[PATCH v3] fix __set_page_dirty_no_writeback() return value

[PATCH v3] fix __set_page_dirty_no_writeback() return value

[Bob Liu]

__set_page_dirty_no_writeback() should return true if it actually transitioned
the page from a clean to dirty state although it seems nobody used its return
value now.

Change from v2:
	* use TestSet to avoid racing

Change from v1:
	* preserving cacheline optimisation as Andrew pointed out

Signed-off-by: Bob Liu <lliubbo@gmail.com>
---
 mm/page-writeback.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index bf85062..1ebfb86 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1158,7 +1158,7 @@ EXPORT_SYMBOL(write_one_page);
 int __set_page_dirty_no_writeback(struct page *page)
 {
 	if (!PageDirty(page))
-		SetPageDirty(page);
+		return !TestSetPageDirty(page);
 	return 0;
 }
 
-- 
1.6.3.3

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Re: [PATCH v3] fix __set_page_dirty_no_writeback() return value

[David Rientjes]

On Thu, 11 Nov 2010, Bob Liu wrote:

> __set_page_dirty_no_writeback() should return true if it actually transitioned
> the page from a clean to dirty state although it seems nobody used its return
> value now.
> 
> Change from v2:
> 	* use TestSet to avoid racing
> 
> Change from v1:
> 	* preserving cacheline optimisation as Andrew pointed out
> 
> Signed-off-by: Bob Liu <lliubbo@gmail.com>
> ---
>  mm/page-writeback.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index bf85062..1ebfb86 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1158,7 +1158,7 @@ EXPORT_SYMBOL(write_one_page);
>  int __set_page_dirty_no_writeback(struct page *page)
>  {
>  	if (!PageDirty(page))
> -		SetPageDirty(page);
> +		return !TestSetPageDirty(page);
>  	return 0;
>  }

No need for a conditional, just return !TestSetPageDirty(page).

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Re: [PATCH v3] fix __set_page_dirty_no_writeback() return value

[David Rientjes]

On Wed, 10 Nov 2010, David Rientjes wrote:

> > diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> > index bf85062..1ebfb86 100644
> > --- a/mm/page-writeback.c
> > +++ b/mm/page-writeback.c
> > @@ -1158,7 +1158,7 @@ EXPORT_SYMBOL(write_one_page);
> >  int __set_page_dirty_no_writeback(struct page *page)
> >  {
> >  	if (!PageDirty(page))
> > -		SetPageDirty(page);
> > +		return !TestSetPageDirty(page);
> >  	return 0;
> >  }
> 
> No need for a conditional, just return !TestSetPageDirty(page).
> 

Oops, just read Andrew's reply to v1 of the patch about the cacheline 
invalidation of bts, sorry for the noise.

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