[PATCH v2 3/7] mm: Add batched versions of ptep_modify_prot_start/commit

[Lorenzo Stoakes]

On Tue, May 06, 2025 at 04:30:18PM +0200, David Hildenbrand wrote:
> On 30.04.25 16:37, Lorenzo Stoakes wrote:
> > On Wed, Apr 30, 2025 at 11:55:12AM +0530, Dev Jain wrote:
> > >
> > >
> > > On 29/04/25 7:22 pm, Lorenzo Stoakes wrote:
> > > > On Tue, Apr 29, 2025 at 10:53:32AM +0530, Dev Jain wrote:
> > > > > Batch ptep_modify_prot_start/commit in preparation for optimizing mprotect.
> > > > > Architecture can override these helpers.
> > > > >
> > > > > Signed-off-by: Dev Jain <dev.jain at arm.com>
> > > > > ---
> > > > >    include/linux/pgtable.h | 38 ++++++++++++++++++++++++++++++++++++++
> > > > >    1 file changed, 38 insertions(+)
> > > > >
> > > > > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> > > > > index b50447ef1c92..ed287289335f 100644
> > > > > --- a/include/linux/pgtable.h
> > > > > +++ b/include/linux/pgtable.h
> > > > > @@ -891,6 +891,44 @@ static inline void wrprotect_ptes(struct mm_struct *mm, unsigned long addr,
> > > > >    }
> > > > >    #endif
> > > > >
> > > > > +/* See the comment for ptep_modify_prot_start */
> > > >
> > > > I feel like you really should add a little more here, perhaps point out
> > > > that it's batched etc.
> > >
> > > Sure. I couldn't easily figure out a way to write the documentation nicely,
> > > I'll do it this time.
> >
> > Thanks! Though see the discussion with Ryan also.
> >
> > >
> > > >
> > > > > +#ifndef modify_prot_start_ptes
> > > > > +static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
> > > > > +		unsigned long addr, pte_t *ptep, unsigned int nr)
> > > >
> > > > This name is a bit confusing, it's not any ptes, it's those pte entries
> > > > belonging to a large folio capped to the PTE table right that you are
> > > > batching right?
> > >
> > > yes, but I am just following the convention. See wrprotect_ptes(), etc. I
> > > don't have a strong preference anyways.
> > >
> > > >
> > > > Perhaps modify_prot_start_large_folio() ? Or something with 'batched' in
> > > > the name?
> > >
> > > How about modify_prot_start_batched_ptes()?
> >
> > I like this :) Ryan - that work for you, or do you feel _batched_ should be
> > dropped here?
>
>
> modify_prot_start_folio_ptes ?
>
> But I would rather go with
>
> modify_prot_folio_ptes_start
>
> The "batched" is implicit, and "large folio" is not required if it's more
> than one pte ...

Yeah that works for me! The mention of folio with plural does neatly imply
the rest.

Naming is hard :P

>
> :)
>
> --
> Cheers,
>
> David / dhildenb
>