Re: [patch 2/6] mm/page_alloc.c:__alloc_pages_nodemask(): don't alter arg gfp_mask

[Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>]

(2014/12/16 8:03), akpm@linux-foundation.org wrote:
> From: Andrew Morton <akpm@linux-foundation.org>
> Subject: mm/page_alloc.c:__alloc_pages_nodemask(): don't alter arg gfp_mask
>
> __alloc_pages_nodemask() strips __GFP_IO when retrying the page
> allocation.  But it does this by altering the function-wide variable
> gfp_mask.  This will cause subsequent allocation attempts to inadvertently
> use the modified gfp_mask.
>
> Cc: Ming Lei <ming.lei@canonical.com>
> Cc: Mel Gorman <mel@csn.ul.ie>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
>   mm/page_alloc.c |    5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff -puN mm/page_alloc.c~mm-page_allocc-__alloc_pages_nodemask-dont-alter-arg-gfp_mask mm/page_alloc.c
> --- a/mm/page_alloc.c~mm-page_allocc-__alloc_pages_nodemask-dont-alter-arg-gfp_mask
> +++ a/mm/page_alloc.c
> @@ -2918,8 +2918,9 @@ retry_cpuset:
>   		 * can deadlock because I/O on the device might not
>   		 * complete.
>   		 */
> -		gfp_mask = memalloc_noio_flags(gfp_mask);
> -		page = __alloc_pages_slowpath(gfp_mask, order,

> +		gfp_t mask = memalloc_noio_flags(gfp_mask);
> +
> +		page = __alloc_pages_slowpath(mask, order,
>   				zonelist, high_zoneidx, nodemask,
>   				preferred_zone, classzone_idx, migratetype);
>   	}

After allocating page, trace_mm_page_alloc(page, order, gfp_mask, migratetype)
is called. But mask is not passed to it. So trace_mm_page_alloc traces wrong
gfp_mask.

Thanks,
Yasuaki Ishimatsu

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