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/swapops.h> 20 #include <linux/shmem_fs.h> 21 22 #include <asm/tlb.h> 23 #include <asm/pgalloc.h> 24 #include "internal.h" 25 26 enum scan_result { 27 SCAN_FAIL, 28 SCAN_SUCCEED, 29 SCAN_PMD_NULL, 30 SCAN_EXCEED_NONE_PTE, 31 SCAN_EXCEED_SWAP_PTE, 32 SCAN_EXCEED_SHARED_PTE, 33 SCAN_PTE_NON_PRESENT, 34 SCAN_PTE_UFFD_WP, 35 SCAN_PAGE_RO, 36 SCAN_LACK_REFERENCED_PAGE, 37 SCAN_PAGE_NULL, 38 SCAN_SCAN_ABORT, 39 SCAN_PAGE_COUNT, 40 SCAN_PAGE_LRU, 41 SCAN_PAGE_LOCK, 42 SCAN_PAGE_ANON, 43 SCAN_PAGE_COMPOUND, 44 SCAN_ANY_PROCESS, 45 SCAN_VMA_NULL, 46 SCAN_VMA_CHECK, 47 SCAN_ADDRESS_RANGE, 48 SCAN_SWAP_CACHE_PAGE, 49 SCAN_DEL_PAGE_LRU, 50 SCAN_ALLOC_HUGE_PAGE_FAIL, 51 SCAN_CGROUP_CHARGE_FAIL, 52 SCAN_TRUNCATED, 53 SCAN_PAGE_HAS_PRIVATE, 54 }; 55 56 #define CREATE_TRACE_POINTS 57 #include <trace/events/huge_memory.h> 58 59 /* default scan 8*512 pte (or vmas) every 30 second */ 60 static unsigned int khugepaged_pages_to_scan __read_mostly; 61 static unsigned int khugepaged_pages_collapsed; 62 static unsigned int khugepaged_full_scans; 63 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 64 /* during fragmentation poll the hugepage allocator once every minute */ 65 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 66 static unsigned long khugepaged_sleep_expire; 67 static DEFINE_SPINLOCK(khugepaged_mm_lock); 68 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 69 /* 70 * default collapse hugepages if there is at least one pte mapped like 71 * it would have happened if the vma was large enough during page 72 * fault. 73 */ 74 static unsigned int khugepaged_max_ptes_none __read_mostly; 75 static unsigned int khugepaged_max_ptes_swap __read_mostly; 76 static unsigned int khugepaged_max_ptes_shared __read_mostly; 77 78 #define MM_SLOTS_HASH_BITS 10 79 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); 80 81 static struct kmem_cache *mm_slot_cache __read_mostly; 82 83 #define MAX_PTE_MAPPED_THP 8 84 85 /** 86 * struct mm_slot - hash lookup from mm to mm_slot 87 * @hash: hash collision list 88 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 89 * @mm: the mm that this information is valid for 90 */ 91 struct mm_slot { 92 struct hlist_node hash; 93 struct list_head mm_node; 94 struct mm_struct *mm; 95 96 /* pte-mapped THP in this mm */ 97 int nr_pte_mapped_thp; 98 unsigned long pte_mapped_thp[MAX_PTE_MAPPED_THP]; 99 }; 100 101 /** 102 * struct khugepaged_scan - cursor for scanning 103 * @mm_head: the head of the mm list to scan 104 * @mm_slot: the current mm_slot we are scanning 105 * @address: the next address inside that to be scanned 106 * 107 * There is only the one khugepaged_scan instance of this cursor structure. 108 */ 109 struct khugepaged_scan { 110 struct list_head mm_head; 111 struct mm_slot *mm_slot; 112 unsigned long address; 113 }; 114 115 static struct khugepaged_scan khugepaged_scan = { 116 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 117 }; 118 119 #ifdef CONFIG_SYSFS 120 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 121 struct kobj_attribute *attr, 122 char *buf) 123 { 124 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 125 } 126 127 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 128 struct kobj_attribute *attr, 129 const char *buf, size_t count) 130 { 131 unsigned long msecs; 132 int err; 133 134 err = kstrtoul(buf, 10, &msecs); 135 if (err || msecs > UINT_MAX) 136 return -EINVAL; 137 138 khugepaged_scan_sleep_millisecs = msecs; 139 khugepaged_sleep_expire = 0; 140 wake_up_interruptible(&khugepaged_wait); 141 142 return count; 143 } 144 static struct kobj_attribute scan_sleep_millisecs_attr = 145 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 146 scan_sleep_millisecs_store); 147 148 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 149 struct kobj_attribute *attr, 150 char *buf) 151 { 152 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 153 } 154 155 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 156 struct kobj_attribute *attr, 157 const char *buf, size_t count) 158 { 159 unsigned long msecs; 160 int err; 161 162 err = kstrtoul(buf, 10, &msecs); 163 if (err || msecs > UINT_MAX) 164 return -EINVAL; 165 166 khugepaged_alloc_sleep_millisecs = msecs; 167 khugepaged_sleep_expire = 0; 168 wake_up_interruptible(&khugepaged_wait); 169 170 return count; 171 } 172 static struct kobj_attribute alloc_sleep_millisecs_attr = 173 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 174 alloc_sleep_millisecs_store); 175 176 static ssize_t pages_to_scan_show(struct kobject *kobj, 177 struct kobj_attribute *attr, 178 char *buf) 179 { 180 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 181 } 182 static ssize_t pages_to_scan_store(struct kobject *kobj, 183 struct kobj_attribute *attr, 184 const char *buf, size_t count) 185 { 186 int err; 187 unsigned long pages; 188 189 err = kstrtoul(buf, 10, &pages); 190 if (err || !pages || pages > UINT_MAX) 191 return -EINVAL; 192 193 khugepaged_pages_to_scan = pages; 194 195 return count; 196 } 197 static struct kobj_attribute pages_to_scan_attr = 198 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 199 pages_to_scan_store); 200 201 static ssize_t pages_collapsed_show(struct kobject *kobj, 202 struct kobj_attribute *attr, 203 char *buf) 204 { 205 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 206 } 207 static struct kobj_attribute pages_collapsed_attr = 208 __ATTR_RO(pages_collapsed); 209 210 static ssize_t full_scans_show(struct kobject *kobj, 211 struct kobj_attribute *attr, 212 char *buf) 213 { 214 return sprintf(buf, "%u\n", khugepaged_full_scans); 215 } 216 static struct kobj_attribute full_scans_attr = 217 __ATTR_RO(full_scans); 218 219 static ssize_t khugepaged_defrag_show(struct kobject *kobj, 220 struct kobj_attribute *attr, char *buf) 221 { 222 return single_hugepage_flag_show(kobj, attr, buf, 223 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 224 } 225 static ssize_t khugepaged_defrag_store(struct kobject *kobj, 226 struct kobj_attribute *attr, 227 const char *buf, size_t count) 228 { 229 return single_hugepage_flag_store(kobj, attr, buf, count, 230 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 231 } 232 static struct kobj_attribute khugepaged_defrag_attr = 233 __ATTR(defrag, 0644, khugepaged_defrag_show, 234 khugepaged_defrag_store); 235 236 /* 237 * max_ptes_none controls if khugepaged should collapse hugepages over 238 * any unmapped ptes in turn potentially increasing the memory 239 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 240 * reduce the available free memory in the system as it 241 * runs. Increasing max_ptes_none will instead potentially reduce the 242 * free memory in the system during the khugepaged scan. 243 */ 244 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 245 struct kobj_attribute *attr, 246 char *buf) 247 { 248 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 249 } 250 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 251 struct kobj_attribute *attr, 252 const char *buf, size_t count) 253 { 254 int err; 255 unsigned long max_ptes_none; 256 257 err = kstrtoul(buf, 10, &max_ptes_none); 258 if (err || max_ptes_none > HPAGE_PMD_NR-1) 259 return -EINVAL; 260 261 khugepaged_max_ptes_none = max_ptes_none; 262 263 return count; 264 } 265 static struct kobj_attribute khugepaged_max_ptes_none_attr = 266 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 267 khugepaged_max_ptes_none_store); 268 269 static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj, 270 struct kobj_attribute *attr, 271 char *buf) 272 { 273 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap); 274 } 275 276 static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj, 277 struct kobj_attribute *attr, 278 const char *buf, size_t count) 279 { 280 int err; 281 unsigned long max_ptes_swap; 282 283 err = kstrtoul(buf, 10, &max_ptes_swap); 284 if (err || max_ptes_swap > HPAGE_PMD_NR-1) 285 return -EINVAL; 286 287 khugepaged_max_ptes_swap = max_ptes_swap; 288 289 return