linux-kernel - Re: [PATCH v2 1/3] testing/radix-tree/maple: Hack around kfree

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Message-ID: <rocriz7qo5is6m2dcimj3qiczgv3eoneqwrqvrcpsrtgqnnmmy@eswbhyo2a6w4>
Date: Fri, 15 Aug 2025 11:11:30 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>
Cc: Pedro Falcato <pfalcato@...e.de>, Matthew Wilcox <willy@...radead.org>,
        maple-tree@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Sidhartha Kumar <sidhartha.kumar@...cle.com>
Subject: Re: [PATCH v2 1/3] testing/radix-tree/maple: Hack around kfree_rcu
 not existing

* Pedro Falcato <pfalcato@...e.de> [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@...cle.com>
> Signed-off-by: Pedro Falcato <pfalcato@...e.de>


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
>