From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:44987 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753087AbaHLSWm (ORCPT ); Tue, 12 Aug 2014 14:22:42 -0400 Message-ID: <53EA5B67.7040109@fb.com> Date: Tue, 12 Aug 2014 14:22:31 -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> In-Reply-To: <1405625944-4883-3-git-send-email-mfasheh@suse.de> Content-Type: text/plain; charset="ISO-8859-1" Sender: linux-btrfs-owner@vger.kernel.org List-ID: 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 ;) -chris