The quilt patch titled
Subject: maple_tree: fix write memory barrier of nodes once dead for RCU mode
has been removed from the -mm tree. Its filename was
maple_tree-fix-write-memory-barrier-of-nodes-once-dead-for-rcu-mode.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
Subject: maple_tree: fix write memory barrier of nodes once dead for RCU mode
Date: Mon, 27 Feb 2023 09:36:04 -0800
During the development of the maple tree, the strategy of freeing multiple
nodes changed and, in the process, the pivots were reused to store
pointers to dead nodes. To ensure the readers see accurate pivots, the
writers need to mark the nodes as dead and call smp_wmb() to ensure any
readers can identify the node as dead before using the pivot values.
There were two places where the old method of marking the node as dead
without smp_wmb() were being used, which resulted in RCU readers seeing
the wrong pivot value before seeing the node was dead. Fix this race
condition by using mte_set_node_dead() which has the smp_wmb() call to
ensure the race is closed.
Add a WARN_ON() to the ma_free_rcu() call to ensure all nodes being freed
are marked as dead to ensure there are no other call paths besides the two
updated paths.
This is necessary for the RCU mode of the maple tree.
Link: https://lkml.kernel.org/r/20230227173632.3292573-6-surenb@xxxxxxxxxx
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/maple_tree.c | 7 +++++--
tools/testing/radix-tree/maple.c | 16 ++++++++++++++++
2 files changed, 21 insertions(+), 2 deletions(-)
--- a/lib/maple_tree.c~maple_tree-fix-write-memory-barrier-of-nodes-once-dead-for-rcu-mode
+++ a/lib/maple_tree.c
@@ -185,7 +185,7 @@ static void mt_free_rcu(struct rcu_head
*/
static void ma_free_rcu(struct maple_node *node)
{
- node->parent = ma_parent_ptr(node);
+ WARN_ON(node->parent != ma_parent_ptr(node));
call_rcu(&node->rcu, mt_free_rcu);
}
@@ -1778,8 +1778,10 @@ static inline void mas_replace(struct ma
rcu_assign_pointer(slots[offset], mas->node);
}
- if (!advanced)
+ if (!advanced) {
+ mte_set_node_dead(old_enode);
mas_free(mas, old_enode);
+ }
}
/*
@@ -4218,6 +4220,7 @@ static inline bool mas_wr_node_store(str
done:
mas_leaf_set_meta(mas, newnode, dst_pivots, maple_leaf_64, new_end);
if (in_rcu) {
+ mte_set_node_dead(mas->node);
mas->node = mt_mk_node(newnode, wr_mas->type);
mas_replace(mas, false);
} else {
--- a/tools/testing/radix-tree/maple.c~maple_tree-fix-write-memory-barrier-of-nodes-once-dead-for-rcu-mode
+++ a/tools/testing/radix-tree/maple.c
@@ -108,6 +108,7 @@ static noinline void check_new_node(stru
MT_BUG_ON(mt, mn->slot[1] != NULL);
MT_BUG_ON(mt, mas_allocated(&mas) != 0);
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
mas.node = MAS_START;
mas_nomem(&mas, GFP_KERNEL);
@@ -160,6 +161,7 @@ static noinline void check_new_node(stru
MT_BUG_ON(mt, mas_allocated(&mas) != i);
MT_BUG_ON(mt, !mn);
MT_BUG_ON(mt, not_empty(mn));
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
}
@@ -192,6 +194,7 @@ static noinline void check_new_node(stru
MT_BUG_ON(mt, not_empty(mn));
MT_BUG_ON(mt, mas_allocated(&mas) != i - 1);
MT_BUG_ON(mt, !mn);
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
}
@@ -210,6 +213,7 @@ static noinline void check_new_node(stru
mn = mas_pop_node(&mas);
MT_BUG_ON(mt, not_empty(mn));
MT_BUG_ON(mt, mas_allocated(&mas) != j - 1);
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
}
MT_BUG_ON(mt, mas_allocated(&mas) != 0);
@@ -233,6 +237,7 @@ static noinline void check_new_node(stru
MT_BUG_ON(mt, mas_allocated(&mas) != i - j);
mn = mas_pop_node(&mas);
MT_BUG_ON(mt, not_empty(mn));
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
MT_BUG_ON(mt, mas_allocated(&mas) != i - j - 1);
}
@@ -269,6 +274,7 @@ static noinline void check_new_node(stru
mn = mas_pop_node(&mas); /* get the next node. */
MT_BUG_ON(mt, mn == NULL);
MT_BUG_ON(mt, not_empty(mn));
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
}
MT_BUG_ON(mt, mas_allocated(&mas) != 0);
@@ -294,6 +300,7 @@ static noinline void check_new_node(stru
mn = mas_pop_node(&mas2); /* get the next node. */
MT_BUG_ON(mt, mn == NULL);
MT_BUG_ON(mt, not_empty(mn));
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
}
MT_BUG_ON(mt, mas_allocated(&mas2) != 0);
@@ -334,10 +341,12 @@ static noinline void check_new_node(stru
MT_BUG_ON(mt, mas_allocated(&mas) != MAPLE_ALLOC_SLOTS + 2);
mn = mas_pop_node(&mas);
MT_BUG_ON(mt, not_empty(mn));
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
for (i = 1; i <= MAPLE_ALLOC_SLOTS + 1; i++) {
mn = mas_pop_node(&mas);
MT_BUG_ON(mt, not_empty(mn));
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
}
MT_BUG_ON(mt, mas_allocated(&mas) != 0);
@@ -375,6 +384,7 @@ static noinline void check_new_node(stru
mas_node_count(&mas, i); /* Request */
mas_nomem(&mas, GFP_KERNEL); /* Fill request */
mn = mas_pop_node(&mas); /* get the next node. */
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
mas_destroy(&mas);
@@ -382,10 +392,13 @@ static noinline void check_new_node(stru
mas_node_count(&mas, i); /* Request */
mas_nomem(&mas, GFP_KERNEL); /* Fill request */
mn = mas_pop_node(&mas); /* get the next node. */
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
mn = mas_pop_node(&mas); /* get the next node. */
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
mn = mas_pop_node(&mas); /* get the next node. */
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
mas_destroy(&mas);
}
@@ -35369,6 +35382,7 @@ static noinline void check_prealloc(stru
MT_BUG_ON(mt, allocated != 1 + height * 3);
mn = mas_pop_node(&mas);
MT_BUG_ON(mt, mas_allocated(&mas) != allocated - 1);
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
MT_BUG_ON(mt, mas_preallocate(&mas, GFP_KERNEL) != 0);
mas_destroy(&mas);
@@ -35386,6 +35400,7 @@ static noinline void check_prealloc(stru
mas_destroy(&mas);
allocated = mas_allocated(&mas);
MT_BUG_ON(mt, allocated != 0);
+ mn->parent = ma_parent_ptr(mn);
ma_free_rcu(mn);
MT_BUG_ON(mt, mas_preallocate(&mas, GFP_KERNEL) != 0);
@@ -35756,6 +35771,7 @@ void farmer_tests(void)
tree.ma_root = mt_mk_node(node, maple_leaf_64);
mt_dump(&tree);
+ node->parent = ma_parent_ptr(node);
ma_free_rcu(node);
/* Check things that will make lockdep angry */
_
Patches currently in -mm which might be from Liam.Howlett@xxxxxxxxxx are
