Re: [PATCH 1/2] mm, page_alloc: Keep pcp count and list contents in sync if struct page is corrupted

[Hillf Danton]

On Friday, December 02, 2016 8:23 AM Mel Gorman wrote:
> Vlastimil Babka pointed out that commit 479f854a207c ("mm, page_alloc:
> defer debugging checks of pages allocated from the PCP") will allow the
> per-cpu list counter to be out of sync with the per-cpu list contents
> if a struct page is corrupted. This patch keeps the accounting in sync.
> 
> Fixes: 479f854a207c ("mm, page_alloc: defer debugging checks of pages allocated from the PCP")
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> cc: stable@xxxxxxxxxxxxxxx [4.7+]
> ---
>  mm/page_alloc.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 6de9440e3ae2..777ed59570df 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2192,7 +2192,7 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
>  			unsigned long count, struct list_head *list,
>  			int migratetype, bool cold)
>  {
> -	int i;
> +	int i, alloced = 0;
> 
>  	spin_lock(&zone->lock);
>  	for (i = 0; i < count; ++i) {
> @@ -2217,13 +2217,14 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
>  		else
>  			list_add_tail(&page->lru, list);
>  		list = &page->lru;
> +		alloced++;
>  		if (is_migrate_cma(get_pcppage_migratetype(page)))
>  			__mod_zone_page_state(zone, NR_FREE_CMA_PAGES,
>  					      -(1 << order));
>  	}
>  	__mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));

Now i is a pure index, yes?

>  	spin_unlock(&zone->lock);
> -	return i;
> +	return alloced;
>  }
> 
>  #ifdef CONFIG_NUMA
> --
> 2.10.2