linux-kernel - Re: [PATCH v4 1/2] mm/sparse.c: Use kvmalloc/kvfree to alloc/free memmap for the classic sparse

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Date:   Mon, 16 Mar 2020 20:40:54 +0800
From:   Baoquan He <bhe@...hat.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, mhocko@...e.com,
        akpm@...ux-foundation.org, willy@...radead.org,
        richard.weiyang@...il.com, vbabka@...e.cz
Subject: Re: [PATCH v4 1/2] mm/sparse.c: Use kvmalloc/kvfree to alloc/free
 memmap for the classic sparse

On 03/16/20 at 12:00pm, David Hildenbrand wrote:
> On 16.03.20 11:21, Baoquan He wrote:
> > This change makes populate_section_memmap()/depopulate_section_memmap
> > much simpler.
> > 
> > Suggested-by: Michal Hocko <mhocko@...nel.org>
> > Signed-off-by: Baoquan He <bhe@...hat.com>
> > Reviewed-by: David Hildenbrand <david@...hat.com>
> > Acked-by: Michal Hocko <mhocko@...e.com>
> > ---
> > v3->v4:
> >   Split the old v3 into two patches, to carve out the using 'nid'
> >   as preferred node to allocate memmap into a separate patch. This
> >   is suggested by Michal, and the carving out is put in patch 2.
> > 
> > v2->v3:
> >   Remove __GFP_NOWARN and use array_size when calling kvmalloc_node()
> >   per Matthew's comments.
> > http://lkml.kernel.org/r/20200312141749.GL27711@MiWiFi-R3L-srv
> > 
> >  mm/sparse.c | 27 +++------------------------
> >  1 file changed, 3 insertions(+), 24 deletions(-)
> > 
> > diff --git a/mm/sparse.c b/mm/sparse.c
> > index e747a238a860..d01d09cc7d99 100644
> > --- a/mm/sparse.c
> > +++ b/mm/sparse.c
> > @@ -719,35 +719,14 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
> >  struct page * __meminit populate_section_memmap(unsigned long pfn,
> >  		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
> >  {
> > -	struct page *page, *ret;
> > -	unsigned long memmap_size = sizeof(struct page) * PAGES_PER_SECTION;
> > -
> > -	page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
> > -	if (page)
> > -		goto got_map_page;
> > -
> > -	ret = vmalloc(memmap_size);
> > -	if (ret)
> > -		goto got_map_ptr;
> > -
> > -	return NULL;
> > -got_map_page:
> > -	ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
> > -got_map_ptr:
> > -
> > -	return ret;
> > +	return kvmalloc(array_size(sizeof(struct page),
> > +			PAGES_PER_SECTION), GFP_KERNEL);
> 
> FWIW, this is what I meant:
> 
>         return kvmalloc(array_size(sizeof(struct page),
>                                    PAGES_PER_SECTION), GFP_KERNEL);
Since there's another parameter, I didn't indent it with sizeof. But
Pankaj and Matthew have added other two votes on this, I will change it,
thanks.