1 /* 2 * Copyright (C) 2009 Red Hat, Inc. 3 * 4 * This work is licensed under the terms of the GNU GPL, version 2. See 5 * the COPYING file in the top-level directory. 6 */ 7 8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 9 10 #include <linux/mm.h> 11 #include <linux/sched.h> 12 #include <linux/highmem.h> 13 #include <linux/hugetlb.h> 14 #include <linux/mmu_notifier.h> 15 #include <linux/rmap.h> 16 #include <linux/swap.h> 17 #include <linux/shrinker.h> 18 #include <linux/mm_inline.h> 19 #include <linux/kthread.h> 20 #include <linux/khugepaged.h> 21 #include <linux/freezer.h> 22 #include <linux/mman.h> 23 #include <linux/pagemap.h> 24 #include <linux/migrate.h> 25 #include <linux/hashtable.h> 26 27 #include <asm/tlb.h> 28 #include <asm/pgalloc.h> 29 #include "internal.h" 30 31 /* 32 * By default transparent hugepage support is disabled in order that avoid 33 * to risk increase the memory footprint of applications without a guaranteed 34 * benefit. When transparent hugepage support is enabled, is for all mappings, 35 * and khugepaged scans all mappings. 36 * Defrag is invoked by khugepaged hugepage allocations and by page faults 37 * for all hugepage allocations. 38 */ 39 unsigned long transparent_hugepage_flags __read_mostly = 40 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS 41 (1<<TRANSPARENT_HUGEPAGE_FLAG)| 42 #endif 43 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE 44 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| 45 #endif 46 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)| 47 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)| 48 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 49 50 /* default scan 8*512 pte (or vmas) every 30 second */ 51 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8; 52 static unsigned int khugepaged_pages_collapsed; 53 static unsigned int khugepaged_full_scans; 54 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 55 /* during fragmentation poll the hugepage allocator once every minute */ 56 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 57 static struct task_struct *khugepaged_thread __read_mostly; 58 static DEFINE_MUTEX(khugepaged_mutex); 59 static DEFINE_SPINLOCK(khugepaged_mm_lock); 60 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 61 /* 62 * default collapse hugepages if there is at least one pte mapped like 63 * it would have happened if the vma was large enough during page 64 * fault. 65 */ 66 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1; 67 68 static int khugepaged(void *none); 69 static int khugepaged_slab_init(void); 70 static void khugepaged_slab_exit(void); 71 72 #define MM_SLOTS_HASH_BITS 10 73 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); 74 75 static struct kmem_cache *mm_slot_cache __read_mostly; 76 77 /** 78 * struct mm_slot - hash lookup from mm to mm_slot 79 * @hash: hash collision list 80 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 81 * @mm: the mm that this information is valid for 82 */ 83 struct mm_slot { 84 struct hlist_node hash; 85 struct list_head mm_node; 86 struct mm_struct *mm; 87 }; 88 89 /** 90 * struct khugepaged_scan - cursor for scanning 91 * @mm_head: the head of the mm list to scan 92 * @mm_slot: the current mm_slot we are scanning 93 * @address: the next address inside that to be scanned 94 * 95 * There is only the one khugepaged_scan instance of this cursor structure. 96 */ 97 struct khugepaged_scan { 98 struct list_head mm_head; 99 struct mm_slot *mm_slot; 100 unsigned long address; 101 }; 102 static struct khugepaged_scan khugepaged_scan = { 103 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 104 }; 105 106 107 static int set_recommended_min_free_kbytes(void) 108 { 109 struct zone *zone; 110 int nr_zones = 0; 111 unsigned long recommended_min; 112 113 for_each_populated_zone(zone) 114 nr_zones++; 115 116 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */ 117 recommended_min = pageblock_nr_pages * nr_zones * 2; 118 119 /* 120 * Make sure that on average at least two pageblocks are almost free 121 * of another type, one for a migratetype to fall back to and a 122 * second to avoid subsequent fallbacks of other types There are 3 123 * MIGRATE_TYPES we care about. 124 */ 125 recommended_min += pageblock_nr_pages * nr_zones * 126 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; 127 128 /* don't ever allow to reserve more than 5% of the lowmem */ 129 recommended_min = min(recommended_min, 130 (unsigned long) nr_free_buffer_pages() / 20); 131 recommended_min <<= (PAGE_SHIFT-10); 132 133 if (recommended_min > min_free_kbytes) { 134 if (user_min_free_kbytes >= 0) 135 pr_info("raising min_free_kbytes from %d to %lu " 136 "to help transparent hugepage allocations\n", 137 min_free_kbytes, recommended_min); 138 139 min_free_kbytes = recommended_min; 140 } 141 setup_per_zone_wmarks(); 142 return 0; 143 } 144 145 static int start_stop_khugepaged(void) 146 { 147 int err = 0; 148 if (khugepaged_enabled()) { 149 if (!khugepaged_thread) 150 khugepaged_thread = kthread_run(khugepaged, NULL, 151 "khugepaged"); 152 if (unlikely(IS_ERR(khugepaged_thread))) { 153 pr_err("khugepaged: kthread_run(khugepaged) failed\n"); 154 err = PTR_ERR(khugepaged_thread); 155 khugepaged_thread = NULL; 156 goto fail; 157 } 158 159 if (!list_empty(&khugepaged_scan.mm_head)) 160 wake_up_interruptible(&khugepaged_wait); 161 162 set_recommended_min_free_kbytes(); 163 } else if (khugepaged_thread) { 164 kthread_stop(khugepaged_thread); 165 khugepaged_thread = NULL; 166 } 167 fail: 168 return err; 169 } 170 171 static atomic_t huge_zero_refcount; 172 struct page *huge_zero_page __read_mostly; 173 174 static inline bool is_huge_zero_pmd(pmd_t pmd) 175 { 176 return is_huge_zero_page(pmd_page(pmd)); 177 } 178 179 static struct page *get_huge_zero_page(void) 180 { 181 struct page *zero_page; 182 retry: 183 if (likely(atomic_inc_not_zero(&huge_zero_refcount))) 184 return READ_ONCE(huge_zero_page); 185 186 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, 187 HPAGE_PMD_ORDER); 188 if (!zero_page) { 189 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); 190 return NULL; 191 } 192 count_vm_event(THP_ZERO_PAGE_ALLOC); 193 preempt_disable(); 194 if (cmpxchg(&huge_zero_page, NULL, zero_page)) { 195 preempt_enable(); 196 __free_pages(zero_page, compound_order(zero_page)); 197 goto retry; 198 } 199 200 /* We take additional reference here. It will be put back by shrinker */ 201 atomic_set(&huge_zero_refcount, 2); 202 preempt_enable(); 203 return READ_ONCE(huge_zero_page); 204 } 205 206 static void put_huge_zero_page(void) 207 { 208 /* 209 * Counter should never go to zero here. Only shrinker can put 210 * last reference. 211 */ 212 BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); 213 } 214 215 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, 216 struct shrink_control *sc) 217 { 218 /* we can free zero page only if last reference remains */ 219 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; 220 } 221 222 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, 223 struct shrink_control *sc) 224 { 225 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { 226 struct page *zero_page = xchg(&huge_zero_page, NULL); 227 BUG_ON(zero_page == NULL); 228 __free_pages(zero_page, compound_order(zero_page)); 229 return HPAGE_PMD_NR; 230 } 231 232 return 0; 233 } 234 235 static struct shrinker huge_zero_page_shrinker = { 236 .count_objects = shrink_huge_zero_page_count, 237 .scan_objects = shrink_huge_zero_page_scan, 238 .seeks = DEFAULT_SEEKS, 239 }; 240 241 #ifdef CONFIG_SYSFS 242 243 static ssize_t double_flag_show(struct kobject *kobj, 244 struct kobj_attribute *attr, char *buf, 245 enum transparent_hugepage_flag enabled, 246 enum transparent_hugepage_flag req_madv) 247 { 248 if (test_bit(enabled, &transparent_hugepage_flags)) { 249 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); 250 return sprintf(buf, "[always] madvise never\n"); 251 } else if (test_bit(req_madv, &transparent_hugepage_flags)) 252 return sprintf(buf, "always [madvise] never\n"); 253 else 254 return sprintf(buf, "always madvise [never]\n"); 255 } 256 static ssize_t double_flag_store(struct kobject *kobj, 257 struct kobj_attribute *attr, 258 const char *buf, size_t count, 259 enum transparent_hugepage_flag enabled, 260 enum transparent_hugepage_flag req_madv) 261 { 262 if (!memcmp("always", buf, 263 min(sizeof("always")-1, count))) { 264 set_bit(enabled, &transparent_hugepage_flags); 265 clear_bit(req_madv, &transparent_hugepage_flags); 266 } else if (!memcmp("madvise", buf, 267 min(sizeof("madvise")-1, count))) { 268 clear_bit(enabled, &transparent_hugepage_flags); 269 set_bit(req_madv, &transparent_hugepage_flags); 270 } else if (!memcmp("never", buf, 271 min(sizeof("never")-1, count))) { 272 clear_bit(enabled, &transparent_hugepage_flags); 273 clear_bit(req_madv, &transparent_hugepage_flags); 274 } else 275 return -EINVAL; 276 277 return count; 278 } 279 280 static ssize_t enabled_show(struct kobject *kobj, 281 struct kobj_attribute *attr, char *buf) 282 { 283 return double_flag_show(kobj, attr, buf, 284 TRANSPARENT_HUGEPAGE_FLAG, 285 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 286 } 287 static ssize_t enabled_store(struct kobject *kobj, 288 struct kobj_attribute *attr, 289 const char *buf, size_t count) 290 { 291 ssize_t ret; 292 293 ret = double_flag_store(kobj, attr, buf, count, 294 TRANSPARENT_HUGEPAGE_FLAG, 295 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 296 297 if (ret > 0) { 298 int err; 299 300 mutex_lock(&khugepaged_mutex); 301 err = start_stop_khugepaged(); 302 mutex_unlock(&khugepaged_mutex); 303 304 if (err) 305 ret = err; 306 } 307 308 return ret; 309 } 310 static struct kobj_attribute enabled_attr = 311 __ATTR(enabled, 0644, enabled_show, enabled_store); 312 313 static ssize_t single_flag_show(struct kobject *kobj, 314 struct kobj_attribute *attr, char *buf, 315 enum transparent_hugepage_flag flag) 316 { 317 return sprintf(buf, "%d\n", 318 !!test_bit(flag, &transparent_hugepage_flags)); 319 } 320 321 static ssize_t single_flag_store(struct kobject *kobj, 322 struct kobj_attribute *attr, 323 const char *buf, size_t count, 324 enum transparent_hugepage_flag flag) 325 { 326 unsigned long value; 327 int ret; 328 329 ret = kstrtoul(buf, 10, &value); 330 if (ret < 0) 331 return ret; 332 if (value > 1) 333 return -EINVAL; 334 335 if (value) 336 set_bit(flag, &transparent_hugepage_flags); 337 else 338 clear_bit(flag, &transparent_hugepage_flags); 339 340 return count; 341 } 342 343 /* 344 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind 345 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of 346 * memory just to allocate one more hugepage. 