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_pages(zero_page, compound_order(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_pages(zero_page, compound_order(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 struct mem_cgroup *memcg; 719 pgtable_t pgtable; 720 spinlock_t *ptl; 721 722 VM_BUG_ON_PAGE(!PageCompound(page), page); 723 724 if (mem_cgroup_try_charge(page, mm, GFP_TRANSHUGE, &memcg)) 725 return VM_FAULT_OOM; 726 727 pgtable = pte_alloc_one(mm, haddr); 728 if (unlikely(!pgtable)) { 729 mem_cgroup_cancel_charge(page, memcg); 730 return VM_FAULT_OOM; 731 } 732 733 clear_huge_page(page, haddr, HPAGE_PMD_NR); 734 /* 735 * The memory barrier inside __SetPageUptodate makes sure that 736 * clear_huge_page writes become visible before the set_pmd_at() 737 * write. 738 */ 739 __SetPageUptodate(page); 740 741 ptl = pmd_lock(mm, pmd); 742 if (unlikely(!pmd_none(*pmd))) { 743 spin_unlock(ptl); 744 mem_cgroup_cancel_charge(page, memcg); 745 put_page(page); 746 pte_free(mm, pgtable); 747 } else { 748 pmd_t entry; 749 entry = mk_huge_pmd(page, vma->vm_page_prot); 750 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 751 page_add_new_anon_rmap(page, vma, haddr); 752 mem_cgroup_commit_charge(page, memcg, false); 753 lru_cache_add_active_or_unevictable(page, vma); 754 pgtable_trans_huge_deposit(mm, pmd, pgtable); 755 set_pmd_at(mm, haddr, pmd, entry); 756 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 757 atomic_long_inc(&mm->nr_ptes); 758 spin_unlock(ptl); 759 } 760 761 return 0; 762 } 763 764 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) 765 { 766 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; 767 } 768 769 static inline struct page *alloc_hugepage_vma(int defrag, 770 struct vm_area_struct *vma, 771 unsigned long haddr, int nd, 772 gfp_t extra_gfp) 773 { 774 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp), 775 HPAGE_PMD_ORDER, vma, haddr, nd); 776 } 777 778 /* Caller must hold page table lock. */ 779 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, 780 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, 781 struct page *zero_page) 782 { 783 pmd_t entry; 784 if (!pmd_none(*pmd)) 785 return false; 786 entry = mk_pmd(zero_page, vma->vm_page_prot); 787 entry = pmd_mkhuge(entry); 788 pgtable_trans_huge_deposit(mm, pmd, pgtable); 789 set_pmd_at(mm, haddr, pmd, entry); 790 atomic_long_inc(&mm->nr_ptes); 791 return true; 792 } 793 794 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 795 unsigned long address, pmd_t *pmd, 796 unsigned int flags) 797 { 798 struct page *page; 799 unsigned long haddr = address & HPAGE_PMD_MASK; 800 801 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end) 802 return VM_FAULT_FALLBACK; 803 if (unlikely(anon_vma_prepare(vma))) 804 return VM_FAULT_OOM; 805 if (unlikely(khugepaged_enter(vma, vma->vm_flags))) 806 return VM_FAULT_OOM; 807 if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) && 808 transparent_hugepage_use_zero_page()) { 809 spinlock_t *ptl; 810 pgtable_t pgtable; 811 struct page *zero_page; 812 bool set; 813 pgtable = pte_alloc_one(mm, haddr); 814 if (unlikely(!pgtable)) 815 return VM_FAULT_OOM; 816 zero_page = get_huge_zero_page(); 817 if (unlikely(!zero_page)) { 818 pte_free(mm, pgtable); 819 count_vm_event(THP_FAULT_FALLBACK); 820 return VM_FAULT_FALLBACK; 821 } 822 ptl = pmd_lock(mm, pmd); 823 set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, 824 zero_page); 825 spin_unlock(ptl); 826 if (!set) { 827 pte_free(mm, pgtable); 828 put_huge_zero_page(); 829 } 830 return 0; 831 } 832 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 833 vma, haddr, numa_node_id(), 0); 834 if (unlikely(!page)) { 835 count_vm_event(THP_FAULT_FALLBACK); 836 return VM_FAULT_FALLBACK; 837 } 838 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page))) { 839 put_page(page); 840 count_vm_event(THP_FAULT_FALLBACK); 841 return VM_FAULT_FALLBACK; 842 } 843 844 count_vm_event(THP_FAULT_ALLOC); 845 return 0; 846 } 847 848 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 849 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 850 struct vm_area_struct *vma) 851 { 852 spinlock_t *dst_ptl, *src_ptl; 853 struct page *src_page; 854 pmd_t pmd; 855 pgtable_t pgtable; 856 int ret; 857 858 ret = -ENOMEM; 859 pgtable = pte_alloc_one(dst_mm, addr); 860 if (unlikely(!pgtable)) 861 goto out; 862 863 dst_ptl = pmd_lock(dst_mm, dst_pmd); 864 src_ptl = pmd_lockptr(src_mm, src_pmd); 865 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); 866 867 ret = -EAGAIN; 868 pmd = *src_pmd; 869 if (unlikely(!pmd_trans_huge(pmd))) { 870 pte_free(dst_mm, pgtable); 871 goto out_unlock; 872 } 873 /* 874 * When page table lock is held, the huge zero pmd should not be 875 * under splitting since we don't split the page itself, only pmd to 876 * a page table. 877 */ 878 if (is_huge_zero_pmd(pmd)) { 879 struct page *zero_page; 880 bool set; 881 /* 882 * get_huge_zero_page() will never allocate a new page here, 883 * since we already have a zero page to copy. It just takes a 884 * reference. 885 */ 886 zero_page = get_huge_zero_page(); 887 set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, 888 zero_page); 889 BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */ 890 ret = 0; 891 goto out_unlock; 892 } 893 894 if (unlikely(pmd_trans_splitting(pmd))) { 895 /* split huge page running from under us */ 896 spin_unlock(src_ptl); 897 spin_unlock(dst_ptl); 898 pte_free(dst_mm, pgtable); 899 900 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ 901 goto out; 902 } 903 src_page = pmd_page(pmd); 904 VM_BUG_ON_PAGE(!PageHead(src_page), src_page); 905 get_page(src_page); 906 page_dup_rmap(src_page); 907 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 908 909 pmdp_set_wrprotect(src_mm, addr, src_pmd); 910 pmd = pmd_mkold(pmd_wrprotect(pmd)); 911 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); 912 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 913 atomic_long_inc(&dst_mm->nr_ptes); 914 915 ret = 0; 916 out_unlock: 917 spin_unlock(src_ptl); 918 spin_unlock(dst_ptl); 919 out: 920 return ret; 921 } 922 923 void huge_pmd_set_accessed(struct mm_struct *mm, 924 struct vm_area_struct *vma, 925 unsigned long address, 926 pmd_t *pmd, pmd_t orig_pmd, 927 int dirty) 928 { 929 spinlock_t *ptl; 930 pmd_t entry; 931 unsigned long haddr; 932 933 ptl = pmd_lock(mm, pmd); 934 if (unlikely(!pmd_same(*pmd, orig_pmd))) 935 goto unlock; 936 937 entry = pmd_mkyoung(orig_pmd); 938 haddr = address & HPAGE_PMD_MASK; 939 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty)) 940 update_mmu_cache_pmd(vma, address, pmd); 941 942 unlock: 943 spin_unlock(ptl); 944 } 945 946 /* 947 * Save CONFIG_DEBUG_PAGEALLOC from faulting falsely on tail pages 948 * during copy_user_huge_page()'s copy_page_rep(): in the case when 949 * the source page gets split and a tail freed before copy completes. 950 * Called under pmd_lock of checked pmd, so safe from splitting itself. 951 */ 952 static void get_user_huge_page(struct page *page) 953 { 954 if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) { 955 struct page *endpage = page + HPAGE_PMD_NR; 956 957 atomic_add(HPAGE_PMD_NR, &page->_count); 958 while (++page < endpage) 959 get_huge_page_tail(page); 960 } else { 961 get_page(page); 962 } 963 } 964 965 static void put_user_huge_page(struct page *page) 966 { 967 if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) { 968 struct page *endpage = page + HPAGE_PMD_NR; 969 970 while (page < endpage) 971 put_page(page++); 972 } else { 973 put_page(page); 974 } 975 } 976 977 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, 978 struct vm_area_struct *vma, 979 unsigned long address, 980 pmd_t *pmd, pmd_t orig_pmd, 981 struct page *page, 982 unsigned long haddr) 983 { 984 struct mem_cgroup *memcg; 985 spinlock_t *ptl; 986 pgtable_t pgtable; 987 pmd_t _pmd; 988 int ret = 0, i; 989 struct page **pages; 990 unsigned long mmun_start; /* For mmu_notifiers */ 991 unsigned long mmun_end; /* For mmu_notifiers */ 992 993 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 994 GFP_KERNEL); 995 if (unlikely(!pages)) { 996 ret |= VM_FAULT_OOM; 997 goto out; 998 } 999 1000 for (i = 0; i < HPAGE_PMD_NR; i++) { 1001 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | 