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 static bool hugepage_vma_check(struct vm_area_struct *vma, 401 unsigned long vm_flags) 402 { 403 if ((!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 404 (vm_flags & VM_NOHUGEPAGE) || 405 test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) 406 return false; 407 if (shmem_file(vma->vm_file)) { 408 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) 409 return false; 410 return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, 411 HPAGE_PMD_NR); 412 } 413 if (!vma->anon_vma || vma->vm_ops) 414 return false; 415 if (is_vma_temporary_stack(vma)) 416 return false; 417 return !(vm_flags & VM_NO_KHUGEPAGED); 418 } 419 420 int __khugepaged_enter(struct mm_struct *mm) 421 { 422 struct mm_slot *mm_slot; 423 int wakeup; 424 425 mm_slot = alloc_mm_slot(); 426 if (!mm_slot) 427 return -ENOMEM; 428 429 /* __khugepaged_exit() must not run from under us */ 430 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); 431 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 432 free_mm_slot(mm_slot); 433 return 0; 434 } 435 436 spin_lock(&khugepaged_mm_lock); 437 insert_to_mm_slots_hash(mm, mm_slot); 438 /* 439 * Insert just behind the scanning cursor, to let the area settle 440 * down a little. 441 */ 442 wakeup = list_empty(&khugepaged_scan.mm_head); 443 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 444 spin_unlock(&khugepaged_mm_lock); 445 446 mmgrab(mm); 447 if (wakeup) 448 wake_up_interruptible(&khugepaged_wait); 449 450 return 0; 451 } 452 453 int khugepaged_enter_vma_merge(struct vm_area_struct *vma, 454 unsigned long vm_flags) 455 { 456 unsigned long hstart, hend; 457 458 /* 459 * khugepaged does not yet work on non-shmem files or special 460 * mappings. And file-private shmem THP is not supported. 461 */ 462 if (!hugepage_vma_check(vma, vm_flags)) 463 return 0; 464 465 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 466 hend = vma->vm_end & HPAGE_PMD_MASK; 467 if (hstart < hend) 468 return khugepaged_enter(vma, vm_flags); 469 return 0; 470 } 471 472 void __khugepaged_exit(struct mm_struct *mm) 473 { 474 struct mm_slot *mm_slot; 475 int free = 0; 476 477 spin_lock(&khugepaged_mm_lock); 478 mm_slot = get_mm_slot(mm); 479 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 480 hash_del(&mm_slot->hash); 481 list_del(&mm_slot->mm_node); 482 free = 1; 483 } 484 spin_unlock(&khugepaged_mm_lock); 485 486 if (free) { 487 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 488 free_mm_slot(mm_slot); 489 mmdrop(mm); 490 } else if (mm_slot) { 491 /* 492 * This is required to serialize against 493 * khugepaged_test_exit() (which is guaranteed to run 494 * under mmap sem read mode). Stop here (after we 495 * return all pagetables will be destroyed) until 496 * khugepaged has finished working on the pagetables 497 * under the mmap_sem. 498 */ 499 down_write(&mm->mmap_sem); 500 up_write(&mm->mmap_sem); 501 } 502 } 503 504 static void release_pte_page(struct page *page) 505 { 506 dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page)); 507 unlock_page(page); 508 putback_lru_page(page); 509 } 510 511 static void release_pte_pages(pte_t *pte, pte_t *_pte) 512 { 513 while (--_pte >= pte) { 514 pte_t pteval = *_pte; 515 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) 516 release_pte_page(pte_page(pteval)); 517 } 518 } 519 520 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 521 unsigned long address, 522 pte_t *pte) 523 { 524 struct page *page = NULL; 525 pte_t *_pte; 526 int none_or_zero = 0, result = 0, referenced = 0; 527 bool writable = false; 528 529 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 530 _pte++, address += PAGE_SIZE) { 531 pte_t pteval = *_pte; 532 if (pte_none(pteval) || (pte_present(pteval) && 533 is_zero_pfn(pte_pfn(pteval)))) { 534 if (!userfaultfd_armed(vma) && 535 ++none_or_zero <= khugepaged_max_ptes_none) { 536 continue; 537 } else { 538 result = SCAN_EXCEED_NONE_PTE; 539 goto out; 540 } 541 } 542 if (!pte_present(pteval)) { 543 result = SCAN_PTE_NON_PRESENT; 544 goto out; 545 } 546 page = vm_normal_page(vma, address, pteval); 547 if (unlikely(!page)) { 548 result = SCAN_PAGE_NULL; 549 goto out; 550 } 551 552 /* TODO: teach khugepaged to collapse THP mapped with pte */ 553 if (PageCompound(page)) { 554 result = SCAN_PAGE_COMPOUND; 555 goto out; 556 } 557 558 VM_BUG_ON_PAGE(!PageAnon(page), page); 559 560 /* 561 * We can do it before isolate_lru_page because the 562 * page can't be freed from under us. NOTE: PG_lock 563 * is needed to serialize against split_huge_page 564 * when invoked from the VM. 565 */ 566 if (!trylock_page(page)) { 567 result = SCAN_PAGE_LOCK; 568 goto out; 569 } 570 571 /* 572 * cannot use mapcount: can't collapse if there's a gup pin. 573 * The page must only be referenced by the scanned process 574 * and page swap cache. 