347 */ 348 static ssize_t defrag_show(struct kobject *kobj, 349 struct kobj_attribute *attr, char *buf) 350 { 351 return double_flag_show(kobj, attr, buf, 352 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 353 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 354 } 355 static ssize_t defrag_store(struct kobject *kobj, 356 struct kobj_attribute *attr, 357 const char *buf, size_t count) 358 { 359 return double_flag_store(kobj, attr, buf, count, 360 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 361 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 362 } 363 static struct kobj_attribute defrag_attr = 364 __ATTR(defrag, 0644, defrag_show, defrag_store); 365 366 static ssize_t use_zero_page_show(struct kobject *kobj, 367 struct kobj_attribute *attr, char *buf) 368 { 369 return single_flag_show(kobj, attr, buf, 370 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 371 } 372 static ssize_t use_zero_page_store(struct kobject *kobj, 373 struct kobj_attribute *attr, const char *buf, size_t count) 374 { 375 return single_flag_store(kobj, attr, buf, count, 376 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 377 } 378 static struct kobj_attribute use_zero_page_attr = 379 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); 380 #ifdef CONFIG_DEBUG_VM 381 static ssize_t debug_cow_show(struct kobject *kobj, 382 struct kobj_attribute *attr, char *buf) 383 { 384 return single_flag_show(kobj, attr, buf, 385 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 386 } 387 static ssize_t debug_cow_store(struct kobject *kobj, 388 struct kobj_attribute *attr, 389 const char *buf, size_t count) 390 { 391 return single_flag_store(kobj, attr, buf, count, 392 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 393 } 394 static struct kobj_attribute debug_cow_attr = 395 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 396 #endif /* CONFIG_DEBUG_VM */ 397 398 static struct attribute *hugepage_attr[] = { 399 &enabled_attr.attr, 400 &defrag_attr.attr, 401 &use_zero_page_attr.attr, 402 #ifdef CONFIG_DEBUG_VM 403 &debug_cow_attr.attr, 404 #endif 405 NULL, 406 }; 407 408 static struct attribute_group hugepage_attr_group = { 409 .attrs = hugepage_attr, 410 }; 411 412 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 413 struct kobj_attribute *attr, 414 char *buf) 415 { 416 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 417 } 418 419 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 420 struct kobj_attribute *attr, 421 const char *buf, size_t count) 422 { 423 unsigned long msecs; 424 int err; 425 426 err = kstrtoul(buf, 10, &msecs); 427 if (err || msecs > UINT_MAX) 428 return -EINVAL; 429 430 khugepaged_scan_sleep_millisecs = msecs; 431 wake_up_interruptible(&khugepaged_wait); 432 433 return count; 434 } 435 static struct kobj_attribute scan_sleep_millisecs_attr = 436 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 437 scan_sleep_millisecs_store); 438 439 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 440 struct kobj_attribute *attr, 441 char *buf) 442 { 443 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 444 } 445 446 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 447 struct kobj_attribute *attr, 448 const char *buf, size_t count) 449 { 450 unsigned long msecs; 451 int err; 452 453 err = kstrtoul(buf, 10, &msecs); 454 if (err || msecs > UINT_MAX) 455 return -EINVAL; 456 457 khugepaged_alloc_sleep_millisecs = msecs; 458 wake_up_interruptible(&khugepaged_wait); 459 460 return count; 461 } 462 static struct kobj_attribute alloc_sleep_millisecs_attr = 463 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 464 alloc_sleep_millisecs_store); 465 466 static ssize_t pages_to_scan_show(struct kobject *kobj, 467 struct kobj_attribute *attr, 468 char *buf) 469 { 470 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 471 } 472 static ssize_t pages_to_scan_store(struct kobject *kobj, 473 struct kobj_attribute *attr, 474 const char *buf, size_t count) 475 { 476 int err; 477 unsigned long pages; 478 479 err = kstrtoul(buf, 10, &pages); 480 if (err || !pages || pages > UINT_MAX) 481 return -EINVAL; 482 483 khugepaged_pages_to_scan = pages; 484 485 return count; 486 } 487 static struct kobj_attribute pages_to_scan_attr = 488 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 489 pages_to_scan_store); 490 491 static ssize_t pages_collapsed_show(struct kobject *kobj, 492 struct kobj_attribute *attr, 493 char *buf) 494 { 495 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 496 } 497 static struct kobj_attribute pages_collapsed_attr = 498 __ATTR_RO(pages_collapsed); 499 500 static ssize_t full_scans_show(struct kobject *kobj, 501 struct kobj_attribute *attr, 502 char *buf) 503 { 504 return sprintf(buf, "%u\n", khugepaged_full_scans); 505 } 506 static struct kobj_attribute full_scans_attr = 507 __ATTR_RO(full_scans); 508 509 static ssize_t khugepaged_defrag_show(struct kobject *kobj, 510 struct kobj_attribute *attr, char *buf) 511 { 512 return single_flag_show(kobj, attr, buf, 513 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 514 } 515 static ssize_t khugepaged_defrag_store(struct kobject *kobj, 516 struct kobj_attribute *attr, 517 const char *buf, size_t count) 518 { 519 return single_flag_store(kobj, attr, buf, count, 520 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 521 } 522 static struct kobj_attribute khugepaged_defrag_attr = 523 __ATTR(defrag, 0644, khugepaged_defrag_show, 524 khugepaged_defrag_store); 525 526 /* 527 * max_ptes_none controls if khugepaged should collapse hugepages over 528 * any unmapped ptes in turn potentially increasing the memory 529 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 530 * reduce the available free memory in the system as it 531 * runs. Increasing max_ptes_none will instead potentially reduce the 532 * free memory in the system during the khugepaged scan. 533 */ 534 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 535 struct kobj_attribute *attr, 536 char *buf) 537 { 538 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 539 } 540 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 541 struct kobj_attribute *attr, 542 const char *buf, size_t count) 543 { 544 int err; 545 unsigned long max_ptes_none; 546 547 err = kstrtoul(buf, 10, &max_ptes_none); 548 if (err || max_ptes_none > HPAGE_PMD_NR-1) 549 return -EINVAL; 550 551 khugepaged_max_ptes_none = max_ptes_none; 552 553 return count; 554 } 555 static struct kobj_attribute khugepaged_max_ptes_none_attr = 556 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 557 khugepaged_max_ptes_none_store); 558 559 static struct attribute *khugepaged_attr[] = { 560 &khugepaged_defrag_attr.attr, 561 &khugepaged_max_ptes_none_attr.attr, 562 &pages_to_scan_attr.attr, 563 &pages_collapsed_attr.attr, 564 &full_scans_attr.attr, 565 &scan_sleep_millisecs_attr.attr, 566 &alloc_sleep_millisecs_attr.attr, 567 NULL, 568 }; 569 570 static struct attribute_group khugepaged_attr_group = { 571 .attrs = khugepaged_attr, 572 .name = "khugepaged", 573 }; 574 575 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) 576 { 577 int err; 578 579 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 580 if (unlikely(!*hugepage_kobj)) { 581 pr_err("failed to create transparent hugepage kobject\n"); 582 return -ENOMEM; 583 } 584 585 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); 586 if (err) { 587 pr_err("failed to register transparent hugepage group\n"); 588 goto delete_obj; 589 } 590 591 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); 592 if (err) { 593 pr_err("failed to register transparent hugepage group\n"); 594 goto remove_hp_group; 595 } 596 597 return 0; 598 599 remove_hp_group: 600 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); 601 delete_obj: 602 kobject_put(*hugepage_kobj); 603 return err; 604 } 605 606 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) 607 { 608 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); 609 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); 610 kobject_put(hugepage_kobj); 611 } 612 #else 613 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) 614 { 615 return 0; 616 } 617 618 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) 619 { 620 } 621 #endif /* CONFIG_SYSFS */ 622 623 static int __init hugepage_init(void) 624 { 625 int err; 626 struct kobject *hugepage_kobj; 627 628 if (!has_transparent_hugepage()) { 629 transparent_hugepage_flags = 0; 630 return -EINVAL; 631 } 632 633 err = hugepage_init_sysfs(&hugepage_kobj); 634 if (err) 635 goto err_sysfs; 636 637 err = khugepaged_slab_init(); 638 if (err) 639 goto err_slab; 640 641 err = register_shrinker(&huge_zero_page_shrinker); 642 if (err) 643 goto err_hzp_shrinker; 644 645 /* 646 * By default disable transparent hugepages on smaller systems, 647 * where the extra memory used could hurt more than TLB overhead 648 * is likely to save. The admin can still enable it through /sys. 649 */ 650 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) { 651 transparent_hugepage_flags = 0; 652 return 0; 653 } 654 655 err = start_stop_khugepaged(); 656 if (err) 657 goto err_khugepaged; 658 659 return 0; 660 err_khugepaged: 661 unregister_shrinker(&huge_zero_page_shrinker); 662 err_hzp_shrinker: 663 khugepaged_slab_exit(); 664 err_slab: 665 hugepage_exit_sysfs(hugepage_kobj); 666 err_sysfs: 667 return err; 668 } 669 subsys_initcall(hugepage_init); 670 671 static int __init setup_transparent_hugepage(char *str) 672 { 673 int ret = 0; 674 if (!str) 675 goto out; 676 if (!strcmp(str, "always")) { 677 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 678 &transparent_hugepage_flags); 679 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 680 &transparent_hugepage_flags); 681 ret = 1; 682 } else if (!strcmp(str, "madvise")) { 683 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 684 &transparent_hugepage_flags); 685 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 686 &transparent_hugepage_flags); 687 ret = 1; 688 } else if (!strcmp(str, "never")) { 689 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 690 &transparent_hugepage_flags); 691 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 692 &transparent_hugepage_flags); 693 ret = 1; 694 } 695 out: 696 if (!ret) 697 pr_warn("transparent_hugepage= cannot parse, ignored\n"); 698 return ret; 699 } 700 __setup("transparent_hugepage=", setup_transparent_hugepage); 701 702 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 703 { 704 if (likely(vma->vm_flags & VM_WRITE)) 705 pmd = pmd_mkwrite(pmd); 706 return pmd; 707 } 708 709 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot) 710 { 711 pmd_t entry; 712 entry = mk_pmd(page, prot); 713 entry = pmd_mkhuge(entry); 714 return entry; 715 } 716 717 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, 718 struct vm_area_struct *vma, 719 unsigned long haddr, pmd_t *pmd, 720 struct page *page, gfp_t gfp) 721 { 722 struct mem_cgroup *memcg; 723 pgtable_t pgtable; 724 spinlock_t *ptl; 725 726 VM_BUG_ON_PAGE(!PageCompound(page), page); 727 728 if (mem_cgroup_try_charge(page, mm, gfp, &memcg)) 729 return VM_FAULT_OOM; 730 731 pgtable = pte_alloc_one(mm, haddr); 732 if (unlikely(!pgtable)) { 733 mem_cgroup_cancel_charge(page, memcg); 734 return VM_FAULT_OOM; 735 } 736 737 clear_huge_page(page, haddr, HPAGE_PMD_NR); 738 /* 739 * The memory barrier inside __SetPageUptodate makes sure that 740 * clear_huge_page writes become visible before the set_pmd_at() 741 * write. 