xfs: unlock inodes when erroring out of xfs_trans_alloc_dir

Debugging a filesystem patch with generic/475 caused the system to hang
after observing the following sequences in dmesg:

 XFS (dm-0): metadata I/O error in "xfs_imap_to_bp+0x61/0xe0 [xfs]" at daddr 0x491520 len 32 error 5
 XFS (dm-0): metadata I/O error in "xfs_btree_read_buf_block+0xba/0x160 [xfs]" at daddr 0x3445608 len 8 error 5
 XFS (dm-0): metadata I/O error in "xfs_imap_to_bp+0x61/0xe0 [xfs]" at daddr 0x138e1c0 len 32 error 5
 XFS (dm-0): log I/O error -5
 XFS (dm-0): Metadata I/O Error (0x1) detected at xfs_trans_read_buf_map+0x1ea/0x4b0 [xfs] (fs/xfs/xfs_trans_buf.c:311).  Shutting down filesystem.
 XFS (dm-0): Please unmount the filesystem and rectify the problem(s)
 XFS (dm-0): Internal error dqp->q_ino.reserved < dqp->q_ino.count at line 869 of file fs/xfs/xfs_trans_dquot.c.  Caller xfs_trans_dqresv+0x236/0x440 [xfs]
 XFS (dm-0): Corruption detected. Unmount and run xfs_repair
 XFS (dm-0): Unmounting Filesystem be6bcbcc-9921-4deb-8d16-7cc94e335fa7

The system is stuck in unmount trying to lock a couple of inodes so that
they can be purged.  The dquot corruption notice above is a clue to what
happened -- a link() call tried to set up a transaction to link a child
into a directory.  Quota reservation for the transaction failed after IO
errors shut down the filesystem, but then we forgot to unlock the inodes
on our way out.  Fix that.

Cc: <stable@vger.kernel.org> # v6.10
Fixes: bd55621 ("xfs: Hold inode locks in xfs_trans_alloc_dir")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

Author: Darrick J. Wong

fs/xfs/xfs_trans.c

@@ -1435,5 +1435,8 @@ xfs_trans_alloc_dir(
 
 out_cancel:
 	xfs_trans_cancel(tp);
+	xfs_iunlock(dp, XFS_ILOCK_EXCL);
+	if (dp != ip)
+		xfs_iunlock(ip, XFS_ILOCK_EXCL);
 	return error;
 }