maple_tree: simplify and clean up mas_wr_node_store()

Simplify and clean up mas_wr_node_store(), remove unnecessary code.

Link: https://lkml.kernel.org/r/20230524031247.65949-10-zhangpeng.00@bytedance.comSigned-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/maple_tree.c

@@ -4074,52 +4074,27 @@ static inline int mas_wr_spanning_store(struct ma_wr_state *wr_mas)
  *
  * Return: True if stored, false otherwise
  */
-static inline bool mas_wr_node_store(struct ma_wr_state *wr_mas)
+static inline bool mas_wr_node_store(struct ma_wr_state *wr_mas,
+				     unsigned char new_end)
 {
 	struct ma_state *mas = wr_mas->mas;
 	void __rcu **dst_slots;
 	unsigned long *dst_pivots;
-	unsigned char dst_offset;
-	unsigned char new_end = wr_mas->node_end;
-	unsigned char offset;
-	unsigned char node_slots = mt_slots[wr_mas->type];
+	unsigned char dst_offset, offset_end = wr_mas->offset_end;
 	struct maple_node reuse, *newnode;
-	unsigned char copy_size, max_piv = mt_pivots[wr_mas->type];
+	unsigned char copy_size, node_pivots = mt_pivots[wr_mas->type];
 	bool in_rcu = mt_in_rcu(mas->tree);
 
-	offset = mas->offset;
-	if (mas->last == wr_mas->r_max) {
-		/* runs right to the end of the node */
-		if (mas->last == mas->max)
-			new_end = offset;
-		/* don't copy this offset */
-		wr_mas->offset_end++;
-	} else if (mas->last < wr_mas->r_max) {
-		/* new range ends in this range */
-		if (unlikely(wr_mas->r_max == ULONG_MAX))
-			mas_bulk_rebalance(mas, wr_mas->node_end, wr_mas->type);
-
-		new_end++;
-	} else {
-		if (wr_mas->end_piv == mas->last)
-			wr_mas->offset_end++;
-
-		new_end -= wr_mas->offset_end - offset - 1;
-	}
-
-	/* new range starts within a range */
-	if (wr_mas->r_min < mas->index)
-		new_end++;
-
-	/* Not enough room */
-	if (new_end >= node_slots)
-		return false;
-
-	/* Not enough data. */
+	/* Check if there is enough data. The room is enough. */
 	if (!mte_is_root(mas->node) && (new_end <= mt_min_slots[wr_mas->type]) &&
 	    !(mas->mas_flags & MA_STATE_BULK))
 		return false;
 
+	if (mas->last == wr_mas->end_piv)
+		offset_end++; /* don't copy this offset */
+	else if (unlikely(wr_mas->r_max == ULONG_MAX))
+		mas_bulk_rebalance(mas, wr_mas->node_end, wr_mas->type);
+
 	/* set up node. */
 	if (in_rcu) {
 		mas_node_count(mas, 1);
@@ -4136,47 +4111,36 @@ static inline bool mas_wr_node_store(struct ma_wr_state *wr_mas)
 	dst_pivots = ma_pivots(newnode, wr_mas->type);
 	dst_slots = ma_slots(newnode, wr_mas->type);
 	/* Copy from start to insert point */
-	memcpy(dst_pivots, wr_mas->pivots, sizeof(unsigned long) * (offset + 1));
-	memcpy(dst_slots, wr_mas->slots, sizeof(void *) * (offset + 1));
-	dst_offset = offset;
+	memcpy(dst_pivots, wr_mas->pivots, sizeof(unsigned long) * mas->offset);
+	memcpy(dst_slots, wr_mas->slots, sizeof(void *) * mas->offset);
 
 	/* Handle insert of new range starting after old range */
 	if (wr_mas->r_min < mas->index) {
-		mas->offset++;
-		rcu_assign_pointer(dst_slots[dst_offset], wr_mas->content);
-		dst_pivots[dst_offset++] = mas->index - 1;
+		rcu_assign_pointer(dst_slots[mas->offset], wr_mas->content);
+		dst_pivots[mas->offset++] = mas->index - 1;
 	}
 
 	/* Store the new entry and range end. */
-	if (dst_offset < max_piv)
-		dst_pivots[dst_offset] = mas->last;
-	mas->offset = dst_offset;
-	rcu_assign_pointer(dst_slots[dst_offset], wr_mas->entry);
+	if (mas->offset < node_pivots)
+		dst_pivots[mas->offset] = mas->last;
+	rcu_assign_pointer(dst_slots[mas->offset], wr_mas->entry);
 
 	/*
 	 * this range wrote to the end of the node or it overwrote the rest of
 	 * the data
 	 */
-	if (wr_mas->offset_end > wr_mas->node_end || mas->last >= mas->max) {
-		new_end = dst_offset;
+	if (offset_end > wr_mas->node_end)
 		goto done;
-	}
 
-	dst_offset++;
+	dst_offset = mas->offset + 1;
 	/* Copy to the end of node if necessary. */
-	copy_size = wr_mas->node_end - wr_mas->offset_end + 1;
-	memcpy(dst_slots + dst_offset, wr_mas->slots + wr_mas->offset_end,
+	copy_size = wr_mas->node_end - offset_end + 1;
+	memcpy(dst_slots + dst_offset, wr_mas->slots + offset_end,
 	       sizeof(void *) * copy_size);
-	if (dst_offset < max_piv) {
-		if (copy_size > max_piv - dst_offset)
-			copy_size = max_piv - dst_offset;
-
-		memcpy(dst_pivots + dst_offset,
-		       wr_mas->pivots + wr_mas->offset_end,
-		       sizeof(unsigned long) * copy_size);
-	}
+	memcpy(dst_pivots + dst_offset, wr_mas->pivots + offset_end,
+	       sizeof(unsigned long) * (copy_size - 1));
 
-	if ((wr_mas->node_end == node_slots - 1) && (new_end < node_slots - 1))
+	if (new_end < node_pivots)
 		dst_pivots[new_end] = mas->max;
 
 done:
@@ -4378,7 +4342,8 @@ static inline void mas_wr_modify(struct ma_wr_state *wr_mas)
 
 	if (new_end == wr_mas->node_end && mas_wr_slot_store(wr_mas))
 		return;
-	else if (mas_wr_node_store(wr_mas))
+
+	if (mas_wr_node_store(wr_mas, new_end))
 		return;
 
 	if (mas_is_err(mas))