742 */ 743 __SetPageUptodate(page); 744 745 ptl = pmd_lock(mm, pmd); 746 if (unlikely(!pmd_none(*pmd))) { 747 spin_unlock(ptl); 748 mem_cgroup_cancel_charge(page, memcg); 749 put_page(page); 750 pte_free(mm, pgtable); 751 } else { 752 pmd_t entry; 753 entry = mk_huge_pmd(page, vma->vm_page_prot); 754 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 755 page_add_new_anon_rmap(page, vma, haddr); 756 mem_cgroup_commit_charge(page, memcg, false); 757 lru_cache_add_active_or_unevictable(page, vma); 758 pgtable_trans_huge_deposit(mm, pmd, pgtable); 759 set_pmd_at(mm, haddr, pmd, entry); 760 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 761 atomic_long_inc(&mm->nr_ptes); 762 spin_unlock(ptl); 763 } 764 765 return 0; 766 } 767 768 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) 769 { 770 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; 771 } 772 773 /* Caller must hold page table lock. */ 774 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, 775 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, 776 struct page *zero_page) 777 { 778 pmd_t entry; 779 if (!pmd_none(*pmd)) 780 return false; 781 entry = mk_pmd(zero_page, vma->vm_page_prot); 782 entry = pmd_mkhuge(entry); 783 pgtable_trans_huge_deposit(mm, pmd, pgtable); 784 set_pmd_at(mm, haddr, pmd, entry); 785 atomic_long_inc(&mm->nr_ptes); 786 return true; 787 } 788 789 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 790 unsigned long address, pmd_t *pmd, 791 unsigned int flags) 792 { 793 gfp_t gfp; 794 struct page *page; 795 unsigned long haddr = address & HPAGE_PMD_MASK; 796 797 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end) 798 return VM_FAULT_FALLBACK; 799 if (unlikely(anon_vma_prepare(vma))) 800 return VM_FAULT_OOM; 801 if (unlikely(khugepaged_enter(vma, vma->vm_flags))) 802 return VM_FAULT_OOM; 803 if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) && 804 transparent_hugepage_use_zero_page()) { 805 spinlock_t *ptl; 806 pgtable_t pgtable; 807 struct page *zero_page; 808 bool set; 809 pgtable = pte_alloc_one(mm, haddr); 810 if (unlikely(!pgtable)) 811 return VM_FAULT_OOM; 812 zero_page = get_huge_zero_page(); 813 if (unlikely(!zero_page)) { 814 pte_free(mm, pgtable); 815 count_vm_event(THP_FAULT_FALLBACK); 816 return VM_FAULT_FALLBACK; 817 } 818 ptl = pmd_lock(mm, pmd); 819 set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, 820 zero_page); 821 spin_unlock(ptl); 822 if (!set) { 823 pte_free(mm, pgtable); 824 put_huge_zero_page(); 825 } 826 return 0; 827 } 828 gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0); 829 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER); 830 if (unlikely(!page)) { 831 count_vm_event(THP_FAULT_FALLBACK); 832 return VM_FAULT_FALLBACK; 833 } 834 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page, gfp))) { 835 put_page(page); 836 count_vm_event(THP_FAULT_FALLBACK); 837 return VM_FAULT_FALLBACK; 838 } 839 840 count_vm_event(THP_FAULT_ALLOC); 841 return 0; 842 } 843 844 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 845 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 846 struct vm_area_struct *vma) 847 { 848 spinlock_t *dst_ptl, *src_ptl; 849 struct page *src_page; 850 pmd_t pmd; 851 pgtable_t pgtable; 852 int ret; 853 854 ret = -ENOMEM; 855 pgtable = pte_alloc_one(dst_mm, addr); 856 if (unlikely(!pgtable)) 857 goto out; 858 859 dst_ptl = pmd_lock(dst_mm, dst_pmd); 860 src_ptl = pmd_lockptr(src_mm, src_pmd); 861 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); 862 863 ret = -EAGAIN; 864 pmd = *src_pmd; 865 if (unlikely(!pmd_trans_huge(pmd))) { 866 pte_free(dst_mm, pgtable); 867 goto out_unlock; 868 } 869 /* 870 * When page table lock is held, the huge zero pmd should not be 871 * under splitting since we don't split the page itself, only pmd to 872 * a page table. 873 */ 874 if (is_huge_zero_pmd(pmd)) { 875 struct page *zero_page; 876 bool set; 877 /* 878 * get_huge_zero_page() will never allocate a new page here, 879 * since we already have a zero page to copy. It just takes a 880 * reference. 881 */ 882 zero_page = get_huge_zero_page(); 883 set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, 884 zero_page); 885 BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */ 886 ret = 0; 887 goto out_unlock; 888 } 889 890 if (unlikely(pmd_trans_splitting(pmd))) { 891 /* split huge page running from under us */ 892 spin_unlock(src_ptl); 893 spin_unlock(dst_ptl); 894 pte_free(dst_mm, pgtable); 895 896 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ 897 goto out; 898 } 899 src_page = pmd_page(pmd); 900 VM_BUG_ON_PAGE(!PageHead(src_page), src_page); 901 get_page(src_page); 902 page_dup_rmap(src_page); 903 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 904 905 pmdp_set_wrprotect(src_mm, addr, src_pmd); 906 pmd = pmd_mkold(pmd_wrprotect(pmd)); 907 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); 908 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 909 atomic_long_inc(&dst_mm->nr_ptes); 910 911 ret = 0; 912 out_unlock: 913 spin_unlock(src_ptl); 914 spin_unlock(dst_ptl); 915 out: 916 return ret; 917 } 918 919 void huge_pmd_set_accessed(struct mm_struct *mm, 920 struct vm_area_struct *vma, 921 unsigned long address, 922 pmd_t *pmd, pmd_t orig_pmd, 923 int dirty) 924 { 925 spinlock_t *ptl; 926 pmd_t entry; 927 unsigned long haddr; 928 929 ptl = pmd_lock(mm, pmd); 930 if (unlikely(!pmd_same(*pmd, orig_pmd))) 931 goto unlock; 932 933 entry = pmd_mkyoung(orig_pmd); 934 haddr = address & HPAGE_PMD_MASK; 935 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty)) 936 update_mmu_cache_pmd(vma, address, pmd); 937 938 unlock: 939 spin_unlock(ptl); 940 } 941 942 /* 943 * Save CONFIG_DEBUG_PAGEALLOC from faulting falsely on tail pages 944 * during copy_user_huge_page()'s copy_page_rep(): in the case when 945 * the source page gets split and a tail freed before copy completes. 946 * Called under pmd_lock of checked pmd, so safe from splitting itself. 947 */ 948 static void get_user_huge_page(struct page *page) 949 { 950 if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) { 951 struct page *endpage = page + HPAGE_PMD_NR; 952 953 atomic_add(HPAGE_PMD_NR, &page->_count); 954 while (++page < endpage) 955 get_huge_page_tail(page); 956 } else { 957 get_page(page); 958 } 959 } 960 961 static void put_user_huge_page(struct page *page) 962 { 963 if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) { 964 struct page *endpage = page + HPAGE_PMD_NR; 965 966 while (page < endpage) 967 put_page(page++); 968 } else { 969 put_page(page); 970 } 971 } 972 973 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, 974 struct vm_area_struct *vma, 975 unsigned long address, 976 pmd_t *pmd, pmd_t orig_pmd, 977 struct page *page, 978 unsigned long haddr) 979 { 980 struct mem_cgroup *memcg; 981 spinlock_t *ptl; 982 pgtable_t pgtable; 983 pmd_t _pmd; 984 int ret = 0, i; 985 struct page **pages; 986 unsigned long mmun_start; /* For mmu_notifiers */ 987 unsigned long mmun_end; /* For mmu_notifiers */ 988 989 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 990 GFP_KERNEL); 991 if (unlikely(!pages)) { 992 ret |= VM_FAULT_OOM; 993 goto out; 994 } 995 996 for (i = 0; i < HPAGE_PMD_NR; i++) { 997 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | 998 __GFP_OTHER_NODE, 999 vma, address, page_to_nid(page)); 1000 if (unlikely(!pages[i] || 1001 mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL, 1002 &memcg))) { 1003 if (pages[i]) 1004 put_page(pages[i]); 1005 while (--i >= 0) { 1006 memcg = (void *)page_private(pages[i]); 1007 set_page_private(pages[i], 0); 1008 mem_cgroup_cancel_charge(pages[i], memcg); 1009 put_page(pages[i]); 1010 } 1011 kfree(pages); 1012 ret |= VM_FAULT_OOM; 1013 goto out; 1014 } 1015 set_page_private(pages[i], (unsigned long)memcg); 1016 } 1017 1018 for (i = 0; i < HPAGE_PMD_NR; i++) { 1019 copy_user_highpage(pages[i], page + i, 1020 haddr + PAGE_SIZE * i, vma); 1021 __SetPageUptodate(pages[i]); 1022 cond_resched(); 1023 } 1024 1025 mmun_start = haddr; 1026 mmun_end = haddr + HPAGE_PMD_SIZE; 1027 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1028 1029 ptl = pmd_lock(mm, pmd); 1030 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1031 goto out_free_pages; 1032 VM_BUG_ON_PAGE(!PageHead(page), page); 1033 1034 pmdp_huge_clear_flush_notify(vma, haddr, pmd); 1035 /* leave pmd empty until pte is filled */ 1036 1037 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1038 pmd_populate(mm, &_pmd, pgtable); 1039 1040 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1041 pte_t *pte, entry; 1042 entry = mk_pte(pages[i], vma->vm_page_prot); 1043 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1044 memcg = (void *)page_private(pages[i]); 1045 set_page_private(pages[i], 0); 1046 page_add_new_anon_rmap(pages[i], vma, haddr); 1047 mem_cgroup_commit_charge(pages[i], memcg, false); 1048 lru_cache_add_active_or_unevictable(pages[i], vma); 1049 pte = pte_offset_map(&_pmd, haddr); 1050 VM_BUG_ON(!pte_none(*pte)); 1051 set_pte_at(mm, haddr, pte, entry); 1052 pte_unmap(pte); 1053 } 1054 kfree(pages); 1055 1056 smp_wmb(); /* make pte visible before pmd */ 1057 pmd_populate(mm, pmd, pgtable); 1058 page_remove_rmap(page); 1059 spin_unlock(ptl); 1060 1061 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1062 1063 ret |= VM_FAULT_WRITE; 1064 put_page(page); 1065 1066 out: 1067 return ret; 1068 1069 out_free_pages: 1070 spin_unlock(ptl); 1071 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1072 for (i = 0; i < HPAGE_PMD_NR; i++) { 1073 memcg = (void *)page_private(pages[i]); 1074 set_page_private(pages[i], 0); 1075 mem_cgroup_cancel_charge(pages[i], memcg); 1076 put_page(pages[i]); 1077 } 1078 kfree(pages); 1079 goto out; 1080 } 1081 1082 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 1083 unsigned long address, pmd_t *pmd, pmd_t orig_pmd) 1084 { 1085 spinlock_t *ptl; 1086 int ret = 0; 1087 struct page *page = NULL, *new_page; 1088 struct mem_cgroup *memcg; 1089 unsigned long haddr; 1090 unsigned long mmun_start; /* For mmu_notifiers */ 1091 unsigned long mmun_end; /* For mmu_notifiers */ 1092 gfp_t huge_gfp; /* for allocation and charge */ 1093 1094 ptl = pmd_lockptr(mm, pmd); 1095 VM_BUG_ON_VMA(!vma->anon_vma, vma); 1096 haddr = address & HPAGE_PMD_MASK; 1097 if (is_huge_zero_pmd(orig_pmd)) 1098 goto alloc; 1099 spin_lock(ptl); 1100 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1101 goto out_unlock; 1102 1103 page = pmd_page(orig_pmd); 1104 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); 1105 if (page_mapcount(page) == 1) { 1106 pmd_t entry; 1107 entry = pmd_mkyoung(orig_pmd); 1108 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1109 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 1110 update_mmu_cache_pmd(vma, address, pmd); 1111 ret |= VM_FAULT_WRITE; 1112 goto out_unlock; 1113 } 1114 get_user_huge_page(page); 1115 spin_unlock(ptl); 1116 alloc: 1117 if (transparent_hugepage_enabled(vma) && 1118 !transparent_hugepage_debug_cow()) { 1119 huge_gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0); 1120 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER); 1121 } else 1122 new_page = NULL; 1123 1124 if (unlikely(!new_page)) { 1125 if (!page) { 1126 split_huge_page_pmd(vma, address, pmd); 1127 ret |= VM_FAULT_FALLBACK; 1128 } else { 1129 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 1130 pmd, orig_pmd, page, haddr); 1131 if (ret & VM_FAULT_OOM) { 1132 split_huge_page(page); 1133 ret |= VM_FAULT_FALLBACK; 1134 } 1135 put_user_huge_page(page); 1136 } 1137 count_vm_event(THP_FAULT_FALLBACK); 1138 goto out; 1139 } 1140 1141 if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg))) { 1142 put_page(new_page); 1143 if (page) { 1144 split_huge_page(page); 1145 put_user_huge_page(page); 1146 } else 1147 split_huge_page_pmd(vma, address, pmd); 1148 ret |= VM_FAULT_FALLBACK; 1149 count_vm_event(THP_FAULT_FALLBACK); 1150 goto out; 1151 } 1152 1153 count_vm_event(THP_FAULT_ALLOC); 1154 1155 if (!page) 1156 clear_huge_page(new_page, haddr, HPAGE_PMD_NR); 1157 else 1158 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 1159 __SetPageUptodate(new_page); 1160 1161 mmun_start = haddr; 1162 mmun_end = haddr + HPAGE_PMD_SIZE; 1163 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1164 1165 spin_lock(ptl); 1166 if (page) 1167 put_user_huge_page(page); 1168 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 1169 spin_unlock(ptl); 1170 mem_cgroup_cancel_charge(new_page, memcg); 1171 put_page(new_page); 1172 goto out_mn; 1173 } else { 1174 pmd_t entry; 1175 entry = mk_huge_pmd(new_page, vma->vm_page_prot); 1176 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1177 pmdp_huge_clear_flush_notify(vma, haddr, pmd); 1178 page_add_new_anon_rmap(new_page, vma, haddr); 1179 mem_cgroup_commit_charge(new_page, memcg, false); 1180 lru_cache_add_active_or_unevictable(new_page, vma); 1181 set_pmd_at(mm, haddr, pmd, entry); 1182 update_mmu_cache_pmd(vma, address, pmd); 1183 if (!page) { 1184 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 1185 put_huge_zero_page(); 1186 } else { 1187 VM_BUG_ON_PAGE(!PageHead(page), page); 1188 page_remove_rmap(page); 1189 put_page(page); 1190 } 1191 ret |= VM_FAULT_WRITE; 1192 } 1193 spin_unlock(ptl); 1194 out_mn: 1195 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1196 out: 1197 return ret; 1198 out_unlock: 1199 spin_unlock(ptl); 1200 return ret; 1201 } 1202 1203 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1204 unsigned long addr, 1205 pmd_t *pmd, 1206 unsigned int flags) 1207 { 1208 struct mm_struct *mm = vma->vm_mm; 1209 struct page *page = NULL; 1210 1211 assert_spin_locked(pmd_lockptr(mm, pmd)); 1212 1213 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 1214 goto out; 1215 1216 /* Avoid dumping huge zero page */ 1217 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) 1218 return ERR_PTR(-EFAULT); 1219 1220 /* Full NUMA hinting faults to serialise migration in fault paths */ 1221 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) 1222 goto out; 1223 1224 page = pmd_page(*pmd); 1225 VM_BUG_ON_PAGE(!PageHead(page), page); 1226 if (flags & FOLL_TOUCH) { 1227 pmd_t _pmd; 1228 /* 1229 * We should set the dirty bit only for FOLL_WRITE but 1230 * for now the dirty bit in the pmd is meaningless. 1231 * And if the dirty bit will become meaningful and 1232 * we'll only set it with FOLL_WRITE, an atomic 1233 * set_bit will be required on the pmd to set the 1234 * young bit, instead of the current set_pmd_at. 1235 */ 1236 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 1237 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, 1238 pmd, _pmd, 1)) 1239 update_mmu_cache_pmd(vma, addr, pmd); 1240 } 1241 if ((flags & FOLL_POPULATE) && (vma->vm_flags & VM_LOCKED)) { 1242 if (page->mapping && trylock_page(page)) { 1243 lru_add_drain(); 1244 if (page->mapping) 1245 mlock_vma_page(page); 1246 unlock_page(page); 1247 } 1248 } 1249 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1250 VM_BUG_ON_PAGE(!PageCompound(page), page); 1251 if (flags & FOLL_GET) 1252 get_page_foll(page); 1253 1254 out: 1255 return page; 1256 } 1257 1258 /* NUMA hinting page fault entry point for trans huge pmds */ 1259 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, 1260 unsigned long addr, pmd_t pmd, pmd_t *pmdp) 1261 { 1262 spinlock_t *ptl; 1263 struct anon_vma *anon_vma = NULL; 1264 struct page *page; 1265 unsigned long haddr = addr & HPAGE_PMD_MASK; 1266 int page_nid = -1, this_nid = numa_node_id(); 1267 int target_nid, last_cpupid = -1; 1268 bool page_locked; 1269 bool migrated = false; 1270 bool was_writable; 1271 int flags = 0; 1272 1273 /* A PROT_NONE fault should not end up here */ 1274 BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))); 1275 1276 ptl = pmd_lock(mm, pmdp); 1277 if (unlikely(!pmd_same(pmd, *pmdp))) 1278 goto out_unlock; 1279 1280 /* 1281 * If there are potential migrations, wait for completion and retry 1282 * without disrupting NUMA hinting information. Do not relock and 1283 * check_same as the page may no longer be mapped. 1284 */ 1285 if (unlikely(pmd_trans_migrating(*pmdp))) { 1286 page = pmd_page(*pmdp); 1287 spin_unlock(ptl); 1288 wait_on_page_locked(page); 1289 goto out; 1290 } 1291 1292 page = pmd_page(pmd); 1293 BUG_ON(is_huge_zero_page(page)); 1294 page_nid = page_to_nid(page); 1295 last_cpupid = page_cpupid_last(page); 1296 count_vm_numa_event(NUMA_HINT_FAULTS); 1297 if (page_nid == this_nid) { 1298 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); 1299 flags |= TNF_FAULT_LOCAL; 1300 } 1301 1302 /* See similar comment in do_numa_page for explanation */ 1303 if (!(vma->vm_flags & VM_WRITE)) 1304 flags |= TNF_NO_GROUP; 1305 1306 /* 1307 * Acquire the page lock to serialise THP migrations but avoid dropping 1308 * page_table_lock if at all possible 1309 */ 1310 page_locked = trylock_page(page); 1311 target_nid = mpol_misplaced(page, vma, haddr); 1312 if (target_nid == -1) { 1313 /* If the page was locked, there are no parallel migrations */ 1314 if (page_locked) 1315 goto clear_pmdnuma; 1316 } 1317 1318 /* Migration could have started since the pmd_trans_migrating check */ 1319 if (!page_locked) { 1320 spin_unlock(ptl); 1321 wait_on_page_locked(page); 1322 page_nid = -1; 1323 goto out; 1324 } 1325 1326 /* 1327 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma 1328 * to serialises splits 1329 */ 1330 get_page(page); 1331 spin_unlock(ptl); 1332 anon_vma = page_lock_anon_vma_read(page); 1333 1334 /* Confirm the PMD did not change while page_table_lock was released */ 1335 spin_lock(ptl); 1336 if (unlikely(!pmd_same(pmd, *pmdp))) { 1337 unlock_page(page); 1338 put_page(page); 1339 page_nid = -1; 1340 goto out_unlock; 1341 } 1342 1343 /* Bail if we fail to protect against THP splits for any reason */ 1344 if (unlikely(!anon_vma)) { 1345 put_page(page); 1346 page_nid = -1; 1347 goto clear_pmdnuma; 1348 } 1349 1350 /* 1351 * Migrate the THP to the requested node, returns with page unlocked 1352 * and access rights restored. 1353 */ 1354 spin_unlock(ptl); 1355 migrated = migrate_misplaced_transhuge_page(mm, vma, 1356 pmdp, pmd, addr, page, target_nid); 1357 if (migrated) { 1358 flags |= TNF_MIGRATED; 1359 page_nid = target_nid; 1360 } else 1361 flags |= TNF_MIGRATE_FAIL; 1362 1363 goto out; 1364 clear_pmdnuma: 1365 BUG_ON(!PageLocked(page)); 1366 was_writable = pmd_write(pmd); 1367 pmd = pmd_modify(pmd, vma->vm_page_prot); 1368 pmd = pmd_mkyoung(pmd); 1369 if (was_writable) 1370 pmd = pmd_mkwrite(pmd); 1371 set_pmd_at(mm, haddr, pmdp, pmd); 1372 update_mmu_cache_pmd(vma, addr, pmdp); 1373 unlock_page(page); 1374 out_unlock: 1375 spin_unlock(ptl); 1376 1377 out: 1378 if (anon_vma) 1379 page_unlock_anon_vma_read(anon_vma); 1380 1381 if (page_nid != -1) 1382 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags); 1383 1384 return 0; 1385 } 1386 1387 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1388 pmd_t *pmd, unsigned long addr) 1389 { 1390 spinlock_t *ptl; 1391 int ret = 0; 1392 1393 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { 1394 struct page *page; 1395 pgtable_t pgtable; 1396 pmd_t orig_pmd; 1397 /* 1398 * For architectures like ppc64 we look at deposited pgtable 1399 * when calling pmdp_huge_get_and_clear. So do the 1400 * pgtable_trans_huge_withdraw after finishing pmdp related 1401 * operations. 1402 */ 1403 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, 1404 tlb->fullmm); 1405 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1406 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd); 1407 if (is_huge_zero_pmd(orig_pmd)) { 1408 atomic_long_dec(&tlb->mm->nr_ptes); 1409 spin_unlock(ptl); 1410 put_huge_zero_page(); 1411 } else { 1412 page = pmd_page(orig_pmd); 1413 page_remove_rmap(page); 1414 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); 1415 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1416 VM_BUG_ON_PAGE(!PageHead(page), page); 1417 atomic_long_dec(&tlb->mm->nr_ptes); 1418 spin_unlock(ptl); 1419 tlb_remove_page(tlb, page); 1420 } 1421 pte_free(tlb->mm, pgtable); 1422 ret = 1; 1423 } 1424 return ret; 1425 } 1426 1427 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, 1428 unsigned long old_addr, 1429 unsigned long new_addr, unsigned long old_end, 1430 pmd_t *old_pmd, pmd_t *new_pmd) 1431 { 1432 spinlock_t *old_ptl, *new_ptl; 1433 int ret = 0; 1434 pmd_t pmd; 1435 1436 struct mm_struct *mm = vma->vm_mm; 1437 1438 if ((old_addr & ~HPAGE_PMD_MASK) || 1439 (new_addr & ~HPAGE_PMD_MASK) || 1440 old_end - old_addr < HPAGE_PMD_SIZE || 1441 (new_vma->vm_flags & VM_NOHUGEPAGE)) 1442 goto out; 1443 1444 /* 1445 * The destination pmd shouldn't be established, free_pgtables() 1446 * should have release it. 1447 */ 1448 if (WARN_ON(!pmd_none(*new_pmd))) { 1449 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1450 goto out; 1451 } 1452 1453 /* 1454 * We don't have to worry about the ordering of src and dst 1455 * ptlocks because exclusive mmap_sem prevents deadlock. 1456 */ 1457 ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl); 1458 if (ret == 1) { 1459 new_ptl = pmd_lockptr(mm, new_pmd); 1460 if (new_ptl != old_ptl) 1461 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 1462 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd); 1463 VM_BUG_ON(!pmd_none(*new_pmd)); 1464 1465 if (pmd_move_must_withdraw(new_ptl, old_ptl)) { 1466 pgtable_t pgtable; 1467 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); 1468 pgtable_trans_huge_deposit(mm, new_pmd, pgtable); 1469 } 1470 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd)); 1471 if (new_ptl != old_ptl) 1472 spin_unlock(new_ptl); 1473 spin_unlock(old_ptl); 1474 } 1475 out: 1476 return ret; 1477 } 1478 1479 /* 1480 * Returns 1481 * - 0 if PMD could not be locked 1482 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary 1483 * - HPAGE_PMD_NR is protections changed and TLB flush necessary 1484 */ 1485 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1486 unsigned long addr, pgprot_t newprot, int prot_numa) 1487 { 1488 struct mm_struct *mm = vma->vm_mm; 1489 spinlock_t *ptl; 1490 int ret = 0; 1491 1492 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { 1493 pmd_t entry; 1494 bool preserve_write = prot_numa && pmd_write(*pmd); 1495 ret = 1; 1496 1497 /* 1498 * Avoid trapping faults against the zero page. The read-only 1499 * data is likely to be read-cached on the local CPU and 1500 * local/remote hits to the zero page are not interesting. 