1 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 2 3 #include <linux/mm.h> 4 #include <linux/sched.h> 5 #include <linux/sched/mm.h> 6 #include <linux/sched/coredump.h> 7 #include <linux/mmu_notifier.h> 8 #include <linux/rmap.h> 9 #include <linux/swap.h> 10 #include <linux/mm_inline.h> 11 #include <linux/kthread.h> 12 #include <linux/khugepaged.h> 13 #include <linux/freezer.h> 14 #include <linux/mman.h> 15 #include <linux/hashtable.h> 16 #include <linux/userfaultfd_k.h> 17 #include <linux/page_idle.h> 18 #include <linux/swapops.h> 19 #include <linux/shmem_fs.h> 20 21 #include <asm/tlb.h> 22 #include <asm/pgalloc.h> 23 #include "internal.h" 24 25 enum scan_result { 26 SCAN_FAIL, 27 SCAN_SUCCEED, 28 SCAN_PMD_NULL, 29 SCAN_EXCEED_NONE_PTE, 30 SCAN_PTE_NON_PRESENT, 31 SCAN_PAGE_RO, 32 SCAN_LACK_REFERENCED_PAGE, 33 SCAN_PAGE_NULL, 34 SCAN_SCAN_ABORT, 35 SCAN_PAGE_COUNT, 36 SCAN_PAGE_LRU, 37 SCAN_PAGE_LOCK, 38 SCAN_PAGE_ANON, 39 SCAN_PAGE_COMPOUND, 40 SCAN_ANY_PROCESS, 41 SCAN_VMA_NULL, 42 SCAN_VMA_CHECK, 43 SCAN_ADDRESS_RANGE, 44 SCAN_SWAP_CACHE_PAGE, 45 SCAN_DEL_PAGE_LRU, 46 SCAN_ALLOC_HUGE_PAGE_FAIL, 47 SCAN_CGROUP_CHARGE_FAIL, 48 SCAN_EXCEED_SWAP_PTE, 49 SCAN_TRUNCATED, 50 }; 51 52 #define CREATE_TRACE_POINTS 53 #include <trace/events/huge_memory.h> 54 55 /* default scan 8*512 pte (or vmas) every 30 second */ 56 static unsigned int khugepaged_pages_to_scan __read_mostly; 57 static unsigned int khugepaged_pages_collapsed; 58 static unsigned int khugepaged_full_scans; 59 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 60 /* during fragmentation poll the hugepage allocator once every minute */ 61 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 62 static unsigned long khugepaged_sleep_expire; 63 static DEFINE_SPINLOCK(khugepaged_mm_lock); 64 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 65 /* 66 * default collapse hugepages if there is at least one pte mapped like 67 * it would have happened if the vma was large enough during page 68 * fault. 69 */ 70 static unsigned int khugepaged_max_ptes_none __read_mostly; 71 static unsigned int khugepaged_max_ptes_swap __read_mostly; 72 73 #define MM_SLOTS_HASH_BITS 10 74 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); 75 76 static struct kmem_cache *mm_slot_cache __read_mostly; 77 78 /** 79 * struct mm_slot - hash lookup from mm to mm_slot 80 * @hash: hash collision list 81 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 82 * @mm: the mm that this information is valid for 83 */ 84 struct mm_slot { 85 struct hlist_node hash; 86 struct list_head mm_node; 87 struct mm_struct *mm; 88 }; 89 90 /** 91 * struct khugepaged_scan - cursor for scanning 92 * @mm_head: the head of the mm list to scan 93 * @mm_slot: the current mm_slot we are scanning 94 * @address: the next address inside that to be scanned 95 * 96 * There is only the one khugepaged_scan instance of this cursor structure. 97 */ 98 struct khugepaged_scan { 99 struct list_head mm_head; 100 struct mm_slot *mm_slot; 101 unsigned long address; 102 }; 103 104 static struct khugepaged_scan khugepaged_scan = { 105 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 106 }; 107 108 #ifdef CONFIG_SYSFS 109 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 110 struct kobj_attribute *attr, 111 char *buf) 112 { 113 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 114 } 115 116 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 117 struct kobj_attribute *attr, 118 const char *buf, size_t count) 119 { 120 unsigned long msecs; 121 int err; 122 123 err = kstrtoul(buf, 10, &msecs); 124 if (err || msecs > UINT_MAX) 125 return -EINVAL; 126 127 khugepaged_scan_sleep_millisecs = msecs; 128 khugepaged_sleep_expire = 0; 129 wake_up_interruptible(&khugepaged_wait); 130 131 return count; 132 } 133 static struct kobj_attribute scan_sleep_millisecs_attr = 134 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 135 scan_sleep_millisecs_store); 136 137 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 138 struct kobj_attribute *attr, 139 char *buf) 140 { 141 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 142 } 143 144 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 145 struct kobj_attribute *attr, 146 const char *buf, size_t count) 147 { 148 unsigned long msecs; 149 int err; 150 151 err = kstrtoul(buf, 10, &msecs); 152 if (err || msecs > UINT_MAX) 153 return -EINVAL; 154 155 khugepaged_alloc_sleep_millisecs = msecs; 156 khugepaged_sleep_expire = 0; 157 wake_up_interruptible(&khugepaged_wait); 158 159 return count; 160 } 161 static struct kobj_attribute alloc_sleep_millisecs_attr = 162 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 163 alloc_sleep_millisecs_store); 164 165 static ssize_t pages_to_scan_show(struct kobject *kobj, 166 struct kobj_attribute *attr, 167 char *buf) 168 { 169 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 170 } 171 static ssize_t pages_to_scan_store(struct kobject *kobj, 172 struct kobj_attribute *attr, 173 const char *buf, size_t count) 174 { 175 int err; 176 unsigned long pages; 177 178 err = kstrtoul(buf, 10, &pages); 179 if (err || !pages || pages > UINT_MAX) 180 return -EINVAL; 181 182 khugepaged_pages_to_scan = pages; 183 184 return count; 185 } 186 static struct kobj_attribute pages_to_scan_attr = 187 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 188 pages_to_scan_store); 189 190 static ssize_t pages_collapsed_show(struct kobject *kobj, 191 struct kobj_attribute *attr, 192 char *buf) 193 { 194 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 195 } 196 static struct kobj_attribute pages_collapsed_attr = 197 __ATTR_RO(pages_collapsed); 198 199 static ssize_t full_scans_show(struct kobject *kobj, 200 struct kobj_attribute *attr, 201 char *buf) 202 { 203 return sprintf(buf, "%u\n", khugepaged_full_scans); 204 } 205 static struct kobj_attribute full_scans_attr = 206 __ATTR_RO(full_scans); 207 208 static ssize_t khugepaged_defrag_show(struct kobject *kobj, 209 struct kobj_attribute *attr, char *buf) 210 { 211 return single_hugepage_flag_show(kobj, attr, buf, 212 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 213 } 214 static ssize_t khugepaged_defrag_store(struct kobject *kobj, 215 struct kobj_attribute *attr, 216 const char *buf, size_t count) 217 { 218 return single_hugepage_flag_store(kobj, attr, buf, count, 219 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 220 } 221 static struct kobj_attribute khugepaged_defrag_attr = 222 __ATTR(defrag, 0644, khugepaged_defrag_show, 223 khugepaged_defrag_store); 224 225 /* 226 * max_ptes_none controls if khugepaged should collapse hugepages over 227 * any unmapped ptes in turn potentially increasing the memory 228 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 229 * reduce the available free memory