xfs: use xfs_ilock_data_map_shared in xfs_qm_dqtobp

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: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_dquot.c

@@ -469,16 +469,17 @@ xfs_qm_dqtobp(
 	struct xfs_mount	*mp = dqp->q_mount;
 	xfs_dqid_t		id = be32_to_cpu(dqp->q_core.d_id);
 	struct xfs_trans	*tp = (tpp ? *tpp : NULL);
+	uint			lock_mode;
 
 	dqp->q_fileoffset = (xfs_fileoff_t)id / mp->m_quotainfo->qi_dqperchunk;
 
-	xfs_ilock(quotip, XFS_ILOCK_SHARED);
+	lock_mode = xfs_ilock_data_map_shared(quotip);
 	if (!xfs_this_quota_on(dqp->q_mount, dqp->dq_flags)) {
 		/*
 		 * Return if this type of quotas is turned off while we
 		 * didn't have the quota inode lock.
 		 */
-		xfs_iunlock(quotip, XFS_ILOCK_SHARED);
+		xfs_iunlock(quotip, lock_mode);
 		return ESRCH;
 	}
 
@@ -488,7 +489,7 @@ xfs_qm_dqtobp(
 	error = xfs_bmapi_read(quotip, dqp->q_fileoffset,
 			       XFS_DQUOT_CLUSTER_SIZE_FSB, &map, &nmaps, 0);
 
-	xfs_iunlock(quotip, XFS_ILOCK_SHARED);
+	xfs_iunlock(quotip, lock_mode);
 	if (error)
 		return error;