1 files changed, 83 insertions, 42 deletions

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 3fa127624520..cd14c1db6b4d 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4828,7 +4828,7 @@ static inline void *mas_prev_nentry(struct ma_state *mas, unsigned long limit,
 				    unsigned long index)
 {
 	unsigned long pivot, min;
-	unsigned char offset;
+	unsigned char offset, count;
 	struct maple_node *mn;
 	enum maple_type mt;
 	unsigned long *pivots;
@@ -4842,29 +4842,42 @@ retry:
 	mn = mas_mn(mas);
 	mt = mte_node_type(mas->node);
 	offset = mas->offset - 1;
-	if (offset >= mt_slots[mt])
-		offset = mt_slots[mt] - 1;
-
 	slots = ma_slots(mn, mt);
 	pivots = ma_pivots(mn, mt);
+	count = ma_data_end(mn, mt, pivots, mas->max);
 	if (unlikely(ma_dead_node(mn))) {
 		mas_rewalk(mas, index);
 		goto retry;
 	}
 
-	if (offset == mt_pivots[mt])
+	offset = mas->offset - 1;
+	if (offset >= mt_slots[mt])
+		offset = mt_slots[mt] - 1;
+
+	if (offset >= count) {
 		pivot = mas->max;
-	else
+		offset = count;
+	} else {
 		pivot = pivots[offset];
+	}
 
 	if (unlikely(ma_dead_node(mn))) {
 		mas_rewalk(mas, index);
 		goto retry;
 	}
 
-	while (offset && ((!mas_slot(mas, slots, offset) && pivot >= limit) ||
-	       !pivot))
+	while (offset && !mas_slot(mas, slots, offset)) {
 		pivot = pivots[--offset];
+		if (pivot >= limit)
+			break;
+	}
+
+	/*
+	 * If the slot was null but we've shifted outside the limits, then set
+	 * the range to the last NULL.
+	 */
+	if (unlikely((pivot < limit) && (offset < mas->offset)))
+		pivot = pivots[++offset];
 
 	min = mas_safe_min(mas, pivots, offset);
 	entry = mas_slot(mas, slots, offset);
@@ -4873,32 +4886,33 @@ retry:
 		goto retry;
 	}
 
-	if (likely(entry)) {
-		mas->offset = offset;
-		mas->last = pivot;
-		mas->index = min;
-	}
+	mas->offset = offset;
+	mas->last = pivot;
+	mas->index = min;
 	return entry;
 }
 
 static inline void *mas_prev_entry(struct ma_state *mas, unsigned long min)
 {
 	void *entry;
+	struct maple_enode *prev_enode;
+	unsigned char prev_offset;
 
-	if (mas->index < min) {
-		mas->index = mas->last = min;
-		mas->node = MAS_NONE;
+	if (mas->index < min)
 		return NULL;
-	}
+
 retry:
+	prev_enode = mas->node;
+	prev_offset = mas->offset;
 	while (likely(!mas_is_none(mas))) {
 		entry = mas_prev_nentry(mas, min, mas->index);
-		if (unlikely(mas->last < min))
-			goto not_found;
 
 		if (likely(entry))
 			return entry;
 
+		if (unlikely(mas->index <= min))
+			return NULL;
+
 		if (unlikely(mas_prev_node(mas, min))) {
 			mas_rewalk(mas, mas->index);
 			goto retry;
@@ -4907,9 +4921,8 @@ retry:
 		mas->offset++;
 	}
 
-	mas->offset--;
-not_found:
-	mas->index = mas->last = min;
+	mas->node = prev_enode;
+	mas->offset = prev_offset;
 	return NULL;
 }
 
@@ -5952,15 +5965,8 @@ 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 (unlikely(mas_is_ptr(mas)))
-		return NULL;
+	if (mas->index <= min)
+		goto none;
 
 	if (mas_is_none(mas) || mas_is_paused(mas))
 		mas->node = MAS_START;
@@ -5968,19 +5974,30 @@ 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;
-		}
-
+	if (unlikely(mas_is_ptr(mas))) {
+		if (!mas->index)
+			goto none;
 		mas->index = mas->last = 0;
-		return mas_root_locked(mas);
+		return mas_root(mas);
+	}
+
+	if (mas_is_none(mas)) {
+		if (mas->index) {
+			/* Walked to out-of-range pointer? */
+			mas->index = mas->last = 0;
+			mas->node = MAS_ROOT;
+			return mas_root(mas);
+		}
+		return NULL;
 	}
 	return mas_prev_entry(mas, min);
+
+none:
+	mas->node = MAS_NONE;
+	return NULL;
 }
 EXPORT_SYMBOL_GPL(mas_prev);
 
@@ -6106,8 +6123,16 @@ 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_START;
+	}
+
 	if (unlikely(mas_is_paused(mas))) {
-		if (unlikely(mas->last == ULONG_MAX)) {
+		if (unlikely(mas->index <= min)) {
 			mas->node = MAS_NONE;
 			return NULL;
 		}
@@ -6127,14 +6152,30 @@ 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))
+			goto none;
+
+		if (mas_is_none(mas)) {
+			/*
+			 * Walked to the location, and there was nothing so the
+			 * previous location is 0.
+			 */
+			mas->last = mas->index = 0;
+			mas->node = MAS_ROOT;
+			return mas_root(mas);
+		}
+	}
 
 	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);