[patch 048/173] fs/buffer.c: add checking buffer head stat before clear

From: Yang Guo <redacted>
Subject: fs/buffer.c: add checking buffer head stat before clear

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.

Link: https://lkml.kernel.org/r/1612332890-57918-1-git-send-email-zhangshaokun@hisilicon.com
Signed-off-by: Yang Guo <redacted>
Signed-off-by: Shaokun Zhang <redacted>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Nick Piggin <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/buffer.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/buffer.c~fs-bufferc-add-checking-buffer-head-stat-before-clear
+++ a/fs/buffer.c

@@ -2083,7 +2083,8 @@ static int __block_commit_write(struct i
 			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;

_