linux-kernel - Re: [PATCH v2] net: fix sk_page_frag() recursion from memory reclaim

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Message-ID: <20191031184346.GM3622521@devbig004.ftw2.facebook.com>
Date:   Thu, 31 Oct 2019 11:43:46 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Michal Hocko <mhocko@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Kernel Team <kernel-team@...com>,
        LKML <linux-kernel@...r.kernel.org>,
        Josef Bacik <josef@...icpanda.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Linux MM <linux-mm@...ck.org>, Mel Gorman <mgorman@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2] net: fix sk_page_frag() recursion from memory reclaim

Hello,

On Thu, Oct 31, 2019 at 11:30:57AM -0700, Shakeel Butt wrote:
> Basically what I wanted to say that MM treats PF_MEMALLOC as the
> reclaim context while __GFP_MEMALLOC just tells to give access to the
> reserves. As gfpflags_allow_blocking() can be used beyond net
> subsystem, my only concern is its potential usage under PF_MEMALLOC
> context but without __GFP_MEMALLOC.

Yeah, PF_MEMALLOC is likely the better condition to check here as we
primarily want to know whether %current might be recursing and that
should be indicated reliably with PF_MEMALLOC.  Wanna prep a patch for
it?

Thanks.

-- 
tejun