[BUG]
When running mkfs tests on a newly rebooted minimal system, it can cause
mkfs/009 to fail.
The reproduce steps requires /tmp to has minimal files in the first
place.
# mkdir /tmp/rootdir
# xfs_io -f -c "pwrite 0 16k" /tmp/rootdir
# mkfs.btrfs --rootdir /tmp/rootdir -f $dev
# btrfs check $dev
Opening filesystem to check...
Checking filesystem on /dev/test/scratch1
UUID: 6821b3db-f056-4c18-b797-32679dcd4272
[1/7] checking root items
[2/7] checking extents
data backref 13631488 root 5 owner 170 offset 0 num_refs 0 not found in extent tree
incorrect local backref count on 13631488 root 5 owner 170 offset 0 found 1 wanted 0 back 0x55ff6cd72260
backref 13631488 root 5 not referenced back 0x55ff6cd4c1f0
incorrect global backref count on 13631488 found 2 wanted 1
backpointer mismatch on [13631488 16384]
ERROR: errors found in extent allocation tree or chunk allocation
[CAUSE]
The extent tree has the following weird item:
item 0 key (13631488 EXTENT_ITEM 16384) itemoff 16250 itemsize 33
refs 1 gen 0 flags DATA
tree block backref root FS_TREE
This is an extent item for data, thus it should not have an inline tree
backref.
Then checking the fs tree:
item 0 key (170 INODE_ITEM 0) itemoff 16123 itemsize 160
generation 7 transid 0 size 16384 nbytes 16384
block group 0 mode 100600 links 1 uid 1000 gid 1000 rdev 0
sequence 0 flags 0x0(none)
atime 1664866393.0 (2022-10-04 14:53:13)
ctime 1664863510.0 (2022-10-04 14:05:10)
mtime 1664863455.0 (2022-10-04 14:04:15)
otime 0.0 (1970-01-01 08:00:00)
There is an inode item before the root dir inode.
And that inode number 170 is causing the problem.
In traverse_directory(), we use the inode number reported from stat()
directly as btrfs inode number, and pass it to
btrfs_record_file_extent(), which finally calls btrfs_inc_extent_ref(),
with above 170 passed as @owner parameter.
But inside btrfs_inc_extent_ref() we use that @owner value to determine
if it's a data backref.
Since we got a smaller than BTRFS_FIRST_FREE_OBJECTID, btrfs treats it
as tree block, and cause the above problem.
[FIX]
As a quick fix, always add BTRFS_FIRST_FREE_OBJECTID to all inode number
directly grabbed from stat().
And add an ASSERT() in __btrfs_record_file_extent() to catch unexpected
objectid.
This is not a perfect solution, as the resulted fs will has a huge gap
in its inodes:
item 0 key (256 INODE_ITEM 0) itemoff 16123 itemsize 160
item 4 key (426 INODE_ITEM 0) itemoff 15883 itemsize 160
For a proper fix, we should allocate new btrfs inode numbers in a
sequential order, but that would be another series of patches.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2cdc8dddbf