btrfs: fix log tree replay failure due to file with 0 links and extents

commit 0a32e4f0025a74c70dcab4478e9b29c22f5ecf2f upstream.

If we log a new inode (not persisted in a past transaction) that has 0
links and extents, then log another inode with an higher inode number, we
end up with failing to replay the log tree with -EINVAL. The steps for
this are:

1) create new file A
2) write some data to file A
3) open an fd on file A
4) unlink file A
5) fsync file A using the previously open fd
6) create file B (has higher inode number than file A)
7) fsync file B
8) power fail before current transaction commits

Now when attempting to mount the fs, the log replay will fail with
-ENOENT at replay_one_extent() when attempting to replay the first
extent of file A. The failure comes when trying to open the inode for
file A in the subvolume tree, since it doesn't exist.

Before commit 5f61b961599a ("btrfs: fix inode lookup error handling
during log replay"), the returned error was -EIO instead of -ENOENT,
since we converted any errors when attempting to read an inode during
log replay to -EIO.

The reason for this is that the log replay procedure fails to ignore
the current inode when we are at the stage LOG_WALK_REPLAY_ALL, our
current inode has 0 links and last inode we processed in the previous
stage has a non 0 link count. In other words, the issue is that at
replay_one_extent() we only update wc->ignore_cur_inode if the current
replay stage is LOG_WALK_REPLAY_INODES.

Fix this by updating wc->ignore_cur_inode whenever we find an inode item
regardless of the current replay stage. This is a simple solution and easy
to backport, but later we can do other alternatives like avoid logging
extents or inode items other than the inode item for inodes with a link
count of 0.

The problem with the wc->ignore_cur_inode logic has been around since
commit f2d72f42 ("Btrfs: fix warning when replaying log after fsync
of a tmpfile") but it only became frequent to hit since the more recent
commit 5e85262e542d ("btrfs: fix fsync of files with no hard links not
persisting deletion"), because we stopped skipping inodes with a link
count of 0 when logging, while before the problem would only be triggered
if trying to replay a log tree created with an older kernel which has a
logged inode with 0 links.

A test case for fstests will be submitted soon.

Reported-by: Peter Jung <ptr1337@cachyos.org>
Link: https://lore.kernel.org/linux-btrfs/fce139db-4458-4788-bb97-c29acf6cb1df@cachyos.org/


Reported-by: burneddi <burneddi@protonmail.com>
Link: https://lore.kernel.org/linux-btrfs/lh4W-Lwc0Mbk-QvBhhQyZxf6VbM3E8VtIvU3fPIQgweP_Q1n7wtlUZQc33sYlCKYd-o6rryJQfhHaNAOWWRKxpAXhM8NZPojzsJPyHMf2qY=@protonmail.com/#t


Reported-by: Russell Haley <yumpusamongus@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/598ecc75-eb80-41b3-83c2-f2317fbb9864@gmail.com/


Fixes: f2d72f42 ("Btrfs: fix warning when replaying log after fsync of a tmpfile")
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>