1 // SPDX-License-Identifier: GPL-2.0 2 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 3 4 #include <linux/mm.h> 5 #include <linux/sched.h> 6 #include <linux/sched/mm.h> 7 #include <linux/sched/coredump.h> 8 #include <linux/mmu_notifier.h> 9 #include <linux/rmap.h> 10 #include <linux/swap.h> 11 #include <linux/mm_inline.h> 12 #include <linux/kthread.h> 13 #include <linux/khugepaged.h> 14 #include <linux/freezer.h> 15 #include <linux/mman.h> 16 #include <linux/hashtable.h> 17 #include <linux/userfaultfd_k.h> 18 #include <linux/page_idle.h> 19 #include <linux/swapops.h> 20 #include <linux/shmem_fs.h> 21 22 #include <asm/tlb.h> 23 #include <asm/pgalloc.h> 24 #include "internal.h" 25 26 enum scan_result { 27 SCAN_FAIL, 28 SCAN_SUCCEED, 29 SCAN_PMD_NULL, 30 SCAN_EXCEED_NONE_PTE, 31 SCAN_PTE_NON_PRESENT, 32 SCAN_PAGE_RO, 33 SCAN_LACK_REFERENCED_PAGE, 34 SCAN_PAGE_NULL, 35 SCAN_SCAN_ABORT, 36 SCAN_PAGE_COUNT, 37 SCAN_PAGE_LRU, 38 SCAN_PAGE_LOCK, 39 SCAN_PAGE_ANON, 40 SCAN_PAGE_COMPOUND, 41 SCAN_ANY_PROCESS, 42 SCAN_VMA_NULL, 43 SCAN_VMA_CHECK, 44 SCAN_ADDRESS_RANGE, 45 SCAN_SWAP_CACHE_PAGE, 46 SCAN_DEL_PAGE_LRU, 47 SCAN_ALLOC_HUGE_PAGE_FAIL, 48 SCAN_CGROUP_CHARGE_FAIL, 49 SCAN_EXCEED_SWAP_PTE, 50 SCAN_TRUNCATED, 51 }; 52 53 #define CREATE_TRACE_POINTS 54 #include <trace/events/huge_memory.h> 55 56 /* default scan 8*512 pte (or vmas) every 30 second */ 57 static unsigned int khugepaged_pages_to_scan __read_mostly; 58 static unsigned int khugepaged_pages_collapsed; 59 static unsigned int khugepaged_full_scans; 60 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 61 /* during fragmentation poll the hugepage allocator once every minute */ 62 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 63 static unsigned long khugepaged_sleep_expire; 64 static DEFINE_SPINLOCK(khugepaged_mm_lock); 65 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 66 /* 67 * default collapse hugepages if there is at least one pte mapped like 68 * it would have happened if the vma was large enough during page 69 * fault. 70 */ 71 static unsigned int khugepaged_max_ptes_none __read_mostly; 72 static unsigned int khugepaged_max_ptes_swap __read_mostly; 73 74 #define MM_SLOTS_HASH_BITS 10 75 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); 76 77 static struct kmem_cache *mm_slot_cache __read_mostly; 78 79 /** 80 * struct mm_slot - hash lookup from mm to mm_slot 81 * @hash: hash collision list 82 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 83 * @mm: the mm that this information is valid for 84 */ 85 struct mm_slot { 86 struct hlist_node hash; 87 struct list_head mm_node; 88 struct mm_struct *mm; 89 }; 90 91 /** 92 * struct khugepaged_scan - cursor for scanning 93 * @mm_head: the head of the mm list to scan 94 * @mm_slot: the current mm_slot we are scanning 95 * @address: the next address inside that to be scanned 96 * 97 * There is only the one khugepaged_scan instance of this cursor structure. 98 */ 99 struct khugepaged_scan { 100 struct list_head mm_head; 101 struct mm_slot *mm_slot; 102 unsigned long address; 103 }; 104 105 static struct khugepaged_scan khugepaged_scan = { 106 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 107 }; 108 109 #ifdef CONFIG_SYSFS 110 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 111 struct kobj_attribute *attr, 112 char *buf) 113 { 114 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 115 } 116 117 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 118 struct kobj_attribute *attr, 119 const char *buf, size_t count) 120 { 121 unsigned long msecs; 122 int err; 123 124 err = kstrtoul(buf, 10, &msecs); 125 if (err || msecs > UINT_MAX) 126 return -EINVAL; 127 128 khugepaged_scan_sleep_millisecs = msecs; 129 khugepaged_sleep_expire = 0; 130 wake_up_interruptible(&khugepaged_wait); 131 132 return count; 133 } 134 static struct kobj_attribute scan_sleep_millisecs_attr = 135 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 136 scan_sleep_millisecs_store); 137 138 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 139 struct kobj_attribute *attr, 140 char *buf) 141 { 142 