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authorLiam R. Howlett <Liam.Howlett@oracle.com>2023-02-27 18:36:04 +0100
committerAndrew Morton <akpm@linux-foundation.org>2023-04-06 03:06:21 +0200
commitc13af03de46ba27674dd9fb31a17c0d480081139 (patch)
tree3ed08fc7f6e49c7695f4b5b9a75d0d43a16c32cc
parentmaple_tree: remove extra smp_wmb() from mas_dead_leaves() (diff)
downloadlinux-c13af03de46ba27674dd9fb31a17c0d480081139.tar.xz
linux-c13af03de46ba27674dd9fb31a17c0d480081139.zip
maple_tree: fix write memory barrier of nodes once dead for RCU mode
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@google.com 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> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--lib/maple_tree.c7
-rw-r--r--tools/testing/radix-tree/maple.c16
2 files changed, 21 insertions, 2 deletions
diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 96d673e4ba5b..5202d89ba56e 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -185,7 +185,7 @@ static void mt_free_rcu(struct rcu_head *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_state *mas, bool advanced)
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(struct ma_wr_state *wr_mas)
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 {
diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/maple.c
index 958ee9bdb316..4c89ff333f6f 100644
--- a/tools/testing/radix-tree/maple.c
+++ b/tools/testing/radix-tree/maple.c
@@ -108,6 +108,7 @@ static noinline void check_new_node(struct maple_tree *mt)
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(struct maple_tree *mt)
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(struct maple_tree *mt)
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(struct maple_tree *mt)
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(struct maple_tree *mt)
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(struct maple_tree *mt)
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(struct maple_tree *mt)
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(struct maple_tree *mt)
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(struct maple_tree *mt)
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(struct maple_tree *mt)
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(struct maple_tree *mt)
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(struct maple_tree *mt)
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 */