@@ -3087,6 +3087,63 @@ static int qgroup_auto_inherit(struct btrfs_fs_info *fs_info,
return 0;
}
+/*
+ * 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 go 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 not possible. */
+ if (list->group->qgroupid != parentid)
+ return 1;
+ nr_parents++;
+ /*
+ * More than one parent qgroups, we're not sure about if qgroup
+ * would be inconsistent.
+ */
+ 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
@@ -3269,14 +3326,17 @@ 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) {