xfs: drop the scrub file's iolock when transaction allocation fails

If the transaction allocation in the !orphanage_available case of
xrep_nlinks_repair_inode fails, we need to drop the IOLOCK of the file
being scrubbed before exiting.

Found by fuzzing u3.sfdir3.list[1].name = zeroes in xfs/1546.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/scrub/nlinks_repair.c

@@ -138,8 +138,10 @@ xrep_nlinks_repair_inode(
 
 		error = xfs_trans_alloc(mp, &M_RES(mp)->tr_link, 0, 0, 0,
 				&sc->tp);
-		if (error)
+		if (error) {
+			xchk_iunlock(sc, XFS_IOLOCK_EXCL);
 			return error;
+		}
 
 		xchk_ilock(sc, XFS_ILOCK_EXCL);
 		xfs_trans_ijoin(sc->tp, ip, 0);