* Vlastimil Babka [off-list ref] [211215 07:54]:

On 12/1/21 15:29, Liam Howlett wrote:

quoted

+/*
+ * mt_find() - Search from the start up until an entry is found.
+ * @mt: The maple tree
+ * @*index: Pointer which contains the start location of the search
+ * @max: The maximum value to check
+ *
+ * Handles locking.
+ *
+ * Return: The entry at or after the @*index or %NULL

Noticed later that the comment doesn't say how *index is updated.

Good point.  I will add to the comment what happens to *index.

quoted

+ */
+void *mt_find(struct maple_tree *mt, unsigned long *index, unsigned long max)
+{
+	MA_STATE(mas, mt, *index, *index);
+	void *entry;
+#ifdef CONFIG_DEBUG_MAPLE_TREE
+	unsigned long copy = *index;
+#endif
+
+	trace_ma_read(__func__, &mas);
+
+	if ((*index) > max)
+		return NULL;
+
+	rcu_read_lock();
+retry:
+	entry = mas_state_walk(&mas);
+	if (mas_is_start(&mas))
+		goto retry;
+
+	if (unlikely(xa_is_zero(entry)))
+		entry = NULL;
+
+	if (entry)
+		goto unlock;
+
+	while (mas_searchable(&mas) && (mas.index < max)) {
+		entry = mas_next_entry(&mas, max);
+		if (likely(entry && !xa_is_zero(entry)))
+			break;
+	}
+
+	if (unlikely(xa_is_zero(entry)))
+		entry = NULL;
+unlock:
+	rcu_read_unlock();
+	if (likely(entry)) {
+		*index = mas.last + 1;
+#ifdef CONFIG_DEBUG_MAPLE_TREE
+		if ((*index) && (*index) <= copy)
+			printk("index not increased! %lx <= %lx\n",
+			       *index, copy);
+		MT_BUG_ON(mt, (*index) && ((*index) <= copy));
+#endif
+	}
+
+	return entry;
+}
+EXPORT_SYMBOL(mt_find);