1002 __GFP_OTHER_NODE, 1003 vma, address, page_to_nid(page)); 1004 if (unlikely(!pages[i] || 1005 mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL, 1006 &memcg))) { 1007 if (pages[i]) 1008 put_page(pages[i]); 1009 while (--i >= 0) { 1010 memcg = (void *)page_private(pages[i]); 1011 set_page_private(pages[i], 0); 1012 mem_cgroup_cancel_charge(pages[i], memcg); 1013 put_page(pages[i]); 1014 } 1015 kfree(pages); 1016 ret |= VM_FAULT_OOM; 1017 goto out; 1018 } 1019 set_page_private(pages[i], (unsigned long)memcg); 1020 } 1021 1022 for (i = 0; i < HPAGE_PMD_NR; i++) { 1023 copy_user_highpage(pages[i], page + i, 1024 haddr + PAGE_SIZE * i, vma); 1025 __SetPageUptodate(pages[i]); 1026 cond_resched(); 1027 } 1028 1029 mmun_start = haddr; 1030 mmun_end = haddr + HPAGE_PMD_SIZE; 1031 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1032 1033 ptl = pmd_lock(mm, pmd); 1034 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1035 goto out_free_pages; 1036 VM_BUG_ON_PAGE(!PageHead(page), page); 1037 1038 pmdp_clear_flush_notify(vma, haddr, pmd); 1039 /* leave pmd empty until pte is filled */ 1040 1041 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1042 pmd_populate(mm, &_pmd, pgtable); 1043 1044 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1045 pte_t *pte, entry; 1046 entry = mk_pte(pages[i], vma->vm_page_prot); 1047 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1048 memcg = (void *)page_private(pages[i]); 1049 set_page_private(pages[i], 0); 1050 page_add_new_anon_rmap(pages[i], vma, haddr); 1051 mem_cgroup_commit_charge(pages[i], memcg, false); 1052 lru_cache_add_active_or_unevictable(pages[i], vma); 1053 pte = pte_offset_map(&_pmd, haddr); 1054 VM_BUG_ON(!pte_none(*pte)); 1055 set_pte_at(mm, haddr, pte, entry); 1056 pte_unmap(pte); 1057 } 1058 kfree(pages); 1059 1060 smp_wmb(); /* make pte visible before pmd */ 1061 pmd_populate(mm, pmd, pgtable); 1062 page_remove_rmap(page); 1063 spin_unlock(ptl); 1064 1065 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1066 1067 ret |= VM_FAULT_WRITE; 1068 put_page(page); 1069 1070 out: 1071 return ret; 1072 1073 out_free_pages: 1074 spin_unlock(ptl); 1075 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1076 for (i = 0; i < HPAGE_PMD_NR; i++) { 1077 memcg = (void *)page_private(pages[i]); 1078 set_page_private(pages[i], 0); 1079 mem_cgroup_cancel_charge(pages[i], memcg); 1080 put_page(pages[i]); 1081 } 1082 kfree(pages); 1083 goto out; 1084 } 1085 1086 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 1087 unsigned long address, pmd_t *pmd, pmd_t orig_pmd) 1088 { 1089 spinlock_t *ptl; 1090 int ret = 0; 1091 struct page *page = NULL, *new_page; 1092 struct mem_cgroup *memcg; 1093 unsigned long haddr; 1094 unsigned long mmun_start; /* For mmu_notifiers */ 1095 unsigned long mmun_end; /* For mmu_notifiers */ 1096 1097 ptl = pmd_lockptr(mm, pmd); 1098 VM_BUG_ON_VMA(!vma->anon_vma, vma); 1099 haddr = address & HPAGE_PMD_MASK; 1100 if (is_huge_zero_pmd(orig_pmd)) 1101 goto alloc; 1102 spin_lock(ptl); 1103 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1104 goto out_unlock; 1105 1106 page = pmd_page(orig_pmd); 1107 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); 1108 if (page_mapcount(page) == 1) { 1109 pmd_t entry; 1110 entry = pmd_mkyoung(orig_pmd); 1111 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1112 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 1113 update_mmu_cache_pmd(vma, address, pmd); 1114 ret |= VM_FAULT_WRITE; 1115 goto out_unlock; 1116 } 1117 get_user_huge_page(page); 1118 spin_unlock(ptl); 1119 alloc: 1120 if (transparent_hugepage_enabled(vma) && 1121 !transparent_hugepage_debug_cow()) 1122 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 1123 vma, haddr, numa_node_id(), 0); 1124 else 1125 new_page = NULL; 1126 1127 if (unlikely(!new_page)) { 1128 if (!page) { 1129 split_huge_page_pmd(vma, address, pmd); 1130 ret |= VM_FAULT_FALLBACK; 1131 } else { 1132 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 1133 pmd, orig_pmd, page, haddr); 1134 if (ret & VM_FAULT_OOM) { 1135 split_huge_page(page); 1136 ret |= VM_FAULT_FALLBACK; 1137 } 1138 put_user_huge_page(page); 1139 } 1140 count_vm_event(THP_FAULT_FALLBACK); 1141 goto out; 1142 } 1143 1144 if (unlikely(mem_cgroup_try_charge(new_page, mm, 1145 GFP_TRANSHUGE, &memcg))) { 1146 put_page(new_page); 1147 if (page) { 1148 split_huge_page(page); 1149 put_user_huge_page(page); 1150 } else 1151 split_huge_page_pmd(vma, address, pmd); 1152 ret |= VM_FAULT_FALLBACK; 1153 count_vm_event(THP_FAULT_FALLBACK); 1154 goto out; 1155 } 1156 1157 count_vm_event(THP_FAULT_ALLOC); 1158 1159 if (!page) 1160 clear_huge_page(new_page, haddr, HPAGE_PMD_NR); 1161 else 1162 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 1163 __SetPageUptodate(new_page); 1164 1165 mmun_start = haddr; 1166 mmun_end = haddr + HPAGE_PMD_SIZE; 1167 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1168 1169 spin_lock(ptl); 1170 if (page) 1171 put_user_huge_page(page); 1172 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 1173 spin_unlock(ptl); 1174 mem_cgroup_cancel_charge(new_page, memcg); 1175 put_page(new_page); 1176 goto out_mn; 1177 } else { 1178 pmd_t entry; 1179 entry = mk_huge_pmd(new_page, vma->vm_page_prot); 1180 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1181 pmdp_clear_flush_notify(vma, haddr, pmd); 1182 page_add_new_anon_rmap(new_page, vma, haddr); 1183 mem_cgroup_commit_charge(new_page, memcg, false); 1184 lru_cache_add_active_or_unevictable(new_page, vma); 1185 set_pmd_at(mm, haddr, pmd, entry); 1186 update_mmu_cache_pmd(vma, address, pmd); 1187 if (!page) { 1188 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 1189 put_huge_zero_page(); 1190 } else { 1191 VM_BUG_ON_PAGE(!PageHead(page), page); 1192 page_remove_rmap(page); 1193 put_page(page); 1194 } 1195 ret |= VM_FAULT_WRITE; 1196 } 1197 spin_unlock(ptl); 1198 out_mn: 1199 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1200 out: 1201 return ret; 1202 out_unlock: 1203 spin_unlock(ptl); 1204 return ret; 1205 } 1206 1207 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1208 unsigned long addr, 1209 pmd_t *pmd, 1210 unsigned int flags) 1211 { 1212 struct mm_struct *mm = vma->vm_mm; 1213 struct page *page = NULL; 1214 1215 assert_spin_locked(pmd_lockptr(mm, pmd)); 1216 1217 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 1218 goto out; 1219 1220 /* Avoid dumping huge zero page */ 1221 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) 1222 return ERR_PTR(-EFAULT); 1223 1224 /* Full NUMA hinting faults to serialise migration in fault paths */ 1225 if ((flags & FOLL_NUMA) && pmd_numa(*pmd)) 1226 goto out; 1227 1228 page = pmd_page(*pmd); 1229 VM_BUG_ON_PAGE(!PageHead(page), page); 1230 if (flags & FOLL_TOUCH) { 1231 pmd_t _pmd; 1232 /* 1233 * We should set the dirty bit only for FOLL_WRITE but 1234 * for now the dirty bit in the pmd is meaningless. 1235 * And if the dirty bit will become meaningful and 1236 * we'll only set it with FOLL_WRITE, an atomic 1237 * set_bit will be required on the pmd to set the 1238 * young bit, instead of the current set_pmd_at. 1239 */ 1240 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 1241 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, 1242 pmd, _pmd, 1)) 1243 update_mmu_cache_pmd(vma, addr, pmd); 1244 } 1245 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 1246 if (page->mapping && trylock_page(page)) { 1247 lru_add_drain(); 1248 if (page->mapping) 1249 mlock_vma_page(page); 1250 unlock_page(page); 1251 } 1252 } 1253 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1254 VM_BUG_ON_PAGE(!PageCompound(page), page); 1255 if (flags & FOLL_GET) 1256 get_page_foll(page); 1257 1258 out: 1259 return page; 1260 } 1261 1262 /* NUMA hinting page fault entry point for trans huge pmds */ 1263 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, 1264 unsigned long addr, pmd_t pmd, pmd_t *pmdp) 1265 { 1266 spinlock_t *ptl; 1267 struct anon_vma *anon_vma = NULL; 1268 struct page *page; 1269 unsigned long haddr = addr & HPAGE_PMD_MASK; 1270 int page_nid = -1, this_nid = numa_node_id(); 1271 int target_nid, last_cpupid = -1; 1272 bool page_locked; 1273 bool migrated = false; 1274 int flags = 0; 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 spin_unlock(ptl); 1287 wait_migrate_huge_page(vma->anon_vma, pmdp); 1288 goto out; 1289 } 1290 1291 page = pmd_page(pmd); 1292 BUG_ON(is_huge_zero_page(page)); 1293 page_nid = page_to_nid(page); 1294 last_cpupid = page_cpupid_last(page); 1295 count_vm_numa_event(NUMA_HINT_FAULTS); 1296 if (page_nid == this_nid) { 1297 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); 1298 flags |= TNF_FAULT_LOCAL; 1299 } 1300 1301 /* 1302 * Avoid grouping on DSO/COW pages in specific and RO pages 1303 * in general, RO pages shouldn't hurt as much anyway since 1304 * they can be in shared cache state. 