mm/sparse-vmemmap: initialize shared tail vmemmap pages on allocation

The shared tail vmemmap page allocated in vmemmap_get_tail() used to be
left uninitialized, because memmap_init_range() would later overwrite it. 
That forced users such as HugeTLB to defer the initialization to their own
setup paths.

Now that memmap_init_range() skips shared tail vmemmap pages, initialize
them immediately in vmemmap_get_tail() with init_compound_tail() instead.

This adds initialization at the point where the shared tail page is
allocated.  The existing HugeTLB initialization remains necessary until
the compound page order is set and memmap_init_range() starts skipping
shared tails.  It is removed when HugeTLB switches to the section-based
mechanism.

Link: https://lore.kernel.org/20260910063256.64386-5-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: Qi Zheng <qi.zheng@linux.dev>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: David Laight <david.laight.linux@gmail.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>

0 files changed, 0 insertions, 0 deletions