From: Liam R. Howlett <Liam.Howlett@oracle.com>
Date: Fri, 10 Feb 2023 21:42:36 +0000 (-0500)
Subject: maple_tree: Fix mas_prev() and mas_find_rev() state handling
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=bcc91be5fc177962b994127e53bcdc0c0da99765;p=users%2Fjedix%2Flinux-maple.git

maple_tree: Fix mas_prev() and mas_find_rev() state handling

mas_prev() and mas_find_rev() were not setting the correct maple state
when there was not a previous entry.  Fix this by setting the state to
MAS_NONE.

mas_prev() was not treating the lower limit correctly on initial call.
Fix this by setting the index and last to the min & set the node to
MAS_NONE.

Clean up mas_prev() return on single entry trees of 0 - 0.  There was a
locking error for lockdep.

There was also a potential for returning a NULL on a single entry tree
of 0 - 0 when mas_find_rev() was used.

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
---

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 65e6b811f17a..35c0f07f1e01 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4853,6 +4853,7 @@ retry:
 	mas->offset--;
 not_found:
 	mas->index = mas->last = min;
+	mas->node = MAS_NONE;
 	return NULL;
 }
 
@@ -5905,15 +5906,11 @@ EXPORT_SYMBOL_GPL(mt_next);
  */
 void *mas_prev(struct ma_state *mas, unsigned long min)
 {
-	if (!mas->index) {
-		/* Nothing comes before 0 */
-		mas->last = 0;
-		mas->node = MAS_NONE;
-		return NULL;
-	}
+	if (mas->index <= min)
+		goto none;
 
 	if (unlikely(mas_is_ptr(mas)))
-		return NULL;
+		goto none;
 
 	if (mas_is_none(mas) || mas_is_paused(mas))
 		mas->node = MAS_START;
@@ -5921,19 +5918,19 @@ void *mas_prev(struct ma_state *mas, unsigned long min)
 	if (mas_is_start(mas)) {
 		mas_walk(mas);
 		if (!mas->index)
-			return NULL;
+			goto none;
 	}
 
 	if (mas_is_ptr(mas)) {
-		if (!mas->index) {
-			mas->last = 0;
-			return NULL;
-		}
-
 		mas->index = mas->last = 0;
-		return mas_root_locked(mas);
+		return mas_root(mas);
 	}
 	return mas_prev_entry(mas, min);
+
+none:
+	mas->last = mas->index = min;
+	mas->node = MAS_NONE;
+	return NULL;
 }
 EXPORT_SYMBOL_GPL(mas_prev);
 
@@ -6056,8 +6053,16 @@ EXPORT_SYMBOL_GPL(mas_find);
  */
 void *mas_find_rev(struct ma_state *mas, unsigned long min)
 {
+	if (unlikely(mas_is_none(mas))) {
+		if (mas->index <= min)
+			goto none;
+
+		mas->last = mas->index;
+		mas->node = MAS_PAUSE;
+	}
+
 	if (unlikely(mas_is_paused(mas))) {
-		if (unlikely(mas->last == ULONG_MAX)) {
+		if (unlikely(mas->index <= min)) {
 			mas->node = MAS_NONE;
 			return NULL;
 		}
@@ -6065,6 +6070,9 @@ void *mas_find_rev(struct ma_state *mas, unsigned long min)
 		mas->last = --mas->index;
 	}
 
+	if (unlikely(mas_is_ptr(mas)))
+		goto none;
+
 	if (unlikely(mas_is_start(mas))) {
 		/* First run or continue */
 		void *entry;
@@ -6077,14 +6085,27 @@ void *mas_find_rev(struct ma_state *mas, unsigned long min)
 			return entry;
 	}
 
-	if (unlikely(!mas_searchable(mas)))
-		return NULL;
+	if (unlikely(!mas_searchable(mas))) {
+		if (mas_is_ptr(mas)) {
+			/*
+			 * Walked to the location, and there was nothing so the
+			 * previous location is 0.
+			 */
+			mas->last = mas->index = 0;
+			return mas_root(mas);
+		}
+		goto none;
+	}
 
 	if (mas->index < min)
 		return NULL;
 
 	/* Retries on dead nodes handled by mas_prev_entry */
 	return mas_prev_entry(mas, min);
+
+none:
+	mas->node = MAS_NONE;
+	return NULL;
 }
 EXPORT_SYMBOL_GPL(mas_find_rev);