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Re: [PATCH 09/14] mm: __first_valid_page skip over offline pages

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On 05/15/2017 10:58 AM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
> 
> __first_valid_page skips over invalid pfns in the range but it might
> still stumble over offline pages. At least start_isolate_page_range
> will mark those set_migratetype_isolate. This doesn't represent
> any immediate AFAICS because alloc_contig_range will fail to isolate
> those pages but it relies on not fully initialized page which will
> become a problem later when we stop associating offline pages to zones.
> Use pfn_to_online_page to handle this.
> 
> This is more a preparatory patch than a fix.
> 
> Signed-off-by: Michal Hocko <mhocko@suse.com>

Iterating over single pages when the whole section is offline seems
rather wasteful, but it should be really rare, so whatever.

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  mm/page_isolation.c | 26 ++++++++++++++++++--------
>  1 file changed, 18 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index 5092e4ef00c8..3606104893e0 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -138,12 +138,18 @@ static inline struct page *
>  __first_valid_page(unsigned long pfn, unsigned long nr_pages)
>  {
>  	int i;
> -	for (i = 0; i < nr_pages; i++)
> -		if (pfn_valid_within(pfn + i))
> -			break;
> -	if (unlikely(i == nr_pages))
> -		return NULL;
> -	return pfn_to_page(pfn + i);
> +
> +	for (i = 0; i < nr_pages; i++) {
> +		struct page *page;
> +
> +		if (!pfn_valid_within(pfn + i))
> +			continue;
> +		page = pfn_to_online_page(pfn + i);
> +		if (!page)
> +			continue;
> +		return page;
> +	}
> +	return NULL;
>  }
>  
>  /*
> @@ -184,8 +190,12 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
>  undo:
>  	for (pfn = start_pfn;
>  	     pfn < undo_pfn;
> -	     pfn += pageblock_nr_pages)
> -		unset_migratetype_isolate(pfn_to_page(pfn), migratetype);
> +	     pfn += pageblock_nr_pages) {
> +		struct page *page = pfn_to_online_page(pfn);
> +		if (!page)
> +			continue;
> +		unset_migratetype_isolate(page, migratetype);
> +	}
>  
>  	return -EBUSY;
>  }
> 

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[PATCH -v4 0/14] mm: make movable onlining suck less Michal Hocko <mhocko@kernel.org> - 2017-05-15 11:00 +0200
  [PATCH 07/14] mm: consider zone which is not fully populated to have holes Michal Hocko <mhocko@kernel.org> - 2017-05-15 11:10 +0200
    Re: [PATCH 07/14] mm: consider zone which is not fully populated to  have holes Vlastimil Babka <vbabka@suse.cz> - 2017-05-18 18:20 +0200
      Re: [PATCH 07/14] mm: consider zone which is not fully populated to  have holes Michal Hocko <mhocko@kernel.org> - 2017-05-18 18:50 +0200
        Re: [PATCH 07/14] mm: consider zone which is not fully populated to  have holes Vlastimil Babka <vbabka@suse.cz> - 2017-05-19 09:30 +0200
  [PATCH 09/14] mm: __first_valid_page skip over offline pages Michal Hocko <mhocko@kernel.org> - 2017-05-15 11:10 +0200
    Re: [PATCH 09/14] mm: __first_valid_page skip over offline pages Vlastimil Babka <vbabka@suse.cz> - 2017-05-19 10:10 +0200
  [PATCH 14/14] mm, memory_hotplug: remove unused cruft after memory hotplug rework Michal Hocko <mhocko@kernel.org> - 2017-05-15 11:10 +0200
  [PATCH 04/14] mm, memory_hotplug: get rid of is_zone_device_section Michal Hocko <mhocko@kernel.org> - 2017-05-15 11:10 +0200
  [PATCH 12/14] mm, memory_hotplug: replace for_device by want_memblock in arch_add_memory Michal Hocko <mhocko@kernel.org> - 2017-05-15 11:10 +0200
  [PATCH 08/14] mm, compaction: skip over holes in __reset_isolation_suitable Michal Hocko <mhocko@kernel.org> - 2017-05-15 11:10 +0200
    Re: [PATCH 08/14] mm, compaction: skip over holes in  __reset_isolation_suitable Vlastimil Babka <vbabka@suse.cz> - 2017-05-19 09:30 +0200
  [PATCH 10/14] mm, vmstat: skip reporting offline pages in pagetypeinfo Michal Hocko <mhocko@kernel.org> - 2017-05-15 11:10 +0200
    Re: [PATCH 10/14] mm, vmstat: skip reporting offline pages in  pagetypeinfo Vlastimil Babka <vbabka@suse.cz> - 2017-05-19 10:20 +0200
  [PATCH 05/14] mm, memory_hotplug: split up register_one_node Michal Hocko <mhocko@kernel.org> - 2017-05-15 11:10 +0200
  [PATCH 11/14] mm, memory_hotplug: do not associate hotadded memory to zones until online Michal Hocko <mhocko@kernel.org> - 2017-05-15 11:10 +0200
    Re: [PATCH 11/14] mm, memory_hotplug: do not associate hotadded  memory to zones until online Vlastimil Babka <vbabka@suse.cz> - 2017-05-19 11:00 +0200
  [PATCH 06/14] mm, memory_hotplug: consider offline memblocks removable Michal Hocko <mhocko@kernel.org> - 2017-05-15 11:10 +0200
  [PATCH 13/14] mm, memory_hotplug: fix the section mismatch warning Michal Hocko <mhocko@kernel.org> - 2017-05-15 11:10 +0200
  [PATCH 03/14] mm: drop page_initialized check from get_nid_for_pfn Michal Hocko <mhocko@kernel.org> - 2017-05-15 11:10 +0200

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