1305 */ 1306 if (!pmd_write(pmd)) 1307 flags |= TNF_NO_GROUP; 1308 1309 /* 1310 * Acquire the page lock to serialise THP migrations but avoid dropping 1311 * page_table_lock if at all possible 1312 */ 1313 page_locked = trylock_page(page); 1314 target_nid = mpol_misplaced(page, vma, haddr); 1315 if (target_nid == -1) { 1316 /* If the page was locked, there are no parallel migrations */ 1317 if (page_locked) 1318 goto clear_pmdnuma; 1319 } 1320 1321 /* Migration could have started since the pmd_trans_migrating check */ 1322 if (!page_locked) { 1323 spin_unlock(ptl); 1324 wait_on_page_locked(page); 1325 page_nid = -1; 1326 goto out; 1327 } 1328 1329 /* 1330 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma 1331 * to serialises splits 1332 */ 1333 get_page(page); 1334 spin_unlock(ptl); 1335 anon_vma = page_lock_anon_vma_read(page); 1336 1337 /* Confirm the PMD did not change while page_table_lock was released */ 1338 spin_lock(ptl); 1339 if (unlikely(!pmd_same(pmd, *pmdp))) { 1340 unlock_page(page); 1341 put_page(page); 1342 page_nid = -1; 1343 goto out_unlock; 1344 } 1345 1346 /* Bail if we fail to protect against THP splits for any reason */ 1347 if (unlikely(!anon_vma)) { 1348 put_page(page); 1349 page_nid = -1; 1350 goto clear_pmdnuma; 1351 } 1352 1353 /* 1354 * Migrate the THP to the requested node, returns with page unlocked 1355 * and pmd_numa cleared. 1356 */ 1357 spin_unlock(ptl); 1358 migrated = migrate_misplaced_transhuge_page(mm, vma, 1359 pmdp, pmd, addr, page, target_nid); 1360 if (migrated) { 1361 flags |= TNF_MIGRATED; 1362 page_nid = target_nid; 1363 } 1364 1365 goto out; 1366 clear_pmdnuma: 1367 BUG_ON(!PageLocked(page)); 1368 pmd = pmd_mknonnuma(pmd); 1369 set_pmd_at(mm, haddr, pmdp, pmd); 1370 VM_BUG_ON(pmd_numa(*pmdp)); 1371 update_mmu_cache_pmd(vma, addr, pmdp); 1372 unlock_page(page); 1373 out_unlock: 1374 spin_unlock(ptl); 1375 1376 out: 1377 if (anon_vma) 1378 page_unlock_anon_vma_read(anon_vma); 1379 1380 if (page_nid != -1) 1381 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags); 1382 1383 return 0; 1384 } 1385 1386 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1387 pmd_t *pmd, unsigned long addr) 1388 { 1389 spinlock_t *ptl; 1390 int ret = 0; 1391 1392 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { 1393 struct page *page; 1394 pgtable_t pgtable; 1395 pmd_t orig_pmd; 1396 /* 1397 * For architectures like ppc64 we look at deposited pgtable 1398 * when calling pmdp_get_and_clear. So do the 1399 * pgtable_trans_huge_withdraw after finishing pmdp related 1400 * operations. 1401 */ 1402 orig_pmd = pmdp_get_and_clear_full(tlb->mm, addr, pmd, 1403 tlb->fullmm); 1404 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1405 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd); 1406 if (is_huge_zero_pmd(orig_pmd)) { 1407 atomic_long_dec(&tlb->mm->nr_ptes); 1408 spin_unlock(ptl); 1409 put_huge_zero_page(); 1410 } else { 1411 page = pmd_page(orig_pmd); 1412 page_remove_rmap(page); 1413 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); 1414 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1415 VM_BUG_ON_PAGE(!PageHead(page), page); 1416 atomic_long_dec(&tlb->mm->nr_ptes); 1417 spin_unlock(ptl); 1418 tlb_remove_page(tlb, page); 1419 } 1420 pte_free(tlb->mm, pgtable); 1421 ret = 1; 1422 } 1423 return ret; 1424 } 1425 1426 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1427 unsigned long addr, unsigned long end, 1428 unsigned char *vec) 1429 { 1430 spinlock_t *ptl; 1431 int ret = 0; 1432 1433 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { 1434 /* 1435 * All logical pages in the range are present 1436 * if backed by a huge page. 1437 */ 1438 spin_unlock(ptl); 1439 memset(vec, 1, (end - addr) >> PAGE_SHIFT); 1440 ret = 1; 1441 } 1442 1443 return ret; 1444 } 1445 1446 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, 1447 unsigned long old_addr, 1448 unsigned long new_addr, unsigned long old_end, 1449 pmd_t *old_pmd, pmd_t *new_pmd) 1450 { 1451 spinlock_t *old_ptl, *new_ptl; 1452 int ret = 0; 1453 pmd_t pmd; 1454 1455 struct mm_struct *mm = vma->vm_mm; 1456 1457 if ((old_addr & ~HPAGE_PMD_MASK) || 1458 (new_addr & ~HPAGE_PMD_MASK) || 1459 old_end - old_addr < HPAGE_PMD_SIZE || 1460 (new_vma->vm_flags & VM_NOHUGEPAGE)) 1461 goto out; 1462 1463 /* 1464 * The destination pmd shouldn't be established, free_pgtables() 1465 * should have release it. 1466 */ 1467 if (WARN_ON(!pmd_none(*new_pmd))) { 1468 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1469 goto out; 1470 } 1471 1472 /* 1473 * We don't have to worry about the ordering of src and dst 1474 * ptlocks because exclusive mmap_sem prevents deadlock. 1475 */ 1476 ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl); 1477 if (ret == 1) { 1478 new_ptl = pmd_lockptr(mm, new_pmd); 1479 if (new_ptl != old_ptl) 1480 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 1481 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); 1482 VM_BUG_ON(!pmd_none(*new_pmd)); 1483 1484 if (pmd_move_must_withdraw(new_ptl, old_ptl)) { 1485 pgtable_t pgtable; 1486 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); 1487 pgtable_trans_huge_deposit(mm, new_pmd, pgtable); 1488 } 1489 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd)); 1490 if (new_ptl != old_ptl) 1491 spin_unlock(new_ptl); 1492 spin_unlock(old_ptl); 1493 } 1494 out: 1495 return ret; 1496 } 1497 1498 /* 1499 * Returns 1500 * - 0 if PMD could not be locked 1501 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary 1502 * - HPAGE_PMD_NR is protections changed and TLB flush necessary 1503 */ 1504 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1505 unsigned long addr, pgprot_t newprot, int prot_numa) 1506 { 1507 struct mm_struct *mm = vma->vm_mm; 1508 spinlock_t *ptl; 1509 int ret = 0; 1510 1511 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { 1512 pmd_t entry; 1513 ret = 1; 1514 if (!prot_numa) { 1515 entry = pmdp_get_and_clear_notify(mm, addr, pmd); 1516 if (pmd_numa(entry)) 1517 entry = pmd_mknonnuma(entry); 1518 entry = pmd_modify(entry, newprot); 1519 ret = HPAGE_PMD_NR; 1520 set_pmd_at(mm, addr, pmd, entry); 1521 BUG_ON(pmd_write(entry)); 1522 } else { 1523 struct page *page = pmd_page(*pmd); 1524 1525 /* 1526 * Do not trap faults against the zero page. The 1527 * read-only data is likely to be read-cached on the 1528 * local CPU cache and it is less useful to know about 1529 * local vs remote hits on the zero page. 1530 */ 1531 if (!is_huge_zero_page(page) && 1532 !pmd_numa(*pmd)) { 1533 pmdp_set_numa(mm, addr, pmd); 1534 ret = HPAGE_PMD_NR; 1535 } 1536 } 1537 spin_unlock(ptl); 1538 } 1539 1540 return ret; 1541 } 1542 1543 /* 1544 * Returns 1 if a given pmd maps a stable (not under splitting) thp. 1545 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise. 1546 * 1547 * Note that if it returns 1, this routine returns without unlocking page 1548 * table locks. So callers must unlock them. 1549 */ 1550 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma, 1551 spinlock_t **ptl) 1552 { 1553 *ptl = pmd_lock(vma->vm_mm, pmd); 1554 if (likely(pmd_trans_huge(*pmd))) { 1555 if (unlikely(pmd_trans_splitting(*pmd))) { 1556 spin_unlock(*ptl); 1557 wait_split_huge_page(vma->anon_vma, pmd); 1558 return -1; 1559 } else { 1560 /* Thp mapped by 'pmd' is stable, so we can 1561 * handle it as it is. */ 1562 return 1; 1563 } 1564 } 1565 spin_unlock(*ptl); 1566 return 0; 1567 } 1568 1569 /* 1570 * This function returns whether a given @page is mapped onto the @address 1571 * in the virtual space of @mm. 1572 * 1573 * When it's true, this function returns *pmd with holding the page table lock 1574 * and passing it back to the caller via @ptl. 1575 * If it's false, returns NULL without holding the page table lock. 1576 */ 1577 pmd_t *page_check_address_pmd(struct page *page, 1578 struct mm_struct *mm, 1579 unsigned long address, 1580 enum page_check_address_pmd_flag flag, 1581 spinlock_t **ptl) 1582 { 1583 pgd_t *pgd; 1584 pud_t *pud; 1585 pmd_t *pmd; 1586 1587 if (address & ~HPAGE_PMD_MASK) 1588 return NULL; 1589 1590 pgd = pgd_offset(mm, address); 1591 if (!pgd_present(*pgd)) 1592 return NULL; 1593 pud = pud_offset(pgd, address); 1594 if (!pud_present(*pud)) 1595 return NULL; 1596 pmd = pmd_offset(pud, address); 1597 1598 *ptl = pmd_lock(mm, pmd); 1599 if (!pmd_present(*pmd)) 1600 goto unlock; 1601 if (pmd_page(*pmd) != page) 1602 goto unlock; 1603 /* 1604 * split_vma() may create temporary aliased mappings. There is 1605 * no risk as long as all huge pmd are found and have their 1606 * splitting bit set before __split_huge_page_refcount 1607 * runs. Finding the same huge pmd more than once during the 1608 * same rmap walk is not a problem. 