1 // SPDX-License-Identifier: GPL-2.0 2 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 3 4 #include <linux/mm.h> 5 #include <linux/sched.h> 6 #include <linux/sched/mm.h> 7 #include <linux/sched/coredump.h> 8 #include <linux/mmu_notifier.h> 9 #include <linux/rmap.h> 10 #include <linux/swap.h> 11 #include <linux/mm_inline.h> 12 #include <linux/kthread.h> 13 #include <linux/khugepaged.h> 14 #include <linux/freezer.h> 15 #include <linux/mman.h> 16 #include <linux/hashtable.h> 17 #include <linux/userfaultfd_k.h> 18 #include <linux/page_idle.h> 19 #include <linux/page_table_check.h> 20 #include <linux/swapops.h> 21 #include <linux/shmem_fs.h> 22 23 #include <asm/tlb.h> 24 #include <asm/pgalloc.h> 25 #include "internal.h" 26 #include "mm_slot.h" 27 28 enum scan_result { 29 SCAN_FAIL, 30 SCAN_SUCCEED, 31 SCAN_PMD_NULL, 32 SCAN_PMD_NONE, 33 SCAN_PMD_MAPPED, 34 SCAN_EXCEED_NONE_PTE, 35 SCAN_EXCEED_SWAP_PTE, 36 SCAN_EXCEED_SHARED_PTE, 37 SCAN_PTE_NON_PRESENT, 38 SCAN_PTE_UFFD_WP, 39 SCAN_PTE_MAPPED_HUGEPAGE, 40 SCAN_PAGE_RO, 41 SCAN_LACK_REFERENCED_PAGE, 42 SCAN_PAGE_NULL, 43 SCAN_SCAN_ABORT, 44 SCAN_PAGE_COUNT, 45 SCAN_PAGE_LRU, 46 SCAN_PAGE_LOCK, 47 SCAN_PAGE_ANON, 48 SCAN_PAGE_COMPOUND, 49 SCAN_ANY_PROCESS, 50 SCAN_VMA_NULL, 51 SCAN_VMA_CHECK, 52 SCAN_ADDRESS_RANGE, 53 SCAN_DEL_PAGE_LRU, 54 SCAN_ALLOC_HUGE_PAGE_FAIL, 55 SCAN_CGROUP_CHARGE_FAIL, 56 SCAN_TRUNCATED, 57 SCAN_PAGE_HAS_PRIVATE, 58 SCAN_STORE_FAILED, 59 }; 60 61 #define CREATE_TRACE_POINTS 62 #include <trace/events/huge_memory.h> 63 64 static struct task_struct *khugepaged_thread __read_mostly; 65 static DEFINE_MUTEX(khugepaged_mutex); 66 67 /* default scan 8*512 pte (or vmas) every 30 second */ 68 static unsigned int khugepaged_pages_to_scan __read_mostly; 69 static unsigned int khugepaged_pages_collapsed; 70 static unsigned int khugepaged_full_scans; 71 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 72 /* during fragmentation poll the hugepage allocator once every minute */ 73 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 74 static unsigned long khugepaged_sleep_expire; 75 static DEFINE_SPINLOCK(khugepaged_mm_lock); 76 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 77 /* 78 * default collapse hugepages if there is at least one pte mapped like 79 * it would have happened if the vma was large enough during page 80 * fault. 81 * 82 * Note that these are only respected if collapse was initiated by khugepaged. 83 */ 84 static unsigned int khugepaged_max_ptes_none __read_mostly; 85 static unsigned int khugepaged_max_ptes_swap __read_mostly; 86 static unsigned int khugepaged_max_ptes_shared __read_mostly; 87 88 #define MM_SLOTS_HASH_BITS 10 89 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); 90 91 static struct kmem_cache *mm_slot_cache __read_mostly; 92 93 #define MAX_PTE_MAPPED_THP 8 94 95 struct collapse_control { 96 bool is_khugepaged; 97 98 /* Num pages scanned per node */ 99 u32 node_load[MAX_NUMNODES]; 100 101 /* nodemask for allocation fallback */ 102 nodemask_t alloc_nmask; 103 }; 104 105 /** 106 * struct khugepaged_mm_slot - khugepaged information per mm that is being scanned 107 * @slot: hash lookup from mm to mm_slot 108 * @nr_pte_mapped_thp: number of pte mapped THP 109 * @pte_mapped_thp: address array corresponding pte mapped THP 110 */ 111 struct khugepaged_mm_slot { 112 struct mm_slot slot; 113 114 /* pte-mapped THP in this mm */ 115 int nr_pte_mapped_thp; 116 unsigned long pte_mapped_thp[MAX_PTE_MAPPED_THP]; 117 }; 118 119 /** 120 * struct khugepaged_scan - cursor for scanning 121 * @mm_head: the head of the mm list to scan 122 * @mm_slot: the current mm_slot we are scanning 123 * @address: the next address inside that to be scanned 124 * 125 * There is only the one khugepaged_scan instance of this cursor structure. 126 */ 127 struct khugepaged_scan { 128 struct list_head mm_head; 129 struct khugepaged_mm_slot *mm_slot; 130 unsigned long address; 131 }; 132 133 static struct khugepaged_scan khugepaged_scan = { 134 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 135 }; 136 137 #ifdef CONFIG_SYSFS 138 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 139 struct kobj_attribute *attr, 140 char *buf) 141 { 142 return sysfs_emit(buf, "%u\n", khugepaged_scan_sleep_millisecs); 143 } 144 145 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 146 struct kobj_attribute *attr, 147 const char *buf, size_t count) 148 { 149 unsigned int msecs; 150 int err; 151 152 err = kstrtouint(buf, 10, &msecs); 153 if (err) 154 return -EINVAL; 155 156 khugepaged_scan_sleep_millisecs = msecs; 157 khugepaged_sleep_expire = 0; 158 wake_up_interruptible(&khugepaged_wait); 159 160 return count; 161 } 162 static struct kobj_attribute scan_sleep_millisecs_attr = 163 __ATTR_RW(scan_sleep_millisecs); 164 165 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 166 struct kobj_attribute *attr, 167 char *buf) 168 { 169 return sysfs_emit(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 170 } 171 172 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 173 struct kobj_attribute *attr, 174 const char *buf, size_t count) 175 { 176 unsigned int msecs; 177 int err; 178 179 err = kstrtouint(buf, 10, &msecs); 180 if (err) 181 return -EINVAL; 182 183 khugepaged_alloc_sleep_millisecs = msecs; 184 khugepaged_sleep_expire = 0; 185 wake_up_interruptible(&khugepaged_wait); 186 187 return count; 188 } 189 static struct kobj_attribute alloc_sleep_millisecs_attr = 190 __ATTR_RW(alloc_sleep_millisecs); 191 192 static ssize_t pages_to_scan_show(struct kobject *kobj, 193 struct kobj_attribute *attr, 194 char *buf) 195 { 196 return sysfs_emit(buf, "%u\n", khugepaged_pages_to_scan); 197 } 198 static ssize_t pages_to_scan_store(struct kobject *kobj, 199 struct kobj_attribute *attr, 200 const char *buf, size_t count) 201 { 202 unsigned int pages; 203 int err; 204 205 err = kstrtouint(buf, 10, &pages); 206 if (err || !pages) 207 return -EINVAL; 208 209 khugepaged_pages_to_scan = pages; 210 211 return count; 212 } 213 static struct kobj_attribute pages_to_scan_attr = 214 __ATTR_RW(pages_to_scan); 215 216 static ssize_t pages_collapsed_show(struct kobject *kobj, 217 struct kobj_attribute *attr, 218 char *buf) 219 { 220 return sysfs_emit(buf, "%u\n", khugepaged_pages_collapsed); 221 } 222 static struct kobj_attribute pages_collapsed_attr = 223 __ATTR_RO(pages_collapsed); 224 225 static ssize_t full_scans_show(struct kobject *kobj, 226 struct kobj_attribute *attr, 227 char *buf) 228 { 229 return sysfs_emit(buf, "%u\n", khugepaged_full_scans); 230 } 231 static struct kobj_attribute full_scans_attr = 232 __ATTR_RO(full_scans); 233 234 static ssize_t defrag_show(struct kobject *kobj, 235 struct kobj_attribute *attr, char *buf) 236 { 237 return single_hugepage_flag_show(kobj, attr, buf, 238 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 239 } 240 static ssize_t defrag_store(struct kobject *kobj, 241 struct kobj_attribute *attr, 242 const char *buf, size_t count) 243 { 244 return single_hugepage_flag_store(kobj, attr, buf, count, 245 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 246 } 247 static struct kobj_attribute khugepaged_defrag_attr = 248 __ATTR_RW(defrag); 249 250 /* 251 * max_ptes_none controls if khugepaged should collapse hugepages over 252 * any unmapped ptes in turn potentially increasing the memory 253 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 254 * reduce the available free memory in the system as it 255 * runs. Increasing max_ptes_none will instead potentially reduce the 256 * free memory in the system during the khugepaged scan. 257 */ 258 static ssize_t max_ptes_none_show(struct kobject *kobj, 259 struct kobj_attribute *attr, 260 char *buf) 261 { 262 return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_none); 263 } 264 static ssize_t max_ptes_none_store(struct kobject *kobj, 265 struct kobj_attribute *attr, 266 const char *buf, size_t count) 267 { 268 int err; 269 unsigned long max_ptes_none; 270 271 err = kstrtoul(buf, 10, &max_ptes_none); 272 if (err || max_ptes_none > HPAGE_PMD_NR - 1) 273 return -EINVAL; 274 275 khugepaged_max_ptes_none = max_ptes_none; 276 277 return count; 278 } 279 static struct kobj_attribute khugepaged_max_ptes_none_attr = 280 __ATTR_RW(max_ptes_none); 281 282 static ssize_t max_ptes_swap_show(struct kobject *kobj, 283 struct kobj_attribute *attr, 284 char *buf) 285 { 286 return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_swap); 287 } 288 289 static ssize_t max_ptes_swap_store(struct kobject *kobj, 290 struct kobj_attribute *attr, 291 const char *buf, size_t count) 292 { 293 int err; 294 unsigned long max_ptes_swap; 295 296 err = kstrtoul(buf, 10, &max_ptes_swap); 297 if (err || max_ptes_swap > HPAGE_PMD_NR - 1) 298 return -EINVAL; 299 300 khugepaged_max_ptes_swap = max_ptes_swap; 301 302 return count; 303 } 304 305 static struct kobj_attribute khugepaged_max_ptes_swap_attr = 306 __ATTR_RW(max_ptes_swap); 307 308 static ssize_t max_ptes_shared_show(struct kobject *kobj, 309 struct kobj_attribute *attr, 310 char *buf) 311 { 312 return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_shared); 313 } 314 315 static ssize_t max_ptes_shared_store(struct kobject *kobj, 316 struct kobj_attribute *attr, 317 const char *buf, size_t count) 318 { 319 int err; 320 unsigned long max_ptes_shared; 321 322 err = kstrtoul(buf, 10, &max_ptes_shared); 323 if (err || max_ptes_shared > HPAGE_PMD_NR - 1) 324 return -EINVAL; 325 326 khugepaged_max_ptes_shared = max_ptes_shared; 327 328 return count; 329 } 330 331 static struct kobj_attribute khugepaged_max_ptes_shared_attr = 332 __ATTR_RW(max_ptes_shared); 333 334 static struct attribute *khugepaged_attr[] = { 335 &khugepaged_defrag_attr.attr, 336 &khugepaged_max_ptes_none_attr.attr, 337 &khugepaged_max_ptes_swap_attr.attr, 338 &khugepaged_max_ptes_shared_attr.attr, 339 &pages_to_scan_attr.attr, 340 &pages_collapsed_attr.attr, 341 &full_scans_attr.attr, 342 &scan_sleep_millisecs_attr.attr, 343 &alloc_sleep_millisecs_attr.attr, 344 NULL, 345 }; 346 347 struct attribute_group khugepaged_attr_group = { 348 .attrs = khugepaged_attr, 349 .name = "khugepaged", 350 }; 351 #endif /* CONFIG_SYSFS */ 352 353 int hugepage_madvise(struct vm_area_struct *vma, 354 unsigned long *vm_flags, int advice) 355 { 356 switch (advice) { 357 case MADV_HUGEPAGE: 358 #ifdef CONFIG_S390 359 /* 360 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 361 * can't handle this properly after s390_enable_sie, so we simply 362 * ignore the madvise to prevent qemu from causing a SIGSEGV. 