in the system as it 230 * runs. Increasing max_ptes_none will instead potentially reduce the 231 * free memory in the system during the khugepaged scan. 232 */ 233 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 234 struct kobj_attribute *attr, 235 char *buf) 236 { 237 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 238 } 239 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 240 struct kobj_attribute *attr, 241 const char *buf, size_t count) 242 { 243 int err; 244 unsigned long max_ptes_none; 245 246 err = kstrtoul(buf, 10, &max_ptes_none); 247 if (err || max_ptes_none > HPAGE_PMD_NR-1) 248 return -EINVAL; 249 250 khugepaged_max_ptes_none = max_ptes_none; 251 252 return count; 253 } 254 static struct kobj_attribute khugepaged_max_ptes_none_attr = 255 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 256 khugepaged_max_ptes_none_store); 257 258 static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj, 259 struct kobj_attribute *attr, 260 char *buf) 261 { 262 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap); 263 } 264 265 static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj, 266 struct kobj_attribute *attr, 267 const char *buf, size_t count) 268 { 269 int err; 270 unsigned long max_ptes_swap; 271 272 err = kstrtoul(buf, 10, &max_ptes_swap); 273 if (err || max_ptes_swap > HPAGE_PMD_NR-1) 274 return -EINVAL; 275 276 khugepaged_max_ptes_swap = max_ptes_swap; 277 278 return count; 279 } 280 281 static struct kobj_attribute khugepaged_max_ptes_swap_attr = 282 __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show, 283 khugepaged_max_ptes_swap_store); 284 285 static struct attribute *khugepaged_attr[] = { 286 &khugepaged_defrag_attr.attr, 287 &khugepaged_max_ptes_none_attr.attr, 288 &pages_to_scan_attr.attr, 289 &pages_collapsed_attr.attr, 290 &full_scans_attr.attr, 291 &scan_sleep_millisecs_attr.attr, 292 &alloc_sleep_millisecs_attr.attr, 293 &khugepaged_max_ptes_swap_attr.attr, 294 NULL, 295 }; 296 297 struct attribute_group khugepaged_attr_group = { 298 .attrs = khugepaged_attr, 299 .name = "khugepaged", 300 }; 301 #endif /* CONFIG_SYSFS */ 302 303 #define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB) 304 305 int hugepage_madvise(struct vm_area_struct *vma, 306 unsigned long *vm_flags, int advice) 307 { 308 switch (advice) { 309 case MADV_HUGEPAGE: 310 #ifdef CONFIG_S390 311 /* 312 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 313 * can't handle this properly after s390_enable_sie, so we simply 314 * ignore the madvise to prevent qemu from causing a SIGSEGV. 315 */ 316 if (mm_has_pgste(vma->vm_mm)) 317 return 0; 318 #endif 319 *vm_flags &= ~VM_NOHUGEPAGE; 320 *vm_flags |= VM_HUGEPAGE; 321 /* 322 * If the vma become good for khugepaged to scan, 323 * register it here without waiting a page fault that 324 * may not happen any time soon. 325 */ 326 if (!(*vm_flags & VM_NO_KHUGEPAGED) && 327 khugepaged_enter_vma_merge(vma, *vm_flags)) 328 return -ENOMEM; 329 break; 330 case MADV_NOHUGEPAGE: 331 *vm_flags &= ~VM_HUGEPAGE; 332 *vm_flags |= VM_NOHUGEPAGE; 333 /* 334 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 335 * this vma even if we leave the mm registered in khugepaged if 336 * it got registered before VM_NOHUGEPAGE was set. 337 */ 338 break; 339 } 340 341 return 0; 342 } 343 344 int __init khugepaged_init(void) 345 { 346 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 347 sizeof(struct mm_slot), 348 __alignof__(struct mm_slot), 0, NULL); 349 if (!mm_slot_cache) 350 return -ENOMEM; 351 352 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; 353 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; 354 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8; 355 356 return 0; 357 } 358 359 void __init khugepaged_destroy(void) 360 { 361 kmem_cache_destroy(mm_slot_cache); 362 } 363 364 static inline struct mm_slot *alloc_mm_slot(void) 365 { 366 if (!mm_slot_cache) /* initialization failed */ 367 return NULL; 368 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 369 } 370 371 static inline void free_mm_slot(struct mm_slot *mm_slot) 372 { 373 kmem_cache_free(mm_slot_cache, mm_slot); 374 } 375 376 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 377 { 378 struct mm_slot *mm_slot; 379 380 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) 381 if (mm == mm_slot->mm) 382 return mm_slot; 383 384 return NULL; 385 } 386 387 static void insert_to_mm_slots_hash(struct mm_struct *mm, 388 struct mm_slot *mm_slot) 389 { 390 mm_slot->mm = mm; 391 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); 392 } 393 394 static inline int khugepaged_test_exit(struct mm_struct *mm) 395 { 396 return atomic_read(&mm->mm_users) == 0; 397 } 398 399 int __khugepaged_enter(struct mm_struct *mm) 400 { 401 struct mm_slot *mm_slot; 402 int wakeup; 403 404 mm_slot = alloc_mm_slot(); 405 if (!mm_slot) 406 return -ENOMEM; 407 408 /* __khugepaged_exit() must not run from under us */ 409 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); 410 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 411 free_mm_slot(mm_slot); 412 return 0; 413 } 414 415 spin_lock(&khugepaged_mm_lock); 416 insert_to_mm_slots_hash(mm, mm_slot); 417 /* 418 * Insert just behind the scanning cursor, to let the area settle 419 * down a little. 420 */ 421 wakeup = list_empty(&khugepaged_scan.mm_head); 422 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 423 spin_unlock(&khugepaged_mm_lock); 424 425 mmgrab(mm); 426 if (wakeup) 427 wake_up_interruptible(&khugepaged_wait); 428 429 return 0; 430 } 431 432 int khugepaged_enter_vma_merge(struct vm_area_struct *vma, 433 unsigned long vm_flags) 434 { 435 unsigned long hstart, hend; 436 if (!vma->anon_vma) 437 /* 438 * Not yet faulted in so we will register later in the 439 * page fault if needed. 