4 files changed, 60 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 05df502c3c9d..0108585d838d 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1002,6 +1002,7 @@ 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 120b7697ab42..0d33d771cee3 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2260,6 +2260,7 @@ 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 89df16dcd83f..f4dc5aa3f700 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1279,6 +1279,7 @@ 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);
@@ -2307,6 +2308,7 @@ 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;
 
@@ -2316,6 +2318,23 @@ 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 gets 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 736d81d911f9..699b54b3acaa 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -2045,6 +2045,44 @@ 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 sysfs_emit(buf, "%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
  *
@@ -2053,6 +2091,7 @@ 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);