363 */ 364 if (mm_has_pgste(vma->vm_mm)) 365 return 0; 366 #endif 367 *vm_flags &= ~VM_NOHUGEPAGE; 368 *vm_flags |= VM_HUGEPAGE; 369 /* 370 * If the vma become good for khugepaged to scan, 371 * register it here without waiting a page fault that 372 * may not happen any time soon. 373 */ 374 khugepaged_enter_vma(vma, *vm_flags); 375 break; 376 case MADV_NOHUGEPAGE: 377 *vm_flags &= ~VM_HUGEPAGE; 378 *vm_flags |= VM_NOHUGEPAGE; 379 /* 380 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 381 * this vma even if we leave the mm registered in khugepaged if 382 * it got registered before VM_NOHUGEPAGE was set. 383 */ 384 break; 385 } 386 387 return 0; 388 } 389 390 int __init khugepaged_init(void) 391 { 392 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 393 sizeof(struct khugepaged_mm_slot), 394 __alignof__(struct khugepaged_mm_slot), 395 0, NULL); 396 if (!mm_slot_cache) 397 return -ENOMEM; 398 399 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; 400 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; 401 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8; 402 khugepaged_max_ptes_shared = HPAGE_PMD_NR / 2; 403 404 return 0; 405 } 406 407 void __init khugepaged_destroy(void) 408 { 409 kmem_cache_destroy(mm_slot_cache); 410 } 411 412 static inline int hpage_collapse_test_exit(struct mm_struct *mm) 413 { 414 return atomic_read(&mm->mm_users) == 0; 415 } 416 417 void __khugepaged_enter(struct mm_struct *mm) 418 { 419 struct khugepaged_mm_slot *mm_slot; 420 struct mm_slot *slot; 421 int wakeup; 422 423 mm_slot = mm_slot_alloc(mm_slot_cache); 424 if (!mm_slot) 425 return; 426 427 slot = &mm_slot->slot; 428 429 /* __khugepaged_exit() must not run from under us */ 430 VM_BUG_ON_MM(hpage_collapse_test_exit(mm), mm); 431 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 432 mm_slot_free(mm_slot_cache, mm_slot); 433 return; 434 } 435 436 spin_lock(&khugepaged_mm_lock); 437 mm_slot_insert(mm_slots_hash, mm, slot); 438 /* 439 * Insert just behind the scanning cursor, to let the area settle 440 * down a little. 441 */ 442 wakeup = list_empty(&khugepaged_scan.mm_head); 443 list_add_tail(&slot->mm_node, &khugepaged_scan.mm_head); 444 spin_unlock(&khugepaged_mm_lock); 445 446 mmgrab(mm); 447 if (wakeup) 448 wake_up_interruptible(&khugepaged_wait); 449 } 450 451 void khugepaged_enter_vma(struct vm_area_struct *vma, 452 unsigned long vm_flags) 453 { 454 if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) && 455 hugepage_flags_enabled()) { 456 if (hugepage_vma_check(vma, vm_flags, false, false, true)) 457 __khugepaged_enter(vma->vm_mm); 458 } 459 } 460 461 void __khugepaged_exit(struct mm_struct *mm) 462 { 463 struct khugepaged_mm_slot *mm_slot; 464 struct mm_slot *slot; 465 int free = 0; 466 467 spin_lock(&khugepaged_mm_lock); 468 slot = mm_slot_lookup(mm_slots_hash, mm); 469 mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot); 470 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 471 hash_del(&slot->hash); 472 list_del(&slot->mm_node); 473 free = 1; 474 } 475 spin_unlock(&khugepaged_mm_lock); 476 477 if (free) { 478 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 479 mm_slot_free(mm_slot_cache, mm_slot); 480 mmdrop(mm); 481 } else if (mm_slot) { 482 /* 483 * This is required to serialize against 484 * hpage_collapse_test_exit() (which is guaranteed to run 485 * under mmap sem read mode). Stop here (after we return all 486 * pagetables will be destroyed) until khugepaged has finished 487 * working on the pagetables under the mmap_lock. 488 */ 489 mmap_write_lock(mm); 490 mmap_write_unlock(mm); 491 } 492 } 493 494 static void release_pte_folio(struct folio *folio) 495 { 496 node_stat_mod_folio(folio, 497 NR_ISOLATED_ANON + folio_is_file_lru(folio), 498 -folio_nr_pages(folio)); 499 folio_unlock(folio); 500 folio_putback_lru(folio); 501 } 502 503 static void release_pte_page(struct page *page) 504 { 505 release_pte_folio(page_folio(page)); 506 } 507 508 static void release_pte_pages(pte_t *pte, pte_t *_pte, 509 struct list_head *compound_pagelist) 510 { 511 struct folio *folio, *tmp; 512 513 while (--_pte >= pte) { 514 pte_t pteval = *_pte; 515 unsigned long pfn; 516 517 if (pte_none(pteval)) 518 continue; 519 pfn = pte_pfn(pteval); 520 if (is_zero_pfn(pfn)) 521 continue; 522 folio = pfn_folio(pfn); 523 if (folio_test_large(folio)) 524 continue; 525 release_pte_folio(folio); 526 } 527 528 list_for_each_entry_safe(folio, tmp, compound_pagelist, lru) { 529 list_del(&folio->lru); 530 release_pte_folio(folio); 531 } 532 } 533 534 static bool is_refcount_suitable(struct page *page) 535 { 536 int expected_refcount; 537 538 expected_refcount = total_mapcount(page); 539 if (PageSwapCache(page)) 540 expected_refcount += compound_nr(page); 541 542 return page_count(page) == expected_refcount; 543 } 544 545 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 546 unsigned long address, 547 pte_t *pte, 548 struct collapse_control *cc, 549 struct list_head *compound_pagelist) 550 { 551 struct page *page = NULL; 552 pte_t *_pte; 553 int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0; 554 bool writable = false; 555 556 for (_pte = pte; _pte < pte + HPAGE_PMD_NR; 557 _pte++, address += PAGE_SIZE) { 558 pte_t pteval = *_pte; 559 if (pte_none(pteval) || (pte_present(pteval) && 560 is_zero_pfn(pte_pfn(pteval)))) { 561 ++none_or_zero; 562 if (!userfaultfd_armed(vma) && 563 (!cc->is_khugepaged || 564 none_or_zero <= khugepaged_max_ptes_none)) { 565 continue; 566 } else { 567 result = SCAN_EXCEED_NONE_PTE; 568 count_vm_event(THP_SCAN_EXCEED_NONE_PTE); 569 goto out; 570 } 571 } 572 if (!pte_present(pteval)) { 573 result = SCAN_PTE_NON_PRESENT; 574 goto out; 575 } 576 if (pte_uffd_wp(pteval)) { 577 result = SCAN_PTE_UFFD_WP; 578 goto out; 579 } 580 page = vm_normal_page(vma, address, pteval); 581 if (unlikely(!page) || unlikely(is_zone_device_page(page))) { 582 result = SCAN_PAGE_NULL; 583 goto out; 584 } 585 586 VM_BUG_ON_PAGE(!PageAnon(page), page); 587 588 if (page_mapcount(page) > 1) { 589 ++shared; 590 if (cc->is_khugepaged && 591 shared > khugepaged_max_ptes_shared) { 592 result = SCAN_EXCEED_SHARED_PTE; 593 count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); 594 goto out; 595 } 596 } 597 598 if (PageCompound(page)) { 599 struct page *p; 600 page = compound_head(page); 601 602 /* 603 * Check if we have dealt with the compound page 604 * already 605 */ 606 list_for_each_entry(p, compound_pagelist, lru) { 607 if (page == p) 608 goto next; 609 } 610 } 611 612 /* 613 * We can do it before isolate_lru_page because the 614 * page can't be freed from under us. NOTE: PG_lock 615 * is needed to serialize against split_huge_page 616 * when invoked from the VM. 617 */ 618 if (!trylock_page(page)) { 619 result = SCAN_PAGE_LOCK; 620 goto out; 621 } 622 623 /* 624 * Check if the page has any GUP (or other external) pins. 625 * 626 * The page table that maps the page has been already unlinked 627 * from the page table tree and this process cannot get 628 * an additional pin on the page. 629 * 630 * New pins can come later if the page is shared across fork, 631 * but not from this process. The other process cannot write to 632 * the page, only trigger CoW. 633 */ 634 if (!is_refcount_suitable(page)) { 635 unlock_page(page); 636 result = SCAN_PAGE_COUNT; 637 goto out; 638 } 639 640 /* 641 * Isolate the page to avoid collapsing an hugepage 642 * currently in use by the VM. 643 */ 644 if (!isolate_lru_page(page)) { 645 unlock_page(page); 646 result = SCAN_DEL_PAGE_LRU; 647 goto out; 648 } 649 mod_node_page_state(page_pgdat(page), 650 NR_ISOLATED_ANON + page_is_file_lru(page), 651 compound_nr(page)); 652 VM_BUG_ON_PAGE(!PageLocked(page), page); 653 VM_BUG_ON_PAGE(PageLRU(page), page); 654 655 if (PageCompound(page)) 656 list_add_tail(&page->lru, compound_pagelist); 657 next: 658 /* 659 * If collapse was initiated by khugepaged, check that there is 660 * enough young pte to justify collapsing the page 661 */ 662 if (cc->is_khugepaged && 663 (pte_young(pteval) || page_is_young(page) || 664 PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm, 665 address))) 666 referenced++; 667 668 if (pte_write(pteval)) 669 writable = true; 670 } 671 672 if (unlikely(!writable)) { 673 result = SCAN_PAGE_RO; 674 } else if (unlikely(cc->is_khugepaged && !referenced)) { 675 result = SCAN_LACK_REFERENCED_PAGE; 676 } else { 677 result = SCAN_SUCCEED; 678 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 679 referenced, writable, result); 680 return result; 681 } 682 out: 683 release_pte_pages(pte, _pte, compound_pagelist); 684 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 685 referenced, writable, result); 686 return result; 687 } 688 689 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 690 struct vm_area_struct *vma, 691 unsigned long address, 692 spinlock_t *ptl, 693 struct list_head *compound_pagelist) 694 { 695 struct page *src_page, *tmp; 696 pte_t *_pte; 697 for (_pte = pte; _pte < pte + HPAGE_PMD_NR; 698 _pte++, page++, address += PAGE_SIZE) { 699 pte_t pteval = *_pte; 700 701 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 702 clear_user_highpage(page, address); 703 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 704 if (is_zero_pfn(pte_pfn(pteval))) { 705 /* 706 * ptl mostly unnecessary. 707 */ 708 spin_lock(ptl); 709 ptep_clear(vma->vm_mm, address, _pte); 710 spin_unlock(ptl); 711 } 712 } else { 713 src_page = pte_page(pteval); 714 copy_user_highpage(page, src_page, address, vma); 715 if (!PageCompound(src_page)) 716 release_pte_page(src_page); 717 /* 718 * ptl mostly unnecessary, but preempt has to 719 * be disabled to update the per-cpu stats 720 * inside page_remove_rmap(). 