1 /* 2 * Memory Migration functionality - linux/mm/migrate.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/backing-dev.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 #include <linux/mmu_notifier.h> 40 #include <linux/page_idle.h> 41 #include <linux/page_owner.h> 42 43 #include <asm/tlbflush.h> 44 45 #define CREATE_TRACE_POINTS 46 #include <trace/events/migrate.h> 47 48 #include "internal.h" 49 50 /* 51 * migrate_prep() needs to be called before we start compiling a list of pages 52 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is 53 * undesirable, use migrate_prep_local() 54 */ 55 int migrate_prep(void) 56 { 57 /* 58 * Clear the LRU lists so pages can be isolated. 59 * Note that pages may be moved off the LRU after we have 60 * drained them. Those pages will fail to migrate like other 61 * pages that may be busy. 62 */ 63 lru_add_drain_all(); 64 65 return 0; 66 } 67 68 /* Do the necessary work of migrate_prep but not if it involves other CPUs */ 69 int migrate_prep_local(void) 70 { 71 lru_add_drain(); 72 73 return 0; 74 } 75 76 /* 77 * Put previously isolated pages back onto the appropriate lists 78 * from where they were once taken off for compaction/migration. 79 * 80 * This function shall be used whenever the isolated pageset has been 81 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range() 82 * and isolate_huge_page(). 83 */ 84 void putback_movable_pages(struct list_head *l) 85 { 86 struct page *page; 87 struct page *page2; 88 89 list_for_each_entry_safe(page, page2, l, lru) { 90 if (unlikely(PageHuge(page))) { 91 putback_active_hugepage(page); 92 continue; 93 } 94 list_del(&page->lru); 95 dec_zone_page_state(page, NR_ISOLATED_ANON + 96 page_is_file_cache(page)); 97 if (unlikely(isolated_balloon_page(page))) 98 balloon_page_putback(page); 99 else 100 putback_lru_page(page); 101 } 102 } 103 104 /* 105 * Restore a potential migration pte to a working pte entry 106 */ 107 static int remove_migration_pte(struct page *new, struct vm_area_struct *vma, 108 unsigned long addr, void *old) 109 { 110 struct mm_struct *mm = vma->vm_mm; 111 swp_entry_t entry; 112 pmd_t *pmd; 113 pte_t *ptep, pte; 114 spinlock_t *ptl; 115 116 if (unlikely(PageHuge(new))) { 117 ptep = huge_pte_offset(mm, addr); 118 if (!ptep) 119 goto out; 120 ptl = huge_pte_lockptr(hstate_vma(vma), mm, ptep); 121 } else { 122 pmd = mm_find_pmd(mm, addr); 123 if (!pmd) 124 goto out; 125 126 ptep = pte_offset_map(pmd, addr); 127 128 /* 129 * Peek to check is_swap_pte() before taking ptlock? No, we 130 * can race mremap's move_ptes(), which skips anon_vma lock. 131 */ 132 133 ptl = pte_lockptr(mm, pmd); 134 } 135 136 spin_lock(ptl); 137 pte = *ptep; 138 if (!is_swap_pte(pte)) 139 goto unlock; 140 141 entry = pte_to_swp_entry(pte); 142 143 if (!is_migration_entry(entry) || 144 migration_entry_to_page(entry) != old) 145 goto unlock; 146 147 get_page(new); 148 pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); 149 if (pte_swp_soft_dirty(*ptep)) 150 pte = pte_mksoft_dirty(pte); 151 152 /* Recheck VMA as permissions can change since migration started */ 153 if (is_write_migration_entry(entry)) 154 pte = maybe_mkwrite(pte, vma); 155 156 #ifdef CONFIG_HUGETLB_PAGE 157 if (PageHuge(new)) { 158 pte = pte_mkhuge(pte); 159 pte = arch_make_huge_pte(pte, vma, new, 0); 160 } 161 #endif 162 flush_dcache_page(new); 163 set_pte_at(mm, addr, ptep, pte); 164 165 if (PageHuge(new)) { 166 if (PageAnon(new)) 167 hugepage_add_anon_rmap(new, vma, addr); 168 else 169 page_dup_rmap(new, true); 170 } else if (PageAnon(new)) 171 page_add_anon_rmap(new, vma, addr, false); 172 else 173 page_add_file_rmap(new); 174 175 if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new)) 176 mlock_vma_page(new); 177 178 /* No need to invalidate - it was non-present before */ 179 update_mmu_cache(vma, addr, ptep); 180 unlock: 181 pte_unmap_unlock(ptep, ptl); 182 out: 183 return SWAP_AGAIN; 184 } 185 186 /* 187 * Get rid of all migration entries and replace them by 188 * references to the indicated page. 189 */ 190 void remove_migration_ptes(struct page *old, struct page *new, bool locked) 191 { 192 struct rmap_walk_control rwc = { 193 .rmap_one = remove_migration_pte, 194 .arg = old, 195 }; 196 197 if (locked) 198 rmap_walk_locked(new, &rwc); 199 else 200 rmap_walk(new, &rwc); 201 } 202 203 /* 204 * Something used the pte of a page under migration. We need to 205 * get to the page and wait until migration is finished. 206 * When we return from this function the fault will be retried. 207 */ 208 void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep, 209 spinlock_t *ptl) 210 { 211 pte_t pte; 212 swp_entry_t entry; 213 struct page *page; 214 215 spin_lock(ptl); 216 pte = *ptep; 217 if (!is_swap_pte(pte)) 218 goto out; 219 220 entry = pte_to_swp_entry(pte); 221 if (!is_migration_entry(entry)) 222 goto out; 223 224 page = migration_entry_to_page(entry); 225 226 /* 227 * Once radix-tree replacement of page migration started, page_count 228 * *must* be zero. And, we don't want to call wait_on_page_locked() 229 * against a page without get_page(). 230 * So, we use get_page_unless_zero(), here. Even failed, page fault 231 * will occur again. 232 */ 233 if (!get_page_unless_zero(page)) 234 goto out; 235 pte_unmap_unlock(ptep, ptl); 236 wait_on_page_locked(page); 237 put_page(page); 238 return; 239 out: 240 pte_unmap_unlock(ptep, ptl); 241 } 242 243 void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, 244 unsigned long address) 245 { 246 spinlock_t *ptl = pte_lockptr(mm, pmd); 247 pte_t *ptep = pte_offset_map(pmd, address); 248 __migration_entry_wait(mm, ptep, ptl); 249 } 250 251 void migration_entry_wait_huge(struct vm_area_struct *vma, 252 struct mm_struct *mm, pte_t *pte) 253 { 254 spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte); 255 __migration_entry_wait(mm, pte, ptl); 256 } 257 258 #ifdef CONFIG_BLOCK 259 /* Returns true if all buffers are successfully locked */ 260 static bool buffer_migrate_lock_buffers(struct buffer_head *head, 261 enum migrate_mode mode) 262 { 263 struct buffer_head *bh = head; 264 265 /* Simple case, sync compaction */ 266 if (mode != MIGRATE_ASYNC) { 267 do { 268 get_bh(bh); 269 lock_buffer(bh); 270 bh = bh->b_this_page; 271 272 } while (bh != head); 273 274 return true; 275 } 276 277 /* async case, we cannot block on lock_buffer so use trylock_buffer */ 278 do { 279 get_bh(bh); 280 if (!trylock_buffer(bh)) { 281 /* 282 * We failed to lock the buffer and cannot stall in 283 * async migration. Release the taken locks 284 */ 285 struct buffer_head *failed_bh = bh; 286 put_bh(failed_bh); 287 bh = head; 288 while (bh != failed_bh) { 289 unlock_buffer(bh); 290 put_bh(bh); 291 bh = bh->b_this_page; 292 } 293 return false; 294 } 295 296 bh = bh->b_this_page; 297 } while (bh != head); 298 return true; 299 } 300 #else 301 static inline bool buffer_migrate_lock_buffers(struct buffer_head *head, 302 enum migrate_mode mode) 303 { 304 return true; 305 } 306 #endif /* CONFIG_BLOCK */ 307 308 /* 309 * Replace the page in the mapping. 