From patchwork Tue Apr 12 07:35:22 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qu Wenruo X-Patchwork-Id: 8807701 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 CDEC99F39A for ; Tue, 12 Apr 2016 07:36:26 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id A6C3B20320 for ; Tue, 12 Apr 2016 07:36:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5742920166 for ; Tue, 12 Apr 2016 07:36:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755926AbcDLHgV (ORCPT ); Tue, 12 Apr 2016 03:36:21 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:39874 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1754609AbcDLHgU (ORCPT ); Tue, 12 Apr 2016 03:36:20 -0400 X-IronPort-AV: E=Sophos;i="5.20,367,1444665600"; d="scan'208";a="432741" Received: from unknown (HELO cn.fujitsu.com) ([10.167.250.3]) by song.cn.fujitsu.com with ESMTP; 12 Apr 2016 15:35:58 +0800 Received: from localhost.localdomain (unknown [10.167.226.34]) by cn.fujitsu.com (Postfix) with ESMTP id 6D8CC4056406 for ; Tue, 12 Apr 2016 15:35:57 +0800 (CST) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH v2] btrfs: qgroup: Fix qgroup accounting when creating snapshot Date: Tue, 12 Apr 2016 15:35:22 +0800 Message-Id: <1460446522-1919-1-git-send-email-quwenruo@cn.fujitsu.com> X-Mailer: git-send-email 2.8.0 MIME-Version: 1.0 X-yoursite-MailScanner-ID: 6D8CC4056406.ACAA5 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) ====== 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 --- changelog: v2: Fix a soft lockup caused by missing switch_commit_root() call. Fix a warning caused by dirty-but-not-committed root. Note: This may be the dirtiest hack I have ever done. As there are already several different judgment to check if a fs root should be updated. From root->last_trans to root->commit_root == root->node. With this patch, we must switch the root of at least related fs tree and extent tree to allow qgroup to call btrfs_qgroup_account_extents(). But this will break some transid judgement, as transid is already updated to current transid. (maybe we need a special sub-transid for qgroup use only?) As long as current qgroup use commit_root to determine old_roots, there is no better idea though. --- fs/btrfs/transaction.c | 96 +++++++++++++++++++++++++++++++++++++------------- 1 file changed, 71 insertions(+), 25 deletions(-) diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index 43885e5..0f299a56 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -311,12 +311,13 @@ 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); + WARN_ON(root->commit_root != root->node && !force); /* * see below for IN_TRANS_SETUP usage rules @@ -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; @@ -1383,7 +1384,7 @@ 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 +1421,7 @@ 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 +1517,62 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, goto fail; } + /* + * Account qgroups before insert the dir item + * As such dir item insert will modify parent_root, which could be + * src root. If we don't do it now, wrong accounting may be inherited + * to snapshot qgroup. + * + * For reason locking tree_log_mutex, see btrfs_commit_transaction() + * comment + */ + mutex_lock(&root->fs_info->tree_log_mutex); + + ret = commit_fs_roots(trans, root); + if (ret) { + mutex_unlock(&root->fs_info->tree_log_mutex); + goto fail; + } + + ret = btrfs_qgroup_prepare_account_extents(trans, root->fs_info); + if (ret < 0) { + mutex_unlock(&root->fs_info->tree_log_mutex); + goto fail; + } + ret = btrfs_qgroup_account_extents(trans, root->fs_info); + if (ret < 0) { + mutex_unlock(&root->fs_info->tree_log_mutex); + goto fail; + } + /* + * Now qgroup are all updated, we can inherit it to new qgroups + */ + ret = btrfs_qgroup_inherit(trans, fs_info, + root->root_key.objectid, + objectid, pending->inherit); + if (ret < 0) { + mutex_unlock(&root->fs_info->tree_log_mutex); + goto fail; + } + /* + * qgroup_account_extents() must be followed by a + * switch_commit_roots(), or next qgroup_account_extents() will + * be corrupted + */ + ret = commit_cowonly_roots(trans, root); + if (ret) { + mutex_unlock(&root->fs_info->tree_log_mutex); + goto fail; + } + /* + * Just like in btrfs_commit_transaction(), we need to + * switch_commit_roots(). + * However this time we don't need to do a full one, + * excluding tree root and chunk root should be OK. + */ + switch_commit_roots(trans->transaction, root->fs_info); + mutex_unlock(&root->fs_info->tree_log_mutex); + ret = btrfs_insert_dir_item(trans, parent_root, dentry->d_name.name, dentry->d_name.len, parent_inode, &key, @@ -1527,6 +1584,12 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, goto fail; } + /* + * Force parent root to be updated, as we recorded it before its + * last_trans == cur_transid + */ + record_root_in_trans(trans, parent_root, 1); + btrfs_i_size_write(parent_inode, parent_inode->i_size + dentry->d_name.len * 2); parent_inode->i_mtime = parent_inode->i_ctime = @@ -1559,23 +1622,6 @@ 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: