1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Memory Migration functionality - linux/mm/migrate.c 4 * 5 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter 6 * 7 * Page migration was first developed in the context of the memory hotplug 8 * project. The main authors of the migration code are: 9 * 10 * IWAMOTO Toshihiro <iwamoto@valinux.co.jp> 11 * Hirokazu Takahashi <taka@valinux.co.jp> 12 * Dave Hansen <haveblue@us.ibm.com> 13 * Christoph Lameter 14 */ 15 16 #include <linux/migrate.h> 17 #include <linux/export.h> 18 #include <linux/swap.h> 19 #include <linux/swapops.h> 20 #include <linux/pagemap.h> 21 #include <linux/buffer_head.h> 22 #include <linux/mm_inline.h> 23 #include <linux/nsproxy.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/compaction.h> 35 #include <linux/syscalls.h> 36 #include <linux/compat.h> 37 #include <linux/hugetlb.h> 38 #include <linux/hugetlb_cgroup.h> 39 #include <linux/gfp.h> 40 #include <linux/pfn_t.h> 41 #include <linux/memremap.h> 42 #include <linux/userfaultfd_k.h> 43 #include <linux/balloon_compaction.h> 44 #include <linux/page_idle.h> 45 #include <linux/page_owner.h> 46 #include <linux/sched/mm.h> 47 #include <linux/ptrace.h> 48 #include <linux/oom.h> 49 #include <linux/memory.h> 50 #include <linux/random.h> 51 #include <linux/sched/sysctl.h> 52 #include <linux/memory-tiers.h> 53 54 #include <asm/tlbflush.h> 55 56 #include <trace/events/migrate.h> 57 58 #include "internal.h" 59 60 bool isolate_movable_page(struct page *page, isolate_mode_t mode) 61 { 62 struct folio *folio = folio_get_nontail_page(page); 63 const struct movable_operations *mops; 64 65 /* 66 * Avoid burning cycles with pages that are yet under __free_pages(), 67 * or just got freed under us. 68 * 69 * In case we 'win' a race for a movable page being freed under us and 70 * raise its refcount preventing __free_pages() from doing its job 71 * the put_page() at the end of this block will take care of 72 * release this page, thus avoiding a nasty leakage. 73 */ 74 if (!folio) 75 goto out; 76 77 if (unlikely(folio_test_slab(folio))) 78 goto out_putfolio; 79 /* Pairs with smp_wmb() in slab freeing, e.g. SLUB's __free_slab() */ 80 smp_rmb(); 81 /* 82 * Check movable flag before taking the page lock because 83 * we use non-atomic bitops on newly allocated page flags so 84 * unconditionally grabbing the lock ruins page's owner side. 85 */ 86 if (unlikely(!__folio_test_movable(folio))) 87 goto out_putfolio; 88 /* Pairs with smp_wmb() in slab allocation, e.g. SLUB's alloc_slab_page() */ 89 smp_rmb(); 90 if (unlikely(folio_test_slab(folio))) 91 goto out_putfolio; 92 93 /* 94 * As movable pages are not isolated from LRU lists, concurrent 95 * compaction threads can race against page migration functions 96 * as well as race against the releasing a page. 97 * 98 * In order to avoid having an already isolated movable page 99 * being (wrongly) re-isolated while it is under migration, 100 * or to avoid attempting to isolate pages being released, 101 * lets be sure we have the page lock 102 * before proceeding with the movable page isolation steps. 103 */ 104 if (unlikely(!folio_trylock(folio))) 105 goto out_putfolio; 106 107 if (!folio_test_movable(folio) || folio_test_isolated(folio)) 108 goto out_no_isolated; 109 110 mops = folio_movable_ops(folio); 111 VM_BUG_ON_FOLIO(!mops, folio); 112 113 if (!mops->isolate_page(&folio->page, mode)) 114 goto out_no_isolated; 115 116 /* Driver shouldn't use PG_isolated bit of page->flags */ 117 WARN_ON_ONCE(folio_test_isolated(folio)); 118 folio_set_isolated(folio); 119 folio_unlock(folio); 120 121 return true; 122 123 out_no_isolated: 124 folio_unlock(folio); 125 out_putfolio: 126 folio_put(folio); 127 out: 128 return false; 129 } 130 131 static void putback_movable_folio(struct folio *folio) 132 { 133 const struct movable_operations *mops = folio_movable_ops(folio); 134 135 mops->putback_page(&folio->page); 136 folio_clear_isolated(folio); 137 } 138 139 /* 140 * Put previously isolated pages back onto the appropriate lists 141 * from where they were once taken off for compaction/migration. 142 * 143 * This function shall be used whenever the isolated pageset has been 144 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range() 145 * and isolate_hugetlb(). 146 */ 147 void putback_movable_pages(struct list_head *l) 148 { 149 struct folio *folio; 150 struct folio *folio2; 151 152 list_for_each_entry_safe(folio, folio2, l, lru) { 153 if (unlikely(folio_test_hugetlb(folio))) { 154 folio_putback_active_hugetlb(folio); 155 continue; 156 } 157 list_del(&folio->lru); 158 /* 159 * We isolated non-lru movable folio so here we can use 160 * __PageMovable because LRU folio's mapping cannot have 161 * PAGE_MAPPING_MOVABLE. 162 */ 163 if (unlikely(__folio_test_movable(folio))) { 164 VM_BUG_ON_FOLIO(!folio_test_isolated(folio), folio); 165 folio_lock(folio); 166 if (folio_test_movable(folio)) 167 putback_movable_folio(folio); 168 else 169 folio_clear_isolated(folio); 170 folio_unlock(folio); 171 folio_put(folio); 172 } else { 173 node_stat_mod_folio(folio, NR_ISOLATED_ANON + 174 folio_is_file_lru(folio), -folio_nr_pages(folio)); 175 folio_putback_lru(folio); 176 } 177 } 178 } 179 180 /* 181 * Restore a potential migration pte to a working pte entry 182 */ 183 static bool remove_migration_pte(struct folio *folio, 184 struct vm_area_struct *vma, unsigned long addr, void *old) 185 { 186 DEFINE_FOLIO_VMA_WALK(pvmw, old, vma, addr, PVMW_SYNC | PVMW_MIGRATION); 187 188 while (page_vma_mapped_walk(&pvmw)) { 189 rmap_t rmap_flags = RMAP_NONE; 190 pte_t old_pte; 191 pte_t pte; 192 swp_entry_t entry; 193 struct page *new; 194 unsigned long idx = 0; 195 196 /* pgoff is invalid for ksm pages, but they are never large */ 197 if (folio_test_large(folio) && !folio_test_hugetlb(folio)) 198 idx = linear_page_index(vma, pvmw.address) - pvmw.pgoff; 199 new = folio_page(folio, idx); 200 201 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 202 /* PMD-mapped THP migration entry */ 203 if (!pvmw.pte) { 204 VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) || 205 !folio_test_pmd_mappable(folio), folio); 206 remove_migration_pmd(&pvmw, new); 207 continue; 208 } 209 #endif 210 211 folio_get(folio); 212 pte = mk_pte(new, READ_ONCE(vma->vm_page_prot)); 213 old_pte = ptep_get(pvmw.pte); 214 if (pte_swp_soft_dirty(old_pte)) 215 pte = pte_mksoft_dirty(pte); 216 217 entry = pte_to_swp_entry(old_pte); 218 if (!is_migration_entry_young(entry)) 219 pte = pte_mkold(pte); 220 if (folio_test_dirty(folio) && is_migration_entry_dirty(entry)) 221 pte = pte_mkdirty(pte); 222 if (is_writable_migration_entry(entry)) 223 pte = pte_mkwrite(pte); 224 else if (pte_swp_uffd_wp(old_pte)) 225 pte = pte_mkuffd_wp(pte); 226 227 if (folio_test_anon(folio) && !is_readable_migration_entry(entry)) 228 rmap_flags |= RMAP_EXCLUSIVE; 229 230 if (unlikely(is_device_private_page(new))) { 231 if (pte_write(pte)) 232 entry = make_writable_device_private_entry( 233 page_to_pfn(new)); 234 else 235 entry = make_readable_device_private_entry( 236 page_to_pfn(new)); 237 pte = swp_entry_to_pte(entry); 238 if (pte_swp_soft_dirty(old_pte)) 239 pte = pte_swp_mksoft_dirty(pte); 240 if (pte_swp_uffd_wp(old_pte)) 241 pte = pte_swp_mkuffd_wp(pte); 242 } 243 244 #ifdef CONFIG_HUGETLB_PAGE 245 if (folio_test_hugetlb(folio)) { 246 unsigned int shift = huge_page_shift(hstate_vma(vma)); 247 248 pte = arch_make_huge_pte(pte, shift, vma->vm_flags); 249 if (folio_test_anon(folio)) 250 hugepage_add_anon_rmap(new, vma, pvmw.address, 251 rmap_flags); 252 else 253 page_dup_file_rmap(new, true); 254 set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); 255 } else 256 #endif 257 { 258 if (folio_test_anon(folio)) 259 page_add_anon_rmap(new, vma, pvmw.address, 260 rmap_flags); 261 else 262 page_add_file_rmap(new, vma, false); 263 set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); 264 } 265 if (vma->vm_flags & VM_LOCKED) 266 mlock_drain_local(); 267 268 trace_remove_migration_pte(pvmw.address, pte_val(pte), 269 compound_order(new)); 270 271 /* No need to invalidate - it was non-present before */ 272 update_mmu_cache(vma, pvmw.address, pvmw.pte); 273 } 274 275 return true; 276 } 277 278 /* 279 * Get rid of all migration entries and replace them by 280 * references to the indicated page. 281 */ 282 void remove_migration_ptes(struct folio *src, struct folio *dst, bool locked) 283 { 284 struct rmap_walk_control rwc = { 285 .rmap_one = remove_migration_pte, 286 .arg = src, 287 }; 288 289 if (locked) 290 rmap_walk_locked(dst, &rwc); 291 else 292 rmap_walk(dst, &rwc); 293 } 294 295 /* 296 * Something used the pte of a page under migration. We need to 297 * get to the page and wait until migration is finished. 298 * When we return from this function the fault will be retried. 299 */ 300 void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, 301 unsigned long address) 302 { 303 spinlock_t *ptl; 304 pte_t *ptep; 305 pte_t pte; 306 swp_entry_t entry; 307 308 ptep = pte_offset_map_lock(mm, pmd, address, &ptl); 309 if (!ptep) 310 return; 311 312 pte = ptep_get(ptep); 313 pte_unmap(ptep); 314 315 if (!is_swap_pte(pte)) 316 goto out; 317 318 entry = pte_to_swp_entry(pte); 319 if (!is_migration_entry(entry)) 320 goto out; 321 322 migration_entry_wait_on_locked(entry, ptl); 323 return; 324 out: 325 spin_unlock(ptl); 326 } 327 328 #ifdef CONFIG_HUGETLB_PAGE 329 /* 330 * The vma read lock must be held upon entry. Holding that lock prevents either 331 * the pte or the ptl from being freed. 332 * 333 * This function will release the vma lock before returning. 