Re: [PATCH slab/for-next-fixes v3 3/4] lib/alloc_tag: introduce mem_alloc_profiling_permanently_disabled()

[Suren Baghdasaryan <surenb@google.com>]

On Mon, Jul 13, 2026 at 7:29 AM Harry Yoo (Oracle) <harry@kernel.org> wrote:
>
> mem_alloc_profiling_enabled() tells whether memalloc profiling is
> currently enabled. However, even when this function returns false,
> it can be enabled later.
>
> However, this is not enough. Some optimizations can be applied only when
> memalloc profiling is permanently disabled. For example, to skip the
> creation of KMALLOC_NO_OBJ_EXT caches at boot time, mem_profiling must
> be set to "never", "0" w/ debugging on, or have been shutdown so that
> it can no longer be enabled.
>
> Introduce mem_alloc_profiling_permanently_disabled() for this purpose.

nit: I would call it mem_alloc_profiling_supported() but this name would do.

>
> Fixes: 4b8736964640 ("mm/slab: add allocation accounting into slab allocation and free paths")
> Cc: stable@vger.kernel.org
> Signed-off-by: Harry Yoo (Oracle) <harry@kernel.org>

Acked-by: Suren Baghdasaryan <surenb@google.com>

> ---
>  include/linux/alloc_tag.h | 3 +++
>  lib/alloc_tag.c           | 9 +++++++++
>  2 files changed, 12 insertions(+)
>
> diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
> index 068ba2e77c5d..6ed9f82e639f 100644
> --- a/include/linux/alloc_tag.h
> +++ b/include/linux/alloc_tag.h
> @@ -134,6 +134,8 @@ static inline bool mem_alloc_profiling_enabled(void)
>                                    &mem_alloc_profiling_key);
>  }
>
> +bool mem_alloc_profiling_permanently_disabled(void);
> +
>  static inline struct alloc_tag_counters alloc_tag_read(struct alloc_tag *tag)
>  {
>         struct alloc_tag_counters v = { 0, 0 };
> @@ -239,6 +241,7 @@ static inline bool alloc_tag_is_inaccurate(struct alloc_tag *tag)
>
>  #define DEFINE_ALLOC_TAG(_alloc_tag)
>  static inline bool mem_alloc_profiling_enabled(void) { return false; }
> +static inline bool mem_alloc_profiling_permanently_disabled(void) { return true; }
>  static inline void alloc_tag_add(union codetag_ref *ref, struct alloc_tag *tag,
>                                  size_t bytes) {}
>  static inline void alloc_tag_sub(union codetag_ref *ref, size_t bytes) {}
> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> index d9be1cf5187d..e5b218176c5a 100644
> --- a/lib/alloc_tag.c
> +++ b/lib/alloc_tag.c
> @@ -26,6 +26,15 @@ static bool mem_profiling_support = true;
>  static bool mem_profiling_support;
>  #endif
>
> +/*
> + * Memory allocation profiling is permanently disabled and cannot be enabled.
> + * Must be called after setup_early_mem_profiling().
> + */
> +bool mem_alloc_profiling_permanently_disabled(void)
> +{
> +       return !mem_profiling_support;
> +}
> +
>  static struct codetag_type *alloc_tag_cttype;
>
>  #ifdef CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU
>
> --
> 2.53.0
>