[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/linux-2.6/xfs_linux.h b/fs/xfs/linux-2.6/xfs_linux.h
index 14d8402..2b0e001 100644
--- a/fs/xfs/linux-2.6/xfs_linux.h
+++ b/fs/xfs/linux-2.6/xfs_linux.h
@@ -332,4 +332,11 @@
 	return(x * y);
 }
 
+static inline __uint64_t howmany_64(__uint64_t x, __uint32_t y)
+{
+	x += y - 1;
+	do_div(x, y);
+	return x;
+}
+
 #endif /* __XFS_LINUX__ */