440 */ 441 return 0; 442 if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED)) 443 /* khugepaged not yet working on file or special mappings */ 444 return 0; 445 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 446 hend = vma->vm_end & HPAGE_PMD_MASK; 447 if (hstart < hend) 448 return khugepaged_enter(vma, vm_flags); 449 return 0; 450 } 451 452 void __khugepaged_exit(struct mm_struct *mm) 453 { 454 struct mm_slot *mm_slot; 455 int free = 0; 456 457 spin_lock(&khugepaged_mm_lock); 458 mm_slot = get_mm_slot(mm); 459 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 460 hash_del(&mm_slot->hash); 461 list_del(&mm_slot->mm_node); 462 free = 1; 463 } 464 spin_unlock(&khugepaged_mm_lock); 465 466 if (free) { 467 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 468 free_mm_slot(mm_slot); 469 mmdrop(mm); 470 } else if (mm_slot) { 471 /* 472 * This is required to serialize against 473 * khugepaged_test_exit() (which is guaranteed to run 474 * under mmap sem read mode). Stop here (after we 475 * return all pagetables will be destroyed) until 476 * khugepaged has finished working on the pagetables 477 * under the mmap_sem. 478 */ 479 down_write(&mm->mmap_sem); 480 up_write(&mm->mmap_sem); 481 } 482 } 483 484 static void release_pte_page(struct page *page) 485 { 486 /* 0 stands for page_is_file_cache(page) == false */ 487 dec_node_page_state(page, NR_ISOLATED_ANON + 0); 488 unlock_page(page); 489 putback_lru_page(page); 490 } 491 492 static void release_pte_pages(pte_t *pte, pte_t *_pte) 493 { 494 while (--_pte >= pte) { 495 pte_t pteval = *_pte; 496 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) 497 release_pte_page(pte_page(pteval)); 498 } 499 } 500 501 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 502 unsigned long address, 503 pte_t *pte) 504 { 505 struct page *page = NULL; 506 pte_t *_pte; 507 int none_or_zero = 0, result = 0, referenced = 0; 508 bool writable = false; 509 510 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 511 _pte++, address += PAGE_SIZE) { 512 pte_t pteval = *_pte; 513 if (pte_none(pteval) || (pte_present(pteval) && 514 is_zero_pfn(pte_pfn(pteval)))) { 515 if (!userfaultfd_armed(vma) && 516 ++none_or_zero <= khugepaged_max_ptes_none) { 517 continue; 518 } else { 519 result = SCAN_EXCEED_NONE_PTE; 520 goto out; 521 } 522 } 523 if (!pte_present(pteval)) { 524 result = SCAN_PTE_NON_PRESENT; 525 goto out; 526 } 527 page = vm_normal_page(vma, address, pteval); 528 if (unlikely(!page)) { 529 result = SCAN_PAGE_NULL; 530 goto out; 531 } 532 533 VM_BUG_ON_PAGE(PageCompound(page), page); 534 VM_BUG_ON_PAGE(!PageAnon(page), page); 535 VM_BUG_ON_PAGE(!PageSwapBacked(page), page); 536 537 /* 538 * We can do it before isolate_lru_page because the 539 * page can't be freed from under us. NOTE: PG_lock 540 * is needed to serialize against split_huge_page 541 * when invoked from the VM. 542 */ 543 if (!trylock_page(page)) { 544 result = SCAN_PAGE_LOCK; 545 goto out; 546 } 547 548 /* 549 * cannot use mapcount: can't collapse if there's a gup pin. 550 * The page must only be referenced by the scanned process 551 * and page swap cache. 552 */ 553 if (page_count(page) != 1 + !!PageSwapCache(page)) { 554 unlock_page(page); 555 result = SCAN_PAGE_COUNT; 556 goto out; 557 } 558 if (pte_write(pteval)) { 559 writable = true; 560 } else { 561 if (PageSwapCache(page) && 562 !reuse_swap_page(page, NULL)) { 563 unlock_page(page); 564 result = SCAN_SWAP_CACHE_PAGE; 565 goto out; 566 } 567 /* 568 * Page is not in the swap cache. It can be collapsed 569 * into a THP. 570 */ 571 } 572 573 /* 574 * Isolate the page to avoid collapsing an hugepage 575 * currently in use by the VM. 576 */ 577 if (isolate_lru_page(page)) { 578 unlock_page(page); 579 result = SCAN_DEL_PAGE_LRU; 580 goto out; 581 } 582 /* 0 stands for page_is_file_cache(page) == false */ 583 inc_node_page_state(page, NR_ISOLATED_ANON + 0); 584 VM_BUG_ON_PAGE(!PageLocked(page), page); 585 VM_BUG_ON_PAGE(PageLRU(page), page); 586 587 /* There should be enough young pte to collapse the page */ 588 if (pte_young(pteval) || 589 page_is_young(page) || PageReferenced(page) || 590 mmu_notifier_test_young(vma->vm_mm, address)) 591 referenced++; 592 } 593 if (likely(writable)) { 594 if (likely(referenced)) { 595 result = SCAN_SUCCEED; 596 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 597 referenced, writable, result); 598 return 1; 599 } 600 } else { 601 result = SCAN_PAGE_RO; 602 } 603 604 out: 605 release_pte_pages(pte, _pte); 606 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 607 referenced, writable, result); 608 return 0; 609 } 610 611 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 612 struct vm_area_struct *vma, 613 unsigned long address, 614 spinlock_t *ptl) 615 { 616 pte_t *_pte; 617 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 618 pte_t pteval = *_pte; 619 struct page *src_page; 620 621 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 622 clear_user_highpage(page, address); 623 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 624 if (is_zero_pfn(pte_pfn(pteval))) { 625 /* 626 * ptl mostly unnecessary. 627 */ 628 spin_lock(ptl); 629 /* 630 * paravirt calls inside pte_clear here are 631 * superfluous. 632 */ 633 pte_clear(vma->vm_mm, address, _pte); 634 spin_unlock(ptl); 635 } 636 } else { 637 src_page = pte_page(pteval); 638 copy_user_highpage(page, src_page, address, vma); 639 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); 640 release_pte_page(src_page); 641 /* 642 * ptl mostly unnecessary, but preempt has to 643 * be disabled to update the per-cpu stats 644 * inside page_remove_rmap(). 645 */ 646 spin_lock(ptl); 647 /* 648 * paravirt calls inside pte_clear here are 649 * superfluous. 650 */ 651 pte_clear(vma->vm_mm, address, _pte); 652 page_remove_rmap(src_page, false); 653 spin_unlock(ptl); 654 free_page_and_swap_cache(src_page); 655 } 656 657 address += PAGE_SIZE; 658 page++; 659 } 660 } 661 662 static void khugepaged_alloc_sleep(void) 663 { 664 DEFINE_WAIT(wait); 665 666 add_wait_queue(&khugepaged_wait, &wait); 667 freezable_schedule_timeout_interruptible( 668 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 669 remove_wait_queue(&khugepaged_wait, &wait); 670 } 671 672 static int khugepaged_node_load[MAX_NUMNODES]; 673 674 static bool khugepaged_scan_abort(int nid) 675 { 676 int i; 677 678 /* 679 * If node_reclaim_mode is disabled, then no extra effort is made to 680 * allocate memory locally. 681 */ 682 if (!node_reclaim_mode) 683 return false; 684 685 /* If there is a count for this node already, it must be acceptable */ 686 if (khugepaged_node_load[nid]) 687 return false; 688 689 for (i = 0; i < MAX_NUMNODES; i++) { 690 if (!khugepaged_node_load[i]) 691 continue; 692 if (node_distance(nid, i) > RECLAIM_DISTANCE) 693 return true; 694 } 695 return false; 696 } 697 698 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ 699 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) 700 { 701 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT; 702 } 703 704 #ifdef CONFIG_NUMA 705 static int khugepaged_find_target_node(void) 706 { 707 static int last_khugepaged_target_node = NUMA_NO_NODE; 708 int nid, target_node = 0, max_value = 0; 709 710 /* find first node with max normal pages hit */ 711 for (nid = 0; nid < MAX_NUMNODES; nid++) 712 if (khugepaged_node_load[nid] > max_value) { 713 max_value = khugepaged_node_load[nid]; 714 target_node = nid; 715 } 716 717 /* do some balance if several nodes have the same hit record */ 718 if (target_node <= last_khugepaged_target_node) 719 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; 720 nid++) 721 if (max_value == khugepaged_node_load[nid]) { 722 target_node = nid; 723 break; 724 } 725 726 last_khugepaged_target_node = target_node; 727 return target_node; 728 } 729 730 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 731 { 732 if (IS_ERR(*hpage)) { 733 if (!*wait) 734 return false; 735 736 *wait = false; 737 *hpage = NULL; 738 khugepaged_alloc_sleep(); 739 } else if (*hpage) { 740 put_page(*hpage); 741 *hpage = NULL; 742 } 743 744 return true; 745 } 746 747 static struct page * 748 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) 749 { 750 VM_BUG_ON_PAGE(*hpage, *hpage); 751 752 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); 753 if (unlikely(!*hpage)) { 754 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 755 *hpage = ERR_PTR(-ENOMEM); 756 return NULL; 757 } 758 759 prep_transhuge_page(*hpage); 760 count_vm_event(THP_COLLAPSE_ALLOC); 761 return *hpage; 762 } 763 #else 764 static int khugepaged_find_target_node(void) 765 { 766 return 0; 767 } 768 769 static inline struct page *alloc_khugepaged_hugepage(void) 770 { 771 struct page *page; 772 773 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), 774 HPAGE_PMD_ORDER); 775 if (page) 776 prep_transhuge_page(page); 777 return page; 778 } 779 780 static struct page *khugepaged_alloc_hugepage(bool *wait) 781 { 782 struct page *hpage; 783 784 do { 785 hpage = alloc_khugepaged_hugepage(); 786 if (!hpage) { 787 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 788 if (!*wait) 789 return NULL; 790 791 *wait = false; 792 khugepaged_alloc_sleep(); 793 } else 794 count_vm_event(THP_COLLAPSE_ALLOC); 795 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 796 797 return hpage; 798 } 799 800 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 801 { 802 if (!*hpage) 803 *hpage = khugepaged_alloc_hugepage(wait); 804 805 if (unlikely(!*hpage)) 806 return false; 807 808 return true; 809 } 810 811 static struct page * 812 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) 813 { 814 VM_BUG_ON(!*hpage); 815 816 return *hpage; 817 } 818 #endif 819 820 static bool hugepage_vma_check(struct vm_area_struct *vma) 821 { 822 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 823 (vma->vm_flags & VM_NOHUGEPAGE)) 824 return false; 825 if (shmem_file(vma->vm_file)) { 826 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) 827 return false; 828 return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, 829 HPAGE_PMD_NR); 830 } 831 if (!vma->anon_vma || vma->vm_ops) 832 return false; 833 if (is_vma_temporary_stack(vma)) 834 return false; 835 return !(vma->vm_flags & VM_NO_KHUGEPAGED); 836 } 837 838 /* 839 * If mmap_sem temporarily dropped, revalidate vma 840 * before taking mmap_sem. 841 * Return 0 if succeeds, otherwise return none-zero 842 * value (scan code). 843 */ 844 845 static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, 846 struct vm_area_struct **vmap) 847 { 848 struct vm_area_struct *vma; 849 unsigned long hstart, hend; 850 851 if (unlikely(khugepaged_test_exit(mm))) 852 return SCAN_ANY_PROCESS; 853 854 *vmap = vma = find_vma(mm, address); 855 if (!vma) 856 return SCAN_VMA_NULL; 857 858 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 859 hend = vma->vm_end & HPAGE_PMD_MASK; 860 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 861 return SCAN_ADDRESS_RANGE; 862 if (!hugepage_vma_check(vma)) 863 return SCAN_VMA_CHECK; 864 return 0; 865 } 866 867 /* 868 * Bring missing pages in from swap, to complete THP collapse. 869 * Only done if khugepaged_scan_pmd believes it is worthwhile. 870 * 871 * Called and returns without pte mapped or spinlocks held, 872 * but with mmap_sem held to protect against vma changes. 873 */ 874 875 static bool __collapse_huge_page_swapin(struct mm_struct *mm, 876 struct vm_area_struct *vma, 877 unsigned long address, pmd_t *pmd, 878 int referenced) 879 { 880 int swapped_in = 0, ret = 0; 881 struct vm_fault vmf = { 882 .vma = vma, 883 .address = address, 884 .flags = FAULT_FLAG_ALLOW_RETRY, 885 .pmd = pmd, 886 .pgoff = linear_page_index(vma, address), 887 }; 888 889 /* we only decide to swapin, if there is enough young ptes */ 890 if (referenced < HPAGE_PMD_NR/2) { 891 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 892 return false; 893 } 894 vmf.pte = pte_offset_map(pmd, address); 895 for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE; 896 vmf.pte++, vmf.address += PAGE_SIZE) { 897 vmf.orig_pte = *vmf.pte; 898 if (!is_swap_pte(vmf.orig_pte)) 899 continue; 900 swapped_in++; 901 ret = do_swap_page(&vmf); 902 903 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */ 904 if (ret & VM_FAULT_RETRY) { 905 down_read(&mm->mmap_sem); 906 if (hugepage_vma_revalidate(mm, address, &vmf.vma)) { 907 /* vma is no longer available, don't continue to swapin */ 908 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 909 return false; 910 } 911 /* check if the pmd is still valid */ 912 if (mm_find_pmd(mm, address) != pmd) 913 return false; 914 } 915 if (ret & VM_FAULT_ERROR) { 916 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 917 return false; 918 } 919 /* pte is unmapped now, we need to map it */ 920 vmf.pte = pte_offset_map(pmd, vmf.address); 921 } 922 vmf.pte--; 923 pte_unmap(vmf.pte); 924 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); 925 return true; 926 } 927 928 static void collapse_huge_page(struct mm_struct *mm, 929 unsigned long address, 930 struct page **hpage, 931 int node, int referenced) 932 { 933 pmd_t *pmd, _pmd; 934 pte_t *pte; 935 pgtable_t pgtable; 936 struct page *new_page; 937 spinlock_t *pmd_ptl, *pte_ptl; 938 int isolated = 0, result = 0; 939 struct mem_cgroup *memcg; 940 struct vm_area_struct *vma; 941 unsigned long mmun_start; /* For mmu_notifiers */ 942 unsigned long mmun_end; /* For mmu_notifiers */ 943 gfp_t gfp; 944 945 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 946 947 /* Only allocate from the target node */ 948 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; 949 950 /* 951 * Before allocating the hugepage, release the mmap_sem read lock. 952 * The allocation can take potentially a long time if it involves 953 * sync compaction, and we do not need to hold the mmap_sem during 954 * that. We will recheck the vma after taking it again in write mode. 955 */ 956 up_read(&mm->mmap_sem); 957 new_page = khugepaged_alloc_page(hpage, gfp, node); 958 if (!new_page) { 959 result = SCAN_ALLOC_HUGE_PAGE_FAIL; 960 goto out_nolock; 961 } 962 963 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { 964 result = SCAN_CGROUP_CHARGE_FAIL; 965 goto out_nolock; 966 } 967 968 down_read(&mm->mmap_sem); 969 result = hugepage_vma_revalidate(mm, address, &vma); 970 if (result) { 971 mem_cgroup_cancel_charge(new_page, memcg, true); 972 up_read(&mm->mmap_sem); 973 goto out_nolock; 974 } 975 976 pmd = mm_find_pmd(mm, address); 977 if (!pmd) { 978 result = SCAN_PMD_NULL; 979 mem_cgroup_cancel_charge(new_page, memcg, true); 980 up_read(&mm->mmap_sem); 981 goto out_nolock; 982 } 983 984 /* 985 * __collapse_huge_page_swapin always returns with mmap_sem locked. 