Re: [PATCH v4 1/2] mm: pass page count and reserved to __init_single_page

[Yajun Deng <yajun.deng@linux.dev>]

On 2023/9/29 16:19, Mike Rapoport wrote:
> On Thu, Sep 28, 2023 at 04:33:01PM +0800, Yajun Deng wrote:
>> Subject: mm: pass page count and reserved to __init_single_page
> We add pass flags that tell __init_single_page() how to initialize page
> count and PG_Reserved, I think a better subject would be:
>
> mm: allow optional initialization of page count and PG_reserved flag
Okay.
>> When we init a single page, we need to mark that page reserved when it
>> is reserved. And some pages need to reset page count, such as compound
>> pages.
>>
>> Introduce enum init_page_flags, the caller will init page count and mark
>> page reserved by passing INIT_PAGE_COUNT and INIT_PAGE_RESERVED.
> This does not really describe why the change is needed. How about
>
> __init_single_page() unconditionally resets page count which is unnecessary
> for reserved pages.
>
> To allow skipping page count initialization and marking a page reserved in
> one go add flags parameter to __init_single_page().
>
> No functional changes.
Okay.
>> Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
>> ---
>> v4: move the changes of __init_zone_device_page().
>> v3: Introduce enum init_page_flags.
>> v2: Introduce INIT_PAGE_COUNT and INIT_PAGE_RESERVED.
>> v1: https://lore.kernel.org/all/20230922070923.355656-1-yajun.deng@linux.dev/
>> ---
>>   mm/hugetlb.c  |  2 +-
>>   mm/internal.h |  8 +++++++-
>>   mm/mm_init.c  | 24 +++++++++++++-----------
>>   3 files changed, 21 insertions(+), 13 deletions(-)
>>
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index a82dc37669b0..bb9c334a8392 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -3196,7 +3196,7 @@ static void __init hugetlb_folio_init_tail_vmemmap(struct folio *folio,
>>   	for (pfn = head_pfn + start_page_number; pfn < end_pfn; pfn++) {
>>   		struct page *page = pfn_to_page(pfn);
>>   
>> -		__init_single_page(page, pfn, zone, nid);
>> +		__init_single_page(page, pfn, zone, nid, INIT_PAGE_COUNT);
>>   		prep_compound_tail((struct page *)folio, pfn - head_pfn);
>>   		ret = page_ref_freeze(page, 1);
>>   		VM_BUG_ON(!ret);
>> diff --git a/mm/internal.h b/mm/internal.h
>> index d7916f1e9e98..449891ad7fdb 100644
>> --- a/mm/internal.h
>> +++ b/mm/internal.h
>> @@ -1209,8 +1209,14 @@ struct vma_prepare {
>>   	struct vm_area_struct *remove2;
>>   };
>>   
>> +enum init_page_flags {
> enum page_init_flags please
Okay.
>> +	INIT_PAGE_COUNT    = (1 << 0),
>> +	INIT_PAGE_RESERVED = (1 << 1),
>> +};
>> +
>>   void __meminit __init_single_page(struct page *page, unsigned long pfn,
>> -				unsigned long zone, int nid);
>> +				  unsigned long zone, int nid,
>> +				  enum init_page_flags flags);
>>   
>>   /* shrinker related functions */
>>   unsigned long shrink_slab(gfp_t gfp_mask, int nid, struct mem_cgroup *memcg,
>> diff --git a/mm/mm_init.c b/mm/mm_init.c
>> index 06a72c223bce..9716c8a7ade9 100644
>> --- a/mm/mm_init.c
>> +++ b/mm/mm_init.c
>> @@ -557,11 +557,11 @@ static void __init find_zone_movable_pfns_for_nodes(void)
>>   }
>>   
>>   void __meminit __init_single_page(struct page *page, unsigned long pfn,
>> -				unsigned long zone, int nid)
>> +				  unsigned long zone, int nid,
>> +				  enum init_page_flags flags)
>>   {
>>   	mm_zero_struct_page(page);
>>   	set_page_links(page, zone, nid, pfn);
>> -	init_page_count(page);
>>   	page_mapcount_reset(page);
>>   	page_cpupid_reset_last(page);
>>   	page_kasan_tag_reset(page);
>> @@ -572,6 +572,10 @@ void __meminit __init_single_page(struct page *page, unsigned long pfn,
>>   	if (!is_highmem_idx(zone))
>>   		set_page_address(page, __va(pfn << PAGE_SHIFT));
>>   #endif
>> +	if (flags & INIT_PAGE_COUNT)
>> +		init_page_count(page);
>> +	if (flags & INIT_PAGE_RESERVED)
>> +		__SetPageReserved(page);
>>   }
>>   
>>   #ifdef CONFIG_NUMA
>> @@ -714,7 +718,7 @@ static void __meminit init_reserved_page(unsigned long pfn, int nid)
>>   		if (zone_spans_pfn(zone, pfn))
>>   			break;
>>   	}
>> -	__init_single_page(pfn_to_page(pfn), pfn, zid, nid);
>> +	__init_single_page(pfn_to_page(pfn), pfn, zid, nid, INIT_PAGE_COUNT);
> There is __SetPageReserved call a few lines below, it can be folded here.
>
No, There is a #ifdef in front of it. If so, I need to add 
__SetPageReserved to another init_reserved_page().

