linux-kernel - Re: [PATCH 2/3] mm, oom: do not enfore OOM killer for __GFP

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Date:   Fri, 20 Jan 2017 16:33:36 +0800
From:   "Hillf Danton" <hillf.zj@...baba-inc.com>
To:     "'Michal Hocko'" <mhocko@...nel.org>,
        "'Andrew Morton'" <akpm@...ux-foundation.org>
Cc:     "'Johannes Weiner'" <hannes@...xchg.org>,
        "'Tetsuo Handa'" <penguin-kernel@...ove.SAKURA.ne.jp>,
        "'David Rientjes'" <rientjes@...gle.com>,
        "'Mel Gorman'" <mgorman@...e.de>, <linux-mm@...ck.org>,
        "'LKML'" <linux-kernel@...r.kernel.org>,
        "'Michal Hocko'" <mhocko@...e.com>
Subject: Re: [PATCH 2/3] mm, oom: do not enfore OOM killer for __GFP_NOFAIL automatically


On Tuesday, December 20, 2016 9:49 PM Michal Hocko wrote: 
> 
> @@ -1013,7 +1013,7 @@ bool out_of_memory(struct oom_control *oc)
>  	 * make sure exclude 0 mask - all other users should have at least
>  	 * ___GFP_DIRECT_RECLAIM to get here.
>  	 */
> -	if (oc->gfp_mask && !(oc->gfp_mask & (__GFP_FS|__GFP_NOFAIL)))
> +	if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS))
>  		return true;
> 
As to GFP_NOFS|__GFP_NOFAIL request, can we check gfp mask
one bit after another?

	if (oc->gfp_mask) {
		if (!(oc->gfp_mask & __GFP_FS))
			return false;

		/* No service for request that can handle fail result itself */
		if (!(oc->gfp_mask & __GFP_NOFAIL))
			return false;
	}

thanks
Hillf