1501 */ 1502 if (prot_numa && is_huge_zero_pmd(*pmd)) { 1503 spin_unlock(ptl); 1504 return ret; 1505 } 1506 1507 if (!prot_numa || !pmd_protnone(*pmd)) { 1508 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd); 1509 entry = pmd_modify(entry, newprot); 1510 if (preserve_write) 1511 entry = pmd_mkwrite(entry); 1512 ret = HPAGE_PMD_NR; 1513 set_pmd_at(mm, addr, pmd, entry); 1514 BUG_ON(!preserve_write && pmd_write(entry)); 1515 } 1516 spin_unlock(ptl); 1517 } 1518 1519 return ret; 1520 } 1521 1522 /* 1523 * Returns 1 if a given pmd maps a stable (not under splitting) thp. 1524 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise. 1525 * 1526 * Note that if it returns 1, this routine returns without unlocking page 1527 * table locks. So callers must unlock them. 1528 */ 1529 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma, 1530 spinlock_t **ptl) 1531 { 1532 *ptl = pmd_lock(vma->vm_mm, pmd); 1533 if (likely(pmd_trans_huge(*pmd))) { 1534 if (unlikely(pmd_trans_splitting(*pmd))) { 1535 spin_unlock(*ptl); 1536 wait_split_huge_page(vma->anon_vma, pmd); 1537 return -1; 1538 } else { 1539 /* Thp mapped by 'pmd' is stable, so we can 1540 * handle it as it is. */ 1541 return 1; 1542 } 1543 } 1544 spin_unlock(*ptl); 1545 return 0; 1546 } 1547 1548 /* 1549 * This function returns whether a given @page is mapped onto the @address 1550 * in the virtual space of @mm. 1551 * 1552 * When it's true, this function returns *pmd with holding the page table lock 1553 * and passing it back to the caller via @ptl. 1554 * If it's false, returns NULL without holding the page table lock. 1555 */ 1556 pmd_t *page_check_address_pmd(struct page *page, 1557 struct mm_struct *mm, 1558 unsigned long address, 1559 enum page_check_address_pmd_flag flag, 1560 spinlock_t **ptl) 1561 { 1562 pgd_t *pgd; 1563 pud_t *pud; 1564 pmd_t *pmd; 1565 1566 if (address & ~HPAGE_PMD_MASK) 1567 return NULL; 1568 1569 pgd = pgd_offset(mm, address); 1570 if (!pgd_present(*pgd)) 1571 return NULL; 1572 pud = pud_offset(pgd, address); 1573 if (!pud_present(*pud)) 1574 return NULL; 1575 pmd = pmd_offset(pud, address); 1576 1577 *ptl = pmd_lock(mm, pmd); 1578 if (!pmd_present(*pmd)) 1579 goto unlock; 1580 if (pmd_page(*pmd) != page) 1581 goto unlock; 1582 /* 1583 * split_vma() may create temporary aliased mappings. There is 1584 * no risk as long as all huge pmd are found and have their 1585 * splitting bit set before __split_huge_page_refcount 1586 * runs. Finding the same huge pmd more than once during the 1587 * same rmap walk is not a problem. 1588 */ 1589 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && 1590 pmd_trans_splitting(*pmd)) 1591 goto unlock; 1592 if (pmd_trans_huge(*pmd)) { 1593 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && 1594 !pmd_trans_splitting(*pmd)); 1595 return pmd; 1596 } 1597 unlock: 1598 spin_unlock(*ptl); 1599 return NULL; 1600 } 1601 1602 static int __split_huge_page_splitting(struct page *page, 1603 struct vm_area_struct *vma, 1604 unsigned long address) 1605 { 1606 struct mm_struct *mm = vma->vm_mm; 1607 spinlock_t *ptl; 1608 pmd_t *pmd; 1609 int ret = 0; 1610 /* For mmu_notifiers */ 1611 const unsigned long mmun_start = address; 1612 const unsigned long mmun_end = address + HPAGE_PMD_SIZE; 1613 1614 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1615 pmd = page_check_address_pmd(page, mm, address, 1616 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG, &ptl); 1617 if (pmd) { 1618 /* 1619 * We can't temporarily set the pmd to null in order 1620 * to split it, the pmd must remain marked huge at all 1621 * times or the VM won't take the pmd_trans_huge paths 1622 * and it won't wait on the anon_vma->root->rwsem to 1623 * serialize against split_huge_page*. 1624 */ 1625 pmdp_splitting_flush(vma, address, pmd); 1626 1627 ret = 1; 1628 spin_unlock(ptl); 1629 } 1630 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1631 1632 return ret; 1633 } 1634 1635 static void __split_huge_page_refcount(struct page *page, 1636 struct list_head *list) 1637 { 1638 int i; 1639 struct zone *zone = page_zone(page); 1640 struct lruvec *lruvec; 1641 int tail_count = 0; 1642 1643 /* prevent PageLRU to go away from under us, and freeze lru stats */ 1644 spin_lock_irq(&zone->lru_lock); 1645 lruvec = mem_cgroup_page_lruvec(page, zone); 1646 1647 compound_lock(page); 1648 /* complete memcg works before add pages to LRU */ 1649 mem_cgroup_split_huge_fixup(page); 1650 1651 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 1652 struct page *page_tail = page + i; 1653 1654 /* tail_page->_mapcount cannot change */ 1655 BUG_ON(page_mapcount(page_tail) < 0); 1656 tail_count += page_mapcount(page_tail); 1657 /* check for overflow */ 1658 BUG_ON(tail_count < 0); 1659 BUG_ON(atomic_read(&page_tail->_count) != 0); 1660 /* 1661 * tail_page->_count is zero and not changing from 1662 * under us. But get_page_unless_zero() may be running 1663 * from under us on the tail_page. If we used 1664 * atomic_set() below instead of atomic_add(), we 1665 * would then run atomic_set() concurrently with 1666 * get_page_unless_zero(), and atomic_set() is 1667 * implemented in C not using locked ops. spin_unlock 1668 * on x86 sometime uses locked ops because of PPro 1669 * errata 66, 92, so unless somebody can guarantee 1670 * atomic_set() here would be safe on all archs (and 1671 * not only on x86), it's safer to use atomic_add(). 1672 */ 1673 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, 1674 &page_tail->_count); 1675 1676 /* after clearing PageTail the gup refcount can be released */ 1677 smp_mb__after_atomic(); 1678 1679 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; 1680 page_tail->flags |= (page->flags & 1681 ((1L << PG_referenced) | 1682 (1L << PG_swapbacked) | 1683 (1L << PG_mlocked) | 1684 (1L << PG_uptodate) | 1685 (1L << PG_active) | 1686 (1L << PG_unevictable))); 1687 page_tail->flags |= (1L << PG_dirty); 1688 1689 /* clear PageTail before overwriting first_page */ 1690 smp_wmb(); 1691 1692 /* 1693 * __split_huge_page_splitting() already set the 1694 * splitting bit in all pmd that could map this 1695 * hugepage, that will ensure no CPU can alter the 1696 * mapcount on the head page. The mapcount is only 1697 * accounted in the head page and it has to be 1698 * transferred to all tail pages in the below code. So 1699 * for this code to be safe, the split the mapcount 1700 * can't change. But that doesn't mean userland can't 1701 * keep changing and reading the page contents while 1702 * we transfer the mapcount, so the pmd splitting 1703 * status is achieved setting a reserved bit in the 1704 * pmd, not by clearing the present bit. 1705 */ 1706 page_tail->_mapcount = page->_mapcount; 1707 1708 BUG_ON(page_tail->mapping); 1709 page_tail->mapping = page->mapping; 1710 1711 page_tail->index = page->index + i; 1712 page_cpupid_xchg_last(page_tail, page_cpupid_last(page)); 1713 1714 BUG_ON(!PageAnon(page_tail)); 1715 BUG_ON(!PageUptodate(page_tail)); 1716 BUG_ON(!PageDirty(page_tail)); 1717 BUG_ON(!PageSwapBacked(page_tail)); 1718 1719 lru_add_page_tail(page, page_tail, lruvec, list); 1720 } 1721 atomic_sub(tail_count, &page->_count); 1722 BUG_ON(atomic_read(&page->_count) <= 0); 1723 1724 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1); 1725 1726 ClearPageCompound(page); 1727 compound_unlock(page); 1728 spin_unlock_irq(&zone->lru_lock); 1729 1730 for (i = 1; i < HPAGE_PMD_NR; i++) { 1731 struct page *page_tail = page + i; 1732 BUG_ON(page_count(page_tail) <= 0); 1733 /* 1734 * Tail pages may be freed if there wasn't any mapping 1735 * like if add_to_swap() is running on a lru page that 1736 * had its mapping zapped. And freeing these pages 1737 * requires taking the lru_lock so we do the put_page 1738 * of the tail pages after the split is complete. 1739 */ 1740 put_page(page_tail); 1741 } 1742 1743 /* 1744 * Only the head page (now become a regular page) is required 1745 * to be pinned by the caller. 1746 */ 1747 BUG_ON(page_count(page) <= 0); 1748 } 1749 1750 static int __split_huge_page_map(struct page *page, 1751 struct vm_area_struct *vma, 1752 unsigned long address) 1753 { 1754 struct mm_struct *mm = vma->vm_mm; 1755 spinlock_t *ptl; 1756 pmd_t *pmd, _pmd; 1757 int ret = 0, i; 1758 pgtable_t pgtable; 1759 unsigned long haddr; 1760 1761 pmd = page_check_address_pmd(page, mm, address, 1762 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl); 1763 if (pmd) { 1764 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1765 pmd_populate(mm, &_pmd, pgtable); 1766 if (pmd_write(*pmd)) 1767 BUG_ON(page_mapcount(page) != 1); 1768 1769 haddr = address; 1770 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1771 pte_t *pte, entry; 1772 BUG_ON(PageCompound(page+i)); 1773 /* 1774 * Note that NUMA hinting access restrictions are not 1775 * transferred to avoid any possibility of altering 1776 * permissions across VMAs. 1777 */ 1778 entry = mk_pte(page + i, vma->vm_page_prot); 1779 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1780 if (!pmd_write(*pmd)) 1781 entry = pte_wrprotect(entry); 1782 if (!pmd_young(*pmd)) 1783 entry = pte_mkold(entry); 1784 pte = pte_offset_map(&_pmd, haddr); 1785 BUG_ON(!pte_none(*pte)); 1786 set_pte_at(mm, haddr, pte, entry); 1787 pte_unmap(pte); 1788 } 1789 1790 smp_wmb(); /* make pte visible before pmd */ 1791 /* 1792 * Up to this point the pmd is present and huge and 1793 * userland has the whole access to the hugepage 1794 * during the split (which happens in place). If we 1795 * overwrite the pmd with the not-huge version 1796 * pointing to the pte here (which of course we could 1797 * if all CPUs were bug free), userland could trigger 1798 * a small page size TLB miss on the small sized TLB 1799 * while the hugepage TLB entry is still established 1800 * in the huge TLB. Some CPU doesn't like that. See 1801 * http://support.amd.com/us/Processor_TechDocs/41322.pdf, 1802 * Erratum 383 on page 93. Intel should be safe but is 1803 * also warns that it's only safe if the permission 1804 * and cache attributes of the two entries loaded in 1805 * the two TLB is identical (which should be the case 1806 * here). But it is generally safer to never allow 1807 * small and huge TLB entries for the same virtual 1808 * address to be loaded simultaneously. So instead of 1809 * doing "pmd_populate(); flush_tlb_range();" we first 1810 * mark the current pmd notpresent (atomically because 1811 * here the pmd_trans_huge and pmd_trans_splitting 1812 * must remain set at all times on the pmd until the 1813 * split is complete for this pmd), then we flush the 1814 * SMP TLB and finally we write the non-huge version 1815 * of the pmd entry with pmd_populate. 