310 * 311 * The number of remaining references must be: 312 * 1 for anonymous pages without a mapping 313 * 2 for pages with a mapping 314 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set. 315 */ 316 int migrate_page_move_mapping(struct address_space *mapping, 317 struct page *newpage, struct page *page, 318 struct buffer_head *head, enum migrate_mode mode, 319 int extra_count) 320 { 321 struct zone *oldzone, *newzone; 322 int dirty; 323 int expected_count = 1 + extra_count; 324 void **pslot; 325 326 if (!mapping) { 327 /* Anonymous page without mapping */ 328 if (page_count(page) != expected_count) 329 return -EAGAIN; 330 331 /* No turning back from here */ 332 newpage->index = page->index; 333 newpage->mapping = page->mapping; 334 if (PageSwapBacked(page)) 335 SetPageSwapBacked(newpage); 336 337 return MIGRATEPAGE_SUCCESS; 338 } 339 340 oldzone = page_zone(page); 341 newzone = page_zone(newpage); 342 343 spin_lock_irq(&mapping->tree_lock); 344 345 pslot = radix_tree_lookup_slot(&mapping->page_tree, 346 page_index(page)); 347 348 expected_count += 1 + page_has_private(page); 349 if (page_count(page) != expected_count || 350 radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) { 351 spin_unlock_irq(&mapping->tree_lock); 352 return -EAGAIN; 353 } 354 355 if (!page_ref_freeze(page, expected_count)) { 356 spin_unlock_irq(&mapping->tree_lock); 357 return -EAGAIN; 358 } 359 360 /* 361 * In the async migration case of moving a page with buffers, lock the 362 * buffers using trylock before the mapping is moved. If the mapping 363 * was moved, we later failed to lock the buffers and could not move 364 * the mapping back due to an elevated page count, we would have to 365 * block waiting on other references to be dropped. 366 */ 367 if (mode == MIGRATE_ASYNC && head && 368 !buffer_migrate_lock_buffers(head, mode)) { 369 page_ref_unfreeze(page, expected_count); 370 spin_unlock_irq(&mapping->tree_lock); 371 return -EAGAIN; 372 } 373 374 /* 375 * Now we know that no one else is looking at the page: 376 * no turning back from here. 377 */ 378 newpage->index = page->index; 379 newpage->mapping = page->mapping; 380 if (PageSwapBacked(page)) 381 SetPageSwapBacked(newpage); 382 383 get_page(newpage); /* add cache reference */ 384 if (PageSwapCache(page)) { 385 SetPageSwapCache(newpage); 386 set_page_private(newpage, page_private(page)); 387 } 388 389 /* Move dirty while page refs frozen and newpage not yet exposed */ 390 dirty = PageDirty(page); 391 if (dirty) { 392 ClearPageDirty(page); 393 SetPageDirty(newpage); 394 } 395 396 radix_tree_replace_slot(pslot, newpage); 397 398 /* 399 * Drop cache reference from old page by unfreezing 400 * to one less reference. 401 * We know this isn't the last reference. 402 */ 403 page_ref_unfreeze(page, expected_count - 1); 404 405 spin_unlock(&mapping->tree_lock); 406 /* Leave irq disabled to prevent preemption while updating stats */ 407 408 /* 409 * If moved to a different zone then also account 410 * the page for that zone. Other VM counters will be 411 * taken care of when we establish references to the 412 * new page and drop references to the old page. 413 * 414 * Note that anonymous pages are accounted for 415 * via NR_FILE_PAGES and NR_ANON_PAGES if they 416 * are mapped to swap space. 417 */ 418 if (newzone != oldzone) { 419 __dec_zone_state(oldzone, NR_FILE_PAGES); 420 __inc_zone_state(newzone, NR_FILE_PAGES); 421 if (PageSwapBacked(page) && !PageSwapCache(page)) { 422 __dec_zone_state(oldzone, NR_SHMEM); 423 __inc_zone_state(newzone, NR_SHMEM); 424 } 425 if (dirty && mapping_cap_account_dirty(mapping)) { 426 __dec_zone_state(oldzone, NR_FILE_DIRTY); 427 __inc_zone_state(newzone, NR_FILE_DIRTY); 428 } 429 } 430 local_irq_enable(); 431 432 return MIGRATEPAGE_SUCCESS; 433 } 434 435 /* 436 * The expected number of remaining references is the same as that 437 * of migrate_page_move_mapping(). 438 */ 439 int migrate_huge_page_move_mapping(struct address_space *mapping, 440 struct page *newpage, struct page *page) 441 { 442 int expected_count; 443 void **pslot; 444 445 spin_lock_irq(&mapping->tree_lock); 446 447 pslot = radix_tree_lookup_slot(&mapping->page_tree, 448 page_index(page)); 449 450 expected_count = 2 + page_has_private(page); 451 if (page_count(page) != expected_count || 452 radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) { 453 spin_unlock_irq(&mapping->tree_lock); 454 return -EAGAIN; 455 } 456 457 if (!page_ref_freeze(page, expected_count)) { 458 spin_unlock_irq(&mapping->tree_lock); 459 return -EAGAIN; 460 } 461 462 newpage->index = page->index; 463 newpage->mapping = page->mapping; 464 465 get_page(newpage); 466 467 radix_tree_replace_slot(pslot, newpage); 468 469 page_ref_unfreeze(page, expected_count - 1); 470 471 spin_unlock_irq(&mapping->tree_lock); 472 473 return MIGRATEPAGE_SUCCESS; 474 } 475 476 /* 477 * Gigantic pages are so large that we do not guarantee that page++ pointer 478 * arithmetic will work across the entire page. We need something more 479 * specialized. 480 */ 481 static void __copy_gigantic_page(struct page *dst, struct page *src, 482 int nr_pages) 483 { 484 int i; 485 struct page *dst_base = dst; 486 struct page *src_base = src; 487 488 for (i = 0; i < nr_pages; ) { 489 cond_resched(); 490 copy_highpage(dst, src); 491 492 i++; 493 dst = mem_map_next(dst, dst_base, i); 494 src = mem_map_next(src, src_base, i); 495 } 496 } 497 498 static void copy_huge_page(struct page *dst, struct page *src) 499 { 500 int i; 501 int nr_pages; 502 503 if (PageHuge(src)) { 504 /* hugetlbfs page */ 505 struct hstate *h = page_hstate(src); 506 nr_pages = pages_per_huge_page(h); 507 508 if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) { 509 __copy_gigantic_page(dst, src, nr_pages); 510 return; 511 } 512 } else { 513 /* thp page */ 514 BUG_ON(!PageTransHuge(src)); 515 nr_pages = hpage_nr_pages(src); 516 } 517 518 for (i = 0; i < nr_pages; i++) { 519 cond_resched(); 520 copy_highpage(dst + i, src + i); 521 } 522 } 523 524 /* 525 * Copy the page to its new location 526 */ 527 void migrate_page_copy(struct page *newpage, struct page *page) 528 { 529 int cpupid; 530 531 if (PageHuge(page) || PageTransHuge(page)) 532 copy_huge_page(newpage, page); 533 else 534 copy_highpage(newpage, page); 535 536 if (PageError(page)) 