From: "Robert P. J. Day" <rpjday@crashcourse.ca>

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/block/rd.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff -puN drivers/block/rd.c~rd-use-is_power_of_2-in-drivers-block-rdc drivers/block/rd.c
--- a/drivers/block/rd.c~rd-use-is_power_of_2-in-drivers-block-rdc
+++ a/drivers/block/rd.c
@@ -56,6 +56,7 @@
 #include <linux/backing-dev.h>
 #include <linux/blkpg.h>
 #include <linux/writeback.h>
+#include <linux/log2.h>
 
 #include <asm/uaccess.h>
 
@@ -450,7 +451,7 @@ static int __init rd_init(void)
 	err = -ENOMEM;
 
 	if (rd_blocksize > PAGE_SIZE || rd_blocksize < 512 ||
-			(rd_blocksize & (rd_blocksize-1))) {
+			!is_power_of_2(rd_blocksize)) {
 		printk("RAMDISK: wrong blocksize %d, reverting to defaults\n",
 		       rd_blocksize);
 		rd_blocksize = BLOCK_SIZE;
_