1 /* 2 * Memory Migration functionality - linux/mm/migration.c 3 * 4 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter 5 * 6 * Page migration was first developed in the context of the memory hotplug 7 * project. The main authors of the migration code are: 8 * 9 * IWAMOTO Toshihiro <iwamoto@valinux.co.jp> 10 * Hirokazu Takahashi <taka@valinux.co.jp> 11 * Dave Hansen <haveblue@us.ibm.com> 12 * Christoph Lameter 13 */ 14 15 #include <linux/migrate.h> 16 #include <linux/export.h> 17 #include <linux/swap.h> 18 #include <linux/swapops.h> 19 #include <linux/pagemap.h> 20 #include <linux/buffer_head.h> 21 #include <linux/mm_inline.h> 22 #include <linux/nsproxy.h> 23 #include <linux/pagevec.h> 24 #include <linux/ksm.h> 25 #include <linux/rmap.h> 26 #include <linux/topology.h> 27 #include <linux/cpu.h> 28 #include <linux/cpuset.h> 29 #include <linux/writeback.h> 30 #include <linux/mempolicy.h> 31 #include <linux/vmalloc.h> 32 #include <linux/security.h> 33 #include <linux/memcontrol.h> 34 #include <linux/syscalls.h> 35 #include <linux/hugetlb.h> 36 #include <linux/hugetlb_cgroup.h> 37 #include <linux/gfp.h> 38 #include <linux/balloon_compaction.h> 39 40 #include <asm/tlbflush.h> 41 42 #define CREATE_TRACE_POINTS 43 #include <trace/events/migrate.h> 44 45 #include "internal.h" 46 47 /* 48 * migrate_prep() needs to be called before we start compiling a list of pages 49 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is 50 * undesirable, use migrate_prep_local() 51 */ 52 int migrate_prep(void) 53 { 54 /* 55 * Clear the LRU lists so pages can be isolated. 56 * Note that pages may be moved off the LRU after we have 57 * drained them. Those pages will fail to migrate like other 58 * pages that may be busy. 59 */ 60 lru_add_drain_all(); 61 62 return 0; 63 } 64 65 /* Do the necessary work of migrate_prep but not if it involves other CPUs */ 66 int migrate_prep_local(void) 67 { 68 lru_add_drain(); 69 70 return 0; 71 } 72 73 /* 74 * Add isolated pages on the list back to the LRU under page lock 75 * to avoid leaking evictable pages back onto unevictable list. 76 */ 77 void putback_lru_pages(struct list_head *l) 78 { 79 struct page *page; 80 struct page *page2; 81 82 list_for_each_entry_safe(page, page2, l, lru) { 83 list_del(&page->lru); 84 dec_zone_page_state(page, NR_ISOLATED_ANON + 85 page_is_file_cache(page)); 86 putback_lru_page(page); 87 } 88 } 89 90 /* 91 * Put previously isolated pages back onto the appropriate lists 92 * from where they were once taken off for compaction/migration. 93 * 94 * This function shall be used instead of putback_lru_pages(), 95 * whenever the isolated pageset has been built by isolate_migratepages_range() 96 */ 97 void putback_movable_pages(struct list_head *l) 98 { 99 struct page *page; 100 struct page *page2; 101 102 list_for_each_entry_safe(page, page2, l, lru) { 103 if (unlikely(PageHuge(page))) { 104 putback_active_hugepage(page); 105 continue; 106 } 107 list_del(&page->lru); 108 dec_zone_page_state(page, NR_ISOLATED_ANON + 109 page_is_file_cache(page)); 110 if (unlikely(isolated_balloon_page(page))) 111 balloon_page_putback(page); 112 else 113 putback_lru_page(page); 114 } 115 } 116 117 /* 118 * Restore a potential migration pte to a working pte entry 119 */ 120 static int remove_migration_pte(struct page *new, struct vm_area_struct *vma, 121 unsigned long addr, void *old) 122 { 123 struct mm_struct *mm = vma->vm_mm; 124 swp_entry_t entry; 125 pmd_t *pmd; 126 pte_t *ptep, pte; 127 spinlock_t *ptl; 128 129 if (unlikely(PageHuge(new))) { 130 ptep = huge_pte_offset(mm, addr); 131 if (!ptep) 132 goto out; 133 ptl = &mm->page_table_lock; 134 } else { 135 pmd = mm_find_pmd(mm, addr); 136 if (!pmd) 137 goto out; 138 if (pmd_trans_huge(*pmd)) 139 goto out; 140 141 ptep = pte_offset_map(pmd, addr); 142 143 /* 144 * Peek to check is_swap_pte() before taking ptlock? No, we 145 * can race mremap's move_ptes(), which skips anon_vma lock. 146 */ 147 148 ptl = pte_lockptr(mm, pmd); 149 } 150 151 spin_lock(ptl); 152 pte = *ptep; 153 if (!is_swap_pte(pte)) 154 goto unlock; 155 156 entry = pte_to_swp_entry(pte); 157 158 if (!is_migration_entry(entry) || 159 migration_entry_to_page(entry) != old) 160 goto unlock; 161 162 get_page(new); 163 pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); 164 if (is_write_migration_entry(entry)) 165 pte = pte_mkwrite(pte); 166 #ifdef CONFIG_HUGETLB_PAGE 167 if (PageHuge(new)) { 168 pte = pte_mkhuge(pte); 169 pte = arch_make_huge_pte(pte, vma, new, 0); 170 } 171 #endif 172 flush_dcache_page(new); 173 set_pte_at(mm, addr, ptep, pte); 174 175 if (PageHuge(new)) { 176 if (PageAnon(new)) 177 hugepage_add_anon_rmap(new, vma, addr); 178 else 179 page_dup_rmap(new); 180 } else if (PageAnon(new)) 181 page_add_anon_rmap(new, vma, addr); 182 else 183 page_add_file_rmap(new); 184 185 /* No need to invalidate - it was non-present before */ 186 update_mmu_cache(vma, addr, ptep); 187 unlock: 188 pte_unmap_unlock(ptep, ptl); 189 out: 190 return SWAP_AGAIN; 191 } 192 193 /* 194 * Get rid of all migration entries and replace them by 195 * references to the indicated page. 196 */ 197 static void remove_migration_ptes(struct page *old, struct page *new) 198 { 199 rmap_walk(new, remove_migration_pte, old); 200 } 201 202 /* 203 * Something used the pte of a page under migration. We need to 204 * get to the page and wait until migration is finished. 205 * When we return from this function the fault will be retried. 206 */ 207 static void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep, 208 spinlock_t *ptl) 209 { 210 pte_t pte; 211 swp_entry_t entry; 212 struct page *page; 213 214 spin_lock(ptl); 215 pte = *ptep; 216 if (!is_swap_pte(pte)) 217 goto out; 218 219 entry = pte_to_swp_entry(pte); 220 if (!is_migration_entry(entry)) 221 goto out; 222 223 page = migration_entry_to_page(entry); 224 225 /* 226 * Once radix-tree replacement of page migration started, page_count 227 * *must* be zero. And, we don't want to call wait_on_page_locked() 228 * against a page without get_page(). 229 * So, we use get_page_unless_zero(), here. Even failed, page fault 230 * will occur again. 