537 SetPageError(newpage); 538 if (PageReferenced(page)) 539 SetPageReferenced(newpage); 540 if (PageUptodate(page)) 541 SetPageUptodate(newpage); 542 if (TestClearPageActive(page)) { 543 VM_BUG_ON_PAGE(PageUnevictable(page), page); 544 SetPageActive(newpage); 545 } else if (TestClearPageUnevictable(page)) 546 SetPageUnevictable(newpage); 547 if (PageChecked(page)) 548 SetPageChecked(newpage); 549 if (PageMappedToDisk(page)) 550 SetPageMappedToDisk(newpage); 551 552 /* Move dirty on pages not done by migrate_page_move_mapping() */ 553 if (PageDirty(page)) 554 SetPageDirty(newpage); 555 556 if (page_is_young(page)) 557 set_page_young(newpage); 558 if (page_is_idle(page)) 559 set_page_idle(newpage); 560 561 /* 562 * Copy NUMA information to the new page, to prevent over-eager 563 * future migrations of this same page. 564 */ 565 cpupid = page_cpupid_xchg_last(page, -1); 566 page_cpupid_xchg_last(newpage, cpupid); 567 568 ksm_migrate_page(newpage, page); 569 /* 570 * Please do not reorder this without considering how mm/ksm.c's 571 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache(). 572 */ 573 if (PageSwapCache(page)) 574 ClearPageSwapCache(page); 575 ClearPagePrivate(page); 576 set_page_private(page, 0); 577 578 /* 579 * If any waiters have accumulated on the new page then 580 * wake them up. 581 */ 582 if (PageWriteback(newpage)) 583 end_page_writeback(newpage); 584 585 copy_page_owner(page, newpage); 586 587 mem_cgroup_migrate(page, newpage); 588 } 589 590 /************************************************************ 591 * Migration functions 592 ***********************************************************/ 593 594 /* 595 * Common logic to directly migrate a single page suitable for 596 * pages that do not use PagePrivate/PagePrivate2. 597 * 598 * Pages are locked upon entry and exit. 599 */ 600 int migrate_page(struct address_space *mapping, 601 struct page *newpage, struct page *page, 602 enum migrate_mode mode) 603 { 604 int rc; 605 606 BUG_ON(PageWriteback(page)); /* Writeback must be complete */ 607 608 rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0); 609 610 if (rc != MIGRATEPAGE_SUCCESS) 611 return rc; 612 613 migrate_page_copy(newpage, page); 614 return MIGRATEPAGE_SUCCESS; 615 } 616 EXPORT_SYMBOL(migrate_page); 617 618 #ifdef CONFIG_BLOCK 619 /* 620 * Migration function for pages with buffers. This function can only be used 621 * if the underlying filesystem guarantees that no other references to "page" 622 * exist. 623 */ 624 int buffer_migrate_page(struct address_space *mapping, 625 struct page *newpage, struct page *page, enum migrate_mode mode) 626 { 627 struct buffer_head *bh, *head; 628 int rc; 629 630 if (!page_has_buffers(page)) 631 return migrate_page(mapping, newpage, page, mode); 632 633 head = page_buffers(page); 634 635 rc = migrate_page_move_mapping(mapping, newpage, page, head, mode, 0); 636 637 if (rc != MIGRATEPAGE_SUCCESS) 638 return rc; 639 640 /* 641 * In the async case, migrate_page_move_mapping locked the buffers 642 * with an IRQ-safe spinlock held. In the sync case, the buffers 643 * need to be locked now 644 */ 645 if (mode != MIGRATE_ASYNC) 646 BUG_ON(!buffer_migrate_lock_buffers(head, mode)); 647 648 ClearPagePrivate(page); 649 set_page_private(newpage, page_private(page)); 650 set_page_private(page, 0); 651 put_page(page); 652 get_page(newpage); 653 654 bh = head; 655 do { 656 set_bh_page(bh, newpage, bh_offset(bh)); 657 bh = bh->b_this_page; 658 659 } while (bh != head); 660 661 SetPagePrivate(newpage); 662 663 migrate_page_copy(newpage, page); 664 665 bh = head; 666 do { 667 unlock_buffer(bh); 668 put_bh(bh); 669 bh = bh->b_this_page; 670 671 } while (bh != head); 672 673 return MIGRATEPAGE_SUCCESS; 674 } 675 EXPORT_SYMBOL(buffer_migrate_page); 676 #endif 677 678 /* 679 * Writeback a page to clean the dirty state 680 */ 681 static int writeout(struct address_space *mapping, struct page *page) 682 { 683 struct writeback_control wbc = { 684 .sync_mode = WB_SYNC_NONE, 685 .nr_to_write = 1, 686 .range_start = 0, 687 .range_end = LLONG_MAX, 688 .for_reclaim = 1 689 }; 690 int rc; 691 692 if (!mapping->a_ops->writepage) 693 /* No write method for the address space */ 694 return -EINVAL; 695 696 if (!clear_page_dirty_for_io(page)) 697 /* Someone else already triggered a write */ 698 return -EAGAIN; 699 700 /* 701 * A dirty page may imply that the underlying filesystem has 702 * the page on some queue. So the page must be clean for 703 * migration. Writeout may mean we loose the lock and the 704 * page state is no longer what we checked for earlier. 705 * At this point we know that the migration attempt cannot 706 * be successful. 707 */ 708 remove_migration_ptes(page, page, false); 709 710 rc = mapping->a_ops->writepage(page, &wbc); 711 712 if (rc != AOP_WRITEPAGE_ACTIVATE) 713 /* unlocked. Relock */ 714 lock_page(page); 715 716 return (rc < 0) ? -EIO : -EAGAIN; 717 } 718 719 /* 720 * Default handling if a filesystem does not provide a migration function. 721 */ 722 static int fallback_migrate_page(struct address_space *mapping, 723 struct page *newpage, struct page *page, enum migrate_mode mode) 724 { 725 if (PageDirty(page)) { 726 /* Only writeback pages in full synchronous migration */ 727 if (mode != MIGRATE_SYNC) 728 return -EBUSY; 729 return writeout(mapping, page); 730 } 731 732 /* 733 * Buffers may be managed in a filesystem specific way. 734 * We must have no buffers or drop them. 735 */ 736 if (page_has_private(page) && 737 !try_to_release_page(page, GFP_KERNEL)) 738 return -EAGAIN; 739 740 return migrate_page(mapping, newpage, page, mode); 741 } 742 743 /* 744 * Move a page to a newly allocated page 745 * The page is locked and all ptes have been successfully removed. 746 * 747 * The new page will have replaced the old page if this function 748 * is successful. 749 * 750 * Return value: 751 * < 0 - error code 752 * MIGRATEPAGE_SUCCESS - success 753 */ 754 static int move_to_new_page(struct page *newpage, struct page *page, 755 enum migrate_mode mode) 756 { 757 struct address_space *mapping; 758 int rc; 759 760 VM_BUG_ON_PAGE(!PageLocked(page), page); 761 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); 762 763 mapping = page_mapping(page); 764 if (!mapping) 765 rc = migrate_page(mapping, newpage, page, mode); 766 else if (mapping->a_ops->migratepage) 767 /* 768 * Most pages have a mapping and most filesystems provide a 769 * migratepage callback. Anonymous pages are part of swap 770 * space which also has its own migratepage callback. This 771 * is the most common path for page migration. 772 */ 773 rc = mapping->a_ops->migratepage(mapping, newpage, page, mode); 774 else 775 rc = fallback_migrate_page(mapping, newpage, page, mode); 776 777 /* 778 * When successful, old pagecache page->mapping must be cleared before 779 * page is freed; but stats require that PageAnon be left as PageAnon. 780 */ 781 if (rc == MIGRATEPAGE_SUCCESS) { 782 if (!PageAnon(page)) 783 page->mapping = NULL; 784 } 785 return rc; 786 } 787 788 static int __unmap_and_move(struct page *page, struct page *newpage, 789 int force, enum migrate_mode mode) 790 { 791 int rc = -EAGAIN; 792 int page_was_mapped = 0; 793 struct anon_vma *anon_vma = NULL; 794 795 if (!trylock_page(page)) { 796 if (!force || mode == MIGRATE_ASYNC) 797 goto out; 798 799 /* 800 * It's not safe for direct compaction to call lock_page. 801 * For example, during page readahead pages are added locked 802 * to the LRU. Later, when the IO completes the pages are 803 * marked uptodate and unlocked. However, the queueing 804 * could be merging multiple pages for one bio (e.g. 805 * mpage_readpages). If an allocation happens for the 806 * second or third page, the process can end up locking 807 * the same page twice and deadlocking. Rather than 808 * trying to be clever about what pages can be locked, 809 * avoid the use of lock_page for direct compaction 810 * altogether. 811 */ 812 if (current->flags & PF_MEMALLOC) 813 goto out; 814 815 lock_page(page); 816 } 817 818 if (PageWriteback(page)) { 819 /* 820 * Only in the case of a full synchronous migration is it 821 * necessary to wait for PageWriteback. In the async case, 822 * the retry loop is too short and in the sync-light case, 823 * the overhead of stalling is too much 824 */ 825 if (mode != MIGRATE_SYNC) { 826 rc = -EBUSY; 827 goto out_unlock; 828 } 829 if (!force) 830 goto out_unlock; 831 wait_on_page_writeback(page); 832 } 833 834 /* 835 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case, 836 * we cannot notice that anon_vma is freed while we migrates a page. 837 * This get_anon_vma() delays freeing anon_vma pointer until the end 838 * of migration. File cache pages are no problem because of page_lock() 839 * File Caches may use write_page() or lock_page() in migration, then, 840 * just care Anon page here. 841 * 842 * Only page_get_anon_vma() understands the subtleties of 843 * getting a hold on an anon_vma from outside one of its mms. 844 * But if we cannot get anon_vma, then we won't need it anyway, 845 * because that implies that the anon page is no longer mapped 846 * (and cannot be remapped so long as we hold the page lock). 847 */ 848 if (PageAnon(page) && !PageKsm(page)) 849 anon_vma = page_get_anon_vma(page); 850 851 /* 852 * Block others from accessing the new page when we get around to 853 * establishing additional references. We are usually the only one 854 * holding a reference to newpage at this point. We used to have a BUG 855 * here if trylock_page(newpage) fails, but would like to allow for 856 * cases where there might be a race with the previous use of newpage. 857 * This is much like races on refcount of oldpage: just don't BUG(). 858 */ 859 if (unlikely(!trylock_page(newpage))) 860 goto out_unlock; 861 862 if (unlikely(isolated_balloon_page(page))) { 863 /* 864 * A ballooned page does not need any special attention from 865 * physical to virtual reverse mapping procedures. 866 * Skip any attempt to unmap PTEs or to remap swap cache, 867 * in order to avoid burning cycles at rmap level, and perform 868 * the page migration right away (proteced by page lock). 869 */ 870 rc = balloon_page_migrate(newpage, page, mode); 871 goto out_unlock_both; 872 } 873 874 /* 875 * Corner case handling: 876 * 1. When a new swap-cache page is read into, it is added to the LRU 877 * and treated as swapcache but it has no rmap yet. 878 * Calling try_to_unmap() against a page->mapping==NULL page will 879 * trigger a BUG. So handle it here. 880 * 2. An orphaned page (see truncate_complete_page) might have 881 * fs-private metadata. The page can be picked up due to memory 882 * offlining. Everywhere else except page reclaim, the page is 883 * invisible to the vm, so the page can not be migrated. So try to 884 * free the metadata, so the page can be freed. 885 */ 886 if (!page->mapping) { 887 VM_BUG_ON_PAGE(PageAnon(page), page); 888 if (page_has_private(page)) { 889 try_to_free_buffers(page); 890 goto out_unlock_both; 891 } 892 } else if (page_mapped(page)) { 893 /* Establish migration ptes */ 894 VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma, 895 page); 896 try_to_unmap(page, 897 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); 898 page_was_mapped = 1; 899 } 900 901 if (!page_mapped(page)) 902 rc = move_to_new_page(newpage, page, mode); 903 904 if (page_was_mapped) 905 remove_migration_ptes(page, 906 rc == MIGRATEPAGE_SUCCESS ? newpage : page, false); 907 908 out_unlock_both: 909 unlock_page(newpage); 910 out_unlock: 911 /* Drop an anon_vma reference if we took one */ 912 if (anon_vma) 913 put_anon_vma(anon_vma); 914 unlock_page(page); 915 out: 916 return rc; 917 } 918 919 /* 920 * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move(). Work 921 * around it. 922 */ 923 #if (GCC_VERSION >= 40700 && GCC_VERSION < 40900) && defined(CONFIG_ARM) 924 #define ICE_noinline noinline 925 #else 926 #define ICE_noinline 927 #endif 928 929 /* 930 * Obtain the lock on page, remove all ptes and migrate the page 931 * to the newly allocated page in newpage. 932 */ 933 static ICE_noinline int unmap_and_move(new_page_t get_new_page, 934 free_page_t put_new_page, 935 unsigned long private, struct page *page, 936 int force, enum migrate_mode mode, 937 enum migrate_reason reason) 938 { 939 int rc = MIGRATEPAGE_SUCCESS; 940 int *result = NULL; 941 struct page *newpage; 942 943 newpage = get_new_page(page, private, &result); 944 if (!newpage) 945 return -ENOMEM; 946 947 if (page_count(page) == 1) { 948 /* page was freed from under us. So we are done. */ 949 goto out; 950 } 951 952 if (unlikely(PageTransHuge(page))) { 953 lock_page(page); 954 rc = split_huge_page(page); 955 unlock_page(page); 956 if (rc) 957 goto out; 958 } 959 960 rc = __unmap_and_move(page, newpage, force, mode); 961 if (rc == MIGRATEPAGE_SUCCESS) { 962 put_new_page = NULL; 963 set_page_owner_migrate_reason(newpage, reason); 964 } 965 966 out: 967 if (rc != -EAGAIN) { 968 /* 969 * A page that has been migrated has all references 970 * removed and will be freed. A page that has not been 971 * migrated will have kepts its references and be 972 * restored. 