From patchwork Fri Apr 15 09:08:22 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qu Wenruo X-Patchwork-Id: 8846301 Return-Path: X-Original-To: patchwork-linux-btrfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 560BE9F54F for ; Fri, 15 Apr 2016 09:11:12 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 1D4A42021F for ; Fri, 15 Apr 2016 09:11:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B5B502021A for ; Fri, 15 Apr 2016 09:11:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752248AbcDOJK6 (ORCPT ); Fri, 15 Apr 2016 05:10:58 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:30643 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750916AbcDOJKy (ORCPT ); Fri, 15 Apr 2016 05:10:54 -0400 X-IronPort-AV: E=Sophos;i="5.20,367,1444665600"; d="scan'208";a="437126" Received: from unknown (HELO cn.fujitsu.com) ([10.167.250.3]) by song.cn.fujitsu.com with ESMTP; 15 Apr 2016 17:10:23 +0800 Received: from localhost.localdomain (unknown [10.167.226.34]) by cn.fujitsu.com (Postfix) with ESMTP id 4A3354056404; Fri, 15 Apr 2016 17:10:23 +0800 (CST) From: Qu Wenruo To: linux-btrfs@vger.kernel.org, mfasheh@suse.de, fdmanana@suse.com Subject: [PATCH v4] btrfs: qgroup: Fix qgroup accounting when creating snapshot Date: Fri, 15 Apr 2016 17:08:22 +0800 Message-Id: <1460711302-2478-1-git-send-email-quwenruo@cn.fujitsu.com> X-Mailer: git-send-email 2.8.0 MIME-Version: 1.0 X-yoursite-MailScanner-ID: 4A3354056404.A769D X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: quwenruo@cn.fujitsu.com X-Spam-Status: No, score=-7.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Current btrfs qgroup design implies a requirement that after calling btrfs_qgroup_account_extents() there must be a commit root switch. Normally this is OK, as btrfs_qgroup_accounting_extents() is only called inside btrfs_commit_transaction() just be commit_cowonly_roots(). However there is a exception at create_pending_snapshot(), which will call btrfs_qgroup_account_extents() but no any commit root switch. In case of creating a snapshot whose parent root is itself (create a snapshot of fs tree), it will corrupt qgroup by the following trace: (skipped unrelated data) Tested-by: holger.hoffstaette@googlemail.com ====== btrfs_qgroup_account_extent: bytenr = 29786112, num_bytes = 16384, nr_old_roots = 0, nr_new_roots = 1 qgroup_update_counters: qgid = 5, cur_old_count = 0, cur_new_count = 1, rfer = 0, excl = 0 qgroup_update_counters: qgid = 5, cur_old_count = 0, cur_new_count = 1, rfer = 16384, excl = 16384 btrfs_qgroup_account_extent: bytenr = 29786112, num_bytes = 16384, nr_old_roots = 0, nr_new_roots = 0 ====== The problem here is in first qgroup_account_extent(), the nr_new_roots of the extent is 1, which means its reference got increased, and qgroup increased its rfer and excl. But at second qgroup_account_extent(), its reference got decreased, but between these two qgroup_account_extent(), there is no switch roots. This leads to the same nr_old_roots, and this extent just got ignored by qgroup, which means this extent is wrongly accounted. Fix it by call commit_cowonly_roots() after qgroup_account_extent() in create_pending_snapshot(), with needed preparation. Reported-by: Mark Fasheh Signed-off-by: Qu Wenruo --- v2: Fix a soft lockup caused by missing switch_commit_root() call. Fix a warning caused by dirty-but-not-committed root. v3: Fix a bug which will cause qgroup accounting for dropping snapshot wrong v4: Fix a bug caused by non-cowed btree modification. To Filipe: I'm sorry I didn't wait for your reply on the dropped roots. I reverted back the version where we deleted dropped roots in switch_commit_roots(). As I think as long as we called btrfs_qgroup_prepare_account_extents() and btrfs_qgroup_account_extents(), it should have already accounted extents for dropped roots, and then we are OK to drop them. It would be very nice if you could point out what I missed. Thanks Qu --- fs/btrfs/transaction.c | 117 +++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 93 insertions(+), 24 deletions(-) diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index 43885e5..92f8193 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -311,10 +311,11 @@ loop: * when the transaction commits */ static int record_root_in_trans(struct btrfs_trans_handle *trans, - struct btrfs_root *root) + struct btrfs_root *root, + int force) { - if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) && - root->last_trans < trans->transid) { + if ((test_bit(BTRFS_ROOT_REF_COWS, &root->state) && + root->last_trans < trans->transid) || force) { WARN_ON(root == root->fs_info->extent_root); WARN_ON(root->commit_root != root->node); @@ -331,7 +332,7 @@ static int