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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 60F7AC43603 for ; Tue, 17 Dec 2019 11:32:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 29C9C21739 for ; Tue, 17 Dec 2019 11:32:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="U/r+VWhK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726947AbfLQLcs (ORCPT ); Tue, 17 Dec 2019 06:32:48 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:47799 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726690AbfLQLcs (ORCPT ); Tue, 17 Dec 2019 06:32:48 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1576582367; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=z1JMpG687TlZYI1rZsEs0q5oO/XB/nju3Ll6ZBixfH4=; b=U/r+VWhKnIu4F0QsxA2xnS/7R4rl5UZRgzxt98el05hskosi+dtWoCgbWm6eeVTgQ3DaeX IL/VfP9tXn1h1cZaeOtREiQ3lVGibbV9CduNCQz7WV2Ed9fSxR6/Lkl0W5jc+uK3ojNXxw nSgDORbCWcPE0dXkMNHiDs6N6GnBoRk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-12-ANxbrtypN2u9QUIlBXWRfw-1; Tue, 17 Dec 2019 06:32:44 -0500 X-MC-Unique: ANxbrtypN2u9QUIlBXWRfw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AFB9710AC5D8; Tue, 17 Dec 2019 11:32:42 +0000 (UTC) Received: from bfoster (dhcp-41-2.bos.redhat.com [10.18.41.2]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 260385C28D; Tue, 17 Dec 2019 11:32:42 +0000 (UTC) Date: Tue, 17 Dec 2019 06:32:40 -0500 From: Brian Foster To: "Darrick J. Wong" Cc: sandeen@sandeen.net, linux-xfs@vger.kernel.org, alex@zadara.com Subject: Re: [PATCH 6/6] xfs_repair: check plausibility of root dir pointer before trashing it\ Message-ID: <20191217113240.GB48778@bfoster> References: <157547906289.974712.8933333382010386076.stgit@magnolia> <157547910268.974712.78208912903649937.stgit@magnolia> <20191205143858.GF48368@bfoster> <20191212224618.GE99875@magnolia> <20191213111908.GA43131@bfoster> <20191216163457.GF99884@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191216163457.GF99884@magnolia> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Mon, Dec 16, 2019 at 08:34:57AM -0800, Darrick J. Wong wrote: > On Fri, Dec 13, 2019 at 06:19:08AM -0500, Brian Foster wrote: > > On Thu, Dec 12, 2019 at 02:46:18PM -0800, Darrick J. Wong wrote: > > > On Thu, Dec 05, 2019 at 09:38:58AM -0500, Brian Foster wrote: > > > > On Wed, Dec 04, 2019 at 09:05:02AM -0800, Darrick J. Wong wrote: > > > > > From: Darrick J. Wong > > > > > > > > > > If sb_rootino doesn't point to where we think mkfs should have allocated > > > > > the root directory, check to see if the alleged root directory actually > > > > > looks like a root directory. If so, we'll let it live because someone > > > > > could have changed sunit since formatting time, and that changes the > > > > > root directory inode estimate. > > > > > > > > > > Signed-off-by: Darrick J. Wong > > > > > --- > > > > > repair/xfs_repair.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ > > > > > 1 file changed, 45 insertions(+) > > > > > > > > > > > > > > > diff --git a/repair/xfs_repair.c b/repair/xfs_repair.c > > > > > index abd568c9..b0407f4b 100644 > > > > > --- a/repair/xfs_repair.c > > > > > +++ b/repair/xfs_repair.c > > > > > @@ -426,6 +426,37 @@ _("would reset superblock %s inode pointer to %"PRIu64"\n"), > > > > > *ino = expected_ino; > > > > > } > > > > > > > > > > +/* Does the root directory inode look like a plausible root directory? */ > > > > > +static bool > > > > > +has_plausible_rootdir( > > > > > + struct xfs_mount *mp) > > > > > +{ > > > > > + struct xfs_inode *ip; > > > > > + xfs_ino_t ino; > > > > > + int error; > > > > > + bool ret = false; > > > > > + > > > > > + error = -libxfs_iget(mp, NULL, mp->m_sb.sb_rootino, 0, &ip, > > > > > + &xfs_default_ifork_ops); > > > > > + if (error) > > > > > + goto out; > > > > > + if (!S_ISDIR(VFS_I(ip)->i_mode)) > > > > > + goto out_rele; > > > > > + > > > > > + error = -libxfs_dir_lookup(NULL, ip, &xfs_name_dotdot, &ino, NULL); > > > > > + if (error) > > > > > + goto out_rele; > > > > > + > > > > > + /* The root directory '..' entry points to the directory. */ > > > > > + if (ino == mp->m_sb.sb_rootino) > > > > > + ret = true; > > > > > + > > > > > +out_rele: > > > > > + libxfs_irele(ip); > > > > > +out: > > > > > + return ret; > > > > > +} > > > > > + > > > > > /* > > > > > * Make sure that the first 3 inodes in the filesystem are the root