Re: [PATCH 11/12] mm: pgtable: introduce generic __tlb_remove_table()

[Peter Zijlstra <peterz@infradead.org>]

On Mon, Dec 16, 2024 at 01:00:43PM +0100, Peter Zijlstra wrote:
> On Sat, Dec 14, 2024 at 05:02:57PM +0800, Qi Zheng wrote:
> 
> > diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c
> > index c73b89811a264..3e002dea6278f 100644
> > --- a/arch/s390/mm/pgalloc.c
> > +++ b/arch/s390/mm/pgalloc.c
> > @@ -193,13 +193,6 @@ void page_table_free(struct mm_struct *mm, unsigned long *table)
> >  	pagetable_dtor_free(ptdesc);
> >  }
> >  
> > -void __tlb_remove_table(void *table)
> > -{
> > -	struct ptdesc *ptdesc = virt_to_ptdesc(table);
> > -
> > -	pagetable_dtor_free(ptdesc);
> > -}
> > -
> >  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> >  static void pte_free_now(struct rcu_head *head)
> >  {
> 
> > diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
> > index 709830274b756..939a813023d7e 100644
> > --- a/include/asm-generic/tlb.h
> > +++ b/include/asm-generic/tlb.h
> 
> >  #define MAX_TABLE_BATCH		\
> >  	((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *))
> >  
> > +#ifndef __HAVE_ARCH_TLB_REMOVE_TABLE
> > +static inline void __tlb_remove_table(void *_table)
> > +{
> > +	struct ptdesc *ptdesc = (struct ptdesc *)_table;
> > +
> > +	pagetable_dtor(ptdesc);
> > +	pagetable_free(ptdesc);
> > +}
> > +#endif
> 
> 
> Spot the fail...
> 
> That said, all this ptdesc stuff is another giant trainwreck. Let me
> clean that up for you.
> 
> ---

> -static inline void __tlb_remove_table(void *_table)
> +static inline void __tlb_remove_table(void *table)
>  {
> -	struct ptdesc *ptdesc = (struct ptdesc *)_table;
> +	struct ptdesc *ptdesc = page_to_ptdesc(table);
>  
>  	pagetable_dtor(ptdesc);
>  	pagetable_free(ptdesc);

And now observe that __tlb_remove_table() is identical to
asm-generic/pgalloc.h pte_free(), pmd_free(), __pud_free() and
__p4d_free().

And I'm sure we don't need 5 copies of this :-), wdyt?