maple_tree: add mas_next_range() and mas_find_range() interfaces

Some users of the maple tree may want to move to the next range in the
tree, even if it stores a NULL.  This family of function provides that
functionality by advancing one slot at a time and returning the result,
while mas_contiguous() will iterate over the range and stop on
encountering the first NULL.

Link: https://lkml.kernel.org/r/20230518145544.1722059-29-Liam.Howlett@oracle.comSigned-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: David Binderman <dcb314@hotmail.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Vernon Yang <vernon2gm@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/maple_tree.h

@@ -455,6 +455,7 @@ void *mas_erase(struct ma_state *mas);
 int mas_store_gfp(struct ma_state *mas, void *entry, gfp_t gfp);
 void mas_store_prealloc(struct ma_state *mas, void *entry);
 void *mas_find(struct ma_state *mas, unsigned long max);
+void *mas_find_range(struct ma_state *mas, unsigned long max);
 void *mas_find_rev(struct ma_state *mas, unsigned long min);
 int mas_preallocate(struct ma_state *mas, gfp_t gfp);
 bool mas_is_err(struct ma_state *mas);
@@ -467,6 +468,7 @@ int mas_expected_entries(struct ma_state *mas, unsigned long nr_entries);
 
 void *mas_prev(struct ma_state *mas, unsigned long min);
 void *mas_next(struct ma_state *mas, unsigned long max);
+void *mas_next_range(struct ma_state *mas, unsigned long max);
 
 int mas_empty_area(struct ma_state *mas, unsigned long min, unsigned long max,
 		   unsigned long size);
@@ -528,7 +530,6 @@ static inline void mas_reset(struct ma_state *mas)
 #define mas_for_each(__mas, __entry, __max) \
 	while (((__entry) = mas_find((__mas), (__max))) != NULL)
 
-
 /**
  * mas_set_range() - Set up Maple Tree operation state for a different index.
  * @mas: Maple Tree operation state.

lib/maple_tree.c

@@ -4793,13 +4793,10 @@ static void *mas_next_slot(struct ma_state *mas, unsigned long max, bool empty)
  */
 static inline void *mas_next_entry(struct ma_state *mas, unsigned long limit)
 {
-	void *entry = NULL;
-
 	if (mas->last >= limit)
 		return NULL;
 
-	entry = mas_next_slot(mas, limit, false);
-	return entry;
+	return mas_next_slot(mas, limit, false);
 }
 
 /*
@@ -5880,18 +5877,8 @@ int mas_expected_entries(struct ma_state *mas, unsigned long nr_entries)
 }
 EXPORT_SYMBOL_GPL(mas_expected_entries);
 
-/**
- * mas_next() - Get the next entry.
- * @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.
- *
- * Return: The next entry or %NULL
- */
-void *mas_next(struct ma_state *mas, unsigned long max)
+static inline bool mas_next_setup(struct ma_state *mas, unsigned long max,
+		void **entry)
 {
 	bool was_none = mas_is_none(mas);
 
@@ -5899,24 +5886,71 @@ void *mas_next(struct ma_state *mas, unsigned long max)
 		mas->node = MAS_START;
 
 	if (mas_is_start(mas))
-		mas_walk(mas); /* Retries on dead nodes handled by mas_walk */
+		*entry = mas_walk(mas); /* Retries on dead nodes handled by mas_walk */
 
 	if (mas_is_ptr(mas)) {
+		*entry = NULL;
 		if (was_none && mas->index == 0) {
 			mas->index = mas->last = 0;
-			return mas_root(mas);
+			return true;
 		}
 		mas->index = 1;
 		mas->last = ULONG_MAX;
 		mas->node = MAS_NONE;
-		return NULL;
+		return true;
 	}
 
-	/* Retries on dead nodes handled by mas_next_entry */
-	return mas_next_entry(mas, max);
+	if (mas_is_none(mas))
+		return true;
+	return false;
+}
+
+/**
+ * mas_next() - Get the next entry.
+ * @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.
+ *
+ * Return: The next entry or %NULL
+ */
+void *mas_next(struct ma_state *mas, unsigned long max)
+{
+	void *entry = NULL;
+
+	if (mas_next_setup(mas, max, &entry))
+		return entry;
+
+	/* Retries on dead nodes handled by mas_next_slot */
+	return mas_next_slot(mas, max, false);
 }
 EXPORT_SYMBOL_GPL(mas_next);
 
