linux-kernel - Re: [PATCH 1/7] mm/sparse.c: Introduce new function fill_subsection

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Message-ID: <0463a54b-12cb-667e-7c86-66cd707cec84@redhat.com>
Date:   Mon, 10 Feb 2020 10:49:47 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Baoquan He <bhe@...hat.com>, linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org,
        dan.j.williams@...el.com, richardw.yang@...ux.intel.com
Subject: Re: [PATCH 1/7] mm/sparse.c: Introduce new function
 fill_subsection_map()

On 09.02.20 11:48, Baoquan He wrote:
> Wrap the codes filling subsection map in section_activate() into
> fill_subsection_map(), this makes section_activate() cleaner and
> easier to follow.
> 
> Signed-off-by: Baoquan He <bhe@...hat.com>
> ---
>  mm/sparse.c | 45 ++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 34 insertions(+), 11 deletions(-)
> 
> diff --git a/mm/sparse.c b/mm/sparse.c
> index c184b69460b7..9ad741ccbeb6 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -788,24 +788,28 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
>  		depopulate_section_memmap(pfn, nr_pages, altmap);
>  }
>  
> -static struct page * __meminit section_activate(int nid, unsigned long pfn,
> -		unsigned long nr_pages, struct vmem_altmap *altmap)
> +/**
> + * fill_subsection_map - fill subsection map of a memory region
> + * @pfn - start pfn of the memory range
> + * @nr_pages - number of pfns to add in the region
> + *
> + * This clears the related subsection map inside one section, and only
> + * intended for hotplug.
> + *
> + * Return:
> + * * 0		- On success.
> + * * -EINVAL	- Invalid memory region.
> + * * -EEXIST	- Subsection map has been set.
> + */
> +static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
>  {
> -	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
>  	struct mem_section *ms = __pfn_to_section(pfn);
> -	struct mem_section_usage *usage = NULL;
> +	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
>  	unsigned long *subsection_map;
> -	struct page *memmap;
>  	int rc = 0;
>  
>  	subsection_mask_set(map, pfn, nr_pages);
>  
> -	if (!ms->usage) {
> -		usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);
> -		if (!usage)
> -			return ERR_PTR(-ENOMEM);
> -		ms->usage = usage;
> -	}
>  	subsection_map = &ms->usage->subsection_map[0];
>  
>  	if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))
> @@ -816,6 +820,25 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,
>  		bitmap_or(subsection_map, map, subsection_map,
>  				SUBSECTIONS_PER_SECTION);
>  
> +	return rc;
> +}
> +
> +static struct page * __meminit section_activate(int nid, unsigned long pfn,
> +		unsigned long nr_pages, struct vmem_altmap *altmap)
> +{
> +	struct mem_section *ms = __pfn_to_section(pfn);
> +	struct mem_section_usage *usage = NULL;
> +	struct page *memmap;
> +	int rc = 0;
> +
> +	if (!ms->usage) {
> +		usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);
> +		if (!usage)
> +			return ERR_PTR(-ENOMEM);
> +		ms->usage = usage;
> +	}
> +
> +	rc = fill_subsection_map(pfn, nr_pages);
>  	if (rc) {
>  		if (usage)
>  			ms->usage = NULL;
> 

What about having two variants of
section_activate()/section_deactivate() instead? Then we don't have any
subsection related stuff in !subsection code.

-- 
Thanks,

David / dhildenb