1609 */ 1610 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && 1611 pmd_trans_splitting(*pmd)) 1612 goto unlock; 1613 if (pmd_trans_huge(*pmd)) { 1614 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && 1615 !pmd_trans_splitting(*pmd)); 1616 return pmd; 1617 } 1618 unlock: 1619 spin_unlock(*ptl); 1620 return NULL; 1621 } 1622 1623 static int __split_huge_page_splitting(struct page *page, 1624 struct vm_area_struct *vma, 1625 unsigned long address) 1626 { 1627 struct mm_struct *mm = vma->vm_mm; 1628 spinlock_t *ptl; 1629 pmd_t *pmd; 1630 int ret = 0; 1631 /* For mmu_notifiers */ 1632 const unsigned long mmun_start = address; 1633 const unsigned long mmun_end = address + HPAGE_PMD_SIZE; 1634 1635 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1636 pmd = page_check_address_pmd(page, mm, address, 1637 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG, &ptl); 1638 if (pmd) { 1639 /* 1640 * We can't temporarily set the pmd to null in order 1641 * to split it, the pmd must remain marked huge at all 1642 * times or the VM won't take the pmd_trans_huge paths 1643 * and it won't wait on the anon_vma->root->rwsem to 1644 * serialize against split_huge_page*. 1645 */ 1646 pmdp_splitting_flush(vma, address, pmd); 1647 1648 ret = 1; 1649 spin_unlock(ptl); 1650 } 1651 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1652 1653 return ret; 1654 } 1655 1656 static void __split_huge_page_refcount(struct page *page, 1657 struct list_head *list) 1658 { 1659 int i; 1660 struct zone *zone = page_zone(page); 1661 struct lruvec *lruvec; 1662 int tail_count = 0; 1663 1664 /* prevent PageLRU to go away from under us, and freeze lru stats */ 1665 spin_lock_irq(&zone->lru_lock); 1666 lruvec = mem_cgroup_page_lruvec(page, zone); 1667 1668 compound_lock(page); 1669 /* complete memcg works before add pages to LRU */ 1670 mem_cgroup_split_huge_fixup(page); 1671 1672 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 1673 struct page *page_tail = page + i; 1674 1675 /* tail_page->_mapcount cannot change */ 1676 BUG_ON(page_mapcount(page_tail) < 0); 1677 tail_count += page_mapcount(page_tail); 1678 /* check for overflow */ 1679 BUG_ON(tail_count < 0); 1680 BUG_ON(atomic_read(&page_tail->_count) != 0); 1681 /* 1682 * tail_page->_count is zero and not changing from 1683 * under us. But get_page_unless_zero() may be running 1684 * from under us on the tail_page. If we used 1685 * atomic_set() below instead of atomic_add(), we 1686 * would then run atomic_set() concurrently with 1687 * get_page_unless_zero(), and atomic_set() is 1688 * implemented in C not using locked ops. spin_unlock 1689 * on x86 sometime uses locked ops because of PPro 1690 * errata 66, 92, so unless somebody can guarantee 1691 * atomic_set() here would be safe on all archs (and 1692 * not only on x86), it's safer to use atomic_add(). 1693 */ 1694 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, 1695 &page_tail->_count); 1696 1697 /* after clearing PageTail the gup refcount can be released */ 1698 smp_mb__after_atomic(); 1699 1700 /* 1701 * retain hwpoison flag of the poisoned tail page: 1702 * fix for the unsuitable process killed on Guest Machine(KVM) 1703 * by the memory-failure. 1704 */ 1705 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON; 1706 page_tail->flags |= (page->flags & 1707 ((1L << PG_referenced) | 1708 (1L << PG_swapbacked) | 1709 (1L << PG_mlocked) | 1710 (1L << PG_uptodate) | 1711 (1L << PG_active) | 1712 (1L << PG_unevictable))); 1713 page_tail->flags |= (1L << PG_dirty); 1714 1715 /* clear PageTail before overwriting first_page */ 1716 smp_wmb(); 1717 1718 /* 1719 * __split_huge_page_splitting() already set the 1720 * splitting bit in all pmd that could map this 1721 * hugepage, that will ensure no CPU can alter the 1722 * mapcount on the head page. The mapcount is only 1723 * accounted in the head page and it has to be 1724 * transferred to all tail pages in the below code. So 1725 * for this code to be safe, the split the mapcount 1726 * can't change. But that doesn't mean userland can't 1727 * keep changing and reading the page contents while 1728 * we transfer the mapcount, so the pmd splitting 1729 * status is achieved setting a reserved bit in the 1730 * pmd, not by clearing the present bit. 1731 */ 1732 page_tail->_mapcount = page->_mapcount; 1733 1734 BUG_ON(page_tail->mapping); 1735 page_tail->mapping = page->mapping; 1736 1737 page_tail->index = page->index + i; 1738 page_cpupid_xchg_last(page_tail, page_cpupid_last(page)); 1739 1740 BUG_ON(!PageAnon(page_tail)); 1741 BUG_ON(!PageUptodate(page_tail)); 1742 BUG_ON(!PageDirty(page_tail)); 1743 BUG_ON(!PageSwapBacked(page_tail)); 1744 1745 lru_add_page_tail(page, page_tail, lruvec, list); 1746 } 1747 atomic_sub(tail_count, &page->_count); 1748 BUG_ON(atomic_read(&page->_count) <= 0); 1749 1750 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1); 1751 1752 ClearPageCompound(page); 1753 compound_unlock(page); 1754 spin_unlock_irq(&zone->lru_lock); 1755 1756 for (i = 1; i < HPAGE_PMD_NR; i++) { 1757 struct page *page_tail = page + i; 1758 BUG_ON(page_count(page_tail) <= 0); 1759 /* 1760 * Tail pages may be freed if there wasn't any mapping 1761 * like if add_to_swap() is running on a lru page that 1762 * had its mapping zapped. And freeing these pages 1763 * requires taking the lru_lock so we do the put_page 1764 * of the tail pages after the split is complete. 1765 */ 1766 put_page(page_tail); 1767 } 1768 1769 /* 1770 * Only the head page (now become a regular page) is required 1771 * to be pinned by the caller. 1772 */ 1773 BUG_ON(page_count(page) <= 0); 1774 } 1775 1776 static int __split_huge_page_map(struct page *page, 1777 struct vm_area_struct *vma, 1778 unsigned long address) 1779 { 1780 struct mm_struct *mm = vma->vm_mm; 1781 spinlock_t *ptl; 1782 pmd_t *pmd, _pmd; 1783 int ret = 0, i; 1784 pgtable_t pgtable; 1785 unsigned long haddr; 1786 1787 pmd = page_check_address_pmd(page, mm, address, 1788 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl); 1789 if (pmd) { 1790 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1791 pmd_populate(mm, &_pmd, pgtable); 1792 if (pmd_write(*pmd)) 1793 BUG_ON(page_mapcount(page) != 1); 1794 1795 haddr = address; 1796 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1797 pte_t *pte, entry; 1798 BUG_ON(PageCompound(page+i)); 1799 /* 1800 * Note that pmd_numa is not transferred deliberately 1801 * to avoid any possibility that pte_numa leaks to 1802 * a PROT_NONE VMA by accident. 