Re: [PATCH v5 01/12] mm/sparse-vmemmap: factor out shared vmemmap tail page allocation

[Muchun Song <muchun.song@linux.dev>]

> On Sep 29, 2026, at 15:16, David Hildenbrand (Arm) <david@kernel.org> wrote:
> 
> On 9/27/26 04:54, Muchun Song wrote:
>> HugeTLB and sparse-vmemmap each have their own helper to allocate the
>> shared vmemmap tail page used by vmemmap optimization.
>> 
>> Factor that logic into a common vmemmap_shared_tail_page() helper. It
>> allocates the page through vmemmap_alloc_block(), initializes the tail
>> struct pages, and uses cmpxchg() to install the per-zone shared page.
>> 
>> This removes duplicate allocation logic while handling both early boot
>> and runtime allocation through the same helper.
>> 
>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>> Acked-by: Qi Zheng <qi.zheng@linux.dev>
>> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
>> ---
>> v5:
>> - Move this patch before CONFIG_VMEMMAP_OPTIMIZATION is introduced
>> 
>> v4:
>> - Update the commit message for the renamed VMEMMAP_OPTIMIZATION config
>> - Collect Acked-by from Mike Rapoport
>> 
>> v2:
>> - Collect Acked-by from Qi Zheng
>> ---
> 
> [...]
> 
>> 
>> #ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
>> -static __meminit struct page *vmemmap_get_tail(unsigned int order, struct zone *zone)
>> +struct page __ref *vmemmap_shared_tail_page(unsigned int order, struct zone *zone)
>> {
>> - 	struct page *p, *tail;
>> - 	unsigned int idx;
>> - 	int node = zone_to_nid(zone);
>> + 	void *addr;
>> + 	struct page *page;
>> + 	const unsigned int idx = order - VMEMMAP_OPTIMIZATION_MIN_ORDER;
> 
> Nit: constants read much nicer all the way at the top.

I can update to this next version.

> 
> 
> Acked-by: David Hildenbrand (Arm) <david@kernel.org>

Thanks.

> 
> -- 
> Cheers,
> 
> David