575 */ 576 if (page_count(page) != 1 + PageSwapCache(page)) { 577 unlock_page(page); 578 result = SCAN_PAGE_COUNT; 579 goto out; 580 } 581 if (pte_write(pteval)) { 582 writable = true; 583 } else { 584 if (PageSwapCache(page) && 585 !reuse_swap_page(page, NULL)) { 586 unlock_page(page); 587 result = SCAN_SWAP_CACHE_PAGE; 588 goto out; 589 } 590 /* 591 * Page is not in the swap cache. It can be collapsed 592 * into a THP. 593 */ 594 } 595 596 /* 597 * Isolate the page to avoid collapsing an hugepage 598 * currently in use by the VM. 599 */ 600 if (isolate_lru_page(page)) { 601 unlock_page(page); 602 result = SCAN_DEL_PAGE_LRU; 603 goto out; 604 } 605 inc_node_page_state(page, 606 NR_ISOLATED_ANON + page_is_file_cache(page)); 607 VM_BUG_ON_PAGE(!PageLocked(page), page); 608 VM_BUG_ON_PAGE(PageLRU(page), page); 609 610 /* There should be enough young pte to collapse the page */ 611 if (pte_young(pteval) || 612 page_is_young(page) || PageReferenced(page) || 613 mmu_notifier_test_young(vma->vm_mm, address)) 614 referenced++; 615 } 616 if (likely(writable)) { 617 if (likely(referenced)) { 618 result = SCAN_SUCCEED; 619 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 620 referenced, writable, result); 621 return 1; 622 } 623 } else { 624 result = SCAN_PAGE_RO; 625 } 626 627 out: 628 release_pte_pages(pte, _pte); 629 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 630 referenced, writable, result); 631 return 0; 632 } 633 634 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 635 struct vm_area_struct *vma, 636 unsigned long address, 637 spinlock_t *ptl) 638 { 639 pte_t *_pte; 640 for (_pte = pte; _pte < pte + HPAGE_PMD_NR; 641 _pte++, page++, address += PAGE_SIZE) { 642 pte_t pteval = *_pte; 643 struct page *src_page; 644 645 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 646 clear_user_highpage(page, address); 647 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 648 if (is_zero_pfn(pte_pfn(pteval))) { 649 /* 650 * ptl mostly unnecessary. 651 */ 652 spin_lock(ptl); 653 /* 654 * paravirt calls inside pte_clear here are 655 * superfluous. 656 */ 657 pte_clear(vma->vm_mm, address, _pte); 658 spin_unlock(ptl); 659 } 660 } else { 661 src_page = pte_page(pteval); 662 copy_user_highpage(page, src_page, address, vma); 663 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); 664 release_pte_page(src_page); 665 /* 666 * ptl mostly unnecessary, but preempt has to 667 * be disabled to update the per-cpu stats 668 * inside page_remove_rmap(). 669 */ 670 spin_lock(ptl); 671 /* 672 * paravirt calls inside pte_clear here are 673 * superfluous. 674 */ 675 pte_clear(vma->vm_mm, address, _pte); 676 page_remove_rmap(src_page, false); 677 spin_unlock(ptl); 678 free_page_and_swap_cache(src_page); 679 } 680 } 681 } 682 683 static void khugepaged_alloc_sleep(void) 684 { 685 DEFINE_WAIT(wait); 686 687 add_wait_queue(&khugepaged_wait, &wait); 688 freezable_schedule_timeout_interruptible( 689 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 690 remove_wait_queue(&khugepaged_wait, &wait); 691 } 692 693 static int khugepaged_node_load[MAX_NUMNODES]; 694 695 static bool khugepaged_scan_abort(int nid) 696 { 697 int i; 698 699 /* 700 * If node_reclaim_mode is disabled, then no extra effort is made to 701 * allocate memory locally. 702 */ 703 if (!node_reclaim_mode) 704 return false; 705 706 /* If there is a count for this node already, it must be acceptable */ 707 if (khugepaged_node_load[nid]) 708 return false; 709 710 for (i = 0; i < MAX_NUMNODES; i++) { 711 if (!khugepaged_node_load[i]) 712 continue; 713 if (node_distance(nid, i) > RECLAIM_DISTANCE) 714 return true; 715 } 716 return false; 717 } 718 719 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ 720 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) 721 { 722 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT; 723 } 724 725 #ifdef CONFIG_NUMA 726 static int khugepaged_find_target_node(void) 727 { 728 static int last_khugepaged_target_node = NUMA_NO_NODE; 729 int nid, target_node = 0, max_value = 0; 730 731 /* find first node with max normal pages hit */ 732 for (nid = 0; nid < MAX_NUMNODES; nid++) 733 if (khugepaged_node_load[nid] > max_value) { 734 max_value = khugepaged_node_load[nid]; 735 target_node = nid; 736 } 737 738 /* do some balance if several nodes have the same hit record */ 739 if (target_node <= last_khugepaged_target_node) 740 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; 741 nid++) 742 if (max_value == khugepaged_node_load[nid]) { 743 target_node = nid; 744 break; 745 } 746 747 last_khugepaged_target_node = target_node; 748 return target_node; 749 } 750 751 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 752 { 753 if (IS_ERR(*hpage)) { 754 if (!*wait) 755 return false; 756 757 *wait = false; 758 *hpage = NULL; 759 khugepaged_alloc_sleep(); 760 } else if (*hpage) { 761 put_page(*hpage); 762 *hpage = NULL; 763 } 764 765 return true; 766 } 767 768 static struct page * 769 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) 770 { 771 VM_BUG_ON_PAGE(*hpage, *hpage); 772 773 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); 774 if (unlikely(!