On Thu, Jun 13, 2024 at 4:30 PM David Hildenbrand <david@xxxxxxxxxx> wrote:
>
> On 10.06.24 14:02, Lance Yang wrote:
> > Introduce the page_vma_mapped_walk_restart() helper to handle scenarios
> > where the page table walk needs to be restarted due to changes in the page
> > table, such as when a PMD is split. It releases the PTL held during the
> > previous walk and resets the state, allowing a new walk to start at the
> > current address stored in pvmw->address.
> >
> > Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> > Signed-off-by: Lance Yang <ioworker0@xxxxxxxxx>
> > ---
> > include/linux/rmap.h | 22 ++++++++++++++++++++++
> > 1 file changed, 22 insertions(+)
> >
> > diff --git a/include/linux/rmap.h b/include/linux/rmap.h
> > index 7229b9baf20d..5f18509610cc 100644
> > --- a/include/linux/rmap.h
> > +++ b/include/linux/rmap.h
> > @@ -710,6 +710,28 @@ static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
> > spin_unlock(pvmw->ptl);
> > }
> >
> > +/**
> > + * page_vma_mapped_walk_restart - Restart the page table walk.
> > + * @pvmw: Pointer to struct page_vma_mapped_walk.
> > + *
> > + * It restarts the page table walk when changes occur in the page
> > + * table, such as splitting a PMD. Ensures that the PTL held during
> > + * the previous walk is released and resets the state to allow for
> > + * a new walk starting at the current address stored in pvmw->address.
> > + */
> > +static inline void
> > +page_vma_mapped_walk_restart(struct page_vma_mapped_walk *pvmw)
> > +{
> > + WARN_ON_ONCE(!pvmw->pmd);
>
> Can we have this more general, like
>
> WARN_ON_ONCE(!pvmw->pmd && !pvmw->pte);
Sure, let’s make it more general.
>
> And then setting both to NULL below?
>
>
> > + WARN_ON_ONCE(!pvmw->ptl);
>
> This is confusing: you check for ptl below. What would be clearer is
>
> if (likely(pvmw->ptl))
> spin_unlock(pvmw->ptl);
> else
> WARN_ON_ONCE(1);
Will adjust as you suggested, thanks!
>
>
> > +
> > + if (pvmw->ptl)
> > + spin_unlock(pvmw->ptl);
> > +
> > + pvmw->ptl = NULL;
> > + pvmw->pmd = NULL;
> > +}
> > +
> > bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
> >
> > /*
>
> I'd suggest squashing that into the next patch.
Got it.
Thanks,
Lance
>
> --
> Cheers,
>
> David / dhildenb
>
