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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 A9A91C34024 for ; Mon, 17 Feb 2020 14:13:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 82794207FD for ; Mon, 17 Feb 2020 14:13:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581948785; bh=tzmWG3PhUjeDzHof24wrlf3ktGXFc/qnRB+HPP6zDzQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=z/J9mmEmFQgwwujJme6aYP6yd4Xw5RFJIkzmuASGv1sUJPvxZM9+V7QIOwGCLXQgx VePNqVhdnT3zVmJno9Po3PysWI42KLM29Cr+1tsYM/GnyDP60K4iePtmi17Xed5TiT KA7vlF2Yb+aQgvGFF0+CLObmRCRd9O+KkFdyho/s= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728964AbgBQONE (ORCPT ); Mon, 17 Feb 2020 09:13:04 -0500 Received: from mail.kernel.org ([198.145.29.99]:46912 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727898AbgBQONE (ORCPT ); Mon, 17 Feb 2020 09:13:04 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DE8662072C; Mon, 17 Feb 2020 14:13:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581948783; bh=tzmWG3PhUjeDzHof24wrlf3ktGXFc/qnRB+HPP6zDzQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=n8xy5FFXPKvAA+8yxLT/UrT0uiW5UfKJEF74D7pGUMoT9DoUdTUlk1zH8kjNRU03o imIMdUlsgP2/47AF+orn+EQoIIIATwGoh8PuzUmSqD9goD8whK2eQ83sYN7axaWAi8 hVTqX2PjmWmf2+Ax/tr1a2pYWKxnVHHdlQ0ErLDc= Date: Mon, 17 Feb 2020 15:13:01 +0100 From: Greg KH To: Zhihao Cheng Cc: richard@nod.at, sashal@kernel.org, yi.zhang@huawei.com, linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, Stable@vger.kernel.org Subject: Re: [PATCH 4.4] ubifs: Fix deadlock in concurrent bulk-read and writepage Message-ID: <20200217141301.GA1096821@kroah.com> References: <1581942239-112920-1-git-send-email-chengzhihao1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1581942239-112920-1-git-send-email-chengzhihao1@huawei.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 17, 2020 at 08:23:59PM +0800, Zhihao Cheng wrote: > [ Upstream commit f5de5b83303e61b1f3fb09bd77ce3ac2d7a475f2 ] > > 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) > Cc: > Fixes: 4793e7c5e1c ("UBIFS: add bulk-read facility") > Link: https://bugzilla.kernel.org/show_bug.cgi?id=206153 > Signed-off-by: Richard Weinberger > --- > fs/ubifs/file.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c > index b895af7d8d80..e6d0a7df341d 100644 > --- a/fs/ubifs/file.c > +++ b/fs/ubifs/file.c > @@ -782,8 +782,9 @@ static int ubifs_do_bulk_read(struct ubifs_info *c, struct bu_info *bu, > > 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)) > -- > 2.7.4 > Now applied, thanks! greg k-h