maple_tree: clear up index and last setting in single entry tree

When there is a single entry tree (range of 0-0 pointing to an entry),
then ensure the limit is either 0-0 or 1-oo, depending on where the user
walks.  Ensure the correct node setting as well; either MAS_ROOT or
MAS_NONE.

Link: https://lkml.kernel.org/r/20230518145544.1722059-33-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: David Binderman <dcb314@hotmail.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>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 59c15f8b47935170b497f48834c102a00017a081..4eb220008f72e33792e2e26bf066a5f3ac314243 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5023,24 +5023,25 @@ void *mas_walk(struct ma_state *mas)
 {
        void *entry;
 
+       if (mas_is_none(mas) || mas_is_paused(mas) || mas_is_ptr(mas))
+               mas->node = MAS_START;
 retry:
        entry = mas_state_walk(mas);
-       if (mas_is_start(mas))
+       if (mas_is_start(mas)) {
                goto retry;
-
-       if (mas_is_ptr(mas)) {
+       } else if (mas_is_none(mas)) {
+               mas->index = 0;
+               mas->last = ULONG_MAX;
+       } else if (mas_is_ptr(mas)) {
                if (!mas->index) {
                        mas->last = 0;
-               } else {
-                       mas->index = 1;
-                       mas->last = ULONG_MAX;
+                       return entry;
                }
-               return entry;
-       }
 
-       if (mas_is_none(mas)) {
-               mas->index = 0;
+               mas->index = 1;
                mas->last = ULONG_MAX;
+               mas->node = MAS_NONE;
+               return NULL;
        }
 
        return entry;