Re: [PATCH 03/12] mm: page_alloc: move set_zone_contiguous() into mm_init.c

["Huang, Ying" <ying.huang@intel.com>]

Kefeng Wang <wangkefeng.wang@huawei.com> writes:

> set_zone_contiguous() is only used in mm init/hotplug, and
> clear_zone_contiguous() only used in hotplug, move them from
> page_alloc.c to the more appropriate file.
>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>  include/linux/memory_hotplug.h |  3 --
>  mm/internal.h                  |  7 +++
>  mm/mm_init.c                   | 74 +++++++++++++++++++++++++++++++
>  mm/page_alloc.c                | 79 ----------------------------------
>  4 files changed, 81 insertions(+), 82 deletions(-)
>
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 9fcbf5706595..04bc286eed42 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -326,9 +326,6 @@ static inline int remove_memory(u64 start, u64 size)
>  static inline void __remove_memory(u64 start, u64 size) {}
>  #endif /* CONFIG_MEMORY_HOTREMOVE */
>  
> -extern void set_zone_contiguous(struct zone *zone);
> -extern void clear_zone_contiguous(struct zone *zone);
> -
>  #ifdef CONFIG_MEMORY_HOTPLUG
>  extern void __ref free_area_init_core_hotplug(struct pglist_data *pgdat);
>  extern int __add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags);
> diff --git a/mm/internal.h b/mm/internal.h
> index e28442c0858a..9482862b28cc 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -371,6 +371,13 @@ static inline struct page *pageblock_pfn_to_page(unsigned long start_pfn,
>  	return __pageblock_pfn_to_page(start_pfn, end_pfn, zone);
>  }
>  
> +void set_zone_contiguous(struct zone *zone);
> +
> +static inline void clear_zone_contiguous(struct zone *zone)
> +{
> +	zone->contiguous = false;
> +}
> +
>  extern int __isolate_free_page(struct page *page, unsigned int order);
>  extern void __putback_isolated_page(struct page *page, unsigned int order,
>  				    int mt);
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index 15201887f8e0..1f30b9e16577 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -2330,6 +2330,80 @@ void __init init_cma_reserved_pageblock(struct page *page)
>  }
>  #endif
>  
> +/*
> + * Check that the whole (or subset of) a pageblock given by the interval of
> + * [start_pfn, end_pfn) is valid and within the same zone, before scanning it
> + * with the migration of free compaction scanner.
> + *
> + * Return struct page pointer of start_pfn, or NULL if checks were not passed.
> + *
> + * It's possible on some configurations to have a setup like node0 node1 node0
> + * i.e. it's possible that all pages within a zones range of pages do not
> + * belong to a single zone. We assume that a border between node0 and node1
> + * can occur within a single pageblock, but not a node0 node1 node0
> + * interleaving within a single pageblock. It is therefore sufficient to check
> + * the first and last page of a pageblock and avoid checking each individual
> + * page in a pageblock.
> + *
> + * Note: the function may return non-NULL struct page even for a page block
> + * which contains a memory hole (i.e. there is no physical memory for a subset
> + * of the pfn range). For example, if the pageblock order is MAX_ORDER, which
> + * will fall into 2 sub-sections, and the end pfn of the pageblock may be hole
> + * even though the start pfn is online and valid. This should be safe most of
> + * the time because struct pages are still initialized via init_unavailable_range()
> + * and pfn walkers shouldn't touch any physical memory range for which they do
> + * not recognize any specific metadata in struct pages.
> + */
> +struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
> +				     unsigned long end_pfn, struct zone *zone)

__pageblock_pfn_to_page() is also called by compaction code too (e.g.,
isolate_freepages_range() -> pageblock_pfn_to_page() ->
__pageblock_pfn_to_page()).

So, it is used not only by initialization and hotplug?

