mm: replace PAGE_MIGRATION with IS_ENABLED(CONFIG_MIGRATION)

Since commit 2a11c8ea20bf ("kconfig: Introduce IS_ENABLED(),
IS_BUILTIN() and IS_MODULE()") there is a generic grep-friendly method
for checking config options in C expressions.

Signed-off-by: Konstantin Khlebnikov <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/migrate.h

···
 typedef struct page *new_page_t(struct page *, unsigned long private, int **);
 
 #ifdef CONFIG_MIGRATION
-#define PAGE_MIGRATION 1
 
 extern void putback_lru_pages(struct list_head *l);
 extern int migrate_page(struct address_space *,
···
 extern int migrate_huge_page_move_mapping(struct address_space *mapping,
 				  struct page *newpage, struct page *page);
 #else
-#define PAGE_MIGRATION 0
 
 static inline void putback_lru_pages(struct list_head *l) {}
 static inline int migrate_pages(struct list_head *l, new_page_t x,

mm/mprotect.c

···
 				ptent = pte_mkwrite(ptent);
 
 			ptep_modify_prot_commit(mm, addr, pte, ptent);
-		} else if (PAGE_MIGRATION && !pte_file(oldpte)) {
+		} else if (IS_ENABLED(CONFIG_MIGRATION) && !pte_file(oldpte)) {
 			swp_entry_t entry = pte_to_swp_entry(oldpte);
 
 			if (is_write_migration_entry(entry)) {

mm/rmap.c

···
 			}
 			dec_mm_counter(mm, MM_ANONPAGES);
 			inc_mm_counter(mm, MM_SWAPENTS);
-		} else if (PAGE_MIGRATION) {
+		} else if (IS_ENABLED(CONFIG_MIGRATION)) {
 			/*
 			 * Store the pfn of the page in a special migration
 			 * pte. do_swap_page() will wait until the migration
···
 		}
 		set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
 		BUG_ON(pte_file(*pte));
-	} else if (PAGE_MIGRATION && (TTU_ACTION(flags) == TTU_MIGRATION)) {
+	} else if (IS_ENABLED(CONFIG_MIGRATION) &&
+		   (TTU_ACTION(flags) == TTU_MIGRATION)) {
 		/* Establish migration entry for a file page */
 		swp_entry_t entry;
 		entry = make_migration_entry(page, pte_write(pteval));
···
 		 * locking requirements of exec(), migration skips
 		 * temporary VMAs until after exec() completes.
 		 */
-		if (PAGE_MIGRATION && (flags & TTU_MIGRATION) &&
+		if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&
 				is_vma_temporary_stack(vma))
 			continue;