record_root_in_trans(struct btrfs_trans_handle *trans, smp_wmb(); spin_lock(&root->fs_info->fs_roots_radix_lock); - if (root->last_trans == trans->transid) { + if (root->last_trans == trans->transid && !force) { spin_unlock(&root->fs_info->fs_roots_radix_lock); return 0; } @@ -402,7 +403,7 @@ int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans, return 0; mutex_lock(&root->fs_info->reloc_mutex); - record_root_in_trans(trans, root); + record_root_in_trans(trans, root, 0); mutex_unlock(&root->fs_info->reloc_mutex); return 0; @@ -1311,6 +1312,80 @@ int btrfs_defrag_root(struct btrfs_root *root) } /* + * Do all special snapshot related qgroup dirty hack. + * + * Will do all needed qgroup inherit and dirty hack like switch commit + * roots inside one transaction and write all btree into disk, to make + * qgroup works. + */ +static int qgroup_account_snapshot(struct btrfs_trans_handle *trans, + struct btrfs_root *src, + struct btrfs_root *parent, + struct btrfs_qgroup_inherit *inherit, + u64 dst_objectid) +{ + struct btrfs_fs_info *fs_info = src->fs_info; + int ret; + + /* + * We are going to commit transaction, see btrfs_commit_transaction() + * comment for reason locking tree_log_mutex + */ + mutex_lock(&fs_info->tree_log_mutex); + + ret = commit_fs_roots(trans, src); + if (ret) + goto out; + ret = btrfs_qgroup_prepare_account_extents(trans, fs_info); + if (ret < 0) + goto out; + ret = btrfs_qgroup_account_extents(trans, fs_info); + if (ret < 0) + goto out; + + /* Now qgroup are all updated, we can inherit it to new qgroups */ + ret = btrfs_qgroup_inherit(trans, fs_info, + src->root_key.objectid, dst_objectid, + inherit); + if (ret < 0) + goto out; + + /* + * Now we do a simplified commit transaction, which will: + * 1) commit all subvolume and extent tree + * To ensure all subvolume and extent tree have a valid + * commit_root to accounting later insert_dir_item() + * 2) write all btree blocks onto disk + * This is to make sure later btree modification will be cowed + * Or commit_root can be populated and cause wrong qgroup numbers + * In this simplified commit, we don't really care about other trees + * like chunk and root tree, as they won't affect qgroup. + * And we don't write super to avoid half committed status. + */ + ret = commit_cowonly_roots(trans, src); + if (ret) + goto out; + switch_commit_roots(trans->transaction, fs_info); + ret = btrfs_write_and_wait_transaction(trans, src); + if (ret) + btrfs_std_error(fs_info, ret, + "Error while writing out transaction for qgroup"); + +out: + mutex_unlock(&fs_info->tree_log_mutex); + + /* + * Force parent root to be updated, as we recorded it before so its + * last_trans == cur_transid. + * Or it won't be committed again onto disk after later + * insert_dir_item() + */ + if (!ret) + record_root_in_trans(trans, parent, 1); + return ret; +} + +/* * new snapshots need to be created at a very specific time in the * transaction commit. This does the actual creation. * @@ -1383,7 +1458,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, dentry = pending->dentry; parent_inode = pending->dir; parent_root = BTRFS_I(parent_inode)->root; - record_root_in_trans(trans, parent_root); + record_root_in_trans(trans, parent_root, 0); cur_time = current_fs_time(parent_inode->i_sb); @@ -1420,7 +1495,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, goto fail; } - record_root_in_trans(trans, root); + record_root_in_trans(trans, root, 0); btrfs_set_root_last_snapshot(&root->root_item, trans->transid); memcpy(new_root_item, &root->root_item, sizeof(*new_root_item)); btrfs_check_and_init_root_item(new_root_item); @@ -1516,6 +1591,17 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, goto fail; } + /* + * Do special qgroup accounting for snapshot, as we do some qgroup + * snapshot hack to do fast snapshot. + * To co-operate with that hack, we do hack again. + * Or snapshot will be greatly slowed down by a subtree qgroup rescan + */ + ret = qgroup_account_snapshot(trans, root, parent_root, + pending->inherit, objectid); + if (ret < 0) + goto fail; + ret = btrfs_insert_dir_item(trans, parent_root, dentry->d_name.name, dentry->d_name.len, parent_inode, &key, @@ -1559,23 +1645,6 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, goto fail; } - /* - * account qgroup counters before qgroup_inherit() - */ - ret = btrfs_qgroup_prepare_account_extents(trans, fs_info); - if (ret) - goto fail; - ret = btrfs_qgroup_account_extents(trans, fs_info); - if (ret) - goto fail; - ret = btrfs_qgroup_inherit(trans, fs_info, - root->root_key.objectid, - objectid, pending->inherit); - if (ret) { - btrfs_abort_transaction(trans, root, ret); - goto fail; - } - fail: pending->error = ret; dir_item_existed: