xfs: use xfs_ilock_attr_map_shared in xfs_attr_get

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_attr.c

@@ -164,6 +164,7 @@ xfs_attr_get(
 {
 	int		error;
 	struct xfs_name	xname;
+	uint		lock_mode;
 
 	XFS_STATS_INC(xs_attr_get);
 
@@ -174,9 +175,9 @@ xfs_attr_get(
 	if (error)
 		return error;
 
-	xfs_ilock(ip, XFS_ILOCK_SHARED);
+	lock_mode = xfs_ilock_attr_map_shared(ip);
 	error = xfs_attr_get_int(ip, &xname, value, valuelenp, flags);
-	xfs_iunlock(ip, XFS_ILOCK_SHARED);
+	xfs_iunlock(ip, lock_mode);
 	return(error);
 }