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

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Message-ID: <20230830175323.GA55006@monkey>
Date:   Wed, 30 Aug 2023 10:53:23 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Muchun Song <muchun.song@...ux.dev>
Cc:     Muchun Song <songmuchun@...edance.com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        David Rientjes <rientjes@...gle.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        Xiongchun Duan <duanxiongchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/12] hugetlb: perform vmemmap restoration on a list of
 pages

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@...cle.com>
> > ---
> >   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