xfs: use xfs_ilock_data_map_shared in xfs_qm_dqiterate

We might not have read in the extent list at this point, so make sure we
take the ilock exclusively if we have to do so.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

fs/xfs/xfs_qm.c

@@ -1222,16 +1222,18 @@ xfs_qm_dqiterate(
 	lblkno = 0;
 	maxlblkcnt = XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);
 	do {
+		uint		lock_mode;
+
 		nmaps = XFS_DQITER_MAP_SIZE;
 		/*
 		 * We aren't changing the inode itself. Just changing
 		 * some of its data. No new blocks are added here, and
 		 * the inode is never added to the transaction.
 		 */
-		xfs_ilock(qip, XFS_ILOCK_SHARED);
+		lock_mode = xfs_ilock_data_map_shared(qip);
 		error = xfs_bmapi_read(qip, lblkno, maxlblkcnt - lblkno,
 				       map, &nmaps, 0);
-		xfs_iunlock(qip, XFS_ILOCK_SHARED);
+		xfs_iunlock(qip, lock_mode);
 		if (error)
 			break;