linux-kernel - Re: [PATCH 1/2] mm/memory_hotplug: Export shrink span functions for zone and node

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Message-ID: <5d02ea0e-aca6-a64b-23de-bc9307572d17@redhat.com>
Date:   Wed, 26 Jan 2022 18:04:50 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Jonghyeon Kim <tome01@...u.ac.kr>, dan.j.williams@...el.com
Cc:     vishal.l.verma@...el.com, dave.jiang@...el.com,
        akpm@...ux-foundation.org, nvdimm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 1/2] mm/memory_hotplug: Export shrink span functions for
 zone and node

On 26.01.22 18:00, Jonghyeon Kim wrote:
> Export shrink_zone_span() and update_pgdat_span() functions to head
> file. We need to update real number of spanned pages for NUMA nodes and
> zones when we add memory device node such as device dax memory.
> 

Can you elaborate a bit more what you intend to fix?

Memory onlining/offlining is reponsible for updating the node/zone span,
and that's triggered when the dax/kmem mamory gets onlined/offlined.

> Signed-off-by: Jonghyeon Kim <tome01@...u.ac.kr>
> ---
>  include/linux/memory_hotplug.h | 3 +++
>  mm/memory_hotplug.c            | 6 ++++--
>  2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index be48e003a518..25c7f60c317e 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -337,6 +337,9 @@ extern void move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn,
>  extern void remove_pfn_range_from_zone(struct zone *zone,
>  				       unsigned long start_pfn,
>  				       unsigned long nr_pages);
> +extern void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
> +			     unsigned long end_pfn);
> +extern void update_pgdat_span(struct pglist_data *pgdat);
>  extern bool is_memblock_offlined(struct memory_block *mem);
>  extern int sparse_add_section(int nid, unsigned long pfn,
>  		unsigned long nr_pages, struct vmem_altmap *altmap);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 2a9627dc784c..38f46a9ef853 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -389,7 +389,7 @@ static unsigned long find_biggest_section_pfn(int nid, struct zone *zone,
>  	return 0;
>  }
>  
> -static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
> +void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
>  			     unsigned long end_pfn)
>  {
>  	unsigned long pfn;
> @@ -428,8 +428,9 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
>  		}
>  	}
>  }
> +EXPORT_SYMBOL_GPL(shrink_zone_span);

Exporting both as symbols feels very wrong. This is memory
onlining/offlining internal stuff.



-- 
Thanks,

David / dhildenb