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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 E046AC43331 for ; Thu, 2 Apr 2020 04:07:26 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9A60E206E9 for ; Thu, 2 Apr 2020 04:07:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="kRfOlfD2" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9A60E206E9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 502D28E004C; Thu, 2 Apr 2020 00:07:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4B3978E000D; Thu, 2 Apr 2020 00:07:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3F05C8E004C; Thu, 2 Apr 2020 00:07:26 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0043.hostedemail.com [216.40.44.43]) by kanga.kvack.org (Postfix) with ESMTP id 28F0C8E000D for ; Thu, 2 Apr 2020 00:07:26 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id DF4A44428 for ; Thu, 2 Apr 2020 04:07:25 +0000 (UTC) X-FDA: 76661580450.15.story50_40d8af8372e4d X-HE-Tag: story50_40d8af8372e4d X-Filterd-Recvd-Size: 3066 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf38.hostedemail.com (Postfix) with ESMTP for ; Thu, 2 Apr 2020 04:07:25 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 98611208E0; Thu, 2 Apr 2020 04:07:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585800445; bh=5GeAWKy+ZszsCZ5pf/q6d0HG3WQuEhG41T4R+DKumVE=; h=Date:From:To:Subject:In-Reply-To:From; b=kRfOlfD2LC9NlQrEQDfVL4Z1qG3fAtx1gQTKxewGxbEbkUWMz56wK8MaIPxP0HQD0 gYaL4GZaeLFwAcLsQ19DT/tOMI07Be2Ntzh8Qcq5zOpzRO/aHJh/FNxeOi5hXUbTlU NRTpKlAJSObxJ5DPsnXQgYTC5WXTxtwIPZZ8yHrc= Date: Wed, 01 Apr 2020 21:07:24 -0700 From: Andrew Morton To: akpm@linux-foundation.org, chris@chrisdown.name, guro@fb.com, hannes@cmpxchg.org, linux-mm@kvack.org, mhocko@suse.com, mm-commits@vger.kernel.org, tj@kernel.org, torvalds@linux-foundation.org Subject: [patch 076/155] mm, memcg: prevent memory.low load/store tearing Message-ID: <20200402040724.6Xz5_-c5d%akpm@linux-foundation.org> In-Reply-To: <20200401210155.09e3b9742e1c6e732f5a7250@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Chris Down Subject: mm, memcg: prevent memory.low load/store tearing This can be set concurrently with reads, which may cause the wrong value to be propagated. Link: http://lkml.kernel.org/r/448206f44b0fa7be9dad2ca2601d2bcb2c0b7844.1584034301.git.chris@chrisdown.name Signed-off-by: Chris Down Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Roman Gushchin Cc: Tejun Heo Signed-off-by: Andrew Morton --- mm/page_counter.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/mm/page_counter.c~mm-memcg-prevent-memorylow-load-store-tearing +++ a/mm/page_counter.c @@ -17,6 +17,7 @@ static void propagate_protected_usage(st unsigned long usage) { unsigned long protected, old_protected; + unsigned long low; long delta; if (!c->parent) @@ -30,8 +31,9 @@ static void propagate_protected_usage(st atomic_long_add(delta, &c->parent->children_min_usage); } - if (c->low || atomic_long_read(&c->low_usage)) { - protected = min(usage, c->low); + low = READ_ONCE(c->low); + if (low || atomic_long_read(&c->low_usage)) { + protected = min(usage, low); old_protected = atomic_long_xchg(&c->low_usage, protected); delta = protected - old_protected; if (delta) @@ -222,7 +224,7 @@ void page_counter_set_low(struct page_co { struct page_counter *c; - counter->low = nr_pages; + WRITE_ONCE(counter->low, nr_pages); for (c = counter; c; c = c->parent) propagate_protected_usage(c, atomic_long_read(&c->usage)); _