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_wrprotect(entry); 788 entry = pmd_mkhuge(entry); 789 pgtable_trans_huge_deposit(mm, pmd, pgtable); 790 set_pmd_at(mm, haddr, pmd, entry); 791 atomic_long_inc(&mm->nr_ptes); 792 return true; 793 } 794 795 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 796 unsigned long address, pmd_t *pmd, 797 unsigned int flags) 798 { 799 struct page *page; 800 unsigned long haddr = address & HPAGE_PMD_MASK; 801 802 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end) 803 return VM_FAULT_FALLBACK; 804 if (unlikely(anon_vma_prepare(vma))) 805 return VM_FAULT_OOM; 806 if (unlikely(khugepaged_enter(vma, vma->vm_flags))) 807 return VM_FAULT_OOM; 808 if (!(flags & FAULT_FLAG_WRITE) && 809 transparent_hugepage_use_zero_page()) { 810 spinlock_t *ptl; 811 pgtable_t pgtable; 812 struct page *zero_page; 813 bool set; 814 pgtable = pte_alloc_one(mm, haddr); 815 if (unlikely(!pgtable)) 816 return VM_FAULT_OOM; 817 zero_page = get_huge_zero_page(); 818 if (unlikely(!zero_page)) { 819 pte_free(mm, pgtable); 820 count_vm_event(THP_FAULT_FALLBACK); 821 return VM_FAULT_FALLBACK; 822 } 823 ptl = pmd_lock(mm, pmd); 824 set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, 825 zero_page); 826 spin_unlock(ptl); 827 if (!set) { 828 pte_free(mm, pgtable); 829 put_huge_zero_page(); 830 } 831 return 0; 832 } 833 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 834 vma, haddr, numa_node_id(), 0); 835 if (unlikely(!page)) { 836 count_vm_event(THP_FAULT_FALLBACK); 837 return VM_FAULT_FALLBACK; 838 } 839 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page))) { 840 put_page(page); 841 count_vm_event(THP_FAULT_FALLBACK); 842 return VM_FAULT_FALLBACK; 843 } 844 845 count_vm_event(THP_FAULT_ALLOC); 846 return 0; 847 } 848 849 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 850 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 851 struct vm_area_struct *vma) 852 { 853 spinlock_t *dst_ptl, *src_ptl; 854 struct page *src_page; 855 pmd_t pmd; 856 pgtable_t pgtable; 857 int ret; 858 859 ret = -ENOMEM; 860 pgtable = pte_alloc_one(dst_mm, addr); 861 if (unlikely(!pgtable)) 862 goto out; 863 864 dst_ptl = pmd_lock(dst_mm, dst_pmd); 865 src_ptl = pmd_lockptr(src_mm, src_pmd); 866 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); 867 868 ret = -EAGAIN; 869 pmd = *src_pmd; 870 if (unlikely(!pmd_trans_huge(pmd))) { 871 pte_free(dst_mm, pgtable); 872 goto out_unlock; 873 } 874 /* 875 * When page table lock is held, the huge zero pmd should not be 876 * under splitting since we don't split the page itself, only pmd to 877 * a page table. 878 */ 879 if (is_huge_zero_pmd(pmd)) { 880 struct page *zero_page; 881 bool set; 882 /* 883 * get_huge_zero_page() will never allocate a new page here, 884 * since we already have a zero page to copy. It just takes a 885 * reference. 886 */ 887 zero_page = get_huge_zero_page(); 888 set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, 889 zero_page); 890 BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */ 891 ret = 0; 892 goto out_unlock; 893 } 894 895 if (unlikely(pmd_trans_splitting(pmd))) { 896 /* split huge page running from under us */ 897 spin_unlock(src_ptl); 898 spin_unlock(dst_ptl); 899 pte_free(dst_mm, pgtable); 900 901 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ 902 goto out; 903 } 904 src_page = pmd_page(pmd); 905 VM_BUG_ON_PAGE(!PageHead(src_page), src_page); 906 get_page(src_page); 907 page_dup_rmap(src_page); 908 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 909 910 pmdp_set_wrprotect(src_mm, addr, src_pmd); 911 pmd = pmd_mkold(pmd_wrprotect(pmd)); 912 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); 913 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 914 atomic_long_inc(&dst_mm->nr_ptes); 915 916 ret = 0; 917 out_unlock: 918 spin_unlock(src_ptl); 919 spin_unlock(dst_ptl); 920 out: 921 return ret; 922 } 923 924 void huge_pmd_set_accessed(struct mm_struct *mm, 925 struct vm_area_struct *vma, 926 unsigned long address, 927 pmd_t *pmd, pmd_t orig_pmd, 928 int dirty) 929 { 930 spinlock_t *ptl; 931 pmd_t entry; 932 unsigned long haddr; 933 934 ptl = pmd_lock(mm, pmd); 935 if (unlikely(!pmd_same(*pmd, orig_pmd))) 936 goto unlock; 937 938 entry = pmd_mkyoung(orig_pmd); 939 haddr = address & HPAGE_PMD_MASK; 940 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty)) 941 update_mmu_cache_pmd(vma, address, pmd); 942 943 unlock: 944 spin_unlock(ptl); 945 } 946 947 /* 948 * Save CONFIG_DEBUG_PAGEALLOC from faulting falsely on tail pages 949 * during copy_user_huge_page()'s copy_page_rep(): in the case when 950 * the source page gets split and a tail freed before copy completes. 