3  * Memory Migration functionality - linux/mm/migrate.c
7  * Page migration was first developed in the context of the memory hotplug
8  * project. The main authors of the migration code are:
86 	 * compaction threads can race against page migration functions  in isolate_movable_page()
90 	 * being (wrongly) re-isolated while it is under migration,  in isolate_movable_page()
132  * from where they were once taken off for compaction/migration.
172  * Restore a potential migration pte to a working pte entry
192 		/* PMD-mapped THP migration entry */  in remove_migration_pte()
207 		 * Recheck VMA as permissions can change since migration started  in remove_migration_pte()
272  * Get rid of all migration entries and replace them by
289  * Something used the pte of a page under migration. We need to
290  * get to the page and wait until migration is finished.
547 	 * migration entries. We can still have PG_anon_exclusive set on an  in folio_migrate_flags()
625  *                    Migration functions
648  * migrate_folio() - Simple folio migration.
689 			 * async migration. Release the taken locks  in buffer_migrate_lock_buffers()
783  * buffer_migrate_folio() - Migration function for folios with buffers.
805  * buffer_migrate_folio_norefs() - Migration function for folios with buffers.
870 	 * migration. Writeout may mean we lose the lock and the  in writeout()
872 	 * At this point we know that the migration attempt cannot  in writeout()
887  * Default handling if a filesystem does not provide a migration function.
893 		/* Only writeback folios in full synchronous migration */  in fallback_migrate_folio()
946 			 * for page migration.  in move_to_new_folio()
957 		 * isolation step. In that case, we shouldn't try migration.  in move_to_new_folio()
1035 		 * Only in the case of a full synchronous migration is it  in __unmap_and_move()
1057 	 * of migration. File cache pages are no problem because of page_lock()  in __unmap_and_move()
1058 	 * File Caches may use write_page() or lock_page() in migration, then,  in __unmap_and_move()
1104 		/* Establish migration ptes */  in __unmap_and_move()
1142 	 * If migration is successful, decrease refcount of dst,  in __unmap_and_move()
1199 	 * If migration is successful, releases reference grabbed during  in unmap_and_move()
1232  * Counterpart of unmap_and_move_page() for hugepage migration.
1235  * because there is no race between I/O and migration for hugepage.
1243  * hugepage migration fails without data corruption.
1245  * There is also no race when direct I/O is issued on the page under migration,
1246  * because then pte is replaced with migration swap entry and direct I/O code
1247  * will wait in the page fault for migration to complete.
1264 	 * This check is necessary because some callers of hugepage migration  in unmap_and_move_huge_page()
1267 	 * kicking migration.  in unmap_and_move_huge_page()
1364 	 * If migration was not successful and there's a freeing callback, use  in unmap_and_move_huge_page()
1391  *		   supplied as the target for the page migration
1395  *			as the target of the page migration.
1396  * @put_new_page:	The function used to free target pages if migration
1399  * @mode:		The migration mode that specifies the constraints for
1400  *			page migration, if any.
1401  * @reason:		The reason for page migration.
1449 			 * during migration.  in migrate_pages()
1476 			 * THP migration might be unsupported or the  in migrate_pages()
1486 				/* THP migration is unsupported */  in migrate_pages()
1493 				/* Hugetlb migration is unsupported */  in migrate_pages()
1520 				 * left in thp_split_pages list. Move them back to migration  in migrate_pages()
1544 				 * removed from migration page list and not  in migrate_pages()
1580 	 * Put the permanent failure page back to migration list, they  in migrate_pages()
1631 		 * clear __GFP_RECLAIM to make the migration callback  in alloc_migration_target()
1837 			/* The page is successfully queued for migration */  in do_pages_move()
2073  * Returns true if this is a safe migration target node for misplaced NUMA
2152 	 * disappearing underneath us during migration.  in numamigrate_isolate_page()