[PATCH stable-5.4 0/6] backport fixes for xfstests btrfs/199,200,203,204

[PATCH stable-5.4 0/6] backport fixes for xfstests btrfs/199,200,203,204

[Anand Jain]

This series backports fixes for the xfstests test cases btrfs/199
btrfs/200 btrfs/203 and btrfs/204.

patch 1 is fix for btrfs/200
patch 2 fixes regression in patch 1 and is fix for btrfs/203 
patch 3 helps to fix conflicts in patch 4
patch 4 is fix for btrfs/199
patch 5 helps to avoid conflicts in patch6
patch 6 is fix for btrfs/204

patch1 Btrfs: send, allow clone operations within the same file
patch2 Btrfs: send, fix emission of invalid clone operations within the same file
patch3 btrfs: volumes: Use more straightforward way to calculate map length
patch4 btrfs: Ensure we trim ranges across block group boundary
patch5 btrfs: fix RWF_NOWAIT write not failling when we need to cow
patch6 btrfs: allow btrfs_truncate_block() to fallback to nocow for data space reservation

Filipe Manana (3):
  Btrfs: send, allow clone operations within the same file
  Btrfs: send, fix emission of invalid clone operations within the same
    file
  btrfs: fix RWF_NOWAIT write not failling when we need to cow

Qu Wenruo (3):
  btrfs: volumes: Use more straightforward way to calculate map length
  btrfs: Ensure we trim ranges across block group boundary
  btrfs: allow btrfs_truncate_block() to fallback to nocow for data
    space reservation

 fs/btrfs/ctree.h       |  2 ++
 fs/btrfs/extent-tree.c | 41 +++++++++++++++++++++++++++++----------
 fs/btrfs/file.c        | 23 ++++++++++++++++++----
 fs/btrfs/inode.c       | 44 +++++++++++++++++++++++++++++++++++-------
 fs/btrfs/send.c        | 19 +++++++++++++-----
 fs/btrfs/volumes.c     |  8 +++++---
 6 files changed, 108 insertions(+), 29 deletions(-)

-- 
2.25.1

[PATCH stable-5.4 1/6] Btrfs: send, allow clone operations within the same file

[Anand Jain]

From: Filipe Manana <fdmanana@suse.com>

commit 11f2069c113e02971b8db6fda62f9b9cd31a030f upstream.

For send we currently skip clone operations when the source and
destination files are the same. This is so because clone didn't support
this case in its early days, but support for it was added back in May
2013 by commit a96fbc72884fcb ("Btrfs: allow file data clone within a
file"). This change adds support for it.

Example:

  $ mkfs.btrfs -f /dev/sdd
  $ mount /dev/sdd /mnt/sdd

  $ xfs_io -f -c "pwrite -S 0xab -b 64K 0 64K" /mnt/sdd/foobar
  $ xfs_io -c "reflink /mnt/sdd/foobar 0 64K 64K" /mnt/sdd/foobar

  $ btrfs subvolume snapshot -r /mnt/sdd /mnt/sdd/snap

  $ mkfs.btrfs -f /dev/sde
  $ mount /dev/sde /mnt/sde

  $ btrfs send /mnt/sdd/snap | btrfs receive /mnt/sde

Without this change file foobar at the destination has a single 128Kb
extent:

  $ filefrag -v /mnt/sde/snap/foobar
  Filesystem type is: 9123683e
  File size of /mnt/sde/snap/foobar is 131072 (32 blocks of 4096 bytes)
   ext:     logical_offset:        physical_offset: length:   expected: flags:
     0:        0..      31:          0..        31:     32:             last,unknown_loc,delalloc,eof
  /mnt/sde/snap/foobar: 1 extent found

With this we get a single 64Kb extent that is shared at file offsets 0
and 64K, just like in the source filesystem:

  $ filefrag -v /mnt/sde/snap/foobar
  Filesystem type is: 9123683e
  File size of /mnt/sde/snap/foobar is 131072 (32 blocks of 4096 bytes)
   ext:     logical_offset:        physical_offset: length:   expected: flags:
     0:        0..      15:       3328..      3343:     16:             shared
     1:       16..      31:       3328..      3343:     16:       3344: last,shared,eof
  /mnt/sde/snap/foobar: 2 extents found

