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=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 7D28ECA9EB9 for ; Wed, 23 Oct 2019 02:35:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 53BE121848 for ; Wed, 23 Oct 2019 02:35:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=mbobrowski-org.20150623.gappssmtp.com header.i=@mbobrowski-org.20150623.gappssmtp.com header.b="T9W+tN14" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388966AbfJWCf2 (ORCPT ); Tue, 22 Oct 2019 22:35:28 -0400 Received: from mail-pf1-f195.google.com ([209.85.210.195]:38822 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733183AbfJWCf1 (ORCPT ); Tue, 22 Oct 2019 22:35:27 -0400 Received: by mail-pf1-f195.google.com with SMTP id c13so699078pfp.5 for ; Tue, 22 Oct 2019 19:35:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mbobrowski-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=Hn8L3oufJuO1A6sNs5ADzt9tjxwA8pxlkCKXiS57bAM=; b=T9W+tN14oYrXYM4Wve7v7M4yAYnFKzjT6mNxo7aM+IsPxMNEYQMzoe0JwOvQqik5BL GPGQOsJ9NuZXOC3x73WNHtr/9ubotCB4cjMbAYG6a2Uf0KRlsVrgOLux5bzWhil9tt3N RdneeIbutQqNBIyBS9JWAF4zsRoLQwuSVSt1Btnti65jn0cX0s+N81+kqnnOKFas6h4b 7QDff7Rfy+MHffN+sZVjlRCM8ACrOKZTjai2VrsRv3FPzAwmDE710HsHaWa/yIZb4akY AFEqbv/4ns3eZ34S/Q5UJE65tQOEBzqGWt/1M3b/uBXy0CjV+nP5y8HbLarSSBQkRM6g 9k2Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=Hn8L3oufJuO1A6sNs5ADzt9tjxwA8pxlkCKXiS57bAM=; b=r+k0J2RjW3yBvoH7ThS9HLftme699SJt2kq8rmvDF0Ri7iVzkXZq5GdIbQrCUQMlSi axjDWmO9bs/2/x/iqtmftzV7xZ9zQDB70mGYQo++dNycyOSWBecT1AW9Thnv4Xl8SuHo znn6Afcx2FADR/n9k/AwSRa5P+1Jy7/sYmrfihEid3uMsmfnSGjfgwIVUDoBgLJMovfC E0zEjceBRhPI3Vc9T2RNEQUu9L/vuqlzbolGP8earScNwUK9qNfIO+FXrtFfk2H6GNl5 Bc+zLkzBynafeMV8NEevWuT2Gb/qgG8FjUwzrbw2wglwtL88dT7+C5tmeWcAXFrZQE1M OqKw== X-Gm-Message-State: APjAAAW7XUXeJo8P/BHDNLFRHNXL4T9gyKs7DYJ9UDN/bE3HybqiuTu2 Dv2LwG5dgXFy7kZsqFuaiumQ X-Google-Smtp-Source: APXvYqxP3lixxl949FFKhXtjPG6Mp4r8GAkhkrIx1SnKHRsGq4Eq9YXZ9Y1zUEwQQDyRpBDL1BHYfg== X-Received: by 2002:aa7:980c:: with SMTP id e12mr6404347pfl.165.1571798126573; Tue, 22 Oct 2019 19:35:26 -0700 (PDT) Received: from bobrowski ([110.232.114.101]) by smtp.gmail.com with ESMTPSA id s90sm6037643pjc.2.2019.10.22.19.35.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Oct 2019 19:35:25 -0700 (PDT) Date: Wed, 23 Oct 2019 13:35:19 +1100 From: Matthew Bobrowski To: Jan Kara Cc: "Theodore Y. Ts'o" , adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, hch@infradead.org, david@fromorbit.com, darrick.wong@oracle.com Subject: Re: [PATCH v5 00/12] ext4: port direct I/O to iomap infrastructure Message-ID: <20191023023519.GA16505@bobrowski> References: <20191021133111.GA4675@mit.edu> <20191021194330.GJ25184@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191021194330.GJ25184@quack2.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Oct 21, 2019 at 09:43:30PM +0200, Jan Kara wrote: > On Mon 21-10-19 09:31:12, Theodore Y. Ts'o wrote: > > Hi Matthew, thanks for your work on this patch series! > > > > I applied it against 4c3, and ran a quick test run on it, and found > > the following locking problem. To reproduce: > > > > kvm-xfstests -c nojournal generic/113 > > > > generic/113 [09:27:19][ 5.841937] run fstests generic/113 at 2019-10-21 09:27:19 > > [ 7.959477] > > [ 7.959798] ============================================ > > [ 7.960518] WARNING: possible recursive locking detected > > [ 7.961225] 5.4.0-rc3-xfstests-00012-g7fe6ea084e48 #1238 Not tainted > > [ 7.961991] -------------------------------------------- > > [ 7.962569] aio-stress/1516 is trying to acquire lock: > > [ 7.963129] ffff9fd4791148c8 (&sb->s_type->i_mutex_key#12){++++}, at: __generic_file_fsync+0x3e/0xb0 > > [ 7.964109] > > [ 7.964109] but task is already holding lock: > > [ 7.964740] ffff9fd4791148c8 (&sb->s_type->i_mutex_key#12){++++}, at: ext4_dio_write_iter+0x15b/0x430 > > This is going to be a tricky one. With iomap, the inode locking is handled > by the filesystem while calling generic_write_sync() is done by > iomap_dio_rw(). I would really prefer to avoid tweaking iomap_dio_rw() not > to call generic_write_sync(). So we need to remove inode_lock from > __generic_file_fsync() (used from ext4_sync_file()). This locking is mostly > for legacy purposes and we don't need this in ext4 AFAICT - but removing > the lock from __generic_file_fsync() would mean auditing all legacy > filesystems that use this to make sure flushing inode & its metadata buffer > list while it is possibly changing cannot result in something unexpected. I > don't want to clutter this series with it so we are left with > reimplementing __generic_file_fsync() inside ext4 without inode_lock. Not > too bad but not great either. Thoughts? So, I just looked at this on my lunch break and I think the simplest approach would be to just transfer the necessary chunks of code from within __generic_file_fsync() into ext4_sync_file() for !journal cases, minus the inode lock, and minus calling into __generic_file_fsync(). I don't forsee this causing any issues, but feel free to correct me if I'm wrong. If this is deemed to be OK, then I will go ahead and include this as a separate patch in my series. ----