Re: [PATCH 07/12] hugetlb: perform vmemmap restoration on a list of pages

[Mike Kravetz]

On 08/30/23 16:33, Muchun Song wrote:
> 
> 
> On 2023/8/26 03:04, Mike Kravetz wrote:
> > When removing hugetlb pages from the pool, we first create a list
> > of removed pages and then free those pages back to low level allocators.
> > Part of the 'freeing process' is to restore vmemmap for all base pages
> > if necessary.  Pass this list of pages to a new routine
> > hugetlb_vmemmap_restore_folios() so that vmemmap restoration can be
> > performed in bulk.
> > 
> > Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> > ---
> >   mm/hugetlb.c         | 3 +++
> >   mm/hugetlb_vmemmap.c | 8 ++++++++
> >   mm/hugetlb_vmemmap.h | 6 ++++++
> >   3 files changed, 17 insertions(+)
> > 
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 3133dbd89696..1bde5e234d5c 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -1833,6 +1833,9 @@ static void update_and_free_pages_bulk(struct hstate *h, struct list_head *list)
> >   {
> >   	struct folio *folio, *t_folio;
> > +	/* First restore vmemmap for all pages on list. */
> > +	hugetlb_vmemmap_restore_folios(h, list);
> > +
> >   	list_for_each_entry_safe(folio, t_folio, list, lru) {
> >   		update_and_free_hugetlb_folio(h, folio, false);
> >   		cond_resched();
> > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> > index 147018a504a6..d5e6b6c76dce 100644
> > --- a/mm/hugetlb_vmemmap.c
> > +++ b/mm/hugetlb_vmemmap.c
> > @@ -479,6 +479,14 @@ int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
> >   	return ret;
> >   }
> 
> Because it is a void function, I'd like to add a comment here like:
> 
>     This function only tries to restore a list of folios' vmemmap pages and
>     does not guarantee that the restoration will succeed after it returns.

Will do.  Thanks!

-- 
Mike Kravetz