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=-22.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, 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 71A3CC433ED for ; Fri, 16 Apr 2021 21:13:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 56265613CE for ; Fri, 16 Apr 2021 21:13:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235809AbhDPVN7 (ORCPT ); Fri, 16 Apr 2021 17:13:59 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:47541 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235807AbhDPVN7 (ORCPT ); Fri, 16 Apr 2021 17:13:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618607613; 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=tTqAE1BwRPeg0oc9CNTnlTDrqLoMwegId6c40f8xg68=; b=FwA6ZJ6/QpTVrXrXtOULCxKVwcbIMd+eflvqur7SPOnZoBtFxWOnWDATGFo695TvT/u6Of Ko2Nqsd5gWsInqrlOKBfmcbm5NbT4eWZLxvZbCu5OpzLjx7voav9Z+hRARRWVPRJYt2VZy Stx8R5kRSr40KBuXnVOVhlFcHm7eC8Y= Received: from mail-pg1-f197.google.com (mail-pg1-f197.google.com [209.85.215.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-71-cMfbACYzNXeGh8ylyzHW6A-1; Fri, 16 Apr 2021 17:13:32 -0400 X-MC-Unique: cMfbACYzNXeGh8ylyzHW6A-1 Received: by mail-pg1-f197.google.com with SMTP id f2-20020a63c5020000b02901fc39812e44so3521960pgd.6 for ; Fri, 16 Apr 2021 14:13:31 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=tTqAE1BwRPeg0oc9CNTnlTDrqLoMwegId6c40f8xg68=; b=TNXsLxcBuhmHwI+A4lLOnzUDnuj7DAPNUgTp6IB+wUQ9EIVVXT2u465ba6yk+A3hyM 8qo9j7mPSdiyOQ+l1e4H3fEStRKklFjW5f3xbjU3WV7gUtfhm6m+1vYPmrjrMRIjTMXB ySWp0r2Z2Z+2jD3nduGu/4On7C1LsBCfcteF6qEsOL0t8FvktwjYvZCm5f80v69j26Mh wqFIa9/oHUu4e+pmW/T2MtRh/my3i8NRt5wX3H2iYw0CkZdTXtn2DmDigtsE56fY6HC0 R7Xc9afiWx1fYpraivFm/ZJ3pJjNjIb4+yfn89g41Eo0fWbwA/XQvGQbdd9CGf5ln8LF DPfg== X-Gm-Message-State: AOAM531OnaB3R1HhlTn9z4CyXmewNbvXojb3In0Efsvb9BEPgXh3JlRV ANSeOCjO7hd3bWoWRn+yXT3JuWmR5iReJxG02jLbQFltRbM0NpUO3AlwrMPi3uiLyDZbHhRRPov RbmWH7zEeKqUuhb0vR3pb X-Received: by 2002:a17:902:8c92:b029:e6:60ad:6924 with SMTP id t18-20020a1709028c92b02900e660ad6924mr11329931plo.16.1618607610852; Fri, 16 Apr 2021 14:13:30 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxgRL4bpHdZpsMw3TtusS2T5aXbHz8GxwdBkP++b/0tMbCrJldBurfCmSawQYA8XZp+/cKpJQ== X-Received: by 2002:a17:902:8c92:b029:e6:60ad:6924 with SMTP id t18-20020a1709028c92b02900e660ad6924mr11329913plo.16.1618607610571; Fri, 16 Apr 2021 14:13:30 -0700 (PDT) Received: from xiangao.remote.csb ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id d6sm6689499pji.43.2021.04.16.14.13.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Apr 2021 14:13:30 -0700 (PDT) Date: Sat, 17 Apr 2021 05:13:20 +0800 From: Gao Xiang To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org, Zorro Lang Subject: Re: [PATCH] xfs: don't use in-core per-cpu fdblocks for !lazysbcount Message-ID: <20210416211320.GB2224153@xiangao.remote.csb> References: <20210416091023.2143162-1-hsiangkao@redhat.com> <20210416160013.GB3122264@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210416160013.GB3122264@magnolia> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org Hi Darrick, On Fri, Apr 16, 2021 at 09:00:13AM -0700, Darrick J. Wong wrote: > On Fri, Apr 16, 2021 at 05:10:23PM +0800, Gao Xiang wrote: > > There are many paths which could trigger xfs_log_sb(), e.g. > > xfs_bmap_add_attrfork() > > -> xfs_log_sb() > > , which overrided on-disk fdblocks by in-core per-CPU fdblocks. > > > > However, for !lazysbcount cases, on-disk fdblocks is actually updated > > by xfs_trans_apply_sb_deltas(), and generally it isn't equal to > > in-core fdblocks due to xfs_reserve_block() or whatever, see the > > comment in xfs_unmountfs(). > > > > It could be observed by the following steps reported by Zorro [1]: > > > > 1. mkfs.xfs -f -l lazy-count=0 -m crc=0 $dev > > 2. mount $dev $mnt > > 3. fsstress -d $mnt -p 100 -n 1000 (maybe need more or less io load) > > 4. umount $mnt > > 5. xfs_repair -n $dev > > > > yet due to commit f46e5a174655("xfs: fold sbcount quiesce logging > > into log covering"), xfs_sync_sb() will be triggered even !lazysbcount > > but xfs_log_need_covered() case when xfs_unmountfs(), so hard to > > reproduce on kernel 5.12+. > > Um, I