count; 290 } 291 292 static struct kobj_attribute khugepaged_max_ptes_swap_attr = 293 __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show, 294 khugepaged_max_ptes_swap_store); 295 296 static ssize_t khugepaged_max_ptes_shared_show(struct kobject *kobj, 297 struct kobj_attribute *attr, 298 char *buf) 299 { 300 return sprintf(buf, "%u\n", khugepaged_max_ptes_shared); 301 } 302 303 static ssize_t khugepaged_max_ptes_shared_store(struct kobject *kobj, 304 struct kobj_attribute *attr, 305 const char *buf, size_t count) 306 { 307 int err; 308 unsigned long max_ptes_shared; 309 310 err = kstrtoul(buf, 10, &max_ptes_shared); 311 if (err || max_ptes_shared > HPAGE_PMD_NR-1) 312 return -EINVAL; 313 314 khugepaged_max_ptes_shared = max_ptes_shared; 315 316 return count; 317 } 318 319 static struct kobj_attribute khugepaged_max_ptes_shared_attr = 320 __ATTR(max_ptes_shared, 0644, khugepaged_max_ptes_shared_show, 321 khugepaged_max_ptes_shared_store); 322 323 static struct attribute *khugepaged_attr[] = { 324 &khugepaged_defrag_attr.attr, 325 &khugepaged_max_ptes_none_attr.attr, 326 &khugepaged_max_ptes_swap_attr.attr, 327 &khugepaged_max_ptes_shared_attr.attr, 328 &pages_to_scan_attr.attr, 329 &pages_collapsed_attr.attr, 330 &full_scans_attr.attr, 331 &scan_sleep_millisecs_attr.attr, 332 &alloc_sleep_millisecs_attr.attr, 333 NULL, 334 }; 335 336 struct attribute_group khugepaged_attr_group = { 337 .attrs = khugepaged_attr, 338 .name = "khugepaged", 339 }; 340 #endif /* CONFIG_SYSFS */ 341 342 int hugepage_madvise(struct vm_area_struct *vma, 343 unsigned long *vm_flags, int advice) 344 { 345 switch (advice) { 346 case MADV_HUGEPAGE: 347 #ifdef CONFIG_S390 348 /* 349 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 350 * can't handle this properly after s390_enable_sie, so we simply 351 * ignore the madvise to prevent qemu from causing a SIGSEGV. 352 */ 353 if (mm_has_pgste(vma->vm_mm)) 354 return 0; 355 #endif 356 *vm_flags &= ~VM_NOHUGEPAGE; 357 *vm_flags |= VM_HUGEPAGE; 358 /* 359 * If the vma become good for khugepaged to scan, 360 * register it here without waiting a page fault that 361 * may not happen any time soon. 362 */ 363 if (!(*vm_flags & VM_NO_KHUGEPAGED) && 364 khugepaged_enter_vma_merge(vma, *vm_flags)) 365 return -ENOMEM; 366 break; 367 case MADV_NOHUGEPAGE: 368 *vm_flags &= ~VM_HUGEPAGE; 369 *vm_flags |= VM_NOHUGEPAGE; 370 /* 371 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 372 * this vma even if we leave the mm registered in khugepaged if 373 * it got registered before VM_NOHUGEPAGE was set. 374 */ 375 break; 376 } 377 378 return 0; 379 } 380 381 int __init khugepaged_init(void) 382 { 383 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 384 sizeof(struct mm_slot), 385 __alignof__(struct mm_slot), 0, NULL); 386 if (!mm_slot_cache) 387 return -ENOMEM; 388 389 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; 390 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; 391 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8; 392 khugepaged_max_ptes_shared = HPAGE_PMD_NR / 2; 393 394 return 0; 395 } 396 397 void __init khugepaged_destroy(void) 398 { 399 kmem_cache_destroy(mm_slot_cache); 400 } 401 402 static inline struct mm_slot *alloc_mm_slot(void) 403 { 404 if (!mm_slot_cache) /* initialization failed */ 405 return NULL; 406 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 407 } 408 409 static inline void free_mm_slot(struct mm_slot *mm_slot) 410 { 411 kmem_cache_free(mm_slot_cache, mm_slot); 412 } 413 414 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 415 { 416 struct mm_slot *mm_slot; 417 418 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) 419 if (mm == mm_slot->mm) 420 return mm_slot; 421 422 return NULL; 423 } 424 425 static void insert_to_mm_slots_hash(struct mm_struct *mm, 426 struct mm_slot *mm_slot) 427 { 428 mm_slot->mm = mm; 429 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); 430 } 431 432 static inline int khugepaged_test_exit(struct mm_struct *mm) 433 { 434 return atomic_read(&mm->mm_users) == 0 || !mmget_still_valid(mm); 435 } 436 437 static bool hugepage_vma_check(struct vm_area_struct *vma, 438 unsigned long vm_flags) 439 { 440 if ((!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 441 (vm_flags & VM_NOHUGEPAGE) || 442 test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) 443 return false; 444 445 if (shmem_file(vma->vm_file) || 446 (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && 447 vma->vm_file && 448 (vm_flags & VM_DENYWRITE))) { 449 return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, 450 HPAGE_PMD_NR); 451 } 452 if (!vma->anon_vma || vma->vm_ops) 453 return false; 454 if (vma_is_temporary_stack(vma)) 455 return false; 456 return !(vm_flags & VM_NO_KHUGEPAGED); 457 } 458 459 int __khugepaged_enter(struct mm_struct *mm) 460 { 461 struct mm_slot *mm_slot; 462 int wakeup; 463 464 mm_slot = alloc_mm_slot(); 465 if (!mm_slot) 466 return -ENOMEM; 467 468 /* __khugepaged_exit() must not run from under us */ 469 VM_BUG_ON_MM(atomic_read(&mm->mm_users) == 0, mm); 470 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 471 free_mm_slot(mm_slot); 472 return 0; 473 } 474 475 spin_lock(&khugepaged_mm_lock); 476 insert_to_mm_slots_hash(mm, mm_slot); 477 /* 478 * Insert just behind the scanning cursor, to let the area settle 479 * down a little. 480 */ 481 wakeup = list_empty(&khugepaged_scan.mm_head); 482 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 483 spin_unlock(&khugepaged_mm_lock); 484 485 mmgrab(mm); 486 if (wakeup) 487 wake_up_interruptible(&khugepaged_wait); 488 489 return 0; 490 } 491 492 int khugepaged_enter_vma_merge(struct vm_area_struct *vma, 493 unsigned long vm_flags) 494 { 495 unsigned long hstart, hend; 496 497 /* 498 * khugepaged only supports read-only files for non-shmem files. 499 * khugepaged does not yet work on special mappings. And 500 * file-private shmem THP is not supported. 501 */ 502 if (!hugepage_vma_check(vma, vm_flags)) 503 return 0; 504 505 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 506 hend = vma->vm_end & HPAGE_PMD_MASK; 507 if (hstart < hend) 508 return khugepaged_enter(vma, vm_flags); 509 return 0; 510 } 511 512 void __khugepaged_exit(struct mm_struct *mm) 513 { 514 struct mm_slot *mm_slot; 515 int free = 0; 516 517 spin_lock(&khugepaged_mm_lock); 518 mm_slot = get_mm_slot(mm); 519 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 520 hash_del(&mm_slot->hash); 521 list_del(&mm_slot->mm_node); 522 free = 1; 523 } 524 spin_unlock(&khugepaged_mm_lock); 525 526 if (free) { 527 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 528 free_mm_slot(mm_slot); 529 mmdrop(mm); 530 } else if (mm_slot) { 531 /* 532 * This is required to serialize against 533 * khugepaged_test_exit() (which is guaranteed to run 534 * under mmap sem read mode). Stop here (after we 535 * return all pagetables will be destroyed) until 536 * khugepaged has finished working on the pagetables 537 * under the mmap_lock. 538 */ 539 mmap_write_lock(mm); 540 mmap_write_unlock(mm); 541 } 542 } 543 544 static void release_pte_page(struct page *page) 545 { 546 mod_node_page_state(page_pgdat(page), 547 NR_ISOLATED_ANON + page_is_file_lru(page), 548 -compound_nr(page)); 549 unlock_page(page); 550 putback_lru_page(page); 551 } 552 553 static void release_pte_pages(pte_t *pte, pte_t *_pte, 554 struct list_head *compound_pagelist) 555 { 556 struct page *page, *tmp; 557 558 while (--_pte >= pte) { 559 pte_t pteval = *_pte; 560 561 page = pte_page(pteval); 562 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)) && 563 !PageCompound(page)) 564 release_pte_page(page); 565 } 566 567 list_for_each_entry_safe(page, tmp, compound_pagelist, lru) { 568 list_del(&page->lru); 569 release_pte_page(page); 570 } 571 } 572 573 static bool is_refcount_suitable(struct page *page) 574 { 575 int expected_refcount; 576 577 expected_refcount = total_mapcount(page); 578 if (PageSwapCache(page)) 579 expected_refcount += compound_nr(page); 580 581 return page_count(page) == expected_refcount; 