maple_tree: fix a few documentation issues

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.

Link: https://lkml.kernel.org/r/87ttw2n556.ffs@tglx
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Shanker Donthineni <sdonthineni@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 21 insertions, 5 deletions

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 4dd73cf936a6..f512bb9766aa 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5750,7 +5750,11 @@ EXPORT_SYMBOL_GPL(mas_next_range);
  * @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)
 {
@@ -5856,7 +5860,11 @@ EXPORT_SYMBOL_GPL(mas_prev_range);
  * @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)
 {
@@ -6468,9 +6476,15 @@ 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
+ *
+ * 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
  *
- * Handles locking.  @index will be incremented to one beyond the range.
+ * 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
  */
@@ -6528,7 +6542,9 @@ 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
  */