1 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 2 3 #include <linux/mm.h> 4 #include <linux/sched.h> 5 #include <linux/mmu_notifier.h> 6 #include <linux/rmap.h> 7 #include <linux/swap.h> 8 #include <linux/mm_inline.h> 9 #include <linux/kthread.h> 10 #include <linux/khugepaged.h> 11 #include <linux/freezer.h> 12 #include <linux/mman.h> 13 #include <linux/hashtable.h> 14 #include <linux/userfaultfd_k.h> 15 #include <linux/page_idle.h> 16 #include <linux/swapops.h> 17 #include <linux/shmem_fs.h> 18 19 #include <asm/tlb.h> 20 #include <asm/pgalloc.h> 21 #include "internal.h" 22 23 enum scan_result { 24 SCAN_FAIL, 25 SCAN_SUCCEED, 26 SCAN_PMD_NULL, 27 SCAN_EXCEED_NONE_PTE, 28 SCAN_PTE_NON_PRESENT, 29 SCAN_PAGE_RO, 30 SCAN_LACK_REFERENCED_PAGE, 31 SCAN_PAGE_NULL, 32 SCAN_SCAN_ABORT, 33 SCAN_PAGE_COUNT, 34 SCAN_PAGE_LRU, 35 SCAN_PAGE_LOCK, 36 SCAN_PAGE_ANON, 37 SCAN_PAGE_COMPOUND, 38 SCAN_ANY_PROCESS, 39 SCAN_VMA_NULL, 40 SCAN_VMA_CHECK, 41 SCAN_ADDRESS_RANGE, 42 SCAN_SWAP_CACHE_PAGE, 43 SCAN_DEL_PAGE_LRU, 44 SCAN_ALLOC_HUGE_PAGE_FAIL, 45 SCAN_CGROUP_CHARGE_FAIL, 46 SCAN_EXCEED_SWAP_PTE, 47 SCAN_TRUNCATED, 48 }; 49 50 #define CREATE_TRACE_POINTS 51 #include <trace/events/huge_memory.h> 52 53 /* default scan 8*512 pte (or vmas) every 30 second */ 54 static unsigned int khugepaged_pages_to_scan __read_mostly; 55 static unsigned int khugepaged_pages_collapsed; 56 static unsigned int khugepaged_full_scans; 57 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 58 /* during fragmentation poll the hugepage allocator once every minute */ 59 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 60 static unsigned long khugepaged_sleep_expire; 61 static DEFINE_SPINLOCK(khugepaged_mm_lock); 62 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 63 /* 64 * default collapse hugepages if there is at least one pte mapped like 65 * it would have happened if the vma was large enough during page 66 * fault. 67 */ 68 static unsigned int khugepaged_max_ptes_none __read_mostly; 69 static unsigned int khugepaged_max_ptes_swap __read_mostly; 70 71 #define MM_SLOTS_HASH_BITS 10 72 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); 73 74 static struct kmem_cache *mm_slot_cache __read_mostly; 75 76 /** 77 * struct mm_slot - hash lookup from mm to mm_slot 78 * @hash: hash collision list 79 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 80 * @mm: the mm that this information is valid for 81 */ 82 struct mm_slot { 83 struct hlist_node hash; 84 struct list_head mm_node; 85 struct mm_struct *mm; 86 }; 87 88 /** 89 * struct khugepaged_scan - cursor for scanning 90 * @mm_head: the head of the mm list to scan 91 * @mm_slot: the current mm_slot we are scanning 92 * @address: the next address inside that to be scanned 93 * 94 * There is only the one khugepaged_scan instance of this cursor structure. 95 */ 96 struct khugepaged_scan { 97 struct list_head mm_head; 98 struct mm_slot *mm_slot; 99 unsigned long address; 100 }; 101 102 static struct khugepaged_scan khugepaged_scan = { 103 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 104 }; 105 106 #ifdef CONFIG_SYSFS 107 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 108 struct kobj_attribute *attr, 109 char *buf) 110 { 111 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 112 } 113 114 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 115 struct kobj_attribute *attr, 116 const char *buf, size_t count) 117 { 118 unsigned long msecs; 119 int err; 120 121 err = kstrtoul(buf, 10, &msecs); 122 if (err || msecs > UINT_MAX) 123 return -EINVAL; 124 125 khugepaged_scan_sleep_millisecs = msecs; 126 khugepaged_sleep_expire = 0; 127 wake_up_interruptible(&khugepaged_wait); 128 129 return count; 130 } 131 static struct kobj_attribute scan_sleep_millisecs_attr = 132 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 133 scan_sleep_millisecs_store); 134 135 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 136 struct kobj_attribute *attr, 137 char *buf) 138 { 139 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 140 } 141 142 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 143 struct kobj_attribute *attr, 144 const char *buf, size_t count) 145 { 146 unsigned long msecs; 147 int err; 148 149 err = kstrtoul(buf, 10, &msecs); 150 if (err || msecs > UINT_MAX) 151 return -EINVAL; 152 153 khugepaged_alloc_sleep_millisecs = msecs; 154 khugepaged_sleep_expire = 0; 155 wake_up_interruptible(&khugepaged_wait); 156 157 return count; 158 } 159 static struct kobj_attribute alloc_sleep_millisecs_attr = 160 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 161 alloc_sleep_millisecs_store); 162 163 static ssize_t pages_to_scan_show(struct kobject *kobj, 164 struct kobj_attribute *attr, 165 char *buf) 166 { 167 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 168 } 169 static ssize_t pages_to_scan_store(struct kobject *kobj, 170 struct kobj_attribute *attr, 171 const char *buf, size_t count) 172 { 173 int err; 174 unsigned long pages; 175 176 err = kstrtoul(buf, 10, &pages); 177 if (err || !pages || pages > UINT_MAX) 178 return -EINVAL; 179 180 khugepaged_pages_to_scan = pages; 181 182 return count; 183 } 184 static struct kobj_attribute pages_to_scan_attr = 185 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 186 pages_to_scan_store); 187 188 static ssize_t pages_collapsed_show(struct kobject *kobj, 189 struct kobj_attribute *attr, 190 char *buf) 191 { 192 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 193 } 194 static struct kobj_attribute pages_collapsed_attr = 195 __ATTR_RO(pages_collapsed); 196 197 static ssize_t full_scans_show(struct kobject *kobj, 198 struct kobj_attribute *attr, 199 char *buf) 200 { 201 return sprintf(buf, "%u\n", khugepaged_full_scans); 202 } 203 static struct kobj_attribute full_scans_attr = 204 __ATTR_RO(full_scans); 205 206 static ssize_t khugepaged_defrag_show(struct kobject *kobj, 207 struct kobj_attribute *attr, char *buf) 208 { 209 return single_hugepage_flag_show(kobj, attr, buf, 210 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 211 } 212 static ssize_t khugepaged_defrag_store(struct kobject *kobj, 213 struct kobj_attribute *attr, 214 const char *buf, size_t count) 215 { 216 return single_hugepage_flag_store(kobj, attr, buf, count, 217 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 218 } 219 static struct kobj_attribute khugepaged_defrag_attr = 220 __ATTR(defrag, 0644, khugepaged_defrag_show, 221 khugepaged_defrag_store); 222 223 /* 224 * max_ptes_none controls if khugepaged should collapse hugepages over 225 * any unmapped ptes in turn potentially increasing the memory 226 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 227 * reduce the available free memory in the system as it 228 * runs. Increasing max_ptes_none will instead potentially reduce the 229 * free memory in