*hpage)) { 775 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 776 *hpage = ERR_PTR(-ENOMEM); 777 return NULL; 778 } 779 780 prep_transhuge_page(*hpage); 781 count_vm_event(THP_COLLAPSE_ALLOC); 782 return *hpage; 783 } 784 #else 785 static int khugepaged_find_target_node(void) 786 { 787 return 0; 788 } 789 790 static inline struct page *alloc_khugepaged_hugepage(void) 791 { 792 struct page *page; 793 794 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), 795 HPAGE_PMD_ORDER); 796 if (page) 797 prep_transhuge_page(page); 798 return page; 799 } 800 801 static struct page *khugepaged_alloc_hugepage(bool *wait) 802 { 803 struct page *hpage; 804 805 do { 806 hpage = alloc_khugepaged_hugepage(); 807 if (!hpage) { 808 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 809 if (!*wait) 810 return NULL; 811 812 *wait = false; 813 khugepaged_alloc_sleep(); 814 } else 815 count_vm_event(THP_COLLAPSE_ALLOC); 816 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 817 818 return hpage; 819 } 820 821 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 822 { 823 if (!*hpage) 824 *hpage = khugepaged_alloc_hugepage(wait); 825 826 if (unlikely(!*hpage)) 827 return false; 828 829 return true; 830 } 831 832 static struct page * 833 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) 834 { 835 VM_BUG_ON(!*hpage); 836 837 return *hpage; 838 } 839 #endif 840 841 /* 842 * If mmap_sem temporarily dropped, revalidate vma 843 * before taking mmap_sem. 844 * Return 0 if succeeds, otherwise return none-zero 845 * value (scan code). 846 */ 847 848 static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, 849 struct vm_area_struct **vmap) 850 { 851 struct vm_area_struct *vma; 852 unsigned long hstart, hend; 853 854 if (unlikely(khugepaged_test_exit(mm))) 855 return SCAN_ANY_PROCESS; 856 857 *vmap = vma = find_vma(mm, address); 858 if (!vma) 859 return SCAN_VMA_NULL; 860 861 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 862 hend = vma->vm_end & HPAGE_PMD_MASK; 863 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 864 return SCAN_ADDRESS_RANGE; 865 if (!hugepage_vma_check(vma, vma->vm_flags)) 866 return SCAN_VMA_CHECK; 867 return 0; 868 } 869 870 /* 871 * Bring missing pages in from swap, to complete THP collapse. 872 * Only done if khugepaged_scan_pmd believes it is worthwhile. 873 * 874 * Called and returns without pte mapped or spinlocks held, 875 * but with mmap_sem held to protect against vma changes. 876 */ 877 878 static bool __collapse_huge_page_swapin(struct mm_struct *mm, 879 struct vm_area_struct *vma, 880 unsigned long address, pmd_t *pmd, 881 int referenced) 882 { 883 int swapped_in = 0; 884 vm_fault_t ret = 0; 885 struct vm_fault vmf = { 886 .vma = vma, 887 .address = address, 888 .flags = FAULT_FLAG_ALLOW_RETRY, 889 .pmd = pmd, 890 .pgoff = linear_page_index(vma, address), 891 }; 892 893 /* we only decide to swapin, if there is enough young ptes */ 894 if (referenced < HPAGE_PMD_NR/2) { 895 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 896 return false; 897 } 898 vmf.pte = pte_offset_map(pmd, address); 899 for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE; 900 vmf.pte++, vmf.address += PAGE_SIZE) { 901 vmf.orig_pte = *vmf.pte; 902 if (!is_swap_pte(vmf.orig_pte)) 903 continue; 904 swapped_in++; 905 ret = do_swap_page(&vmf); 906 907 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */ 908 if (ret & VM_FAULT_RETRY) { 909 down_read(&mm->mmap_sem); 910 if (hugepage_vma_revalidate(mm, address, &vmf.vma)) { 911 /* vma is no longer available, don't continue to swapin */ 912 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 913 return false; 914 } 915 /* check if the pmd is still valid */ 916 if (mm_find_pmd(mm, address) != pmd) { 917 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 918 return false; 919 } 920 } 921 if (ret & VM_FAULT_ERROR) { 922 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); 923 return false; 924 } 925 /* pte is unmapped now, we need to map it */ 926 vmf.pte = pte_offset_map(pmd, vmf.address); 927 } 928 vmf.pte--; 929 pte_unmap(vmf.pte); 930 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); 931 return true; 932 } 933 934 static void collapse_huge_page(struct mm_struct *mm, 935 unsigned long address, 936 struct page **hpage, 937 int node, int referenced) 938 { 939 pmd_t *pmd, _pmd; 940 pte_t *pte; 941 pgtable_t pgtable; 942 struct page *new_page; 943 spinlock_t *pmd_ptl, *pte_ptl; 944 int isolated = 0, result = 0; 945 struct mem_cgroup *memcg; 946 struct vm_area_struct *vma; 947 unsigned long mmun_start; /* For mmu_notifiers */ 948 unsigned long mmun_end; /* For mmu_notifiers */ 949 gfp_t gfp; 950 951 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 952 953 /* Only allocate from the target node */ 954 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; 955 956 /* 957 * Before allocating the hugepage, release the mmap_sem read lock. 958 * The allocation can take potentially a long time if it involves 959 * sync compaction, and we do not need to hold the mmap_sem during 960 * that. We will recheck the vma after taking it again in write mode. 961 */ 962 up_read(&mm->mmap_sem); 963 new_page = khugepaged_alloc_page(hpage, gfp, node); 964 if (!new_page) { 965 result = SCAN_ALLOC_HUGE_PAGE_FAIL; 966 goto out_nolock; 967 } 968 969 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { 970 result = SCAN_CGROUP_CHARGE_FAIL; 971 goto out_nolock; 972 } 973 974 down_read(&mm->mmap_sem); 975 result = hugepage_vma_revalidate(mm, address, &vma); 976 if (result) { 977 mem_cgroup_cancel_charge(new_page, memcg, true); 978 up_read(&mm->mmap_sem); 979 goto out_nolock; 980 } 981 982 pmd = mm_find_pmd(mm, address); 983 if (!pmd) { 984 result = SCAN_PMD_NULL; 985 mem_cgroup_cancel_charge(new_page, memcg, true); 986 up_read(&mm->mmap_sem); 987 goto out_nolock; 988 } 989 990 /* 991 * __collapse_huge_page_swapin always returns with mmap_sem locked. 