[RFC PATCH 1/3] mm: make persistent huge zero folio read-only

[Xueyuan Chen]

On Wed, May 27, 2026 at 07:02:55PM +0530, Dev Jain wrote:

[...]
>>  static atomic_t huge_zero_refcount;
>> +#ifdef CONFIG_READONLY_HUGE_ZERO_FOLIO
>> +struct folio *huge_zero_folio __ro_after_init;
>
>
>Can we guard this with CONFIG_PERSISTENT_HUGE_ZERO_FOLIO? Since
>in that case too the pointer is never written after init.
>

Yes, that makes sense. The pointer lifetime is tied to
CONFIG_PERSISTENT_HUGE_ZERO_FOLIO. I'll fix this in v2.

>>  
>> +#ifdef CONFIG_READONLY_HUGE_ZERO_FOLIO
>> +static bool __init make_huge_zero_folio_readonly(void)
>> +{
>> +	return arch_make_huge_zero_folio_readonly(READ_ONCE(huge_zero_folio));
>
>
>I think READ_ONCE is not required since no one is going to change the
>pointer after allocation?
>

Agreed, READ_ONCE is not needed here. I'll drop it in v2.

Thanks,
Xueyuan