986 * If it fails, we release mmap_sem and jump out_nolock. 987 * Continuing to collapse causes inconsistency. 988 */ 989 if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) { 990 mem_cgroup_cancel_charge(new_page, memcg, true); 991 up_read(&mm->mmap_sem); 992 goto out_nolock; 993 } 994 995 up_read(&mm->mmap_sem); 996 /* 997 * Prevent all access to pagetables with the exception of 998 * gup_fast later handled by the ptep_clear_flush and the VM 999 * handled by the anon_vma lock + PG_lock. 1000 */ 1001 down_write(&mm->mmap_sem); 1002 result = hugepage_vma_revalidate(mm, address, &vma); 1003 if (result) 1004 goto out; 1005 /* check if the pmd is still valid */ 1006 if (mm_find_pmd(mm, address) != pmd) 1007 goto out; 1008 1009 anon_vma_lock_write(vma->anon_vma); 1010 1011 pte = pte_offset_map(pmd, address); 1012 pte_ptl = pte_lockptr(mm, pmd); 1013 1014 mmun_start = address; 1015 mmun_end = address + HPAGE_PMD_SIZE; 1016 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1017 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ 1018 /* 1019 * After this gup_fast can't run anymore. This also removes 1020 * any huge TLB entry from the CPU so we won't allow 1021 * huge and small TLB entries for the same virtual address 1022 * to avoid the risk of CPU bugs in that area. 1023 */ 1024 _pmd = pmdp_collapse_flush(vma, address, pmd); 1025 spin_unlock(pmd_ptl); 1026 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1027 1028 spin_lock(pte_ptl); 1029 isolated = __collapse_huge_page_isolate(vma, address, pte); 1030 spin_unlock(pte_ptl); 1031 1032 if (unlikely(!isolated)) { 1033 pte_unmap(pte); 1034 spin_lock(pmd_ptl); 1035 BUG_ON(!pmd_none(*pmd)); 1036 /* 1037 * We can only use set_pmd_at when establishing 1038 * hugepmds and never for establishing regular pmds that 1039 * points to regular pagetables. Use pmd_populate for that 1040 */ 1041 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 1042 spin_unlock(pmd_ptl); 1043 anon_vma_unlock_write(vma->anon_vma); 1044 result = SCAN_FAIL; 1045 goto out; 1046 } 1047 1048 /* 1049 * All pages are isolated and locked so anon_vma rmap 1050 * can't run anymore. 1051 */ 1052 anon_vma_unlock_write(vma->anon_vma); 1053 1054 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); 1055 pte_unmap(pte); 1056 __SetPageUptodate(new_page); 1057 pgtable = pmd_pgtable(_pmd); 1058 1059 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); 1060 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 1061 1062 /* 1063 * spin_lock() below is not the equivalent of smp_wmb(), so 1064 * this is needed to avoid the copy_huge_page writes to become 1065 * visible after the set_pmd_at() write. 1066 */ 1067 smp_wmb(); 1068 1069 spin_lock(pmd_ptl); 1070 BUG_ON(!pmd_none(*pmd)); 1071 page_add_new_anon_rmap(new_page, vma, address, true); 1072 mem_cgroup_commit_charge(new_page, memcg, false, true); 1073 lru_cache_add_active_or_unevictable(new_page, vma); 1074 pgtable_trans_huge_deposit(mm, pmd, pgtable); 1075 set_pmd_at(mm, address, pmd, _pmd); 1076 update_mmu_cache_pmd(vma, address, pmd); 1077 spin_unlock(pmd_ptl); 1078 1079 *hpage = NULL; 1080 1081 khugepaged_pages_collapsed++; 1082 result = SCAN_SUCCEED; 1083 out_up_write: 1084 up_write(&mm->mmap_sem); 1085 out_nolock: 1086 trace_mm_collapse_huge_page(mm, isolated, result); 1087 return; 1088 out: 1089 mem_cgroup_cancel_charge(new_page, memcg, true); 1090 goto out_up_write; 1091 } 1092 1093 static int khugepaged_scan_pmd(struct mm_struct *mm, 1094 struct vm_area_struct *vma, 1095 unsigned long address, 1096 struct page **hpage) 1097 { 1098 pmd_t *pmd; 1099 pte_t *pte, *_pte; 1100 int ret = 0, none_or_zero = 0, result = 0, referenced = 0; 1101 struct page *page = NULL; 1102 unsigned long _address; 1103 spinlock_t *ptl; 1104 int node = NUMA_NO_NODE, unmapped = 0; 1105 bool writable = false; 1106 1107 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1108 1109 pmd = mm_find_pmd(mm, address); 1110 if (!pmd) { 1111 result = SCAN_PMD_NULL; 1112 goto out; 1113 } 1114 1115 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 1116 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 1117 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 1118 _pte++, _address += PAGE_SIZE) { 1119 pte_t pteval = *_pte; 1120 if (is_swap_pte(pteval)) { 1121 if (++unmapped <= khugepaged_max_ptes_swap) { 1122 continue; 1123 } else { 1124 result = SCAN_EXCEED_SWAP_PTE; 1125 goto out_unmap; 1126 } 1127 } 1128 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 1129 if (!userfaultfd_armed(vma) && 1130 ++none_or_zero <= khugepaged_max_ptes_none) { 1131 continue; 1132 } else { 1133 result = SCAN_EXCEED_NONE_PTE; 1134 goto out_unmap; 1135 } 1136 } 1137 if (!pte_present(pteval)) { 1138 result = SCAN_PTE_NON_PRESENT; 1139 goto out_unmap; 1140 } 1141 if (pte_write(pteval)) 1142 writable = true; 1143 1144 page = vm_normal_page(vma, _address, pteval); 1145 if (unlikely(!page)) { 1146 result = SCAN_PAGE_NULL; 1147 goto out_unmap; 1148 } 1149 1150 /* TODO: teach khugepaged to collapse THP mapped with pte */ 1151 if (PageCompound(page)) { 1152 result = SCAN_PAGE_COMPOUND; 1153 goto out_unmap; 1154 } 1155 1156 /* 1157 * Record which node the original page is from and save this 1158 * information to khugepaged_node_load[]. 1159 * Khupaged will allocate hugepage from the node has the max 1160 * hit record. 1161 */ 1162 node = page_to_nid(page); 1163 if (khugepaged_scan_abort(node)) { 1164 result = SCAN_SCAN_ABORT; 1165 goto out_unmap; 1166 } 1167 khugepaged_node_load[node]++; 1168 if (!PageLRU(page)) { 1169 result = SCAN_PAGE_LRU; 1170 goto out_unmap; 1171 } 1172 if (PageLocked(page)) { 1173 result = SCAN_PAGE_LOCK; 1174 goto out_unmap; 1175 } 1176 if (!PageAnon(page)) { 1177 result = SCAN_PAGE_ANON; 1178 goto out_unmap; 1179 } 1180 1181 /* 1182 * cannot use mapcount: can't collapse if there's a gup pin. 1183 * The page must only be referenced by the scanned process 1184 * and page swap cache. 1185 */ 1186 if (page_count(page) != 1 + !!PageSwapCache(page)) { 1187 result = SCAN_PAGE_COUNT; 1188 goto out_unmap; 1189 } 1190 if (pte_young(pteval) || 1191 page_is_young(page) || PageReferenced(page) || 1192 mmu_notifier_test_young(vma->vm_mm, address)) 1193 referenced++; 1194 } 1195 if (writable) { 1196 if (referenced) { 1197 result = SCAN_SUCCEED; 1198 ret = 1; 1199 } else { 1200 result = SCAN_LACK_REFERENCED_PAGE; 1201 } 1202 } else { 1203 result = SCAN_PAGE_RO; 1204 } 1205 out_unmap: 1206 pte_unmap_unlock(pte, ptl); 1207 if (ret) { 1208 node = khugepaged_find_target_node(); 1209 /* collapse_huge_page will return with the mmap_sem released */ 1210 collapse_huge_page(mm, address, hpage, node, referenced); 1211 } 1212 out: 1213 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, 1214 none_or_zero, result, unmapped); 1215 return ret; 1216 } 1217 1218 static void collect_mm_slot(struct mm_slot *mm_slot) 1219 { 1220 struct mm_struct *mm = mm_slot->mm; 1221 1222 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 1223 1224 if (khugepaged_test_exit(mm)) { 1225 /* free mm_slot */ 1226 hash_del(&mm_slot->hash); 1227 list_del(&mm_slot->mm_node); 1228 1229 /* 1230 * Not strictly needed because the mm exited already. 