linux-kernel - [PATCH v8 18/23] maple_tree: Use kfree_rcu in ma_free

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Message-Id: <20250910-slub-percpu-caches-v8-18-ca3099d8352c@suse.cz>
Date: Wed, 10 Sep 2025 10:01:20 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Suren Baghdasaryan <surenb@...gle.com>, 
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
 Christoph Lameter <cl@...two.org>, David Rientjes <rientjes@...gle.com>
Cc: Roman Gushchin <roman.gushchin@...ux.dev>, 
 Harry Yoo <harry.yoo@...cle.com>, Uladzislau Rezki <urezki@...il.com>, 
 Sidhartha Kumar <sidhartha.kumar@...cle.com>, linux-mm@...ck.org, 
 linux-kernel@...r.kernel.org, rcu@...r.kernel.org, 
 maple-tree@...ts.infradead.org, vbabka@...e.cz, 
 Pedro Falcato <pfalcato@...e.de>
Subject: [PATCH v8 18/23] maple_tree: Use kfree_rcu in ma_free_rcu

From: Pedro Falcato <pfalcato@...e.de>

kfree_rcu is an optimized version of call_rcu + kfree. It used to not be
possible to call it on non-kmalloc objects, but this restriction was
lifted ever since SLOB was dropped from the kernel, and since commit
6c6c47b063b5 ("mm, slab: call kvfree_rcu_barrier() from kmem_cache_destroy()").

Thus, replace call_rcu + mt_free_rcu with kfree_rcu.

Signed-off-by: Pedro Falcato <pfalcato@...e.de>
Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 lib/maple_tree.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index d034f170ac897341b40cfd050b6aee86b6d2cf60..c706e2e48f884fd156e25be2b17eb5e154774db7 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -187,13 +187,6 @@ static inline void mt_free_bulk(size_t size, void __rcu **nodes)
 	kmem_cache_free_bulk(maple_node_cache, size, (void **)nodes);
 }

-static void mt_free_rcu(struct rcu_head *head)
-{
-	struct maple_node *node = container_of(head, struct maple_node, rcu);
-
-	kmem_cache_free(maple_node_cache, node);
-}
-
 /*
  * ma_free_rcu() - Use rcu callback to free a maple node
  * @node: The node to free
@@ -204,7 +197,7 @@ static void mt_free_rcu(struct rcu_head *head)
 static void ma_free_rcu(struct maple_node *node)
 {
 	WARN_ON(node->parent != ma_parent_ptr(node));
-	call_rcu(&node->rcu, mt_free_rcu);
+	kfree_rcu(node, rcu);
 }

 static void mt_set_height(struct maple_tree *mt, unsigned char height)
@@ -5099,7 +5092,7 @@ static void mt_free_walk(struct rcu_head *head)
 	mt_free_bulk(node->slot_len, slots);

 free_leaf:
-	mt_free_rcu(&node->rcu);
+	mt_free_one(node);
 }

 static inline void __rcu **mte_destroy_descend(struct maple_enode **enode,
@@ -5183,7 +5176,7 @@ static void mt_destroy_walk(struct maple_enode *enode, struct maple_tree *mt,

 free_leaf:
 	if (free)
-		mt_free_rcu(&node->rcu);
+		mt_free_one(node);
 	else
 		mt_clear_meta(mt, node, node->type);
 }

-- 
2.51.0