231 */ 232 if (!get_page_unless_zero(page)) 233 goto out; 234 pte_unmap_unlock(ptep, ptl); 235 wait_on_page_locked(page); 236 put_page(page); 237 return; 238 out: 239 pte_unmap_unlock(ptep, ptl); 240 } 241 242 void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, 243 unsigned long address) 244 { 245 spinlock_t *ptl = pte_lockptr(mm, pmd); 246 pte_t *ptep = pte_offset_map(pmd, address); 247 __migration_entry_wait(mm, ptep, ptl); 248 } 249 250 void migration_entry_wait_huge(struct mm_struct *mm, pte_t *pte) 251 { 252 spinlock_t *ptl = &(mm)->page_table_lock; 253 __migration_entry_wait(mm, pte, ptl); 254 } 255 256 #ifdef CONFIG_BLOCK 257 /* Returns true if all buffers are successfully locked */ 258 static bool buffer_migrate_lock_buffers(struct buffer_head *head, 259 enum migrate_mode mode) 260 { 261 struct buffer_head *bh = head; 262 263 /* Simple case, sync compaction */ 264 if (mode != MIGRATE_ASYNC) { 265 do { 266 get_bh(bh); 267 lock_buffer(bh); 268 bh = bh->b_this_page; 269 270 } while (bh != head); 271 272 return true; 273 } 274 275 /* async case, we cannot block on lock_buffer so use trylock_buffer */ 276 do { 277 get_bh(bh); 278 if (!trylock_buffer(bh)) { 279 /* 280 * We failed to lock the buffer and cannot stall in 281 * async migration. Release the taken locks 282 */ 283 struct buffer_head *failed_bh = bh; 284 put_bh(failed_bh); 285 bh = head; 286 while (bh != failed_bh) { 287 unlock_buffer(bh); 288 put_bh(bh); 289 bh = bh->b_this_page; 290 } 291 return false; 292 } 293 294 bh = bh->b_this_page; 295 } while (bh != head); 296 return true; 297 } 298 #else 299 static inline bool buffer_migrate_lock_buffers(struct buffer_head *head, 300 enum migrate_mode mode) 301 { 302 return true; 303 } 304 #endif /* CONFIG_BLOCK */ 305 306 /* 307 * Replace the page in the mapping. 308 * 309 * The number of remaining references must be: 310 * 1 for anonymous pages without a mapping 311 * 2 for pages with a mapping 312 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set. 313 */ 314 int migrate_page_move_mapping(struct address_space *mapping, 315 struct page *newpage, struct page *page, 316 struct buffer_head *head, enum migrate_mode mode) 317 { 318 int expected_count = 0; 319 void **pslot; 320 321 if (!mapping) { 322 /* Anonymous page without mapping */ 323 if (page_count(page) != 1) 324 return -EAGAIN; 325 return MIGRATEPAGE_SUCCESS; 326 } 327 328 spin_lock_irq(&mapping->tree_lock); 329 330 pslot = radix_tree_lookup_slot(&mapping->page_tree, 331 page_index(page)); 332 333 expected_count = 2 + page_has_private(page); 334 if (page_count(page) != expected_count || 335 radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) { 336 spin_unlock_irq(&mapping->tree_lock); 337 return -EAGAIN; 338 } 339 340 if (!page_freeze_refs(page, expected_count)) { 341 spin_unlock_irq(&mapping->tree_lock); 342 return -EAGAIN; 343 } 344 345 /* 346 * In the async migration case of moving a page with buffers, lock the 347 * buffers using trylock before the mapping is moved. If the mapping 348 * was moved, we later failed to lock the buffers and could not move 349 * the mapping back due to an elevated page count, we would have to 350 * block waiting on other references to be dropped. 351 */ 352 if (mode == MIGRATE_ASYNC && head && 353 !buffer_migrate_lock_buffers(head, mode)) { 354 page_unfreeze_refs(page, expected_count); 355 spin_unlock_irq(&mapping->tree_lock); 356 return -EAGAIN; 357 } 358 359 /* 360 * Now we know that no one else is looking at the page. 361 */ 362 get_page(newpage); /* add cache reference */ 363 if (PageSwapCache(page)) { 364 SetPageSwapCache(newpage); 365 set_page_private(newpage, page_private(page)); 366 } 367 368 radix_tree_replace_slot(pslot, newpage); 369 370 /* 371 * Drop cache reference from old page by unfreezing 372 * to one less reference. 373 * We know this isn't the last reference. 374 */ 375 page_unfreeze_refs(page, expected_count - 1); 376 377 /* 378 * If moved to a different zone then also account 379 * the page for that zone. Other VM counters will be 380 * taken care of when we establish references to the 381 * new page and drop references to the old page. 382 * 383 * Note that anonymous pages are accounted for 384 * via NR_FILE_PAGES and NR_ANON_PAGES if they 385 * are mapped to swap space. 386 */ 387 __dec_zone_page_state(page, NR_FILE_PAGES); 388 __inc_zone_page_state(newpage, NR_FILE_PAGES); 389 if (!PageSwapCache(page) && PageSwapBacked(page)) { 390 __dec_zone_page_state(page, NR_SHMEM); 391 __inc_zone_page_state(newpage, NR_SHMEM); 392 } 393 spin_unlock_irq(&mapping->tree_lock); 394 395 return MIGRATEPAGE_SUCCESS; 396 } 397 398 /* 399 * The expected number of remaining references is the same as that 400 * of migrate_page_move_mapping(). 401 */ 402 int migrate_huge_page_move_mapping(struct address_space *mapping, 403 struct page *newpage, struct page *page) 404 { 405 int expected_count; 406 void **pslot; 407 408 if (!mapping) { 409 if (page_count(page) != 1) 410 return -EAGAIN; 411 return MIGRATEPAGE_SUCCESS; 412 } 413 414 spin_lock_irq(&mapping->tree_lock); 415 416 pslot = radix_tree_lookup_slot(&mapping->page_tree, 417 page_index(page)); 418 419 expected_count = 2 + page_has_private(page); 420 if (page_count(page) != expected_count || 421 radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) { 422 spin_unlock_irq(&mapping->tree_lock); 423 return -EAGAIN; 424 } 425 426 if (!page_freeze_refs(page, expected_count)) { 427 spin_unlock_irq(&mapping->tree_lock); 428 return -EAGAIN; 429 } 430 431 get_page(newpage); 432 433 radix_tree_replace_slot(pslot, newpage); 434 435 page_unfreeze_refs(page, expected_count - 1); 436 437 spin_unlock_irq(&mapping->tree_lock); 438 return MIGRATEPAGE_SUCCESS; 439 } 440 441 /* 442 * Copy the page to its new location 443 */ 444 void migrate_page_copy(struct page *newpage, struct page *page) 445 { 446 if (PageHuge(page) || PageTransHuge(page)) 447 copy_huge_page(newpage, page); 448 else 449 copy_highpage(newpage, page); 450 451 if (PageError(page)) 452 SetPageError(newpage); 453 if (PageReferenced(page)) 454 SetPageReferenced(newpage); 455 if (PageUptodate(page)) 456 SetPageUptodate(newpage); 457 if (TestClearPageActive(page)) { 458 VM_BUG_ON(PageUnevictable(page)); 459 SetPageActive(newpage); 460 } else if (TestClearPageUnevictable(page)) 461 SetPageUnevictable(newpage); 462 if (PageChecked(page)) 463 SetPageChecked(newpage); 464 if (PageMappedToDisk(page)) 465 SetPageMappedToDisk(newpage); 466 467 if (PageDirty(page)) { 468 clear_page_dirty_for_io(page); 469 /* 470 * Want to mark the page and the radix tree as dirty, and 471 * redo the accounting that clear_page_dirty_for_io undid, 472 * but we can't use set_page_dirty because that function 473 * is actually a signal that all of the page has become dirty. 