334 */ 335 void migration_entry_wait_huge(struct vm_area_struct *vma, pte_t *ptep) 336 { 337 spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), vma->vm_mm, ptep); 338 pte_t pte; 339 340 hugetlb_vma_assert_locked(vma); 341 spin_lock(ptl); 342 pte = huge_ptep_get(ptep); 343 344 if (unlikely(!is_hugetlb_entry_migration(pte))) { 345 spin_unlock(ptl); 346 hugetlb_vma_unlock_read(vma); 347 } else { 348 /* 349 * If migration entry existed, safe to release vma lock 350 * here because the pgtable page won't be freed without the 351 * pgtable lock released. See comment right above pgtable 352 * lock release in migration_entry_wait_on_locked(). 353 */ 354 hugetlb_vma_unlock_read(vma); 355 migration_entry_wait_on_locked(pte_to_swp_entry(pte), ptl); 356 } 357 } 358 #endif 359 360 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 361 void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd) 362 { 363 spinlock_t *ptl; 364 365 ptl = pmd_lock(mm, pmd); 366 if (!is_pmd_migration_entry(*pmd)) 367 goto unlock; 368 migration_entry_wait_on_locked(pmd_to_swp_entry(*pmd), ptl); 369 return; 370 unlock: 371 spin_unlock(ptl); 372 } 373 #endif 374 375 static int folio_expected_refs(struct address_space *mapping, 376 struct folio *folio) 377 { 378 int refs = 1; 379 if (!mapping) 380 return refs; 381 382 refs += folio_nr_pages(folio); 383 if (folio_test_private(folio)) 384 refs++; 385 386 return refs; 387 } 388 389 /* 390 * Replace the page in the mapping. 391 * 392 * The number of remaining references must be: 393 * 1 for anonymous pages without a mapping 394 * 2 for pages with a mapping 395 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set. 396 */ 397 int folio_migrate_mapping(struct address_space *mapping, 398 struct folio *newfolio, struct folio *folio, int extra_count) 399 { 400 XA_STATE(xas, &mapping->i_pages, folio_index(folio)); 401 struct zone *oldzone, *newzone; 402 int dirty; 403 int expected_count = folio_expected_refs(mapping, folio) + extra_count; 404 long nr = folio_nr_pages(folio); 405 406 if (!mapping) { 407 /* Anonymous page without mapping */ 408 if (folio_ref_count(folio) != expected_count) 409 return -EAGAIN; 410 411 /* No turning back from here */ 412 newfolio->index = folio->index; 413 newfolio->mapping = folio->mapping; 414 if (folio_test_swapbacked(folio)) 415 __folio_set_swapbacked(newfolio); 416 417 return MIGRATEPAGE_SUCCESS; 418 } 419 420 oldzone = folio_zone(folio); 421 newzone = folio_zone(newfolio); 422 423 xas_lock_irq(&xas); 424 if (!folio_ref_freeze(folio, expected_count)) { 425 xas_unlock_irq(&xas); 426 return -EAGAIN; 427 } 428 429 /* 430 * Now we know that no one else is looking at the folio: 431 * no turning back from here. 432 */ 433 newfolio->index = folio->index; 434 newfolio->mapping = folio->mapping; 435 folio_ref_add(newfolio, nr); /* add cache reference */ 436 if (folio_test_swapbacked(folio)) { 437 __folio_set_swapbacked(newfolio); 438 if (folio_test_swapcache(folio)) { 439 folio_set_swapcache(newfolio); 440 newfolio->private = folio_get_private(folio); 441 } 442 } else { 443 VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio); 444 } 445 446 /* Move dirty while page refs frozen and newpage not yet exposed */ 447 dirty = folio_test_dirty(folio); 448 if (dirty) { 449 folio_clear_dirty(folio); 450 folio_set_dirty(newfolio); 451 } 452 453 xas_store(&xas, newfolio); 454 455 /* 456 * Drop cache reference from old page by unfreezing 457 * to one less reference. 458 * We know this isn't the last reference. 459 */ 460 folio_ref_unfreeze(folio, expected_count - nr); 461 462 xas_unlock(&xas); 463 /* Leave irq disabled to prevent preemption while updating stats */ 464 465 /* 466 * If moved to a different zone then also account 467 * the page for that zone. Other VM counters will be 468 * taken care of when we establish references to the 469 * new page and drop references to the old page. 470 * 471 * Note that anonymous pages are accounted for 472 * via NR_FILE_PAGES and NR_ANON_MAPPED if they 473 * are mapped to swap space. 474 */ 475 if (newzone != oldzone) { 476 struct lruvec *old_lruvec, *new_lruvec; 477 struct mem_cgroup *memcg; 478 479 memcg = folio_memcg(folio); 480 old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat); 481 new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat); 482 483 __mod_lruvec_state(old_lruvec, NR_FILE_PAGES, -nr); 484 __mod_lruvec_state(new_lruvec, NR_FILE_PAGES, nr); 485 if (folio_test_swapbacked(folio) && !folio_test_swapcache(folio)) { 486 __mod_lruvec_state(old_lruvec, NR_SHMEM, -nr); 487 __mod_lruvec_state(new_lruvec, NR_SHMEM, nr); 488 489 if (folio_test_pmd_mappable(folio)) { 490 __mod_lruvec_state(old_lruvec, NR_SHMEM_THPS, -nr); 491 __mod_lruvec_state(new_lruvec, NR_SHMEM_THPS, nr); 492 } 493 } 494 #ifdef CONFIG_SWAP 495 if (folio_test_swapcache(folio)) { 496 __mod_lruvec_state(old_lruvec, NR_SWAPCACHE, -nr); 497 __mod_lruvec_state(new_lruvec, NR_SWAPCACHE, nr); 498 } 499 #endif 500 if (dirty && mapping_can_writeback(mapping)) { 501 __mod_lruvec_state(old_lruvec, NR_FILE_DIRTY, -nr); 502 __mod_zone_page_state(oldzone, NR_ZONE_WRITE_PENDING, -nr); 503 __mod_lruvec_state(new_lruvec, NR_FILE_DIRTY, nr); 504 __mod_zone_page_state(newzone, NR_ZONE_WRITE_PENDING, nr); 505 } 506 } 507 local_irq_enable(); 508 509 return MIGRATEPAGE_SUCCESS; 510 } 511 EXPORT_SYMBOL(folio_migrate_mapping); 512 513 /* 514 * The expected number of remaining references is the same as that 515 * of folio_migrate_mapping(). 516 */ 517 int migrate_huge_page_move_mapping(struct address_space *mapping, 518 struct folio *dst, struct folio *src) 519 { 520 XA_STATE(xas, &mapping->i_pages, folio_index(src)); 521 int expected_count; 522 523 xas_lock_irq(&xas); 524 expected_count = 2 + folio_has_private(src); 525 if (!folio_ref_freeze(src, expected_count)) { 526 xas_unlock_irq(&xas); 527 return -EAGAIN; 528 } 529 530 dst->index = src->index; 531 dst->mapping = src->mapping; 532 533 folio_get(dst); 534 535 xas_store(&xas, dst); 536 537 folio_ref_unfreeze(src, expected_count - 1); 538 539 xas_unlock_irq(&xas); 540 541 return MIGRATEPAGE_SUCCESS; 542 } 543 544 /* 545 * Copy the flags and some other ancillary information 546 */ 547 void folio_migrate_flags(struct folio *newfolio, struct folio *folio) 548 { 549 int cpupid; 550 551 if (folio_test_error(folio)) 552 folio_set_error(newfolio); 553 if (folio_test_referenced(folio)) 554 folio_set_referenced(newfolio); 555 if (folio_test_uptodate(folio)) 556 folio_mark_uptodate(newfolio); 557 if (folio_test_clear_active(folio)) { 558 VM_BUG_ON_FOLIO(folio_test_unevictable(folio), folio); 559 folio_set_active(newfolio); 560 } else if (folio_test_clear_unevictable(folio)) 561 folio_set_unevictable(newfolio); 562 if (folio_test_workingset(folio)) 563 folio_set_workingset(newfolio); 564 if (folio_test_checked(folio)) 565 folio_set_checked(newfolio); 566 /* 567 * PG_anon_exclusive (-> PG_mappedtodisk) is always migrated via 568 * migration entries. We can still have PG_anon_exclusive set on an 569 * effectively unmapped and unreferenced first sub-pages of an 570 * anonymous THP: we can simply copy it here via PG_mappedtodisk. 571 */ 572 if (folio_test_mappedtodisk(folio)) 573 folio_set_mappedtodisk(newfolio); 574 575 /* Move dirty on pages not done by folio_migrate_mapping() */ 576 if (folio_test_dirty(folio)) 577 folio_set_dirty(newfolio); 578 579 if (folio_test_young(folio)) 580 folio_set_young(newfolio); 581 if (folio_test_idle(folio)) 582 folio_set_idle(newfolio); 583 584 /* 585 * Copy NUMA information to the new page, to prevent over-eager 586 * future migrations of this same page. 587 */ 588 cpupid = page_cpupid_xchg_last(&folio->page, -1); 589 /* 590 * For memory tiering mode, when migrate between slow and fast 591 * memory node, reset cpupid, because that is used to record 592 * page access time in slow memory node. 593 */ 594 if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) { 595 bool f_toptier = node_is_toptier(page_to_nid(&folio->page)); 596 bool t_toptier = node_is_toptier(page_to_nid(&newfolio->page)); 597 598 if (f_toptier != t_toptier) 599 cpupid = -1; 600 } 601 page_cpupid_xchg_last(&newfolio->page, cpupid); 602 603 folio_migrate_ksm(newfolio, folio); 604 /* 605 * Please do not reorder this without considering how mm/ksm.c's 606 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache(). 607 */ 608 if (folio_test_swapcache(folio)) 609 folio_clear_swapcache(folio); 610 folio_clear_private(folio); 611 612 /* page->private contains hugetlb specific flags */ 613 if (!folio_test_hugetlb(folio)) 614 folio->private = NULL; 615 616 /* 617 * If any waiters have accumulated on the new page then 618 * wake them up. 619 */ 620 if (folio_test_writeback(newfolio)) 621 folio_end_writeback(newfolio); 622 623 /* 624 * PG_readahead shares the same bit with PG_reclaim. The above 625 * end_page_writeback() may clear PG_readahead mistakenly, so set the 626 * bit after that. 627 */ 628 if (folio_test_readahead(folio)) 629 folio_set_readahead(newfolio); 630 631 folio_copy_owner(newfolio, folio); 632 633 if (!folio_test_hugetlb(folio)) 634 mem_cgroup_migrate(folio, newfolio); 635 } 636 EXPORT_SYMBOL(folio_migrate_flags); 637 638 void folio_migrate_copy(struct folio *newfolio, struct folio *folio) 639 { 640 folio_copy(newfolio, folio); 641 folio_migrate_flags(newfolio, folio); 642 } 643 EXPORT_SYMBOL(folio_migrate_copy); 644 645 /************************************************************ 646 * Migration functions 647 ***********************************************************/ 648 649 int migrate_folio_extra(struct address_space *mapping, struct folio *dst, 650 struct folio *src, enum migrate_mode mode, int extra_count) 651 { 652 int rc; 653 654 BUG_ON(folio_test_writeback(src)); /* Writeback must be complete */ 655 656 rc = folio_migrate_mapping(mapping, dst, src, extra_count); 657 658 if (rc != MIGRATEPAGE_SUCCESS) 659 return rc; 660 661 if (mode != MIGRATE_SYNC_NO_COPY) 662 folio_migrate_copy(dst, src); 663 else 664 folio_migrate_flags(dst, src); 665 return MIGRATEPAGE_SUCCESS; 666 } 667 668 /** 669 * migrate_folio() - Simple folio migration. 