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/send.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 6ad216e8178e..48d028b1cfaf 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -1257,12 +1257,20 @@ static int __iterate_backrefs(u64 ino, u64 offset, u64 root, void *ctx_)
 	 */
 	if (found->root == bctx->sctx->send_root) {
 		/*
-		 * TODO for the moment we don't accept clones from the inode
-		 * that is currently send. We may change this when
-		 * BTRFS_IOC_CLONE_RANGE supports cloning from and to the same
-		 * file.
+		 * If the source inode was not yet processed we can't issue a
+		 * clone operation, as the source extent does not exist yet at
+		 * the destination of the stream.
 		 */
-		if (ino >= bctx->cur_objectid)
+		if (ino > bctx->cur_objectid)
+			return 0;
+		/*
+		 * We clone from the inode currently being sent as long as the
+		 * source extent is already processed, otherwise we could try
+		 * to clone from an extent that does not exist yet at the
+		 * destination of the stream.
+		 */
+		if (ino == bctx->cur_objectid &&
+		    offset >= bctx->sctx->cur_inode_next_write_offset)
 			return 0;
 	}
 
-- 
2.25.1

[PATCH stable-5.4 2/6] Btrfs: send, fix emission of invalid clone operations within the same file

[Anand Jain]

From: Filipe Manana <fdmanana@suse.com>

commit 9722b10148504c4153a74a9c89725af271e490fc upstream.

When doing an incremental send and a file has extents shared with itself
at different file offsets, it's possible for send to emit clone operations
that will fail at the destination because the source range goes beyond the
file's current size. This happens when the file size has increased in the
send snapshot, there is a hole between the shared extents and both shared
extents are at file offsets which are greater the file's size in the
parent snapshot.

Example:

  $ mkfs.btrfs -f /dev/sdb
  $ mount /dev/sdb /mnt/sdb

  $ xfs_io -f -c "pwrite -S 0xf1 0 64K" /mnt/sdb/foobar
  $ btrfs subvolume snapshot -r /mnt/sdb /mnt/sdb/base
  $ btrfs send -f /tmp/1.snap /mnt/sdb/base

  # Create a 320K extent at file offset 512K.
  $ xfs_io -c "pwrite -S 0xab 512K 64K" /mnt/sdb/foobar
  $ xfs_io -c "pwrite -S 0xcd 576K 64K" /mnt/sdb/foobar
  $ xfs_io -c "pwrite -S 0xef 640K 64K" /mnt/sdb/foobar
  $ xfs_io -c "pwrite -S 0x64 704K 64K" /mnt/sdb/foobar
  $ xfs_io -c "pwrite -S 0x73 768K 64K" /mnt/sdb/foobar

  # Clone part of that 320K extent into a lower file offset (192K).
  # This file offset is greater than the file's size in the parent
  # snapshot (64K). Also the clone range is a bit behind the offset of
  # the 320K extent so that we leave a hole between the shared extents.
  $ xfs_io -c "reflink /mnt/sdb/foobar 448K 192K 192K" /mnt/sdb/foobar

  $ btrfs subvolume snapshot -r /mnt/sdb /mnt/sdb/incr
  $ btrfs send -p /mnt/sdb/base -f /tmp/2.snap /mnt/sdb/incr

  $ mkfs.btrfs -f /dev/sdc
  $ mount /dev/sdc /mnt/sdc

  $ btrfs receive -f /tmp/1.snap /mnt/sdc
  $ btrfs receive -f /tmp/2.snap /mnt/sdc
  ERROR: failed to clone extents to foobar: Invalid argument

The problem is that after processing the extent at file offset 256K, which
refers to the first 128K of the 320K extent created by the buffered write
operations, we have 'cur_inode_next_write_offset' set to 384K, which
corresponds to the end offset of the partially shared extent (256K + 128K)
and to the current file size in the receiver. Then when we process the
extent at offset 512K, we do extent backreference iteration to figure out
if we can clone the extent from some other inode or from the same inode,
and we consider the extent at offset 256K of the same inode as a valid
source for a clone operation, which is not correct because at that point
the current file size in the receiver is 384K, which corresponds to the
end of last processed extent (at file offset 256K), so using a clone
source range from 256K to 256K + 320K is invalid because that goes past
the current size of the file (384K) - this makes the receiver get an
-EINVAL error when attempting the clone operation.

