From patchwork Thu Jan 16 01:31:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wei Yang X-Patchwork-Id: 11335807 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 54CBB1398 for ; Thu, 16 Jan 2020 01:31:19 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 21A872084D for ; Thu, 16 Jan 2020 01:31:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 21A872084D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 45F418E001D; Wed, 15 Jan 2020 20:31:18 -0500 (EST) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 40FD28E001C; Wed, 15 Jan 2020 20:31:18 -0500 (EST) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 325608E001D; Wed, 15 Jan 2020 20:31:18 -0500 (EST) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0024.hostedemail.com [216.40.44.24]) by kanga.kvack.org (Postfix) with ESMTP id 1B0BD8E001C for ; Wed, 15 Jan 2020 20:31:18 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id C9C6E40FB for ; Thu, 16 Jan 2020 01:31:17 +0000 (UTC) X-FDA: 76381769394.24.bead09_2853e9ecb8619 X-Spam-Summary: 1,0,0,,d41d8cd98f00b204,richardw.yang@linux.intel.com,:hannes@cmpxchg.org:mhocko@kernel.org:vdavydov.dev@gmail.com:akpm@linux-foundation.org:ktkhai@virtuozzo.com:kirill.shutemov@linux.intel.com:yang.shi@linux.alibaba.com:cgroups@vger.kernel.org::linux-kernel@vger.kernel.org:alexander.duyck@gmail.com:rientjes@google.com:richardw.yang@linux.intel.com:stable@vger.kernel.org,RULES_HIT:30045:30054:30070:30090,0,RBL:134.134.136.31:@linux.intel.com:.lbl8.mailshell.net-62.18.0.100 64.95.201.95,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:25,LUA_SUMMARY:none X-HE-Tag: bead09_2853e9ecb8619 X-Filterd-Recvd-Size: 4187 Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by imf15.hostedemail.com (Postfix) with ESMTP for ; Thu, 16 Jan 2020 01:31:16 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 15 Jan 2020 17:31:15 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,323,1574150400"; d="scan'208";a="213906940" Received: from unknown (HELO localhost) ([10.239.159.54]) by orsmga007.jf.intel.com with ESMTP; 15 Jan 2020 17:31:13 -0800 From: Wei Yang To: hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, ktkhai@virtuozzo.com, kirill.shutemov@linux.intel.com, yang.shi@linux.alibaba.com Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, alexander.duyck@gmail.com, rientjes@google.com, Wei Yang , stable@vger.kernel.org Subject: [Patch v3] mm: thp: grab the lock before manipulation defer list Date: Thu, 16 Jan 2020 09:31:00 +0800 Message-Id: <20200116013100.7679-1-richardw.yang@linux.intel.com> X-Mailer: git-send-email 2.17.1 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: As all the other places, we grab the lock before manipulate the defer list. Current implementation may face a race condition. For example, the potential race would be: CPU1 CPU2 mem_cgroup_move_account deferred_split_huge_page list_empty lock list_empty list_add_tail unlock lock # list_empty might not hold anymore list_add_tail unlock When this sequence happens, the list_add_tail() in mem_cgroup_move_account() corrupt the list since which is already been added to some split_queue in split_huge_page_to_list(). Besides this, David Rientjes points out the split_queue_len would be in a wrong state, which would be a significant issue for shrinkers. Fixes: 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware") Signed-off-by: Wei Yang Cc: [5.4+] --- v3: * remove all review/ack tag since rewrite the changelog * use deferred_split_huge_page as the example of race * add cc stable 5.4+ tag as suggested by David Rientjes v2: * move check on compound outside suggested by Alexander * an example of the race condition, suggested by Michal --- mm/memcontrol.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c5b5f74cfd4d..6450bbe394e2 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5360,10 +5360,12 @@ static int mem_cgroup_move_account(struct page *page, } #ifdef CONFIG_TRANSPARENT_HUGEPAGE - if (compound && !list_empty(page_deferred_list(page))) { + if (compound) { spin_lock(&from->deferred_split_queue.split_queue_lock); - list_del_init(page_deferred_list(page)); - from->deferred_split_queue.split_queue_len--; + if (!list_empty(page_deferred_list(page))) { + list_del_init(page_deferred_list(page)); + from->deferred_split_queue.split_queue_len--; + } spin_unlock(&from->deferred_split_queue.split_queue_lock); } #endif @@ -5377,11 +5379,13 @@ static int mem_cgroup_move_account(struct page *page, page->mem_cgroup = to; #ifdef CONFIG_TRANSPARENT_HUGEPAGE - if (compound && list_empty(page_deferred_list(page))) { + if (compound) { spin_lock(&to->deferred_split_queue.split_queue_lock); - list_add_tail(page_deferred_list(page), - &to->deferred_split_queue.split_queue); - to->deferred_split_queue.split_queue_len++; + if (list_empty(page_deferred_list(page))) { + list_add_tail(page_deferred_list(page), + &to->deferred_split_queue.split_queue); + to->deferred_split_queue.split_queue_len++; + } spin_unlock(&to->deferred_split_queue.split_queue_lock); } #endif