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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 08D59C433DF for ; Wed, 20 May 2020 14:25:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DB6AF205CB for ; Wed, 20 May 2020 14:25:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728392AbgETOZx (ORCPT ); Wed, 20 May 2020 10:25:53 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:32994 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727000AbgETOW1 (ORCPT ); Wed, 20 May 2020 10:22:27 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1jbPbv-00035i-RX; Wed, 20 May 2020 15:22:19 +0100 Received: from ben by deadeye with local (Exim 4.93) (envelope-from ) id 1jbPbv-007DS7-Ml; Wed, 20 May 2020 15:22:19 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Zhihao Cheng" , "zhangyi (F)" , "Richard Weinberger" Date: Wed, 20 May 2020 15:14:21 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 53/99] ubifs: Fix deadlock in concurrent bulk-read and writepage In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.84-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Zhihao Cheng commit f5de5b83303e61b1f3fb09bd77ce3ac2d7a475f2 upstream. In ubifs, concurrent execution of writepage and bulk read on the same file may cause ABBA deadlock, for example (Reproduce method see Link): Process A(Bulk-read starts from page4) Process B(write page4 back) vfs_read wb_workfn or fsync ... ... generic_file_buffered_read write_cache_pages ubifs_readpage LOCK(page4) ubifs_bulk_read ubifs_writepage LOCK(ui->ui_mutex) ubifs_write_inode ubifs_do_bulk_read LOCK(ui->ui_mutex) find_or_create_page(alloc page4) ↑ LOCK(page4) <-- ABBA deadlock occurs! In order to ensure the serialization execution of bulk read, we can't remove the big lock 'ui->ui_mutex' in ubifs_bulk_read(). Instead, we allow ubifs_do_bulk_read() to lock page failed by replacing find_or_create_page(FGP_LOCK) with pagecache_get_page(FGP_LOCK | FGP_NOWAIT). Signed-off-by: Zhihao Cheng Suggested-by: zhangyi (F) Fixes: 4793e7c5e1c ("UBIFS: add bulk-read facility") Link: https://bugzilla.kernel.org/show_bug.cgi?id=206153 Signed-off-by: Richard Weinberger [bwh: Backported to 3.16: Keep using constant GFP flags parameter.] Signed-off-by: Ben Hutchings --- fs/ubifs/file.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/fs/ubifs/file.c +++ b/fs/ubifs/file.c @@ -782,8 +782,9 @@ static int ubifs_do_bulk_read(struct ubi if (page_offset > end_index) break; - page = find_or_create_page(mapping, page_offset, - GFP_NOFS | __GFP_COLD); + page = pagecache_get_page(mapping, page_offset, + FGP_LOCK|FGP_ACCESSED|FGP_CREAT|FGP_NOWAIT, + GFP_NOFS | __GFP_COLD); if (!page) break; if (!PageUptodate(page))