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=-2.2 required=3.0 tests=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 B94E7C2BA19 for ; Sat, 11 Apr 2020 22:28:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 87AE720787 for ; Sat, 11 Apr 2020 22:28:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726812AbgDKW2e (ORCPT ); Sat, 11 Apr 2020 18:28:34 -0400 Received: from mail104.syd.optusnet.com.au ([211.29.132.246]:39485 "EHLO mail104.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726167AbgDKW2e (ORCPT ); Sat, 11 Apr 2020 18:28:34 -0400 Received: from dread.disaster.area (pa49-180-167-53.pa.nsw.optusnet.com.au [49.180.167.53]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id B113558B984; Sun, 12 Apr 2020 08:28:30 +1000 (AEST) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1jNOc1-0005AG-Az; Sun, 12 Apr 2020 08:28:29 +1000 Date: Sun, 12 Apr 2020 08:28:29 +1000 From: Dave Chinner To: Konstantin Khlebnikov Cc: linux-fsdevel@vger.kernel.org, Miklos Szeredi , linux-kernel@vger.kernel.org, Alexander Viro , linux-unionfs@vger.kernel.org, Dmitry Monakhov Subject: Re: [PATCH] ovl: skip overlayfs superblocks at global sync Message-ID: <20200411222829.GO10737@dread.disaster.area> References: <158642098777.5635.10501704178160375549.stgit@buzz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <158642098777.5635.10501704178160375549.stgit@buzz> User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.3 cv=W5xGqiek c=1 sm=1 tr=0 a=2xmR08VVv0jSFCMMkhec0Q==:117 a=2xmR08VVv0jSFCMMkhec0Q==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=cl8xLZFz6L8A:10 a=7-415B0cAAAA:8 a=haEqjSr0uQTM00mUMRMA:9 a=CjuIK1q_8ugA:10 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 09, 2020 at 11:29:47AM +0300, Konstantin Khlebnikov wrote: > Stacked filesystems like overlayfs has no own writeback, but they have to > forward syncfs() requests to backend for keeping data integrity. > > During global sync() each overlayfs instance calls method ->sync_fs() > for backend although it itself is in global list of superblocks too. > As a result one syscall sync() could write one superblock several times > and send multiple disk barriers. > > This patch adds flag SB_I_SKIP_SYNC into sb->sb_iflags to avoid that. Why wouldn't you just remove the ->sync_fs method from overlay? I mean, if you don't need the filesystem to do anything special for one specific data integrity sync_fs call, you don't need it for any of them, yes? -Dave. -- Dave Chinner david@fromorbit.com