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 <guoyang2@huawei.com>
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/buffer.c b/fs/buffer.c
index 32647d2..f1c3a5b 100644 (file)
--- 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;