mm: convert split_huge_pages_pid() to use a folio

Replaces five calls to compound_head with one.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Cc: Jens Axboe <[e-mail]>
Cc: Sidhartha Kumar <[e-mail]>
Cc: Yanteng Si <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

mm/huge_memory.c

···
 	folio_set_large_rmappable(folio);
 }
 
-static inline bool is_transparent_hugepage(struct page *page)
+static inline bool is_transparent_hugepage(struct folio *folio)
 {
-	struct folio *folio;
-
-	if (!PageCompound(page))
+	if (!folio_test_large(folio))
 		return false;
 
-	folio = page_folio(page);
 	return is_huge_zero_page(&folio->page) ||
 		folio_test_large_rmappable(folio);
 }
···
 	for (addr = vaddr_start; addr < vaddr_end; addr += PAGE_SIZE) {
 		struct vm_area_struct *vma = vma_lookup(mm, addr);
 		struct page *page;
+		struct folio *folio;
 
 		if (!vma)
 			break;
···
 		if (IS_ERR_OR_NULL(page))
 			continue;
 
-		if (!is_transparent_hugepage(page))
+		folio = page_folio(page);
+		if (!is_transparent_hugepage(folio))
 			goto next;
 
 		total++;
-		if (!can_split_folio(page_folio(page), NULL))
+		if (!can_split_folio(folio, NULL))
 			goto next;
 
-		if (!trylock_page(page))
+		if (!folio_trylock(folio))
 			goto next;
 
-		if (!split_huge_page(page))
+		if (!split_folio(folio))
 			split++;
 
-		unlock_page(page);
+		folio_unlock(folio);
 next:
-		put_page(page);
+		folio_put(folio);
 		cond_resched();
 	}
 	mmap_read_unlock(mm);