the system during the khugepaged scan. 230 */ 231 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 232 struct kobj_attribute *attr, 233 char *buf) 234 { 235 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 236 } 237 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 238 struct kobj_attribute *attr, 239 const char *buf, size_t count) 240 { 241 int err; 242 unsigned long max_ptes_none; 243 244 err = kstrtoul(buf, 10, &max_ptes_none); 245 if (err || max_ptes_none > HPAGE_PMD_NR-1) 246 return -EINVAL; 247 248 khugepaged_max_ptes_none = max_ptes_none; 249 250 return count; 251 } 252 static struct kobj_attribute khugepaged_max_ptes_none_attr = 253 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 254 khugepaged_max_ptes_none_store); 255 256 static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj, 257 struct kobj_attribute *attr, 258 char *buf) 259 { 260 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap); 261 } 262 263 static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj, 264 struct kobj_attribute *attr, 265 const char *buf, size_t count) 266 { 267 int err; 268 unsigned long max_ptes_swap; 269 270 err = kstrtoul(buf, 10, &max_ptes_swap); 271 if (err || max_ptes_swap > HPAGE_PMD_NR-1) 272 return -EINVAL; 273 274 khugepaged_max_ptes_swap = max_ptes_swap; 275 276 return count; 277 } 278 279 static struct kobj_attribute khugepaged_max_ptes_swap_attr = 280 __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show, 281 khugepaged_max_ptes_swap_store); 282 283 static struct attribute *khugepaged_attr[] = { 284 &khugepaged_defrag_attr.attr, 285 &khugepaged_max_ptes_none_attr.attr, 286 &pages_to_scan_attr.attr, 287 &pages_collapsed_attr.attr, 288 &full_scans_attr.attr, 289 &scan_sleep_millisecs_attr.attr, 290 &alloc_sleep_millisecs_attr.attr, 291 &khugepaged_max_ptes_swap_attr.attr, 292 NULL, 293 }; 294 295 struct attribute_group khugepaged_attr_group = { 296 .attrs = khugepaged_attr, 297 .name = "khugepaged", 298 }; 299 #endif /* CONFIG_SYSFS */ 300 301 #define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB) 302 303 int hugepage_madvise(struct vm_area_struct *vma, 304 unsigned long *vm_flags, int advice) 305 { 306 switch (advice) { 307 case MADV_HUGEPAGE: 308 #ifdef CONFIG_S390 309 /* 310 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 311 * can't handle this properly after s390_enable_sie, so we simply 312 * ignore the madvise to prevent qemu from causing a SIGSEGV. 313 */ 314 if (mm_has_pgste(vma->vm_mm)) 315 return 0; 316 #endif 317 *vm_flags &= ~VM_NOHUGEPAGE; 318 *vm_flags |= VM_HUGEPAGE; 319 /* 320 * If the vma become good for khugepaged to scan, 321 * register it here without waiting a page fault that 322 * may not happen any time soon. 323 */ 324 if (!(*vm_flags & VM_NO_KHUGEPAGED) && 325 khugepaged_enter_vma_merge(vma, *vm_flags)) 326 return -ENOMEM; 327 break; 328 case MADV_NOHUGEPAGE: 329 *vm_flags &= ~VM_HUGEPAGE; 330 *vm_flags |= VM_NOHUGEPAGE; 331 /* 332 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 333 * this vma even if we leave the mm registered in khugepaged if 334 * it got registered before VM_NOHUGEPAGE was set. 335 */ 336 break; 337 } 338 339 return 0; 340 } 341 342 int __init khugepaged_init(void) 343 { 344 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 345 sizeof(struct mm_slot), 346 __alignof__(struct mm_slot), 0, NULL); 347 if (!mm_slot_cache) 348 return -ENOMEM; 349 350 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; 351 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; 352 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8; 353 354 return 0; 355 } 356 357 void __init khugepaged_destroy(void) 358 { 359 kmem_cache_destroy(mm_slot_cache); 360 } 361 362 static inline struct mm_slot *alloc_mm_slot(void) 363 { 364 if (!mm_slot_cache) /* initialization failed */ 365 return NULL; 366 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 367 } 368 369 static inline void free_mm_slot(struct mm_slot *mm_slot) 370 { 371 kmem_cache_free(mm_slot_cache, mm_slot); 372 } 373 374 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 375 { 376 struct mm_slot *mm_slot; 377 378 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) 379 if (mm == mm_slot->mm) 380 return mm_slot; 381 382 return NULL; 383 } 384 385 static void insert_to_mm_slots_hash(struct mm_struct *mm, 386 struct mm_slot *mm_slot) 387 { 388 mm_slot->mm = mm; 389 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); 390 } 391 392 static inline int khugepaged_test_exit(struct mm_struct *mm) 393 { 394 return atomic_read(&mm->mm_users) == 0; 395 } 396 397 int __khugepaged_enter(struct mm_struct *mm) 398 { 399 struct mm_slot *mm_slot; 400 int wakeup; 401 402 mm_slot = alloc_mm_slot(); 403 if (!mm_slot) 404 return -ENOMEM; 405 406 /* __khugepaged_exit() must not run from under us */ 407 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); 408 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 409 free_mm_slot(mm_slot); 410 return 0; 411 } 412 413 spin_lock(&khugepaged_mm_lock); 414 insert_to_mm_slots_hash(mm, mm_slot); 415 /* 416 * Insert just behind the scanning cursor, to let the area settle 417 * down a little. 418 */ 419 wakeup = list_empty(&khugepaged_scan.mm_head); 420 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 421 spin_unlock(&khugepaged_mm_lock); 422 423 atomic_inc(&mm->mm_count); 424 if (wakeup) 425 wake_up_interruptible(&khugepaged_wait); 426 427 return 0; 428 } 429 430 int khugepaged_enter_vma_merge(struct vm_area_struct *vma, 431 unsigned long vm_flags) 432 { 433 unsigned long hstart, hend; 434 if (!vma->anon_vma) 435 /* 436 * Not yet faulted in so we will register later in the 437 * page fault if needed. 438 */ 439 return 0; 440 if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED)) 441 /* khugepaged not yet working on file or special mappings */ 442 return 0; 443 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 444 hend = vma->vm_end & HPAGE_PMD_MASK; 445 if (hstart < hend) 446 return khugepaged_enter(vma, vm_flags); 447 return 0; 448 } 449 450 void __khugepaged_exit(struct mm_struct *mm) 451 { 452 struct mm_slot *mm_slot; 453 int free = 0; 454 455 spin_lock(&khugepaged_mm_lock); 456 mm_slot = get_mm_slot(mm); 457 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 458 hash_del(&mm_slot->hash); 459 list_del(&mm_slot->mm_node); 460 free = 1; 461 } 462 spin_unlock(&khugepaged_mm_lock); 463 464 if (free) { 465 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 466 free_mm_slot(mm_slot); 467 mmdrop(mm); 468 } else if (mm_slot) { 469 /* 470 * This is required to serialize against 471 * khugepaged_test_exit() (which is guaranteed to run 472 * under mmap sem read mode). Stop here (after we 473 * return all pagetables will be destroyed) until 474 * khugepaged has finished working on the pagetables 475 * under the