951 * Called under pmd_lock of checked pmd, so safe from splitting itself. 952 */ 953 static void get_user_huge_page(struct page *page) 954 { 955 if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) { 956 struct page *endpage = page + HPAGE_PMD_NR; 957 958 atomic_add(HPAGE_PMD_NR, &page->_count); 959 while (++page < endpage) 960 get_huge_page_tail(page); 961 } else { 962 get_page(page); 963 } 964 } 965 966 static void put_user_huge_page(struct page *page) 967 { 968 if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) { 969 struct page *endpage = page + HPAGE_PMD_NR; 970 971 while (page < endpage) 972 put_page(page++); 973 } else { 974 put_page(page); 975 } 976 } 977 978 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, 979 struct vm_area_struct *vma, 980 unsigned long address, 981 pmd_t *pmd, pmd_t orig_pmd, 982 struct page *page, 983 unsigned long haddr) 984 { 985 struct mem_cgroup *memcg; 986 spinlock_t *ptl; 987 pgtable_t pgtable; 988 pmd_t _pmd; 989 int ret = 0, i; 990 struct page **pages; 991 unsigned long mmun_start; /* For mmu_notifiers */ 992 unsigned long mmun_end; /* For mmu_notifiers */ 993 994 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 995 GFP_KERNEL); 996 if (unlikely(!pages)) { 997 ret |= VM_FAULT_OOM; 998 goto out; 999 } 1000 1001 for (i = 0; i < HPAGE_PMD_NR; i++) { 1002 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | 1003 __GFP_OTHER_NODE, 1004 vma, address, page_to_nid(page)); 1005 if (unlikely(!pages[i] || 1006 mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL, 1007 &memcg))) { 1008 if (pages[i]) 1009 put_page(pages[i]); 1010 while (--i >= 0) { 1011 memcg = (void *)page_private(pages[i]); 1012 set_page_private(pages[i], 0); 1013 mem_cgroup_cancel_charge(pages[i], memcg); 1014 put_page(pages[i]); 1015 } 1016 kfree(pages); 1017 ret |= VM_FAULT_OOM; 1018 goto out; 1019 } 1020 set_page_private(pages[i], (unsigned long)memcg); 1021 } 1022 1023 for (i = 0; i < HPAGE_PMD_NR; i++) { 1024 copy_user_highpage(pages[i], page + i, 1025 haddr + PAGE_SIZE * i, vma); 1026 __SetPageUptodate(pages[i]); 1027 cond_resched(); 1028 } 1029 1030 mmun_start = haddr; 1031 mmun_end = haddr + HPAGE_PMD_SIZE; 1032 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1033 1034 ptl = pmd_lock(mm, pmd); 1035 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1036 goto out_free_pages; 1037 VM_BUG_ON_PAGE(!PageHead(page), page); 1038 1039 pmdp_clear_flush(vma, haddr, pmd); 1040 /* leave pmd empty until pte is filled */ 1041 1042 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1043 pmd_populate(mm, &_pmd, pgtable); 1044 1045 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1046 pte_t *pte, entry; 1047 entry = mk_pte(pages[i], vma->vm_page_prot); 1048 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1049 memcg = (void *)page_private(pages[i]); 1050 set_page_private(pages[i], 0); 1051 page_add_new_anon_rmap(pages[i], vma, haddr); 1052 mem_cgroup_commit_charge(pages[i], memcg, false); 1053 lru_cache_add_active_or_unevictable(pages[i], vma); 1054 pte = pte_offset_map(&_pmd, haddr); 1055 VM_BUG_ON(!pte_none(*pte)); 1056 set_pte_at(mm, haddr, pte, entry); 1057 pte_unmap(pte); 1058 } 1059 kfree(pages); 1060 1061 smp_wmb(); /* make pte visible before pmd */ 1062 pmd_populate(mm, pmd, pgtable); 1063 page_remove_rmap(page); 1064 spin_unlock(ptl); 1065 1066 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1067 1068 ret |= VM_FAULT_WRITE; 1069 put_page(page); 1070 1071 out: 1072 return ret; 1073 1074 out_free_pages: 1075 spin_unlock(ptl); 1076 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1077 for (i = 0; i < HPAGE_PMD_NR; i++) { 1078 memcg = (void *)page_private(pages[i]); 1079 set_page_private(pages[i], 0); 1080 mem_cgroup_cancel_charge(pages[i], memcg); 1081 put_page(pages[i]); 1082 } 1083 kfree(pages); 1084 goto out; 1085 } 1086 1087 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 1088 unsigned long address, pmd_t *pmd, pmd_t orig_pmd) 1089 { 1090 spinlock_t *ptl; 1091 int ret = 0; 1092 struct page *page = NULL, *new_page; 1093 struct mem_cgroup *memcg; 1094 unsigned long haddr; 1095 unsigned long mmun_start; /* For mmu_notifiers */ 1096 unsigned long mmun_end; /* For mmu_notifiers */ 1097 1098 ptl = pmd_lockptr(mm, pmd); 1099 VM_BUG_ON_VMA(!vma->anon_vma, vma); 1100 haddr = address & HPAGE_PMD_MASK; 1101 if (is_huge_zero_pmd(orig_pmd)) 1102 goto