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 143 } 144 145 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 146 struct kobj_attribute *attr, 147 const char *buf, size_t count) 148 { 149 unsigned long msecs; 150 int err; 151 152 err = kstrtoul(buf, 10, &msecs); 153 if (err || msecs > UINT_MAX) 154 return -EINVAL; 155 156 khugepaged_alloc_sleep_millisecs = msecs; 157 khugepaged_sleep_expire = 0; 158 wake_up_interruptible(&khugepaged_wait); 159 160 return count; 161 } 162 static struct kobj_attribute alloc_sleep_millisecs_attr = 163 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 164 alloc_sleep_millisecs_store); 165 166 static ssize_t pages_to_scan_show(struct kobject *kobj, 167 struct kobj_attribute *attr, 168 char *buf) 169 { 170 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 171 } 172 static ssize_t pages_to_scan_store(struct kobject *kobj, 173 struct kobj_attribute *attr, 174 const char *buf, size_t count) 175 { 176 int err; 177 unsigned long pages; 178 179 err = kstrtoul(buf, 10, &pages); 180 if (err || !pages || pages > UINT_MAX) 181 return -EINVAL; 182 183 khugepaged_pages_to_scan = pages; 184 185 return count; 186 } 187 static struct kobj_attribute pages_to_scan_attr = 188 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 189 pages_to_scan_store); 190 191 static ssize_t pages_collapsed_show(struct kobject *kobj, 192 struct kobj_attribute *attr, 193 char *buf) 194 { 195 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 196 } 197 static struct kobj_attribute pages_collapsed_attr = 198 __ATTR_RO(pages_collapsed); 199 200 static ssize_t full_scans_show(struct kobject *kobj, 201 struct kobj_attribute *attr, 202 char *buf) 203 { 204 return sprintf(buf, "%u\n", khugepaged_full_scans); 205 } 206 static struct kobj_attribute full_scans_attr = 207 __ATTR_RO(full_scans); 208 209 static ssize_t khugepaged_defrag_show(struct kobject *kobj, 210 struct kobj_attribute *attr, char *buf) 211 { 212 return single_hugepage_flag_show(kobj, attr, buf, 213 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 214 } 215 static ssize_t khugepaged_defrag_store(struct kobject *kobj, 216 struct kobj_attribute *attr, 217 const char *buf, size_t count) 218 { 219 return single_hugepage_flag_store(kobj, attr, buf, count, 220 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 221 } 222 static struct kobj_attribute khugepaged_defrag_attr = 223 __ATTR(defrag, 0644, khugepaged_defrag_show, 224 khugepaged_defrag_store); 225 226 /* 227 * max_ptes_none controls if khugepaged should collapse hugepages over 228 * any unmapped ptes in turn potentially increasing the memory 229 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 230 * reduce the available free memory in the system as it 231 * runs. Increasing max_ptes_none will instead potentially reduce the 232 * free memory in the system during the khugepaged scan. 233 */ 234 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 235 struct kobj_attribute *attr, 236 char *buf) 237 { 238 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 239 } 240 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 241 struct kobj_attribute *attr, 242 const char *buf, size_t count) 243 { 244 int err; 245 unsigned long max_ptes_none; 246 247 err = kstrtoul(buf, 10, &max_ptes_none); 248 if (err || max_ptes_none > HPAGE_PMD_NR-1) 249 return -EINVAL; 250 251 khugepaged_max_ptes_none = max_ptes_none; 252 253 return count; 254 } 255 static struct kobj_attribute khugepaged_max_ptes_none_attr = 256 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 257 khugepaged_max_ptes_none_store); 258 259 static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj, 260 struct kobj_attribute *attr, 261 char *buf) 262 { 263 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap); 264 } 265 266 static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj, 267 struct kobj_attribute *attr, 268 const char *buf, size_t count) 269 { 270 int err; 271 unsigned long max_ptes_swap; 272 273 err = kstrtoul(buf, 10, &max_ptes_swap); 274 if (err || max_ptes_swap > HPAGE_PMD_NR-1) 275 return -EINVAL; 276 277 