670 * @mapping: The address_space containing the folio. 671 * @dst: The folio to migrate the data to. 672 * @src: The folio containing the current data. 673 * @mode: How to migrate the page. 674 * 675 * Common logic to directly migrate a single LRU folio suitable for 676 * folios that do not use PagePrivate/PagePrivate2. 677 * 678 * Folios are locked upon entry and exit. 679 */ 680 int migrate_folio(struct address_space *mapping, struct folio *dst, 681 struct folio *src, enum migrate_mode mode) 682 { 683 return migrate_folio_extra(mapping, dst, src, mode, 0); 684 } 685 EXPORT_SYMBOL(migrate_folio); 686 687 #ifdef CONFIG_BLOCK 688 /* Returns true if all buffers are successfully locked */ 689 static bool buffer_migrate_lock_buffers(struct buffer_head *head, 690 enum migrate_mode mode) 691 { 692 struct buffer_head *bh = head; 693 struct buffer_head *failed_bh; 694 695 do { 696 if (!trylock_buffer(bh)) { 697 if (mode == MIGRATE_ASYNC) 698 goto unlock; 699 if (mode == MIGRATE_SYNC_LIGHT && !buffer_uptodate(bh)) 700 goto unlock; 701 lock_buffer(bh); 702 } 703 704 bh = bh->b_this_page; 705 } while (bh != head); 706 707 return true; 708 709 unlock: 710 /* We failed to lock the buffer and cannot stall. */ 711 failed_bh = bh; 712 bh = head; 713 while (bh != failed_bh) { 714 unlock_buffer(bh); 715 bh = bh->b_this_page; 716 } 717 718 return false; 719 } 720 721 static int __buffer_migrate_folio(struct address_space *mapping, 722 struct folio *dst, struct folio *src, enum migrate_mode mode, 723 bool check_refs) 724 { 725 struct buffer_head *bh, *head; 726 int rc; 727 int expected_count; 728 729 head = folio_buffers(src); 730 if (!head) 731 return migrate_folio(mapping, dst, src, mode); 732 733 /* Check whether page does not have extra refs before we do more work */ 734 expected_count = folio_expected_refs(mapping, src); 735 if (folio_ref_count(src) != expected_count) 736 return -EAGAIN; 737 738 if (!buffer_migrate_lock_buffers(head, mode)) 739 return -EAGAIN; 740 741 if (check_refs) { 742 bool busy; 743 bool invalidated = false; 744 745 recheck_buffers: 746 busy = false; 747 spin_lock(&mapping->private_lock); 748 bh = head; 749 do { 750 if (atomic_read(&bh->b_count)) { 751 busy = true; 752 break; 753 } 754 bh = bh->b_this_page; 755 } while (bh != head); 756 if (busy) { 757 if (invalidated) { 758 rc = -EAGAIN; 759 goto unlock_buffers; 760 } 761 spin_unlock(&mapping->private_lock); 762 invalidate_bh_lrus(); 763 invalidated = true; 764 goto recheck_buffers; 765 } 766 } 767 768 rc = folio_migrate_mapping(mapping, dst, src, 0); 769 if (rc != MIGRATEPAGE_SUCCESS) 770 goto unlock_buffers; 771 772 folio_attach_private(dst, folio_detach_private(src)); 773 774 bh = head; 775 do { 776 set_bh_page(bh, &dst->page, bh_offset(bh)); 777 bh = bh->b_this_page; 778 } while (bh != head); 779 780 if (mode != MIGRATE_SYNC_NO_COPY) 781 folio_migrate_copy(dst, src); 782 else 783 folio_migrate_flags(dst, src); 784 785 rc = MIGRATEPAGE_SUCCESS; 786 unlock_buffers: 787 if (check_refs) 788 spin_unlock(&mapping->private_lock); 789 bh = head; 790 do { 791 unlock_buffer(bh); 792 bh = bh->b_this_page; 793 } while (bh != head); 794 795 return rc; 796 } 797 798 /** 799 * buffer_migrate_folio() - Migration function for folios with buffers. 800 * @mapping: The address space containing @src. 801 * @dst: The folio to migrate to. 802 * @src: The folio to migrate from. 803 * @mode: How to migrate the folio. 804 * 805 * This function can only be used if the underlying filesystem guarantees 806 * that no other references to @src exist. For example attached buffer 807 * heads are accessed only under the folio lock. If your filesystem cannot 808 * provide this guarantee, buffer_migrate_folio_norefs() may be more 809 * appropriate. 810 * 811 * Return: 0 on success or a negative errno on failure. 812 */ 813 int buffer_migrate_folio(struct address_space *mapping, 814 struct folio *dst, struct folio *src, enum migrate_mode mode) 815 { 816 return __buffer_migrate_folio(mapping, dst, src, mode, false); 817 } 818 EXPORT_SYMBOL(buffer_migrate_folio); 819 820 /** 821 * buffer_migrate_folio_norefs() - Migration function for folios with buffers. 822 * @mapping: The address space containing @src. 823 * @dst: The folio to migrate to. 824 * @src: The folio to migrate from. 825 * @mode: How to migrate the folio. 826 * 827 * Like buffer_migrate_folio() except that this variant is more careful 828 * and checks that there are also no buffer head references. This function 829 * is the right one for mappings where buffer heads are directly looked 830 * up and referenced (such as block device mappings). 831 * 832 * Return: 0 on success or a negative errno on failure. 833 */ 834 int buffer_migrate_folio_norefs(struct address_space *mapping, 835 struct folio *dst, struct folio *src, enum migrate_mode mode) 836 { 837 return __buffer_migrate_folio(mapping, dst, src, mode, true); 838 } 839 EXPORT_SYMBOL_GPL(buffer_migrate_folio_norefs); 840 #endif 841 842 int filemap_migrate_folio(struct address_space *mapping, 843 struct folio *dst, struct folio *src, enum migrate_mode mode) 844 { 845 int ret; 846 847 ret = folio_migrate_mapping(mapping, dst, src, 0); 848 if (ret != MIGRATEPAGE_SUCCESS) 849 return ret; 850 851 if (folio_get_private(src)) 852 folio_attach_private(dst, folio_detach_private(src)); 853 854 if (mode != MIGRATE_SYNC_NO_COPY) 855 folio_migrate_copy(dst, src); 856 else 857 folio_migrate_flags(dst, src); 858 return MIGRATEPAGE_SUCCESS; 859 } 860 EXPORT_SYMBOL_GPL(filemap_migrate_folio); 861 862 /* 863 * Writeback a folio to clean the dirty state 864 */ 865 static int writeout(struct address_space *mapping, struct folio *folio) 866 { 867 struct writeback_control wbc = { 868 .sync_mode = WB_SYNC_NONE, 869 .nr_to_write = 1, 870 .range_start = 0, 871 .range_end = LLONG_MAX, 872 .for_reclaim = 1 873 }; 874 int rc; 875 876 if (!mapping->a_ops->writepage) 877 /* No write method for the address space */ 878 return -EINVAL; 879 880 if (!folio_clear_dirty_for_io(folio)) 881 /* Someone else already triggered a write */ 882 return -EAGAIN; 883 884 /* 885 * A dirty folio may imply that the underlying filesystem has 886 * the folio on some queue. So the folio must be clean for 887 * migration. Writeout may mean we lose the lock and the 888 * folio state is no longer what we checked for earlier. 889 * At this point we know that the migration attempt cannot 890 * be successful. 891 */ 892 remove_migration_ptes(folio, folio, false); 893 894 rc = mapping->a_ops->writepage(&folio->page, &wbc); 895 896 if (rc != AOP_WRITEPAGE_ACTIVATE) 897 /* unlocked. Relock */ 898 folio_lock(folio); 899 900 return (rc < 0) ? -EIO : -EAGAIN; 901 } 902 903 /* 904 * Default handling if a filesystem does not provide a migration function. 905 */ 906 static int fallback_migrate_folio(struct address_space *mapping, 907 struct folio *dst, struct folio *src, enum migrate_mode mode) 908 { 909 if (folio_test_dirty(src)) { 910 /* Only writeback folios in full synchronous migration */ 911 switch (mode) { 912 case MIGRATE_SYNC: 913 case MIGRATE_SYNC_NO_COPY: 914 break; 915 default: 916 return -EBUSY; 917 } 918 return writeout(mapping, src); 919 } 920 921 /* 922 * Buffers may be managed in a filesystem specific way. 923 * We must have no buffers or drop them. 924 */ 925 if (folio_test_private(src) && 926 !filemap_release_folio(src, GFP_KERNEL)) 927 return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY; 928 929 return migrate_folio(mapping, dst, src, mode); 930 } 931 932 /* 933 * Move a page to a newly allocated page 934 * The page is locked and all ptes have been successfully removed. 935 * 936 * The new page will have replaced the old page if this function 937 * is successful. 938 * 939 * Return value: 940 * < 0 - error code 941 * MIGRATEPAGE_SUCCESS - success 942 */ 943 static int move_to_new_folio(struct folio *dst, struct folio *src, 944 enum migrate_mode mode) 945 { 946 int rc = -EAGAIN; 947 bool is_lru = !__PageMovable(&src->page); 948 949 VM_BUG_ON_FOLIO(!folio_test_locked(src), src); 950 VM_BUG_ON_FOLIO(!folio_test_locked(dst), dst); 951 952 if (likely(is_lru)) { 953 struct address_space *mapping = folio_mapping(src); 954 955 if (!mapping) 956 rc = migrate_folio(mapping, dst, src, mode); 957 else if (mapping->a_ops->migrate_folio) 958 /* 959 * Most folios have a mapping and most filesystems 960 * provide a migrate_folio callback. Anonymous folios 961 * are part of swap space which also has its own 962 * migrate_folio callback. This is the most common path 963 * for page migration. 964 */ 965 rc = mapping->a_ops->migrate_folio(mapping, dst, src, 966 mode); 967 else 968 rc = fallback_migrate_folio(mapping, dst, src, mode); 969 } else { 970 const struct movable_operations *mops; 971 972 /* 973 * In case of non-lru page, it could be released after 974 * isolation step. In that case, we shouldn't try migration. 975 */ 976 VM_BUG_ON_FOLIO(!folio_test_isolated(src), src); 977 if (!folio_test_movable(src)) { 978 rc = MIGRATEPAGE_SUCCESS; 979 folio_clear_isolated(src); 980 goto out; 981 } 982 983 mops = folio_movable_ops(src); 984 rc = mops->migrate_page(&dst->page, &src->page, mode); 985 WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS && 986 !folio_test_isolated(src)); 987 } 988 989 /* 990 * When successful, old pagecache src->mapping must be cleared before 991 * src is freed; but stats require that PageAnon be left as PageAnon. 