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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 73BA2C433DB for ; Thu, 18 Feb 2021 04:46:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3ECD464E76 for ; Thu, 18 Feb 2021 04:46:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229864AbhBREqF (ORCPT ); Wed, 17 Feb 2021 23:46:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:49782 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229720AbhBREqE (ORCPT ); Wed, 17 Feb 2021 23:46:04 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7016F64E3E; Thu, 18 Feb 2021 04:45:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1613623523; bh=YlNAiOVHY4cpn9zXxJn/GOG0FOtdgY/+G+oyyGDB+QY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BJbxIpoFNXkfXqBKNZe5zpFqnJ3et3pwLtyQGD9BTHkvnHmhwnMQzOuWMZepF24uj l/nYVp9bQlub2YkdIQ3OABFMnUJaFTsEHj8KB8T+WMu8+fNmD6cthlDgq2bJMM7y6d vbKjKCe47wnGE5/8VGEDaEMISGvY1MZuK8MTnG2f24y7EHVPHxyRbgIxruKADNG6ui wKjNfm05EnurWIsTspPTQJ8ErmHTsy3zL71UylwIOZfQRDEfy5cIvMNI/keJLsceSk lhkgb7SsQQV64MuH9wGLBg5TTwkiCDFbPRCgYo7sst3hfIJLCbhxHEEaN6ts//W6Cr JmjaF+/0YPZkg== Date: Wed, 17 Feb 2021 20:45:22 -0800 From: "Darrick J. Wong" To: Brian Foster Cc: sandeen@sandeen.net, linux-xfs@vger.kernel.org Subject: Re: [PATCH 1/3] xfs_repair: set NEEDSREPAIR the first time we write to a filesystem Message-ID: <20210218044522.GR7193@magnolia> References: <161319520460.422860.10568013013578673175.stgit@magnolia> <161319521070.422860.2540813932323979688.stgit@magnolia> <20210216115534.GB534175@bfoster> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210216115534.GB534175@bfoster> Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Tue, Feb 16, 2021 at 06:55:34AM -0500, Brian Foster wrote: > On Fri, Feb 12, 2021 at 09:46:50PM -0800, Darrick J. Wong wrote: > > From: Darrick J. Wong > > > > Add a hook to the buffer cache so that xfs_repair can intercept the > > first write to a V5 filesystem to set the NEEDSREPAIR flag. In the > > event that xfs_repair dirties the filesystem and goes down, this ensures > > that the sysadmin will have to re-start repair before mounting. > > > > Signed-off-by: Darrick J. Wong > > --- > > include/xfs_mount.h | 4 ++ > > libxfs/rdwr.c | 4 ++ > > repair/xfs_repair.c | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++ > > 3 files changed, 103 insertions(+) > > > > > ... > > diff --git a/repair/xfs_repair.c b/repair/xfs_repair.c > > index 90d1a95a..12e319ae 100644 > > --- a/repair/xfs_repair.c > > +++ b/repair/xfs_repair.c > > @@ -720,6 +720,8 @@ clear_needsrepair( > > struct xfs_buf *bp; > > int error; > > > > + mp->m_buf_writeback_fn = NULL; > > + > > Slight impedence mismatch in that we set the callback unconditionally > (assuming crc=1) but we only get to this call if needsrepair is set. I'll remove that. > > /* > > * If we're going to clear NEEDSREPAIR, we need to make absolutely sure > > * that everything is ok with the ondisk filesystem. Make sure any > > @@ -751,6 +753,95 @@ clear_needsrepair( > > libxfs_buf_relse(bp); > > } > > > > +static void > > +update_sb_crc_only( > > + struct xfs_buf *bp) > > +{ > > + xfs_buf_update_cksum(bp, XFS_SB_CRC_OFF); > > +} > > + > > +/* Forcibly write the primary superblock with the NEEDSREPAIR flag set. */ > > +static void > > +force_needsrepair( > > + struct xfs_mount *mp) > > +{ > > + struct xfs_buf_ops fake_ops; > > + struct xfs_buf *bp; > > + int error; > > + > > + if (!xfs_sb_version_hascrc(&mp->m_sb) || > > + xfs_sb_version_needsrepair(&mp->m_sb)) > > + return; > > + > > + bp = libxfs_getsb(mp); > > + if (!bp || bp->b_error) { > > + do_log( > > + _("couldn't get superblock to set needsrepair, err=%d\n"), > > + bp ? bp->b_error : ENOMEM); > > + return; > > + } else { > > + /* > > + * It's possible that we need to set NEEDSREPAIR before we've > > + * had a chance to fix the summary counters in the primary sb. > > + * With the exception of those counters, phase 1 already > > + * ensured that the geometry makes sense. > > + * > > + * Bad summary counters in the primary super can cause the > > + * write verifier to fail, so substitute a dummy that only sets > > + * the CRC. In the event of a crash, NEEDSREPAIR will prevent > > + * the kernel from mounting our potentially damaged filesystem > > + * until repair is run again, so it's ok to bypass the usual > > + * verification in this one case. > > + */ > > + fake_ops = xfs_sb_buf_ops; /* struct copy */ > > + fake_ops.verify_write = update_sb_crc_only; > > + > > + mp->m_sb.sb_features_incompat |= > > + XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR; > > + libxfs_sb_to_disk(bp->b_addr, &mp->m_sb); > > + > > + /* Force the primary super to disk immediately. */ > > + bp->b_ops = &fake_ops; > > + error = -libxfs_bwrite(bp); > > This looks like it calls back into the writeback hook before it's been > cleared. Yes, it does... > I'm guessing the xfs_sb_version_needsrepair() check above cuts > off any recursion issues, ...but as soon as we end up in the writeback hook, the b_ops and XFS_SB_DADDR checks cause the hook to return without doing anything. > but it might be cleaner to clear the callback pointer first. We need to block all other writers until /after/ we've written the primary super, which means that we can't clear the callback until some time after the bwrite. > > > + bp->b_ops = &xfs_sb_buf_ops; > > + if (error) > > + do_log(_("couldn't force needsrepair, err=%d\n"), error); > > + } > > + if (bp) > > + libxfs_buf_relse(bp); > > Doesn't appear we can get here with bp == NULL. Otherwise the rest looks > reasonable to me. Yep, will fix. --D > Brian > > > +} > > + > > +/* Intercept the first write to the filesystem so we can set NEEDSREPAIR. */ > > +static void > > +repair_capture_writeback( > > + struct xfs_buf *bp) > > +{ > > + struct xfs_mount *mp = bp->b_mount; > > + static pthread_mutex_t wb_mutex = PTHREAD_MUTEX_INITIALIZER; > > + > > + /* Higher level code modifying a superblock must set NEEDSREPAIR. */ > > + if (bp->b_ops == &xfs_sb_buf_ops || bp->b_bn == XFS_SB_DADDR) > > + return; > > + > > + pthread_mutex_lock(&wb_mutex); > > + > > + /* > > + * If someone else already dropped the hook, then needsrepair has > > + * already been set on the filesystem and we can unlock. > > + */ > > + if (mp->m_buf_writeback_fn != repair_capture_writeback) > > + goto unlock; > > + > > + /* > > + * If we get here, the buffer being written is not a superblock, and > > + * needsrepair needs to be set. > > + */ > > + force_needsrepair(mp); > > + mp->m_buf_writeback_fn = NULL; > > +unlock: > > + pthread_mutex_unlock(&wb_mutex); > > +} > > + > > int > > main(int argc, char **argv) > > { > > @@ -847,6 +938,10 @@ main(int argc, char **argv) > > if (verbose > 2) > > mp->m_flags |= LIBXFS_MOUNT_WANT_CORRUPTED; > > > > + /* Capture the first writeback so that we can set needsrepair. */ > > + if (xfs_sb_version_hascrc(&mp->m_sb)) > > + mp->m_buf_writeback_fn = repair_capture_writeback; > > + > > /* > > * set XFS-independent status vars from the mount/sb structure > > */ > > >