mmap_sem. 476 */ 477 down_write(&mm->mmap_sem); 478 up_write(&mm->mmap_sem); 479 } 480 } 481 482 static void release_pte_page(struct page *page) 483 { 484 /* 0 stands for page_is_file_cache(page) == false */ 485 dec_node_page_state(page, NR_ISOLATED_ANON + 0); 486 unlock_page(page); 487 putback_lru_page(page); 488 } 489 490 static void release_pte_pages(pte_t *pte, pte_t *_pte) 491 { 492 while (--_pte >= pte) { 493 pte_t pteval = *_pte; 494 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) 495 release_pte_page(pte_page(pteval)); 496 } 497 } 498 499 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 500 unsigned long address, 501 pte_t *pte) 502 { 503 struct page *page = NULL; 504 pte_t *_pte; 505 int none_or_zero = 0, result = 0, referenced = 0; 506 bool writable = false; 507 508 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 509 _pte++, address += PAGE_SIZE) { 510 pte_t pteval = *_pte; 511 if (pte_none(pteval) || (pte_present(pteval) && 512 is_zero_pfn(pte_pfn(pteval)))) { 513 if (!userfaultfd_armed(vma) && 514 ++none_or_zero <= khugepaged_max_ptes_none) { 515 continue; 516 } else { 517 result = SCAN_EXCEED_NONE_PTE; 518 goto out; 519 } 520 } 521 if (!pte_present(pteval)) { 522 result = SCAN_PTE_NON_PRESENT; 523 goto out; 524 } 525 page = vm_normal_page(vma, address, pteval); 526 if (unlikely(!page)) { 527 result = SCAN_PAGE_NULL; 528 goto out; 529 } 530 531 VM_BUG_ON_PAGE(PageCompound(page), page); 532 VM_BUG_ON_PAGE(!PageAnon(page), page); 533 VM_BUG_ON_PAGE(!PageSwapBacked(page), page); 534 535 /* 536 * We can do it before isolate_lru_page because the 537 * page can't be freed from under us. NOTE: PG_lock 538 * is needed to serialize against split_huge_page 539 * when invoked from the VM. 540 */ 541 if (!trylock_page(page)) { 542 result = SCAN_PAGE_LOCK; 543 goto out; 544 } 545 546 /* 547 * cannot use mapcount: can't collapse if there's a gup pin. 548 * The page must only be referenced by the scanned process 549 * and page swap cache. 550 */ 551 if (page_count(page) != 1 + !!PageSwapCache(page)) { 552 unlock_page(page); 553 result = SCAN_PAGE_COUNT; 554 goto out; 555 } 556 if (pte_write(pteval)) { 557 writable = true; 558 } else { 559 if (PageSwapCache(page) && 560 !reuse_swap_page(page, NULL)) { 561 unlock_page(page); 562 result = SCAN_SWAP_CACHE_PAGE; 563 goto out; 564 } 565 /* 566 * Page is not in the swap cache. It can be collapsed 567 * into a THP. 568 */ 569 } 570 571 /* 572 * Isolate the page to avoid collapsing an hugepage 573 * currently in use by the VM. 574 */ 575 if (isolate_lru_page(page)) { 576 unlock_page(page); 577 result = SCAN_DEL_PAGE_LRU; 578 goto out; 579 } 580 /* 0 stands for page_is_file_cache(page) == false */ 581 inc_node_page_state(page, NR_ISOLATED_ANON + 0); 582 VM_BUG_ON_PAGE(!PageLocked(page), page); 583 VM_BUG_ON_PAGE(PageLRU(page), page); 584 585 /* There should be enough young pte to collapse the page */ 586 if (pte_young(pteval) || 587 page_is_young(page) || PageReferenced(page) || 588 mmu_notifier_test_young(vma->vm_mm, address)) 589 referenced++; 590 } 591 if (likely(writable)) { 592 if (likely(referenced)) { 593 result = SCAN_SUCCEED; 594 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 595 referenced, writable, result); 596 return 1; 597 } 598 } else { 599 result = SCAN_PAGE_RO; 600 } 601 602 out: 603 release_pte_pages(pte, _pte); 604 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 605 referenced, writable, result); 606 return 0; 607 } 608 609 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 610 struct vm_area_struct *vma, 611 unsigned long address, 612 spinlock_t *ptl) 613 { 614 pte_t *_pte; 615 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 616 pte_t pteval = *_pte; 617 struct page *src_page; 618 619 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 620 clear_user_highpage(page, address); 621 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 622 if (is_zero_pfn(pte_pfn(pteval))) { 623 /* 624 * ptl mostly unnecessary. 625 */ 626 spin_lock(ptl); 627 /* 628 * paravirt calls inside pte_clear here are 629 * superfluous. 630 */ 631 pte_clear(vma->vm_mm, address, _pte); 632 spin_unlock(ptl); 633 } 634 } else { 635 src_page = pte_page(pteval); 636 copy_user_highpage(page, src_page, address, vma); 637 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); 638 release_pte_page(src_page); 639 /* 640 * ptl mostly unnecessary, but preempt has to 641 * be disabled to update the per-cpu stats 642 * inside page_remove_rmap(). 643 */ 644 spin_lock(ptl); 645 /* 646 * paravirt calls inside pte_clear here are 647 * superfluous. 648 */ 649 pte_clear(vma->vm_mm, address, _pte); 650 page_remove_rmap(src_page, false); 651 spin_unlock(ptl); 652 free_page_and_swap_cache(src_page); 653 } 654 655 address += PAGE_SIZE; 656 page++; 657 } 658 } 659 660 static void khugepaged_alloc_sleep(void) 661 { 662 DEFINE_WAIT(wait); 663 664 add_wait_queue(&khugepaged_wait, &wait); 665 freezable_schedule_timeout_interruptible( 666 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 667 remove_wait_queue(&khugepaged_wait, &wait); 668 } 669 670 static int khugepaged_node_load[MAX_NUMNODES]; 671 672 static bool khugepaged_scan_abort(int nid) 673 { 674 int i; 675 676 /* 677 * If node_reclaim_mode is disabled, then no extra effort is made to 678 * allocate memory locally. 679 */ 680 if (!node_reclaim_mode) 681 return false; 682 683 /* If there is a count for this node already, it must be acceptable */ 684 if (khugepaged_node_load[nid]) 685 return false; 686 687 for (i = 0; i < MAX_NUMNODES; i++) { 688 if (!khugepaged_node_load[i]) 689 continue; 690 if (node_distance(nid, i) > RECLAIM_DISTANCE) 691 return true; 692 } 693 return false; 694 } 695 696 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ 697 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) 698 { 699 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT; 700 } 701 702 #ifdef CONFIG_NUMA 703 static int khugepaged_find_target_node(void) 704 { 705 static int last_khugepaged_target_node = NUMA_NO_NODE; 706 int nid, target_node = 0, max_value = 0; 707 708 /* find first node with max normal pages hit */ 709 for (nid = 0; nid < MAX_NUMNODES; nid++) 710 if (khugepaged_node_load[nid] > max_value) { 711 max_value = khugepaged_node_load[nid]; 712 target_node = nid; 713 } 714 715 /* do some balance if several nodes have the same hit record */ 716 if (target_node <= last_khugepaged_target_node) 717 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; 718 nid++) 719 if (max_value == khugepaged_node_load[nid]) { 720 target_node = nid; 721 break; 722 } 723 724 last_khugepaged_target_node = target_node; 725 return target_node; 726 } 727 728 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 729 { 730 if (IS_ERR(*hpage)) { 731 if (!