diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index c2e13db145631858f4f0efce91d7e5134037eaa5..164790c1b41984cc1003cfca18bad5e8e2633502 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -49,6 +49,7 @@
 #include "xfs_rmap.h"
 #include "xfs_ag_resv.h"
 #include "xfs_refcount.h"
+#include "xfs_rmap_btree.h"
 
 
 kmem_zone_t		*xfs_bmap_free_item_zone;
@@ -190,8 +191,12 @@ xfs_bmap_worst_indlen(
 	int		maxrecs;	/* maximum record count at this level */
 	xfs_mount_t	*mp;		/* mount structure */
 	xfs_filblks_t	rval;		/* return value */
+	xfs_filblks_t   orig_len;
 
 	mp = ip->i_mount;
+
+	/* Calculate the worst-case size of the bmbt. */
+	orig_len = len;
 	maxrecs = mp->m_bmap_dmxr[0];
 	for (level = 0, rval = 0;
 	     level < XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK);
@@ -199,12 +204,20 @@ xfs_bmap_worst_indlen(
 		len += maxrecs - 1;
 		do_div(len, maxrecs);
 		rval += len;
-		if (len == 1)
-			return rval + XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) -
+		if (len == 1) {
+			rval += XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) -
 				level - 1;
+			break;
+		}
 		if (level == 0)
 			maxrecs = mp->m_bmap_dmxr[1];
 	}
+
+	/* Calculate the worst-case size of the rmapbt. */
+	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
+		rval += 1 + xfs_rmapbt_calc_size(mp, orig_len) +
+				mp->m_rmap_maxlevels;
+
 	return rval;
 }