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_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 32847C433DF for ; Tue, 23 Jun 2020 02:37:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 15DF720720 for ; Tue, 23 Jun 2020 02:37:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731494AbgFWChN (ORCPT ); Mon, 22 Jun 2020 22:37:13 -0400 Received: from mail109.syd.optusnet.com.au ([211.29.132.80]:33400 "EHLO mail109.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731312AbgFWChN (ORCPT ); Mon, 22 Jun 2020 22:37:13 -0400 Received: from dread.disaster.area (pa49-180-124-177.pa.nsw.optusnet.com.au [49.180.124.177]) by mail109.syd.optusnet.com.au (Postfix) with ESMTPS id C6D4BD7C1AF; Tue, 23 Jun 2020 12:37:10 +1000 (AEST) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1jnYoA-0002E9-2X; Tue, 23 Jun 2020 12:37:10 +1000 Date: Tue, 23 Jun 2020 12:37:10 +1000 From: Dave Chinner To: "Darrick J. Wong" Cc: xfs Subject: Re: [PATCH] xfs: don't eat an EIO/ENOSPC writeback error when scrubbing data fork Message-ID: <20200623023710.GY2005@dread.disaster.area> References: <20200622171713.GG11245@magnolia> <20200622220839.GV2005@dread.disaster.area> <20200622232843.GA7625@magnolia> <20200622235800.GX2005@dread.disaster.area> <20200623010240.GB7625@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200623010240.GB7625@magnolia> User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.3 cv=QIgWuTDL c=1 sm=1 tr=0 a=k3aV/LVJup6ZGWgigO6cSA==:117 a=k3aV/LVJup6ZGWgigO6cSA==:17 a=kj9zAlcOel0A:10 a=nTHF0DUjJn0A:10 a=yPCof4ZbAAAA:8 a=7-415B0cAAAA:8 a=6GGPcQwYyyFdXKniBhcA:9 a=vulXiEgSq1gc1aws:21 a=a6F02cx2gL6fYFrv:21 a=CjuIK1q_8ugA:10 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Mon, Jun 22, 2020 at 06:02:40PM -0700, Darrick J. Wong wrote: > On Tue, Jun 23, 2020 at 09:58:00AM +1000, Dave Chinner wrote: > > On Mon, Jun 22, 2020 at 04:28:43PM -0700, Darrick J. Wong wrote: > > > On Tue, Jun 23, 2020 at 08:08:39AM +1000, Dave Chinner wrote: > > > > On Mon, Jun 22, 2020 at 10:17:13AM -0700, Darrick J. Wong wrote: > > > > > From: Darrick J. Wong > > > > > > > > > > The data fork scrubber calls filemap_write_and_wait to flush dirty pages > > > > > and delalloc reservations out to disk prior to checking the data fork's > > > > > extent mappings. Unfortunately, this means that scrub can consume the > > > > > EIO/ENOSPC errors that would otherwise have stayed around in the address > > > > > space until (we hope) the writer application calls fsync to persist data > > > > > and collect errors. The end result is that programs that wrote to a > > > > > file might never see the error code and proceed as if nothing were > > > > > wrong. > > > > > > > > > > xfs_scrub is not in a position to notify file writers about the > > > > > writeback failure, and it's only here to check metadata, not file > > > > > contents. Therefore, if writeback fails, we should stuff the error code > > > > > back into the address space so that an fsync by the writer application > > > > > can pick that up. > > > > > > > > > > Fixes: 99d9d8d05da2 ("xfs: scrub inode block mappings") > > > > > Signed-off-by: Darrick J. Wong > > > > > --- > > > > > fs/xfs/scrub/bmap.c | 10 +++++++++- > > > > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/fs/xfs/scrub/bmap.c b/fs/xfs/scrub/bmap.c > > > > > index 7badd6dfe544..03be7cf3fe5a 100644 > > > > > --- a/fs/xfs/scrub/bmap.c > > > > > +++ b/fs/xfs/scrub/bmap.c > > > > > @@ -47,7 +47,15 @@ xchk_setup_inode_bmap( > > > > > sc->sm->sm_type == XFS_SCRUB_TYPE_BMBTD) { > > > > > inode_dio_wait(VFS_I(sc->ip)); > > > > > error = filemap_write_and_wait(VFS_I(sc->ip)->i_mapping); > > > > > - if (error) > > > > > + if (error == -ENOSPC || error == -EIO) { > > > > > + /* > > > > > + * If writeback hits EIO or ENOSPC, reflect it back > > > > > + * into the address space mapping so that a writer > > > > > + * program calling fsync to look for errors will still > > > > > + * capture the error. > > > > > + */ > > > > > + mapping_set_error(VFS_I(sc->ip)->i_mapping, error); > > > > > + } else if (error) > > > > > goto out; > > > > > > > > calling mapping_set_error() seems reasonable here and you've > > > > explained that well, but shouldn't the error then be processed the > > > > same way as all other errors? i.e. by jumping to out? > > > > > > > > If we are now continuing to scrub the bmap after ENOSPC/EIO occur, > > > > why? > > > > > > Heh, ok, more explanation is needed. How about this? > > > > > > /* > > > * If writeback hits EIO or ENOSPC, reflect it back into the > > > * address space mapping so that a writer program calling fsync > > > * to look for errors will still capture the error. > > > * > > > * However, we continue into the extent mapping checks because > > > * write failures do not necessarily imply anything about the > > > * correctness of the file metadata. The metadata and the file > > > * data could be on completely separate devices; a media failure > > > * might only affect a subset of the disk, etc. > > > */ > > > > Ok. Does scrub deal with left-over delalloc extents correctly in > > this case? > > It ignores the ones in the incore extent tree and flags them if they > show up in the ondisk metadata. OK. Perhaps add this to the comment? Cheers, Dave. -- Dave Chinner david@fromorbit.com