From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 BB102C18E5B for ; Mon, 16 Mar 2020 14:58:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 909C620674 for ; Mon, 16 Mar 2020 14:58:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584370710; bh=rikuuZQsZu+0+s0Rnkfg5Cr73Zpx5Xty7Dh30fLYcIM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=N8sH+bSC0lvwFNrEpFZIDQqNhis5HjRzocu5aC3H7oUjwUPECZdFJZqAgc9gG1RSA opYHBVnwDpuos1vsvMyT4Z/MicwReBDVxxWHov9AjZvEddvqLVbKrpAeAxkKzVpdeE 26pnInb11YBAp9XbB/lUMHUV7zMcjRdNbUjVW4KM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731757AbgCPO63 (ORCPT ); Mon, 16 Mar 2020 10:58:29 -0400 Received: from mail-wr1-f68.google.com ([209.85.221.68]:35490 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731630AbgCPO62 (ORCPT ); Mon, 16 Mar 2020 10:58:28 -0400 Received: by mail-wr1-f68.google.com with SMTP id h4so1008850wru.2; Mon, 16 Mar 2020 07:58:27 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=aoR8qIRYYjNc/yM1/A0XpgWDiePb9Xg/ztquG02cRtE=; b=IqzE8TNLGcg+JDkk4y+JjiXBmg4Nq6DKIb8TM4I1lMDcUsUL9h5SHGRqmGKkIH+nSN aSh0AUwciwQQ6R61fVd6nt5tpb/qUQJt2m9NpuTHcdgmZKL3z1V7PADRAUIQp9qI/aT2 pfF57ZwbugHsWY0RkgFseCScujPYUZWLaOreq7U9cIn8fgetUgMykL7bHB/sAPGgdibE kHa7o/ZwVg8qpFdJEBKKv/fBGBYCVMXCIVrFhJEHc5NvYd51FWcitDN52IGERwlMaTjT Kc/QO/1wZAeVIfxyssIkAvsLQ0qwFmQ774HH3ZwBuByyIputga2KJscvXn6UJEuTp9I0 lLRw== X-Gm-Message-State: ANhLgQ2RRHChjhevuLWQtyQQ9KgKiCY3OdlV3sBJrpr/NYtzJIxgwP5A qAXHQiGEAacRc8YnmA0OePg= X-Google-Smtp-Source: ADFU+vsPKyYiawBkTj9oGFRYMq6Z5hOmF8SOoxdkq/Ce4cCbYx6zmtCzkHhfr6njw0405WWhAAAk7A== X-Received: by 2002:adf:bbcd:: with SMTP id z13mr31549004wrg.389.1584370707117; Mon, 16 Mar 2020 07:58:27 -0700 (PDT) Received: from localhost ([37.188.132.163]) by smtp.gmail.com with ESMTPSA id f15sm331657wrt.9.2020.03.16.07.58.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Mar 2020 07:58:26 -0700 (PDT) Date: Mon, 16 Mar 2020 15:58:25 +0100 From: Michal Hocko To: Chris Down Cc: Andrew Morton , Johannes Weiner , Tejun Heo , Roman Gushchin , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 4/6] mm, memcg: Prevent memory.min load/store tearing Message-ID: <20200316145825.GP11482@dhcp22.suse.cz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 12-03-20 17:33:07, Chris Down wrote: > This can be set concurrently with reads, which may cause the wrong value > to be propagated. > > Signed-off-by: Chris Down > Cc: Andrew Morton > Cc: Johannes Weiner > Cc: Roman Gushchin > Cc: Tejun Heo > Cc: linux-mm@kvack.org > Cc: cgroups@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Cc: kernel-team@fb.com Acked-by: Michal Hocko > --- > mm/memcontrol.c | 4 ++-- > mm/page_counter.c | 10 ++++++---- > 2 files changed, 8 insertions(+), 6 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index c85a304fa4a1..e0ed790a2a8c 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6261,7 +6261,7 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root, > if (!usage) > return MEMCG_PROT_NONE; > > - emin = memcg->memory.min; > + emin = READ_ONCE(memcg->memory.min); > elow = READ_ONCE(memcg->memory.low); > > parent = parent_mem_cgroup(memcg); > @@ -6277,7 +6277,7 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root, > if (emin && parent_emin) { > unsigned long min_usage, siblings_min_usage; > > - min_usage = min(usage, memcg->memory.min); > + min_usage = min(usage, READ_ONCE(memcg->memory.min)); > siblings_min_usage = atomic_long_read( > &parent->memory.children_min_usage); > > diff --git a/mm/page_counter.c b/mm/page_counter.c > index 18b7f779f2e2..ae471c7d255f 100644 > --- a/mm/page_counter.c > +++ b/mm/page_counter.c > @@ -17,14 +17,16 @@ static void propagate_protected_usage(struct page_counter *c, > unsigned long usage) > { > unsigned long protected, old_protected; > - unsigned long low; > + unsigned long low, min; > long delta; > > if (!c->parent) > return; > > - if (c->min || atomic_long_read(&c->min_usage)) { > - if (usage <= c->min) > + min = READ_ONCE(c->min); > + > + if (min || atomic_long_read(&c->min_usage)) { > + if (usage <= min) > protected = usage; > else > protected = 0; > @@ -217,7 +219,7 @@ void page_counter_set_min(struct page_counter *counter, unsigned long nr_pages) > { > struct page_counter *c; > > - counter->min = nr_pages; > + WRITE_ONCE(counter->min, nr_pages); > > for (c = counter; c; c = c->parent) > propagate_protected_usage(c, atomic_long_read(&c->usage)); > -- > 2.25.1 > -- Michal Hocko SUSE Labs