+/**
+ * mas_next_range() - Advance the maple state to the next range
+ * @mas: The maple state
+ * @max: The maximum index to check.
+ *
+ * Sets @mas->index and @mas->last to the range.
+ * Must hold rcu_read_lock or the write lock.
+ * Can return the zero entry.
+ *
+ * Return: The next entry or %NULL
+ */
+void *mas_next_range(struct ma_state *mas, unsigned long max)
+{
+	void *entry = NULL;
+
+	if (mas_next_setup(mas, max, &entry))
+		return entry;
+
+	/* Retries on dead nodes handled by mas_next_slot */
+	return mas_next_slot(mas, max, true);
+}
+EXPORT_SYMBOL_GPL(mas_next_range);
+
 /**
  * mt_next() - get the next value in the maple tree
  * @mt: The maple tree
@@ -6026,49 +6060,41 @@ void mas_pause(struct ma_state *mas)
 EXPORT_SYMBOL_GPL(mas_pause);
 
 /**
- * mas_find() - On the first call, find the entry at or after mas->index up to
- * %max.  Otherwise, find the entry after mas->index.
+ * mas_find_setup() - Internal function to set up mas_find*().
  * @mas: The maple state
- * @max: The maximum value to check.
- *
- * Must hold rcu_read_lock or the write lock.
- * If an entry exists, last and index are updated accordingly.
- * May set @mas->node to MAS_NONE.
+ * @max: The maximum index
+ * @entry: Pointer to the entry
  *
- * Return: The entry or %NULL.
+ * Returns: True if entry is the answer, false otherwise.
  */
-void *mas_find(struct ma_state *mas, unsigned long max)
+static inline bool mas_find_setup(struct ma_state *mas, unsigned long max,
+		void **entry)
 {
+	*entry = NULL;
+
 	if (unlikely(mas_is_none(mas))) {
 		if (unlikely(mas->last >= max))
-			return NULL;
+			return true;
 
 		mas->index = mas->last;
 		mas->node = MAS_START;
-	}
-
-	if (unlikely(mas_is_paused(mas))) {
+	} else if (unlikely(mas_is_paused(mas))) {
 		if (unlikely(mas->last >= max))
-			return NULL;
+			return true;
 
 		mas->node = MAS_START;
 		mas->index = ++mas->last;
-	}
-
-
-	if (unlikely(mas_is_ptr(mas)))
+	} else if (unlikely(mas_is_ptr(mas)))
 		goto ptr_out_of_range;
 
 	if (unlikely(mas_is_start(mas))) {
 		/* First run or continue */
-		void *entry;
-
 		if (mas->index > max)
-			return NULL;
+			return true;
 
-		entry = mas_walk(mas);
-		if (entry)
-			return entry;
+		*entry = mas_walk(mas);
+		if (*entry)
+			return true;
 
 	}
 
@@ -6076,23 +6102,69 @@ void *mas_find(struct ma_state *mas, unsigned long max)
 		if (unlikely(mas_is_ptr(mas)))
 			goto ptr_out_of_range;
 
-		return NULL;
+		return true;
 	}
 
 	if (mas->index == max)
-		return NULL;
+		return true;
 
-	/* Retries on dead nodes handled by mas_next_slot */
-	return mas_next_slot(mas, max, false);
+	return false;
 
 ptr_out_of_range:
 	mas->node = MAS_NONE;
 	mas->index = 1;
 	mas->last = ULONG_MAX;
-	return NULL;
+	return true;
+}
+
+/**
+ * mas_find() - On the first call, find the entry at or after mas->index up to
+ * %max.  Otherwise, find the entry after mas->index.
+ * @mas: The maple state
+ * @max: The maximum value to check.
+ *
+ * Must hold rcu_read_lock or the write lock.
+ * If an entry exists, last and index are updated accordingly.
+ * May set @mas->node to MAS_NONE.
+ *
+ * Return: The entry or %NULL.
+ */
+void *mas_find(struct ma_state *mas, unsigned long max)
+{
+	void *entry = NULL;
+
+	if (mas_find_setup(mas, max, &entry))
+		return entry;
+
+	/* Retries on dead nodes handled by mas_next_slot */
+	return mas_next_slot(mas, max, false);
 }
 EXPORT_SYMBOL_GPL(mas_find);
 
+/**
+ * mas_find_range() - On the first call, find the entry at or after
+ * mas->index up to %max.  Otherwise, advance to the next slot mas->index.
+ * @mas: The maple state
+ * @max: The maximum value to check.
+ *
+ * Must hold rcu_read_lock or the write lock.
+ * If an entry exists, last and index are updated accordingly.
+ * May set @mas->node to MAS_NONE.
+ *
+ * Return: The entry or %NULL.
+ */
+void *mas_find_range(struct ma_state *mas, unsigned long max)
+{
+	void *entry;
+
+	if (mas_find_setup(mas, max, &entry))
+		return entry;
+
+	/* Retries on dead nodes handled by mas_next_slot */
+	return mas_next_slot(mas, max, true);
+}
+EXPORT_SYMBOL_GPL(mas_find_range);
+
 /**
  * mas_find_rev: On the first call, find the first non-null entry at or below
  * mas->index down to %min.  Otherwise find the first non-null entry below