
+	}
+
+	/* Report any free space at the end of the AG */
+	info->last = true;
+	error = xfs_getfsmap_datadev_helper(bt_cur, &info->high, info);
+	if (error)
+		goto err;
+
+err:
+	if (bt_cur)
+		xfs_btree_del_cursor(bt_cur, error < 0 ? XFS_BTREE_ERROR :
+							 XFS_BTREE_NOERROR);
+	if (info->agf_bp)
+		info->agf_bp = NULL;
+
+	return error;
+}
+
+/* Do we recognize the device? */
+STATIC bool
+xfs_getfsmap_is_valid_device(
+	struct xfs_mount	*mp,
+	struct xfs_fsmap	*fm)
+{
+	if (fm->fmr_device == 0 || fm->fmr_device == UINT_MAX ||
+	    fm->fmr_device == new_encode_dev(mp->m_ddev_targp->bt_dev))
+		return true;
+	if (mp->m_logdev_targp &&
+	    fm->fmr_device == new_encode_dev(mp->m_logdev_targp->bt_dev))
+		return true;
+	return false;
+}
+
+/* Ensure that the low key is less than the high key. */
+STATIC bool
+xfs_getfsmap_check_keys(
+	struct xfs_fsmap		*low_key,
+	struct xfs_fsmap		*high_key)
+{
+	if (low_key->fmr_device > high_key->fmr_device)
+		return false;
+	if (low_key->fmr_device < high_key->fmr_device)
+		return true;
+
+	if (low_key->fmr_physical > high_key->fmr_physical)
+		return false;
+	if (low_key->fmr_physical < high_key->fmr_physical)
+		return true;
+
+	if (low_key->fmr_owner > high_key->fmr_owner)
+		return false;
+	if (low_key->fmr_owner < high_key->fmr_owner)
+		return true;
+
+	if (low_key->fmr_offset > high_key->fmr_offset)
+		return false;
+	if (low_key->fmr_offset < high_key->fmr_offset)
+		return true;
+
+	return false;
+}
+
+#define XFS_GETFSMAP_DEVS	3
+/*
+ * Get filesystem's extents as described in head, and format for
+ * output.  Calls formatter to fill the user's buffer until all
+ * extents are mapped, until the passed-in head->fmh_count slots have
+ * been filled, or until the formatter short-circuits the loop, if it
+ * is tracking filled-in extents on its own.
+ */
+int
+xfs_getfsmap(
+	struct xfs_mount		*mp,
+	struct xfs_fsmap_head		*head,
+	xfs_fsmap_format_t		formatter,
+	void				*arg)
+{
+	struct xfs_trans		*tp = NULL;
+	struct xfs_fsmap		*rkey_low;	/* request keys */
+	struct xfs_fsmap		*rkey_high;
+	struct xfs_fsmap		dkeys[2];	/* per-dev keys */
+	struct xfs_getfsmap_dev		handlers[XFS_GETFSMAP_DEVS];
+	struct xfs_getfsmap_info	info = {0};
+	int				i;
+	int				error = 0;
+
+	if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
+		return -EOPNOTSUPP;
+	if (head->fmh_iflags & ~FMH_IF_VALID)
+		return -EINVAL;
+	rkey_low = head->fmh_keys;
+	rkey_high = rkey_low + 1;
+	if (!xfs_getfsmap_is_valid_device(mp, rkey_low) ||
+	    !xfs_getfsmap_is_valid_device(mp, rkey_high))
+		return -EINVAL;
+
+	head->fmh_entries = 0;
+
+	/* Set up our device handlers. */
+	memset(handlers, 0, sizeof(handlers));
+	handlers[0].dev = new_encode_dev(mp->m_ddev_targp->bt_dev);
+	handlers[0].fn = xfs_getfsmap_datadev;
+	if (mp->m_logdev_targp != mp->m_ddev_targp) {
+		handlers[1].dev = new_encode_dev(mp->m_logdev_targp->bt_dev);
+		handlers[1].fn = xfs_getfsmap_logdev;
+	}
+
+	xfs_sort(handlers, XFS_GETFSMAP_DEVS, sizeof(struct xfs_getfsmap_dev),
+			xfs_getfsmap_dev_compare);
+
+	/*
+	 * Since we allow the user to copy the last mapping from a previous
+	 * call into the low key slot, we have to advance the low key by
+	 * whatever the reported length is.  If the offset field doesn't apply,
+	 * move up the start block to the next extent and start over with the
+	 * lowest owner/offset possible; otherwise it's file data, so move up
+	 * the offset only.
+	 */
+	dkeys[0] = *rkey_low;
+	if (dkeys[0].fmr_flags & (FMR_OF_SPECIAL_OWNER | FMR_OF_EXTENT_MAP)) {
+		dkeys[0].fmr_physical += dkeys[0].fmr_length;
+		dkeys[0].fmr_owner = 0;
+		dkeys[0].fmr_offset = 0;
+	} else
+		dkeys[0].fmr_offset += dkeys[0].fmr_length;
+	memset(&dkeys[1], 0xFF, sizeof(struct xfs_fsmap));
+
+	if (!xfs_getfsmap_check_keys(dkeys, rkey_high))
+		return -EINVAL;
+
+	info.rkey_low = rkey_low;
+	info.formatter = formatter;
+	info.format_arg = arg;
+	info.head = head;
+
+	/* For each device we support... */
+	for (i = 0; i < XFS_GETFSMAP_DEVS; i++) {
+		/* Is this device within the range the user asked for? */
+		if (!handlers[i].fn)
+			continue;
+		if (rkey_low->fmr_device > handlers[i].dev)
+			continue;
+		if (rkey_high->fmr_device < handlers[i].dev)
+			break;
+
+		/*
+		 * If this device number matches the high key, we have
+		 * to pass the high key to the handler to limit the
+		 * query results.  If the device number exceeds the
+		 * low key, zero out the low key so that we get
+		 * everything from the beginning.
+		 */
+		if (handlers[i].dev == rkey_high->fmr_device)
+			dkeys[1] = *rkey_high;
+		if (handlers[i].dev > rkey_low->fmr_device)
+			memset(&dkeys[0], 0, sizeof(struct xfs_fsmap));
+
+		error = xfs_trans_alloc_empty(mp, &tp);
+		if (error)
+			break;
+
+		info.next_daddr = dkeys[0].fmr_physical;
+		info.dev = handlers[i].dev;
+		info.last = false;
+		info.agno = NULLAGNUMBER;
+		error = handlers[i].fn(tp, dkeys, &info);
+		if (error)
+			break;
+		xfs_trans_cancel(tp);
+		tp = NULL;
+	}
+
+	if (tp)
+		xfs_trans_cancel(tp);
+	head->fmh_oflags = FMH_OF_DEV_T;
+	return error;
+}
diff --git a/fs/xfs/xfs_fsmap.h b/fs/xfs/xfs_fsmap.h
new file mode 100644
index 0000000..1943047
--- /dev/null
+++ b/fs/xfs/xfs_fsmap.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2017 Oracle.  All Rights Reserved.
+ *
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+#ifndef __XFS_FSMAP_H__
+#define	__XFS_FSMAP_H__
+
+/* internal fsmap representation */
+struct xfs_fsmap {
+	dev_t		fmr_device;	/* device id */
+	uint32_t	fmr_flags;	/* mapping flags */
+	uint64_t	fmr_physical;	/* device offset of segment */
+	uint64_t	fmr_owner;	/* owner id */
+	xfs_fileoff_t	fmr_offset;	/* file offset of segment */
+	xfs_filblks_t	fmr_length;	/* length of segment, blocks */
+};
+
+struct xfs_fsmap_head {
+	uint32_t	fmh_iflags;	/* control flags */
+	uint32_t	fmh_oflags;	/* output flags */
+	unsigned int	fmh_count;	/* # of entries in array incl. input */
+	unsigned int	fmh_entries;	/* # of entries filled in (output). */
+
+	struct xfs_fsmap fmh_keys[2];	/* low and high keys */
+};
+
+void xfs_fsmap_from_internal(struct fsmap *dest, struct xfs_fsmap *src);
+void xfs_fsmap_to_internal(struct xfs_fsmap *dest, struct fsmap *src);
+
+/* fsmap to userspace formatter - copy to user & advance pointer */
+typedef int (*xfs_fsmap_format_t)(struct xfs_fsmap *, void *);
+
+int xfs_getfsmap(struct xfs_mount *mp, struct xfs_fsmap_head *head,
+		xfs_fsmap_format_t formatter, void *arg);
+
+#endif /* __XFS_FSMAP_H__ */
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index c67cfb4..bbe1b58 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -41,6 +41,9 @@
 #include "xfs_trans.h"
 #include "xfs_pnfs.h"
 #include "xfs_acl.h"
+#include "xfs_btree.h"
+#include <linux/fsmap.h>
+#include "xfs_fsmap.h"
 
 #include <linux/capability.h>
 #include <linux/dcache.h>
@@ -1607,6 +1610,103 @@ xfs_ioc_getbmapx(
 	return 0;
 }
 
+struct getfsmap_info {
+	struct xfs_mount	*mp;
+	struct fsmap __user	*data;
+	__u32			last_flags;
+};
+
+STATIC int
+xfs_getfsmap_format(struct xfs_fsmap *xfm, void *priv)
+{
+	struct getfsmap_info	*info = priv;
+	struct fsmap		fm;
+
+	trace_xfs_getfsmap_mapping(info->mp, xfm->fmr_device, xfm->fmr_physical,
+			xfm->fmr_length, xfm->fmr_owner, xfm->fmr_offset,
+			xfm->fmr_flags);
+
+	info->last_flags = xfm->fmr_flags;
+	xfs_fsmap_from_internal(&fm, xfm);
+	if (copy_to_user(info->data, &fm, sizeof(struct fsmap)))
+		return -EFAULT;
+
+	info->data++;
+	return 0;
+}
+
+STATIC int
+xfs_ioc_getfsmap(
+	struct xfs_inode	*ip,
+	void			__user *arg)
+{
+	struct getfsmap_info	info;
+	struct xfs_fsmap_head	xhead = {0};
+	struct fsmap_head	head;
+	bool			aborted = false;
+	int			error;
+
+	if (copy_from_user(&head, arg, sizeof(struct fsmap_head)))
+		return -EFAULT;
+	if (head.fmh_reserved[0] || head.fmh_reserved[1] ||
+	    head.fmh_reserved[2] || head.fmh_reserved[3] ||
+	    head.fmh_reserved[4] || head.fmh_reserved[5] ||
+	    head.fmh_keys[0].fmr_reserved[0] ||
+	    head.fmh_keys[0].fmr_reserved[1] ||
+	    head.fmh_keys[0].fmr_reserved[2] ||
+	    head.fmh_keys[1].fmr_reserved[0] ||
+	    head.fmh_keys[1].fmr_reserved[1] ||
+	    head.fmh_keys[1].fmr_reserved[2])
+		return -EINVAL;
+
+	xhead.fmh_iflags = head.fmh_iflags;
+	xhead.fmh_count = head.fmh_count;
+	xfs_fsmap_to_internal(&xhead.fmh_keys[0], &head.fmh_keys[0]);
+	xfs_fsmap_to_internal(&xhead.fmh_keys[1], &head.fmh_keys[1]);
+
+	trace_xfs_getfsmap_low_key(ip->i_mount,
+			xhead.fmh_keys[0].fmr_device,
+			xhead.fmh_keys[0].fmr_physical,
+			xhead.fmh_keys[0].fmr_length,
+			xhead.fmh_keys[0].fmr_owner,
+			xhead.fmh_keys[0].fmr_offset,
+			xhead.fmh_keys[0].fmr_flags);
+
+	trace_xfs_getfsmap_high_key(ip->i_mount,
+			xhead.fmh_keys[1].fmr_device,
+			xhead.fmh_keys[1].fmr_physical,
+			xhead.fmh_keys[1].fmr_length,
+			xhead.fmh_keys[1].fmr_owner,
+			xhead.fmh_keys[1].fmr_offset,
+			xhead.fmh_keys[1].fmr_flags);
+
+	info.mp = ip->i_mount;
+	info.data = ((__force struct fsmap_head *)arg)->fmh_recs;
+	error = xfs_getfsmap(ip->i_mount, &xhead, xfs_getfsmap_format, &info);
+	if (error == XFS_BTREE_QUERY_RANGE_ABORT) {
+		error = 0;
+		aborted = true;
+	} else if (error)
+		return error;
+
+	/* If we didn't abort, set the "last" flag in the last fmx */
+	if (!aborted && xhead.fmh_entries) {
+		info.data--;
+		info.last_flags |= FMR_OF_LAST;
+		if (copy_to_user(&info.data->fmr_flags, &info.last_flags,
+				sizeof(info.last_flags)))
+			return -EFAULT;
+	}
+
+	/* copy back header */
+	head.fmh_entries = xhead.fmh_entries;
+	head.fmh_oflags = xhead.fmh_oflags;
+	if (copy_to_user(arg, &head, sizeof(struct fsmap_head)))
+		return -EFAULT;
+
+	return 0;
+}
+
 int
 xfs_ioc_swapext(
 	xfs_swapext_t	*sxp)
@@ -1787,6 +1887,9 @@ xfs_file_ioctl(
 	case XFS_IOC_GETBMAPX:
 		return xfs_ioc_getbmapx(ip, arg);
 
+	case FS_IOC_GETFSMAP:
+		return xfs_ioc_getfsmap(ip, arg);
+
 	case XFS_IOC_FD_TO_HANDLE:
 	case XFS_IOC_PATH_TO_HANDLE:
 	case XFS_IOC_PATH_TO_FSHANDLE: {
diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
index 7c49938..fa0bc4d 100644
--- a/fs/xfs/xfs_ioctl32.c
+++ b/fs/xfs/xfs_ioctl32.c
@@ -20,6 +20,7 @@
 #include <linux/mount.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
+#include <linux/fsmap.h>
 #include "xfs.h"
 #include "xfs_fs.h"
 #include "xfs_format.h"
@@ -554,6 +555,7 @@ xfs_file_compat_ioctl(
 	case XFS_IOC_GOINGDOWN:
 	case XFS_IOC_ERROR_INJECTION:
 	case XFS_IOC_ERROR_CLEARALL:
+	case FS_IOC_GETFSMAP:
 		return xfs_file_ioctl(filp, cmd, p);
 #ifndef BROKEN_X86_ALIGNMENT
 	/* These are handled fine if no alignment issues */
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index d3d11905..125d568 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -3270,6 +3270,91 @@ DEFINE_INODE_IREC_EVENT(xfs_swap_extent_rmap_remap);
 DEFINE_INODE_IREC_EVENT(xfs_swap_extent_rmap_remap_piece);
 DEFINE_INODE_ERROR_EVENT(xfs_swap_extent_rmap_error);
 
+/* fsmap traces */
+DECLARE_EVENT_CLASS(xfs_fsmap_class,
+	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_agnumber_t agno,
+		 xfs_fsblock_t bno, xfs_filblks_t len, __uint64_t owner,
+		 __uint64_t offset),
+	TP_ARGS(mp, keydev, agno, bno, len, owner, offset),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(dev_t, keydev)
+		__field(xfs_agnumber_t, agno)
+		__field(xfs_fsblock_t, bno)
+		__field(xfs_filblks_t, len)
+		__field(__uint64_t, owner)
+		__field(__uint64_t, offset)
+	),
+	TP_fast_assign(
+		__entry->dev = mp->m_super->s_dev;
+		__entry->keydev = new_decode_dev(keydev);
+		__entry->agno = agno;
+		__entry->bno = bno;
+		__entry->len = len;
+		__entry->owner = owner;
+		__entry->offset = offset;
+	),
+	TP_printk("dev %d:%d keydev %d:%d agno %u bno %llu len %llu owner %lld offset 0x%llx\n",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  MAJOR(__entry->keydev), MINOR(__entry->keydev),
+		  __entry->agno,
+		  __entry->bno,
+		  __entry->len,
+		  __entry->owner,
+		  __entry->offset)
+)
+#define DEFINE_FSMAP_EVENT(name) \
+DEFINE_EVENT(xfs_fsmap_class, name, \
+	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_agnumber_t agno, \
+		 xfs_fsblock_t bno, xfs_filblks_t len, __uint64_t owner, \
+		 __uint64_t offset), \
+	TP_ARGS(mp, keydev, agno, bno, len, owner, offset))
+DEFINE_FSMAP_EVENT(xfs_fsmap_low_key);
+DEFINE_FSMAP_EVENT(xfs_fsmap_high_key);
+DEFINE_FSMAP_EVENT(xfs_fsmap_mapping);
+
+DECLARE_EVENT_CLASS(xfs_getfsmap_class,
+	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block,
+		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset,
+		 __uint64_t flags),
+	TP_ARGS(mp, keydev, block, len, owner, offset, flags),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(dev_t, keydev)
+		__field(xfs_daddr_t, block)
+		__field(xfs_daddr_t, len)
+		__field(__uint64_t, owner)
+		__field(__uint64_t, offset)
+		__field(__uint64_t, flags)
+	),
+	TP_fast_assign(
+		__entry->dev = mp->m_super->s_dev;
+		__entry->keydev = new_decode_dev(keydev);
+		__entry->block = block;
+		__entry->len = len;
+		__entry->owner = owner;
+		__entry->offset = offset;
+		__entry->flags = flags;
+	),
+	TP_printk("dev %d:%d keydev %d:%d block %llu len %llu owner %lld offset %llu flags 0x%llx\n",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  MAJOR(__entry->keydev), MINOR(__entry->keydev),
+		  __entry->block,
+		  __entry->len,
+		  __entry->owner,
+		  __entry->offset,
+		  __entry->flags)
+)
+#define DEFINE_GETFSMAP_EVENT(name) \
+DEFINE_EVENT(xfs_getfsmap_class, name, \
+	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block, \
+		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset, \
+		 __uint64_t flags), \
+	TP_ARGS(mp, keydev, block, len, owner, offset, flags))
+DEFINE_GETFSMAP_EVENT(xfs_getfsmap_low_key);
+DEFINE_GETFSMAP_EVENT(xfs_getfsmap_high_key);
+DEFINE_GETFSMAP_EVENT(xfs_getfsmap_mapping);
+
 #endif /* _TRACE_XFS_H */
 
 #undef TRACE_INCLUDE_PATH
diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 70f42ea..a280e12 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -263,6 +263,28 @@ xfs_trans_alloc(
 }
 
 /*
+ * Create an empty transaction with no reservation.  This is a defensive
+ * mechanism for routines that query metadata without actually modifying
+ * them -- if the metadata being queried is somehow cross-linked (think a
+ * btree block pointer that points higher in the tree), we risk deadlock.
+ * However, blocks grabbed as part of a transaction can be re-grabbed.
+ * The verifiers will notice the corrupt block and the operation will fail
+ * back to userspace without deadlocking.
+ *
+ * Note the zero-length reservation; this transaction MUST be cancelled
+ * without any dirty data.
+ */
+int
+xfs_trans_alloc_empty(
+	struct xfs_mount		*mp,
+	struct xfs_trans		**tpp)
+{
+	struct xfs_trans_res		resv = {0};
+
+	return xfs_trans_alloc(mp, &resv, 0, 0, XFS_TRANS_NO_WRITECOUNT, tpp);
+}
+
+/*
  * Record the indicated change to the given field for application
  * to the file system's superblock when the transaction commits.
  * For now, just store the change in the transaction structure.
diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
index 61b7fbd..98024cb 100644
--- a/fs/xfs/xfs_trans.h
+++ b/fs/xfs/xfs_trans.h
@@ -159,6 +159,8 @@ typedef struct xfs_trans {
 int		xfs_trans_alloc(struct xfs_mount *mp, struct xfs_trans_res *resp,
 			uint blocks, uint rtextents, uint flags,
 			struct xfs_trans **tpp);
+int		xfs_trans_alloc_empty(struct xfs_mount *mp,
+			struct xfs_trans **tpp);
 void		xfs_trans_mod_sb(xfs_trans_t *, uint, int64_t);
 
 struct xfs_buf	*xfs_trans_get_buf_map(struct xfs_trans *tp,

Re: [PATCH 5/8] xfs: introduce the XFS_IOC_GETFSMAP ioctl

[Brian Foster]

On Fri, Feb 17, 2017 at 05:17:49PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Introduce a new ioctl that uses the reverse mapping btree to return
> information about the physical layout of the filesystem.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

Mostly looks good, though there's a decent amount of indirection here so
I'll probably need another pass through it. Mostly minor comments, a
couple potential issues and some questions..

>  fs/xfs/Makefile        |    1 
>  fs/xfs/libxfs/xfs_fs.h |   13 +
>  fs/xfs/xfs_fsmap.c     |  782 ++++++++++++++++++++++++++++++++++++++++++++++++
>  fs/xfs/xfs_fsmap.h     |   51 +++
>  fs/xfs/xfs_ioctl.c     |  103 ++++++
>  fs/xfs/xfs_ioctl32.c   |    2 
>  fs/xfs/xfs_trace.h     |   85 +++++
>  fs/xfs/xfs_trans.c     |   22 +
>  fs/xfs/xfs_trans.h     |    2 
>  9 files changed, 1061 insertions(+)
>  create mode 100644 fs/xfs/xfs_fsmap.c
>  create mode 100644 fs/xfs/xfs_fsmap.h
> 
> 
> diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile
> index c7515d4..0e7ee30 100644
> --- a/fs/xfs/Makefile
> +++ b/fs/xfs/Makefile
> @@ -80,6 +80,7 @@ xfs-y				+= xfs_aops.o \
>  				   xfs_extent_busy.o \
>  				   xfs_file.o \
>  				   xfs_filestream.o \
> +				   xfs_fsmap.o \
>  				   xfs_fsops.o \
>  				   xfs_globals.o \
>  				   xfs_icache.o \
> diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
> index b72dc82..095bdf0 100644
> --- a/fs/xfs/libxfs/xfs_fs.h
> +++ b/fs/xfs/libxfs/xfs_fs.h
> @@ -92,6 +92,18 @@ struct getbmapx {
>  #define BMV_OF_LAST		0x4	/* segment is the last in the file */
>  #define BMV_OF_SHARED		0x8	/* segment shared with another file */
>  
> +/*	fmr_owner special values for FS_IOC_GETFSMAP */
> +#define XFS_FMR_OWN_FREE	FMR_OWN_FREE      /* free space */
> +#define XFS_FMR_OWN_UNKNOWN	FMR_OWN_UNKNOWN   /* unknown owner */
> +#define XFS_FMR_OWN_FS		FMR_OWNER('X', 1) /* static fs metadata */
> +#define XFS_FMR_OWN_LOG		FMR_OWNER('X', 2) /* journalling log */
> +#define XFS_FMR_OWN_AG		FMR_OWNER('X', 3) /* per-AG metadata */
> +#define XFS_FMR_OWN_INOBT	FMR_OWNER('X', 4) /* inode btree blocks */
> +#define XFS_FMR_OWN_INODES	FMR_OWNER('X', 5) /* inodes */
> +#define XFS_FMR_OWN_REFC	FMR_OWNER('X', 6) /* refcount tree */
> +#define XFS_FMR_OWN_COW		FMR_OWNER('X', 7) /* cow staging */
> +#define XFS_FMR_OWN_DEFECTIVE	FMR_OWNER('X', 8) /* bad blocks */
> +
>  /*
>   * Structure for XFS_IOC_FSSETDM.
>   * For use by backup and restore programs to set the XFS on-disk inode
> @@ -502,6 +514,7 @@ typedef struct xfs_swapext
>  #define XFS_IOC_GETBMAPX	_IOWR('X', 56, struct getbmap)
>  #define XFS_IOC_ZERO_RANGE	_IOW ('X', 57, struct xfs_flock64)
>  #define XFS_IOC_FREE_EOFBLOCKS	_IOR ('X', 58, struct xfs_fs_eofblocks)
> +/*	XFS_IOC_GETFSMAP ------ hoisted 59         */
>  
>  /*
>   * ioctl commands that replace IRIX syssgi()'s
> diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
> new file mode 100644
> index 0000000..09d6b92
> --- /dev/null
> +++ b/fs/xfs/xfs_fsmap.c
> @@ -0,0 +1,782 @@
> +/*
> + * Copyright (C) 2017 Oracle.  All Rights Reserved.
> + *
> + * Author: Darrick J. Wong <darrick.wong@oracle.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version 2
> + * of the License, or (at your option) any later version.
> + *
> + * This program is distributed in the hope that it would be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write the Free Software Foundation,
> + * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
> + */
> +#include "xfs.h"
> +#include "xfs_fs.h"
> +#include "xfs_shared.h"
> +#include "xfs_format.h"
> +#include "xfs_log_format.h"
> +#include "xfs_trans_resv.h"
> +#include "xfs_sb.h"
> +#include "xfs_mount.h"
> +#include "xfs_defer.h"
> +#include "xfs_inode.h"
> +#include "xfs_trans.h"
> +#include "xfs_error.h"
> +#include "xfs_btree.h"
> +#include "xfs_rmap_btree.h"
> +#include "xfs_trace.h"
> +#include "xfs_log.h"
> +#include "xfs_rmap.h"
> +#include "xfs_alloc.h"
> +#include "xfs_bit.h"
> +#include <linux/fsmap.h>
> +#include "xfs_fsmap.h"
> +#include "xfs_refcount.h"
> +#include "xfs_refcount_btree.h"
> +
> +/* Convert an xfs_fsmap to an fsmap. */
> +void
> +xfs_fsmap_from_internal(
> +	struct fsmap		*dest,
> +	struct xfs_fsmap	*src)
> +{
> +	dest->fmr_device = src->fmr_device;
> +	dest->fmr_flags = src->fmr_flags;
> +	dest->fmr_physical = BBTOB(src->fmr_physical);
> +	dest->fmr_owner = src->fmr_owner;
> +	dest->fmr_offset = BBTOB(src->fmr_offset);
> +	dest->fmr_length = BBTOB(src->fmr_length);
> +	dest->fmr_reserved[0] = 0;
> +	dest->fmr_reserved[1] = 0;
> +	dest->fmr_reserved[2] = 0;
> +}
> +
> +/* Convert an fsmap to an xfs_fsmap. */
> +void
> +xfs_fsmap_to_internal(
> +	struct xfs_fsmap	*dest,
> +	struct fsmap		*src)
> +{
> +	dest->fmr_device = src->fmr_device;
> +	dest->fmr_flags = src->fmr_flags;
> +	dest->fmr_physical = BTOBBT(src->fmr_physical);
> +	dest->fmr_owner = src->fmr_owner;
> +	dest->fmr_offset = BTOBBT(src->fmr_offset);
> +	dest->fmr_length = BTOBBT(src->fmr_length);
> +}
> +
> +/* Convert an fsmap owner into an rmapbt owner. */
> +static int
> +xfs_fsmap_owner_to_rmap(
> +	struct xfs_fsmap	*fmr,
> +	struct xfs_rmap_irec	*rm)

I find the inconsistent semantics a little confusing here. E.g., the
xfs_fsmap_[to|from]_*() helpers use consistent dest, src parameter
ordering. Here we use the opposite. I don't care much which way we go,
but could we use the same semantics between all of such helpers?

> +{
> +	if (!(fmr->fmr_flags & FMR_OF_SPECIAL_OWNER)) {
> +		rm->rm_owner = fmr->fmr_owner;
> +		return 0;
> +	}
> +
> +	switch (fmr->fmr_owner) {
> +	case 0:			/* "lowest owner id possible" */
> +	case -1ULL:		/* "highest owner id possible" */
> +		rm->rm_owner = 0;
> +		break;
> +	case XFS_FMR_OWN_FREE:
> +		rm->rm_owner = XFS_RMAP_OWN_NULL;
> +		break;
> +	case XFS_FMR_OWN_UNKNOWN:
> +		rm->rm_owner = XFS_RMAP_OWN_UNKNOWN;
> +		break;
> +	case XFS_FMR_OWN_FS:
> +		rm->rm_owner = XFS_RMAP_OWN_FS;
> +		break;
> +	case XFS_FMR_OWN_LOG:
> +		rm->rm_owner = XFS_RMAP_OWN_LOG;
> +		break;
> +	case XFS_FMR_OWN_AG:
> +		rm->rm_owner = XFS_RMAP_OWN_AG;
> +		break;
> +	case XFS_FMR_OWN_INOBT:
> +		rm->rm_owner = XFS_RMAP_OWN_INOBT;
> +		break;
> +	case XFS_FMR_OWN_INODES:
> +		rm->rm_owner = XFS_RMAP_OWN_INODES;
> +		break;
> +	case XFS_FMR_OWN_REFC:
> +		rm->rm_owner = XFS_RMAP_OWN_REFC;
> +		break;
> +	case XFS_FMR_OWN_COW:
> +		rm->rm_owner = XFS_RMAP_OWN_COW;
> +		break;
> +	case XFS_FMR_OWN_DEFECTIVE:	/* not implemented */
> +		/* fall through */
> +	default:
> +		return -EINVAL;
> +	}
> +	return 0;
> +}
> +
> +/* Convert an rmapbt owner into an fsmap owner. */
> +static int
> +xfs_fsmap_owner_from_rmap(
> +	struct xfs_rmap_irec	*rm,
> +	struct xfs_fsmap	*fmr)
> +{
> +	fmr->fmr_flags = 0;
> +	if (!XFS_RMAP_NON_INODE_OWNER(rm->rm_owner)) {
> +		fmr->fmr_owner = rm->rm_owner;
> +		return 0;
> +	}
> +	fmr->fmr_flags |= FMR_OF_SPECIAL_OWNER;
> +
> +	switch (rm->rm_owner) {
> +	case XFS_RMAP_OWN_FS:
> +		fmr->fmr_owner = XFS_FMR_OWN_FS;
> +		break;
> +	case XFS_RMAP_OWN_LOG:
> +		fmr->fmr_owner = XFS_FMR_OWN_LOG;
> +		break;
> +	case XFS_RMAP_OWN_AG:
> +		fmr->fmr_owner = XFS_FMR_OWN_AG;
> +		break;
> +	case XFS_RMAP_OWN_INOBT:
> +		fmr->fmr_owner = XFS_FMR_OWN_INOBT;
> +		break;
> +	case XFS_RMAP_OWN_INODES:
> +		fmr->fmr_owner = XFS_FMR_OWN_INODES;
> +		break;
> +	case XFS_RMAP_OWN_REFC:
> +		fmr->fmr_owner = XFS_FMR_OWN_REFC;
> +		break;
> +	case XFS_RMAP_OWN_COW:
> +		fmr->fmr_owner = XFS_FMR_OWN_COW;
> +		break;
> +	default:
> +		return -EFSCORRUPTED;
> +	}
> +	return 0;
> +}
> +
> +/* getfsmap query state */
> +struct xfs_getfsmap_info {
> +	struct xfs_fsmap_head	*head;
> +	struct xfs_fsmap	*rkey_low;	/* lowest key */
> +	xfs_fsmap_format_t	formatter;	/* formatting fn */
> +	void			*format_arg;	/* format buffer */
> +	bool			last;		/* last extent? */
> +	xfs_daddr_t		next_daddr;	/* next daddr we expect */
> +	u32			dev;		/* device id */
> +	u64			missing_owner;	/* owner of holes */
> +
> +	xfs_agnumber_t		agno;		/* AG number, if applicable */
> +	struct xfs_buf		*agf_bp;	/* AGF, for refcount queries */
> +	struct xfs_rmap_irec	low;		/* low rmap key */
> +	struct xfs_rmap_irec	high;		/* high rmap key */
> +};
> +
> +/* Associate a device with a getfsmap handler. */
> +struct xfs_getfsmap_dev {
> +	u32			dev;
> +	int			(*fn)(struct xfs_trans *tp,
> +				      struct xfs_fsmap *keys,
> +				      struct xfs_getfsmap_info *info);
> +};
> +
> +/* Compare two getfsmap device handlers. */
> +static int
> +xfs_getfsmap_dev_compare(
> +	const void			*p1,
> +	const void			*p2)
> +{
> +	const struct xfs_getfsmap_dev	*d1 = p1;
> +	const struct xfs_getfsmap_dev	*d2 = p2;
> +
> +	return d1->dev - d2->dev;
> +}
> +
> +/* Compare a record against our starting point */
> +static bool
> +xfs_getfsmap_rec_before_low_key(
> +	struct xfs_getfsmap_info	*info,
> +	struct xfs_rmap_irec		*rec)
> +{
> +	uint64_t			x, y;
> +
> +	if (rec->rm_startblock < info->low.rm_startblock)
> +		return true;
> +	if (rec->rm_startblock > info->low.rm_startblock)
> +		return false;
> +
> +	if (rec->rm_owner < info->low.rm_owner)
> +		return true;
> +	if (rec->rm_owner > info->low.rm_owner)
> +		return false;
> +
> +	x = xfs_rmap_irec_offset_pack(rec);
> +	y = xfs_rmap_irec_offset_pack(&info->low);

It looks like these functions incorporate flags bits into the offset. Is
that intentional? If so.. comment?

> +	if (x < y)
> +		return true;
> +	return false;
> +}
> +
> +/* Decide if this mapping is shared. */
> +STATIC int
> +xfs_getfsmap_is_shared(
> +	struct xfs_trans		*tp,
> +	struct xfs_getfsmap_info	*info,
> +	struct xfs_rmap_irec		*rec,
> +	bool				*stat)
> +{
> +	struct xfs_mount		*mp = tp->t_mountp;
> +	struct xfs_btree_cur		*cur;
> +	xfs_agblock_t			fbno;
> +	xfs_extlen_t			flen;
> +	int				error;
> +
> +	*stat = false;
> +	if (!xfs_sb_version_hasreflink(&mp->m_sb))
> +		return 0;
> +	/* rt files will have agno set to NULLAGNUMBER */
> +	if (info->agno == NULLAGNUMBER)
> +		return 0;
> +
> +	/* Are there any shared blocks here? */
> +	flen = 0;
> +	cur = xfs_refcountbt_init_cursor(mp, tp, info->agf_bp,
> +			info->agno, NULL);
> +
> +	error = xfs_refcount_find_shared(cur, rec->rm_startblock,
> +			rec->rm_blockcount, &fbno, &flen, false);
> +
> +	xfs_btree_del_cursor(cur, error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
> +	if (error)
> +		return error;
> +
> +	*stat = flen > 0;
> +	return 0;
> +}
> +
> +/*
> + * Format a reverse mapping for getfsmap, having translated rm_startblock
> + * into the appropriate daddr units.
> + */
> +STATIC int
> +xfs_getfsmap_helper(
> +	struct xfs_trans		*tp,
> +	struct xfs_getfsmap_info	*info,
> +	struct xfs_rmap_irec		*rec,
> +	xfs_daddr_t			rec_daddr)
> +{
> +	struct xfs_fsmap		fmr;
> +	struct xfs_mount		*mp = tp->t_mountp;
> +	xfs_daddr_t			key_end;
> +	bool				shared;
> +	int				error;
> +
> +	if (fatal_signal_pending(current))
> +		return -EAGAIN;
> +

I wonder if -EINTR is more appropriate here..?

> +	/*
> +	 * Filter out records that start before our startpoint, if the
> +	 * caller requested that.
> +	 */
> +	if (xfs_getfsmap_rec_before_low_key(info, rec)) {
> +		rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
> +		if (info->next_daddr < rec_daddr)
> +			info->next_daddr = rec_daddr;
> +		return XFS_BTREE_QUERY_RANGE_CONTINUE;
> +	}
> +
> +	/*
> +	 * If the caller passed in a length with the low record and
> +	 * the record represents a file data extent, we incremented
> +	 * the offset in the low key by the length in the hopes of
> +	 * finding reverse mappings for the physical blocks we just
> +	 * saw.  We did /not/ increment next_daddr by the length
> +	 * because the range query would not be able to find shared
> +	 * extents within the same physical block range.
> +	 *
> +	 * However, the extent we've been fed could have a startblock
> +	 * past the passed-in low record.  If this is the case,
> +	 * advance next_daddr to the end of the passed-in low record
> +	 * so we don't report the extent prior to this extent as
> +	 * free.
> +	 */
> +	key_end = info->rkey_low->fmr_physical + info->rkey_low->fmr_length;
> +	if (info->dev == info->rkey_low->fmr_device &&
> +	    info->next_daddr < key_end && rec_daddr >= key_end)
> +		info->next_daddr = key_end;
> +

Hmm, so I think I follow what this is trying to do..

In the case where we left off on a file mapping, we bump the offset of
the passed in low key but next_daddr remains at the same physical block
because we could have more mappings there. If we don't, however, and the
next mapping occurs at a higher physical block, we need to make sure we
don't map the previous range as free space. So we bump next_daddr here
to make sure that if free space does exist, it shown to start at the end
of the previous mapping. Yes?

If I'm following that correctly, what about the case where we have
bumped fmr_physical? It doesn't look like we've reset fmr_length, so
couldn't this cause us to skip legitimate free space if for e.g. the
current record is much farther ahead?

