xfs: nlink scrub must take IOLOCK before determining ILOCK state

xfs: nlink scrub must take IOLOCK before determining ILOCK state

In xchk_nlinks_ilock_dir, take the IOLOCK before accessing internal
inode state to figure out if we need to take ILOCK shared or exclusive.
That way we can't race with directory updates.  LOLLM pointed out that
the code was initially correct w.r.t. the IOLOCK, but then I broke it.

Cc: stable@vger.kernel.org # v6.18
Fixes: f477af0cfa0487 ("xfs: fix locking in xchk_nlinks_collect_dir")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Assisted-by: LOLLM # finding obvious bugs
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>