*wait) 732 return false; 733 734 *wait = false; 735 *hpage = NULL; 736 khugepaged_alloc_sleep(); 737 } else if (*hpage) { 738 put_page(*hpage); 739 *hpage = NULL; 740 } 741 742 return true; 743 } 744 745 static struct page * 746 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) 747 { 748 VM_BUG_ON_PAGE(*hpage, *hpage); 749 750 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); 751 if (unlikely(!*hpage)) { 752 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 753 *hpage = ERR_PTR(-ENOMEM); 754 return NULL; 755 } 756 757 prep_transhuge_page(*hpage); 758 count_vm_event(THP_COLLAPSE_ALLOC); 759 return *hpage; 760 } 761 #else 762 static int khugepaged_find_target_node(void) 763 { 764 return 0; 765 } 766 767 static inline struct page *alloc_khugepaged_hugepage(void) 768 { 769 struct page *page; 770 771 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), 772 HPAGE_PMD_ORDER); 773 if (page) 774 prep_transhuge_page(page); 775 return page; 776 } 777 778 static struct page *khugepaged_alloc_hugepage(bool *wait) 779 { 780 struct page *hpage; 781 782 do { 783 hpage = alloc_khugepaged_hugepage(); 784 if (!hpage) { 785 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 786 if (!*wait) 787 return NULL; 788 789 *wait = false; 790 khugepaged_alloc_sleep(); 791 } else 792 count_vm_event(THP_COLLAPSE_ALLOC); 793 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 794 795 return hpage; 796 } 797 798 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 799 { 800 if (!*hpage) 801 *hpage = khugepaged_alloc_hugepage(wait); 802 803 if (unlikely(!*hpage)) 804 return false; 805 806 return true; 807 } 808 809 static struct page * 810 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) 811 { 812 VM_BUG_ON(!*hpage); 813 814 return *hpage; 815 } 816 #endif 817 818 static bool hugepage_vma_check(struct vm_area_struct *vma) 819 { 820 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 821 (vma->vm_flags & VM_NOHUGEPAGE)) 822 return false; 823 if (shmem_file(vma->vm_file)) { 824 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) 825 return false; 826 return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, 827 HPAGE_PMD_NR); 828 } 829 if (!vma->anon_vma || vma->vm_ops) 830 return false; 831 if (is_vma_temporary_stack(vma)) 832 return false; 833 return !(vma->vm_flags & VM_NO_KHUGEPAGED); 834 } 835 836 /* 837 * If mmap_sem temporarily dropped, revalidate vma 838 * before taking mmap_sem. 839 * Return 0 if succeeds, otherwise return none-zero 840 * value (scan code). 841 */ 842 843 static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, 844 struct vm_area_struct **vmap) 845 { 846 struct vm_area_struct *vma; 847 unsigned long hstart, hend; 848 849 if (unlikely(khugepaged_test_exit(mm))) 850 return SCAN_ANY_PROCESS; 851 852 *vmap = vma = find_vma(mm, address); 853 if (!vma) 854 return SCAN_VMA_NULL; 855 856 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 857 hend = vma->vm_end & HPAGE_PMD_MASK; 858 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 859 return SCAN_ADDRESS_RANGE; 860 if (!hugepage_vma_check(vma)) 861 return SCAN_VMA_CHECK; 862 return 0; 863 } 864 865 /* 866 * Bring missing pages in from swap, to complete THP collapse. 867 * Only done if khugepaged_scan_pmd believes it is worthwhile. 868 * 869 * Called and returns without pte mapped or spinlocks held, 870 * but with mmap_sem held to protect against vma changes. 871 */ 872 873 static bool __collapse_huge_page_swapin(struct mm_struct *mm, 874 struct vm_area_struct *vma, 875 unsigned long address, pmd_t *pmd, 876 int referenced) 877 { 878 int swapped_in = 0, ret = 0; 879 struct vm_fault vmf = { 880 .vma = vma, 881 .address = address, 882 .flags = FAULT_FLAG_ALLOW_RETRY, 883 .pmd = pmd, 884 .pgoff = linear_page_index(vma, address), 885 }; 886 887 /* we only decide to swapin, if there is enough young ptes */ 888 if (referenced < HPAGE_PMD_NR/2) { 889 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 890 return false; 891 } 892 vmf.pte = pte_offset_map(pmd, address); 893 for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE; 894 vmf.pte++, vmf.address += PAGE_SIZE) { 895 vmf.orig_pte = *vmf.pte; 896 if (!is_swap_pte(vmf.orig_pte)) 897 continue; 898 swapped_in++; 899 ret = do_swap_page(&vmf); 900 901 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */ 902 if (ret & VM_FAULT_RETRY) { 903 down_read(&mm->mmap_sem); 904 if (hugepage_vma_revalidate(mm, address, &vmf.vma)) { 905 /* vma is no longer available, don't continue to swapin */ 906 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 907 return false; 908 } 909 /* check if the pmd is still valid */ 910 if (mm_find_pmd(mm, address) != pmd) 911 return false; 912 } 913 if (ret & VM_FAULT_ERROR) { 914 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 915 return false; 916 } 917 /* pte is unmapped now, we need to map it */ 918 vmf.pte = pte_offset_map(pmd, vmf.address); 919 } 920 vmf.pte--; 921 pte_unmap(vmf.pte); 922 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); 923 return true; 924 } 925 926 static void collapse_huge_page(struct mm_struct *mm, 927 unsigned long address, 928 struct page **hpage, 929 int node, int referenced) 930 { 931 pmd_t *pmd, _pmd; 932 pte_t *pte; 933 pgtable_t pgtable; 934 struct page *new_page; 935 spinlock_t *pmd_ptl, *pte_ptl; 936 int isolated = 0, result = 0; 937 struct mem_cgroup *memcg; 938 struct vm_area_struct *vma; 939 unsigned long mmun_start; /* For mmu_notifiers */ 940 unsigned long mmun_end; /* For mmu_notifiers */ 941 gfp_t gfp; 942 943 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 944 945 /* Only allocate from the target node */ 946 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE; 947 948 /* 949 * Before allocating the hugepage, release the mmap_sem read lock. 950 * The allocation can take potentially a long time if it involves 951 * sync compaction, and we do not need to hold the mmap_sem during 952 * that. We will recheck the vma after taking it again in write mode. 953 */ 954 up_read(&mm->mmap_sem); 955 new_page = khugepaged_alloc_page(hpage, gfp, node); 956 if (!new_page) { 957 result = SCAN_ALLOC_HUGE_PAGE_FAIL; 958 goto out_nolock; 959 } 960 961 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { 962 result = SCAN_CGROUP_CHARGE_FAIL; 963 goto out_nolock; 964 } 965 966 down_read(&mm->mmap_sem); 967 result = hugepage_vma_revalidate(mm, address, &vma); 968 if (result) { 969 mem_cgroup_cancel_charge(new_page, memcg, true); 970 up_read(&mm->mmap_sem); 971 goto out_nolock; 972 } 973 974 pmd = mm_find_pmd(mm, address); 975 if (!pmd) { 976 result = SCAN_PMD_NULL; 977 mem_cgroup_cancel_charge(new_page, memcg, true); 978 up_read(&mm->mmap_sem); 979 goto out_nolock; 980 } 981 982 /* 983 * __collapse_huge_page_swapin always returns with mmap_sem locked. 984 * If it fails, we release mmap_sem and jump out_nolock. 985 * Continuing to collapse causes inconsistency. 