1803 */ 1804 entry = mk_pte(page + i, vma->vm_page_prot); 1805 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1806 if (!pmd_write(*pmd)) 1807 entry = pte_wrprotect(entry); 1808 if (!pmd_young(*pmd)) 1809 entry = pte_mkold(entry); 1810 pte = pte_offset_map(&_pmd, haddr); 1811 BUG_ON(!pte_none(*pte)); 1812 set_pte_at(mm, haddr, pte, entry); 1813 pte_unmap(pte); 1814 } 1815 1816 smp_wmb(); /* make pte visible before pmd */ 1817 /* 1818 * Up to this point the pmd is present and huge and 1819 * userland has the whole access to the hugepage 1820 * during the split (which happens in place). If we 1821 * overwrite the pmd with the not-huge version 1822 * pointing to the pte here (which of course we could 1823 * if all CPUs were bug free), userland could trigger 1824 * a small page size TLB miss on the small sized TLB 1825 * while the hugepage TLB entry is still established 1826 * in the huge TLB. Some CPU doesn't like that. See 1827 * http://support.amd.com/us/Processor_TechDocs/41322.pdf, 1828 * Erratum 383 on page 93. Intel should be safe but is 1829 * also warns that it's only safe if the permission 1830 * and cache attributes of the two entries loaded in 1831 * the two TLB is identical (which should be the case 1832 * here). But it is generally safer to never allow 1833 * small and huge TLB entries for the same virtual 1834 * address to be loaded simultaneously. So instead of 1835 * doing "pmd_populate(); flush_tlb_range();" we first 1836 * mark the current pmd notpresent (atomically because 1837 * here the pmd_trans_huge and pmd_trans_splitting 1838 * must remain set at all times on the pmd until the 1839 * split is complete for this pmd), then we flush the 1840 * SMP TLB and finally we write the non-huge version 1841 * of the pmd entry with pmd_populate. 1842 */ 1843 pmdp_invalidate(vma, address, pmd); 1844 pmd_populate(mm, pmd, pgtable); 1845 ret = 1; 1846 spin_unlock(ptl); 1847 } 1848 1849 return ret; 1850 } 1851 1852 /* must be called with anon_vma->root->rwsem held */ 1853 static void __split_huge_page(struct page *page, 1854 struct anon_vma *anon_vma, 1855 struct list_head *list) 1856 { 1857 int mapcount, mapcount2; 1858 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 1859 struct anon_vma_chain *avc; 1860 1861 BUG_ON(!PageHead(page)); 1862 BUG_ON(PageTail(page)); 1863 1864 mapcount = 0; 1865 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1866 struct vm_area_struct *vma = avc->vma; 1867 unsigned long addr = vma_address(page, vma); 1868 BUG_ON(is_vma_temporary_stack(vma)); 1869 mapcount += __split_huge_page_splitting(page, vma, addr); 1870 } 1871 /* 1872 * It is critical that new vmas are added to the tail of the 1873 * anon_vma list. This guarantes that if copy_huge_pmd() runs 1874 * and establishes a child pmd before 1875 * __split_huge_page_splitting() freezes the parent pmd (so if 1876 * we fail to prevent copy_huge_pmd() from running until the 1877 * whole __split_huge_page() is complete), we will still see 1878 * the newly established pmd of the child later during the 1879 * walk, to be able to set it as pmd_trans_splitting too. 1880 */ 1881 if (mapcount != page_mapcount(page)) { 1882 pr_err("mapcount %d page_mapcount %d\n", 1883 mapcount, page_mapcount(page)); 1884 BUG(); 1885 } 1886 1887 __split_huge_page_refcount(page, list); 1888 1889 mapcount2 = 0; 1890 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1891 struct vm_area_struct *vma = avc->vma; 1892 unsigned long addr = vma_address(page, vma); 1893 BUG_ON(is_vma_temporary_stack(vma)); 1894 mapcount2 += __split_huge_page_map(page, vma, addr); 1895 } 1896 if (mapcount != mapcount2) { 1897 pr_err("mapcount %d mapcount2 %d page_mapcount %d\n", 1898 mapcount, mapcount2, page_mapcount(page)); 1899 BUG(); 1900 } 1901 } 1902 1903 /* 1904 * Split a hugepage into normal pages. This doesn't change the position of head 1905 * page. If @list is null, tail pages will be added to LRU list, otherwise, to 1906 * @list. Both head page and tail pages will inherit mapping, flags, and so on 1907 * from the hugepage. 1908 * Return 0 if the hugepage is split successfully otherwise return 1. 1909 */ 1910 int split_huge_page_to_list(struct page *page, struct list_head *list) 1911 { 1912 struct anon_vma *anon_vma; 1913 int ret = 1; 1914 1915 BUG_ON(is_huge_zero_page(page)); 1916 BUG_ON(!PageAnon(page)); 1917 1918 /* 1919 * The caller does not necessarily hold an mmap_sem that would prevent 1920 * the anon_vma disappearing so we first we take a reference to it 1921 * and then lock the anon_vma for write. This is similar to 1922 * page_lock_anon_vma_read except the write lock is taken to serialise 1923 * against parallel split or collapse operations. 1924 */ 1925 anon_vma = page_get_anon_vma(page); 1926 if (!anon_vma) 1927 goto out; 1928 anon_vma_lock_write(anon_vma); 1929 1930 ret = 0; 1931 if (!PageCompound(page)) 1932 goto out_unlock; 1933 1934 BUG_ON(!PageSwapBacked(page)); 1935 __split_huge_page(page, anon_vma, list); 1936 count_vm_event(THP_SPLIT); 1937 1938 BUG_ON(PageCompound(page)); 1939 out_unlock: 1940 anon_vma_unlock_write(anon_vma); 1941 put_anon_vma(anon_vma); 1942 out: 1943 return ret; 1944 } 1945 1946 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE) 1947 1948 int hugepage_madvise(struct vm_area_struct *vma, 1949 unsigned long *vm_flags, int advice) 1950 { 1951 switch (advice) { 1952 case MADV_HUGEPAGE: 1953 #ifdef CONFIG_S390 1954 /* 1955 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 1956 * can't handle this properly after s390_enable_sie, so we simply 1957 * ignore the madvise to prevent qemu from causing a SIGSEGV. 1958 */ 1959 if (mm_has_pgste(vma->vm_mm)) 1960 return 0; 1961 #endif 1962 /* 1963 * Be somewhat over-protective like KSM for now! 1964 */ 1965 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) 1966 return -EINVAL; 1967 *vm_flags &= ~VM_NOHUGEPAGE; 1968 *vm_flags |= VM_HUGEPAGE; 1969 /* 1970 * If the vma become good for khugepaged to scan, 1971 * register it here without waiting a page fault that 1972 * may not happen any time soon. 1973 */ 1974 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags))) 1975 return -ENOMEM; 1976 break; 1977 case MADV_NOHUGEPAGE: 1978 /* 1979 * Be somewhat over-protective like KSM for now! 1980 */ 1981 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) 1982 return -EINVAL; 1983 *vm_flags &= ~VM_HUGEPAGE; 1984 *vm_flags |= VM_NOHUGEPAGE; 1985 /* 1986 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1987 * this vma even if we leave the mm registered in khugepaged if 1988 * it got registered before VM_NOHUGEPAGE was set. 1989 */ 1990 break; 1991 } 1992 1993 return 0; 1994 } 1995 1996 static int __init khugepaged_slab_init(void) 1997 { 1998 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1999 sizeof(struct mm_slot), 2000 __alignof__(struct mm_slot), 0, NULL); 2001 if (!mm_slot_cache) 2002 return -ENOMEM; 2003 2004 return 0; 2005 } 2006 2007 static inline struct mm_slot *alloc_mm_slot(void) 2008 { 2009 if (!mm_slot_cache) /* initialization failed */ 2010 return NULL; 2011 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 2012 } 2013 2014 static inline void free_mm_slot(struct mm_slot *mm_slot) 2015 { 2016 kmem_cache_free(mm_slot_cache, mm_slot); 2017 } 2018 2019 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 2020 { 2021 struct mm_slot *mm_slot; 2022 2023 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) 2024 if (mm == mm_slot->mm) 2025 return mm_slot; 2026 2027 return NULL; 2028 } 2029 2030 static void insert_to_mm_slots_hash(struct mm_struct *mm, 2031 struct mm_slot *mm_slot) 2032 { 2033 mm_slot->mm = mm; 2034 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); 2035 } 2036 2037 static inline int khugepaged_test_exit(struct mm_struct *mm) 2038 { 2039 return atomic_read(&mm->mm_users) == 0; 2040 } 2041 2042 int __khugepaged_enter(struct mm_struct *mm) 2043 { 2044 struct mm_slot *mm_slot; 2045 int wakeup; 2046 2047 mm_slot = alloc_mm_slot(); 2048 if (!mm_slot) 2049 return -ENOMEM; 2050 2051 /* __khugepaged_exit() must not run from under us */ 2052 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); 2053 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 2054 free_mm_slot(mm_slot); 2055 return 0; 2056 } 2057 2058 spin_lock(&khugepaged_mm_lock); 2059 insert_to_mm_slots_hash(mm, mm_slot); 2060 /* 2061 * Insert just behind the scanning cursor, to let the area settle 2062 * down a little. 2063 */ 2064 wakeup = list_empty(&khugepaged_scan.mm_head); 2065 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 2066 spin_unlock(&khugepaged_mm_lock); 2067 2068 atomic_inc(&mm->mm_count); 2069 if (wakeup) 2070 wake_up_interruptible(&khugepaged_wait); 2071 2072 return 0; 2073 } 2074 2075 int khugepaged_enter_vma_merge(struct vm_area_struct *vma, 2076 unsigned long vm_flags) 2077 { 2078 unsigned long hstart, hend; 2079 if (!vma->anon_vma) 2080 /* 2081 * Not yet faulted in so we will register later in the 2082 * page fault if needed. 