474 * Whereas only part of our page may be dirty. 475 */ 476 if (PageSwapBacked(page)) 477 SetPageDirty(newpage); 478 else 479 __set_page_dirty_nobuffers(newpage); 480 } 481 482 mlock_migrate_page(newpage, page); 483 ksm_migrate_page(newpage, page); 484 /* 485 * Please do not reorder this without considering how mm/ksm.c's 486 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache(). 487 */ 488 ClearPageSwapCache(page); 489 ClearPagePrivate(page); 490 set_page_private(page, 0); 491 492 /* 493 * If any waiters have accumulated on the new page then 494 * wake them up. 495 */ 496 if (PageWriteback(newpage)) 497 end_page_writeback(newpage); 498 } 499 500 /************************************************************ 501 * Migration functions 502 ***********************************************************/ 503 504 /* Always fail migration. Used for mappings that are not movable */ 505 int fail_migrate_page(struct address_space *mapping, 506 struct page *newpage, struct page *page) 507 { 508 return -EIO; 509 } 510 EXPORT_SYMBOL(fail_migrate_page); 511 512 /* 513 * Common logic to directly migrate a single page suitable for 514 * pages that do not use PagePrivate/PagePrivate2. 515 * 516 * Pages are locked upon entry and exit. 517 */ 518 int migrate_page(struct address_space *mapping, 519 struct page *newpage, struct page *page, 520 enum migrate_mode mode) 521 { 522 int rc; 523 524 BUG_ON(PageWriteback(page)); /* Writeback must be complete */ 525 526 rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode); 527 528 if (rc != MIGRATEPAGE_SUCCESS) 529 return rc; 530 531 migrate_page_copy(newpage, page); 532 return MIGRATEPAGE_SUCCESS; 533 } 534 EXPORT_SYMBOL(migrate_page); 535 536 #ifdef CONFIG_BLOCK 537 /* 538 * Migration function for pages with buffers. This function can only be used 539 * if the underlying filesystem guarantees that no other references to "page" 540 * exist. 541 */ 542 int buffer_migrate_page(struct address_space *mapping, 543 struct page *newpage, struct page *page, enum migrate_mode mode) 544 { 545 struct buffer_head *bh, *head; 546 int rc; 547 548 if (!page_has_buffers(page)) 549 return migrate_page(mapping, newpage, page, mode); 550 551 head = page_buffers(page); 552 553 rc = migrate_page_move_mapping(mapping, newpage, page, head, mode); 554 555 if (rc != MIGRATEPAGE_SUCCESS) 556 return rc; 557 558 /* 559 * In the async case, migrate_page_move_mapping locked the buffers 560 * with an IRQ-safe spinlock held. In the sync case, the buffers 561 * need to be locked now 562 */ 563 if (mode != MIGRATE_ASYNC) 564 BUG_ON(!buffer_migrate_lock_buffers(head, mode)); 565 566 ClearPagePrivate(page); 567 set_page_private(newpage, page_private(page)); 568 set_page_private(page, 0); 569 put_page(page); 570 get_page(newpage); 571 572 bh = head; 573 do { 574 set_bh_page(bh, newpage, bh_offset(bh)); 575 bh = bh->b_this_page; 576 577 } while (bh != head); 578 579 SetPagePrivate(newpage); 580 581 migrate_page_copy(newpage, page); 582 583 bh = head; 584 do { 585 unlock_buffer(bh); 586 put_bh(bh); 587 bh = bh->b_this_page; 588 589 } while (bh != head); 590 591 return MIGRATEPAGE_SUCCESS; 592 } 593 EXPORT_SYMBOL(buffer_migrate_page); 594 #endif 595 596 /* 597 * Writeback a page to clean the dirty state 598 */ 599 static int writeout(struct address_space *mapping, struct page *page) 600 { 601 struct writeback_control wbc = { 602 .sync_mode = WB_SYNC_NONE, 603 .nr_to_write = 1, 604 .range_start = 0, 605 .range_end = LLONG_MAX, 606 .for_reclaim = 1 607 }; 608 int rc; 609 610 if (!mapping->a_ops->writepage) 611 /* No write method for the address space */ 612 return -EINVAL; 613 614 if (!clear_page_dirty_for_io(page)) 615 /* Someone else already triggered a write */ 616 return -EAGAIN; 617 618 /* 619 * A dirty page may imply that the underlying filesystem has 620 * the page on some queue. So the page must be clean for 621 * migration. Writeout may mean we loose the lock and the 622 * page state is no longer what we checked for earlier. 623 * At this point we know that the migration attempt cannot 624 * be successful. 625 */ 626 remove_migration_ptes(page, page); 627 628 rc = mapping->a_ops->writepage(page, &wbc); 629 630 if (rc != AOP_WRITEPAGE_ACTIVATE) 631 /* unlocked. Relock */ 632 lock_page(page); 633 634 return (rc < 0) ? -EIO : -EAGAIN; 635 } 636 637 /* 638 * Default handling if a filesystem does not provide a migration function. 639 */ 640 static int fallback_migrate_page(struct address_space *mapping, 641 struct page *newpage, struct page *page, enum migrate_mode mode) 642 { 643 if (PageDirty(page)) { 644 /* Only writeback pages in full synchronous migration */ 645 if (mode != MIGRATE_SYNC) 646 return -EBUSY; 647 return writeout(mapping, page); 648 } 649 650 /* 651 * Buffers may be managed in a filesystem specific way. 652 * We must have no buffers or drop them. 653 */ 654 if (page_has_private(page) && 655 !try_to_release_page(page, GFP_KERNEL)) 656 return -EAGAIN; 657 658 return migrate_page(mapping, newpage, page, mode); 659 } 660 661 /* 662 * Move a page to a newly allocated page 663 * The page is locked and all ptes have been successfully removed. 664 * 665 * The new page will have replaced the old page if this function 666 * is successful. 667 * 668 * Return value: 669 * < 0 - error code 670 * MIGRATEPAGE_SUCCESS - success 671 */ 672 static int move_to_new_page(struct page *newpage, struct page *page, 673 int remap_swapcache, enum migrate_mode mode) 674 { 675 struct address_space *mapping; 676 int rc; 677 678 /* 679 * Block others from accessing the page when we get around to 680 * establishing additional references. We are the only one 681 * holding a reference to the new page at this point. 682 */ 683 if (!trylock_page(newpage)) 684 BUG(); 685 686 /* Prepare mapping for the new page.