maple_tree: rework mas_wr_slot_store() to be cleaner and more efficient.

Get whether the two gaps to be overwritten are empty to avoid calling
mas_update_gap() all the time.  Also clean up the code and add comments.

Link: https://lkml.kernel.org/r/20230524031247.65949-9-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 676976a..1a2b9bb 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4202,49 +4202,34 @@ done:
 static inline bool mas_wr_slot_store(struct ma_wr_state *wr_mas)
 {
        struct ma_state *mas = wr_mas->mas;
-       unsigned long lmax; /* Logical max. */
        unsigned char offset = mas->offset;
+       bool gap = false;
 
-       if ((wr_mas->r_max > mas->last) && ((wr_mas->r_min != mas->index) ||
-                                 (offset != wr_mas->node_end)))
+       if (wr_mas->offset_end - offset != 1)
                return false;
 
-       if (offset == wr_mas->node_end - 1)
-               lmax = mas->max;
-       else
-               lmax = wr_mas->pivots[offset + 1];
-
-       /* going to overwrite too many slots. */
-       if (lmax < mas->last)
-               return false;
-
-       if (wr_mas->r_min == mas->index) {
-               /* overwriting two or more ranges with one. */
-               if (lmax == mas->last)
-                       return false;
+       gap |= !mt_slot_locked(mas->tree, wr_mas->slots, offset);
+       gap |= !mt_slot_locked(mas->tree, wr_mas->slots, offset + 1);
 
-               /* Overwriting all of offset and a portion of offset + 1. */
+       if (mas->index == wr_mas->r_min) {
+               /* Overwriting the range and over a part of the next range. */
                rcu_assign_pointer(wr_mas->slots[offset], wr_mas->entry);
                wr_mas->pivots[offset] = mas->last;
-               goto done;
+       } else {
+               /* Overwriting a part of the range and over the next range */
+               rcu_assign_pointer(wr_mas->slots[offset + 1], wr_mas->entry);
+               wr_mas->pivots[offset] = mas->index - 1;
+               mas->offset++; /* Keep mas accurate. */
        }
 
-       /* Doesn't end on the next range end. */
-       if (lmax != mas->last)
-               return false;
-
-       /* Overwriting a portion of offset and all of offset + 1 */
-       if ((offset + 1 < mt_pivots[wr_mas->type]) &&
-           (wr_mas->entry || wr_mas->pivots[offset + 1]))
-               wr_mas->pivots[offset + 1] = mas->last;
-
-       rcu_assign_pointer(wr_mas->slots[offset + 1], wr_mas->entry);
-       wr_mas->pivots[offset] = mas->index - 1;
-       mas->offset++; /* Keep mas accurate. */
-
-done:
        trace_ma_write(__func__, mas, 0, wr_mas->entry);
-       mas_update_gap(mas);
+       /*
+        * Only update gap when the new entry is empty or there is an empty
+        * entry in the original two ranges.
+        */
+       if (!wr_mas->entry || gap)
+               mas_update_gap(mas);
+
        return true;
 }
 
@@ -4391,7 +4376,7 @@ static inline void mas_wr_modify(struct ma_wr_state *wr_mas)
        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))
+       if (new_end == wr_mas->node_end && mas_wr_slot_store(wr_mas))
                return;
        else if (mas_wr_node_store(wr_mas))
                return;