2083 */ 2084 return 0; 2085 if (vma->vm_ops) 2086 /* khugepaged not yet working on file or special mappings */ 2087 return 0; 2088 VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma); 2089 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2090 hend = vma->vm_end & HPAGE_PMD_MASK; 2091 if (hstart < hend) 2092 return khugepaged_enter(vma, vm_flags); 2093 return 0; 2094 } 2095 2096 void __khugepaged_exit(struct mm_struct *mm) 2097 { 2098 struct mm_slot *mm_slot; 2099 int free = 0; 2100 2101 spin_lock(&khugepaged_mm_lock); 2102 mm_slot = get_mm_slot(mm); 2103 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 2104 hash_del(&mm_slot->hash); 2105 list_del(&mm_slot->mm_node); 2106 free = 1; 2107 } 2108 spin_unlock(&khugepaged_mm_lock); 2109 2110 if (free) { 2111 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2112 free_mm_slot(mm_slot); 2113 mmdrop(mm); 2114 } else if (mm_slot) { 2115 /* 2116 * This is required to serialize against 2117 * khugepaged_test_exit() (which is guaranteed to run 2118 * under mmap sem read mode). Stop here (after we 2119 * return all pagetables will be destroyed) until 2120 * khugepaged has finished working on the pagetables 2121 * under the mmap_sem. 2122 */ 2123 down_write(&mm->mmap_sem); 2124 up_write(&mm->mmap_sem); 2125 } 2126 } 2127 2128 static void release_pte_page(struct page *page) 2129 { 2130 /* 0 stands for page_is_file_cache(page) == false */ 2131 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 2132 unlock_page(page); 2133 putback_lru_page(page); 2134 } 2135 2136 static void release_pte_pages(pte_t *pte, pte_t *_pte) 2137 { 2138 while (--_pte >= pte) { 2139 pte_t pteval = *_pte; 2140 if (!pte_none(pteval)) 2141 release_pte_page(pte_page(pteval)); 2142 } 2143 } 2144 2145 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 2146 unsigned long address, 2147 pte_t *pte) 2148 { 2149 struct page *page; 2150 pte_t *_pte; 2151 int referenced = 0, none = 0; 2152 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 2153 _pte++, address += PAGE_SIZE) { 2154 pte_t pteval = *_pte; 2155 if (pte_none(pteval)) { 2156 if (++none <= khugepaged_max_ptes_none) 2157 continue; 2158 else 2159 goto out; 2160 } 2161 if (!pte_present(pteval) || !pte_write(pteval)) 2162 goto out; 2163 page = vm_normal_page(vma, address, pteval); 2164 if (unlikely(!page)) 2165 goto out; 2166 2167 VM_BUG_ON_PAGE(PageCompound(page), page); 2168 VM_BUG_ON_PAGE(!PageAnon(page), page); 2169 VM_BUG_ON_PAGE(!PageSwapBacked(page), page); 2170 2171 /* cannot use mapcount: can't collapse if there's a gup pin */ 2172 if (page_count(page) != 1) 2173 goto out; 2174 /* 2175 * We can do it before isolate_lru_page because the 2176 * page can't be freed from under us. NOTE: PG_lock 2177 * is needed to serialize against split_huge_page 2178 * when invoked from the VM. 2179 */ 2180 if (!trylock_page(page)) 2181 goto out; 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 = 1; 2199 } 2200 if (likely(referenced)) 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)) { 2218 clear_user_highpage(page, address); 2219 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 2220 } else { 2221 src_page = pte_page(pteval); 2222 copy_user_highpage(page, src_page, address, vma); 2223 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); 2224 release_pte_page(src_page); 2225 /* 2226 * ptl mostly unnecessary, but preempt has to 2227 * be disabled to update the per-cpu stats 2228 * inside page_remove_rmap(). 2229 */ 2230 spin_lock(ptl); 2231 /* 2232 * paravirt calls inside pte_clear here are 2233 * superfluous. 2234 */ 2235 pte_clear(vma->vm_mm, address, _pte); 2236 page_remove_rmap(src_page); 2237 spin_unlock(ptl); 2238 free_page_and_swap_cache(src_page); 2239 } 2240 2241 address += PAGE_SIZE; 2242 page++; 2243 } 2244 } 2245 2246 static void khugepaged_alloc_sleep(void) 2247 { 2248 wait_event_freezable_timeout(khugepaged_wait, false, 2249 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 2250 } 2251 2252 static int khugepaged_node_load[MAX_NUMNODES]; 2253 2254 static bool khugepaged_scan_abort(int nid) 2255 { 2256 int i; 2257 2258 /* 2259 * If zone_reclaim_mode is disabled, then no extra effort is made to 2260 * allocate memory locally. 2261 */ 2262 if (!zone_reclaim_mode) 2263 return false; 2264 2265 /* If there is a count for this node already, it must be acceptable */ 2266 if (khugepaged_node_load[nid]) 2267 return false; 2268 2269 for (i = 0; i < MAX_NUMNODES; i++) { 2270 if (!khugepaged_node_load[i]) 2271 continue; 2272 if (node_distance(nid, i) > RECLAIM_DISTANCE) 2273 return true; 2274 } 2275 return false; 2276 } 2277 2278 #ifdef CONFIG_NUMA 2279 static int khugepaged_find_target_node(void) 2280 { 2281 static int last_khugepaged_target_node = NUMA_NO_NODE; 2282 int nid, target_node = 0, max_value = 0; 2283 2284 /* find first node with max normal pages hit */ 2285 for (nid = 0; nid < MAX_NUMNODES; nid++) 2286 if (khugepaged_node_load[nid] > max_value) { 2287 max_value = khugepaged_node_load[nid]; 2288 target_node = nid; 2289 } 2290 2291 /* do some balance if several nodes have the same hit record */ 2292 if (target_node <= last_khugepaged_target_node) 2293 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; 2294 nid++) 2295 if (max_value == khugepaged_node_load[nid]) { 2296 target_node = nid; 2297 break; 2298 } 2299 2300 last_khugepaged_target_node = target_node; 2301 return target_node; 2302 } 2303 2304 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2305 { 2306 if (IS_ERR(*hpage)) { 2307 if (!*wait) 2308 return false; 2309 2310 *wait = false; 2311 *hpage = NULL; 2312 khugepaged_alloc_sleep(); 2313 } else if (*hpage) { 2314 put_page(*hpage); 2315 *hpage = NULL; 2316 } 2317 2318 return true; 2319 } 2320 2321 static struct page 2322 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 2323 struct vm_area_struct *vma, unsigned long address, 2324 int node) 2325 { 2326 VM_BUG_ON_PAGE(*hpage, *hpage); 2327 2328 /* 2329 * Before allocating the hugepage, release the mmap_sem read lock. 2330 * The allocation can take potentially a long time if it involves 2331 * sync compaction, and we do not need to hold the mmap_sem during 2332 * that. We will recheck the vma after taking it again in write mode. 2333 */ 2334 up_read(&mm->mmap_sem); 2335 2336 *hpage = alloc_pages_exact_node(node, alloc_hugepage_gfpmask( 2337 khugepaged_defrag(), __GFP_OTHER_NODE), HPAGE_PMD_ORDER); 2338 if (unlikely(!*hpage)) { 2339 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2340 *hpage = ERR_PTR(-ENOMEM); 2341 return NULL; 2342 } 2343 2344 count_vm_event(THP_COLLAPSE_ALLOC); 2345 return *hpage; 2346 } 2347 #else 2348 static int khugepaged_find_target_node(void) 2349 { 2350 return 0; 2351 } 2352 2353 static inline struct page *alloc_hugepage(int defrag) 2354 { 2355 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), 2356 HPAGE_PMD_ORDER); 2357 } 2358 2359 static struct page *khugepaged_alloc_hugepage(bool *wait) 2360 { 2361 struct page *hpage; 2362 2363 do { 2364 hpage = alloc_hugepage(khugepaged_defrag()); 2365 if (!hpage) { 2366 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2367 if (!*wait) 2368 return NULL; 2369 2370 *wait = false; 2371 khugepaged_alloc_sleep(); 2372 } else 2373 count_vm_event(THP_COLLAPSE_ALLOC); 2374 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 2375 2376 return hpage; 2377 } 2378 2379 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2380 { 2381 if (!*hpage) 2382 *hpage = khugepaged_alloc_hugepage(wait); 2383 2384 if (unlikely(!*hpage)) 2385 return false; 2386 2387 return true; 2388 } 2389 2390 static struct page 2391 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 2392 struct vm_area_struct *vma, unsigned long address, 2393 int node) 2394 { 2395 up_read(&mm->mmap_sem); 2396 VM_BUG_ON(!