btrfs: test log replay after directory fsync and moving a child directory

btrfs: test log replay after directory fsync and moving a child directory

Test a particular scenario where we fsync a directory, then move one of
its children directories into another directory and then finally sync the
log trees by fsyncing any other inode. We want to check that after a power
failure we are able to mount the filesystem and that the moved directory
exists only as a child of the directory we moved it into.

This currently fails on a 5.12 kernel (and 5.13-rc1) but is fixed by a
patch with the following subject:

  "btrfs: fix removed dentries still existing after log is synced"

The failure is due to ending up with a directory that has 2 hard links
(two parent directories) as soon as the log replay procedure finishes,
which causes the tree checker to detect the issue and cause the mount
operation to fail with -EIO.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>