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Subject[PATCH Fix 1/2] maple_tree: Fix mas_spanning_rebalance() corner case
Date
When a node is insufficient during a spanning rebalance loop and
mast_spanning_rebalance() is called to combine neighbouring nodes, the
loop should not terminate regardless of if neighbours exist or not.
This will allow the data to be stored in the correct node.

Reported-by: Yu Zhao <yuzhao@google.com>
Fixes: 37a4d714b7d9 (maple_tree: fix underflow in mas_spanning_rebalance())
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
---
lib/maple_tree.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index d8457122ca5d..2cccd8f2153f 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -3029,8 +3029,7 @@ static int mas_spanning_rebalance(struct ma_state *mas,
if (mas_is_root_limits(mast->orig_l))
break;

- if (!mast_spanning_rebalance(mast))
- break;
+ mast_spanning_rebalance(mast);

/* rebalancing from other nodes may require another loop. */
if (!count)
@@ -6521,6 +6520,7 @@ static inline void *mas_first_entry(struct ma_state *mas, struct maple_node *mn,
max = mas->max;
mas->offset = 0;
while (likely(!ma_is_leaf(mt))) {
+ MT_BUG_ON(mas->tree, mte_dead_node(mas->node));
slots = ma_slots(mn, mt);
pivots = ma_pivots(mn, mt);
max = pivots[0];
@@ -6531,6 +6531,7 @@ static inline void *mas_first_entry(struct ma_state *mas, struct maple_node *mn,
mn = mas_mn(mas);
mt = mte_node_type(mas->node);
}
+ MT_BUG_ON(mas->tree, mte_dead_node(mas->node));

mas->max = max;
slots = ma_slots(mn, mt);
--
2.35.1
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