maple_tree: add comments and some minor cleanups to mas_wr_append()

Add comment for mas_wr_append(), move mas_update_gap() into
mas_wr_append(), and other cleanups to make mas_wr_modify() cleaner.

Link: https://lkml.kernel.org/r/20230524031247.65949-8-zhangpeng.00@bytedance.com
Signed-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>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 07c5c7a..676976a 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4311,6 +4311,12 @@ static inline unsigned char mas_wr_new_end(struct ma_wr_state *wr_mas)
        return new_end;
 }
 
+/*
+ * mas_wr_append: Attempt to append
+ * @wr_mas: the maple write state
+ *
+ * Return: True if appended, false otherwise
+ */
 static inline bool mas_wr_append(struct ma_wr_state *wr_mas)
 {
        unsigned char end = wr_mas->node_end;
@@ -4318,34 +4324,30 @@ static inline bool mas_wr_append(struct ma_wr_state *wr_mas)
        struct ma_state *mas = wr_mas->mas;
        unsigned char node_pivots = mt_pivots[wr_mas->type];
 
-       if ((mas->index != wr_mas->r_min) && (mas->last == wr_mas->r_max)) {
-               if (new_end < node_pivots)
-                       wr_mas->pivots[new_end] = wr_mas->pivots[end];
+       if (mas->offset != wr_mas->node_end)
+               return false;
 
-               if (new_end < node_pivots)
-                       ma_set_meta(wr_mas->node, maple_leaf_64, 0, new_end);
+       if (new_end < node_pivots) {
+               wr_mas->pivots[new_end] = wr_mas->pivots[end];
+               ma_set_meta(wr_mas->node, maple_leaf_64, 0, new_end);
+       }
 
+       if (mas->last == wr_mas->r_max) {
+               /* Append to end of range */
                rcu_assign_pointer(wr_mas->slots[new_end], wr_mas->entry);
-               mas->offset = new_end;
                wr_mas->pivots[end] = mas->index - 1;
-
-               return true;
-       }
-
-       if ((mas->index == wr_mas->r_min) && (mas->last < wr_mas->r_max)) {
-               if (new_end < node_pivots)
-                       wr_mas->pivots[new_end] = wr_mas->pivots[end];
-
+               mas->offset = new_end;
+       } else {
+               /* Append to start of range */
                rcu_assign_pointer(wr_mas->slots[new_end], wr_mas->content);
-               if (new_end < node_pivots)
-                       ma_set_meta(wr_mas->node, maple_leaf_64, 0, new_end);
-
                wr_mas->pivots[end] = mas->last;
                rcu_assign_pointer(wr_mas->slots[end], wr_mas->entry);
-               return true;
        }
 
-       return false;
+       if (!wr_mas->content || !wr_mas->entry)
+               mas_update_gap(mas);
+
+       return  true;
 }
 
 /*
@@ -4385,12 +4387,9 @@ static inline void mas_wr_modify(struct ma_wr_state *wr_mas)
        if (new_end >= mt_slots[wr_mas->type])
                goto slow_path;
 
-       if (wr_mas->entry && (wr_mas->node_end < mt_slots[wr_mas->type] - 1) &&
-           (mas->offset == wr_mas->node_end) && mas_wr_append(wr_mas)) {
-               if (!wr_mas->content || !wr_mas->entry)
-                       mas_update_gap(mas);
+       /* Attempt to append */
+       if (new_end == wr_mas->node_end + 1 && mas_wr_append(wr_mas))
                return;
-       }
 
        if ((wr_mas->offset_end - mas->offset <= 1) && mas_wr_slot_store(wr_mas))
                return;