khugepaged_max_ptes_swap = max_ptes_swap; 278 279 return count; 280 } 281 282 static struct kobj_attribute khugepaged_max_ptes_swap_attr = 283 __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show, 284 khugepaged_max_ptes_swap_store); 285 286 static struct attribute *khugepaged_attr[] = { 287 &khugepaged_defrag_attr.attr, 288 &khugepaged_max_ptes_none_attr.attr, 289 &pages_to_scan_attr.attr, 290 &pages_collapsed_attr.attr, 291 &full_scans_attr.attr, 292 &scan_sleep_millisecs_attr.attr, 293 &alloc_sleep_millisecs_attr.attr, 294 &khugepaged_max_ptes_swap_attr.attr, 295 NULL, 296 }; 297 298 struct attribute_group khugepaged_attr_group = { 299 .attrs = khugepaged_attr, 300 .name = "khugepaged", 301 }; 302 #endif /* CONFIG_SYSFS */ 303 304 #define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB) 305 306 int hugepage_madvise(struct vm_area_struct *vma, 307 unsigned long *vm_flags, int advice) 308 { 309 switch (advice) { 310 case MADV_HUGEPAGE: 311 #ifdef CONFIG_S390 312 /* 313 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 314 * can't handle this properly after s390_enable_sie, so we simply 315 * ignore the madvise to prevent qemu from causing a SIGSEGV. 316 */ 317 if (mm_has_pgste(vma->vm_mm)) 318 return 0; 319 #endif 320 *vm_flags &= ~VM_NOHUGEPAGE; 321 *vm_flags |= VM_HUGEPAGE; 322 /* 323 * If the vma become good for khugepaged to scan, 324 * register it here without waiting a page fault that 325 * may not happen any time soon. 326 */ 327 if (!(*vm_flags & VM_NO_KHUGEPAGED) && 328 khugepaged_enter_vma_merge(vma, *vm_flags)) 329 return -ENOMEM; 330 break; 331 case MADV_NOHUGEPAGE: 332 *vm_flags &= ~VM_HUGEPAGE; 333 *vm_flags |= VM_NOHUGEPAGE; 334 /* 335 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 336 * this vma even if we leave the mm registered in khugepaged if 337 * it got registered before VM_NOHUGEPAGE was set. 338 */ 339 break; 340 } 341 342 return 0; 343 } 344 345 int __init khugepaged_init(void) 346 { 347 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 348 sizeof(struct mm_slot), 349 __alignof__(struct mm_slot), 0, NULL); 350 if (!mm_slot_cache) 351 return -ENOMEM; 352 353 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; 354 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; 355 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8; 356 357 return 0; 358 } 359 360 void __init khugepaged_destroy(void) 361 { 362 kmem_cache_destroy(mm_slot_cache); 363 } 364 365 static inline struct mm_slot *alloc_mm_slot(void) 366 { 367 if (!mm_slot_cache) /* initialization failed */ 368 return NULL; 369 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 370 } 371 372 static inline void free_mm_slot(struct mm_slot *mm_slot) 373 { 374 kmem_cache_free(mm_slot_cache, mm_slot); 375 } 376 377 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 378 { 379 struct mm_slot *mm_slot; 380 381 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) 382 if (mm == mm_slot->mm) 383 return mm_slot; 384 385 return NULL; 386 } 387 388 static void insert_to_mm_slots_hash(struct mm_struct *mm, 389 struct mm_slot *mm_slot) 390 { 391 mm_slot->mm = mm; 392 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); 393 } 394 395 static inline int khugepaged_test_exit(struct mm_struct *mm) 396 { 397 return atomic_read(&mm->mm_users) == 0; 398 } 399 400 int __khugepaged_enter(struct mm_struct *mm) 401 { 402 struct mm_slot *mm_slot; 403 int wakeup; 404 405 mm_slot = alloc_mm_slot(); 406 if (!mm_slot) 407 return -ENOMEM; 408 409 /* __khugepaged_exit() must not run from under us */ 410 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); 411 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 412 free_mm_slot(mm_slot); 413 return 0; 414 } 415 416 spin_lock(&khugepaged_mm_lock); 417 insert_to_mm_slots_hash(mm, mm_slot); 418 /* 419 * Insert just behind the scanning cursor, to let the area settle 420 * down a little. 