582 } 583 584 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 585 unsigned long address, 586 pte_t *pte, 587 struct list_head *compound_pagelist) 588 { 589 struct page *page = NULL; 590 pte_t *_pte; 591 int none_or_zero = 0, shared = 0, result = 0, referenced = 0; 592 bool writable = false; 593 594 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 595 _pte++, address += PAGE_SIZE) { 596 pte_t pteval = *_pte; 597 if (pte_none(pteval) || (pte_present(pteval) && 598 is_zero_pfn(pte_pfn(pteval)))) { 599 if (!userfaultfd_armed(vma) && 600 ++none_or_zero <= khugepaged_max_ptes_none) { 601 continue; 602 } else { 603 result = SCAN_EXCEED_NONE_PTE; 604 goto out; 605 } 606 } 607 if (!pte_present(pteval)) { 608 result = SCAN_PTE_NON_PRESENT; 609 goto out; 610 } 611 page = vm_normal_page(vma, address, pteval); 612 if (unlikely(!page)) { 613 result = SCAN_PAGE_NULL; 614 goto out; 615 } 616 617 VM_BUG_ON_PAGE(!PageAnon(page), page); 618 619 if (page_mapcount(page) > 1 && 620 ++shared > khugepaged_max_ptes_shared) { 621 result = SCAN_EXCEED_SHARED_PTE; 622 goto out; 623 } 624 625 if (PageCompound(page)) { 626 struct page *p; 627 page = compound_head(page); 628 629 /* 630 * Check if we have dealt with the compound page 631 * already 632 */ 633 list_for_each_entry(p, compound_pagelist, lru) { 634 if (page == p) 635 goto next; 636 } 637 } 638 639 /* 640 * We can do it before isolate_lru_page because the 641 * page can't be freed from under us. NOTE: PG_lock 642 * is needed to serialize against split_huge_page 643 * when invoked from the VM. 644 */ 645 if (!trylock_page(page)) { 646 result = SCAN_PAGE_LOCK; 647 goto out; 648 } 649 650 /* 651 * Check if the page has any GUP (or other external) pins. 652 * 653 * The page table that maps the page has been already unlinked 654 * from the page table tree and this process cannot get 655 * an additinal pin on the page. 656 * 657 * New pins can come later if the page is shared across fork, 658 * but not from this process. The other process cannot write to 659 * the page, only trigger CoW. 660 */ 661 if (!is_refcount_suitable(page)) { 662 unlock_page(page); 663 result = SCAN_PAGE_COUNT; 664 goto out; 665 } 666 if (!pte_write(pteval) && PageSwapCache(page) && 667 !reuse_swap_page(page, NULL)) { 668 /* 669 * Page is in the swap cache and cannot be re-used. 670 * It cannot be collapsed into a THP. 671 */ 672 unlock_page(page); 673 result = SCAN_SWAP_CACHE_PAGE; 674 goto out; 675 } 676 677 /* 678 * Isolate the page to avoid collapsing an hugepage 679 * currently in use by the VM. 680 */ 681 if (isolate_lru_page(page)) { 682 unlock_page(page); 683 result = SCAN_DEL_PAGE_LRU; 684 goto out; 685 } 686 mod_node_page_state(page_pgdat(page), 687 NR_ISOLATED_ANON + page_is_file_lru(page), 688 compound_nr(page)); 689 VM_BUG_ON_PAGE(!PageLocked(page), page); 690 VM_BUG_ON_PAGE(PageLRU(page), page); 691 692 if (PageCompound(page)) 693 list_add_tail(&page->lru, compound_pagelist); 694 next: 695 /* There should be enough young pte to collapse the page */ 696 if (pte_young(pteval) || 697 page_is_young(page) || PageReferenced(page) || 698 mmu_notifier_test_young(vma->vm_mm, address)) 699 referenced++; 700 701 if (pte_write(pteval)) 702 writable = true; 703 } 704 if (likely(writable)) { 705 if (likely(referenced)) { 706 result = SCAN_SUCCEED; 707 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 708 referenced, writable, result); 709 return 1; 710 } 711 } else { 712 result = SCAN_PAGE_RO; 713 } 714 715 out: 716 release_pte_pages(pte, _pte, compound_pagelist); 717 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 718 referenced, writable, result); 719 return 0; 720 } 721 722 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 723 struct vm_area_struct *vma, 724 unsigned long address, 725 spinlock_t *ptl, 726 struct list_head *compound_pagelist) 727 { 728 struct page *src_page, *tmp; 729 pte_t *_pte; 730 for (_pte = pte; _pte < pte + HPAGE_PMD_NR; 731 _pte++, page++, address += PAGE_SIZE) { 732 pte_t pteval = *_pte; 733 734 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 735 clear_user_highpage(page, address); 736 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 737 if (is_zero_pfn(pte_pfn(pteval))) { 738 /* 739 * ptl mostly unnecessary. 740 */ 741 spin_lock(ptl); 742 /* 743 * paravirt calls inside pte_clear here are 744 * superfluous. 745 */ 746 pte_clear(vma->vm_mm, address, _pte); 747 spin_unlock(ptl); 748 } 749 } else { 750 src_page = pte_page(pteval); 751 copy_user_highpage(page, src_page, address, vma); 752 if (!PageCompound(src_page)) 753 release_pte_page(src_page); 754 /* 755 * ptl mostly unnecessary, but preempt has to 756 * be disabled to update the per-cpu stats 757 * inside page_remove_rmap(). 758 */ 759 spin_lock(ptl); 760 /* 761 * paravirt calls inside pte_clear here are 762 * superfluous. 763 */ 764 pte_clear(vma->vm_mm, address, _pte); 765 page_remove_rmap(src_page, false); 766 spin_unlock(ptl); 767 free_page_and_swap_cache(src_page); 768 } 769 } 770 771 list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) { 772 list_del(&src_page->lru); 773 release_pte_page(src_page); 774 } 775 } 776 777 static void khugepaged_alloc_sleep(void) 778 { 779 DEFINE_WAIT(wait); 780 781 add_wait_queue(&khugepaged_wait, &wait); 782 freezable_schedule_timeout_interruptible( 783 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 784 remove_wait_queue(&khugepaged_wait, &wait); 785 } 786 787 static int khugepaged_node_load[MAX_NUMNODES]; 788 789 static bool khugepaged_scan_abort(int nid) 790 { 791 int i; 792 793 /* 794 * If node_reclaim_mode is disabled, then no extra effort is made to 795 * allocate memory locally. 796 */ 797 if (!node_reclaim_mode) 798 return false; 799 800 /* If there is a count for this node already, it must be acceptable */ 801 if (khugepaged_node_load[nid]) 802 return false; 803 804 for (i = 0; i < MAX_NUMNODES; i++) { 805 if (!khugepaged_node_load[i]) 806 continue; 807 if (node_distance(nid, i) > node_reclaim_distance) 808 return true; 809 } 810 return false; 811 } 812 813 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ 814 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) 815 { 816 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT; 817 } 818 819 #ifdef CONFIG_NUMA 820 static int khugepaged_find_target_node(void) 821 { 822 static int last_khugepaged_target_node = NUMA_NO_NODE; 823 int nid, target_node = 0, max_value = 0; 824 825 /* find first node with max normal pages hit */ 826 for (nid = 0; nid < MAX_NUMNODES; nid++) 827 if (khugepaged_node_load[nid] > max_value) { 828 max_value = khugepaged_node_load[nid]; 829 target_node = nid; 830 } 831 832 /* do some balance if several nodes have the same hit record */ 833 if (target_node <= last_khugepaged_target_node) 834 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; 835 nid++) 836 if (max_value == khugepaged_node_load[nid]) { 837 target_node = nid; 838 break; 839 } 840 841 last_khugepaged_target_node = target_node; 842 return target_node; 843 } 844 845 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 846 { 847 if (IS_ERR(*hpage)) { 848 if (!*wait) 849 return false; 850 851 *wait = false; 852 *hpage = NULL; 853 khugepaged_alloc_sleep(); 854 } else if (*hpage) { 855 put_page(*hpage); 856 *hpage = NULL; 857 } 858 859 return true; 860 } 861 862 static struct page * 863 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) 864 { 865 VM_BUG_ON_PAGE(*hpage, *hpage); 866 867 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); 868 if (unlikely(!*hpage)) { 869 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 870 *hpage = ERR_PTR(-ENOMEM); 871 return NULL; 872 } 873 874 prep_transhuge_page(*hpage); 875 count_vm_event(THP_COLLAPSE_ALLOC); 876 return *hpage; 877 } 878 #else 879 static int khugepaged_find_target_node(void) 880 { 881 return 0; 882 } 883 884 static inline struct page *alloc_khugepaged_hugepage(void) 885 { 886 struct page *page; 887 888 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), 889 HPAGE_PMD_ORDER); 890 if (page) 891 prep_transhuge_page(page); 892 return page; 893 } 894 895 static struct page *khugepaged_alloc_hugepage(bool *wait) 896 { 897 struct page *hpage; 898 899 do { 900 hpage = alloc_khugepaged_hugepage(); 901 if (!hpage) { 902 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 903 if (!