alloc; 1103 spin_lock(ptl); 1104 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1105 goto out_unlock; 1106 1107 page = pmd_page(orig_pmd); 1108 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); 1109 if (page_mapcount(page) == 1) { 1110 pmd_t entry; 1111 entry = pmd_mkyoung(orig_pmd); 1112 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1113 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 1114 update_mmu_cache_pmd(vma, address, pmd); 1115 ret |= VM_FAULT_WRITE; 1116 goto out_unlock; 1117 } 1118 get_user_huge_page(page); 1119 spin_unlock(ptl); 1120 alloc: 1121 if (transparent_hugepage_enabled(vma) && 1122 !transparent_hugepage_debug_cow()) 1123 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 1124 vma, haddr, numa_node_id(), 0); 1125 else 1126 new_page = NULL; 1127 1128 if (unlikely(!new_page)) { 1129 if (!page) { 1130 split_huge_page_pmd(vma, address, pmd); 1131 ret |= VM_FAULT_FALLBACK; 1132 } else { 1133 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 1134 pmd, orig_pmd, page, haddr); 1135 if (ret & VM_FAULT_OOM) { 1136 split_huge_page(page); 1137 ret |= VM_FAULT_FALLBACK; 1138 } 1139 put_user_huge_page(page); 1140 } 1141 count_vm_event(THP_FAULT_FALLBACK); 1142 goto out; 1143 } 1144 1145 if (unlikely(mem_cgroup_try_charge(new_page, mm, 1146 GFP_TRANSHUGE, &memcg))) { 1147 put_page(new_page); 1148 if (page) { 1149 split_huge_page(page); 1150 put_user_huge_page(page); 1151 } else 1152 split_huge_page_pmd(vma, address, pmd); 1153 ret |= VM_FAULT_FALLBACK; 1154 count_vm_event(THP_FAULT_FALLBACK); 1155 goto out; 1156 } 1157 1158 count_vm_event(THP_FAULT_ALLOC); 1159 1160 if (!page) 1161 clear_huge_page(new_page, haddr, HPAGE_PMD_NR); 1162 else 1163 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 1164 __SetPageUptodate(new_page); 1165 1166 mmun_start = haddr; 1167 mmun_end = haddr + HPAGE_PMD_SIZE; 1168 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1169 1170 spin_lock(ptl); 1171 if (page) 1172 put_user_huge_page(page); 1173 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 1174 spin_unlock(ptl); 1175 mem_cgroup_cancel_charge(new_page, memcg); 1176 put_page(new_page); 1177 goto out_mn; 1178 } else { 1179 pmd_t entry; 1180 entry = mk_huge_pmd(new_page, vma->vm_page_prot); 1181 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1182 pmdp_clear_flush(vma, haddr, pmd); 1183 page_add_new_anon_rmap(new_page, vma, haddr); 1184 mem_cgroup_commit_charge(new_page, memcg, false); 1185 lru_cache_add_active_or_unevictable(new_page, vma); 1186 set_pmd_at(mm, haddr, pmd, entry); 1187 update_mmu_cache_pmd(vma, address, pmd); 1188 if (!page) { 1189 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 1190 put_huge_zero_page(); 1191 } else { 1192 VM_BUG_ON_PAGE(!PageHead(page), page); 1193 page_remove_rmap(page); 1194 put_page(page); 1195 } 1196 ret |= VM_FAULT_WRITE; 1197 } 1198 spin_unlock(ptl); 1199 out_mn: 1200 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1201 out: 1202 return ret; 1203 out_unlock: 1204 spin_unlock(ptl); 1205 return ret; 1206 } 1207 1208 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1209 unsigned long addr, 1210 pmd_t *pmd, 1211 unsigned int flags) 1212 { 1213 struct mm_struct *mm = vma->vm_mm; 1214 struct page *page = NULL; 1215 1216 assert_spin_locked(pmd_lockptr(mm, pmd)); 1217 1218 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 1219 goto out; 1220 1221 /* Avoid dumping huge zero page */ 1222 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) 1223 return ERR_PTR(-EFAULT); 1224 1225 /* Full NUMA hinting faults to serialise migration in fault paths */ 1226 if ((flags & FOLL_NUMA) && pmd_numa(*pmd)) 1227 goto out; 1228 1229 page = pmd_page(*pmd); 1230 VM_BUG_ON_PAGE(!PageHead(page), page); 1231 if (flags & FOLL_TOUCH) { 1232 pmd_t _pmd; 1233 /* 1234 * We should set the dirty bit only for FOLL_WRITE but 1235 * for now the dirty bit in the pmd is meaningless. 