> +	/* Are we just counting mappings? */
> +	if (info->head->fmh_count == 0) {
> +		if (rec_daddr > info->next_daddr)
> +			info->head->fmh_entries++;
> +
> +		if (info->last)
> +			return XFS_BTREE_QUERY_RANGE_CONTINUE;
> +
> +		info->head->fmh_entries++;
> +
> +		rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
> +		if (info->next_daddr < rec_daddr)
> +			info->next_daddr = rec_daddr;
> +		return XFS_BTREE_QUERY_RANGE_CONTINUE;
> +	}
> +
> +	/*
> +	 * If the record starts past the last physical block we saw,
> +	 * then we've found some free space.  Report that too.
> +	 */
> +	if (rec_daddr > info->next_daddr) {
> +		if (info->head->fmh_entries >= info->head->fmh_count)
> +			return XFS_BTREE_QUERY_RANGE_ABORT;
> +
> +		trace_xfs_fsmap_mapping(mp, info->dev, info->agno,
> +				XFS_DADDR_TO_FSB(mp, info->next_daddr),
> +				XFS_DADDR_TO_FSB(mp, rec_daddr -
> +						info->next_daddr),
> +				info->missing_owner, 0);
> +
> +		fmr.fmr_device = info->dev;
> +		fmr.fmr_physical = info->next_daddr;
> +		fmr.fmr_owner = info->missing_owner;
> +		fmr.fmr_offset = 0;
> +		fmr.fmr_length = rec_daddr - info->next_daddr;
> +		fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
> +		error = info->formatter(&fmr, info->format_arg);
> +		if (error)
> +			return error;
> +		info->head->fmh_entries++;
> +	}
> +
> +	if (info->last)
> +		goto out;
> +
> +	/* Fill out the extent we found */
> +	if (info->head->fmh_entries >= info->head->fmh_count)
> +		return XFS_BTREE_QUERY_RANGE_ABORT;
> +
> +	trace_xfs_fsmap_mapping(mp, info->dev, info->agno,
> +			rec->rm_startblock, rec->rm_blockcount, rec->rm_owner,
> +			rec->rm_offset);
> +
> +	fmr.fmr_device = info->dev;
> +	fmr.fmr_physical = rec_daddr;
> +	error = xfs_fsmap_owner_from_rmap(rec, &fmr);
> +	if (error)
> +		return error;
> +	fmr.fmr_offset = XFS_FSB_TO_BB(mp, rec->rm_offset);
> +	fmr.fmr_length = XFS_FSB_TO_BB(mp, rec->rm_blockcount);
> +	if (rec->rm_flags & XFS_RMAP_UNWRITTEN)
> +		fmr.fmr_flags |= FMR_OF_PREALLOC;
> +	if (rec->rm_flags & XFS_RMAP_ATTR_FORK)
> +		fmr.fmr_flags |= FMR_OF_ATTR_FORK;
> +	if (rec->rm_flags & XFS_RMAP_BMBT_BLOCK)
> +		fmr.fmr_flags |= FMR_OF_EXTENT_MAP;
> +	if (fmr.fmr_flags == 0) {
> +		error = xfs_getfsmap_is_shared(tp, info, rec, &shared);
> +		if (error)
> +			return error;
> +		if (shared)
> +			fmr.fmr_flags |= FMR_OF_SHARED;
> +	}
> +	error = info->formatter(&fmr, info->format_arg);
> +	if (error)
> +		return error;
> +	info->head->fmh_entries++;
> +
> +out:
> +	rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
> +	if (info->next_daddr < rec_daddr)
> +		info->next_daddr = rec_daddr;
> +	return XFS_BTREE_QUERY_RANGE_CONTINUE;
> +}
> +
> +/* Transform a rmapbt irec into a fsmap */
> +STATIC int
> +xfs_getfsmap_datadev_helper(
> +	struct xfs_btree_cur		*cur,
> +	struct xfs_rmap_irec		*rec,
> +	void				*priv)
> +{
> +	struct xfs_mount		*mp = cur->bc_mp;
> +	struct xfs_getfsmap_info	*info = priv;
> +	xfs_fsblock_t			fsb;
> +	xfs_daddr_t			rec_daddr;
> +
> +	fsb = XFS_AGB_TO_FSB(mp, cur->bc_private.a.agno, rec->rm_startblock);
> +	rec_daddr = XFS_FSB_TO_DADDR(mp, fsb);
> +
> +	return xfs_getfsmap_helper(cur->bc_tp, info, rec, rec_daddr);
> +}
> +
> +/* Transform a absolute-startblock rmap (rtdev, logdev) into a fsmap */
> +STATIC int
> +xfs_getfsmap_rtdev_helper(
> +	struct xfs_btree_cur		*cur,
> +	struct xfs_rmap_irec		*rec,
> +	void				*priv)
> +{
> +	struct xfs_mount		*mp = cur->bc_mp;
> +	struct xfs_getfsmap_info	*info = priv;
> +	xfs_daddr_t			rec_daddr;
> +
> +	rec_daddr = XFS_FSB_TO_BB(mp, rec->rm_startblock);
> +
> +	return xfs_getfsmap_helper(cur->bc_tp, info, rec, rec_daddr);
> +}
> +
> +/* Set rmap flags based on the getfsmap flags */
> +static void
> +xfs_getfsmap_set_irec_flags(
> +	struct xfs_rmap_irec	*irec,
> +	struct xfs_fsmap	*fmr)
> +{
> +	irec->rm_flags = 0;
> +	if (fmr->fmr_flags & FMR_OF_ATTR_FORK)
> +		irec->rm_flags |= XFS_RMAP_ATTR_FORK;
> +	if (fmr->fmr_flags & FMR_OF_EXTENT_MAP)
> +		irec->rm_flags |= XFS_RMAP_BMBT_BLOCK;
> +	if (fmr->fmr_flags & FMR_OF_PREALLOC)
> +		irec->rm_flags |= XFS_RMAP_UNWRITTEN;
> +}
> +
> +/* Execute a getfsmap query against the log device. */
> +STATIC int
> +xfs_getfsmap_logdev(
> +	struct xfs_trans		*tp,
> +	struct xfs_fsmap		*keys,
> +	struct xfs_getfsmap_info	*info)
> +{
> +	struct xfs_mount		*mp = tp->t_mountp;
> +	struct xfs_fsmap		*dkey_low = keys;
> +	struct xfs_btree_cur		cur;
> +	struct xfs_rmap_irec		rmap;
> +	int				error;
> +
> +	/* Set up search keys */
> +	info->low.rm_startblock = XFS_BB_TO_FSBT(mp, dkey_low->fmr_physical);
> +	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
> +	error = xfs_fsmap_owner_to_rmap(keys, &info->low);
> +	if (error)
> +		return error;
> +	info->low.rm_blockcount = 0;
> +	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
> +
> +	error = xfs_fsmap_owner_to_rmap(keys + 1, &info->high);
> +	if (error)
> +		return error;
> +	info->high.rm_startblock = -1U;
> +	info->high.rm_owner = ULLONG_MAX;
> +	info->high.rm_offset = ULLONG_MAX;
> +	info->high.rm_blockcount = 0;
> +	info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;
> +	info->missing_owner = XFS_FMR_OWN_FREE;
> +
> +	trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
> +			info->low.rm_startblock,
> +			info->low.rm_blockcount,
> +			info->low.rm_owner,
> +			info->low.rm_offset);
> +
> +	trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
> +			info->high.rm_startblock,
> +			info->high.rm_blockcount,
> +			info->high.rm_owner,
> +			info->high.rm_offset);
> +
> +
> +	if (dkey_low->fmr_physical > 0)
> +		return 0;
> +

A comment to point out we're fabricating an rmap record here would be
nice. Also, (how) do we handle/report internal log blocks?

> +	rmap.rm_startblock = 0;
> +	rmap.rm_blockcount = mp->m_sb.sb_logblocks;
> +	rmap.rm_owner = XFS_RMAP_OWN_LOG;
> +	rmap.rm_offset = 0;
> +	rmap.rm_flags = 0;
> +
> +	cur.bc_mp = mp;
> +	cur.bc_tp = tp;
> +	return xfs_getfsmap_rtdev_helper(&cur, &rmap, info);
> +}
> +
> +/* Execute a getfsmap query against the regular data device. */
> +STATIC int
> +xfs_getfsmap_datadev(
> +	struct xfs_trans		*tp,
> +	struct xfs_fsmap		*keys,
> +	struct xfs_getfsmap_info	*info)
> +{
> +	struct xfs_mount		*mp = tp->t_mountp;
> +	struct xfs_btree_cur		*bt_cur = NULL;
> +	struct xfs_fsmap		*dkey_low;
> +	struct xfs_fsmap		*dkey_high;
> +	xfs_fsblock_t			start_fsb;
> +	xfs_fsblock_t			end_fsb;
> +	xfs_agnumber_t			start_ag;
> +	xfs_agnumber_t			end_ag;
> +	xfs_daddr_t			eofs;
> +	int				error = 0;
> +
> +	dkey_low = keys;
> +	dkey_high = keys + 1;
> +	eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks);
> +	if (dkey_low->fmr_physical >= eofs)
> +		return 0;
> +	if (dkey_high->fmr_physical >= eofs)
> +		dkey_high->fmr_physical = eofs - 1;
> +	start_fsb = XFS_DADDR_TO_FSB(mp, dkey_low->fmr_physical);
> +	end_fsb = XFS_DADDR_TO_FSB(mp, dkey_high->fmr_physical);
> +
> +	/* Set up search keys */

I think we could use slightly better comments here and below just to
point out why we set low/high to these values. E.g., something like:

/*
 * Convert the fsmap low/high keys to AG based keys. Initialize low to
 * the fsmap low key and max out the high key to the end of the AG.
 */

> +	info->low.rm_startblock = XFS_FSB_TO_AGBNO(mp, start_fsb);
> +	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
> +	error = xfs_fsmap_owner_to_rmap(dkey_low, &info->low);
> +	if (error)
> +		return error;
> +	info->low.rm_blockcount = 0;
> +	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
> +
> +	info->high.rm_startblock = -1U;
> +	info->high.rm_owner = ULLONG_MAX;
> +	info->high.rm_offset = ULLONG_MAX;
> +	info->high.rm_blockcount = 0;
> +	info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;
> +	info->missing_owner = XFS_FMR_OWN_FREE;
> +
> +	start_ag = XFS_FSB_TO_AGNO(mp, start_fsb);
> +	end_ag = XFS_FSB_TO_AGNO(mp, end_fsb);
> +
> +	/* Query each AG */
> +	for (info->agno = start_ag; info->agno <= end_ag; info->agno++) {

/*
 * Incorporate the fsmap high key for the last AG.
 */

> +		if (info->agno == end_ag) {
> +			info->high.rm_startblock = XFS_FSB_TO_AGBNO(mp,
> +					end_fsb);
> +			info->high.rm_offset = XFS_BB_TO_FSBT(mp,
> +					dkey_high->fmr_offset);
> +			error = xfs_fsmap_owner_to_rmap(dkey_high, &info->high);
> +			if (error)
> +				goto err;
> +			xfs_getfsmap_set_irec_flags(&info->high, dkey_high);
> +		}
> +
> +		if (bt_cur) {
> +			xfs_btree_del_cursor(bt_cur, XFS_BTREE_NOERROR);
> +			bt_cur = NULL;
> +			info->agf_bp = NULL;
> +		}
> +
> +		error = xfs_alloc_read_agf(mp, tp, info->agno, 0,
> +				&info->agf_bp);
> +		if (error)
> +			goto err;
> +
> +		trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
> +				info->low.rm_startblock,
> +				info->low.rm_blockcount,
> +				info->low.rm_owner,
> +				info->low.rm_offset);
> +
> +		trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
> +				info->high.rm_startblock,
> +				info->high.rm_blockcount,
> +				info->high.rm_owner,
> +				info->high.rm_offset);
> +
> +		bt_cur = xfs_rmapbt_init_cursor(mp, tp, info->agf_bp,
> +				info->agno);
> +		error = xfs_rmap_query_range(bt_cur, &info->low, &info->high,
> +				xfs_getfsmap_datadev_helper, info);
> +		if (error)
> +			goto err;
> +

/*
 * Reset the low key for the start of the next AG.
 */

> +		if (info->agno == start_ag) {
> +			info->low.rm_startblock = 0;
> +			info->low.rm_owner = 0;
> +			info->low.rm_offset = 0;
> +			info->low.rm_flags = 0;
> +		}
> +	}

Do I follow this loop correctly in that we lock each AGF buffer as we
progress through the fs, holding the locks until we've traversed the
entire fs? If so, is that really necessary or can we release the
previous previous buffer once we move on to the next AG? Not doing so
seems like it makes this a very heavyweight operation...

> +
> +	/* Report any free space at the end of the AG */
> +	info->last = true;
> +	error = xfs_getfsmap_datadev_helper(bt_cur, &info->high, info);
> +	if (error)
> +		goto err;
> +
> +err:
> +	if (bt_cur)
> +		xfs_btree_del_cursor(bt_cur, error < 0 ? XFS_BTREE_ERROR :
> +							 XFS_BTREE_NOERROR);
> +	if (info->agf_bp)
> +		info->agf_bp = NULL;
> +
> +	return error;
> +}
> +
> +/* Do we recognize the device? */
> +STATIC bool
> +xfs_getfsmap_is_valid_device(
> +	struct xfs_mount	*mp,
> +	struct xfs_fsmap	*fm)
> +{
> +	if (fm->fmr_device == 0 || fm->fmr_device == UINT_MAX ||
> +	    fm->fmr_device == new_encode_dev(mp->m_ddev_targp->bt_dev))
> +		return true;
> +	if (mp->m_logdev_targp &&
> +	    fm->fmr_device == new_encode_dev(mp->m_logdev_targp->bt_dev))
> +		return true;
> +	return false;
> +}
> +
> +/* Ensure that the low key is less than the high key. */
> +STATIC bool
> +xfs_getfsmap_check_keys(
> +	struct xfs_fsmap		*low_key,
> +	struct xfs_fsmap		*high_key)
> +{
> +	if (low_key->fmr_device > high_key->fmr_device)
> +		return false;
> +	if (low_key->fmr_device < high_key->fmr_device)
> +		return true;
> +
> +	if (low_key->fmr_physical > high_key->fmr_physical)
> +		return false;
> +	if (low_key->fmr_physical < high_key->fmr_physical)
> +		return true;
> +
> +	if (low_key->fmr_owner > high_key->fmr_owner)
> +		return false;
> +	if (low_key->fmr_owner < high_key->fmr_owner)
> +		return true;
> +
> +	if (low_key->fmr_offset > high_key->fmr_offset)
> +		return false;
> +	if (low_key->fmr_offset < high_key->fmr_offset)
> +		return true;
> +
> +	return false;
> +}
> +
> +#define XFS_GETFSMAP_DEVS	3

Why 3 (looks like we use 2 below)?

> +/*
> + * Get filesystem's extents as described in head, and format for
> + * output.  Calls formatter to fill the user's buffer until all
> + * extents are mapped, until the passed-in head->fmh_count slots have
> + * been filled, or until the formatter short-circuits the loop, if it
> + * is tracking filled-in extents on its own.
> + */
> +int
> +xfs_getfsmap(
> +	struct xfs_mount		*mp,
> +	struct xfs_fsmap_head		*head,
> +	xfs_fsmap_format_t		formatter,
> +	void				*arg)
> +{
> +	struct xfs_trans		*tp = NULL;
> +	struct xfs_fsmap		*rkey_low;	/* request keys */
> +	struct xfs_fsmap		*rkey_high;
> +	struct xfs_fsmap		dkeys[2];	/* per-dev keys */
> +	struct xfs_getfsmap_dev		handlers[XFS_GETFSMAP_DEVS];
> +	struct xfs_getfsmap_info	info = {0};
> +	int				i;
> +	int				error = 0;
> +
> +	if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
> +		return -EOPNOTSUPP;
> +	if (head->fmh_iflags & ~FMH_IF_VALID)
> +		return -EINVAL;
> +	rkey_low = head->fmh_keys;
> +	rkey_high = rkey_low + 1;

This is more clear IMO if we just use fmh_keys[0] and fmh_keys[1] (the
same pattern exists in one or two other places as well..).

> +	if (!xfs_getfsmap_is_valid_device(mp, rkey_low) ||
> +	    !xfs_getfsmap_is_valid_device(mp, rkey_high))
> +		return -EINVAL;
> +
> +	head->fmh_entries = 0;
> +
> +	/* Set up our device handlers. */
> +	memset(handlers, 0, sizeof(handlers));
> +	handlers[0].dev = new_encode_dev(mp->m_ddev_targp->bt_dev);
> +	handlers[0].fn = xfs_getfsmap_datadev;
> +	if (mp->m_logdev_targp != mp->m_ddev_targp) {
> +		handlers[1].dev = new_encode_dev(mp->m_logdev_targp->bt_dev);
> +		handlers[1].fn = xfs_getfsmap_logdev;
> +	}
> +
> +	xfs_sort(handlers, XFS_GETFSMAP_DEVS, sizeof(struct xfs_getfsmap_dev),
> +			xfs_getfsmap_dev_compare);
> +
> +	/*
> +	 * Since we allow the user to copy the last mapping from a previous
> +	 * call into the low key slot, we have to advance the low key by
> +	 * whatever the reported length is.  If the offset field doesn't apply,
> +	 * move up the start block to the next extent and start over with the
> +	 * lowest owner/offset possible; otherwise it's file data, so move up
> +	 * the offset only.
> +	 */
> +	dkeys[0] = *rkey_low;
> +	if (dkeys[0].fmr_flags & (FMR_OF_SPECIAL_OWNER | FMR_OF_EXTENT_MAP)) {
> +		dkeys[0].fmr_physical += dkeys[0].fmr_length;
> +		dkeys[0].fmr_owner = 0;
> +		dkeys[0].fmr_offset = 0;

Should these values already be zero in this case? 

> +	} else
> +		dkeys[0].fmr_offset += dkeys[0].fmr_length;
> +	memset(&dkeys[1], 0xFF, sizeof(struct xfs_fsmap));

Ok, it took me a bit to grok this hunk for some reason. I had to come
back to it after reading deeper into the code. It could just be me, but
something like the following comment helps me understand it a bit better
(feel free to take it entirely, reword/update the existing comment or
just ignore):

/*
 * To continue where we left off, we allow userspace to use the last
 * mapping from a previous call as the low key of the next. This is
 * identified by a non-zero length in the low key. We have to increment
 * the low key in this scenario to ensure we don't return the same
 * mapping again, and instead return the very next mapping.
 *
 * If the low key mapping refers to fs owned blocks, bump the physical
 * offset as there can be no other mapping for the same physical block
 * range. If the mapping refers to file data, however, the same physical
 * blocks could be mapped to several other files/offsets. According to
 * rmapbt record ordering, the minimal next possible record for the
 * block range is the next starting offset in the same inode. Therefore,
 * bump the file offset to continue the search appropriately.
 */

> +
> +	if (!xfs_getfsmap_check_keys(dkeys, rkey_high))
> +		return -EINVAL;
> +
> +	info.rkey_low = rkey_low;
> +	info.formatter = formatter;
> +	info.format_arg = arg;
> +	info.head = head;
> +
> +	/* For each device we support... */
> +	for (i = 0; i < XFS_GETFSMAP_DEVS; i++) {
> +		/* Is this device within the range the user asked for? */
> +		if (!handlers[i].fn)
> +			continue;
> +		if (rkey_low->fmr_device > handlers[i].dev)
> +			continue;
> +		if (rkey_high->fmr_device < handlers[i].dev)
> +			break;
> +
> +		/*
> +		 * If this device number matches the high key, we have
> +		 * to pass the high key to the handler to limit the
> +		 * query results.  If the device number exceeds the
> +		 * low key, zero out the low key so that we get
> +		 * everything from the beginning.
> +		 */
> +		if (handlers[i].dev == rkey_high->fmr_device)
> +			dkeys[1] = *rkey_high;
> +		if (handlers[i].dev > rkey_low->fmr_device)
> +			memset(&dkeys[0], 0, sizeof(struct xfs_fsmap));
> +
> +		error = xfs_trans_alloc_empty(mp, &tp);
> +		if (error)
> +			break;
> +
> +		info.next_daddr = dkeys[0].fmr_physical;
> +		info.dev = handlers[i].dev;
> +		info.last = false;
> +		info.agno = NULLAGNUMBER;
> +		error = handlers[i].fn(tp, dkeys, &info);
> +		if (error)
> +			break;
> +		xfs_trans_cancel(tp);
> +		tp = NULL;
> +	}
> +
> +	if (tp)
> +		xfs_trans_cancel(tp);
> +	head->fmh_oflags = FMH_OF_DEV_T;
> +	return error;
> +}
> diff --git a/fs/xfs/xfs_fsmap.h b/fs/xfs/xfs_fsmap.h
> new file mode 100644
> index 0000000..1943047
> --- /dev/null
> +++ b/fs/xfs/xfs_fsmap.h
> @@ -0,0 +1,51 @@
> +/*
> + * Copyright (C) 2017 Oracle.  All Rights Reserved.
> + *
> + * Author: Darrick J. Wong <darrick.wong@oracle.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version 2
> + * of the License, or (at your option) any later version.
> + *
> + * This program is distributed in the hope that it would be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write the Free Software Foundation,
> + * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
> + */
> +#ifndef __XFS_FSMAP_H__
> +#define	__XFS_FSMAP_H__
> +
> +/* internal fsmap representation */
> +struct xfs_fsmap {
> +	dev_t		fmr_device;	/* device id */
> +	uint32_t	fmr_flags;	/* mapping flags */
> +	uint64_t	fmr_physical;	/* device offset of segment */
> +	uint64_t	fmr_owner;	/* owner id */
> +	xfs_fileoff_t	fmr_offset;	/* file offset of segment */
> +	xfs_filblks_t	fmr_length;	/* length of segment, blocks */
> +};
> +
> +struct xfs_fsmap_head {
> +	uint32_t	fmh_iflags;	/* control flags */
> +	uint32_t	fmh_oflags;	/* output flags */
> +	unsigned int	fmh_count;	/* # of entries in array incl. input */
> +	unsigned int	fmh_entries;	/* # of entries filled in (output). */
> +
> +	struct xfs_fsmap fmh_keys[2];	/* low and high keys */
> +};
> +
> +void xfs_fsmap_from_internal(struct fsmap *dest, struct xfs_fsmap *src);
> +void xfs_fsmap_to_internal(struct xfs_fsmap *dest, struct fsmap *src);
> +
> +/* fsmap to userspace formatter - copy to user & advance pointer */
> +typedef int (*xfs_fsmap_format_t)(struct xfs_fsmap *, void *);
> +
> +int xfs_getfsmap(struct xfs_mount *mp, struct xfs_fsmap_head *head,
> +		xfs_fsmap_format_t formatter, void *arg);
> +
> +#endif /* __XFS_FSMAP_H__ */
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index c67cfb4..bbe1b58 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -41,6 +41,9 @@
>  #include "xfs_trans.h"
>  #include "xfs_pnfs.h"
>  #include "xfs_acl.h"
> +#include "xfs_btree.h"
> +#include <linux/fsmap.h>
> +#include "xfs_fsmap.h"
>  
>  #include <linux/capability.h>
>  #include <linux/dcache.h>
> @@ -1607,6 +1610,103 @@ xfs_ioc_getbmapx(
>  	return 0;
>  }
>  
> +struct getfsmap_info {
> +	struct xfs_mount	*mp;
> +	struct fsmap __user	*data;
> +	__u32			last_flags;
> +};
> +
> +STATIC int
> +xfs_getfsmap_format(struct xfs_fsmap *xfm, void *priv)
> +{
> +	struct getfsmap_info	*info = priv;
> +	struct fsmap		fm;
> +
> +	trace_xfs_getfsmap_mapping(info->mp, xfm->fmr_device, xfm->fmr_physical,
> +			xfm->fmr_length, xfm->fmr_owner, xfm->fmr_offset,
> +			xfm->fmr_flags);
> +
> +	info->last_flags = xfm->fmr_flags;
> +	xfs_fsmap_from_internal(&fm, xfm);
> +	if (copy_to_user(info->data, &fm, sizeof(struct fsmap)))
> +		return -EFAULT;
> +
> +	info->data++;
> +	return 0;
> +}
> +
> +STATIC int
> +xfs_ioc_getfsmap(
> +	struct xfs_inode	*ip,
> +	void			__user *arg)
> +{
> +	struct getfsmap_info	info;
> +	struct xfs_fsmap_head	xhead = {0};
> +	struct fsmap_head	head;
> +	bool			aborted = false;
> +	int			error;
> +
> +	if (copy_from_user(&head, arg, sizeof(struct fsmap_head)))
> +		return -EFAULT;
> +	if (head.fmh_reserved[0] || head.fmh_reserved[1] ||
> +	    head.fmh_reserved[2] || head.fmh_reserved[3] ||
> +	    head.fmh_reserved[4] || head.fmh_reserved[5] ||
> +	    head.fmh_keys[0].fmr_reserved[0] ||
> +	    head.fmh_keys[0].fmr_reserved[1] ||
> +	    head.fmh_keys[0].fmr_reserved[2] ||
> +	    head.fmh_keys[1].fmr_reserved[0] ||
> +	    head.fmh_keys[1].fmr_reserved[1] ||
> +	    head.fmh_keys[1].fmr_reserved[2])
> +		return -EINVAL;

Probably better to use memchr_inv() here.

> +
> +	xhead.fmh_iflags = head.fmh_iflags;
> +	xhead.fmh_count = head.fmh_count;
> +	xfs_fsmap_to_internal(&xhead.fmh_keys[0], &head.fmh_keys[0]);
> +	xfs_fsmap_to_internal(&xhead.fmh_keys[1], &head.fmh_keys[1]);
> +
> +	trace_xfs_getfsmap_low_key(ip->i_mount,
> +			xhead.fmh_keys[0].fmr_device,
> +			xhead.fmh_keys[0].fmr_physical,
> +			xhead.fmh_keys[0].fmr_length,
> +			xhead.fmh_keys[0].fmr_owner,
> +			xhead.fmh_keys[0].fmr_offset,
> +			xhead.fmh_keys[0].fmr_flags);
> +
> +	trace_xfs_getfsmap_high_key(ip->i_mount,
> +			xhead.fmh_keys[1].fmr_device,
> +			xhead.fmh_keys[1].fmr_physical,
> +			xhead.fmh_keys[1].fmr_length,
> +			xhead.fmh_keys[1].fmr_owner,
> +			xhead.fmh_keys[1].fmr_offset,
> +			xhead.fmh_keys[1].fmr_flags);
> +

Hmm.. could we combine these into one call that looks like:

	trace_xfs_getfsmap(mp, &fmh_keys[0], &fmh_keys[1]);

... and has the trace handler pull the relevant data out of the key
structure (same comment for the similar trace_xfs_fsmap*())?

> +	info.mp = ip->i_mount;
> +	info.data = ((__force struct fsmap_head *)arg)->fmh_recs;
> +	error = xfs_getfsmap(ip->i_mount, &xhead, xfs_getfsmap_format, &info);
> +	if (error == XFS_BTREE_QUERY_RANGE_ABORT) {
> +		error = 0;
> +		aborted = true;
> +	} else if (error)
> +		return error;
> +
> +	/* If we didn't abort, set the "last" flag in the last fmx */
> +	if (!aborted && xhead.fmh_entries) {
> +		info.data--;
> +		info.last_flags |= FMR_OF_LAST;

Isn't this kind of implied by a short return? It looks like if a real
error occurs at any point during the search, we just return the error. I
guess there is still the case where the remaining mappings exactly match
the number of entries in the data structure passed in and you'd have to
make another call to identify EOF. If we do want the flag, I'm also
wondering why we couldn't stuff it in oflags in the header. Is there
some reason I'm not yet aware of why we want the LAST flag in the flags
of the last entry?

Brian

> +		if (copy_to_user(&info.data->fmr_flags, &info.last_flags,
> +				sizeof(info.last_flags)))
> +			return -EFAULT;
> +	}
> +
> +	/* copy back header */
> +	head.fmh_entries = xhead.fmh_entries;
> +	head.fmh_oflags = xhead.fmh_oflags;
> +	if (copy_to_user(arg, &head, sizeof(struct fsmap_head)))
> +		return -EFAULT;
> +
> +	return 0;
> +}
> +
>  int
>  xfs_ioc_swapext(
>  	xfs_swapext_t	*sxp)
> @@ -1787,6 +1887,9 @@ xfs_file_ioctl(
>  	case XFS_IOC_GETBMAPX:
>  		return xfs_ioc_getbmapx(ip, arg);
>  
> +	case FS_IOC_GETFSMAP:
> +		return xfs_ioc_getfsmap(ip, arg);
> +
>  	case XFS_IOC_FD_TO_HANDLE:
>  	case XFS_IOC_PATH_TO_HANDLE:
>  	case XFS_IOC_PATH_TO_FSHANDLE: {
> diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
> index 7c49938..fa0bc4d 100644
> --- a/fs/xfs/xfs_ioctl32.c
> +++ b/fs/xfs/xfs_ioctl32.c
> @@ -20,6 +20,7 @@
>  #include <linux/mount.h>
>  #include <linux/slab.h>
>  #include <linux/uaccess.h>
> +#include <linux/fsmap.h>
>  #include "xfs.h"
>  #include "xfs_fs.h"
>  #include "xfs_format.h"
> @@ -554,6 +555,7 @@ xfs_file_compat_ioctl(
>  	case XFS_IOC_GOINGDOWN:
>  	case XFS_IOC_ERROR_INJECTION:
>  	case XFS_IOC_ERROR_CLEARALL:
> +	case FS_IOC_GETFSMAP:
>  		return xfs_file_ioctl(filp, cmd, p);
>  #ifndef BROKEN_X86_ALIGNMENT
>  	/* These are handled fine if no alignment issues */
> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index d3d11905..125d568 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -3270,6 +3270,91 @@ DEFINE_INODE_IREC_EVENT(xfs_swap_extent_rmap_remap);
>  DEFINE_INODE_IREC_EVENT(xfs_swap_extent_rmap_remap_piece);
>  DEFINE_INODE_ERROR_EVENT(xfs_swap_extent_rmap_error);
>  
> +/* fsmap traces */
> +DECLARE_EVENT_CLASS(xfs_fsmap_class,
> +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_agnumber_t agno,
> +		 xfs_fsblock_t bno, xfs_filblks_t len, __uint64_t owner,
> +		 __uint64_t offset),
> +	TP_ARGS(mp, keydev, agno, bno, len, owner, offset),
> +	TP_STRUCT__entry(
> +		__field(dev_t, dev)
> +		__field(dev_t, keydev)
> +		__field(xfs_agnumber_t, agno)
> +		__field(xfs_fsblock_t, bno)
> +		__field(xfs_filblks_t, len)
> +		__field(__uint64_t, owner)
> +		__field(__uint64_t, offset)
> +	),
> +	TP_fast_assign(
> +		__entry->dev = mp->m_super->s_dev;
> +		__entry->keydev = new_decode_dev(keydev);
> +		__entry->agno = agno;
> +		__entry->bno = bno;
> +		__entry->len = len;
> +		__entry->owner = owner;
> +		__entry->offset = offset;
> +	),
> +	TP_printk("dev %d:%d keydev %d:%d agno %u bno %llu len %llu owner %lld offset 0x%llx\n",
> +		  MAJOR(__entry->dev), MINOR(__entry->dev),
> +		  MAJOR(__entry->keydev), MINOR(__entry->keydev),
> +		  __entry->agno,
> +		  __entry->bno,
> +		  __entry->len,
> +		  __entry->owner,
> +		  __entry->offset)
> +)
> +#define DEFINE_FSMAP_EVENT(name) \
> +DEFINE_EVENT(xfs_fsmap_class, name, \
> +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_agnumber_t agno, \
> +		 xfs_fsblock_t bno, xfs_filblks_t len, __uint64_t owner, \
> +		 __uint64_t offset), \
> +	TP_ARGS(mp, keydev, agno, bno, len, owner, offset))
> +DEFINE_FSMAP_EVENT(xfs_fsmap_low_key);
> +DEFINE_FSMAP_EVENT(xfs_fsmap_high_key);
> +DEFINE_FSMAP_EVENT(xfs_fsmap_mapping);
> +
> +DECLARE_EVENT_CLASS(xfs_getfsmap_class,
> +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block,
> +		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset,
> +		 __uint64_t flags),
> +	TP_ARGS(mp, keydev, block, len, owner, offset, flags),
> +	TP_STRUCT__entry(
> +		__field(dev_t, dev)
> +		__field(dev_t, keydev)
> +		__field(xfs_daddr_t, block)
> +		__field(xfs_daddr_t, len)
> +		__field(__uint64_t, owner)
> +		__field(__uint64_t, offset)
> +		__field(__uint64_t, flags)
> +	),
> +	TP_fast_assign(
> +		__entry->dev = mp->m_super->s_dev;
> +		__entry->keydev = new_decode_dev(keydev);
> +		__entry->block = block;
> +		__entry->len = len;
> +		__entry->owner = owner;
> +		__entry->offset = offset;
> +		__entry->flags = flags;
> +	),
> +	TP_printk("dev %d:%d keydev %d:%d block %llu len %llu owner %lld offset %llu flags 0x%llx\n",
> +		  MAJOR(__entry->dev), MINOR(__entry->dev),
> +		  MAJOR(__entry->keydev), MINOR(__entry->keydev),
> +		  __entry->block,
> +		  __entry->len,
> +		  __entry->owner,
> +		  __entry->offset,
> +		  __entry->flags)
> +)
> +#define DEFINE_GETFSMAP_EVENT(name) \
> +DEFINE_EVENT(xfs_getfsmap_class, name, \
> +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block, \
> +		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset, \
> +		 __uint64_t flags), \
> +	TP_ARGS(mp, keydev, block, len, owner, offset, flags))
> +DEFINE_GETFSMAP_EVENT(xfs_getfsmap_low_key);
> +DEFINE_GETFSMAP_EVENT(xfs_getfsmap_high_key);
> +DEFINE_GETFSMAP_EVENT(xfs_getfsmap_mapping);
> +
>  #endif /* _TRACE_XFS_H */
>  
>  #undef TRACE_INCLUDE_PATH
> diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> index 70f42ea..a280e12 100644
> --- a/fs/xfs/xfs_trans.c
> +++ b/fs/xfs/xfs_trans.c
> @@ -263,6 +263,28 @@ xfs_trans_alloc(
>  }
>  
>  /*
> + * Create an empty transaction with no reservation.  This is a defensive
> + * mechanism for routines that query metadata without actually modifying
> + * them -- if the metadata being queried is somehow cross-linked (think a
> + * btree block pointer that points higher in the tree), we risk deadlock.
> + * However, blocks grabbed as part of a transaction can be re-grabbed.
> + * The verifiers will notice the corrupt block and the operation will fail
> + * back to userspace without deadlocking.
> + *
> + * Note the zero-length reservation; this transaction MUST be cancelled
> + * without any dirty data.
> + */
> +int
> +xfs_trans_alloc_empty(
> +	struct xfs_mount		*mp,
> +	struct xfs_trans		**tpp)
> +{
> +	struct xfs_trans_res		resv = {0};
> +
> +	return xfs_trans_alloc(mp, &resv, 0, 0, XFS_TRANS_NO_WRITECOUNT, tpp);
> +}
> +
> +/*
>   * Record the indicated change to the given field for application
>   * to the file system's superblock when the transaction commits.
>   * For now, just store the change in the transaction structure.
> diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
> index 61b7fbd..98024cb 100644
> --- a/fs/xfs/xfs_trans.h
> +++ b/fs/xfs/xfs_trans.h
> @@ -159,6 +159,8 @@ typedef struct xfs_trans {
>  int		xfs_trans_alloc(struct xfs_mount *mp, struct xfs_trans_res *resp,
>  			uint blocks, uint rtextents, uint flags,
>  			struct xfs_trans **tpp);
> +int		xfs_trans_alloc_empty(struct xfs_mount *mp,
> +			struct xfs_trans **tpp);
>  void		xfs_trans_mod_sb(xfs_trans_t *, uint, int64_t);
>  
>  struct xfs_buf	*xfs_trans_get_buf_map(struct xfs_trans *tp,
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 5/8] xfs: introduce the XFS_IOC_GETFSMAP ioctl

[Darrick J. Wong]

On Wed, Feb 22, 2017 at 10:02:47AM -0500, Brian Foster wrote:
> On Fri, Feb 17, 2017 at 05:17:49PM -0800, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Introduce a new ioctl that uses the reverse mapping btree to return
> > information about the physical layout of the filesystem.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> 
> Mostly looks good, though there's a decent amount of indirection here so
> I'll probably need another pass through it. Mostly minor comments, a
> couple potential issues and some questions..

<nod>

> >  fs/xfs/Makefile        |    1 
> >  fs/xfs/libxfs/xfs_fs.h |   13 +
> >  fs/xfs/xfs_fsmap.c     |  782 ++++++++++++++++++++++++++++++++++++++++++++++++
> >  fs/xfs/xfs_fsmap.h     |   51 +++
> >  fs/xfs/xfs_ioctl.c     |  103 ++++++
> >  fs/xfs/xfs_ioctl32.c   |    2 
> >  fs/xfs/xfs_trace.h     |   85 +++++
> >  fs/xfs/xfs_trans.c     |   22 +
> >  fs/xfs/xfs_trans.h     |    2 
> >  9 files changed, 1061 insertions(+)
> >  create mode 100644 fs/xfs/xfs_fsmap.c
> >  create mode 100644 fs/xfs/xfs_fsmap.h
> > 
> > 
> > diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile
> > index c7515d4..0e7ee30 100644
> > --- a/fs/xfs/Makefile
> > +++ b/fs/xfs/Makefile
> > @@ -80,6 +80,7 @@ xfs-y				+= xfs_aops.o \
> >  				   xfs_extent_busy.o \
> >  				   xfs_file.o \
> >  				   xfs_filestream.o \
> > +				   xfs_fsmap.o \
> >  				   xfs_fsops.o \
> >  				   xfs_globals.o \
> >  				   xfs_icache.o \
> > diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
> > index b72dc82..095bdf0 100644
> > --- a/fs/xfs/libxfs/xfs_fs.h
> > +++ b/fs/xfs/libxfs/xfs_fs.h
> > @@ -92,6 +92,18 @@ struct getbmapx {
> >  #define BMV_OF_LAST		0x4	/* segment is the last in the file */
> >  #define BMV_OF_SHARED		0x8	/* segment shared with another file */
> >  
> > +/*	fmr_owner special values for FS_IOC_GETFSMAP */
> > +#define XFS_FMR_OWN_FREE	FMR_OWN_FREE      /* free space */
> > +#define XFS_FMR_OWN_UNKNOWN	FMR_OWN_UNKNOWN   /* unknown owner */
> > +#define XFS_FMR_OWN_FS		FMR_OWNER('X', 1) /* static fs metadata */
> > +#define XFS_FMR_OWN_LOG		FMR_OWNER('X', 2) /* journalling log */
> > +#define XFS_FMR_OWN_AG		FMR_OWNER('X', 3) /* per-AG metadata */
> > +#define XFS_FMR_OWN_INOBT	FMR_OWNER('X', 4) /* inode btree blocks */
> > +#define XFS_FMR_OWN_INODES	FMR_OWNER('X', 5) /* inodes */
> > +#define XFS_FMR_OWN_REFC	FMR_OWNER('X', 6) /* refcount tree */
> > +#define XFS_FMR_OWN_COW		FMR_OWNER('X', 7) /* cow staging */
> > +#define XFS_FMR_OWN_DEFECTIVE	FMR_OWNER('X', 8) /* bad blocks */
> > +
> >  /*
> >   * Structure for XFS_IOC_FSSETDM.
> >   * For use by backup and restore programs to set the XFS on-disk inode
> > @@ -502,6 +514,7 @@ typedef struct xfs_swapext
> >  #define XFS_IOC_GETBMAPX	_IOWR('X', 56, struct getbmap)
> >  #define XFS_IOC_ZERO_RANGE	_IOW ('X', 57, struct xfs_flock64)
> >  #define XFS_IOC_FREE_EOFBLOCKS	_IOR ('X', 58, struct xfs_fs_eofblocks)
> > +/*	XFS_IOC_GETFSMAP ------ hoisted 59         */
> >  
> >  /*
> >   * ioctl commands that replace IRIX syssgi()'s
> > diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
> > new file mode 100644
> > index 0000000..09d6b92
> > --- /dev/null
> > +++ b/fs/xfs/xfs_fsmap.c
> > @@ -0,0 +1,782 @@
> > +/*
> > + * Copyright (C) 2017 Oracle.  All Rights Reserved.
> > + *
> > + * Author: Darrick J. Wong <darrick.wong@oracle.com>
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > + * as published by the Free Software Foundation; either version 2
> > + * of the License, or (at your option) any later version.
> > + *
> > + * This program is distributed in the hope that it would be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program; if not, write the Free Software Foundation,
> > + * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
> > + */
> > +#include "xfs.h"
> > +#include "xfs_fs.h"
> > +#include "xfs_shared.h"
> > +#include "xfs_format.h"
> > +#include "xfs_log_format.h"
> > +#include "xfs_trans_resv.h"
> > +#include "xfs_sb.h"
> > +#include "xfs_mount.h"
> > +#include "xfs_defer.h"
> > +#include "xfs_inode.h"
> > +#include "xfs_trans.h"
> > +#include "xfs_error.h"
> > +#include "xfs_btree.h"
> > +#include "xfs_rmap_btree.h"
> > +#include "xfs_trace.h"
> > +#include "xfs_log.h"
> > +#include "xfs_rmap.h"
> > +#include "xfs_alloc.h"
> > +#include "xfs_bit.h"
> > +#include <linux/fsmap.h>
> > +#include "xfs_fsmap.h"
> > +#include "xfs_refcount.h"
> > +#include "xfs_refcount_btree.h"
> > +
> > +/* Convert an xfs_fsmap to an fsmap. */
> > +void
> > +xfs_fsmap_from_internal(
> > +	struct fsmap		*dest,
> > +	struct xfs_fsmap	*src)
> > +{
> > +	dest->fmr_device = src->fmr_device;
> > +	dest->fmr_flags = src->fmr_flags;
> > +	dest->fmr_physical = BBTOB(src->fmr_physical);
> > +	dest->fmr_owner = src->fmr_owner;
> > +	dest->fmr_offset = BBTOB(src->fmr_offset);
> > +	dest->fmr_length = BBTOB(src->fmr_length);
> > +	dest->fmr_reserved[0] = 0;
> > +	dest->fmr_reserved[1] = 0;
> > +	dest->fmr_reserved[2] = 0;
> > +}
> > +
> > +/* Convert an fsmap to an xfs_fsmap. */
> > +void
> > +xfs_fsmap_to_internal(
> > +	struct xfs_fsmap	*dest,
> > +	struct fsmap		*src)
> > +{
> > +	dest->fmr_device = src->fmr_device;
> > +	dest->fmr_flags = src->fmr_flags;
> > +	dest->fmr_physical = BTOBBT(src->fmr_physical);
> > +	dest->fmr_owner = src->fmr_owner;
> > +	dest->fmr_offset = BTOBBT(src->fmr_offset);
> > +	dest->fmr_length = BTOBBT(src->fmr_length);
> > +}
> > +
> > +/* Convert an fsmap owner into an rmapbt owner. */
> > +static int
> > +xfs_fsmap_owner_to_rmap(
> > +	struct xfs_fsmap	*fmr,
> > +	struct xfs_rmap_irec	*rm)
> 
> I find the inconsistent semantics a little confusing here. E.g., the
> xfs_fsmap_[to|from]_*() helpers use consistent dest, src parameter
> ordering. Here we use the opposite. I don't care much which way we go,
> but could we use the same semantics between all of such helpers?

