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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 432FAC77B6C for ; Tue, 28 Mar 2023 23:22:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229739AbjC1XWN (ORCPT ); Tue, 28 Mar 2023 19:22:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35374 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229604AbjC1XWC (ORCPT ); Tue, 28 Mar 2023 19:22:02 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4B54030EF for ; Tue, 28 Mar 2023 16:21:48 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id DA84EB81F55 for ; Tue, 28 Mar 2023 23:21:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 86995C4339B; Tue, 28 Mar 2023 23:21:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1680045705; bh=yImhTqJW3KIp0Rl61yZnTgmns0ltJAOOnXdUJD93Rvg=; h=Date:To:From:Subject:From; b=KHHeI7xY8mKePWOjeRImBQHfDQyS+BxXAPEDqnC2NzWV5jRtICbZQECdhYQBEbuin xCiImfUQJXPBL9UwLdGbys+d0LefwlnbIFBdScTMk1qRUJxYtkDy0Edjf43g9rtjiy jFcj6SoVL+pqH7j/js6JbUUARv3aeCKOfVTMEwHU= Date: Tue, 28 Mar 2023 16:21:45 -0700 To: mm-commits@vger.kernel.org, willy@infradead.org, tangyeechou@gmail.com, shakeelb@google.com, roman.gushchin@linux.dev, muchun.song@linux.dev, mhocko@suse.com, hannes@cmpxchg.org, findns94@gmail.com, akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-memcg-prevent-memoryswappiness-load-store-tearing.patch removed from -mm tree Message-Id: <20230328232145.86995C4339B@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The quilt patch titled Subject: mm, memcg: prevent memory.swappiness load/store tearing has been removed from the -mm tree. Its filename was mm-memcg-prevent-memoryswappiness-load-store-tearing.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Yue Zhao Subject: mm, memcg: Prevent memory.swappiness load/store tearing Date: Mon, 6 Mar 2023 23:41:36 +0800 The knob for cgroup v1 memory controller: memory.swappiness is not protected by any locking so it can be modified while it is used. This is not an actual problem because races are unlikely. But it is better to use [READ|WRITE]_ONCE to prevent compiler from doing anything funky. The access of memcg->swappiness and vm_swappiness is lockless, so both of them can be concurrently set at the same time as we are trying to read them. All occurrences of memcg->swappiness and vm_swappiness are updated with [READ|WRITE]_ONCE. [findns94@gmail.com: v3] Link: https://lkml.kernel.org/r/20230308162555.14195-3-findns94@gmail.com Link: https://lkml.kernel.org/r/20230306154138.3775-3-findns94@gmail.com Signed-off-by: Yue Zhao Acked-by: Michal Hocko Acked-by: Shakeel Butt Acked-by: Roman Gushchin Cc: Johannes Weiner Cc: Matthew Wilcox (Oracle) Cc: Muchun Song Cc: Tang Yizhou Signed-off-by: Andrew Morton --- include/linux/swap.h | 8 ++++---- mm/memcontrol.c | 6 +++--- 2 files changed, 7 insertions(+), 7 deletions(-) --- a/include/linux/swap.h~mm-memcg-prevent-memoryswappiness-load-store-tearing +++ a/include/linux/swap.h @@ -620,18 +620,18 @@ static inline int mem_cgroup_swappiness( { /* Cgroup2 doesn't have per-cgroup swappiness */ if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) - return vm_swappiness; + return READ_ONCE(vm_swappiness); /* root ? */ if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg)) - return vm_swappiness; + return READ_ONCE(vm_swappiness); - return memcg->swappiness; + return READ_ONCE(memcg->swappiness); } #else static inline int mem_cgroup_swappiness(struct mem_cgroup *mem) { - return vm_swappiness; + return READ_ONCE(vm_swappiness); } #endif --- a/mm/memcontrol.c~mm-memcg-prevent-memoryswappiness-load-store-tearing +++ a/mm/memcontrol.c @@ -4179,9 +4179,9 @@ static int mem_cgroup_swappiness_write(s return -EINVAL; if (!mem_cgroup_is_root(memcg)) - memcg->swappiness = val; + WRITE_ONCE(memcg->swappiness, val); else - vm_swappiness = val; + WRITE_ONCE(vm_swappiness, val); return 0; } @@ -5353,7 +5353,7 @@ mem_cgroup_css_alloc(struct cgroup_subsy #endif page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX); if (parent) { - memcg->swappiness = mem_cgroup_swappiness(parent); + WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent)); memcg->oom_kill_disable = parent->oom_kill_disable; page_counter_init(&memcg->memory, &parent->memory); _ Patches currently in -mm which might be from findns94@gmail.com are