diff --git a/fs/bio.c b/fs/bio.c
index 6e0b6f6..ab05e02 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -26,6 +26,7 @@
 #include <linux/mempool.h>
 #include <linux/workqueue.h>
 #include <linux/blktrace_api.h>
+#include <linux/log2.h>
 #include <scsi/sg.h>		/* for struct sg_iovec */
 
 #define BIO_POOL_SIZE 2
@@ -84,12 +85,9 @@ static inline struct bio_vec *bvec_alloc_bs(gfp_t gfp_mask, int nr, unsigned lon
 	 * see comment near bvec_array define!
 	 */
 	switch (nr) {
-		case   1        : *idx = 0; break;
-		case   2 ...   4: *idx = 1; break;
-		case   5 ...  16: *idx = 2; break;
-		case  17 ...  64: *idx = 3; break;
-		case  65 ... 128: *idx = 4; break;
-		case 129 ... BIO_MAX_PAGES: *idx = 5; break;
+		case 1 ... BIO_MAX_PAGES:
+			*idx = ilog2(nr);
+			break;
 		default:
 			return NULL;
 	}