1236 * And if the dirty bit will become meaningful and 1237 * we'll only set it with FOLL_WRITE, an atomic 1238 * set_bit will be required on the pmd to set the 1239 * young bit, instead of the current set_pmd_at. 1240 */ 1241 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 1242 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, 1243 pmd, _pmd, 1)) 1244 update_mmu_cache_pmd(vma, addr, pmd); 1245 } 1246 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 1247 if (page->mapping && trylock_page(page)) { 1248 lru_add_drain(); 1249 if (page->mapping) 1250 mlock_vma_page(page); 1251 unlock_page(page); 1252 } 1253 } 1254 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1255 VM_BUG_ON_PAGE(!PageCompound(page), page); 1256 if (flags & FOLL_GET) 1257 get_page_foll(page); 1258 1259 out: 1260 return page; 1261 } 1262 1263 /* NUMA hinting page fault entry point for trans huge pmds */ 1264 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, 1265 unsigned long addr, pmd_t pmd, pmd_t *pmdp) 1266 { 1267 spinlock_t *ptl; 1268 struct anon_vma *anon_vma = NULL; 1269 struct page *page; 1270 unsigned long haddr = addr & HPAGE_PMD_MASK; 1271 int page_nid = -1, this_nid = numa_node_id(); 1272 int target_nid, last_cpupid = -1; 1273 bool page_locked; 1274 bool migrated = false; 1275 int flags = 0; 1276 1277 ptl = pmd_lock(mm, pmdp); 1278 if (unlikely(!pmd_same(pmd, *pmdp))) 1279 goto out_unlock; 1280 1281 /* 1282 * If there are potential migrations, wait for completion and retry 1283 * without disrupting NUMA hinting information. Do not relock and 1284 * check_same as the page may no longer be mapped. 1285 */ 1286 if (unlikely(pmd_trans_migrating(*pmdp))) { 1287 spin_unlock(ptl); 1288 wait_migrate_huge_page(vma->anon_vma, pmdp); 1289 goto out; 1290 } 1291 1292 page = pmd_page(pmd); 1293 BUG_ON(is_huge_zero_page(page)); 1294 page_nid = page_to_nid(page); 1295 last_cpupid = page_cpupid_last(page); 1296 count_vm_numa_event(NUMA_HINT_FAULTS); 1297 if (page_nid == this_nid) { 1298 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); 1299 flags |= TNF_FAULT_LOCAL; 1300 } 1301 1302 /* 1303 * Avoid grouping on DSO/COW pages in specific and RO pages 1304 * in general, RO pages shouldn't hurt as much anyway since 1305 * they can be in shared cache state. 1306 */ 1307 if (!pmd_write(pmd)) 1308 flags |= TNF_NO_GROUP; 1309 1310 /* 1311 * Acquire the page lock to serialise THP migrations but avoid dropping 1312 * page_table_lock if at all possible 1313 */ 1314 page_locked = trylock_page(page); 1315 target_nid = mpol_misplaced(page, vma, haddr); 1316 if (target_nid == -1) { 1317 /* If the page was locked, there are no parallel migrations */ 1318 if (page_locked) 1319 goto clear_pmdnuma; 1320 } 1321 1322 /* Migration could have started since the pmd_trans_migrating check */ 1323 if (!page_locked) { 1324 spin_unlock(ptl); 1325 wait_on_page_locked(page); 1326 page_nid = -1; 1327 goto out; 1328 } 1329 1330 /* 1331 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma 1332 * to serialises splits 1333 */ 1334 get_page(page); 1335 spin_unlock(ptl); 1336 anon_vma = page_lock_anon_vma_read(page); 1337 1338 /* Confirm the PMD did not change while page_table_lock was released */ 1339 spin_lock(ptl); 1340 if (unlikely(!pmd_same(pmd, *pmdp))) { 1341 unlock_page(page); 1342 put_page(page); 1343 page_nid = -1; 1344 goto out_unlock; 1345 } 1346 1347 /* Bail if we fail to protect against THP splits for any reason */ 1348 if (unlikely(!anon_vma)) { 1349 put_page(page); 1350 page_nid = -1; 1351 goto clear_pmdnuma; 1352 } 1353 1354 /* 1355 * Migrate the THP to the requested node, returns with page unlocked 1356 * and pmd_numa cleared. 1357 */ 1358 spin_unlock(ptl); 1359 migrated = migrate_misplaced_transhuge_page(mm, vma, 1360 pmdp, pmd, addr, page, target_nid); 1361 if (migrated) { 1362 flags |= TNF_MIGRATED; 1363 page_nid = target_nid; 1364 } 1365 1366 goto out; 1367 clear_pmdnuma: 1368 BUG_ON(!PageLocked(page)); 1369 pmd = pmd_mknonnuma(pmd); 1370 set_pmd_at(mm, haddr, pmdp, pmd); 1371 VM_BUG_ON(pmd_numa(*pmdp)); 1372 update_mmu_cache_pmd(vma, addr, pmdp); 1373 unlock_page(page); 1374 out_unlock: 1375 spin_unlock(ptl); 1376 1377 out: 1378 if (anon_vma) 1379 page_unlock_anon_vma_read(anon_vma); 1380 1381 if (page_nid != -1) 1382 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags); 1383 1384 return 0; 1385 } 1386 1387 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1388 pmd_t *pmd, unsigned long addr) 1389 { 1390 spinlock_t *ptl; 1391 int ret = 0; 1392 1393 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { 1394 struct page *page; 1395 pgtable_t pgtable; 1396 pmd_t orig_pmd; 1397 /* 1398 * For architectures like ppc64 we look at deposited pgtable 1399 * when calling pmdp_get_and_clear. So do the 1400 * pgtable_trans_huge_withdraw after finishing pmdp related 1401 * operations. 