721 */ 722 spin_lock(ptl); 723 ptep_clear(vma->vm_mm, address, _pte); 724 page_remove_rmap(src_page, vma, false); 725 spin_unlock(ptl); 726 free_page_and_swap_cache(src_page); 727 } 728 } 729 730 list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) { 731 list_del(&src_page->lru); 732 mod_node_page_state(page_pgdat(src_page), 733 NR_ISOLATED_ANON + page_is_file_lru(src_page), 734 -compound_nr(src_page)); 735 unlock_page(src_page); 736 free_swap_cache(src_page); 737 putback_lru_page(src_page); 738 } 739 } 740 741 static void khugepaged_alloc_sleep(void) 742 { 743 DEFINE_WAIT(wait); 744 745 add_wait_queue(&khugepaged_wait, &wait); 746 __set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE); 747 schedule_timeout(msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 748 remove_wait_queue(&khugepaged_wait, &wait); 749 } 750 751 struct collapse_control khugepaged_collapse_control = { 752 .is_khugepaged = true, 753 }; 754 755 static bool hpage_collapse_scan_abort(int nid, struct collapse_control *cc) 756 { 757 int i; 758 759 /* 760 * If node_reclaim_mode is disabled, then no extra effort is made to 761 * allocate memory locally. 762 */ 763 if (!node_reclaim_enabled()) 764 return false; 765 766 /* If there is a count for this node already, it must be acceptable */ 767 if (cc->node_load[nid]) 768 return false; 769 770 for (i = 0; i < MAX_NUMNODES; i++) { 771 if (!cc->node_load[i]) 772 continue; 773 if (node_distance(nid, i) > node_reclaim_distance) 774 return true; 775 } 776 return false; 777 } 778 779 #define khugepaged_defrag() \ 780 (transparent_hugepage_flags & \ 781 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)) 782 783 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ 784 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) 785 { 786 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT; 787 } 788 789 #ifdef CONFIG_NUMA 790 static int hpage_collapse_find_target_node(struct collapse_control *cc) 791 { 792 int nid, target_node = 0, max_value = 0; 793 794 /* find first node with max normal pages hit */ 795 for (nid = 0; nid < MAX_NUMNODES; nid++) 796 if (cc->node_load[nid] > max_value) { 797 max_value = cc->node_load[nid]; 798 target_node = nid; 799 } 800 801 for_each_online_node(nid) { 802 if (max_value == cc->node_load[nid]) 803 node_set(nid, cc->alloc_nmask); 804 } 805 806 return target_node; 807 } 808 #else 809 static int hpage_collapse_find_target_node(struct collapse_control *cc) 810 { 811 return 0; 812 } 813 #endif 814 815 static bool hpage_collapse_alloc_page(struct page **hpage, gfp_t gfp, int node, 816 nodemask_t *nmask) 817 { 818 *hpage = __alloc_pages(gfp, HPAGE_PMD_ORDER, node, nmask); 819 if (unlikely(!*hpage)) { 820 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 821 return false; 822 } 823 824 prep_transhuge_page(*hpage); 825 count_vm_event(THP_COLLAPSE_ALLOC); 826 return true; 827 } 828 829 /* 830 * If mmap_lock temporarily dropped, revalidate vma 831 * before taking mmap_lock. 832 * Returns enum scan_result value. 833 */ 834 835 static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, 836 bool expect_anon, 837 struct vm_area_struct **vmap, 838 struct collapse_control *cc) 839 { 840 struct vm_area_struct *vma; 841 842 if (unlikely(hpage_collapse_test_exit(mm))) 843 return SCAN_ANY_PROCESS; 844 845 *vmap = vma = find_vma(mm, address); 846 if (!vma) 847 return SCAN_VMA_NULL; 848 849 if (!transhuge_vma_suitable(vma, address)) 850 return SCAN_ADDRESS_RANGE; 851 if (!hugepage_vma_check(vma, vma->vm_flags, false, false, 852 cc->is_khugepaged)) 853 return SCAN_VMA_CHECK; 854 /* 855 * Anon VMA expected, the address may be unmapped then 856 * remapped to file after khugepaged reaquired the mmap_lock. 857 * 858 * hugepage_vma_check may return true for qualified file 859 * vmas. 860 */ 861 if (expect_anon && (!(*vmap)->anon_vma || !vma_is_anonymous(*vmap))) 862 return SCAN_PAGE_ANON; 863 return SCAN_SUCCEED; 864 } 865 866 /* 867 * See pmd_trans_unstable() for how the result may change out from 868 * underneath us, even if we hold mmap_lock in read. 869 */ 870 static int find_pmd_or_thp_or_none(struct mm_struct *mm, 871 unsigned long address, 872 pmd_t **pmd) 873 { 874 pmd_t pmde; 875 876 *pmd = mm_find_pmd(mm, address); 877 if (!*pmd) 878 return SCAN_PMD_NULL; 879 880 pmde = pmdp_get_lockless(*pmd); 881 882 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 883 /* See comments in pmd_none_or_trans_huge_or_clear_bad() */ 884 barrier(); 885 #endif 886 if (pmd_none(pmde)) 887 return SCAN_PMD_NONE; 888 if (!pmd_present(pmde)) 889 return SCAN_PMD_NULL; 890 if (pmd_trans_huge(pmde)) 891 return SCAN_PMD_MAPPED; 892 if (pmd_devmap(pmde)) 893 return SCAN_PMD_NULL; 894 if (pmd_bad(pmde)) 895 return SCAN_PMD_NULL; 896 return SCAN_SUCCEED; 897 } 898 899 static int check_pmd_still_valid(struct mm_struct *mm, 900 unsigned long address, 901 pmd_t *pmd) 902 { 903 pmd_t *new_pmd; 904 int result = find_pmd_or_thp_or_none(mm, address, &new_pmd); 905 906 if (result != SCAN_SUCCEED) 907 return result; 908 if (new_pmd != pmd) 909 return SCAN_FAIL; 910 return SCAN_SUCCEED; 911 } 912 913 /* 914 * Bring missing pages in from swap, to complete THP collapse. 915 * Only done if hpage_collapse_scan_pmd believes it is worthwhile. 916 * 917 * Called and returns without pte mapped or spinlocks held. 918 * Note that if false is returned, mmap_lock will be released. 919 */ 920 921 static int __collapse_huge_page_swapin(struct mm_struct *mm, 922 struct vm_area_struct *vma, 923 unsigned long haddr, pmd_t *pmd, 924 int referenced) 925 { 926 int swapped_in = 0; 927 vm_fault_t ret = 0; 928 unsigned long address, end = haddr + (HPAGE_PMD_NR * PAGE_SIZE); 929 930 for (address = haddr; address < end; address += PAGE_SIZE) { 931 struct vm_fault vmf = { 932 .vma = vma, 933 .address = address, 934 .pgoff = linear_page_index(vma, haddr), 935 .flags = FAULT_FLAG_ALLOW_RETRY, 936 .pmd = pmd, 937 }; 938 939 vmf.pte = pte_offset_map(pmd, address); 940 vmf.orig_pte = *vmf.pte; 941 if (!is_swap_pte(vmf.orig_pte)) { 942 pte_unmap(vmf.pte); 943 continue; 944 } 945 ret = do_swap_page(&vmf); 946 947 /* 948 * do_swap_page returns VM_FAULT_RETRY with released mmap_lock. 949 * Note we treat VM_FAULT_RETRY as VM_FAULT_ERROR here because 950 * we do not retry here and swap entry will remain in pagetable 951 * resulting in later failure. 952 */ 953 if (ret & VM_FAULT_RETRY) { 954 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 955 /* Likely, but not guaranteed, that page lock failed */ 956 return SCAN_PAGE_LOCK; 957 } 958 if (ret & VM_FAULT_ERROR) { 959 mmap_read_unlock(mm); 960 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 961 return SCAN_FAIL; 962 } 963 swapped_in++; 964 } 965 966 /* Drain LRU add pagevec to remove extra pin on the swapped in pages */ 967 if (swapped_in) 968 lru_add_drain(); 969 970 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); 971 return SCAN_SUCCEED; 972 } 973 974 static int alloc_charge_hpage(struct page **hpage, struct mm_struct *mm, 975 struct collapse_control *cc) 976 { 977 gfp_t gfp = (cc->is_khugepaged ? alloc_hugepage_khugepaged_gfpmask() : 978 GFP_TRANSHUGE); 979 int node = hpage_collapse_find_target_node(cc); 980 struct folio *folio; 981 982 if (!hpage_collapse_alloc_page(hpage, gfp, node, &cc->alloc_nmask)) 983 return SCAN_ALLOC_HUGE_PAGE_FAIL; 984 985 folio = page_folio(*hpage); 986 if (unlikely(mem_cgroup_charge(folio, mm, gfp))) { 987 folio_put(folio); 988 *hpage = NULL; 989 return SCAN_CGROUP_CHARGE_FAIL; 990 } 991 count_memcg_page_event(*hpage, THP_COLLAPSE_ALLOC); 992 993 return SCAN_SUCCEED; 994 } 995 996 static int collapse_huge_page(struct mm_struct *mm, unsigned long address, 997 int referenced, int unmapped, 998 struct collapse_control *cc) 999 { 1000 LIST_HEAD(compound_pagelist); 1001 pmd_t *pmd, _pmd; 1002 pte_t *pte; 1003 pgtable_t pgtable; 1004 struct page *hpage; 1005 spinlock_t *pmd_ptl, *pte_ptl; 1006 int result = SCAN_FAIL; 1007 struct vm_area_struct *vma; 1008 struct mmu_notifier_range range; 1009 1010 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1011 1012 /* 1013 * Before allocating the hugepage, release the mmap_lock read lock. 1014 * The allocation can take potentially a long time if it involves 1015 * sync compaction, and we do not need to hold the mmap_lock during 1016 * that. We will recheck the vma after taking it again in write mode. 1017 */ 1018 mmap_read_unlock(mm); 1019 1020 result = alloc_charge_hpage(&hpage, mm, cc); 1021 if (result != SCAN_SUCCEED) 1022 goto out_nolock; 1023 1024 mmap_read_lock(mm); 1025 result = hugepage_vma_revalidate(mm, address, true, &vma, cc); 1026 if (result != SCAN_SUCCEED) { 1027 mmap_read_unlock(mm); 1028 goto out_nolock; 1029 } 1030 1031 result = find_pmd_or_thp_or_none(mm, address, &pmd); 1032 if (result != SCAN_SUCCEED) { 1033 mmap_read_unlock(mm); 1034 goto out_nolock; 1035 } 1036 1037 if (unmapped) { 1038 /* 1039 * __collapse_huge_page_swapin will return with mmap_lock 1040 * released when it fails. So we jump out_nolock directly in 1041 * that case. Continuing to collapse causes inconsistency. 1042 */ 1043 result = __collapse_huge_page_swapin(mm, vma, address, pmd, 1044 referenced); 1045 if (result != SCAN_SUCCEED) 1046 goto out_nolock; 1047 } 1048 1049 mmap_read_unlock(mm); 1050 /* 1051 * Prevent all access to pagetables with the exception of 1052 * gup_fast later handled by the ptep_clear_flush and the VM 1053 * handled by the anon_vma lock + PG_lock. 1054 */ 1055 mmap_write_lock(mm); 1056 result = hugepage_vma_revalidate(mm, address, true, &vma, cc); 1057 if (result != SCAN_SUCCEED) 1058 goto out_up_write; 1059 /* check if the pmd is still valid */ 1060 result = check_pmd_still_valid(mm, address, pmd); 1061 if (result != SCAN_SUCCEED) 1062 goto out_up_write; 1063 1064 vma_start_write(vma); 1065 anon_vma_lock_write(vma->anon_vma); 1066 1067 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, address, 1068 address + HPAGE_PMD_SIZE); 1069 mmu_notifier_invalidate_range_start(&range); 1070 1071 pte = pte_offset_map(pmd, address); 1072 pte_ptl = pte_lockptr(mm, pmd); 1073 1074 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ 1075 /* 1076 * This removes any huge TLB entry from the CPU so we won't allow 1077 * huge and small TLB entries for the same virtual address to 1078 * avoid the risk of CPU bugs in that area. 1079 * 1080 * Parallel fast GUP is fine since fast GUP will back off when 1081 * it detects PMD is changed. 