directory, > > > > > * the realtime bitmap, and the realtime summary, in that order. > > > > > @@ -436,6 +467,20 @@ calc_mkfs( > > > > > { > > > > > xfs_ino_t rootino = libxfs_ialloc_calc_rootino(mp, -1); > > > > > > > > > > + /* > > > > > + * If the root inode isn't where we think it is, check its plausibility > > > > > + * as a root directory. It's possible that somebody changed sunit > > > > > + * since the filesystem was created, which can change the value of the > > > > > + * above computation. Don't blow up the root directory if this is the > > > > > + * case. > > > > > + */ > > > > > + if (mp->m_sb.sb_rootino != rootino && has_plausible_rootdir(mp)) { > > > > > + do_warn( > > > > > +_("sb root inode value %" PRIu64 " inconsistent with alignment (expected %"PRIu64")\n"), > > > > > + mp->m_sb.sb_rootino, rootino); > > > > > + rootino = mp->m_sb.sb_rootino; > > > > > + } > > > > > + > > > > > > > > A slightly unfortunate side effect of this is that there's seemingly no > > > > straightforward way for a user to "clear" this state/warning. We've > > > > solved the major problem by allowing repair to handle this condition, > > > > but AFAICT this warning will persist unless the stripe unit is changed > > > > back to its original value. > > > > > > Heh, I apparently never replied to this. :( > > > > > > > IOW, what if this problem exists simply because a user made a mistake > > > > and wants to undo it? It's probably easy enough for us to say "use > > > > whatever you did at mkfs time," but what if that's unknown or was set > > > > automatically? I feel like that is the type of thing that in practice > > > > could result in unnecessary bugs or error reports unless the tool can > > > > make a better suggestion to the end user. For example, could we check > > > > the geometry on secondary supers (if they exist) against the current > > > > rootino and use that as a secondary form of verification and/or suggest > > > > the user reset to that geometry (if desired)? > > > > > > That sounds reasonable. > > > > > > > OTOH, I guess we'd have to consider what happens if the filesystem was > > > > grown in that scenario too.. :/ > > > > > > I think it would be fine, so long as we're careful with the if-then > > > chain. Specifically: > > > > > > a. If we dislike the rootino that we compute with the ondisk sunit value, > > > and... > > > > > > b. The thing sb_rootino points to actually does look like the root > > > directory, and... > > > > > > c. One of the secondary supers has an sunit value that gives us a > > > rootino calculation that matches the sb_rootino that we just checked > > > out... > > > > > > ...then we'll propose correcting the primary sb_unit to the value we > > > found in (c). > > > > > > > Yeah, that makes sense. My broader concern was addressing the situation > > where we aren't lucky enough to glean original alignment from the fs. > > Perhaps we could 1.) update the warning message to unconditionally > > recommend an alignment and 2.) if nothing is gleaned from secondary > > supers (and all your above conditions apply), calculate and recommend > > the max alignment that accommodates the root inode chunk..? It might not > > be the original value, but at least guides the user to a solution to > > quiet the warning.. > > Hmm, I suppose if the secondary sb scan didn't produce any usable values > then we could just try increasing powers of two until the computed > rootino value >= sb_rootino in the hopes of finding one. > > I'm not sure how I feel about repair guessing values until it finds one > that shuts off the warning light, though. Is doing so foolishness, or > is it AI? :) > Heh. I'm not sure what the right answer is on that. I guess if we dumped out the minimum valid alignment and then made it clear that we couldn't detect historical alignment from the fs (so it's a guess/recommendation to clear the warning), that might be the best we can do. Brian > --D > > > Brian > > > > > > > > > > (Actually on a quick test, it looks like growfs updates every super, > > > > even preexisting..). > > > > > > I'll throw that onto the V3 series. > > > > > > --D > > > > > > > > > > > Brian > > > > > > > > > ensure_fixed_ino(&mp->m_sb.sb_rootino, rootino, > > > > > _("root")); > > > > > ensure_fixed_ino(&mp->m_sb.sb_rbmino, rootino + 1, > > > > > > > > > > > > > > >