992 * If it fails, we release mmap_sem and jump out_nolock. 993 * Continuing to collapse causes inconsistency. 994 */ 995 if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) { 996 mem_cgroup_cancel_charge(new_page, memcg, true); 997 up_read(&mm->mmap_sem); 998 goto out_nolock; 999 } 1000 1001 up_read(&mm->mmap_sem); 1002 /* 1003 * Prevent all access to pagetables with the exception of 1004 * gup_fast later handled by the ptep_clear_flush and the VM 1005 * handled by the anon_vma lock + PG_lock. 1006 */ 1007 down_write(&mm->mmap_sem); 1008 result = hugepage_vma_revalidate(mm, address, &vma); 1009 if (result) 1010 goto out; 1011 /* check if the pmd is still valid */ 1012 if (mm_find_pmd(mm, address) != pmd) 1013 goto out; 1014 1015 anon_vma_lock_write(vma->anon_vma); 1016 1017 pte = pte_offset_map(pmd, address); 1018 pte_ptl = pte_lockptr(mm, pmd); 1019 1020 mmun_start = address; 1021 mmun_end = address + HPAGE_PMD_SIZE; 1022 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1023 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ 1024 /* 1025 * After this gup_fast can't run anymore. This also removes 1026 * any huge TLB entry from the CPU so we won't allow 1027 * huge and small TLB entries for the same virtual address 1028 * to avoid the risk of CPU bugs in that area. 1029 */ 1030 _pmd = pmdp_collapse_flush(vma, address, pmd); 1031 spin_unlock(pmd_ptl); 1032 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1033 1034 spin_lock(pte_ptl); 1035 isolated = __collapse_huge_page_isolate(vma, address, pte); 1036 spin_unlock(pte_ptl); 1037 1038 if (unlikely(!isolated)) { 1039 pte_unmap(pte); 1040 spin_lock(pmd_ptl); 1041 BUG_ON(!pmd_none(*pmd)); 1042 /* 1043 * We can only use set_pmd_at when establishing 1044 * hugepmds and never for establishing regular pmds that 1045 * points to regular pagetables. Use pmd_populate for that 1046 */ 1047 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 1048 spin_unlock(pmd_ptl); 1049 anon_vma_unlock_write(vma->anon_vma); 1050 result = SCAN_FAIL; 1051 goto out; 1052 } 1053 1054 /* 1055 * All pages are isolated and locked so anon_vma rmap 1056 * can't run anymore. 1057 */ 1058 anon_vma_unlock_write(vma->anon_vma); 1059 1060 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); 1061 pte_unmap(pte); 1062 __SetPageUptodate(new_page); 1063 pgtable = pmd_pgtable(_pmd); 1064 1065 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); 1066 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 1067 1068 /* 1069 * spin_lock() below is not the equivalent of smp_wmb(), so 1070 * this is needed to avoid the copy_huge_page writes to become 1071 * visible after the set_pmd_at() write. 1072 */ 1073 smp_wmb(); 1074 1075 spin_lock(pmd_ptl); 1076 BUG_ON(!pmd_none(*pmd)); 1077 page_add_new_anon_rmap(new_page, vma, address, true); 1078 mem_cgroup_commit_charge(new_page, memcg, false, true); 1079 lru_cache_add_active_or_unevictable(new_page, vma); 1080 pgtable_trans_huge_deposit(mm, pmd, pgtable); 1081 set_pmd_at(mm, address, pmd, _pmd); 1082 update_mmu_cache_pmd(vma, address, pmd); 1083 spin_unlock(pmd_ptl); 1084 1085 *hpage = NULL; 1086 1087 khugepaged_pages_collapsed++; 1088 result = SCAN_SUCCEED; 1089 out_up_write: 1090 up_write(&mm->mmap_sem); 1091 out_nolock: 1092 trace_mm_collapse_huge_page(mm, isolated, result); 1093 return; 1094 out: 1095 mem_cgroup_cancel_charge(new_page, memcg, true); 1096 goto out_up_write; 1097 } 1098 1099 static int khugepaged_scan_pmd(struct mm_struct *mm, 1100 struct vm_area_struct *vma, 1101 unsigned long address, 1102 struct page **hpage) 1103 { 1104 pmd_t *pmd; 1105 pte_t *pte, *_pte; 1106 int ret = 0, none_or_zero = 0, result = 0, referenced = 0; 1107 struct page *page = NULL; 1108 unsigned long _address; 1109 spinlock_t *ptl; 1110 int node = NUMA_NO_NODE, unmapped = 0; 1111 bool writable = false; 1112 1113 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1114 1115 pmd = mm_find_pmd(mm, address); 1116 if (!pmd) { 1117 result = SCAN_PMD_NULL; 1118 goto out; 1119 } 1120 1121 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 1122 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 1123 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 1124 _pte++, _address += PAGE_SIZE) { 1125 pte_t pteval = *_pte; 1126 if (is_swap_pte(pteval)) { 1127 if (++unmapped <= khugepaged_max_ptes_swap) { 1128 continue; 1129 } else { 1130 result = SCAN_EXCEED_SWAP_PTE; 1131 goto out_unmap; 1132 } 1133 } 1134 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 1135 if (!userfaultfd_armed(vma) && 1136 ++none_or_zero <= khugepaged_max_ptes_none) { 1137 continue; 1138 } else { 1139 result = SCAN_EXCEED_NONE_PTE; 1140 goto out_unmap; 1141 } 1142 } 1143 if (!pte_present(pteval)) { 1144 result = SCAN_PTE_NON_PRESENT; 1145 goto out_unmap; 1146 } 1147 if (pte_write(pteval)) 1148 writable = true; 1149 1150 page = vm_normal_page(vma, _address, pteval); 1151 if (unlikely(!page)) { 1152 result = SCAN_PAGE_NULL; 1153 goto out_unmap; 1154 } 1155 1156 /* TODO: teach khugepaged to collapse THP mapped with pte */ 1157 if (PageCompound(page)) { 1158 result = SCAN_PAGE_COMPOUND; 1159 goto out_unmap; 1160 } 1161 1162 /* 1163 * Record which node the original page is from and save this 1164 * information to khugepaged_node_load[]. 