Okay, yeah, I'll rename the parameters to reflect src/dest and fix the
ordering to be consistent.

> > +{
> > +	if (!(fmr->fmr_flags & FMR_OF_SPECIAL_OWNER)) {
> > +		rm->rm_owner = fmr->fmr_owner;
> > +		return 0;
> > +	}
> > +
> > +	switch (fmr->fmr_owner) {
> > +	case 0:			/* "lowest owner id possible" */
> > +	case -1ULL:		/* "highest owner id possible" */
> > +		rm->rm_owner = 0;
> > +		break;
> > +	case XFS_FMR_OWN_FREE:
> > +		rm->rm_owner = XFS_RMAP_OWN_NULL;
> > +		break;
> > +	case XFS_FMR_OWN_UNKNOWN:
> > +		rm->rm_owner = XFS_RMAP_OWN_UNKNOWN;
> > +		break;
> > +	case XFS_FMR_OWN_FS:
> > +		rm->rm_owner = XFS_RMAP_OWN_FS;
> > +		break;
> > +	case XFS_FMR_OWN_LOG:
> > +		rm->rm_owner = XFS_RMAP_OWN_LOG;
> > +		break;
> > +	case XFS_FMR_OWN_AG:
> > +		rm->rm_owner = XFS_RMAP_OWN_AG;
> > +		break;
> > +	case XFS_FMR_OWN_INOBT:
> > +		rm->rm_owner = XFS_RMAP_OWN_INOBT;
> > +		break;
> > +	case XFS_FMR_OWN_INODES:
> > +		rm->rm_owner = XFS_RMAP_OWN_INODES;
> > +		break;
> > +	case XFS_FMR_OWN_REFC:
> > +		rm->rm_owner = XFS_RMAP_OWN_REFC;
> > +		break;
> > +	case XFS_FMR_OWN_COW:
> > +		rm->rm_owner = XFS_RMAP_OWN_COW;
> > +		break;
> > +	case XFS_FMR_OWN_DEFECTIVE:	/* not implemented */
> > +		/* fall through */
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +	return 0;
> > +}
> > +
> > +/* Convert an rmapbt owner into an fsmap owner. */
> > +static int
> > +xfs_fsmap_owner_from_rmap(
> > +	struct xfs_rmap_irec	*rm,
> > +	struct xfs_fsmap	*fmr)
> > +{
> > +	fmr->fmr_flags = 0;
> > +	if (!XFS_RMAP_NON_INODE_OWNER(rm->rm_owner)) {
> > +		fmr->fmr_owner = rm->rm_owner;
> > +		return 0;
> > +	}
> > +	fmr->fmr_flags |= FMR_OF_SPECIAL_OWNER;
> > +
> > +	switch (rm->rm_owner) {
> > +	case XFS_RMAP_OWN_FS:
> > +		fmr->fmr_owner = XFS_FMR_OWN_FS;
> > +		break;
> > +	case XFS_RMAP_OWN_LOG:
> > +		fmr->fmr_owner = XFS_FMR_OWN_LOG;
> > +		break;
> > +	case XFS_RMAP_OWN_AG:
> > +		fmr->fmr_owner = XFS_FMR_OWN_AG;
> > +		break;
> > +	case XFS_RMAP_OWN_INOBT:
> > +		fmr->fmr_owner = XFS_FMR_OWN_INOBT;
> > +		break;
> > +	case XFS_RMAP_OWN_INODES:
> > +		fmr->fmr_owner = XFS_FMR_OWN_INODES;
> > +		break;
> > +	case XFS_RMAP_OWN_REFC:
> > +		fmr->fmr_owner = XFS_FMR_OWN_REFC;
> > +		break;
> > +	case XFS_RMAP_OWN_COW:
> > +		fmr->fmr_owner = XFS_FMR_OWN_COW;
> > +		break;
> > +	default:
> > +		return -EFSCORRUPTED;
> > +	}
> > +	return 0;
> > +}
> > +
> > +/* getfsmap query state */
> > +struct xfs_getfsmap_info {
> > +	struct xfs_fsmap_head	*head;
> > +	struct xfs_fsmap	*rkey_low;	/* lowest key */
> > +	xfs_fsmap_format_t	formatter;	/* formatting fn */
> > +	void			*format_arg;	/* format buffer */
> > +	bool			last;		/* last extent? */
> > +	xfs_daddr_t		next_daddr;	/* next daddr we expect */
> > +	u32			dev;		/* device id */
> > +	u64			missing_owner;	/* owner of holes */
> > +
> > +	xfs_agnumber_t		agno;		/* AG number, if applicable */
> > +	struct xfs_buf		*agf_bp;	/* AGF, for refcount queries */
> > +	struct xfs_rmap_irec	low;		/* low rmap key */
> > +	struct xfs_rmap_irec	high;		/* high rmap key */
> > +};
> > +
> > +/* Associate a device with a getfsmap handler. */
> > +struct xfs_getfsmap_dev {
> > +	u32			dev;
> > +	int			(*fn)(struct xfs_trans *tp,
> > +				      struct xfs_fsmap *keys,
> > +				      struct xfs_getfsmap_info *info);
> > +};
> > +
> > +/* Compare two getfsmap device handlers. */
> > +static int
> > +xfs_getfsmap_dev_compare(
> > +	const void			*p1,
> > +	const void			*p2)
> > +{
> > +	const struct xfs_getfsmap_dev	*d1 = p1;
> > +	const struct xfs_getfsmap_dev	*d2 = p2;
> > +
> > +	return d1->dev - d2->dev;
> > +}
> > +
> > +/* Compare a record against our starting point */
> > +static bool
> > +xfs_getfsmap_rec_before_low_key(
> > +	struct xfs_getfsmap_info	*info,
> > +	struct xfs_rmap_irec		*rec)
> > +{
> > +	uint64_t			x, y;
> > +
> > +	if (rec->rm_startblock < info->low.rm_startblock)
> > +		return true;
> > +	if (rec->rm_startblock > info->low.rm_startblock)
> > +		return false;
> > +
> > +	if (rec->rm_owner < info->low.rm_owner)
> > +		return true;
> > +	if (rec->rm_owner > info->low.rm_owner)
> > +		return false;
> > +
> > +	x = xfs_rmap_irec_offset_pack(rec);
> > +	y = xfs_rmap_irec_offset_pack(&info->low);
> 
> It looks like these functions incorporate flags bits into the offset. Is
> that intentional? If so.. comment?

/*
 * Separate data and attr rmaps into non-overlapping parts of the 2^64
 * offset space to simplify the comparison logic.  The on-disk rmapbt
 * code already has bit packing helpers that do this, so reuse them
 * here.
 */

> > +	if (x < y)
> > +		return true;
> > +	return false;
> > +}
> > +
> > +/* Decide if this mapping is shared. */
> > +STATIC int
> > +xfs_getfsmap_is_shared(
> > +	struct xfs_trans		*tp,
> > +	struct xfs_getfsmap_info	*info,
> > +	struct xfs_rmap_irec		*rec,
> > +	bool				*stat)
> > +{
> > +	struct xfs_mount		*mp = tp->t_mountp;
> > +	struct xfs_btree_cur		*cur;
> > +	xfs_agblock_t			fbno;
> > +	xfs_extlen_t			flen;
> > +	int				error;
> > +
> > +	*stat = false;
> > +	if (!xfs_sb_version_hasreflink(&mp->m_sb))
> > +		return 0;
> > +	/* rt files will have agno set to NULLAGNUMBER */
> > +	if (info->agno == NULLAGNUMBER)
> > +		return 0;
> > +
> > +	/* Are there any shared blocks here? */
> > +	flen = 0;
> > +	cur = xfs_refcountbt_init_cursor(mp, tp, info->agf_bp,
> > +			info->agno, NULL);
> > +
> > +	error = xfs_refcount_find_shared(cur, rec->rm_startblock,
> > +			rec->rm_blockcount, &fbno, &flen, false);
> > +
> > +	xfs_btree_del_cursor(cur, error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
> > +	if (error)
> > +		return error;
> > +
> > +	*stat = flen > 0;
> > +	return 0;
> > +}
> > +
> > +/*
> > + * Format a reverse mapping for getfsmap, having translated rm_startblock
> > + * into the appropriate daddr units.
> > + */
> > +STATIC int
> > +xfs_getfsmap_helper(
> > +	struct xfs_trans		*tp,
> > +	struct xfs_getfsmap_info	*info,
> > +	struct xfs_rmap_irec		*rec,
> > +	xfs_daddr_t			rec_daddr)
> > +{
> > +	struct xfs_fsmap		fmr;
> > +	struct xfs_mount		*mp = tp->t_mountp;
> > +	xfs_daddr_t			key_end;
> > +	bool				shared;
> > +	int				error;
> > +
> > +	if (fatal_signal_pending(current))
> > +		return -EAGAIN;
> > +
> 
> I wonder if -EINTR is more appropriate here..?

Practically I doubt it matters since the process is going to die anyway,
but you're right that EINTR is more appropriate.

> > +	/*
> > +	 * Filter out records that start before our startpoint, if the
> > +	 * caller requested that.
> > +	 */
> > +	if (xfs_getfsmap_rec_before_low_key(info, rec)) {
> > +		rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
> > +		if (info->next_daddr < rec_daddr)
> > +			info->next_daddr = rec_daddr;
> > +		return XFS_BTREE_QUERY_RANGE_CONTINUE;
> > +	}
> > +
> > +	/*
> > +	 * If the caller passed in a length with the low record and
> > +	 * the record represents a file data extent, we incremented
> > +	 * the offset in the low key by the length in the hopes of
> > +	 * finding reverse mappings for the physical blocks we just
> > +	 * saw.  We did /not/ increment next_daddr by the length
> > +	 * because the range query would not be able to find shared
> > +	 * extents within the same physical block range.
> > +	 *
> > +	 * However, the extent we've been fed could have a startblock
> > +	 * past the passed-in low record.  If this is the case,
> > +	 * advance next_daddr to the end of the passed-in low record
> > +	 * so we don't report the extent prior to this extent as
> > +	 * free.
> > +	 */
> > +	key_end = info->rkey_low->fmr_physical + info->rkey_low->fmr_length;
> > +	if (info->dev == info->rkey_low->fmr_device &&
> > +	    info->next_daddr < key_end && rec_daddr >= key_end)
> > +		info->next_daddr = key_end;
> > +
> 
> Hmm, so I think I follow what this is trying to do..
> 
> In the case where we left off on a file mapping, we bump the offset of
> the passed in low key but next_daddr remains at the same physical block
> because we could have more mappings there. If we don't, however, and the
> next mapping occurs at a higher physical block, we need to make sure we
> don't map the previous range as free space. So we bump next_daddr here
> to make sure that if free space does exist, it shown to start at the end
> of the previous mapping. Yes?

Yes.

> If I'm following that correctly, what about the case where we have
> bumped fmr_physical? It doesn't look like we've reset fmr_length, so
> couldn't this cause us to skip legitimate free space if for e.g. the
> current record is much farther ahead?

rkey_low->fmr_{physical,length} are from the low key passed in from
userspace, and therefore, key_end is the physical end of the unadjusted
low key provided by userspace.

dkey[0] is the low key after its fmr_physical/fmr_offset value has been
adjusted; and next_daddr's first value is dkey[0].fmr_physical.
Therefore, next_daddr points to the first block of the low key in the
data fsmap case; or points to the next block after the low key in all
other cases.

So to answer your question quickly, key_end is always computed from
non-bumped values.

This is kind of confusing, so let's work a few examples...

Say userspace gives us head->fmh_keys = [(8:0, 24, 8, OWN_INOBT, 0), (-1)].
That means that the last record userspace saw was 8 sectors of inobt
starting at sector 24.  Then set info.rkey_low = &head->fmh_keys[0].
Because inobt is a special owner, dkeys[0] = (8:0, 32, 8, OWN_INOBT, 0),
and next_daddr = 32.  We should probably decrease the length from 8 to 0
but the length is not a key field so it doesn't really matter.

Say that _getfsmap_helper is passed the rmap (8:0, 64, 8, OWN_REFCOUNT, 0).
When we get to line 318, set key_end = 24 + 8.

The test
if (devices match && next_daddr < key_end && rec_daddr >= key_end)
becomes
if (devices match && 32 < 32 && we don't care after this point)

So the branch test is false and we don't set next_daddr = key_end.
We synthesize an fsmap record for free space spanning sector 32 to 64,
emit the OWN_REFCOUNT record, and set next_daddr = 72 and move on.

[If you're wondering how it works for regular data extents, keep
reading.]

Second example: fmh_keys = [(8:0, 24, 16, 128, 0), (-1)].  Now we have
that userspace last saw 16 sectors of file data (inode 128, offset 0)
starting at block 24.  We again set info.rkey_low = &head->fmh_keys[0].
Because the lowkey is a data extent, dkeys[0] = (8:0, 24, 16, 128, 16),
and next_daddr = 24.

The first rmap passed to _getfsmap_helper is the same (8:0, 24, 16, 128,
0) that we emitted as the last fsmap returned from the previous getfsmap
call, because we started the query_range at dkeys[0].physical, which is
24.  xfs_getfsmap_rec_before_low_key notices that the key of this record
is less than the rkey_low that was passed in and so increments
next_daddr to 40.

Assuming _getfsmap_helper is passed the same refcount rmap as before.
rec_daddr = 64, and when we get to line 318, key_end = 24 + 16.

The test is now:
if (devices match && 40 < 40 && 64 >= 40)
So we leave next_daddr at 40.

The correct output here is to synthesize an fsmap record for free space
between 40-64, and then to emit the refcount record at 64.

Third example: fmh_keys = [(8:0, 24, 16, 128, 0), (-1)] and next_daddr = 24
as before.  _getfsmap_helper again sees (8:0, 24, 16, 128, 0) and sets
next_daddr = 40.

This time, however, _getfsmap_helper is passed (8:0, 32, 8, 129, 0),
which is 8 sectors of inode 129's data at offset 0.  rec_daddr = 32,
key_end = 24 + 16 as before.

The test is now:
if (devices match && 40 < 40 && 32 >= 40)
So we again leave next_daddr at 40, then emit the fsmap for inode 129.

> > +	/* Are we just counting mappings? */
> > +	if (info->head->fmh_count == 0) {
> > +		if (rec_daddr > info->next_daddr)
> > +			info->head->fmh_entries++;
> > +
> > +		if (info->last)
> > +			return XFS_BTREE_QUERY_RANGE_CONTINUE;
> > +
> > +		info->head->fmh_entries++;
> > +
> > +		rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
> > +		if (info->next_daddr < rec_daddr)
> > +			info->next_daddr = rec_daddr;
> > +		return XFS_BTREE_QUERY_RANGE_CONTINUE;
> > +	}
> > +
> > +	/*
> > +	 * If the record starts past the last physical block we saw,
> > +	 * then we've found some free space.  Report that too.
> > +	 */
> > +	if (rec_daddr > info->next_daddr) {
> > +		if (info->head->fmh_entries >= info->head->fmh_count)
> > +			return XFS_BTREE_QUERY_RANGE_ABORT;
> > +
> > +		trace_xfs_fsmap_mapping(mp, info->dev, info->agno,
> > +				XFS_DADDR_TO_FSB(mp, info->next_daddr),
> > +				XFS_DADDR_TO_FSB(mp, rec_daddr -
> > +						info->next_daddr),
> > +				info->missing_owner, 0);
> > +
> > +		fmr.fmr_device = info->dev;
> > +		fmr.fmr_physical = info->next_daddr;
> > +		fmr.fmr_owner = info->missing_owner;
> > +		fmr.fmr_offset = 0;
> > +		fmr.fmr_length = rec_daddr - info->next_daddr;
> > +		fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
> > +		error = info->formatter(&fmr, info->format_arg);
> > +		if (error)
> > +			return error;
> > +		info->head->fmh_entries++;
> > +	}
> > +
> > +	if (info->last)
> > +		goto out;
> > +
> > +	/* Fill out the extent we found */
> > +	if (info->head->fmh_entries >= info->head->fmh_count)
> > +		return XFS_BTREE_QUERY_RANGE_ABORT;
> > +
> > +	trace_xfs_fsmap_mapping(mp, info->dev, info->agno,
> > +			rec->rm_startblock, rec->rm_blockcount, rec->rm_owner,
> > +			rec->rm_offset);
> > +
> > +	fmr.fmr_device = info->dev;
> > +	fmr.fmr_physical = rec_daddr;
> > +	error = xfs_fsmap_owner_from_rmap(rec, &fmr);
> > +	if (error)
> > +		return error;
> > +	fmr.fmr_offset = XFS_FSB_TO_BB(mp, rec->rm_offset);
> > +	fmr.fmr_length = XFS_FSB_TO_BB(mp, rec->rm_blockcount);
> > +	if (rec->rm_flags & XFS_RMAP_UNWRITTEN)
> > +		fmr.fmr_flags |= FMR_OF_PREALLOC;
> > +	if (rec->rm_flags & XFS_RMAP_ATTR_FORK)
> > +		fmr.fmr_flags |= FMR_OF_ATTR_FORK;
> > +	if (rec->rm_flags & XFS_RMAP_BMBT_BLOCK)
> > +		fmr.fmr_flags |= FMR_OF_EXTENT_MAP;
> > +	if (fmr.fmr_flags == 0) {
> > +		error = xfs_getfsmap_is_shared(tp, info, rec, &shared);
> > +		if (error)
> > +			return error;
> > +		if (shared)
> > +			fmr.fmr_flags |= FMR_OF_SHARED;
> > +	}
> > +	error = info->formatter(&fmr, info->format_arg);
> > +	if (error)
> > +		return error;
> > +	info->head->fmh_entries++;
> > +
> > +out:
> > +	rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
> > +	if (info->next_daddr < rec_daddr)
> > +		info->next_daddr = rec_daddr;
> > +	return XFS_BTREE_QUERY_RANGE_CONTINUE;
> > +}
> > +
> > +/* Transform a rmapbt irec into a fsmap */
> > +STATIC int
> > +xfs_getfsmap_datadev_helper(
> > +	struct xfs_btree_cur		*cur,
> > +	struct xfs_rmap_irec		*rec,
> > +	void				*priv)
> > +{
> > +	struct xfs_mount		*mp = cur->bc_mp;
> > +	struct xfs_getfsmap_info	*info = priv;
> > +	xfs_fsblock_t			fsb;
> > +	xfs_daddr_t			rec_daddr;
> > +
> > +	fsb = XFS_AGB_TO_FSB(mp, cur->bc_private.a.agno, rec->rm_startblock);
> > +	rec_daddr = XFS_FSB_TO_DADDR(mp, fsb);
> > +
> > +	return xfs_getfsmap_helper(cur->bc_tp, info, rec, rec_daddr);
> > +}
> > +
> > +/* Transform a absolute-startblock rmap (rtdev, logdev) into a fsmap */
> > +STATIC int
> > +xfs_getfsmap_rtdev_helper(
> > +	struct xfs_btree_cur		*cur,
> > +	struct xfs_rmap_irec		*rec,
> > +	void				*priv)
> > +{
> > +	struct xfs_mount		*mp = cur->bc_mp;
> > +	struct xfs_getfsmap_info	*info = priv;
> > +	xfs_daddr_t			rec_daddr;
> > +
> > +	rec_daddr = XFS_FSB_TO_BB(mp, rec->rm_startblock);
> > +
> > +	return xfs_getfsmap_helper(cur->bc_tp, info, rec, rec_daddr);
> > +}
> > +
> > +/* Set rmap flags based on the getfsmap flags */
> > +static void
> > +xfs_getfsmap_set_irec_flags(
> > +	struct xfs_rmap_irec	*irec,
> > +	struct xfs_fsmap	*fmr)
> > +{
> > +	irec->rm_flags = 0;
> > +	if (fmr->fmr_flags & FMR_OF_ATTR_FORK)
> > +		irec->rm_flags |= XFS_RMAP_ATTR_FORK;
> > +	if (fmr->fmr_flags & FMR_OF_EXTENT_MAP)
> > +		irec->rm_flags |= XFS_RMAP_BMBT_BLOCK;
> > +	if (fmr->fmr_flags & FMR_OF_PREALLOC)
> > +		irec->rm_flags |= XFS_RMAP_UNWRITTEN;
> > +}
> > +
> > +/* Execute a getfsmap query against the log device. */
> > +STATIC int
> > +xfs_getfsmap_logdev(
> > +	struct xfs_trans		*tp,
> > +	struct xfs_fsmap		*keys,
> > +	struct xfs_getfsmap_info	*info)
> > +{
> > +	struct xfs_mount		*mp = tp->t_mountp;
> > +	struct xfs_fsmap		*dkey_low = keys;
> > +	struct xfs_btree_cur		cur;
> > +	struct xfs_rmap_irec		rmap;
> > +	int				error;
> > +
> > +	/* Set up search keys */
> > +	info->low.rm_startblock = XFS_BB_TO_FSBT(mp, dkey_low->fmr_physical);
> > +	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
> > +	error = xfs_fsmap_owner_to_rmap(keys, &info->low);
> > +	if (error)
> > +		return error;
> > +	info->low.rm_blockcount = 0;
> > +	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
> > +
> > +	error = xfs_fsmap_owner_to_rmap(keys + 1, &info->high);
> > +	if (error)
> > +		return error;
> > +	info->high.rm_startblock = -1U;
> > +	info->high.rm_owner = ULLONG_MAX;
> > +	info->high.rm_offset = ULLONG_MAX;
> > +	info->high.rm_blockcount = 0;
> > +	info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;
> > +	info->missing_owner = XFS_FMR_OWN_FREE;
> > +
> > +	trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
> > +			info->low.rm_startblock,
> > +			info->low.rm_blockcount,
> > +			info->low.rm_owner,
> > +			info->low.rm_offset);
> > +
> > +	trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
> > +			info->high.rm_startblock,
> > +			info->high.rm_blockcount,
> > +			info->high.rm_owner,
> > +			info->high.rm_offset);
> > +
> > +
> > +	if (dkey_low->fmr_physical > 0)
> > +		return 0;
> > +
> 
> A comment to point out we're fabricating an rmap record here would be

Ok.

> nice. Also, (how) do we handle/report internal log blocks?

The AG containing the log will have an rmapbt record for RMAP_OWN_LOG,
so that'll be in with the datadev records.

> > +	rmap.rm_startblock = 0;
> > +	rmap.rm_blockcount = mp->m_sb.sb_logblocks;
> > +	rmap.rm_owner = XFS_RMAP_OWN_LOG;
> > +	rmap.rm_offset = 0;
> > +	rmap.rm_flags = 0;
> > +
> > +	cur.bc_mp = mp;
> > +	cur.bc_tp = tp;
> > +	return xfs_getfsmap_rtdev_helper(&cur, &rmap, info);
> > +}
> > +
> > +/* Execute a getfsmap query against the regular data device. */
> > +STATIC int
> > +xfs_getfsmap_datadev(
> > +	struct xfs_trans		*tp,
> > +	struct xfs_fsmap		*keys,
> > +	struct xfs_getfsmap_info	*info)
> > +{
> > +	struct xfs_mount		*mp = tp->t_mountp;
> > +	struct xfs_btree_cur		*bt_cur = NULL;
> > +	struct xfs_fsmap		*dkey_low;
> > +	struct xfs_fsmap		*dkey_high;
> > +	xfs_fsblock_t			start_fsb;
> > +	xfs_fsblock_t			end_fsb;
> > +	xfs_agnumber_t			start_ag;
> > +	xfs_agnumber_t			end_ag;
> > +	xfs_daddr_t			eofs;
> > +	int				error = 0;
> > +
> > +	dkey_low = keys;
> > +	dkey_high = keys + 1;
> > +	eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks);
> > +	if (dkey_low->fmr_physical >= eofs)
> > +		return 0;
> > +	if (dkey_high->fmr_physical >= eofs)
> > +		dkey_high->fmr_physical = eofs - 1;
> > +	start_fsb = XFS_DADDR_TO_FSB(mp, dkey_low->fmr_physical);
> > +	end_fsb = XFS_DADDR_TO_FSB(mp, dkey_high->fmr_physical);
> > +
> > +	/* Set up search keys */
> 
> I think we could use slightly better comments here and below just to
> point out why we set low/high to these values. E.g., something like:
> 
> /*
>  * Convert the fsmap low/high keys to AG based keys. Initialize low to
>  * the fsmap low key and max out the high key to the end of the AG.
>  */

Added.

> > +	info->low.rm_startblock = XFS_FSB_TO_AGBNO(mp, start_fsb);
> > +	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
> > +	error = xfs_fsmap_owner_to_rmap(dkey_low, &info->low);
> > +	if (error)
> > +		return error;
> > +	info->low.rm_blockcount = 0;
> > +	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
> > +
> > +	info->high.rm_startblock = -1U;
> > +	info->high.rm_owner = ULLONG_MAX;
> > +	info->high.rm_offset = ULLONG_MAX;
> > +	info->high.rm_blockcount = 0;
> > +	info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;
> > +	info->missing_owner = XFS_FMR_OWN_FREE;
> > +
> > +	start_ag = XFS_FSB_TO_AGNO(mp, start_fsb);
> > +	end_ag = XFS_FSB_TO_AGNO(mp, end_fsb);
> > +
> > +	/* Query each AG */
> > +	for (info->agno = start_ag; info->agno <= end_ag; info->agno++) {
> 
> /*
>  * Incorporate the fsmap high key for the last AG.
>  */

I prefer the wording:

"Set the AG high key from the fsmap high key if this is the last AG that
we're querying."

> > +		if (info->agno == end_ag) {
> > +			info->high.rm_startblock = XFS_FSB_TO_AGBNO(mp,
> > +					end_fsb);
> > +			info->high.rm_offset = XFS_BB_TO_FSBT(mp,
> > +					dkey_high->fmr_offset);
> > +			error = xfs_fsmap_owner_to_rmap(dkey_high, &info->high);
> > +			if (error)
> > +				goto err;
> > +			xfs_getfsmap_set_irec_flags(&info->high, dkey_high);
> > +		}
> > +
> > +		if (bt_cur) {
> > +			xfs_btree_del_cursor(bt_cur, XFS_BTREE_NOERROR);
> > +			bt_cur = NULL;
> > +			info->agf_bp = NULL;
> > +		}
> > +
> > +		error = xfs_alloc_read_agf(mp, tp, info->agno, 0,
> > +				&info->agf_bp);
> > +		if (error)
> > +			goto err;
> > +
> > +		trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
> > +				info->low.rm_startblock,
> > +				info->low.rm_blockcount,
> > +				info->low.rm_owner,
> > +				info->low.rm_offset);
> > +
> > +		trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
> > +				info->high.rm_startblock,
> > +				info->high.rm_blockcount,
> > +				info->high.rm_owner,
> > +				info->high.rm_offset);
> > +
> > +		bt_cur = xfs_rmapbt_init_cursor(mp, tp, info->agf_bp,
> > +				info->agno);
> > +		error = xfs_rmap_query_range(bt_cur, &info->low, &info->high,
> > +				xfs_getfsmap_datadev_helper, info);
> > +		if (error)
> > +			goto err;
> > +
> 
> /*
>  * Reset the low key for the start of the next AG.
>  */

"Set the AG low key to the start of the AG prior to moving on to the
next AG."

> > +		if (info->agno == start_ag) {
> > +			info->low.rm_startblock = 0;
> > +			info->low.rm_owner = 0;
> > +			info->low.rm_offset = 0;
> > +			info->low.rm_flags = 0;
> > +		}
> > +	}
> 
> Do I follow this loop correctly in that we lock each AGF buffer as we
> progress through the fs, holding the locks until we've traversed the
> entire fs? If so, is that really necessary or can we release the
> previous previous buffer once we move on to the next AG? Not doing so
> seems like it makes this a very heavyweight operation...

Yes, it should _trans_brelse the AGF after deleting the rmapbt cursor.
The AGF buffers get dumped when we cancel the transaction, but there's
no reason to hang on to them any longer than we have to.

> > +
> > +	/* Report any free space at the end of the AG */
> > +	info->last = true;
> > +	error = xfs_getfsmap_datadev_helper(bt_cur, &info->high, info);
> > +	if (error)
> > +		goto err;
> > +
> > +err:
> > +	if (bt_cur)
> > +		xfs_btree_del_cursor(bt_cur, error < 0 ? XFS_BTREE_ERROR :
> > +							 XFS_BTREE_NOERROR);
> > +	if (info->agf_bp)
> > +		info->agf_bp = NULL;
> > +
> > +	return error;
> > +}
> > +
> > +/* Do we recognize the device? */
> > +STATIC bool
> > +xfs_getfsmap_is_valid_device(
> > +	struct xfs_mount	*mp,
> > +	struct xfs_fsmap	*fm)
> > +{
> > +	if (fm->fmr_device == 0 || fm->fmr_device == UINT_MAX ||
> > +	    fm->fmr_device == new_encode_dev(mp->m_ddev_targp->bt_dev))
> > +		return true;
> > +	if (mp->m_logdev_targp &&
> > +	    fm->fmr_device == new_encode_dev(mp->m_logdev_targp->bt_dev))
> > +		return true;
> > +	return false;
> > +}
> > +
> > +/* Ensure that the low key is less than the high key. */
> > +STATIC bool
> > +xfs_getfsmap_check_keys(
> > +	struct xfs_fsmap		*low_key,
> > +	struct xfs_fsmap		*high_key)
> > +{
> > +	if (low_key->fmr_device > high_key->fmr_device)
> > +		return false;
> > +	if (low_key->fmr_device < high_key->fmr_device)
> > +		return true;
> > +
> > +	if (low_key->fmr_physical > high_key->fmr_physical)
> > +		return false;
> > +	if (low_key->fmr_physical < high_key->fmr_physical)
> > +		return true;
> > +
> > +	if (low_key->fmr_owner > high_key->fmr_owner)
> > +		return false;
> > +	if (low_key->fmr_owner < high_key->fmr_owner)
> > +		return true;
> > +
> > +	if (low_key->fmr_offset > high_key->fmr_offset)
> > +		return false;
> > +	if (low_key->fmr_offset < high_key->fmr_offset)
> > +		return true;
> > +
> > +	return false;
> > +}
> > +
> > +#define XFS_GETFSMAP_DEVS	3
> 
> Why 3 (looks like we use 2 below)?

A subsequent patch adds reporting for the realtime device, but I
probably just merged the extra array cell in here by accident.

> > +/*
> > + * Get filesystem's extents as described in head, and format for
> > + * output.  Calls formatter to fill the user's buffer until all
> > + * extents are mapped, until the passed-in head->fmh_count slots have
> > + * been filled, or until the formatter short-circuits the loop, if it
> > + * is tracking filled-in extents on its own.
> > + */
> > +int
> > +xfs_getfsmap(
> > +	struct xfs_mount		*mp,
> > +	struct xfs_fsmap_head		*head,
> > +	xfs_fsmap_format_t		formatter,
> > +	void				*arg)
> > +{
> > +	struct xfs_trans		*tp = NULL;
> > +	struct xfs_fsmap		*rkey_low;	/* request keys */
> > +	struct xfs_fsmap		*rkey_high;
> > +	struct xfs_fsmap		dkeys[2];	/* per-dev keys */
> > +	struct xfs_getfsmap_dev		handlers[XFS_GETFSMAP_DEVS];
> > +	struct xfs_getfsmap_info	info = {0};
> > +	int				i;
> > +	int				error = 0;
> > +
> > +	if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
> > +		return -EOPNOTSUPP;
> > +	if (head->fmh_iflags & ~FMH_IF_VALID)
> > +		return -EINVAL;
> > +	rkey_low = head->fmh_keys;
> > +	rkey_high = rkey_low + 1;
> 
> This is more clear IMO if we just use fmh_keys[0] and fmh_keys[1] (the
> same pattern exists in one or two other places as well..).

Ok.

> > +	if (!xfs_getfsmap_is_valid_device(mp, rkey_low) ||
> > +	    !xfs_getfsmap_is_valid_device(mp, rkey_high))
> > +		return -EINVAL;
> > +
> > +	head->fmh_entries = 0;
> > +
> > +	/* Set up our device handlers. */
> > +	memset(handlers, 0, sizeof(handlers));
> > +	handlers[0].dev = new_encode_dev(mp->m_ddev_targp->bt_dev);
> > +	handlers[0].fn = xfs_getfsmap_datadev;
> > +	if (mp->m_logdev_targp != mp->m_ddev_targp) {
> > +		handlers[1].dev = new_encode_dev(mp->m_logdev_targp->bt_dev);
> > +		handlers[1].fn = xfs_getfsmap_logdev;
> > +	}
> > +
> > +	xfs_sort(handlers, XFS_GETFSMAP_DEVS, sizeof(struct xfs_getfsmap_dev),
> > +			xfs_getfsmap_dev_compare);
> > +
> > +	/*
> > +	 * Since we allow the user to copy the last mapping from a previous
> > +	 * call into the low key slot, we have to advance the low key by
> > +	 * whatever the reported length is.  If the offset field doesn't apply,
> > +	 * move up the start block to the next extent and start over with the
> > +	 * lowest owner/offset possible; otherwise it's file data, so move up
> > +	 * the offset only.
> > +	 */
> > +	dkeys[0] = *rkey_low;
> > +	if (dkeys[0].fmr_flags & (FMR_OF_SPECIAL_OWNER | FMR_OF_EXTENT_MAP)) {
> > +		dkeys[0].fmr_physical += dkeys[0].fmr_length;
> > +		dkeys[0].fmr_owner = 0;
> > +		dkeys[0].fmr_offset = 0;
> 
> Should these values already be zero in this case? 

fmr_owner could be anything (special owner or any inode number) coming
in, so we need the fsmap key owner to be zero.  fmr_offset is poorly
defined for special/bmbt rmaps, but generally we write a zero and ignore
anything coming in.

<shrug> I suppose we could be stricter about returning EINVAL for
!offset in these two cases.

> > +	} else
> > +		dkeys[0].fmr_offset += dkeys[0].fmr_length;
> > +	memset(&dkeys[1], 0xFF, sizeof(struct xfs_fsmap));
> 
> Ok, it took me a bit to grok this hunk for some reason. I had to come
> back to it after reading deeper into the code. It could just be me, but
> something like the following comment helps me understand it a bit better
> (feel free to take it entirely, reword/update the existing comment or
> just ignore):
> 
> /*
>  * To continue where we left off, we allow userspace to use the last
>  * mapping from a previous call as the low key of the next. This is
>  * identified by a non-zero length in the low key. We have to increment
>  * the low key in this scenario to ensure we don't return the same
>  * mapping again, and instead return the very next mapping.
>  *
>  * If the low key mapping refers to fs owned blocks, bump the physical                                                                                
>  * offset as there can be no other mapping for the same physical block                                                                                
>  * range. If the mapping refers to file data, however, the same physical                                                                              
>  * blocks could be mapped to several other files/offsets. According to                                                                                
>  * rmapbt record ordering, the minimal next possible record for the                                                                                   
>  * block range is the next starting offset in the same inode. Therefore,                                                                              
>  * bump the file offset to continue the search appropriately.     
>  */

Almost -- I'll reword the second paragraph as follows:

"If the low key mapping refers to file data, the same physical blocks
could be mapped to several other files/offsets. According to rmapbt
record ordering, the minimal next possible record for the block range is
the next starting offset in the same inode. Therefore, bump the file
offset to continue the search appropriately.  For all other low key
mapping types (attr blocks, metadata), bump the physical offset as there
can be no other mapping for the same physical block range."

Basically, I consider extended attributes to be owned by the files, not
by the fs.

> > +
> > +	if (!xfs_getfsmap_check_keys(dkeys, rkey_high))
> > +		return -EINVAL;
> > +
> > +	info.rkey_low = rkey_low;
> > +	info.formatter = formatter;
> > +	info.format_arg = arg;
> > +	info.head = head;
> > +
> > +	/* For each device we support... */
> > +	for (i = 0; i < XFS_GETFSMAP_DEVS; i++) {
> > +		/* Is this device within the range the user asked for? */
> > +		if (!handlers[i].fn)
> > +			continue;
> > +		if (rkey_low->fmr_device > handlers[i].dev)
> > +			continue;
> > +		if (rkey_high->fmr_device < handlers[i].dev)
> > +			break;
> > +
> > +		/*
> > +		 * If this device number matches the high key, we have
> > +		 * to pass the high key to the handler to limit the
> > +		 * query results.  If the device number exceeds the
> > +		 * low key, zero out the low key so that we get
> > +		 * everything from the beginning.
> > +		 */
> > +		if (handlers[i].dev == rkey_high->fmr_device)
> > +			dkeys[1] = *rkey_high;
> > +		if (handlers[i].dev > rkey_low->fmr_device)
> > +			memset(&dkeys[0], 0, sizeof(struct xfs_fsmap));
> > +
> > +		error = xfs_trans_alloc_empty(mp, &tp);
> > +		if (error)
> > +			break;
> > +
> > +		info.next_daddr = dkeys[0].fmr_physical;
> > +		info.dev = handlers[i].dev;
> > +		info.last = false;
> > +		info.agno = NULLAGNUMBER;
> > +		error = handlers[i].fn(tp, dkeys, &info);
> > +		if (error)
> > +			break;
> > +		xfs_trans_cancel(tp);
> > +		tp = NULL;
> > +	}
> > +
> > +	if (tp)
> > +		xfs_trans_cancel(tp);
> > +	head->fmh_oflags = FMH_OF_DEV_T;
> > +	return error;
> > +}
> > diff --git a/fs/xfs/xfs_fsmap.h b/fs/xfs/xfs_fsmap.h
> > new file mode 100644
> > index 0000000..1943047
> > --- /dev/null
> > +++ b/fs/xfs/xfs_fsmap.h
> > @@ -0,0 +1,51 @@
> > +/*
> > + * Copyright (C) 2017 Oracle.  All Rights Reserved.
> > + *
> > + * Author: Darrick J. Wong <darrick.wong@oracle.com>
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > + * as published by the Free Software Foundation; either version 2
> > + * of the License, or (at your option) any later version.
> > + *
> > + * This program is distributed in the hope that it would be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program; if not, write the Free Software Foundation,
> > + * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
> > + */
> > +#ifndef __XFS_FSMAP_H__
> > +#define	__XFS_FSMAP_H__
> > +
> > +/* internal fsmap representation */
> > +struct xfs_fsmap {
> > +	dev_t		fmr_device;	/* device id */
> > +	uint32_t	fmr_flags;	/* mapping flags */
> > +	uint64_t	fmr_physical;	/* device offset of segment */
> > +	uint64_t	fmr_owner;	/* owner id */
> > +	xfs_fileoff_t	fmr_offset;	/* file offset of segment */
> > +	xfs_filblks_t	fmr_length;	/* length of segment, blocks */
> > +};
> > +
> > +struct xfs_fsmap_head {
> > +	uint32_t	fmh_iflags;	/* control flags */
> > +	uint32_t	fmh_oflags;	/* output flags */
> > +	unsigned int	fmh_count;	/* # of entries in array incl. input */
> > +	unsigned int	fmh_entries;	/* # of entries filled in (output). */
> > +
> > +	struct xfs_fsmap fmh_keys[2];	/* low and high keys */
> > +};
> > +
> > +void xfs_fsmap_from_internal(struct fsmap *dest, struct xfs_fsmap *src);
> > +void xfs_fsmap_to_internal(struct xfs_fsmap *dest, struct fsmap *src);
> > +
> > +/* fsmap to userspace formatter - copy to user & advance pointer */
> > +typedef int (*xfs_fsmap_format_t)(struct xfs_fsmap *, void *);
> > +
> > +int xfs_getfsmap(struct xfs_mount *mp, struct xfs_fsmap_head *head,
> > +		xfs_fsmap_format_t formatter, void *arg);
> > +
> > +#endif /* __XFS_FSMAP_H__ */
> > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> > index c67cfb4..bbe1b58 100644
> > --- a/fs/xfs/xfs_ioctl.c
> > +++ b/fs/xfs/xfs_ioctl.c
> > @@ -41,6 +41,9 @@
> >  #include "xfs_trans.h"
> >  #include "xfs_pnfs.h"
> >  #include "xfs_acl.h"
> > +#include "xfs_btree.h"
> > +#include <linux/fsmap.h>
> > +#include "xfs_fsmap.h"
> >  
> >  #include <linux/capability.h>
> >  #include <linux/dcache.h>
> > @@ -1607,6 +1610,103 @@ xfs_ioc_getbmapx(
> >  	return 0;
> >  }
> >  
> > +struct getfsmap_info {
> > +	struct xfs_mount	*mp;
> > +	struct fsmap __user	*data;
> > +	__u32			last_flags;
> > +};
> > +
> > +STATIC int
> > +xfs_getfsmap_format(struct xfs_fsmap *xfm, void *priv)
> > +{
> > +	struct getfsmap_info	*info = priv;
> > +	struct fsmap		fm;
> > +
> > +	trace_xfs_getfsmap_mapping(info->mp, xfm->fmr_device, xfm->fmr_physical,
> > +			xfm->fmr_length, xfm->fmr_owner, xfm->fmr_offset,
> > +			xfm->fmr_flags);
> > +
> > +	info->last_flags = xfm->fmr_flags;
> > +	xfs_fsmap_from_internal(&fm, xfm);
> > +	if (copy_to_user(info->data, &fm, sizeof(struct fsmap)))
> > +		return -EFAULT;
> > +
> > +	info->data++;
> > +	return 0;
> > +}
> > +
> > +STATIC int
> > +xfs_ioc_getfsmap(
> > +	struct xfs_inode	*ip,
> > +	void			__user *arg)
> > +{
> > +	struct getfsmap_info	info;
> > +	struct xfs_fsmap_head	xhead = {0};
> > +	struct fsmap_head	head;
> > +	bool			aborted = false;
> > +	int			error;
> > +
> > +	if (copy_from_user(&head, arg, sizeof(struct fsmap_head)))
> > +		return -EFAULT;
> > +	if (head.fmh_reserved[0] || head.fmh_reserved[1] ||
> > +	    head.fmh_reserved[2] || head.fmh_reserved[3] ||
> > +	    head.fmh_reserved[4] || head.fmh_reserved[5] ||
> > +	    head.fmh_keys[0].fmr_reserved[0] ||
> > +	    head.fmh_keys[0].fmr_reserved[1] ||
> > +	    head.fmh_keys[0].fmr_reserved[2] ||
> > +	    head.fmh_keys[1].fmr_reserved[0] ||
> > +	    head.fmh_keys[1].fmr_reserved[1] ||
> > +	    head.fmh_keys[1].fmr_reserved[2])
> > +		return -EINVAL;
> 
> Probably better to use memchr_inv() here.