986 */ 987 if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) { 988 mem_cgroup_cancel_charge(new_page, memcg, true); 989 up_read(&mm->mmap_sem); 990 goto out_nolock; 991 } 992 993 up_read(&mm->mmap_sem); 994 /* 995 * Prevent all access to pagetables with the exception of 996 * gup_fast later handled by the ptep_clear_flush and the VM 997 * handled by the anon_vma lock + PG_lock. 998 */ 999 down_write(&mm->mmap_sem); 1000 result = hugepage_vma_revalidate(mm, address, &vma); 1001 if (result) 1002 goto out; 1003 /* check if the pmd is still valid */ 1004 if (mm_find_pmd(mm, address) != pmd) 1005 goto out; 1006 1007 anon_vma_lock_write(vma->anon_vma); 1008 1009 pte = pte_offset_map(pmd, address); 1010 pte_ptl = pte_lockptr(mm, pmd); 1011 1012 mmun_start = address; 1013 mmun_end = address + HPAGE_PMD_SIZE; 1014 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1015 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ 1016 /* 1017 * After this gup_fast can't run anymore. This also removes 1018 * any huge TLB entry from the CPU so we won't allow 1019 * huge and small TLB entries for the same virtual address 1020 * to avoid the risk of CPU bugs in that area. 1021 */ 1022 _pmd = pmdp_collapse_flush(vma, address, pmd); 1023 spin_unlock(pmd_ptl); 1024 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1025 1026 spin_lock(pte_ptl); 1027 isolated = __collapse_huge_page_isolate(vma, address, pte); 1028 spin_unlock(pte_ptl); 1029 1030 if (unlikely(!isolated)) { 1031 pte_unmap(pte); 1032 spin_lock(pmd_ptl); 1033 BUG_ON(!pmd_none(*pmd)); 1034 /* 1035 * We can only use set_pmd_at when establishing 1036 * hugepmds and never for establishing regular pmds that 1037 * points to regular pagetables. Use pmd_populate for that 1038 */ 1039 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 1040 spin_unlock(pmd_ptl); 1041 anon_vma_unlock_write(vma->anon_vma); 1042 result = SCAN_FAIL; 1043 goto out; 1044 } 1045 1046 /* 1047 * All pages are isolated and locked so anon_vma rmap 1048 * can't run anymore. 1049 */ 1050 anon_vma_unlock_write(vma->anon_vma); 1051 1052 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); 1053 pte_unmap(pte); 1054 __SetPageUptodate(new_page); 1055 pgtable = pmd_pgtable(_pmd); 1056 1057 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); 1058 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 1059 1060 /* 1061 * spin_lock() below is not the equivalent of smp_wmb(), so 1062 * this is needed to avoid the copy_huge_page writes to become 1063 * visible after the set_pmd_at() write. 1064 */ 1065 smp_wmb(); 1066 1067 spin_lock(pmd_ptl); 1068 BUG_ON(!pmd_none(*pmd)); 1069 page_add_new_anon_rmap(new_page, vma, address, true); 1070 mem_cgroup_commit_charge(new_page, memcg, false, true); 1071 lru_cache_add_active_or_unevictable(new_page, vma); 1072 pgtable_trans_huge_deposit(mm, pmd, pgtable); 1073 set_pmd_at(mm, address, pmd, _pmd); 1074 update_mmu_cache_pmd(vma, address, pmd); 1075 spin_unlock(pmd_ptl); 1076 1077 *hpage = NULL; 1078 1079 khugepaged_pages_collapsed++; 1080 result = SCAN_SUCCEED; 1081 out_up_write: 1082 up_write(&mm->mmap_sem); 1083 out_nolock: 1084 trace_mm_collapse_huge_page(mm, isolated, result); 1085 return; 1086 out: 1087 mem_cgroup_cancel_charge(new_page, memcg, true); 1088 goto out_up_write; 1089 } 1090 1091 static int khugepaged_scan_pmd(struct mm_struct *mm, 1092 struct vm_area_struct *vma, 1093 unsigned long address, 1094 struct page **hpage) 1095 { 1096 pmd_t *pmd; 1097 pte_t *pte, *_pte; 1098 int ret = 0, none_or_zero = 0, result = 0, referenced = 0; 1099 struct page *page = NULL; 1100 unsigned long _address; 1101 spinlock_t *ptl; 1102 int node = NUMA_NO_NODE, unmapped = 0; 1103 bool writable = false; 1104 1105 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1106 1107 pmd = mm_find_pmd(mm, address); 1108 if (!pmd) { 1109 result = SCAN_PMD_NULL; 1110 goto out; 1111 } 1112 1113 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 1114 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 1115 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 1116 _pte++, _address += PAGE_SIZE) { 1117 pte_t pteval = *_pte; 1118 if (is_swap_pte(pteval)) { 1119 if (++unmapped <= khugepaged_max_ptes_swap) { 1120 continue; 1121 } else { 1122 result = SCAN_EXCEED_SWAP_PTE; 1123 goto out_unmap; 1124 } 1125 } 1126 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 1127 if (!userfaultfd_armed(vma) && 1128 ++none_or_zero <= khugepaged_max_ptes_none) { 1129 continue; 1130 } else { 1131 result = SCAN_EXCEED_NONE_PTE; 1132 goto out_unmap; 1133 } 1134 } 1135 if (!pte_present(pteval)) { 1136 result = SCAN_PTE_NON_PRESENT; 1137 goto out_unmap; 1138 } 1139 if (pte_write(pteval)) 1140 writable = true; 1141 1142 page = vm_normal_page(vma, _address, pteval); 1143 if (unlikely(!page)) { 1144 result = SCAN_PAGE_NULL; 1145 goto out_unmap; 1146 } 1147 1148 /* TODO: teach khugepaged to collapse THP mapped with pte */ 1149 if (PageCompound(page)) { 1150 result = SCAN_PAGE_COMPOUND; 1151 goto out_unmap; 1152 } 1153 1154 /* 1155 * Record which node the original page is from and save this 1156 * information to khugepaged_node_load[]. 1157 * Khupaged will allocate hugepage from the node has the max 1158 * hit record. 1159 */ 1160 node = page_to_nid(page); 1161 if (khugepaged_scan_abort(node)) { 1162 result = SCAN_SCAN_ABORT; 1163 goto out_unmap; 1164 } 1165 khugepaged_node_load[node]++; 1166 if (!PageLRU(page)) { 1167 result = SCAN_PAGE_LRU; 1168 goto out_unmap; 1169 } 1170 if (PageLocked(page)) { 1171 result = SCAN_PAGE_LOCK; 1172 goto out_unmap; 1173 } 1174 if (!PageAnon(page)) { 1175 result = SCAN_PAGE_ANON; 1176 goto out_unmap; 1177 } 1178 1179 /* 1180 * cannot use mapcount: can't collapse if there's a gup pin. 1181 * The page must only be referenced by the scanned process 1182 * and page swap cache. 1183 */ 1184 if (page_count(page) != 1 + !!PageSwapCache(page)) { 1185 result = SCAN_PAGE_COUNT; 1186 goto out_unmap; 1187 } 1188 if (pte_young(pteval) || 1189 page_is_young(page) || PageReferenced(page) || 1190 mmu_notifier_test_young(vma->vm_mm, address)) 1191 referenced++; 1192 } 1193 if (writable) { 1194 if (referenced) { 1195 result = SCAN_SUCCEED; 1196 ret = 1; 1197 } else { 1198 result = SCAN_LACK_REFERENCED_PAGE; 1199 } 1200 } else { 1201 result = SCAN_PAGE_RO; 1202 } 1203 out_unmap: 1204 pte_unmap_unlock(pte, ptl); 1205 if (ret) { 1206 node = khugepaged_find_target_node(); 1207 /* collapse_huge_page will return with the mmap_sem released */ 1208 collapse_huge_page(mm, address, hpage, node, referenced); 1209 } 1210 out: 1211 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, 1212 none_or_zero, result, unmapped); 1213 return ret; 1214 } 1215 1216 static void collect_mm_slot(struct mm_slot *mm_slot) 1217 { 1218 struct mm_struct *mm = mm_slot->mm; 1219 1220 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 1221 1222 if (khugepaged_test_exit(mm)) { 1223 /* free mm_slot */ 1224 hash_del(&mm_slot->hash); 1225 list_del(&mm_slot->mm_node); 1226 1227 /* 1228 * Not strictly needed because the mm exited already. 