linux-kernel - [RFC] fs: change lookup_bh

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Message-Id: <1443496574-12623-1-git-send-email-yalin.wang2010@gmail.com>
Date:	Tue, 29 Sep 2015 11:16:14 +0800
From:	yalin wang <yalin.wang2010@...il.com>
To:	viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	yalin wang <yalin.wang2010@...il.com>
Subject: [RFC] fs: change lookup_bh_lru() to use memmove()

This patch make a little change to lookup_bh_lru() function
to use memmove() to set new buffer_head,
better performance for some platforms.

Signed-off-by: yalin wang <yalin.wang2010@...il.com>
---
 fs/buffer.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index d6769f1..af14d69 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1331,11 +1331,9 @@ lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
 		if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
 		    bh->b_size == size) {
 			if (i) {
-				while (i) {
-					__this_cpu_write(bh_lrus.bhs[i],
-						__this_cpu_read(bh_lrus.bhs[i - 1]));
-					i--;
-				}
+				memmove(&this_cpu_ptr(&bh_lrus)->bhs[1],
+					&this_cpu_ptr(&bh_lrus)->bhs[0],
+					sizeof(bh)*i);
 				__this_cpu_write(bh_lrus.bhs[0], bh);
 			}
 			get_bh(bh);
-- 
1.9.1

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