992 */ 993 if (rc == MIGRATEPAGE_SUCCESS) { 994 if (__PageMovable(&src->page)) { 995 VM_BUG_ON_FOLIO(!folio_test_isolated(src), src); 996 997 /* 998 * We clear PG_movable under page_lock so any compactor 999 * cannot try to migrate this page. 1000 */ 1001 folio_clear_isolated(src); 1002 } 1003 1004 /* 1005 * Anonymous and movable src->mapping will be cleared by 1006 * free_pages_prepare so don't reset it here for keeping 1007 * the type to work PageAnon, for example. 1008 */ 1009 if (!folio_mapping_flags(src)) 1010 src->mapping = NULL; 1011 1012 if (likely(!folio_is_zone_device(dst))) 1013 flush_dcache_folio(dst); 1014 } 1015 out: 1016 return rc; 1017 } 1018 1019 /* 1020 * To record some information during migration, we use some unused 1021 * fields (mapping and private) of struct folio of the newly allocated 1022 * destination folio. This is safe because nobody is using them 1023 * except us. 1024 */ 1025 union migration_ptr { 1026 struct anon_vma *anon_vma; 1027 struct address_space *mapping; 1028 }; 1029 static void __migrate_folio_record(struct folio *dst, 1030 unsigned long page_was_mapped, 1031 struct anon_vma *anon_vma) 1032 { 1033 union migration_ptr ptr = { .anon_vma = anon_vma }; 1034 dst->mapping = ptr.mapping; 1035 dst->private = (void *)page_was_mapped; 1036 } 1037 1038 static void __migrate_folio_extract(struct folio *dst, 1039 int *page_was_mappedp, 1040 struct anon_vma **anon_vmap) 1041 { 1042 union migration_ptr ptr = { .mapping = dst->mapping }; 1043 *anon_vmap = ptr.anon_vma; 1044 *page_was_mappedp = (unsigned long)dst->private; 1045 dst->mapping = NULL; 1046 dst->private = NULL; 1047 } 1048 1049 /* Restore the source folio to the original state upon failure */ 1050 static void migrate_folio_undo_src(struct folio *src, 1051 int page_was_mapped, 1052 struct anon_vma *anon_vma, 1053 bool locked, 1054 struct list_head *ret) 1055 { 1056 if (page_was_mapped) 1057 remove_migration_ptes(src, src, false); 1058 /* Drop an anon_vma reference if we took one */ 1059 if (anon_vma) 1060 put_anon_vma(anon_vma); 1061 if (locked) 1062 folio_unlock(src); 1063 if (ret) 1064 list_move_tail(&src->lru, ret); 1065 } 1066 1067 /* Restore the destination folio to the original state upon failure */ 1068 static void migrate_folio_undo_dst(struct folio *dst, bool locked, 1069 free_folio_t put_new_folio, unsigned long private) 1070 { 1071 if (locked) 1072 folio_unlock(dst); 1073 if (put_new_folio) 1074 put_new_folio(dst, private); 1075 else 1076 folio_put(dst); 1077 } 1078 1079 /* Cleanup src folio upon migration success */ 1080 static void migrate_folio_done(struct folio *src, 1081 enum migrate_reason reason) 1082 { 1083 /* 1084 * Compaction can migrate also non-LRU pages which are 1085 * not accounted to NR_ISOLATED_*. They can be recognized 1086 * as __PageMovable 1087 */ 1088 if (likely(!__folio_test_movable(src))) 1089 mod_node_page_state(folio_pgdat(src), NR_ISOLATED_ANON + 1090 folio_is_file_lru(src), -folio_nr_pages(src)); 1091 1092 if (reason != MR_MEMORY_FAILURE) 1093 /* We release the page in page_handle_poison. */ 1094 folio_put(src); 1095 } 1096 1097 /* Obtain the lock on page, remove all ptes. */ 1098 static int migrate_folio_unmap(new_folio_t get_new_folio, 1099 free_folio_t put_new_folio, unsigned long private, 1100 struct folio *src, struct folio **dstp, enum migrate_mode mode, 1101 enum migrate_reason reason, struct list_head *ret) 1102 { 1103 struct folio *dst; 1104 int rc = -EAGAIN; 1105 int page_was_mapped = 0; 1106 struct anon_vma *anon_vma = NULL; 1107 bool is_lru = !__PageMovable(&src->page); 1108 bool locked = false; 1109 bool dst_locked = false; 1110 1111 if (folio_ref_count(src) == 1) { 1112 /* Folio was freed from under us. So we are done. */ 1113 folio_clear_active(src); 1114 folio_clear_unevictable(src); 1115 /* free_pages_prepare() will clear PG_isolated. */ 1116 list_del(&src->lru); 1117 migrate_folio_done(src, reason); 1118 return MIGRATEPAGE_SUCCESS; 1119 } 1120 1121 dst = get_new_folio(src, private); 1122 if (!dst) 1123 return -ENOMEM; 1124 *dstp = dst; 1125 1126 dst->private = NULL; 1127 1128 if (!folio_trylock(src)) { 1129 if (mode == MIGRATE_ASYNC) 1130 goto out; 1131 1132 /* 1133 * It's not safe for direct compaction to call lock_page. 1134 * For example, during page readahead pages are added locked 1135 * to the LRU. Later, when the IO completes the pages are 1136 * marked uptodate and unlocked. However, the queueing 1137 * could be merging multiple pages for one bio (e.g. 1138 * mpage_readahead). If an allocation happens for the 1139 * second or third page, the process can end up locking 1140 * the same page twice and deadlocking. Rather than 1141 * trying to be clever about what pages can be locked, 1142 * avoid the use of lock_page for direct compaction 1143 * altogether. 1144 */ 1145 if (current->flags & PF_MEMALLOC) 1146 goto out; 1147 1148 /* 1149 * In "light" mode, we can wait for transient locks (eg 1150 * inserting a page into the page table), but it's not 1151 * worth waiting for I/O. 1152 */ 1153 if (mode == MIGRATE_SYNC_LIGHT && !folio_test_uptodate(src)) 1154 goto out; 1155 1156 folio_lock(src); 1157 } 1158 locked = true; 1159 1160 if (folio_test_writeback(src)) { 1161 /* 1162 * Only in the case of a full synchronous migration is it 1163 * necessary to wait for PageWriteback. In the async case, 1164 * the retry loop is too short and in the sync-light case, 1165 * the overhead of stalling is too much 1166 */ 1167 switch (mode) { 1168 case MIGRATE_SYNC: 1169 case MIGRATE_SYNC_NO_COPY: 1170 break; 1171 default: 1172 rc = -EBUSY; 1173 goto out; 1174 } 1175 folio_wait_writeback(src); 1176 } 1177 1178 /* 1179 * By try_to_migrate(), src->mapcount goes down to 0 here. In this case, 1180 * we cannot notice that anon_vma is freed while we migrate a page. 1181 * This get_anon_vma() delays freeing anon_vma pointer until the end 1182 * of migration. File cache pages are no problem because of page_lock() 1183 * File Caches may use write_page() or lock_page() in migration, then, 1184 * just care Anon page here. 1185 * 1186 * Only folio_get_anon_vma() understands the subtleties of 1187 * getting a hold on an anon_vma from outside one of its mms. 1188 * But if we cannot get anon_vma, then we won't need it anyway, 1189 * because that implies that the anon page is no longer mapped 1190 * (and cannot be remapped so long as we hold the page lock). 1191 */ 1192 if (folio_test_anon(src) && !folio_test_ksm(src)) 1193 anon_vma = folio_get_anon_vma(src); 1194 1195 /* 1196 * Block others from accessing the new page when we get around to 1197 * establishing additional references. We are usually the only one 1198 * holding a reference to dst at this point. We used to have a BUG 1199 * here if folio_trylock(dst) fails, but would like to allow for 1200 * cases where there might be a race with the previous use of dst. 1201 * This is much like races on refcount of oldpage: just don't BUG(). 1202 */ 1203 if (unlikely(!folio_trylock(dst))) 1204 goto out; 1205 dst_locked = true; 1206 1207 if (unlikely(!is_lru)) { 1208 __migrate_folio_record(dst, page_was_mapped, anon_vma); 1209 return MIGRATEPAGE_UNMAP; 1210 } 1211 1212 /* 1213 * Corner case handling: 1214 * 1. When a new swap-cache page is read into, it is added to the LRU 1215 * and treated as swapcache but it has no rmap yet. 1216 * Calling try_to_unmap() against a src->mapping==NULL page will 1217 * trigger a BUG. So handle it here. 1218 * 2. An orphaned page (see truncate_cleanup_page) might have 1219 * fs-private metadata. The page can be picked up due to memory 1220 * offlining. Everywhere else except page reclaim, the page is 1221 * invisible to the vm, so the page can not be migrated. So try to 1222 * free the metadata, so the page can be freed. 1223 */ 1224 if (!src->mapping) { 1225 if (folio_test_private(src)) { 1226 try_to_free_buffers(src); 1227 goto out; 1228 } 1229 } else if (folio_mapped(src)) { 1230 /* Establish migration ptes */ 1231 VM_BUG_ON_FOLIO(folio_test_anon(src) && 1232 !folio_test_ksm(src) && !anon_vma, src); 1233 try_to_migrate(src, mode == MIGRATE_ASYNC ? TTU_BATCH_FLUSH : 0); 1234 page_was_mapped = 1; 1235 } 1236 1237 if (!folio_mapped(src)) { 1238 __migrate_folio_record(dst, page_was_mapped, anon_vma); 1239 return MIGRATEPAGE_UNMAP; 1240 } 1241 1242 out: 1243 /* 1244 * A folio that has not been unmapped will be restored to 1245 * right list unless we want to retry. 1246 */ 1247 if (rc == -EAGAIN) 1248 ret = NULL; 1249 1250 migrate_folio_undo_src(src, page_was_mapped, anon_vma, locked, ret); 1251 migrate_folio_undo_dst(dst, dst_locked, put_new_folio, private); 1252 1253 return rc; 1254 } 1255 1256 /* Migrate the folio to the newly allocated folio in dst. */ 1257 static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private, 1258 struct folio *src, struct folio *dst, 1259 enum migrate_mode mode, enum migrate_reason reason, 1260 struct list_head *ret) 1261 { 1262 int rc; 1263 int page_was_mapped = 0; 1264 struct anon_vma *anon_vma = NULL; 1265 bool is_lru = !__PageMovable(&src->page); 1266 struct list_head *prev; 1267 1268 __migrate_folio_extract(dst, &page_was_mapped, &anon_vma); 1269 prev = dst->lru.prev; 1270 list_del(&dst->lru); 1271 1272 rc = move_to_new_folio(dst, src, mode); 1273 if (rc) 1274 goto out; 1275 1276 if (unlikely(!is_lru)) 1277 goto out_unlock_both; 1278 1279 /* 1280 * When successful, push dst to LRU immediately: so that if it 1281 * turns out to be an mlocked page, remove_migration_ptes() will 1282 * automatically build up the correct dst->mlock_count for it. 1283 * 1284 * We would like to do something similar for the old page, when 1285 * unsuccessful, and other cases when a page has been temporarily 1286 * isolated from the unevictable LRU: but this case is the easiest. 