Re: [PATCH v3] alloc_tag: check mem_profiling_support in alloc_tag_init

[Suren Baghdasaryan <surenb@google.com>]

On Mon, May 12, 2025 at 12:42 PM Casey Chen <cachen@purestorage.com> wrote:
>
> If mem_profiling_support is false, for example by
> sysctl.vm.mem_profiling=never, alloc_tag_init should skip
> module tags allocation, codetag type registration and
> procfs init.
>
> Signed-off-by: Casey Chen <cachen@purestorage.com>
> Reviewed-by: Yuanyuan Zhong <yzhong@purestorage.com>
> ---
>  lib/alloc_tag.c | 34 +++++++++++++++++++---------------
>  1 file changed, 19 insertions(+), 15 deletions(-)
>
> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> index 25ecc1334b67..7c798778669c 100644
> --- a/lib/alloc_tag.c
> +++ b/lib/alloc_tag.c
> @@ -244,17 +244,6 @@ static void shutdown_mem_profiling(bool remove_file)
>         mem_profiling_support = false;
>  }
>
> -static void __init procfs_init(void)
> -{
> -       if (!mem_profiling_support)
> -               return;
> -
> -       if (!proc_create_seq(ALLOCINFO_FILE_NAME, 0400, NULL, &allocinfo_seq_op)) {
> -               pr_err("Failed to create %s file\n", ALLOCINFO_FILE_NAME);
> -               shutdown_mem_profiling(false);
> -       }
> -}
> -
>  void __init alloc_tag_sec_init(void)
>  {
>         struct alloc_tag *last_codetag;
> @@ -762,19 +751,34 @@ static int __init alloc_tag_init(void)
>         };
>         int res;
>
> +       sysctl_init();
> +
> +       if (!mem_profiling_support) {
> +               pr_info("Memory allocation profiling is not supported!\n");
> +               return 0;
> +       }
> +
> +       if (!proc_create_seq(ALLOCINFO_FILE_NAME, 0400, NULL, &allocinfo_seq_op)) {

I suggest keeping file creation as the last step so that we don't have
to remove it if later steps fail.

> +               pr_err("Failed to create %s file\n", ALLOCINFO_FILE_NAME);
> +               shutdown_mem_profiling(false);
> +               return -EAGAIN;

Why EAGAIN? I would just let it fall through returning 0 (after moving
this to the end as I suggested in my previous comment).

> +       }
> +
>         res = alloc_mod_tags_mem();
> -       if (res)
> +       if (res) {
> +               pr_err("Failed to allocate module tags\n");

The error message is a bit misleading here since we are not allocating
module tags but reserving virtual space for them. Maybe:
"Failed to reserve address space for module tags"

> +               shutdown_mem_profiling(true);
>                 return res;
> +       }
>
>         alloc_tag_cttype = codetag_register_type(&desc);
>         if (IS_ERR(alloc_tag_cttype)) {
> +               pr_err("Failed to register codetag type with desc %s\n", desc.section);

pr_err("Allocation tags registration failed, errno = %d\n", ret);

>                 free_mod_tags_mem();
> +               shutdown_mem_profiling(true);
>                 return PTR_ERR(alloc_tag_cttype);
>         }
>
> -       sysctl_init();
> -       procfs_init();
> -
>         return 0;
>  }
>  module_init(alloc_tag_init);
> --
> 2.49.0
>