421 */ 422 wakeup = list_empty(&khugepaged_scan.mm_head); 423 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 424 spin_unlock(&khugepaged_mm_lock); 425 426 mmgrab(mm); 427 if (wakeup) 428 wake_up_interruptible(&khugepaged_wait); 429 430 return 0; 431 } 432 433 int khugepaged_enter_vma_merge(struct vm_area_struct *vma, 434 unsigned long vm_flags) 435 { 436 unsigned long hstart, hend; 437 if (!vma->anon_vma) 438 /* 439 * Not yet faulted in so we will register later in the 440 * page fault if needed. 441 */ 442 return 0; 443 if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED)) 444 /* khugepaged not yet working on file or special mappings */ 445 return 0; 446 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 447 hend = vma->vm_end & HPAGE_PMD_MASK; 448 if (hstart < hend) 449 return khugepaged_enter(vma, vm_flags); 450 return 0; 451 } 452 453 void __khugepaged_exit(struct mm_struct *mm) 454 { 455 struct mm_slot *mm_slot; 456 int free = 0; 457 458 spin_lock(&khugepaged_mm_lock); 459 mm_slot = get_mm_slot(mm); 460 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 461 hash_del(&mm_slot->hash); 462 list_del(&mm_slot->mm_node); 463 free = 1; 464 } 465 spin_unlock(&khugepaged_mm_lock); 466 467 if (free) { 468 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 469 free_mm_slot(mm_slot); 470 mmdrop(mm); 471 } else if (mm_slot) { 472 /* 473 * This is required to serialize against 474 * khugepaged_test_exit() (which is guaranteed to run 475 * under mmap sem read mode). Stop here (after we 476 * return all pagetables will be destroyed) until 477 * khugepaged has finished working on the pagetables 478 * under the mmap_sem. 479 */ 480 down_write(&mm->mmap_sem); 481 up_write(&mm->mmap_sem); 482 } 483 } 484 485 static void release_pte_page(struct page *page) 486 { 487 dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page)); 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); 535 536 /* 537 * We can do it before isolate_lru_page because the 538 * page can't be freed from under us. NOTE: PG_lock 539 * is needed to serialize against split_huge_page 540 * when invoked from the VM. 541 */ 542 if (!trylock_page(page)) { 543 result = SCAN_PAGE_LOCK; 544 goto out; 545 } 546 547 /* 548 * cannot use mapcount: can't collapse if there's a gup pin. 549 * The page must only be referenced by the scanned process 550 * and page swap cache. 551 */ 552 if (page_count(page) != 1 + PageSwapCache(page)) { 553 unlock_page(page); 554 result = SCAN_PAGE_COUNT; 555 goto out; 556 } 557 if (pte_write(pteval)) { 558 writable = true; 559 } else { 560 if (PageSwapCache(page) && 561 !reuse_swap_page(page, NULL)) { 562 unlock_page(page); 563 result = SCAN_SWAP_CACHE_PAGE; 564 goto out; 565 } 566 /* 567 * Page is not in the swap cache. It can be collapsed 568 * into a THP. 569 */ 570 } 571 572 /* 573 * Isolate the page to avoid collapsing an hugepage 574 * currently in use by the VM. 575 */ 576 if (isolate_lru_page(page)) { 577 unlock_page(page); 578 result = SCAN_DEL_PAGE_LRU; 579 goto out; 580 } 581 inc_node_page_state(page, 582 NR_ISOLATED_ANON + page_is_file_cache(page)); 583 VM_BUG_ON_PAGE(!PageLocked(page), page); 584 VM_BUG_ON_PAGE(PageLRU(page), page); 585 586 /* There should be enough young pte to collapse the page */ 587 if (pte_young(pteval) || 588 page_is_young(page) || PageReferenced(page) || 589 mmu_notifier_test_young(vma->vm_mm, address)) 590 referenced++; 591 } 592 if (likely(writable)) { 593 if (likely(referenced)) { 594 result = SCAN_SUCCEED; 595 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 596 referenced, writable, result); 597 return 1; 598 } 599 } else { 600 result = SCAN_PAGE_RO; 601 } 602 603 out: 604 release_pte_pages(pte, _pte); 605 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 606 referenced, writable, result); 607 return 0; 608 } 609 610 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 611 struct vm_area_struct *vma, 612 unsigned long address, 613 spinlock_t *ptl) 614 { 615 pte_t *_pte; 616 for (_pte = pte; _pte < pte + HPAGE_PMD_NR; 617 _pte++, page++, address += PAGE_SIZE) { 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 } 658 659 static void khugepaged_alloc_sleep(void) 660 { 661 DEFINE_WAIT(wait); 662 663 add_wait_queue(&khugepaged_wait, &wait); 664 freezable_schedule_timeout_interruptible( 665 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 666 remove_wait_queue(&khugepaged_wait, &wait); 667 } 668 669 static int khugepaged_node_load[MAX_NUMNODES]; 670 671 static bool khugepaged_scan_abort(int nid) 672 { 673 int i; 674 675 /* 676 * If node_reclaim_mode is disabled, then no extra effort is made to 677 * allocate memory locally. 