1287 */ 1288 folio_add_lru(dst); 1289 if (page_was_mapped) 1290 lru_add_drain(); 1291 1292 if (page_was_mapped) 1293 remove_migration_ptes(src, dst, false); 1294 1295 out_unlock_both: 1296 folio_unlock(dst); 1297 set_page_owner_migrate_reason(&dst->page, reason); 1298 /* 1299 * If migration is successful, decrease refcount of dst, 1300 * which will not free the page because new page owner increased 1301 * refcounter. 1302 */ 1303 folio_put(dst); 1304 1305 /* 1306 * A folio that has been migrated has all references removed 1307 * and will be freed. 1308 */ 1309 list_del(&src->lru); 1310 /* Drop an anon_vma reference if we took one */ 1311 if (anon_vma) 1312 put_anon_vma(anon_vma); 1313 folio_unlock(src); 1314 migrate_folio_done(src, reason); 1315 1316 return rc; 1317 out: 1318 /* 1319 * A folio that has not been migrated will be restored to 1320 * right list unless we want to retry. 1321 */ 1322 if (rc == -EAGAIN) { 1323 list_add(&dst->lru, prev); 1324 __migrate_folio_record(dst, page_was_mapped, anon_vma); 1325 return rc; 1326 } 1327 1328 migrate_folio_undo_src(src, page_was_mapped, anon_vma, true, ret); 1329 migrate_folio_undo_dst(dst, true, put_new_folio, private); 1330 1331 return rc; 1332 } 1333 1334 /* 1335 * Counterpart of unmap_and_move_page() for hugepage migration. 1336 * 1337 * This function doesn't wait the completion of hugepage I/O 1338 * because there is no race between I/O and migration for hugepage. 1339 * Note that currently hugepage I/O occurs only in direct I/O 1340 * where no lock is held and PG_writeback is irrelevant, 1341 * and writeback status of all subpages are counted in the reference 1342 * count of the head page (i.e. if all subpages of a 2MB hugepage are 1343 * under direct I/O, the reference of the head page is 512 and a bit more.) 1344 * This means that when we try to migrate hugepage whose subpages are 1345 * doing direct I/O, some references remain after try_to_unmap() and 1346 * hugepage migration fails without data corruption. 1347 * 1348 * There is also no race when direct I/O is issued on the page under migration, 1349 * because then pte is replaced with migration swap entry and direct I/O code 1350 * will wait in the page fault for migration to complete. 1351 */ 1352 static int unmap_and_move_huge_page(new_folio_t get_new_folio, 1353 free_folio_t put_new_folio, unsigned long private, 1354 struct folio *src, int force, enum migrate_mode mode, 1355 int reason, struct list_head *ret) 1356 { 1357 struct folio *dst; 1358 int rc = -EAGAIN; 1359 int page_was_mapped = 0; 1360 struct anon_vma *anon_vma = NULL; 1361 struct address_space *mapping = NULL; 1362 1363 if (folio_ref_count(src) == 1) { 1364 /* page was freed from under us. So we are done. */ 1365 folio_putback_active_hugetlb(src); 1366 return MIGRATEPAGE_SUCCESS; 1367 } 1368 1369 dst = get_new_folio(src, private); 1370 if (!dst) 1371 return -ENOMEM; 1372 1373 if (!folio_trylock(src)) { 1374 if (!force) 1375 goto out; 1376 switch (mode) { 1377 case MIGRATE_SYNC: 1378 case MIGRATE_SYNC_NO_COPY: 1379 break; 1380 default: 1381 goto out; 1382 } 1383 folio_lock(src); 1384 } 1385 1386 /* 1387 * Check for pages which are in the process of being freed. Without 1388 * folio_mapping() set, hugetlbfs specific move page routine will not 1389 * be called and we could leak usage counts for subpools. 1390 */ 1391 if (hugetlb_folio_subpool(src) && !folio_mapping(src)) { 1392 rc = -EBUSY; 1393 goto out_unlock; 1394 } 1395 1396 if (folio_test_anon(src)) 1397 anon_vma = folio_get_anon_vma(src); 1398 1399 if (unlikely(!folio_trylock(dst))) 1400 goto put_anon; 1401 1402 if (folio_mapped(src)) { 1403 enum ttu_flags ttu = 0; 1404 1405 if (!folio_test_anon(src)) { 1406 /* 1407 * In shared mappings, try_to_unmap could potentially 1408 * call huge_pmd_unshare. Because of this, take 1409 * semaphore in write mode here and set TTU_RMAP_LOCKED 1410 * to let lower levels know we have taken the lock. 1411 */ 1412 mapping = hugetlb_page_mapping_lock_write(&src->page); 1413 if (unlikely(!mapping)) 1414 goto unlock_put_anon; 1415 1416 ttu = TTU_RMAP_LOCKED; 1417 } 1418 1419 try_to_migrate(src, ttu); 1420 page_was_mapped = 1; 1421 1422 if (ttu & TTU_RMAP_LOCKED) 1423 i_mmap_unlock_write(mapping); 1424 } 1425 1426 if (!folio_mapped(src)) 1427 rc = move_to_new_folio(dst, src, mode); 1428 1429 if (page_was_mapped) 1430 remove_migration_ptes(src, 1431 rc == MIGRATEPAGE_SUCCESS ? dst : src, false); 1432 1433 unlock_put_anon: 1434 folio_unlock(dst); 1435 1436 put_anon: 1437 if (anon_vma) 1438 put_anon_vma(anon_vma); 1439 1440 if (rc == MIGRATEPAGE_SUCCESS) { 1441 move_hugetlb_state(src, dst, reason); 1442 put_new_folio = NULL; 1443 } 1444 1445 out_unlock: 1446 folio_unlock(src); 1447 out: 1448 if (rc == MIGRATEPAGE_SUCCESS) 1449 folio_putback_active_hugetlb(src); 1450 else if (rc != -EAGAIN) 1451 list_move_tail(&src->lru, ret); 1452 1453 /* 1454 * If migration was not successful and there's a freeing callback, use 1455 * it. Otherwise, put_page() will drop the reference grabbed during 1456 * isolation. 1457 */ 1458 if (put_new_folio) 1459 put_new_folio(dst, private); 1460 else 1461 folio_putback_active_hugetlb(dst); 1462 1463 return rc; 1464 } 1465 1466 static inline int try_split_folio(struct folio *folio, struct list_head *split_folios) 1467 { 1468 int rc; 1469 1470 folio_lock(folio); 1471 rc = split_folio_to_list(folio, split_folios); 1472 folio_unlock(folio); 1473 if (!rc) 1474 list_move_tail(&folio->lru, split_folios); 1475 1476 return rc; 1477 } 1478 1479 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 1480 #define NR_MAX_BATCHED_MIGRATION HPAGE_PMD_NR 1481 #else 1482 #define NR_MAX_BATCHED_MIGRATION 512 1483 #endif 1484 #define NR_MAX_MIGRATE_PAGES_RETRY 10 1485 #define NR_MAX_MIGRATE_ASYNC_RETRY 3 1486 #define NR_MAX_MIGRATE_SYNC_RETRY \ 1487 (NR_MAX_MIGRATE_PAGES_RETRY - NR_MAX_MIGRATE_ASYNC_RETRY) 1488 1489 struct migrate_pages_stats { 1490 int nr_succeeded; /* Normal and large folios migrated successfully, in 1491 units of base pages */ 1492 int nr_failed_pages; /* Normal and large folios failed to be migrated, in 1493 units of base pages. Untried folios aren't counted */ 1494 int nr_thp_succeeded; /* THP migrated successfully */ 1495 int nr_thp_failed; /* THP failed to be migrated */ 1496 int nr_thp_split; /* THP split before migrating */ 1497 }; 1498 1499 /* 1500 * Returns the number of hugetlb folios that were not migrated, or an error code 1501 * after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no hugetlb folios are movable 1502 * any more because the list has become empty or no retryable hugetlb folios 1503 * exist any more. It is caller's responsibility to call putback_movable_pages() 1504 * only if ret != 0. 1505 */ 1506 static int migrate_hugetlbs(struct list_head *from, new_folio_t get_new_folio, 1507 free_folio_t put_new_folio, unsigned long private, 1508 enum migrate_mode mode, int reason, 1509 struct migrate_pages_stats *stats, 1510 struct list_head *ret_folios) 1511 { 1512 int retry = 1; 1513 int nr_failed = 0; 1514 int nr_retry_pages = 0; 1515 int pass = 0; 1516 struct folio *folio, *folio2; 1517 int rc, nr_pages; 1518 1519 for (pass = 0; pass < NR_MAX_MIGRATE_PAGES_RETRY && retry; pass++) { 1520 retry = 0; 1521 nr_retry_pages = 0; 1522 1523 list_for_each_entry_safe(folio, folio2, from, lru) { 1524 if (!folio_test_hugetlb(folio)) 1525 continue; 1526 1527 nr_pages = folio_nr_pages(folio); 1528 1529 cond_resched(); 1530 1531 /* 1532 * Migratability of hugepages depends on architectures and 1533 * their size. This check is necessary because some callers 1534 * of hugepage migration like soft offline and memory 1535 * hotremove don't walk through page tables or check whether 1536 * the hugepage is pmd-based or not before kicking migration. 1537 */ 1538 if (!hugepage_migration_supported(folio_hstate(folio))) { 1539 nr_failed++; 1540 stats->nr_failed_pages += nr_pages; 1541 list_move_tail(&folio->lru, ret_folios); 1542 continue; 1543 } 1544 1545 rc = unmap_and_move_huge_page(get_new_folio, 1546 put_new_folio, private, 1547 folio, pass > 2, mode, 1548 reason, ret_folios); 1549 /* 1550 * The rules are: 1551 * Success: hugetlb folio will be put back 1552 * -EAGAIN: stay on the from list 1553 * -ENOMEM: stay on the from list 1554 * Other errno: put on ret_folios list 1555 */ 1556 switch(rc) { 1557 case -ENOMEM: 1558 /* 1559 * When memory is low, don't bother to try to migrate 1560 * other folios, just exit. 1561 */ 1562 stats->nr_failed_pages += nr_pages + nr_retry_pages; 1563 return -ENOMEM; 1564 case -EAGAIN: 1565 retry++; 1566 nr_retry_pages += nr_pages; 1567 break; 1568 case MIGRATEPAGE_SUCCESS: 1569 stats->nr_succeeded += nr_pages; 1570 break; 1571 default: 1572 /* 1573 * Permanent failure (-EBUSY, etc.): 1574 * unlike -EAGAIN case, the failed folio is 1575 * removed from migration folio list and not 1576 * retried in the next outer loop. 1577 */ 1578 nr_failed++; 1579 stats->nr_failed_pages += nr_pages; 1580 break; 1581 } 1582 } 1583 } 1584 /* 1585 * nr_failed is number of hugetlb folios failed to be migrated. After 1586 * NR_MAX_MIGRATE_PAGES_RETRY attempts, give up and count retried hugetlb 1587 * folios as failed. 1588 */ 1589 nr_failed += retry; 1590 stats->nr_failed_pages += nr_retry_pages; 1591 1592 return nr_failed; 1593 } 1594 1595 /* 1596 * migrate_pages_batch() first unmaps folios in the from list as many as 1597 * possible, then move the unmapped folios. 