Re: [PATCH v2 02/15] mm: pgtable: introduce generic p4d_alloc_one() and p4d_free()

[Qi Zheng]

Hi Alexander,

On 2024/12/20 00:32, Alexander Gordeev wrote:
> On Wed, Dec 18, 2024 at 09:04:38PM +0800, Qi Zheng wrote:
> > For these architectures, provide a generic implementation in
> > asm-generic/pgalloc.h and convert them to use it. And like other levels
> > of page tables, add statistics for P4D level page table.
>
> FWIW, introducing the generic implementation and adding ctor|dtors
> look as separate changes to me.

OK, will separate it in v3.

> ...
> >   static inline void p4d_free(struct mm_struct *mm, p4d_t *p4d)
> >   {
> > -	if (!pgtable_l5_enabled())
> > -		return;
> > -	BUG_ON((unsigned long)p4d & (PAGE_SIZE-1));
>
> Or maybe?
>
> 	BUG_ON(!IS_ALIGNED((unsigned long)p4d, PAGE_SIZE));

Do you mean to keep BUG_ON() and change it to the above form?

I would prefer to just drop BUG_ON() as is done with the other
page tables.

Thanks,
Qi

> > -	free_page((unsigned long)p4d);
> > +	if (pgtable_l5_enabled())
> > +		__p4d_free(mm, p4d);
> >   }