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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A5941C433EF for ; Thu, 14 Oct 2021 23:17:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7154560C41 for ; Thu, 14 Oct 2021 23:17:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231139AbhJNXTK (ORCPT ); Thu, 14 Oct 2021 19:19:10 -0400 Received: from mail110.syd.optusnet.com.au ([211.29.132.97]:42632 "EHLO mail110.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230032AbhJNXTK (ORCPT ); Thu, 14 Oct 2021 19:19:10 -0400 Received: from dread.disaster.area (pa49-195-238-16.pa.nsw.optusnet.com.au [49.195.238.16]) by mail110.syd.optusnet.com.au (Postfix) with ESMTPS id 7646C10D1DD; Fri, 15 Oct 2021 10:17:03 +1100 (AEDT) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1mb9yA-006JlD-SP; Fri, 15 Oct 2021 10:17:02 +1100 Date: Fri, 15 Oct 2021 10:17:02 +1100 From: Dave Chinner To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org, chandan.babu@oracle.com, hch@lst.de Subject: Re: [PATCH 01/17] xfs: fix incorrect decoding in xchk_btree_cur_fsbno Message-ID: <20211014231702.GW2361455@dread.disaster.area> References: <163424261462.756780.16294781570977242370.stgit@magnolia> <163424262046.756780.2366797746965376855.stgit@magnolia> <20211014224813.GN2361455@dread.disaster.area> <20211014230549.GM24307@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211014230549.GM24307@magnolia> X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.4 cv=epq8cqlX c=1 sm=1 tr=0 ts=6168ba70 a=DzKKRZjfViQTE5W6EVc0VA==:117 a=DzKKRZjfViQTE5W6EVc0VA==:17 a=kj9zAlcOel0A:10 a=8gfv0ekSlNoA:10 a=VwQbUJbxAAAA:8 a=7-415B0cAAAA:8 a=tfPEP7of1_Icnt5Zq8kA:9 a=CjuIK1q_8ugA:10 a=AjGcO6oz07-iQ99wixmX:22 a=biEYGPWJfzWAr4FL6Ov7:22 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Thu, Oct 14, 2021 at 04:05:49PM -0700, Darrick J. Wong wrote: > On Fri, Oct 15, 2021 at 09:48:13AM +1100, Dave Chinner wrote: > > On Thu, Oct 14, 2021 at 01:17:00PM -0700, Darrick J. Wong wrote: > > > From: Darrick J. Wong > > > > > > During review of subsequent patches, Dave and I noticed that this > > > function doesn't work quite right -- accessing cur->bc_ino depends on > > > the ROOT_IN_INODE flag, not LONG_PTRS. Fix that and the parentheses > > > isssue. While we're at it, remove the piece that accesses cur->bc_ag, > > > because block 0 of an AG is never part of a btree. > > > > > > Signed-off-by: Darrick J. Wong > > > --- > > > fs/xfs/scrub/trace.c | 7 ++++--- > > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > > > > > > diff --git a/fs/xfs/scrub/trace.c b/fs/xfs/scrub/trace.c > > > index c0ef53fe6611..93c13763c15e 100644 > > > --- a/fs/xfs/scrub/trace.c > > > +++ b/fs/xfs/scrub/trace.c > > > @@ -24,10 +24,11 @@ xchk_btree_cur_fsbno( > > > if (level < cur->bc_nlevels && cur->bc_bufs[level]) > > > return XFS_DADDR_TO_FSB(cur->bc_mp, > > > xfs_buf_daddr(cur->bc_bufs[level])); > > > - if (level == cur->bc_nlevels - 1 && cur->bc_flags & XFS_BTREE_LONG_PTRS) > > > + > > > + if (level == cur->bc_nlevels - 1 && > > > + (cur->bc_flags & XFS_BTREE_ROOT_IN_INODE)) > > > return XFS_INO_TO_FSB(cur->bc_mp, cur->bc_ino.ip->i_ino); > > > > Ok. > > > > > - if (!(cur->bc_flags & XFS_BTREE_LONG_PTRS)) > > > - return XFS_AGB_TO_FSB(cur->bc_mp, cur->bc_ag.pag->pag_agno, 0); > > > + > > > > But doesn't this break the tracing code on short pointers as the > > tracing code does: > > > > TP_fast_assign( > > xfs_fsblock_t fsbno = xchk_btree_cur_fsbno(cur, level); > > ... > > __entry->agno = XFS_FSB_TO_AGNO(cur->bc_mp, fsbno); > > > > > > i.e. the tracing will no longer give the correct agno for per-ag > > cursors that don't have any buffers attached to them at the current > > level? > > Hmmm. By that logic, maybe we should get rid of the (level == > cur->bc_nlevels - 1) check entirely so that any cursor without a buffer > attached at that level will always provide *some* kind of breadcrumb to > the tracepoints? Perhaps so. > I almost did that instead, except for the consideration that if you're > tracing the online fsck code, you should /probably/ have at least one of > xchk_stop/xrep_attempt/xchk_done included in the filter list so you can > be certain of what the kernel is checking. It doesn't worry me how we resolve this - I just pointed it out because it's not mentioned in the commit message and I wanted to make sure it wasn't an oversight. If there are better ways to get this information from tracepoints and XFS_FSB_TO_AGNO() does something safe and obvious with NULLFSBLOCK (e.g. ends up as -1) then as long as there's mention of this change in the commit message I'm fine with it as it is. Cheers, Dave. -- Dave Chinner david@fromorbit.com