From patchwork Wed Aug 24 01:14:09 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qu Wenruo X-Patchwork-Id: 12952791 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B24C9C38142 for ; Wed, 24 Aug 2022 01:14:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233013AbiHXBOh (ORCPT ); Tue, 23 Aug 2022 21:14:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33326 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233010AbiHXBOg (ORCPT ); Tue, 23 Aug 2022 21:14:36 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 85F15F40 for ; Tue, 23 Aug 2022 18:14:35 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 24A54336B7 for ; Wed, 24 Aug 2022 01:14:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1661303674; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TjGdLmgJK5Ug1zn8Fj1fn3o+9e5IBvVk90Rbm3IDiD0=; b=H8IGSiPbMGAO8XxPjCV89Mifj9EV/OoFbPg03qGjeLNzBG0E19SxfdGZcAQWmdzD4ArBsU sZDWIuOeYEwKWC7oSaga2KQOsL/9H48feZtooyyHlSKWZ1TgGjYOE9UklhTjULx5h0cofa jdmSAZ0+9kLfr285AKOJZGnuyw0q2TU= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 5CB3413A89 for ; Wed, 24 Aug 2022 01:14:33 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id CDj4CHl7BWNnWAAAMHmgww (envelope-from ) for ; Wed, 24 Aug 2022 01:14:33 +0000 From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH v4 5/5] btrfs: skip subtree scan if it's too high to avoid low stall in btrfs_commit_transaction() Date: Wed, 24 Aug 2022 09:14:09 +0800 Message-Id: X-Mailer: git-send-email 2.37.2 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Btrfs qgroup has a long history of bringing performance penalty in btrfs_commit_transaction(). Although we tried our best to migrate such impact, there is still an unsolved call site, btrfs_drop_snapshot(). This function will find the highest shared tree block and modify its extent ownership to do a subvolume/snapshot dropping. Such change will affect the whole subtree, and cause tons of qgroup dirty extents and stall btrfs_commit_transaction(). To avoid such problem, here we introduce a new sysfs interface, /sys/fs/btrfs//qgroups/drop_subptree_threshold, to determine at whether and at which level we should skip qgroup accounting for subtree dropping. The default value is BTRFS_MAX_LEVEL, thus every subtree drop will go through qgroup accounting, to ensure qgroup numbers are kept as consistent as possible. While for performance sensitive users, they can change the values to more reasonable values like 3, to make any subtree, which is at or higher than level 3, to mark qgroup inconsistent and skip the accounting. The cost is obvious, the qgroup number is no longer consistent, but at least performance is more reasonable, and users have the control. Signed-off-by: Qu Wenruo --- fs/btrfs/ctree.h | 1 + fs/btrfs/disk-io.c | 1 + fs/btrfs/qgroup.c | 18 ++++++++++++++++++ fs/btrfs/sysfs.c | 39 +++++++++++++++++++++++++++++++++++++++ 4 files changed, 59 insertions(+) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 3dc30f5e6fd0..db3b0014452e 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -1006,6 +1006,7 @@ struct btrfs_fs_info { struct completion qgroup_rescan_completion; struct btrfs_work qgroup_rescan_work; bool qgroup_rescan_running; /* protected by qgroup_rescan_lock */ + u8 qgroup_drop_subtree_thres; /* filesystem state */ unsigned long fs_state; diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index e67614afcf4f..bb3feb3d2b23 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -2266,6 +2266,7 @@ static void btrfs_init_qgroup(struct btrfs_fs_info *fs_info) fs_info->qgroup_seq = 1; fs_info->qgroup_ulist = NULL; fs_info->qgroup_rescan_running = false; + fs_info->qgroup_drop_subtree_thres = BTRFS_MAX_LEVEL; mutex_init(&fs_info->qgroup_rescan_lock); } diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index dcd2669e16cd..4c7ade3f1b77 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -1283,6 +1283,7 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info) quota_root = fs_info->quota_root; fs_info->quota_root = NULL; fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_ON; + fs_info->qgroup_drop_subtree_thres = BTRFS_MAX_LEVEL; spin_unlock(&fs_info->qgroup_lock); btrfs_free_qgroup_config(fs_info); @@ -2312,6 +2313,7 @@ int btrfs_qgroup_trace_subtree(struct btrfs_trans_handle *trans, struct btrfs_fs_info *fs_info = trans->fs_info; int ret = 0; int level; + u8 drop_subptree_thres; struct extent_buffer *eb = root_eb; struct btrfs_path *path = NULL; @@ -2321,6 +2323,22 @@ int btrfs_qgroup_trace_subtree(struct btrfs_trans_handle *trans, if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)) return 0; + spin_lock(&fs_info->qgroup_lock); + drop_subptree_thres = fs_info->qgroup_drop_subtree_thres; + spin_unlock(&fs_info->qgroup_lock); + /* + * This function only get called for snapshot drop, if we hit a high + * node here, it means we are going to change ownership for quite a lot + * of extents, which will greatly slow down btrfs_commit_transaction(). + * + * So here if we find a high tree here, we just skip the accounting and + * mark qgroup inconsistent. + */ + if (root_level >= drop_subptree_thres) { + qgroup_mark_inconsistent(fs_info); + return 0; + } + if (!extent_buffer_uptodate(root_eb)) { ret = btrfs_read_extent_buffer(root_eb, root_gen, root_level, NULL); if (ret) diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index 6dc06300b666..05ac6363d7b1 100644 --- a/fs/btrfs/sysfs.c +++ b/fs/btrfs/sysfs.c @@ -2056,6 +2056,44 @@ static ssize_t qgroup_inconsistent_show(struct kobject *qgroups_kobj, BTRFS_ATTR(qgroups, inconsistent, qgroup_inconsistent_show); +static ssize_t qgroup_drop_subtree_thres_show(struct kobject *qgroups_kobj, + struct kobj_attribute *a, + char *buf) +{ + struct btrfs_fs_info *fs_info = to_fs_info(qgroups_kobj->parent); + u8 result; + + spin_lock(&fs_info->qgroup_lock); + result = fs_info->qgroup_drop_subtree_thres; + spin_unlock(&fs_info->qgroup_lock); + + return scnprintf(buf, PAGE_SIZE, "%d\n", result); +} + +static ssize_t qgroup_drop_subtree_thres_store(struct kobject *qgroups_kobj, + struct kobj_attribute *a, + const char *buf, size_t len) +{ + struct btrfs_fs_info *fs_info = to_fs_info(qgroups_kobj->parent); + u8 new_thres; + int ret; + + ret = kstrtou8(buf, 10, &new_thres); + if (ret) + return -EINVAL; + + if (new_thres > BTRFS_MAX_LEVEL) + return -EINVAL; + + spin_lock(&fs_info->qgroup_lock); + fs_info->qgroup_drop_subtree_thres = new_thres; + spin_unlock(&fs_info->qgroup_lock); + return len; +} + +BTRFS_ATTR_RW(qgroups, drop_subtree_threshold, qgroup_drop_subtree_thres_show, + qgroup_drop_subtree_thres_store); + /* * Qgroups global info * @@ -2064,6 +2102,7 @@ BTRFS_ATTR(qgroups, inconsistent, qgroup_inconsistent_show); static struct attribute *qgroups_attrs[] = { BTRFS_ATTR_PTR(qgroups, enabled), BTRFS_ATTR_PTR(qgroups, inconsistent), + BTRFS_ATTR_PTR(qgroups, drop_subtree_threshold), NULL }; ATTRIBUTE_GROUPS(qgroups);