973 */ 974 list_del(&page->lru); 975 dec_zone_page_state(page, NR_ISOLATED_ANON + 976 page_is_file_cache(page)); 977 /* Soft-offlined page shouldn't go through lru cache list */ 978 if (reason == MR_MEMORY_FAILURE) { 979 put_page(page); 980 if (!test_set_page_hwpoison(page)) 981 num_poisoned_pages_inc(); 982 } else 983 putback_lru_page(page); 984 } 985 986 /* 987 * If migration was not successful and there's a freeing callback, use 988 * it. Otherwise, putback_lru_page() will drop the reference grabbed 989 * during isolation. 990 */ 991 if (put_new_page) 992 put_new_page(newpage, private); 993 else if (unlikely(__is_movable_balloon_page(newpage))) { 994 /* drop our reference, page already in the balloon */ 995 put_page(newpage); 996 } else 997 putback_lru_page(newpage); 998 999 if (result) { 1000 if (rc) 1001 *result = rc; 1002 else 1003 *result = page_to_nid(newpage); 1004 } 1005 return rc; 1006 } 1007 1008 /* 1009 * Counterpart of unmap_and_move_page() for hugepage migration. 1010 * 1011 * This function doesn't wait the completion of hugepage I/O 1012 * because there is no race between I/O and migration for hugepage. 1013 * Note that currently hugepage I/O occurs only in direct I/O 1014 * where no lock is held and PG_writeback is irrelevant, 1015 * and writeback status of all subpages are counted in the reference 1016 * count of the head page (i.e. if all subpages of a 2MB hugepage are 1017 * under direct I/O, the reference of the head page is 512 and a bit more.) 1018 * This means that when we try to migrate hugepage whose subpages are 1019 * doing direct I/O, some references remain after try_to_unmap() and 1020 * hugepage migration fails without data corruption. 1021 * 1022 * There is also no race when direct I/O is issued on the page under migration, 1023 * because then pte is replaced with migration swap entry and direct I/O code 1024 * will wait in the page fault for migration to complete. 1025 */ 1026 static int unmap_and_move_huge_page(new_page_t get_new_page, 1027 free_page_t put_new_page, unsigned long private, 1028 struct page *hpage, int force, 1029 enum migrate_mode mode, int reason) 1030 { 1031 int rc = -EAGAIN; 1032 int *result = NULL; 1033 int page_was_mapped = 0; 1034 struct page *new_hpage; 1035 struct anon_vma *anon_vma = NULL; 1036 1037 /* 1038 * Movability of hugepages depends on architectures and hugepage size. 1039 * This check is necessary because some callers of hugepage migration 1040 * like soft offline and memory hotremove don't walk through page 1041 * tables or check whether the hugepage is pmd-based or not before 1042 * kicking migration. 1043 */ 1044 if (!hugepage_migration_supported(page_hstate(hpage))) { 1045 putback_active_hugepage(hpage); 1046 return -ENOSYS; 1047 } 1048 1049 new_hpage = get_new_page(hpage, private, &result); 1050 if (!new_hpage) 1051 return -ENOMEM; 1052 1053 if (!trylock_page(hpage)) { 1054 if (!force || mode != MIGRATE_SYNC) 1055 goto out; 1056 lock_page(hpage); 1057 } 1058 1059 if (PageAnon(hpage)) 1060 anon_vma = page_get_anon_vma(hpage); 1061 1062 if (unlikely(!trylock_page(new_hpage))) 1063 goto put_anon; 1064 1065 if (page_mapped(hpage)) { 1066 try_to_unmap(hpage, 1067 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); 1068 page_was_mapped = 1; 1069 } 1070 1071 if (!page_mapped(hpage)) 1072 rc = move_to_new_page(new_hpage, hpage, mode); 1073 1074 if (page_was_mapped) 1075 remove_migration_ptes(hpage, 1076 rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false); 1077 1078 unlock_page(new_hpage); 1079 1080 put_anon: 1081 if (anon_vma) 1082 put_anon_vma(anon_vma); 1083 1084 if (rc == MIGRATEPAGE_SUCCESS) { 1085 hugetlb_cgroup_migrate(hpage, new_hpage); 1086 put_new_page = NULL; 1087 set_page_owner_migrate_reason(new_hpage, reason); 1088 } 1089 1090 unlock_page(hpage); 1091 out: 1092 if (rc != -EAGAIN) 1093 putback_active_hugepage(hpage); 1094 1095 /* 1096 * If migration was not successful and there's a freeing callback, use 1097 * it. Otherwise, put_page() will drop the reference grabbed during 1098 * isolation. 1099 */ 1100 if (put_new_page) 1101 put_new_page(new_hpage, private); 1102 else 1103 putback_active_hugepage(new_hpage); 1104 1105 if (result) { 1106 if (rc) 1107 *result = rc; 1108 else 1109 *result = page_to_nid(new_hpage); 1110 } 1111 return rc; 1112 } 1113 1114 /* 1115 * migrate_pages - migrate the pages specified in a list, to the free pages 1116 * supplied as the target for the page migration 1117 * 1118 * @from: The list of pages to be migrated. 1119 * @get_new_page: The function used to allocate free pages to be used 1120 * as the target of the page migration. 1121 * @put_new_page: The function used to free target pages if migration 1122 * fails, or NULL if no special handling is necessary. 1123 * @private: Private data to be passed on to get_new_page() 1124 * @mode: The migration mode that specifies the constraints for 1125 * page migration, if any. 1126 * @reason: The reason for page migration. 1127 * 1128 * The function returns after 10 attempts or if no pages are movable any more 1129 * because the list has become empty or no retryable pages exist any more. 1130 * The caller should call putback_movable_pages() to return pages to the LRU 1131 * or free list only if ret != 0. 1132 * 1133 * Returns the number of pages that were not migrated, or an error code. 1134 */ 1135 int migrate_pages(struct list_head *from, new_page_t get_new_page, 1136 free_page_t put_new_page, unsigned long private, 1137 enum migrate_mode mode, int reason) 1138 { 1139 int retry = 1; 1140 int nr_failed = 0; 1141 int nr_succeeded = 0; 1142 int pass = 0; 1143 struct page *page; 1144 struct page *page2; 1145 int swapwrite = current->flags & PF_SWAPWRITE; 1146 int rc; 1147 1148 if (!swapwrite) 1149 current->flags |= PF_SWAPWRITE; 1150 1151 for(pass = 0; pass < 10 && retry; pass++) { 1152 retry = 0; 1153 1154 list_for_each_entry_safe(page, page2, from, lru) { 1155 cond_resched(); 1156 1157 if (PageHuge(page)) 1158 rc = unmap_and_move_huge_page(get_new_page, 1159 put_new_page, private, page, 1160 pass > 2, mode, reason); 1161 else 1162 rc = unmap_and_move(get_new_page, put_new_page, 1163 private, page, pass > 2, mode, 1164 reason); 1165 1166 switch(rc) { 1167 case -ENOMEM: 1168 goto out; 1169 case -EAGAIN: 1170 retry++; 1171 break; 1172 case MIGRATEPAGE_SUCCESS: 1173 nr_succeeded++; 1174 break; 1175 default: 1176 /* 1177 * Permanent failure (-EBUSY, -ENOSYS, etc.): 1178 * unlike -EAGAIN case, the failed page is 1179 * removed from migration page list and not 1180 * retried in the next outer loop. 1181 */ 1182 nr_failed++; 1183 break; 1184 } 1185 } 1186 } 1187 nr_failed += retry; 1188 rc = nr_failed; 1189 out: 1190 if (nr_succeeded) 1191 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded); 1192 if (nr_failed) 1193 count_vm_events(PGMIGRATE_FAIL, nr_failed); 1194 trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason); 1195 1196 if (!swapwrite) 1197 current->flags &= ~PF_SWAPWRITE; 1198 1199 return rc; 1200 } 1201 1202 #ifdef CONFIG_NUMA 1203 /* 1204 * Move a list of individual pages 1205 */ 1206 struct page_to_node { 1207 unsigned long addr; 1208 struct page *page; 1209 int node; 1210 int status; 1211 }; 1212 1213 static struct page *new_page_node(struct page *p, unsigned long private, 1214 int **result) 1215 { 1216 struct page_to_node *pm = (struct page_to_node *)private; 1217 1218 while (pm->node != MAX_NUMNODES && pm->page != p) 1219 pm++; 1220 1221 if (pm->node == MAX_NUMNODES) 1222 return NULL; 1223 1224 *result = &pm->status; 1225 1226 if (PageHuge(p)) 1227 return alloc_huge_page_node(page_hstate(compound_head(p)), 1228 pm->node); 1229 else 1230 return __alloc_pages_node(pm->node, 1231 GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, 0); 1232 } 1233 1234 /* 1235 * Move a set of pages as indicated in the pm array. The addr 1236 * field must be set to the virtual address of the page to be moved 1237 * and the node number must contain a valid target node. 1238 * The pm array ends with node = MAX_NUMNODES. 1239 */ 1240 static int do_move_page_to_node_array(struct mm_struct *mm, 1241 struct page_to_node *pm, 1242 int migrate_all) 1243 { 1244 int err; 1245 struct page_to_node *pp; 1246 LIST_HEAD(pagelist); 1247 1248 down_read(&mm->mmap_sem); 1249 1250 /* 1251 * Build a list of pages to migrate 1252 */ 1253 for (pp = pm; pp->node != MAX_NUMNODES; pp++) { 1254 struct vm_area_struct *vma; 1255 struct page *page; 1256 1257 err = -EFAULT; 1258 vma = find_vma(mm, pp->addr); 1259 if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma)) 1260 goto set_status; 1261 1262 /* FOLL_DUMP to ignore special (like zero) pages */ 1263 page = follow_page(vma, pp->addr, 1264 FOLL_GET | FOLL_SPLIT | FOLL_DUMP); 1265 1266 err = PTR_ERR(page); 1267 if (IS_ERR(page)) 1268 goto set_status; 1269 1270 err = -ENOENT; 1271 if (!page) 1272 goto set_status; 1273 1274 pp->page = page; 1275 err = page_to_nid(page); 1276 1277 if (err == pp->node) 1278 /* 1279 * Node already in the right place 1280 */ 1281 goto put_and_set; 1282 1283 err = -EACCES; 1284 if (page_mapcount(page) > 1 && 1285 !migrate_all) 1286 goto put_and_set; 1287 1288 if (PageHuge(page)) { 1289 if (PageHead(page)) 1290 isolate_huge_page(page, &pagelist); 1291 goto put_and_set; 1292 } 1293 1294 err = isolate_lru_page(page); 1295 if (!err) { 1296 list_add_tail(&page->lru, &pagelist); 1297 inc_zone_page_state(page, NR_ISOLATED_ANON + 1298 page_is_file_cache(page)); 1299 } 1300 put_and_set: 1301 /* 1302 * Either remove the duplicate refcount from 1303 * isolate_lru_page() or drop the page ref if it was 1304 * not isolated. 1305 */ 1306 put_page(page); 1307 set_status: 1308 pp->status = err; 1309 } 1310 1311 err = 0; 1312 if (!list_empty(&pagelist)) { 1313 err = migrate_pages(&pagelist, new_page_node, NULL, 1314 (unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL); 1315 if (err) 1316 putback_movable_pages(&pagelist); 1317 } 1318 1319 up_read(&mm->mmap_sem); 1320 return err; 1321 } 1322 1323 /* 1324 * Migrate an array of page address onto an array of nodes and fill 1325 * the corresponding array of status. 1326 */ 1327 static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, 1328 unsigned long nr_pages, 1329 const void __user * __user *pages, 1330 const int __user *nodes, 1331 int __user *status, int flags) 1332 { 1333 struct page_to_node *pm; 1334 unsigned long chunk_nr_pages; 1335 unsigned long chunk_start; 1336 int err; 1337 1338 err = -ENOMEM; 1339 pm = (struct page_to_node *)__get_free_page(GFP_KERNEL); 1340 if (!pm) 1341 goto out; 1342 1343 migrate_prep(); 1344 1345 /* 1346 * Store a chunk of page_to_node array in a page, 1347 * but keep the last one as a marker 1348 */ 1349 chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1; 1350 1351 for (chunk_start = 0; 1352 chunk_start < nr_pages; 1353 chunk_start += chunk_nr_pages) { 1354 int j; 1355 1356 if (chunk_start + chunk_nr_pages > nr_pages) 1357 chunk_nr_pages = nr_pages - chunk_start; 1358 1359 /* fill the chunk pm with addrs and nodes from user-space */ 1360 for (j = 0; j < chunk_nr_pages; j++) { 1361 const void __user *p; 1362 int node; 1363 1364 err = -EFAULT; 1365 if (get_user(p, pages + j + chunk_start)) 1366 goto out_pm; 1367 pm[j].addr = (unsigned long) p; 1368 1369 if (get_user(node, nodes + j + chunk_start)) 1370 goto out_pm; 1371 1372 err = -ENODEV; 1373 if (node < 0 || node >= MAX_NUMNODES) 1374 goto out_pm; 1375 1376 if (!node_state(node, N_MEMORY)) 1377 goto out_pm; 1378 1379 err = -EACCES; 1380 if (!node_isset(node, task_nodes)) 1381 goto out_pm; 1382 1383 pm[j].node = node; 1384 } 1385 1386 /* End marker for this chunk */ 1387 pm[chunk_nr_pages].node = MAX_NUMNODES; 1388 1389 /* Migrate this chunk */ 1390 err = do_move_page_to_node_array(mm, pm, 1391 flags & MPOL_MF_MOVE_ALL); 1392 if (err < 0) 1393 goto out_pm; 1394 1395 /* Return status information */ 1396 for (j = 0; j < chunk_nr_pages; j++) 1397 if (put_user(pm[j].status, status + j + chunk_start)) { 1398 err = -EFAULT; 1399 goto out_pm; 1400 } 1401 } 1402 err = 0; 1403 1404 out_pm: 1405 free_page((unsigned long)pm); 1406 out: 1407 return err; 1408 } 1409 1410 /* 1411 * Determine the nodes of an array of pages and store it in an array of status. 1412 */ 1413 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, 1414 const void __user **pages, int *status) 1415 { 1416 unsigned long i; 1417 1418 down_read(&mm->mmap_sem); 1419 1420 for (i = 0; i < nr_pages; i++) { 1421 unsigned long addr = (unsigned long)(*pages); 1422 struct vm_area_struct *vma; 1423 struct page *page; 1424 int err = -EFAULT; 1425 1426 vma = find_vma(mm, addr); 1427 if (!vma || addr < vma->vm_start) 1428 goto set_status; 1429 1430 /* FOLL_DUMP to ignore special (like zero) pages */ 1431 page = follow_page(vma, addr, FOLL_DUMP); 1432 1433 err = PTR_ERR(page); 1434 if (IS_ERR(page)) 1435 goto set_status; 1436 1437 err = page ? page_to_nid(page) : -ENOENT; 1438 set_status: 1439 *status = err; 1440 1441 pages++; 1442 status++; 1443 } 1444 1445 up_read(&mm->mmap_sem); 1446 } 1447 1448 /* 1449 * Determine the nodes of a user array of pages and store it in 1450 * a user array of status. 