1229 * 1230 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1231 */ 1232 1233 /* khugepaged_mm_lock actually not necessary for the below */ 1234 free_mm_slot(mm_slot); 1235 mmdrop(mm); 1236 } 1237 } 1238 1239 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) 1240 static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) 1241 { 1242 struct vm_area_struct *vma; 1243 unsigned long addr; 1244 pmd_t *pmd, _pmd; 1245 bool deposited = false; 1246 1247 i_mmap_lock_write(mapping); 1248 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { 1249 /* probably overkill */ 1250 if (vma->anon_vma) 1251 continue; 1252 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); 1253 if (addr & ~HPAGE_PMD_MASK) 1254 continue; 1255 if (vma->vm_end < addr + HPAGE_PMD_SIZE) 1256 continue; 1257 pmd = mm_find_pmd(vma->vm_mm, addr); 1258 if (!pmd) 1259 continue; 1260 /* 1261 * We need exclusive mmap_sem to retract page table. 1262 * If trylock fails we would end up with pte-mapped THP after 1263 * re-fault. Not ideal, but it's more important to not disturb 1264 * the system too much. 1265 */ 1266 if (down_write_trylock(&vma->vm_mm->mmap_sem)) { 1267 spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd); 1268 /* assume page table is clear */ 1269 _pmd = pmdp_collapse_flush(vma, addr, pmd); 1270 /* 1271 * now deposit the pgtable for arch that need it 1272 * otherwise free it. 1273 */ 1274 if (arch_needs_pgtable_deposit()) { 1275 /* 1276 * The deposit should be visibile only after 1277 * collapse is seen by others. 1278 */ 1279 smp_wmb(); 1280 pgtable_trans_huge_deposit(vma->vm_mm, pmd, 1281 pmd_pgtable(_pmd)); 1282 deposited = true; 1283 } 1284 spin_unlock(ptl); 1285 up_write(&vma->vm_mm->mmap_sem); 1286 if (!deposited) { 1287 atomic_long_dec(&vma->vm_mm->nr_ptes); 1288 pte_free(vma->vm_mm, pmd_pgtable(_pmd)); 1289 } 1290 } 1291 } 1292 i_mmap_unlock_write(mapping); 1293 } 1294 1295 /** 1296 * collapse_shmem - collapse small tmpfs/shmem pages into huge one. 1297 * 1298 * Basic scheme is simple, details are more complex: 1299 * - allocate and freeze a new huge page; 1300 * - scan over radix tree replacing old pages the new one 1301 * + swap in pages if necessary; 1302 * + fill in gaps; 1303 * + keep old pages around in case if rollback is required; 1304 * - if replacing succeed: 1305 * + copy data over; 1306 * + free old pages; 1307 * + unfreeze huge page; 1308 * - if replacing failed; 1309 * + put all pages back and unfreeze them; 1310 * + restore gaps in the radix-tree; 1311 * + free huge page; 1312 */ 1313 static void collapse_shmem(struct mm_struct *mm, 1314 struct address_space *mapping, pgoff_t start, 1315 struct page **hpage, int node) 1316 { 1317 gfp_t gfp; 1318 struct page *page, *new_page, *tmp; 1319 struct mem_cgroup *memcg; 1320 pgoff_t index, end = start + HPAGE_PMD_NR; 1321 LIST_HEAD(pagelist); 1322 struct radix_tree_iter iter; 1323 void **slot; 1324 int nr_none = 0, result = SCAN_SUCCEED; 1325 1326 VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); 1327 1328 /* Only allocate from the target node */ 1329 gfp = alloc_hugepage_khugepaged_gfpmask() | 1330 __GFP_OTHER_NODE | __GFP_THISNODE; 1331 1332 new_page = khugepaged_alloc_page(hpage, gfp, node); 1333 if (!new_page) { 1334 result = SCAN_ALLOC_HUGE_PAGE_FAIL; 1335 goto out; 1336 } 1337 1338 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { 1339 result = SCAN_CGROUP_CHARGE_FAIL; 1340 goto out; 1341 } 1342 1343 new_page->index = start; 1344 new_page->mapping = mapping; 1345 __SetPageSwapBacked(new_page); 1346 __SetPageLocked(new_page); 1347 BUG_ON(!page_ref_freeze(new_page, 1)); 1348 1349 1350 /* 1351 * At this point the new_page is 'frozen' (page_count() is zero), locked 1352 * and not up-to-date. It's safe to insert it into radix tree, because 1353 * nobody would be able to map it or use it in other way until we 1354 * unfreeze it. 1355 */ 1356 1357 index = start; 1358 spin_lock_irq(&mapping->tree_lock); 1359 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { 1360 int n = min(iter.index, end) - index; 1361 1362 /* 1363 * Handle holes in the radix tree: charge it from shmem and 1364 * insert relevant subpage of new_page into the radix-tree. 1365 */ 1366 if (n && !shmem_charge(mapping->host, n)) { 1367 result = SCAN_FAIL; 1368 break; 1369 } 1370 nr_none += n; 1371 for (; index < min(iter.index, end); index++) { 1372 radix_tree_insert(&mapping->page_tree, index, 1373 new_page + (index % HPAGE_PMD_NR)); 1374 } 1375 1376 /* We are done. */ 1377 if (index >= end) 1378 break; 1379 1380 page = radix_tree_deref_slot_protected(slot, 1381 &mapping->tree_lock); 1382 if (radix_tree_exceptional_entry(page) || !PageUptodate(page)) { 1383 spin_unlock_irq(&mapping->tree_lock); 1384 /* swap in or instantiate fallocated page */ 1385 if (shmem_getpage(mapping->host, index, &page, 1386 SGP_NOHUGE)) { 1387 result = SCAN_FAIL; 1388 goto tree_unlocked; 1389 } 1390 spin_lock_irq(&mapping->tree_lock); 1391 } else if (trylock_page(page)) { 1392 get_page(page); 1393 } else { 1394 result = SCAN_PAGE_LOCK; 1395 break; 1396 } 1397 1398 /* 1399 * The page must be locked, so we can drop the tree_lock 1400 * without racing with truncate. 1401 */ 1402 VM_BUG_ON_PAGE(!PageLocked(page), page); 1403 VM_BUG_ON_PAGE(!PageUptodate(page), page); 1404 VM_BUG_ON_PAGE(PageTransCompound(page), page); 1405 1406 if (page_mapping(page) != mapping) { 1407 result = SCAN_TRUNCATED; 1408 goto out_unlock; 1409 } 1410 spin_unlock_irq(&mapping->tree_lock); 1411 1412 if (isolate_lru_page(page)) { 1413 result = SCAN_DEL_PAGE_LRU; 1414 goto out_isolate_failed; 1415 } 1416 1417 if (page_mapped(page)) 1418 unmap_mapping_range(mapping, index << PAGE_SHIFT, 1419 PAGE_SIZE, 0); 1420 1421 spin_lock_irq(&mapping->tree_lock); 1422 1423 slot = radix_tree_lookup_slot(&mapping->page_tree, index); 1424 VM_BUG_ON_PAGE(page != radix_tree_deref_slot_protected(slot, 1425 &mapping->tree_lock), page); 1426 VM_BUG_ON_PAGE(page_mapped(page), page); 1427 1428 /* 1429 * The page is expected to have page_count() == 3: 1430 * - we hold a pin on it; 1431 * - one reference from radix tree; 1432 * - one from isolate_lru_page; 1433 */ 1434 if (!page_ref_freeze(page, 3)) { 1435 result = SCAN_PAGE_COUNT; 1436 goto out_lru; 1437 } 1438 1439 /* 1440 * Add the page to the list to be able to undo the collapse if 1441 * something go wrong. 