*wait) 904 return NULL; 905 906 *wait = false; 907 khugepaged_alloc_sleep(); 908 } else 909 count_vm_event(THP_COLLAPSE_ALLOC); 910 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 911 912 return hpage; 913 } 914 915 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 916 { 917 if (!*hpage) 918 *hpage = khugepaged_alloc_hugepage(wait); 919 920 if (unlikely(!*hpage)) 921 return false; 922 923 return true; 924 } 925 926 static struct page * 927 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) 928 { 929 VM_BUG_ON(!*hpage); 930 931 return *hpage; 932 } 933 #endif 934 935 /* 936 * If mmap_lock temporarily dropped, revalidate vma 937 * before taking mmap_lock. 938 * Return 0 if succeeds, otherwise return none-zero 939 * value (scan code). 940 */ 941 942 static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, 943 struct vm_area_struct **vmap) 944 { 945 struct vm_area_struct *vma; 946 unsigned long hstart, hend; 947 948 if (unlikely(khugepaged_test_exit(mm))) 949 return SCAN_ANY_PROCESS; 950 951 *vmap = vma = find_vma(mm, address); 952 if (!vma) 953 return SCAN_VMA_NULL; 954 955 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 956 hend = vma->vm_end & HPAGE_PMD_MASK; 957 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 958 return SCAN_ADDRESS_RANGE; 959 if (!hugepage_vma_check(vma, vma->vm_flags)) 960 return SCAN_VMA_CHECK; 961 /* Anon VMA expected */ 962 if (!vma->anon_vma || vma->vm_ops) 963 return SCAN_VMA_CHECK; 964 return 0; 965 } 966 967 /* 968 * Bring missing pages in from swap, to complete THP collapse. 969 * Only done if khugepaged_scan_pmd believes it is worthwhile. 970 * 971 * Called and returns without pte mapped or spinlocks held, 972 * but with mmap_lock held to protect against vma changes. 973 */ 974 975 static bool __collapse_huge_page_swapin(struct mm_struct *mm, 976 struct vm_area_struct *vma, 977 unsigned long address, pmd_t *pmd, 978 int referenced) 979 { 980 int swapped_in = 0; 981 vm_fault_t ret = 0; 982 struct vm_fault vmf = { 983 .vma = vma, 984 .address = address, 985 .flags = FAULT_FLAG_ALLOW_RETRY, 986 .pmd = pmd, 987 .pgoff = linear_page_index(vma, address), 988 }; 989 990 vmf.pte = pte_offset_map(pmd, address); 991 for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE; 992 vmf.pte++, vmf.address += PAGE_SIZE) { 993 vmf.orig_pte = *vmf.pte; 994 if (!is_swap_pte(vmf.orig_pte)) 995 continue; 996 swapped_in++; 997 ret = do_swap_page(&vmf); 998 999 /* do_swap_page returns VM_FAULT_RETRY with released mmap_lock */ 1000 if (ret & VM_FAULT_RETRY) { 1001 mmap_read_lock(mm); 1002 if (hugepage_vma_revalidate(mm, address, &vmf.vma)) { 1003 /* vma is no longer available, don't continue to swapin */ 1004 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 1005 return false; 1006 } 1007 /* check if the pmd is still valid */ 1008 if (mm_find_pmd(mm, address) != pmd) { 1009 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 1010 return false; 1011 } 1012 } 1013 if (ret & VM_FAULT_ERROR) { 1014 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 1015 return false; 1016 } 1017 /* pte is unmapped now, we need to map it */ 1018 vmf.pte = pte_offset_map(pmd, vmf.address); 1019 } 1020 vmf.pte--; 1021 pte_unmap(vmf.pte); 1022 1023 /* Drain LRU add pagevec to remove extra pin on the swapped in pages */ 1024 if (swapped_in) 1025 lru_add_drain(); 1026 1027 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); 1028 return true; 1029 } 1030 1031 static void collapse_huge_page(struct mm_struct *mm, 1032 unsigned long address, 1033 struct page **hpage, 1034 int node, int referenced, int unmapped) 1035 { 1036 LIST_HEAD(compound_pagelist); 1037 pmd_t *pmd, _pmd; 1038 pte_t *pte; 1039 pgtable_t pgtable; 1040 struct page *new_page; 1041 spinlock_t *pmd_ptl, *pte_ptl; 1042 int isolated = 0, result = 0; 1043 struct vm_area_struct *vma; 1044 struct mmu_notifier_range range; 1045 gfp_t gfp; 1046 1047 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1048 1049 /* Only allocate from the target node */ 1050 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; 1051 1052 /* 1053 * Before allocating the hugepage, release the mmap_lock read lock. 1054 * The allocation can take potentially a long time if it involves 1055 * sync compaction, and we do not need to hold the mmap_lock during 1056 * that. We will recheck the vma after taking it again in write mode. 1057 */ 1058 mmap_read_unlock(mm); 1059 new_page = khugepaged_alloc_page(hpage, gfp, node); 1060 if (!new_page) { 1061 result = SCAN_ALLOC_HUGE_PAGE_FAIL; 1062 goto out_nolock; 1063 } 1064 1065 if (unlikely(mem_cgroup_charge(new_page, mm, gfp))) { 1066 result = SCAN_CGROUP_CHARGE_FAIL; 1067 goto out_nolock; 1068 } 1069 count_memcg_page_event(new_page, THP_COLLAPSE_ALLOC); 1070 1071 mmap_read_lock(mm); 1072 result = hugepage_vma_revalidate(mm, address, &vma); 1073 if (result) { 1074 mmap_read_unlock(mm); 1075 goto out_nolock; 1076 } 1077 1078 pmd = mm_find_pmd(mm, address); 1079 if (!pmd) { 1080 result = SCAN_PMD_NULL; 1081 mmap_read_unlock(mm); 1082 goto out_nolock; 1083 } 1084 1085 /* 1086 * __collapse_huge_page_swapin always returns with mmap_lock locked. 1087 * If it fails, we release mmap_lock and jump out_nolock. 1088 * Continuing to collapse causes inconsistency. 1089 */ 1090 if (unmapped && !__collapse_huge_page_swapin(mm, vma, address, 1091 pmd, referenced)) { 1092 mmap_read_unlock(mm); 1093 goto out_nolock; 1094 } 1095 1096 mmap_read_unlock(mm); 1097 /* 1098 * Prevent all access to pagetables with the exception of 1099 * gup_fast later handled by the ptep_clear_flush and the VM 1100 * handled by the anon_vma lock + PG_lock. 1101 */ 1102 mmap_write_lock(mm); 1103 result = hugepage_vma_revalidate(mm, address, &vma); 1104 if (result) 1105 goto out; 1106 /* check if the pmd is still valid */ 1107 if (mm_find_pmd(mm, address) != pmd) 1108 goto out; 1109 1110 anon_vma_lock_write(vma->anon_vma); 1111 1112 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, 1113 address, address + HPAGE_PMD_SIZE); 1114 mmu_notifier_invalidate_range_start(&range); 1115 1116 pte = pte_offset_map(pmd, address); 1117 pte_ptl = pte_lockptr(mm, pmd); 1118 1119 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ 1120 /* 1121 * After this gup_fast can't run anymore. This also removes 1122 * any huge TLB entry from the CPU so we won't allow 1123 * huge and small TLB entries for the same virtual address 1124 * to avoid the risk of CPU bugs in that area. 1125 */ 1126 _pmd = pmdp_collapse_flush(vma, address, pmd); 1127 spin_unlock(pmd_ptl); 1128 mmu_notifier_invalidate_range_end(&range); 1129 1130 spin_lock(pte_ptl); 1131 isolated = __collapse_huge_page_isolate(vma, address, pte, 1132 &compound_pagelist); 1133 spin_unlock(pte_ptl); 1134 1135 if (unlikely(!isolated)) { 1136 pte_unmap(pte); 1137 spin_lock(pmd_ptl); 1138 BUG_ON(!pmd_none(*pmd)); 1139 /* 1140 * We can only use set_pmd_at when establishing 1141 * hugepmds and never for establishing regular pmds that 1142 * points to regular pagetables. Use pmd_populate for that 1143 */ 1144 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 1145 spin_unlock(pmd_ptl); 1146 anon_vma_unlock_write(vma->anon_vma); 1147 result = SCAN_FAIL; 1148 goto out; 1149 } 1150 1151 /* 1152 * All pages are isolated and locked so anon_vma rmap 1153 * can't run anymore. 1154 */ 1155 anon_vma_unlock_write(vma->anon_vma); 1156 1157 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl, 1158 &compound_pagelist); 1159 pte_unmap(pte); 1160 __SetPageUptodate(new_page); 1161 pgtable = pmd_pgtable(_pmd); 1162 1163 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); 1164 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 1165 1166 /* 1167 * spin_lock() below is not the equivalent of smp_wmb(), so 1168 * this is needed to avoid the copy_huge_page writes to become 1169 * visible after the set_pmd_at() write. 