Noted.

> > +
> > +	xhead.fmh_iflags = head.fmh_iflags;
> > +	xhead.fmh_count = head.fmh_count;
> > +	xfs_fsmap_to_internal(&xhead.fmh_keys[0], &head.fmh_keys[0]);
> > +	xfs_fsmap_to_internal(&xhead.fmh_keys[1], &head.fmh_keys[1]);
> > +
> > +	trace_xfs_getfsmap_low_key(ip->i_mount,
> > +			xhead.fmh_keys[0].fmr_device,
> > +			xhead.fmh_keys[0].fmr_physical,
> > +			xhead.fmh_keys[0].fmr_length,
> > +			xhead.fmh_keys[0].fmr_owner,
> > +			xhead.fmh_keys[0].fmr_offset,
> > +			xhead.fmh_keys[0].fmr_flags);
> > +
> > +	trace_xfs_getfsmap_high_key(ip->i_mount,
> > +			xhead.fmh_keys[1].fmr_device,
> > +			xhead.fmh_keys[1].fmr_physical,
> > +			xhead.fmh_keys[1].fmr_length,
> > +			xhead.fmh_keys[1].fmr_owner,
> > +			xhead.fmh_keys[1].fmr_offset,
> > +			xhead.fmh_keys[1].fmr_flags);
> > +
> 
> Hmm.. could we combine these into one call that looks like:
> 
> 	trace_xfs_getfsmap(mp, &fmh_keys[0], &fmh_keys[1]);
> 
> ... and has the trace handler pull the relevant data out of the key
> structure (same comment for the similar trace_xfs_fsmap*())?

I'd prefer to leave it as-is, because passing struct xfs_fsmap into a
tracepoint requires every file that includes xfs_trace.h to also include
xfs_fsmap.h to get the structure definition.

For debugging I also prefer only logging one big structure per
tracepoint, though I'm more willing to combine the two into one big
trace.  Also, as far as trace reporting goes, what do you think of:

xfs_io-1441  [002]  2363.403451: xfs_getfsmap_low_key: dev 8:80 keydev 0:0 block 0 len 0 owner 0 offset 0 flags 0x0
xfs_io-1441  [002]  2363.403521: xfs_getfsmap_high_key: dev 8:80 keydev 4095:1048575 block 36028797018963967 len 0 owner -1 offset 36028797018963967 flags 0xffffffff

versus:

xfs_io-1441  [002]  2363.403451: xfs_getfsmap_key: dev 8:80 lkeydev 0:0 lblock 0 llen 0 lowner 0 loffset 0 lflags 0x0 hkeydev 4095:1048575 hblock 36028797018963967 hlen 0 howner -1 hoffset 36028797018963967 hflags 0xffffffff

It's harder for me to dig through the second version of that for the
high key data since the column offset of hkeydev depends on the low key
contents.

> > +	info.mp = ip->i_mount;
> > +	info.data = ((__force struct fsmap_head *)arg)->fmh_recs;
> > +	error = xfs_getfsmap(ip->i_mount, &xhead, xfs_getfsmap_format, &info);
> > +	if (error == XFS_BTREE_QUERY_RANGE_ABORT) {
> > +		error = 0;
> > +		aborted = true;
> > +	} else if (error)
> > +		return error;
> > +
> > +	/* If we didn't abort, set the "last" flag in the last fmx */
> > +	if (!aborted && xhead.fmh_entries) {
> > +		info.data--;
> > +		info.last_flags |= FMR_OF_LAST;
> 
> Isn't this kind of implied by a short return? It looks like if a real
> error occurs at any point during the search, we just return the error. I
> guess there is still the case where the remaining mappings exactly match
> the number of entries in the data structure passed in and you'd have to
> make another call to identify EOF.

Yep.

> If we do want the flag, I'm also wondering why we couldn't stuff it in
> oflags in the header. Is there some reason I'm not yet aware of why we
> want the LAST flag in the flags of the last entry?

Basically I'm copying the LAST flag from fiemap/bmapx, for which you
could make the same argument.  I'm trying to mirror the same semantics
and the same meaning. :)

ATM the sole real user of OF_LAST is scrub, which during the data block
verification phase will use the flag as a shortcut for "ok, this is the
last rmap entry we're going to see; kick off any IO that we've queued
but were holding onto just in case the next extent is contiguous".

The OF_LAST flag applies to just that last fsmap record, so (at least
in my mind) it belongs in the fsmap record, not the fsmap header.
Also, from the perspective of a userspace iterator of the fsmap data,
the iterator function would have to know that "OH_LAST means that I need
to communicate last-record status to the function I'm being passed, but
the fsmap record does not itself have a last flag, so lastness becomes a
second out-of-band parameter".  Easier just to build it into the
specific record it applies to.

xfs_scrub could get by without the flag at all, I suppose.

Thanks for working on the review, I really appreciate it. :)

--D

> Brian
> 
> > +		if (copy_to_user(&info.data->fmr_flags, &info.last_flags,
> > +				sizeof(info.last_flags)))
> > +			return -EFAULT;
> > +	}
> > +
> > +	/* copy back header */
> > +	head.fmh_entries = xhead.fmh_entries;
> > +	head.fmh_oflags = xhead.fmh_oflags;
> > +	if (copy_to_user(arg, &head, sizeof(struct fsmap_head)))
> > +		return -EFAULT;
> > +
> > +	return 0;
> > +}
> > +
> >  int
> >  xfs_ioc_swapext(
> >  	xfs_swapext_t	*sxp)
> > @@ -1787,6 +1887,9 @@ xfs_file_ioctl(
> >  	case XFS_IOC_GETBMAPX:
> >  		return xfs_ioc_getbmapx(ip, arg);
> >  
> > +	case FS_IOC_GETFSMAP:
> > +		return xfs_ioc_getfsmap(ip, arg);
> > +
> >  	case XFS_IOC_FD_TO_HANDLE:
> >  	case XFS_IOC_PATH_TO_HANDLE:
> >  	case XFS_IOC_PATH_TO_FSHANDLE: {
> > diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
> > index 7c49938..fa0bc4d 100644
> > --- a/fs/xfs/xfs_ioctl32.c
> > +++ b/fs/xfs/xfs_ioctl32.c
> > @@ -20,6 +20,7 @@
> >  #include <linux/mount.h>
> >  #include <linux/slab.h>
> >  #include <linux/uaccess.h>
> > +#include <linux/fsmap.h>
> >  #include "xfs.h"
> >  #include "xfs_fs.h"
> >  #include "xfs_format.h"
> > @@ -554,6 +555,7 @@ xfs_file_compat_ioctl(
> >  	case XFS_IOC_GOINGDOWN:
> >  	case XFS_IOC_ERROR_INJECTION:
> >  	case XFS_IOC_ERROR_CLEARALL:
> > +	case FS_IOC_GETFSMAP:
> >  		return xfs_file_ioctl(filp, cmd, p);
> >  #ifndef BROKEN_X86_ALIGNMENT
> >  	/* These are handled fine if no alignment issues */
> > diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> > index d3d11905..125d568 100644
> > --- a/fs/xfs/xfs_trace.h
> > +++ b/fs/xfs/xfs_trace.h
> > @@ -3270,6 +3270,91 @@ DEFINE_INODE_IREC_EVENT(xfs_swap_extent_rmap_remap);
> >  DEFINE_INODE_IREC_EVENT(xfs_swap_extent_rmap_remap_piece);
> >  DEFINE_INODE_ERROR_EVENT(xfs_swap_extent_rmap_error);
> >  
> > +/* fsmap traces */
> > +DECLARE_EVENT_CLASS(xfs_fsmap_class,
> > +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_agnumber_t agno,
> > +		 xfs_fsblock_t bno, xfs_filblks_t len, __uint64_t owner,
> > +		 __uint64_t offset),
> > +	TP_ARGS(mp, keydev, agno, bno, len, owner, offset),
> > +	TP_STRUCT__entry(
> > +		__field(dev_t, dev)
> > +		__field(dev_t, keydev)
> > +		__field(xfs_agnumber_t, agno)
> > +		__field(xfs_fsblock_t, bno)
> > +		__field(xfs_filblks_t, len)
> > +		__field(__uint64_t, owner)
> > +		__field(__uint64_t, offset)
> > +	),
> > +	TP_fast_assign(
> > +		__entry->dev = mp->m_super->s_dev;
> > +		__entry->keydev = new_decode_dev(keydev);
> > +		__entry->agno = agno;
> > +		__entry->bno = bno;
> > +		__entry->len = len;
> > +		__entry->owner = owner;
> > +		__entry->offset = offset;
> > +	),
> > +	TP_printk("dev %d:%d keydev %d:%d agno %u bno %llu len %llu owner %lld offset 0x%llx\n",
> > +		  MAJOR(__entry->dev), MINOR(__entry->dev),
> > +		  MAJOR(__entry->keydev), MINOR(__entry->keydev),
> > +		  __entry->agno,
> > +		  __entry->bno,
> > +		  __entry->len,
> > +		  __entry->owner,
> > +		  __entry->offset)
> > +)
> > +#define DEFINE_FSMAP_EVENT(name) \
> > +DEFINE_EVENT(xfs_fsmap_class, name, \
> > +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_agnumber_t agno, \
> > +		 xfs_fsblock_t bno, xfs_filblks_t len, __uint64_t owner, \
> > +		 __uint64_t offset), \
> > +	TP_ARGS(mp, keydev, agno, bno, len, owner, offset))
> > +DEFINE_FSMAP_EVENT(xfs_fsmap_low_key);
> > +DEFINE_FSMAP_EVENT(xfs_fsmap_high_key);
> > +DEFINE_FSMAP_EVENT(xfs_fsmap_mapping);
> > +
> > +DECLARE_EVENT_CLASS(xfs_getfsmap_class,
> > +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block,
> > +		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset,
> > +		 __uint64_t flags),
> > +	TP_ARGS(mp, keydev, block, len, owner, offset, flags),
> > +	TP_STRUCT__entry(
> > +		__field(dev_t, dev)
> > +		__field(dev_t, keydev)
> > +		__field(xfs_daddr_t, block)
> > +		__field(xfs_daddr_t, len)
> > +		__field(__uint64_t, owner)
> > +		__field(__uint64_t, offset)
> > +		__field(__uint64_t, flags)
> > +	),
> > +	TP_fast_assign(
> > +		__entry->dev = mp->m_super->s_dev;
> > +		__entry->keydev = new_decode_dev(keydev);
> > +		__entry->block = block;
> > +		__entry->len = len;
> > +		__entry->owner = owner;
> > +		__entry->offset = offset;
> > +		__entry->flags = flags;
> > +	),
> > +	TP_printk("dev %d:%d keydev %d:%d block %llu len %llu owner %lld offset %llu flags 0x%llx\n",
> > +		  MAJOR(__entry->dev), MINOR(__entry->dev),
> > +		  MAJOR(__entry->keydev), MINOR(__entry->keydev),
> > +		  __entry->block,
> > +		  __entry->len,
> > +		  __entry->owner,
> > +		  __entry->offset,
> > +		  __entry->flags)
> > +)
> > +#define DEFINE_GETFSMAP_EVENT(name) \
> > +DEFINE_EVENT(xfs_getfsmap_class, name, \
> > +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block, \
> > +		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset, \
> > +		 __uint64_t flags), \
> > +	TP_ARGS(mp, keydev, block, len, owner, offset, flags))
> > +DEFINE_GETFSMAP_EVENT(xfs_getfsmap_low_key);
> > +DEFINE_GETFSMAP_EVENT(xfs_getfsmap_high_key);
> > +DEFINE_GETFSMAP_EVENT(xfs_getfsmap_mapping);
> > +
> >  #endif /* _TRACE_XFS_H */
> >  
> >  #undef TRACE_INCLUDE_PATH
> > diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> > index 70f42ea..a280e12 100644
> > --- a/fs/xfs/xfs_trans.c
> > +++ b/fs/xfs/xfs_trans.c
> > @@ -263,6 +263,28 @@ xfs_trans_alloc(
> >  }
> >  
> >  /*
> > + * Create an empty transaction with no reservation.  This is a defensive
> > + * mechanism for routines that query metadata without actually modifying
> > + * them -- if the metadata being queried is somehow cross-linked (think a
> > + * btree block pointer that points higher in the tree), we risk deadlock.
> > + * However, blocks grabbed as part of a transaction can be re-grabbed.
> > + * The verifiers will notice the corrupt block and the operation will fail
> > + * back to userspace without deadlocking.
> > + *
> > + * Note the zero-length reservation; this transaction MUST be cancelled
> > + * without any dirty data.
> > + */
> > +int
> > +xfs_trans_alloc_empty(
> > +	struct xfs_mount		*mp,
> > +	struct xfs_trans		**tpp)
> > +{
> > +	struct xfs_trans_res		resv = {0};
> > +
> > +	return xfs_trans_alloc(mp, &resv, 0, 0, XFS_TRANS_NO_WRITECOUNT, tpp);
> > +}
> > +
> > +/*
> >   * Record the indicated change to the given field for application
> >   * to the file system's superblock when the transaction commits.
> >   * For now, just store the change in the transaction structure.
> > diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
> > index 61b7fbd..98024cb 100644
> > --- a/fs/xfs/xfs_trans.h
> > +++ b/fs/xfs/xfs_trans.h
> > @@ -159,6 +159,8 @@ typedef struct xfs_trans {
> >  int		xfs_trans_alloc(struct xfs_mount *mp, struct xfs_trans_res *resp,
> >  			uint blocks, uint rtextents, uint flags,
> >  			struct xfs_trans **tpp);
> > +int		xfs_trans_alloc_empty(struct xfs_mount *mp,
> > +			struct xfs_trans **tpp);
> >  void		xfs_trans_mod_sb(xfs_trans_t *, uint, int64_t);
> >  
> >  struct xfs_buf	*xfs_trans_get_buf_map(struct xfs_trans *tp,
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
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Re: [PATCH 5/8] xfs: introduce the XFS_IOC_GETFSMAP ioctl

[Brian Foster]

On Wed, Feb 22, 2017 at 01:17:57PM -0800, Darrick J. Wong wrote:
> On Wed, Feb 22, 2017 at 10:02:47AM -0500, Brian Foster wrote:
> > On Fri, Feb 17, 2017 at 05:17:49PM -0800, Darrick J. Wong wrote:
> > > From: Darrick J. Wong <darrick.wong@oracle.com>
> > > 
> > > Introduce a new ioctl that uses the reverse mapping btree to return
> > > information about the physical layout of the filesystem.
> > > 
> > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > > ---
> > 
> > Mostly looks good, though there's a decent amount of indirection here so
> > I'll probably need another pass through it. Mostly minor comments, a
> > couple potential issues and some questions..
> 
> <nod>
> 
> > >  fs/xfs/Makefile        |    1 
> > >  fs/xfs/libxfs/xfs_fs.h |   13 +
> > >  fs/xfs/xfs_fsmap.c     |  782 ++++++++++++++++++++++++++++++++++++++++++++++++
> > >  fs/xfs/xfs_fsmap.h     |   51 +++
> > >  fs/xfs/xfs_ioctl.c     |  103 ++++++
> > >  fs/xfs/xfs_ioctl32.c   |    2 
> > >  fs/xfs/xfs_trace.h     |   85 +++++
> > >  fs/xfs/xfs_trans.c     |   22 +
> > >  fs/xfs/xfs_trans.h     |    2 
> > >  9 files changed, 1061 insertions(+)
> > >  create mode 100644 fs/xfs/xfs_fsmap.c
> > >  create mode 100644 fs/xfs/xfs_fsmap.h
> > > 
> > > 
...
> > > diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
> > > index b72dc82..095bdf0 100644
> > > --- a/fs/xfs/libxfs/xfs_fs.h
> > > +++ b/fs/xfs/libxfs/xfs_fs.h
...
> > > +	/*
> > > +	 * Filter out records that start before our startpoint, if the
> > > +	 * caller requested that.
> > > +	 */
> > > +	if (xfs_getfsmap_rec_before_low_key(info, rec)) {
> > > +		rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
> > > +		if (info->next_daddr < rec_daddr)
> > > +			info->next_daddr = rec_daddr;
> > > +		return XFS_BTREE_QUERY_RANGE_CONTINUE;
> > > +	}
> > > +
> > > +	/*
> > > +	 * If the caller passed in a length with the low record and
> > > +	 * the record represents a file data extent, we incremented
> > > +	 * the offset in the low key by the length in the hopes of
> > > +	 * finding reverse mappings for the physical blocks we just
> > > +	 * saw.  We did /not/ increment next_daddr by the length
> > > +	 * because the range query would not be able to find shared
> > > +	 * extents within the same physical block range.
> > > +	 *
> > > +	 * However, the extent we've been fed could have a startblock
> > > +	 * past the passed-in low record.  If this is the case,
> > > +	 * advance next_daddr to the end of the passed-in low record
> > > +	 * so we don't report the extent prior to this extent as
> > > +	 * free.
> > > +	 */
> > > +	key_end = info->rkey_low->fmr_physical + info->rkey_low->fmr_length;
> > > +	if (info->dev == info->rkey_low->fmr_device &&
> > > +	    info->next_daddr < key_end && rec_daddr >= key_end)
> > > +		info->next_daddr = key_end;
> > > +
> > 
> > Hmm, so I think I follow what this is trying to do..
> > 
> > In the case where we left off on a file mapping, we bump the offset of
> > the passed in low key but next_daddr remains at the same physical block
> > because we could have more mappings there. If we don't, however, and the
> > next mapping occurs at a higher physical block, we need to make sure we
> > don't map the previous range as free space. So we bump next_daddr here
> > to make sure that if free space does exist, it shown to start at the end
> > of the previous mapping. Yes?
> 
> Yes.
> 
> > If I'm following that correctly, what about the case where we have
> > bumped fmr_physical? It doesn't look like we've reset fmr_length, so
> > couldn't this cause us to skip legitimate free space if for e.g. the
> > current record is much farther ahead?
> 
> rkey_low->fmr_{physical,length} are from the low key passed in from
> userspace, and therefore, key_end is the physical end of the unadjusted
> low key provided by userspace.
> 

Ok, so in xfs_getfsmap() we have rkey_low/high from the userspace
header. The local dkeys array is initialized from these values, bumped
as necessary based on the userspace low key, and then truncated per
device. We also set info.rkey_low based on the userspace value and
info.next_daddr based on the (potentially bumped) physical offset.

We call into xfs_getfsmap_datadev() with dkeys and the info object.
Here we set up info->low/high based on the device keys, now truncated as
appropriate for the per-ag walk, and run the query based on
info->low/high. We pass the info object along to the rmap query...

We ultimately get here in xfs_getfsmap_helper() with the info object and
the visited record. key_end is calculated based on info->rkey_low, which
as you point out, is the unmodified key from userspace. The 'if
(info->next_daddr < key_end)' check basically means 'if the low key is
file data,' because that's the case where we've bumped the file offset
rather than the physical offset. The 'rec_daddr >= key_end' check means
that we have no more records at the physical offset of the low key, and
we now have to fix up next_daddr (of which the primary purpose is to
detect free space ranges in the gaps of rmapbt records) lest we
mistakenly report a free space record for the previous range...

> dkey[0] is the low key after its fmr_physical/fmr_offset value has been
> adjusted; and next_daddr's first value is dkey[0].fmr_physical.
> Therefore, next_daddr points to the first block of the low key in the
> data fsmap case; or points to the next block after the low key in all
> other cases.
> 
> So to answer your question quickly, key_end is always computed from
> non-bumped values.
> 

Makes sense now, provided I'm following the logic correctly above..
thanks. I think I just lost track of what keys are what.

(It sure would be nice to make this easier to follow somehow, but my
brain hurts and I can't really think of anything more clear atm... :P).

> This is kind of confusing, so let's work a few examples...
> 
> Say userspace gives us head->fmh_keys = [(8:0, 24, 8, OWN_INOBT, 0), (-1)].
> That means that the last record userspace saw was 8 sectors of inobt
> starting at sector 24.  Then set info.rkey_low = &head->fmh_keys[0].
> Because inobt is a special owner, dkeys[0] = (8:0, 32, 8, OWN_INOBT, 0),
> and next_daddr = 32.  We should probably decrease the length from 8 to 0
> but the length is not a key field so it doesn't really matter.
> 
> Say that _getfsmap_helper is passed the rmap (8:0, 64, 8, OWN_REFCOUNT, 0).
> When we get to line 318, set key_end = 24 + 8.
> 
> The test
> if (devices match && next_daddr < key_end && rec_daddr >= key_end)
> becomes
> if (devices match && 32 < 32 && we don't care after this point)
> 
> So the branch test is false and we don't set next_daddr = key_end.
> We synthesize an fsmap record for free space spanning sector 32 to 64,
> emit the OWN_REFCOUNT record, and set next_daddr = 72 and move on.
> 

Makes sense...

> [If you're wondering how it works for regular data extents, keep
> reading.]
> 
> Second example: fmh_keys = [(8:0, 24, 16, 128, 0), (-1)].  Now we have
> that userspace last saw 16 sectors of file data (inode 128, offset 0)
> starting at block 24.  We again set info.rkey_low = &head->fmh_keys[0].
> Because the lowkey is a data extent, dkeys[0] = (8:0, 24, 16, 128, 16),
> and next_daddr = 24.
> 

So we've bumped the file offset only and kept next_daddr equivalent as
it is safe to expect more mappings for the same physical offset..

> The first rmap passed to _getfsmap_helper is the same (8:0, 24, 16, 128,
> 0) that we emitted as the last fsmap returned from the previous getfsmap
> call, because we started the query_range at dkeys[0].physical, which is
> 24.  xfs_getfsmap_rec_before_low_key notices that the key of this record
> is less than the rkey_low that was passed in and so increments
> next_daddr to 40.
> 

So the rmapbt query doesn't incorporate the full getfsmap key in the
search and we thus we have to include finer grained filtering..? If so,
I think this bit could be noted explicitly in the comment..

Also, I'm kind of wondering why we couldn't have just set next_daddr to
40 in the first place based on the low key. Is there some other corner
case that breaks..?

> Assuming _getfsmap_helper is passed the same refcount rmap as before.
> rec_daddr = 64, and when we get to line 318, key_end = 24 + 16.
> 
> The test is now:
> if (devices match && 40 < 40 && 64 >= 40)
> So we leave next_daddr at 40.
> 
> The correct output here is to synthesize an fsmap record for free space
> between 40-64, and then to emit the refcount record at 64.
> 
> Third example: fmh_keys = [(8:0, 24, 16, 128, 0), (-1)] and next_daddr = 24
> as before.  _getfsmap_helper again sees (8:0, 24, 16, 128, 0) and sets
> next_daddr = 40.
> 
> This time, however, _getfsmap_helper is passed (8:0, 32, 8, 129, 0),
> which is 8 sectors of inode 129's data at offset 0.  rec_daddr = 32,
> key_end = 24 + 16 as before.
> 
> The test is now:
> if (devices match && 40 < 40 && 32 >= 40)
> So we again leave next_daddr at 40, then emit the fsmap for inode 129.
> 

Thanks for the explanation.

...
> > > +/* Execute a getfsmap query against the log device. */
> > > +STATIC int
> > > +xfs_getfsmap_logdev(
> > > +	struct xfs_trans		*tp,
> > > +	struct xfs_fsmap		*keys,
> > > +	struct xfs_getfsmap_info	*info)
> > > +{
> > > +	struct xfs_mount		*mp = tp->t_mountp;
> > > +	struct xfs_fsmap		*dkey_low = keys;
> > > +	struct xfs_btree_cur		cur;
> > > +	struct xfs_rmap_irec		rmap;
> > > +	int				error;
> > > +
> > > +	/* Set up search keys */
> > > +	info->low.rm_startblock = XFS_BB_TO_FSBT(mp, dkey_low->fmr_physical);
> > > +	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
> > > +	error = xfs_fsmap_owner_to_rmap(keys, &info->low);
> > > +	if (error)
> > > +		return error;
> > > +	info->low.rm_blockcount = 0;
> > > +	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
> > > +
> > > +	error = xfs_fsmap_owner_to_rmap(keys + 1, &info->high);
> > > +	if (error)
> > > +		return error;
> > > +	info->high.rm_startblock = -1U;
> > > +	info->high.rm_owner = ULLONG_MAX;
> > > +	info->high.rm_offset = ULLONG_MAX;
> > > +	info->high.rm_blockcount = 0;
> > > +	info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;
> > > +	info->missing_owner = XFS_FMR_OWN_FREE;
> > > +
> > > +	trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
> > > +			info->low.rm_startblock,
> > > +			info->low.rm_blockcount,
> > > +			info->low.rm_owner,
> > > +			info->low.rm_offset);
> > > +
> > > +	trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
> > > +			info->high.rm_startblock,
> > > +			info->high.rm_blockcount,
> > > +			info->high.rm_owner,
> > > +			info->high.rm_offset);
> > > +
> > > +
> > > +	if (dkey_low->fmr_physical > 0)
> > > +		return 0;
> > > +
> > 
> > A comment to point out we're fabricating an rmap record here would be
> 
> Ok.
> 
> > nice. Also, (how) do we handle/report internal log blocks?
> 
> The AG containing the log will have an rmapbt record for RMAP_OWN_LOG,
> so that'll be in with the datadev records.
> 

Ok, I recall now that the internal log is basically just permanently
allocated space in whatever AG covers it.

> > > +	rmap.rm_startblock = 0;
> > > +	rmap.rm_blockcount = mp->m_sb.sb_logblocks;
> > > +	rmap.rm_owner = XFS_RMAP_OWN_LOG;
> > > +	rmap.rm_offset = 0;
> > > +	rmap.rm_flags = 0;
> > > +
> > > +	cur.bc_mp = mp;
> > > +	cur.bc_tp = tp;
> > > +	return xfs_getfsmap_rtdev_helper(&cur, &rmap, info);
> > > +}
> > > +
...
> > > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> > > index c67cfb4..bbe1b58 100644
> > > --- a/fs/xfs/xfs_ioctl.c
> > > +++ b/fs/xfs/xfs_ioctl.c
...
> > > +STATIC int
> > > +xfs_ioc_getfsmap(
> > > +	struct xfs_inode	*ip,
> > > +	void			__user *arg)
> > > +{
> > > +	struct getfsmap_info	info;
> > > +	struct xfs_fsmap_head	xhead = {0};
> > > +	struct fsmap_head	head;
> > > +	bool			aborted = false;
> > > +	int			error;
> > > +
...
> > > +	xhead.fmh_iflags = head.fmh_iflags;
> > > +	xhead.fmh_count = head.fmh_count;
> > > +	xfs_fsmap_to_internal(&xhead.fmh_keys[0], &head.fmh_keys[0]);
> > > +	xfs_fsmap_to_internal(&xhead.fmh_keys[1], &head.fmh_keys[1]);
> > > +
> > > +	trace_xfs_getfsmap_low_key(ip->i_mount,
> > > +			xhead.fmh_keys[0].fmr_device,
> > > +			xhead.fmh_keys[0].fmr_physical,
> > > +			xhead.fmh_keys[0].fmr_length,
> > > +			xhead.fmh_keys[0].fmr_owner,
> > > +			xhead.fmh_keys[0].fmr_offset,
> > > +			xhead.fmh_keys[0].fmr_flags);
> > > +
> > > +	trace_xfs_getfsmap_high_key(ip->i_mount,
> > > +			xhead.fmh_keys[1].fmr_device,
> > > +			xhead.fmh_keys[1].fmr_physical,
> > > +			xhead.fmh_keys[1].fmr_length,
> > > +			xhead.fmh_keys[1].fmr_owner,
> > > +			xhead.fmh_keys[1].fmr_offset,
> > > +			xhead.fmh_keys[1].fmr_flags);
> > > +
> > 
> > Hmm.. could we combine these into one call that looks like:
> > 
> > 	trace_xfs_getfsmap(mp, &fmh_keys[0], &fmh_keys[1]);
> > 
> > ... and has the trace handler pull the relevant data out of the key
> > structure (same comment for the similar trace_xfs_fsmap*())?
> 
> I'd prefer to leave it as-is, because passing struct xfs_fsmap into a
> tracepoint requires every file that includes xfs_trace.h to also include
> xfs_fsmap.h to get the structure definition.
> 

I think you can get around that with a structure declaration in
xfs_trace.h, as the only code that actually requires the full definition
is xfs_trace.c. If that works, that could at least reduce the tracepoint
calls to a couple lines of code, even if we retain the independent
low/high key tp's.

> For debugging I also prefer only logging one big structure per
> tracepoint, though I'm more willing to combine the two into one big
> trace.  Also, as far as trace reporting goes, what do you think of:
> 
> xfs_io-1441  [002]  2363.403451: xfs_getfsmap_low_key: dev 8:80 keydev 0:0 block 0 len 0 owner 0 offset 0 flags 0x0
> xfs_io-1441  [002]  2363.403521: xfs_getfsmap_high_key: dev 8:80 keydev 4095:1048575 block 36028797018963967 len 0 owner -1 offset 36028797018963967 flags 0xffffffff
> 
> versus:
> 
> xfs_io-1441  [002]  2363.403451: xfs_getfsmap_key: dev 8:80 lkeydev 0:0 lblock 0 llen 0 lowner 0 loffset 0 lflags 0x0 hkeydev 4095:1048575 hblock 36028797018963967 hlen 0 howner -1 hoffset 36028797018963967 hflags 0xffffffff
> 
> It's harder for me to dig through the second version of that for the
> high key data since the column offset of hkeydev depends on the low key
> contents.
> 

Ok, seems reasonable. I guess I try to think of tracepoints as more
event oriented than data oriented, but they're still just tracepoints so
no big deal.

> > > +	info.mp = ip->i_mount;
> > > +	info.data = ((__force struct fsmap_head *)arg)->fmh_recs;
> > > +	error = xfs_getfsmap(ip->i_mount, &xhead, xfs_getfsmap_format, &info);
> > > +	if (error == XFS_BTREE_QUERY_RANGE_ABORT) {
> > > +		error = 0;
> > > +		aborted = true;
> > > +	} else if (error)
> > > +		return error;
> > > +
> > > +	/* If we didn't abort, set the "last" flag in the last fmx */
> > > +	if (!aborted && xhead.fmh_entries) {
> > > +		info.data--;
> > > +		info.last_flags |= FMR_OF_LAST;
> > 
> > Isn't this kind of implied by a short return? It looks like if a real
> > error occurs at any point during the search, we just return the error. I
> > guess there is still the case where the remaining mappings exactly match
> > the number of entries in the data structure passed in and you'd have to
> > make another call to identify EOF.
> 
> Yep.
> 
> > If we do want the flag, I'm also wondering why we couldn't stuff it in
> > oflags in the header. Is there some reason I'm not yet aware of why we
> > want the LAST flag in the flags of the last entry?
> 
> Basically I'm copying the LAST flag from fiemap/bmapx, for which you
> could make the same argument.  I'm trying to mirror the same semantics
> and the same meaning. :)
> 

Ok, kind of figured that since bmap has the similar flag. I just wanted
to bring it up because it looks like we require some roundabout support
code to actually place it into the record flags after the fact. I
suppose this is more of an API design matter anyways.

Brian

> ATM the sole real user of OF_LAST is scrub, which during the data block
> verification phase will use the flag as a shortcut for "ok, this is the
> last rmap entry we're going to see; kick off any IO that we've queued
> but were holding onto just in case the next extent is contiguous".
> 
> The OF_LAST flag applies to just that last fsmap record, so (at least
> in my mind) it belongs in the fsmap record, not the fsmap header.
> Also, from the perspective of a userspace iterator of the fsmap data,
> the iterator function would have to know that "OH_LAST means that I need
> to communicate last-record status to the function I'm being passed, but
> the fsmap record does not itself have a last flag, so lastness becomes a
> second out-of-band parameter".  Easier just to build it into the
> specific record it applies to.
> 
> xfs_scrub could get by without the flag at all, I suppose.
> 
> Thanks for working on the review, I really appreciate it. :)
> 
> --D
> 
> > Brian
> > 
> > > +		if (copy_to_user(&info.data->fmr_flags, &info.last_flags,
> > > +				sizeof(info.last_flags)))
> > > +			return -EFAULT;
> > > +	}
> > > +
> > > +	/* copy back header */
> > > +	head.fmh_entries = xhead.fmh_entries;
> > > +	head.fmh_oflags = xhead.fmh_oflags;
> > > +	if (copy_to_user(arg, &head, sizeof(struct fsmap_head)))
> > > +		return -EFAULT;
> > > +
> > > +	return 0;
> > > +}
> > > +
> > >  int
> > >  xfs_ioc_swapext(
> > >  	xfs_swapext_t	*sxp)
> > > @@ -1787,6 +1887,9 @@ xfs_file_ioctl(
> > >  	case XFS_IOC_GETBMAPX:
> > >  		return xfs_ioc_getbmapx(ip, arg);
> > >  
> > > +	case FS_IOC_GETFSMAP:
> > > +		return xfs_ioc_getfsmap(ip, arg);
> > > +
> > >  	case XFS_IOC_FD_TO_HANDLE:
> > >  	case XFS_IOC_PATH_TO_HANDLE:
> > >  	case XFS_IOC_PATH_TO_FSHANDLE: {
> > > diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
> > > index 7c49938..fa0bc4d 100644
> > > --- a/fs/xfs/xfs_ioctl32.c
> > > +++ b/fs/xfs/xfs_ioctl32.c
> > > @@ -20,6 +20,7 @@
> > >  #include <linux/mount.h>
> > >  #include <linux/slab.h>
> > >  #include <linux/uaccess.h>
> > > +#include <linux/fsmap.h>
> > >  #include "xfs.h"
> > >  #include "xfs_fs.h"
> > >  #include "xfs_format.h"
> > > @@ -554,6 +555,7 @@ xfs_file_compat_ioctl(
> > >  	case XFS_IOC_GOINGDOWN:
> > >  	case XFS_IOC_ERROR_INJECTION:
> > >  	case XFS_IOC_ERROR_CLEARALL:
> > > +	case FS_IOC_GETFSMAP:
> > >  		return xfs_file_ioctl(filp, cmd, p);
> > >  #ifndef BROKEN_X86_ALIGNMENT
> > >  	/* These are handled fine if no alignment issues */
> > > diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> > > index d3d11905..125d568 100644
> > > --- a/fs/xfs/xfs_trace.h
> > > +++ b/fs/xfs/xfs_trace.h
> > > @@ -3270,6 +3270,91 @@ DEFINE_INODE_IREC_EVENT(xfs_swap_extent_rmap_remap);
> > >  DEFINE_INODE_IREC_EVENT(xfs_swap_extent_rmap_remap_piece);
> > >  DEFINE_INODE_ERROR_EVENT(xfs_swap_extent_rmap_error);
> > >  
> > > +/* fsmap traces */
> > > +DECLARE_EVENT_CLASS(xfs_fsmap_class,
> > > +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_agnumber_t agno,
> > > +		 xfs_fsblock_t bno, xfs_filblks_t len, __uint64_t owner,
> > > +		 __uint64_t offset),
> > > +	TP_ARGS(mp, keydev, agno, bno, len, owner, offset),
> > > +	TP_STRUCT__entry(
> > > +		__field(dev_t, dev)
> > > +		__field(dev_t, keydev)
> > > +		__field(xfs_agnumber_t, agno)
> > > +		__field(xfs_fsblock_t, bno)
> > > +		__field(xfs_filblks_t, len)
> > > +		__field(__uint64_t, owner)
> > > +		__field(__uint64_t, offset)
> > > +	),
> > > +	TP_fast_assign(
> > > +		__entry->dev = mp->m_super->s_dev;
> > > +		__entry->keydev = new_decode_dev(keydev);
> > > +		__entry->agno = agno;
> > > +		__entry->bno = bno;
> > > +		__entry->len = len;
> > > +		__entry->owner = owner;
> > > +		__entry->offset = offset;
> > > +	),
> > > +	TP_printk("dev %d:%d keydev %d:%d agno %u bno %llu len %llu owner %lld offset 0x%llx\n",
> > > +		  MAJOR(__entry->dev), MINOR(__entry->dev),
> > > +		  MAJOR(__entry->keydev), MINOR(__entry->keydev),
> > > +		  __entry->agno,
> > > +		  __entry->bno,
> > > +		  __entry->len,
> > > +		  __entry->owner,
> > > +		  __entry->offset)
> > > +)
> > > +#define DEFINE_FSMAP_EVENT(name) \
> > > +DEFINE_EVENT(xfs_fsmap_class, name, \
> > > +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_agnumber_t agno, \
> > > +		 xfs_fsblock_t bno, xfs_filblks_t len, __uint64_t owner, \
> > > +		 __uint64_t offset), \
> > > +	TP_ARGS(mp, keydev, agno, bno, len, owner, offset))
> > > +DEFINE_FSMAP_EVENT(xfs_fsmap_low_key);
> > > +DEFINE_FSMAP_EVENT(xfs_fsmap_high_key);
> > > +DEFINE_FSMAP_EVENT(xfs_fsmap_mapping);
> > > +
> > > +DECLARE_EVENT_CLASS(xfs_getfsmap_class,
> > > +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block,
> > > +		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset,
> > > +		 __uint64_t flags),
> > > +	TP_ARGS(mp, keydev, block, len, owner, offset, flags),
> > > +	TP_STRUCT__entry(
> > > +		__field(dev_t, dev)
> > > +		__field(dev_t, keydev)
> > > +		__field(xfs_daddr_t, block)
> > > +		__field(xfs_daddr_t, len)
> > > +		__field(__uint64_t, owner)
> > > +		__field(__uint64_t, offset)
> > > +		__field(__uint64_t, flags)
> > > +	),
> > > +	TP_fast_assign(
> > > +		__entry->dev = mp->m_super->s_dev;
> > > +		__entry->keydev = new_decode_dev(keydev);
> > > +		__entry->block = block;
> > > +		__entry->len = len;
> > > +		__entry->owner = owner;
> > > +		__entry->offset = offset;
> > > +		__entry->flags = flags;
> > > +	),
> > > +	TP_printk("dev %d:%d keydev %d:%d block %llu len %llu owner %lld offset %llu flags 0x%llx\n",
> > > +		  MAJOR(__entry->dev), MINOR(__entry->dev),
> > > +		  MAJOR(__entry->keydev), MINOR(__entry->keydev),
> > > +		  __entry->block,
> > > +		  __entry->len,
> > > +		  __entry->owner,
> > > +		  __entry->offset,
> > > +		  __entry->flags)
> > > +)
> > > +#define DEFINE_GETFSMAP_EVENT(name) \
> > > +DEFINE_EVENT(xfs_getfsmap_class, name, \
> > > +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block, \
> > > +		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset, \
> > > +		 __uint64_t flags), \
> > > +	TP_ARGS(mp, keydev, block, len, owner, offset, flags))
> > > +DEFINE_GETFSMAP_EVENT(xfs_getfsmap_low_key);
> > > +DEFINE_GETFSMAP_EVENT(xfs_getfsmap_high_key);
> > > +DEFINE_GETFSMAP_EVENT(xfs_getfsmap_mapping);
> > > +
> > >  #endif /* _TRACE_XFS_H */
> > >  
> > >  #undef TRACE_INCLUDE_PATH
> > > diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> > > index 70f42ea..a280e12 100644
> > > --- a/fs/xfs/xfs_trans.c
> > > +++ b/fs/xfs/xfs_trans.c
> > > @@ -263,6 +263,28 @@ xfs_trans_alloc(
> > >  }
> > >  
> > >  /*
> > > + * Create an empty transaction with no reservation.  This is a defensive
> > > + * mechanism for routines that query metadata without actually modifying
> > > + * them -- if the metadata being queried is somehow cross-linked (think a
> > > + * btree block pointer that points higher in the tree), we risk deadlock.
> > > + * However, blocks grabbed as part of a transaction can be re-grabbed.
> > > + * The verifiers will notice the corrupt block and the operation will fail
> > > + * back to userspace without deadlocking.
> > > + *
> > > + * Note the zero-length reservation; this transaction MUST be cancelled
> > > + * without any dirty data.
> > > + */
> > > +int
> > > +xfs_trans_alloc_empty(
> > > +	struct xfs_mount		*mp,
> > > +	struct xfs_trans		**tpp)
> > > +{
> > > +	struct xfs_trans_res		resv = {0};
> > > +
> > > +	return xfs_trans_alloc(mp, &resv, 0, 0, XFS_TRANS_NO_WRITECOUNT, tpp);
> > > +}
> > > +
> > > +/*
> > >   * Record the indicated change to the given field for application
> > >   * to the file system's superblock when the transaction commits.
> > >   * For now, just store the change in the transaction structure.
> > > diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
> > > index 61b7fbd..98024cb 100644
> > > --- a/fs/xfs/xfs_trans.h
> > > +++ b/fs/xfs/xfs_trans.h
> > > @@ -159,6 +159,8 @@ typedef struct xfs_trans {
> > >  int		xfs_trans_alloc(struct xfs_mount *mp, struct xfs_trans_res *resp,
> > >  			uint blocks, uint rtextents, uint flags,
> > >  			struct xfs_trans **tpp);
> > > +int		xfs_trans_alloc_empty(struct xfs_mount *mp,
> > > +			struct xfs_trans **tpp);
> > >  void		xfs_trans_mod_sb(xfs_trans_t *, uint, int64_t);
> > >  
> > >  struct xfs_buf	*xfs_trans_get_buf_map(struct xfs_trans *tp,
> > > 
> > > --
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> > > the body of a message to majordomo@vger.kernel.org
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > --
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> --
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Re: [PATCH 5/8] xfs: introduce the XFS_IOC_GETFSMAP ioctl

