Re: [PATCH 1/2] alloc_tag: skip percpu counter allocation when profiling is disabled

[Suren Baghdasaryan]

On Sun, Aug 16, 2026 at 11:26 PM Hao Ge <hao.ge@xxxxxxxxx> wrote:
>
> After shutdown_mem_profiling() clears mem_profiling_support,
> needs_section_mem() returns false, so later modules have their codetag
> section placed as regular data and never enter the alloc_tag maple tree.
> codetag_load_module() still called load_module(), which allocated a percpu
> counter for every tag; release_module_tags() could not find these modules
> on unload, so the counters leaked.
>
> Return -EOPNOTSUPP from load_module() when profiling is off:
> codetag_module_init() drops the module's cmod, no counters are allocated
> and the module loads without its tags. codetag_unload_module() now always
> calls free_section_mem(), since a module whose module_load() returned
> -EOPNOTSUPP is not in the idr but may still hold a reserved section.
>
> Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
> Fixes: 4835f747d3ed ("alloc_tag: support for page allocation tag compression")
> Cc: stable@xxxxxxxxxxxxxxx
> Suggested-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> Signed-off-by: Hao Ge <hao.ge@xxxxxxxxx>

Acked-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>

> ---
>  lib/codetag.c  | 10 ++++++++--
>  mm/alloc_tag.c |  4 ++++
>  2 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/lib/codetag.c b/lib/codetag.c
> index a9cda4c962a3..a0b600720afc 100644
> --- a/lib/codetag.c
> +++ b/lib/codetag.c
> @@ -240,7 +240,9 @@ static int codetag_module_init(struct codetag_type *cttype, struct module *mod)
>
>         if (err < 0) {
>                 kfree(cmod);
> -               return err;
> +               /* -EOPNOTSUPP means we can load the module without its tag. */
> +               if (err != -EOPNOTSUPP)
> +                       return err;
>         }
>
>         return 0;
> @@ -388,7 +390,11 @@ void codetag_unload_module(struct module *mod)
>                         ++cttype->content_id;
>                 }
>                 up_write(&cttype->mod_lock);
> -               if (found && cttype->desc.free_section_mem)
> +               /*
> +                * A module whose module_load() returned -EOPNOTSUPP is not
> +                * in the idr but may still hold reserved section memory.
> +                */
> +               if (cttype->desc.free_section_mem)
>                         cttype->desc.free_section_mem(mod, true);
>         }
>         mutex_unlock(&codetag_lock);
> diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c
> index 52aece27b00e..80eccaca665a 100644
> --- a/mm/alloc_tag.c
> +++ b/mm/alloc_tag.c
> @@ -975,6 +975,10 @@ static int load_module(struct module *mod, struct codetag *start, struct codetag
>         struct alloc_tag *stop_tag;
>         struct alloc_tag *tag;
>
> +       /* Profiling disabled: load the module without its tags. */
> +       if (!mem_profiling_support)
> +               return -EOPNOTSUPP;
> +
>         /* percpu counters for core allocations are already statically allocated */
>         if (!mod)
>                 return 0;
> --
> 2.25.1
>