maple_tree: Rework mas_prev_node

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

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 0426085a56ac53f188b0d535945f47ea3f4d57d5..f72e24d2db3e8ffdc4454147fd4256cd9240fbdd 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -3155,70 +3155,56 @@ static inline int mas_dead_node(struct ma_state *mas, unsigned long index);
  */
 static inline void mas_prev_node(struct ma_state *mas, unsigned long limit)
 {
-       unsigned long pivot, start_piv, min;
-       int offset = mas_offset(mas);
-       struct maple_enode *mn;
-       int level;
+       unsigned long start_piv;
+       enum maple_type mt;
+       int offset, level;
        void **slots;
 
+       if (mas_is_none(mas))
+               return;
+
+       if (mte_is_root(mas->node))
+               goto no_entry;
+
+       offset = mte_parent_slot(mas->node);
        start_piv = mas_safe_pivot(mas, offset);
 restart_prev_node:
        level = 0;
-       if (mas->node == MAS_NONE)
-               goto no_entry;
-
-       while (1) {
-
+       do {
                if (mte_is_root(mas->node))
                        goto no_entry;
 
+               // Walk up.
                offset = mte_parent_slot(mas->node);
                mas_ascend(mas);
                level++;
-
                if (mas_dead_node(mas, start_piv))
                        goto restart_prev_node;
+       } while (!offset);
 
-               if (!offset)
-                       continue;
-
-               offset--;
-               slots = ma_get_slots(mas_mn(mas), mte_node_type(mas->node));
-               do {
-                       pivot = mas_safe_pivot(mas, offset);
-
-                       min = mas_safe_min(mas, offset);
-                       if (pivot < limit)
-                               goto no_entry;
-
-                       if (!pivot && offset) // end of node.
-                               break;
-
-                       mn = rcu_dereference_check(slots[offset],
-                               lockdep_is_held(mas->tree->ma_lock));
-                       if (!mn)
-                               continue;
-
-                       if (level == 1) {
-                               mas_set_offset(mas, offset);
-                               mas->node = mn;
-                               mas->max = pivot;
-                               mas->min = min;
-                               if (mas_dead_node(mas, start_piv))
-                                       goto restart_prev_node;
-                               return;
-                       }
-
-                       level--;
-                       mas->node = mn;
-                       mas->max = pivot;
-                       mas->min = min;
-                       offset = mas_data_end(mas) + 1;
-                       slots = ma_get_slots(mas_mn(mas),
-                                            mte_node_type(mas->node));
-               } while (offset-- > 0);
+       offset--;
+       mt = mte_node_type(mas->node);
+       slots = ma_get_slots(mas_mn(mas), mte_node_type(mas->node));
+       mas->max = mas_safe_pivot(mas, offset);
+       while (level > 1) {
+               level--;
+               mas->node = rcu_dereference(slots[offset]);
+               if (mas_dead_node(mas, start_piv))
+                       goto restart_prev_node;
+               mt = mte_node_type(mas->node);
+               slots = ma_get_slots(mas_mn(mas), mt);
+               offset = mt_slots[mt];
+               do {} while(!mas_get_slot(mas, --offset));
+               mas->max = mas_safe_pivot(mas, offset);
        }
 
+       mas_set_offset(mas, offset);
+       mas->min = mas_safe_min(mas, offset);
+       mas->node = rcu_dereference(slots[offset]);
+       if (mas_dead_node(mas, start_piv))
+               goto restart_prev_node;
+       return;
+
 no_entry:
        mas->node = MAS_NONE;
 }