linux-kernel - Re: [PATCH 1/2] mm/page_idle.c: Skip offline pages

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Date:   Fri, 5 Jun 2020 11:31:12 +0200
From:   Pankaj Gupta <pankaj.gupta.linux@...il.com>
To:     SeongJae Park <sjpark@...zon.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        SeongJae Park <sjpark@...zon.de>
Subject: Re: [PATCH 1/2] mm/page_idle.c: Skip offline pages

> From: SeongJae Park <sjpark@...zon.de>
>
> 'Idle page tracking' users can pass random pfn that might be mapped to
> an offline page.  To avoid accessing such pages, this commit modifies
> the 'page_idle_get_page()' to use 'pfn_to_online_page()' instead of
> 'pfn_valid()' and 'pfn_to_page()' combination, so that the pfn mapped to
> an offline page can be skipped.
>
> Signed-off-by: SeongJae Park <sjpark@...zon.de>
> Reported-by: David Hildenbrand <david@...hat.com>
> ---
>  mm/page_idle.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/mm/page_idle.c b/mm/page_idle.c
> index 295512465065..057c61df12db 100644
> --- a/mm/page_idle.c
> +++ b/mm/page_idle.c
> @@ -4,6 +4,7 @@
>  #include <linux/fs.h>
>  #include <linux/sysfs.h>
>  #include <linux/kobject.h>
> +#include <linux/memory_hotplug.h>
>  #include <linux/mm.h>
>  #include <linux/mmzone.h>
>  #include <linux/pagemap.h>
> @@ -30,13 +31,9 @@
>   */
>  static struct page *page_idle_get_page(unsigned long pfn)
>  {
> -       struct page *page;
> +       struct page *page = pfn_to_online_page(pfn);
>         pg_data_t *pgdat;
>
> -       if (!pfn_valid(pfn))
> -               return NULL;
> -
> -       page = pfn_to_page(pfn);
>         if (!page || !PageLRU(page) ||
>             !get_page_unless_zero(page))
>                 return NULL;

Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@...il.com>