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