lib/maple_tree: Fix allocation walk iterators.

Do not reset mas->node or mas->offset and advance the slot on
continuing.

This also drops mas_rev_awalk() and instead pulls it into
mas_empty_area_rev().

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

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index ba89ebfc2af0a6b9919996fe75f85a435b71231b..eabe5c503f227ca526d3e0ac82849f85cdc96878 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4496,6 +4496,7 @@ static bool _mas_rev_awalk(struct ma_state *mas, unsigned long size)
        }
 
        if (unlikely(ma_is_leaf(type))) {
+               mas->offset = offset;
                mas->min = min;
                mas->max = min + gap - 1;
                return true;
@@ -4519,7 +4520,7 @@ static inline bool _mas_awalk(struct ma_state *mas, unsigned long size)
 {
        enum maple_type type = mte_node_type(mas->node);
        unsigned long pivot, min, gap = 0;
-       unsigned char count, offset = 0;
+       unsigned char count, offset;
        unsigned long *gaps = NULL, *pivots = ma_pivots(mas_mn(mas), type);
        void **slots = ma_slots(mas_mn(mas), type);
        bool found = false;
@@ -4529,11 +4530,10 @@ static inline bool _mas_awalk(struct ma_state *mas, unsigned long size)
                return true;
        }
 
-       if (!ma_is_leaf(type)) {
-               offset = mas->offset;
+       if (!ma_is_leaf(type))
                gaps = ma_gaps(mte_to_node(mas->node), type);
-       }
 
+       offset = mas->offset;
        count = mt_slots[type];
        min = mas_safe_min(mas, pivots, offset);
        for (; offset < count; offset++) {
@@ -4640,10 +4640,8 @@ static inline bool mas_rewind_node(struct ma_state *mas)
        do {
                if (mte_is_root(mas->node)) {
                        slot = mas->offset;
-                       if (!slot) {
-                               mas_set_err(mas, -EBUSY);
+                       if (!slot)
                                return false;
-                       }
                } else {
                        slot = mte_parent_slot(mas->node);
                        mas_ascend(mas);
@@ -4654,38 +4652,6 @@ static inline bool mas_rewind_node(struct ma_state *mas)
        return true;
 }
 
-/*
- * mas_rev_awalk() - Reverse allocation walk for a given size.
- * @mas: The maple state
- * @size: The size of the gap
- *
- * Reverse search from @mas->last to @mas->index for a gap of @size.
- *
- * Return: true if found, false otherwise.
- */
-static bool mas_rev_awalk(struct ma_state *mas, unsigned long size)
-{
-       struct maple_enode *last = NULL;
-
-       mas->offset = mas_data_end(mas);
-
-       /* There are 4 options:
-        * go to child (descend)
-        * go back to parent (ascend)
-        * no gap found. (return, slot == MAPLE_NODE_SLOTS)
-        * found the gap. (return, slot != MAPLE_NODE_SLOTS)
-        */
-       while (!_mas_rev_awalk(mas, size)) {
-               if (last == mas->node) {
-                       if (!mas_rewind_node(mas))
-                               return false;
-               } else {
-                       last = mas->node;
-               }
-       }
-       return true;
-}
-
 /*
  * mas_skip_node() - Internal function.  Skip over a node.
  * @mas: The maple state.
@@ -4738,13 +4704,6 @@ static inline void mas_awalk(struct ma_state *mas, unsigned long size)
 {
        struct maple_enode *last = NULL;
 
-       mas_start(mas);
-       if (mas_is_none(mas))
-               return;
-
-       if (mas_is_ptr(mas))
-               return;
-
        /* There are 4 options:
         * go to child (descend)
         * go back to parent (ascend)
@@ -4839,7 +4798,14 @@ int mas_empty_area(struct ma_state *mas, unsigned long min,
        unsigned char offset;
        unsigned long *pivots;
        enum maple_type mt;
-       mas_start(mas);
+
+       if (mas_is_start(mas)) {
+               mas_start(mas);
+       } else if (mas->offset >= 2) {
+               mas->offset -= 2;
+       } else if (!mas_skip_node(mas)) {
+               return -EBUSY;
+       }
 
        // Empty set.
        if (mas_is_none(mas) || mas_is_ptr(mas)) {
@@ -4885,7 +4851,16 @@ int mas_empty_area(struct ma_state *mas, unsigned long min,
 int mas_empty_area_rev(struct ma_state *mas, unsigned long min,
                unsigned long max, unsigned long size)
 {
-       mas_start(mas);
+       struct maple_enode *last = mas->node;
+
+       if (mas_is_start(mas)) {
+               mas_start(mas);
+               mas->offset = mas_data_end(mas);
+       } else if (mas->offset >= 2) {
+               mas->offset -= 2;
+       } else if (!mas_rewind_node(mas)) {
+               return -EBUSY;
+       }
 
        // Empty set.
        if (mas_is_none(mas) || mas_is_ptr(mas)) {
@@ -4896,8 +4871,15 @@ int mas_empty_area_rev(struct ma_state *mas, unsigned long min,
        // The start of the window can only be within these values.
        mas->index = min;
        mas->last = max;
-       if (unlikely(!mas_rev_awalk(mas, size)))
-               return xa_err(mas->node);
+
+       while (!_mas_rev_awalk(mas, size)) {
+               if (last == mas->node) {
+                       if (!mas_rewind_node(mas))
+                               return -EBUSY;
+               } else {
+                       last = mas->node;
+               }
+       }
 
        if (unlikely(mas->offset == MAPLE_NODE_SLOTS))
                return -EBUSY;