1816 */ 1817 pmdp_invalidate(vma, address, pmd); 1818 pmd_populate(mm, pmd, pgtable); 1819 ret = 1; 1820 spin_unlock(ptl); 1821 } 1822 1823 return ret; 1824 } 1825 1826 /* must be called with anon_vma->root->rwsem held */ 1827 static void __split_huge_page(struct page *page, 1828 struct anon_vma *anon_vma, 1829 struct list_head *list) 1830 { 1831 int mapcount, mapcount2; 1832 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 1833 struct anon_vma_chain *avc; 1834 1835 BUG_ON(!PageHead(page)); 1836 BUG_ON(PageTail(page)); 1837 1838 mapcount = 0; 1839 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1840 struct vm_area_struct *vma = avc->vma; 1841 unsigned long addr = vma_address(page, vma); 1842 BUG_ON(is_vma_temporary_stack(vma)); 1843 mapcount += __split_huge_page_splitting(page, vma, addr); 1844 } 1845 /* 1846 * It is critical that new vmas are added to the tail of the 1847 * anon_vma list. This guarantes that if copy_huge_pmd() runs 1848 * and establishes a child pmd before 1849 * __split_huge_page_splitting() freezes the parent pmd (so if 1850 * we fail to prevent copy_huge_pmd() from running until the 1851 * whole __split_huge_page() is complete), we will still see 1852 * the newly established pmd of the child later during the 1853 * walk, to be able to set it as pmd_trans_splitting too. 1854 */ 1855 if (mapcount != page_mapcount(page)) { 1856 pr_err("mapcount %d page_mapcount %d\n", 1857 mapcount, page_mapcount(page)); 1858 BUG(); 1859 } 1860 1861 __split_huge_page_refcount(page, list); 1862 1863 mapcount2 = 0; 1864 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1865 struct vm_area_struct *vma = avc->vma; 1866 unsigned long addr = vma_address(page, vma); 1867 BUG_ON(is_vma_temporary_stack(vma)); 1868 mapcount2 += __split_huge_page_map(page, vma, addr); 1869 } 1870 if (mapcount != mapcount2) { 1871 pr_err("mapcount %d mapcount2 %d page_mapcount %d\n", 1872 mapcount, mapcount2, page_mapcount(page)); 1873 BUG(); 1874 } 1875 } 1876 1877 /* 1878 * Split a hugepage into normal pages. This doesn't change the position of head 1879 * page. If @list is null, tail pages will be added to LRU list, otherwise, to 1880 * @list. Both head page and tail pages will inherit mapping, flags, and so on 1881 * from the hugepage. 1882 * Return 0 if the hugepage is split successfully otherwise return 1. 1883 */ 1884 int split_huge_page_to_list(struct page *page, struct list_head *list) 1885 { 1886 struct anon_vma *anon_vma; 1887 int ret = 1; 1888 1889 BUG_ON(is_huge_zero_page(page)); 1890 BUG_ON(!PageAnon(page)); 1891 1892 /* 1893 * The caller does not necessarily hold an mmap_sem that would prevent 1894 * the anon_vma disappearing so we first we take a reference to it 1895 * and then lock the anon_vma for write. This is similar to 1896 * page_lock_anon_vma_read except the write lock is taken to serialise 1897 * against parallel split or collapse operations. 1898 */ 1899 anon_vma = page_get_anon_vma(page); 1900 if (!anon_vma) 1901 goto out; 1902 anon_vma_lock_write(anon_vma); 1903 1904 ret = 0; 1905 if (!PageCompound(page)) 1906 goto out_unlock; 1907 1908 BUG_ON(!PageSwapBacked(page)); 1909 __split_huge_page(page, anon_vma, list); 1910 count_vm_event(THP_SPLIT); 1911 1912 BUG_ON(PageCompound(page)); 1913 out_unlock: 1914 anon_vma_unlock_write(anon_vma); 1915 put_anon_vma(anon_vma); 1916 out: 1917 return ret; 1918 } 1919 1920 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE) 1921 1922 int hugepage_madvise(struct vm_area_struct *vma, 1923 unsigned long *vm_flags, int advice) 1924 { 1925 switch (advice) { 1926 case MADV_HUGEPAGE: 1927 #ifdef CONFIG_S390 1928 /* 1929 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 1930 * can't handle this properly after s390_enable_sie, so we simply 1931 * ignore the madvise to prevent qemu from causing a SIGSEGV. 1932 */ 1933 if (mm_has_pgste(vma->vm_mm)) 1934 return 0; 1935 #endif 1936 /* 1937 * Be somewhat over-protective like KSM for now! 1938 */ 1939 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) 1940 return -EINVAL; 1941 *vm_flags &= ~VM_NOHUGEPAGE; 1942 *vm_flags |= VM_HUGEPAGE; 1943 /* 1944 * If the vma become good for khugepaged to scan, 1945 * register it here without waiting a page fault that 1946 * may not happen any time soon. 1947 */ 1948 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags))) 1949 return -ENOMEM; 1950 break; 1951 case MADV_NOHUGEPAGE: 1952 /* 1953 * Be somewhat over-protective like KSM for now! 1954 */ 1955 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) 1956 return -EINVAL; 1957 *vm_flags &= ~VM_HUGEPAGE; 1958 *vm_flags |= VM_NOHUGEPAGE; 1959 /* 1960 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1961 * this vma even if we leave the mm registered in khugepaged if 1962 * it got registered before VM_NOHUGEPAGE was set. 1963 */ 1964 break; 1965 } 1966 1967 return 0; 1968 } 1969 1970 static int __init khugepaged_slab_init(void) 1971 { 1972 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1973 sizeof(struct mm_slot), 1974 __alignof__(struct mm_slot), 0, NULL); 1975 if (!mm_slot_cache) 1976 return -ENOMEM; 1977 1978 return 0; 1979 } 1980 1981 static void __init khugepaged_slab_exit(void) 1982 { 1983 kmem_cache_destroy(mm_slot_cache); 1984 } 1985 1986 static inline struct mm_slot *alloc_mm_slot(void) 1987 { 1988 if (!mm_slot_cache) /* initialization failed */ 1989 return NULL; 1990 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 1991 } 1992 1993 static inline void free_mm_slot(struct mm_slot *mm_slot) 1994 { 1995 kmem_cache_free(mm_slot_cache, mm_slot); 1996 } 1997 1998 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 1999 { 2000 struct mm_slot *mm_slot; 2001 2002 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) 2003 if (mm == mm_slot->mm) 2004 return mm_slot; 2005 2006 return NULL; 2007 } 2008 2009 static void insert_to_mm_slots_hash(struct mm_struct *mm, 2010 struct mm_slot *mm_slot) 2011 { 2012 mm_slot->mm = mm; 2013 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); 2014 } 2015 2016 static inline int khugepaged_test_exit(struct mm_struct *mm) 2017 { 2018 return atomic_read(&mm->mm_users) == 0; 2019 } 2020 2021 int __khugepaged_enter(struct mm_struct *mm) 2022 { 2023 struct mm_slot *mm_slot; 2024 int wakeup; 2025 2026 mm_slot = alloc_mm_slot(); 2027 if (!mm_slot) 2028 return -ENOMEM; 2029 2030 /* __khugepaged_exit() must not run from under us */ 2031 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); 2032 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 2033 free_mm_slot(mm_slot); 2034 return 0; 2035 } 2036 2037 spin_lock(&khugepaged_mm_lock); 2038 insert_to_mm_slots_hash(mm, mm_slot); 2039 /* 2040 * Insert just behind the scanning cursor, to let the area settle 2041 * down a little. 2042 */ 2043 wakeup = list_empty(&khugepaged_scan.mm_head); 2044 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 2045 spin_unlock(&khugepaged_mm_lock); 2046 2047 atomic_inc(&mm->mm_count); 2048 if (wakeup) 2049 wake_up_interruptible(&khugepaged_wait); 2050 2051 return 0; 2052 } 2053 2054 int khugepaged_enter_vma_merge(struct vm_area_struct *vma, 2055 unsigned long vm_flags) 2056 { 2057 unsigned long hstart, hend; 2058 if (!vma->anon_vma) 2059 /* 2060 * Not yet faulted in so we will register later in the 2061 * page fault if needed. 2062 */ 2063 return 0; 2064 if (vma->vm_ops) 2065 /* khugepaged not yet working on file or special mappings */ 2066 return 0; 2067 VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma); 2068 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2069 hend = vma->vm_end & HPAGE_PMD_MASK; 2070 if (hstart < hend) 2071 return khugepaged_enter(vma, vm_flags); 2072 return 0; 2073 } 2074 2075 void __khugepaged_exit(struct mm_struct *mm) 2076 { 2077 struct mm_slot *mm_slot; 2078 int free = 0; 2079 2080 spin_lock(&khugepaged_mm_lock); 2081 mm_slot = get_mm_slot(mm); 2082 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 2083 hash_del(&mm_slot->hash); 2084 list_del(&mm_slot->mm_node); 2085 free = 1; 2086 } 2087 spin_unlock(&khugepaged_mm_lock); 2088 2089 if (free) { 2090 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2091 free_mm_slot(mm_slot); 2092 mmdrop(mm); 2093 } else if (mm_slot) { 2094 /* 2095 * This is required to serialize against 2096 * khugepaged_test_exit() (which is guaranteed to run 2097 * under mmap sem read mode). Stop here (after we 2098 * return all pagetables will be destroyed) until 2099 * khugepaged has finished working on the pagetables 2100 * under the mmap_sem. 2101 */ 2102 down_write(&mm->mmap_sem); 2103 up_write(&mm->mmap_sem); 2104 } 2105 } 2106 2107 static void release_pte_page(struct page *page) 2108 { 2109 /* 0 stands for page_is_file_cache(page) == false */ 2110 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 2111 unlock_page(page); 2112 putback_lru_page(page); 2113 } 2114 2115 static void release_pte_pages(pte_t *pte, pte_t *_pte) 2116 { 2117 while (--_pte >= pte) { 2118 pte_t pteval = *_pte; 2119 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) 2120 release_pte_page(pte_page(pteval)); 2121 } 2122 } 2123 2124 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 2125 unsigned long address, 2126 pte_t *pte) 2127 { 2128 struct page *page; 2129 pte_t *_pte; 2130 int none_or_zero = 0; 2131 bool referenced = false, writable = false; 2132 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 2133 _pte++, address += PAGE_SIZE) { 2134 pte_t pteval = *_pte; 2135 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 2136 if (++none_or_zero <= khugepaged_max_ptes_none) 2137 continue; 2138 else 2139 goto out; 2140 } 2141 if (!pte_present(pteval)) 2142 goto out; 2143 page = vm_normal_page(vma, address, pteval); 2144 if (unlikely(!page)) 2145 goto out; 2146 2147 VM_BUG_ON_PAGE(PageCompound(page), page); 2148 VM_BUG_ON_PAGE(!PageAnon(page), page); 2149 VM_BUG_ON_PAGE(!PageSwapBacked(page), page); 2150 2151 /* 2152 * We can do it before isolate_lru_page because the 2153 * page can't be freed from under us. NOTE: PG_lock 2154 * is needed to serialize against split_huge_page 2155 * when invoked from the VM. 2156 */ 2157 if (!trylock_page(page)) 2158 goto out; 2159 2160 /* 2161 * cannot use mapcount: can't collapse if there's a gup pin. 2162 * The page must only be referenced by the scanned process 2163 * and page swap cache. 2164 */ 2165 if (page_count(page) != 1 + !!PageSwapCache(page)) { 2166 unlock_page(page); 2167 goto out; 2168 } 2169 if (pte_write(pteval)) { 2170 writable = true; 2171 } else { 2172 if (PageSwapCache(page) && !reuse_swap_page(page)) { 2173 unlock_page(page); 2174 goto out; 2175 } 2176 /* 2177 * Page is not in the swap cache. It can be collapsed 2178 * into a THP. 2179 */ 2180 } 2181 2182 /* 2183 * Isolate the page to avoid collapsing an hugepage 2184 * currently in use by the VM. 2185 */ 2186 if (isolate_lru_page(page)) { 2187 unlock_page(page); 2188 goto out; 2189 } 2190 /* 0 stands for page_is_file_cache(page) == false */ 2191 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 2192 VM_BUG_ON_PAGE(!PageLocked(page), page); 2193 VM_BUG_ON_PAGE(PageLRU(page), page); 2194 2195 /* If there is no mapped pte young don't collapse the page */ 2196 if (pte_young(pteval) || PageReferenced(page) || 2197 mmu_notifier_test_young(vma->vm_mm, address)) 2198 referenced = true; 2199 } 2200 if (likely(referenced && writable)) 2201 return 1; 2202 out: 2203 release_pte_pages(pte, _pte); 2204 return 0; 2205 } 2206 2207 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 2208 struct vm_area_struct *vma, 2209 unsigned long address, 2210 spinlock_t *ptl) 2211 { 2212 pte_t *_pte; 2213 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 2214 pte_t pteval = *_pte; 2215 struct page *src_page; 2216 2217 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 2218 clear_user_highpage(page, address); 2219 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 2220 if (is_zero_pfn(pte_pfn(pteval))) { 2221 /* 2222 * ptl mostly unnecessary. 