[PATCH] maple_tree: remove undocumented CONFIG_MAPLE_RCU_DISABLED macro

[PATCH] maple_tree: remove undocumented CONFIG_MAPLE_RCU_DISABLED macro

[Ethan Nelson-Moore]

<linux/maple_tree.h> consults the macro CONFIG_MAPLE_RCU_DISABLED to
determine whether to disable the mt_in_rcu() function (by making it
always return false). This macro is not reachable via Kconfig, despite
its name, and is not documented anywhere. Remove it to avoid polluting
the CONFIG_* namespace.

Discovered while searching for CONFIG_* symbols referenced in code but
not defined in any Kconfig file.

Signed-off-by: Ethan Nelson-Moore <enelsonmoore@gmail.com>
---
 include/linux/maple_tree.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
index 4a5631906aff..1b3014377105 100644
--- a/include/linux/maple_tree.h
+++ b/include/linux/maple_tree.h
@@ -11,7 +11,6 @@
 #include <linux/kernel.h>
 #include <linux/rcupdate.h>
 #include <linux/spinlock.h>
-/* #define CONFIG_MAPLE_RCU_DISABLED */
 
 /*
  * Allocated nodes are mutable until they have been inserted into the tree,
@@ -864,9 +863,6 @@ static inline void mt_init(struct maple_tree *mt)
 
 static inline bool mt_in_rcu(struct maple_tree *mt)
 {
-#ifdef CONFIG_MAPLE_RCU_DISABLED
-	return false;
-#endif
 	return mt->ma_flags & MT_FLAGS_USE_RCU;
 }
 
-- 
2.43.0

Re: [PATCH] maple_tree: remove undocumented CONFIG_MAPLE_RCU_DISABLED macro

[SeongJae Park]

On Wed, 10 Jun 2026 15:09:04 -0700 Ethan Nelson-Moore <enelsonmoore@gmail.com> wrote:

> <linux/maple_tree.h> consults the macro CONFIG_MAPLE_RCU_DISABLED to
> determine whether to disable the mt_in_rcu() function (by making it
> always return false). This macro is not reachable via Kconfig, despite
> its name, and is not documented anywhere. Remove it to avoid polluting
> the CONFIG_* namespace.
> 
> Discovered while searching for CONFIG_* symbols referenced in code but
> not defined in any Kconfig file.

Seems this was also found in the past [1], and apparently this is not
intended to be as is.

I also think it is better to be removed or renamed.

[1] https://lore.kernel.org/20230906152325.dblzauybyoq5kd35@revolver

> 
> Signed-off-by: Ethan Nelson-Moore <enelsonmoore@gmail.com>

Acked-by: SeongJae Park <sj@kernel.org>


Thanks,
SJ

[...]

Re: [PATCH] maple_tree: remove undocumented CONFIG_MAPLE_RCU_DISABLED macro

[Liam R. Howlett]

On 26/06/10 03:09PM, Ethan Nelson-Moore wrote:
> <linux/maple_tree.h> consults the macro CONFIG_MAPLE_RCU_DISABLED to
> determine whether to disable the mt_in_rcu() function (by making it
> always return false). This macro is not reachable via Kconfig, despite
> its name, and is not documented anywhere. Remove it to avoid polluting
> the CONFIG_* namespace.
> 
> Discovered while searching for CONFIG_* symbols referenced in code but
> not defined in any Kconfig file.
> 
> Signed-off-by: Ethan Nelson-Moore <enelsonmoore@gmail.com>

Reviewed-by: "Liam R. Howlett (Oracle)" <liam@infradead.org>

> ---
>  include/linux/maple_tree.h | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
> index 4a5631906aff..1b3014377105 100644
> --- a/include/linux/maple_tree.h
> +++ b/include/linux/maple_tree.h
> @@ -11,7 +11,6 @@
>  #include <linux/kernel.h>
>  #include <linux/rcupdate.h>
>  #include <linux/spinlock.h>
> -/* #define CONFIG_MAPLE_RCU_DISABLED */
>  
>  /*
>   * Allocated nodes are mutable until they have been inserted into the tree,
> @@ -864,9 +863,6 @@ static inline void mt_init(struct maple_tree *mt)
>  
>  static inline bool mt_in_rcu(struct maple_tree *mt)
>  {
> -#ifdef CONFIG_MAPLE_RCU_DISABLED
> -	return false;
> -#endif
>  	return mt->ma_flags & MT_FLAGS_USE_RCU;
>  }
>  
> -- 
> 2.43.0
> 

Re: [PATCH] maple_tree: remove undocumented CONFIG_MAPLE_RCU_DISABLED macro

[Alice Ryhl]

On Wed, Jun 10, 2026 at 03:09:04PM -0700, Ethan Nelson-Moore wrote:
> <linux/maple_tree.h> consults the macro CONFIG_MAPLE_RCU_DISABLED to
> determine whether to disable the mt_in_rcu() function (by making it
> always return false). This macro is not reachable via Kconfig, despite
> its name, and is not documented anywhere. Remove it to avoid polluting
> the CONFIG_* namespace.
> 
> Discovered while searching for CONFIG_* symbols referenced in code but
> not defined in any Kconfig file.
> 
> Signed-off-by: Ethan Nelson-Moore <enelsonmoore@gmail.com>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>