1082 */ 1083 _pmd = pmdp_collapse_flush(vma, address, pmd); 1084 spin_unlock(pmd_ptl); 1085 mmu_notifier_invalidate_range_end(&range); 1086 tlb_remove_table_sync_one(); 1087 1088 spin_lock(pte_ptl); 1089 result = __collapse_huge_page_isolate(vma, address, pte, cc, 1090 &compound_pagelist); 1091 spin_unlock(pte_ptl); 1092 1093 if (unlikely(result != SCAN_SUCCEED)) { 1094 pte_unmap(pte); 1095 spin_lock(pmd_ptl); 1096 BUG_ON(!pmd_none(*pmd)); 1097 /* 1098 * We can only use set_pmd_at when establishing 1099 * hugepmds and never for establishing regular pmds that 1100 * points to regular pagetables. Use pmd_populate for that 1101 */ 1102 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 1103 spin_unlock(pmd_ptl); 1104 anon_vma_unlock_write(vma->anon_vma); 1105 goto out_up_write; 1106 } 1107 1108 /* 1109 * All pages are isolated and locked so anon_vma rmap 1110 * can't run anymore. 1111 */ 1112 anon_vma_unlock_write(vma->anon_vma); 1113 1114 __collapse_huge_page_copy(pte, hpage, vma, address, pte_ptl, 1115 &compound_pagelist); 1116 pte_unmap(pte); 1117 /* 1118 * spin_lock() below is not the equivalent of smp_wmb(), but 1119 * the smp_wmb() inside __SetPageUptodate() can be reused to 1120 * avoid the copy_huge_page writes to become visible after 1121 * the set_pmd_at() write. 1122 */ 1123 __SetPageUptodate(hpage); 1124 pgtable = pmd_pgtable(_pmd); 1125 1126 _pmd = mk_huge_pmd(hpage, vma->vm_page_prot); 1127 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 1128 1129 spin_lock(pmd_ptl); 1130 BUG_ON(!pmd_none(*pmd)); 1131 page_add_new_anon_rmap(hpage, vma, address); 1132 lru_cache_add_inactive_or_unevictable(hpage, vma); 1133 pgtable_trans_huge_deposit(mm, pmd, pgtable); 1134 set_pmd_at(mm, address, pmd, _pmd); 1135 update_mmu_cache_pmd(vma, address, pmd); 1136 spin_unlock(pmd_ptl); 1137 1138 hpage = NULL; 1139 1140 result = SCAN_SUCCEED; 1141 out_up_write: 1142 mmap_write_unlock(mm); 1143 out_nolock: 1144 if (hpage) 1145 put_page(hpage); 1146 trace_mm_collapse_huge_page(mm, result == SCAN_SUCCEED, result); 1147 return result; 1148 } 1149 1150 static int hpage_collapse_scan_pmd(struct mm_struct *mm, 1151 struct vm_area_struct *vma, 1152 unsigned long address, bool *mmap_locked, 1153 struct collapse_control *cc) 1154 { 1155 pmd_t *pmd; 1156 pte_t *pte, *_pte; 1157 int result = SCAN_FAIL, referenced = 0; 1158 int none_or_zero = 0, shared = 0; 1159 struct page *page = NULL; 1160 unsigned long _address; 1161 spinlock_t *ptl; 1162 int node = NUMA_NO_NODE, unmapped = 0; 1163 bool writable = false; 1164 1165 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1166 1167 result = find_pmd_or_thp_or_none(mm, address, &pmd); 1168 if (result != SCAN_SUCCEED) 1169 goto out; 1170 1171 memset(cc->node_load, 0, sizeof(cc->node_load)); 1172 nodes_clear(cc->alloc_nmask); 1173 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 1174 for (_address = address, _pte = pte; _pte < pte + HPAGE_PMD_NR; 1175 _pte++, _address += PAGE_SIZE) { 1176 pte_t pteval = *_pte; 1177 if (is_swap_pte(pteval)) { 1178 ++unmapped; 1179 if (!cc->is_khugepaged || 1180 unmapped <= khugepaged_max_ptes_swap) { 1181 /* 1182 * Always be strict with uffd-wp 1183 * enabled swap entries. Please see 1184 * comment below for pte_uffd_wp(). 1185 */ 1186 if (pte_swp_uffd_wp_any(pteval)) { 1187 result = SCAN_PTE_UFFD_WP; 1188 goto out_unmap; 1189 } 1190 continue; 1191 } else { 1192 result = SCAN_EXCEED_SWAP_PTE; 1193 count_vm_event(THP_SCAN_EXCEED_SWAP_PTE); 1194 goto out_unmap; 1195 } 1196 } 1197 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 1198 ++none_or_zero; 1199 if (!userfaultfd_armed(vma) && 1200 (!cc->is_khugepaged || 1201 none_or_zero <= khugepaged_max_ptes_none)) { 1202 continue; 1203 } else { 1204 result = SCAN_EXCEED_NONE_PTE; 1205 count_vm_event(THP_SCAN_EXCEED_NONE_PTE); 1206 goto out_unmap; 1207 } 1208 } 1209 if (pte_uffd_wp(pteval)) { 1210 /* 1211 * Don't collapse the page if any of the small 1212 * PTEs are armed with uffd write protection. 1213 * Here we can also mark the new huge pmd as 1214 * write protected if any of the small ones is 1215 * marked but that could bring unknown 1216 * userfault messages that falls outside of 1217 * the registered range. So, just be simple. 1218 */ 1219 result = SCAN_PTE_UFFD_WP; 1220 goto out_unmap; 1221 } 1222 if (pte_write(pteval)) 1223 writable = true; 1224 1225 page = vm_normal_page(vma, _address, pteval); 1226 if (unlikely(!page) || unlikely(is_zone_device_page(page))) { 1227 result = SCAN_PAGE_NULL; 1228 goto out_unmap; 1229 } 1230 1231 if (page_mapcount(page) > 1) { 1232 ++shared; 1233 if (cc->is_khugepaged && 1234 shared > khugepaged_max_ptes_shared) { 1235 result = SCAN_EXCEED_SHARED_PTE; 1236 count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); 1237 goto out_unmap; 1238 } 1239 } 1240 1241 page = compound_head(page); 1242 1243 /* 1244 * Record which node the original page is from and save this 1245 * information to cc->node_load[]. 1246 * Khugepaged will allocate hugepage from the node has the max 1247 * hit record. 1248 */ 1249 node = page_to_nid(page); 1250 if (hpage_collapse_scan_abort(node, cc)) { 1251 result = SCAN_SCAN_ABORT; 1252 goto out_unmap; 1253 } 1254 cc->node_load[node]++; 1255 if (!PageLRU(page)) { 1256 result = SCAN_PAGE_LRU; 1257 goto out_unmap; 1258 } 1259 if (PageLocked(page)) { 1260 result = SCAN_PAGE_LOCK; 1261 goto out_unmap; 1262 } 1263 if (!PageAnon(page)) { 1264 result = SCAN_PAGE_ANON; 1265 goto out_unmap; 1266 } 1267 1268 /* 1269 * Check if the page has any GUP (or other external) pins. 1270 * 1271 * Here the check may be racy: 1272 * it may see total_mapcount > refcount in some cases? 1273 * But such case is ephemeral we could always retry collapse 1274 * later. However it may report false positive if the page 1275 * has excessive GUP pins (i.e. 512). Anyway the same check 1276 * will be done again later the risk seems low. 1277 */ 1278 if (!is_refcount_suitable(page)) { 1279 result = SCAN_PAGE_COUNT; 1280 goto out_unmap; 1281 } 1282 1283 /* 1284 * If collapse was initiated by khugepaged, check that there is 1285 * enough young pte to justify collapsing the page 1286 */ 1287 if (cc->is_khugepaged && 1288 (pte_young(pteval) || page_is_young(page) || 1289 PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm, 1290 address))) 1291 referenced++; 1292 } 1293 if (!writable) { 1294 result = SCAN_PAGE_RO; 1295 } else if (cc->is_khugepaged && 1296 (!referenced || 1297 (unmapped && referenced < HPAGE_PMD_NR / 2))) { 1298 result = SCAN_LACK_REFERENCED_PAGE; 1299 } else { 1300 result = SCAN_SUCCEED; 1301 } 1302 out_unmap: 1303 pte_unmap_unlock(pte, ptl); 1304 if (result == SCAN_SUCCEED) { 1305 result = collapse_huge_page(mm, address, referenced, 1306 unmapped, cc); 1307 /* collapse_huge_page will return with the mmap_lock released */ 1308 *mmap_locked = false; 1309 } 1310 out: 1311 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, 1312 none_or_zero, result, unmapped); 1313 return result; 1314 } 1315 1316 static void collect_mm_slot(struct khugepaged_mm_slot *mm_slot) 1317 { 1318 struct mm_slot *slot = &mm_slot->slot; 1319 struct mm_struct *mm = slot->mm; 1320 1321 lockdep_assert_held(&khugepaged_mm_lock); 1322 1323 if (hpage_collapse_test_exit(mm)) { 1324 /* free mm_slot */ 1325 hash_del(&slot->hash); 1326 list_del(&slot->mm_node); 1327 1328 /* 1329 * Not strictly needed because the mm exited already. 1330 * 1331 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1332 */ 1333 1334 /* khugepaged_mm_lock actually not necessary for the below */ 1335 mm_slot_free(mm_slot_cache, mm_slot); 1336 mmdrop(mm); 1337 } 1338 } 1339 1340 #ifdef CONFIG_SHMEM 1341 /* 1342 * Notify khugepaged that given addr of the mm is pte-mapped THP. Then 1343 * khugepaged should try to collapse the page table. 1344 * 1345 * Note that following race exists: 1346 * (1) khugepaged calls khugepaged_collapse_pte_mapped_thps() for mm_struct A, 1347 * emptying the A's ->pte_mapped_thp[] array. 1348 * (2) MADV_COLLAPSE collapses some file extent with target mm_struct B, and 1349 * retract_page_tables() finds a VMA in mm_struct A mapping the same extent 1350 * (at virtual address X) and adds an entry (for X) into mm_struct A's 1351 * ->pte-mapped_thp[] array. 1352 * (3) khugepaged calls khugepaged_collapse_scan_file() for mm_struct A at X, 1353 * sees a pte-mapped THP (SCAN_PTE_MAPPED_HUGEPAGE) and adds an entry 1354 * (for X) into mm_struct A's ->pte-mapped_thp[] array. 1355 * Thus, it's possible the same address is added multiple times for the same 1356 * mm_struct. Should this happen, we'll simply attempt 1357 * collapse_pte_mapped_thp() multiple times for the same address, under the same 1358 * exclusive mmap_lock, and assuming the first call is successful, subsequent 1359 * attempts will return quickly (without grabbing any additional locks) when 1360 * a huge pmd is found in find_pmd_or_thp_or_none(). Since this is a cheap 1361 * check, and since this is a rare occurrence, the cost of preventing this 1362 * "multiple-add" is thought to be more expensive than just handling it, should 1363 * it occur. 