1598 * 1599 * We only batch migration if mode == MIGRATE_ASYNC to avoid to wait a 1600 * lock or bit when we have locked more than one folio. Which may cause 1601 * deadlock (e.g., for loop device). So, if mode != MIGRATE_ASYNC, the 1602 * length of the from list must be <= 1. 1603 */ 1604 static int migrate_pages_batch(struct list_head *from, 1605 new_folio_t get_new_folio, free_folio_t put_new_folio, 1606 unsigned long private, enum migrate_mode mode, int reason, 1607 struct list_head *ret_folios, struct list_head *split_folios, 1608 struct migrate_pages_stats *stats, int nr_pass) 1609 { 1610 int retry = 1; 1611 int thp_retry = 1; 1612 int nr_failed = 0; 1613 int nr_retry_pages = 0; 1614 int pass = 0; 1615 bool is_thp = false; 1616 struct folio *folio, *folio2, *dst = NULL, *dst2; 1617 int rc, rc_saved = 0, nr_pages; 1618 LIST_HEAD(unmap_folios); 1619 LIST_HEAD(dst_folios); 1620 bool nosplit = (reason == MR_NUMA_MISPLACED); 1621 1622 VM_WARN_ON_ONCE(mode != MIGRATE_ASYNC && 1623 !list_empty(from) && !list_is_singular(from)); 1624 1625 for (pass = 0; pass < nr_pass && retry; pass++) { 1626 retry = 0; 1627 thp_retry = 0; 1628 nr_retry_pages = 0; 1629 1630 list_for_each_entry_safe(folio, folio2, from, lru) { 1631 is_thp = folio_test_large(folio) && folio_test_pmd_mappable(folio); 1632 nr_pages = folio_nr_pages(folio); 1633 1634 cond_resched(); 1635 1636 /* 1637 * Large folio migration might be unsupported or 1638 * the allocation might be failed so we should retry 1639 * on the same folio with the large folio split 1640 * to normal folios. 1641 * 1642 * Split folios are put in split_folios, and 1643 * we will migrate them after the rest of the 1644 * list is processed. 1645 */ 1646 if (!thp_migration_supported() && is_thp) { 1647 nr_failed++; 1648 stats->nr_thp_failed++; 1649 if (!try_split_folio(folio, split_folios)) { 1650 stats->nr_thp_split++; 1651 continue; 1652 } 1653 stats->nr_failed_pages += nr_pages; 1654 list_move_tail(&folio->lru, ret_folios); 1655 continue; 1656 } 1657 1658 rc = migrate_folio_unmap(get_new_folio, put_new_folio, 1659 private, folio, &dst, mode, reason, 1660 ret_folios); 1661 /* 1662 * The rules are: 1663 * Success: folio will be freed 1664 * Unmap: folio will be put on unmap_folios list, 1665 * dst folio put on dst_folios list 1666 * -EAGAIN: stay on the from list 1667 * -ENOMEM: stay on the from list 1668 * Other errno: put on ret_folios list 1669 */ 1670 switch(rc) { 1671 case -ENOMEM: 1672 /* 1673 * When memory is low, don't bother to try to migrate 1674 * other folios, move unmapped folios, then exit. 1675 */ 1676 nr_failed++; 1677 stats->nr_thp_failed += is_thp; 1678 /* Large folio NUMA faulting doesn't split to retry. */ 1679 if (folio_test_large(folio) && !nosplit) { 1680 int ret = try_split_folio(folio, split_folios); 1681 1682 if (!ret) { 1683 stats->nr_thp_split += is_thp; 1684 break; 1685 } else if (reason == MR_LONGTERM_PIN && 1686 ret == -EAGAIN) { 1687 /* 1688 * Try again to split large folio to 1689 * mitigate the failure of longterm pinning. 1690 */ 1691 retry++; 1692 thp_retry += is_thp; 1693 nr_retry_pages += nr_pages; 1694 /* Undo duplicated failure counting. */ 1695 nr_failed--; 1696 stats->nr_thp_failed -= is_thp; 1697 break; 1698 } 1699 } 1700 1701 stats->nr_failed_pages += nr_pages + nr_retry_pages; 1702 /* nr_failed isn't updated for not used */ 1703 stats->nr_thp_failed += thp_retry; 1704 rc_saved = rc; 1705 if (list_empty(&unmap_folios)) 1706 goto out; 1707 else 1708 goto move; 1709 case -EAGAIN: 1710 retry++; 1711 thp_retry += is_thp; 1712 nr_retry_pages += nr_pages; 1713 break; 1714 case MIGRATEPAGE_SUCCESS: 1715 stats->nr_succeeded += nr_pages; 1716 stats->nr_thp_succeeded += is_thp; 1717 break; 1718 case MIGRATEPAGE_UNMAP: 1719 list_move_tail(&folio->lru, &unmap_folios); 1720 list_add_tail(&dst->lru, &dst_folios); 1721 break; 1722 default: 1723 /* 1724 * Permanent failure (-EBUSY, etc.): 1725 * unlike -EAGAIN case, the failed folio is 1726 * removed from migration folio list and not 1727 * retried in the next outer loop. 1728 */ 1729 nr_failed++; 1730 stats->nr_thp_failed += is_thp; 1731 stats->nr_failed_pages += nr_pages; 1732 break; 1733 } 1734 } 1735 } 1736 nr_failed += retry; 1737 stats->nr_thp_failed += thp_retry; 1738 stats->nr_failed_pages += nr_retry_pages; 1739 move: 1740 /* Flush TLBs for all unmapped folios */ 1741 try_to_unmap_flush(); 1742 1743 retry = 1; 1744 for (pass = 0; pass < nr_pass && retry; pass++) { 1745 retry = 0; 1746 thp_retry = 0; 1747 nr_retry_pages = 0; 1748 1749 dst = list_first_entry(&dst_folios, struct folio, lru); 1750 dst2 = list_next_entry(dst, lru); 1751 list_for_each_entry_safe(folio, folio2, &unmap_folios, lru) { 1752 is_thp = folio_test_large(folio) && folio_test_pmd_mappable(folio); 1753 nr_pages = folio_nr_pages(folio); 1754 1755 cond_resched(); 1756 1757 rc = migrate_folio_move(put_new_folio, private, 1758 folio, dst, mode, 1759 reason, ret_folios); 1760 /* 1761 * The rules are: 1762 * Success: folio will be freed 1763 * -EAGAIN: stay on the unmap_folios list 1764 * Other errno: put on ret_folios list 1765 */ 1766 switch(rc) { 1767 case -EAGAIN: 1768 retry++; 1769 thp_retry += is_thp; 1770 nr_retry_pages += nr_pages; 1771 break; 1772 case MIGRATEPAGE_SUCCESS: 1773 stats->nr_succeeded += nr_pages; 1774 stats->nr_thp_succeeded += is_thp; 1775 break; 1776 default: 1777 nr_failed++; 1778 stats->nr_thp_failed += is_thp; 1779 stats->nr_failed_pages += nr_pages; 1780 break; 1781 } 1782 dst = dst2; 1783 dst2 = list_next_entry(dst, lru); 1784 } 1785 } 1786 nr_failed += retry; 1787 stats->nr_thp_failed += thp_retry; 1788 stats->nr_failed_pages += nr_retry_pages; 1789 1790 rc = rc_saved ? : nr_failed; 1791 out: 1792 /* Cleanup remaining folios */ 1793 dst = list_first_entry(&dst_folios, struct folio, lru); 1794 dst2 = list_next_entry(dst, lru); 1795 list_for_each_entry_safe(folio, folio2, &unmap_folios, lru) { 1796 int page_was_mapped = 0; 1797 struct anon_vma *anon_vma = NULL; 1798 1799 __migrate_folio_extract(dst, &page_was_mapped, &anon_vma); 1800 migrate_folio_undo_src(folio, page_was_mapped, anon_vma, 1801 true, ret_folios); 1802 list_del(&dst->lru); 1803 migrate_folio_undo_dst(dst, true, put_new_folio, private); 1804 dst = dst2; 1805 dst2 = list_next_entry(dst, lru); 1806 } 1807 1808 return rc; 1809 } 1810 1811 static int migrate_pages_sync(struct list_head *from, new_folio_t get_new_folio, 1812 free_folio_t put_new_folio, unsigned long private, 1813 enum migrate_mode mode, int reason, 1814 struct list_head *ret_folios, struct list_head *split_folios, 1815 struct migrate_pages_stats *stats) 1816 { 1817 int rc, nr_failed = 0; 1818 LIST_HEAD(folios); 1819 struct migrate_pages_stats astats; 1820 1821 memset(&astats, 0, sizeof(astats)); 1822 /* Try to migrate in batch with MIGRATE_ASYNC mode firstly */ 1823 rc = migrate_pages_batch(from, get_new_folio, put_new_folio, private, MIGRATE_ASYNC, 1824 reason, &folios, split_folios, &astats, 1825 NR_MAX_MIGRATE_ASYNC_RETRY); 1826 stats->nr_succeeded += astats.nr_succeeded; 1827 stats->nr_thp_succeeded += astats.nr_thp_succeeded; 1828 stats->nr_thp_split += astats.nr_thp_split; 1829 if (rc < 0) { 1830 stats->nr_failed_pages += astats.nr_failed_pages; 1831 stats->nr_thp_failed += astats.nr_thp_failed; 1832 list_splice_tail(&folios, ret_folios); 1833 return rc; 1834 } 1835 stats->nr_thp_failed += astats.nr_thp_split; 1836 nr_failed += astats.nr_thp_split; 1837 /* 1838 * Fall back to migrate all failed folios one by one synchronously. All 1839 * failed folios except split THPs will be retried, so their failure 1840 * isn't counted 1841 */ 1842 list_splice_tail_init(&folios, from); 1843 while (!list_empty(from)) { 1844 list_move(from->next, &folios); 1845 rc = migrate_pages_batch(&folios, get_new_folio, put_new_folio, 1846 private, mode, reason, ret_folios, 1847 split_folios, stats, NR_MAX_MIGRATE_SYNC_RETRY); 1848 list_splice_tail_init(&folios, ret_folios); 1849 if (rc < 0) 1850 return rc; 1851 nr_failed += rc; 1852 } 1853 1854 return nr_failed; 1855 } 1856 1857 /* 1858 * migrate_pages - migrate the folios specified in a list, to the free folios 1859 * supplied as the target for the page migration 1860 * 1861 * @from: The list of folios to be migrated. 1862 * @get_new_folio: The function used to allocate free folios to be used 1863 * as the target of the folio migration. 1864 * @put_new_folio: The function used to free target folios if migration 1865 * fails, or NULL if no special handling is necessary. 1866 * @private: Private data to be passed on to get_new_folio() 1867 * @mode: The migration mode that specifies the constraints for 1868 * folio migration, if any. 1869 * @reason: The reason for folio migration. 1870 * @ret_succeeded: Set to the number of folios migrated successfully if 1871 * the caller passes a non-NULL pointer. 1872 * 1873 * The function returns after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no folios 1874 * are movable any more because the list has become empty or no retryable folios 1875 * exist any more. It is caller's responsibility to call putback_movable_pages() 1876 * only if ret != 0. 1877 * 1878 * Returns the number of {normal folio, large folio, hugetlb} that were not 1879 * migrated, or an error code. The number of large folio splits will be 1880 * considered as the number of non-migrated large folio, no matter how many 1881 * split folios of the large folio are migrated successfully. 