So fix this by excluding clone sources that have a range that goes beyond
the current file size in the receiver when iterating extent backreferences.

A test case for fstests follows soon.

Fixes: 11f2069c113e02 ("Btrfs: send, allow clone operations within the same file")
CC: stable@vger.kernel.org # 5.5+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/send.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 48d028b1cfaf..b0e5dfb9be7a 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -1270,7 +1270,8 @@ static int __iterate_backrefs(u64 ino, u64 offset, u64 root, void *ctx_)
 		 * destination of the stream.
 		 */
 		if (ino == bctx->cur_objectid &&
-		    offset >= bctx->sctx->cur_inode_next_write_offset)
+		    offset + bctx->extent_len >
+		    bctx->sctx->cur_inode_next_write_offset)
 			return 0;
 	}
 
-- 
2.25.1

[PATCH stable-5.4 3/6] btrfs: volumes: Use more straightforward way to calculate map length

[Anand Jain]

From: Qu Wenruo <wqu@suse.com>

commit 2d974619a77f106f3d1341686dea95c0eaad601f upstream.

The old code goes:

 	offset = logical - em->start;
	length = min_t(u64, em->len - offset, length);

Where @length calculation is dependent on offset, it can take reader
several more seconds to find it's just the same code as:

 	offset = logical - em->start;
	length = min_t(u64, em->start + em->len - logical, length);

Use above code to make the length calculate independent from other
variable, thus slightly increase the readability.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/volumes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 196ddbcd2936..1dba45d43485 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5712,7 +5712,7 @@ static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
 	}
 
 	offset = logical - em->start;
-	length = min_t(u64, em->len - offset, length);
+	length = min_t(u64, em->start + em->len - logical, length);
 
 	stripe_len = map->stripe_len;
 	/*
-- 
2.25.1

[PATCH stable-5.4 4/6] btrfs: Ensure we trim ranges across block group boundary

[Anand Jain]

From: Qu Wenruo <wqu@suse.com>

commit 6b7faadd985c990324b5b5bd18cc4ba5c395eb65 upstream.

[BUG]
When deleting large files (which cross block group boundary) with
discard mount option, we find some btrfs_discard_extent() calls only
trimmed part of its space, not the whole range:

  btrfs_discard_extent: type=0x1 start=19626196992 len=2144530432 trimmed=1073741824 ratio=50%

type:		bbio->map_type, in above case, it's SINGLE DATA.
start:		Logical address of this trim
len:		Logical length of this trim
trimmed:	Physically trimmed bytes
ratio:		trimmed / len

Thus leaving some unused space not discarded.

[CAUSE]
When discard mount option is specified, after a transaction is fully
committed (super block written to disk), we begin to cleanup pinned
extents in the following call chain:

btrfs_commit_transaction()
|- btrfs_finish_extent_commit()
   |- find_first_extent_bit(unpin, 0, &start, &end, EXTENT_DIRTY);
   |- btrfs_discard_extent()

However, pinned extents are recorded in an extent_io_tree, which can
merge adjacent extent states.

When a large file gets deleted and it has adjacent file extents across
block group boundary, we will get a large merged range like this:

      |<---    BG1    --->|<---      BG2     --->|
      |//////|<--   Range to discard   --->|/////|

To discard that range, we have the following calls:

  btrfs_discard_extent()
  |- btrfs_map_block()
  |  Returned bbio will end at BG1's end. As btrfs_map_block()
  |  never returns result across block group boundary.
  |- btrfs_issuse_discard()
     Issue discard for each stripe.

So we will only discard the range in BG1, not the remaining part in BG2.

Furthermore, this bug is not that reliably observed, for above case, if
there is no other extent in BG2, BG2 will be empty and btrfs will trim
all space of BG2, covering up the bug.

[FIX]
- Allow __btrfs_map_block_for_discard() to modify @length parameter
  btrfs_map_block() uses its @length paramter to notify the caller how
  many bytes are mapped in current call.
  With __btrfs_map_block_for_discard() also modifing the @length,
  btrfs_discard_extent() now understands when to do extra trim.