1364 */ 1365 static bool khugepaged_add_pte_mapped_thp(struct mm_struct *mm, 1366 unsigned long addr) 1367 { 1368 struct khugepaged_mm_slot *mm_slot; 1369 struct mm_slot *slot; 1370 bool ret = false; 1371 1372 VM_BUG_ON(addr & ~HPAGE_PMD_MASK); 1373 1374 spin_lock(&khugepaged_mm_lock); 1375 slot = mm_slot_lookup(mm_slots_hash, mm); 1376 mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot); 1377 if (likely(mm_slot && mm_slot->nr_pte_mapped_thp < MAX_PTE_MAPPED_THP)) { 1378 mm_slot->pte_mapped_thp[mm_slot->nr_pte_mapped_thp++] = addr; 1379 ret = true; 1380 } 1381 spin_unlock(&khugepaged_mm_lock); 1382 return ret; 1383 } 1384 1385 /* hpage must be locked, and mmap_lock must be held in write */ 1386 static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr, 1387 pmd_t *pmdp, struct page *hpage) 1388 { 1389 struct vm_fault vmf = { 1390 .vma = vma, 1391 .address = addr, 1392 .flags = 0, 1393 .pmd = pmdp, 1394 }; 1395 1396 VM_BUG_ON(!PageTransHuge(hpage)); 1397 mmap_assert_write_locked(vma->vm_mm); 1398 1399 if (do_set_pmd(&vmf, hpage)) 1400 return SCAN_FAIL; 1401 1402 get_page(hpage); 1403 return SCAN_SUCCEED; 1404 } 1405 1406 /* 1407 * A note about locking: 1408 * Trying to take the page table spinlocks would be useless here because those 1409 * are only used to synchronize: 1410 * 1411 * - modifying terminal entries (ones that point to a data page, not to another 1412 * page table) 1413 * - installing *new* non-terminal entries 1414 * 1415 * Instead, we need roughly the same kind of protection as free_pgtables() or 1416 * mm_take_all_locks() (but only for a single VMA): 1417 * The mmap lock together with this VMA's rmap locks covers all paths towards 1418 * the page table entries we're messing with here, except for hardware page 1419 * table walks and lockless_pages_from_mm(). 1420 */ 1421 static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *vma, 1422 unsigned long addr, pmd_t *pmdp) 1423 { 1424 pmd_t pmd; 1425 struct mmu_notifier_range range; 1426 1427 mmap_assert_write_locked(mm); 1428 if (vma->vm_file) 1429 lockdep_assert_held_write(&vma->vm_file->f_mapping->i_mmap_rwsem); 1430 /* 1431 * All anon_vmas attached to the VMA have the same root and are 1432 * therefore locked by the same lock. 1433 */ 1434 if (vma->anon_vma) 1435 lockdep_assert_held_write(&vma->anon_vma->root->rwsem); 1436 1437 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, addr, 1438 addr + HPAGE_PMD_SIZE); 1439 mmu_notifier_invalidate_range_start(&range); 1440 pmd = pmdp_collapse_flush(vma, addr, pmdp); 1441 tlb_remove_table_sync_one(); 1442 mmu_notifier_invalidate_range_end(&range); 1443 mm_dec_nr_ptes(mm); 1444 page_table_check_pte_clear_range(mm, addr, pmd); 1445 pte_free(mm, pmd_pgtable(pmd)); 1446 } 1447 1448 /** 1449 * collapse_pte_mapped_thp - Try to collapse a pte-mapped THP for mm at 1450 * address haddr. 1451 * 1452 * @mm: process address space where collapse happens 1453 * @addr: THP collapse address 1454 * @install_pmd: If a huge PMD should be installed 1455 * 1456 * This function checks whether all the PTEs in the PMD are pointing to the 1457 * right THP. If so, retract the page table so the THP can refault in with 1458 * as pmd-mapped. Possibly install a huge PMD mapping the THP. 1459 */ 1460 int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr, 1461 bool install_pmd) 1462 { 1463 unsigned long haddr = addr & HPAGE_PMD_MASK; 1464 struct vm_area_struct *vma = vma_lookup(mm, haddr); 1465 struct page *hpage; 1466 pte_t *start_pte, *pte; 1467 pmd_t *pmd; 1468 spinlock_t *ptl; 1469 int count = 0, result = SCAN_FAIL; 1470 int i; 1471 1472 mmap_assert_write_locked(mm); 1473 1474 /* Fast check before locking page if already PMD-mapped */ 1475 result = find_pmd_or_thp_or_none(mm, haddr, &pmd); 1476 if (result == SCAN_PMD_MAPPED) 1477 return result; 1478 1479 if (!vma || !vma->vm_file || 1480 !range_in_vma(vma, haddr, haddr + HPAGE_PMD_SIZE)) 1481 return SCAN_VMA_CHECK; 1482 1483 /* 1484 * If we are here, we've succeeded in replacing all the native pages 1485 * in the page cache with a single hugepage. If a mm were to fault-in 1486 * this memory (mapped by a suitably aligned VMA), we'd get the hugepage 1487 * and map it by a PMD, regardless of sysfs THP settings. As such, let's 1488 * analogously elide sysfs THP settings here. 1489 */ 1490 if (!hugepage_vma_check(vma, vma->vm_flags, false, false, false)) 1491 return SCAN_VMA_CHECK; 1492 1493 /* Keep pmd pgtable for uffd-wp; see comment in retract_page_tables() */ 1494 if (userfaultfd_wp(vma)) 1495 return SCAN_PTE_UFFD_WP; 1496 1497 hpage = find_lock_page(vma->vm_file->f_mapping, 1498 linear_page_index(vma, haddr)); 1499 if (!hpage) 1500 return SCAN_PAGE_NULL; 1501 1502 if (!PageHead(hpage)) { 1503 result = SCAN_FAIL; 1504 goto drop_hpage; 1505 } 1506 1507 if (compound_order(hpage) != HPAGE_PMD_ORDER) { 1508 result = SCAN_PAGE_COMPOUND; 1509 goto drop_hpage; 1510 } 1511 1512 switch (result) { 1513 case SCAN_SUCCEED: 1514 break; 1515 case SCAN_PMD_NONE: 1516 /* 1517 * In MADV_COLLAPSE path, possible race with khugepaged where 1518 * all pte entries have been removed and pmd cleared. If so, 1519 * skip all the pte checks and just update the pmd mapping. 1520 */ 1521 goto maybe_install_pmd; 1522 default: 1523 goto drop_hpage; 1524 } 1525 1526 /* Lock the vma before taking i_mmap and page table locks */ 1527 vma_start_write(vma); 1528 1529 /* 1530 * We need to lock the mapping so that from here on, only GUP-fast and 1531 * hardware page walks can access the parts of the page tables that 1532 * we're operating on. 1533 * See collapse_and_free_pmd(). 1534 */ 1535 i_mmap_lock_write(vma->vm_file->f_mapping); 1536 1537 /* 1538 * This spinlock should be unnecessary: Nobody else should be accessing 1539 * the page tables under spinlock protection here, only 1540 * lockless_pages_from_mm() and the hardware page walker can access page 1541 * tables while all the high-level locks are held in write mode. 1542 */ 1543 start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl); 1544 result = SCAN_FAIL; 1545 1546 /* step 1: check all mapped PTEs are to the right huge page */ 1547 for (i = 0, addr = haddr, pte = start_pte; 1548 i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) { 1549 struct page *page; 1550 1551 /* empty pte, skip */ 1552 if (pte_none(*pte)) 1553 continue; 1554 1555 /* page swapped out, abort */ 1556 if (!pte_present(*pte)) { 1557 result = SCAN_PTE_NON_PRESENT; 1558 goto abort; 1559 } 1560 1561 page = vm_normal_page(vma, addr, *pte); 1562 if (WARN_ON_ONCE(page && is_zone_device_page(page))) 1563 page = NULL; 1564 /* 1565 * Note that uprobe, debugger, or MAP_PRIVATE may change the 1566 * page table, but the new page will not be a subpage of hpage. 1567 */ 1568 if (hpage + i != page) 1569 goto abort; 1570 count++; 1571 } 1572 1573 /* step 2: adjust rmap */ 1574 for (i = 0, addr = haddr, pte = start_pte; 1575 i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) { 1576 struct page *page; 1577 1578 if (pte_none(*pte)) 1579 continue; 1580 page = vm_normal_page(vma, addr, *pte); 1581 if (WARN_ON_ONCE(page && is_zone_device_page(page))) 1582 goto abort; 1583 page_remove_rmap(page, vma, false); 1584 } 1585 1586 pte_unmap_unlock(start_pte, ptl); 1587 1588 /* step 3: set proper refcount and mm_counters. */ 1589 if (count) { 1590 page_ref_sub(hpage, count); 1591 add_mm_counter(vma->vm_mm, mm_counter_file(hpage), -count); 1592 } 1593 1594 /* step 4: remove pte entries */ 1595 /* we make no change to anon, but protect concurrent anon page lookup */ 1596 if (vma->anon_vma) 1597 anon_vma_lock_write(vma->anon_vma); 1598 1599 collapse_and_free_pmd(mm, vma, haddr, pmd); 1600 1601 if (vma->anon_vma) 1602 anon_vma_unlock_write(vma->anon_vma); 1603 i_mmap_unlock_write(vma->vm_file->f_mapping); 1604 1605 maybe_install_pmd: 1606 /* step 5: install pmd entry */ 1607 result = install_pmd 1608 ? set_huge_pmd(vma, haddr, pmd, hpage) 1609 : SCAN_SUCCEED; 1610 1611 drop_hpage: 1612 unlock_page(hpage); 1613 put_page(hpage); 1614 return result; 1615 1616 abort: 1617 pte_unmap_unlock(start_pte, ptl); 1618 i_mmap_unlock_write(vma->vm_file->f_mapping); 1619 goto drop_hpage; 1620 } 1621 1622 static void khugepaged_collapse_pte_mapped_thps(struct khugepaged_mm_slot *mm_slot) 1623 { 1624 struct mm_slot *slot = &mm_slot->slot; 1625 struct mm_struct *mm = slot->mm; 1626 int i; 1627 1628 if (likely(mm_slot->nr_pte_mapped_thp == 0)) 1629 return; 1630 1631 if (!mmap_write_trylock(mm)) 1632 return; 1633 1634 if (unlikely(hpage_collapse_test_exit(mm))) 1635 goto out; 1636 1637 for (i = 0; i < mm_slot->nr_pte_mapped_thp; i++) 1638 collapse_pte_mapped_thp(mm, mm_slot->pte_mapped_thp[i], false); 1639 1640 out: 1641 mm_slot->nr_pte_mapped_thp = 0; 1642 mmap_write_unlock(mm); 1643 } 1644 1645 static int retract_page_tables(struct address_space *mapping, pgoff_t pgoff, 1646 struct mm_struct *target_mm, 1647 unsigned long target_addr, struct page *hpage, 1648 struct collapse_control *cc) 1649 { 1650 struct vm_area_struct *vma; 1651 int target_result = SCAN_FAIL; 1652 1653 i_mmap_lock_write(mapping); 1654 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { 1655 int result = SCAN_FAIL; 1656 struct mm_struct *mm = NULL; 1657 unsigned long addr = 0; 1658 pmd_t *pmd; 1659 bool is_target = false; 1660 1661 /* 1662 * Check vma->anon_vma to exclude MAP_PRIVATE mappings that 1663 * got written to. These VMAs are likely not worth investing 1664 * mmap_write_lock(mm) as PMD-mapping is likely to be split 1665 * later. 1666 * 1667 * Note that vma->anon_vma check is racy: it can be set up after 1668 * the check but before we took mmap_lock by the fault path. 1669 * But page lock would prevent establishing any new ptes of the 1670 * page, so we are safe. 1671 * 1672 * An alternative would be drop the check, but check that page 1673 * table is clear before calling pmdp_collapse_flush() under 1674 * ptl. It has higher chance to recover THP for the VMA, but 1675 * has higher cost too. It would also probably require locking 1676 * the anon_vma. 1677 */ 1678 if (READ_ONCE(vma->anon_vma)) { 1679 result = SCAN_PAGE_ANON; 1680 goto next; 1681 } 1682 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); 1683 if (addr & ~HPAGE_PMD_MASK || 1684 vma->vm_end < addr + HPAGE_PMD_SIZE) { 1685 result = SCAN_VMA_CHECK; 1686 goto next; 1687 } 1688 mm = vma->vm_mm; 1689 is_target = mm == target_mm && addr == target_addr; 1690 result = find_pmd_or_thp_or_none(mm, addr, &pmd); 1691 if (result != SCAN_SUCCEED) 1692 goto next; 1693 /* 1694 * We need exclusive mmap_lock to retract page table. 1695 * 1696 * We use trylock due to lock inversion: we need to acquire 1697 * mmap_lock while holding page lock. Fault path does it in 1698 * reverse order. Trylock is a way to avoid deadlock. 