Verify that a filesystem check operation (fsck) does not report the
following scenario as an error:
An extent is shared between two inodes, as a result of clone/reflink
operation, and for one of the inodes, lets call it inode A, the extent is
referenced through a file extent item as a prealloc extent, while for the
other inode, call it inode B, the extent is referenced through a regular
file extent item, that is, it was written to. The goal of this test is to
make sure a filesystem check operation will not report "odd csum items"
errors for the prealloc extent at inode A, because this scenario is valid
since the extent was written through inode B and therefore it is expected
to have checksum items in the filesystem's checksum btree for that shared
extent.
Such scenario can be created with the following steps for example:
mkfs.btrfs -f /dev/sdb
mount /dev/sdb /mnt
touch /mnt/foo
xfs_io -c "falloc 0 256K" /mnt/foo
sync
xfs_io -c "pwrite -S 0xab 0 256K" /mnt/foo
touch /mnt/bar
xfs_io -c "reflink /mnt/foo 0 0 256K" /mnt/bar
xfs_io -c "fsync" /mnt/bar
<power fail>
mount /dev/sdb /mnt
umount /mnt
This scenario is fixed by the following patch for the filesystem checker:
"Btrfs-progs: check, fix false error reports for shared prealloc extents"
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Filipe Manana