1402 */ 1403 orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd); 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(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 ret = 1; 1648 spin_unlock(ptl); 1649 } 1650 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1651 1652 return ret; 1653 } 1654 1655 static void __split_huge_page_refcount(struct page *page, 1656 struct list_head *list) 1657 { 1658 int i; 1659 struct zone *zone = page_zone(page); 1660 struct lruvec *lruvec; 1661 int tail_count = 0; 1662 1663 /* prevent PageLRU to go away from under us, and freeze lru stats */ 1664 spin_lock_irq(&zone->lru_lock); 1665 lruvec = mem_cgroup_page_lruvec(page, zone); 1666 1667 compound_lock(page); 1668 /* complete memcg works before add pages to LRU */ 1669 mem_cgroup_split_huge_fixup(page); 1670 1671 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 1672 struct page *page_tail = page + i; 1673 1674 /* tail_page->_mapcount cannot change */ 1675 BUG_ON(page_mapcount(page_tail) < 0); 1676 tail_count += page_mapcount(page_tail); 1677 /* check for overflow */ 1678 BUG_ON(tail_count < 0); 1679 BUG_ON(atomic_read(&page_tail->_count) != 0); 1680 /* 1681 * tail_page->_count is zero and not changing from 1682 * under us. But get_page_unless_zero() may be running 1683 * from under us on the tail_page. If we used 1684 * atomic_set() below instead of atomic_add(), we 1685 * would then run atomic_set() concurrently with 1686 * get_page_unless_zero(), and atomic_set() is 1687 * implemented in C not using locked ops. spin_unlock 1688 * on x86 sometime uses locked ops because of PPro 1689 * errata 66, 92, so unless somebody can guarantee 1690 * atomic_set() here would be safe on all archs (and 1691 * not only on x86), it's safer to use atomic_add(). 1692 */ 1693 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, 1694 &page_tail->_count); 1695 1696 /* after clearing PageTail the gup refcount can be released */ 1697 smp_mb__after_atomic(); 1698 1699 /* 1700 * retain hwpoison flag of the poisoned tail page: 1701 * fix for the unsuitable process killed on Guest Machine(KVM) 1702 * by the memory-failure. 1703 */ 1704 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON; 1705 page_tail->flags |= (page->flags & 1706 ((1L << PG_referenced) | 1707 (1L << PG_swapbacked) | 1708 (1L << PG_mlocked) | 1709 (1L << PG_uptodate) | 1710 (1L << PG_active) | 1711 (1L << PG_unevictable))); 1712 page_tail->flags |= (1L << PG_dirty); 1713 1714 /* clear PageTail before overwriting first_page */ 1715 smp_wmb(); 1716 1717 /* 1718 * __split_huge_page_splitting() already set the 1719 * splitting bit in all pmd that could map this 1720 * hugepage, that will ensure no CPU can alter the 1721 * mapcount on the head page. The mapcount is only 1722 * accounted in the head page and it has to be 1723 * transferred to all tail pages in the below code. So 1724 * for this code to be safe, the split the mapcount 1725 * can't change. But that doesn't mean userland can't 1726 * keep changing and reading the page contents while 1727 * we transfer the mapcount, so the pmd splitting 1728 * status is achieved setting a reserved bit in the 1729 * pmd, not by clearing the present bit. 1730 */ 1731 page_tail->_mapcount = page->_mapcount; 1732 1733 BUG_ON(page_tail->mapping); 1734 page_tail->mapping = page->mapping; 1735 1736 page_tail->index = page->index + i; 1737 page_cpupid_xchg_last(page_tail, page_cpupid_last(page)); 1738 1739 BUG_ON(!PageAnon(page_tail)); 1740 BUG_ON(!PageUptodate(page_tail)); 1741 BUG_ON(!PageDirty(page_tail)); 1742 BUG_ON(!PageSwapBacked(page_tail)); 1743 1744 lru_add_page_tail(page, page_tail, lruvec, list); 1745 } 1746 atomic_sub(tail_count, &page->_count); 1747 BUG_ON(atomic_read(&page->_count) <= 0); 1748 1749 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1); 1750 1751 ClearPageCompound(page); 1752 compound_unlock(page); 1753 spin_unlock_irq(&zone->lru_lock); 1754 1755 for (i = 1; i < HPAGE_PMD_NR; i++) { 1756 struct page *page_tail = page + i; 1757 BUG_ON(page_count(page_tail) <= 0); 1758 /* 1759 * Tail pages may be freed if there wasn't any mapping 1760 * like if add_to_swap() is running on a lru page that 1761 * had its mapping zapped. And freeing these pages 1762 * requires taking the lru_lock so we do the put_page 1763 * of the tail pages after the split is complete. 1764 */ 1765 put_page(page_tail); 1766 } 1767 1768 /* 1769 * Only the head page (now become a regular page) is required 1770 * to be pinned by the caller. 