From patchwork Tue Dec 19 09:00:12 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 10122771 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id B8AF4603B5 for ; Tue, 19 Dec 2017 09:02:51 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id AC435283BD for ; Tue, 19 Dec 2017 09:02:51 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A0F2828685; Tue, 19 Dec 2017 09:02:51 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 28D8F283BD for ; Tue, 19 Dec 2017 09:02:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966830AbdLSJAS (ORCPT ); Tue, 19 Dec 2017 04:00:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40622 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965041AbdLSJAO (ORCPT ); Tue, 19 Dec 2017 04:00:14 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AF322C0AD1E2; Tue, 19 Dec 2017 09:00:14 +0000 (UTC) Received: from warthog.procyon.org.uk.com (ovpn-120-161.rdu2.redhat.com [10.10.120.161]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1701F1915E; Tue, 19 Dec 2017 09:00:12 +0000 (UTC) From: David Howells To: torvalds@linux-foundation.org Cc: dhowells@redhat.com, linux-afs@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] fscache: Fix the default for fscache_maybe_release_page() Date: Tue, 19 Dec 2017 09:00:12 +0000 Message-Id: <151367401217.25136.187680479747634726.stgit@warthog.procyon.org.uk> Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Tue, 19 Dec 2017 09:00:14 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Fix the default for fscache_maybe_release_page() for when the cookie isn't valid or the page isn't cached. It mustn't return false as that indicates the page cannot yet be freed. The problem with the default is that if, say, there's no cache, but a network filesystem's pages are using up almost all the available memory, a system can OOM because the filesystem ->releasepage() op will not allow them to be released as fscache_maybe_release_page() incorrectly prevents it. This can be tested by writing a sequence of 512MiB files to an AFS mount. It does not affect NFS or CIFS because both of those wrap the call in a check of PG_fscache and it shouldn't bother Ceph as that only has PG_private set whilst writeback is in progress. This might be an issue for 9P, however. Note that the pages aren't entirely stuck. Removing a file or unmounting will clear things because that uses ->invalidatepage() instead. Fixes: 201a15428bd5 ("FS-Cache: Handle pages pending storage that get evicted under OOM conditions") Reported-by: Marc Dionne Signed-off-by: David Howells Reviewed-by: Jeff Layton Acked-by: Al Viro cc: stable@vger.kernel.org # 2.6.32+ --- include/linux/fscache.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/fscache.h b/include/linux/fscache.h index f4ff47d4a893..fe0c349684fa 100644 --- a/include/linux/fscache.h +++ b/include/linux/fscache.h @@ -755,7 +755,7 @@ bool fscache_maybe_release_page(struct fscache_cookie *cookie, { if (fscache_cookie_valid(cookie) && PageFsCache(page)) return __fscache_maybe_release_page(cookie, page, gfp); - return false; + return true; } /**