1165 * Khupaged will allocate hugepage from the node has the max 1166 * hit record. 1167 */ 1168 node = page_to_nid(page); 1169 if (khugepaged_scan_abort(node)) { 1170 result = SCAN_SCAN_ABORT; 1171 goto out_unmap; 1172 } 1173 khugepaged_node_load[node]++; 1174 if (!PageLRU(page)) { 1175 result = SCAN_PAGE_LRU; 1176 goto out_unmap; 1177 } 1178 if (PageLocked(page)) { 1179 result = SCAN_PAGE_LOCK; 1180 goto out_unmap; 1181 } 1182 if (!PageAnon(page)) { 1183 result = SCAN_PAGE_ANON; 1184 goto out_unmap; 1185 } 1186 1187 /* 1188 * cannot use mapcount: can't collapse if there's a gup pin. 1189 * The page must only be referenced by the scanned process 1190 * and page swap cache. 1191 */ 1192 if (page_count(page) != 1 + PageSwapCache(page)) { 1193 result = SCAN_PAGE_COUNT; 1194 goto out_unmap; 1195 } 1196 if (pte_young(pteval) || 1197 page_is_young(page) || PageReferenced(page) || 1198 mmu_notifier_test_young(vma->vm_mm, address)) 1199 referenced++; 1200 } 1201 if (writable) { 1202 if (referenced) { 1203 result = SCAN_SUCCEED; 1204 ret = 1; 1205 } else { 1206 result = SCAN_LACK_REFERENCED_PAGE; 1207 } 1208 } else { 1209 result = SCAN_PAGE_RO; 1210 } 1211 out_unmap: 1212 pte_unmap_unlock(pte, ptl); 1213 if (ret) { 1214 node = khugepaged_find_target_node(); 1215 /* collapse_huge_page will return with the mmap_sem released */ 1216 collapse_huge_page(mm, address, hpage, node, referenced); 1217 } 1218 out: 1219 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, 1220 none_or_zero, result, unmapped); 1221 return ret; 1222 } 1223 1224 static void collect_mm_slot(struct mm_slot *mm_slot) 1225 { 1226 struct mm_struct *mm = mm_slot->mm; 1227 1228 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 1229 1230 if (khugepaged_test_exit(mm)) { 1231 /* free mm_slot */ 1232 hash_del(&mm_slot->hash); 1233 list_del(&mm_slot->mm_node); 1234 1235 /* 1236 * Not strictly needed because the mm exited already. 1237 * 1238 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1239 */ 1240 1241 /* khugepaged_mm_lock actually not necessary for the below */ 1242 free_mm_slot(mm_slot); 1243 mmdrop(mm); 1244 } 1245 } 1246 1247 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) 1248 static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) 1249 { 1250 struct vm_area_struct *vma; 1251 unsigned long addr; 1252 pmd_t *pmd, _pmd; 1253 1254 i_mmap_lock_write(mapping); 1255 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { 1256 /* probably overkill */ 1257 if (vma->anon_vma) 1258 continue; 1259 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); 1260 if (addr & ~HPAGE_PMD_MASK) 1261 continue; 1262 if (vma->vm_end < addr + HPAGE_PMD_SIZE) 1263 continue; 1264 pmd = mm_find_pmd(vma->vm_mm, addr); 1265 if (!pmd) 1266 continue; 1267 /* 1268 * We need exclusive mmap_sem to retract page table. 1269 * If trylock fails we would end up with pte-mapped THP after 1270 * re-fault. Not ideal, but it's more important to not disturb 1271 * the system too much. 1272 */ 1273 if (down_write_trylock(&vma->vm_mm->mmap_sem)) { 1274 spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd); 1275 /* assume page table is clear */ 1276 _pmd = pmdp_collapse_flush(vma, addr, pmd); 1277 spin_unlock(ptl); 1278 up_write(&vma->vm_mm->mmap_sem); 1279 mm_dec_nr_ptes(vma->vm_mm); 1280 pte_free(vma->vm_mm, pmd_pgtable(_pmd)); 1281 } 1282 } 1283 i_mmap_unlock_write(mapping); 1284 } 1285 1286 /** 1287 * collapse_shmem - collapse small tmpfs/shmem pages into huge one. 1288 * 1289 * Basic scheme is simple, details are more complex: 1290 * - allocate and freeze a new huge page; 1291 * - scan over radix tree replacing old pages the new one 1292 * + swap in pages if necessary; 1293 * + fill in gaps; 1294 * + keep old pages around in case if rollback is required; 1295 * - if replacing succeed: 1296 * + copy data over; 1297 * + free old pages; 1298 * + unfreeze huge page; 1299 * - if replacing failed; 1300 * + put all pages back and unfreeze them; 1301 * + restore gaps in the radix-tree; 1302 * + free huge page; 1303 */ 1304 static void collapse_shmem(struct mm_struct *mm, 1305 struct address_space *mapping, pgoff_t start, 1306 struct page **hpage, int node) 1307 { 1308 gfp_t gfp; 1309 struct page *page, *new_page, *tmp; 1310 struct mem_cgroup *memcg; 1311 pgoff_t index, end = start + HPAGE_PMD_NR; 1312 LIST_HEAD(pagelist); 1313 struct radix_tree_iter iter; 1314 void **slot; 1315 int nr_none = 0, result = SCAN_SUCCEED; 1316 1317 VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); 1318 1319 /* Only allocate from the target node */ 1320 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; 1321 1322 new_page = khugepaged_alloc_page(hpage, gfp, node); 