[PATCH v4 1/6] maple_tree: add mas_for_each_rev() helper

[Suren Baghdasaryan <surenb@google.com>]

Add mas_for_each_rev() function to iterate maple tree nodes in reverse
order.

Suggested-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---
 include/linux/maple_tree.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
index 61c236850ca8..cbbcd18d4186 100644
--- a/include/linux/maple_tree.h
+++ b/include/linux/maple_tree.h
@@ -592,6 +592,20 @@ static __always_inline void mas_reset(struct ma_state *mas)
 #define mas_for_each(__mas, __entry, __max) \
 	while (((__entry) = mas_find((__mas), (__max))) != NULL)
 
+/**
+ * mas_for_each_rev() - Iterate over a range of the maple tree in reverse order.
+ * @__mas: Maple Tree operation state (maple_state)
+ * @__entry: Entry retrieved from the tree
+ * @__min: minimum index to retrieve from the tree
+ *
+ * When returned, mas->index and mas->last will hold the entire range for the
+ * entry.
+ *
+ * Note: may return the zero entry.
+ */
+#define mas_for_each_rev(__mas, __entry, __min) \
+	while (((__entry) = mas_find_rev((__mas), (__min))) != NULL)
+
 #ifdef CONFIG_DEBUG_MAPLE_TREE
 enum mt_dump_format {
 	mt_dump_dec,
-- 
2.47.0.105.g07ac214952-goog