Under some cases the filesystem checker reports an error when it finds
checksum items for an extent that is referenced by an inode as a prealloc
extent. Such cases are not an error when the extent is actually shared
(was cloned/reflinked) with other inodes and was written through one of
those other inodes.
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
$ btrfs check /dev/sdc
Checking filesystem on /dev/sdb
UUID: 52d3006e-ee3b-40eb-aa21-e56253a03d39
checking extents
checking free space cache
checking fs roots
root 5 inode 257 errors 800, odd csum item
ERROR: errors found in fs roots
found 688128 bytes used, error(s) found
total csum bytes: 256
total tree bytes: 163840
total fs tree bytes: 65536
total extent tree bytes: 16384
btree space waste bytes: 138819
file data blocks allocated: 10747904
referenced 10747904
$ echo $?
1
So teach check to not report such cases as errors by checking if the
extent is shared with other inodes and if so, consider it an error the
existence of checksum items only if all those other inodes are referencing
the extent as a prealloc extent.
This case can be hit often when running the generic/475 testcase from
fstests.
A test case will follow in a separate patch.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Btrfs can delay inode deletion and in that case btrfs will unlink the
victim inode from its parent dir, and insert a marker to info btrfs to
delete it later.
In that case, such victim inode will have nlinks == 0, but is still
completely valid.
Original mode won't report such problem, but lowmem mode doesn't check
the ORPHAN_ITEM key for such inode, and can report false alert like:
------
ERROR: root 257 INODE[28891726] is orphan item
------
Fix such false alert by checking orphan item for inode whose nlink is 0.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Su Yue <suy.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Btrfs lowmem check reports the following false alert:
------
ERROR: file extent[267 2162688] root 256 owner 5 backref lost
------
The file extent is in the leaf which is shared by file tree 256 and fs
tree.
------
leaf 30605312 items 46 free space 4353 generation 7 owner 5
......
item 45 key (267 EXTENT_DATA 2162688) itemoff 5503 itemsize 53
generation 7 type 2 (prealloc)
prealloc data disk byte 13631488 nr 65536
prealloc data offset 32768 nr 32768
------
And there is the corresponding extent_data_ref item in the extent tree.
------
item 1 key (13631488 EXTENT_DATA_REF 1007496934287921081) itemoff 15274 itemsize 28
extent data backref root 5 objectid 267 offset 2129920 count 1
------
The offset of EXTENT_DATA_REF which is the hash of the owner root objectid,
the inode number and the calculated offset (file offset - extent offset).
What caused the false alert is the code mix up the owner root objectid and
the file tree objectid.
Fixes: b0d360b541 ("btrfs-progs: check: introduce function to check data backref in extent tree")
Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Instead of the disk_bytenr and disk_num_bytes of the extent_item which the
file extent references, we should output the objectid and offset of the
file extent. And the leaf may be shared by the file trees, we should print
the objectid of the root and the owner of the leaf.
Fixes: b0d360b541 ("btrfs-progs: check: introduce function to check data backref in extent tree")
Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Qu Wenruo