linux-kernel - RE: [PATCH RFC] mm/swap: make release_pages() and put

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Date:   Fri, 24 May 2019 20:08:42 +0000
From:   "Weiny, Ira" <ira.weiny@...el.com>
To:     Shakeel Butt <shakeelb@...gle.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH RFC] mm/swap: make release_pages() and put_pages() match

> 
> On Fri, May 24, 2019 at 12:33 PM <ira.weiny@...el.com> wrote:
> >
> > From: Ira Weiny <ira.weiny@...el.com>
> >
> > RFC I have no idea if this is correct or not.  But looking at
> > release_pages() I see a call to both __ClearPageActive() and
> > __ClearPageWaiters() while in __page_cache_release() I do not.
> >
> > Is this a bug which needs to be fixed?  Did I miss clearing active
> > somewhere else in the call chain of put_page?
> >
> > This was found via code inspection while determining if
> > release_pages() and the new put_user_pages() could be interchangeable.
> >
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> > ---
> >  mm/swap.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/mm/swap.c b/mm/swap.c
> > index 3a75722e68a9..9d0432baddb0 100644
> > --- a/mm/swap.c
> > +++ b/mm/swap.c
> > @@ -69,6 +69,7 @@ static void __page_cache_release(struct page *page)
> >                 del_page_from_lru_list(page, lruvec,
> > page_off_lru(page));
> 
> see page_off_lru(page) above which clear active bit.

Thanks,  Sorry for the noise,
Ira


> 
> >                 spin_unlock_irqrestore(&pgdat->lru_lock, flags);
> >         }
> > +       __ClearPageActive(page);
> >         __ClearPageWaiters(page);
> >         mem_cgroup_uncharge(page);
> >  }
> > --
> > 2.20.1
> >