From: Mikulas Patocka <mpatocka@redhat.com>
Date: Mon, 22 Mar 2021 14:05:05 +0000 (-0400)
Subject: buffer: a small optimization in grow_buffers
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=90432e600619cbd3f38ec817374a5db0caf1d600;p=linux.git

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 0cb7ffd4977c9..c2e052c0fc5d6 100644
--- 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;
 
 	/*