- Call btrfs_map_block() in a loop until we hit the range end Since we
  now know how many bytes are mapped each time, we can iterate through
  each block group boundary and issue correct trim for each range.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Tested-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/extent-tree.c | 41 +++++++++++++++++++++++++++++++----------
 fs/btrfs/volumes.c     |  6 ++++--
 2 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index ef05cbacef73..a546212594e8 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1306,8 +1306,10 @@ static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len,
 int btrfs_discard_extent(struct btrfs_fs_info *fs_info, u64 bytenr,
 			 u64 num_bytes, u64 *actual_bytes)
 {
-	int ret;
+	int ret = 0;
 	u64 discarded_bytes = 0;
+	u64 end = bytenr + num_bytes;
+	u64 cur = bytenr;
 	struct btrfs_bio *bbio = NULL;
 
 
@@ -1316,15 +1318,23 @@ int btrfs_discard_extent(struct btrfs_fs_info *fs_info, u64 bytenr,
 	 * associated to its stripes that don't go away while we are discarding.
 	 */
 	btrfs_bio_counter_inc_blocked(fs_info);
-	/* Tell the block device(s) that the sectors can be discarded */
-	ret = btrfs_map_block(fs_info, BTRFS_MAP_DISCARD, bytenr, &num_bytes,
-			      &bbio, 0);
-	/* Error condition is -ENOMEM */
-	if (!ret) {
-		struct btrfs_bio_stripe *stripe = bbio->stripes;
+	while (cur < end) {
+		struct btrfs_bio_stripe *stripe;
 		int i;
 
+		num_bytes = end - cur;
+		/* Tell the block device(s) that the sectors can be discarded */
+		ret = btrfs_map_block(fs_info, BTRFS_MAP_DISCARD, cur,
+				      &num_bytes, &bbio, 0);
+		/*
+		 * Error can be -ENOMEM, -ENOENT (no such chunk mapping) or
+		 * -EOPNOTSUPP. For any such error, @num_bytes is not updated,
+		 * thus we can't continue anyway.
+		 */
+		if (ret < 0)
+			goto out;
 
+		stripe = bbio->stripes;
 		for (i = 0; i < bbio->num_stripes; i++, stripe++) {
 			u64 bytes;
 			struct request_queue *req_q;
@@ -1341,10 +1351,19 @@ int btrfs_discard_extent(struct btrfs_fs_info *fs_info, u64 bytenr,
 						  stripe->physical,
 						  stripe->length,
 						  &bytes);
-			if (!ret)
+			if (!ret) {
 				discarded_bytes += bytes;
-			else if (ret != -EOPNOTSUPP)
-				break; /* Logic errors or -ENOMEM, or -EIO but I don't know how that could happen JDM */
+			} else if (ret != -EOPNOTSUPP) {
+				/*
+				 * Logic errors or -ENOMEM, or -EIO, but
+				 * unlikely to happen.
+				 *
+				 * And since there are two loops, explicitly
+				 * go to out to avoid confusion.
+				 */
+				btrfs_put_bbio(bbio);
+				goto out;
+			}
 
 			/*
 			 * Just in case we get back EOPNOTSUPP for some reason,
@@ -1354,7 +1373,9 @@ int btrfs_discard_extent(struct btrfs_fs_info *fs_info, u64 bytenr,
 			ret = 0;
 		}
 		btrfs_put_bbio(bbio);
+		cur += num_bytes;
 	}
+out:
 	btrfs_bio_counter_dec(fs_info);
 
 	if (actual_bytes)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 1dba45d43485..ad540283d455 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5674,12 +5674,13 @@ void btrfs_put_bbio(struct btrfs_bio *bbio)
  * replace.
  */
 static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
-					 u64 logical, u64 length,
+					 u64 logical, u64 *length_ret,
 					 struct btrfs_bio **bbio_ret)
 {
 	struct extent_map *em;
 	struct map_lookup *map;
 	struct btrfs_bio *bbio;
+	u64 length = *length_ret;
 	u64 offset;
 	u64 stripe_nr;
 	u64 stripe_nr_end;
@@ -5713,6 +5714,7 @@ static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
 
 	offset = logical - em->start;
 	length = min_t(u64, em->start + em->len - logical, length);
+	*length_ret = length;
 
 	stripe_len = map->stripe_len;
 	/*
@@ -6127,7 +6129,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
 
 	if (op == BTRFS_MAP_DISCARD)
 		return __btrfs_map_block_for_discard(fs_info, logical,
-						     *length, bbio_ret);
+						     length, bbio_ret);
 
 	ret = btrfs_get_io_geometry(fs_info, op, logical, *length, &geom);
 	if (ret < 0)
-- 
2.25.1

[PATCH stable-5.4 5/6] btrfs: fix RWF_NOWAIT write not failling when we need to cow

[Anand Jain]

From: Filipe Manana <fdmanana@suse.com>

commit 260a63395f90f67d6ab89e4266af9e3dc34a77e9 upstream.