*/ 687 newpage->index = page->index; 688 newpage->mapping = page->mapping; 689 if (PageSwapBacked(page)) 690 SetPageSwapBacked(newpage); 691 692 mapping = page_mapping(page); 693 if (!mapping) 694 rc = migrate_page(mapping, newpage, page, mode); 695 else if (mapping->a_ops->migratepage) 696 /* 697 * Most pages have a mapping and most filesystems provide a 698 * migratepage callback. Anonymous pages are part of swap 699 * space which also has its own migratepage callback. This 700 * is the most common path for page migration. 701 */ 702 rc = mapping->a_ops->migratepage(mapping, 703 newpage, page, mode); 704 else 705 rc = fallback_migrate_page(mapping, newpage, page, mode); 706 707 if (rc != MIGRATEPAGE_SUCCESS) { 708 newpage->mapping = NULL; 709 } else { 710 if (remap_swapcache) 711 remove_migration_ptes(page, newpage); 712 page->mapping = NULL; 713 } 714 715 unlock_page(newpage); 716 717 return rc; 718 } 719 720 static int __unmap_and_move(struct page *page, struct page *newpage, 721 int force, enum migrate_mode mode) 722 { 723 int rc = -EAGAIN; 724 int remap_swapcache = 1; 725 struct mem_cgroup *mem; 726 struct anon_vma *anon_vma = NULL; 727 728 if (!trylock_page(page)) { 729 if (!force || mode == MIGRATE_ASYNC) 730 goto out; 731 732 /* 733 * It's not safe for direct compaction to call lock_page. 734 * For example, during page readahead pages are added locked 735 * to the LRU. Later, when the IO completes the pages are 736 * marked uptodate and unlocked. However, the queueing 737 * could be merging multiple pages for one bio (e.g. 738 * mpage_readpages). If an allocation happens for the 739 * second or third page, the process can end up locking 740 * the same page twice and deadlocking. Rather than 741 * trying to be clever about what pages can be locked, 742 * avoid the use of lock_page for direct compaction 743 * altogether. 744 */ 745 if (current->flags & PF_MEMALLOC) 746 goto out; 747 748 lock_page(page); 749 } 750 751 /* charge against new page */ 752 mem_cgroup_prepare_migration(page, newpage, &mem); 753 754 if (PageWriteback(page)) { 755 /* 756 * Only in the case of a full synchronous migration is it 757 * necessary to wait for PageWriteback. In the async case, 758 * the retry loop is too short and in the sync-light case, 759 * the overhead of stalling is too much 760 */ 761 if (mode != MIGRATE_SYNC) { 762 rc = -EBUSY; 763 goto uncharge; 764 } 765 if (!force) 766 goto uncharge; 767 wait_on_page_writeback(page); 768 } 769 /* 770 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case, 771 * we cannot notice that anon_vma is freed while we migrates a page. 772 * This get_anon_vma() delays freeing anon_vma pointer until the end 773 * of migration. File cache pages are no problem because of page_lock() 774 * File Caches may use write_page() or lock_page() in migration, then, 775 * just care Anon page here. 776 */ 777 if (PageAnon(page) && !PageKsm(page)) { 778 /* 779 * Only page_lock_anon_vma_read() understands the subtleties of 780 * getting a hold on an anon_vma from outside one of its mms. 781 */ 782 anon_vma = page_get_anon_vma(page); 783 if (anon_vma) { 784 /* 785 * Anon page 786 */ 787 } else if (PageSwapCache(page)) { 788 /* 789 * We cannot be sure that the anon_vma of an unmapped 790 * swapcache page is safe to use because we don't 791 * know in advance if the VMA that this page belonged 792 * to still exists. If the VMA and others sharing the 793 * data have been freed, then the anon_vma could 794 * already be invalid. 795 * 796 * To avoid this possibility, swapcache pages get 797 * migrated but are not remapped when migration 798 * completes 799 */ 800 remap_swapcache = 0; 801 } else { 802 goto uncharge; 803 } 804 } 805 806 if (unlikely(balloon_page_movable(page))) { 807 /* 808 * A ballooned page does not need any special attention from 809 * physical to virtual reverse mapping procedures. 810 * Skip any attempt to unmap PTEs or to remap swap cache, 811 * in order to avoid burning cycles at rmap level, and perform 812 * the page migration right away (proteced by page lock). 813 */ 814 rc = balloon_page_migrate(newpage, page, mode); 815 goto uncharge; 816 } 817 818 /* 819 * Corner case handling: 820 * 1. When a new swap-cache page is read into, it is added to the LRU 821 * and treated as swapcache but it has no rmap yet. 822 * Calling try_to_unmap() against a page->mapping==NULL page will 823 * trigger a BUG. So handle it here. 824 * 2. An orphaned page (see truncate_complete_page) might have 825 * fs-private metadata. The page can be picked up due to memory 826 * offlining. Everywhere else except page reclaim, the page is 827 * invisible to the vm, so the page can not be migrated. So try to 828 * free the metadata, so the page can be freed. 829 */ 830 if (!page->mapping) { 831 VM_BUG_ON(PageAnon(page)); 832 if (page_has_private(page)) { 833 try_to_free_buffers(page); 834 goto uncharge; 835 } 836 goto skip_unmap; 837 } 838 839 /* Establish migration ptes or remove ptes */ 840 try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); 841 842 skip_unmap: 843 if (!page_mapped(page)) 844 rc = move_to_new_page(newpage, page, remap_swapcache, mode); 845 846 if (rc && remap_swapcache) 847 remove_migration_ptes(page, page); 848 849 /* Drop an anon_vma reference if we took one */ 850 if (anon_vma) 851 put_anon_vma(anon_vma); 852 853 uncharge: 854 mem_cgroup_end_migration(mem, page, newpage, 855 (rc == MIGRATEPAGE_SUCCESS || 856 rc == MIGRATEPAGE_BALLOON_SUCCESS)); 857 unlock_page(page); 858 out: 859 return rc; 860 } 861 862 /* 863 * Obtain the lock on page, remove all ptes and migrate the page 864 * to the newly allocated page in newpage. 865 */ 866 static int unmap_and_move(new_page_t get_new_page, unsigned long private, 867 struct page *page, int force, enum migrate_mode mode) 868 { 869 int rc = 0; 870 int *result = NULL; 871 struct page *newpage = get_new_page(page, private, &result); 872 873 if (!newpage) 874 return -ENOMEM; 875 876 if (page_count(page) == 1) { 877 /* page was freed from under us. So we are done. */ 878 goto out; 879 } 880 881 if (unlikely(PageTransHuge(page))) 882 if (unlikely(split_huge_page(page))) 883 goto out; 884 885 rc = __unmap_and_move(page, newpage, force, mode); 886 887 if (unlikely(rc == MIGRATEPAGE_BALLOON_SUCCESS)) { 888 /* 889 * A ballooned page has been migrated already. 890 * Now, it's the time to wrap-up counters, 891 * handle the page back to Buddy and return. 