1699 * 1700 * Also, it's not MADV_COLLAPSE's job to collapse other 1701 * mappings - let khugepaged take care of them later. 1702 */ 1703 result = SCAN_PTE_MAPPED_HUGEPAGE; 1704 if ((cc->is_khugepaged || is_target) && 1705 mmap_write_trylock(mm)) { 1706 /* trylock for the same lock inversion as above */ 1707 if (!vma_try_start_write(vma)) 1708 goto unlock_next; 1709 1710 /* 1711 * Re-check whether we have an ->anon_vma, because 1712 * collapse_and_free_pmd() requires that either no 1713 * ->anon_vma exists or the anon_vma is locked. 1714 * We already checked ->anon_vma above, but that check 1715 * is racy because ->anon_vma can be populated under the 1716 * mmap lock in read mode. 1717 */ 1718 if (vma->anon_vma) { 1719 result = SCAN_PAGE_ANON; 1720 goto unlock_next; 1721 } 1722 /* 1723 * When a vma is registered with uffd-wp, we can't 1724 * recycle the pmd pgtable because there can be pte 1725 * markers installed. Skip it only, so the rest mm/vma 1726 * can still have the same file mapped hugely, however 1727 * it'll always mapped in small page size for uffd-wp 1728 * registered ranges. 1729 */ 1730 if (hpage_collapse_test_exit(mm)) { 1731 result = SCAN_ANY_PROCESS; 1732 goto unlock_next; 1733 } 1734 if (userfaultfd_wp(vma)) { 1735 result = SCAN_PTE_UFFD_WP; 1736 goto unlock_next; 1737 } 1738 collapse_and_free_pmd(mm, vma, addr, pmd); 1739 if (!cc->is_khugepaged && is_target) 1740 result = set_huge_pmd(vma, addr, pmd, hpage); 1741 else 1742 result = SCAN_SUCCEED; 1743 1744 unlock_next: 1745 mmap_write_unlock(mm); 1746 goto next; 1747 } 1748 /* 1749 * Calling context will handle target mm/addr. Otherwise, let 1750 * khugepaged try again later. 1751 */ 1752 if (!is_target) { 1753 khugepaged_add_pte_mapped_thp(mm, addr); 1754 continue; 1755 } 1756 next: 1757 if (is_target) 1758 target_result = result; 1759 } 1760 i_mmap_unlock_write(mapping); 1761 return target_result; 1762 } 1763 1764 /** 1765 * collapse_file - collapse filemap/tmpfs/shmem pages into huge one. 1766 * 1767 * @mm: process address space where collapse happens 1768 * @addr: virtual collapse start address 1769 * @file: file that collapse on 1770 * @start: collapse start address 1771 * @cc: collapse context and scratchpad 1772 * 1773 * Basic scheme is simple, details are more complex: 1774 * - allocate and lock a new huge page; 1775 * - scan page cache replacing old pages with the new one 1776 * + swap/gup in pages if necessary; 1777 * + fill in gaps; 1778 * + keep old pages around in case rollback is required; 1779 * - if replacing succeeds: 1780 * + copy data over; 1781 * + free old pages; 1782 * + unlock huge page; 1783 * - if replacing failed; 1784 * + put all pages back and unfreeze them; 1785 * + restore gaps in the page cache; 1786 * + unlock and free huge page; 1787 */ 1788 static int collapse_file(struct mm_struct *mm, unsigned long addr, 1789 struct file *file, pgoff_t start, 1790 struct collapse_control *cc) 1791 { 1792 struct address_space *mapping = file->f_mapping; 1793 struct page *hpage; 1794 pgoff_t index = 0, end = start + HPAGE_PMD_NR; 1795 LIST_HEAD(pagelist); 1796 XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER); 1797 int nr_none = 0, result = SCAN_SUCCEED; 1798 bool is_shmem = shmem_file(file); 1799 int nr = 0; 1800 1801 VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); 1802 VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); 1803 1804 result = alloc_charge_hpage(&hpage, mm, cc); 1805 if (result != SCAN_SUCCEED) 1806 goto out; 1807 1808 /* 1809 * Ensure we have slots for all the pages in the range. This is 1810 * almost certainly a no-op because most of the pages must be present 1811 */ 1812 do { 1813 xas_lock_irq(&xas); 1814 xas_create_range(&xas); 1815 if (!xas_error(&xas)) 1816 break; 1817 xas_unlock_irq(&xas); 1818 if (!xas_nomem(&xas, GFP_KERNEL)) { 1819 result = SCAN_FAIL; 1820 goto out; 1821 } 1822 } while (1); 1823 1824 __SetPageLocked(hpage); 1825 if (is_shmem) 1826 __SetPageSwapBacked(hpage); 1827 hpage->index = start; 1828 hpage->mapping = mapping; 1829 1830 /* 1831 * At this point the hpage is locked and not up-to-date. 1832 * It's safe to insert it into the page cache, because nobody would 1833 * be able to map it or use it in another way until we unlock it. 1834 */ 1835 1836 xas_set(&xas, start); 1837 for (index = start; index < end; index++) { 1838 struct page *page = xas_next(&xas); 1839 struct folio *folio; 1840 1841 VM_BUG_ON(index != xas.xa_index); 1842 if (is_shmem) { 1843 if (!page) { 1844 /* 1845 * Stop if extent has been truncated or 1846 * hole-punched, and is now completely 1847 * empty. 1848 */ 1849 if (index == start) { 1850 if (!xas_next_entry(&xas, end - 1)) { 1851 result = SCAN_TRUNCATED; 1852 goto xa_locked; 1853 } 1854 xas_set(&xas, index); 1855 } 1856 if (!shmem_charge(mapping->host, 1)) { 1857 result = SCAN_FAIL; 1858 goto xa_locked; 1859 } 1860 xas_store(&xas, hpage); 1861 if (xas_error(&xas)) { 1862 /* revert shmem_charge performed 1863 * in the previous condition 1864 */ 1865 mapping->nrpages--; 1866 shmem_uncharge(mapping->host, 1); 1867 result = SCAN_STORE_FAILED; 1868 goto xa_locked; 1869 } 1870 nr_none++; 1871 continue; 1872 } 1873 1874 if (xa_is_value(page) || !PageUptodate(page)) { 1875 xas_unlock_irq(&xas); 1876 /* swap in or instantiate fallocated page */ 1877 if (shmem_get_folio(mapping->host, index, 1878 &folio, SGP_NOALLOC)) { 1879 result = SCAN_FAIL; 1880 goto xa_unlocked; 1881 } 1882 page = folio_file_page(folio, index); 1883 } else if (trylock_page(page)) { 1884 get_page(page); 1885 xas_unlock_irq(&xas); 1886 } else { 1887 result = SCAN_PAGE_LOCK; 1888 goto xa_locked; 1889 } 1890 } else { /* !is_shmem */ 1891 if (!page || xa_is_value(page)) { 1892 xas_unlock_irq(&xas); 1893 page_cache_sync_readahead(mapping, &file->f_ra, 1894 file, index, 1895 end - index); 1896 /* drain pagevecs to help isolate_lru_page() */ 1897 lru_add_drain(); 1898 page = find_lock_page(mapping, index); 1899 if (unlikely(page == NULL)) { 1900 result = SCAN_FAIL; 1901 goto xa_unlocked; 1902 } 1903 } else if (PageDirty(page)) { 1904 /* 1905 * khugepaged only works on read-only fd, 1906 * so this page is dirty because it hasn't 1907 * been flushed since first write. There 1908 * won't be new dirty pages. 1909 * 1910 * Trigger async flush here and hope the 1911 * writeback is done when khugepaged 1912 * revisits this page. 1913 * 1914 * This is a one-off situation. We are not 1915 * forcing writeback in loop. 1916 */ 1917 xas_unlock_irq(&xas); 1918 filemap_flush(mapping); 1919 result = SCAN_FAIL; 1920 goto xa_unlocked; 1921 } else if (PageWriteback(page)) { 1922 xas_unlock_irq(&xas); 1923 result = SCAN_FAIL; 1924 goto xa_unlocked; 1925 } else if (trylock_page(page)) { 1926 get_page(page); 1927 xas_unlock_irq(&xas); 1928 } else { 1929 result = SCAN_PAGE_LOCK; 1930 goto xa_locked; 1931 } 1932 } 1933 1934 /* 1935 * The page must be locked, so we can drop the i_pages lock 1936 * without racing with truncate. 1937 */ 1938 VM_BUG_ON_PAGE(!PageLocked(page), page); 1939 1940 /* make sure the page is up to date */ 1941 if (unlikely(!PageUptodate(page))) { 1942 result = SCAN_FAIL; 1943 goto out_unlock; 1944 } 1945 1946 /* 1947 * If file was truncated then extended, or hole-punched, before 1948 * we locked the first page, then a THP might be there already. 1949 * This will be discovered on the first iteration. 1950 */ 1951 if (PageTransCompound(page)) { 1952 struct page *head = compound_head(page); 1953 1954 result = compound_order(head) == HPAGE_PMD_ORDER && 1955 head->index == start 1956 /* Maybe PMD-mapped */ 1957 ? SCAN_PTE_MAPPED_HUGEPAGE 1958 : SCAN_PAGE_COMPOUND; 1959 goto out_unlock; 1960 } 1961 1962 folio = page_folio(page); 1963 1964 if (folio_mapping(folio) != mapping) { 1965 result = SCAN_TRUNCATED; 1966 goto out_unlock; 1967 } 1968 1969 if (!is_shmem && (folio_test_dirty(folio) || 1970 folio_test_writeback(folio))) { 1971 /* 1972 * khugepaged only works on read-only fd, so this 1973 * page is dirty because it hasn't been flushed 1974 * since first write. 1975 */ 1976 result = SCAN_FAIL; 1977 goto out_unlock; 1978 } 1979 1980 if (!folio_isolate_lru(folio)) { 1981 result = SCAN_DEL_PAGE_LRU; 1982 goto out_unlock; 1983 } 1984 1985 if (folio_has_private(folio) && 1986 !filemap_release_folio(folio, GFP_KERNEL)) { 1987 result = SCAN_PAGE_HAS_PRIVATE; 1988 folio_putback_lru(folio); 1989 goto out_unlock; 1990 } 1991 1992 if (folio_mapped(folio)) 1993 try_to_unmap(folio, 1994 TTU_IGNORE_MLOCK | TTU_BATCH_FLUSH); 1995 1996 xas_lock_irq(&xas); 1997 xas_set(&xas, index); 1998 1999 VM_BUG_ON_PAGE(page != xas_load(&xas), page); 2000 2001 /* 2002 * The page is expected to have page_count() == 3: 2003 * - we hold a pin on it; 2004 * - one reference from page cache; 2005 * - one from isolate_lru_page; 2006 */ 2007 if (!page_ref_freeze(page, 3)) { 2008 result = SCAN_PAGE_COUNT; 2009 xas_unlock_irq(&xas); 2010 putback_lru_page(page); 2011 goto out_unlock; 2012 } 2013 2014 /* 2015 * Add the page to the list to be able to undo the collapse if 2016 * something go wrong. 2017 */ 2018 list_add_tail(&page->lru, &pagelist); 2019 2020 /* Finally, replace with the new page. */ 2021 xas_store(&xas, hpage); 2022 /* We can't get an ENOMEM here (because the allocation happened before) 2023 * but let's check for errors (XArray implementation can be 2024 * changed in the future) 2025 */ 2026 WARN_ON_ONCE(xas_error(&xas)); 2027 continue; 2028 out_unlock: 2029 unlock_page(page); 2030 put_page(page); 2031 goto xa_unlocked; 2032 } 2033 nr = thp_nr_pages(hpage); 2034 2035 if (is_shmem) 2036 __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr); 2037 else { 2038 __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr); 2039 filemap_nr_thps_inc(mapping); 2040 /* 2041 * Paired with smp_mb() in do_dentry_open() to ensure 2042 * i_writecount is up to date and the update to nr_thps is 2043 * visible. Ensures the page cache will be truncated if the 2044 * file is opened writable. 