1170 */ 1171 smp_wmb(); 1172 1173 spin_lock(pmd_ptl); 1174 BUG_ON(!pmd_none(*pmd)); 1175 page_add_new_anon_rmap(new_page, vma, address, true); 1176 lru_cache_add_inactive_or_unevictable(new_page, vma); 1177 pgtable_trans_huge_deposit(mm, pmd, pgtable); 1178 set_pmd_at(mm, address, pmd, _pmd); 1179 update_mmu_cache_pmd(vma, address, pmd); 1180 spin_unlock(pmd_ptl); 1181 1182 *hpage = NULL; 1183 1184 khugepaged_pages_collapsed++; 1185 result = SCAN_SUCCEED; 1186 out_up_write: 1187 mmap_write_unlock(mm); 1188 out_nolock: 1189 if (!IS_ERR_OR_NULL(*hpage)) 1190 mem_cgroup_uncharge(*hpage); 1191 trace_mm_collapse_huge_page(mm, isolated, result); 1192 return; 1193 out: 1194 goto out_up_write; 1195 } 1196 1197 static int khugepaged_scan_pmd(struct mm_struct *mm, 1198 struct vm_area_struct *vma, 1199 unsigned long address, 1200 struct page **hpage) 1201 { 1202 pmd_t *pmd; 1203 pte_t *pte, *_pte; 1204 int ret = 0, result = 0, referenced = 0; 1205 int none_or_zero = 0, shared = 0; 1206 struct page *page = NULL; 1207 unsigned long _address; 1208 spinlock_t *ptl; 1209 int node = NUMA_NO_NODE, unmapped = 0; 1210 bool writable = false; 1211 1212 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1213 1214 pmd = mm_find_pmd(mm, address); 1215 if (!pmd) { 1216 result = SCAN_PMD_NULL; 1217 goto out; 1218 } 1219 1220 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 1221 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 1222 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 1223 _pte++, _address += PAGE_SIZE) { 1224 pte_t pteval = *_pte; 1225 if (is_swap_pte(pteval)) { 1226 if (++unmapped <= khugepaged_max_ptes_swap) { 1227 /* 1228 * Always be strict with uffd-wp 1229 * enabled swap entries. Please see 1230 * comment below for pte_uffd_wp(). 1231 */ 1232 if (pte_swp_uffd_wp(pteval)) { 1233 result = SCAN_PTE_UFFD_WP; 1234 goto out_unmap; 1235 } 1236 continue; 1237 } else { 1238 result = SCAN_EXCEED_SWAP_PTE; 1239 goto out_unmap; 1240 } 1241 } 1242 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 1243 if (!userfaultfd_armed(vma) && 1244 ++none_or_zero <= khugepaged_max_ptes_none) { 1245 continue; 1246 } else { 1247 result = SCAN_EXCEED_NONE_PTE; 1248 goto out_unmap; 1249 } 1250 } 1251 if (!pte_present(pteval)) { 1252 result = SCAN_PTE_NON_PRESENT; 1253 goto out_unmap; 1254 } 1255 if (pte_uffd_wp(pteval)) { 1256 /* 1257 * Don't collapse the page if any of the small 1258 * PTEs are armed with uffd write protection. 1259 * Here we can also mark the new huge pmd as 1260 * write protected if any of the small ones is 1261 * marked but that could bring uknown 1262 * userfault messages that falls outside of 1263 * the registered range. So, just be simple. 1264 */ 1265 result = SCAN_PTE_UFFD_WP; 1266 goto out_unmap; 1267 } 1268 if (pte_write(pteval)) 1269 writable = true; 1270 1271 page = vm_normal_page(vma, _address, pteval); 1272 if (unlikely(!page)) { 1273 result = SCAN_PAGE_NULL; 1274 goto out_unmap; 1275 } 1276 1277 if (page_mapcount(page) > 1 && 1278 ++shared > khugepaged_max_ptes_shared) { 1279 result = SCAN_EXCEED_SHARED_PTE; 1280 goto out_unmap; 1281 } 1282 1283 page = compound_head(page); 1284 1285 /* 1286 * Record which node the original page is from and save this 1287 * information to khugepaged_node_load[]. 1288 * Khupaged will allocate hugepage from the node has the max 1289 * hit record. 1290 */ 1291 node = page_to_nid(page); 1292 if (khugepaged_scan_abort(node)) { 1293 result = SCAN_SCAN_ABORT; 1294 goto out_unmap; 1295 } 1296 khugepaged_node_load[node]++; 1297 if (!PageLRU(page)) { 1298 result = SCAN_PAGE_LRU; 1299 goto out_unmap; 1300 } 1301 if (PageLocked(page)) { 1302 result = SCAN_PAGE_LOCK; 1303 goto out_unmap; 1304 } 1305 if (!PageAnon(page)) { 1306 result = SCAN_PAGE_ANON; 1307 goto out_unmap; 1308 } 1309 1310 /* 1311 * Check if the page has any GUP (or other external) pins. 1312 * 1313 * Here the check is racy it may see totmal_mapcount > refcount 1314 * in some cases. 1315 * For example, one process with one forked child process. 1316 * The parent has the PMD split due to MADV_DONTNEED, then 1317 * the child is trying unmap the whole PMD, but khugepaged 1318 * may be scanning the parent between the child has 1319 * PageDoubleMap flag cleared and dec the mapcount. So 1320 * khugepaged may see total_mapcount > refcount. 1321 * 1322 * But such case is ephemeral we could always retry collapse 1323 * later. However it may report false positive if the page 1324 * has excessive GUP pins (i.e. 512). Anyway the same check 1325 * will be done again later the risk seems low. 1326 */ 1327 if (!is_refcount_suitable(page)) { 1328 result = SCAN_PAGE_COUNT; 1329 goto out_unmap; 1330 } 1331 if (pte_young(pteval) || 1332 page_is_young(page) || PageReferenced(page) || 1333 mmu_notifier_test_young(vma->vm_mm, address)) 1334 referenced++; 1335 } 1336 if (!writable) { 1337 result = SCAN_PAGE_RO; 1338 } else if (!referenced || (unmapped && referenced < HPAGE_PMD_NR/2)) { 1339 result = SCAN_LACK_REFERENCED_PAGE; 1340 } else { 1341 result = SCAN_SUCCEED; 1342 ret = 1; 1343 } 1344 out_unmap: 1345 pte_unmap_unlock(pte, ptl); 1346 if (ret) { 1347 node = khugepaged_find_target_node(); 1348 /* collapse_huge_page will return with the mmap_lock released */ 1349 collapse_huge_page(mm, address, hpage, node, 1350 referenced, unmapped); 1351 } 1352 out: 1353 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, 1354 none_or_zero, result, unmapped); 1355 return ret; 1356 } 1357 1358 static void collect_mm_slot(struct mm_slot *mm_slot) 1359 { 1360 struct mm_struct *mm = mm_slot->mm; 1361 1362 lockdep_assert_held(&khugepaged_mm_lock); 1363 1364 if (khugepaged_test_exit(mm)) { 1365 /* free mm_slot */ 1366 hash_del(&mm_slot->hash); 1367 list_del(&mm_slot->mm_node); 1368 1369 /* 1370 * Not strictly needed because the mm exited already. 1371 * 1372 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1373 */ 1374 1375 /* khugepaged_mm_lock actually not necessary for the below */ 1376 free_mm_slot(mm_slot); 1377 mmdrop(mm); 1378 } 1379 } 1380 1381 #ifdef CONFIG_SHMEM 1382 /* 1383 * Notify khugepaged that given addr of the mm is pte-mapped THP. Then 1384 * khugepaged should try to collapse the page table. 1385 */ 1386 static int khugepaged_add_pte_mapped_thp(struct mm_struct *mm, 1387 unsigned long addr) 1388 { 1389 struct mm_slot *mm_slot; 1390 1391 VM_BUG_ON(addr & ~HPAGE_PMD_MASK); 1392 1393 spin_lock(&khugepaged_mm_lock); 1394 mm_slot = get_mm_slot(mm); 1395 if (likely(mm_slot && mm_slot->nr_pte_mapped_thp < MAX_PTE_MAPPED_THP)) 1396 mm_slot->pte_mapped_thp[mm_slot->nr_pte_mapped_thp++] = addr; 1397 spin_unlock(&khugepaged_mm_lock); 1398 return 0; 1399 } 1400 1401 /** 1402 * Try to collapse a pte-mapped THP for mm at address haddr. 1403 * 1404 * This function checks whether all the PTEs in the PMD are pointing to the 1405 * right THP. If so, retract the page table so the THP can refault in with 1406 * as pmd-mapped. 1407 */ 1408 void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) 1409 { 1410 unsigned long haddr = addr & HPAGE_PMD_MASK; 1411 struct vm_area_struct *vma = find_vma(mm, haddr); 1412 struct page *hpage; 1413 pte_t *start_pte, *pte; 1414 pmd_t *pmd, _pmd; 1415 spinlock_t *ptl; 1416 int count = 0; 1417 int i; 1418 1419 if (!vma || !vma->vm_file || 1420 vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE) 1421 return; 1422 1423 /* 1424 * This vm_flags may not have VM_HUGEPAGE if the page was not 1425 * collapsed by this mm. But we can still collapse if the page is 1426 * the valid THP. Add extra VM_HUGEPAGE so hugepage_vma_check() 1427 * will not fail the vma for missing VM_HUGEPAGE 1428 */ 1429 if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE)) 1430 return; 1431 1432 hpage = find_lock_page(vma->vm_file->f_mapping, 1433 linear_page_index(vma, haddr)); 1434 if (!hpage) 1435 return; 1436 1437 if (!PageHead(hpage)) 1438 goto drop_hpage; 1439 1440 pmd = mm_find_pmd(mm, haddr); 1441 if (!pmd) 1442 goto drop_hpage; 1443 1444 start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl); 1445 1446 /* step 1: check all mapped PTEs are to the right huge page */ 1447 for (i = 0, addr = haddr, pte = start_pte; 1448 i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) { 1449 struct page *page; 1450 1451 /* empty pte, skip */ 1452 if (pte_none(*pte)) 1453 continue; 1454 1455 /* page swapped out, abort */ 1456 if (!pte_present(*pte)) 1457 goto abort; 1458 1459 page = vm_normal_page(vma, addr, *pte); 1460 1461 /* 1462 * Note that uprobe, debugger, or MAP_PRIVATE may change the 1463 * page table, but the new page will not be a subpage of hpage. 