If we a find that an extent is shared but its end offset is not sector
size aligned, then we don't clone it and issue write operations instead.
This is because the reflink (remap_file_range) operation does not allow
to clone unaligned ranges, except if the end offset of the range matches
the i_size of the source and destination files (and the start offset is
sector size aligned).
While this is not incorrect because send can only guarantee that a file
has the same data in the source and destination snapshots, it's not
optimal and generates confusion and surprising behaviour for users.
For example, running this test:
$ cat test.sh
#!/bin/bash
DEV=/dev/sdi
MNT=/mnt/sdi
mkfs.btrfs -f $DEV
mount $DEV $MNT
# Use a file size not aligned to any possible sector size.
file_size=$((1 * 1024 * 1024 + 5)) # 1MB + 5 bytes
dd if=/dev/random of=$MNT/foo bs=$file_size count=1
cp --reflink=always $MNT/foo $MNT/bar
btrfs subvolume snapshot -r $MNT/ $MNT/snap
rm -f /tmp/send-test
btrfs send -f /tmp/send-test $MNT/snap
umount $MNT
mkfs.btrfs -f $DEV
mount $DEV $MNT
btrfs receive -vv -f /tmp/send-test $MNT
xfs_io -r -c "fiemap -v" $MNT/snap/bar
umount $MNT
Gives the following result:
(...)
mkfile o258-7-0
rename o258-7-0 -> bar
write bar - offset=0 length=49152
write bar - offset=49152 length=49152
write bar - offset=98304 length=49152
write bar - offset=147456 length=49152
write bar - offset=196608 length=49152
write bar - offset=245760 length=49152
write bar - offset=294912 length=49152
write bar - offset=344064 length=49152
write bar - offset=393216 length=49152
write bar - offset=442368 length=49152
write bar - offset=491520 length=49152
write bar - offset=540672 length=49152
write bar - offset=589824 length=49152
write bar - offset=638976 length=49152
write bar - offset=688128 length=49152
write bar - offset=737280 length=49152
write bar - offset=786432 length=49152
write bar - offset=835584 length=49152
write bar - offset=884736 length=49152
write bar - offset=933888 length=49152
write bar - offset=983040 length=49152
write bar - offset=1032192 length=16389
chown bar - uid=0, gid=0
chmod bar - mode=0644
utimes bar
utimes
BTRFS_IOC_SET_RECEIVED_SUBVOL uuid=06d640da-9ca1-604c-b87c-3375175a8eb3, stransid=7
/mnt/sdi/snap/bar:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..2055]: 26624..28679 2056 0x1
There's no clone operation to clone extents from the file foo into file
bar and fiemap confirms there's no shared flag (0x2000).
So update send_write_or_clone() so that it proceeds with cloning if the
source and destination ranges end at the i_size of the respective files.
After this changes the result of the test is:
(...)
mkfile o258-7-0
rename o258-7-0 -> bar
clone bar - source=foo source offset=0 offset=0 length=1048581
chown bar - uid=0, gid=0
chmod bar - mode=0644
utimes bar
utimes
BTRFS_IOC_SET_RECEIVED_SUBVOL uuid=582420f3-ea7d-564e-bbe5-ce440d622190, stransid=7
/mnt/sdi/snap/bar:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..2055]: 26624..28679 2056 0x2001
A test case for fstests will also follow up soon.
Link: https://github.com/kdave/btrfs-progs/issues/572#issuecomment-2282841416
CC: stable@xxxxxxxxxxxxxxx # 5.10+
Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>
Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 4ca711a773ef..7fc692fc76e1 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -6157,25 +6157,51 @@ static int send_write_or_clone(struct send_ctx *sctx,
u64 offset = key->offset;
u64 end;
u64 bs = sctx->send_root->fs_info->sectorsize;
+ struct btrfs_file_extent_item *ei;
+ u64 disk_byte;
+ u64 data_offset;
+ u64 num_bytes;
+ struct btrfs_inode_info info = { 0 };
end = min_t(u64, btrfs_file_extent_end(path), sctx->cur_inode_size);
if (offset >= end)
return 0;
- if (clone_root && IS_ALIGNED(end, bs)) {
- struct btrfs_file_extent_item *ei;
- u64 disk_byte;
- u64 data_offset;
+ num_bytes = end - offset;
- ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
- struct btrfs_file_extent_item);
- disk_byte = btrfs_file_extent_disk_bytenr(path->nodes[0], ei);
- data_offset = btrfs_file_extent_offset(path->nodes[0], ei);
- ret = clone_range(sctx, path, clone_root, disk_byte,
- data_offset, offset, end - offset);
- } else {
- ret = send_extent_data(sctx, path, offset, end - offset);
- }
+ if (!clone_root)
+ goto write_data;
+
+ if (IS_ALIGNED(end, bs))
+ goto clone_data;
+
+ /*
+ * If the extent end is not aligned, we can clone if the extent ends at
+ * the i_size of the inode and the clone range ends at the i_size of the
+ * source inode, otherwise the clone operation fails with -EINVAL.
+ */
+ if (end != sctx->cur_inode_size)
+ goto write_data;
+
+ ret = get_inode_info(clone_root->root, clone_root->ino, &info);
+ if (ret < 0)
+ return ret;
+
+ if (clone_root->offset + num_bytes == info.size)
+ goto clone_data;
+
+write_data:
+ ret = send_extent_data(sctx, path, offset, num_bytes);
+ sctx->cur_inode_next_write_offset = end;
+ return ret;
+
+clone_data:
+ ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
+ struct btrfs_file_extent_item);
+ disk_byte = btrfs_file_extent_disk_bytenr(path->nodes[0], ei);
+ data_offset = btrfs_file_extent_offset(path->nodes[0], ei);
+ ret = clone_range(sctx, path, clone_root, disk_byte, data_offset, offset,
+ num_bytes);
sctx->cur_inode_next_write_offset = end;
return ret;
}
