Subject: Re: [PATCH v1 2/2] mm/memory_hotplug: remove is_mem_section_removable()

From: Baoquan He <[email-masked]>
Date: Wed, 8 Apr 2020 10:48:24 +0800

On 04/07/20 at 03:54pm, David Hildenbrand wrote:
> Fortunately, all users of is_mem_section_removable() are gone. Get rid of
> it, including some now unnecessary functions.
> 
> Cc: Michael Ellerman <[email-masked]>
> Cc: Benjamin Herrenschmidt <[email-masked]>
> Cc: Michal Hocko <[email-masked]>
> Cc: Andrew Morton <[email-masked]>
> Cc: Oscar Salvador <[email-masked]>
> Cc: Baoquan He <[email-masked]>
> Cc: Wei Yang <[email-masked]>
> Signed-off-by: David Hildenbrand <[email-masked]>

Assuming no issue to patch 1, this one looks good.

Reviewed-by: Baoquan He <[email-masked]>

> ---
>  include/linux/memory_hotplug.h |  7 ----
>  mm/memory_hotplug.c            | 75 ----------------------------------
>  2 files changed, 82 deletions(-)
> 
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 93d9ada74ddd..7dca9cd6076b 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -314,19 +314,12 @@ static inline void pgdat_resize_init(struct pglist_data *pgdat) {}
>  
>  #ifdef CONFIG_MEMORY_HOTREMOVE
>  
> -extern bool is_mem_section_removable(unsigned long pfn, unsigned long nr_pages);
>  extern void try_offline_node(int nid);
>  extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
>  extern int remove_memory(int nid, u64 start, u64 size);
>  extern void __remove_memory(int nid, u64 start, u64 size);
>  
>  #else
> -static inline bool is_mem_section_removable(unsigned long pfn,
> -					unsigned long nr_pages)
> -{
> -	return false;
> -}
> -
>  static inline void try_offline_node(int nid) {}
>  
>  static inline int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 47cf6036eb31..4d338d546d52 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1112,81 +1112,6 @@ int add_memory(int nid, u64 start, u64 size)
>  EXPORT_SYMBOL_GPL(add_memory);
>  
>  #ifdef CONFIG_MEMORY_HOTREMOVE
> -/*
> - * A free page on the buddy free lists (not the per-cpu lists) has PageBuddy
> - * set and the size of the free page is given by page_order(). Using this,
> - * the function determines if the pageblock contains only free pages.
> - * Due to buddy contraints, a free page at least the size of a pageblock will
> - * be located at the start of the pageblock
> - */
> -static inline int pageblock_free(struct page *page)
> -{
> -	return PageBuddy(page) && page_order(page) >= pageblock_order;
> -}
> -
> -/* Return the pfn of the start of the next active pageblock after a given pfn */
> -static unsigned long next_active_pageblock(unsigned long pfn)
> -{
> -	struct page *page = pfn_to_page(pfn);
> -
> -	/* Ensure the starting page is pageblock-aligned */
> -	BUG_ON(pfn & (pageblock_nr_pages - 1));
> -
> -	/* If the entire pageblock is free, move to the end of free page */
> -	if (pageblock_free(page)) {
> -		int order;
> -		/* be careful. we don't have locks, page_order can be changed.*/
> -		order = page_order(page);
> -		if ((order < MAX_ORDER) && (order >= pageblock_order))
> -			return pfn + (1 << order);
> -	}
> -
> -	return pfn + pageblock_nr_pages;
> -}
> -
> -static bool is_pageblock_removable_nolock(unsigned long pfn)
> -{
> -	struct page *page = pfn_to_page(pfn);
> -	struct zone *zone;
> -
> -	/*
> -	 * We have to be careful here because we are iterating over memory
> -	 * sections which are not zone aware so we might end up outside of
> -	 * the zone but still within the section.
> -	 * We have to take care about the node as well. If the node is offline
> -	 * its NODE_DATA will be NULL - see page_zone.
> -	 */
> -	if (!node_online(page_to_nid(page)))
> -		return false;
> -
> -	zone = page_zone(page);
> -	pfn = page_to_pfn(page);
> -	if (!zone_spans_pfn(zone, pfn))
> -		return false;
> -
> -	return !has_unmovable_pages(zone, page, MIGRATE_MOVABLE,
> -				    MEMORY_OFFLINE);
> -}
> -
> -/* Checks if this range of memory is likely to be hot-removable. */
> -bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
> -{
> -	unsigned long end_pfn, pfn;
> -
> -	end_pfn = min(start_pfn + nr_pages,
> -			zone_end_pfn(page_zone(pfn_to_page(start_pfn))));
> -
> -	/* Check the starting page of each pageblock within the range */
> -	for (pfn = start_pfn; pfn < end_pfn; pfn = next_active_pageblock(pfn)) {
> -		if (!is_pageblock_removable_nolock(pfn))
> -			return false;
> -		cond_resched();
> -	}
> -
> -	/* All pageblocks in the memory block are likely to be hot-removable */
> -	return true;
> -}
> -
>  /*
>   * Confirm all pages in a range [start, end) belong to the same zone (skipping
>   * memory holes). When true, return the zone.
> -- 
> 2.25.1
>