If we attempt to do a RWF_NOWAIT write against a file range for which we
can only do NOCOW for a part of it, due to the existence of holes or
shared extents for example, we proceed with the write as if it were
possible to NOCOW the whole range.

Example:

  $ mkfs.btrfs -f /dev/sdb
  $ mount /dev/sdb /mnt

  $ touch /mnt/sdj/bar
  $ chattr +C /mnt/sdj/bar

  $ xfs_io -d -c "pwrite -S 0xab -b 256K 0 256K" /mnt/bar
  wrote 262144/262144 bytes at offset 0
  256 KiB, 1 ops; 0.0003 sec (694.444 MiB/sec and 2777.7778 ops/sec)

  $ xfs_io -c "fpunch 64K 64K" /mnt/bar
  $ sync

  $ xfs_io -d -c "pwrite -N -V 1 -b 128K -S 0xfe 0 128K" /mnt/bar
  wrote 131072/131072 bytes at offset 0
  128 KiB, 1 ops; 0.0007 sec (160.051 MiB/sec and 1280.4097 ops/sec)

This last write should fail with -EAGAIN since the file range from 64K to
128K is a hole. On xfs it fails, as expected, but on ext4 it currently
succeeds because apparently it is expensive to check if there are extents
allocated for the whole range, but I'll check with the ext4 people.

Fix the issue by checking if check_can_nocow() returns a number of
NOCOW'able bytes smaller then the requested number of bytes, and if it
does return -EAGAIN.

Fixes: edf064e7c6fec3 ("btrfs: nowait aio support")
CC: stable@vger.kernel.org # 4.14+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/file.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 4e4ddd5629e5..4d0e1f9452a5 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1919,13 +1919,27 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 	pos = iocb->ki_pos;
 	count = iov_iter_count(from);
 	if (iocb->ki_flags & IOCB_NOWAIT) {
+		size_t nocow_bytes = count;
+
 		/*
 		 * We will allocate space in case nodatacow is not set,
 		 * so bail
 		 */
 		if (!(BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW |
 					      BTRFS_INODE_PREALLOC)) ||
-		    check_can_nocow(BTRFS_I(inode), pos, &count) <= 0) {
+		    check_can_nocow(BTRFS_I(inode), pos, &nocow_bytes) <= 0) {
+			inode_unlock(inode);
+			return -EAGAIN;
+		}
+
+		/* check_can_nocow() locks the snapshot lock on success */
+		btrfs_end_write_no_snapshotting(root);
+		/*
+		 * There are holes in the range or parts of the range that must
+		 * be COWed (shared extents, RO block groups, etc), so just bail
+		 * out.
+		 */
+		if (nocow_bytes < count) {
 			inode_unlock(inode);
 			return -EAGAIN;
 		}
-- 
2.25.1

[PATCH stable-5.4 6/6] btrfs: allow btrfs_truncate_block() to fallback to nocow for data space reservation

[Anand Jain]

From: Qu Wenruo <wqu@suse.com>

commit 6d4572a9d71d5fc2affee0258d8582d39859188c upstream.

[BUG]
When the data space is exhausted, even if the inode has NOCOW attribute,
we will still refuse to truncate unaligned range due to ENOSPC.

The following script can reproduce it pretty easily:
  #!/bin/bash

  dev=/dev/test/test
  mnt=/mnt/btrfs

  umount $dev &> /dev/null
  umount $mnt &> /dev/null

  mkfs.btrfs -f $dev -b 1G
  mount -o nospace_cache $dev $mnt
  touch $mnt/foobar
  chattr +C $mnt/foobar

  xfs_io -f -c "pwrite -b 4k 0 4k" $mnt/foobar > /dev/null
  xfs_io -f -c "pwrite -b 4k 0 1G" $mnt/padding &> /dev/null
  sync

  xfs_io -c "fpunch 0 2k" $mnt/foobar
  umount $mnt

Currently this will fail at the fpunch part.

