From: Liam R. Howlett <Liam.Howlett@Oracle.com>
Date: Mon, 5 Jul 2021 19:30:41 +0000 (-0400)
Subject: maple_tree: Change mas_next() behaviour
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=6be6e70864e3ec42d3927ff07d5649c56d994f35;p=users%2Fjedix%2Flinux-maple.git

maple_tree: Change mas_next() behaviour

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---

diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
index eea2d2a0e26e2..7ccca75d4e3bd 100644
--- a/include/linux/maple_tree.h
+++ b/include/linux/maple_tree.h
@@ -243,6 +243,7 @@ struct ma_state {
 #define MAS_START	((struct maple_enode *)1UL)
 #define MAS_ROOT	((struct maple_enode *)5UL)
 #define MAS_NONE	((struct maple_enode *)9UL)
+#define MAS_PAUSE	((struct maple_enode *)17UL)
 #define MA_ERROR(err) \
 		((struct maple_enode *)(((unsigned long)err << 2) | 2UL))
 
@@ -286,6 +287,12 @@ static inline bool mas_is_none(struct ma_state *mas)
 	return mas->node == MAS_NONE;
 }
 
+/* Checks if a mas has been paused */
+static inline bool mas_is_paused(struct ma_state *mas)
+{
+	return mas->node == MAS_PAUSE;
+}
+
 void mas_dup_tree(struct ma_state *oldmas, struct ma_state *mas);
 void mas_dup_store(struct ma_state *mas, void *entry);
 /* This finds an empty area from the highest address to the lowest.
diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index e0e55c861a6e8..7e977ac2d6321 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4800,7 +4800,7 @@ void *mas_walk(struct ma_state *mas)
 	unsigned long index = mas->index;
 	void *entry;
 
-	if (mas_is_none(mas))
+	if (mas_is_none(mas) || mas_is_paused(mas))
 		mas->node = MAS_START;
 
 	_mas_walk(mas, &range_min, &range_max);
@@ -5197,7 +5197,7 @@ static inline void *mas_range_load(struct ma_state *mas,
 	unsigned long index = mas->index;
 	void *entry;
 
-	if (mas_is_none(mas))
+	if (mas_is_none(mas) || mas_is_paused(mas))
 		mas->node = MAS_START;
 
 	if (_mas_walk(mas, range_min, range_max))
@@ -5226,11 +5226,9 @@ retry:
  */
 static void *_mas_next(struct ma_state *mas, unsigned long limit)
 {
-	void *entry = NULL;
-
-
 	if (unlikely(mas_is_start(mas))) {
 		/* First run */
+		void *entry = NULL;
 		unsigned long range_max;
 		unsigned long range_start;
 
@@ -5245,8 +5243,7 @@ static void *_mas_next(struct ma_state *mas, unsigned long limit)
 	if (unlikely(!mas_searchable(mas)))
 		return NULL;
 
-	entry = __mas_next(mas, limit);
-	return entry;
+	return __mas_next(mas, limit);
 }
 
 /*
@@ -5585,6 +5582,7 @@ void mas_destroy(struct ma_state *mas)
  * @mas: The maple state
  * @max: The maximum index to check.
  *
+ * Returns the next entry after @mas->index.
  * Must hold rcu_read_lock or the write lock.
  * Can return the zero entry.
  *
@@ -5592,14 +5590,29 @@ void mas_destroy(struct ma_state *mas)
  */
 void *mas_next(struct ma_state *mas, unsigned long max)
 {
-	if (mas_is_none(mas))
+	if (mas_is_none(mas) || mas_is_paused(mas))
 		mas->node = MAS_START;
 
-	return _mas_next(mas, max);
+	if (unlikely(!mas_searchable(mas)))
+		return NULL;
+
+	if (mas_is_start(mas)) {
+		mas->index = ++mas->last;
+		return mas_find(mas, max);
+	}
+
+	return __mas_next(mas, max);
 }
 EXPORT_SYMBOL_GPL(mas_next);
 
-
+/*
+ * mt_next() - get the next value in the maple tree
+ * @mt: The maple tree
+ * @index: The start index
+ * @max: The maximum index to check
+ *
+ * Returns: The entry at @index or higher, or %NULL if nothing is found.
+ */
 void *mt_next(struct maple_tree *mt, unsigned long index, unsigned long max)
 {
 	void *entry = NULL;
@@ -5620,7 +5633,8 @@ EXPORT_SYMBOL_GPL(mt_next);
  * Must hold rcu_read_lock or the write lock.
  * Will reset mas to MAS_START if the node is MAS_NONE.  Will stop on not
  * searchable nodes.  If mas->node is MAS_START, it will first look up the
- * index, then get the previous entry.
+ * index and return.  If there is nothing at mas->index, then the prev entry
+ * will be returned.
  *
  * Return: the previous value or %NULL.
  */
@@ -5634,13 +5648,12 @@ void *mas_prev(struct ma_state *mas, unsigned long min)
 		return NULL;
 	}
 
-	if (mas_is_none(mas))
+	if (mas_is_none(mas) || mas_is_paused(mas))
 		mas->node = MAS_START;
 
 	if (!mas_searchable(mas))
 		return NULL;
 
-
 	if (mas_is_start(mas)) {
 		mas_start(mas);
 		mas_walk(mas);
@@ -5654,6 +5667,14 @@ void *mas_prev(struct ma_state *mas, unsigned long min)
 }
 EXPORT_SYMBOL_GPL(mas_prev);
 
+/*
+ * mt_prev() - get the previous value in the maple tree
+ * @mt: The maple tree
+ * @index: The start index
+ * @max: The minumum index to check
+ *
+ * Returns: The entry at @index or lower, or %NULL if nothing is found.
+ */
 void *mt_prev(struct maple_tree *mt, unsigned long index, unsigned long min)
 {
 	void *entry = NULL;
@@ -5680,18 +5701,27 @@ EXPORT_SYMBOL_GPL(mt_prev);
  */
 void mas_pause(struct ma_state *mas)
 {
-	/* Overflow protection */
-	if (mas->last == ULONG_MAX) {
-		mas->node = MAS_NONE;
-		return;
-	}
-
-	mas_reset(mas);
-	mas->last++;
-	mas->index = mas->last;
+	mas->node = MAS_PAUSE;
 }
 EXPORT_SYMBOL_GPL(mas_pause);
 
+/*
+ * mas_resume_fwd() - resume a forward search.
+ * @mas: The maple state
+ *
+ * Returns: 0 on success, -EFAULT on overflow.
+ */
+static inline int mas_resume_fwd(struct ma_state *mas) {
+	if (mas_is_paused(mas)) {
+		if (unlikely(mas->last == ULONG_MAX)) {
+			mas->node = MAS_NONE;
+			return -EFAULT;
+		}
+		mas->node = MAS_START;
+		mas->index = ++mas->last;
+	}
+	return 0;
+}
 
 /*
  * mas_find: If mas->node == MAS_START, find the first
@@ -5714,6 +5744,8 @@ void *mas_find(struct ma_state *mas, unsigned long max)
 
 	if (mas_is_start(mas) && (mas->index <= max))
 		first = true;
+	else if (mas_resume_fwd(mas))
+		return NULL;
 
 retry:
 	while (mas_search_cont(mas, mas->index, max, entry))