Re: [PATCH v2 1/6] mm: introduce vma->vm_flags modifier functions

[Suren Baghdasaryan <surenb@xxxxxxxxxx>]

On Wed, Jan 25, 2023 at 1:10 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> On Wed, Jan 25, 2023 at 12:38:46AM -0800, Suren Baghdasaryan wrote:
>
> > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> > index 2d6d790d9bed..6c7c70bf50dd 100644
> > --- a/include/linux/mm_types.h
> > +++ b/include/linux/mm_types.h
> > @@ -491,7 +491,13 @@ struct vm_area_struct {
> >        * See vmf_insert_mixed_prot() for discussion.
> >        */
> >       pgprot_t vm_page_prot;
> > -     unsigned long vm_flags;         /* Flags, see mm.h. */
> > +
> > +     /*
> > +      * Flags, see mm.h.
> > +      * WARNING! Do not modify directly.
> > +      * Use {init|reset|set|clear|mod}_vm_flags() functions instead.
> > +      */
> > +     unsigned long vm_flags;
>
> We have __private and ACCESS_PRIVATE() to help with enforcing this.

Thanks for pointing this out, Peter! I guess for that I'll need to
convert all read accesses and provide get_vm_flags() too? That will
cause some additional churt (a quick search shows 801 hits over 248
files) but maybe it's worth it? I think Michal suggested that too in
another patch. Should I do that while we are at it?

>