Re: [PATCH 02/11] mm/sparse-vmemmap: factor out shared vmemmap tail page allocation

[Qi Zheng <qi.zheng@linux.dev>]

On 8/31/26 3:53 PM, 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(), and uses cmpxchg()
> to install the per-zone shared page.
> 
> Expose zone->vmemmap_tails under CONFIG_SPARSEMEM_VMEMMAP to match the
> shared helper's build condition. This avoids a
> !CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION stub; when optimization is
> disabled, the array has no entries and the compiler folds away the unused
> paths, so no storage or runtime overhead is added.
> 
> This removes duplicate allocation logic while still handling both the
> early boot and runtime paths through the same helper.
> 
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
>   include/linux/mmzone.h |  2 +-
>   mm/hugetlb_vmemmap.c   | 28 +---------------
>   mm/sparse-vmemmap.c    | 74 +++++++++++++++++-------------------------
>   mm/sparse.h            |  1 +
>   4 files changed, 33 insertions(+), 72 deletions(-)
> 

Acked-by: Qi Zheng <qi.zheng@linux.dev>

Thanks,
Qi