[Darrick J. Wong]

On Thu, Feb 23, 2017 at 09:45:43AM -0500, Brian Foster wrote:
> On Wed, Feb 22, 2017 at 01:17:57PM -0800, Darrick J. Wong wrote:
> > On Wed, Feb 22, 2017 at 10:02:47AM -0500, Brian Foster wrote:
> > > On Fri, Feb 17, 2017 at 05:17:49PM -0800, Darrick J. Wong wrote:
> > > > From: Darrick J. Wong <darrick.wong@oracle.com>
> > > > 
> > > > Introduce a new ioctl that uses the reverse mapping btree to return
> > > > information about the physical layout of the filesystem.
> > > > 
> > > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > > > ---
> > > 
> > > Mostly looks good, though there's a decent amount of indirection here so
> > > I'll probably need another pass through it. Mostly minor comments, a
> > > couple potential issues and some questions..
> > 
> > <nod>
> > 
> > > >  fs/xfs/Makefile        |    1 
> > > >  fs/xfs/libxfs/xfs_fs.h |   13 +
> > > >  fs/xfs/xfs_fsmap.c     |  782 ++++++++++++++++++++++++++++++++++++++++++++++++
> > > >  fs/xfs/xfs_fsmap.h     |   51 +++
> > > >  fs/xfs/xfs_ioctl.c     |  103 ++++++
> > > >  fs/xfs/xfs_ioctl32.c   |    2 
> > > >  fs/xfs/xfs_trace.h     |   85 +++++
> > > >  fs/xfs/xfs_trans.c     |   22 +
> > > >  fs/xfs/xfs_trans.h     |    2 
> > > >  9 files changed, 1061 insertions(+)
> > > >  create mode 100644 fs/xfs/xfs_fsmap.c
> > > >  create mode 100644 fs/xfs/xfs_fsmap.h
> > > > 
> > > > 
> ...
> > > > diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
> > > > index b72dc82..095bdf0 100644
> > > > --- a/fs/xfs/libxfs/xfs_fs.h
> > > > +++ b/fs/xfs/libxfs/xfs_fs.h
> ...
> > > > +	/*
> > > > +	 * Filter out records that start before our startpoint, if the
> > > > +	 * caller requested that.
> > > > +	 */
> > > > +	if (xfs_getfsmap_rec_before_low_key(info, rec)) {
> > > > +		rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
> > > > +		if (info->next_daddr < rec_daddr)
> > > > +			info->next_daddr = rec_daddr;
> > > > +		return XFS_BTREE_QUERY_RANGE_CONTINUE;
> > > > +	}
> > > > +
> > > > +	/*
> > > > +	 * If the caller passed in a length with the low record and
> > > > +	 * the record represents a file data extent, we incremented
> > > > +	 * the offset in the low key by the length in the hopes of
> > > > +	 * finding reverse mappings for the physical blocks we just
> > > > +	 * saw.  We did /not/ increment next_daddr by the length
> > > > +	 * because the range query would not be able to find shared
> > > > +	 * extents within the same physical block range.
> > > > +	 *
> > > > +	 * However, the extent we've been fed could have a startblock
> > > > +	 * past the passed-in low record.  If this is the case,
> > > > +	 * advance next_daddr to the end of the passed-in low record
> > > > +	 * so we don't report the extent prior to this extent as
> > > > +	 * free.
> > > > +	 */
> > > > +	key_end = info->rkey_low->fmr_physical + info->rkey_low->fmr_length;
> > > > +	if (info->dev == info->rkey_low->fmr_device &&
> > > > +	    info->next_daddr < key_end && rec_daddr >= key_end)
> > > > +		info->next_daddr = key_end;
> > > > +
> > > 
> > > Hmm, so I think I follow what this is trying to do..
> > > 
> > > In the case where we left off on a file mapping, we bump the offset of
> > > the passed in low key but next_daddr remains at the same physical block
> > > because we could have more mappings there. If we don't, however, and the
> > > next mapping occurs at a higher physical block, we need to make sure we
> > > don't map the previous range as free space. So we bump next_daddr here
> > > to make sure that if free space does exist, it shown to start at the end
> > > of the previous mapping. Yes?
> > 
> > Yes.
> > 
> > > If I'm following that correctly, what about the case where we have
> > > bumped fmr_physical? It doesn't look like we've reset fmr_length, so
> > > couldn't this cause us to skip legitimate free space if for e.g. the
> > > current record is much farther ahead?
> > 
> > rkey_low->fmr_{physical,length} are from the low key passed in from
> > userspace, and therefore, key_end is the physical end of the unadjusted
> > low key provided by userspace.
> > 
> 
> Ok, so in xfs_getfsmap() we have rkey_low/high from the userspace
> header. The local dkeys array is initialized from these values, bumped
> as necessary based on the userspace low key, and then truncated per
> device. We also set info.rkey_low based on the userspace value and
> info.next_daddr based on the (potentially bumped) physical offset.
> 
> We call into xfs_getfsmap_datadev() with dkeys and the info object.
> Here we set up info->low/high based on the device keys, now truncated as
> appropriate for the per-ag walk, and run the query based on
> info->low/high. We pass the info object along to the rmap query...
> 
> We ultimately get here in xfs_getfsmap_helper() with the info object and
> the visited record. key_end is calculated based on info->rkey_low, which
> as you point out, is the unmodified key from userspace. The 'if
> (info->next_daddr < key_end)' check basically means 'if the low key is
> file data,' because that's the case where we've bumped the file offset
> rather than the physical offset. The 'rec_daddr >= key_end' check means
> that we have no more records at the physical offset of the low key, and
> we now have to fix up next_daddr (of which the primary purpose is to
> detect free space ranges in the gaps of rmapbt records) lest we
> mistakenly report a free space record for the previous range...

Correct.

> > dkey[0] is the low key after its fmr_physical/fmr_offset value has been
> > adjusted; and next_daddr's first value is dkey[0].fmr_physical.
> > Therefore, next_daddr points to the first block of the low key in the
> > data fsmap case; or points to the next block after the low key in all
> > other cases.
> > 
> > So to answer your question quickly, key_end is always computed from
> > non-bumped values.
> > 
> 
> Makes sense now, provided I'm following the logic correctly above..
> thanks. I think I just lost track of what keys are what.
> 
> (It sure would be nice to make this easier to follow somehow, but my
> brain hurts and I can't really think of anything more clear atm... :P).

I'll enhance the comments for xfs_getfsmap() to discuss all the keys and
*_daddr counters floating around, and how they interact.

> > This is kind of confusing, so let's work a few examples...
> > 
> > Say userspace gives us head->fmh_keys = [(8:0, 24, 8, OWN_INOBT, 0), (-1)].
> > That means that the last record userspace saw was 8 sectors of inobt
> > starting at sector 24.  Then set info.rkey_low = &head->fmh_keys[0].
> > Because inobt is a special owner, dkeys[0] = (8:0, 32, 8, OWN_INOBT, 0),
> > and next_daddr = 32.  We should probably decrease the length from 8 to 0
> > but the length is not a key field so it doesn't really matter.
> > 
> > Say that _getfsmap_helper is passed the rmap (8:0, 64, 8, OWN_REFCOUNT, 0).
> > When we get to line 318, set key_end = 24 + 8.
> > 
> > The test
> > if (devices match && next_daddr < key_end && rec_daddr >= key_end)
> > becomes
> > if (devices match && 32 < 32 && we don't care after this point)
> > 
> > So the branch test is false and we don't set next_daddr = key_end.
> > We synthesize an fsmap record for free space spanning sector 32 to 64,
> > emit the OWN_REFCOUNT record, and set next_daddr = 72 and move on.
> > 
> 
> Makes sense...
> 
> > [If you're wondering how it works for regular data extents, keep
> > reading.]
> > 
> > Second example: fmh_keys = [(8:0, 24, 16, 128, 0), (-1)].  Now we have
> > that userspace last saw 16 sectors of file data (inode 128, offset 0)
> > starting at block 24.  We again set info.rkey_low = &head->fmh_keys[0].
> > Because the lowkey is a data extent, dkeys[0] = (8:0, 24, 16, 128, 16),
> > and next_daddr = 24.
> > 
> 
> So we've bumped the file offset only and kept next_daddr equivalent as
> it is safe to expect more mappings for the same physical offset..
> 
> > The first rmap passed to _getfsmap_helper is the same (8:0, 24, 16, 128,
> > 0) that we emitted as the last fsmap returned from the previous getfsmap
> > call, because we started the query_range at dkeys[0].physical, which is
> > 24.  xfs_getfsmap_rec_before_low_key notices that the key of this record
> > is less than the rkey_low that was passed in and so increments
> > next_daddr to 40.
> > 
> 
> So the rmapbt query doesn't incorporate the full getfsmap key in the
> search and we thus we have to include finer grained filtering..? If so,
> I think this bit could be noted explicitly in the comment..

It's a funny quirk of how queries have to work when record keys contain
multiple overlapping ranges interacting with the current design of
query_range.

rmap tuple format is still (start, length, owner, offset).

Say you have the rmaps (24, 8, 128, 0) and (30, 10, 128, 8).  The low
key of the first rmap is (24, 128, 0) and the high key is (31, 128, 7).
That way you can query the rmapbt for start == 27 and it'll return the
above rmap.  _btree_query_range was designed to return any record
overlapping with any part of the interval, even if the record start or
record end themselves are not within the interval.

However, if you want to look for the next tuple after (24, 8, 128, 0)
you can't just tell it to search for (31...) because 31 > 30 and it'll
miss that second rmap.  You can however tell it to search (24, 128, 8)
and ignore any records if any part of the low key is not greater than
the low search key.

Theoretically, we could enhance query_range to take an operator so that
you could tell it to return any record overlapping with any part of the
interval so long as the start of the record is strictly greater than the
start of the query interval.

FWIW the comment for _btree_query_range says it returns all records
overlapping with the interval passed in.

> Also, I'm kind of wondering why we couldn't have just set next_daddr to
> 40 in the first place based on the low key. Is there some other corner
> case that breaks..?

Aha, looking through my notes, the original version also used next_daddr
(buggily) to decide if a record actually started before the bumped low
key so that it could ignore it.  Subsequent revisions created an
explicit test function (_getfsmap_rec_before_low_key) so you're right,
we can set next_daddr to 40 (fmh_keys[0]->fmr_physical + fmr_length) for
the first loop iteration and zero for subsequent iterations.  With that
the key_end business also goes away.

> > Assuming _getfsmap_helper is passed the same refcount rmap as before.
> > rec_daddr = 64, and when we get to line 318, key_end = 24 + 16.
> > 
> > The test is now:
> > if (devices match && 40 < 40 && 64 >= 40)
> > So we leave next_daddr at 40.
> > 
> > The correct output here is to synthesize an fsmap record for free space
> > between 40-64, and then to emit the refcount record at 64.
> > 
> > Third example: fmh_keys = [(8:0, 24, 16, 128, 0), (-1)] and next_daddr = 24
> > as before.  _getfsmap_helper again sees (8:0, 24, 16, 128, 0) and sets
> > next_daddr = 40.
> > 
> > This time, however, _getfsmap_helper is passed (8:0, 32, 8, 129, 0),
> > which is 8 sectors of inode 129's data at offset 0.  rec_daddr = 32,
> > key_end = 24 + 16 as before.
> > 
> > The test is now:
> > if (devices match && 40 < 40 && 32 >= 40)
> > So we again leave next_daddr at 40, then emit the fsmap for inode 129.
> > 
> 
> Thanks for the explanation.
> 
> ...
> > > > +/* Execute a getfsmap query against the log device. */
> > > > +STATIC int
> > > > +xfs_getfsmap_logdev(
> > > > +	struct xfs_trans		*tp,
> > > > +	struct xfs_fsmap		*keys,
> > > > +	struct xfs_getfsmap_info	*info)
> > > > +{
> > > > +	struct xfs_mount		*mp = tp->t_mountp;
> > > > +	struct xfs_fsmap		*dkey_low = keys;
> > > > +	struct xfs_btree_cur		cur;
> > > > +	struct xfs_rmap_irec		rmap;
> > > > +	int				error;
> > > > +
> > > > +	/* Set up search keys */
> > > > +	info->low.rm_startblock = XFS_BB_TO_FSBT(mp, dkey_low->fmr_physical);
> > > > +	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
> > > > +	error = xfs_fsmap_owner_to_rmap(keys, &info->low);
> > > > +	if (error)
> > > > +		return error;
> > > > +	info->low.rm_blockcount = 0;
> > > > +	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
> > > > +
> > > > +	error = xfs_fsmap_owner_to_rmap(keys + 1, &info->high);
> > > > +	if (error)
> > > > +		return error;
> > > > +	info->high.rm_startblock = -1U;
> > > > +	info->high.rm_owner = ULLONG_MAX;
> > > > +	info->high.rm_offset = ULLONG_MAX;
> > > > +	info->high.rm_blockcount = 0;
> > > > +	info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;
> > > > +	info->missing_owner = XFS_FMR_OWN_FREE;
> > > > +
> > > > +	trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
> > > > +			info->low.rm_startblock,
> > > > +			info->low.rm_blockcount,
> > > > +			info->low.rm_owner,
> > > > +			info->low.rm_offset);
> > > > +
> > > > +	trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
> > > > +			info->high.rm_startblock,
> > > > +			info->high.rm_blockcount,
> > > > +			info->high.rm_owner,
> > > > +			info->high.rm_offset);
> > > > +
> > > > +
> > > > +	if (dkey_low->fmr_physical > 0)
> > > > +		return 0;
> > > > +
> > > 
> > > A comment to point out we're fabricating an rmap record here would be
> > 
> > Ok.
> > 
> > > nice. Also, (how) do we handle/report internal log blocks?
> > 
> > The AG containing the log will have an rmapbt record for RMAP_OWN_LOG,
> > so that'll be in with the datadev records.
> > 
> 
> Ok, I recall now that the internal log is basically just permanently
> allocated space in whatever AG covers it.
> 
> > > > +	rmap.rm_startblock = 0;
> > > > +	rmap.rm_blockcount = mp->m_sb.sb_logblocks;
> > > > +	rmap.rm_owner = XFS_RMAP_OWN_LOG;
> > > > +	rmap.rm_offset = 0;
> > > > +	rmap.rm_flags = 0;
> > > > +
> > > > +	cur.bc_mp = mp;
> > > > +	cur.bc_tp = tp;
> > > > +	return xfs_getfsmap_rtdev_helper(&cur, &rmap, info);
> > > > +}
> > > > +
> ...
> > > > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> > > > index c67cfb4..bbe1b58 100644
> > > > --- a/fs/xfs/xfs_ioctl.c
> > > > +++ b/fs/xfs/xfs_ioctl.c
> ...
> > > > +STATIC int
> > > > +xfs_ioc_getfsmap(
> > > > +	struct xfs_inode	*ip,
> > > > +	void			__user *arg)
> > > > +{
> > > > +	struct getfsmap_info	info;
> > > > +	struct xfs_fsmap_head	xhead = {0};
> > > > +	struct fsmap_head	head;
> > > > +	bool			aborted = false;
> > > > +	int			error;
> > > > +
> ...
> > > > +	xhead.fmh_iflags = head.fmh_iflags;
> > > > +	xhead.fmh_count = head.fmh_count;
> > > > +	xfs_fsmap_to_internal(&xhead.fmh_keys[0], &head.fmh_keys[0]);
> > > > +	xfs_fsmap_to_internal(&xhead.fmh_keys[1], &head.fmh_keys[1]);
> > > > +
> > > > +	trace_xfs_getfsmap_low_key(ip->i_mount,
> > > > +			xhead.fmh_keys[0].fmr_device,
> > > > +			xhead.fmh_keys[0].fmr_physical,
> > > > +			xhead.fmh_keys[0].fmr_length,
> > > > +			xhead.fmh_keys[0].fmr_owner,
> > > > +			xhead.fmh_keys[0].fmr_offset,
> > > > +			xhead.fmh_keys[0].fmr_flags);
> > > > +
> > > > +	trace_xfs_getfsmap_high_key(ip->i_mount,
> > > > +			xhead.fmh_keys[1].fmr_device,
> > > > +			xhead.fmh_keys[1].fmr_physical,
> > > > +			xhead.fmh_keys[1].fmr_length,
> > > > +			xhead.fmh_keys[1].fmr_owner,
> > > > +			xhead.fmh_keys[1].fmr_offset,
> > > > +			xhead.fmh_keys[1].fmr_flags);
> > > > +
> > > 
> > > Hmm.. could we combine these into one call that looks like:
> > > 
> > > 	trace_xfs_getfsmap(mp, &fmh_keys[0], &fmh_keys[1]);
> > > 
> > > ... and has the trace handler pull the relevant data out of the key
> > > structure (same comment for the similar trace_xfs_fsmap*())?
> > 
> > I'd prefer to leave it as-is, because passing struct xfs_fsmap into a
> > tracepoint requires every file that includes xfs_trace.h to also include
> > xfs_fsmap.h to get the structure definition.
> > 
> 
> I think you can get around that with a structure declaration in
> xfs_trace.h, as the only code that actually requires the full definition
> is xfs_trace.c. If that works, that could at least reduce the tracepoint
> calls to a couple lines of code, even if we retain the independent
> low/high key tp's.

But then we'd have two definitions of the same structure, and anyone
touching xfs_fsmap would have to remember to update both.  I think it's
fine to pass pointers to core libxfs/*format.h structures directly into
tracepoints, but fsmap is on the periphery.

> > For debugging I also prefer only logging one big structure per
> > tracepoint, though I'm more willing to combine the two into one big
> > trace.  Also, as far as trace reporting goes, what do you think of:
> > 
> > xfs_io-1441  [002]  2363.403451: xfs_getfsmap_low_key: dev 8:80 keydev 0:0 block 0 len 0 owner 0 offset 0 flags 0x0
> > xfs_io-1441  [002]  2363.403521: xfs_getfsmap_high_key: dev 8:80 keydev 4095:1048575 block 36028797018963967 len 0 owner -1 offset 36028797018963967 flags 0xffffffff
> > 
> > versus:
> > 
> > xfs_io-1441  [002]  2363.403451: xfs_getfsmap_key: dev 8:80 lkeydev 0:0 lblock 0 llen 0 lowner 0 loffset 0 lflags 0x0 hkeydev 4095:1048575 hblock 36028797018963967 hlen 0 howner -1 hoffset 36028797018963967 hflags 0xffffffff
> > 
> > It's harder for me to dig through the second version of that for the
> > high key data since the column offset of hkeydev depends on the low key
> > contents.
> > 
> 
> Ok, seems reasonable. I guess I try to think of tracepoints as more
> event oriented than data oriented, but they're still just tracepoints so
> no big deal.
> 
> > > > +	info.mp = ip->i_mount;
> > > > +	info.data = ((__force struct fsmap_head *)arg)->fmh_recs;
> > > > +	error = xfs_getfsmap(ip->i_mount, &xhead, xfs_getfsmap_format, &info);
> > > > +	if (error == XFS_BTREE_QUERY_RANGE_ABORT) {
> > > > +		error = 0;
> > > > +		aborted = true;
> > > > +	} else if (error)
> > > > +		return error;
> > > > +
> > > > +	/* If we didn't abort, set the "last" flag in the last fmx */
> > > > +	if (!aborted && xhead.fmh_entries) {
> > > > +		info.data--;
> > > > +		info.last_flags |= FMR_OF_LAST;
> > > 
> > > Isn't this kind of implied by a short return? It looks like if a real
> > > error occurs at any point during the search, we just return the error. I
> > > guess there is still the case where the remaining mappings exactly match
> > > the number of entries in the data structure passed in and you'd have to
> > > make another call to identify EOF.
> > 
> > Yep.
> > 
> > > If we do want the flag, I'm also wondering why we couldn't stuff it in
> > > oflags in the header. Is there some reason I'm not yet aware of why we
> > > want the LAST flag in the flags of the last entry?
> > 
> > Basically I'm copying the LAST flag from fiemap/bmapx, for which you
> > could make the same argument.  I'm trying to mirror the same semantics
> > and the same meaning. :)
> > 
> 
> Ok, kind of figured that since bmap has the similar flag. I just wanted
> to bring it up because it looks like we require some roundabout support
> code to actually place it into the record flags after the fact. I
> suppose this is more of an API design matter anyways.

Yeah, it's tricky to reason around this because I'm not really familiar
with the reasons why those other ioctls have LAST flags.  I too figure
that the implementations either fill up the buffer to the maximum extent
possible or return an error.

--D

> 
> Brian
> 
> > ATM the sole real user of OF_LAST is scrub, which during the data block
> > verification phase will use the flag as a shortcut for "ok, this is the
> > last rmap entry we're going to see; kick off any IO that we've queued
> > but were holding onto just in case the next extent is contiguous".
> > 
> > The OF_LAST flag applies to just that last fsmap record, so (at least
> > in my mind) it belongs in the fsmap record, not the fsmap header.
> > Also, from the perspective of a userspace iterator of the fsmap data,
> > the iterator function would have to know that "OH_LAST means that I need
> > to communicate last-record status to the function I'm being passed, but
> > the fsmap record does not itself have a last flag, so lastness becomes a
> > second out-of-band parameter".  Easier just to build it into the
> > specific record it applies to.
> > 
> > xfs_scrub could get by without the flag at all, I suppose.
> > 
> > Thanks for working on the review, I really appreciate it. :)
> > 
> > --D
> > 
> > > Brian
> > > 
> > > > +		if (copy_to_user(&info.data->fmr_flags, &info.last_flags,
> > > > +				sizeof(info.last_flags)))
> > > > +			return -EFAULT;
> > > > +	}
> > > > +
> > > > +	/* copy back header */
> > > > +	head.fmh_entries = xhead.fmh_entries;
> > > > +	head.fmh_oflags = xhead.fmh_oflags;
> > > > +	if (copy_to_user(arg, &head, sizeof(struct fsmap_head)))
> > > > +		return -EFAULT;
> > > > +
> > > > +	return 0;
> > > > +}
> > > > +
> > > >  int
> > > >  xfs_ioc_swapext(
> > > >  	xfs_swapext_t	*sxp)
> > > > @@ -1787,6 +1887,9 @@ xfs_file_ioctl(
> > > >  	case XFS_IOC_GETBMAPX:
> > > >  		return xfs_ioc_getbmapx(ip, arg);
> > > >  
> > > > +	case FS_IOC_GETFSMAP:
> > > > +		return xfs_ioc_getfsmap(ip, arg);
> > > > +
> > > >  	case XFS_IOC_FD_TO_HANDLE:
> > > >  	case XFS_IOC_PATH_TO_HANDLE:
> > > >  	case XFS_IOC_PATH_TO_FSHANDLE: {
> > > > diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
> > > > index 7c49938..fa0bc4d 100644
> > > > --- a/fs/xfs/xfs_ioctl32.c
> > > > +++ b/fs/xfs/xfs_ioctl32.c
> > > > @@ -20,6 +20,7 @@
> > > >  #include <linux/mount.h>
> > > >  #include <linux/slab.h>
> > > >  #include <linux/uaccess.h>
> > > > +#include <linux/fsmap.h>
> > > >  #include "xfs.h"
> > > >  #include "xfs_fs.h"
> > > >  #include "xfs_format.h"
> > > > @@ -554,6 +555,7 @@ xfs_file_compat_ioctl(
> > > >  	case XFS_IOC_GOINGDOWN:
> > > >  	case XFS_IOC_ERROR_INJECTION:
> > > >  	case XFS_IOC_ERROR_CLEARALL:
> > > > +	case FS_IOC_GETFSMAP:
> > > >  		return xfs_file_ioctl(filp, cmd, p);
> > > >  #ifndef BROKEN_X86_ALIGNMENT
> > > >  	/* These are handled fine if no alignment issues */
> > > > diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> > > > index d3d11905..125d568 100644
> > > > --- a/fs/xfs/xfs_trace.h
> > > > +++ b/fs/xfs/xfs_trace.h
> > > > @@ -3270,6 +3270,91 @@ DEFINE_INODE_IREC_EVENT(xfs_swap_extent_rmap_remap);
> > > >  DEFINE_INODE_IREC_EVENT(xfs_swap_extent_rmap_remap_piece);
> > > >  DEFINE_INODE_ERROR_EVENT(xfs_swap_extent_rmap_error);
> > > >  
> > > > +/* fsmap traces */
> > > > +DECLARE_EVENT_CLASS(xfs_fsmap_class,
> > > > +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_agnumber_t agno,
> > > > +		 xfs_fsblock_t bno, xfs_filblks_t len, __uint64_t owner,
> > > > +		 __uint64_t offset),
> > > > +	TP_ARGS(mp, keydev, agno, bno, len, owner, offset),
> > > > +	TP_STRUCT__entry(
> > > > +		__field(dev_t, dev)
> > > > +		__field(dev_t, keydev)
> > > > +		__field(xfs_agnumber_t, agno)
> > > > +		__field(xfs_fsblock_t, bno)
> > > > +		__field(xfs_filblks_t, len)
> > > > +		__field(__uint64_t, owner)
> > > > +		__field(__uint64_t, offset)
> > > > +	),
> > > > +	TP_fast_assign(
> > > > +		__entry->dev = mp->m_super->s_dev;
> > > > +		__entry->keydev = new_decode_dev(keydev);
> > > > +		__entry->agno = agno;
> > > > +		__entry->bno = bno;
> > > > +		__entry->len = len;
> > > > +		__entry->owner = owner;
> > > > +		__entry->offset = offset;
> > > > +	),
> > > > +	TP_printk("dev %d:%d keydev %d:%d agno %u bno %llu len %llu owner %lld offset 0x%llx\n",
> > > > +		  MAJOR(__entry->dev), MINOR(__entry->dev),
> > > > +		  MAJOR(__entry->keydev), MINOR(__entry->keydev),
> > > > +		  __entry->agno,
> > > > +		  __entry->bno,
> > > > +		  __entry->len,
> > > > +		  __entry->owner,
> > > > +		  __entry->offset)
> > > > +)
> > > > +#define DEFINE_FSMAP_EVENT(name) \
> > > > +DEFINE_EVENT(xfs_fsmap_class, name, \
> > > > +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_agnumber_t agno, \
> > > > +		 xfs_fsblock_t bno, xfs_filblks_t len, __uint64_t owner, \
> > > > +		 __uint64_t offset), \
> > > > +	TP_ARGS(mp, keydev, agno, bno, len, owner, offset))
> > > > +DEFINE_FSMAP_EVENT(xfs_fsmap_low_key);
> > > > +DEFINE_FSMAP_EVENT(xfs_fsmap_high_key);
> > > > +DEFINE_FSMAP_EVENT(xfs_fsmap_mapping);
> > > > +
> > > > +DECLARE_EVENT_CLASS(xfs_getfsmap_class,
> > > > +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block,
> > > > +		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset,
> > > > +		 __uint64_t flags),
> > > > +	TP_ARGS(mp, keydev, block, len, owner, offset, flags),
> > > > +	TP_STRUCT__entry(
> > > > +		__field(dev_t, dev)
> > > > +		__field(dev_t, keydev)
> > > > +		__field(xfs_daddr_t, block)
> > > > +		__field(xfs_daddr_t, len)
> > > > +		__field(__uint64_t, owner)
> > > > +		__field(__uint64_t, offset)
> > > > +		__field(__uint64_t, flags)
> > > > +	),
> > > > +	TP_fast_assign(
> > > > +		__entry->dev = mp->m_super->s_dev;
> > > > +		__entry->keydev = new_decode_dev(keydev);
> > > > +		__entry->block = block;
> > > > +		__entry->len = len;
> > > > +		__entry->owner = owner;
> > > > +		__entry->offset = offset;
> > > > +		__entry->flags = flags;
> > > > +	),
> > > > +	TP_printk("dev %d:%d keydev %d:%d block %llu len %llu owner %lld offset %llu flags 0x%llx\n",
> > > > +		  MAJOR(__entry->dev), MINOR(__entry->dev),
> > > > +		  MAJOR(__entry->keydev), MINOR(__entry->keydev),
> > > > +		  __entry->block,
> > > > +		  __entry->len,
> > > > +		  __entry->owner,
> > > > +		  __entry->offset,
> > > > +		  __entry->flags)
> > > > +)
> > > > +#define DEFINE_GETFSMAP_EVENT(name) \
> > > > +DEFINE_EVENT(xfs_getfsmap_class, name, \
> > > > +	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block, \
> > > > +		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset, \
> > > > +		 __uint64_t flags), \
> > > > +	TP_ARGS(mp, keydev, block, len, owner, offset, flags))
> > > > +DEFINE_GETFSMAP_EVENT(xfs_getfsmap_low_key);
> > > > +DEFINE_GETFSMAP_EVENT(xfs_getfsmap_high_key);
> > > > +DEFINE_GETFSMAP_EVENT(xfs_getfsmap_mapping);
> > > > +
> > > >  #endif /* _TRACE_XFS_H */
> > > >  
> > > >  #undef TRACE_INCLUDE_PATH
> > > > diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> > > > index 70f42ea..a280e12 100644
> > > > --- a/fs/xfs/xfs_trans.c
> > > > +++ b/fs/xfs/xfs_trans.c
> > > > @@ -263,6 +263,28 @@ xfs_trans_alloc(
> > > >  }
> > > >  
> > > >  /*
> > > > + * Create an empty transaction with no reservation.  This is a defensive
> > > > + * mechanism for routines that query metadata without actually modifying
> > > > + * them -- if the metadata being queried is somehow cross-linked (think a
> > > > + * btree block pointer that points higher in the tree), we risk deadlock.
> > > > + * However, blocks grabbed as part of a transaction can be re-grabbed.
> > > > + * The verifiers will notice the corrupt block and the operation will fail
> > > > + * back to userspace without deadlocking.
> > > > + *
> > > > + * Note the zero-length reservation; this transaction MUST be cancelled
> > > > + * without any dirty data.
> > > > + */
> > > > +int
> > > > +xfs_trans_alloc_empty(
> > > > +	struct xfs_mount		*mp,
> > > > +	struct xfs_trans		**tpp)
> > > > +{
> > > > +	struct xfs_trans_res		resv = {0};
> > > > +
> > > > +	return xfs_trans_alloc(mp, &resv, 0, 0, XFS_TRANS_NO_WRITECOUNT, tpp);
> > > > +}
> > > > +
> > > > +/*
> > > >   * Record the indicated change to the given field for application
> > > >   * to the file system's superblock when the transaction commits.
> > > >   * For now, just store the change in the transaction structure.
> > > > diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
> > > > index 61b7fbd..98024cb 100644
> > > > --- a/fs/xfs/xfs_trans.h
> > > > +++ b/fs/xfs/xfs_trans.h
> > > > @@ -159,6 +159,8 @@ typedef struct xfs_trans {
> > > >  int		xfs_trans_alloc(struct xfs_mount *mp, struct xfs_trans_res *resp,
> > > >  			uint blocks, uint rtextents, uint flags,
> > > >  			struct xfs_trans **tpp);
> > > > +int		xfs_trans_alloc_empty(struct xfs_mount *mp,
> > > > +			struct xfs_trans **tpp);
> > > >  void		xfs_trans_mod_sb(xfs_trans_t *, uint, int64_t);
> > > >  
> > > >  struct xfs_buf	*xfs_trans_get_buf_map(struct xfs_trans *tp,
> > > > 
> > > > --
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Re: [PATCH 5/8] xfs: introduce the XFS_IOC_GETFSMAP ioctl

[Brian Foster]

On Thu, Feb 23, 2017 at 12:44:05PM -0800, Darrick J. Wong wrote:
> On Thu, Feb 23, 2017 at 09:45:43AM -0500, Brian Foster wrote:
> > On Wed, Feb 22, 2017 at 01:17:57PM -0800, Darrick J. Wong wrote:
> > > On Wed, Feb 22, 2017 at 10:02:47AM -0500, Brian Foster wrote:
> > > > On Fri, Feb 17, 2017 at 05:17:49PM -0800, Darrick J. Wong wrote:
> > > > > From: Darrick J. Wong <darrick.wong@oracle.com>
> > > > > 
> > > > > Introduce a new ioctl that uses the reverse mapping btree to return
> > > > > information about the physical layout of the filesystem.
> > > > > 
> > > > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > > > > ---
> > > > 
...
> > So the rmapbt query doesn't incorporate the full getfsmap key in the
> > search and we thus we have to include finer grained filtering..? If so,
> > I think this bit could be noted explicitly in the comment..
> 
> It's a funny quirk of how queries have to work when record keys contain
> multiple overlapping ranges interacting with the current design of
> query_range.
> 
> rmap tuple format is still (start, length, owner, offset).
> 
> Say you have the rmaps (24, 8, 128, 0) and (30, 10, 128, 8).  The low
> key of the first rmap is (24, 128, 0) and the high key is (31, 128, 7).
> That way you can query the rmapbt for start == 27 and it'll return the
> above rmap.  _btree_query_range was designed to return any record
> overlapping with any part of the interval, even if the record start or
> record end themselves are not within the interval.
> 
> However, if you want to look for the next tuple after (24, 8, 128, 0)
> you can't just tell it to search for (31...) because 31 > 30 and it'll
> miss that second rmap.  You can however tell it to search (24, 128, 8)
> and ignore any records if any part of the low key is not greater than
> the low search key.
> 
> Theoretically, we could enhance query_range to take an operator so that
> you could tell it to return any record overlapping with any part of the
> interval so long as the start of the record is strictly greater than the
> start of the query interval.
> 
> FWIW the comment for _btree_query_range says it returns all records
> overlapping with the interval passed in.
> 

Gotcha, thanks.

> > Also, I'm kind of wondering why we couldn't have just set next_daddr to
> > 40 in the first place based on the low key. Is there some other corner
> > case that breaks..?
> 
> Aha, looking through my notes, the original version also used next_daddr
> (buggily) to decide if a record actually started before the bumped low
> key so that it could ignore it.  Subsequent revisions created an
> explicit test function (_getfsmap_rec_before_low_key) so you're right,
> we can set next_daddr to 40 (fmh_keys[0]->fmr_physical + fmr_length) for
> the first loop iteration and zero for subsequent iterations.  With that
> the key_end business also goes away.
> 

Oh, Ok. That sounds like a nice cleanup then.

> > > Assuming _getfsmap_helper is passed the same refcount rmap as before.
> > > rec_daddr = 64, and when we get to line 318, key_end = 24 + 16.
> > > 
> > > The test is now:
> > > if (devices match && 40 < 40 && 64 >= 40)
> > > So we leave next_daddr at 40.
> > > 
> > > The correct output here is to synthesize an fsmap record for free space
> > > between 40-64, and then to emit the refcount record at 64.
> > > 
> > > Third example: fmh_keys = [(8:0, 24, 16, 128, 0), (-1)] and next_daddr = 24
> > > as before.  _getfsmap_helper again sees (8:0, 24, 16, 128, 0) and sets
> > > next_daddr = 40.
> > > 
> > > This time, however, _getfsmap_helper is passed (8:0, 32, 8, 129, 0),
> > > which is 8 sectors of inode 129's data at offset 0.  rec_daddr = 32,
> > > key_end = 24 + 16 as before.
> > > 
> > > The test is now:
> > > if (devices match && 40 < 40 && 32 >= 40)
> > > So we again leave next_daddr at 40, then emit the fsmap for inode 129.
> > > 
...
> > > > 
> > > > Hmm.. could we combine these into one call that looks like:
> > > > 
> > > > 	trace_xfs_getfsmap(mp, &fmh_keys[0], &fmh_keys[1]);
> > > > 
> > > > ... and has the trace handler pull the relevant data out of the key
> > > > structure (same comment for the similar trace_xfs_fsmap*())?
> > > 
> > > I'd prefer to leave it as-is, because passing struct xfs_fsmap into a
> > > tracepoint requires every file that includes xfs_trace.h to also include
> > > xfs_fsmap.h to get the structure definition.
> > > 
> > 
> > I think you can get around that with a structure declaration in
> > xfs_trace.h, as the only code that actually requires the full definition
> > is xfs_trace.c. If that works, that could at least reduce the tracepoint
> > calls to a couple lines of code, even if we retain the independent
> > low/high key tp's.
> 
> But then we'd have two definitions of the same structure, and anyone
> touching xfs_fsmap would have to remember to update both.  I think it's
> fine to pass pointers to core libxfs/*format.h structures directly into
> tracepoints, but fsmap is on the periphery.
> 

No, it's just a declaration (not the full structure definition). I.e.,
add 'struct xfs_fsmap;' to the list of similarly declared structures at
the top of xfs_trace.h.

See the appended diff for what I mean. It only changes one of the
classes, but compiles clean for me (compile tested only)..

