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

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Message-ID: <CALvZod6skK6NxeRXjKS64+1jpF9NwbLp7DhpWueB0F6Tj4MNUw@mail.gmail.com>
Date:   Fri, 24 May 2019 12:44:38 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     ira.weiny@...el.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.

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