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=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 5CE24C43460 for ; Wed, 21 Apr 2021 06:27:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3C1AB61422 for ; Wed, 21 Apr 2021 06:27:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235933AbhDUG1m (ORCPT ); Wed, 21 Apr 2021 02:27:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35240 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231821AbhDUG1k (ORCPT ); Wed, 21 Apr 2021 02:27:40 -0400 Received: from mail-pf1-x42d.google.com (mail-pf1-x42d.google.com [IPv6:2607:f8b0:4864:20::42d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17CB2C06174A for ; Tue, 20 Apr 2021 23:27:07 -0700 (PDT) Received: by mail-pf1-x42d.google.com with SMTP id h15so10048665pfv.2 for ; Tue, 20 Apr 2021 23:27:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=NwnAlOdpq+wyEz2WSM+M0ERvUu6M/uBx7vTFXtXONT4=; b=DpIowsWi2GfYdgnpGRG8PtbRNT39ZRaQsFFJ5oLJ9+3EOrj9hfz0JCDdJiCLwuEoco o81qgNZNZifrLUbeAXhtHe07RgTSpgh20obxivdBnMWN+NX47ciykaqNZ2236xRhCPR5 dI+DRXHMwBrxRqmwNFiUmgyI2Hva/D8s9c0wlaVgA/WgJ/3FgglZiKEp5NEHEt65IKBH IsxzKGGeyX75qzv870Z3ePiYScI3KHDQ1W041YCdpGIKCkwRG8UyA/GmdksQd2dM9H9m uen8OPQe96aeTj/qxhObVXapCWIjFHWeEipdcgyzcaQI4AC/NTxWOB7XnWOx343DN3Dj CTig== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=NwnAlOdpq+wyEz2WSM+M0ERvUu6M/uBx7vTFXtXONT4=; b=RcO1kruLqsXTMLkOtJ9Alrucaxw14sSOaGkPEbtCjHlhTeXf3YoQImhHfi/yYz/3ar uACOW7mohfzfGE7WKCYwt/cgcZfXQe0bj7y8FveB65oXVIc/VPKvdsdLh7yXncV2uWwS /lcUwIoXwEJAWkvCJZtqfvBkBkcmkmbc+2LOemn2tg1LWedlFeJGOImzl9SVpi7SM00i gclMfhr6bkPPti6GB0RPbGV/jhubE/z09P3xbLaYj6dL1teD4nRbuueRc/YBAiYZVEVH k0XdBLChaHUMuGxT7A4DDoB2d/dbfC3B/eju83rV6+RtkFLNvkbk+Y8iDtTsOM/tEN97 cXjw== X-Gm-Message-State: AOAM531TtM21srF6tkomqBQc0zf8vQfTgh5n1VCrHx3DtjDykG3eE2my VB0aqmgC1YPKBGbdpFB8DZ4xcA== X-Google-Smtp-Source: ABdhPJxCzYXXUqO8j2cBW2d2M9mtDgb+DXVVcxKJlmj3wxUTj6B4DT5Sxtyal7651FOA3ZSRsIsMGg== X-Received: by 2002:a17:90b:30c6:: with SMTP id hi6mr9129329pjb.26.1618986426710; Tue, 20 Apr 2021 23:27:06 -0700 (PDT) Received: from localhost.localdomain ([139.177.225.255]) by smtp.gmail.com with ESMTPSA id w10sm815408pfq.184.2021.04.20.23.27.02 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 20 Apr 2021 23:27:06 -0700 (PDT) From: Muchun Song To: guro@fb.com, hannes@cmpxchg.org, mhocko@kernel.org, akpm@linux-foundation.org, shakeelb@google.com, vdavydov.dev@gmail.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, fam.zheng@bytedance.com, Muchun Song Subject: [PATCH] mm: memcontrol: fix root_mem_cgroup charging Date: Wed, 21 Apr 2021 14:26:44 +0800 Message-Id: <20210421062644.68331-1-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The below scenario can cause the page counters of the root_mem_cgroup to be out of balance. CPU0: CPU1: objcg = get_obj_cgroup_from_current() obj_cgroup_charge_pages(objcg) memcg_reparent_objcgs() // reparent to root_mem_cgroup WRITE_ONCE(iter->memcg, parent) // memcg == root_mem_cgroup memcg = get_mem_cgroup_from_objcg(objcg) // do not charge to the root_mem_cgroup try_charge(memcg) obj_cgroup_uncharge_pages(objcg) memcg = get_mem_cgroup_from_objcg(objcg) // uncharge from the root_mem_cgroup page_counter_uncharge(&memcg->memory) This can cause the page counter to be less than the actual value, Although we do not display the value (mem_cgroup_usage) so there shouldn't be any actual problem, but there is a WARN_ON_ONCE in the page_counter_cancel(). Who knows if it will trigger? So it is better to fix it. Signed-off-by: Muchun Song --- mm/memcontrol.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 1e68a9992b01..81b54bd9b9e0 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2686,8 +2686,8 @@ void mem_cgroup_handle_over_high(void) css_put(&memcg->css); } -static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, - unsigned int nr_pages) +static int __try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, + unsigned int nr_pages) { unsigned int batch = max(MEMCG_CHARGE_BATCH, nr_pages); int nr_retries = MAX_RECLAIM_RETRIES; @@ -2699,8 +2699,6 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, bool drained = false; unsigned long pflags; - if (mem_cgroup_is_root(memcg)) - return 0; retry: if (consume_stock(memcg, nr_pages)) return 0; @@ -2880,6 +2878,15 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, return 0; } +static inline int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, + unsigned int nr_pages) +{ + if (mem_cgroup_is_root(memcg)) + return 0; + + return __try_charge(memcg, gfp_mask, nr_pages); +} + #if defined(CONFIG_MEMCG_KMEM) || defined(CONFIG_MMU) static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages) { @@ -3125,7 +3132,7 @@ static int obj_cgroup_charge_pages(struct obj_cgroup *objcg, gfp_t gfp, memcg = get_mem_cgroup_from_objcg(objcg); - ret = try_charge(memcg, gfp, nr_pages); + ret = __try_charge(memcg, gfp, nr_pages); if (ret) goto out; -- 2.11.0