892 */ 893 dec_zone_page_state(page, NR_ISOLATED_ANON + 894 page_is_file_cache(page)); 895 balloon_page_free(page); 896 return MIGRATEPAGE_SUCCESS; 897 } 898 out: 899 if (rc != -EAGAIN) { 900 /* 901 * A page that has been migrated has all references 902 * removed and will be freed. A page that has not been 903 * migrated will have kepts its references and be 904 * restored. 905 */ 906 list_del(&page->lru); 907 dec_zone_page_state(page, NR_ISOLATED_ANON + 908 page_is_file_cache(page)); 909 putback_lru_page(page); 910 } 911 /* 912 * Move the new page to the LRU. If migration was not successful 913 * then this will free the page. 914 */ 915 putback_lru_page(newpage); 916 if (result) { 917 if (rc) 918 *result = rc; 919 else 920 *result = page_to_nid(newpage); 921 } 922 return rc; 923 } 924 925 /* 926 * Counterpart of unmap_and_move_page() for hugepage migration. 927 * 928 * This function doesn't wait the completion of hugepage I/O 929 * because there is no race between I/O and migration for hugepage. 930 * Note that currently hugepage I/O occurs only in direct I/O 931 * where no lock is held and PG_writeback is irrelevant, 932 * and writeback status of all subpages are counted in the reference 933 * count of the head page (i.e. if all subpages of a 2MB hugepage are 934 * under direct I/O, the reference of the head page is 512 and a bit more.) 935 * This means that when we try to migrate hugepage whose subpages are 936 * doing direct I/O, some references remain after try_to_unmap() and 937 * hugepage migration fails without data corruption. 938 * 939 * There is also no race when direct I/O is issued on the page under migration, 940 * because then pte is replaced with migration swap entry and direct I/O code 941 * will wait in the page fault for migration to complete. 942 */ 943 static int unmap_and_move_huge_page(new_page_t get_new_page, 944 unsigned long private, struct page *hpage, 945 int force, enum migrate_mode mode) 946 { 947 int rc = 0; 948 int *result = NULL; 949 struct page *new_hpage = get_new_page(hpage, private, &result); 950 struct anon_vma *anon_vma = NULL; 951 952 /* 953 * Movability of hugepages depends on architectures and hugepage size. 954 * This check is necessary because some callers of hugepage migration 955 * like soft offline and memory hotremove don't walk through page 956 * tables or check whether the hugepage is pmd-based or not before 957 * kicking migration. 958 */ 959 if (!hugepage_migration_support(page_hstate(hpage))) 960 return -ENOSYS; 961 962 if (!new_hpage) 963 return -ENOMEM; 964 965 rc = -EAGAIN; 966 967 if (!trylock_page(hpage)) { 968 if (!force || mode != MIGRATE_SYNC) 969 goto out; 970 lock_page(hpage); 971 } 972 973 if (PageAnon(hpage)) 974 anon_vma = page_get_anon_vma(hpage); 975 976 try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); 977 978 if (!page_mapped(hpage)) 979 rc = move_to_new_page(new_hpage, hpage, 1, mode); 980 981 if (rc) 982 remove_migration_ptes(hpage, hpage); 983 984 if (anon_vma) 985 put_anon_vma(anon_vma); 986 987 if (!rc) 988 hugetlb_cgroup_migrate(hpage, new_hpage); 989 990 unlock_page(hpage); 991 out: 992 if (rc != -EAGAIN) 993 putback_active_hugepage(hpage); 994 put_page(new_hpage); 995 if (result) { 996 if (rc) 997 *result = rc; 998 else 999 *result = page_to_nid(new_hpage); 1000 } 1001 return rc; 1002 } 1003 1004 /* 1005 * migrate_pages - migrate the pages specified in a list, to the free pages 1006 * supplied as the target for the page migration 1007 * 1008 * @from: The list of pages to be migrated. 1009 * @get_new_page: The function used to allocate free pages to be used 1010 * as the target of the page migration. 1011 * @private: Private data to be passed on to get_new_page() 1012 * @mode: The migration mode that specifies the constraints for 1013 * page migration, if any. 1014 * @reason: The reason for page migration. 1015 * 1016 * The function returns after 10 attempts or if no pages are movable any more 1017 * because the list has become empty or no retryable pages exist any more. 1018 * The caller should call putback_lru_pages() to return pages to the LRU 1019 * or free list only if ret != 0. 1020 * 1021 * Returns the number of pages that were not migrated, or an error code. 1022 */ 1023 int migrate_pages(struct list_head *from, new_page_t get_new_page, 1024 unsigned long private, enum migrate_mode mode, int reason) 1025 { 1026 int retry = 1; 1027 int nr_failed = 0; 1028 int nr_succeeded = 0; 1029 int pass = 0; 1030 struct page *page; 1031 struct page *page2; 1032 int swapwrite = current->flags & PF_SWAPWRITE; 1033 int rc; 1034 1035 if (!swapwrite) 1036 current->flags |= PF_SWAPWRITE; 1037 1038 for(pass = 0; pass < 10 && retry; pass++) { 1039 retry = 0; 1040 1041 list_for_each_entry_safe(page, page2, from, lru) { 1042 cond_resched(); 1043 1044 if (PageHuge(page)) 1045 rc = unmap_and_move_huge_page(get_new_page, 1046 private, page, pass > 2, mode); 1047 else 1048 rc = unmap_and_move(get_new_page, private, 1049 page, pass > 2, mode); 1050 1051 switch(rc) { 1052 case -ENOMEM: 1053 goto out; 1054 case -EAGAIN: 1055 retry++; 1056 break; 1057 case MIGRATEPAGE_SUCCESS: 1058 nr_succeeded++; 1059 break; 1060 default: 1061 /* Permanent failure */ 1062 nr_failed++; 1063 break; 1064 } 1065 } 1066 } 1067 rc = nr_failed + retry; 1068 out: 1069 if (nr_succeeded) 1070 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded); 1071 if (nr_failed) 1072 count_vm_events(PGMIGRATE_FAIL, nr_failed); 1073 trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason); 1074 1075 if (!swapwrite) 1076 current->flags &= ~PF_SWAPWRITE; 1077 1078 return rc; 1079 } 1080 1081 #ifdef CONFIG_NUMA 1082 /* 1083 * Move a list of individual pages 1084 */ 1085 struct page_to_node { 1086 unsigned long addr; 1087 struct page *page; 1088 int node; 1089 int status; 1090 }; 1091 1092 static struct page *new_page_node(struct page *p, unsigned long private, 1093 int **result) 1094 { 1095 struct page_to_node *pm = (struct page_to_node *)private; 1096 1097 while (pm->node != MAX_NUMNODES && pm->page != p) 1098 pm++; 1099 1100 if (pm->node == MAX_NUMNODES) 1101 return NULL; 1102 1103 *result = &pm->status; 1104 1105 if (PageHuge(p)) 1106 return alloc_huge_page_node(page_hstate(compound_head(p)), 1107 pm->node); 1108 else 1109 return alloc_pages_exact_node(pm->node, 1110 GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0); 1111 } 1112 1113 /* 1114 * Move a set of pages as indicated in the pm array. The addr 1115 * field must be set to the virtual address of the page to be moved 1116 * and the node number must contain a valid target node. 1117 * The pm array ends with node = MAX_NUMNODES. 