*hpage); 2397 return *hpage; 2398 } 2399 #endif 2400 2401 static bool hugepage_vma_check(struct vm_area_struct *vma) 2402 { 2403 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 2404 (vma->vm_flags & VM_NOHUGEPAGE)) 2405 return false; 2406 2407 if (!vma->anon_vma || vma->vm_ops) 2408 return false; 2409 if (is_vma_temporary_stack(vma)) 2410 return false; 2411 VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma); 2412 return true; 2413 } 2414 2415 static void collapse_huge_page(struct mm_struct *mm, 2416 unsigned long address, 2417 struct page **hpage, 2418 struct vm_area_struct *vma, 2419 int node) 2420 { 2421 pmd_t *pmd, _pmd; 2422 pte_t *pte; 2423 pgtable_t pgtable; 2424 struct page *new_page; 2425 spinlock_t *pmd_ptl, *pte_ptl; 2426 int isolated; 2427 unsigned long hstart, hend; 2428 struct mem_cgroup *memcg; 2429 unsigned long mmun_start; /* For mmu_notifiers */ 2430 unsigned long mmun_end; /* For mmu_notifiers */ 2431 2432 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2433 2434 /* release the mmap_sem read lock. */ 2435 new_page = khugepaged_alloc_page(hpage, mm, vma, address, node); 2436 if (!new_page) 2437 return; 2438 2439 if (unlikely(mem_cgroup_try_charge(new_page, mm, 2440 GFP_TRANSHUGE, &memcg))) 2441 return; 2442 2443 /* 2444 * Prevent all access to pagetables with the exception of 2445 * gup_fast later hanlded by the ptep_clear_flush and the VM 2446 * handled by the anon_vma lock + PG_lock. 2447 */ 2448 down_write(&mm->mmap_sem); 2449 if (unlikely(khugepaged_test_exit(mm))) 2450 goto out; 2451 2452 vma = find_vma(mm, address); 2453 if (!vma) 2454 goto out; 2455 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2456 hend = vma->vm_end & HPAGE_PMD_MASK; 2457 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 2458 goto out; 2459 if (!hugepage_vma_check(vma)) 2460 goto out; 2461 pmd = mm_find_pmd(mm, address); 2462 if (!pmd) 2463 goto out; 2464 2465 anon_vma_lock_write(vma->anon_vma); 2466 2467 pte = pte_offset_map(pmd, address); 2468 pte_ptl = pte_lockptr(mm, pmd); 2469 2470 mmun_start = address; 2471 mmun_end = address + HPAGE_PMD_SIZE; 2472 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2473 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ 2474 /* 2475 * After this gup_fast can't run anymore. This also removes 2476 * any huge TLB entry from the CPU so we won't allow 2477 * huge and small TLB entries for the same virtual address 2478 * to avoid the risk of CPU bugs in that area. 2479 */ 2480 _pmd = pmdp_clear_flush(vma, address, pmd); 2481 spin_unlock(pmd_ptl); 2482 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2483 2484 spin_lock(pte_ptl); 2485 isolated = __collapse_huge_page_isolate(vma, address, pte); 2486 spin_unlock(pte_ptl); 2487 2488 if (unlikely(!isolated)) { 2489 pte_unmap(pte); 2490 spin_lock(pmd_ptl); 2491 BUG_ON(!pmd_none(*pmd)); 2492 /* 2493 * We can only use set_pmd_at when establishing 2494 * hugepmds and never for establishing regular pmds that 2495 * points to regular pagetables. Use pmd_populate for that 2496 */ 2497 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 2498 spin_unlock(pmd_ptl); 2499 anon_vma_unlock_write(vma->anon_vma); 2500 goto out; 2501 } 2502 2503 /* 2504 * All pages are isolated and locked so anon_vma rmap 2505 * can't run anymore. 2506 */ 2507 anon_vma_unlock_write(vma->anon_vma); 2508 2509 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); 2510 pte_unmap(pte); 2511 __SetPageUptodate(new_page); 2512 pgtable = pmd_pgtable(_pmd); 2513 2514 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); 2515 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 2516 2517 /* 2518 * spin_lock() below is not the equivalent of smp_wmb(), so 2519 * this is needed to avoid the copy_huge_page writes to become 2520 * visible after the set_pmd_at() write. 2521 */ 2522 smp_wmb(); 2523 2524 spin_lock(pmd_ptl); 2525 BUG_ON(!pmd_none(*pmd)); 2526 page_add_new_anon_rmap(new_page, vma, address); 2527 mem_cgroup_commit_charge(new_page, memcg, false); 2528 lru_cache_add_active_or_unevictable(new_page, vma); 2529 pgtable_trans_huge_deposit(mm, pmd, pgtable); 2530 set_pmd_at(mm, address, pmd, _pmd); 2531 update_mmu_cache_pmd(vma, address, pmd); 2532 spin_unlock(pmd_ptl); 2533 2534 *hpage = NULL; 2535 2536 khugepaged_pages_collapsed++; 2537 out_up_write: 2538 up_write(&mm->mmap_sem); 2539 return; 2540 2541 out: 2542 mem_cgroup_cancel_charge(new_page, memcg); 2543 goto out_up_write; 2544 } 2545 2546 static int khugepaged_scan_pmd(struct mm_struct *mm, 2547 struct vm_area_struct *vma, 2548 unsigned long address, 2549 struct page **hpage) 2550 { 2551 pmd_t *pmd; 2552 pte_t *pte, *_pte; 2553 int ret = 0, referenced = 0, none = 0; 2554 struct page *page; 2555 unsigned long _address; 2556 spinlock_t *ptl; 2557 int node = NUMA_NO_NODE; 2558 2559 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2560 2561 pmd = mm_find_pmd(mm, address); 2562 if (!pmd) 2563 goto out; 2564 2565 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 2566 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2567 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2568 _pte++, _address += PAGE_SIZE) { 2569 pte_t pteval = *_pte; 2570 if (pte_none(pteval)) { 2571 if (++none <= khugepaged_max_ptes_none) 2572 continue; 2573 else 2574 goto out_unmap; 2575 } 2576 if (!pte_present(pteval) || !pte_write(pteval)) 2577 goto out_unmap; 2578 page = vm_normal_page(vma, _address, pteval); 2579 if (unlikely(!page)) 2580 goto out_unmap; 2581 /* 2582 * Record which node the original page is from and save this 2583 * information to khugepaged_node_load[]. 2584 * Khupaged will allocate hugepage from the node has the max 2585 * hit record. 2586 */ 2587 node = page_to_nid(page); 2588 if (khugepaged_scan_abort(node)) 2589 goto out_unmap; 2590 khugepaged_node_load[node]++; 2591 VM_BUG_ON_PAGE(PageCompound(page), page); 2592 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) 2593 goto out_unmap; 2594 /* cannot use mapcount: can't collapse if there's a gup pin */ 2595 if (page_count(page) != 1) 2596 goto out_unmap; 2597 if (pte_young(pteval) || PageReferenced(page) || 2598 mmu_notifier_test_young(vma->vm_mm, address)) 2599 referenced = 1; 2600 } 2601 if (referenced) 2602 ret = 1; 2603 out_unmap: 2604 pte_unmap_unlock(pte, ptl); 2605 if (ret) { 2606 node = khugepaged_find_target_node(); 2607 /* collapse_huge_page will return with the mmap_sem released */ 2608 collapse_huge_page(mm, address, hpage, vma, node); 2609 } 2610 out: 2611 return ret; 2612 } 2613 2614 static void collect_mm_slot(struct mm_slot *mm_slot) 2615 { 2616 struct mm_struct *mm = mm_slot->mm; 2617 2618 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2619 2620 if (khugepaged_test_exit(mm)) { 2621 /* free mm_slot */ 2622 hash_del(&mm_slot->hash); 2623 list_del(&mm_slot->mm_node); 2624 2625 /* 2626 * Not strictly needed because the mm exited already. 2627 * 2628 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2629 */ 2630 2631 /* khugepaged_mm_lock actually not necessary for the below */ 2632 free_mm_slot(mm_slot); 2633 mmdrop(mm); 2634 } 2635 } 2636 2637 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2638 struct page **hpage) 2639 __releases(&khugepaged_mm_lock) 2640 __acquires(&khugepaged_mm_lock) 2641 { 2642 struct mm_slot *mm_slot; 2643 struct mm_struct *mm; 2644 struct vm_area_struct *vma; 2645 int progress = 0; 2646 2647 VM_BUG_ON(!pages); 2648 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2649 2650 if (khugepaged_scan.mm_slot) 2651 mm_slot = khugepaged_scan.mm_slot; 2652 else { 2653 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2654 struct mm_slot, mm_node); 2655 khugepaged_scan.address = 0; 2656 khugepaged_scan.mm_slot = mm_slot; 2657 } 2658 spin_unlock(&khugepaged_mm_lock); 2659 2660 mm = mm_slot->mm; 2661 down_read(&mm->mmap_sem); 2662 if (unlikely(khugepaged_test_exit(mm))) 2663 vma = NULL; 2664 else 2665 vma = find_vma(mm, khugepaged_scan.address); 2666 2667 progress++; 2668 for (; vma; vma = vma->vm_next) { 2669 unsigned long hstart, hend; 2670 2671 cond_resched(); 2672 if (unlikely(khugepaged_test_exit(mm))) { 2673 progress++; 2674 break; 2675 } 2676 if (!hugepage_vma_check(vma)) { 2677 skip: 2678 progress++; 2679 continue; 2680 } 2681 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2682 hend = vma->vm_end & HPAGE_PMD_MASK; 2683 if (hstart >= hend) 2684 goto skip; 2685 if (khugepaged_scan.address > hend) 2686 goto skip; 2687 if (khugepaged_scan.address < hstart) 2688 khugepaged_scan.address = hstart; 2689 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2690 2691 while (khugepaged_scan.address < hend) { 2692 int ret; 2693 cond_resched(); 2694 if (unlikely(khugepaged_test_exit(mm))) 2695 goto breakouterloop; 2696 2697 VM_BUG_ON(khugepaged_scan.address < hstart || 2698 khugepaged_scan.address + HPAGE_PMD_SIZE > 2699 hend); 2700 ret = khugepaged_scan_pmd(mm, vma, 2701 khugepaged_scan.address, 2702 hpage); 2703 /* move to next address */ 2704 khugepaged_scan.address += HPAGE_PMD_SIZE; 2705 progress += HPAGE_PMD_NR; 2706 if (ret) 2707 /* we released mmap_sem so break loop */ 2708 goto breakouterloop_mmap_sem; 2709 if (progress >= pages) 2710 goto breakouterloop; 2711 } 2712 } 2713 breakouterloop: 2714 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2715 breakouterloop_mmap_sem: 2716 2717 spin_lock(&khugepaged_mm_lock); 2718 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2719 /* 2720 * Release the current mm_slot if this mm is about to die, or 2721 * if we scanned all vmas of this mm. 2722 */ 2723 if (khugepaged_test_exit(mm) || !vma) { 2724 /* 2725 * Make sure that if mm_users is reaching zero while 2726 * khugepaged runs here, khugepaged_exit will find 2727 * mm_slot not pointing to the exiting mm. 2728 */ 2729 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2730 khugepaged_scan.mm_slot = list_entry( 2731 mm_slot->mm_node.next, 2732 struct mm_slot, mm_node); 2733 khugepaged_scan.address = 0; 2734 } else { 2735 khugepaged_scan.mm_slot = NULL; 2736 khugepaged_full_scans++; 2737 } 2738 2739 collect_mm_slot(mm_slot); 2740 } 2741 2742 return progress; 2743 } 2744 2745 static int khugepaged_has_work(void) 2746 { 2747 return !list_empty(&khugepaged_scan.mm_head) && 2748 khugepaged_enabled(); 2749 } 2750 2751 static int khugepaged_wait_event(void) 2752 { 2753 return !list_empty(&khugepaged_scan.mm_head) || 2754 kthread_should_stop(); 2755 } 2756 2757 static void khugepaged_do_scan(void) 2758 { 2759 struct page *hpage = NULL; 2760 unsigned int progress = 0, pass_through_head = 0; 2761 unsigned int pages = khugepaged_pages_to_scan; 2762 bool wait = true; 2763 2764 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2765 2766 while (progress < pages) { 2767 if (!khugepaged_prealloc_page(&hpage, &wait)) 2768 break; 2769 2770 cond_resched(); 2771 2772 if (unlikely(kthread_should_stop() || freezing(current))) 2773 break; 2774 2775 spin_lock(&khugepaged_mm_lock); 2776 if (!khugepaged_scan.mm_slot) 2777 pass_through_head++; 2778 if (khugepaged_has_work() && 2779 pass_through_head < 2) 2780 progress += khugepaged_scan_mm_slot(pages - progress, 2781 &hpage); 2782 else 2783 progress = pages; 2784 spin_unlock(&khugepaged_mm_lock); 2785 } 2786 2787 if (!IS_ERR_OR_NULL(hpage)) 2788 put_page(hpage); 2789 } 2790 2791 static void khugepaged_wait_work(void) 2792 { 2793 try_to_freeze(); 2794 2795 if (khugepaged_has_work()) { 2796 if (!khugepaged_scan_sleep_millisecs) 2797 return; 2798 2799 wait_event_freezable_timeout(khugepaged_wait, 2800 kthread_should_stop(), 2801 msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); 2802 return; 2803 } 2804 2805 if (khugepaged_enabled()) 2806 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 2807 } 2808 2809 static int khugepaged(void *none) 2810 { 2811 struct mm_slot *mm_slot; 2812 2813 set_freezable(); 2814 set_user_nice(current, MAX_NICE); 2815 2816 while (!kthread_should_stop()) { 2817 khugepaged_do_scan(); 2818 khugepaged_wait_work(); 2819 } 2820 2821 spin_lock(&khugepaged_mm_lock); 2822 mm_slot = khugepaged_scan.mm_slot; 2823 khugepaged_scan.mm_slot = NULL; 2824 if (mm_slot) 2825 collect_mm_slot(mm_slot); 2826 spin_unlock(&khugepaged_mm_lock); 2827 return 0; 2828 } 2829 2830 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2831 unsigned long haddr, pmd_t *pmd) 2832 { 2833 struct mm_struct *mm = vma->vm_mm; 2834 pgtable_t pgtable; 2835 pmd_t _pmd; 2836 int i; 2837 2838 pmdp_clear_flush_notify(vma, haddr, pmd); 2839 /* leave pmd empty until pte is filled */ 2840 2841 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2842 pmd_populate(mm, &_pmd, pgtable); 2843 2844 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2845 pte_t *pte, entry; 2846 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2847 entry = pte_mkspecial(entry); 2848 pte = pte_offset_map(&_pmd, haddr); 2849 VM_BUG_ON(!pte_none(*pte)); 2850 set_pte_at(mm, haddr, pte, entry); 2851 pte_unmap(pte); 2852 } 2853 smp_wmb(); /* make pte visible before pmd */ 2854 pmd_populate(mm, pmd, pgtable); 2855 put_huge_zero_page(); 2856 } 2857 2858 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address, 2859 pmd_t *pmd) 2860 { 2861 spinlock_t *ptl; 2862 struct page *page; 2863 struct mm_struct *mm = vma->vm_mm; 2864 unsigned long haddr = address & HPAGE_PMD_MASK; 2865 unsigned long mmun_start; /* For mmu_notifiers */ 2866 unsigned long mmun_end; /* For mmu_notifiers */ 2867 2868 BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE); 2869 2870 mmun_start = haddr; 2871 mmun_end = haddr + HPAGE_PMD_SIZE; 2872 again: 2873 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2874 ptl = pmd_lock(mm, pmd); 2875 if (unlikely(!pmd_trans_huge(*pmd))) { 2876 spin_unlock(ptl); 2877 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2878 return; 2879 } 2880 if (is_huge_zero_pmd(*pmd)) { 2881 __split_huge_zero_page_pmd(vma, haddr, pmd); 2882 spin_unlock(ptl); 2883 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2884 return; 2885 } 2886 page = pmd_page(*pmd); 2887 VM_BUG_ON_PAGE(!page_count(page), page); 2888 get_page(page); 2889 spin_unlock(ptl); 2890 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2891 2892 split_huge_page(page); 2893 2894 put_page(page); 2895 2896 /* 2897 * We don't always have down_write of mmap_sem here: a racing 2898 * do_huge_pmd_wp_page() might have copied-on-write to another 2899 * huge page before our split_huge_page() got the anon_vma lock. 2900 */ 2901 if (unlikely(pmd_trans_huge(*pmd))) 2902 goto again; 2903 } 2904 2905 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address, 2906 pmd_t *pmd) 2907 { 2908 struct vm_area_struct *vma; 2909 2910 vma = find_vma(mm, address); 2911 BUG_ON(vma == NULL); 2912 split_huge_page_pmd(vma, address, pmd); 2913 } 2914 2915 static void split_huge_page_address(struct mm_struct *mm, 2916 unsigned long address) 2917 { 2918 pgd_t *pgd; 2919 pud_t *pud; 2920 pmd_t *pmd; 2921 2922 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); 2923 2924 pgd = pgd_offset(mm, address); 2925 if (!pgd_present(*pgd)) 2926 return; 2927 2928 pud = pud_offset(pgd, address); 2929 if (!pud_present(*pud)) 2930 return; 2931 2932 pmd = pmd_offset(pud, address); 2933 if (!pmd_present(*pmd)) 2934 return; 2935 /* 2936 * Caller holds the mmap_sem write mode, so a huge pmd cannot 2937 * materialize from under us. 2938 */ 2939 split_huge_page_pmd_mm(mm, address, pmd); 2940 } 2941 2942 void __vma_adjust_trans_huge(struct vm_area_struct *vma, 2943 unsigned long start, 2944 unsigned long end, 2945 long adjust_next) 2946 { 2947 /* 2948 * If the new start address isn't hpage aligned and it could 2949 * previously contain an hugepage: check if we need to split 2950 * an huge pmd. 2951 */ 2952 if (start & ~HPAGE_PMD_MASK && 2953 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2954 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2955 split_huge_page_address(vma->vm_mm, start); 2956 2957 /* 2958 * If the new end address isn't hpage aligned and it could 2959 * previously contain an hugepage: check if we need to split 2960 * an huge pmd. 2961 */ 2962 if (end & ~HPAGE_PMD_MASK && 2963 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2964 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2965 split_huge_page_address(vma->vm_mm, end); 2966 2967 /* 2968 * If we're also updating the vma->vm_next->vm_start, if the new 2969 * vm_next->vm_start isn't page aligned and it could previously 2970 * contain an hugepage: check if we need to split an huge pmd. 2971 */ 2972 if (adjust_next > 0) { 2973 struct vm_area_struct *next = vma->vm_next; 2974 unsigned long nstart = next->vm_start; 2975 nstart += adjust_next << PAGE_SHIFT; 2976 if (nstart & ~HPAGE_PMD_MASK && 2977 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2978 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2979 split_huge_page_address(next->vm_mm, nstart); 2980 } 2981 } 2982