Re: [PATCH 12/41] mm: add per-VMA lock and helper functions to control it

[Suren Baghdasaryan]

On Tue, Jan 17, 2023 at 7:07 AM Michal Hocko <mhocko@xxxxxxxx> wrote:
>
> On Mon 09-01-23 12:53:07, Suren Baghdasaryan wrote:
> > diff --git a/kernel/fork.c b/kernel/fork.c
> > index 5986817f393c..c026d75108b3 100644
> > --- a/kernel/fork.c
> > +++ b/kernel/fork.c
> > @@ -474,6 +474,7 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
> >                */
> >               *new = data_race(*orig);
> >               INIT_LIST_HEAD(&new->anon_vma_chain);
> > +             vma_init_lock(new);
> >               dup_anon_vma_name(orig, new);
> >       }
> >       return new;
> > @@ -1145,6 +1146,9 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
> >       seqcount_init(&mm->write_protect_seq);
> >       mmap_init_lock(mm);
> >       INIT_LIST_HEAD(&mm->mmlist);
> > +#ifdef CONFIG_PER_VMA_LOCK
> > +     WRITE_ONCE(mm->mm_lock_seq, 0);
> > +#endif
>
> The mm shouldn't be visible so why WRITE_ONCE?

True. Will change to a simple assignment.

>
> --
> Michal Hocko
> SUSE Labs