From 86d9de0898908aebc6b97a38c5dbf0f5b376643e Mon Sep 17 00:00:00 2001
From: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Date: Thu, 18 May 2023 10:55:41 -0400
Subject: [PATCH] FROMGIT: 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>

(cherry picked from commit c0b1bdd9011ef34b654fe62f2607bff0eb1ef0a8
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm mm-unstable)

Bug: 274059236
Change-Id: I22a41c01e525fde88774b509cd5cbc60f56f6dc5
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 lib/maple_tree.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index cd731b89d9bf..01be00aefef8 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5050,24 +5050,25 @@ 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)) {
-		if (!mas->index) {
-			mas->last = 0;
-		} else {
-			mas->index = 1;
-			mas->last = ULONG_MAX;
-		}
-		return entry;
-	}
-
-	if (mas_is_none(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;
+			return entry;
+		}
+
+		mas->index = 1;
+		mas->last = ULONG_MAX;
+		mas->node = MAS_NONE;
+		return NULL;
 	}
 
 	return entry;