1464 */ 1465 if (hpage + i != page) 1466 goto abort; 1467 count++; 1468 } 1469 1470 /* step 2: adjust rmap */ 1471 for (i = 0, addr = haddr, pte = start_pte; 1472 i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) { 1473 struct page *page; 1474 1475 if (pte_none(*pte)) 1476 continue; 1477 page = vm_normal_page(vma, addr, *pte); 1478 page_remove_rmap(page, false); 1479 } 1480 1481 pte_unmap_unlock(start_pte, ptl); 1482 1483 /* step 3: set proper refcount and mm_counters. */ 1484 if (count) { 1485 page_ref_sub(hpage, count); 1486 add_mm_counter(vma->vm_mm, mm_counter_file(hpage), -count); 1487 } 1488 1489 /* step 4: collapse pmd */ 1490 ptl = pmd_lock(vma->vm_mm, pmd); 1491 _pmd = pmdp_collapse_flush(vma, haddr, pmd); 1492 spin_unlock(ptl); 1493 mm_dec_nr_ptes(mm); 1494 pte_free(mm, pmd_pgtable(_pmd)); 1495 1496 drop_hpage: 1497 unlock_page(hpage); 1498 put_page(hpage); 1499 return; 1500 1501 abort: 1502 pte_unmap_unlock(start_pte, ptl); 1503 goto drop_hpage; 1504 } 1505 1506 static int khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot) 1507 { 1508 struct mm_struct *mm = mm_slot->mm; 1509 int i; 1510 1511 if (likely(mm_slot->nr_pte_mapped_thp == 0)) 1512 return 0; 1513 1514 if (!mmap_write_trylock(mm)) 1515 return -EBUSY; 1516 1517 if (unlikely(khugepaged_test_exit(mm))) 1518 goto out; 1519 1520 for (i = 0; i < mm_slot->nr_pte_mapped_thp; i++) 1521 collapse_pte_mapped_thp(mm, mm_slot->pte_mapped_thp[i]); 1522 1523 out: 1524 mm_slot->nr_pte_mapped_thp = 0; 1525 mmap_write_unlock(mm); 1526 return 0; 1527 } 1528 1529 static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) 1530 { 1531 struct vm_area_struct *vma; 1532 struct mm_struct *mm; 1533 unsigned long addr; 1534 pmd_t *pmd, _pmd; 1535 1536 i_mmap_lock_write(mapping); 1537 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { 1538 /* 1539 * Check vma->anon_vma to exclude MAP_PRIVATE mappings that 1540 * got written to. These VMAs are likely not worth investing 1541 * mmap_write_lock(mm) as PMD-mapping is likely to be split 1542 * later. 1543 * 1544 * Not that vma->anon_vma check is racy: it can be set up after 1545 * the check but before we took mmap_lock by the fault path. 1546 * But page lock would prevent establishing any new ptes of the 1547 * page, so we are safe. 1548 * 1549 * An alternative would be drop the check, but check that page 1550 * table is clear before calling pmdp_collapse_flush() under 1551 * ptl. It has higher chance to recover THP for the VMA, but 1552 * has higher cost too. 1553 */ 1554 if (vma->anon_vma) 1555 continue; 1556 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); 1557 if (addr & ~HPAGE_PMD_MASK) 1558 continue; 1559 if (vma->vm_end < addr + HPAGE_PMD_SIZE) 1560 continue; 1561 mm = vma->vm_mm; 1562 pmd = mm_find_pmd(mm, addr); 1563 if (!pmd) 1564 continue; 1565 /* 1566 * We need exclusive mmap_lock to retract page table. 1567 * 1568 * We use trylock due to lock inversion: we need to acquire 1569 * mmap_lock while holding page lock. Fault path does it in 1570 * reverse order. Trylock is a way to avoid deadlock. 1571 */ 1572 if (mmap_write_trylock(mm)) { 1573 if (!khugepaged_test_exit(mm)) { 1574 spinlock_t *ptl = pmd_lock(mm, pmd); 1575 /* assume page table is clear */ 1576 _pmd = pmdp_collapse_flush(vma, addr, pmd); 1577 spin_unlock(ptl); 1578 mm_dec_nr_ptes(mm); 1579 pte_free(mm, pmd_pgtable(_pmd)); 1580 } 1581 mmap_write_unlock(mm); 1582 } else { 1583 /* Try again later */ 1584 khugepaged_add_pte_mapped_thp(mm, addr); 1585 } 1586 } 1587 i_mmap_unlock_write(mapping); 1588 } 1589 1590 /** 1591 * collapse_file - collapse filemap/tmpfs/shmem pages into huge one. 1592 * 1593 * Basic scheme is simple, details are more complex: 1594 * - allocate and lock a new huge page; 1595 * - scan page cache replacing old pages with the new one 1596 * + swap/gup in pages if necessary; 1597 * + fill in gaps; 1598 * + keep old pages around in case rollback is required; 1599 * - if replacing succeeds: 1600 * + copy data over; 1601 * + free old pages; 1602 * + unlock huge page; 1603 * - if replacing failed; 1604 * + put all pages back and unfreeze them; 1605 * + restore gaps in the page cache; 1606 * + unlock and free huge page; 1607 */ 1608 static void collapse_file(struct mm_struct *mm, 1609 struct file *file, pgoff_t start, 1610 struct page **hpage, int node) 1611 { 1612 struct address_space *mapping = file->f_mapping; 1613 gfp_t gfp; 1614 struct page *new_page; 1615 pgoff_t index, end = start + HPAGE_PMD_NR; 1616 LIST_HEAD(pagelist); 1617 XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER); 1618 int nr_none = 0, result = SCAN_SUCCEED; 1619 bool is_shmem = shmem_file(file); 1620 1621 VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); 1622 VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); 1623 1624 /* Only allocate from the target node */ 1625 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; 1626 1627 new_page = khugepaged_alloc_page(hpage, gfp, node); 1628 if (!new_page) { 1629 result = SCAN_ALLOC_HUGE_PAGE_FAIL; 1630 goto out; 1631 } 1632 1633 if (unlikely(mem_cgroup_charge(new_page, mm, gfp))) { 1634 result = SCAN_CGROUP_CHARGE_FAIL; 1635 goto out; 1636 } 1637 count_memcg_page_event(new_page, THP_COLLAPSE_ALLOC); 1638 1639 /* This will be less messy when we use multi-index entries */ 1640 do { 1641 xas_lock_irq(&xas); 1642 xas_create_range(&xas); 1643 if (!xas_error(&xas)) 1644 break; 1645 xas_unlock_irq(&xas); 1646 if (!xas_nomem(&xas, GFP_KERNEL)) { 1647 result = SCAN_FAIL; 1648 goto out; 1649 } 1650 } while (1); 1651 1652 __SetPageLocked(new_page); 1653 if (is_shmem) 1654 __SetPageSwapBacked(new_page); 1655 new_page->index = start; 1656 new_page->mapping = mapping; 1657 1658 /* 1659 * At this point the new_page is locked and not up-to-date. 1660 * It's safe to insert it into the page cache, because nobody would 1661 * be able to map it or use it in another way until we unlock it. 1662 */ 1663 1664 xas_set(&xas, start); 1665 for (index = start; index < end; index++) { 1666 struct page *page = xas_next(&xas); 1667 1668 VM_BUG_ON(index != xas.xa_index); 1669 if (is_shmem) { 1670 if (!page) { 1671 /* 1672 * Stop if extent has been truncated or 1673 * hole-punched, and is now completely 1674 * empty. 1675 */ 1676 if (index == start) { 1677 if (!xas_next_entry(&xas, end - 1)) { 1678 result = SCAN_TRUNCATED; 1679 goto xa_locked; 1680 } 1681 xas_set(&xas, index); 1682 } 1683 if (!shmem_charge(mapping->host, 1)) { 1684 result = SCAN_FAIL; 1685 goto xa_locked; 1686 } 1687 xas_store(&xas, new_page); 1688 nr_none++; 1689 continue; 1690 } 1691 1692 if (xa_is_value(page) || !PageUptodate(page)) { 1693 xas_unlock_irq(&xas); 1694 /* swap in or instantiate fallocated page */ 1695 if (shmem_getpage(mapping->host, index, &page, 1696 SGP_NOHUGE)) { 1697 result = SCAN_FAIL; 1698 goto xa_unlocked; 1699 } 1700 } else if (trylock_page(page)) { 1701 get_page(page); 1702 xas_unlock_irq(&xas); 1703 } else { 1704 result = SCAN_PAGE_LOCK; 1705 goto xa_locked; 1706 } 1707 } else { /* !is_shmem */ 1708 if (!page || xa_is_value(page)) { 1709 xas_unlock_irq(&xas); 1710 page_cache_sync_readahead(mapping, &file->f_ra, 1711 file, index, 1712 PAGE_SIZE); 1713 /* drain pagevecs to help isolate_lru_page() */ 1714 lru_add_drain(); 1715 page = find_lock_page(mapping, index); 1716 if (unlikely(page == NULL)) { 1717 result = SCAN_FAIL; 1718 goto xa_unlocked; 1719 } 1720 } else if (PageDirty(page)) { 1721 /* 1722 * khugepaged only works on read-only fd, 1723 * so this page is dirty because it hasn't 1724 * been flushed since first write. There 1725 * won't be new dirty pages. 