From patchwork Tue Dec 15 20:33:42 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 11975727 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 18EAAC4361B for ; Tue, 15 Dec 2020 20:33:47 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C73D222CAE for ; Tue, 15 Dec 2020 20:33:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C73D222CAE Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6072E6B0080; Tue, 15 Dec 2020 15:33:46 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 59FF36B0082; Tue, 15 Dec 2020 15:33:46 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 40A996B0081; Tue, 15 Dec 2020 15:33:46 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0170.hostedemail.com [216.40.44.170]) by kanga.kvack.org (Postfix) with ESMTP id 20C306B007E for ; Tue, 15 Dec 2020 15:33:46 -0500 (EST) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id E19208249980 for ; Tue, 15 Dec 2020 20:33:45 +0000 (UTC) X-FDA: 77596667610.13.spade31_1d17e6e27426 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin13.hostedemail.com (Postfix) with ESMTP id BC3AC18140B70 for ; Tue, 15 Dec 2020 20:33:45 +0000 (UTC) X-HE-Tag: spade31_1d17e6e27426 X-Filterd-Recvd-Size: 5882 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf19.hostedemail.com (Postfix) with ESMTP for ; Tue, 15 Dec 2020 20:33:45 +0000 (UTC) Date: Tue, 15 Dec 2020 12:33:42 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1608064424; bh=nBG3JTxx41P3NkdiTpJL/2E1ZKUvgP0xDWYDNugdXGA=; h=From:To:Subject:In-Reply-To:From; b=ML92VQmQxblPj/4XWaGMQaZmAjB8Mi9TmjcHTftEIgcQNaIXYmc+tKJUUlTa2q26Y xfKMBW9g4gAyhSv/QPZj1BDlgErNC0gawSaJyWWAR4Xk63BW1iz09SXgtiqRT1zEdP dkNmw20YpDI0GWydwpVwvn4zsajlKB0pFI6ChGB0= From: Andrew Morton To: aarcange@redhat.com, akpm@linux-foundation.org, alex.shi@linux.alibaba.com, alexander.duyck@gmail.com, aryabinin@virtuozzo.com, daniel.m.jordan@oracle.com, hannes@cmpxchg.org, hughd@google.com, iamjoonsoo.kim@lge.com, jannh@google.com, khlebnikov@yandex-team.ru, kirill.shutemov@linux.intel.com, kirill@shutemov.name, linux-mm@kvack.org, mgorman@techsingularity.net, mhocko@kernel.org, mhocko@suse.com, mika.penttila@nextfour.com, minchan@kernel.org, mm-commits@vger.kernel.org, richard.weiyang@gmail.com, rong.a.chen@intel.com, shakeelb@google.com, tglx@linutronix.de, tj@kernel.org, torvalds@linux-foundation.org, vbabka@suse.cz, vdavydov.dev@gmail.com, willy@infradead.org, yang.shi@linux.alibaba.com, ying.huang@intel.com Subject: [patch 06/19] mm/rmap: stop store reordering issue on page->mapping Message-ID: <20201215203342.X_2LUvA2i%akpm@linux-foundation.org> In-Reply-To: <20201215123253.954eca9a5ef4c0d52fd381fa@linux-foundation.org> User-Agent: s-nail v14.8.16 MIME-Version: 1.0 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: From: Alex Shi Subject: mm/rmap: stop store reordering issue on page->mapping Hugh Dickins and Minchan Kim observed a long time issue which discussed here, but actully the mentioned fix missed. https://lore.kernel.org/lkml/20150504031722.GA2768@blaptop/ The store reordering may cause problem in the scenario: CPU 0 CPU1 do_anonymous_page page_add_new_anon_rmap() page->mapping = anon_vma + PAGE_MAPPING_ANON lru_cache_add_inactive_or_unevictable() spin_lock(lruvec->lock) SetPageLRU() spin_unlock(lruvec->lock) /* idletacking judged it as LRU * page so pass the page in * page_idle_clear_pte_refs */ page_idle_clear_pte_refs rmap_walk if PageAnon(page) Johannes give detailed examples how the store reordering could cause a trouble: "The concern is the SetPageLRU may get reorder before 'page->mapping' setting, That would make CPU 1 will observe at page->mapping after observing PageLRU set on the page. 1. anon_vma + PAGE_MAPPING_ANON That's the in-order scenario and is fine. 2. NULL That's possible if the page->mapping store gets reordered to occur after SetPageLRU. That's fine too because we check for it. 3. anon_vma without the PAGE_MAPPING_ANON bit That would be a problem and could lead to all kinds of undesirable behavior including crashes and data corruption. Is it possible? AFAICT the compiler is allowed to tear the store to page->mapping and I don't see anything that would prevent it. That said, I also don't see how the reader testing PageLRU under the lru_lock would prevent that in the first place. AFAICT we need that WRITE_ONCE() around the page->mapping assignment." [alex.shi@linux.alibaba.com: updated for comments change from Johannes] Link: https://lkml.kernel.org/r/e66ef2e5-c74c-6498-e8b3-56c37b9d2d15@linux.alibaba.com Link: https://lkml.kernel.org/r/1604566549-62481-7-git-send-email-alex.shi@linux.alibaba.com Signed-off-by: Alex Shi Acked-by: Johannes Weiner Acked-by: Hugh Dickins Cc: Matthew Wilcox Cc: Minchan Kim Cc: Vladimir Davydov Cc: Alexander Duyck Cc: Andrea Arcangeli Cc: Andrey Ryabinin Cc: "Chen, Rong A" Cc: Daniel Jordan Cc: "Huang, Ying" Cc: Jann Horn Cc: Joonsoo Kim Cc: Kirill A. Shutemov Cc: Kirill A. Shutemov Cc: Konstantin Khlebnikov Cc: Mel Gorman Cc: Michal Hocko Cc: Michal Hocko Cc: Mika Penttilä Cc: Shakeel Butt Cc: Tejun Heo Cc: Thomas Gleixner Cc: Vlastimil Babka Cc: Wei Yang Cc: Yang Shi Signed-off-by: Andrew Morton --- mm/rmap.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/mm/rmap.c~mm-rmap-stop-store-reordering-issue-on-page-mapping +++ a/mm/rmap.c @@ -1054,8 +1054,14 @@ static void __page_set_anon_rmap(struct if (!exclusive) anon_vma = anon_vma->root; + /* + * page_idle does a lockless/optimistic rmap scan on page->mapping. + * Make sure the compiler doesn't split the stores of anon_vma and + * the PAGE_MAPPING_ANON type identifier, otherwise the rmap code + * could mistake the mapping for a struct address_space and crash. + */ anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; - page->mapping = (struct address_space *) anon_vma; + WRITE_ONCE(page->mapping, (struct address_space *) anon_vma); page->index = linear_page_index(vma, address); }