Re: [PATCH 1/3] page-allocator: Allow too high-order warning messages to be suppressed with __GFP_NOWARN

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

> The page allocator warns once when an order >= MAX_ORDER is specified.
> This is to catch callers of the allocator that are always falling back
> to their worst-case when it was not expected. However, there are cases
> where the caller is behaving correctly but cannot suppress the warning.
> This patch allows the warning to be suppressed by the callers by
> specifying __GFP_NOWARN.
> 
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> ---
>  mm/page_alloc.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index caa9268..b469a05 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1740,8 +1740,10 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>  	 * be using allocators in order of preference for an area that is
>  	 * too large.
>  	 */
> -	if (WARN_ON_ONCE(order >= MAX_ORDER))
> +	if (order >= MAX_ORDER) {
> +		WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN));
>  		return NULL;
> +	}

Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>


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