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=-15.9 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1, USER_IN_DEF_DKIM_WL 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 998ABC2D0C2 for ; Fri, 3 Jan 2020 19:29:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 66A0A215A4 for ; Fri, 3 Jan 2020 19:29:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="otHt/I+p" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728542AbgACT3I (ORCPT ); Fri, 3 Jan 2020 14:29:08 -0500 Received: from mail-pj1-f68.google.com ([209.85.216.68]:35051 "EHLO mail-pj1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728503AbgACT3I (ORCPT ); Fri, 3 Jan 2020 14:29:08 -0500 Received: by mail-pj1-f68.google.com with SMTP id s7so5088275pjc.0 for ; Fri, 03 Jan 2020 11:29:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version; bh=xiCyHmcnUXsbcQ7aHolyREhLRtQlcm0tNcQpv0xj54g=; b=otHt/I+pw8YEKdneORJaQbqVOMxTvFzuxsTLLo7ZOfnkm7+sA/s/x+b5ZiwnwdyNsM mfRl/YbfDdxHzR2Rfe0dAizN3JrCsQ76Os4SjYyo9S1ECVmqUOML8K8S/YBi5lHfUumH I5sRO4W4LYYWzpp+g2tfXYM8x+1i2fRx+TVLGkGcDO7rAoq4BzN5giqoCdnq10C+hw+o NVmD4trJFm7qSbm58YTvtBPmdSOVfFH9OlPvaUYGTkLBuR4W1QJa14C5GlU267SLGDIk nJvj1z52hjwCB/qZkkakQbkJqE7ovBP/lPjUGrjm7HuF9J8UTNwBPO9jMGL9+KBvpBx7 97Og== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version; bh=xiCyHmcnUXsbcQ7aHolyREhLRtQlcm0tNcQpv0xj54g=; b=MWNzux7wlrk18UBmFnJmL8f0J+AuS27G9rux8MeHKu4omoQ6IOct7Z8AsNUtBjHevk /9aJvD4wz+36mevgE6GFzWgAm+J9Nor1+eM84ZbQAwFj2vj1zxWitplyb7KLn+mE3uGa 9L6DpewpTXdzcQNTX8LrUxTnx40MMZvnw97s4SBGTl0BI44jU9jNu1wSe9SBRVa/h7Wu 3KttIU6VIQoES+ib2vXujRMJoiPaQUh+k7Wpma3pRnMpB1lTEk+dZp4NZCeKw37hZdrv vpa4ioWFc7s8/+/F4twpnSCi9Ey5JFfM9ra0k1zlmoSUzsr6TKiCQ40QHBRPzA6f2omW h1tQ== X-Gm-Message-State: APjAAAWRm4iMujlFvS0T6Dp6+ykarr6xm68SmcJQRMho2RB9vwUgh5PS dXIlX2R7AE2upoUhre/4HA/Olg== X-Google-Smtp-Source: APXvYqwNpsVSpllqMOsBw0KVEfj6ixi9vpK94YoxKUCK8BvVN+K2rt+0zmH9iLuSgofxUQodtrJbFA== X-Received: by 2002:a17:902:9a42:: with SMTP id x2mr15707448plv.194.1578079747357; Fri, 03 Jan 2020 11:29:07 -0800 (PST) Received: from [2620:15c:17:3:3a5:23a7:5e32:4598] ([2620:15c:17:3:3a5:23a7:5e32:4598]) by smtp.gmail.com with ESMTPSA id u23sm68353574pfm.29.2020.01.03.11.29.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Jan 2020 11:29:06 -0800 (PST) Date: Fri, 3 Jan 2020 11:29:06 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Wei Yang cc: hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yang.shi@linux.alibaba.com Subject: Re: [RFC PATCH] mm: thp: grab the lock before manipulation defer list In-Reply-To: <20200103143407.1089-1-richardw.yang@linux.intel.com> Message-ID: References: <20200103143407.1089-1-richardw.yang@linux.intel.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 3 Jan 2020, Wei Yang wrote: > As all the other places, we grab the lock before manipulate the defer list. > Current implementation may face a race condition. > > Fixes: 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware") > > Signed-off-by: Wei Yang > > --- > I notice the difference during code reading and just confused about the > difference. No specific test is done since limited knowledge about cgroup. > > Maybe I miss something important? The check for !list_empty(page_deferred_list(page)) must certainly be serialized with doing list_del_init(page_deferred_list(page)). > --- > mm/memcontrol.