diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 0a44298fb3535bc2b5f7efae268387c065c130d1..8e67634e79a0d1f16d033e9e7ecdf3bcdd416f56 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1444,8 +1444,7 @@ int bitmap_create(mddev_t *mddev)
 	if (err)
 		goto error;
 
-	bitmap->chunkshift = find_first_bit(&bitmap->chunksize,
-					sizeof(bitmap->chunksize));
+	bitmap->chunkshift = ffz(~bitmap->chunksize);
 
 	/* now that chunksize and chunkshift are set, we can use these macros */
  	chunks = (blocks + CHUNK_BLOCK_RATIO(bitmap) - 1) /