1442 */ 1443 list_add_tail(&page->lru, &pagelist); 1444 1445 /* Finally, replace with the new page. */ 1446 radix_tree_replace_slot(&mapping->page_tree, slot, 1447 new_page + (index % HPAGE_PMD_NR)); 1448 1449 slot = radix_tree_iter_resume(slot, &iter); 1450 index++; 1451 continue; 1452 out_lru: 1453 spin_unlock_irq(&mapping->tree_lock); 1454 putback_lru_page(page); 1455 out_isolate_failed: 1456 unlock_page(page); 1457 put_page(page); 1458 goto tree_unlocked; 1459 out_unlock: 1460 unlock_page(page); 1461 put_page(page); 1462 break; 1463 } 1464 1465 /* 1466 * Handle hole in radix tree at the end of the range. 1467 * This code only triggers if there's nothing in radix tree 1468 * beyond 'end'. 1469 */ 1470 if (result == SCAN_SUCCEED && index < end) { 1471 int n = end - index; 1472 1473 if (!shmem_charge(mapping->host, n)) { 1474 result = SCAN_FAIL; 1475 goto tree_locked; 1476 } 1477 1478 for (; index < end; index++) { 1479 radix_tree_insert(&mapping->page_tree, index, 1480 new_page + (index % HPAGE_PMD_NR)); 1481 } 1482 nr_none += n; 1483 } 1484 1485 tree_locked: 1486 spin_unlock_irq(&mapping->tree_lock); 1487 tree_unlocked: 1488 1489 if (result == SCAN_SUCCEED) { 1490 unsigned long flags; 1491 struct zone *zone = page_zone(new_page); 1492 1493 /* 1494 * Replacing old pages with new one has succeed, now we need to 1495 * copy the content and free old pages. 1496 */ 1497 list_for_each_entry_safe(page, tmp, &pagelist, lru) { 1498 copy_highpage(new_page + (page->index % HPAGE_PMD_NR), 1499 page); 1500 list_del(&page->lru); 1501 unlock_page(page); 1502 page_ref_unfreeze(page, 1); 1503 page->mapping = NULL; 1504 ClearPageActive(page); 1505 ClearPageUnevictable(page); 1506 put_page(page); 1507 } 1508 1509 local_irq_save(flags); 1510 __inc_node_page_state(new_page, NR_SHMEM_THPS); 1511 if (nr_none) { 1512 __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none); 1513 __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none); 1514 } 1515 local_irq_restore(flags); 1516 1517 /* 1518 * Remove pte page tables, so we can re-faulti 1519 * the page as huge. 1520 */ 1521 retract_page_tables(mapping, start); 1522 1523 /* Everything is ready, let's unfreeze the new_page */ 1524 set_page_dirty(new_page); 1525 SetPageUptodate(new_page); 1526 page_ref_unfreeze(new_page, HPAGE_PMD_NR); 1527 mem_cgroup_commit_charge(new_page, memcg, false, true); 1528 lru_cache_add_anon(new_page); 1529 unlock_page(new_page); 1530 1531 *hpage = NULL; 1532 } else { 1533 /* Something went wrong: rollback changes to the radix-tree */ 1534 shmem_uncharge(mapping->host, nr_none); 1535 spin_lock_irq(&mapping->tree_lock); 1536 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, 1537 start) { 1538 if (iter.index >= end) 1539 break; 1540 page = list_first_entry_or_null(&pagelist, 1541 struct page, lru); 1542 if (!page || iter.index < page->index) { 1543 if (!nr_none) 1544 break; 1545 nr_none--; 1546 /* Put holes back where they were */ 1547 radix_tree_delete(&mapping->page_tree, 1548 iter.index); 1549 continue; 1550 } 1551 1552 VM_BUG_ON_PAGE(page->index != iter.index, page); 1553 1554 /* Unfreeze the page. */ 1555 list_del(&page->lru); 1556 page_ref_unfreeze(page, 2); 1557 radix_tree_replace_slot(&mapping->page_tree, 1558 slot, page); 1559 slot = radix_tree_iter_resume(slot, &iter); 1560 spin_unlock_irq(&mapping->tree_lock); 1561 putback_lru_page(page); 1562 unlock_page(page); 1563 spin_lock_irq(&mapping->tree_lock); 1564 } 1565 VM_BUG_ON(nr_none); 1566 spin_unlock_irq(&mapping->tree_lock); 1567 1568 /* Unfreeze new_page, caller would take care about freeing it */ 1569 page_ref_unfreeze(new_page, 1); 1570 mem_cgroup_cancel_charge(new_page, memcg, true); 1571 unlock_page(new_page); 1572 new_page->mapping = NULL; 1573 } 1574 out: 1575 VM_BUG_ON(!list_empty(&pagelist)); 1576 /* TODO: tracepoints */ 1577 } 1578 1579 static void khugepaged_scan_shmem(struct mm_struct *mm, 1580 struct address_space *mapping, 1581 pgoff_t start, struct page **hpage) 1582 { 1583 struct page *page = NULL; 1584 struct radix_tree_iter iter; 1585 void **slot; 1586 int present, swap; 1587 int node = NUMA_NO_NODE; 1588 int result = SCAN_SUCCEED; 1589 1590 present = 0; 1591 swap = 0; 1592 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 1593 rcu_read_lock(); 1594 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { 1595 if (iter.index >= start + HPAGE_PMD_NR) 1596 break; 1597 1598 page = radix_tree_deref_slot(slot); 1599 if (radix_tree_deref_retry(page)) { 1600 slot = radix_tree_iter_retry(&iter); 1601 continue; 1602 } 1603 1604 if (radix_tree_exception(page)) { 1605 if (++swap > khugepaged_max_ptes_swap) { 1606 result = SCAN_EXCEED_SWAP_PTE; 1607 break; 1608 } 1609 continue; 1610 } 1611 1612 if (PageTransCompound(page)) { 1613 result = SCAN_PAGE_COMPOUND; 1614 break; 1615 } 1616 1617 node = page_to_nid(page); 1618 if (khugepaged_scan_abort(node)) { 1619 result = SCAN_SCAN_ABORT; 1620 break; 1621 } 1622 khugepaged_node_load[node]++; 1623 1624 if (!PageLRU(page)) { 1625 result = SCAN_PAGE_LRU; 1626 break; 1627 } 1628 1629 if (page_count(page) != 1 + page_mapcount(page)) { 1630 result = SCAN_PAGE_COUNT; 1631 break; 1632 } 1633 1634 /* 1635 * We probably should check if the page is referenced here, but 1636 * nobody would transfer pte_young() to PageReferenced() for us. 1637 * And rmap walk here is just too costly... 1638 */ 1639 1640 present++; 1641 1642 if (need_resched()) { 1643 slot = radix_tree_iter_resume(slot, &iter); 1644 cond_resched_rcu(); 1645 } 1646 } 1647 rcu_read_unlock(); 1648 1649 if (result == SCAN_SUCCEED) { 1650 if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) { 1651 result = SCAN_EXCEED_NONE_PTE; 1652 } else { 1653 node = khugepaged_find_target_node(); 1654 collapse_shmem(mm, mapping, start, hpage, node); 1655 } 1656 } 1657 1658 /* TODO: tracepoints */ 1659 } 1660 #else 1661 static void khugepaged_scan_shmem(struct mm_struct *mm, 1662 struct address_space *mapping, 1663 pgoff_t start, struct page **hpage) 1664 { 1665 BUILD_BUG(); 1666 } 1667 #endif 1668 1669 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 1670 struct page **hpage) 1671 __releases(&khugepaged_mm_lock) 1672 __acquires(&khugepaged_mm_lock) 1673 { 1674 struct mm_slot *mm_slot; 1675 struct mm_struct *mm; 1676 struct vm_area_struct *vma; 1677 int progress = 0; 1678 1679 VM_BUG_ON(!pages); 1680 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 1681 1682 if (khugepaged_scan.mm_slot) 1683 mm_slot = khugepaged_scan.mm_slot; 1684 else { 1685 mm_slot = list_entry(khugepaged_scan.mm_head.next, 1686 struct mm_slot, mm_node); 1687 khugepaged_scan.address = 0; 1688 khugepaged_scan.mm_slot = mm_slot; 1689 } 1690 spin_unlock(&khugepaged_mm_lock); 1691 1692 mm = mm_slot->mm; 1693 down_read(&mm->mmap_sem); 1694 if (unlikely(khugepaged_test_exit(mm))) 1695 vma = NULL; 1696 else 1697 vma = find_vma(mm, khugepaged_scan.address); 1698 1699 progress++; 1700 for (; vma; vma = vma->vm_next) { 1701 unsigned long hstart, hend; 1702 1703 cond_resched(); 1704 if (unlikely(khugepaged_test_exit(mm))) { 