Best Regards,
Huang, Ying

> +{
> +	struct page *start_page;
> +	struct page *end_page;
> +
> +	/* end_pfn is one past the range we are checking */
> +	end_pfn--;
> +
> +	if (!pfn_valid(end_pfn))
> +		return NULL;
> +
> +	start_page = pfn_to_online_page(start_pfn);
> +	if (!start_page)
> +		return NULL;
> +
> +	if (page_zone(start_page) != zone)
> +		return NULL;
> +
> +	end_page = pfn_to_page(end_pfn);
> +
> +	/* This gives a shorter code than deriving page_zone(end_page) */
> +	if (page_zone_id(start_page) != page_zone_id(end_page))
> +		return NULL;
> +
> +	return start_page;
> +}
> +
> +void set_zone_contiguous(struct zone *zone)
> +{
> +	unsigned long block_start_pfn = zone->zone_start_pfn;
> +	unsigned long block_end_pfn;
> +
> +	block_end_pfn = pageblock_end_pfn(block_start_pfn);
> +	for (; block_start_pfn < zone_end_pfn(zone);
> +			block_start_pfn = block_end_pfn,
> +			 block_end_pfn += pageblock_nr_pages) {
> +
> +		block_end_pfn = min(block_end_pfn, zone_end_pfn(zone));
> +
> +		if (!__pageblock_pfn_to_page(block_start_pfn,
> +					     block_end_pfn, zone))
> +			return;
> +		cond_resched();
> +	}
> +
> +	/* We confirm that there is no hole */
> +	zone->contiguous = true;
> +}
> +
>  void __init page_alloc_init_late(void)
>  {
>  	struct zone *zone;
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 4f094ba7c8fb..fe7c1ee5becd 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1480,85 +1480,6 @@ void __free_pages_core(struct page *page, unsigned int order)
>  	__free_pages_ok(page, order, FPI_TO_TAIL);
>  }
>  
> -/*
> - * Check that the whole (or subset of) a pageblock given by the interval of
> - * [start_pfn, end_pfn) is valid and within the same zone, before scanning it
> - * with the migration of free compaction scanner.
> - *
> - * Return struct page pointer of start_pfn, or NULL if checks were not passed.
> - *
> - * It's possible on some configurations to have a setup like node0 node1 node0
> - * i.e. it's possible that all pages within a zones range of pages do not
> - * belong to a single zone. We assume that a border between node0 and node1
> - * can occur within a single pageblock, but not a node0 node1 node0
> - * interleaving within a single pageblock. It is therefore sufficient to check
> - * the first and last page of a pageblock and avoid checking each individual
> - * page in a pageblock.
> - *
> - * Note: the function may return non-NULL struct page even for a page block
> - * which contains a memory hole (i.e. there is no physical memory for a subset
> - * of the pfn range). For example, if the pageblock order is MAX_ORDER, which
> - * will fall into 2 sub-sections, and the end pfn of the pageblock may be hole
> - * even though the start pfn is online and valid. This should be safe most of
> - * the time because struct pages are still initialized via init_unavailable_range()
> - * and pfn walkers shouldn't touch any physical memory range for which they do
> - * not recognize any specific metadata in struct pages.
> - */
> -struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
> -				     unsigned long end_pfn, struct zone *zone)
> -{
> -	struct page *start_page;
> -	struct page *end_page;
> -
> -	/* end_pfn is one past the range we are checking */
> -	end_pfn--;
> -
> -	if (!pfn_valid(end_pfn))
> -		return NULL;
> -
> -	start_page = pfn_to_online_page(start_pfn);
> -	if (!start_page)
> -		return NULL;
> -
> -	if (page_zone(start_page) != zone)
> -		return NULL;
> -
> -	end_page = pfn_to_page(end_pfn);
> -
> -	/* This gives a shorter code than deriving page_zone(end_page) */
> -	if (page_zone_id(start_page) != page_zone_id(end_page))
> -		return NULL;
> -
> -	return start_page;
> -}
> -
> -void set_zone_contiguous(struct zone *zone)
> -{
> -	unsigned long block_start_pfn = zone->zone_start_pfn;
> -	unsigned long block_end_pfn;
> -
> -	block_end_pfn = pageblock_end_pfn(block_start_pfn);
> -	for (; block_start_pfn < zone_end_pfn(zone);
> -			block_start_pfn = block_end_pfn,
> -			 block_end_pfn += pageblock_nr_pages) {
> -
> -		block_end_pfn = min(block_end_pfn, zone_end_pfn(zone));
> -
> -		if (!__pageblock_pfn_to_page(block_start_pfn,
> -					     block_end_pfn, zone))
> -			return;
> -		cond_resched();
> -	}
> -
> -	/* We confirm that there is no hole */
> -	zone->contiguous = true;
> -}
> -
> -void clear_zone_contiguous(struct zone *zone)
> -{
> -	zone->contiguous = false;
> -}
> -
>  /*
>   * The order of subdivision here is critical for the IO subsystem.
>   * Please do not alter this order without good reasons and regression