2045 */ 2046 smp_mb(); 2047 if (inode_is_open_for_write(mapping->host)) { 2048 result = SCAN_FAIL; 2049 __mod_lruvec_page_state(hpage, NR_FILE_THPS, -nr); 2050 filemap_nr_thps_dec(mapping); 2051 goto xa_locked; 2052 } 2053 } 2054 2055 if (nr_none) { 2056 __mod_lruvec_page_state(hpage, NR_FILE_PAGES, nr_none); 2057 /* nr_none is always 0 for non-shmem. */ 2058 __mod_lruvec_page_state(hpage, NR_SHMEM, nr_none); 2059 } 2060 2061 /* Join all the small entries into a single multi-index entry */ 2062 xas_set_order(&xas, start, HPAGE_PMD_ORDER); 2063 xas_store(&xas, hpage); 2064 /* Here we can't get an ENOMEM (because entries were 2065 * previously allocated) But let's check for errors 2066 * (XArray implementation can be changed in the future) 2067 */ 2068 WARN_ON_ONCE(xas_error(&xas)); 2069 xa_locked: 2070 xas_unlock_irq(&xas); 2071 xa_unlocked: 2072 2073 /* 2074 * If collapse is successful, flush must be done now before copying. 2075 * If collapse is unsuccessful, does flush actually need to be done? 2076 * Do it anyway, to clear the state. 2077 */ 2078 try_to_unmap_flush(); 2079 2080 if (result == SCAN_SUCCEED) { 2081 struct page *page, *tmp; 2082 struct folio *folio; 2083 2084 /* 2085 * Replacing old pages with new one has succeeded, now we 2086 * need to copy the content and free the old pages. 2087 */ 2088 index = start; 2089 list_for_each_entry_safe(page, tmp, &pagelist, lru) { 2090 while (index < page->index) { 2091 clear_highpage(hpage + (index % HPAGE_PMD_NR)); 2092 index++; 2093 } 2094 copy_highpage(hpage + (page->index % HPAGE_PMD_NR), 2095 page); 2096 list_del(&page->lru); 2097 page->mapping = NULL; 2098 page_ref_unfreeze(page, 1); 2099 ClearPageActive(page); 2100 ClearPageUnevictable(page); 2101 unlock_page(page); 2102 put_page(page); 2103 index++; 2104 } 2105 while (index < end) { 2106 clear_highpage(hpage + (index % HPAGE_PMD_NR)); 2107 index++; 2108 } 2109 2110 folio = page_folio(hpage); 2111 folio_mark_uptodate(folio); 2112 folio_ref_add(folio, HPAGE_PMD_NR - 1); 2113 2114 if (is_shmem) 2115 folio_mark_dirty(folio); 2116 folio_add_lru(folio); 2117 2118 /* 2119 * Remove pte page tables, so we can re-fault the page as huge. 2120 */ 2121 result = retract_page_tables(mapping, start, mm, addr, hpage, 2122 cc); 2123 unlock_page(hpage); 2124 hpage = NULL; 2125 } else { 2126 struct page *page; 2127 2128 /* Something went wrong: roll back page cache changes */ 2129 xas_lock_irq(&xas); 2130 if (nr_none) { 2131 mapping->nrpages -= nr_none; 2132 shmem_uncharge(mapping->host, nr_none); 2133 } 2134 2135 xas_set(&xas, start); 2136 xas_for_each(&xas, page, end - 1) { 2137 page = list_first_entry_or_null(&pagelist, 2138 struct page, lru); 2139 if (!page || xas.xa_index < page->index) { 2140 if (!nr_none) 2141 break; 2142 nr_none--; 2143 /* Put holes back where they were */ 2144 xas_store(&xas, NULL); 2145 continue; 2146 } 2147 2148 VM_BUG_ON_PAGE(page->index != xas.xa_index, page); 2149 2150 /* Unfreeze the page. */ 2151 list_del(&page->lru); 2152 page_ref_unfreeze(page, 2); 2153 xas_store(&xas, page); 2154 xas_pause(&xas); 2155 xas_unlock_irq(&xas); 2156 unlock_page(page); 2157 putback_lru_page(page); 2158 xas_lock_irq(&xas); 2159 } 2160 VM_BUG_ON(nr_none); 2161 xas_unlock_irq(&xas); 2162 2163 hpage->mapping = NULL; 2164 } 2165 2166 if (hpage) 2167 unlock_page(hpage); 2168 out: 2169 VM_BUG_ON(!list_empty(&pagelist)); 2170 if (hpage) 2171 put_page(hpage); 2172 2173 trace_mm_khugepaged_collapse_file(mm, hpage, index, is_shmem, addr, file, nr, result); 2174 return result; 2175 } 2176 2177 static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr, 2178 struct file *file, pgoff_t start, 2179 struct collapse_control *cc) 2180 { 2181 struct page *page = NULL; 2182 struct address_space *mapping = file->f_mapping; 2183 XA_STATE(xas, &mapping->i_pages, start); 2184 int present, swap; 2185 int node = NUMA_NO_NODE; 2186 int result = SCAN_SUCCEED; 2187 2188 present = 0; 2189 swap = 0; 2190 memset(cc->node_load, 0, sizeof(cc->node_load)); 2191 nodes_clear(cc->alloc_nmask); 2192 rcu_read_lock(); 2193 xas_for_each(&xas, page, start + HPAGE_PMD_NR - 1) { 2194 if (xas_retry(&xas, page)) 2195 continue; 2196 2197 if (xa_is_value(page)) { 2198 ++swap; 2199 if (cc->is_khugepaged && 2200 swap > khugepaged_max_ptes_swap) { 2201 result = SCAN_EXCEED_SWAP_PTE; 2202 count_vm_event(THP_SCAN_EXCEED_SWAP_PTE); 2203 break; 2204 } 2205 continue; 2206 } 2207 2208 /* 2209 * TODO: khugepaged should compact smaller compound pages 2210 * into a PMD sized page 2211 */ 2212 if (PageTransCompound(page)) { 2213 struct page *head = compound_head(page); 2214 2215 result = compound_order(head) == HPAGE_PMD_ORDER && 2216 head->index == start 2217 /* Maybe PMD-mapped */ 2218 ? SCAN_PTE_MAPPED_HUGEPAGE 2219 : SCAN_PAGE_COMPOUND; 2220 /* 2221 * For SCAN_PTE_MAPPED_HUGEPAGE, further processing 2222 * by the caller won't touch the page cache, and so 2223 * it's safe to skip LRU and refcount checks before 2224 * returning. 2225 */ 2226 break; 2227 } 2228 2229 node = page_to_nid(page); 2230 if (hpage_collapse_scan_abort(node, cc)) { 2231 result = SCAN_SCAN_ABORT; 2232 break; 2233 } 2234 cc->node_load[node]++; 2235 2236 if (!PageLRU(page)) { 2237 result = SCAN_PAGE_LRU; 2238 break; 2239 } 2240 2241 if (page_count(page) != 2242 1 + page_mapcount(page) + page_has_private(page)) { 2243 result = SCAN_PAGE_COUNT; 2244 break; 2245 } 2246 2247 /* 2248 * We probably should check if the page is referenced here, but 2249 * nobody would transfer pte_young() to PageReferenced() for us. 2250 * And rmap walk here is just too costly... 2251 */ 2252 2253 present++; 2254 2255 if (need_resched()) { 2256 xas_pause(&xas); 2257 cond_resched_rcu(); 2258 } 2259 } 2260 rcu_read_unlock(); 2261 2262 if (result == SCAN_SUCCEED) { 2263 if (cc->is_khugepaged && 2264 present < HPAGE_PMD_NR - khugepaged_max_ptes_none) { 2265 result = SCAN_EXCEED_NONE_PTE; 2266 count_vm_event(THP_SCAN_EXCEED_NONE_PTE); 2267 } else { 2268 result = collapse_file(mm, addr, file, start, cc); 2269 } 2270 } 2271 2272 trace_mm_khugepaged_scan_file(mm, page, file, present, swap, result); 2273 return result; 2274 } 2275 #else 2276 static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr, 2277 struct file *file, pgoff_t start, 2278 struct collapse_control *cc) 2279 { 2280 BUILD_BUG(); 2281 } 2282 2283 static void khugepaged_collapse_pte_mapped_thps(struct khugepaged_mm_slot *mm_slot) 2284 { 2285 } 2286 2287 static bool khugepaged_add_pte_mapped_thp(struct mm_struct *mm, 2288 unsigned long addr) 2289 { 2290 return false; 2291 } 2292 #endif 2293 2294 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result, 2295 struct collapse_control *cc) 2296 __releases(&khugepaged_mm_lock) 2297 __acquires(&khugepaged_mm_lock) 2298 { 2299 struct vma_iterator vmi; 2300 struct khugepaged_mm_slot *mm_slot; 2301 struct mm_slot *slot; 2302 struct mm_struct *mm; 2303 struct vm_area_struct *vma; 2304 int progress = 0; 2305 2306 VM_BUG_ON(!pages); 2307 lockdep_assert_held(&khugepaged_mm_lock); 2308 *result = SCAN_FAIL; 2309 2310 if (khugepaged_scan.mm_slot) { 2311 mm_slot = khugepaged_scan.mm_slot; 2312 slot = &mm_slot->slot; 2313 } else { 2314 slot = list_entry(khugepaged_scan.mm_head.next, 2315 struct mm_slot, mm_node); 2316 mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot); 2317 khugepaged_scan.address = 0; 2318 khugepaged_scan.mm_slot = mm_slot; 2319 } 2320 spin_unlock(&khugepaged_mm_lock); 2321 khugepaged_collapse_pte_mapped_thps(mm_slot); 2322 2323 mm = slot->mm; 2324 /* 2325 * Don't wait for semaphore (to avoid long wait times). Just move to 2326 * the next mm on the list. 2327 */ 2328 vma = NULL; 2329 if (unlikely(!mmap_read_trylock(mm))) 2330 goto breakouterloop_mmap_lock; 2331 2332 progress++; 2333 if (unlikely(hpage_collapse_test_exit(mm))) 2334 goto breakouterloop; 2335 2336 vma_iter_init(&vmi, mm, khugepaged_scan.address); 2337 for_each_vma(vmi, vma) { 2338 unsigned long hstart, hend; 2339 2340 cond_resched(); 2341 if (unlikely(hpage_collapse_test_exit(mm))) { 2342 progress++; 2343 break; 2344 } 2345 if (!hugepage_vma_check(vma, vma->vm_flags, false, false, true)) { 2346 skip: 2347 progress++; 2348 continue; 2349 } 2350 hstart = round_up(vma->vm_start, HPAGE_PMD_SIZE); 2351 hend = round_down(vma->vm_end, HPAGE_PMD_SIZE); 2352 if (khugepaged_scan.address > hend) 2353 goto skip; 2354 if (khugepaged_scan.address < hstart) 2355 khugepaged_scan.address = hstart; 2356 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2357 2358 while (khugepaged_scan.address < hend) { 2359 bool mmap_locked = true; 2360 2361 cond_resched(); 2362 if (unlikely(hpage_collapse_test_exit(mm))) 2363 goto breakouterloop; 2364 2365 VM_BUG_ON(khugepaged_scan.address < hstart || 2366 khugepaged_scan.address + HPAGE_PMD_SIZE > 2367 hend); 2368 if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) { 2369 struct file *file = get_file(vma->vm_file); 2370 pgoff_t pgoff = linear_page_index(vma, 2371 khugepaged_scan.address); 2372 2373 mmap_read_unlock(mm); 2374 *result = hpage_collapse_scan_file(mm, 2375 khugepaged_scan.address, 2376 file, pgoff, cc); 2377 mmap_locked = false; 2378 fput(file); 2379 } else { 2380 *result = hpage_collapse_scan_pmd(mm, vma, 2381 khugepaged_scan.address, 2382 &mmap_locked, 2383 cc); 2384 } 2385 switch (*result) { 2386 case SCAN_PTE_MAPPED_HUGEPAGE: { 2387 pmd_t *pmd; 2388 2389 *result = find_pmd_or_thp_or_none(mm, 2390 khugepaged_scan.address, 2391 &pmd); 2392 if (*result != SCAN_SUCCEED) 2393 break; 2394 if (!khugepaged_add_pte_mapped_thp(mm, 2395 khugepaged_scan.address)) 2396 break; 2397 } fallthrough; 2398 case SCAN_SUCCEED: 2399 ++khugepaged_pages_collapsed; 2400 break; 2401 default: 2402 break; 2403 } 2404 2405 /* move to next address */ 2406 khugepaged_scan.address += HPAGE_PMD_SIZE; 2407 progress += HPAGE_PMD_NR; 2408 if (!mmap_locked) 2409 /* 2410 * We released mmap_lock so break loop. Note 2411 * that we drop mmap_lock before all hugepage 2412 * allocations, so if allocation fails, we are 2413 * guaranteed to break here and report the 2414 * correct result back to caller. 