1771 */ 1772 BUG_ON(page_count(page) <= 0); 1773 } 1774 1775 static int __split_huge_page_map(struct page *page, 1776 struct vm_area_struct *vma, 1777 unsigned long address) 1778 { 1779 struct mm_struct *mm = vma->vm_mm; 1780 spinlock_t *ptl; 1781 pmd_t *pmd, _pmd; 1782 int ret = 0, i; 1783 pgtable_t pgtable; 1784 unsigned long haddr; 1785 1786 pmd = page_check_address_pmd(page, mm, address, 1787 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl); 1788 if (pmd) { 1789 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1790 pmd_populate(mm, &_pmd, pgtable); 1791 if (pmd_write(*pmd)) 1792 BUG_ON(page_mapcount(page) != 1); 1793 1794 haddr = address; 1795 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1796 pte_t *pte, entry; 1797 BUG_ON(PageCompound(page+i)); 1798 /* 1799 * Note that pmd_numa is not transferred deliberately 1800 * to avoid any possibility that pte_numa leaks to 1801 * a PROT_NONE VMA by accident. 1802 */ 1803 entry = mk_pte(page + i, vma->vm_page_prot); 1804 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1805 if (!pmd_write(*pmd)) 1806 entry = pte_wrprotect(entry); 1807 if (!pmd_young(*pmd)) 1808 entry = pte_mkold(entry); 1809 pte = pte_offset_map(&_pmd, haddr); 1810 BUG_ON(!pte_none(*pte)); 1811 set_pte_at(mm, haddr, pte, entry); 1812 pte_unmap(pte); 1813 } 1814 1815 smp_wmb(); /* make pte visible before pmd */ 1816 /* 1817 * Up to this point the pmd is present and huge and 1818 * userland has the whole access to the hugepage 1819 * during the split (which happens in place). If we 1820 * overwrite the pmd with the not-huge version 1821 * pointing to the pte here (which of course we could 1822 * if all CPUs were bug free), userland could trigger 1823 * a small page size TLB miss on the small sized TLB 1824 * while the hugepage TLB entry is still established 1825 * in the huge TLB. Some CPU doesn't like that. See 1826 * http://support.amd.com/us/Processor_TechDocs/41322.pdf, 1827 * Erratum 383 on page 93. Intel should be safe but is 1828 * also warns that it's only safe if the permission 1829 * and cache attributes of the two entries loaded in 1830 * the two TLB is identical (which should be the case 1831 * here). But it is generally safer to never allow 1832 * small and huge TLB entries for the same virtual 1833 * address to be loaded simultaneously. So instead of 1834 * doing "pmd_populate(); flush_tlb_range();" we first 1835 * mark the current pmd notpresent (atomically because 1836 * here the pmd_trans_huge and pmd_trans_splitting 1837 * must remain set at all times on the pmd until the 1838 * split is complete for this pmd), then we flush the 1839 * SMP TLB and finally we write the non-huge version 1840 * of the pmd entry with pmd_populate. 1841 */ 1842 pmdp_invalidate(vma, address, pmd); 1843 pmd_populate(mm, pmd, pgtable); 1844 ret = 1; 1845 spin_unlock(ptl); 1846 } 1847 1848 return ret; 1849 } 1850 1851 /* must be called with anon_vma->root->rwsem held */ 1852 static void __split_huge_page(struct page *page, 1853 struct anon_vma *anon_vma, 1854 struct list_head *list) 1855 { 1856 int mapcount, mapcount2; 1857 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 1858 struct anon_vma_chain *avc; 1859 1860 BUG_ON(!PageHead(page)); 1861 BUG_ON(PageTail(page)); 1862 1863 mapcount = 0; 1864 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1865 struct vm_area_struct *vma = avc->vma; 1866 unsigned long addr = vma_address(page, vma); 1867 BUG_ON(is_vma_temporary_stack(vma)); 1868 mapcount += __split_huge_page_splitting(page, vma, addr); 1869 } 1870 /* 1871 * It is critical that new vmas are added to the tail of the 1872 * anon_vma list. This guarantes that if copy_huge_pmd() runs 1873 * and establishes a child pmd before 1874 * __split_huge_page_splitting() freezes the parent pmd (so if 1875 * we fail to prevent copy_huge_pmd() from running until the 1876 * whole __split_huge_page() is complete), we will still see 1877 * the newly established pmd of the child later during the 1878 * walk, to be able to set it as pmd_trans_splitting too. 1879 */ 1880 if (mapcount != page_mapcount(page)) { 1881 pr_err("mapcount %d page_mapcount %d\n", 1882 mapcount, page_mapcount(page)); 1883 BUG(); 1884 } 1885 1886 __split_huge_page_refcount(page, list); 1887 1888 mapcount2 = 0; 1889 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1890 struct vm_area_struct *vma = avc->vma; 1891 unsigned long addr = vma_address(page, vma); 1892 BUG_ON(is_vma_temporary_stack(vma)); 1893 mapcount2 += __split_huge_page_map(page, vma, addr); 1894 } 1895 if (mapcount != mapcount2) { 1896 pr_err("mapcount %d mapcount2 %d page_mapcount %d\n", 1897 mapcount, mapcount2, page_mapcount(page)); 1898 BUG(); 1899 } 1900 } 1901 1902 /* 1903 * Split a hugepage into normal pages. This doesn't change the position of head 1904 * page. If @list is null, tail pages will be added to LRU list, otherwise, to 1905 * @list. Both head page and tail pages will inherit mapping, flags, and so on 1906 * from the hugepage. 