Brian

--- 8< ---

diff --git a/fs/xfs/xfs_fsmap.h b/fs/xfs/xfs_fsmap.h
index 1943047..55f7c85 100644
--- a/fs/xfs/xfs_fsmap.h
+++ b/fs/xfs/xfs_fsmap.h
@@ -20,6 +20,8 @@
 #ifndef __XFS_FSMAP_H__
 #define	__XFS_FSMAP_H__
 
+struct fsmap;
+
 /* internal fsmap representation */
 struct xfs_fsmap {
 	dev_t		fmr_device;	/* device id */
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index e1f3fbf..95f4923 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1622,9 +1622,7 @@ xfs_getfsmap_format(struct xfs_fsmap *xfm, void *priv)
 	struct getfsmap_info	*info = priv;
 	struct fsmap		fm;
 
-	trace_xfs_getfsmap_mapping(info->mp, xfm->fmr_device, xfm->fmr_physical,
-			xfm->fmr_length, xfm->fmr_owner, xfm->fmr_offset,
-			xfm->fmr_flags);
+	trace_xfs_getfsmap_mapping(info->mp, xfm);
 
 	info->last_flags = xfm->fmr_flags;
 	xfs_fsmap_from_internal(&fm, xfm);
@@ -1664,21 +1662,8 @@ xfs_ioc_getfsmap(
 	xfs_fsmap_to_internal(&xhead.fmh_keys[0], &head.fmh_keys[0]);
 	xfs_fsmap_to_internal(&xhead.fmh_keys[1], &head.fmh_keys[1]);
 
-	trace_xfs_getfsmap_low_key(ip->i_mount,
-			xhead.fmh_keys[0].fmr_device,
-			xhead.fmh_keys[0].fmr_physical,
-			xhead.fmh_keys[0].fmr_length,
-			xhead.fmh_keys[0].fmr_owner,
-			xhead.fmh_keys[0].fmr_offset,
-			xhead.fmh_keys[0].fmr_flags);
-
-	trace_xfs_getfsmap_high_key(ip->i_mount,
-			xhead.fmh_keys[1].fmr_device,
-			xhead.fmh_keys[1].fmr_physical,
-			xhead.fmh_keys[1].fmr_length,
-			xhead.fmh_keys[1].fmr_owner,
-			xhead.fmh_keys[1].fmr_offset,
-			xhead.fmh_keys[1].fmr_flags);
+	trace_xfs_getfsmap_low_key(ip->i_mount, &xhead.fmh_keys[0]);
+	trace_xfs_getfsmap_high_key(ip->i_mount, &xhead.fmh_keys[1]);
 
 	info.mp = ip->i_mount;
 	info.data = ((__force struct fsmap_head *)arg)->fmh_recs;
diff --git a/fs/xfs/xfs_trace.c b/fs/xfs/xfs_trace.c
index 7f17ae6..5d95fe3 100644
--- a/fs/xfs/xfs_trace.c
+++ b/fs/xfs/xfs_trace.c
@@ -47,6 +47,7 @@
 #include "xfs_inode_item.h"
 #include "xfs_bmap_btree.h"
 #include "xfs_filestream.h"
+#include "xfs_fsmap.h"
 
 /*
  * We include this last to have the helpers above available for the trace
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index dbfc4db..a8eaf34 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -40,6 +40,7 @@ struct xfs_inode_log_format;
 struct xfs_bmbt_irec;
 struct xfs_btree_cur;
 struct xfs_refcount_irec;
+struct xfs_fsmap;
 
 DECLARE_EVENT_CLASS(xfs_attr_list_class,
 	TP_PROTO(struct xfs_attr_list_context *ctx),
@@ -3311,10 +3312,8 @@ DEFINE_FSMAP_EVENT(xfs_fsmap_high_key);
 DEFINE_FSMAP_EVENT(xfs_fsmap_mapping);
 
 DECLARE_EVENT_CLASS(xfs_getfsmap_class,
-	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block,
-		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset,
-		 __uint64_t flags),
-	TP_ARGS(mp, keydev, block, len, owner, offset, flags),
+	TP_PROTO(struct xfs_mount *mp, struct xfs_fsmap *fsmap),
+	TP_ARGS(mp, fsmap),
 	TP_STRUCT__entry(
 		__field(dev_t, dev)
 		__field(dev_t, keydev)
@@ -3326,12 +3325,12 @@ DECLARE_EVENT_CLASS(xfs_getfsmap_class,
 	),
 	TP_fast_assign(
 		__entry->dev = mp->m_super->s_dev;
-		__entry->keydev = new_decode_dev(keydev);
-		__entry->block = block;
-		__entry->len = len;
-		__entry->owner = owner;
-		__entry->offset = offset;
-		__entry->flags = flags;
+		__entry->keydev = new_decode_dev(fsmap->fmr_device);
+		__entry->block = fsmap->fmr_physical;
+		__entry->len = fsmap->fmr_length;
+		__entry->owner = fsmap->fmr_owner;
+		__entry->offset = fsmap->fmr_offset;
+		__entry->flags = fsmap->fmr_flags;
 	),
 	TP_printk("dev %d:%d keydev %d:%d block %llu len %llu owner %lld offset %llu flags 0x%llx\n",
 		  MAJOR(__entry->dev), MINOR(__entry->dev),
@@ -3344,10 +3343,8 @@ DECLARE_EVENT_CLASS(xfs_getfsmap_class,
 )
 #define DEFINE_GETFSMAP_EVENT(name) \
 DEFINE_EVENT(xfs_getfsmap_class, name, \
-	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block, \
-		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset, \
-		 __uint64_t flags), \
-	TP_ARGS(mp, keydev, block, len, owner, offset, flags))
+	TP_PROTO(struct xfs_mount *mp, struct xfs_fsmap *fsmap), \
+	TP_ARGS(mp, fsmap))
 DEFINE_GETFSMAP_EVENT(xfs_getfsmap_low_key);
 DEFINE_GETFSMAP_EVENT(xfs_getfsmap_high_key);
 DEFINE_GETFSMAP_EVENT(xfs_getfsmap_mapping);

Re: [PATCH 5/8] xfs: introduce the XFS_IOC_GETFSMAP ioctl

[Darrick J. Wong]

On Thu, Feb 23, 2017 at 06:43:01PM -0500, Brian Foster wrote:
> On Thu, Feb 23, 2017 at 12:44:05PM -0800, Darrick J. Wong wrote:
> > On Thu, Feb 23, 2017 at 09:45:43AM -0500, Brian Foster wrote:
> > > On Wed, Feb 22, 2017 at 01:17:57PM -0800, Darrick J. Wong wrote:
> > > > On Wed, Feb 22, 2017 at 10:02:47AM -0500, Brian Foster wrote:
> > > > > On Fri, Feb 17, 2017 at 05:17:49PM -0800, Darrick J. Wong wrote:
> > > > > > From: Darrick J. Wong <darrick.wong@oracle.com>
> > > > > > 
> > > > > > Introduce a new ioctl that uses the reverse mapping btree to return
> > > > > > information about the physical layout of the filesystem.
> > > > > > 
> > > > > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > > > > > ---
> > > > > 
> ...
> > > So the rmapbt query doesn't incorporate the full getfsmap key in the
> > > search and we thus we have to include finer grained filtering..? If so,
> > > I think this bit could be noted explicitly in the comment..
> > 
> > It's a funny quirk of how queries have to work when record keys contain
> > multiple overlapping ranges interacting with the current design of
> > query_range.
> > 
> > rmap tuple format is still (start, length, owner, offset).
> > 
> > Say you have the rmaps (24, 8, 128, 0) and (30, 10, 128, 8).  The low
> > key of the first rmap is (24, 128, 0) and the high key is (31, 128, 7).
> > That way you can query the rmapbt for start == 27 and it'll return the
> > above rmap.  _btree_query_range was designed to return any record
> > overlapping with any part of the interval, even if the record start or
> > record end themselves are not within the interval.
> > 
> > However, if you want to look for the next tuple after (24, 8, 128, 0)
> > you can't just tell it to search for (31...) because 31 > 30 and it'll
> > miss that second rmap.  You can however tell it to search (24, 128, 8)
> > and ignore any records if any part of the low key is not greater than
> > the low search key.
> > 
> > Theoretically, we could enhance query_range to take an operator so that
> > you could tell it to return any record overlapping with any part of the
> > interval so long as the start of the record is strictly greater than the
> > start of the query interval.
> > 
> > FWIW the comment for _btree_query_range says it returns all records
> > overlapping with the interval passed in.
> > 
> 
> Gotcha, thanks.
> 
> > > Also, I'm kind of wondering why we couldn't have just set next_daddr to
> > > 40 in the first place based on the low key. Is there some other corner
> > > case that breaks..?
> > 
> > Aha, looking through my notes, the original version also used next_daddr
> > (buggily) to decide if a record actually started before the bumped low
> > key so that it could ignore it.  Subsequent revisions created an
> > explicit test function (_getfsmap_rec_before_low_key) so you're right,
> > we can set next_daddr to 40 (fmh_keys[0]->fmr_physical + fmr_length) for
> > the first loop iteration and zero for subsequent iterations.  With that
> > the key_end business also goes away.
> > 
> 
> Oh, Ok. That sounds like a nice cleanup then.
> 
> > > > Assuming _getfsmap_helper is passed the same refcount rmap as before.
> > > > rec_daddr = 64, and when we get to line 318, key_end = 24 + 16.
> > > > 
> > > > The test is now:
> > > > if (devices match && 40 < 40 && 64 >= 40)
> > > > So we leave next_daddr at 40.
> > > > 
> > > > The correct output here is to synthesize an fsmap record for free space
> > > > between 40-64, and then to emit the refcount record at 64.
> > > > 
> > > > Third example: fmh_keys = [(8:0, 24, 16, 128, 0), (-1)] and next_daddr = 24
> > > > as before.  _getfsmap_helper again sees (8:0, 24, 16, 128, 0) and sets
> > > > next_daddr = 40.
> > > > 
> > > > This time, however, _getfsmap_helper is passed (8:0, 32, 8, 129, 0),
> > > > which is 8 sectors of inode 129's data at offset 0.  rec_daddr = 32,
> > > > key_end = 24 + 16 as before.
> > > > 
> > > > The test is now:
> > > > if (devices match && 40 < 40 && 32 >= 40)
> > > > So we again leave next_daddr at 40, then emit the fsmap for inode 129.
> > > > 
> ...
> > > > > 
> > > > > Hmm.. could we combine these into one call that looks like:
> > > > > 
> > > > > 	trace_xfs_getfsmap(mp, &fmh_keys[0], &fmh_keys[1]);
> > > > > 
> > > > > ... and has the trace handler pull the relevant data out of the key
> > > > > structure (same comment for the similar trace_xfs_fsmap*())?
> > > > 
> > > > I'd prefer to leave it as-is, because passing struct xfs_fsmap into a
> > > > tracepoint requires every file that includes xfs_trace.h to also include
> > > > xfs_fsmap.h to get the structure definition.
> > > > 
> > > 
> > > I think you can get around that with a structure declaration in
> > > xfs_trace.h, as the only code that actually requires the full definition
> > > is xfs_trace.c. If that works, that could at least reduce the tracepoint
> > > calls to a couple lines of code, even if we retain the independent
> > > low/high key tp's.
> > 
> > But then we'd have two definitions of the same structure, and anyone
> > touching xfs_fsmap would have to remember to update both.  I think it's
> > fine to pass pointers to core libxfs/*format.h structures directly into
> > tracepoints, but fsmap is on the periphery.
> > 
> 
> No, it's just a declaration (not the full structure definition). I.e.,
> add 'struct xfs_fsmap;' to the list of similarly declared structures at
> the top of xfs_trace.h.
> 
> See the appended diff for what I mean. It only changes one of the
> classes, but compiles clean for me (compile tested only)..

Oh, you're right, that does work.  I forgot that xfs_trace.h is a magic
headerfile on account of CREATE_TRACE_POINTS.  Ok, I'll go fix that too.

--D

> 
> Brian
> 
> --- 8< ---
> 
> diff --git a/fs/xfs/xfs_fsmap.h b/fs/xfs/xfs_fsmap.h
> index 1943047..55f7c85 100644
> --- a/fs/xfs/xfs_fsmap.h
> +++ b/fs/xfs/xfs_fsmap.h
> @@ -20,6 +20,8 @@
>  #ifndef __XFS_FSMAP_H__
>  #define	__XFS_FSMAP_H__
>  
> +struct fsmap;
> +
>  /* internal fsmap representation */
>  struct xfs_fsmap {
>  	dev_t		fmr_device;	/* device id */
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index e1f3fbf..95f4923 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -1622,9 +1622,7 @@ xfs_getfsmap_format(struct xfs_fsmap *xfm, void *priv)
>  	struct getfsmap_info	*info = priv;
>  	struct fsmap		fm;
>  
> -	trace_xfs_getfsmap_mapping(info->mp, xfm->fmr_device, xfm->fmr_physical,
> -			xfm->fmr_length, xfm->fmr_owner, xfm->fmr_offset,
> -			xfm->fmr_flags);
> +	trace_xfs_getfsmap_mapping(info->mp, xfm);
>  
>  	info->last_flags = xfm->fmr_flags;
>  	xfs_fsmap_from_internal(&fm, xfm);
> @@ -1664,21 +1662,8 @@ xfs_ioc_getfsmap(
>  	xfs_fsmap_to_internal(&xhead.fmh_keys[0], &head.fmh_keys[0]);
>  	xfs_fsmap_to_internal(&xhead.fmh_keys[1], &head.fmh_keys[1]);
>  
> -	trace_xfs_getfsmap_low_key(ip->i_mount,
> -			xhead.fmh_keys[0].fmr_device,
> -			xhead.fmh_keys[0].fmr_physical,
> -			xhead.fmh_keys[0].fmr_length,
> -			xhead.fmh_keys[0].fmr_owner,
> -			xhead.fmh_keys[0].fmr_offset,
> -			xhead.fmh_keys[0].fmr_flags);
> -
> -	trace_xfs_getfsmap_high_key(ip->i_mount,
> -			xhead.fmh_keys[1].fmr_device,
> -			xhead.fmh_keys[1].fmr_physical,
> -			xhead.fmh_keys[1].fmr_length,
> -			xhead.fmh_keys[1].fmr_owner,
> -			xhead.fmh_keys[1].fmr_offset,
> -			xhead.fmh_keys[1].fmr_flags);
> +	trace_xfs_getfsmap_low_key(ip->i_mount, &xhead.fmh_keys[0]);
> +	trace_xfs_getfsmap_high_key(ip->i_mount, &xhead.fmh_keys[1]);
>  
>  	info.mp = ip->i_mount;
>  	info.data = ((__force struct fsmap_head *)arg)->fmh_recs;
> diff --git a/fs/xfs/xfs_trace.c b/fs/xfs/xfs_trace.c
> index 7f17ae6..5d95fe3 100644
> --- a/fs/xfs/xfs_trace.c
> +++ b/fs/xfs/xfs_trace.c
> @@ -47,6 +47,7 @@
>  #include "xfs_inode_item.h"
>  #include "xfs_bmap_btree.h"
>  #include "xfs_filestream.h"
> +#include "xfs_fsmap.h"
>  
>  /*
>   * We include this last to have the helpers above available for the trace
> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index dbfc4db..a8eaf34 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -40,6 +40,7 @@ struct xfs_inode_log_format;
>  struct xfs_bmbt_irec;
>  struct xfs_btree_cur;
>  struct xfs_refcount_irec;
> +struct xfs_fsmap;
>  
>  DECLARE_EVENT_CLASS(xfs_attr_list_class,
>  	TP_PROTO(struct xfs_attr_list_context *ctx),
> @@ -3311,10 +3312,8 @@ DEFINE_FSMAP_EVENT(xfs_fsmap_high_key);
>  DEFINE_FSMAP_EVENT(xfs_fsmap_mapping);
>  
>  DECLARE_EVENT_CLASS(xfs_getfsmap_class,
> -	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block,
> -		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset,
> -		 __uint64_t flags),
> -	TP_ARGS(mp, keydev, block, len, owner, offset, flags),
> +	TP_PROTO(struct xfs_mount *mp, struct xfs_fsmap *fsmap),
> +	TP_ARGS(mp, fsmap),
>  	TP_STRUCT__entry(
>  		__field(dev_t, dev)
>  		__field(dev_t, keydev)
> @@ -3326,12 +3325,12 @@ DECLARE_EVENT_CLASS(xfs_getfsmap_class,
>  	),
>  	TP_fast_assign(
>  		__entry->dev = mp->m_super->s_dev;
> -		__entry->keydev = new_decode_dev(keydev);
> -		__entry->block = block;
> -		__entry->len = len;
> -		__entry->owner = owner;
> -		__entry->offset = offset;
> -		__entry->flags = flags;
> +		__entry->keydev = new_decode_dev(fsmap->fmr_device);
> +		__entry->block = fsmap->fmr_physical;
> +		__entry->len = fsmap->fmr_length;
> +		__entry->owner = fsmap->fmr_owner;
> +		__entry->offset = fsmap->fmr_offset;
> +		__entry->flags = fsmap->fmr_flags;
>  	),
>  	TP_printk("dev %d:%d keydev %d:%d block %llu len %llu owner %lld offset %llu flags 0x%llx\n",
>  		  MAJOR(__entry->dev), MINOR(__entry->dev),
> @@ -3344,10 +3343,8 @@ DECLARE_EVENT_CLASS(xfs_getfsmap_class,
>  )
>  #define DEFINE_GETFSMAP_EVENT(name) \
>  DEFINE_EVENT(xfs_getfsmap_class, name, \
> -	TP_PROTO(struct xfs_mount *mp, u32 keydev, xfs_daddr_t block, \
> -		 xfs_daddr_t len, __uint64_t owner, __uint64_t offset, \
> -		 __uint64_t flags), \
> -	TP_ARGS(mp, keydev, block, len, owner, offset, flags))
> +	TP_PROTO(struct xfs_mount *mp, struct xfs_fsmap *fsmap), \
> +	TP_ARGS(mp, fsmap))
>  DEFINE_GETFSMAP_EVENT(xfs_getfsmap_low_key);
>  DEFINE_GETFSMAP_EVENT(xfs_getfsmap_high_key);
>  DEFINE_GETFSMAP_EVENT(xfs_getfsmap_mapping);
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

[PATCH 6/8] xfs: have getfsmap fall back to the freesp btrees when rmap is not present

[Darrick J. Wong]

From: Darrick J. Wong <darrick.wong@oracle.com>

If the reverse-mapping btree isn't available, fall back to the
free space btrees to provide partial reverse mapping information.
The online scrub tool can make use of even partial information to
speed up the data block scan.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/xfs_fsmap.c |  155 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 152 insertions(+), 3 deletions(-)


diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
index 09d6b92..82e44a9 100644
--- a/fs/xfs/xfs_fsmap.c
+++ b/fs/xfs/xfs_fsmap.c
@@ -40,6 +40,7 @@
 #include "xfs_fsmap.h"
 #include "xfs_refcount.h"
 #include "xfs_refcount_btree.h"
+#include "xfs_alloc_btree.h"
 
 /* Convert an xfs_fsmap to an fsmap. */
 void
@@ -158,6 +159,9 @@ xfs_fsmap_owner_from_rmap(
 	case XFS_RMAP_OWN_COW:
 		fmr->fmr_owner = XFS_FMR_OWN_COW;
 		break;
+	case XFS_RMAP_OWN_NULL:	/* "free" */
+		fmr->fmr_owner = XFS_FMR_OWN_FREE;
+		break;
 	default:
 		return -EFSCORRUPTED;
 	}
@@ -433,6 +437,31 @@ xfs_getfsmap_rtdev_helper(
 	return xfs_getfsmap_helper(cur->bc_tp, info, rec, rec_daddr);
 }
 
+/* Transform a bnobt irec into a fsmap */
+STATIC int
+xfs_getfsmap_datadev_bnobt_helper(
+	struct xfs_btree_cur		*cur,
+	struct xfs_alloc_rec_incore	*rec,
+	void				*priv)
+{
+	struct xfs_mount		*mp = cur->bc_mp;
+	struct xfs_getfsmap_info	*info = priv;
+	struct xfs_rmap_irec		irec;
+	xfs_fsblock_t			fsb;
+	xfs_daddr_t			rec_daddr;
+
+	fsb = XFS_AGB_TO_FSB(mp, cur->bc_private.a.agno, rec->ar_startblock);
+	rec_daddr = XFS_FSB_TO_DADDR(mp, fsb);
+
+	irec.rm_startblock = rec->ar_startblock;
+	irec.rm_blockcount = rec->ar_blockcount;
+	irec.rm_owner = XFS_RMAP_OWN_NULL;	/* "free" */
+	irec.rm_offset = 0;
+	irec.rm_flags = 0;
+
+	return xfs_getfsmap_helper(cur->bc_tp, info, &irec, rec_daddr);
+}
+
 /* Set rmap flags based on the getfsmap flags */
 static void
 xfs_getfsmap_set_irec_flags(
@@ -621,6 +650,125 @@ xfs_getfsmap_datadev(
 	return error;
 }
 
+/* Execute a getfsmap query against the regular data device's bnobt. */
+STATIC int
+xfs_getfsmap_datadev_bnobt(
+	struct xfs_trans		*tp,
+	struct xfs_fsmap		*keys,
+	struct xfs_getfsmap_info	*info)
+{
+	struct xfs_mount		*mp = tp->t_mountp;
+	struct xfs_btree_cur		*bt_cur = NULL;
+	struct xfs_fsmap		*dkey_low;
+	struct xfs_fsmap		*dkey_high;
+	struct xfs_alloc_rec_incore	alow;
+	struct xfs_alloc_rec_incore	ahigh;
+	xfs_fsblock_t			start_fsb;
+	xfs_fsblock_t			end_fsb;
+	xfs_agnumber_t			start_ag;
+	xfs_agnumber_t			end_ag;
+	xfs_daddr_t			eofs;
+	int				error = 0;
+
+	dkey_low = keys;
+	dkey_high = keys + 1;
+	eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks);
+	if (dkey_low->fmr_physical >= eofs)
+		return 0;
+	if (dkey_high->fmr_physical >= eofs)
+		dkey_high->fmr_physical = eofs - 1;
+	start_fsb = XFS_DADDR_TO_FSB(mp, dkey_low->fmr_physical);
+	end_fsb = XFS_DADDR_TO_FSB(mp, dkey_high->fmr_physical);
+
+	/* Set up search keys */
+	info->low.rm_startblock = XFS_FSB_TO_AGBNO(mp, start_fsb);
+	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
+	error = xfs_fsmap_owner_to_rmap(dkey_low, &info->low);
+	if (error)
+		return error;
+	info->low.rm_blockcount = 0;
+	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
+
+	info->high.rm_startblock = -1U;
+	info->high.rm_owner = ULLONG_MAX;
+	info->high.rm_offset = ULLONG_MAX;
+	info->high.rm_blockcount = 0;
+	info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;
+
+	info->missing_owner = XFS_FMR_OWN_UNKNOWN;
+
+	start_ag = XFS_FSB_TO_AGNO(mp, start_fsb);
+	end_ag = XFS_FSB_TO_AGNO(mp, end_fsb);
+
+	/* Query each AG */
+	for (info->agno = start_ag; info->agno <= end_ag; info->agno++) {
+		if (info->agno == end_ag) {
+			info->high.rm_startblock = XFS_FSB_TO_AGBNO(mp,
+					end_fsb);
+			info->high.rm_offset = XFS_BB_TO_FSBT(mp,
+					dkey_high->fmr_offset);
+			error = xfs_fsmap_owner_to_rmap(dkey_high, &info->high);
+			if (error)
+				goto err;
+			xfs_getfsmap_set_irec_flags(&info->high, dkey_high);
+		}
+
+		if (bt_cur) {
+			xfs_btree_del_cursor(bt_cur, XFS_BTREE_NOERROR);
+			bt_cur = NULL;
+			info->agf_bp = NULL;
+		}
+
+		error = xfs_alloc_read_agf(mp, tp, info->agno, 0,
+				&info->agf_bp);
+		if (error)
+			goto err;
+
+		trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
+				info->low.rm_startblock,
+				info->low.rm_blockcount,
+				info->low.rm_owner,
+				info->low.rm_offset);
+
+		trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
+				info->high.rm_startblock,
+				info->high.rm_blockcount,
+				info->high.rm_owner,
+				info->high.rm_offset);
+
+		bt_cur = xfs_allocbt_init_cursor(mp, tp, info->agf_bp,
+				info->agno, XFS_BTNUM_BNO);
+		alow.ar_startblock = info->low.rm_startblock;
+		ahigh.ar_startblock = info->high.rm_startblock;
+		error = xfs_alloc_query_range(bt_cur, &alow, &ahigh,
+				xfs_getfsmap_datadev_bnobt_helper, info);
+		if (error)
+			goto err;
+
+		if (info->agno == start_ag) {
+			info->low.rm_startblock = 0;
+			info->low.rm_owner = 0;
+			info->low.rm_offset = 0;
+			info->low.rm_flags = 0;
+		}
+	}
+
+	/* Report any free space at the end of the AG */
+	info->last = true;
+	error = xfs_getfsmap_datadev_bnobt_helper(bt_cur, &ahigh, info);
+	if (error)
+		goto err;
+
+err:
+	if (bt_cur)
+		xfs_btree_del_cursor(bt_cur, error < 0 ? XFS_BTREE_ERROR :
+							 XFS_BTREE_NOERROR);
+	if (info->agf_bp)
+		info->agf_bp = NULL;
+
+	return error;
+}
+
 /* Do we recognize the device? */
 STATIC bool
 xfs_getfsmap_is_valid_device(
@@ -689,8 +837,6 @@ xfs_getfsmap(
 	int				i;
 	int				error = 0;
 
-	if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
-		return -EOPNOTSUPP;
 	if (head->fmh_iflags & ~FMH_IF_VALID)
 		return -EINVAL;
 	rkey_low = head->fmh_keys;
@@ -704,7 +850,10 @@ xfs_getfsmap(
 	/* Set up our device handlers. */
 	memset(handlers, 0, sizeof(handlers));
 	handlers[0].dev = new_encode_dev(mp->m_ddev_targp->bt_dev);
-	handlers[0].fn = xfs_getfsmap_datadev;
+	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
+		handlers[0].fn = xfs_getfsmap_datadev;
+	else
+		handlers[0].fn = xfs_getfsmap_datadev_bnobt;
 	if (mp->m_logdev_targp != mp->m_ddev_targp) {
 		handlers[1].dev = new_encode_dev(mp->m_logdev_targp->bt_dev);
 		handlers[1].fn = xfs_getfsmap_logdev;

Re: [PATCH 6/8] xfs: have getfsmap fall back to the freesp btrees when rmap is not present

[Brian Foster]

On Fri, Feb 17, 2017 at 05:17:55PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> If the reverse-mapping btree isn't available, fall back to the
> free space btrees to provide partial reverse mapping information.
> The online scrub tool can make use of even partial information to
> speed up the data block scan.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/xfs/xfs_fsmap.c |  155 +++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 152 insertions(+), 3 deletions(-)
> 
> 
> diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
> index 09d6b92..82e44a9 100644
> --- a/fs/xfs/xfs_fsmap.c
> +++ b/fs/xfs/xfs_fsmap.c
> @@ -40,6 +40,7 @@
>  #include "xfs_fsmap.h"
>  #include "xfs_refcount.h"
>  #include "xfs_refcount_btree.h"
> +#include "xfs_alloc_btree.h"
>  
>  /* Convert an xfs_fsmap to an fsmap. */
>  void
> @@ -158,6 +159,9 @@ xfs_fsmap_owner_from_rmap(
>  	case XFS_RMAP_OWN_COW:
>  		fmr->fmr_owner = XFS_FMR_OWN_COW;
>  		break;
> +	case XFS_RMAP_OWN_NULL:	/* "free" */
> +		fmr->fmr_owner = XFS_FMR_OWN_FREE;
> +		break;
>  	default:
>  		return -EFSCORRUPTED;
>  	}
> @@ -433,6 +437,31 @@ xfs_getfsmap_rtdev_helper(
>  	return xfs_getfsmap_helper(cur->bc_tp, info, rec, rec_daddr);
>  }
>  
> +/* Transform a bnobt irec into a fsmap */
> +STATIC int
> +xfs_getfsmap_datadev_bnobt_helper(
> +	struct xfs_btree_cur		*cur,
> +	struct xfs_alloc_rec_incore	*rec,
> +	void				*priv)
> +{
> +	struct xfs_mount		*mp = cur->bc_mp;
> +	struct xfs_getfsmap_info	*info = priv;
> +	struct xfs_rmap_irec		irec;
> +	xfs_fsblock_t			fsb;
> +	xfs_daddr_t			rec_daddr;
> +
> +	fsb = XFS_AGB_TO_FSB(mp, cur->bc_private.a.agno, rec->ar_startblock);
> +	rec_daddr = XFS_FSB_TO_DADDR(mp, fsb);
> +
> +	irec.rm_startblock = rec->ar_startblock;
> +	irec.rm_blockcount = rec->ar_blockcount;
> +	irec.rm_owner = XFS_RMAP_OWN_NULL;	/* "free" */
> +	irec.rm_offset = 0;
> +	irec.rm_flags = 0;
> +

Slightly confused... if we directly pass free space records to
xfs_getfsmap_helper(), won't it also assume the gaps between the records
are free space?

> +	return xfs_getfsmap_helper(cur->bc_tp, info, &irec, rec_daddr);
> +}
> +
>  /* Set rmap flags based on the getfsmap flags */
>  static void
>  xfs_getfsmap_set_irec_flags(
> @@ -621,6 +650,125 @@ xfs_getfsmap_datadev(
>  	return error;
>  }
>  
> +/* Execute a getfsmap query against the regular data device's bnobt. */
> +STATIC int
> +xfs_getfsmap_datadev_bnobt(
> +	struct xfs_trans		*tp,
> +	struct xfs_fsmap		*keys,
> +	struct xfs_getfsmap_info	*info)
> +{
> +	struct xfs_mount		*mp = tp->t_mountp;
> +	struct xfs_btree_cur		*bt_cur = NULL;
> +	struct xfs_fsmap		*dkey_low;
> +	struct xfs_fsmap		*dkey_high;
> +	struct xfs_alloc_rec_incore	alow;
> +	struct xfs_alloc_rec_incore	ahigh;
> +	xfs_fsblock_t			start_fsb;
> +	xfs_fsblock_t			end_fsb;
> +	xfs_agnumber_t			start_ag;
> +	xfs_agnumber_t			end_ag;
> +	xfs_daddr_t			eofs;
> +	int				error = 0;
> +
> +	dkey_low = keys;
> +	dkey_high = keys + 1;
> +	eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks);
> +	if (dkey_low->fmr_physical >= eofs)
> +		return 0;
> +	if (dkey_high->fmr_physical >= eofs)
> +		dkey_high->fmr_physical = eofs - 1;
> +	start_fsb = XFS_DADDR_TO_FSB(mp, dkey_low->fmr_physical);
> +	end_fsb = XFS_DADDR_TO_FSB(mp, dkey_high->fmr_physical);
> +
> +	/* Set up search keys */
> +	info->low.rm_startblock = XFS_FSB_TO_AGBNO(mp, start_fsb);
> +	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
> +	error = xfs_fsmap_owner_to_rmap(dkey_low, &info->low);
> +	if (error)
> +		return error;
> +	info->low.rm_blockcount = 0;
> +	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
> +
> +	info->high.rm_startblock = -1U;
> +	info->high.rm_owner = ULLONG_MAX;
> +	info->high.rm_offset = ULLONG_MAX;
> +	info->high.rm_blockcount = 0;
> +	info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;
> +
> +	info->missing_owner = XFS_FMR_OWN_UNKNOWN;
> +

Ok, I see. We've swapped the meaning of the gaps in the record space to
allocated blocks with an unknown owner. Comment please :). Also, I
suppose the comments in xfs_getfsmap_helper() could be more discrete
about this as they currently explicitly say that gaps refer to free
space in one or two places.

> +	start_ag = XFS_FSB_TO_AGNO(mp, start_fsb);
> +	end_ag = XFS_FSB_TO_AGNO(mp, end_fsb);
> +
> +	/* Query each AG */
> +	for (info->agno = start_ag; info->agno <= end_ag; info->agno++) {
> +		if (info->agno == end_ag) {
> +			info->high.rm_startblock = XFS_FSB_TO_AGBNO(mp,
> +					end_fsb);
> +			info->high.rm_offset = XFS_BB_TO_FSBT(mp,
> +					dkey_high->fmr_offset);
> +			error = xfs_fsmap_owner_to_rmap(dkey_high, &info->high);
> +			if (error)
> +				goto err;
> +			xfs_getfsmap_set_irec_flags(&info->high, dkey_high);
> +		}
> +
> +		if (bt_cur) {
> +			xfs_btree_del_cursor(bt_cur, XFS_BTREE_NOERROR);
> +			bt_cur = NULL;
> +			info->agf_bp = NULL;
> +		}
> +
> +		error = xfs_alloc_read_agf(mp, tp, info->agno, 0,
> +				&info->agf_bp);
> +		if (error)
> +			goto err;
> +
> +		trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
> +				info->low.rm_startblock,
> +				info->low.rm_blockcount,
> +				info->low.rm_owner,
> +				info->low.rm_offset);
> +
> +		trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
> +				info->high.rm_startblock,
> +				info->high.rm_blockcount,
> +				info->high.rm_owner,
> +				info->high.rm_offset);
> +
> +		bt_cur = xfs_allocbt_init_cursor(mp, tp, info->agf_bp,
> +				info->agno, XFS_BTNUM_BNO);
> +		alow.ar_startblock = info->low.rm_startblock;
> +		ahigh.ar_startblock = info->high.rm_startblock;
> +		error = xfs_alloc_query_range(bt_cur, &alow, &ahigh,
> +				xfs_getfsmap_datadev_bnobt_helper, info);
> +		if (error)
> +			goto err;
> +
> +		if (info->agno == start_ag) {
> +			info->low.rm_startblock = 0;
> +			info->low.rm_owner = 0;
> +			info->low.rm_offset = 0;
> +			info->low.rm_flags = 0;
> +		}
> +	}
> +
> +	/* Report any free space at the end of the AG */
> +	info->last = true;
> +	error = xfs_getfsmap_datadev_bnobt_helper(bt_cur, &ahigh, info);
> +	if (error)
> +		goto err;
> +

I guess the comment here is a little misleading too because we aren't
looking for more free space. Rather, any more allocated ranges beyond
the last free space record, right?

FWIW, this handler overall looks quite similar to xfs_datadev_helper().
It might be interesting to see if the guts of the two could be combined
into an internal function (called by both _datadev() and
_datadev_bnobt() as wrappers) that has the unique bits passed to it
(i.e., cursor, missing owner).

Brian

> +err:
> +	if (bt_cur)
> +		xfs_btree_del_cursor(bt_cur, error < 0 ? XFS_BTREE_ERROR :
> +							 XFS_BTREE_NOERROR);
> +	if (info->agf_bp)
> +		info->agf_bp = NULL;
> +
> +	return error;
> +}
> +
>  /* Do we recognize the device? */
>  STATIC bool
>  xfs_getfsmap_is_valid_device(
> @@ -689,8 +837,6 @@ xfs_getfsmap(
>  	int				i;
>  	int				error = 0;
>  
> -	if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
> -		return -EOPNOTSUPP;
>  	if (head->fmh_iflags & ~FMH_IF_VALID)
>  		return -EINVAL;
>  	rkey_low = head->fmh_keys;
> @@ -704,7 +850,10 @@ xfs_getfsmap(
>  	/* Set up our device handlers. */
>  	memset(handlers, 0, sizeof(handlers));
>  	handlers[0].dev = new_encode_dev(mp->m_ddev_targp->bt_dev);
> -	handlers[0].fn = xfs_getfsmap_datadev;
> +	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
> +		handlers[0].fn = xfs_getfsmap_datadev;
> +	else
> +		handlers[0].fn = xfs_getfsmap_datadev_bnobt;
>  	if (mp->m_logdev_targp != mp->m_ddev_targp) {
>  		handlers[1].dev = new_encode_dev(mp->m_logdev_targp->bt_dev);
>  		handlers[1].fn = xfs_getfsmap_logdev;
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 6/8] xfs: have getfsmap fall back to the freesp btrees when rmap is not present

[Darrick J. Wong]

On Fri, Feb 24, 2017 at 08:04:49AM -0500, Brian Foster wrote:
> On Fri, Feb 17, 2017 at 05:17:55PM -0800, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > If the reverse-mapping btree isn't available, fall back to the
> > free space btrees to provide partial reverse mapping information.
> > The online scrub tool can make use of even partial information to
> > speed up the data block scan.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  fs/xfs/xfs_fsmap.c |  155 +++++++++++++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 152 insertions(+), 3 deletions(-)
> > 
> > 
> > diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
> > index 09d6b92..82e44a9 100644
> > --- a/fs/xfs/xfs_fsmap.c
> > +++ b/fs/xfs/xfs_fsmap.c
> > @@ -40,6 +40,7 @@
> >  #include "xfs_fsmap.h"
> >  #include "xfs_refcount.h"
> >  #include "xfs_refcount_btree.h"
> > +#include "xfs_alloc_btree.h"
> >  
> >  /* Convert an xfs_fsmap to an fsmap. */
> >  void
> > @@ -158,6 +159,9 @@ xfs_fsmap_owner_from_rmap(
> >  	case XFS_RMAP_OWN_COW:
> >  		fmr->fmr_owner = XFS_FMR_OWN_COW;
> >  		break;
> > +	case XFS_RMAP_OWN_NULL:	/* "free" */
> > +		fmr->fmr_owner = XFS_FMR_OWN_FREE;
> > +		break;
> >  	default:
> >  		return -EFSCORRUPTED;
> >  	}
> > @@ -433,6 +437,31 @@ xfs_getfsmap_rtdev_helper(
> >  	return xfs_getfsmap_helper(cur->bc_tp, info, rec, rec_daddr);
> >  }
> >  
> > +/* Transform a bnobt irec into a fsmap */
> > +STATIC int
> > +xfs_getfsmap_datadev_bnobt_helper(
> > +	struct xfs_btree_cur		*cur,
> > +	struct xfs_alloc_rec_incore	*rec,
> > +	void				*priv)
> > +{
> > +	struct xfs_mount		*mp = cur->bc_mp;
> > +	struct xfs_getfsmap_info	*info = priv;
> > +	struct xfs_rmap_irec		irec;
> > +	xfs_fsblock_t			fsb;
> > +	xfs_daddr_t			rec_daddr;
> > +
> > +	fsb = XFS_AGB_TO_FSB(mp, cur->bc_private.a.agno, rec->ar_startblock);
> > +	rec_daddr = XFS_FSB_TO_DADDR(mp, fsb);
> > +
> > +	irec.rm_startblock = rec->ar_startblock;
> > +	irec.rm_blockcount = rec->ar_blockcount;
> > +	irec.rm_owner = XFS_RMAP_OWN_NULL;	/* "free" */
> > +	irec.rm_offset = 0;
> > +	irec.rm_flags = 0;
> > +
> 
> Slightly confused... if we directly pass free space records to
> xfs_getfsmap_helper(), won't it also assume the gaps between the records
> are free space?
> 
> > +	return xfs_getfsmap_helper(cur->bc_tp, info, &irec, rec_daddr);
> > +}
> > +
> >  /* Set rmap flags based on the getfsmap flags */
> >  static void
> >  xfs_getfsmap_set_irec_flags(
> > @@ -621,6 +650,125 @@ xfs_getfsmap_datadev(
> >  	return error;
> >  }
> >  
> > +/* Execute a getfsmap query against the regular data device's bnobt. */
> > +STATIC int
> > +xfs_getfsmap_datadev_bnobt(
> > +	struct xfs_trans		*tp,
> > +	struct xfs_fsmap		*keys,
> > +	struct xfs_getfsmap_info	*info)
> > +{
> > +	struct xfs_mount		*mp = tp->t_mountp;
> > +	struct xfs_btree_cur		*bt_cur = NULL;
> > +	struct xfs_fsmap		*dkey_low;
> > +	struct xfs_fsmap		*dkey_high;
> > +	struct xfs_alloc_rec_incore	alow;
> > +	struct xfs_alloc_rec_incore	ahigh;
> > +	xfs_fsblock_t			start_fsb;
> > +	xfs_fsblock_t			end_fsb;
> > +	xfs_agnumber_t			start_ag;
> > +	xfs_agnumber_t			end_ag;
> > +	xfs_daddr_t			eofs;
> > +	int				error = 0;
> > +
> > +	dkey_low = keys;
> > +	dkey_high = keys + 1;
> > +	eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks);
> > +	if (dkey_low->fmr_physical >= eofs)
> > +		return 0;
> > +	if (dkey_high->fmr_physical >= eofs)
> > +		dkey_high->fmr_physical = eofs - 1;
> > +	start_fsb = XFS_DADDR_TO_FSB(mp, dkey_low->fmr_physical);
> > +	end_fsb = XFS_DADDR_TO_FSB(mp, dkey_high->fmr_physical);
> > +
> > +	/* Set up search keys */
> > +	info->low.rm_startblock = XFS_FSB_TO_AGBNO(mp, start_fsb);
> > +	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
> > +	error = xfs_fsmap_owner_to_rmap(dkey_low, &info->low);
> > +	if (error)
> > +		return error;
> > +	info->low.rm_blockcount = 0;
> > +	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
> > +
> > +	info->high.rm_startblock = -1U;
> > +	info->high.rm_owner = ULLONG_MAX;
> > +	info->high.rm_offset = ULLONG_MAX;
> > +	info->high.rm_blockcount = 0;
> > +	info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;
> > +
> > +	info->missing_owner = XFS_FMR_OWN_UNKNOWN;
> > +
> 
> Ok, I see. We've swapped the meaning of the gaps in the record space to
> allocated blocks with an unknown owner. Comment please :). Also, I
> suppose the comments in xfs_getfsmap_helper() could be more discrete
> about this as they currently explicitly say that gaps refer to free
> space in one or two places.