2415 */ 2416 goto breakouterloop_mmap_lock; 2417 if (progress >= pages) 2418 goto breakouterloop; 2419 } 2420 } 2421 breakouterloop: 2422 mmap_read_unlock(mm); /* exit_mmap will destroy ptes after this */ 2423 breakouterloop_mmap_lock: 2424 2425 spin_lock(&khugepaged_mm_lock); 2426 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2427 /* 2428 * Release the current mm_slot if this mm is about to die, or 2429 * if we scanned all vmas of this mm. 2430 */ 2431 if (hpage_collapse_test_exit(mm) || !vma) { 2432 /* 2433 * Make sure that if mm_users is reaching zero while 2434 * khugepaged runs here, khugepaged_exit will find 2435 * mm_slot not pointing to the exiting mm. 2436 */ 2437 if (slot->mm_node.next != &khugepaged_scan.mm_head) { 2438 slot = list_entry(slot->mm_node.next, 2439 struct mm_slot, mm_node); 2440 khugepaged_scan.mm_slot = 2441 mm_slot_entry(slot, struct khugepaged_mm_slot, slot); 2442 khugepaged_scan.address = 0; 2443 } else { 2444 khugepaged_scan.mm_slot = NULL; 2445 khugepaged_full_scans++; 2446 } 2447 2448 collect_mm_slot(mm_slot); 2449 } 2450 2451 return progress; 2452 } 2453 2454 static int khugepaged_has_work(void) 2455 { 2456 return !list_empty(&khugepaged_scan.mm_head) && 2457 hugepage_flags_enabled(); 2458 } 2459 2460 static int khugepaged_wait_event(void) 2461 { 2462 return !list_empty(&khugepaged_scan.mm_head) || 2463 kthread_should_stop(); 2464 } 2465 2466 static void khugepaged_do_scan(struct collapse_control *cc) 2467 { 2468 unsigned int progress = 0, pass_through_head = 0; 2469 unsigned int pages = READ_ONCE(khugepaged_pages_to_scan); 2470 bool wait = true; 2471 int result = SCAN_SUCCEED; 2472 2473 lru_add_drain_all(); 2474 2475 while (true) { 2476 cond_resched(); 2477 2478 if (unlikely(kthread_should_stop() || try_to_freeze())) 2479 break; 2480 2481 spin_lock(&khugepaged_mm_lock); 2482 if (!khugepaged_scan.mm_slot) 2483 pass_through_head++; 2484 if (khugepaged_has_work() && 2485 pass_through_head < 2) 2486 progress += khugepaged_scan_mm_slot(pages - progress, 2487 &result, cc); 2488 else 2489 progress = pages; 2490 spin_unlock(&khugepaged_mm_lock); 2491 2492 if (progress >= pages) 2493 break; 2494 2495 if (result == SCAN_ALLOC_HUGE_PAGE_FAIL) { 2496 /* 2497 * If fail to allocate the first time, try to sleep for 2498 * a while. When hit again, cancel the scan. 2499 */ 2500 if (!wait) 2501 break; 2502 wait = false; 2503 khugepaged_alloc_sleep(); 2504 } 2505 } 2506 } 2507 2508 static bool khugepaged_should_wakeup(void) 2509 { 2510 return kthread_should_stop() || 2511 time_after_eq(jiffies, khugepaged_sleep_expire); 2512 } 2513 2514 static void khugepaged_wait_work(void) 2515 { 2516 if (khugepaged_has_work()) { 2517 const unsigned long scan_sleep_jiffies = 2518 msecs_to_jiffies(khugepaged_scan_sleep_millisecs); 2519 2520 if (!scan_sleep_jiffies) 2521 return; 2522 2523 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies; 2524 wait_event_freezable_timeout(khugepaged_wait, 2525 khugepaged_should_wakeup(), 2526 scan_sleep_jiffies); 2527 return; 2528 } 2529 2530 if (hugepage_flags_enabled()) 2531 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 2532 } 2533 2534 static int khugepaged(void *none) 2535 { 2536 struct khugepaged_mm_slot *mm_slot; 2537 2538 set_freezable(); 2539 set_user_nice(current, MAX_NICE); 2540 2541 while (!kthread_should_stop()) { 2542 khugepaged_do_scan(&khugepaged_collapse_control); 2543 khugepaged_wait_work(); 2544 } 2545 2546 spin_lock(&khugepaged_mm_lock); 2547 mm_slot = khugepaged_scan.mm_slot; 2548 khugepaged_scan.mm_slot = NULL; 2549 if (mm_slot) 2550 collect_mm_slot(mm_slot); 2551 spin_unlock(&khugepaged_mm_lock); 2552 return 0; 2553 } 2554 2555 static void set_recommended_min_free_kbytes(void) 2556 { 2557 struct zone *zone; 2558 int nr_zones = 0; 2559 unsigned long recommended_min; 2560 2561 if (!hugepage_flags_enabled()) { 2562 calculate_min_free_kbytes(); 2563 goto update_wmarks; 2564 } 2565 2566 for_each_populated_zone(zone) { 2567 /* 2568 * We don't need to worry about fragmentation of 2569 * ZONE_MOVABLE since it only has movable pages. 2570 */ 2571 if (zone_idx(zone) > gfp_zone(GFP_USER)) 2572 continue; 2573 2574 nr_zones++; 2575 } 2576 2577 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */ 2578 recommended_min = pageblock_nr_pages * nr_zones * 2; 2579 2580 /* 2581 * Make sure that on average at least two pageblocks are almost free 2582 * of another type, one for a migratetype to fall back to and a 2583 * second to avoid subsequent fallbacks of other types There are 3 2584 * MIGRATE_TYPES we care about. 2585 */ 2586 recommended_min += pageblock_nr_pages * nr_zones * 2587 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; 2588 2589 /* don't ever allow to reserve more than 5% of the lowmem */ 2590 recommended_min = min(recommended_min, 2591 (unsigned long) nr_free_buffer_pages() / 20); 2592 recommended_min <<= (PAGE_SHIFT-10); 2593 2594 if (recommended_min > min_free_kbytes) { 2595 if (user_min_free_kbytes >= 0) 2596 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", 2597 min_free_kbytes, recommended_min); 2598 2599 min_free_kbytes = recommended_min; 2600 } 2601 2602 update_wmarks: 2603 setup_per_zone_wmarks(); 2604 } 2605 2606 int start_stop_khugepaged(void) 2607 { 2608 int err = 0; 2609 2610 mutex_lock(&khugepaged_mutex); 2611 if (hugepage_flags_enabled()) { 2612 if (!khugepaged_thread) 2613 khugepaged_thread = kthread_run(khugepaged, NULL, 2614 "khugepaged"); 2615 if (IS_ERR(khugepaged_thread)) { 2616 pr_err("khugepaged: kthread_run(khugepaged) failed\n"); 2617 err = PTR_ERR(khugepaged_thread); 2618 khugepaged_thread = NULL; 2619 goto fail; 2620 } 2621 2622 if (!list_empty(&khugepaged_scan.mm_head)) 2623 wake_up_interruptible(&khugepaged_wait); 2624 } else if (khugepaged_thread) { 2625 kthread_stop(khugepaged_thread); 2626 khugepaged_thread = NULL; 2627 } 2628 set_recommended_min_free_kbytes(); 2629 fail: 2630 mutex_unlock(&khugepaged_mutex); 2631 return err; 2632 } 2633 2634 void khugepaged_min_free_kbytes_update(void) 2635 { 2636 mutex_lock(&khugepaged_mutex); 2637 if (hugepage_flags_enabled() && khugepaged_thread) 2638 set_recommended_min_free_kbytes(); 2639 mutex_unlock(&khugepaged_mutex); 2640 } 2641 2642 bool current_is_khugepaged(void) 2643 { 2644 return kthread_func(current) == khugepaged; 2645 } 2646 2647 static int madvise_collapse_errno(enum scan_result r) 2648 { 2649 /* 2650 * MADV_COLLAPSE breaks from existing madvise(2) conventions to provide 2651 * actionable feedback to caller, so they may take an appropriate 2652 * fallback measure depending on the nature of the failure. 2653 */ 2654 switch (r) { 2655 case SCAN_ALLOC_HUGE_PAGE_FAIL: 2656 return -ENOMEM; 2657 case SCAN_CGROUP_CHARGE_FAIL: 2658 return -EBUSY; 2659 /* Resource temporary unavailable - trying again might succeed */ 2660 case SCAN_PAGE_COUNT: 2661 case SCAN_PAGE_LOCK: 2662 case SCAN_PAGE_LRU: 2663 case SCAN_DEL_PAGE_LRU: 2664 return -EAGAIN; 2665 /* 2666 * Other: Trying again likely not to succeed / error intrinsic to 2667 * specified memory range. khugepaged likely won't be able to collapse 2668 * either. 2669 */ 2670 default: 2671 return -EINVAL; 2672 } 2673 } 2674 2675 int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev, 2676 unsigned long start, unsigned long end) 2677 { 2678 struct collapse_control *cc; 2679 struct mm_struct *mm = vma->vm_mm; 2680 unsigned long hstart, hend, addr; 2681 int thps = 0, last_fail = SCAN_FAIL; 2682 bool mmap_locked = true; 2683 2684 BUG_ON(vma->vm_start > start); 2685 BUG_ON(vma->vm_end < end); 2686 2687 *prev = vma; 2688 2689 if (!hugepage_vma_check(vma, vma->vm_flags, false, false, false)) 2690 return -EINVAL; 2691 2692 cc = kmalloc(sizeof(*cc), GFP_KERNEL); 2693 if (!cc) 2694 return -ENOMEM; 2695 cc->is_khugepaged = false; 2696 2697 mmgrab(mm); 2698 lru_add_drain_all(); 2699 2700 hstart = (start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2701 hend = end & HPAGE_PMD_MASK; 2702 2703 for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) { 2704 int result = SCAN_FAIL; 2705 2706 if (!mmap_locked) { 2707 cond_resched(); 2708 mmap_read_lock(mm); 2709 mmap_locked = true; 2710 result = hugepage_vma_revalidate(mm, addr, false, &vma, 2711 cc); 2712 if (result != SCAN_SUCCEED) { 2713 last_fail = result; 2714 goto out_nolock; 2715 } 2716 2717 hend = min(hend, vma->vm_end & HPAGE_PMD_MASK); 2718 } 2719 mmap_assert_locked(mm); 2720 memset(cc->node_load, 0, sizeof(cc->node_load)); 2721 nodes_clear(cc->alloc_nmask); 2722 if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) { 2723 struct file *file = get_file(vma->vm_file); 2724 pgoff_t pgoff = linear_page_index(vma, addr); 2725 2726 mmap_read_unlock(mm); 2727 mmap_locked = false; 2728 result = hpage_collapse_scan_file(mm, addr, file, pgoff, 2729 cc); 2730 fput(file); 2731 } else { 2732 result = hpage_collapse_scan_pmd(mm, vma, addr, 2733 &mmap_locked, cc); 2734 } 2735 if (!mmap_locked) 2736 *prev = NULL; /* Tell caller we dropped mmap_lock */ 2737 2738 handle_result: 2739 switch (result) { 2740 case SCAN_SUCCEED: 2741 case SCAN_PMD_MAPPED: 2742 ++thps; 2743 break; 2744 case SCAN_PTE_MAPPED_HUGEPAGE: 2745 BUG_ON(mmap_locked); 2746 BUG_ON(*prev); 2747 mmap_write_lock(mm); 2748 result = collapse_pte_mapped_thp(mm, addr, true); 2749 mmap_write_unlock(mm); 2750 goto handle_result; 2751 /* Whitelisted set of results where continuing OK */ 2752 case SCAN_PMD_NULL: 2753 case SCAN_PTE_NON_PRESENT: 2754 case SCAN_PTE_UFFD_WP: 2755 case SCAN_PAGE_RO: 2756 case SCAN_LACK_REFERENCED_PAGE: 2757 case SCAN_PAGE_NULL: 2758 case SCAN_PAGE_COUNT: 2759 case SCAN_PAGE_LOCK: 2760 case SCAN_PAGE_COMPOUND: 2761 case SCAN_PAGE_LRU: 2762 case SCAN_DEL_PAGE_LRU: 2763 last_fail = result; 2764 break; 2765 default: 2766 last_fail = result; 2767 /* Other error, exit */ 2768 goto out_maybelock; 2769 } 2770 } 2771 2772 out_maybelock: 2773 /* Caller expects us to hold mmap_lock on return */ 2774 if (!mmap_locked) 2775 mmap_read_lock(mm); 2776 out_nolock: 2777 mmap_assert_locked(mm); 2778 mmdrop(mm); 2779 kfree(cc); 2780 2781 return thps == ((hend - hstart) >> HPAGE_PMD_SHIFT) ? 0 2782 : madvise_collapse_errno(last_fail); 2783 } 2784