1 files changed, 27 insertions, 13 deletions

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index ef66be963798..b4ee2d29d7a9 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -1053,7 +1053,7 @@ static inline void mte_set_gap(const struct maple_enode *mn,
  * mas_ascend() - Walk up a level of the tree.
  * @mas: The maple state
  *
- * Sets the @mas->max and @mas->min to the correct values when walking up.  This
+ * Sets the @mas->max and @mas->min for the parent node of mas->node.  This
  * may cause several levels of walking up to find the correct min and max.
  * May find a dead node which will cause a premature return.
  * Return: 1 on dead node, 0 otherwise
@@ -1098,6 +1098,12 @@ static int mas_ascend(struct ma_state *mas)
 
 	min = 0;
 	max = ULONG_MAX;
+
+	/*
+	 * !mas->offset implies that parent node min == mas->min.
+	 * mas->offset > 0 implies that we need to walk up to find the
+	 * implied pivot min.
+	 */
 	if (!mas->offset) {
 		min = mas->min;
 		set_min = true;
@@ -4560,15 +4566,12 @@ again:
 	if (unlikely(mas_rewalk_if_dead(mas, node, save_point)))
 		goto retry;
 
-
 	if (likely(entry))
 		return entry;
 
 	if (!empty) {
-		if (mas->index <= min) {
-			mas->status = ma_underflow;
-			return NULL;
-		}
+		if (mas->index <= min)
+			goto underflow;
 
 		goto again;
 	}
@@ -4930,7 +4933,7 @@ void *mas_walk(struct ma_state *mas)
 {
 	void *entry;
 
-	if (!mas_is_active(mas) || !mas_is_start(mas))
+	if (!mas_is_active(mas) && !mas_is_start(mas))
 		mas->status = ma_start;
 retry:
 	entry = mas_state_walk(mas);
@@ -5659,6 +5662,17 @@ int mas_expected_entries(struct ma_state *mas, unsigned long nr_entries)
 }
 EXPORT_SYMBOL_GPL(mas_expected_entries);
 
+static void mas_may_activate(struct ma_state *mas)
+{
+	if (!mas->node) {
+		mas->status = ma_start;
+	} else if (mas->index > mas->max || mas->index < mas->min) {
+		mas->status = ma_start;
+	} else {
+		mas->status = ma_active;
+	}
+}
+
 static bool mas_next_setup(struct ma_state *mas, unsigned long max,
 		void **entry)
 {
@@ -5682,11 +5696,11 @@ static bool mas_next_setup(struct ma_state *mas, unsigned long max,
 		break;
 	case ma_overflow:
 		/* Overflowed before, but the max changed */
-		mas->status = ma_active;
+		mas_may_activate(mas);
 		break;
 	case ma_underflow:
 		/* The user expects the mas to be one before where it is */
-		mas->status = ma_active;
+		mas_may_activate(mas);
 		*entry = mas_walk(mas);
 		if (*entry)
 			return true;
@@ -5807,11 +5821,11 @@ static bool mas_prev_setup(struct ma_state *mas, unsigned long min, void **entry
 		break;
 	case ma_underflow:
 		/* underflowed before but the min changed */
-		mas->status = ma_active;
+		mas_may_activate(mas);
 		break;
 	case ma_overflow:
 		/* User expects mas to be one after where it is */
-		mas->status = ma_active;
+		mas_may_activate(mas);
 		*entry = mas_walk(mas);
 		if (*entry)
 			return true;
@@ -5976,7 +5990,7 @@ static __always_inline bool mas_find_setup(struct ma_state *mas, unsigned long m
 			return true;
 		}
 
-		mas->status = ma_active;
+		mas_may_activate(mas);
 		*entry = mas_walk(mas);
 		if (*entry)
 			return true;
@@ -5985,7 +5999,7 @@ static __always_inline bool mas_find_setup(struct ma_state *mas, unsigned long m
 		if (unlikely(mas->last >= max))
 			return true;
 
-		mas->status = ma_active;
+		mas_may_activate(mas);
 		*entry = mas_walk(mas);
 		if (*entry)
 			return true;