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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 22950C33CB1 for ; Wed, 15 Jan 2020 14:56:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EC7B22084D for ; Wed, 15 Jan 2020 14:56:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="MULYh9qQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729125AbgAOO4u (ORCPT ); Wed, 15 Jan 2020 09:56:50 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:60024 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729015AbgAOO4t (ORCPT ); Wed, 15 Jan 2020 09:56:49 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=ueg3OFT4kDDVnrKmNSjzXklCJQ8E0kesClJTnzAK4Hw=; b=MULYh9qQhPZifhFoRWQQ4MEro 40Hq2YrEYrRHHXRHThQgih82mfaN4X/wJ5eee8qJSBPxdNnDWmKqYKOLBPwuYQAKjidtNplUL0hWb G6m9o3yZSQrT/uIdSWC/nt2Dp920J4ItjGKZEa0a1rySLUNACa2JYLslwfxzIQL6SJNyP6BhpcpXb eZ9p6LwD8iWXOjqcKihqE5iy6m5aTaxAPydLiCylgeAE0F4QNad5HCd7/wwjxQ74dXoqJEwazhiKK KOnLa05rzfKIJjcRQ0SDiCewj6A5Iwqvm6jwbRUdRvbN5YooPekV+mYCgh5ZD+5NkidMwyh7uUVFt CI8Rkp3lw==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1irk6B-00049E-3F; Wed, 15 Jan 2020 14:56:47 +0000 Date: Wed, 15 Jan 2020 06:56:47 -0800 From: Christoph Hellwig To: Jan Kara Cc: Christoph Hellwig , "Darrick J. Wong" , Ritesh Harjani , linux-ext4@vger.kernel.org, tytso@mit.edu Subject: Re: [RFC 1/2] iomap: direct-io: Move inode_dio_begin before filemap_write_and_wait_range Message-ID: <20200115145647.GA8791@infradead.org> References: <27607a16327fe9664f32d09abe565af0d1ae56c9.1578907891.git.riteshh@linux.ibm.com> <20200113215159.GA8235@magnolia> <20200114090507.GA6466@quack2.suse.cz> <20200114163818.GB7127@infradead.org> <20200115091925.GC31450@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200115091925.GC31450@quack2.suse.cz> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Wed, Jan 15, 2020 at 10:19:25AM +0100, Jan Kara wrote: > On Tue 14-01-20 08:38:18, Christoph Hellwig wrote: > > On Tue, Jan 14, 2020 at 10:05:07AM +0100, Jan Kara wrote: > > > > > > Well, XFS always performs buffered writeback using unwritten extents so at > > > least the immediate problem of stale data exposure ext4 has does not happen > > > there AFAICT. > > > > Currently XFS never uses unwritten extents when converting delalloc > > extents. > > I see, it is a long time since I last looked at that part of XFS code. So > then I think XFS might be prone to the same kind of race and data exposure > as I outlined in [1]... I think not using unwritten extents for filling holes inside i_size will always lead to the potential for stale data exposure in one form or another. Because of that Darrick has started looking into always using unwritten extents for buffered writes inside i_size.