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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 57457C4360F for ; Thu, 4 Apr 2019 10:18:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2F12A20882 for ; Thu, 4 Apr 2019 10:18:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729290AbfDDKS3 (ORCPT ); Thu, 4 Apr 2019 06:18:29 -0400 Received: from mx2.suse.de ([195.135.220.15]:60948 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726694AbfDDKS2 (ORCPT ); Thu, 4 Apr 2019 06:18:28 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id B74CDAF1F; Thu, 4 Apr 2019 10:18:27 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id ED42C1E11C8; Thu, 4 Apr 2019 12:18:23 +0200 (CEST) Date: Thu, 4 Apr 2019 12:18:23 +0200 From: Jan Kara To: "zhangyi (F)" Cc: linux-ext4@vger.kernel.org, tytso@mit.edu, jack@suse.cz, adilger.kernel@dilger.ca, miaoxie@huawei.com Subject: Re: [PATCH] ext4: add inode to ordered data list when extending file without block allocation Message-ID: <20190404101823.GA22313@quack2.suse.cz> References: <1554370192-113254-1-git-send-email-yi.zhang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1554370192-113254-1-git-send-email-yi.zhang@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Thu 04-04-19 17:29:52, zhangyi (F) wrote: > Currently we capture a NULL data exposure problem after a crash or > poweroff when append writing a file in the data=ordered mode. The > problem is that we were not add inode to the transaction's order data > list when updating i_disksize without new block allocation no matter > the delay allocated block feature is enabled or not. > > write jbd2 writeback > append write in allocated block > mark buffer dirty > update i_disksize > mark inode dirty > commit transaction > write inode > (data exposure after a crash) > write dirty buffer > > It's fine in the case of new block allocation because we do this job in > ext4_map_blocks(). To fix this problem, this patch add inode to current > transaction's order data list after new data is copied and needing > update i_disksize in the case of no block allocation. > > Fixes: 06bd3c36a733ac ("ext4: fix data exposure after a crash") > Fixes: f3b59291a69d0b ("ext4: remove calls to ext4_jbd2_file_inode() from delalloc write path") > Signed-off-by: zhangyi (F) Thanks for the patch. The current behavior is a deliberate decision. data=ordered mode does guarantee there is no stale data visible in case of crash. However it does not guarantee you cannot see zeros where data was written. Honza > --- > fs/ext4/inode.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index b32a57b..5cfa066 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -1419,6 +1419,16 @@ static int ext4_write_end(struct file *file, > if (i_size_changed || inline_data) > ext4_mark_inode_dirty(handle, inode); > > + /* > + * Updating i_disksize when extending file without block > + * allocation, the newly written data where should be visible > + * after transaction commit must be on transaction's ordered > + * data list. > + */ > + if (copied && (i_size_changed & 0x2) && > + ext4_should_order_data(inode)) > + ext4_jbd2_inode_add_write(handle, inode); > + > if (pos + len > inode->i_size && ext4_can_truncate(inode)) > /* if we have allocated more blocks and copied > * less. We will have blocks allocated outside > @@ -3185,6 +3195,15 @@ static int ext4_da_write_end(struct file *file, > * bu greater than i_disksize.(hint delalloc) > */ > ext4_mark_inode_dirty(handle, inode); > + > + /* > + * Updating i_disksize when extending file without > + * block allocation, the newly written data where > + * should be visible after transaction commit must > + * be on transaction's ordered data list. > + */ > + if (ext4_should_order_data(inode)) > + ext4_jbd2_inode_add_write(handle, inode); > } > } > > -- > 2.7.4 > -- Jan Kara SUSE Labs, CR