From patchwork Thu May 28 00:20:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Jerome Glisse X-Patchwork-Id: 11574083 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 49285912 for ; Thu, 28 May 2020 00:23:13 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 013C5208C3 for ; Thu, 28 May 2020 00:23:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ZqFXG1rf"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="DtC9ez39" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 013C5208C3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: Content-Transfer-Encoding:Content-Type:MIME-Version:Message-ID:Subject:To: From:Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=MoDp61WoGDoXfGN1naQOJpCHxFS5LyHnwfZXqb9FRjY=; b=ZqFXG1rf2lgvxS nGKsdhrN7BekbqgjhpgkODIv5O+DaI2+XRDcn90P4wwdm0ZL2kJQXLt4V7Gi7rf/MWAhVoppyE9MX CrkY3670GoOj6jN9IBbXSgz9Th3JxshPQAZ2Me+lg8SaiONpHS7ljrkIqfaxBCJ48K5mZDoOMHmSZ ndpIh9x67x364EUpFb2rm4pauw/iBwG4xfsRnulDLOA34jfBsSnficOWrCdhFwJCEL8O0RoHVtNPj ZACY04z0EWND196+fr0oZq7sbyPxfQuyuRj6I/oK7Lim6KsPy2zLBp6vFqCuUQmvuJ22du1zvYRar Y2bcj1KMYWOw2peJ5H8A==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1je6KC-0005yc-KF; Thu, 28 May 2020 00:23:08 +0000 Received: from us-smtp-1.mimecast.com ([207.211.31.81] helo=us-smtp-delivery-1.mimecast.com) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1je6K8-0005xe-S7 for linux-arm-kernel@lists.infradead.org; Thu, 28 May 2020 00:23:06 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590625381; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=3NfM/YRWw8tWtCVntluiCugDqJX5J7Mi6y5RyulO5Co=; b=DtC9ez39MIRaRkHUY0UQA794jqsVcW7kxaLCrUXsPs86TOSWcskoUyvPOReoQ1k0mSvVmD ry6D6mQI2T7LNNrBUJb0bRds9FkyQblbQnkLWiyAMEGgsntgY2fswh0QnuVjRNAOas+R1V UEGCsiRCAmPlilvPMbbf5dqx11PEoVA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-262--4PlExgtPwKJVseeIiuy9A-1; Wed, 27 May 2020 20:20:44 -0400 X-MC-Unique: -4PlExgtPwKJVseeIiuy9A-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D96EC460; Thu, 28 May 2020 00:20:40 +0000 (UTC) Received: from redhat.com (ovpn-119-19.rdu2.redhat.com [10.10.119.19]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2FCE85D9CC; Thu, 28 May 2020 00:20:35 +0000 (UTC) Date: Wed, 27 May 2020 20:20:33 -0400 From: Jerome Glisse To: linux-mm@kvack.org, Andrew Morton , Huang Ying Subject: Cache flush issue with page_mapping_file() and swap back shmem page ? Message-ID: <20200528002033.GB1992500@redhat.com> MIME-Version: 1.0 Content-Disposition: inline X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200527_172305_115518_36BD1A71 X-CRM114-Status: GOOD ( 17.41 ) X-Spam-Score: -0.2 (/) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.infradead.org summary: Content analysis details: (-0.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [207.211.31.81 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain 0.0 RCVD_IN_MSPIKE_H4 RBL: Very Good reputation (+4) [207.211.31.81 listed in wl.mailspike.net] 0.0 RCVD_IN_MSPIKE_WL Mailspike good senders -0.0 DKIMWL_WL_HIGH DKIMwl.org - Whitelisted High sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Rich Felker , linux-sh@vger.kernel.org, Catalin Marinas , linux-mips@vger.kernel.org, "James E.J. Bottomley" , linux-mm@kvack.org, Guo Ren , sparclinux@vger.kernel.org, Paul Burton , Helge Deller , James Hogan , rmk+kernel@arm.linux.org.uk, linux-xtensa@linux-xtensa.org, Steven Capper , Rabin Vincent , Ley Foon Tan , Guan Xuetao , linux-arm-kernel@lists.infradead.org, Chris Zankel , Yoshinori Sato , linux-parisc@vger.kernel.org, Max Filippov , linux-kernel@vger.kernel.org, Ralf Baechle , nios2-dev@lists.rocketboards.org, "David S. Miller" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org So any arch code which uses page_mapping_file() might get the wrong answer, this function will return NULL for a swap backed page which can be a shmem pages. But shmem pages can still be shared among multiple process (and possibly at different virtual addresses if mremap was use). Attached is a patch that changes page_mapping_file() to return the shmem mapping for swap backed shmem page. I have not tested it (no way for me to test all those architecture) and i spotted this while working on something else. So i hope someone can take a closer look. Cheers, Jérôme From 6c76b9f8baa87ff872f6be5a44805a74c1e07fea Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= Date: Wed, 27 May 2020 20:18:59 -0400 Subject: [PATCH] mm: fix cache flush for shmem page that are swap backed. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This might be a shmem page that is in a sense a file that can be mapped multiple times in different processes at possibly different virtual addresses (fork + mremap). So return the shmem mapping that will allow any arch code to find all mappings of the page. Note that even if page is not anonymous then the page might have a NULL page->mapping field if it is being truncated, but then it is fine as each pte poiting to the page will be remove and cache flushing should be handled properly by that part of the code. Signed-off-by: Jérôme Glisse Cc: "Huang, Ying" Cc: Michal Hocko Cc: Mel Gorman Cc: Russell King Cc: Andrew Morton Cc: Mike Rapoport Cc: "David S. Miller" Cc: "James E.J. Bottomley" --- mm/util.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/mm/util.c b/mm/util.c index 988d11e6c17c..ec8739ab0cc3 100644 --- a/mm/util.c +++ b/mm/util.c @@ -685,8 +685,24 @@ EXPORT_SYMBOL(page_mapping); */ struct address_space *page_mapping_file(struct page *page) { - if (unlikely(PageSwapCache(page))) + if (unlikely(PageSwapCache(page))) { + /* + * This might be a shmem page that is in a sense a file that + * can be mapped multiple times in different processes at + * possibly different virtual addresses (fork + mremap). So + * return the shmem mapping that will allow any arch code to + * find all mappings of the page. + * + * Note that even if page is not anonymous then the page might + * have a NULL page->mapping field if it is being truncated, + * but then it is fine as each pte poiting to the page will be + * remove and cache flushing should be handled properly by that + * part of the code. + */ + if (!PageAnon(page)) + return page->mapping; return NULL; + } return page_mapping(page); }