678 */ 679 if (!node_reclaim_mode) 680 return false; 681 682 /* If there is a count for this node already, it must be acceptable */ 683 if (khugepaged_node_load[nid]) 684 return false; 685 686 for (i = 0; i < MAX_NUMNODES; i++) { 687 if (!khugepaged_node_load[i]) 688 continue; 689 if (node_distance(nid, i) > RECLAIM_DISTANCE) 690 return true; 691 } 692 return false; 693 } 694 695 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ 696 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) 697 { 698 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT; 699 } 700 701 #ifdef CONFIG_NUMA 702 static int khugepaged_find_target_node(void) 703 { 704 static int last_khugepaged_target_node = NUMA_NO_NODE; 705 int nid, target_node = 0, max_value = 0; 706 707 /* find first node with max normal pages hit */ 708 for (nid = 0; nid < MAX_NUMNODES; nid++) 709 if (khugepaged_node_load[nid] > max_value) { 710 max_value = khugepaged_node_load[nid]; 711 target_node = nid; 712 } 713 714 /* do some balance if several nodes have the same hit record */ 715 if (target_node <= last_khugepaged_target_node) 716 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; 717 nid++) 718 if (max_value == khugepaged_node_load[nid]) { 719 target_node = nid; 720 break; 721 } 722 723 last_khugepaged_target_node = target_node; 724 return target_node; 725 } 726 727 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 728 { 729 if (IS_ERR(*hpage)) { 730 if (!*wait) 731 return false; 732 733 *wait = false; 734 *hpage = NULL; 735 khugepaged_alloc_sleep(); 736 } else if (*hpage) { 737 put_page(*hpage); 738 *hpage = NULL; 739 } 740 741 return true; 742 } 743 744 static struct page * 745 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) 746 { 747 VM_BUG_ON_PAGE(*hpage, *hpage); 748 749 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); 750 if (unlikely(!*hpage)) { 751 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 752 *hpage = ERR_PTR(-ENOMEM); 753 return NULL; 754 } 755 756 prep_transhuge_page(*hpage); 757 count_vm_event(THP_COLLAPSE_ALLOC); 758 return *hpage; 759 } 760 #else 761 static int khugepaged_find_target_node(void) 762 { 763 return 0; 764 } 765 766 static inline struct page *alloc_khugepaged_hugepage(void) 767 { 768 struct page *page; 769 770 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), 771 HPAGE_PMD_ORDER); 772 if (page) 773 prep_transhuge_page(page); 774 return page; 775 } 776 777 static struct page *khugepaged_alloc_hugepage(bool *wait) 778 { 779 struct page *hpage; 780 781 do { 782 hpage = alloc_khugepaged_hugepage(); 783 if (!hpage) { 784 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 785 if (!*wait) 786 return NULL; 787 788 *wait = false; 789 khugepaged_alloc_sleep(); 790 } else 791 count_vm_event(THP_COLLAPSE_ALLOC); 792 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 793 794 return hpage; 795 } 796 797 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 798 { 799 if (!*hpage) 800 *hpage = khugepaged_alloc_hugepage(wait); 801 802 if (unlikely(!*hpage)) 803 return false; 804 805 return true; 806 } 807 808 static struct page * 809 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) 810 { 811 VM_BUG_ON(!*hpage); 812 813 return *hpage; 814 } 815 #endif 816 817 static bool hugepage_vma_check(struct vm_area_struct *vma) 818 { 819 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 820 (vma->vm_flags & VM_NOHUGEPAGE) || 821 test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) 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 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 912 return false; 913 } 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 mm_dec_nr_ptes(vma->vm_mm); 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