2223 */ 2224 spin_lock(ptl); 2225 /* 2226 * paravirt calls inside pte_clear here are 2227 * superfluous. 2228 */ 2229 pte_clear(vma->vm_mm, address, _pte); 2230 spin_unlock(ptl); 2231 } 2232 } else { 2233 src_page = pte_page(pteval); 2234 copy_user_highpage(page, src_page, address, vma); 2235 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); 2236 release_pte_page(src_page); 2237 /* 2238 * ptl mostly unnecessary, but preempt has to 2239 * be disabled to update the per-cpu stats 2240 * inside page_remove_rmap(). 2241 */ 2242 spin_lock(ptl); 2243 /* 2244 * paravirt calls inside pte_clear here are 2245 * superfluous. 2246 */ 2247 pte_clear(vma->vm_mm, address, _pte); 2248 page_remove_rmap(src_page); 2249 spin_unlock(ptl); 2250 free_page_and_swap_cache(src_page); 2251 } 2252 2253 address += PAGE_SIZE; 2254 page++; 2255 } 2256 } 2257 2258 static void khugepaged_alloc_sleep(void) 2259 { 2260 wait_event_freezable_timeout(khugepaged_wait, false, 2261 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 2262 } 2263 2264 static int khugepaged_node_load[MAX_NUMNODES]; 2265 2266 static bool khugepaged_scan_abort(int nid) 2267 { 2268 int i; 2269 2270 /* 2271 * If zone_reclaim_mode is disabled, then no extra effort is made to 2272 * allocate memory locally. 2273 */ 2274 if (!zone_reclaim_mode) 2275 return false; 2276 2277 /* If there is a count for this node already, it must be acceptable */ 2278 if (khugepaged_node_load[nid]) 2279 return false; 2280 2281 for (i = 0; i < MAX_NUMNODES; i++) { 2282 if (!khugepaged_node_load[i]) 2283 continue; 2284 if (node_distance(nid, i) > RECLAIM_DISTANCE) 2285 return true; 2286 } 2287 return false; 2288 } 2289 2290 #ifdef CONFIG_NUMA 2291 static int khugepaged_find_target_node(void) 2292 { 2293 static int last_khugepaged_target_node = NUMA_NO_NODE; 2294 int nid, target_node = 0, max_value = 0; 2295 2296 /* find first node with max normal pages hit */ 2297 for (nid = 0; nid < MAX_NUMNODES; nid++) 2298 if (khugepaged_node_load[nid] > max_value) { 2299 max_value = khugepaged_node_load[nid]; 2300 target_node = nid; 2301 } 2302 2303 /* do some balance if several nodes have the same hit record */ 2304 if (target_node <= last_khugepaged_target_node) 2305 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; 2306 nid++) 2307 if (max_value == khugepaged_node_load[nid]) { 2308 target_node = nid; 2309 break; 2310 } 2311 2312 last_khugepaged_target_node = target_node; 2313 return target_node; 2314 } 2315 2316 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2317 { 2318 if (IS_ERR(*hpage)) { 2319 if (!*wait) 2320 return false; 2321 2322 *wait = false; 2323 *hpage = NULL; 2324 khugepaged_alloc_sleep(); 2325 } else if (*hpage) { 2326 put_page(*hpage); 2327 *hpage = NULL; 2328 } 2329 2330 return true; 2331 } 2332 2333 static struct page * 2334 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm, 2335 struct vm_area_struct *vma, unsigned long address, 2336 int node) 2337 { 2338 VM_BUG_ON_PAGE(*hpage, *hpage); 2339 2340 /* 2341 * Before allocating the hugepage, release the mmap_sem read lock. 2342 * The allocation can take potentially a long time if it involves 2343 * sync compaction, and we do not need to hold the mmap_sem during 2344 * that. We will recheck the vma after taking it again in write mode. 2345 */ 2346 up_read(&mm->mmap_sem); 2347 2348 *hpage = alloc_pages_exact_node(node, gfp, HPAGE_PMD_ORDER); 2349 if (unlikely(!*hpage)) { 2350 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2351 *hpage = ERR_PTR(-ENOMEM); 2352 return NULL; 2353 } 2354 2355 count_vm_event(THP_COLLAPSE_ALLOC); 2356 return *hpage; 2357 } 2358 #else 2359 static int khugepaged_find_target_node(void) 2360 { 2361 return 0; 2362 } 2363 2364 static inline struct page *alloc_hugepage(int defrag) 2365 { 2366 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), 2367 HPAGE_PMD_ORDER); 2368 } 2369 2370 static struct page *khugepaged_alloc_hugepage(bool *wait) 2371 { 2372 struct page *hpage; 2373 2374 do { 2375 hpage = alloc_hugepage(khugepaged_defrag()); 2376 if (!hpage) { 2377 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2378 if (!*wait) 2379 return NULL; 2380 2381 *wait = false; 2382 khugepaged_alloc_sleep(); 2383 } else 2384 count_vm_event(THP_COLLAPSE_ALLOC); 2385 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 2386 2387 return hpage; 2388 } 2389 2390 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2391 { 2392 if (!*hpage) 2393 *hpage = khugepaged_alloc_hugepage(wait); 2394 2395 if (unlikely(!*hpage)) 2396 return false; 2397 2398 return true; 2399 } 2400 2401 static struct page * 2402 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm, 2403 struct vm_area_struct *vma, unsigned long address, 2404 int node) 2405 { 2406 up_read(&mm->mmap_sem); 2407 VM_BUG_ON(!*hpage); 2408 2409 return *hpage; 2410 } 2411 #endif 2412 2413 static bool hugepage_vma_check(struct vm_area_struct *vma) 2414 { 2415 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 2416 (vma->vm_flags & VM_NOHUGEPAGE)) 2417 return false; 2418 2419 if (!vma->anon_vma || vma->vm_ops) 2420 return false; 2421 if (is_vma_temporary_stack(vma)) 2422 return false; 2423 VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma); 2424 return true; 2425 } 2426 2427 static void collapse_huge_page(struct mm_struct *mm, 2428 unsigned long address, 2429 struct page **hpage, 2430 struct vm_area_struct *vma, 2431 int node) 2432 { 2433 pmd_t *pmd, _pmd; 2434 pte_t *pte; 2435 pgtable_t pgtable; 2436 struct page *new_page; 2437 spinlock_t *pmd_ptl, *pte_ptl; 2438 int isolated; 2439 unsigned long hstart, hend; 2440 struct mem_cgroup *memcg; 2441 unsigned long mmun_start; /* For mmu_notifiers */ 2442 unsigned long mmun_end; /* For mmu_notifiers */ 2443 gfp_t gfp; 2444 2445 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2446 2447 /* Only allocate from the target node */ 2448 gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) | 2449 __GFP_THISNODE; 2450 2451 /* release the mmap_sem read lock. */ 2452 new_page = khugepaged_alloc_page(hpage, gfp, mm, vma, address, node); 2453 if (!new_page) 2454 return; 2455 2456 if (unlikely(mem_cgroup_try_charge(new_page, mm, 2457 gfp, &memcg))) 2458 return; 2459 2460 /* 2461 * Prevent all access to pagetables with the exception of 2462 * gup_fast later hanlded by the ptep_clear_flush and the VM 2463 * handled by the anon_vma lock + PG_lock. 2464 */ 2465 down_write(&mm->mmap_sem); 2466 if (unlikely(khugepaged_test_exit(mm))) 2467 goto out; 2468 2469 vma = find_vma(mm, address); 2470 if (!vma) 2471 goto out; 2472 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2473 hend = vma->vm_end & HPAGE_PMD_MASK; 2474 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 2475 goto out; 2476 if (!hugepage_vma_check(vma)) 2477 goto out; 2478 pmd = mm_find_pmd(mm, address); 2479 if (!pmd) 2480 goto out; 2481 2482 anon_vma_lock_write(vma->anon_vma); 2483 2484 pte = pte_offset_map(pmd, address); 2485 pte_ptl = pte_lockptr(mm, pmd); 2486 2487 mmun_start = address; 2488 mmun_end = address + HPAGE_PMD_SIZE; 2489 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2490 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ 2491 /* 2492 * After this gup_fast can't run anymore. This also removes 2493 * any huge TLB entry from the CPU so we won't allow 2494 * huge and small TLB entries for the same virtual address 2495 * to avoid the risk of CPU bugs in that area. 2496 */ 2497 _pmd = pmdp_collapse_flush(vma, address, pmd); 2498 spin_unlock(pmd_ptl); 2499 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2500 2501 spin_lock(pte_ptl); 2502 isolated = __collapse_huge_page_isolate(vma, address, pte); 2503 spin_unlock(pte_ptl); 2504 2505 if (unlikely(!isolated)) { 2506 pte_unmap(pte); 2507 spin_lock(pmd_ptl); 2508 BUG_ON(!pmd_none(*pmd)); 2509 /* 2510 * We can only use set_pmd_at when establishing 2511 * hugepmds and never for establishing regular pmds that 2512 * points to regular pagetables. Use pmd_populate for that 2513 */ 2514 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 2515 spin_unlock(pmd_ptl); 2516 anon_vma_unlock_write(vma->anon_vma); 2517 goto out; 2518 } 2519 2520 /* 2521 * All pages are isolated and locked so anon_vma rmap 2522 * can't run anymore. 2523 */ 2524 anon_vma_unlock_write(vma->anon_vma); 2525 2526 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); 2527 pte_unmap(pte); 2528 __SetPageUptodate(new_page); 2529 pgtable = pmd_pgtable(_pmd); 2530 2531 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); 2532 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 2533 2534 /* 2535 * spin_lock() below is not the equivalent of smp_wmb(), so 2536 * this is needed to avoid the copy_huge_page writes to become 2537 * visible after the set_pmd_at() write. 2538 */ 2539 smp_wmb(); 2540 2541 spin_lock(pmd_ptl); 2542 BUG_ON(!pmd_none(*pmd)); 2543 page_add_new_anon_rmap(new_page, vma, address); 2544 mem_cgroup_commit_charge(new_page, memcg, false); 2545 lru_cache_add_active_or_unevictable(new_page, vma); 2546 pgtable_trans_huge_deposit(mm, pmd, pgtable); 2547 set_pmd_at(mm, address, pmd, _pmd); 2548 update_mmu_cache_pmd(vma, address, pmd); 2549 spin_unlock(pmd_ptl); 2550 2551 *hpage = NULL; 2552 2553 khugepaged_pages_collapsed++; 2554 out_up_write: 2555 up_write(&mm->mmap_sem); 2556 return; 2557 2558 out: 2559 mem_cgroup_cancel_charge(new_page, memcg); 2560 goto out_up_write; 2561 } 2562 2563 static int khugepaged_scan_pmd(struct mm_struct *mm, 2564 struct vm_area_struct *vma, 2565 unsigned long address, 2566 struct page **hpage) 2567 { 2568 pmd_t *pmd; 2569 pte_t *pte, *_pte; 2570 int ret = 0, none_or_zero = 0; 2571 struct page *page; 2572 unsigned long _address; 2573 spinlock_t *ptl; 2574 int node = NUMA_NO_NODE; 2575 bool writable = false, referenced = false; 2576 2577 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2578 2579 pmd = mm_find_pmd(mm, address); 2580 if (!pmd) 2581 goto out; 2582 2583 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 2584 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2585 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2586 _pte++, _address += PAGE_SIZE) { 2587 pte_t pteval = *_pte; 2588 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 2589 if (++none_or_zero <= khugepaged_max_ptes_none) 2590 continue; 2591 else 2592 goto out_unmap; 2593 } 2594 if (!pte_present(pteval)) 2595 goto out_unmap; 2596 if (pte_write(pteval)) 2597 writable = true; 2598 2599 page = vm_normal_page(vma, _address, pteval); 2600 if (unlikely(!page)) 2601 goto out_unmap; 2602 /* 2603 * Record which node the original page is from and save this 2604 * information to khugepaged_node_load[]. 2605 * Khupaged will allocate hugepage from the node has the max 2606 * hit record. 