From patchwork Mon Aug 18 21:01:17 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Fasheh X-Patchwork-Id: 4739211 Return-Path: X-Original-To: patchwork-linux-btrfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id C640FC0338 for ; Mon, 18 Aug 2014 21:01:24 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 0683E2012E for ; Mon, 18 Aug 2014 21:01:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1ECC020125 for ; Mon, 18 Aug 2014 21:01:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752237AbaHRVBT (ORCPT ); Mon, 18 Aug 2014 17:01:19 -0400 Received: from cantor2.suse.de ([195.135.220.15]:39515 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752026AbaHRVBT (ORCPT ); Mon, 18 Aug 2014 17:01:19 -0400 Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 9FCE575016; Mon, 18 Aug 2014 21:01:17 +0000 (UTC) Date: Mon, 18 Aug 2014 14:01:17 -0700 From: Mark Fasheh To: linux-btrfs@vger.kernel.org Cc: Chris Mason Subject: [PATCH] btrfs: don't go readonly on existing qgroup items Message-ID: <20140818210117.GB2203@wotan.suse.de> Reply-To: Mark Fasheh MIME-Version: 1.0 Content-Disposition: inline Organization: SUSE Labs User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Spam-Status: No, score=-7.6 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP btrfs_drop_snapshot() leaves subvolume qgroup items on disk after completion. This can cause problems with snapshot creation. If a new snapshot tries to claim the deleted subvolumes id, btrfs will get -EEXIST from add_qgroup_item() and go read-only. The following commands will reproduce this problem (assume btrfs is on /dev/sda and is mounted at /btrfs) mkfs.btrfs -f /dev/sda mount -t btrfs /dev/sda /btrfs/ btrfs quota enable /btrfs/ btrfs su sna /btrfs/ /btrfs/snap btrfs su de /btrfs/snap sleep 45 umount /btrfs/ mount -t btrfs /dev/sda /btrfs/ We can fix this by catching -EEXIST in add_qgroup_item() and initializing the existing items. We have the problem of orphaned relation items being on disk from an old snapshot but that is outside the scope of this patch. Signed-off-by: Mark Fasheh --- fs/btrfs/qgroup.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index b497498..8477d33 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -551,9 +551,15 @@ static int add_qgroup_item(struct btrfs_trans_handle *trans, key.type = BTRFS_QGROUP_INFO_KEY; key.offset = qgroupid; + /* + * Avoid a transaction abort by catching -EEXIST here. In that + * case, we proceed by re-initializing the existing structure + * on disk. + */ + ret = btrfs_insert_empty_item(trans, quota_root, path, &key, sizeof(*qgroup_info)); - if (ret) + if (ret && ret != -EEXIST) goto out; leaf = path->nodes[0]; @@ -572,7 +578,7 @@ static int add_qgroup_item(struct btrfs_trans_handle *trans, key.type = BTRFS_QGROUP_LIMIT_KEY; ret = btrfs_insert_empty_item(trans, quota_root, path, &key, sizeof(*qgroup_limit)); - if (ret) + if (ret && ret != -EEXIST) goto out; leaf = path->nodes[0];