From b20fe56cd285dbbf64874ec9d1c81f8a8ac2f821 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Mon, 26 Feb 2024 14:21:13 +1030 Subject: btrfs: qgroup: allow quick inherit if snapshot is created and added to the same parent Currently "btrfs subvolume snapshot -i " would always mark the qgroup inconsistent. This can be annoying if the fs has a lot of snapshots, and needs qgroup to get the accounting for the amount of bytes it can free for each snapshot. Although we have the new simple quote as a solution, there is also a case where we can skip the full scan, if all the following conditions are met: - The source subvolume belongs to a higher level parent qgroup - The parent qgroup already owns all its bytes exclusively - The new snapshot is also added to the same parent qgroup In that case, we only need to add nodesize to the parent qgroup and avoid a full rescan. This patch would add the extra quick accounting update for such inherit. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/qgroup.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 72 insertions(+), 7 deletions(-) (limited to 'fs/btrfs') diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index af241aaa654a..5f90f0605b12 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -3138,6 +3138,62 @@ static int qgroup_auto_inherit(struct btrfs_fs_info *fs_info, return 0; } +/* + * Check if we can skip rescan when inheriting qgroups. If @src has a single + * @parent, and that @parent is owning all its bytes exclusively, we can skip + * the full rescan, by just adding nodesize to the @parent's excl/rfer. + * + * Return <0 for fatal errors (like srcid/parentid has no qgroup). + * Return 0 if a quick inherit is done. + * Return >0 if a quick inherit is not possible, and a full rescan is needed. + */ +static int qgroup_snapshot_quick_inherit(struct btrfs_fs_info *fs_info, + u64 srcid, u64 parentid) +{ + struct btrfs_qgroup *src; + struct btrfs_qgroup *parent; + struct btrfs_qgroup_list *list; + int nr_parents = 0; + + src = find_qgroup_rb(fs_info, srcid); + if (!src) + return -ENOENT; + parent = find_qgroup_rb(fs_info, parentid); + if (!parent) + return -ENOENT; + + /* + * Source has no parent qgroup, but our new qgroup would have one. + * Qgroup numbers would become inconsistent. + */ + if (list_empty(&src->groups)) + return 1; + + list_for_each_entry(list, &src->groups, next_group) { + /* The parent is not the same, quick update is not possible. */ + if (list->group->qgroupid != parentid) + return 1; + nr_parents++; + /* + * More than one parent qgroup, we can't be sure about accounting + * consistency. + */ + if (nr_parents > 1) + return 1; + } + + /* + * The parent is not exclusively owning all its bytes. We're not sure + * if the source has any bytes not fully owned by the parent. + */ + if (parent->excl != parent->rfer) + return 1; + + parent->excl += fs_info->nodesize; + parent->rfer += fs_info->nodesize; + return 0; +} + /* * Copy the accounting information between qgroups. This is necessary * when a snapshot or a subvolume is created. Throwing an error will @@ -3306,6 +3362,13 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid, qgroup_dirty(fs_info, dstgroup); qgroup_dirty(fs_info, srcgroup); + + /* + * If the source qgroup has parent but the new one doesn't, + * we need a full rescan. + */ + if (!inherit && !list_empty(&srcgroup->groups)) + need_rescan = true; } if (!inherit) @@ -3320,14 +3383,16 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid, if (ret) goto unlock; } + if (srcid) { + /* Check if we can do a quick inherit. */ + ret = qgroup_snapshot_quick_inherit(fs_info, srcid, *i_qgroups); + if (ret < 0) + goto unlock; + if (ret > 0) + need_rescan = true; + ret = 0; + } ++i_qgroups; - - /* - * If we're doing a snapshot, and adding the snapshot to a new - * qgroup, the numbers are guaranteed to be incorrect. - */ - if (srcid) - need_rescan = true; } for (i = 0; i < inherit->num_ref_copies; ++i, i_qgroups += 2) { -- cgit v1.2.3