And there is an return before __init_single_page.
I will change INIT_PAGE_COUNT to 0 in next patch.

>>   }
>>   #else
>>   static inline void pgdat_set_deferred_range(pg_data_t *pgdat) {}
>> @@ -821,8 +825,8 @@ static void __init init_unavailable_range(unsigned long spfn,
>>   			pfn = pageblock_end_pfn(pfn) - 1;
>>   			continue;
>>   		}
>> -		__init_single_page(pfn_to_page(pfn), pfn, zone, node);
>> -		__SetPageReserved(pfn_to_page(pfn));
>> +		__init_single_page(pfn_to_page(pfn), pfn, zone, node,
>> +				   INIT_PAGE_COUNT | INIT_PAGE_RESERVED);
>>   		pgcnt++;
>>   	}
>>   
>> @@ -884,7 +888,7 @@ void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone
>>   		}
>>   
>>   		page = pfn_to_page(pfn);
>> -		__init_single_page(page, pfn, zone, nid);
>> +		__init_single_page(page, pfn, zone, nid, INIT_PAGE_COUNT);
>>   		if (context == MEMINIT_HOTPLUG)
>>   			__SetPageReserved(page);
>>   
>> @@ -967,9 +971,6 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn,
>>   					  unsigned long zone_idx, int nid,
>>   					  struct dev_pagemap *pgmap)
>>   {
>> -
>> -	__init_single_page(page, pfn, zone_idx, nid);
>> -
>>   	/*
>>   	 * Mark page reserved as it will need to wait for onlining
>>   	 * phase for it to be fully associated with a zone.
>> @@ -977,7 +978,8 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn,
>>   	 * We can use the non-atomic __set_bit operation for setting
>>   	 * the flag as we are still initializing the pages.
>>   	 */
>> -	__SetPageReserved(page);
>> +	__init_single_page(page, pfn, zone_idx, nid,
>> +			   INIT_PAGE_COUNT | INIT_PAGE_RESERVED);
>>   
>>   	/*
>>   	 * ZONE_DEVICE pages union ->lru with a ->pgmap back pointer
>> @@ -2058,7 +2060,7 @@ static unsigned long  __init deferred_init_pages(struct zone *zone,
>>   		} else {
>>   			page++;
>>   		}
>> -		__init_single_page(page, pfn, zid, nid);
>> +		__init_single_page(page, pfn, zid, nid, INIT_PAGE_COUNT);
>>   		nr_pages++;
>>   	}
>>   	return (nr_pages);
>> -- 
>> 2.25.1
>>