Er... yeah.  My first reaction to this was "Oh, I should introduce
info.missing_owner in the first patch" but apparently I already did but
evidently forgot to update the comments. :(

So, just to be clear, xfs_getfsmap_helper notices gaps between the rmaps
it's being fed, and emits synthesized fsmaps for the gaps that are owned
by info.missing_owner.

> > +	start_ag = XFS_FSB_TO_AGNO(mp, start_fsb);
> > +	end_ag = XFS_FSB_TO_AGNO(mp, end_fsb);
> > +
> > +	/* Query each AG */
> > +	for (info->agno = start_ag; info->agno <= end_ag; info->agno++) {
> > +		if (info->agno == end_ag) {
> > +			info->high.rm_startblock = XFS_FSB_TO_AGBNO(mp,
> > +					end_fsb);
> > +			info->high.rm_offset = XFS_BB_TO_FSBT(mp,
> > +					dkey_high->fmr_offset);
> > +			error = xfs_fsmap_owner_to_rmap(dkey_high, &info->high);
> > +			if (error)
> > +				goto err;
> > +			xfs_getfsmap_set_irec_flags(&info->high, dkey_high);
> > +		}
> > +
> > +		if (bt_cur) {
> > +			xfs_btree_del_cursor(bt_cur, XFS_BTREE_NOERROR);
> > +			bt_cur = NULL;
> > +			info->agf_bp = NULL;
> > +		}
> > +
> > +		error = xfs_alloc_read_agf(mp, tp, info->agno, 0,
> > +				&info->agf_bp);
> > +		if (error)
> > +			goto err;
> > +
> > +		trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
> > +				info->low.rm_startblock,
> > +				info->low.rm_blockcount,
> > +				info->low.rm_owner,
> > +				info->low.rm_offset);
> > +
> > +		trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
> > +				info->high.rm_startblock,
> > +				info->high.rm_blockcount,
> > +				info->high.rm_owner,
> > +				info->high.rm_offset);
> > +
> > +		bt_cur = xfs_allocbt_init_cursor(mp, tp, info->agf_bp,
> > +				info->agno, XFS_BTNUM_BNO);
> > +		alow.ar_startblock = info->low.rm_startblock;
> > +		ahigh.ar_startblock = info->high.rm_startblock;
> > +		error = xfs_alloc_query_range(bt_cur, &alow, &ahigh,
> > +				xfs_getfsmap_datadev_bnobt_helper, info);
> > +		if (error)
> > +			goto err;
> > +
> > +		if (info->agno == start_ag) {
> > +			info->low.rm_startblock = 0;
> > +			info->low.rm_owner = 0;
> > +			info->low.rm_offset = 0;
> > +			info->low.rm_flags = 0;
> > +		}
> > +	}
> > +
> > +	/* Report any free space at the end of the AG */
> > +	info->last = true;
> > +	error = xfs_getfsmap_datadev_bnobt_helper(bt_cur, &ahigh, info);
> > +	if (error)
> > +		goto err;
> > +
> 
> I guess the comment here is a little misleading too because we aren't
> looking for more free space. Rather, any more allocated ranges beyond
> the last free space record, right?

Yes.  "Report any used space at the end of the AG"

> FWIW, this handler overall looks quite similar to xfs_datadev_helper().
> It might be interesting to see if the guts of the two could be combined
> into an internal function (called by both _datadev() and
> _datadev_bnobt() as wrappers) that has the unique bits passed to it
> (i.e., cursor, missing owner).

Hmm.  You're right, I bet they could be parameterized fairly easily.

--D

> 
> Brian
> 
> > +err:
> > +	if (bt_cur)
> > +		xfs_btree_del_cursor(bt_cur, error < 0 ? XFS_BTREE_ERROR :
> > +							 XFS_BTREE_NOERROR);
> > +	if (info->agf_bp)
> > +		info->agf_bp = NULL;
> > +
> > +	return error;
> > +}
> > +
> >  /* Do we recognize the device? */
> >  STATIC bool
> >  xfs_getfsmap_is_valid_device(
> > @@ -689,8 +837,6 @@ xfs_getfsmap(
> >  	int				i;
> >  	int				error = 0;
> >  
> > -	if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
> > -		return -EOPNOTSUPP;
> >  	if (head->fmh_iflags & ~FMH_IF_VALID)
> >  		return -EINVAL;
> >  	rkey_low = head->fmh_keys;
> > @@ -704,7 +850,10 @@ xfs_getfsmap(
> >  	/* Set up our device handlers. */
> >  	memset(handlers, 0, sizeof(handlers));
> >  	handlers[0].dev = new_encode_dev(mp->m_ddev_targp->bt_dev);
> > -	handlers[0].fn = xfs_getfsmap_datadev;
> > +	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
> > +		handlers[0].fn = xfs_getfsmap_datadev;
> > +	else
> > +		handlers[0].fn = xfs_getfsmap_datadev_bnobt;
> >  	if (mp->m_logdev_targp != mp->m_ddev_targp) {
> >  		handlers[1].dev = new_encode_dev(mp->m_logdev_targp->bt_dev);
> >  		handlers[1].fn = xfs_getfsmap_logdev;
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 6/8] xfs: have getfsmap fall back to the freesp btrees when rmap is not present

[Darrick J. Wong]

On Fri, Feb 24, 2017 at 09:48:52AM -0800, Darrick J. Wong wrote:
> On Fri, Feb 24, 2017 at 08:04:49AM -0500, Brian Foster wrote:
> > On Fri, Feb 17, 2017 at 05:17:55PM -0800, Darrick J. Wong wrote:
> > > From: Darrick J. Wong <darrick.wong@oracle.com>
> > > 
> > > If the reverse-mapping btree isn't available, fall back to the
> > > free space btrees to provide partial reverse mapping information.
> > > The online scrub tool can make use of even partial information to
> > > speed up the data block scan.
> > > 
> > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > > ---
> > >  fs/xfs/xfs_fsmap.c |  155 +++++++++++++++++++++++++++++++++++++++++++++++++++-
> > >  1 file changed, 152 insertions(+), 3 deletions(-)
> > > 
> > > 
> > > diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
> > > index 09d6b92..82e44a9 100644
> > > --- a/fs/xfs/xfs_fsmap.c
> > > +++ b/fs/xfs/xfs_fsmap.c
> > > @@ -40,6 +40,7 @@
> > >  #include "xfs_fsmap.h"
> > >  #include "xfs_refcount.h"
> > >  #include "xfs_refcount_btree.h"
> > > +#include "xfs_alloc_btree.h"
> > >  
> > >  /* Convert an xfs_fsmap to an fsmap. */
> > >  void
> > > @@ -158,6 +159,9 @@ xfs_fsmap_owner_from_rmap(
> > >  	case XFS_RMAP_OWN_COW:
> > >  		fmr->fmr_owner = XFS_FMR_OWN_COW;
> > >  		break;
> > > +	case XFS_RMAP_OWN_NULL:	/* "free" */
> > > +		fmr->fmr_owner = XFS_FMR_OWN_FREE;
> > > +		break;
> > >  	default:
> > >  		return -EFSCORRUPTED;
> > >  	}
> > > @@ -433,6 +437,31 @@ xfs_getfsmap_rtdev_helper(
> > >  	return xfs_getfsmap_helper(cur->bc_tp, info, rec, rec_daddr);
> > >  }
> > >  
> > > +/* Transform a bnobt irec into a fsmap */
> > > +STATIC int
> > > +xfs_getfsmap_datadev_bnobt_helper(
> > > +	struct xfs_btree_cur		*cur,
> > > +	struct xfs_alloc_rec_incore	*rec,
> > > +	void				*priv)
> > > +{
> > > +	struct xfs_mount		*mp = cur->bc_mp;
> > > +	struct xfs_getfsmap_info	*info = priv;
> > > +	struct xfs_rmap_irec		irec;
> > > +	xfs_fsblock_t			fsb;
> > > +	xfs_daddr_t			rec_daddr;
> > > +
> > > +	fsb = XFS_AGB_TO_FSB(mp, cur->bc_private.a.agno, rec->ar_startblock);
> > > +	rec_daddr = XFS_FSB_TO_DADDR(mp, fsb);
> > > +
> > > +	irec.rm_startblock = rec->ar_startblock;
> > > +	irec.rm_blockcount = rec->ar_blockcount;
> > > +	irec.rm_owner = XFS_RMAP_OWN_NULL;	/* "free" */
> > > +	irec.rm_offset = 0;
> > > +	irec.rm_flags = 0;
> > > +
> > 
> > Slightly confused... if we directly pass free space records to
> > xfs_getfsmap_helper(), won't it also assume the gaps between the records
> > are free space?
> > 
> > > +	return xfs_getfsmap_helper(cur->bc_tp, info, &irec, rec_daddr);
> > > +}
> > > +
> > >  /* Set rmap flags based on the getfsmap flags */
> > >  static void
> > >  xfs_getfsmap_set_irec_flags(
> > > @@ -621,6 +650,125 @@ xfs_getfsmap_datadev(
> > >  	return error;
> > >  }
> > >  
> > > +/* Execute a getfsmap query against the regular data device's bnobt. */
> > > +STATIC int
> > > +xfs_getfsmap_datadev_bnobt(
> > > +	struct xfs_trans		*tp,
> > > +	struct xfs_fsmap		*keys,
> > > +	struct xfs_getfsmap_info	*info)
> > > +{
> > > +	struct xfs_mount		*mp = tp->t_mountp;
> > > +	struct xfs_btree_cur		*bt_cur = NULL;
> > > +	struct xfs_fsmap		*dkey_low;
> > > +	struct xfs_fsmap		*dkey_high;
> > > +	struct xfs_alloc_rec_incore	alow;
> > > +	struct xfs_alloc_rec_incore	ahigh;
> > > +	xfs_fsblock_t			start_fsb;
> > > +	xfs_fsblock_t			end_fsb;
> > > +	xfs_agnumber_t			start_ag;
> > > +	xfs_agnumber_t			end_ag;
> > > +	xfs_daddr_t			eofs;
> > > +	int				error = 0;
> > > +
> > > +	dkey_low = keys;
> > > +	dkey_high = keys + 1;
> > > +	eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks);
> > > +	if (dkey_low->fmr_physical >= eofs)
> > > +		return 0;
> > > +	if (dkey_high->fmr_physical >= eofs)
> > > +		dkey_high->fmr_physical = eofs - 1;
> > > +	start_fsb = XFS_DADDR_TO_FSB(mp, dkey_low->fmr_physical);
> > > +	end_fsb = XFS_DADDR_TO_FSB(mp, dkey_high->fmr_physical);
> > > +
> > > +	/* Set up search keys */
> > > +	info->low.rm_startblock = XFS_FSB_TO_AGBNO(mp, start_fsb);
> > > +	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
> > > +	error = xfs_fsmap_owner_to_rmap(dkey_low, &info->low);
> > > +	if (error)
> > > +		return error;
> > > +	info->low.rm_blockcount = 0;
> > > +	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
> > > +
> > > +	info->high.rm_startblock = -1U;
> > > +	info->high.rm_owner = ULLONG_MAX;
> > > +	info->high.rm_offset = ULLONG_MAX;
> > > +	info->high.rm_blockcount = 0;
> > > +	info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;
> > > +
> > > +	info->missing_owner = XFS_FMR_OWN_UNKNOWN;
> > > +
> > 
> > Ok, I see. We've swapped the meaning of the gaps in the record space to
> > allocated blocks with an unknown owner. Comment please :). Also, I
> > suppose the comments in xfs_getfsmap_helper() could be more discrete
> > about this as they currently explicitly say that gaps refer to free
> > space in one or two places.
> 
> Er... yeah.  My first reaction to this was "Oh, I should introduce
> info.missing_owner in the first patch" but apparently I already did but
> evidently forgot to update the comments. :(
> 
> So, just to be clear, xfs_getfsmap_helper notices gaps between the rmaps
> it's being fed, and emits synthesized fsmaps for the gaps that are owned
> by info.missing_owner.
> 
> > > +	start_ag = XFS_FSB_TO_AGNO(mp, start_fsb);
> > > +	end_ag = XFS_FSB_TO_AGNO(mp, end_fsb);
> > > +
> > > +	/* Query each AG */
> > > +	for (info->agno = start_ag; info->agno <= end_ag; info->agno++) {
> > > +		if (info->agno == end_ag) {
> > > +			info->high.rm_startblock = XFS_FSB_TO_AGBNO(mp,
> > > +					end_fsb);
> > > +			info->high.rm_offset = XFS_BB_TO_FSBT(mp,
> > > +					dkey_high->fmr_offset);
> > > +			error = xfs_fsmap_owner_to_rmap(dkey_high, &info->high);
> > > +			if (error)
> > > +				goto err;
> > > +			xfs_getfsmap_set_irec_flags(&info->high, dkey_high);
> > > +		}
> > > +
> > > +		if (bt_cur) {
> > > +			xfs_btree_del_cursor(bt_cur, XFS_BTREE_NOERROR);
> > > +			bt_cur = NULL;
> > > +			info->agf_bp = NULL;
> > > +		}
> > > +
> > > +		error = xfs_alloc_read_agf(mp, tp, info->agno, 0,
> > > +				&info->agf_bp);
> > > +		if (error)
> > > +			goto err;
> > > +
> > > +		trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
> > > +				info->low.rm_startblock,
> > > +				info->low.rm_blockcount,
> > > +				info->low.rm_owner,
> > > +				info->low.rm_offset);
> > > +
> > > +		trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
> > > +				info->high.rm_startblock,
> > > +				info->high.rm_blockcount,
> > > +				info->high.rm_owner,
> > > +				info->high.rm_offset);
> > > +
> > > +		bt_cur = xfs_allocbt_init_cursor(mp, tp, info->agf_bp,
> > > +				info->agno, XFS_BTNUM_BNO);
> > > +		alow.ar_startblock = info->low.rm_startblock;
> > > +		ahigh.ar_startblock = info->high.rm_startblock;
> > > +		error = xfs_alloc_query_range(bt_cur, &alow, &ahigh,
> > > +				xfs_getfsmap_datadev_bnobt_helper, info);
> > > +		if (error)
> > > +			goto err;
> > > +
> > > +		if (info->agno == start_ag) {
> > > +			info->low.rm_startblock = 0;
> > > +			info->low.rm_owner = 0;
> > > +			info->low.rm_offset = 0;
> > > +			info->low.rm_flags = 0;
> > > +		}
> > > +	}
> > > +
> > > +	/* Report any free space at the end of the AG */
> > > +	info->last = true;
> > > +	error = xfs_getfsmap_datadev_bnobt_helper(bt_cur, &ahigh, info);
> > > +	if (error)
> > > +		goto err;
> > > +
> > 
> > I guess the comment here is a little misleading too because we aren't
> > looking for more free space. Rather, any more allocated ranges beyond
> > the last free space record, right?
> 
> Yes.  "Report any used space at the end of the AG"
> 
> > FWIW, this handler overall looks quite similar to xfs_datadev_helper().
> > It might be interesting to see if the guts of the two could be combined
> > into an internal function (called by both _datadev() and
> > _datadev_bnobt() as wrappers) that has the unique bits passed to it
> > (i.e., cursor, missing owner).
> 
> Hmm.  You're right, I bet they could be parameterized fairly easily.

Yes, they can be parameterized pretty easily.  The two rtdev getfsmap
implementations can also be collapsed into a single driver function,
which is particularly slick if I introduce the rtalloc query_range
functions as part of the getfsmap patchset, because then I no longer
have to open-code iteration of the rtbitmap free extents.

--D

> 
> --D
> 
> > 
> > Brian
> > 
> > > +err:
> > > +	if (bt_cur)
> > > +		xfs_btree_del_cursor(bt_cur, error < 0 ? XFS_BTREE_ERROR :
> > > +							 XFS_BTREE_NOERROR);
> > > +	if (info->agf_bp)
> > > +		info->agf_bp = NULL;
> > > +
> > > +	return error;
> > > +}
> > > +
> > >  /* Do we recognize the device? */
> > >  STATIC bool
> > >  xfs_getfsmap_is_valid_device(
> > > @@ -689,8 +837,6 @@ xfs_getfsmap(
> > >  	int				i;
> > >  	int				error = 0;
> > >  
> > > -	if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
> > > -		return -EOPNOTSUPP;
> > >  	if (head->fmh_iflags & ~FMH_IF_VALID)
> > >  		return -EINVAL;
> > >  	rkey_low = head->fmh_keys;
> > > @@ -704,7 +850,10 @@ xfs_getfsmap(
> > >  	/* Set up our device handlers. */
> > >  	memset(handlers, 0, sizeof(handlers));
> > >  	handlers[0].dev = new_encode_dev(mp->m_ddev_targp->bt_dev);
> > > -	handlers[0].fn = xfs_getfsmap_datadev;
> > > +	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
> > > +		handlers[0].fn = xfs_getfsmap_datadev;
> > > +	else
> > > +		handlers[0].fn = xfs_getfsmap_datadev_bnobt;
> > >  	if (mp->m_logdev_targp != mp->m_ddev_targp) {
> > >  		handlers[1].dev = new_encode_dev(mp->m_logdev_targp->bt_dev);
> > >  		handlers[1].fn = xfs_getfsmap_logdev;
> > > 
> > > --
> > > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> > > the body of a message to majordomo@vger.kernel.org
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
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[PATCH 7/8] xfs: getfsmap should fall back to rtbitmap when rtrmapbt not present

[Darrick J. Wong]

From: Darrick J. Wong <darrick.wong@oracle.com>

Use the realtime bitmap to return freespace information when the
rtrmapbt isn't present.  Note that the rtrmapbt fsmap implementation
will show up later with the rtrmapbt patchset.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/xfs_fsmap.c   |  134 ++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_rtalloc.h |    2 +
 2 files changed, 136 insertions(+)


diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
index 82e44a9..e769322 100644
--- a/fs/xfs/xfs_fsmap.c
+++ b/fs/xfs/xfs_fsmap.c
@@ -41,6 +41,7 @@
 #include "xfs_refcount.h"
 #include "xfs_refcount_btree.h"
 #include "xfs_alloc_btree.h"
+#include "xfs_rtalloc.h"
 
 /* Convert an xfs_fsmap to an fsmap. */
 void
@@ -437,6 +438,30 @@ xfs_getfsmap_rtdev_helper(
 	return xfs_getfsmap_helper(cur->bc_tp, info, rec, rec_daddr);
 }
 
+/* Transform a rtbitmap "record" into a fsmap */
+STATIC int
+xfs_getfsmap_rtdev_rtbitmap_helper(
+	struct xfs_trans		*tp,
+	xfs_rtblock_t			start,
+	xfs_rtblock_t			end,
+	void				*priv)
+{
+	struct xfs_mount		*mp = tp->t_mountp;
+	struct xfs_getfsmap_info	*info = priv;
+	struct xfs_rmap_irec		irec;
+	xfs_daddr_t			rec_daddr;
+
+	rec_daddr = XFS_FSB_TO_BB(mp, start);
+
+	irec.rm_startblock = start;
+	irec.rm_blockcount = end - start + 1;
+	irec.rm_owner = XFS_RMAP_OWN_NULL;	/* "free" */
+	irec.rm_offset = 0;
+	irec.rm_flags = 0;
+
+	return xfs_getfsmap_helper(tp, info, &irec, rec_daddr);
+}
+
 /* Transform a bnobt irec into a fsmap */
 STATIC int
 xfs_getfsmap_datadev_bnobt_helper(
@@ -536,6 +561,108 @@ xfs_getfsmap_logdev(
 	return xfs_getfsmap_rtdev_helper(&cur, &rmap, info);
 }
 
+/* Execute a getfsmap query against the realtime data device (rtbitmap). */
+STATIC int
+xfs_getfsmap_rtdev_rtbitmap(
+	struct xfs_trans		*tp,
+	struct xfs_fsmap		*keys,
+	struct xfs_getfsmap_info	*info)
+{
+	struct xfs_mount		*mp = tp->t_mountp;
+	struct xfs_fsmap		*dkey_low;
+	struct xfs_fsmap		*dkey_high;
+	xfs_fsblock_t			start_fsb;
+	xfs_fsblock_t			end_fsb;
+	xfs_rtblock_t			rtstart;
+	xfs_rtblock_t			rtend;
+	xfs_rtblock_t			rem;
+	xfs_daddr_t			eofs;
+	int				is_free;
+	int				error = 0;
+
+	dkey_low = keys;
+	dkey_high = keys + 1;
+	eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_rblocks);
+	if (dkey_low->fmr_physical >= eofs)
+		return 0;
+	if (dkey_high->fmr_physical >= eofs)
+		dkey_high->fmr_physical = eofs - 1;
+	start_fsb = XFS_BB_TO_FSBT(mp, dkey_low->fmr_physical);
+	end_fsb = XFS_BB_TO_FSB(mp, dkey_high->fmr_physical);
+
+	/* Set up search keys */
+	info->low.rm_startblock = start_fsb;
+	error = xfs_fsmap_owner_to_rmap(dkey_low, &info->low);
+	if (error)
+		return error;
+	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
+	info->low.rm_blockcount = 0;
+	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
+
+	info->high.rm_startblock = end_fsb;
+	error = xfs_fsmap_owner_to_rmap(dkey_high, &info->high);
+	if (error)
+		return error;
+	info->high.rm_offset = XFS_BB_TO_FSBT(mp, dkey_high->fmr_offset);
+	info->high.rm_blockcount = 0;
+	xfs_getfsmap_set_irec_flags(&info->high, dkey_high);
+
+	info->missing_owner = XFS_FMR_OWN_UNKNOWN;
+
+	trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
+			info->low.rm_startblock,
+			info->low.rm_blockcount,
+			info->low.rm_owner,
+			info->low.rm_offset);
+
+	trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
+			info->high.rm_startblock,
+			info->high.rm_blockcount,
+			info->high.rm_owner,
+			info->high.rm_offset);
+
+	xfs_ilock(mp->m_rbmip, XFS_ILOCK_SHARED | XFS_ILOCK_RTBITMAP);
+
+	/* Iterate the bitmap, looking for discrepancies. */
+	rtstart = 0;
+	rem = mp->m_sb.sb_rblocks;
+	while (rem) {
+		/* Is the first block free? */
+		error = xfs_rtcheck_range(mp, tp, rtstart, 1, 1, &rtend,
+				&is_free);
+		if (error)
+			goto out_unlock;
+
+		/* How long does the extent go for? */
+		error = xfs_rtfind_forw(mp, tp, rtstart,
+				mp->m_sb.sb_rblocks - 1, &rtend);
+		if (error)
+			goto out_unlock;
+
+		if (is_free) {
+			error = xfs_getfsmap_rtdev_rtbitmap_helper(tp,
+					rtstart, rtend, info);
+			if (error)
+				goto out_unlock;
+		}
+
+		rem -= rtend - rtstart + 1;
+		rtstart = rtend + 1;
+	}
+
+out_unlock:
+	xfs_iunlock(mp->m_rbmip, XFS_ILOCK_SHARED | XFS_ILOCK_RTBITMAP);
+
+	/* Report any free space at the end of the rtdev */
+	info->last = true;
+	error = xfs_getfsmap_rtdev_rtbitmap_helper(tp, end_fsb, 0, info);
+	if (error)
+		goto err;
+
+err:
+	return error;
+}
+
 /* Execute a getfsmap query against the regular data device. */
 STATIC int
 xfs_getfsmap_datadev(
@@ -781,6 +908,9 @@ xfs_getfsmap_is_valid_device(
 	if (mp->m_logdev_targp &&
 	    fm->fmr_device == new_encode_dev(mp->m_logdev_targp->bt_dev))
 		return true;
+	if (mp->m_rtdev_targp &&
+	    fm->fmr_device == new_encode_dev(mp->m_rtdev_targp->bt_dev))
+		return true;
 	return false;
 }
 
@@ -858,6 +988,10 @@ xfs_getfsmap(
 		handlers[1].dev = new_encode_dev(mp->m_logdev_targp->bt_dev);
 		handlers[1].fn = xfs_getfsmap_logdev;
 	}
+	if (mp->m_rtdev_targp) {
+		handlers[2].dev = new_encode_dev(mp->m_rtdev_targp->bt_dev);
+		handlers[2].fn = xfs_getfsmap_rtdev_rtbitmap;
+	}
 
 	xfs_sort(handlers, XFS_GETFSMAP_DEVS, sizeof(struct xfs_getfsmap_dev),
 			xfs_getfsmap_dev_compare);
diff --git a/fs/xfs/xfs_rtalloc.h b/fs/xfs/xfs_rtalloc.h
index 355dd9e..f798a3e 100644
--- a/fs/xfs/xfs_rtalloc.h
+++ b/fs/xfs/xfs_rtalloc.h
@@ -126,6 +126,8 @@ int xfs_rtfree_range(struct xfs_mount *mp, struct xfs_trans *tp,
 # define xfs_rtfree_extent(t,b,l)                       (ENOSYS)
 # define xfs_rtpick_extent(m,t,l,rb)                    (ENOSYS)
 # define xfs_growfs_rt(mp,in)                           (ENOSYS)
+# define xfs_rtcheck_range(...)                         (ENOSYS)
+# define xfs_rtfind_forw(...)                           (ENOSYS)
 static inline int		/* error */
 xfs_rtmount_init(
 	xfs_mount_t	*mp)	/* file system mount structure */

[PATCH 8/8] ext4: support GETFSMAP ioctls

[Darrick J. Wong]

From: Darrick J. Wong <darrick.wong@oracle.com>

Support the GETFSMAP ioctls so that we can use the xfs free space
management tools to probe ext4 as well.  Note that this is a partial
implementation -- we only report fixed-location metadata and free space;
everything else is reported as "unknown".

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/ext4/Makefile            |    2 
 fs/ext4/fsmap.c             |  742 +++++++++++++++++++++++++++++++++++++++++++
 fs/ext4/fsmap.h             |   72 ++++
 fs/ext4/ioctl.c             |  108 ++++++
 fs/ext4/mballoc.c           |   49 +++
 fs/ext4/mballoc.h           |   17 +
 include/trace/events/ext4.h |   78 +++++
 7 files changed, 1067 insertions(+), 1 deletion(-)
 create mode 100644 fs/ext4/fsmap.c
 create mode 100644 fs/ext4/fsmap.h


diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile
index 354103f..be515aa 100644
--- a/fs/ext4/Makefile
+++ b/fs/ext4/Makefile
@@ -8,7 +8,7 @@ ext4-y	:= balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \
 		ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o \
 		ext4_jbd2.o migrate.o mballoc.o block_validity.o move_extent.o \
 		mmp.o indirect.o extents_status.o xattr.o xattr_user.o \
-		xattr_trusted.o inline.o readpage.o sysfs.o
+		xattr_trusted.o inline.o readpage.o sysfs.o fsmap.o
 