1907 * Return 0 if the hugepage is split successfully otherwise return 1. 1908 */ 1909 int split_huge_page_to_list(struct page *page, struct list_head *list) 1910 { 1911 struct anon_vma *anon_vma; 1912 int ret = 1; 1913 1914 BUG_ON(is_huge_zero_page(page)); 1915 BUG_ON(!PageAnon(page)); 1916 1917 /* 1918 * The caller does not necessarily hold an mmap_sem that would prevent 1919 * the anon_vma disappearing so we first we take a reference to it 1920 * and then lock the anon_vma for write. This is similar to 1921 * page_lock_anon_vma_read except the write lock is taken to serialise 1922 * against parallel split or collapse operations. 1923 */ 1924 anon_vma = page_get_anon_vma(page); 1925 if (!anon_vma) 1926 goto out; 1927 anon_vma_lock_write(anon_vma); 1928 1929 ret = 0; 1930 if (!PageCompound(page)) 1931 goto out_unlock; 1932 1933 BUG_ON(!PageSwapBacked(page)); 1934 __split_huge_page(page, anon_vma, list); 1935 count_vm_event(THP_SPLIT); 1936 1937 BUG_ON(PageCompound(page)); 1938 out_unlock: 1939 anon_vma_unlock_write(anon_vma); 1940 put_anon_vma(anon_vma); 1941 out: 1942 return ret; 1943 } 1944 1945 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE) 1946 1947 int hugepage_madvise(struct vm_area_struct *vma, 1948 unsigned long *vm_flags, int advice) 1949 { 1950 switch (advice) { 1951 case MADV_HUGEPAGE: 1952 #ifdef CONFIG_S390 1953 /* 1954 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 1955 * can't handle this properly after s390_enable_sie, so we simply 1956 * ignore the madvise to prevent qemu from causing a SIGSEGV. 1957 */ 1958 if (mm_has_pgste(vma->vm_mm)) 1959 return 0; 1960 #endif 1961 /* 1962 * Be somewhat over-protective like KSM for now! 1963 */ 1964 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) 1965 return -EINVAL; 1966 *vm_flags &= ~VM_NOHUGEPAGE; 1967 *vm_flags |= VM_HUGEPAGE; 1968 /* 1969 * If the vma become good for khugepaged to scan, 1970 * register it here without waiting a page fault that 1971 * may not happen any time soon. 1972 */ 1973 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags))) 1974 return -ENOMEM; 1975 break; 1976 case MADV_NOHUGEPAGE: 1977 /* 1978 * Be somewhat over-protective like KSM for now! 1979 */ 1980 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) 1981 return -EINVAL; 1982 *vm_flags &= ~VM_HUGEPAGE; 1983 *vm_flags |= VM_NOHUGEPAGE; 1984 /* 1985 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1986 * this vma even if we leave the mm registered in khugepaged if 1987 * it got registered before VM_NOHUGEPAGE was set. 1988 */ 1989 break; 1990 } 1991 1992 return 0; 1993 } 1994 1995 static int __init khugepaged_slab_init(void) 1996 { 1997 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1998 sizeof(struct mm_slot), 1999 __alignof__(struct mm_slot), 0, NULL); 2000 if (!mm_slot_cache) 2001 return -ENOMEM; 2002 2003 return 0; 2004 } 2005 2006 static inline struct mm_slot *alloc_mm_slot(void) 2007 { 2008 if (!mm_slot_cache) /* initialization failed */ 2009 return NULL; 2010 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 2011 } 2012 2013 static inline void free_mm_slot(struct mm_slot *mm_slot) 2014 { 2015 kmem_cache_free(mm_slot_cache, mm_slot); 2016 } 2017 2018 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 2019 { 2020 struct mm_slot *mm_slot; 2021 2022 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) 2023 if (mm == mm_slot->mm) 2024 return mm_slot; 2025 2026 return NULL; 2027 } 2028 2029 static void insert_to_mm_slots_hash(struct mm_struct *mm, 2030 struct mm_slot *mm_slot) 2031 { 2032 mm_slot->mm = mm; 2033 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); 2034 } 2035 2036 static inline int khugepaged_test_exit(struct mm_struct *mm) 2037 { 2038 return atomic_read(&mm->mm_users) == 0; 2039 } 2040 2041 int __khugepaged_enter(struct mm_struct *mm) 2042 { 2043 struct mm_slot *mm_slot; 2044 int wakeup; 2045 2046 mm_slot = alloc_mm_slot(); 2047 if (!mm_slot) 2048 return -ENOMEM; 2049 2050 /* __khugepaged_exit() must not run from under us */ 2051 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); 2052 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 2053 free_mm_slot(mm_slot); 2054 return 0; 2055 } 2056 2057 spin_lock(&khugepaged_mm_lock); 2058 insert_to_mm_slots_hash(mm, mm_slot); 2059 /* 2060 * Insert just behind the scanning cursor, to let the area settle 2061 * down a little. 