linux-kernel - Re: [PATCH v1 1/4] mm/mempolicy: skip nodemask intersect check for 'interleave' when oom

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Date:   Thu, 27 May 2021 15:15:04 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Feng Tang <feng.tang@...el.com>
Cc:     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,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        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 v1 1/4] mm/mempolicy: skip nodemask intersect check for
 'interleave' when oom

On Thu 27-05-21 21:05:01, Feng Tang wrote:
> On Thu, May 27, 2021 at 09:30:00AM +0200, Michal Hocko wrote:
[...]
> > Until now this was not a real problem even for OOM context because
> > alloc_page_interleave is always used for the interleaving policy
> > and that one doesn't use any node mask so the code is not really
> > exercised. With your MPOL_PREFERRED this would no longer be the case.
>  
> Given the 'interleave' task may have memory allocated from all nodes,
> shouldn't the mempolicy_nodemask_intersects() return true for 'interleave'?
> or I'm still missing something?

Well, if you go with the renaming then it should be quite obvious that
any policies which are not a hard binding should return true. 

-- 
Michal Hocko
SUSE Labs