1882 */ 1883 int migrate_pages(struct list_head *from, new_folio_t get_new_folio, 1884 free_folio_t put_new_folio, unsigned long private, 1885 enum migrate_mode mode, int reason, unsigned int *ret_succeeded) 1886 { 1887 int rc, rc_gather; 1888 int nr_pages; 1889 struct folio *folio, *folio2; 1890 LIST_HEAD(folios); 1891 LIST_HEAD(ret_folios); 1892 LIST_HEAD(split_folios); 1893 struct migrate_pages_stats stats; 1894 1895 trace_mm_migrate_pages_start(mode, reason); 1896 1897 memset(&stats, 0, sizeof(stats)); 1898 1899 rc_gather = migrate_hugetlbs(from, get_new_folio, put_new_folio, private, 1900 mode, reason, &stats, &ret_folios); 1901 if (rc_gather < 0) 1902 goto out; 1903 1904 again: 1905 nr_pages = 0; 1906 list_for_each_entry_safe(folio, folio2, from, lru) { 1907 /* Retried hugetlb folios will be kept in list */ 1908 if (folio_test_hugetlb(folio)) { 1909 list_move_tail(&folio->lru, &ret_folios); 1910 continue; 1911 } 1912 1913 nr_pages += folio_nr_pages(folio); 1914 if (nr_pages >= NR_MAX_BATCHED_MIGRATION) 1915 break; 1916 } 1917 if (nr_pages >= NR_MAX_BATCHED_MIGRATION) 1918 list_cut_before(&folios, from, &folio2->lru); 1919 else 1920 list_splice_init(from, &folios); 1921 if (mode == MIGRATE_ASYNC) 1922 rc = migrate_pages_batch(&folios, get_new_folio, put_new_folio, 1923 private, mode, reason, &ret_folios, 1924 &split_folios, &stats, 1925 NR_MAX_MIGRATE_PAGES_RETRY); 1926 else 1927 rc = migrate_pages_sync(&folios, get_new_folio, put_new_folio, 1928 private, mode, reason, &ret_folios, 1929 &split_folios, &stats); 1930 list_splice_tail_init(&folios, &ret_folios); 1931 if (rc < 0) { 1932 rc_gather = rc; 1933 list_splice_tail(&split_folios, &ret_folios); 1934 goto out; 1935 } 1936 if (!list_empty(&split_folios)) { 1937 /* 1938 * Failure isn't counted since all split folios of a large folio 1939 * is counted as 1 failure already. And, we only try to migrate 1940 * with minimal effort, force MIGRATE_ASYNC mode and retry once. 1941 */ 1942 migrate_pages_batch(&split_folios, get_new_folio, 1943 put_new_folio, private, MIGRATE_ASYNC, reason, 1944 &ret_folios, NULL, &stats, 1); 1945 list_splice_tail_init(&split_folios, &ret_folios); 1946 } 1947 rc_gather += rc; 1948 if (!list_empty(from)) 1949 goto again; 1950 out: 1951 /* 1952 * Put the permanent failure folio back to migration list, they 1953 * will be put back to the right list by the caller. 1954 */ 1955 list_splice(&ret_folios, from); 1956 1957 /* 1958 * Return 0 in case all split folios of fail-to-migrate large folios 1959 * are migrated successfully. 1960 */ 1961 if (list_empty(from)) 1962 rc_gather = 0; 1963 1964 count_vm_events(PGMIGRATE_SUCCESS, stats.nr_succeeded); 1965 count_vm_events(PGMIGRATE_FAIL, stats.nr_failed_pages); 1966 count_vm_events(THP_MIGRATION_SUCCESS, stats.nr_thp_succeeded); 1967 count_vm_events(THP_MIGRATION_FAIL, stats.nr_thp_failed); 1968 count_vm_events(THP_MIGRATION_SPLIT, stats.nr_thp_split); 1969 trace_mm_migrate_pages(stats.nr_succeeded, stats.nr_failed_pages, 1970 stats.nr_thp_succeeded, stats.nr_thp_failed, 1971 stats.nr_thp_split, mode, reason); 1972 1973 if (ret_succeeded) 1974 *ret_succeeded = stats.nr_succeeded; 1975 1976 return rc_gather; 1977 } 1978 1979 struct folio *alloc_migration_target(struct folio *src, unsigned long private) 1980 { 1981 struct migration_target_control *mtc; 1982 gfp_t gfp_mask; 1983 unsigned int order = 0; 1984 int nid; 1985 int zidx; 1986 1987 mtc = (struct migration_target_control *)private; 1988 gfp_mask = mtc->gfp_mask; 1989 nid = mtc->nid; 1990 if (nid == NUMA_NO_NODE) 1991 nid = folio_nid(src); 1992 1993 if (folio_test_hugetlb(src)) { 1994 struct hstate *h = folio_hstate(src); 1995 1996 gfp_mask = htlb_modify_alloc_mask(h, gfp_mask); 1997 return alloc_hugetlb_folio_nodemask(h, nid, 1998 mtc->nmask, gfp_mask); 1999 } 2000 2001 if (folio_test_large(src)) { 2002 /* 2003 * clear __GFP_RECLAIM to make the migration callback 2004 * consistent with regular THP allocations. 2005 */ 2006 gfp_mask &= ~__GFP_RECLAIM; 2007 gfp_mask |= GFP_TRANSHUGE; 2008 order = folio_order(src); 2009 } 2010 zidx = zone_idx(folio_zone(src)); 2011 if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE) 2012 gfp_mask |= __GFP_HIGHMEM; 2013 2014 return __folio_alloc(gfp_mask, order, nid, mtc->nmask); 2015 } 2016 2017 #ifdef CONFIG_NUMA 2018 2019 static int store_status(int __user *status, int start, int value, int nr) 2020 { 2021 while (nr-- > 0) { 2022 if (put_user(value, status + start)) 2023 return -EFAULT; 2024 start++; 2025 } 2026 2027 return 0; 2028 } 2029 2030 static int do_move_pages_to_node(struct mm_struct *mm, 2031 struct list_head *pagelist, int node) 2032 { 2033 int err; 2034 struct migration_target_control mtc = { 2035 .nid = node, 2036 .gfp_mask = GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, 2037 }; 2038 2039 err = migrate_pages(pagelist, alloc_migration_target, NULL, 2040 (unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL, NULL); 2041 if (err) 2042 putback_movable_pages(pagelist); 2043 return err; 2044 } 2045 2046 /* 2047 * Resolves the given address to a struct page, isolates it from the LRU and 2048 * puts it to the given pagelist. 2049 * Returns: 2050 * errno - if the page cannot be found/isolated 2051 * 0 - when it doesn't have to be migrated because it is already on the 2052 * target node 2053 * 1 - when it has been queued 2054 */ 2055 static int add_page_for_migration(struct mm_struct *mm, const void __user *p, 2056 int node, struct list_head *pagelist, bool migrate_all) 2057 { 2058 struct vm_area_struct *vma; 2059 unsigned long addr; 2060 struct page *page; 2061 int err; 2062 bool isolated; 2063 2064 mmap_read_lock(mm); 2065 addr = (unsigned long)untagged_addr_remote(mm, p); 2066 2067 err = -EFAULT; 2068 vma = vma_lookup(mm, addr); 2069 if (!vma || !vma_migratable(vma)) 2070 goto out; 2071 2072 /* FOLL_DUMP to ignore special (like zero) pages */ 2073 page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); 2074 2075 err = PTR_ERR(page); 2076 if (IS_ERR(page)) 2077 goto out; 2078 2079 err = -ENOENT; 2080 if (!page) 2081 goto out; 2082 2083 if (is_zone_device_page(page)) 2084 goto out_putpage; 2085 2086 err = 0; 2087 if (page_to_nid(page) == node) 2088 goto out_putpage; 2089 2090 err = -EACCES; 2091 if (page_mapcount(page) > 1 && !migrate_all) 2092 goto out_putpage; 2093 2094 if (PageHuge(page)) { 2095 if (PageHead(page)) { 2096 isolated = isolate_hugetlb(page_folio(page), pagelist); 2097 err = isolated ? 1 : -EBUSY; 2098 } 2099 } else { 2100 struct page *head; 2101 2102 head = compound_head(page); 2103 isolated = isolate_lru_page(head); 2104 if (!isolated) { 2105 err = -EBUSY; 2106 goto out_putpage; 2107 } 2108 2109 err = 1; 2110 list_add_tail(&head->lru, pagelist); 2111 mod_node_page_state(page_pgdat(head), 2112 NR_ISOLATED_ANON + page_is_file_lru(head), 2113 thp_nr_pages(head)); 2114 } 2115 out_putpage: 2116 /* 2117 * Either remove the duplicate refcount from 2118 * isolate_lru_page() or drop the page ref if it was 2119 * not isolated. 2120 */ 2121 put_page(page); 2122 out: 2123 mmap_read_unlock(mm); 2124 return err; 2125 } 2126 2127 static int move_pages_and_store_status(struct mm_struct *mm, int node, 2128 struct list_head *pagelist, int __user *status, 2129 int start, int i, unsigned long nr_pages) 2130 { 2131 int err; 2132 2133 if (list_empty(pagelist)) 2134 return 0; 2135 2136 err = do_move_pages_to_node(mm, pagelist, node); 2137 if (err) { 2138 /* 2139 * Positive err means the number of failed 2140 * pages to migrate. Since we are going to 2141 * abort and return the number of non-migrated 2142 * pages, so need to include the rest of the 2143 * nr_pages that have not been attempted as 2144 * well. 2145 */ 2146 if (err > 0) 2147 err += nr_pages - i; 2148 return err; 2149 } 2150 return store_status(status, start, node, i - start); 2151 } 2152 2153 /* 2154 * Migrate an array of page address onto an array of nodes and fill 2155 * the corresponding array of status. 2156 */ 2157 static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, 2158 unsigned long nr_pages, 2159 const void __user * __user *pages, 2160 const int __user *nodes, 2161 int __user *status, int flags) 2162 { 2163 int current_node = NUMA_NO_NODE; 2164 LIST_HEAD(pagelist); 2165 int start, i; 2166 int err = 0, err1; 2167 2168 lru_cache_disable(); 2169 2170 for (i = start = 0; i < nr_pages; i++) { 2171 const void __user *p; 2172 int node; 2173 2174 err = -EFAULT; 2175 if (get_user(p, pages + i)) 2176 goto out_flush; 2177 if (get_user(node, nodes + i)) 2178 goto out_flush; 2179 2180 err = -ENODEV; 2181 if (node < 0 || node >= MAX_NUMNODES) 2182 goto out_flush; 2183 if (!node_state(node, N_MEMORY)) 2184 goto out_flush; 2185 2186 err = -EACCES; 2187 if (!node_isset(node, task_nodes)) 2188 goto out_flush; 2189 2190 if (current_node == NUMA_NO_NODE) { 2191 current_node = node; 2192 start = i; 2193 } else if (node != current_node) { 2194 err = move_pages_and_store_status(mm, current_node, 2195 &pagelist, status, start, i, nr_pages); 2196 if (err) 2197 goto out; 2198 start = i; 2199 current_node = node; 2200 } 2201 2202 /* 2203 * Errors in the page lookup or isolation are not fatal and we simply 2204 * report them via status 2205 */ 2206 err = add_page_for_migration(mm, p, current_node, &pagelist, 2207 flags & MPOL_MF_MOVE_ALL); 2208 2209 if (err > 0) { 2210 /* The page is successfully queued for migration */ 2211 continue; 2212 } 2213 2214 /* 2215 * The move_pages() man page does not have an -EEXIST choice, so 2216 * use -EFAULT instead. 