maple_tree: fix mas_empty_area() search

The internal function of mas_awalk() was incorrectly skipping the last
entry in a node, which could potentially be NULL.  This is only a problem
for the left-most node in the tree - otherwise that NULL would not exist.

Fix mas_awalk() by using the metadata to obtain the end of the node for
the loop and the logical pivot as apposed to the raw pivot value.

Link: https://lkml.kernel.org/r/20230414145728.4067069-2-Liam.Howlett@oracle.com
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index d197b49eee67abc806a7086c2744012eecea1bbe..1281a40d5735c423c47a451c53eec273dd8deda1 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5056,10 +5056,10 @@ static inline bool mas_anode_descend(struct ma_state *mas, unsigned long size)
 {
        enum maple_type type = mte_node_type(mas->node);
        unsigned long pivot, min, gap = 0;
-       unsigned char offset;
-       unsigned long *gaps;
-       unsigned long *pivots = ma_pivots(mas_mn(mas), type);
-       void __rcu **slots = ma_slots(mas_mn(mas), type);
+       unsigned char offset, data_end;
+       unsigned long *gaps, *pivots;
+       void __rcu **slots;
+       struct maple_node *node;
        bool found = false;
 
        if (ma_is_dense(type)) {
@@ -5067,13 +5067,15 @@ static inline bool mas_anode_descend(struct ma_state *mas, unsigned long size)
                return true;
        }
 
-       gaps = ma_gaps(mte_to_node(mas->node), type);
+       node = mas_mn(mas);
+       pivots = ma_pivots(node, type);
+       slots = ma_slots(node, type);
+       gaps = ma_gaps(node, type);
        offset = mas->offset;
        min = mas_safe_min(mas, pivots, offset);
-       for (; offset < mt_slots[type]; offset++) {
-               pivot = mas_safe_pivot(mas, pivots, offset, type);
-               if (offset && !pivot)
-                       break;
+       data_end = ma_data_end(node, type, pivots, mas->max);
+       for (; offset <= data_end; offset++) {
+               pivot = mas_logical_pivot(mas, pivots, offset, type);
 
                /* Not within lower bounds */
                if (mas->index > pivot)