1705 progress++; 1706 break; 1707 } 1708 if (!hugepage_vma_check(vma)) { 1709 skip: 1710 progress++; 1711 continue; 1712 } 1713 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1714 hend = vma->vm_end & HPAGE_PMD_MASK; 1715 if (hstart >= hend) 1716 goto skip; 1717 if (khugepaged_scan.address > hend) 1718 goto skip; 1719 if (khugepaged_scan.address < hstart) 1720 khugepaged_scan.address = hstart; 1721 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 1722 1723 while (khugepaged_scan.address < hend) { 1724 int ret; 1725 cond_resched(); 1726 if (unlikely(khugepaged_test_exit(mm))) 1727 goto breakouterloop; 1728 1729 VM_BUG_ON(khugepaged_scan.address < hstart || 1730 khugepaged_scan.address + HPAGE_PMD_SIZE > 1731 hend); 1732 if (shmem_file(vma->vm_file)) { 1733 struct file *file; 1734 pgoff_t pgoff = linear_page_index(vma, 1735 khugepaged_scan.address); 1736 if (!shmem_huge_enabled(vma)) 1737 goto skip; 1738 file = get_file(vma->vm_file); 1739 up_read(&mm->mmap_sem); 1740 ret = 1; 1741 khugepaged_scan_shmem(mm, file->f_mapping, 1742 pgoff, hpage); 1743 fput(file); 1744 } else { 1745 ret = khugepaged_scan_pmd(mm, vma, 1746 khugepaged_scan.address, 1747 hpage); 1748 } 1749 /* move to next address */ 1750 khugepaged_scan.address += HPAGE_PMD_SIZE; 1751 progress += HPAGE_PMD_NR; 1752 if (ret) 1753 /* we released mmap_sem so break loop */ 1754 goto breakouterloop_mmap_sem; 1755 if (progress >= pages) 1756 goto breakouterloop; 1757 } 1758 } 1759 breakouterloop: 1760 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 1761 breakouterloop_mmap_sem: 1762 1763 spin_lock(&khugepaged_mm_lock); 1764 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 1765 /* 1766 * Release the current mm_slot if this mm is about to die, or 1767 * if we scanned all vmas of this mm. 1768 */ 1769 if (khugepaged_test_exit(mm) || !vma) { 1770 /* 1771 * Make sure that if mm_users is reaching zero while 1772 * khugepaged runs here, khugepaged_exit will find 1773 * mm_slot not pointing to the exiting mm. 1774 */ 1775 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 1776 khugepaged_scan.mm_slot = list_entry( 1777 mm_slot->mm_node.next, 1778 struct mm_slot, mm_node); 1779 khugepaged_scan.address = 0; 1780 } else { 1781 khugepaged_scan.mm_slot = NULL; 1782 khugepaged_full_scans++; 1783 } 1784 1785 collect_mm_slot(mm_slot); 1786 } 1787 1788 return progress; 1789 } 1790 1791 static int khugepaged_has_work(void) 1792 { 1793 return !list_empty(&khugepaged_scan.mm_head) && 1794 khugepaged_enabled(); 1795 } 1796 1797 static int khugepaged_wait_event(void) 1798 { 1799 return !list_empty(&khugepaged_scan.mm_head) || 1800 kthread_should_stop(); 1801 } 1802 1803 static void khugepaged_do_scan(void) 1804 { 1805 struct page *hpage = NULL; 1806 unsigned int progress = 0, pass_through_head = 0; 1807 unsigned int pages = khugepaged_pages_to_scan; 1808 bool wait = true; 1809 1810 barrier(); /* write khugepaged_pages_to_scan to local stack */ 1811 1812 while (progress < pages) { 1813 if (!khugepaged_prealloc_page(&hpage, &wait)) 1814 break; 1815 1816 cond_resched(); 1817 1818 if (unlikely(kthread_should_stop() || try_to_freeze())) 1819 break; 1820 1821 spin_lock(&khugepaged_mm_lock); 1822 if (!khugepaged_scan.mm_slot) 1823 pass_through_head++; 1824 if (khugepaged_has_work() && 1825 pass_through_head < 2) 1826 progress += khugepaged_scan_mm_slot(pages - progress, 1827 &hpage); 1828 else 1829 progress = pages; 1830 spin_unlock(&khugepaged_mm_lock); 1831 } 1832 1833 if (!IS_ERR_OR_NULL(hpage)) 1834 put_page(hpage); 1835 } 1836 1837 static bool khugepaged_should_wakeup(void) 1838 { 1839 return kthread_should_stop() || 1840 time_after_eq(jiffies, khugepaged_sleep_expire); 1841 } 1842 1843 static void khugepaged_wait_work(void) 1844 { 1845 if (khugepaged_has_work()) { 1846 const unsigned long scan_sleep_jiffies = 1847 msecs_to_jiffies(khugepaged_scan_sleep_millisecs); 1848 1849 if (!scan_sleep_jiffies) 1850 return; 1851 1852 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies; 1853 wait_event_freezable_timeout(khugepaged_wait, 1854 khugepaged_should_wakeup(), 1855 scan_sleep_jiffies); 1856 return; 1857 } 1858 1859 if (khugepaged_enabled()) 1860 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 1861 } 1862 1863 static int khugepaged(void *none) 1864 { 1865 struct mm_slot *mm_slot; 1866 1867 set_freezable(); 1868 set_user_nice(current, MAX_NICE); 1869 1870 while (!kthread_should_stop()) { 1871 khugepaged_do_scan(); 1872 khugepaged_wait_work(); 1873 } 1874 1875 spin_lock(&khugepaged_mm_lock); 1876 mm_slot = khugepaged_scan.mm_slot; 1877 khugepaged_scan.mm_slot = NULL; 1878 if (mm_slot) 1879 collect_mm_slot(mm_slot); 1880 spin_unlock(&khugepaged_mm_lock); 1881 return 0; 1882 } 1883 1884 static void set_recommended_min_free_kbytes(void) 1885 { 1886 struct zone *zone; 1887 int nr_zones = 0; 1888 unsigned long recommended_min; 1889 1890 for_each_populated_zone(zone) 1891 nr_zones++; 1892 1893 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */ 1894 recommended_min = pageblock_nr_pages * nr_zones * 2; 1895 1896 /* 1897 * Make sure that on average at least two pageblocks are almost free 1898 * of another type, one for a migratetype to fall back to and a 1899 * second to avoid subsequent fallbacks of other types There are 3 1900 * MIGRATE_TYPES we care about. 1901 */ 1902 recommended_min += pageblock_nr_pages * nr_zones * 1903 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; 1904 1905 /* don't ever allow to reserve more than 5% of the lowmem */ 1906 recommended_min = min(recommended_min, 1907 (unsigned long) nr_free_buffer_pages() / 20); 1908 recommended_min <<= (PAGE_SHIFT-10); 1909 1910 if (recommended_min > min_free_kbytes) { 1911 if (user_min_free_kbytes >= 0) 1912 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", 1913 min_free_kbytes, recommended_min); 1914 1915 min_free_kbytes = recommended_min; 1916 } 1917 setup_per_zone_wmarks(); 1918 } 1919 1920 int start_stop_khugepaged(void) 1921 { 1922 static struct task_struct *khugepaged_thread __read_mostly; 1923 static DEFINE_MUTEX(khugepaged_mutex); 1924 int err = 0; 1925 1926 mutex_lock(&khugepaged_mutex); 1927 if (khugepaged_enabled()) { 1928 if (!khugepaged_thread) 1929 khugepaged_thread = kthread_run(khugepaged, NULL, 1930 "khugepaged"); 1931 if (IS_ERR(khugepaged_thread)) { 1932 pr_err("khugepaged: kthread_run(khugepaged) failed\n"); 1933 err = PTR_ERR(khugepaged_thread); 1934 khugepaged_thread = NULL; 1935 goto fail; 1936 } 1937 1938 if (!list_empty(&khugepaged_scan.mm_head)) 1939 wake_up_interruptible(&khugepaged_wait); 1940 1941 set_recommended_min_free_kbytes(); 1942 } else if (khugepaged_thread) { 1943 kthread_stop(khugepaged_thread); 1944 khugepaged_thread = NULL; 1945 } 1946 fail: 1947 mutex_unlock(&khugepaged_mutex); 1948 return err; 1949 } 1950