 ext4-$(CONFIG_EXT4_FS_POSIX_ACL)	+= acl.o
 ext4-$(CONFIG_EXT4_FS_SECURITY)		+= xattr_security.o
diff --git a/fs/ext4/fsmap.c b/fs/ext4/fsmap.c
new file mode 100644
index 0000000..a9033c8d
--- /dev/null
+++ b/fs/ext4/fsmap.c
@@ -0,0 +1,742 @@
+/*
+ * Copyright (C) 2017 Oracle.  All Rights Reserved.
+ *
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+#include "ext4.h"
+#include <linux/fsmap.h>
+#include "fsmap.h"
+#include "mballoc.h"
+#include <linux/sort.h>
+#include <linux/list_sort.h>
+#include <trace/events/ext4.h>
+
+/* Convert an ext4_fsmap to an fsmap. */
+void
+ext4_fsmap_from_internal(
+	struct super_block	*sb,
+	struct fsmap		*dest,
+	struct ext4_fsmap	*src)
+{
+	dest->fmr_device = src->fmr_device;
+	dest->fmr_flags = src->fmr_flags;
+	dest->fmr_physical = src->fmr_physical << sb->s_blocksize_bits;
+	dest->fmr_owner = src->fmr_owner;
+	dest->fmr_offset = 0;
+	dest->fmr_length = src->fmr_length << sb->s_blocksize_bits;
+	dest->fmr_reserved[0] = 0;
+	dest->fmr_reserved[1] = 0;
+	dest->fmr_reserved[2] = 0;
+}
+
+/* Convert an fsmap to an ext4_fsmap. */
+void
+ext4_fsmap_to_internal(
+	struct super_block	*sb,
+	struct ext4_fsmap	*dest,
+	struct fsmap		*src)
+{
+	dest->fmr_device = src->fmr_device;
+	dest->fmr_flags = src->fmr_flags;
+	dest->fmr_physical = src->fmr_physical >> sb->s_blocksize_bits;
+	dest->fmr_owner = src->fmr_owner;
+	dest->fmr_length = src->fmr_length >> sb->s_blocksize_bits;
+}
+
+/* getfsmap query state */
+struct ext4_getfsmap_info {
+	struct ext4_fsmap_head	*head;
+	struct ext4_fsmap	*rkey_low;	/* lowest key */
+	ext4_fsmap_format_t	formatter;	/* formatting fn */
+	void			*format_arg;	/* format buffer */
+	bool			last;		/* last extent? */
+	ext4_fsblk_t		next_fsblk;	/* next fsblock we expect */
+	u32			dev;		/* device id */
+
+	ext4_group_t		agno;		/* AG number, if applicable */
+	struct ext4_fsmap	low;		/* low rmap key */
+	struct ext4_fsmap	high;		/* high rmap key */
+	struct ext4_fsmap	lastfree;	/* free ext at end of last AG */
+	struct list_head	meta_list;	/* fixed metadata list */
+};
+
+/* Associate a device with a getfsmap handler. */
+struct ext4_getfsmap_dev {
+	u32			dev;
+	int			(*fn)(struct super_block *sb,
+				      struct ext4_fsmap *keys,
+				      struct ext4_getfsmap_info *info);
+};
+
+/* Compare two getfsmap device handlers. */
+static int
+ext4_getfsmap_dev_compare(
+	const void			*p1,
+	const void			*p2)
+{
+	const struct ext4_getfsmap_dev	*d1 = p1;
+	const struct ext4_getfsmap_dev	*d2 = p2;
+
+	return d1->dev - d2->dev;
+}
+
+/* Compare a record against our starting point */
+static bool
+ext4_getfsmap_rec_before_low_key(
+	struct ext4_getfsmap_info	*info,
+	struct ext4_fsmap		*rec)
+{
+	return rec->fmr_physical < info->low.fmr_physical;
+}
+
+/*
+ * Format a reverse mapping for getfsmap, having translated rm_startblock
+ * into the appropriate daddr units.
+ */
+static int
+ext4_getfsmap_helper(
+	struct super_block		*sb,
+	struct ext4_getfsmap_info	*info,
+	struct ext4_fsmap		*rec)
+{
+	struct ext4_fsmap		fmr;
+	struct ext4_sb_info		*sbi = EXT4_SB(sb);
+	ext4_fsblk_t			rec_fsblk = rec->fmr_physical;
+	ext4_fsblk_t			key_end;
+	ext4_group_t			agno;
+	ext4_grpblk_t			cno;
+	int				error;
+
+	if (fatal_signal_pending(current))
+		return -EAGAIN;
+
+	/*
+	 * Filter out records that start before our startpoint, if the
+	 * caller requested that.
+	 */
+	if (ext4_getfsmap_rec_before_low_key(info, rec)) {
+		rec_fsblk += rec->fmr_length;
+		if (info->next_fsblk < rec_fsblk)
+			info->next_fsblk = rec_fsblk;
+		return EXT4_QUERY_RANGE_CONTINUE;
+	}
+
+	/*
+	 * If the caller passed in a length with the low record and
+	 * the record represents a file data extent, we incremented
+	 * the offset in the low key by the length in the hopes of
+	 * finding reverse mappings for the physical blocks we just
+	 * saw.  We did /not/ increment next_daddr by the length
+	 * because the range query would not be able to find shared
+	 * extents within the same physical block range.
+	 *
+	 * However, the extent we've been fed could have a startblock
+	 * past the passed-in low record.  If this is the case,
+	 * advance next_daddr to the end of the passed-in low record
+	 * so we don't report the extent prior to this extent as
+	 * free.
+	 */
+	key_end = info->rkey_low->fmr_physical + info->rkey_low->fmr_length;
+	if (info->dev == info->rkey_low->fmr_device &&
+	    info->next_fsblk < key_end && rec_fsblk >= key_end)
+		info->next_fsblk = key_end;
+
+	/* Are we just counting mappings? */
+	if (info->head->fmh_count == 0) {
+		if (rec_fsblk > info->next_fsblk)
+			info->head->fmh_entries++;
+
+		if (info->last)
+			return EXT4_QUERY_RANGE_CONTINUE;
+
+		info->head->fmh_entries++;
+
+		rec_fsblk += rec->fmr_length;
+		if (info->next_fsblk < rec_fsblk)
+			info->next_fsblk = rec_fsblk;
+		return EXT4_QUERY_RANGE_CONTINUE;
+	}
+
+	/*
+	 * If the record starts past the last physical block we saw,
+	 * then we've found some free space.  Report that too.
+	 */
+	if (rec_fsblk > info->next_fsblk) {
+		if (info->head->fmh_entries >= info->head->fmh_count)
+			return EXT4_QUERY_RANGE_ABORT;
+
+		ext4_get_group_no_and_offset(sb, info->next_fsblk, &agno, &cno);
+		trace_ext4_fsmap_mapping(sb, info->dev, agno,
+				EXT4_C2B(sbi, cno),
+				rec_fsblk - info->next_fsblk,
+				EXT4_FMR_OWN_UNKNOWN);
+
+		fmr.fmr_device = info->dev;
+		fmr.fmr_physical = info->next_fsblk;
+		fmr.fmr_owner = EXT4_FMR_OWN_UNKNOWN;
+		fmr.fmr_length = rec_fsblk - info->next_fsblk;
+		fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
+		error = info->formatter(&fmr, info->format_arg);
+		if (error)
+			return error;
+		info->head->fmh_entries++;
+	}
+
+	if (info->last)
+		goto out;
+
+	/* Fill out the extent we found */
+	if (info->head->fmh_entries >= info->head->fmh_count)
+		return EXT4_QUERY_RANGE_ABORT;
+
+	ext4_get_group_no_and_offset(sb, rec_fsblk, &agno, &cno);
+	trace_ext4_fsmap_mapping(sb, info->dev, agno, EXT4_C2B(sbi, cno),
+			rec->fmr_length, rec->fmr_owner);
+
+	fmr.fmr_device = info->dev;
+	fmr.fmr_physical = rec_fsblk;
+	fmr.fmr_owner = rec->fmr_owner;
+	fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
+	fmr.fmr_length = rec->fmr_length;
+	error = info->formatter(&fmr, info->format_arg);
+	if (error)
+		return error;
+	info->head->fmh_entries++;
+
+out:
+	rec_fsblk += rec->fmr_length;
+	if (info->next_fsblk < rec_fsblk)
+		info->next_fsblk = rec_fsblk;
+	return EXT4_QUERY_RANGE_CONTINUE;
+}
+
+static inline ext4_fsblk_t
+ext4_fsmap_next_pblk(
+	struct ext4_fsmap		*f)
+{
+	return f->fmr_physical + f->fmr_length;
+}
+
+/* Transform a blockgroup's free record into a fsmap */
+static int
+ext4_getfsmap_datadev_helper(
+	struct super_block		*sb,
+	ext4_group_t			agno,
+	ext4_grpblk_t			start,
+	ext4_grpblk_t			len,
+	void				*priv)
+{
+	struct ext4_fsmap		irec;
+	struct ext4_getfsmap_info	*info = priv;
+	struct ext4_metadata_fsmap	*p;
+	struct ext4_metadata_fsmap	*tmp;
+	struct ext4_sb_info		*sbi = EXT4_SB(sb);
+	ext4_fsblk_t			fsb;
+	ext4_fsblk_t			fslen;
+	int				error;
+
+	fsb = (EXT4_C2B(sbi, start) + ext4_group_first_block_no(sb, agno));
+	fslen = EXT4_C2B(sbi, len);
+
+	/* If the retained free extent record is set... */
+	if (info->lastfree.fmr_owner) {
+		/* ...and abuts this one, lengthen it and return. */
+		if (ext4_fsmap_next_pblk(&info->lastfree) == fsb) {
+			info->lastfree.fmr_length += fslen;
+			return 0;
+		}
+
+		/*
+		 * There's a gap between the two free extents; emit the
+		 * retained extent prior to merging the meta_list.
+		 */
+		error = ext4_getfsmap_helper(sb, info, &info->lastfree);
+		if (error)
+			return error;
+		info->lastfree.fmr_owner = 0;
+	}
+
+	/* Merge in any relevant extents from the meta_list */
+	list_for_each_entry_safe(p, tmp, &info->meta_list, mf_list) {
+		if (p->mf_physical + p->mf_length <= info->next_fsblk) {
+			list_del(&p->mf_list);
+			kfree(p);
+		} else if (p->mf_physical < fsb) {
+			irec.fmr_physical = p->mf_physical;
+			irec.fmr_length = p->mf_length;
+			irec.fmr_owner = p->mf_owner;
+			irec.fmr_flags = 0;
+
+			error = ext4_getfsmap_helper(sb, info, &irec);
+			if (error)
+				return error;
+
+			list_del(&p->mf_list);
+			kfree(p);
+		}
+	}
+
+	irec.fmr_physical = fsb;
+	irec.fmr_length = fslen;
+	irec.fmr_owner = EXT4_FMR_OWN_FREE;
+	irec.fmr_flags = 0;
+
+	/* If this is a free extent at the end of an AG, buffer it. */
+	if (ext4_fsmap_next_pblk(&irec) ==
+			ext4_group_first_block_no(sb, agno + 1)) {
+		info->lastfree = irec;
+		return 0;
+	}
+
+	/* Otherwise, emit it */
+	return ext4_getfsmap_helper(sb, info, &irec);
+}
+
+/* Execute a getfsmap query against the log device. */
+static int
+ext4_getfsmap_logdev(
+	struct super_block		*sb,
+	struct ext4_fsmap		*keys,
+	struct ext4_getfsmap_info	*info)
+{
+	struct ext4_fsmap		*dkey_low = keys;
+	journal_t			*journal = EXT4_SB(sb)->s_journal;
+	struct ext4_fsmap		irec;
+
+	/* Set up search keys */
+	info->low = *dkey_low;
+	info->low.fmr_length = 0;
+
+	memset(&info->high, 0xFF, sizeof(info->high));
+
+	trace_ext4_fsmap_low_key(sb, info->dev, 0,
+			info->low.fmr_physical,
+			info->low.fmr_length,
+			info->low.fmr_owner);
+
+	trace_ext4_fsmap_high_key(sb, info->dev, 0,
+			info->high.fmr_physical,
+			info->high.fmr_length,
+			info->high.fmr_owner);
+
+	if (dkey_low->fmr_physical > 0)
+		return 0;
+	irec.fmr_physical = journal->j_blk_offset;
+	irec.fmr_length = journal->j_maxlen;
+	irec.fmr_owner = EXT4_FMR_OWN_LOG;
+	irec.fmr_flags = 0;
+
+	return ext4_getfsmap_helper(sb, info, &irec);
+}
+
+/*
+ * This function returns the number of file system metadata blocks at
+ * the beginning of a block group, including the reserved gdt blocks.
+ */
+static unsigned int
+ext4_getfsmap_count_group_meta_blocks(
+	struct super_block	*sb,
+	ext4_group_t		block_group)
+{
+	struct ext4_sb_info	*sbi = EXT4_SB(sb);
+	unsigned int		num;
+
+	/* Check for superblock and gdt backups in this group */
+	num = ext4_bg_has_super(sb, block_group);
+
+	if (!ext4_has_feature_meta_bg(sb) ||
+	    block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
+			  sbi->s_desc_per_block) {
+		if (num) {
+			num += ext4_bg_num_gdb(sb, block_group);
+			num += le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
+		}
+	} else { /* For META_BG_BLOCK_GROUPS */
+		num += ext4_bg_num_gdb(sb, block_group);
+	}
+	return num;
+}
+
+/* Compare two fixed metadata items. */
+static int
+ext4_getfsmap_compare_fixed_metadata(
+	void				*priv,
+	struct list_head		*a,
+	struct list_head		*b)
+{
+	struct ext4_metadata_fsmap	*fa;
+	struct ext4_metadata_fsmap	*fb;
+
+	fa = container_of(a, struct ext4_metadata_fsmap, mf_list);
+	fb = container_of(b, struct ext4_metadata_fsmap, mf_list);
+	if (fa->mf_physical < fb->mf_physical)
+		return -1;
+	else if (fa->mf_physical > fb->mf_physical)
+		return 1;
+	return 0;
+}
+
+/* Merge adjacent extents of fixed metadata. */
+static void
+ext4_getfsmap_merge_fixed_metadata(
+	struct list_head		*meta_list)
+{
+	struct ext4_metadata_fsmap	*p;
+	struct ext4_metadata_fsmap	*prev = NULL;
+	struct ext4_metadata_fsmap	*tmp;
+
+	list_for_each_entry_safe(p, tmp, meta_list, mf_list) {
+		if (!prev) {
+			prev = p;
+			continue;
+		}
+
+		if (prev->mf_owner == p->mf_owner &&
+		    prev->mf_physical + prev->mf_length == p->mf_physical) {
+			prev->mf_length += p->mf_length;
+			list_del(&p->mf_list);
+			kfree(p);
+		} else
+			prev = p;
+	}
+}
+
+/* Free a list of fixed metadata. */
+static void
+ext4_getfsmap_free_fixed_metadata(
+	struct list_head		*meta_list)
+{
+	struct ext4_metadata_fsmap	*p;
+	struct ext4_metadata_fsmap	*tmp;
+
+	list_for_each_entry_safe(p, tmp, meta_list, mf_list) {
+		list_del(&p->mf_list);
+		kfree(p);
+	}
+}
+
+/* Find all the fixed metadata in the filesystem. */
+int
+ext4_getfsmap_find_fixed_metadata(
+	struct super_block		*sb,
+	struct list_head		*meta_list)
+{
+	struct ext4_metadata_fsmap	*fsm;
+	struct ext4_group_desc		*gdp;
+	ext4_group_t			agno;
+	unsigned int			nr_super;
+	int				error;
+
+	INIT_LIST_HEAD(meta_list);
+
+	/* Collect everything. */
+	for (agno = 0; agno < EXT4_SB(sb)->s_groups_count; agno++) {
+		gdp = ext4_get_group_desc(sb, agno, NULL);
+		if (!gdp) {
+			error = -EFSCORRUPTED;
+			goto err;
+		}
+
+		/* Superblock & GDT */
+		nr_super = ext4_getfsmap_count_group_meta_blocks(sb, agno);
+		if (nr_super) {
+			fsm = kmalloc(sizeof(*fsm), GFP_NOFS);
+			if (!fsm) {
+				error = -ENOMEM;
+				goto err;
+			}
+			fsm->mf_physical = ext4_group_first_block_no(sb, agno);
+			fsm->mf_owner = EXT4_FMR_OWN_FS;
+			fsm->mf_length = nr_super;
+			list_add_tail(&fsm->mf_list, meta_list);
+		}
+
+		/* Block bitmap */
+		fsm = kmalloc(sizeof(*fsm), GFP_NOFS);
+		if (!fsm) {
+			error = -ENOMEM;
+			goto err;
+		}
+		fsm->mf_physical = ext4_block_bitmap(sb, gdp);
+		fsm->mf_owner = EXT4_FMR_OWN_BLKBM;
+		fsm->mf_length = 1;
+		list_add_tail(&fsm->mf_list, meta_list);
+
+		/* Inode bitmap */
+		fsm = kmalloc(sizeof(*fsm), GFP_NOFS);
+		if (!fsm) {
+			error = -ENOMEM;
+			goto err;
+		}
+		fsm->mf_physical = ext4_inode_bitmap(sb, gdp);
+		fsm->mf_owner = EXT4_FMR_OWN_INOBM;
+		fsm->mf_length = 1;
+		list_add_tail(&fsm->mf_list, meta_list);
+
+		/* Inodes */
+		fsm = kmalloc(sizeof(*fsm), GFP_NOFS);
+		if (!fsm) {
+			error = -ENOMEM;
+			goto err;
+		}
+		fsm->mf_physical = ext4_inode_table(sb, gdp);
+		fsm->mf_owner = EXT4_FMR_OWN_INODES;
+		fsm->mf_length = EXT4_SB(sb)->s_itb_per_group;
+		list_add_tail(&fsm->mf_list, meta_list);
+	}
+
+	/* Sort the list */
+	list_sort(NULL, meta_list, ext4_getfsmap_compare_fixed_metadata);
+
+	/* Merge adjacent extents */
+	ext4_getfsmap_merge_fixed_metadata(meta_list);
+
+	return 0;
+err:
+	ext4_getfsmap_free_fixed_metadata(meta_list);
+	return error;
+}
+
+/* Execute a getfsmap query against the buddy bitmaps */
+static int
+ext4_getfsmap_datadev(
+	struct super_block		*sb,
+	struct ext4_fsmap		*keys,
+	struct ext4_getfsmap_info	*info)
+{
+	struct ext4_fsmap		*dkey_low;
+	struct ext4_fsmap		*dkey_high;
+	struct ext4_sb_info		*sbi = EXT4_SB(sb);
+	ext4_fsblk_t			start_fsb;
+	ext4_fsblk_t			end_fsb;
+	ext4_fsblk_t			eofs;
+	ext4_group_t			start_ag;
+	ext4_group_t			end_ag;
+	ext4_grpblk_t			first_cluster;
+	ext4_grpblk_t			last_cluster;
+	int				error = 0;
+
+	dkey_low = keys;
+	dkey_high = keys + 1;
+	eofs = ext4_blocks_count(sbi->s_es);
+	if (dkey_low->fmr_physical >= eofs)
+		return 0;
+	if (dkey_high->fmr_physical >= eofs)
+		dkey_high->fmr_physical = eofs - 1;
+	start_fsb = dkey_low->fmr_physical;
+	end_fsb = dkey_high->fmr_physical;
+
+	/* Determine first and last group to examine based on start and end */
+	ext4_get_group_no_and_offset(sb, start_fsb, &start_ag, &first_cluster);
+	ext4_get_group_no_and_offset(sb, end_fsb, &end_ag, &last_cluster);
+
+	/* Set up search keys */
+	info->low = *dkey_low;
+	info->low.fmr_physical = EXT4_C2B(sbi, first_cluster);
+	info->low.fmr_length = 0;
+
+	memset(&info->high, 0xFF, sizeof(info->high));
+
+	/* Assemble a list of all the fixed-location metadata. */
+	error = ext4_getfsmap_find_fixed_metadata(sb, &info->meta_list);
+	if (error)
+		goto err;
+
+	/* Query each AG */
+	for (info->agno = start_ag; info->agno <= end_ag; info->agno++) {
+		if (info->agno == end_ag) {
+			info->high = *dkey_high;
+			info->high.fmr_physical = EXT4_C2B(sbi, last_cluster);
+			info->high.fmr_length = 0;
+		}
+
+		trace_ext4_fsmap_low_key(sb, info->dev, info->agno,
+				info->low.fmr_physical,
+				info->low.fmr_length,
+				info->low.fmr_owner);
+
+		trace_ext4_fsmap_high_key(sb, info->dev, info->agno,
+				info->high.fmr_physical,
+				info->high.fmr_length,
+				info->high.fmr_owner);
+
+		error = ext4_mballoc_query_range(sb, info->agno,
+				EXT4_B2C(sbi, info->low.fmr_physical),
+				EXT4_B2C(sbi, info->high.fmr_physical),
+				ext4_getfsmap_datadev_helper, info);
+		if (error)
+			goto err;
+
+		if (info->agno == start_ag)
+			memset(&info->low, 0, sizeof(info->low));
+	}
+
+	/* Do we have a retained free extent? */
+	if (info->lastfree.fmr_owner) {
+		error = ext4_getfsmap_helper(sb, info, &info->lastfree);
+		if (error)
+			goto err;
+	}
+
+	/* Report any free space at the end of the AG */
+	info->last = true;
+	error = ext4_getfsmap_datadev_helper(sb, end_ag, last_cluster, 0, info);
+	if (error)
+		goto err;
+
+err:
+	ext4_getfsmap_free_fixed_metadata(&info->meta_list);
+	return error;
+}
+
+/* Do we recognize the device? */
+static bool
+ext4_getfsmap_is_valid_device(
+	struct super_block	*sb,
+	struct ext4_fsmap	*fm)
+{
+	if (fm->fmr_device == 0 || fm->fmr_device == UINT_MAX ||
+	    fm->fmr_device == new_encode_dev(sb->s_bdev->bd_dev))
+		return true;
+	if (EXT4_SB(sb)->journal_bdev &&
+	    fm->fmr_device == new_encode_dev(EXT4_SB(sb)->journal_bdev->bd_dev))
+		return true;
+	return false;
+}
+
+/* Ensure that the low key is less than the high key. */
+static bool
+ext4_getfsmap_check_keys(
+	struct ext4_fsmap		*low_key,
+	struct ext4_fsmap		*high_key)
+{
+	if (low_key->fmr_device > high_key->fmr_device)
+		return false;
+	if (low_key->fmr_device < high_key->fmr_device)
+		return true;
+
+	if (low_key->fmr_physical > high_key->fmr_physical)
+		return false;
+	if (low_key->fmr_physical < high_key->fmr_physical)
+		return true;
+
+	if (low_key->fmr_owner > high_key->fmr_owner)
+		return false;
+	if (low_key->fmr_owner < high_key->fmr_owner)
+		return true;
+
+	return false;
+}
+
+#define EXT4_GETFSMAP_DEVS	2
+/*
+ * Get filesystem's extents as described in head, and format for
+ * output.  Calls formatter to fill the user's buffer until all
+ * extents are mapped, until the passed-in head->fmh_count slots have
+ * been filled, or until the formatter short-circuits the loop, if it
+ * is tracking filled-in extents on its own.
+ */
+int
+ext4_getfsmap(
+	struct super_block		*sb,
+	struct ext4_fsmap_head		*head,
+	ext4_fsmap_format_t		formatter,
+	void				*arg)
+{
+	struct ext4_fsmap		*rkey_low;	/* request keys */
+	struct ext4_fsmap		*rkey_high;
+	struct ext4_fsmap		dkeys[2];	/* per-dev keys */
+	struct ext4_getfsmap_dev	handlers[EXT4_GETFSMAP_DEVS];
+	struct ext4_getfsmap_info	info = {0};
+	int				i;
+	int				error = 0;
+
+	if (head->fmh_iflags & ~FMH_IF_VALID)
+		return -EINVAL;
+	rkey_low = head->fmh_keys;
+	rkey_high = rkey_low + 1;
+	if (!ext4_getfsmap_is_valid_device(sb, rkey_low) ||
+	    !ext4_getfsmap_is_valid_device(sb, rkey_high))
+		return -EINVAL;
+
+	head->fmh_entries = 0;
+
+	/* Set up our device handlers. */
+	memset(handlers, 0, sizeof(handlers));
+	handlers[0].dev = new_encode_dev(sb->s_bdev->bd_dev);
+	handlers[0].fn = ext4_getfsmap_datadev;
+	if (EXT4_SB(sb)->journal_bdev) {
+		handlers[1].dev = new_encode_dev(
+				EXT4_SB(sb)->journal_bdev->bd_dev);
+		handlers[1].fn = ext4_getfsmap_logdev;
+	}
+
+	sort(handlers, EXT4_GETFSMAP_DEVS, sizeof(struct ext4_getfsmap_dev),
+			ext4_getfsmap_dev_compare, NULL);
+
+	/*
+	 * Since we allow the user to copy the last mapping from a previous
+	 * call into the low key slot, we have to advance the low key by
+	 * whatever the reported length is.
+	 */
+	dkeys[0] = *rkey_low;
+	dkeys[0].fmr_physical += dkeys[0].fmr_length;
+	dkeys[0].fmr_owner = 0;
+	memset(&dkeys[1], 0xFF, sizeof(struct ext4_fsmap));
+
+	if (!ext4_getfsmap_check_keys(dkeys, rkey_high))
+		return -EINVAL;
+
+	info.rkey_low = rkey_low;
+	info.formatter = formatter;
+	info.format_arg = arg;
+	info.head = head;
+
+	/* For each device we support... */
+	for (i = 0; i < EXT4_GETFSMAP_DEVS; i++) {
+		/* Is this device within the range the user asked for? */
+		if (!handlers[i].fn)
+			continue;
+		if (rkey_low->fmr_device > handlers[i].dev)
+			continue;
+		if (rkey_high->fmr_device < handlers[i].dev)
+			break;
+
+		/*
+		 * If this device number matches the high key, we have
+		 * to pass the high key to the handler to limit the
+		 * query results.  If the device number exceeds the
+		 * low key, zero out the low key so that we get
+		 * everything from the beginning.
+		 */
+		if (handlers[i].dev == rkey_high->fmr_device)
+			dkeys[1] = *rkey_high;
+		if (handlers[i].dev > rkey_low->fmr_device)
+			memset(&dkeys[0], 0, sizeof(struct ext4_fsmap));
+
+		info.next_fsblk = dkeys[0].fmr_physical;
+		info.dev = handlers[i].dev;
+		info.last = false;
+		info.agno = -1;
+		error = handlers[i].fn(sb, dkeys, &info);
+		if (error)
+			break;
+	}
+
+	head->fmh_oflags = FMH_OF_DEV_T;
+	return error;
+}
diff --git a/fs/ext4/fsmap.h b/fs/ext4/fsmap.h
new file mode 100644
index 0000000..e2e721d
--- /dev/null
+++ b/fs/ext4/fsmap.h
@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2017 Oracle.  All Rights Reserved.
+ *
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+#ifndef __EXT4_FSMAP_H__
+#define	__EXT4_FSMAP_H__
+
+struct ext4_metadata_fsmap {
+	struct list_head	mf_list;
+	uint64_t	mf_physical;	/* device offset of segment */
+	uint64_t	mf_owner;	/* owner id */
+	uint64_t	mf_length;	/* length of segment, blocks */
+};
+
+/* internal fsmap representation */
+struct ext4_fsmap {
+	struct list_head	fmr_list;
+	dev_t		fmr_device;	/* device id */
+	uint32_t	fmr_flags;	/* mapping flags */
+	uint64_t	fmr_physical;	/* device offset of segment */
+	uint64_t	fmr_owner;	/* owner id */
+	uint64_t	fmr_length;	/* length of segment, blocks */
+};
+
+struct ext4_fsmap_head {
+	uint32_t	fmh_iflags;	/* control flags */
+	uint32_t	fmh_oflags;	/* output flags */
+	unsigned int	fmh_count;	/* # of entries in array incl. input */
+	unsigned int	fmh_entries;	/* # of entries filled in (output). */
+
+	struct ext4_fsmap fmh_keys[2];	/* low and high keys */
+};
+
+void ext4_fsmap_from_internal(struct super_block *sb, struct fsmap *dest,
+		struct ext4_fsmap *src);
+void ext4_fsmap_to_internal(struct super_block *sb, struct ext4_fsmap *dest,
+		struct fsmap *src);
+
+/* fsmap to userspace formatter - copy to user & advance pointer */
+typedef int (*ext4_fsmap_format_t)(struct ext4_fsmap *, void *);
+
+int ext4_getfsmap(struct super_block *sb, struct ext4_fsmap_head *head,
+		ext4_fsmap_format_t formatter, void *arg);
+
+#define EXT4_QUERY_RANGE_ABORT		1
+#define EXT4_QUERY_RANGE_CONTINUE	0
+
+/*	fmr_owner special values for FS_IOC_GETFSMAP; some share w/ XFS */
+#define EXT4_FMR_OWN_FREE	FMR_OWN_FREE      /* free space */
+#define EXT4_FMR_OWN_UNKNOWN	FMR_OWN_UNKNOWN   /* unknown owner */
+#define EXT4_FMR_OWN_FS		FMR_OWNER('X', 1) /* static fs metadata */
+#define EXT4_FMR_OWN_LOG	FMR_OWNER('X', 2) /* journalling log */
+#define EXT4_FMR_OWN_INODES	FMR_OWNER('X', 5) /* inodes */
+#define EXT4_FMR_OWN_BLKBM	FMR_OWNER('f', 1) /* inode bitmap */
+#define EXT4_FMR_OWN_INOBM	FMR_OWNER('f', 2) /* block bitmap */
+
+#endif /* __EXT4_FSMAP_H__ */
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index d534399..ed62465 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -18,6 +18,9 @@
 #include <linux/uaccess.h>
 #include "ext4_jbd2.h"
 #include "ext4.h"
+#include <linux/fsmap.h>
+#include "fsmap.h"
+#include <trace/events/ext4.h>
 
 /**
  * Swap memory between @a and @b for @len bytes.
@@ -442,6 +445,108 @@ static inline unsigned long ext4_xflags_to_iflags(__u32 xflags)
 	return iflags;
 }
 
+struct getfsmap_info {
+	struct super_block	*sb;
+	struct fsmap __user	*data;
+	__u32			last_flags;
+};
+
+static int
+ext4_getfsmap_format(
+	struct ext4_fsmap	*xfm,
+	void			*priv)
+{
+	struct getfsmap_info	*info = priv;
+	struct fsmap		fm;
+
+	trace_ext4_getfsmap_mapping(info->sb, xfm->fmr_device,
+			xfm->fmr_physical, xfm->fmr_length, xfm->fmr_owner,
+			0, xfm->fmr_flags);
+
+	info->last_flags = xfm->fmr_flags;
+	ext4_fsmap_from_internal(info->sb, &fm, xfm);
+	if (copy_to_user(info->data, &fm, sizeof(struct fsmap)))
+		return -EFAULT;
+
+	info->data++;
+	return 0;
+}
+
+static int
+ext4_ioc_getfsmap(
+	struct super_block	*sb,
+	void			__user *arg)
+{
+	struct getfsmap_info	info;
+	struct ext4_fsmap_head	xhead = {0};
+	struct fsmap_head	head;
+	bool			aborted = false;
+	int			error;
+
+	if (copy_from_user(&head, arg, sizeof(struct fsmap_head)))
+		return -EFAULT;
+	if (head.fmh_reserved[0] || head.fmh_reserved[1] ||
+	    head.fmh_reserved[2] || head.fmh_reserved[3] ||
+	    head.fmh_reserved[4] || head.fmh_reserved[5] ||
+	    head.fmh_keys[0].fmr_offset ||
+	    (head.fmh_keys[1].fmr_offset != 0 &&
+	     head.fmh_keys[1].fmr_offset != -1ULL) ||
+	    head.fmh_keys[0].fmr_reserved[0] ||
+	    head.fmh_keys[0].fmr_reserved[1] ||
+	    head.fmh_keys[0].fmr_reserved[2] ||
+	    head.fmh_keys[1].fmr_reserved[0] ||
+	    head.fmh_keys[1].fmr_reserved[1] ||
+	    head.fmh_keys[1].fmr_reserved[2])
+		return -EINVAL;
+
+	xhead.fmh_iflags = head.fmh_iflags;
+	xhead.fmh_count = head.fmh_count;
+	ext4_fsmap_to_internal(sb, &xhead.fmh_keys[0], &head.fmh_keys[0]);
+	ext4_fsmap_to_internal(sb, &xhead.fmh_keys[1], &head.fmh_keys[1]);
+
+	trace_ext4_getfsmap_low_key(sb,
+			xhead.fmh_keys[0].fmr_device,
+			xhead.fmh_keys[0].fmr_physical,
+			xhead.fmh_keys[0].fmr_length,
+			xhead.fmh_keys[0].fmr_owner,
+			0,
+			xhead.fmh_keys[0].fmr_flags);
+
+	trace_ext4_getfsmap_high_key(sb,
+			xhead.fmh_keys[1].fmr_device,
+			xhead.fmh_keys[1].fmr_physical,
+			xhead.fmh_keys[1].fmr_length,
+			xhead.fmh_keys[1].fmr_owner,
+			0,
+			xhead.fmh_keys[1].fmr_flags);
+
+	info.sb = sb;
+	info.data = ((__force struct fsmap_head *)arg)->fmh_recs;
+	error = ext4_getfsmap(sb, &xhead, ext4_getfsmap_format, &info);
+	if (error == EXT4_QUERY_RANGE_ABORT) {
+		error = 0;
+		aborted = true;
+	} else if (error)
+		return error;
+
+	/* If we didn't abort, set the "last" flag in the last fmx */
+	if (!aborted && xhead.fmh_entries) {
+		info.data--;
+		info.last_flags |= FMR_OF_LAST;
+		if (copy_to_user(&info.data->fmr_flags, &info.last_flags,
+				sizeof(info.last_flags)))
+			return -EFAULT;
+	}
+
+	/* copy back header */
+	head.fmh_entries = xhead.fmh_entries;
+	head.fmh_oflags = xhead.fmh_oflags;
+	if (copy_to_user(arg, &head, sizeof(struct fsmap_head)))
+		return -EFAULT;
+
+	return 0;
+}
+
 long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	struct inode *inode = file_inode(filp);
@@ -452,6 +557,8 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	ext4_debug("cmd = %u, arg = %lu\n", cmd, arg);
 
 	switch (cmd) {
+	case FS_IOC_GETFSMAP:
+		return ext4_ioc_getfsmap(sb, (void __user *)arg);
 	case EXT4_IOC_GETFLAGS:
 		ext4_get_inode_flags(ei);
 		flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
@@ -959,6 +1066,7 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case EXT4_IOC_SET_ENCRYPTION_POLICY:
 	case EXT4_IOC_GET_ENCRYPTION_PWSALT:
 	case EXT4_IOC_GET_ENCRYPTION_POLICY:
+	case FS_IOC_GETFSMAP:
 		break;
 	default:
 		return -ENOIOCTLCMD;
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 7ae43c5..8813c54 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -5258,3 +5258,52 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
 	range->len = EXT4_C2B(EXT4_SB(sb), trimmed) << sb->s_blocksize_bits;
 	return ret;
 }
+
+/* Iterate all the free extents in the group. */
+int
+ext4_mballoc_query_range(
+	struct super_block		*sb,
+	ext4_group_t			group,
+	ext4_grpblk_t			start,
+	ext4_grpblk_t			end,
+	ext4_mballoc_query_range_fn	formatter,
+	void				*priv)
+{
+	void				*bitmap;
+	ext4_grpblk_t			next;
+	struct ext4_buddy		e4b;
+	int				error;
+
+	error = ext4_mb_load_buddy(sb, group, &e4b);
+	if (error)
+		return error;
+	bitmap = e4b.bd_bitmap;
+
+	ext4_lock_group(sb, group);
+
+	start = (e4b.bd_info->bb_first_free > start) ?
+		e4b.bd_info->bb_first_free : start;
+	if (end >= EXT4_CLUSTERS_PER_GROUP(sb))
+		end = EXT4_CLUSTERS_PER_GROUP(sb) - 1;
+
+	while (start <= end) {
+		start = mb_find_next_zero_bit(bitmap, end + 1, start);
+		if (start > end)
+			break;
+		next = mb_find_next_bit(bitmap, end + 1, start);
+
+		ext4_unlock_group(sb, group);
+		error = formatter(sb, group, start, next - start, priv);
+		if (error)
+			goto out_unload;
+		ext4_lock_group(sb, group);
+
+		start = next + 1;
+	}
+
+	ext4_unlock_group(sb, group);
+out_unload:
+	ext4_mb_unload_buddy(&e4b);
+
+	return error;
+}
diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
index 1aba469..2bed620 100644
--- a/fs/ext4/mballoc.h
+++ b/fs/ext4/mballoc.h
@@ -199,4 +199,21 @@ static inline ext4_fsblk_t ext4_grp_offs_to_block(struct super_block *sb,
 	return ext4_group_first_block_no(sb, fex->fe_group) +
 		(fex->fe_start << EXT4_SB(sb)->s_cluster_bits);
 }
+
+typedef int (*ext4_mballoc_query_range_fn)(
+	struct super_block		*sb,
+	ext4_group_t			agno,
+	ext4_grpblk_t			start,
+	ext4_grpblk_t			len,
+	void				*priv);
+
+int
+ext4_mballoc_query_range(
+	struct super_block		*sb,
+	ext4_group_t			agno,
+	ext4_grpblk_t			start,
+	ext4_grpblk_t			end,
+	ext4_mballoc_query_range_fn	formatter,
+	void				*priv);
+
 #endif
diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
index 09c71e9..922baeb 100644
--- a/include/trace/events/ext4.h
+++ b/include/trace/events/ext4.h
@@ -2529,6 +2529,84 @@ TRACE_EVENT(ext4_es_shrink,
 		  __entry->scan_time, __entry->nr_skipped, __entry->retried)
 );
 
+/* fsmap traces */
+DECLARE_EVENT_CLASS(ext4_fsmap_class,
+	TP_PROTO(struct super_block *sb, u32 keydev, u32 agno, u64 bno, u64 len,
+		 u64 owner),
+	TP_ARGS(sb, keydev, agno, bno, len, owner),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(dev_t, keydev)
+		__field(u32, agno)
+		__field(u64, bno)
+		__field(u64, len)
+		__field(u64, owner)
+	),
+	TP_fast_assign(
+		__entry->dev = sb->s_bdev->bd_dev;
+		__entry->keydev = new_decode_dev(keydev);
+		__entry->agno = agno;
+		__entry->bno = bno;
+		__entry->len = len;
+		__entry->owner = owner;
+	),
+	TP_printk("dev %d:%d keydev %d:%d agno %u bno %llu len %llu owner %lld\n",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  MAJOR(__entry->keydev), MINOR(__entry->keydev),
+		  __entry->agno,
+		  __entry->bno,
+		  __entry->len,
+		  __entry->owner)
+)
+#define DEFINE_FSMAP_EVENT(name) \
+DEFINE_EVENT(ext4_fsmap_class, name, \
+	TP_PROTO(struct super_block *sb, u32 keydev, u32 agno, u64 bno, u64 len, \
+		 u64 owner), \
+	TP_ARGS(sb, keydev, agno, bno, len, owner))
+DEFINE_FSMAP_EVENT(ext4_fsmap_low_key);
+DEFINE_FSMAP_EVENT(ext4_fsmap_high_key);
+DEFINE_FSMAP_EVENT(ext4_fsmap_mapping);
+
+DECLARE_EVENT_CLASS(ext4_getfsmap_class,
+	TP_PROTO(struct super_block *sb, u32 keydev, u64 block, u64 len,
+		 u64 owner, u64 offset, u64 flags),
+	TP_ARGS(sb, keydev, block, len, owner, offset, flags),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(dev_t, keydev)
+		__field(u64, block)
+		__field(u64, len)
+		__field(u64, owner)
+		__field(u64, offset)
+		__field(u64, flags)
+	),
+	TP_fast_assign(
+		__entry->dev = sb->s_bdev->bd_dev;
+		__entry->keydev = new_decode_dev(keydev);
+		__entry->block = block;
+		__entry->len = len;
+		__entry->owner = owner;
+		__entry->offset = offset;
+		__entry->flags = flags;
+	),
+	TP_printk("dev %d:%d keydev %d:%d block %llu len %llu owner %lld offset %llu flags 0x%llx\n",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  MAJOR(__entry->keydev), MINOR(__entry->keydev),
+		  __entry->block,
+		  __entry->len,
+		  __entry->owner,
+		  __entry->offset,
+		  __entry->flags)
+)
+#define DEFINE_GETFSMAP_EVENT(name) \
+DEFINE_EVENT(ext4_getfsmap_class, name, \
+	TP_PROTO(struct super_block *sb, u32 keydev, u64 block, u64 len, \
+		 u64 owner, u64 offset, u64 flags), \
+	TP_ARGS(sb, keydev, block, len, owner, offset, flags))
+DEFINE_GETFSMAP_EVENT(ext4_getfsmap_low_key);
+DEFINE_GETFSMAP_EVENT(ext4_getfsmap_high_key);
+DEFINE_GETFSMAP_EVENT(ext4_getfsmap_mapping);
+
 #endif /* _TRACE_EXT4_H */
 
 /* This part must be outside protection */

[PATCH] ioctl_getfsmap.2: document the GETFSMAP ioctl

[Darrick J. Wong]

Document the new GETFSMAP ioctl that returns the physical layout of a
(disk-based) filesystem.  This time around the fs-specific parts have
been moved to a separate section; I'll move move them into separate
xfsprogs/e2fsprogs manpages when we get closer to landing the ioctl.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 man2/ioctl_getfsmap.2 |  359 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 359 insertions(+)
 create mode 100644 man2/ioctl_getfsmap.2

diff --git a/man2/ioctl_getfsmap.2 b/man2/ioctl_getfsmap.2
new file mode 100644
index 0000000..7121d61
--- /dev/null
+++ b/man2/ioctl_getfsmap.2
@@ -0,0 +1,359 @@
+.\" Copyright (c) 2017, Oracle.  All rights reserved.
+.\"
+.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
+.\" This is free documentation; you can redistribute it and/or
+.\" modify it under the terms of the GNU General Public License as
+.\" published by the Free Software Foundation; either version 2 of
+.\" the License, or (at your option) any later version.
+.\"
+.\" The GNU General Public License's references to "object code"
+.\" and "executables" are to be interpreted as the output of any
+.\" document formatting or typesetting system, including
+.\" intermediate and printed output.
+.\"
+.\" This manual is distributed in the hope that it will be useful,
+.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
+.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+.\" GNU General Public License for more details.
+.\"
+.\" You should have received a copy of the GNU General Public
+.\" License along with this manual; if not, see
+.\" <http://www.gnu.org/licenses/>.
+.\" %%%LICENSE_END
+.TH IOCTL-GETFSMAP 2 2017-02-10 "Linux" "Linux Programmer's Manual"
+.SH NAME
+ioctl_getfsmap \- retrieve the physical layout of the filesystem
+.SH SYNOPSIS
+.br
+.B #include <sys/ioctl.h>
+.br
+.B #include <linux/fs.h>
+.br
+.B #include <linux/fsmap.h>
+.sp
+.BI "int ioctl(int " fd ", GETFSMAP, struct fsmap_head * " arg );
+.SH DESCRIPTION
+This
+.BR ioctl (2)
+retrieves physical extent mappings for a filesystem.
+This information can be used to discover which files are mapped to a physical
+block, examine free space, or find known bad blocks, among other things.
+
+The sole argument to this ioctl should be a pointer to a single
+.BR "struct fsmap_head" ":"
+.in +4n
+.nf
+
+struct fsmap {
+	__u32		fmr_device;	/* device id */
+	__u32		fmr_flags;	/* mapping flags */
+	__u64		fmr_physical;	/* device offset of segment */
+	__u64		fmr_owner;	/* owner id */
+	__u64		fmr_offset;	/* file offset of segment */
+	__u64		fmr_length;	/* length of segment */
+	__u64		fmr_reserved[3];	/* must be zero */
+};
+
+struct fsmap_head {
+	__u32		fmh_iflags;	/* control flags */
+	__u32		fmh_oflags;	/* output flags */
+	__u32		fmh_count;	/* # of entries in array incl. input */
+	__u32		fmh_entries;	/* # of entries filled in (output). */
+	__u64		fmh_reserved[6];	/* must be zero */
+
+	struct fsmap	fmh_keys[2];	/* low and high keys for the mapping search */
+	struct fsmap	fmh_recs[];	/* returned records */
+};
+
+.fi
+.in
+The two
+.I fmh_keys
+array elements specify the lowest and highest reverse-mapping
+keys, respectively, for which userspace would like physical mapping
+information.
+A reverse mapping key consists of the tuple (device, block, owner, offset).
+The owner and offset fields are part of the key because some filesystems
+support sharing physical blocks between multiple files and
+therefore may return multiple mappings for a given physical block.
+.PP
+Filesystem mappings are copied into the
+.I fmh_recs
+array, which immediately follows the header data.
+.SS Fields of struct fsmap_head
+.PP
+The
+.I fmh_iflags
+field is a bitmask passed to the kernel to alter the output.
+There are no flags defined, so this value must be zero.
+
+.PP
+The
+.I fmh_oflags
+field is a bitmask of flags that concern all output mappings.
+If
+.B FMH_OF_DEV_T
+is set, then the
+.I fmr_device
+field represents a
+.B dev_t
+structure containing the major and minor numbers of the block device.
+
+.PP
+The
+.I fmh_count
+field contains the number of elements in the array being passed to the
+kernel.
+If this value is 0,
+.I fmh_entries
+will be set to the number of records that would have been returned had
+the array been large enough;
+no mapping information will be returned.
+
+.PP
+The
+.I fmh_entries
+field contains the number of elements in the
+.I fmh_recs
+array that contain useful information.
+
+.PP
+The
+.I fmh_reserved
+fields must be set to zero.
+
+.SS Keys
+.PP
+The two key records in
+.B fsmap_head.fmh_keys
+specify the lowest and highest extent records in the keyspace that the caller
+wants returned.
+A filesystem that can share blocks between files likely requires the tuple
+.RI "(" "device" ", " "physical" ", " "owner" ", " "offset" ", " "flags" ")"
+to uniquely index any filesystem mapping record.
+Classic non-sharing filesystems might be able to identify any record with only
+.RI "(" "device" ", " "physical" ", " "flags" ")."
+For example, if the low key is set to (0, 36864, 0, 0, 0), the filesystem will
+only return records for extents starting at or above 36KiB on disk.
+If the high key is set to (0, 1048576, 0, 0, 0), only records below 1MiB will
+be returned.
+By convention, the field
+.B fsmap_head.fmh_keys[0]
+must contain the low key and
+.B fsmap_head.fmh_keys[1]
+must contain the high key for the request.
+.PP
+For convenience, if
+.B fmr_length
+is set in the low key, it will be added to
+.IR fmr_block " or " fmr_offset
+as appropriate.
+The caller can take advantage of this subtlety to set up subsequent calls
+by copying
+.B fsmap_head.fmh_recs[fsmap_head.fmh_entries - 1]
+into the low key.
+The function
+.B fsmap_advance
+provides this functionality.
+
+.SS Fields of struct fsmap
+.PP
+The
+.I fmr_device
+field contains a 32-bit cookie to uniquely identify the underlying storage
+device.
+If the
+.B FMH_OF_DEV_T
+flag is set in the header's
+.I fmh_oflags
+field, this field contains a
+.B dev_t
+from which major and minor numbers can be extracted.
+If the flag is not set, this field contains a value that must be unique
+for each unique storage device.
+
+.PP
+The
+.I fmr_physical
+field contains the disk address of the extent in bytes.
+
+.PP
+The
+.I fmr_owner
+field contains the owner of the extent.
+This is an inode number unless
+.B FMR_OF_SPECIAL_OWNER
+is set in the
+.I fmr_flags
+field, in which case the value is determined by the filesystem.
+See the section below about special owner values for more details.
+
+.PP
+The
+.I fmr_offset
+field contains the logical address in the mapping record in bytes.
+This field has no meaning if the
+.BR FMR_OF_SPECIAL_OWNER " or " FMR_OF_EXTENT_MAP
+flags are set in
+.IR fmr_flags "."
+
+.PP
+The
+.I fmr_length
+field contains the length of the extent in bytes.
+
+.PP
+The
+.I fmr_flags
+field is a bitmask of extent state flags.
+The bits are:
+.RS 0.4i
+.TP
+.B FMR_OF_PREALLOC
+The extent is allocated but not yet written.
+.TP
+.B FMR_OF_ATTR_FORK
+This extent contains extended attribute data.
+.TP
+.B FMR_OF_EXTENT_MAP
+This extent contains extent map information for the owner.
+.TP
+.B FMR_OF_SHARED
+Parts of this extent may be shared.
+.TP
+.B FMR_OF_SPECIAL_OWNER
+The
+.I fmr_owner
+field contains a special value instead of an inode number.
+.TP
+.B FMR_OF_LAST
+This is the last record in the filesystem.
+.RE
+
+.PP
+The
+.I fmr_reserved
+field will be set to zero.
+
+.SS Special Owner Values
+The following special owner values are generic to all filesystems:
+.RS 0.4i
+.TP
+.B FMR_OWN_FREE
+Free space.
+.TP
+.B FMR_OWN_UNKNOWN
+This extent is in use but its owner is not known.
+.TP
+.B FMR_OWN_METADATA
+This extent is filesystem metadata.
+.RE
+
+XFS can return the following special owner values:
+.RS 0.4i
+.TP
+.B XFS_FMR_OWN_FREE
+Free space.
+.TP
+.B XFS_FMR_OWN_UNKNOWN
+This extent is in use but its owner is not known.
+.TP
+.B XFS_FMR_OWN_FS
+Static filesystem metadata which exists at a fixed address.
+These are the AG superblock, the AGF, the AGFL, and the AGI headers.
+.TP
+.B XFS_FMR_OWN_LOG
+The filesystem journal.
+.TP
+.B XFS_FMR_OWN_AG
+Allocation group metadata, such as the free space btrees and the
+reverse mapping btrees.
+.TP
+.B XFS_FMR_OWN_INOBT
+The inode and free inode btrees.
+.TP
+.B XFS_FMR_OWN_INODES
+Inode records.
+.TP
+.B XFS_FMR_OWN_REFC
+Reference count information.
+.TP
+.B XFS_FMR_OWN_COW
+This extent is being used to stage a copy-on-write.
+.TP
+.B XFS_FMR_OWN_DEFECTIVE:
+This extent has been marked defective either by the filesystem or the
+underlying device.
+.RE
+
+ext4 can return the following special owner values:
+.RS 0.4i
+.TP
+.B EXT4_FMR_OWN_FREE
+Free space.
+.TP
+.B EXT4_FMR_OWN_UNKNOWN
+This extent is in use but its owner is not known.
+.TP
+.B EXT4_FMR_OWN_FS
+Static filesystem metadata which exists at a fixed address.
+This is the superblock and the group descriptors.
+.TP
+.B EXT4_FMR_OWN_LOG
+The filesystem journal.
+.TP
+.B EXT4_FMR_OWN_INODES
+Inode records.
+.TP
+.B EXT4_FMR_OWN_BLKBM
+Block bitmap.
+.TP
+.B EXT4_FMR_OWN_INOBM
+Inode bitmap.
+.RE
+
+.SH RETURN VALUE
+On error, \-1 is returned, and
+.I errno
+is set to indicate the error.
+.PP
+.SH ERRORS
+Error codes can be one of, but are not limited to, the following:
+.TP
+.B EINVAL
+The array is not long enough, or a non-zero value was passed in one of the
+fields that must be zero.
+.TP
+.B EFAULT
+The pointer passed in was not mapped to a valid memory address.
+.TP
+.B EBADF
+.IR fd
+is not open for reading.
+.TP
+.B EPERM
+This query is not allowed.
+.TP
+.B EOPNOTSUPP
+The filesystem does not support this command.
+.TP
+.B EUCLEAN
+The filesystem metadata is corrupt and needs repair.
+.TP
+.B EBADMSG
+The filesystem has detected a checksum error in the metadata.
+.TP
+.B ENOMEM
+Insufficient memory to process the request.
+
+.SH EXAMPLE
+.TP
+Please see io/fsmap.c in the xfsprogs distribution for a sample program.
+
+.SH CONFORMING TO
+This API is Linux-specific.
+Not all filesystems support it.
+.fi
+.in
+.SH SEE ALSO
+.BR ioctl (2)