1323 if (!new_page) { 1324 result = SCAN_ALLOC_HUGE_PAGE_FAIL; 1325 goto out; 1326 } 1327 1328 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { 1329 result = SCAN_CGROUP_CHARGE_FAIL; 1330 goto out; 1331 } 1332 1333 new_page->index = start; 1334 new_page->mapping = mapping; 1335 __SetPageSwapBacked(new_page); 1336 __SetPageLocked(new_page); 1337 BUG_ON(!page_ref_freeze(new_page, 1)); 1338 1339 1340 /* 1341 * At this point the new_page is 'frozen' (page_count() is zero), locked 1342 * and not up-to-date. It's safe to insert it into radix tree, because 1343 * nobody would be able to map it or use it in other way until we 1344 * unfreeze it. 1345 */ 1346 1347 index = start; 1348 xa_lock_irq(&mapping->i_pages); 1349 radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) { 1350 int n = min(iter.index, end) - index; 1351 1352 /* 1353 * Handle holes in the radix tree: charge it from shmem and 1354 * insert relevant subpage of new_page into the radix-tree. 1355 */ 1356 if (n && !shmem_charge(mapping->host, n)) { 1357 result = SCAN_FAIL; 1358 break; 1359 } 1360 nr_none += n; 1361 for (; index < min(iter.index, end); index++) { 1362 radix_tree_insert(&mapping->i_pages, index, 1363 new_page + (index % HPAGE_PMD_NR)); 1364 } 1365 1366 /* We are done. */ 1367 if (index >= end) 1368 break; 1369 1370 page = radix_tree_deref_slot_protected(slot, 1371 &mapping->i_pages.xa_lock); 1372 if (radix_tree_exceptional_entry(page) || !PageUptodate(page)) { 1373 xa_unlock_irq(&mapping->i_pages); 1374 /* swap in or instantiate fallocated page */ 1375 if (shmem_getpage(mapping->host, index, &page, 1376 SGP_NOHUGE)) { 1377 result = SCAN_FAIL; 1378 goto tree_unlocked; 1379 } 1380 xa_lock_irq(&mapping->i_pages); 1381 } else if (trylock_page(page)) { 1382 get_page(page); 1383 } else { 1384 result = SCAN_PAGE_LOCK; 1385 break; 1386 } 1387 1388 /* 1389 * The page must be locked, so we can drop the i_pages lock 1390 * without racing with truncate. 1391 */ 1392 VM_BUG_ON_PAGE(!PageLocked(page), page); 1393 VM_BUG_ON_PAGE(!PageUptodate(page), page); 1394 VM_BUG_ON_PAGE(PageTransCompound(page), page); 1395 1396 if (page_mapping(page) != mapping) { 1397 result = SCAN_TRUNCATED; 1398 goto out_unlock; 1399 } 1400 xa_unlock_irq(&mapping->i_pages); 1401 1402 if (isolate_lru_page(page)) { 1403 result = SCAN_DEL_PAGE_LRU; 1404 goto out_isolate_failed; 1405 } 1406 1407 if (page_mapped(page)) 1408 unmap_mapping_pages(mapping, index, 1, false); 1409 1410 xa_lock_irq(&mapping->i_pages); 1411 1412 slot = radix_tree_lookup_slot(&mapping->i_pages, index); 1413 VM_BUG_ON_PAGE(page != radix_tree_deref_slot_protected(slot, 1414 &mapping->i_pages.xa_lock), page); 1415 VM_BUG_ON_PAGE(page_mapped(page), page); 1416 1417 /* 1418 * The page is expected to have page_count() == 3: 1419 * - we hold a pin on it; 1420 * - one reference from radix tree; 1421 * - one from isolate_lru_page; 1422 */ 1423 if (!page_ref_freeze(page, 3)) { 1424 result = SCAN_PAGE_COUNT; 1425 goto out_lru; 1426 } 1427 1428 /* 1429 * Add the page to the list to be able to undo the collapse if 1430 * something go wrong. 1431 */ 1432 list_add_tail(&page->lru, &pagelist); 1433 1434 /* Finally, replace with the new page. */ 1435 radix_tree_replace_slot(&mapping->i_pages, slot, 1436 new_page + (index % HPAGE_PMD_NR)); 1437 1438 slot = radix_tree_iter_resume(slot, &iter); 1439 index++; 1440 continue; 1441 out_lru: 1442 xa_unlock_irq(&mapping->i_pages); 1443 putback_lru_page(page); 1444 out_isolate_failed: 1445 unlock_page(page); 1446 put_page(page); 1447 goto tree_unlocked; 1448 out_unlock: 1449 unlock_page(page); 1450 put_page(page); 1451 break; 1452 } 1453 1454 /* 1455 * Handle hole in radix tree at the end of the range. 1456 * This code only triggers if there's nothing in radix tree 1457 * beyond 'end'. 1458 */ 1459 if (result == SCAN_SUCCEED && index < end) { 1460 int n = end - index; 1461 1462 if (!shmem_charge(mapping->host, n)) { 1463 result = SCAN_FAIL; 1464 goto tree_locked; 1465 } 1466 1467 for (; index < end; index++) { 1468 radix_tree_insert(&mapping->i_pages, index, 1469 new_page + (index % HPAGE_PMD_NR)); 1470 } 1471 nr_none += n; 1472 } 1473 1474 tree_locked: 1475 xa_unlock_irq(&mapping->i_pages); 1476 tree_unlocked: 1477 1478 if (result == SCAN_SUCCEED) { 1479 unsigned long flags; 1480 struct zone *zone = page_zone(new_page); 1481 1482 /* 1483 * Replacing old pages with new one has succeed, now we need to 1484 * copy the content and free old pages. 