mm/sparse: keep mem_section_usage_size() internal

mem_section_usage_size() is only needed by sparsemem implementation code
after commit ae751d567baa ("mm/bootmem_info: stop marking
mem_section_usage as MIX_SECTION_INFO"), so keeping the declaration in
mmzone.h now exposes the helper to all mmzone.h users for no reason.

Move the helper to sparse.h so sparse.c and sparse-vmemmap.c can share it
through the internal header.  While doing so, calculate the allocation
size with struct_size_t(), which ties the expression to the
pageblock_flags trailing array instead of open-coding the struct header
plus bitmap size.

Link: https://lore.kernel.org/20260805022536.1206575-1-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

0 files changed, 0 insertions, 0 deletions