linux-kernel - Re: [PATCH v3 7/7] mm/sparse.c: Use __get_free_pages() instead in populate_section

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Message-ID: <20200311093132.GJ27711@MiWiFi-R3L-srv>
Date:   Wed, 11 Mar 2020 17:31:32 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, david@...hat.com,
        richardw.yang@...ux.intel.com, dan.j.williams@...el.com,
        osalvador@...e.de, rppt@...ux.ibm.com
Subject: Re: [PATCH v3 7/7] mm/sparse.c: Use __get_free_pages() instead in
 populate_section_memmap()

On 03/10/20 at 03:56pm, Michal Hocko wrote:
> On Sat 07-03-20 16:42:29, Baoquan He wrote:
> > This removes the unnecessary goto, and simplify codes.
> > 
> > Signed-off-by: Baoquan He <bhe@...hat.com>
> > Reviewed-by: Wei Yang <richardw.yang@...ux.intel.com>
> > ---
> >  mm/sparse.c | 16 ++++++----------
> >  1 file changed, 6 insertions(+), 10 deletions(-)
> > 
> > diff --git a/mm/sparse.c b/mm/sparse.c
> > index fde651ab8741..266f7f5040fb 100644
> > --- a/mm/sparse.c
> > +++ b/mm/sparse.c
> > @@ -735,23 +735,19 @@ static void free_map_bootmem(struct page *memmap)
> >  struct page * __meminit populate_section_memmap(unsigned long pfn,
> >  		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
> >  {
> > -	struct page *page, *ret;
> > +	struct 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 = (void*)__get_free_pages(GFP_KERNEL|__GFP_NOWARN,
> > +				get_order(memmap_size));
> > +	if (ret)
> > +		return ret;
> >  
> >  	ret = vmalloc(memmap_size);
> >  	if (ret)
> > -		goto got_map_ptr;
> > +		return ret;
> >  
> >  	return NULL;
> > -got_map_page:
> > -	ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
> > -got_map_ptr:
> > -
> > -	return ret;
> >  }
> 
> Boy this code is ugly. Is there any reason we cannot simply use
> kvmalloc_array(PAGES_PER_SECTION, sizeof(struct page), GFP_KERNEL | __GFP_NOWARN)
> 
> And if we care about locality then go even one step further
> kvmalloc_node(PAGES_PER_SECTION * sizeof(struct page), GFP_KERNEL | __GFP_NOWARN, nid)

Yes, this looks better. I will use this to make a new version. Thanks.