1231 * 1232 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1233 */ 1234 1235 /* khugepaged_mm_lock actually not necessary for the below */ 1236 free_mm_slot(mm_slot); 1237 mmdrop(mm); 1238 } 1239 } 1240 1241 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) 1242 static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) 1243 { 1244 struct vm_area_struct *vma; 1245 unsigned long addr; 1246 pmd_t *pmd, _pmd; 1247 1248 i_mmap_lock_write(mapping); 1249 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { 1250 /* probably overkill */ 1251 if (vma->anon_vma) 1252 continue; 1253 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); 1254 if (addr & ~HPAGE_PMD_MASK) 1255 continue; 1256 if (vma->vm_end < addr + HPAGE_PMD_SIZE) 1257 continue; 1258 pmd = mm_find_pmd(vma->vm_mm, addr); 1259 if (!pmd) 1260 continue; 1261 /* 1262 * We need exclusive mmap_sem to retract page table. 1263 * If trylock fails we would end up with pte-mapped THP after 1264 * re-fault. Not ideal, but it's more important to not disturb 1265 * the system too much. 1266 */ 1267 if (down_write_trylock(&vma->vm_mm->mmap_sem)) { 1268 spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd); 1269 /* assume page table is clear */ 1270 _pmd = pmdp_collapse_flush(vma, addr, pmd); 1271 spin_unlock(ptl); 1272 up_write(&vma->vm_mm->mmap_sem); 1273 atomic_long_dec(&vma->vm_mm->nr_ptes); 1274 pte_free(vma->vm_mm, pmd_pgtable(_pmd)); 1275 } 1276 } 1277 i_mmap_unlock_write(mapping); 1278 } 1279 1280 /** 1281 * collapse_shmem - collapse small tmpfs/shmem pages into huge one. 1282 * 1283 * Basic scheme is simple, details are more complex: 1284 * - allocate and freeze a new huge page; 1285 * - scan over radix tree replacing old pages the new one 1286 * + swap in pages if necessary; 1287 * + fill in gaps; 1288 * + keep old pages around in case if rollback is required; 1289 * - if replacing succeed: 1290 * + copy data over; 1291 * + free old pages; 1292 * + unfreeze huge page; 1293 * - if replacing failed; 1294 * + put all pages back and unfreeze them; 1295 * + restore gaps in the radix-tree; 1296 * + free huge page; 1297 */ 1298 static void collapse_shmem(struct mm_struct *mm, 1299 struct address_space *mapping, pgoff_t start, 1300 struct page **hpage, int node) 1301 { 1302 gfp_t gfp; 1303 struct page *page, *new_page, *tmp; 1304 struct mem_cgroup *memcg; 1305 pgoff_t index, end = start + HPAGE_PMD_NR; 1306 LIST_HEAD(pagelist); 1307 struct radix_tree_iter iter; 1308 void **slot; 1309 int nr_none = 0, result = SCAN_SUCCEED; 1310 1311 VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); 1312 1313 /* Only allocate from the target node */ 1314 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; 1315 1316 new_page = khugepaged_alloc_page(hpage, gfp, node); 1317 if (!new_page) { 1318 result = SCAN_ALLOC_HUGE_PAGE_FAIL; 1319 goto out; 1320 } 1321 1322 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { 1323 result = SCAN_CGROUP_CHARGE_FAIL; 1324 goto out; 1325 } 1326 1327 new_page->index = start; 1328 new_page->mapping = mapping; 1329 __SetPageSwapBacked(new_page); 1330 __SetPageLocked(new_page); 1331 BUG_ON(!page_ref_freeze(new_page, 1)); 1332 1333 1334 /* 1335 * At this point the new_page is 'frozen' (page_count() is zero), locked 1336 * and not up-to-date. It's safe to insert it into radix tree, because 1337 * nobody would be able to map it or use it in other way until we 1338 * unfreeze it. 1339 */ 1340 1341 index = start; 1342 spin_lock_irq(&mapping->tree_lock); 1343 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { 1344 int n = min(iter.index, end) - index; 1345 1346 /* 1347 * Handle holes in the radix tree: charge it from shmem and 1348 * insert relevant subpage of new_page into the radix-tree. 1349 */ 1350 if (n && !shmem_charge(mapping->host, n)) { 1351 result = SCAN_FAIL; 1352 break; 1353 } 1354 nr_none += n; 1355 for (; index < min(iter.index, end); index++) { 1356 radix_tree_insert(&mapping->page_tree, index, 1357 new_page + (index % HPAGE_PMD_NR)); 1358 } 1359 1360 /* We are done. */ 1361 if (index >= end) 1362 break; 1363 1364 page = radix_tree_deref_slot_protected(slot, 1365 &mapping->tree_lock); 1366 if (radix_tree_exceptional_entry(page) || !PageUptodate(page)) { 1367 spin_unlock_irq(&mapping->tree_lock); 1368 /* swap in or instantiate fallocated page */ 1369 if (shmem_getpage(mapping->host, index, &page, 1370 SGP_NOHUGE)) { 1371 result = SCAN_FAIL; 1372 goto tree_unlocked; 1373 } 1374 spin_lock_irq(&mapping->tree_lock); 1375 } else if (trylock_page(page)) { 1376 get_page(page); 1377 } else { 1378 result = SCAN_PAGE_LOCK; 1379 break; 1380 } 1381 1382 /* 1383 * The page must be locked, so we can drop the tree_lock 1384 * without racing with truncate. 1385 */ 1386 VM_BUG_ON_PAGE(!PageLocked(page), page); 1387 VM_BUG_ON_PAGE(!PageUptodate(page), page); 1388 VM_BUG_ON_PAGE(PageTransCompound(page), page); 1389 1390 if (page_mapping(page) != mapping) { 1391 result = SCAN_TRUNCATED; 1392 goto out_unlock; 1393 } 1394 spin_unlock_irq(&mapping->tree_lock); 1395 1396 if (isolate_lru_page(page)) { 1397 result = SCAN_DEL_PAGE_LRU; 1398 goto out_isolate_failed; 1399 } 1400 1401 if (page_mapped(page)) 1402 unmap_mapping_range(mapping, index << PAGE_SHIFT, 1403 PAGE_SIZE, 0); 1404 1405 spin_lock_irq(&mapping->tree_lock); 1406 1407 slot = radix_tree_lookup_slot(&mapping->page_tree, index); 1408 VM_BUG_ON_PAGE(page != radix_tree_deref_slot_protected(slot, 1409 &mapping->tree_lock), page); 1410 VM_BUG_ON_PAGE(page_mapped(page), page); 1411 1412 /* 1413 * The page is expected to have page_count() == 3: 1414 * - we hold a pin on it; 1415 * - one reference from radix tree; 1416 * - one from isolate_lru_page; 1417 */ 1418 if (!page_ref_freeze(page, 3)) { 1419 result = SCAN_PAGE_COUNT; 1420 goto out_lru; 1421 } 1422 1423 /* 1424 * Add the page to the list to be able to undo the collapse if 1425 * something go wrong. 1426 */ 1427 list_add_tail(&page->lru, &pagelist); 1428 1429 /* Finally, replace with the new page. */ 1430 radix_tree_replace_slot(&mapping->page_tree, slot, 1431 new_page + (index % HPAGE_PMD_NR)); 1432 1433 slot = radix_tree_iter_resume(slot, &iter); 1434 index++; 1435 continue; 1436 out_lru: 1437 spin_unlock_irq(&mapping->tree_lock); 1438 putback_lru_page(page); 1439 out_isolate_failed: 1440 unlock_page(page); 1441 put_page(page); 1442 goto tree_unlocked; 1443 out_unlock: 1444 unlock_page(page); 1445 put_page(page); 1446 break; 1447 } 1448 1449 /* 1450 * Handle hole in radix tree at the end of the range. 