1451 */ 1452 static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, 1453 const void __user * __user *pages, 1454 int __user *status) 1455 { 1456 #define DO_PAGES_STAT_CHUNK_NR 16 1457 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR]; 1458 int chunk_status[DO_PAGES_STAT_CHUNK_NR]; 1459 1460 while (nr_pages) { 1461 unsigned long chunk_nr; 1462 1463 chunk_nr = nr_pages; 1464 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR) 1465 chunk_nr = DO_PAGES_STAT_CHUNK_NR; 1466 1467 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages))) 1468 break; 1469 1470 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status); 1471 1472 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status))) 1473 break; 1474 1475 pages += chunk_nr; 1476 status += chunk_nr; 1477 nr_pages -= chunk_nr; 1478 } 1479 return nr_pages ? -EFAULT : 0; 1480 } 1481 1482 /* 1483 * Move a list of pages in the address space of the currently executing 1484 * process. 1485 */ 1486 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages, 1487 const void __user * __user *, pages, 1488 const int __user *, nodes, 1489 int __user *, status, int, flags) 1490 { 1491 const struct cred *cred = current_cred(), *tcred; 1492 struct task_struct *task; 1493 struct mm_struct *mm; 1494 int err; 1495 nodemask_t task_nodes; 1496 1497 /* Check flags */ 1498 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL)) 1499 return -EINVAL; 1500 1501 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE)) 1502 return -EPERM; 1503 1504 /* Find the mm_struct */ 1505 rcu_read_lock(); 1506 task = pid ? find_task_by_vpid(pid) : current; 1507 if (!task) { 1508 rcu_read_unlock(); 1509 return -ESRCH; 1510 } 1511 get_task_struct(task); 1512 1513 /* 1514 * Check if this process has the right to modify the specified 1515 * process. The right exists if the process has administrative 1516 * capabilities, superuser privileges or the same 1517 * userid as the target process. 1518 */ 1519 tcred = __task_cred(task); 1520 if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) && 1521 !uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) && 1522 !capable(CAP_SYS_NICE)) { 1523 rcu_read_unlock(); 1524 err = -EPERM; 1525 goto out; 1526 } 1527 rcu_read_unlock(); 1528 1529 err = security_task_movememory(task); 1530 if (err) 1531 goto out; 1532 1533 task_nodes = cpuset_mems_allowed(task); 1534 mm = get_task_mm(task); 1535 put_task_struct(task); 1536 1537 if (!mm) 1538 return -EINVAL; 1539 1540 if (nodes) 1541 err = do_pages_move(mm, task_nodes, nr_pages, pages, 1542 nodes, status, flags); 1543 else 1544 err = do_pages_stat(mm, nr_pages, pages, status); 1545 1546 mmput(mm); 1547 return err; 1548 1549 out: 1550 put_task_struct(task); 1551 return err; 1552 } 1553 1554 #ifdef CONFIG_NUMA_BALANCING 1555 /* 1556 * Returns true if this is a safe migration target node for misplaced NUMA 1557 * pages. Currently it only checks the watermarks which crude 1558 */ 1559 static bool migrate_balanced_pgdat(struct pglist_data *pgdat, 1560 unsigned long nr_migrate_pages) 1561 { 1562 int z; 1563 for (z = pgdat->nr_zones - 1; z >= 0; z--) { 1564 struct zone *zone = pgdat->node_zones + z; 1565 1566 if (!populated_zone(zone)) 1567 continue; 1568 1569 if (!zone_reclaimable(zone)) 1570 continue; 1571 1572 /* Avoid waking kswapd by allocating pages_to_migrate pages. */ 1573 if (!zone_watermark_ok(zone, 0, 1574 high_wmark_pages(zone) + 1575 nr_migrate_pages, 1576 0, 0)) 1577 continue; 1578 return true; 1579 } 1580 return false; 1581 } 1582 1583 static struct page *alloc_misplaced_dst_page(struct page *page, 1584 unsigned long data, 1585 int **result) 1586 { 1587 int nid = (int) data; 1588 struct page *newpage; 1589 1590 newpage = __alloc_pages_node(nid, 1591 (GFP_HIGHUSER_MOVABLE | 1592 __GFP_THISNODE | __GFP_NOMEMALLOC | 1593 __GFP_NORETRY | __GFP_NOWARN) & 1594 ~__GFP_RECLAIM, 0); 1595 1596 return newpage; 1597 } 1598 1599 /* 1600 * page migration rate limiting control. 1601 * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs 1602 * window of time. Default here says do not migrate more than 1280M per second. 1603 */ 1604 static unsigned int migrate_interval_millisecs __read_mostly = 100; 1605 static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT); 1606 1607 /* Returns true if the node is migrate rate-limited after the update */ 1608 static bool numamigrate_update_ratelimit(pg_data_t *pgdat, 1609 unsigned long nr_pages) 1610 { 1611 /* 1612 * Rate-limit the amount of data that is being migrated to a node. 1613 * Optimal placement is no good if the memory bus is saturated and 1614 * all the time is being spent migrating! 1615 */ 1616 if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) { 1617 spin_lock(&pgdat->numabalancing_migrate_lock); 1618 pgdat->numabalancing_migrate_nr_pages = 0; 1619 pgdat->numabalancing_migrate_next_window = jiffies + 1620 msecs_to_jiffies(migrate_interval_millisecs); 1621 spin_unlock(&pgdat->numabalancing_migrate_lock); 1622 } 1623 if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages) { 1624 trace_mm_numa_migrate_ratelimit(current, pgdat->node_id, 1625 nr_pages); 1626 return true; 1627 } 1628 1629 /* 1630 * This is an unlocked non-atomic update so errors are possible. 1631 * The consequences are failing to migrate when we potentiall should 1632 * have which is not severe enough to warrant locking. If it is ever 1633 * a problem, it can be converted to a per-cpu counter. 1634 */ 1635 pgdat->numabalancing_migrate_nr_pages += nr_pages; 1636 return false; 1637 } 1638 1639 static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) 1640 { 1641 int page_lru; 1642 1643 VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page); 1644 1645 /* Avoid migrating to a node that is nearly full */ 1646 if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page))) 1647 return 0; 1648 1649 if (isolate_lru_page(page)) 1650 return 0; 1651 1652 /* 1653 * migrate_misplaced_transhuge_page() skips page migration's usual 1654 * check on page_count(), so we must do it here, now that the page 1655 * has been isolated: a GUP pin, or any other pin, prevents migration. 1656 * The expected page count is 3: 1 for page's mapcount and 1 for the 1657 * caller's pin and 1 for the reference taken by isolate_lru_page(). 1658 */ 1659 if (PageTransHuge(page) && page_count(page) != 3) { 1660 putback_lru_page(page); 1661 return 0; 1662 } 1663 1664 page_lru = page_is_file_cache(page); 1665 mod_zone_page_state(page_zone(page), NR_ISOLATED_ANON + page_lru, 1666 hpage_nr_pages(page)); 1667 1668 /* 1669 * Isolating the page has taken another reference, so the 1670 * caller's reference can be safely dropped without the page 1671 * disappearing underneath us during migration. 1672 */ 1673 put_page(page); 1674 return 1; 1675 } 1676 1677 bool pmd_trans_migrating(pmd_t pmd) 1678 { 1679 struct page *page = pmd_page(pmd); 1680 return PageLocked(page); 1681 } 1682 1683 /* 1684 * Attempt to migrate a misplaced page to the specified destination 1685 * node. Caller is expected to have an elevated reference count on 1686 * the page that will be dropped by this function before returning. 