buffer: a small optimization in grow_buffers

This patch replaces a loop with a "tzcnt" instruction.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/buffer.c b/fs/buffer.c
index 0cb7ffd4977c9283aba3794f4da84ecb1758ec47..c2e052c0fc5d6a3190443049192ce5941ff6ff14 100644 (file)
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1020,11 +1020,7 @@ grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
        pgoff_t index;
        int sizebits;
 
-       sizebits = -1;
-       do {
-               sizebits++;
-       } while ((size << sizebits) < PAGE_SIZE);
-
+       sizebits = PAGE_SHIFT - __ffs(size);
        index = block >> sizebits;
 
        /*