[PATCH 01/10] xfs: introduce the XFS_IOC_GETFSMAP ioctl

["Darrick J. Wong" <darrick.wong@oracle.com>]

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>
[sandeen: rework to have less autoconf magic]
Modified-by: Eric Sandeen <sandeen@redhat.com>
---
v3: rework the whole mess to have less autoconf magic; now we only
track if the system headers actually define getfsmap.
v2: shorten the device field to u32 since that's all we need for
dev_t.  Support reporting reverse mapping information for all the
devices that XFS supports (data, log).
---
 configure.ac          |    1 
 include/builddefs.in  |    4 ++
 include/linux.h       |  103 +++++++++++++++++++++++++++++++++++++++++++++++++
 m4/package_libcdev.m4 |   20 ++++++++++
 4 files changed, 128 insertions(+)


diff --git a/configure.ac b/configure.ac
index aa102e4..9534986 100644
--- a/configure.ac
+++ b/configure.ac
@@ -142,6 +142,7 @@ AC_HAVE_READDIR
 AC_HAVE_FSETXATTR
 AC_HAVE_MREMAP
 AC_NEED_INTERNAL_FSXATTR
+AC_HAVE_GETFSMAP
 
 if test "$enable_blkid" = yes; then
 AC_HAVE_BLKID_TOPO
diff --git a/include/builddefs.in b/include/builddefs.in
index 4d6bb2d..ec630bd 100644
--- a/include/builddefs.in
+++ b/include/builddefs.in
@@ -112,6 +112,7 @@ HAVE_FLS = @have_fls@
 HAVE_FSETXATTR = @have_fsetxattr@
 HAVE_MREMAP = @have_mremap@
 NEED_INTERNAL_FSXATTR = @need_internal_fsxattr@
+HAVE_GETFSMAP = @have_getfsmap@
 
 GCCFLAGS = -funsigned-char -fno-strict-aliasing -Wall
 #	   -Wbitwise -Wno-transparent-union -Wno-old-initializer -Wno-decl
@@ -150,6 +151,9 @@ endif
 ifeq ($(NEED_INTERNAL_FSXATTR),yes)
 PCFLAGS+= -DOVERRIDE_SYSTEM_FSXATTR
 endif
+ifeq ($(HAVE_GETFSMAP),yes)
+PCFLAGS+= -DHAVE_GETFSMAP
+endif
 
 
 GCFLAGS = $(DEBUG) \
diff --git a/include/linux.h b/include/linux.h
index 6a676ca..38969d1 100644
--- a/include/linux.h
+++ b/include/linux.h
@@ -222,4 +222,107 @@ struct fsxattr {
 #define FS_XFLAG_COWEXTSIZE	0x00010000	/* CoW extent size allocator hint */
 #endif
 
+#ifndef HAVE_GETFSMAP
+/*
+ *	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 XFS_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_OWNER_TYPE(owner)	((__u32)((__u64)owner >> 32))
+#define FMR_OWNER_CODE(owner)	((__u32)(((__u64)owner & 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)
+
+#define HAVE_GETFSMAP
+#endif /* HAVE_GETFSMAP */
+
 #endif	/* __XFS_LINUX_H__ */
diff --git a/m4/package_libcdev.m4 b/m4/package_libcdev.m4
index bc3b4ce..fa5b639 100644
--- a/m4/package_libcdev.m4
+++ b/m4/package_libcdev.m4
@@ -277,3 +277,23 @@ AC_DEFUN([AC_NEED_INTERNAL_FSXATTR],
     )
     AC_SUBST(need_internal_fsxattr)
   ])
+
+#
+# Check if we have a FS_IOC_GETFSMAP ioctl (Linux)
+#
+AC_DEFUN([AC_HAVE_GETFSMAP],
+  [ AC_MSG_CHECKING([for GETFSMAP])
+    AC_TRY_LINK([
+#define _GNU_SOURCE
+#include <sys/syscall.h>
+#include <unistd.h>
+#include <linux/fs.h>
+#include <linux/fsmap.h>
+    ], [
+         unsigned long x = FS_IOC_GETFSMAP;
+         struct fsmap_head fh;
+    ], have_getfsmap=yes
+       AC_MSG_RESULT(yes),
+       AC_MSG_RESULT(no))
+    AC_SUBST(have_getfsmap)
+  ])