[CAUSE]
Because btrfs_truncate_block() always reserves space without checking
the NOCOW attribute.

Since the writeback path follows NOCOW bit, we only need to bother the
space reservation code in btrfs_truncate_block().

[FIX]
Make btrfs_truncate_block() follow btrfs_buffered_write() to try to
reserve data space first, and fall back to NOCOW check only when we
don't have enough space.

Such always-try-reserve is an optimization introduced in
btrfs_buffered_write(), to avoid expensive btrfs_check_can_nocow() call.

This patch will export check_can_nocow() as btrfs_check_can_nocow(), and
use it in btrfs_truncate_block() to fix the problem.

Reported-by: Martin Doucha <martin.doucha@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
 Conflicts:
	fs/btrfs/ctree.h
	fs/btrfs/file.c
	fs/btrfs/inode.c
---
 fs/btrfs/ctree.h |  2 ++
 fs/btrfs/file.c  |  9 +++++----
 fs/btrfs/inode.c | 44 +++++++++++++++++++++++++++++++++++++-------
 3 files changed, 44 insertions(+), 11 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 9a690c10afaa..23b4f38e2392 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2956,6 +2956,8 @@ int btrfs_fdatawrite_range(struct inode *inode, loff_t start, loff_t end);
 loff_t btrfs_remap_file_range(struct file *file_in, loff_t pos_in,
 			      struct file *file_out, loff_t pos_out,
 			      loff_t len, unsigned int remap_flags);
+int btrfs_check_can_nocow(struct btrfs_inode *inode, loff_t pos,
+			  size_t *write_bytes);
 
 /* tree-defrag.c */
 int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 4d0e1f9452a5..4126513e2429 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1546,8 +1546,8 @@ lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page **pages,
 	return ret;
 }
 
-static noinline int check_can_nocow(struct btrfs_inode *inode, loff_t pos,
-				    size_t *write_bytes)
+int btrfs_check_can_nocow(struct btrfs_inode *inode, loff_t pos,
+			  size_t *write_bytes)
 {
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	struct btrfs_root *root = inode->root;
@@ -1647,7 +1647,7 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb,
 		if (ret < 0) {
 			if ((BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW |
 						      BTRFS_INODE_PREALLOC)) &&
-			    check_can_nocow(BTRFS_I(inode), pos,
+			    btrfs_check_can_nocow(BTRFS_I(inode), pos,
 					&write_bytes) > 0) {
 				/*
 				 * For nodata cow case, no need to reserve
@@ -1927,7 +1927,8 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 		 */
 		if (!(BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW |
 					      BTRFS_INODE_PREALLOC)) ||
-		    check_can_nocow(BTRFS_I(inode), pos, &nocow_bytes) <= 0) {
+		    btrfs_check_can_nocow(BTRFS_I(inode), pos,
+					  &nocow_bytes) <= 0) {
 			inode_unlock(inode);
 			return -EAGAIN;
 		}
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 9ac40991a640..2356b28afebe 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5133,11 +5133,13 @@ int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len,
 	struct extent_state *cached_state = NULL;
 	struct extent_changeset *data_reserved = NULL;
 	char *kaddr;
+	bool only_release_metadata = false;
 	u32 blocksize = fs_info->sectorsize;
 	pgoff_t index = from >> PAGE_SHIFT;
 	unsigned offset = from & (blocksize - 1);
 	struct page *page;
 	gfp_t mask = btrfs_alloc_write_mask(mapping);
+	size_t write_bytes = blocksize;
 	int ret = 0;
 	u64 block_start;
 	u64 block_end;
@@ -5149,11 +5151,27 @@ int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len,
 	block_start = round_down(from, blocksize);
 	block_end = block_start + blocksize - 1;
 
-	ret = btrfs_delalloc_reserve_space(inode, &data_reserved,
-					   block_start, blocksize);
-	if (ret)
-		goto out;
 
