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