mm, hugetlb: mark some bootstrap functions as __init

Both prep_compound_huge_page() and prep_compound_gigantic_page() are
only called at bootstrap and can be marked as __init.

The __SetPageTail(page) in prep_compound_gigantic_page() happening
before page->first_page is initialized is not concerning since this is
bootstrap.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Reviewed-by: NMichal Hocko <mhocko@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reviewed-by: NDavidlohr Bueso <davidlohr@hp.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/hugetlb.c

@@ -689,7 +689,8 @@ static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
 	put_page(page); /* free it into the hugepage allocator */
 }
 
-static void prep_compound_gigantic_page(struct page *page, unsigned long order)
+static void __init prep_compound_gigantic_page(struct page *page,
+					       unsigned long order)
 {
 	int i;
 	int nr_pages = 1 << order;
@@ -1319,7 +1320,7 @@ int __weak alloc_bootmem_huge_page(struct hstate *h)
 	return 1;
 }
 
-static void prep_compound_huge_page(struct page *page, int order)
+static void __init prep_compound_huge_page(struct page *page, int order)
 {
 	if (unlikely(order > (MAX_ORDER - 1)))
 		prep_compound_gigantic_page(page, order);