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

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Message-ID: <461f1350-7fdc-4136-a1cf-7f1f0d01d9ed@lucifer.local>
Date: Sun, 10 Aug 2025 15:23:56 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Pedro Falcato <pfalcato@...e.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        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 2/2] testing/radix-tree/maple: Hack around kfree_rcu not
 existing

On Fri, Jul 18, 2025 at 06:21:37PM +0100, 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>

So, patch 1/2 of this series has broken the VMA tests for the same reason.

Let's fix this by putting it in a shared place.

The fix enclosed works for me (assuming the patch is reverted).

Cheers, Lorenzo

> ---
>  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"
>
> --
> 2.50.1
>
>

----8<----
>From 7bbe839b520df5e9aa350fcf7ea96a0c1806729f Mon Sep 17 00:00:00 2001
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Date: Sun, 10 Aug 2025 15:21:42 +0100
Subject: [PATCH] fix maple/vma tests in shared place

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 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