rd: use is_power_of_2() in drivers/block/rd.c.

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

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;