linux-kernel - Re: [PATCH v6 4/6] mm/hugetlb: add support for mempolicy MPOL_PREFERRED

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Message-ID: <YPk9hTQ5KQCv7KFw@dhcp22.suse.cz>
Date:   Thu, 22 Jul 2021 11:42:29 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     Feng Tang <feng.tang@...el.com>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Ben Widawsky <ben.widawsky@...el.com>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Randy Dunlap <rdunlap@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andi Kleen <ak@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>, ying.huang@...el.com
Subject: Re: [PATCH v6 4/6] mm/hugetlb: add support for mempolicy
 MPOL_PREFERRED_MANY

On Wed 21-07-21 13:49:15, Mike Kravetz wrote:
> On 7/12/21 1:09 AM, Feng Tang wrote:
[...]
> > +#ifdef CONFIG_NUMA
> > +	if (mpol->mode == MPOL_PREFERRED_MANY) {
> > +		gfp_t gfp = (gfp_mask | __GFP_NOWARN) & ~__GFP_DIRECT_RECLAIM;
> 
> I believe __GFP_NOWARN will be added later in alloc_buddy_huge_page, so
> no need to add here?

The mask is manipulated here anyway and the __GFP_NOWARN is really
telling that there is no need to report the failure for _this_
allocation request. alloc_surplus_huge_page might alter that in whatever
way in the future. So I would keep NOWARN here for the code clarity
rather than rely on some implicit assumption down the path.
-- 
Michal Hocko
SUSE Labs