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 12:00:04 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Baoquan He <bhe@...hat.com>, linux-kernel@...r.kernel.org
Cc:     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 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);



-- 
Thanks,

David / dhildenb