diff mbox series

[v2,06/33] maple_tree: Add smp_rmb() to dead node detection

Message ID 20230127194110.533103-7-surenb@google.com (mailing list archive)
State New
Headers show
Series Per-VMA locks | expand

Commit Message

Suren Baghdasaryan Jan. 27, 2023, 7:40 p.m. UTC 
From: "Liam R. Howlett" <Liam.Howlett@oracle.com>

Add an smp_rmb() before reading the parent pointer to ensure that
anything read from the node prior to the parent pointer hasn't been
reordered ahead of this check.

The is necessary for RCU mode.

Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 lib/maple_tree.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
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Patch

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 49e399e8afaa..859303d2da90 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -532,9 +532,11 @@  static inline struct maple_node *mte_parent(const struct maple_enode *enode)
  */
 static inline bool ma_dead_node(const struct maple_node *node)
 {
-	struct maple_node *parent = (void *)((unsigned long)
-					     node->parent & ~MAPLE_NODE_MASK);
+	struct maple_node *parent;
 
+	/* Do not reorder reads from the node prior to the parent check */
+	smp_rmb();
+	parent = (void *)((unsigned long) node->parent & ~MAPLE_NODE_MASK);
 	return (parent == node);
 }
 
@@ -549,6 +551,8 @@  static inline bool mte_dead_node(const struct maple_enode *enode)
 	struct maple_node *parent, *node;
 
 	node = mte_to_node(enode);
+	/* Do not reorder reads from the node prior to the parent check */
+	smp_rmb();
 	parent = mte_parent(enode);
 	return (parent == node);
 }