linux-kernel - [PATCH 1/2] maple_tree: Use kfree_rcu in ma_free

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Message-ID: <20250718172138.103116-1-pfalcato@suse.de>
Date: Fri, 18 Jul 2025 18:21:36 +0100
From: Pedro Falcato <pfalcato@...e.de>
To: Andrew Morton <akpm@...ux-foundation.org>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Matthew Wilcox <willy@...radead.org>
Cc: maple-tree@...ts.infradead.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Pedro Falcato <pfalcato@...e.de>
Subject: [PATCH 1/2] maple_tree: Use kfree_rcu in ma_free_rcu

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>
---
 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 b4ee2d29d7a9..91da2d9d00c3 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -191,13 +191,6 @@ 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
@@ -208,7 +201,7 @@ 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)
@@ -5281,7 +5274,7 @@ 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,
@@ -5365,7 +5358,7 @@ 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);
 }
-- 
2.50.1