From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from acsinet15.oracle.com ([141.146.126.227]:39685 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751115Ab2JHMSs (ORCPT ); Mon, 8 Oct 2012 08:18:48 -0400 Message-ID: <5072C492.8040205@oracle.com> Date: Mon, 08 Oct 2012 20:18:26 +0800 From: Liu Bo MIME-Version: 1.0 To: Chris Mason , Mitch Harder CC: "linux-btrfs@vger.kernel.org" , "dave@jikos.cz" Subject: Re: [PATCH 2/2 v3] Btrfs: snapshot-aware defrag References: <1347875936-14165-1-git-send-email-bo.li.liu@oracle.com> <1347875936-14165-2-git-send-email-bo.li.liu@oracle.com> <50625569.9040102@oracle.com> <20121003140259.GA4458@shiny> In-Reply-To: <20121003140259.GA4458@shiny> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 10/03/2012 10:02 PM, Chris Mason wrote: > On Tue, Sep 25, 2012 at 07:07:53PM -0600, Liu Bo wrote: >> On 09/26/2012 01:39 AM, Mitch Harder wrote: >>> On Mon, Sep 17, 2012 at 4:58 AM, Liu Bo wrote: >>>> This comes from one of btrfs's project ideas, >>>> As we defragment files, we break any sharing from other snapshots. >>>> The balancing code will preserve the sharing, and defrag needs to grow this >>>> as well. >>>> >>>> Now we're able to fill the blank with this patch, in which we make full use of >>>> backref walking stuff. >>>> >>>> Here is the basic idea, >>>> o set the writeback ranges started by defragment with flag EXTENT_DEFRAG >>>> o at endio, after we finish updating fs tree, we use backref walking to find >>>> all parents of the ranges and re-link them with the new COWed file layout by >>>> adding corresponding backrefs. >>>> >>>> Originally patch by Li Zefan >>>> Signed-off-by: Liu Bo >>> >>> I'm hitting the WARN_ON in record_extent_backrefs() indicating a >>> problem with the return value from iterate_inodes_from_logical(). > > Me too. It triggers reliably with mount -o autodefrag, and then crashes > a in the next function ;) > > -chris > Hi Chris, Mitch, I'm afraid that I may need a little more time to fix all bugs in it because there seems to be some backref walking bugs mixed in, and at least 4 different crashes make it harder to address bugs. I use an 1G random write fio job running in background, following by creating 20 snapshots in background, and mount -o autodefrag. So if your crash is quite stable in one place, please let me know the steps. thanks, liubo