1726 * 1727 * Trigger async flush here and hope the 1728 * writeback is done when khugepaged 1729 * revisits this page. 1730 * 1731 * This is a one-off situation. We are not 1732 * forcing writeback in loop. 1733 */ 1734 xas_unlock_irq(&xas); 1735 filemap_flush(mapping); 1736 result = SCAN_FAIL; 1737 goto xa_unlocked; 1738 } else if (trylock_page(page)) { 1739 get_page(page); 1740 xas_unlock_irq(&xas); 1741 } else { 1742 result = SCAN_PAGE_LOCK; 1743 goto xa_locked; 1744 } 1745 } 1746 1747 /* 1748 * The page must be locked, so we can drop the i_pages lock 1749 * without racing with truncate. 1750 */ 1751 VM_BUG_ON_PAGE(!PageLocked(page), page); 1752 1753 /* make sure the page is up to date */ 1754 if (unlikely(!PageUptodate(page))) { 1755 result = SCAN_FAIL; 1756 goto out_unlock; 1757 } 1758 1759 /* 1760 * If file was truncated then extended, or hole-punched, before 1761 * we locked the first page, then a THP might be there already. 1762 */ 1763 if (PageTransCompound(page)) { 1764 result = SCAN_PAGE_COMPOUND; 1765 goto out_unlock; 1766 } 1767 1768 if (page_mapping(page) != mapping) { 1769 result = SCAN_TRUNCATED; 1770 goto out_unlock; 1771 } 1772 1773 if (!is_shmem && PageDirty(page)) { 1774 /* 1775 * khugepaged only works on read-only fd, so this 1776 * page is dirty because it hasn't been flushed 1777 * since first write. 1778 */ 1779 result = SCAN_FAIL; 1780 goto out_unlock; 1781 } 1782 1783 if (isolate_lru_page(page)) { 1784 result = SCAN_DEL_PAGE_LRU; 1785 goto out_unlock; 1786 } 1787 1788 if (page_has_private(page) && 1789 !try_to_release_page(page, GFP_KERNEL)) { 1790 result = SCAN_PAGE_HAS_PRIVATE; 1791 putback_lru_page(page); 1792 goto out_unlock; 1793 } 1794 1795 if (page_mapped(page)) 1796 unmap_mapping_pages(mapping, index, 1, false); 1797 1798 xas_lock_irq(&xas); 1799 xas_set(&xas, index); 1800 1801 VM_BUG_ON_PAGE(page != xas_load(&xas), page); 1802 VM_BUG_ON_PAGE(page_mapped(page), page); 1803 1804 /* 1805 * The page is expected to have page_count() == 3: 1806 * - we hold a pin on it; 1807 * - one reference from page cache; 1808 * - one from isolate_lru_page; 1809 */ 1810 if (!page_ref_freeze(page, 3)) { 1811 result = SCAN_PAGE_COUNT; 1812 xas_unlock_irq(&xas); 1813 putback_lru_page(page); 1814 goto out_unlock; 1815 } 1816 1817 /* 1818 * Add the page to the list to be able to undo the collapse if 1819 * something go wrong. 1820 */ 1821 list_add_tail(&page->lru, &pagelist); 1822 1823 /* Finally, replace with the new page. */ 1824 xas_store(&xas, new_page); 1825 continue; 1826 out_unlock: 1827 unlock_page(page); 1828 put_page(page); 1829 goto xa_unlocked; 1830 } 1831 1832 if (is_shmem) 1833 __inc_node_page_state(new_page, NR_SHMEM_THPS); 1834 else { 1835 __inc_node_page_state(new_page, NR_FILE_THPS); 1836 filemap_nr_thps_inc(mapping); 1837 } 1838 1839 if (nr_none) { 1840 __mod_lruvec_page_state(new_page, NR_FILE_PAGES, nr_none); 1841 if (is_shmem) 1842 __mod_lruvec_page_state(new_page, NR_SHMEM, nr_none); 1843 } 1844 1845 xa_locked: 1846 xas_unlock_irq(&xas); 1847 xa_unlocked: 1848 1849 if (result == SCAN_SUCCEED) { 1850 struct page *page, *tmp; 1851 1852 /* 1853 * Replacing old pages with new one has succeeded, now we 1854 * need to copy the content and free the old pages. 1855 */ 1856 index = start; 1857 list_for_each_entry_safe(page, tmp, &pagelist, lru) { 1858 while (index < page->index) { 1859 clear_highpage(new_page + (index % HPAGE_PMD_NR)); 1860 index++; 1861 } 1862 copy_highpage(new_page + (page->index % HPAGE_PMD_NR), 1863 page); 1864 list_del(&page->lru); 1865 page->mapping = NULL; 1866 page_ref_unfreeze(page, 1); 1867 ClearPageActive(page); 1868 ClearPageUnevictable(page); 1869 unlock_page(page); 1870 put_page(page); 1871 index++; 1872 } 1873 while (index < end) { 1874 clear_highpage(new_page + (index % HPAGE_PMD_NR)); 1875 index++; 1876 } 1877 1878 SetPageUptodate(new_page); 1879 page_ref_add(new_page, HPAGE_PMD_NR - 1); 1880 if (is_shmem) 1881 set_page_dirty(new_page); 1882 lru_cache_add(new_page); 1883 1884 /* 1885 * Remove pte page tables, so we can re-fault the page as huge. 1886 */ 1887 retract_page_tables(mapping, start); 1888 *hpage = NULL; 1889 1890 khugepaged_pages_collapsed++; 1891 } else { 1892 struct page *page; 1893 1894 /* Something went wrong: roll back page cache changes */ 1895 xas_lock_irq(&xas); 1896 mapping->nrpages -= nr_none; 1897 1898 if (is_shmem) 1899 shmem_uncharge(mapping->host, nr_none); 1900 1901 xas_set(&xas, start); 1902 xas_for_each(&xas, page, end - 1) { 1903 page = list_first_entry_or_null(&pagelist, 1904 struct page, lru); 1905 if (!page || xas.xa_index < page->index) { 1906 if (!nr_none) 1907 break; 1908 nr_none--; 1909 /* Put holes back where they were */ 1910 xas_store(&xas, NULL); 1911 continue; 1912 } 1913 1914 VM_BUG_ON_PAGE(page->index != xas.xa_index, page); 1915 1916 /* Unfreeze the page. */ 1917 list_del(&page->lru); 1918 page_ref_unfreeze(page, 2); 1919 xas_store(&xas, page); 1920 xas_pause(&xas); 1921 xas_unlock_irq(&xas); 1922 unlock_page(page); 1923 putback_lru_page(page); 1924 xas_lock_irq(&xas); 1925 } 1926 VM_BUG_ON(nr_none); 1927 xas_unlock_irq(&xas); 1928 1929 new_page->mapping = NULL; 1930 } 1931 1932 unlock_page(new_page); 1933 out: 1934 VM_BUG_ON(!list_empty(&pagelist)); 1935 if (!IS_ERR_OR_NULL(*hpage)) 1936 mem_cgroup_uncharge(*hpage); 1937 /* TODO: tracepoints */ 1938 } 1939 1940 static void khugepaged_scan_file(struct mm_struct *mm, 1941 struct file *file, pgoff_t start, struct page **hpage) 1942 { 1943 struct page *page = NULL; 1944 struct address_space *mapping = file->f_mapping; 1945 XA_STATE(xas, &mapping->i_pages, start); 1946 int present, swap; 1947 int node = NUMA_NO_NODE; 1948 int result = SCAN_SUCCEED; 1949 1950 present = 0; 1951 swap = 0; 1952 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 1953 rcu_read_lock(); 1954 xas_for_each(&xas, page, start + HPAGE_PMD_NR - 1) { 1955 if (xas_retry(&xas, page)) 1956 continue; 1957 1958 if (xa_is_value(page)) { 1959 if (++swap > khugepaged_max_ptes_swap) { 1960 result = SCAN_EXCEED_SWAP_PTE; 1961 break; 1962 } 1963 continue; 1964 } 1965 1966 if (PageTransCompound(page)) { 1967 result = SCAN_PAGE_COMPOUND; 1968 break; 1969 } 1970 1971 node = page_to_nid(page); 1972 if (khugepaged_scan_abort(node)) { 1973 result = SCAN_SCAN_ABORT; 1974 break; 1975 } 1976 khugepaged_node_load[node]++; 1977 1978 if (!PageLRU(page)) { 1979 result = SCAN_PAGE_LRU; 1980 break; 1981 } 1982 1983 if (page_count(page) != 1984 1 + page_mapcount(page) + page_has_private(page)) { 1985 result = SCAN_PAGE_COUNT; 1986 break; 1987 } 1988 1989 /* 1990 * We probably should check if the page is referenced here, but 1991 * nobody would transfer pte_young() to PageReferenced() for us. 1992 * And rmap walk here is just too costly... 