can't understand this(?), possibly because I can't get to RHBZ and > therefore have very little context to start from. :( Very sorry about that.. I realized it doesn't access at all without some permission after sending out the patch. :( > > Are you saying that because the f46e commit removed the xfs_sync_sb > calls from unmountfs for !lazysb filesystems, we no longer log the > summary counters at unmount? Which means that we no longer write the > incore percpu fdblocks count to disk at unmount after we've torn down > all the incore space reservations (when sb_fdblocks == m_fdblocks)? Er.. I think that is by reverse, before commit f46e, we no longer logged the summary counters at unmount, due to https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/xfs/xfs_mount.c?h=v5.11#n1177 xfs_unmountfs -> xfs_log_sbcount -> !xfs_sb_version_haslazysbcount -> return 0 (xfs_sync_sb bypassed). So the only time we update the ondisk fdblocks was during transactions, but xfs_log_sb() corrupted this (due to no summary counters logging at unmount). After f46e, it became https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/xfs/xfs_log.c?h=v5.12-rc2#n982 xfs_unmountfs -> xfs_log_unmount -> xfs_log_clean -> xfs_log_cover So if xfs_log_need_covered(mp) == true and !xfs_sb_version_haslazysbcount(&mp->m_sb), xfs_sync_sb() will be triggered to cover the log, So it's hard to reproduce on the current kernel (at least on my side.) But I have no idea xfs_log_need_covered(mp) is always true at that time, and the patchset seems a bit large and (possibly) hard to backport... > > So that means that for !lazysb fses, the only time we log the sb > counters is during transactions, and when we do log the counters we > actually log the wrong value, since the incore reservations should never > escape to disk? Hence the fix below? Yes > > And then by extension, is the reason that nobody noticed before is that > we always used to log the correct value at unmount, so fses with clean > logs always have the correct value, and fses with dirty logs will > recompute fdblocks after log recovery by summing the AGF free blocks > counts? Nope, prior to 5.12-rc1, I think it was broken for a very long time... > > (Or possibly nobody uses !lazysb filesystems anymore?) > Zorro found this days ago on rhel 8 kernel (4.18, maybe he's doing some new testcases to cover this), and I think it was broken for much much long time (I don't know which version it was broken first), maybe it has little impact since it's just a freespace block counter. So I think it should be backported to many stable kernel versions (?) But I have no idea when it was broken... > I /think/ the code change looks ok, but as you might surmise from the > large quantity of questions, I'm not ready to RVB this yet. The commit > message seems like a good place to answer those questions. > > > After this patch, I've seen no strange so far on older kernels > > for the testcase above without lazysbcount. > > > > [1] https://bugzilla.redhat.com/show_bug.cgi?id=1949515 > > This strangely doesn't seem to be accessible to the public at > large, since someone at RedHat decided to block all Oracle IPs > . will get rid of it the next time... Thanks, Gao Xiang > > --D > > > > > Reported-by: Zorro Lang > > Signed-off-by: Gao Xiang > > --- > > fs/xfs/libxfs/xfs_sb.c | 8 +++++++- > > 1 file changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c > > index 60e6d255e5e2..423dada3f64c 100644 > > --- a/fs/xfs/libxfs/xfs_sb.c > > +++ b/fs/xfs/libxfs/xfs_sb.c > > @@ -928,7 +928,13 @@ xfs_log_sb( > > > > mp->m_sb.sb_icount = percpu_counter_sum(&mp->m_icount); > > mp->m_sb.sb_ifree = percpu_counter_sum(&mp->m_ifree); > > - mp->m_sb.sb_fdblocks = percpu_counter_sum(&mp->m_fdblocks); > > + if (!xfs_sb_version_haslazysbcount(&mp->m_sb)) { > > + struct xfs_dsb *dsb = bp->b_addr; > > + > > + mp->m_sb.sb_fdblocks = be64_to_cpu(dsb->sb_fdblocks); > > + } else { > > + mp->m_sb.sb_fdblocks = percpu_counter_sum(&mp->m_fdblocks); > > + } > > > > xfs_sb_to_disk(bp->b_addr, &mp->m_sb); > > xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SB_BUF); > > -- > > 2.27.0 > > >