1118 */ 1119 static int do_move_page_to_node_array(struct mm_struct *mm, 1120 struct page_to_node *pm, 1121 int migrate_all) 1122 { 1123 int err; 1124 struct page_to_node *pp; 1125 LIST_HEAD(pagelist); 1126 1127 down_read(&mm->mmap_sem); 1128 1129 /* 1130 * Build a list of pages to migrate 1131 */ 1132 for (pp = pm; pp->node != MAX_NUMNODES; pp++) { 1133 struct vm_area_struct *vma; 1134 struct page *page; 1135 1136 err = -EFAULT; 1137 vma = find_vma(mm, pp->addr); 1138 if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma)) 1139 goto set_status; 1140 1141 page = follow_page(vma, pp->addr, FOLL_GET|FOLL_SPLIT); 1142 1143 err = PTR_ERR(page); 1144 if (IS_ERR(page)) 1145 goto set_status; 1146 1147 err = -ENOENT; 1148 if (!page) 1149 goto set_status; 1150 1151 /* Use PageReserved to check for zero page */ 1152 if (PageReserved(page)) 1153 goto put_and_set; 1154 1155 pp->page = page; 1156 err = page_to_nid(page); 1157 1158 if (err == pp->node) 1159 /* 1160 * Node already in the right place 1161 */ 1162 goto put_and_set; 1163 1164 err = -EACCES; 1165 if (page_mapcount(page) > 1 && 1166 !migrate_all) 1167 goto put_and_set; 1168 1169 if (PageHuge(page)) { 1170 isolate_huge_page(page, &pagelist); 1171 goto put_and_set; 1172 } 1173 1174 err = isolate_lru_page(page); 1175 if (!err) { 1176 list_add_tail(&page->lru, &pagelist); 1177 inc_zone_page_state(page, NR_ISOLATED_ANON + 1178 page_is_file_cache(page)); 1179 } 1180 put_and_set: 1181 /* 1182 * Either remove the duplicate refcount from 1183 * isolate_lru_page() or drop the page ref if it was 1184 * not isolated. 1185 */ 1186 put_page(page); 1187 set_status: 1188 pp->status = err; 1189 } 1190 1191 err = 0; 1192 if (!list_empty(&pagelist)) { 1193 err = migrate_pages(&pagelist, new_page_node, 1194 (unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL); 1195 if (err) 1196 putback_movable_pages(&pagelist); 1197 } 1198 1199 up_read(&mm->mmap_sem); 1200 return err; 1201 } 1202 1203 /* 1204 * Migrate an array of page address onto an array of nodes and fill 1205 * the corresponding array of status. 1206 */ 1207 static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, 1208 unsigned long nr_pages, 1209 const void __user * __user *pages, 1210 const int __user *nodes, 1211 int __user *status, int flags) 1212 { 1213 struct page_to_node *pm; 1214 unsigned long chunk_nr_pages; 1215 unsigned long chunk_start; 1216 int err; 1217 1218 err = -ENOMEM; 1219 pm = (struct page_to_node *)__get_free_page(GFP_KERNEL); 1220 if (!pm) 1221 goto out; 1222 1223 migrate_prep(); 1224 1225 /* 1226 * Store a chunk of page_to_node array in a page, 1227 * but keep the last one as a marker 1228 */ 1229 chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1; 1230 1231 for (chunk_start = 0; 1232 chunk_start < nr_pages; 1233 chunk_start += chunk_nr_pages) { 1234 int j; 1235 1236 if (chunk_start + chunk_nr_pages > nr_pages) 1237 chunk_nr_pages = nr_pages - chunk_start; 1238 1239 /* fill the chunk pm with addrs and nodes from user-space */ 1240 for (j = 0; j < chunk_nr_pages; j++) { 1241 const void __user *p; 1242 int node; 1243 1244 err = -EFAULT; 1245 if (get_user(p, pages + j + chunk_start)) 1246 goto out_pm; 1247 pm[j].addr = (unsigned long) p; 1248 1249 if (get_user(node, nodes + j + chunk_start)) 1250 goto out_pm; 1251 1252 err = -ENODEV; 1253 if (node < 0 || node >= MAX_NUMNODES) 1254 goto out_pm; 1255 1256 if (!node_state(node, N_MEMORY)) 1257 goto out_pm; 1258 1259 err = -EACCES; 1260 if (!node_isset(node, task_nodes)) 1261 goto out_pm; 1262 1263 pm[j].node = node; 1264 } 1265 1266 /* End marker for this chunk */ 1267 pm[chunk_nr_pages].node = MAX_NUMNODES; 1268 1269 /* Migrate this chunk */ 1270 err = do_move_page_to_node_array(mm, pm, 1271 flags & MPOL_MF_MOVE_ALL); 1272 if (err < 0) 1273 goto out_pm; 1274 1275 /* Return status information */ 1276 for (j = 0; j < chunk_nr_pages; j++) 1277 if (put_user(pm[j].status, status + j + chunk_start)) { 1278 err = -EFAULT; 1279 goto out_pm; 1280 } 1281 } 1282 err = 0; 1283 1284 out_pm: 1285 free_page((unsigned long)pm); 1286 out: 1287 return err; 1288 } 1289 1290 /* 1291 * Determine the nodes of an array of pages and store it in an array of status. 1292 */ 1293 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, 1294 const void __user **pages, int *status) 1295 { 1296 unsigned long i; 1297 1298 down_read(&mm->mmap_sem); 1299 1300 for (i = 0; i < nr_pages; i++) { 1301 unsigned long addr = (unsigned long)(*pages); 1302 struct vm_area_struct *vma; 1303 struct page *page; 1304 int err = -EFAULT; 1305 1306 vma = find_vma(mm, addr); 1307 if (!vma || addr < vma->vm_start) 1308 goto set_status; 1309 1310 page = follow_page(vma, addr, 0); 1311 1312 err = PTR_ERR(page); 1313 if (IS_ERR(page)) 1314 goto set_status; 1315 1316 err = -ENOENT; 1317 /* Use PageReserved to check for zero page */ 1318 if (!page || PageReserved(page)) 1319 goto set_status; 1320 1321 err = page_to_nid(page); 1322 set_status: 1323 *status = err; 1324 1325 pages++; 1326 status++; 1327 } 1328 1329 up_read(&mm->mmap_sem); 1330 } 1331 1332 /* 1333 * Determine the nodes of a user array of pages and store it in 1334 * a user array of status. 1335 */ 1336 static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, 1337 const void __user * __user *pages, 1338 int __user *status) 1339 { 1340 #define DO_PAGES_STAT_CHUNK_NR 16 1341 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR]; 1342 int chunk_status[DO_PAGES_STAT_CHUNK_NR]; 1343 1344 while (nr_pages) { 1345 unsigned long chunk_nr; 1346 1347 chunk_nr = nr_pages; 1348 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR) 1349 chunk_nr = DO_PAGES_STAT_CHUNK_NR; 1350 1351 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages))) 1352 break; 1353 1354 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status); 1355 1356 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status))) 1357 break; 1358 1359 pages += chunk_nr; 1360 status += chunk_nr; 1361 nr_pages -= chunk_nr; 1362 } 1363 return nr_pages ? -EFAULT : 0; 1364 } 1365 1366 /* 1367 * Move a list of pages in the address space of the currently executing 1368 * process. 