From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:34891 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753878AbaHLTI6 (ORCPT ); Tue, 12 Aug 2014 15:08:58 -0400 Message-ID: <53EA6641.4070003@fb.com> Date: Tue, 12 Aug 2014 15:08:49 -0400 From: Chris Mason MIME-Version: 1.0 To: Mark Fasheh CC: , Josef Bacik Subject: Re: [PATCH 2/5] btrfs: qgroup: account shared subtrees during snapshot delete References: <1405625944-4883-1-git-send-email-mfasheh@suse.de> <1405625944-4883-3-git-send-email-mfasheh@suse.de> <53EA5B67.7040109@fb.com> <20140812183216.GR2203@wotan.suse.de> <53EA5EA1.8090505@fb.com> <20140812190110.GS2203@wotan.suse.de> In-Reply-To: <20140812190110.GS2203@wotan.suse.de> Content-Type: text/plain; charset="ISO-8859-1" Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 08/12/2014 03:01 PM, Mark Fasheh wrote: > On Tue, Aug 12, 2014 at 02:36:17PM -0400, Chris Mason wrote: >> >> >> On 08/12/2014 02:32 PM, Mark Fasheh wrote: >>> On Tue, Aug 12, 2014 at 02:22:31PM -0400, Chris Mason wrote: >>>> >>>> >>>> On 07/17/2014 03:39 PM, Mark Fasheh wrote: >>>>> During its tree walk, btrfs_drop_snapshot() will skip any shared >>>>> subtrees it encounters. This is incorrect when we have qgroups >>>>> turned on as those subtrees need to have their contents >>>>> accounted. In particular, the case we're concerned with is when >>>>> removing our snapshot root leaves the subtree with only one root >>>>> reference. >>>>> >>>>> In those cases we need to find the last remaining root and add >>>>> each extent in the subtree to the corresponding qgroup exclusive >>>>> counts. >>>>> >>>>> This patch implements the shared subtree walk and a new qgroup >>>>> operation, BTRFS_QGROUP_OPER_SUB_SUBTREE. When an operation of >>>>> this type is encountered during qgroup accounting, we search for >>>>> any root references to that extent and in the case that we find >>>>> only one reference left, we go ahead and do the math on it's >>>>> exclusive counts. >>>>> >>>>> Signed-off-by: Mark Fasheh >>>>> Reviewed-by: Josef Bacik >>>>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c >>>>> index 813537f..1aa4325 100644 >>>>> --- a/fs/btrfs/extent-tree.c >>>>> +++ b/fs/btrfs/extent-tree.c >>>>> @@ -8078,6 +8331,14 @@ int btrfs_drop_snapshot(struct btrfs_root *root, >>>>> } >>>>> root_dropped = true; >>>>> out_end_trans: >>>>> + ret = btrfs_delayed_qgroup_accounting(trans, root->fs_info); >>>> ^^^^^^^^^^^ >>>> >>>> CONFIG_DEBUG_PAGEALLOC noticed that root is already free at this point. >>>> I switched it to tree_root instead ;) >>> >>> Oh nice catch, thanks for pointing it out. >>> >>> Time to go update my suse patches. >> >> Grin, pretty sure it doesn't count as a catch if CONFIG_DEBUG_PAGEALLOC >> finds it. > > Fair enough, on my end I get to add CONFIG_DEBUG_PAGEALLOC to my testing :) Best debugging feature ever! > >> But it did make it through the balance test we were crashing >> in before. It's probably faster to hand edit the incremental in for the >> suse patch, but here you go just in case: > > Yeah we haven't hit anything internally and like I said we've been running > with it for a while. It's probably hard to hit as I can promise that code > has been executed more than a couple times by now. > > The delete-items path is definitely broken so maybe you hit something from > that? > I had that one removed, so it was just the s/root/tree_root/ I needed. > Btw, I should be sending a two-liner fix that can be extracted from the > delete-items patch soon. Great, thanks. -chris