From patchwork Thu Oct 29 16:44:29 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Muchun Song X-Patchwork-Id: 1329166 Return-Path: Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9C8DC4363A for ; Thu, 29 Oct 2020 16:44:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7BDD120EDD for ; Thu, 29 Oct 2020 16:44:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=bytedance-com.20150623.gappssmtp.com header.i=@bytedance-com.20150623.gappssmtp.com header.b="hfspaErk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728059AbgJ2Qot (ORCPT ); Thu, 29 Oct 2020 12:44:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57960 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727468AbgJ2Qos (ORCPT ); Thu, 29 Oct 2020 12:44:48 -0400 Received: from mail-pl1-x644.google.com (mail-pl1-x644.google.com [IPv6:2607:f8b0:4864:20::644]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CD833C0613CF for ; Thu, 29 Oct 2020 09:44:47 -0700 (PDT) Received: by mail-pl1-x644.google.com with SMTP id b19so1579876pld.0 for ; Thu, 29 Oct 2020 09:44:47 -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=WMTjr2+W+gNVsgeHGd8A7YK4eqPL28HpThgEaSeH9eU=; b=hfspaErkNEk3rAQDqD3A0QgoFYIiQkGUXf8U4LtwDIZRnTaq5uY+72sOy4F8Tecu7/ S10JQrb+7JGVOXgAIaOvAXO67dScyeX13atrBB4zM+n0Vnq+wRAjitHeNE4ZuCqVjq/T y1K07iO66M5EAMlOc0n1HSwbJUn8tCD1O10RG0i3r2KoxYlwfxpn3eJjkJamTOQhXQdz WRu4N0U20Nh5rSCsry63lSKA1ytldBRzUIhbDSqHt73GjcTEdUL5KABUa1mss8WbXjsR IAJ/w6jdyyyMBerGnkWLXBgWJR/Zw+o2nEuA5MEUGTCnJccPYfUJRhZrugg2P3djBpW3 d5QQ== 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=WMTjr2+W+gNVsgeHGd8A7YK4eqPL28HpThgEaSeH9eU=; b=tXbWxvnKIe0O36ioW+JyDBLoTdk3XCRtr0xVEpvFAKOyvtSbBeyRlNaIZ1BNgdGh3Q s81uEKsGPIB13kXkFaeRP4Wed2uAwAFev9O3+p9Qxt1+47RESlLE7FmgyBi1+DRnjGGE +qEr0OY6govYFCB7GARmAa5OMIuZB/zVd6DhBgZr7avTBKz3FCMSjdfgQHqfl+aMClZw c38h3LlQ1Gao9+NPPbvhKg/9fYGO66p7ctVjwUZuqoOG4yPg2rEpr5sSnDwYYE952yu0 lWmY2qY9TYJ2LRMdU26+f2foHCYxOgczretLASee7CmMrOq2iSEo7WJ5wmr5ZyPtw8LL Xwow== X-Gm-Message-State: AOAM531Ze0GTMAZLlG6ryMrDd7Jr88QUOPmkPYbd6ED/S77TCBtyhGKh WodBlQSfNHuIJ+BrgpFAGZmBvQ== X-Google-Smtp-Source: ABdhPJwQrJmv/aoXAfRDFvHvxaf+pIXE+6B7vM/dhQRAubpFI5YbGj/chIP9FmZN25gkwUQQYOHgsQ== X-Received: by 2002:a17:902:b497:b029:d5:c01a:f06b with SMTP id y23-20020a170902b497b02900d5c01af06bmr5152085plr.13.1603989887265; Thu, 29 Oct 2020 09:44:47 -0700 (PDT) Received: from localhost.localdomain ([103.136.220.95]) by smtp.gmail.com with ESMTPSA id 197sm3429491pfa.170.2020.10.29.09.44.40 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 29 Oct 2020 09:44:46 -0700 (PDT) From: Muchun Song To: hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, shakeelb@google.com, guro@fb.com, iamjoonsoo.kim@lge.com, laoar.shao@gmail.com, chris@chrisdown.name, christian.brauner@ubuntu.com, peterz@infradead.org, mingo@kernel.org, keescook@chromium.org, tglx@linutronix.de, esyr@redhat.com, surenb@google.com, areber@redhat.com, elver@google.com Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Muchun Song Subject: [PATCH v3] mm: memcg/slab: Fix return child memcg objcg for root memcg Date: Fri, 30 Oct 2020 00:44:29 +0800 Message-Id: <20201029164429.58703-1-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Consider the following memcg hierarchy. root / \ A B If we failed to get the reference on objcg of memcg A, the get_obj_cgroup_from_current can return the wrong objcg for the root memcg. Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") Signed-off-by: Muchun Song Acked-by: Roman Gushchin --- changelog in v3: 1. Fix commit grammar, thanks to Shakeel. changelog in v2: 1. Do not use a comparison with the root_mem_cgroup mm/memcontrol.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 1337775b04f3..8c8b4c3ed5a0 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2961,6 +2961,7 @@ __always_inline struct obj_cgroup *get_obj_cgroup_from_current(void) objcg = rcu_dereference(memcg->objcg); if (objcg && obj_cgroup_tryget(objcg)) break; + objcg = NULL; } rcu_read_unlock();