1993 */ 1994 1995 present++; 1996 1997 if (need_resched()) { 1998 xas_pause(&xas); 1999 cond_resched_rcu(); 2000 } 2001 } 2002 rcu_read_unlock(); 2003 2004 if (result == SCAN_SUCCEED) { 2005 if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) { 2006 result = SCAN_EXCEED_NONE_PTE; 2007 } else { 2008 node = khugepaged_find_target_node(); 2009 collapse_file(mm, file, start, hpage, node); 2010 } 2011 } 2012 2013 /* TODO: tracepoints */ 2014 } 2015 #else 2016 static void khugepaged_scan_file(struct mm_struct *mm, 2017 struct file *file, pgoff_t start, struct page **hpage) 2018 { 2019 BUILD_BUG(); 2020 } 2021 2022 static int khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot) 2023 { 2024 return 0; 2025 } 2026 #endif 2027 2028 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2029 struct page **hpage) 2030 __releases(&khugepaged_mm_lock) 2031 __acquires(&khugepaged_mm_lock) 2032 { 2033 struct mm_slot *mm_slot; 2034 struct mm_struct *mm; 2035 struct vm_area_struct *vma; 2036 int progress = 0; 2037 2038 VM_BUG_ON(!pages); 2039 lockdep_assert_held(&khugepaged_mm_lock); 2040 2041 if (khugepaged_scan.mm_slot) 2042 mm_slot = khugepaged_scan.mm_slot; 2043 else { 2044 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2045 struct mm_slot, mm_node); 2046 khugepaged_scan.address = 0; 2047 khugepaged_scan.mm_slot = mm_slot; 2048 } 2049 spin_unlock(&khugepaged_mm_lock); 2050 khugepaged_collapse_pte_mapped_thps(mm_slot); 2051 2052 mm = mm_slot->mm; 2053 /* 2054 * Don't wait for semaphore (to avoid long wait times). Just move to 2055 * the next mm on the list. 2056 */ 2057 vma = NULL; 2058 if (unlikely(!mmap_read_trylock(mm))) 2059 goto breakouterloop_mmap_lock; 2060 if (likely(!khugepaged_test_exit(mm))) 2061 vma = find_vma(mm, khugepaged_scan.address); 2062 2063 progress++; 2064 for (; vma; vma = vma->vm_next) { 2065 unsigned long hstart, hend; 2066 2067 cond_resched(); 2068 if (unlikely(khugepaged_test_exit(mm))) { 2069 progress++; 2070 break; 2071 } 2072 if (!hugepage_vma_check(vma, vma->vm_flags)) { 2073 skip: 2074 progress++; 2075 continue; 2076 } 2077 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2078 hend = vma->vm_end & HPAGE_PMD_MASK; 2079 if (hstart >= hend) 2080 goto skip; 2081 if (khugepaged_scan.address > hend) 2082 goto skip; 2083 if (khugepaged_scan.address < hstart) 2084 khugepaged_scan.address = hstart; 2085 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2086 if (shmem_file(vma->vm_file) && !shmem_huge_enabled(vma)) 2087 goto skip; 2088 2089 while (khugepaged_scan.address < hend) { 2090 int ret; 2091 cond_resched(); 2092 if (unlikely(khugepaged_test_exit(mm))) 2093 goto breakouterloop; 2094 2095 VM_BUG_ON(khugepaged_scan.address < hstart || 2096 khugepaged_scan.address + HPAGE_PMD_SIZE > 2097 hend); 2098 if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) { 2099 struct file *file = get_file(vma->vm_file); 2100 pgoff_t pgoff = linear_page_index(vma, 2101 khugepaged_scan.address); 2102 2103 mmap_read_unlock(mm); 2104 ret = 1; 2105 khugepaged_scan_file(mm, file, pgoff, hpage); 2106 fput(file); 2107 } else { 2108 ret = khugepaged_scan_pmd(mm, vma, 2109 khugepaged_scan.address, 2110 hpage); 2111 } 2112 /* move to next address */ 2113 khugepaged_scan.address += HPAGE_PMD_SIZE; 2114 progress += HPAGE_PMD_NR; 2115 if (ret) 2116 /* we released mmap_lock so break loop */ 2117 goto breakouterloop_mmap_lock; 2118 if (progress >= pages) 2119 goto breakouterloop; 2120 } 2121 } 2122 breakouterloop: 2123 mmap_read_unlock(mm); /* exit_mmap will destroy ptes after this */ 2124 breakouterloop_mmap_lock: 2125 2126 spin_lock(&khugepaged_mm_lock); 2127 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2128 /* 2129 * Release the current mm_slot if this mm is about to die, or 2130 * if we scanned all vmas of this mm. 2131 */ 2132 if (khugepaged_test_exit(mm) || !vma) { 2133 /* 2134 * Make sure that if mm_users is reaching zero while 2135 * khugepaged runs here, khugepaged_exit will find 2136 * mm_slot not pointing to the exiting mm. 2137 */ 2138 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2139 khugepaged_scan.mm_slot = list_entry( 2140 mm_slot->mm_node.next, 2141 struct mm_slot, mm_node); 2142 khugepaged_scan.address = 0; 2143 } else { 2144 khugepaged_scan.mm_slot = NULL; 2145 khugepaged_full_scans++; 2146 } 2147 2148 collect_mm_slot(mm_slot); 2149 } 2150 2151 return progress; 2152 } 2153 2154 static int khugepaged_has_work(void) 2155 { 2156 return !list_empty(&khugepaged_scan.mm_head) && 2157 khugepaged_enabled(); 2158 } 2159 2160 static int khugepaged_wait_event(void) 2161 { 2162 return !list_empty(&khugepaged_scan.mm_head) || 2163 kthread_should_stop(); 2164 } 2165 2166 static void khugepaged_do_scan(void) 2167 { 2168 struct page *hpage = NULL; 2169 unsigned int progress = 0, pass_through_head = 0; 2170 unsigned int pages = khugepaged_pages_to_scan; 2171 bool wait = true; 2172 2173 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2174 2175 lru_add_drain_all(); 2176 2177 while (progress < pages) { 2178 if (!khugepaged_prealloc_page(&hpage, &wait)) 2179 break; 2180 2181 cond_resched(); 2182 2183 if (unlikely(kthread_should_stop() || try_to_freeze())) 2184 break; 2185 2186 spin_lock(&khugepaged_mm_lock); 2187 if (!khugepaged_scan.mm_slot) 2188 pass_through_head++; 2189 if (khugepaged_has_work() && 2190 pass_through_head < 2) 2191 progress += khugepaged_scan_mm_slot(pages - progress, 2192 &hpage); 2193 else 2194 progress = pages; 2195 spin_unlock(&khugepaged_mm_lock); 2196 } 2197 2198 if (!IS_ERR_OR_NULL(hpage)) 2199 put_page(hpage); 2200 } 2201 2202 static bool khugepaged_should_wakeup(void) 2203 { 2204 return kthread_should_stop() || 2205 time_after_eq(jiffies, khugepaged_sleep_expire); 2206 } 2207 2208 static void khugepaged_wait_work(void) 2209 { 2210 if (khugepaged_has_work()) { 2211 const unsigned long scan_sleep_jiffies = 2212 msecs_to_jiffies(khugepaged_scan_sleep_millisecs); 2213 2214 if (!scan_sleep_jiffies) 2215 return; 2216 2217 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies; 2218 wait_event_freezable_timeout(khugepaged_wait, 2219 khugepaged_should_wakeup(), 2220 scan_sleep_jiffies); 2221 return; 2222 } 2223 2224 if (khugepaged_enabled()) 2225 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 2226 } 2227 2228 static int khugepaged(void *none) 2229 { 2230 struct mm_slot *mm_slot; 2231 2232 set_freezable(); 2233 set_user_nice(current, MAX_NICE); 2234 2235 while (!kthread_should_stop()) { 2236 khugepaged_do_scan(); 2237 khugepaged_wait_work(); 2238 } 2239 2240 spin_lock(&khugepaged_mm_lock); 2241 mm_slot = khugepaged_scan.mm_slot; 2242 khugepaged_scan.mm_slot = NULL; 2243 if (mm_slot) 2244 collect_mm_slot(mm_slot); 2245 spin_unlock(&khugepaged_mm_lock); 2246 return 0; 2247 } 2248 2249 static void set_recommended_min_free_kbytes(void) 2250 { 2251 struct zone *zone; 2252 int nr_zones = 0; 2253 unsigned long recommended_min; 2254 2255 for_each_populated_zone(zone) { 2256 /* 2257 * We don't need to worry about fragmentation of 2258 * ZONE_MOVABLE since it only has movable pages. 2259 */ 2260 if (zone_idx(zone) > gfp_zone(GFP_USER)) 2261 continue; 2262 2263 nr_zones++; 2264 } 2265 2266 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */ 2267 recommended_min = pageblock_nr_pages * nr_zones * 2; 2268 2269 /* 2270 * Make sure that on average at least two pageblocks are almost free 2271 * of another type, one for a migratetype to fall back to and a 2272 * second to avoid subsequent fallbacks of other types There are 3 2273 * MIGRATE_TYPES we care about. 2274 */ 2275 recommended_min += pageblock_nr_pages * nr_zones * 2276 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; 2277 2278 /* don't ever allow to reserve more than 5% of the lowmem */ 2279 recommended_min = min(recommended_min, 2280 (unsigned long) nr_free_buffer_pages() / 20); 2281 recommended_min <<= (PAGE_SHIFT-10); 2282 2283 if (recommended_min > min_free_kbytes) { 2284 if (user_min_free_kbytes >= 0) 2285 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", 2286 min_free_kbytes, recommended_min); 2287 2288 min_free_kbytes = recommended_min; 2289 } 2290 setup_per_zone_wmarks(); 2291 } 2292 2293 int start_stop_khugepaged(void) 2294 { 2295 static struct task_struct *khugepaged_thread __read_mostly; 2296 static DEFINE_MUTEX(khugepaged_mutex); 2297 int err = 0; 2298 2299 mutex_lock(&khugepaged_mutex); 2300 if (khugepaged_enabled()) { 2301 if (!khugepaged_thread) 2302 khugepaged_thread = kthread_run(khugepaged, NULL, 2303 "khugepaged"); 2304 if (IS_ERR(khugepaged_thread)) { 2305 pr_err("khugepaged: kthread_run(khugepaged) failed\n"); 2306 err = PTR_ERR(khugepaged_thread); 2307 khugepaged_thread = NULL; 2308 goto fail; 2309 } 2310 2311 if (!list_empty(&khugepaged_scan.mm_head)) 2312 wake_up_interruptible(&khugepaged_wait); 2313 2314 set_recommended_min_free_kbytes(); 2315 } else if (khugepaged_thread) { 2316 kthread_stop(khugepaged_thread); 2317 khugepaged_thread = NULL; 2318 } 2319 fail: 2320 mutex_unlock(&khugepaged_mutex); 2321 return err; 2322 } 2323