1485 */ 1486 list_for_each_entry_safe(page, tmp, &pagelist, lru) { 1487 copy_highpage(new_page + (page->index % HPAGE_PMD_NR), 1488 page); 1489 list_del(&page->lru); 1490 unlock_page(page); 1491 page_ref_unfreeze(page, 1); 1492 page->mapping = NULL; 1493 ClearPageActive(page); 1494 ClearPageUnevictable(page); 1495 put_page(page); 1496 } 1497 1498 local_irq_save(flags); 1499 __inc_node_page_state(new_page, NR_SHMEM_THPS); 1500 if (nr_none) { 1501 __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none); 1502 __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none); 1503 } 1504 local_irq_restore(flags); 1505 1506 /* 1507 * Remove pte page tables, so we can re-faulti 1508 * the page as huge. 1509 */ 1510 retract_page_tables(mapping, start); 1511 1512 /* Everything is ready, let's unfreeze the new_page */ 1513 set_page_dirty(new_page); 1514 SetPageUptodate(new_page); 1515 page_ref_unfreeze(new_page, HPAGE_PMD_NR); 1516 mem_cgroup_commit_charge(new_page, memcg, false, true); 1517 lru_cache_add_anon(new_page); 1518 unlock_page(new_page); 1519 1520 *hpage = NULL; 1521 1522 khugepaged_pages_collapsed++; 1523 } else { 1524 /* Something went wrong: rollback changes to the radix-tree */ 1525 shmem_uncharge(mapping->host, nr_none); 1526 xa_lock_irq(&mapping->i_pages); 1527 radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) { 1528 if (iter.index >= end) 1529 break; 1530 page = list_first_entry_or_null(&pagelist, 1531 struct page, lru); 1532 if (!page || iter.index < page->index) { 1533 if (!nr_none) 1534 break; 1535 nr_none--; 1536 /* Put holes back where they were */ 1537 radix_tree_delete(&mapping->i_pages, iter.index); 1538 continue; 1539 } 1540 1541 VM_BUG_ON_PAGE(page->index != iter.index, page); 1542 1543 /* Unfreeze the page. */ 1544 list_del(&page->lru); 1545 page_ref_unfreeze(page, 2); 1546 radix_tree_replace_slot(&mapping->i_pages, slot, page); 1547 slot = radix_tree_iter_resume(slot, &iter); 1548 xa_unlock_irq(&mapping->i_pages); 1549 putback_lru_page(page); 1550 unlock_page(page); 1551 xa_lock_irq(&mapping->i_pages); 1552 } 1553 VM_BUG_ON(nr_none); 1554 xa_unlock_irq(&mapping->i_pages); 1555 1556 /* Unfreeze new_page, caller would take care about freeing it */ 1557 page_ref_unfreeze(new_page, 1); 1558 mem_cgroup_cancel_charge(new_page, memcg, true); 1559 unlock_page(new_page); 1560 new_page->mapping = NULL; 1561 } 1562 out: 1563 VM_BUG_ON(!list_empty(&pagelist)); 1564 /* TODO: tracepoints */ 1565 } 1566 1567 static void khugepaged_scan_shmem(struct mm_struct *mm, 1568 struct address_space *mapping, 1569 pgoff_t start, struct page **hpage) 1570 { 1571 struct page *page = NULL; 1572 struct radix_tree_iter iter; 1573 void **slot; 1574 int present, swap; 1575 int node = NUMA_NO_NODE; 1576 int result = SCAN_SUCCEED; 1577 1578 present = 0; 1579 swap = 0; 1580 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 1581 rcu_read_lock(); 1582 radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) { 1583 if (iter.index >= start + HPAGE_PMD_NR) 1584 break; 1585 1586 page = radix_tree_deref_slot(slot); 1587 if (radix_tree_deref_retry(page)) { 1588 slot = radix_tree_iter_retry(&iter); 1589 continue; 1590 } 1591 1592 if (radix_tree_exception(page)) { 1593 if (++swap > khugepaged_max_ptes_swap) { 1594 result = SCAN_EXCEED_SWAP_PTE; 1595 break; 1596 } 1597 continue; 1598 } 1599 1600 if (PageTransCompound(page)) { 1601 result = SCAN_PAGE_COMPOUND; 1602 break; 1603 } 1604 1605 node = page_to_nid(page); 1606 if (khugepaged_scan_abort(node)) { 1607 result = SCAN_SCAN_ABORT; 1608 break; 1609 } 1610 khugepaged_node_load[node]++; 1611 1612 if (!PageLRU(page)) { 1613 result = SCAN_PAGE_LRU; 1614 break; 1615 } 1616 1617 if (page_count(page) != 1 + page_mapcount(page)) { 1618 result = SCAN_PAGE_COUNT; 1619 break; 1620 } 1621 1622 /* 1623 * We probably should check if the page is referenced here, but 1624 * nobody would transfer pte_young() to PageReferenced() for us. 1625 * And rmap walk here is just too costly... 1626 */ 1627 1628 present++; 1629 1630 if (need_resched()) { 1631 slot = radix_tree_iter_resume(slot, &iter); 1632 cond_resched_rcu(); 1633 } 1634 } 1635 rcu_read_unlock(); 1636 1637 if (result == SCAN_SUCCEED) { 1638 if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) { 1639 result = SCAN_EXCEED_NONE_PTE; 1640 } else { 1641 node = khugepaged_find_target_node(); 1642 collapse_shmem(mm, mapping, start, hpage, node); 1643 } 1644 } 1645 1646 /* TODO: tracepoints */ 1647 } 1648 #else 1649 static void khugepaged_scan_shmem(struct mm_struct *mm, 1650 struct address_space *mapping, 1651 pgoff_t start, struct page **hpage) 1652 { 1653 BUILD_BUG(); 1654 } 1655 #endif 1656 1657 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 1658 struct page **hpage) 1659 __releases(&khugepaged_mm_lock) 1660 __acquires(&khugepaged_mm_lock) 1661 { 1662 struct mm_slot *mm_slot; 1663 struct mm_struct *mm; 1664 struct vm_area_struct *vma; 1665 int progress = 0; 1666 1667 VM_BUG_ON(!pages); 1668 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 1669 1670 if (khugepaged_scan.mm_slot) 1671 mm_slot = khugepaged_scan.mm_slot; 1672 else { 1673 mm_slot = list_entry(khugepaged_scan.mm_head.next, 1674 struct mm_slot, mm_node); 1675 khugepaged_scan.address = 0; 1676 khugepaged_scan.mm_slot = mm_slot; 1677 } 1678 spin_unlock(&khugepaged_mm_lock); 1679 1680 mm = mm_slot->mm; 1681 /* 1682 * Don't wait for semaphore (to avoid long wait times). Just move to 1683 * the next mm on the list. 1684 */ 1685 vma = NULL; 1686 if (unlikely(!down_read_trylock(&mm->mmap_sem))) 1687 goto breakouterloop_mmap_sem; 1688 if (likely(!khugepaged_test_exit(mm))) 1689 vma = find_vma(mm, khugepaged_scan.address); 1690 1691 progress++; 1692 for (; vma; vma = vma->vm_next) { 1693 unsigned long hstart, hend; 1694 1695 cond_resched(); 1696 if (unlikely(khugepaged_test_exit(mm))) { 1697 progress++; 1698 break; 