1451 * This code only triggers if there's nothing in radix tree 1452 * beyond 'end'. 1453 */ 1454 if (result == SCAN_SUCCEED && index < end) { 1455 int n = end - index; 1456 1457 if (!shmem_charge(mapping->host, n)) { 1458 result = SCAN_FAIL; 1459 goto tree_locked; 1460 } 1461 1462 for (; index < end; index++) { 1463 radix_tree_insert(&mapping->page_tree, index, 1464 new_page + (index % HPAGE_PMD_NR)); 1465 } 1466 nr_none += n; 1467 } 1468 1469 tree_locked: 1470 spin_unlock_irq(&mapping->tree_lock); 1471 tree_unlocked: 1472 1473 if (result == SCAN_SUCCEED) { 1474 unsigned long flags; 1475 struct zone *zone = page_zone(new_page); 1476 1477 /* 1478 * Replacing old pages with new one has succeed, now we need to 1479 * copy the content and free old pages. 1480 */ 1481 list_for_each_entry_safe(page, tmp, &pagelist, lru) { 1482 copy_highpage(new_page + (page->index % HPAGE_PMD_NR), 1483 page); 1484 list_del(&page->lru); 1485 unlock_page(page); 1486 page_ref_unfreeze(page, 1); 1487 page->mapping = NULL; 1488 ClearPageActive(page); 1489 ClearPageUnevictable(page); 1490 put_page(page); 1491 } 1492 1493 local_irq_save(flags); 1494 __inc_node_page_state(new_page, NR_SHMEM_THPS); 1495 if (nr_none) { 1496 __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none); 1497 __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none); 1498 } 1499 local_irq_restore(flags); 1500 1501 /* 1502 * Remove pte page tables, so we can re-faulti 1503 * the page as huge. 1504 */ 1505 retract_page_tables(mapping, start); 1506 1507 /* Everything is ready, let's unfreeze the new_page */ 1508 set_page_dirty(new_page); 1509 SetPageUptodate(new_page); 1510 page_ref_unfreeze(new_page, HPAGE_PMD_NR); 1511 mem_cgroup_commit_charge(new_page, memcg, false, true); 1512 lru_cache_add_anon(new_page); 1513 unlock_page(new_page); 1514 1515 *hpage = NULL; 1516 } else { 1517 /* Something went wrong: rollback changes to the radix-tree */ 1518 shmem_uncharge(mapping->host, nr_none); 1519 spin_lock_irq(&mapping->tree_lock); 1520 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, 1521 start) { 1522 if (iter.index >= end) 1523 break; 1524 page = list_first_entry_or_null(&pagelist, 1525 struct page, lru); 1526 if (!page || iter.index < page->index) { 1527 if (!nr_none) 1528 break; 1529 nr_none--; 1530 /* Put holes back where they were */ 1531 radix_tree_delete(&mapping->page_tree, 1532 iter.index); 1533 continue; 1534 } 1535 1536 VM_BUG_ON_PAGE(page->index != iter.index, page); 1537 1538 /* Unfreeze the page. */ 1539 list_del(&page->lru); 1540 page_ref_unfreeze(page, 2); 1541 radix_tree_replace_slot(&mapping->page_tree, 1542 slot, page); 1543 slot = radix_tree_iter_resume(slot, &iter); 1544 spin_unlock_irq(&mapping->tree_lock); 1545 putback_lru_page(page); 1546 unlock_page(page); 1547 spin_lock_irq(&mapping->tree_lock); 1548 } 1549 VM_BUG_ON(nr_none); 1550 spin_unlock_irq(&mapping->tree_lock); 1551 1552 /* Unfreeze new_page, caller would take care about freeing it */ 1553 page_ref_unfreeze(new_page, 1); 1554 mem_cgroup_cancel_charge(new_page, memcg, true); 1555 unlock_page(new_page); 1556 new_page->mapping = NULL; 1557 } 1558 out: 1559 VM_BUG_ON(!list_empty(&pagelist)); 1560 /* TODO: tracepoints */ 1561 } 1562 1563 static void khugepaged_scan_shmem(struct mm_struct *mm, 1564 struct address_space *mapping, 1565 pgoff_t start, struct page **hpage) 1566 { 1567 struct page *page = NULL; 1568 struct radix_tree_iter iter; 1569 void **slot; 1570 int present, swap; 1571 int node = NUMA_NO_NODE; 1572 int result = SCAN_SUCCEED; 1573 1574 present = 0; 1575 swap = 0; 1576 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 1577 rcu_read_lock(); 1578 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { 1579 if (iter.index >= start + HPAGE_PMD_NR) 1580 break; 1581 1582 page = radix_tree_deref_slot(slot); 1583 if (radix_tree_deref_retry(page)) { 1584 slot = radix_tree_iter_retry(&iter); 1585 continue; 1586 } 1587 1588 if (radix_tree_exception(page)) { 1589 if (++swap > khugepaged_max_ptes_swap) { 1590 result = SCAN_EXCEED_SWAP_PTE; 1591 break; 1592 } 1593 continue; 1594 } 1595 1596 if (PageTransCompound(page)) { 1597 result = SCAN_PAGE_COMPOUND; 1598 break; 1599 } 1600 1601 node = page_to_nid(page); 1602 if (khugepaged_scan_abort(node)) { 1603 result = SCAN_SCAN_ABORT; 1604 break; 1605 } 1606 khugepaged_node_load[node]++; 1607 1608 if (!PageLRU(page)) { 1609 result = SCAN_PAGE_LRU; 1610 break; 1611 } 1612 1613 if (page_count(page) != 1 + page_mapcount(page)) { 1614 result = SCAN_PAGE_COUNT; 1615 break; 1616 } 1617 1618 /* 1619 * We probably should check if the page is referenced here, but 1620 * nobody would transfer pte_young() to PageReferenced() for us. 1621 * And rmap walk here is just too costly... 1622 */ 1623 1624 present++; 1625 1626 if (need_resched()) { 1627 slot = radix_tree_iter_resume(slot, &iter); 1628 cond_resched_rcu(); 1629 } 1630 } 1631 rcu_read_unlock(); 1632 1633 if (result == SCAN_SUCCEED) { 1634 if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) { 1635 result = SCAN_EXCEED_NONE_PTE; 1636 } else { 1637 node = khugepaged_find_target_node(); 1638 collapse_shmem(mm, mapping, start, hpage, node); 1639 } 1640 } 1641 1642 /* TODO: tracepoints */ 1643 } 1644 #else 1645 static void khugepaged_scan_shmem(struct mm_struct *mm, 1646 struct address_space *mapping, 1647 pgoff_t start, struct page **hpage) 1648 { 1649 BUILD_BUG(); 1650 } 1651 #endif 1652 1653 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 1654 struct page **hpage) 1655 __releases(&khugepaged_mm_lock) 1656 __acquires(&khugepaged_mm_lock) 1657 { 1658 struct mm_slot *mm_slot; 1659 struct mm_struct *mm; 1660 struct vm_area_struct *vma; 1661 int progress = 0; 1662 1663 VM_BUG_ON(!pages); 1664 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 1665 1666 if (khugepaged_scan.mm_slot) 1667 mm_slot = khugepaged_scan.mm_slot; 1668 else { 1669 mm_slot = list_entry(khugepaged_scan.mm_head.next, 1670 struct mm_slot, mm_node); 1671 khugepaged_scan.address = 0; 1672 khugepaged_scan.mm_slot = mm_slot; 1673 } 1674 spin_unlock(&khugepaged_mm_lock); 1675 1676 mm = mm_slot->mm; 1677 down_read(&mm->mmap_sem); 1678 if (unlikely(khugepaged_test_exit(mm))) 1679 vma = NULL; 1680 else 1681 vma = find_vma(mm, khugepaged_scan.address); 1682 1683 progress++; 1684 for (; vma; vma = vma->vm_next) { 1685 unsigned long hstart, hend; 1686 1687 cond_resched(); 1688 if (unlikely(khugepaged_test_exit(mm))) { 1689 progress++; 1690 break; 1691 } 