From: Liam R. Howlett <Liam.Howlett@Oracle.com>
Date: Wed, 9 Sep 2020 19:40:57 +0000 (-0400)
Subject: maple_tree: Rewrite mas_next_node to be less complex.
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=657fd9442644fa93b51ce3009e5e2332edd53dfe;p=users%2Fjedix%2Flinux-maple.git

maple_tree: Rewrite mas_next_node to be less complex.

Remove double while (1) loop, pull in parent slot lookup.

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

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index ff4fc500c640..8647337a66df 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -1818,8 +1818,6 @@ static inline bool mast_cousin_rebalance_right(struct maple_subtree_state *mast)
 	MA_STATE(tmp, mast->orig_r->tree, mast->orig_r->index, mast->orig_r->last);
 
 	mas_dup_state(&tmp, mast->orig_r);
-	mas_set_offset(mast->orig_r,
-		     mte_parent_slot(mast->orig_r->node));
 	mas_next_node(mast->orig_r, ULONG_MAX);
 	if (!mas_is_none(mast->orig_r)) {
 		mast_rebalance_next(mast, old_r);
@@ -3239,76 +3237,57 @@ no_entry:
 static inline unsigned long mas_next_node(struct ma_state *mas,
 		unsigned long max)
 {
-	int level;
-	unsigned long start_piv;
+	unsigned long start_piv, prev_piv, pivot;
+	int offset, level = 0;
+	enum maple_type mt;
+	void **slots;
 
 restart_next_node:
 	level = 0;
-	while (1) {
-		int offset;
-		struct maple_enode *mn;
-		unsigned long prev_piv;
-		enum maple_type mt;
-		void **slots;
-
-		if (mte_is_root(mas->node) || mas->node == MAS_NONE)
+	while (!mas_is_none(mas)) {
+		if (mte_is_root(mas->node))
 			goto no_entry;
 
-		mn = mas->node;
-		offset= mas_offset(mas);
-		start_piv = mas_safe_pivot(mas, offset);
-		level++;
+		offset = mte_parent_slot(mas->node);
 		mas_ascend(mas);
-
+		start_piv = mas_safe_pivot(mas, offset);
 		if (mas_dead_node(mas, start_piv))
 			goto restart_next_node;
 
+		level++;
 		mt = mte_node_type(mas->node);
 		slots = ma_get_slots(mas_mn(mas), mt);
 		prev_piv = mas_safe_pivot(mas, offset);
-		while (++offset< mt_slots[mt]) {
-			unsigned long pivot = mas_safe_pivot(mas, offset);
-
-			if (prev_piv > max)
-				goto no_entry;
-
-			if (!pivot && offset)
-				break;
-
-			mn = rcu_dereference(slots[offset]);
-			if (!mn) {
-				prev_piv = pivot;
-				continue;
-			}
+		if (prev_piv > max)
+			goto no_entry;
 
-			mas->min = prev_piv + 1;
-			mas->max = pivot;
+		if (prev_piv == mas->max) // last in node.
+			continue;
 
-			if (level == 1) {
-				mas_set_offset(mas, offset);
-				mas->node = mn;
-				if (mas_dead_node(mas, start_piv))
-					goto restart_next_node;
+		if (++offset >= mt_slots[mt])
+			continue;
 
-				return pivot;
-			}
+		pivot = mas_safe_pivot(mas, offset);
 
+		// Descend, if necessary.
+		while (level > 1) {
 			level--;
-			mas->node = mn;
-			offset = -1;
+			mas->node = rcu_dereference(slots[offset]);
 			mt = mte_node_type(mas->node);
 			slots = ma_get_slots(mas_mn(mas), mt);
+			offset = 0;
+			pivot = mas_safe_pivot(mas, offset);
 		}
 
-		if (mte_is_root(mas->node))
-			goto no_entry;
-		mas_set_offset(mas, mte_parent_slot(mas->node));
+		mas->node = rcu_dereference(slots[offset]);
+		mas->min = prev_piv + 1;
+		mas->max = pivot;
+		return mas->max;
 	}
 
 no_entry:
 	mas->node = MAS_NONE;
 	return mas->max;
-
 }
 
 /*
@@ -3459,7 +3438,6 @@ retry:
 	*range_start = mas->last + 1;
 
 	while (!mas_is_none(mas)) {
-		unsigned char p_slot = 0;
 		struct maple_enode *last_node = mas->node;
 
 		slot = mas_offset(mas);
@@ -3483,8 +3461,6 @@ retry:
 		}
 
 next_node:
-		p_slot = mte_parent_slot(mas->node);
-		mas_set_offset(mas, p_slot);
 		mas_next_node(mas, limit);
 		mas_set_offset(mas, 0);
 	}
@@ -5175,7 +5151,6 @@ static inline void mas_dfs_postorder(struct ma_state *mas, unsigned long max)
 	struct maple_enode *p = MAS_NONE, *mn = mas->node;
 	unsigned long p_min, p_max;
 
-	mas_set_offset(mas, mte_parent_slot(mas->node));
 	mas_next_node(mas, max);
 	if (!mas_is_none(mas))
 		return;