linux-kernel - Re: [PATCH 2/2] testing/radix-tree/maple: Hack around kfree

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Message-ID: <8c4e8451-72b7-4c34-8660-faa2a23a4667@oracle.com>
Date: Fri, 18 Jul 2025 14:05:31 -0400
From: Sidhartha Kumar <sidhartha.kumar@...cle.com>
To: Pedro Falcato <pfalcato@...e.de>,
        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
Subject: Re: [PATCH 2/2] testing/radix-tree/maple: Hack around kfree_rcu not
 existing

On 7/18/25 1:21 PM, Pedro Falcato wrote:
> liburcu doesn't have kfree_rcu (or anything similar). Despite that, we
> can hack around it in a trivial fashion, by adding a wrapper.
> 
> This wrapper only works for maple_nodes, and not anything else (due to
> us not being able to know rcu_head offsets in any way), and thus we take
> advantage of the type checking to avoid future silent breakage.
> 
> Signed-off-by: Pedro Falcato <pfalcato@...e.de>

Reviewed-by: Sidhartha Kumar <sidhartha.kumar@...cle.com>

> ---
>   tools/testing/radix-tree/maple.c | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
> 
> diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/maple.c
> index 172700fb7784..bfdc93c36cf9 100644
> --- a/tools/testing/radix-tree/maple.c
> +++ b/tools/testing/radix-tree/maple.c
> @@ -23,6 +23,23 @@
>   #define MODULE_LICENSE(x)
>   #define dump_stack()	assert(0)
>   
> +
> +#include <linux/maple_tree.h>
> +
> +static void free_node(struct rcu_head *head)
> +{
> +	struct maple_node *node = container_of(head, struct maple_node, rcu);
> +
> +	free(node);
> +}
> +
> +static void kfree_rcu_node(struct maple_node *node)
> +{
> +	call_rcu(&node->rcu, free_node);
> +}
> +
> +#define kfree_rcu(ptr, memb) kfree_rcu_node(ptr)
> +
>   #include "../../../lib/maple_tree.c"
>   #include "../../../lib/test_maple_tree.c"
>