#ifdef in *.c file decrease source readability a bit.  removing is better.
This patch doesn't have any functional change.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 typedef struct page *new_page_t(struct page *, unsigned long private, int **);
 
 #ifdef CONFIG_MIGRATION
+#define PAGE_MIGRATION 1
+
 extern int putback_lru_pages(struct list_head *l);
 extern int migrate_page(struct address_space *,
                        struct page *, struct page *);
                const nodemask_t *from, const nodemask_t *to,
                unsigned long flags);
 #else
+#define PAGE_MIGRATION 0
+
 static inline int putback_lru_pages(struct list_head *l) { return 0; }
 static inline int migrate_pages(struct list_head *l, new_page_t x,
                unsigned long private) { return -ENOSYS; }
 
 #include <linux/swap.h>
 #include <linux/swapops.h>
 #include <linux/mmu_notifier.h>
+#include <linux/migrate.h>
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
 #include <asm/cacheflush.h>
                                ptent = pte_mkwrite(ptent);
 
                        ptep_modify_prot_commit(mm, addr, pte, ptent);
-#ifdef CONFIG_MIGRATION
-               } else if (!pte_file(oldpte)) {
+               } else if (PAGE_MIGRATION && !pte_file(oldpte)) {
                        swp_entry_t entry = pte_to_swp_entry(oldpte);
 
                        if (is_write_migration_entry(entry)) {
                                set_pte_at(mm, addr, pte,
                                        swp_entry_to_pte(entry));
                        }
-#endif
                }
-
        } while (pte++, addr += PAGE_SIZE, addr != end);
        arch_leave_lazy_mmu_mode();
        pte_unmap_unlock(pte - 1, ptl);
 
 #include <linux/kallsyms.h>
 #include <linux/memcontrol.h>
 #include <linux/mmu_notifier.h>
+#include <linux/migrate.h>
 
 #include <asm/tlbflush.h>
 
                                spin_unlock(&mmlist_lock);
                        }
                        dec_mm_counter(mm, anon_rss);
-#ifdef CONFIG_MIGRATION
-               } else {
+               } else if (PAGE_MIGRATION) {
                        /*
                         * Store the pfn of the page in a special migration
                         * pte. do_swap_page() will wait until the migration
                         */
                        BUG_ON(!migration);
                        entry = make_migration_entry(page, pte_write(pteval));
-#endif
                }
                set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
                BUG_ON(pte_file(*pte));
-       } else
-#ifdef CONFIG_MIGRATION
-       if (migration) {
+       } else if (PAGE_MIGRATION && migration) {
                /* Establish migration entry for a file page */
                swp_entry_t entry;
                entry = make_migration_entry(page, pte_write(pteval));
                set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
        } else
-#endif
                dec_mm_counter(mm, file_rss);