2217 */ 2218 if (err == -EEXIST) 2219 err = -EFAULT; 2220 2221 /* 2222 * If the page is already on the target node (!err), store the 2223 * node, otherwise, store the err. 2224 */ 2225 err = store_status(status, i, err ? : current_node, 1); 2226 if (err) 2227 goto out_flush; 2228 2229 err = move_pages_and_store_status(mm, current_node, &pagelist, 2230 status, start, i, nr_pages); 2231 if (err) { 2232 /* We have accounted for page i */ 2233 if (err > 0) 2234 err--; 2235 goto out; 2236 } 2237 current_node = NUMA_NO_NODE; 2238 } 2239 out_flush: 2240 /* Make sure we do not overwrite the existing error */ 2241 err1 = move_pages_and_store_status(mm, current_node, &pagelist, 2242 status, start, i, nr_pages); 2243 if (err >= 0) 2244 err = err1; 2245 out: 2246 lru_cache_enable(); 2247 return err; 2248 } 2249 2250 /* 2251 * Determine the nodes of an array of pages and store it in an array of status. 2252 */ 2253 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, 2254 const void __user **pages, int *status) 2255 { 2256 unsigned long i; 2257 2258 mmap_read_lock(mm); 2259 2260 for (i = 0; i < nr_pages; i++) { 2261 unsigned long addr = (unsigned long)(*pages); 2262 struct vm_area_struct *vma; 2263 struct page *page; 2264 int err = -EFAULT; 2265 2266 vma = vma_lookup(mm, addr); 2267 if (!vma) 2268 goto set_status; 2269 2270 /* FOLL_DUMP to ignore special (like zero) pages */ 2271 page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); 2272 2273 err = PTR_ERR(page); 2274 if (IS_ERR(page)) 2275 goto set_status; 2276 2277 err = -ENOENT; 2278 if (!page) 2279 goto set_status; 2280 2281 if (!is_zone_device_page(page)) 2282 err = page_to_nid(page); 2283 2284 put_page(page); 2285 set_status: 2286 *status = err; 2287 2288 pages++; 2289 status++; 2290 } 2291 2292 mmap_read_unlock(mm); 2293 } 2294 2295 static int get_compat_pages_array(const void __user *chunk_pages[], 2296 const void __user * __user *pages, 2297 unsigned long chunk_nr) 2298 { 2299 compat_uptr_t __user *pages32 = (compat_uptr_t __user *)pages; 2300 compat_uptr_t p; 2301 int i; 2302 2303 for (i = 0; i < chunk_nr; i++) { 2304 if (get_user(p, pages32 + i)) 2305 return -EFAULT; 2306 chunk_pages[i] = compat_ptr(p); 2307 } 2308 2309 return 0; 2310 } 2311 2312 /* 2313 * Determine the nodes of a user array of pages and store it in 2314 * a user array of status. 2315 */ 2316 static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, 2317 const void __user * __user *pages, 2318 int __user *status) 2319 { 2320 #define DO_PAGES_STAT_CHUNK_NR 16UL 2321 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR]; 2322 int chunk_status[DO_PAGES_STAT_CHUNK_NR]; 2323 2324 while (nr_pages) { 2325 unsigned long chunk_nr = min(nr_pages, DO_PAGES_STAT_CHUNK_NR); 2326 2327 if (in_compat_syscall()) { 2328 if (get_compat_pages_array(chunk_pages, pages, 2329 chunk_nr)) 2330 break; 2331 } else { 2332 if (copy_from_user(chunk_pages, pages, 2333 chunk_nr * sizeof(*chunk_pages))) 2334 break; 2335 } 2336 2337 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status); 2338 2339 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status))) 2340 break; 2341 2342 pages += chunk_nr; 2343 status += chunk_nr; 2344 nr_pages -= chunk_nr; 2345 } 2346 return nr_pages ? -EFAULT : 0; 2347 } 2348 2349 static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes) 2350 { 2351 struct task_struct *task; 2352 struct mm_struct *mm; 2353 2354 /* 2355 * There is no need to check if current process has the right to modify 2356 * the specified process when they are same. 2357 */ 2358 if (!pid) { 2359 mmget(current->mm); 2360 *mem_nodes = cpuset_mems_allowed(current); 2361 return current->mm; 2362 } 2363 2364 /* Find the mm_struct */ 2365 rcu_read_lock(); 2366 task = find_task_by_vpid(pid); 2367 if (!task) { 2368 rcu_read_unlock(); 2369 return ERR_PTR(-ESRCH); 2370 } 2371 get_task_struct(task); 2372 2373 /* 2374 * Check if this process has the right to modify the specified 2375 * process. Use the regular "ptrace_may_access()" checks. 2376 */ 2377 if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) { 2378 rcu_read_unlock(); 2379 mm = ERR_PTR(-EPERM); 2380 goto out; 2381 } 2382 rcu_read_unlock(); 2383 2384 mm = ERR_PTR(security_task_movememory(task)); 2385 if (IS_ERR(mm)) 2386 goto out; 2387 *mem_nodes = cpuset_mems_allowed(task); 2388 mm = get_task_mm(task); 2389 out: 2390 put_task_struct(task); 2391 if (!mm) 2392 mm = ERR_PTR(-EINVAL); 2393 return mm; 2394 } 2395 2396 /* 2397 * Move a list of pages in the address space of the currently executing 2398 * process. 2399 */ 2400 static int kernel_move_pages(pid_t pid, unsigned long nr_pages, 2401 const void __user * __user *pages, 2402 const int __user *nodes, 2403 int __user *status, int flags) 2404 { 2405 struct mm_struct *mm; 2406 int err; 2407 nodemask_t task_nodes; 2408 2409 /* Check flags */ 2410 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL)) 2411 return -EINVAL; 2412 2413 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE)) 2414 return -EPERM; 2415 2416 mm = find_mm_struct(pid, &task_nodes); 2417 if (IS_ERR(mm)) 2418 return PTR_ERR(mm); 2419 2420 if (nodes) 2421 err = do_pages_move(mm, task_nodes, nr_pages, pages, 2422 nodes, status, flags); 2423 else 2424 err = do_pages_stat(mm, nr_pages, pages, status); 2425 2426 mmput(mm); 2427 return err; 2428 } 2429 2430 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages, 2431 const void __user * __user *, pages, 2432 const int __user *, nodes, 2433 int __user *, status, int, flags) 2434 { 2435 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags); 2436 } 2437 2438 #ifdef CONFIG_NUMA_BALANCING 2439 /* 2440 * Returns true if this is a safe migration target node for misplaced NUMA 2441 * pages. Currently it only checks the watermarks which is crude. 2442 */ 2443 static bool migrate_balanced_pgdat(struct pglist_data *pgdat, 2444 unsigned long nr_migrate_pages) 2445 { 2446 int z; 2447 2448 for (z = pgdat->nr_zones - 1; z >= 0; z--) { 2449 struct zone *zone = pgdat->node_zones + z; 2450 2451 if (!managed_zone(zone)) 2452 continue; 2453 2454 /* Avoid waking kswapd by allocating pages_to_migrate pages. */ 2455 if (!zone_watermark_ok(zone, 0, 2456 high_wmark_pages(zone) + 2457 nr_migrate_pages, 2458 ZONE_MOVABLE, 0)) 2459 continue; 2460 return true; 2461 } 2462 return false; 2463 } 2464 2465 static struct folio *alloc_misplaced_dst_folio(struct folio *src, 2466 unsigned long data) 2467 { 2468 int nid = (int) data; 2469 int order = folio_order(src); 2470 gfp_t gfp = __GFP_THISNODE; 2471 2472 if (order > 0) 2473 gfp |= GFP_TRANSHUGE_LIGHT; 2474 else { 2475 gfp |= GFP_HIGHUSER_MOVABLE | __GFP_NOMEMALLOC | __GFP_NORETRY | 2476 __GFP_NOWARN; 2477 gfp &= ~__GFP_RECLAIM; 2478 } 2479 return __folio_alloc_node(gfp, order, nid); 2480 } 2481 2482 static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) 2483 { 2484 int nr_pages = thp_nr_pages(page); 2485 int order = compound_order(page); 2486 2487 VM_BUG_ON_PAGE(order && !PageTransHuge(page), page); 2488 2489 /* Do not migrate THP mapped by multiple processes */ 2490 if (PageTransHuge(page) && total_mapcount(page) > 1) 2491 return 0; 2492 2493 /* Avoid migrating to a node that is nearly full */ 2494 if (!migrate_balanced_pgdat(pgdat, nr_pages)) { 2495 int z; 2496 2497 if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)) 2498 return 0; 2499 for (z = pgdat->nr_zones - 1; z >= 0; z--) { 2500 if (managed_zone(pgdat->node_zones + z)) 2501 break; 2502 } 2503 wakeup_kswapd(pgdat->node_zones + z, 0, order, ZONE_MOVABLE); 2504 return 0; 2505 } 2506 2507 if (!isolate_lru_page(page)) 2508 return 0; 2509 2510 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_is_file_lru(page), 2511 nr_pages); 2512 2513 /* 2514 * Isolating the page has taken another reference, so the 2515 * caller's reference can be safely dropped without the page 2516 * disappearing underneath us during migration. 2517 */ 2518 put_page(page); 2519 return 1; 2520 } 2521 2522 /* 2523 * Attempt to migrate a misplaced page to the specified destination 2524 * node. Caller is expected to have an elevated reference count on 2525 * the page that will be dropped by this function before returning. 2526 */ 2527 int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma, 2528 int node) 2529 { 2530 pg_data_t *pgdat = NODE_DATA(node); 2531 int isolated; 2532 int nr_remaining; 2533 unsigned int nr_succeeded; 2534 LIST_HEAD(migratepages); 2535 int nr_pages = thp_nr_pages(page); 2536 2537 /* 2538 * Don't migrate file pages that are mapped in multiple processes 2539 * with execute permissions as they are probably shared libraries. 2540 */ 2541 if (page_mapcount(page) != 1 && page_is_file_lru(page) && 2542 (vma->vm_flags & VM_EXEC)) 2543 goto out; 2544 2545 /* 2546 * Also do not migrate dirty pages as not all filesystems can move 2547 * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles. 2548 */ 2549 if (page_is_file_lru(page) && PageDirty(page)) 2550 goto out; 2551 2552 isolated = numamigrate_isolate_page(pgdat, page); 2553 if (!isolated) 2554 goto out; 2555 2556 list_add(&page->lru, &migratepages); 2557 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_folio, 2558 NULL, node, MIGRATE_ASYNC, 2559 MR_NUMA_MISPLACED, &nr_succeeded); 2560 if (nr_remaining) { 2561 if (!list_empty(&migratepages)) { 2562 list_del(&page->lru); 2563 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + 2564 page_is_file_lru(page), -nr_pages); 2565 putback_lru_page(page); 2566 } 2567 isolated = 0; 2568 } 2569 if (nr_succeeded) { 2570 count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded); 2571 if (!node_is_toptier(page_to_nid(page)) && node_is_toptier(node)) 2572 mod_node_page_state(pgdat, PGPROMOTE_SUCCESS, 2573 nr_succeeded); 2574 } 2575 BUG_ON(!list_empty(&migratepages)); 2576 return isolated; 2577 2578 out: 2579 put_page(page); 2580 return 0; 2581 } 2582 #endif /* CONFIG_NUMA_BALANCING */ 2583 #endif /* CONFIG_NUMA */ 2584