+	ret = btrfs_check_data_free_space(inode, &data_reserved, block_start,
+					  blocksize);
+	if (ret < 0) {
+		if ((BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW |
+					      BTRFS_INODE_PREALLOC)) &&
+		    btrfs_check_can_nocow(BTRFS_I(inode), block_start,
+					  &write_bytes) > 0) {
+			/* For nocow case, no need to reserve data space */
+			only_release_metadata = true;
+		} else {
+			goto out;
+		}
+	}
+	ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode), blocksize);
+	if (ret < 0) {
+		if (!only_release_metadata)
+			btrfs_free_reserved_data_space(inode, data_reserved,
+					block_start, blocksize);
+		goto out;
+	}
 again:
 	page = find_or_create_page(mapping, index, mask);
 	if (!page) {
@@ -5222,14 +5240,26 @@ int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len,
 	set_page_dirty(page);
 	unlock_extent_cached(io_tree, block_start, block_end, &cached_state);
 
+	if (only_release_metadata)
+		set_extent_bit(&BTRFS_I(inode)->io_tree, block_start,
+				block_end, EXTENT_NORESERVE, NULL, NULL,
+				GFP_NOFS);
+
 out_unlock:
-	if (ret)
-		btrfs_delalloc_release_space(inode, data_reserved, block_start,
-					     blocksize, true);
+	if (ret) {
+		if (only_release_metadata)
+			btrfs_delalloc_release_metadata(BTRFS_I(inode),
+					blocksize, true);
+		else
+			btrfs_delalloc_release_space(inode, data_reserved,
+					block_start, blocksize, true);
+	}
 	btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize);
 	unlock_page(page);
 	put_page(page);
 out:
+	if (only_release_metadata)
+		btrfs_end_write_no_snapshotting(BTRFS_I(inode)->root);
 	extent_changeset_free(data_reserved);
 	return ret;
 }
-- 
2.25.1

Re: [PATCH stable-5.4 6/6] btrfs: allow btrfs_truncate_block() to fallback to nocow for data space reservation

[Greg KH]

On Thu, Oct 08, 2020 at 06:59:54PM +0800, Anand Jain wrote:
> From: Qu Wenruo <wqu@suse.com>
> 
> commit 6d4572a9d71d5fc2affee0258d8582d39859188c upstream.
> 
> [BUG]
> When the data space is exhausted, even if the inode has NOCOW attribute,
> we will still refuse to truncate unaligned range due to ENOSPC.
> 
> The following script can reproduce it pretty easily:
>   #!/bin/bash
> 
>   dev=/dev/test/test
>   mnt=/mnt/btrfs
> 
>   umount $dev &> /dev/null
>   umount $mnt &> /dev/null
> 
>   mkfs.btrfs -f $dev -b 1G
>   mount -o nospace_cache $dev $mnt
>   touch $mnt/foobar
>   chattr +C $mnt/foobar
> 
>   xfs_io -f -c "pwrite -b 4k 0 4k" $mnt/foobar > /dev/null
>   xfs_io -f -c "pwrite -b 4k 0 1G" $mnt/padding &> /dev/null
>   sync
> 
>   xfs_io -c "fpunch 0 2k" $mnt/foobar
>   umount $mnt
> 
> Currently this will fail at the fpunch part.
> 
> [CAUSE]
> Because btrfs_truncate_block() always reserves space without checking
> the NOCOW attribute.
> 
> Since the writeback path follows NOCOW bit, we only need to bother the
> space reservation code in btrfs_truncate_block().
> 
> [FIX]
> Make btrfs_truncate_block() follow btrfs_buffered_write() to try to
> reserve data space first, and fall back to NOCOW check only when we
> don't have enough space.
> 
> Such always-try-reserve is an optimization introduced in
> btrfs_buffered_write(), to avoid expensive btrfs_check_can_nocow() call.
> 
> This patch will export check_can_nocow() as btrfs_check_can_nocow(), and
> use it in btrfs_truncate_block() to fix the problem.
> 
> Reported-by: Martin Doucha <martin.doucha@suse.com>
> Reviewed-by: Filipe Manana <fdmanana@suse.com>
> Reviewed-by: Anand Jain <anand.jain@oracle.com>
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> Reviewed-by: David Sterba <dsterba@suse.com>
> Signed-off-by: David Sterba <dsterba@suse.com>
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>  Conflicts:
> 	fs/btrfs/ctree.h
> 	fs/btrfs/file.c
> 	fs/btrfs/inode.c

Why are these Conflicts: lines here?

Anyway, fixed up, and all queued up now, thansk!

greg k-h