Re: [External] Re: [PATCH v10 03/11] mm/hugetlb: Free the vmemmap pages associated with each HugeTLB page

[Muchun Song]

On Tue, Dec 22, 2020 at 2:00 AM Oscar Salvador <osalvador@xxxxxxx> wrote:
>
> On Mon, Dec 21, 2020 at 11:52:30PM +0800, Muchun Song wrote:
> > On Mon, Dec 21, 2020 at 9:44 PM Oscar Salvador <osalvador@xxxxxxx> wrote:
> > >
> > > On Mon, Dec 21, 2020 at 07:25:15PM +0800, Muchun Song wrote:
> > >
> > > > Should we add a BUG_ON in vmemmap_remap_free() for now?
> > > >
> > > >         BUG_ON(reuse != start + PAGE_SIZE);
> > >
> > > I do not think we have to, plus we would be BUG_ing for some specific use
> > > case in "generic" function.
> >
> > The vmemmap_remap_range() walks page table range [start, end),
> > if reuse is equal to (start + PAGE_SIZE), the range can adjust to
> > [start - PAGE_SIZE, end). But if not, we need some work to
> > implement the "generic" function.
> >
> >   - adjust range to [min(start, reuse), end) and call
> >     vmemmap_remap_rangeand which skip the hole
> >     which is [reuse + PAGE_SIZE, start) or [end, reuse).
> >   - call vmemmap_remap_range(reuse, reuse + PAGE_SIZE)
> >     to get the reuse page.Then, call vmemmap_remap_range(start, end)
> >     again to remap.
> >
> > Which one do you prefer?
>
> I would not overcomplicate things at this stage.
> Just follow my sugestion and add a BUG_ON as you said, that might be the
> easier way now.
> We can overthink this in the future when some other usecases come
> around, right?

You are right. Will do this. Thanks for your suggestions.

>
> Thanks
>
>
> --
> Oscar Salvador
> SUSE L3



-- 
Yours,
Muchun