1687 */ 1688 int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma, 1689 int node) 1690 { 1691 pg_data_t *pgdat = NODE_DATA(node); 1692 int isolated; 1693 int nr_remaining; 1694 LIST_HEAD(migratepages); 1695 1696 /* 1697 * Don't migrate file pages that are mapped in multiple processes 1698 * with execute permissions as they are probably shared libraries. 1699 */ 1700 if (page_mapcount(page) != 1 && page_is_file_cache(page) && 1701 (vma->vm_flags & VM_EXEC)) 1702 goto out; 1703 1704 /* 1705 * Rate-limit the amount of data that is being migrated to a node. 1706 * Optimal placement is no good if the memory bus is saturated and 1707 * all the time is being spent migrating! 1708 */ 1709 if (numamigrate_update_ratelimit(pgdat, 1)) 1710 goto out; 1711 1712 isolated = numamigrate_isolate_page(pgdat, page); 1713 if (!isolated) 1714 goto out; 1715 1716 list_add(&page->lru, &migratepages); 1717 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page, 1718 NULL, node, MIGRATE_ASYNC, 1719 MR_NUMA_MISPLACED); 1720 if (nr_remaining) { 1721 if (!list_empty(&migratepages)) { 1722 list_del(&page->lru); 1723 dec_zone_page_state(page, NR_ISOLATED_ANON + 1724 page_is_file_cache(page)); 1725 putback_lru_page(page); 1726 } 1727 isolated = 0; 1728 } else 1729 count_vm_numa_event(NUMA_PAGE_MIGRATE); 1730 BUG_ON(!list_empty(&migratepages)); 1731 return isolated; 1732 1733 out: 1734 put_page(page); 1735 return 0; 1736 } 1737 #endif /* CONFIG_NUMA_BALANCING */ 1738 1739 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE) 1740 /* 1741 * Migrates a THP to a given target node. page must be locked and is unlocked 1742 * before returning. 1743 */ 1744 int migrate_misplaced_transhuge_page(struct mm_struct *mm, 1745 struct vm_area_struct *vma, 1746 pmd_t *pmd, pmd_t entry, 1747 unsigned long address, 1748 struct page *page, int node) 1749 { 1750 spinlock_t *ptl; 1751 pg_data_t *pgdat = NODE_DATA(node); 1752 int isolated = 0; 1753 struct page *new_page = NULL; 1754 int page_lru = page_is_file_cache(page); 1755 unsigned long mmun_start = address & HPAGE_PMD_MASK; 1756 unsigned long mmun_end = mmun_start + HPAGE_PMD_SIZE; 1757 pmd_t orig_entry; 1758 1759 /* 1760 * Rate-limit the amount of data that is being migrated to a node. 1761 * Optimal placement is no good if the memory bus is saturated and 1762 * all the time is being spent migrating! 1763 */ 1764 if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR)) 1765 goto out_dropref; 1766 1767 new_page = alloc_pages_node(node, 1768 (GFP_TRANSHUGE | __GFP_THISNODE) & ~__GFP_RECLAIM, 1769 HPAGE_PMD_ORDER); 1770 if (!new_page) 1771 goto out_fail; 1772 prep_transhuge_page(new_page); 1773 1774 isolated = numamigrate_isolate_page(pgdat, page); 1775 if (!isolated) { 1776 put_page(new_page); 1777 goto out_fail; 1778 } 1779 /* 1780 * We are not sure a pending tlb flush here is for a huge page 1781 * mapping or not. Hence use the tlb range variant 1782 */ 1783 if (mm_tlb_flush_pending(mm)) 1784 flush_tlb_range(vma, mmun_start, mmun_end); 1785 1786 /* Prepare a page as a migration target */ 1787 __SetPageLocked(new_page); 1788 SetPageSwapBacked(new_page); 1789 1790 /* anon mapping, we can simply copy page->mapping to the new page: */ 1791 new_page->mapping = page->mapping; 1792 new_page->index = page->index; 1793 migrate_page_copy(new_page, page); 1794 WARN_ON(PageLRU(new_page)); 1795 1796 /* Recheck the target PMD */ 1797 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1798 ptl = pmd_lock(mm, pmd); 1799 if (unlikely(!pmd_same(*pmd, entry) || page_count(page) != 2)) { 1800 fail_putback: 1801 spin_unlock(ptl); 1802 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1803 1804 /* Reverse changes made by migrate_page_copy() */ 1805 if (TestClearPageActive(new_page)) 1806 SetPageActive(page); 1807 if (TestClearPageUnevictable(new_page)) 1808 SetPageUnevictable(page); 1809 1810 unlock_page(new_page); 1811 put_page(new_page); /* Free it */ 1812 1813 /* Retake the callers reference and putback on LRU */ 1814 get_page(page); 1815 putback_lru_page(page); 1816 mod_zone_page_state(page_zone(page), 1817 NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR); 1818 1819 goto out_unlock; 1820 } 1821 1822 orig_entry = *pmd; 1823 entry = mk_pmd(new_page, vma->vm_page_prot); 1824 entry = pmd_mkhuge(entry); 1825 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1826 1827 /* 1828 * Clear the old entry under pagetable lock and establish the new PTE. 1829 * Any parallel GUP will either observe the old page blocking on the 1830 * page lock, block on the page table lock or observe the new page. 1831 * The SetPageUptodate on the new page and page_add_new_anon_rmap 1832 * guarantee the copy is visible before the pagetable update. 1833 */ 1834 flush_cache_range(vma, mmun_start, mmun_end); 1835 page_add_anon_rmap(new_page, vma, mmun_start, true); 1836 pmdp_huge_clear_flush_notify(vma, mmun_start, pmd); 1837 set_pmd_at(mm, mmun_start, pmd, entry); 1838 update_mmu_cache_pmd(vma, address, &entry); 1839 1840 if (page_count(page) != 2) { 1841 set_pmd_at(mm, mmun_start, pmd, orig_entry); 1842 flush_pmd_tlb_range(vma, mmun_start, mmun_end); 1843 mmu_notifier_invalidate_range(mm, mmun_start, mmun_end); 1844 update_mmu_cache_pmd(vma, address, &entry); 1845 page_remove_rmap(new_page, true); 1846 goto fail_putback; 1847 } 1848 1849 mlock_migrate_page(new_page, page); 1850 page_remove_rmap(page, true); 1851 set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED); 1852 1853 spin_unlock(ptl); 1854 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1855 1856 /* Take an "isolate" reference and put new page on the LRU. */ 1857 get_page(new_page); 1858 putback_lru_page(new_page); 1859 1860 unlock_page(new_page); 1861 unlock_page(page); 1862 put_page(page); /* Drop the rmap reference */ 1863 put_page(page); /* Drop the LRU isolation reference */ 1864 1865 count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR); 1866 count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR); 1867 1868 mod_zone_page_state(page_zone(page), 1869 NR_ISOLATED_ANON + page_lru, 1870 -HPAGE_PMD_NR); 1871 return isolated; 1872 1873 out_fail: 1874 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR); 1875 out_dropref: 1876 ptl = pmd_lock(mm, pmd); 1877 if (pmd_same(*pmd, entry)) { 1878 entry = pmd_modify(entry, vma->vm_page_prot); 1879 set_pmd_at(mm, mmun_start, pmd, entry); 1880 update_mmu_cache_pmd(vma, address, &entry); 1881 } 1882 spin_unlock(ptl); 1883 1884 out_unlock: 1885 unlock_page(page); 1886 put_page(page); 1887 return 0; 1888 } 1889 #endif /* CONFIG_NUMA_BALANCING */ 1890 1891 #endif /* CONFIG_NUMA */ 1892