From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
X-Spam-Level: 
X-Spam-Status: No, score=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED,
	DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no
	autolearn_force=no version=3.4.0
Received: from mail.kernel.org (mail.kernel.org [198.145.29.99])
	by smtp.lore.kernel.org (Postfix) with ESMTP id 2D712C4338F
	for <linux-kernel@archiver.kernel.org>; Fri, 23 Jul 2021 13:41:11 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [23.128.96.18])
	by mail.kernel.org (Postfix) with ESMTP id 1734660EBD
	for <linux-kernel@archiver.kernel.org>; Fri, 23 Jul 2021 13:41:11 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S235275AbhGWNAg (ORCPT <rfc822;linux-kernel@archiver.kernel.org>);
        Fri, 23 Jul 2021 09:00:36 -0400
Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52526 "EHLO
        lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S233486AbhGWNAe (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 23 Jul 2021 09:00:34 -0400
Received: from mail-lf1-x12b.google.com (mail-lf1-x12b.google.com [IPv6:2a00:1450:4864:20::12b])
        by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 08800C061757
        for <linux-kernel@vger.kernel.org>; Fri, 23 Jul 2021 06:41:07 -0700 (PDT)
Received: by mail-lf1-x12b.google.com with SMTP id h14so2127607lfv.7
        for <linux-kernel@vger.kernel.org>; Fri, 23 Jul 2021 06:41:06 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=google.com; s=20161025;
        h=mime-version:references:in-reply-to:from:date:message-id:subject:to
         :cc;
        bh=8IUOnTm1w1NEGAKUMKN9++OeCABD3VuZuK8Yv72862w=;
        b=gA0KTI9EjtWRrS83kMofDP16+r28w0JxI7MivS3NNKG3D7h0NX3kFG8jahIo/K4+j/
         InBy0eAqybKo30iUV2ObUz79y65QEqzuqfkNGtvlG9qDbovYf1u1un6Ke2X6l0BQcFu3
         q2ilMtGg0WxDs+eaJxTJ42jKEAk8ZC5FQCcKy9F9rN4zkZMmZAtFEsm862G3Sp4rfXt+
         bWn2TLAs2bbq/De8aok+VvnJvts2urLLECzI97u8kviZl9k23Vte7DZGLFmO1BEBPF5P
         xDFQ7wrG07ut5ziGOcjIEp43y+8WGHUOdB6/5aXhk06UdWjH2dL5UeZuP/j6p+J6uGi+
         INXg==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=1e100.net; s=20161025;
        h=x-gm-message-state:mime-version:references:in-reply-to:from:date
         :message-id:subject:to:cc;
        bh=8IUOnTm1w1NEGAKUMKN9++OeCABD3VuZuK8Yv72862w=;
        b=gs6Rt6K7L4HA/HzZPHTQFmp+nbp3UW3A1CK6UCxQhSZTXrYf38vR+n8BF3DG6j4yxr
         WuEOpd7x2m4xp9MG72Zi42IycVJmQp9w0MyAYmxYmMV8nzl4XNg2jSlF/aquZbR1gYkb
         XM20t0V5jGrbX1+0k4EXfy6Z8okvpLy5Rel+2zGlXu4ijwH3Ef8usxFLZuKBTDuiMruR
         ibEWHiu0ipyxRtQKuEMrNUYGA1qumvdjS3ME7YFnCazlqquYjwJ5+/5Vhm3iIY0SY44b
         qqyXTozPHYr2PiWaXkr7iTiWXIH9Q5/OsNVdynZZMJTCxGWuGa5L/2gMTtliLFZ8OQnx
         qmXg==
X-Gm-Message-State: AOAM5332Bkeu0w6cAw3n3DBOtn8jtdbEJxAUCZV8Ti3ciMoYqGHnYrCK
        rAqNJs0l4XofVJsWb4s/GZQguI2ehDsVsxw1mi2XcQ==
X-Google-Smtp-Source: ABdhPJw8jqOznbPrS2TBhfpe4BhYyrVrnm33Cq5MfitNfhmTtB11IoaLYUskZkWSJpsoHlUm0sPAcJR3h0yAR38JgHQ=
X-Received: by 2002:ac2:4d86:: with SMTP id g6mr3049839lfe.549.1627047665042;
 Fri, 23 Jul 2021 06:41:05 -0700 (PDT)
MIME-Version: 1.0
References: <20210723011436.60960-1-surenb@google.com> <CALvZod7ehaHoWRD-Pzvet5c1LQ6DYDHjs=xbJWZYEdMsgTpRgA@mail.gmail.com>
 <CAJuCfpFZeQez77CB7odfaSpi3JcLQ_Nz0WvDTsra1VPoA-j7sg@mail.gmail.com> <YPpfo2z8feq0vTlE@dhcp22.suse.cz>
In-Reply-To: <YPpfo2z8feq0vTlE@dhcp22.suse.cz>
From:   Shakeel Butt <shakeelb@google.com>
Date:   Fri, 23 Jul 2021 06:40:53 -0700
Message-ID: <CALvZod470Q9yZzjRGZr5q3oZ2z7-EYc3fEGtoridk8MJu3k7jg@mail.gmail.com>
Subject: Re: [PATCH v3 1/2] mm: introduce process_mrelease system call
To:     Michal Hocko <mhocko@suse.com>
Cc:     Suren Baghdasaryan <surenb@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Rientjes <rientjes@google.com>,
        Matthew Wilcox <willy@infradead.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Roman Gushchin <guro@fb.com>, Rik van Riel <riel@surriel.com>,
        Minchan Kim <minchan@kernel.org>,
        Christian Brauner <christian@brauner.io>,
        Christoph Hellwig <hch@infradead.org>,
        Oleg Nesterov <oleg@redhat.com>,
        David Hildenbrand <david@redhat.com>,
        Jann Horn <jannh@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Florian Weimer <fweimer@redhat.com>,
        Jan Engelhardt <jengelh@inai.de>,
        Tim Murray <timmurray@google.com>,
        Linux API <linux-api@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        kernel-team <kernel-team@android.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, Jul 22, 2021 at 11:20 PM Michal Hocko <mhocko@suse.com> wrote:
>
> On Thu 22-07-21 21:47:56, Suren Baghdasaryan wrote:
> > On Thu, Jul 22, 2021, 7:04 PM Shakeel Butt <shakeelb@google.com> wrote:
> >
> > > On Thu, Jul 22, 2021 at 6:14 PM Suren Baghdasaryan <surenb@google.com>
> > > wrote:
> > > >
> > > [...]
> > > > +
> > > > +       mmap_read_lock(mm);
> > >
> > > How about mmap_read_trylock(mm) and return -EAGAIN on failure?
> > >
> >
> > That sounds like a good idea. Thanks! I'll add that in the next respin.
>
> Why is that a good idea? Can you do anything meaningful about the
> failure other than immediately retry the syscall and hope for the best?
>

Yes we can. Based on the situation/impact we can select more victims.