The documentation of mt_next() claims that it starts the search at the
provided index. That's incorrect as it starts the search after the provided
index.
The documentation of mt_find() is slightly confusing. "Handles locking" is
not really helpful as it does not explain how the "locking" works. Also the
documentation of index talks about a range, while in reality the index
is updated on a succesful search to the index of the found entry plus one.
Fix similar issues for mt_find_after() and mt_prev().
Reword the confusing "Note: Will not return the zero entry." comment on
mt_for_each() and document @__index correctly.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
V2: Address review feedback. Add pointer to documentation, reword the
zero entry and the index explanations. - Liam
---
include/linux/maple_tree.h | 5 +++--
lib/maple_tree.c | 26 +++++++++++++++++++++-----
2 files changed, 24 insertions(+), 7 deletions(-)
--- a/include/linux/maple_tree.h
+++ b/include/linux/maple_tree.h
@@ -659,10 +659,11 @@ void *mt_next(struct maple_tree *mt, uns
* mt_for_each - Iterate over each entry starting at index until max.
* @__tree: The Maple Tree
* @__entry: The current entry
- * @__index: The index to update to track the location in the tree
+ * @__index: The index to start the search from. Subsequently used as iterator.
* @__max: The maximum limit for @index
*
- * Note: Will not return the zero entry.
+ * This iterator skips all entries, which resolve to a NULL pointer,
+ * e.g. entries which has been reserved with XA_ZERO_ENTRY.
*/
#define mt_for_each(__tree, __entry, __index, __max) \
for (__entry = mt_find(__tree, &(__index), __max); \
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5947,7 +5947,11 @@ EXPORT_SYMBOL_GPL(mas_next);
* @index: The start index
* @max: The maximum index to check
*
- * Return: The entry at @index or higher, or %NULL if nothing is found.
+ * Takes RCU read lock internally to protect the search, which does not
+ * protect the returned pointer after dropping RCU read lock.
+ * See also: Documentation/core-api/maple_tree.rst
+ *
+ * Return: The entry higher than @index or %NULL if nothing is found.
*/
void *mt_next(struct maple_tree *mt, unsigned long index, unsigned long max)
{
@@ -6012,7 +6016,11 @@ EXPORT_SYMBOL_GPL(mas_prev);
* @index: The start index
* @min: The minimum index to check
*
- * Return: The entry at @index or lower, or %NULL if nothing is found.
+ * Takes RCU read lock internally to protect the search, which does not
+ * protect the returned pointer after dropping RCU read lock.
+ * See also: Documentation/core-api/maple_tree.rst
+ *
+ * Return: The entry before @index or %NULL if nothing is found.
*/
void *mt_prev(struct maple_tree *mt, unsigned long index, unsigned long min)
{
@@ -6487,9 +6495,15 @@ EXPORT_SYMBOL(mtree_destroy);
* 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
+ * @max: The maximum value of the search range
*
- * Handles locking. @index will be incremented to one beyond the range.
+ * Takes RCU read lock internally to protect the search, which does not
+ * protect the returned pointer after dropping RCU read lock.
+ * See also: Documentation/core-api/maple_tree.rst
+ *
+ * In case that an entry is found @index is updated to point to the next
+ * possible entry independent whether the found entry is occupying a
+ * single index or a range if indices.
*
* Return: The entry at or after the @index or %NULL
*/
@@ -6548,7 +6562,9 @@ EXPORT_SYMBOL(mt_find);
* @index: Pointer which contains the start location of the search
* @max: The maximum value to check
*
- * Handles locking, detects wrapping on index == 0
+ * Same as mt_find() except that it checks @index for 0 before
+ * searching. If @index == 0, the search is aborted. This covers a wrap
+ * around of @index to 0 in an iterator loop.
*
* Return: The entry at or after the @index or %NULL
*/
