linux-kernel - [PATCH] fs/buffer.c: Add checking buffer head stat before clear

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Date:   Wed, 3 Feb 2021 14:14:50 +0800
From:   Shaokun Zhang <zhangshaokun@...ilicon.com>
To:     <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     Yang Guo <guoyang2@...wei.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nick Piggin <npiggin@...e.de>,
        Shaokun Zhang <zhangshaokun@...ilicon.com>
Subject: [PATCH] fs/buffer.c: Add checking buffer head stat before clear

From: Yang Guo <guoyang2@...wei.com>

clear_buffer_new() is used to clear buffer new stat. When PAGE_SIZE
is 64K, most buffer heads in the list are not needed to clear.
clear_buffer_new() has an enpensive atomic modification operation,
Let's add checking buffer head before clear it as __block_write_begin_int
does which is good for performance.

Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Nick Piggin <npiggin@...e.de>
Signed-off-by: Yang Guo <guoyang2@...wei.com>
Signed-off-by: Shaokun Zhang <zhangshaokun@...ilicon.com>
---
 fs/buffer.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 32647d2011df..f1c3a5b27a90 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2083,7 +2083,8 @@ static int __block_commit_write(struct inode *inode, struct page *page,
 			set_buffer_uptodate(bh);
 			mark_buffer_dirty(bh);
 		}
-		clear_buffer_new(bh);
+		if (buffer_new(bh))
+			clear_buffer_new(bh);
 
 		block_start = block_end;
 		bh = bh->b_this_page;
-- 
2.7.4