[PATCH v2 11/19] maple_tree: Add bulk parent set helper

["Liam R. Howlett (Oracle)" <liam@infradead.org>]

Instead of calculating the parent pointer each time for a child,
cache the majority of the parent pointer and only change the slot per
child.

Drop the mas_set_parent() function since the last user has been removed.

Testing on a tree containing 2048 entries of height 4 had an increased
gain of 3.51% on nodes tracking gaps.

Signed-off-by: Liam R. Howlett (Oracle) <liam@infradead.org>
---
 lib/maple_tree.c | 97 +++++++++++++++++++++---------------------------
 1 file changed, 42 insertions(+), 55 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 999a1d095e369..768193406c3db 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -455,46 +455,6 @@ enum maple_type mas_parent_type(struct ma_state *mas, struct maple_enode *enode)
 	return 0;
 }
 
-/*
- * mas_set_parent() - Set the parent node and encode the slot
- * @mas: The maple state
- * @enode: The encoded maple node.
- * @parent: The encoded maple node that is the parent of @enode.
- * @slot: The slot that @enode resides in @parent.
- *
- * Slot number is encoded in the enode->parent bit 3-6 or 2-6, depending on the
- * parent type.
- */
-static inline
-void mas_set_parent(struct ma_state *mas, struct maple_enode *enode,
-		    const struct maple_enode *parent, unsigned char slot)
-{
-	unsigned long val = (unsigned long)parent;
-	unsigned long shift;
-	unsigned long type;
-	enum maple_type p_type = mte_node_type(parent);
-
-	MAS_BUG_ON(mas, p_type == maple_dense);
-	MAS_BUG_ON(mas, p_type == maple_leaf_64);
-
-	switch (p_type) {
-	case maple_range_64:
-	case maple_arange_64:
-		shift = MAPLE_PARENT_SLOT_SHIFT;
-		type = MAPLE_PARENT_RANGE64;
-		break;
-	default:
-	case maple_dense:
-	case maple_leaf_64:
-		shift = type = 0;
-		break;
-	}
-
-	val &= ~MAPLE_NODE_MASK; /* Clear all node metadata in parent */
-	val |= (slot << shift) | type;
-	mte_to_node(enode)->parent = ma_parent_ptr(val);
-}
-
 /*
  * mte_parent_slot() - get the parent slot of @enode.
  * @enode: The encoded maple node.
@@ -876,6 +836,42 @@ static inline void ma_set_meta_gap(struct maple_node *mn, enum maple_type mt,
 	meta->gap = offset;
 }
 
+/*
+ * mas_set_parent_slots() - Bulk operation to set many slot parent pointers
+ * @mas: The maple state
+ * @parent: The encoded maple node that is the parent of @enode.
+ * @slot: The slot that of the @enode.
+ * @start_slot: The offset into @slot
+ * @count: The number of slots to set (eg: exclusive)
+ */
+static inline
+void mas_set_parent_slots(struct ma_state *mas, struct maple_enode *parent,
+	void __rcu **slots, unsigned char start_slot, unsigned char count)
+{
+	unsigned long val;
+	unsigned long shift;
+	unsigned long type;
+	enum maple_type p_type = mte_node_type(parent);
+	unsigned char i;
+
+	MAS_BUG_ON(mas, p_type != maple_range_64 &&
+			p_type != maple_arange_64);
+
+	shift = MAPLE_PARENT_SLOT_SHIFT;
+	type = MAPLE_PARENT_RANGE64;
+
+	val = (unsigned long)parent;
+	val &= ~MAPLE_NODE_MASK;
+
+	for (i = 0; i < count; i++) {
+		unsigned long pval = val | ((start_slot + i) << shift) | type;
+		struct maple_enode *child;
+
+		child = mt_slot_locked(mas->tree, slots, i);
+		mte_to_node(child)->parent = ma_parent_ptr(pval);
+	}
+}
+
 /*
  * mat_add() - Add a @dead_enode to the ma_topiary of a list of dead nodes.
  * @mat: the ma_topiary, a linked list of dead nodes.
@@ -1608,14 +1604,10 @@ static inline void mas_adopt_children(struct ma_state *mas,
 	struct maple_node *node = mte_to_node(parent);
 	void __rcu **slots = ma_slots(node, type);
 	unsigned long *pivots = ma_pivots(node, type);
-	struct maple_enode *child;
-	unsigned char offset;
+	unsigned char end;
 
-	offset = ma_data_end(node, type, pivots, mas->max);
-	do {
-		child = mas_slot_locked(mas, slots, offset);
-		mas_set_parent(mas, child, parent, offset);
-	} while (offset--);
+	end = ma_data_end(node, type, pivots, mas->max);
+	mas_set_parent_slots(mas, parent, slots, 0, end + 1);
 }
 
 /*
@@ -1997,15 +1989,10 @@ unsigned long node_copy(struct ma_state *mas, struct maple_node *src,
 	s_slots = ma_slots(src, s_mt) + start;
 	s_pivots = ma_pivots(src, s_mt) + start;
 	memcpy(d_slots, s_slots, size * sizeof(void __rcu *));
-	if (!ma_is_leaf(d_mt) && s_mt == maple_copy) {
-		struct maple_enode *edst = mt_mk_node(dst, d_mt);
-
 
-		for (int i = 0; i < size; i++)
-			mas_set_parent(mas,
-				       mt_slot_locked(mas->tree, d_slots, i),
-				       edst, d_start + i);
-	}
+	if (!ma_is_leaf(d_mt) && s_mt == maple_copy)
+		mas_set_parent_slots(mas, mt_mk_node(dst, d_mt),
+				     d_slots, d_start, size);
 
 	d_gaps = ma_gaps(dst, d_mt);
 	if (d_gaps) {
-- 
2.47.3