On Thu, Nov 11, 2010 at 11:36:48AM +0800, Bob Liu wrote:
> On Thu, Nov 11, 2010 at 11:26 AM, Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:
> > On Thu, Nov 11, 2010 at 11:05:54AM +0800, 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 v1:
> >> Â Â Â * preserving cacheline optimisation as Andrew pointed out
> >>
> >> Signed-off-by: Bob Liu <lliubbo@xxxxxxxxx>
> >> ---
> >> Âmm/page-writeback.c | Â Â4 +++-
> >> Â1 files changed, 3 insertions(+), 1 deletions(-)
> >>
> >> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> >> index bf85062..ac7018a 100644
> >> --- a/mm/page-writeback.c
> >> +++ b/mm/page-writeback.c
> >> @@ -1157,8 +1157,10 @@ EXPORT_SYMBOL(write_one_page);
> >> Â */
> >> Âint __set_page_dirty_no_writeback(struct page *page)
> >> Â{
> >> - Â Â if (!PageDirty(page))
> >> + Â Â if (!PageDirty(page)) {
> >> Â Â Â Â Â Â Â SetPageDirty(page);
> >> + Â Â Â Â Â Â return 1;
> >> + Â Â }
> >> Â Â Â return 0;
> >> Â}
> >
> > It's still racy if not using TestSetPageDirty(). In fact
> > set_page_dirty() has a default reference implementation:
>
> Yes, Andrew had also pointed out that. And I have send v3 fix this.
> Could you ack it?
Acked-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Thanks!
> >
> > Â Â Â Âif (!PageDirty(page)) {
> > Â Â Â Â Â Â Â Âif (!TestSetPageDirty(page))
> > Â Â Â Â Â Â Â Â Â Â Â Âreturn 1;
>
> return !TestSetPageDirty(page) is more simply?
Yeah that's fine.
> > Â Â Â Â}
> > Â Â Â Âreturn 0;
> >
> > It seems the return value currently is only tested for doing
> > balance_dirty_pages_ratelimited(). So not a big problem.
> >
>
> yeah, all those are small changes no matter with any problem:-).
It's always good to make it correct :) I looked at the users mainly to
answer the question: is it a must fix for 2.6.37 or even 2.6.36.x?
Thanks,
Fengguang
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