1692 if (!hugepage_vma_check(vma)) { 1693 skip: 1694 progress++; 1695 continue; 1696 } 1697 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1698 hend = vma->vm_end & HPAGE_PMD_MASK; 1699 if (hstart >= hend) 1700 goto skip; 1701 if (khugepaged_scan.address > hend) 1702 goto skip; 1703 if (khugepaged_scan.address < hstart) 1704 khugepaged_scan.address = hstart; 1705 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 1706 1707 while (khugepaged_scan.address < hend) { 1708 int ret; 1709 cond_resched(); 1710 if (unlikely(khugepaged_test_exit(mm))) 1711 goto breakouterloop; 1712 1713 VM_BUG_ON(khugepaged_scan.address < hstart || 1714 khugepaged_scan.address + HPAGE_PMD_SIZE > 1715 hend); 1716 if (shmem_file(vma->vm_file)) { 1717 struct file *file; 1718 pgoff_t pgoff = linear_page_index(vma, 1719 khugepaged_scan.address); 1720 if (!shmem_huge_enabled(vma)) 1721 goto skip; 1722 file = get_file(vma->vm_file); 1723 up_read(&mm->mmap_sem); 1724 ret = 1; 1725 khugepaged_scan_shmem(mm, file->f_mapping, 1726 pgoff, hpage); 1727 fput(file); 1728 } else { 1729 ret = khugepaged_scan_pmd(mm, vma, 1730 khugepaged_scan.address, 1731 hpage); 1732 } 1733 /* move to next address */ 1734 khugepaged_scan.address += HPAGE_PMD_SIZE; 1735 progress += HPAGE_PMD_NR; 1736 if (ret) 1737 /* we released mmap_sem so break loop */ 1738 goto breakouterloop_mmap_sem; 1739 if (progress >= pages) 1740 goto breakouterloop; 1741 } 1742 } 1743 breakouterloop: 1744 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 1745 breakouterloop_mmap_sem: 1746 1747 spin_lock(&khugepaged_mm_lock); 1748 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 1749 /* 1750 * Release the current mm_slot if this mm is about to die, or 1751 * if we scanned all vmas of this mm. 1752 */ 1753 if (khugepaged_test_exit(mm) || !vma) { 1754 /* 1755 * Make sure that if mm_users is reaching zero while 1756 * khugepaged runs here, khugepaged_exit will find 1757 * mm_slot not pointing to the exiting mm. 1758 */ 1759 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 1760 khugepaged_scan.mm_slot = list_entry( 1761 mm_slot->mm_node.next, 1762 struct mm_slot, mm_node); 1763 khugepaged_scan.address = 0; 1764 } else { 1765 khugepaged_scan.mm_slot = NULL; 1766 khugepaged_full_scans++; 1767 } 1768 1769 collect_mm_slot(mm_slot); 1770 } 1771 1772 return progress; 1773 } 1774 1775 static int khugepaged_has_work(void) 1776 { 1777 return !list_empty(&khugepaged_scan.mm_head) && 1778 khugepaged_enabled(); 1779 } 1780 1781 static int khugepaged_wait_event(void) 1782 { 1783 return !list_empty(&khugepaged_scan.mm_head) || 1784 kthread_should_stop(); 1785 } 1786 1787 static void khugepaged_do_scan(void) 1788 { 1789 struct page *hpage = NULL; 1790 unsigned int progress = 0, pass_through_head = 0; 1791 unsigned int pages = khugepaged_pages_to_scan; 1792 bool wait = true; 1793 1794 barrier(); /* write khugepaged_pages_to_scan to local stack */ 1795 1796 while (progress < pages) { 1797 if (!khugepaged_prealloc_page(&hpage, &wait)) 1798 break; 1799 1800 cond_resched(); 1801 1802 if (unlikely(kthread_should_stop() || try_to_freeze())) 1803 break; 1804 1805 spin_lock(&khugepaged_mm_lock); 1806 if (!khugepaged_scan.mm_slot) 1807 pass_through_head++; 1808 if (khugepaged_has_work() && 1809 pass_through_head < 2) 1810 progress += khugepaged_scan_mm_slot(pages - progress, 1811 &hpage); 1812 else 1813 progress = pages; 1814 spin_unlock(&khugepaged_mm_lock); 1815 } 1816 1817 if (!IS_ERR_OR_NULL(hpage)) 1818 put_page(hpage); 1819 } 1820 1821 static bool khugepaged_should_wakeup(void) 1822 { 1823 return kthread_should_stop() || 1824 time_after_eq(jiffies, khugepaged_sleep_expire); 1825 } 1826 1827 static void khugepaged_wait_work(void) 1828 { 1829 if (khugepaged_has_work()) { 1830 const unsigned long scan_sleep_jiffies = 1831 msecs_to_jiffies(khugepaged_scan_sleep_millisecs); 1832 1833 if (!scan_sleep_jiffies) 1834 return; 1835 1836 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies; 1837 wait_event_freezable_timeout(khugepaged_wait, 1838 khugepaged_should_wakeup(), 1839 scan_sleep_jiffies); 1840 return; 1841 } 1842 1843 if (khugepaged_enabled()) 1844 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 1845 } 1846 1847 static int khugepaged(void *none) 1848 { 1849 struct mm_slot *mm_slot; 1850 1851 set_freezable(); 1852 set_user_nice(current, MAX_NICE); 1853 1854 while (!kthread_should_stop()) { 1855 khugepaged_do_scan(); 1856 khugepaged_wait_work(); 1857 } 1858 1859 spin_lock(&khugepaged_mm_lock); 1860 mm_slot = khugepaged_scan.mm_slot; 1861 khugepaged_scan.mm_slot = NULL; 1862 if (mm_slot) 1863 collect_mm_slot(mm_slot); 1864 spin_unlock(&khugepaged_mm_lock); 1865 return 0; 1866 } 1867 1868 static void set_recommended_min_free_kbytes(void) 1869 { 1870 struct zone *zone; 1871 int nr_zones = 0; 1872 unsigned long recommended_min; 1873 1874 for_each_populated_zone(zone) 1875 nr_zones++; 1876 1877 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */ 1878 recommended_min = pageblock_nr_pages * nr_zones * 2; 1879 1880 /* 1881 * Make sure that on average at least two pageblocks are almost free 1882 * of another type, one for a migratetype to fall back to and a 1883 * second to avoid subsequent fallbacks of other types There are 3 1884 * MIGRATE_TYPES we care about. 1885 */ 1886 recommended_min += pageblock_nr_pages * nr_zones * 1887 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; 1888 1889 /* don't ever allow to reserve more than 5% of the lowmem */ 1890 recommended_min = min(recommended_min, 1891 (unsigned long) nr_free_buffer_pages() / 20); 1892 recommended_min <<= (PAGE_SHIFT-10); 1893 1894 if (recommended_min > min_free_kbytes) { 1895 if (user_min_free_kbytes >= 0) 1896 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", 1897 min_free_kbytes, recommended_min); 1898 1899 min_free_kbytes = recommended_min; 1900 } 1901 setup_per_zone_wmarks(); 1902 } 1903 1904 int start_stop_khugepaged(void) 1905 { 1906 static struct task_struct *khugepaged_thread __read_mostly; 1907 static DEFINE_MUTEX(khugepaged_mutex); 1908 int err = 0; 1909 1910 mutex_lock(&khugepaged_mutex); 1911 if (khugepaged_enabled()) { 1912 if (!khugepaged_thread) 1913 khugepaged_thread = kthread_run(khugepaged, NULL, 1914 "khugepaged"); 1915 if (IS_ERR(khugepaged_thread)) { 1916 pr_err("khugepaged: kthread_run(khugepaged) failed\n"); 1917 err = PTR_ERR(khugepaged_thread); 1918 khugepaged_thread = NULL; 1919 goto fail; 1920 } 1921 1922 if (!list_empty(&khugepaged_scan.mm_head)) 1923 wake_up_interruptible(&khugepaged_wait); 1924 1925 set_recommended_min_free_kbytes(); 1926 } else if (khugepaged_thread) { 1927 kthread_stop(khugepaged_thread); 1928 khugepaged_thread = NULL; 1929 } 1930 fail: 1931 mutex_unlock(&khugepaged_mutex); 1932 return err; 1933 } 1934