Remove redundant if judgment overhead.

Signed-off-by: Zhiguo Jiang <justinjiang@vivo.com>
---
 mm/page-writeback.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index fcd4c1439cb9..2d2c3f4e640d
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2715,9 +2715,7 @@ int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
  */
 bool noop_dirty_folio(struct address_space *mapping, struct folio *folio)
 {
-	if (!folio_test_dirty(folio))
-		return !folio_test_set_dirty(folio);
-	return false;
+	return !folio_test_set_dirty(folio);
 }
 EXPORT_SYMBOL(noop_dirty_folio);
 
-- 
2.39.0

On Tue, Sep 10, 2024 at 10:39:45PM +0800, Zhiguo Jiang wrote:
> Remove redundant if judgment overhead.

It's not redundant; it avoids dirtying the cacheline if the folio
is already marked as dirty.

>  bool noop_dirty_folio(struct address_space *mapping, struct folio *folio)
>  {
> -	if (!folio_test_dirty(folio))
> -		return !folio_test_set_dirty(folio);
> -	return false;
> +	return !folio_test_set_dirty(folio);
>  }

在 2024/9/11 0:03, Matthew Wilcox 写道:
> On Tue, Sep 10, 2024 at 10:39:45PM +0800, Zhiguo Jiang wrote:
>> Remove redundant if judgment overhead.
> It's not redundant; it avoids dirtying the cacheline if the folio
> is already marked as dirty.
Ok, Is it necessary to add comments here to explain and avoid readers'
misunderstandings? E.g. 'Avoid dirtying the cacheline if the folio is
already marked as dirty.'
>>   bool noop_dirty_folio(struct address_space *mapping, struct folio *folio)
>>   {
>> -	if (!folio_test_dirty(folio))
>> -		return !folio_test_set_dirty(folio);
>> -	return false;
>> +	return !folio_test_set_dirty(folio);
>>   }
Thanks
Zhiguo

On Wed, Sep 11, 2024 at 09:14:10AM +0800, zhiguojiang wrote:
> 在 2024/9/11 0:03, Matthew Wilcox 写道:
> > On Tue, Sep 10, 2024 at 10:39:45PM +0800, Zhiguo Jiang wrote:
> > > Remove redundant if judgment overhead.
> > It's not redundant; it avoids dirtying the cacheline if the folio
> > is already marked as dirty.

> Ok, Is it necessary to add comments here to explain and avoid readers'
> misunderstandings? E.g. 'Avoid dirtying the cacheline if the folio is
> already marked as dirty.'

No, it's a fairly common pattern to test-and-test-and-set(or clear)