[XFS] Fix a porting botch on the realtime subvol growfs code path.

SGI-PV: 955515
SGI-Modid: xfs-linux-melb:xfs-kern:26806a

Signed-off-by: Nathan Scott <nathans@sgi.com>
Signed-off-by: Tim Shimmin <tes@sgi.com>
diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index e050987..880c732 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -1948,7 +1948,7 @@
 	 */
 	nrextents = nrblocks;
 	do_div(nrextents, in->extsize);
-	nrbmblocks = roundup_64(nrextents, NBBY * sbp->sb_blocksize);
+	nrbmblocks = howmany_64(nrextents, NBBY * sbp->sb_blocksize);
 	nrextslog = xfs_highbit32(nrextents);
 	nrsumlevels = nrextslog + 1;
 	nrsumsize = (uint)sizeof(xfs_suminfo_t) * nrsumlevels * nrbmblocks;