1369 */ 1370 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages, 1371 const void __user * __user *, pages, 1372 const int __user *, nodes, 1373 int __user *, status, int, flags) 1374 { 1375 const struct cred *cred = current_cred(), *tcred; 1376 struct task_struct *task; 1377 struct mm_struct *mm; 1378 int err; 1379 nodemask_t task_nodes; 1380 1381 /* Check flags */ 1382 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL)) 1383 return -EINVAL; 1384 1385 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE)) 1386 return -EPERM; 1387 1388 /* Find the mm_struct */ 1389 rcu_read_lock(); 1390 task = pid ? find_task_by_vpid(pid) : current; 1391 if (!task) { 1392 rcu_read_unlock(); 1393 return -ESRCH; 1394 } 1395 get_task_struct(task); 1396 1397 /* 1398 * Check if this process has the right to modify the specified 1399 * process. The right exists if the process has administrative 1400 * capabilities, superuser privileges or the same 1401 * userid as the target process. 1402 */ 1403 tcred = __task_cred(task); 1404 if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) && 1405 !uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) && 1406 !capable(CAP_SYS_NICE)) { 1407 rcu_read_unlock(); 1408 err = -EPERM; 1409 goto out; 1410 } 1411 rcu_read_unlock(); 1412 1413 err = security_task_movememory(task); 1414 if (err) 1415 goto out; 1416 1417 task_nodes = cpuset_mems_allowed(task); 1418 mm = get_task_mm(task); 1419 put_task_struct(task); 1420 1421 if (!mm) 1422 return -EINVAL; 1423 1424 if (nodes) 1425 err = do_pages_move(mm, task_nodes, nr_pages, pages, 1426 nodes, status, flags); 1427 else 1428 err = do_pages_stat(mm, nr_pages, pages, status); 1429 1430 mmput(mm); 1431 return err; 1432 1433 out: 1434 put_task_struct(task); 1435 return err; 1436 } 1437 1438 /* 1439 * Call migration functions in the vma_ops that may prepare 1440 * memory in a vm for migration. migration functions may perform 1441 * the migration for vmas that do not have an underlying page struct. 1442 */ 1443 int migrate_vmas(struct mm_struct *mm, const nodemask_t *to, 1444 const nodemask_t *from, unsigned long flags) 1445 { 1446 struct vm_area_struct *vma; 1447 int err = 0; 1448 1449 for (vma = mm->mmap; vma && !err; vma = vma->vm_next) { 1450 if (vma->vm_ops && vma->vm_ops->migrate) { 1451 err = vma->vm_ops->migrate(vma, to, from, flags); 1452 if (err) 1453 break; 1454 } 1455 } 1456 return err; 1457 } 1458 1459 #ifdef CONFIG_NUMA_BALANCING 1460 /* 1461 * Returns true if this is a safe migration target node for misplaced NUMA 1462 * pages. Currently it only checks the watermarks which crude 1463 */ 1464 static bool migrate_balanced_pgdat(struct pglist_data *pgdat, 1465 unsigned long nr_migrate_pages) 1466 { 1467 int z; 1468 for (z = pgdat->nr_zones - 1; z >= 0; z--) { 1469 struct zone *zone = pgdat->node_zones + z; 1470 1471 if (!populated_zone(zone)) 1472 continue; 1473 1474 if (!zone_reclaimable(zone)) 1475 continue; 1476 1477 /* Avoid waking kswapd by allocating pages_to_migrate pages. */ 1478 if (!zone_watermark_ok(zone, 0, 1479 high_wmark_pages(zone) + 1480 nr_migrate_pages, 1481 0, 0)) 1482 continue; 1483 return true; 1484 } 1485 return false; 1486 } 1487 1488 static struct page *alloc_misplaced_dst_page(struct page *page, 1489 unsigned long data, 1490 int **result) 1491 { 1492 int nid = (int) data; 1493 struct page *newpage; 1494 1495 newpage = alloc_pages_exact_node(nid, 1496 (GFP_HIGHUSER_MOVABLE | GFP_THISNODE | 1497 __GFP_NOMEMALLOC | __GFP_NORETRY | 1498 __GFP_NOWARN) & 1499 ~GFP_IOFS, 0); 1500 if (newpage) 1501 page_nid_xchg_last(newpage, page_nid_last(page)); 1502 1503 return newpage; 1504 } 1505 1506 /* 1507 * page migration rate limiting control. 1508 * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs 1509 * window of time. Default here says do not migrate more than 1280M per second. 1510 * If a node is rate-limited then PTE NUMA updates are also rate-limited. However 1511 * as it is faults that reset the window, pte updates will happen unconditionally 1512 * if there has not been a fault since @pteupdate_interval_millisecs after the 1513 * throttle window closed. 1514 */ 1515 static unsigned int migrate_interval_millisecs __read_mostly = 100; 1516 static unsigned int pteupdate_interval_millisecs __read_mostly = 1000; 1517 static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT); 1518 1519 /* Returns true if NUMA migration is currently rate limited */ 1520 bool migrate_ratelimited(int node) 1521 { 1522 pg_data_t *pgdat = NODE_DATA(node); 1523 1524 if (time_after(jiffies, pgdat->numabalancing_migrate_next_window + 1525 msecs_to_jiffies(pteupdate_interval_millisecs))) 1526 return false; 1527 1528 if (pgdat->numabalancing_migrate_nr_pages < ratelimit_pages) 1529 return false; 1530 1531 return true; 1532 } 1533 1534 /* Returns true if the node is migrate rate-limited after the update */ 1535 bool numamigrate_update_ratelimit(pg_data_t *pgdat, unsigned long nr_pages) 1536 { 1537 bool rate_limited = false; 1538 1539 /* 1540 * Rate-limit the amount of data that is being migrated to a node. 1541 * Optimal placement is no good if the memory bus is saturated and 1542 * all the time is being spent migrating! 1543 */ 1544 spin_lock(&pgdat->numabalancing_migrate_lock); 1545 if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) { 1546 pgdat->numabalancing_migrate_nr_pages = 0; 1547 pgdat->numabalancing_migrate_next_window = jiffies + 1548 msecs_to_jiffies(migrate_interval_millisecs); 1549 } 1550 if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages) 1551 rate_limited = true; 1552 else 1553 pgdat->numabalancing_migrate_nr_pages += nr_pages; 1554 spin_unlock(&pgdat->numabalancing_migrate_lock); 1555 1556 return rate_limited; 1557 } 1558 1559 int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) 1560 { 1561 int page_lru; 1562 1563 VM_BUG_ON(compound_order(page) && !PageTransHuge(page)); 1564 1565 /* Avoid migrating to a node that is nearly full */ 1566 if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page))) 1567 return 0; 1568 1569 if (isolate_lru_page(page)) 1570 return 0; 1571 1572 /* 1573 * migrate_misplaced_transhuge_page() skips page migration's usual 1574 * check on page_count(), so we must do it here, now that the page 1575 * has been isolated: a GUP pin, or any other pin, prevents migration. 