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Subject: Re: [PATCH 1/2] mm/page_idle.c: Skip offline pages
To:     SeongJae Park <sjpark@amazon.com>, akpm@linux-foundation.org
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        SeongJae Park <sjpark@amazon.de>
References: <20200605092502.18018-1-sjpark@amazon.com>
 <20200605092502.18018-2-sjpark@amazon.com>
From:   David Hildenbrand <david@redhat.com>
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Organization: Red Hat GmbH
Message-ID: <dabb8aad-d3c2-6667-44e0-7e07606bb820@redhat.com>
Date:   Fri, 5 Jun 2020 11:27:00 +0200
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On 05.06.20 11:25, SeongJae Park wrote:
> From: SeongJae Park <sjpark@amazon.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@amazon.de>
> Reported-by: David Hildenbrand <david@redhat.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: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb