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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/btrfs/send.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/fs/btrfs/send.c +++ b/fs/btrfs/send.c @@ -1270,7 +1270,8 @@ static int __iterate_backrefs(u64 ino, u * 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; }