1576 * The expected page count is 3: 1 for page's mapcount and 1 for the 1577 * caller's pin and 1 for the reference taken by isolate_lru_page(). 1578 */ 1579 if (PageTransHuge(page) && page_count(page) != 3) { 1580 putback_lru_page(page); 1581 return 0; 1582 } 1583 1584 page_lru = page_is_file_cache(page); 1585 mod_zone_page_state(page_zone(page), NR_ISOLATED_ANON + page_lru, 1586 hpage_nr_pages(page)); 1587 1588 /* 1589 * Isolating the page has taken another reference, so the 1590 * caller's reference can be safely dropped without the page 1591 * disappearing underneath us during migration. 1592 */ 1593 put_page(page); 1594 return 1; 1595 } 1596 1597 /* 1598 * Attempt to migrate a misplaced page to the specified destination 1599 * node. Caller is expected to have an elevated reference count on 1600 * the page that will be dropped by this function before returning. 1601 */ 1602 int migrate_misplaced_page(struct page *page, int node) 1603 { 1604 pg_data_t *pgdat = NODE_DATA(node); 1605 int isolated; 1606 int nr_remaining; 1607 LIST_HEAD(migratepages); 1608 1609 /* 1610 * Don't migrate pages that are mapped in multiple processes. 1611 * TODO: Handle false sharing detection instead of this hammer 1612 */ 1613 if (page_mapcount(page) != 1) 1614 goto out; 1615 1616 /* 1617 * Rate-limit the amount of data that is being migrated to a node. 1618 * Optimal placement is no good if the memory bus is saturated and 1619 * all the time is being spent migrating! 1620 */ 1621 if (numamigrate_update_ratelimit(pgdat, 1)) 1622 goto out; 1623 1624 isolated = numamigrate_isolate_page(pgdat, page); 1625 if (!isolated) 1626 goto out; 1627 1628 list_add(&page->lru, &migratepages); 1629 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page, 1630 node, MIGRATE_ASYNC, MR_NUMA_MISPLACED); 1631 if (nr_remaining) { 1632 putback_lru_pages(&migratepages); 1633 isolated = 0; 1634 } else 1635 count_vm_numa_event(NUMA_PAGE_MIGRATE); 1636 BUG_ON(!list_empty(&migratepages)); 1637 return isolated; 1638 1639 out: 1640 put_page(page); 1641 return 0; 1642 } 1643 #endif /* CONFIG_NUMA_BALANCING */ 1644 1645 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE) 1646 /* 1647 * Migrates a THP to a given target node. page must be locked and is unlocked 1648 * before returning. 1649 */ 1650 int migrate_misplaced_transhuge_page(struct mm_struct *mm, 1651 struct vm_area_struct *vma, 1652 pmd_t *pmd, pmd_t entry, 1653 unsigned long address, 1654 struct page *page, int node) 1655 { 1656 unsigned long haddr = address & HPAGE_PMD_MASK; 1657 pg_data_t *pgdat = NODE_DATA(node); 1658 int isolated = 0; 1659 struct page *new_page = NULL; 1660 struct mem_cgroup *memcg = NULL; 1661 int page_lru = page_is_file_cache(page); 1662 1663 /* 1664 * Don't migrate pages that are mapped in multiple processes. 1665 * TODO: Handle false sharing detection instead of this hammer 1666 */ 1667 if (page_mapcount(page) != 1) 1668 goto out_dropref; 1669 1670 /* 1671 * Rate-limit the amount of data that is being migrated to a node. 1672 * Optimal placement is no good if the memory bus is saturated and 1673 * all the time is being spent migrating! 1674 */ 1675 if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR)) 1676 goto out_dropref; 1677 1678 new_page = alloc_pages_node(node, 1679 (GFP_TRANSHUGE | GFP_THISNODE) & ~__GFP_WAIT, HPAGE_PMD_ORDER); 1680 if (!new_page) 1681 goto out_fail; 1682 1683 page_nid_xchg_last(new_page, page_nid_last(page)); 1684 1685 isolated = numamigrate_isolate_page(pgdat, page); 1686 if (!isolated) { 1687 put_page(new_page); 1688 goto out_fail; 1689 } 1690 1691 /* Prepare a page as a migration target */ 1692 __set_page_locked(new_page); 1693 SetPageSwapBacked(new_page); 1694 1695 /* anon mapping, we can simply copy page->mapping to the new page: */ 1696 new_page->mapping = page->mapping; 1697 new_page->index = page->index; 1698 migrate_page_copy(new_page, page); 1699 WARN_ON(PageLRU(new_page)); 1700 1701 /* Recheck the target PMD */ 1702 spin_lock(&mm->page_table_lock); 1703 if (unlikely(!pmd_same(*pmd, entry))) { 1704 spin_unlock(&mm->page_table_lock); 1705 1706 /* Reverse changes made by migrate_page_copy() */ 1707 if (TestClearPageActive(new_page)) 1708 SetPageActive(page); 1709 if (TestClearPageUnevictable(new_page)) 1710 SetPageUnevictable(page); 1711 mlock_migrate_page(page, new_page); 1712 1713 unlock_page(new_page); 1714 put_page(new_page); /* Free it */ 1715 1716 unlock_page(page); 1717 putback_lru_page(page); 1718 1719 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR); 1720 isolated = 0; 1721 goto out; 1722 } 1723 1724 /* 1725 * Traditional migration needs to prepare the memcg charge 1726 * transaction early to prevent the old page from being 1727 * uncharged when installing migration entries. Here we can 1728 * save the potential rollback and start the charge transfer 1729 * only when migration is already known to end successfully. 1730 */ 1731 mem_cgroup_prepare_migration(page, new_page, &memcg); 1732 1733 entry = mk_pmd(new_page, vma->vm_page_prot); 1734 entry = pmd_mknonnuma(entry); 1735 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1736 entry = pmd_mkhuge(entry); 1737 1738 page_add_new_anon_rmap(new_page, vma, haddr); 1739 1740 set_pmd_at(mm, haddr, pmd, entry); 1741 update_mmu_cache_pmd(vma, address, &entry); 1742 page_remove_rmap(page); 1743 /* 1744 * Finish the charge transaction under the page table lock to 1745 * prevent split_huge_page() from dividing up the charge 1746 * before it's fully transferred to the new page. 1747 */ 1748 mem_cgroup_end_migration(memcg, page, new_page, true); 1749 spin_unlock(&mm->page_table_lock); 1750 1751 unlock_page(new_page); 1752 unlock_page(page); 1753 put_page(page); /* Drop the rmap reference */ 1754 put_page(page); /* Drop the LRU isolation reference */ 1755 1756 count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR); 1757 count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR); 1758 1759 out: 1760 mod_zone_page_state(page_zone(page), 1761 NR_ISOLATED_ANON + page_lru, 1762 -HPAGE_PMD_NR); 1763 return isolated; 1764 1765 out_fail: 1766 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR); 1767 out_dropref: 1768 unlock_page(page); 1769 put_page(page); 1770 return 0; 1771 } 1772 #endif /* CONFIG_NUMA_BALANCING */ 1773 1774 #endif /* CONFIG_NUMA */ 1775