2607 */ 2608 node = page_to_nid(page); 2609 if (khugepaged_scan_abort(node)) 2610 goto out_unmap; 2611 khugepaged_node_load[node]++; 2612 VM_BUG_ON_PAGE(PageCompound(page), page); 2613 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) 2614 goto out_unmap; 2615 /* 2616 * cannot use mapcount: can't collapse if there's a gup pin. 2617 * The page must only be referenced by the scanned process 2618 * and page swap cache. 2619 */ 2620 if (page_count(page) != 1 + !!PageSwapCache(page)) 2621 goto out_unmap; 2622 if (pte_young(pteval) || PageReferenced(page) || 2623 mmu_notifier_test_young(vma->vm_mm, address)) 2624 referenced = true; 2625 } 2626 if (referenced && writable) 2627 ret = 1; 2628 out_unmap: 2629 pte_unmap_unlock(pte, ptl); 2630 if (ret) { 2631 node = khugepaged_find_target_node(); 2632 /* collapse_huge_page will return with the mmap_sem released */ 2633 collapse_huge_page(mm, address, hpage, vma, node); 2634 } 2635 out: 2636 return ret; 2637 } 2638 2639 static void collect_mm_slot(struct mm_slot *mm_slot) 2640 { 2641 struct mm_struct *mm = mm_slot->mm; 2642 2643 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2644 2645 if (khugepaged_test_exit(mm)) { 2646 /* free mm_slot */ 2647 hash_del(&mm_slot->hash); 2648 list_del(&mm_slot->mm_node); 2649 2650 /* 2651 * Not strictly needed because the mm exited already. 2652 * 2653 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2654 */ 2655 2656 /* khugepaged_mm_lock actually not necessary for the below */ 2657 free_mm_slot(mm_slot); 2658 mmdrop(mm); 2659 } 2660 } 2661 2662 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2663 struct page **hpage) 2664 __releases(&khugepaged_mm_lock) 2665 __acquires(&khugepaged_mm_lock) 2666 { 2667 struct mm_slot *mm_slot; 2668 struct mm_struct *mm; 2669 struct vm_area_struct *vma; 2670 int progress = 0; 2671 2672 VM_BUG_ON(!pages); 2673 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2674 2675 if (khugepaged_scan.mm_slot) 2676 mm_slot = khugepaged_scan.mm_slot; 2677 else { 2678 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2679 struct mm_slot, mm_node); 2680 khugepaged_scan.address = 0; 2681 khugepaged_scan.mm_slot = mm_slot; 2682 } 2683 spin_unlock(&khugepaged_mm_lock); 2684 2685 mm = mm_slot->mm; 2686 down_read(&mm->mmap_sem); 2687 if (unlikely(khugepaged_test_exit(mm))) 2688 vma = NULL; 2689 else 2690 vma = find_vma(mm, khugepaged_scan.address); 2691 2692 progress++; 2693 for (; vma; vma = vma->vm_next) { 2694 unsigned long hstart, hend; 2695 2696 cond_resched(); 2697 if (unlikely(khugepaged_test_exit(mm))) { 2698 progress++; 2699 break; 2700 } 2701 if (!hugepage_vma_check(vma)) { 2702 skip: 2703 progress++; 2704 continue; 2705 } 2706 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2707 hend = vma->vm_end & HPAGE_PMD_MASK; 2708 if (hstart >= hend) 2709 goto skip; 2710 if (khugepaged_scan.address > hend) 2711 goto skip; 2712 if (khugepaged_scan.address < hstart) 2713 khugepaged_scan.address = hstart; 2714 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2715 2716 while (khugepaged_scan.address < hend) { 2717 int ret; 2718 cond_resched(); 2719 if (unlikely(khugepaged_test_exit(mm))) 2720 goto breakouterloop; 2721 2722 VM_BUG_ON(khugepaged_scan.address < hstart || 2723 khugepaged_scan.address + HPAGE_PMD_SIZE > 2724 hend); 2725 ret = khugepaged_scan_pmd(mm, vma, 2726 khugepaged_scan.address, 2727 hpage); 2728 /* move to next address */ 2729 khugepaged_scan.address += HPAGE_PMD_SIZE; 2730 progress += HPAGE_PMD_NR; 2731 if (ret) 2732 /* we released mmap_sem so break loop */ 2733 goto breakouterloop_mmap_sem; 2734 if (progress >= pages) 2735 goto breakouterloop; 2736 } 2737 } 2738 breakouterloop: 2739 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2740 breakouterloop_mmap_sem: 2741 2742 spin_lock(&khugepaged_mm_lock); 2743 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2744 /* 2745 * Release the current mm_slot if this mm is about to die, or 2746 * if we scanned all vmas of this mm. 2747 */ 2748 if (khugepaged_test_exit(mm) || !vma) { 2749 /* 2750 * Make sure that if mm_users is reaching zero while 2751 * khugepaged runs here, khugepaged_exit will find 2752 * mm_slot not pointing to the exiting mm. 2753 */ 2754 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2755 khugepaged_scan.mm_slot = list_entry( 2756 mm_slot->mm_node.next, 2757 struct mm_slot, mm_node); 2758 khugepaged_scan.address = 0; 2759 } else { 2760 khugepaged_scan.mm_slot = NULL; 2761 khugepaged_full_scans++; 2762 } 2763 2764 collect_mm_slot(mm_slot); 2765 } 2766 2767 return progress; 2768 } 2769 2770 static int khugepaged_has_work(void) 2771 { 2772 return !list_empty(&khugepaged_scan.mm_head) && 2773 khugepaged_enabled(); 2774 } 2775 2776 static int khugepaged_wait_event(void) 2777 { 2778 return !list_empty(&khugepaged_scan.mm_head) || 2779 kthread_should_stop(); 2780 } 2781 2782 static void khugepaged_do_scan(void) 2783 { 2784 struct page *hpage = NULL; 2785 unsigned int progress = 0, pass_through_head = 0; 2786 unsigned int pages = khugepaged_pages_to_scan; 2787 bool wait = true; 2788 2789 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2790 2791 while (progress < pages) { 2792 if (!khugepaged_prealloc_page(&hpage, &wait)) 2793 break; 2794 2795 cond_resched(); 2796 2797 if (unlikely(kthread_should_stop() || try_to_freeze())) 2798 break; 2799 2800 spin_lock(&khugepaged_mm_lock); 2801 if (!khugepaged_scan.mm_slot) 2802 pass_through_head++; 2803 if (khugepaged_has_work() && 2804 pass_through_head < 2) 2805 progress += khugepaged_scan_mm_slot(pages - progress, 2806 &hpage); 2807 else 2808 progress = pages; 2809 spin_unlock(&khugepaged_mm_lock); 2810 } 2811 2812 if (!IS_ERR_OR_NULL(hpage)) 2813 put_page(hpage); 2814 } 2815 2816 static void khugepaged_wait_work(void) 2817 { 2818 if (khugepaged_has_work()) { 2819 if (!khugepaged_scan_sleep_millisecs) 2820 return; 2821 2822 wait_event_freezable_timeout(khugepaged_wait, 2823 kthread_should_stop(), 2824 msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); 2825 return; 2826 } 2827 2828 if (khugepaged_enabled()) 2829 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 2830 } 2831 2832 static int khugepaged(void *none) 2833 { 2834 struct mm_slot *mm_slot; 2835 2836 set_freezable(); 2837 set_user_nice(current, MAX_NICE); 2838 2839 while (!kthread_should_stop()) { 2840 khugepaged_do_scan(); 2841 khugepaged_wait_work(); 2842 } 2843 2844 spin_lock(&khugepaged_mm_lock); 2845 mm_slot = khugepaged_scan.mm_slot; 2846 khugepaged_scan.mm_slot = NULL; 2847 if (mm_slot) 2848 collect_mm_slot(mm_slot); 2849 spin_unlock(&khugepaged_mm_lock); 2850 return 0; 2851 } 2852 2853 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2854 unsigned long haddr, pmd_t *pmd) 2855 { 2856 struct mm_struct *mm = vma->vm_mm; 2857 pgtable_t pgtable; 2858 pmd_t _pmd; 2859 int i; 2860 2861 pmdp_huge_clear_flush_notify(vma, haddr, pmd); 2862 /* leave pmd empty until pte is filled */ 2863 2864 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2865 pmd_populate(mm, &_pmd, pgtable); 2866 2867 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2868 pte_t *pte, entry; 2869 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2870 entry = pte_mkspecial(entry); 2871 pte = pte_offset_map(&_pmd, haddr); 2872 VM_BUG_ON(!pte_none(*pte)); 2873 set_pte_at(mm, haddr, pte, entry); 2874 pte_unmap(pte); 2875 } 2876 smp_wmb(); /* make pte visible before pmd */ 2877 pmd_populate(mm, pmd, pgtable); 2878 put_huge_zero_page(); 2879 } 2880 2881 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address, 2882 pmd_t *pmd) 2883 { 2884 spinlock_t *ptl; 2885 struct page *page; 2886 struct mm_struct *mm = vma->vm_mm; 2887 unsigned long haddr = address & HPAGE_PMD_MASK; 2888 unsigned long mmun_start; /* For mmu_notifiers */ 2889 unsigned long mmun_end; /* For mmu_notifiers */ 2890 2891 BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE); 2892 2893 mmun_start = haddr; 2894 mmun_end = haddr + HPAGE_PMD_SIZE; 2895 again: 2896 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2897 ptl = pmd_lock(mm, pmd); 2898 if (unlikely(!pmd_trans_huge(*pmd))) { 2899 spin_unlock(ptl); 2900 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2901 return; 2902 } 2903 if (is_huge_zero_pmd(*pmd)) { 2904 __split_huge_zero_page_pmd(vma, haddr, pmd); 2905 spin_unlock(ptl); 2906 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2907 return; 2908 } 2909 page = pmd_page(*pmd); 2910 VM_BUG_ON_PAGE(!page_count(page), page); 2911 get_page(page); 2912 spin_unlock(ptl); 2913 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2914 2915 split_huge_page(page); 2916 2917 put_page(page); 2918 2919 /* 2920 * We don't always have down_write of mmap_sem here: a racing 2921 * do_huge_pmd_wp_page() might have copied-on-write to another 2922 * huge page before our split_huge_page() got the anon_vma lock. 2923 */ 2924 if (unlikely(pmd_trans_huge(*pmd))) 2925 goto again; 2926 } 2927 2928 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address, 2929 pmd_t *pmd) 2930 { 2931 struct vm_area_struct *vma; 2932 2933 vma = find_vma(mm, address); 2934 BUG_ON(vma == NULL); 2935 split_huge_page_pmd(vma, address, pmd); 2936 } 2937 2938 static void split_huge_page_address(struct mm_struct *mm, 2939 unsigned long address) 2940 { 2941 pgd_t *pgd; 2942 pud_t *pud; 2943 pmd_t *pmd; 2944 2945 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); 2946 2947 pgd = pgd_offset(mm, address); 2948 if (!pgd_present(*pgd)) 2949 return; 2950 2951 pud = pud_offset(pgd, address); 2952 if (!pud_present(*pud)) 2953 return; 2954 2955 pmd = pmd_offset(pud, address); 2956 if (!pmd_present(*pmd)) 2957 return; 2958 /* 2959 * Caller holds the mmap_sem write mode, so a huge pmd cannot 2960 * materialize from under us. 2961 */ 2962 split_huge_page_pmd_mm(mm, address, pmd); 2963 } 2964 2965 void __vma_adjust_trans_huge(struct vm_area_struct *vma, 2966 unsigned long start, 2967 unsigned long end, 2968 long adjust_next) 2969 { 2970 /* 2971 * If the new start address isn't hpage aligned and it could 2972 * previously contain an hugepage: check if we need to split 2973 * an huge pmd. 2974 */ 2975 if (start & ~HPAGE_PMD_MASK && 2976 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2977 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2978 split_huge_page_address(vma->vm_mm, start); 2979 2980 /* 2981 * If the new end address isn't hpage aligned and it could 2982 * previously contain an hugepage: check if we need to split 2983 * an huge pmd. 2984 */ 2985 if (end & ~HPAGE_PMD_MASK && 2986 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2987 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2988 split_huge_page_address(vma->vm_mm, end); 2989 2990 /* 2991 * If we're also updating the vma->vm_next->vm_start, if the new 2992 * vm_next->vm_start isn't page aligned and it could previously 2993 * contain an hugepage: check if we need to split an huge pmd. 2994 */ 2995 if (adjust_next > 0) { 2996 struct vm_area_struct *next = vma->vm_next; 2997 unsigned long nstart = next->vm_start; 2998 nstart += adjust_next << PAGE_SHIFT; 2999 if (nstart & ~HPAGE_PMD_MASK && 3000 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 3001 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 3002 split_huge_page_address(next->vm_mm, nstart); 3003 } 3004 } 3005