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index bc01423277c5..62b7ec34ef1a 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -5368,12 +5368,12 @@ static int mem_cgroup_move_account(struct page *page, > } > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > + spin_lock(&from->deferred_split_queue.split_queue_lock); > if (compound && !list_empty(page_deferred_list(page))) { > - spin_lock(&from->deferred_split_queue.split_queue_lock); > list_del_init(page_deferred_list(page)); > from->deferred_split_queue.split_queue_len--; > - spin_unlock(&from->deferred_split_queue.split_queue_lock); > } > + spin_unlock(&from->deferred_split_queue.split_queue_lock); > #endif > /* > * It is safe to change page->mem_cgroup here because the page > @@ -5385,13 +5385,13 @@ static int mem_cgroup_move_account(struct page *page, > page->mem_cgroup = to; > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > + spin_lock(&to->deferred_split_queue.split_queue_lock); > if (compound && list_empty(page_deferred_list(page))) { > - 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++; > - spin_unlock(&to->deferred_split_queue.split_queue_lock); > } > + spin_unlock(&to->deferred_split_queue.split_queue_lock); > #endif > > spin_unlock_irqrestore(&from->move_lock, flags); > -- > 2.17.1 > > > From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Rientjes Subject: Re: [RFC PATCH] mm: thp: grab the lock before manipulation defer list Date: Fri, 3 Jan 2020 11:29:06 -0800 (PST) Message-ID: References: <20200103143407.1089-1-richardw.yang@linux.intel.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version; bh=xiCyHmcnUXsbcQ7aHolyREhLRtQlcm0tNcQpv0xj54g=; b=otHt/I+pw8YEKdneORJaQbqVOMxTvFzuxsTLLo7ZOfnkm7+sA/s/x+b5ZiwnwdyNsM mfRl/YbfDdxHzR2Rfe0dAizN3JrCsQ76Os4SjYyo9S1ECVmqUOML8K8S/YBi5lHfUumH I5sRO4W4LYYWzpp+g2tfXYM8x+1i2fRx+TVLGkGcDO7rAoq4BzN5giqoCdnq10C+hw+o NVmD4trJFm7qSbm58YTvtBPmdSOVfFH9OlPvaUYGTkLBuR4W1QJa14C5GlU267SLGDIk nJvj1z52hjwCB/qZkkakQbkJqE7ovBP/lPjUGrjm7HuF9J8UTNwBPO9jMGL9+KBvpBx7 97Og== In-Reply-To: <20200103143407.1089-1-richardw.yang@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Wei Yang Cc: hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yang.shi@linux.alibaba.com On Fri, 3 Jan 2020, Wei Yang wrote: > As all the other places, we grab the lock before manipulate the defer list. > Current implementation may face a race condition. > > Fixes: 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware") > > Signed-off-by: Wei Yang > > --- > I notice the difference during code reading and just confused about the > difference. No specific test is done since limited knowledge about cgroup. > > Maybe I miss something important? The check for !list_empty(page_deferred_list(page)) must certainly be serialized with doing list_del_init(page_deferred_list(page)). > --- > mm/memcontrol.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index bc01423277c5..62b7ec34ef1a 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -5368,12 +5368,12 @@ static int mem_cgroup_move_account(struct page *page, > } > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > + spin_lock(&from->deferred_split_queue.split_queue_lock); > if (compound && !list_empty(page_deferred_list(page))) { > - spin_lock(&from->deferred_split_queue.split_queue_lock); > list_del_init(page_deferred_list(page)); > from->deferred_split_queue.split_queue_len--; > - spin_unlock(&from->deferred_split_queue.split_queue_lock); > } > + spin_unlock(&from->deferred_split_queue.split_queue_lock); > #endif > /* > * It is safe to change page->mem_cgroup here because the page > @@ -5385,13 +5385,13 @@ static int mem_cgroup_move_account(struct page *page, > page->mem_cgroup = to; > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > + spin_lock(&to->deferred_split_queue.split_queue_lock); > if (compound && list_empty(page_deferred_list(page))) { > - 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++; > - spin_unlock(&to->deferred_split_queue.split_queue_lock); > } > + spin_unlock(&to->deferred_split_queue.split_queue_lock); > #endif > > spin_unlock_irqrestore(&from->move_lock, flags); > -- > 2.17.1 > > >