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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,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 6DC9EC433E0 for ; Tue, 22 Dec 2020 05:21:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3594223127 for ; Tue, 22 Dec 2020 05:21:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725913AbgLVFVr (ORCPT ); Tue, 22 Dec 2020 00:21:47 -0500 Received: from out30-133.freemail.mail.aliyun.com ([115.124.30.133]:35224 "EHLO out30-133.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725782AbgLVFVr (ORCPT ); Tue, 22 Dec 2020 00:21:47 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R741e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04395;MF=alex.shi@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0UJPqUQy_1608614460; Received: from aliy80.localdomain(mailfrom:alex.shi@linux.alibaba.com fp:SMTPD_---0UJPqUQy_1608614460) by smtp.aliyun-inc.com(127.0.0.1); Tue, 22 Dec 2020 13:21:00 +0800 From: Alex Shi To: hughd@google.com Cc: Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 2/3] mm/memcg: remove rcu locking for lock_page_lruvec function series Date: Tue, 22 Dec 2020 13:20:52 +0800 Message-Id: <1608614453-10739-2-git-send-email-alex.shi@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1608614453-10739-1-git-send-email-alex.shi@linux.alibaba.com> References: <1608614453-10739-1-git-send-email-alex.shi@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org lock_page_lruvec() and its variants used rcu_read_lock() with the intention of safeguarding against the mem_cgroup being destroyed concurrently; but so long as they are called under the specified conditions (as they are), there is no way for the page's mem_cgroup to be destroyed. Delete the unnecessary rcu_read_lock() and _unlock(). Hugh Dickin's polished the commit log, Thanks a lot! Signed-off-by: Alex Shi Acked-by: Hugh Dickins Cc: Hugh Dickins Cc: Johannes Weiner Cc: Michal Hocko Cc: Vladimir Davydov Cc: Andrew Morton Cc: cgroups@vger.kernel.org Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org --- mm/memcontrol.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 8d400efc81b9..0af13c4fe4b3 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1356,10 +1356,8 @@ struct lruvec *lock_page_lruvec(struct page *page) struct lruvec *lruvec; struct pglist_data *pgdat = page_pgdat(page); - rcu_read_lock(); lruvec = mem_cgroup_page_lruvec(page, pgdat); spin_lock(&lruvec->lru_lock); - rcu_read_unlock(); lruvec_memcg_debug(lruvec, page); @@ -1371,10 +1369,8 @@ struct lruvec *lock_page_lruvec_irq(struct page *page) struct lruvec *lruvec; struct pglist_data *pgdat = page_pgdat(page); - rcu_read_lock(); lruvec = mem_cgroup_page_lruvec(page, pgdat); spin_lock_irq(&lruvec->lru_lock); - rcu_read_unlock(); lruvec_memcg_debug(lruvec, page); @@ -1386,10 +1382,8 @@ struct lruvec *lock_page_lruvec_irqsave(struct page *page, unsigned long *flags) struct lruvec *lruvec; struct pglist_data *pgdat = page_pgdat(page); - rcu_read_lock(); lruvec = mem_cgroup_page_lruvec(page, pgdat); spin_lock_irqsave(&lruvec->lru_lock, *flags); - rcu_read_unlock(); lruvec_memcg_debug(lruvec, page); -- 2.29.GIT