1699 } 1700 if (!hugepage_vma_check(vma, vma->vm_flags)) { 1701 skip: 1702 progress++; 1703 continue; 1704 } 1705 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1706 hend = vma->vm_end & HPAGE_PMD_MASK; 1707 if (hstart >= hend) 1708 goto skip; 1709 if (khugepaged_scan.address > hend) 1710 goto skip; 1711 if (khugepaged_scan.address < hstart) 1712 khugepaged_scan.address = hstart; 1713 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 1714 1715 while (khugepaged_scan.address < hend) { 1716 int ret; 1717 cond_resched(); 1718 if (unlikely(khugepaged_test_exit(mm))) 1719 goto breakouterloop; 1720 1721 VM_BUG_ON(khugepaged_scan.address < hstart || 1722 khugepaged_scan.address + HPAGE_PMD_SIZE > 1723 hend); 1724 if (shmem_file(vma->vm_file)) { 1725 struct file *file; 1726 pgoff_t pgoff = linear_page_index(vma, 1727 khugepaged_scan.address); 1728 if (!shmem_huge_enabled(vma)) 1729 goto skip; 1730 file = get_file(vma->vm_file); 1731 up_read(&mm->mmap_sem); 1732 ret = 1; 1733 khugepaged_scan_shmem(mm, file->f_mapping, 1734 pgoff, hpage); 1735 fput(file); 1736 } else { 1737 ret = khugepaged_scan_pmd(mm, vma, 1738 khugepaged_scan.address, 1739 hpage); 1740 } 1741 /* move to next address */ 1742 khugepaged_scan.address += HPAGE_PMD_SIZE; 1743 progress += HPAGE_PMD_NR; 1744 if (ret) 1745 /* we released mmap_sem so break loop */ 1746 goto breakouterloop_mmap_sem; 1747 if (progress >= pages) 1748 goto breakouterloop; 1749 } 1750 } 1751 breakouterloop: 1752 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 1753 breakouterloop_mmap_sem: 1754 1755 spin_lock(&khugepaged_mm_lock); 1756 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 1757 /* 1758 * Release the current mm_slot if this mm is about to die, or 1759 * if we scanned all vmas of this mm. 1760 */ 1761 if (khugepaged_test_exit(mm) || !vma) { 1762 /* 1763 * Make sure that if mm_users is reaching zero while 1764 * khugepaged runs here, khugepaged_exit will find 1765 * mm_slot not pointing to the exiting mm. 1766 */ 1767 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 1768 khugepaged_scan.mm_slot = list_entry( 1769 mm_slot->mm_node.next, 1770 struct mm_slot, mm_node); 1771 khugepaged_scan.address = 0; 1772 } else { 1773 khugepaged_scan.mm_slot = NULL; 1774 khugepaged_full_scans++; 1775 } 1776 1777 collect_mm_slot(mm_slot); 1778 } 1779 1780 return progress; 1781 } 1782 1783 static int khugepaged_has_work(void) 1784 { 1785 return !list_empty(&khugepaged_scan.mm_head) && 1786 khugepaged_enabled(); 1787 } 1788 1789 static int khugepaged_wait_event(void) 1790 { 1791 return !list_empty(&khugepaged_scan.mm_head) || 1792 kthread_should_stop(); 1793 } 1794 1795 static void khugepaged_do_scan(void) 1796 { 1797 struct page *hpage = NULL; 1798 unsigned int progress = 0, pass_through_head = 0; 1799 unsigned int pages = khugepaged_pages_to_scan; 1800 bool wait = true; 1801 1802 barrier(); /* write khugepaged_pages_to_scan to local stack */ 1803 1804 while (progress < pages) { 1805 if (!khugepaged_prealloc_page(&hpage, &wait)) 1806 break; 1807 1808 cond_resched(); 1809 1810 if (unlikely(kthread_should_stop() || try_to_freeze())) 1811 break; 1812 1813 spin_lock(&khugepaged_mm_lock); 1814 if (!khugepaged_scan.mm_slot) 1815 pass_through_head++; 1816 if (khugepaged_has_work() && 1817 pass_through_head < 2) 1818 progress += khugepaged_scan_mm_slot(pages - progress, 1819 &hpage); 1820 else 1821 progress = pages; 1822 spin_unlock(&khugepaged_mm_lock); 1823 } 1824 1825 if (!IS_ERR_OR_NULL(hpage)) 1826 put_page(hpage); 1827 } 1828 1829 static bool khugepaged_should_wakeup(void) 1830 { 1831 return kthread_should_stop() || 1832 time_after_eq(jiffies, khugepaged_sleep_expire); 1833 } 1834 1835 static void khugepaged_wait_work(void) 1836 { 1837 if (khugepaged_has_work()) { 1838 const unsigned long scan_sleep_jiffies = 1839 msecs_to_jiffies(khugepaged_scan_sleep_millisecs); 1840 1841 if (!scan_sleep_jiffies) 1842 return; 1843 1844 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies; 1845 wait_event_freezable_timeout(khugepaged_wait, 1846 khugepaged_should_wakeup(), 1847 scan_sleep_jiffies); 1848 return; 1849 } 1850 1851 if (khugepaged_enabled()) 1852 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 1853 } 1854 1855 static int khugepaged(void *none) 1856 { 1857 struct mm_slot *mm_slot; 1858 1859 set_freezable(); 1860 set_user_nice(current, MAX_NICE); 1861 1862 while (!kthread_should_stop()) { 1863 khugepaged_do_scan(); 1864 khugepaged_wait_work(); 1865 } 1866 1867 spin_lock(&khugepaged_mm_lock); 1868 mm_slot = khugepaged_scan.mm_slot; 1869 khugepaged_scan.mm_slot = NULL; 1870 if (mm_slot) 1871 collect_mm_slot(mm_slot); 1872 spin_unlock(&khugepaged_mm_lock); 1873 return 0; 1874 } 1875 1876 static void set_recommended_min_free_kbytes(void) 1877 { 1878 struct zone *zone; 1879 int nr_zones = 0; 1880 unsigned long recommended_min; 1881 1882 for_each_populated_zone(zone) { 1883 /* 1884 * We don't need to worry about fragmentation of 1885 * ZONE_MOVABLE since it only has movable pages. 1886 */ 1887 if (zone_idx(zone) > gfp_zone(GFP_USER)) 1888 continue; 1889 1890 nr_zones++; 1891 } 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