Re: [PATCH 03/12] mm: shmem: don't expose 'deny' and 'force' via the kernel command line

[Barry Song]

On Fri, Sep 18, 2026 at 11:58 AM Baolin Wang
<baolin.wang@xxxxxxxxxxxxxxxxx> wrote:
>
> Based on the previous discussion with Lorenzo[1], the 'deny' and 'force'
> options are testing-only configurations and shouldn't be exposed via the
> shmem kernel command line.
>
> So drop these debug options from the shmem kernel command line and update
> the documentation to make this clear.

If it is a debug option, it should not be exposed through sysfs :-)

Maybe we could rephrase this to say that it can only be switched at
runtime through the `shmem_enabled` sysfs interface?

>
> [1] https://lore.kernel.org/all/6e4aae7b-2c71-4109-945c-6481efde3636@xxxxxxxxxxxxxxxxx/
> Suggested-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> ---
[...]
> +static int shmem_parse_huge(const char *str, bool skip_deny_force)
>  {

The name is a bit weird. What about `allow_deny_force`?

>         int huge;
>
> @@ -683,9 +683,9 @@ static int shmem_parse_huge(const char *str)
>                 huge = SHMEM_HUGE_WITHIN_SIZE;
>         else if (!strcmp(str, "advise"))
>                 huge = SHMEM_HUGE_ADVISE;
> -       else if (!strcmp(str, "deny"))
> +       else if (!strcmp(str, "deny") && !skip_deny_force)
>                 huge = SHMEM_HUGE_DENY;
> -       else if (!strcmp(str, "force"))
> +       else if (!strcmp(str, "force") && !skip_deny_force)
>                 huge = SHMEM_HUGE_FORCE;
>         else
>                 return -EINVAL;
> @@ -5680,7 +5680,7 @@ static ssize_t shmem_enabled_store(struct kobject *kobj,
>         if (count && tmp[count - 1] == '\n')
>                 tmp[count - 1] = '\0';
>
> -       huge = shmem_parse_huge(tmp);
> +       huge = shmem_parse_huge(tmp, /*skip_deny_force=*/false);

/*allow_deny_force=*/true

>         if (huge == -EINVAL)
>                 return huge;
>
> @@ -5807,7 +5807,7 @@ static int __init setup_transparent_hugepage_shmem(char *str)
>  {
>         int huge;
>
> -       huge = shmem_parse_huge(str);
> +       huge = shmem_parse_huge(str, /*skip_deny_force=*/true);

/*allow_deny_force=*/false

>         if (huge == -EINVAL) {
>                 pr_warn("transparent_hugepage_shmem= cannot parse, ignored\n");
>                 return huge;
> @@ -5822,7 +5822,7 @@ static int __init setup_transparent_hugepage_tmpfs(char *str)
>  {
>         int huge;
>
> -       huge = shmem_parse_huge(str);
> +       huge = shmem_parse_huge(str, /*skip_deny_force=*/true);

/*allow_deny_force=*/false

>         if (huge < 0) {
>                 pr_warn("transparent_hugepage_tmpfs= cannot parse, ignored\n");
>                 return huge;
> --
> 2.47.3
>

Best Regards
Barry