Re: [PATCH v2 1/3] testing/radix-tree/maple: Hack around kfree_rcu not existing
From: Liam R. Howlett
Date: Fri Aug 15 2025 - 11:12:20 EST
* Pedro Falcato <pfalcato@xxxxxxx> [250812 12:21]:
> 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.
>
> Reviewed-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
> Signed-off-by: Pedro Falcato <pfalcato@xxxxxxx>
Andrew,
Please drop this patch set. We will have it go through Vlastimil's tree
to avoid conflicts with other work and to maintain the userspace testing
in mm-new while that happens.
Thanks,
Liam
> ---
> v2:
> - Move kfree_rcu hack to maple-shared.h, to fix userland VMA tests, per
> Lorenzo
>
> tools/testing/shared/maple-shared.h | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/tools/testing/shared/maple-shared.h b/tools/testing/shared/maple-shared.h
> index dc4d30f3860b..572cd2580123 100644
> --- a/tools/testing/shared/maple-shared.h
> +++ b/tools/testing/shared/maple-shared.h
> @@ -9,5 +9,20 @@
> #include <stdlib.h>
> #include <time.h>
> #include "linux/init.h"
> +#include <linux/maple_tree.h>
> +
> +static inline void free_node(struct rcu_head *head)
> +{
> + struct maple_node *node = container_of(head, struct maple_node, rcu);
> +
> + free(node);
> +}
> +
> +static inline void kfree_rcu_node(struct maple_node *node)
> +{
> + call_rcu(&node->rcu, free_node);
> +}
> +
> +#define kfree_rcu(ptr, memb) kfree_rcu_node(ptr)
>
> #endif /* __MAPLE_SHARED_H__ */
> --
> 2.50.1
>