Re: [PATCH] mm: mempolicy: keep VMA walk if both MPOL_MF_STRICT and MPOL_MF_MOVE are specified

[Yang Shi]

On 9/28/23 9:38 AM, Andrew Morton wrote:
> On Wed, 27 Sep 2023 14:39:21 -0700 Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
>
> > > > > The code should conceptually do:
> > > > >
> > > > >    if (MPOL_MF_MOVE|MOVEALL)
> > > > >        scan all vmas
> > > > >        try to migrate the existing pages
> > > > >        return success
> > > > >    else if (MPOL_MF_MOVE* | MPOL_MF_STRICT)
> > > > >        scan all vmas
> > > > >        try to migrate the existing pages
> > > > >        return -EIO if unmovable or migration failed
> > > > >    else /* MPOL_MF_STRICT alone */
> > > > >        break early if meets unmovable and don't call mbind_range() at all
> > > > >    else /* none of those flags */
> > > > >        check the ranges in test_walk, EFAULT without mbind_range() if discontig.
> > With this change I think my temporary fix at
> > https://lore.kernel.org/all/20230918211608.3580629-1-surenb@xxxxxxxxxx/
> > can be removed because we either scan all vmas (which means we locked
> > them all) or we break early and do not call mbind_range() at all (in
> > which case we don't need vmas to be locked).

Yes, we could just drop it. Keep the code not depend on the subtle 
behavior of queue_pages_range() by keeping it is ok to me either. I 
don't have strong preference.

> Thanks, I dropped "mm: lock VMAs skipped by a failed queue_pages_range()"

Thanks, Andrew.