2062 */ 2063 wakeup = list_empty(&khugepaged_scan.mm_head); 2064 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 2065 spin_unlock(&khugepaged_mm_lock); 2066 2067 atomic_inc(&mm->mm_count); 2068 if (wakeup) 2069 wake_up_interruptible(&khugepaged_wait); 2070 2071 return 0; 2072 } 2073 2074 int khugepaged_enter_vma_merge(struct vm_area_struct *vma, 2075 unsigned long vm_flags) 2076 { 2077 unsigned long hstart, hend; 2078 if (!vma->anon_vma) 2079 /* 2080 * Not yet faulted in so we will register later in the 2081 * page fault if needed. 2082 */ 2083 return 0; 2084 if (vma->vm_ops) 2085 /* khugepaged not yet working on file or special mappings */ 2086 return 0; 2087 VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma); 2088 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2089 hend = vma->vm_end & HPAGE_PMD_MASK; 2090 if (hstart < hend) 2091 return khugepaged_enter(vma, vm_flags); 2092 return 0; 2093 } 2094 2095 void __khugepaged_exit(struct mm_struct *mm) 2096 { 2097 struct mm_slot *mm_slot; 2098 int free = 0; 2099 2100 spin_lock(&khugepaged_mm_lock); 2101 mm_slot = get_mm_slot(mm); 2102 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 2103 hash_del(&mm_slot->hash); 2104 list_del(&mm_slot->mm_node); 2105 free = 1; 2106 } 2107 spin_unlock(&khugepaged_mm_lock); 2108 2109 if (free) { 2110 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2111 free_mm_slot(mm_slot); 2112 mmdrop(mm); 2113 } else if (mm_slot) { 2114 /* 2115 * This is required to serialize against 2116 * khugepaged_test_exit() (which is guaranteed to run 2117 * under mmap sem read mode). Stop here (after we 2118 * return all pagetables will be destroyed) until 2119 * khugepaged has finished working on the pagetables 2120 * under the mmap_sem. 2121 */ 2122 down_write(&mm->mmap_sem); 2123 up_write(&mm->mmap_sem); 2124 } 2125 } 2126 2127 static void release_pte_page(struct page *page) 2128 { 2129 /* 0 stands for page_is_file_cache(page) == false */ 2130 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 2131 unlock_page(page); 2132 putback_lru_page(page); 2133 } 2134 2135 static void release_pte_pages(pte_t *pte, pte_t *_pte) 2136 { 2137 while (--_pte >= pte) { 2138 pte_t pteval = *_pte; 2139 if (!pte_none(pteval)) 2140 release_pte_page(pte_page(pteval)); 2141 } 2142 } 2143 2144 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 2145 unsigned long address, 2146 pte_t *pte) 2147 { 2148 struct page *page; 2149 pte_t *_pte; 2150 int referenced = 0, none = 0; 2151 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 2152 _pte++, address += PAGE_SIZE) { 2153 pte_t pteval = *_pte; 2154 if (pte_none(pteval)) { 2155 if (++none <= khugepaged_max_ptes_none) 2156 continue; 2157 else 2158 goto out; 2159 } 2160 if (!pte_present(pteval) || !pte_write(pteval)) 2161 goto out; 2162 page = vm_normal_page(vma, address, pteval); 2163 if (unlikely(!page)) 2164 goto out; 2165 2166 VM_BUG_ON_PAGE(PageCompound(page), page); 2167 VM_BUG_ON_PAGE(!PageAnon(page), page); 2168 VM_BUG_ON_PAGE(!PageSwapBacked(page), page); 2169 2170 /* cannot use mapcount: can't collapse if there's a gup pin */ 2171 if (page_count(page) != 1) 2172 goto out; 2173 /* 2174 * We can do it before isolate_lru_page because the 2175 * page can't be freed from under us. NOTE: PG_lock 2176 * is needed to serialize against split_huge_page 2177 * when invoked from the VM. 2178 */ 2179 if (!trylock_page(page)) 2180 goto out; 2181 /* 2182 * Isolate the page to avoid collapsing an hugepage 2183 * currently in use by the VM. 2184 */ 2185 if (isolate_lru_page(page)) { 2186 unlock_page(page); 2187 goto out; 2188 } 2189 /* 0 stands for page_is_file_cache(page) == false */ 2190 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 2191 VM_BUG_ON_PAGE(!PageLocked(page), page); 2192 VM_BUG_ON_PAGE(PageLRU(page), page); 2193 2194 /* If there is no mapped pte young don't collapse the page */ 2195 if (pte_young(pteval) || PageReferenced(page) || 2196 mmu_notifier_test_young(vma->vm_mm, address)) 2197 referenced = 1; 2198 } 2199 if (likely(referenced)) 2200 return 1; 2201 out: 2202 release_pte_pages(pte, _pte); 2203 return 0; 2204 } 2205 2206 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 2207 struct vm_area_struct *vma, 2208 unsigned long address, 2209 spinlock_t *ptl) 2210 { 2211 pte_t *_pte; 2212 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 2213 pte_t pteval = *_pte; 2214 struct page *src_page; 2215 2216 if (pte_none(pteval)) { 2217 clear_user_highpage(page, address); 2218 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 2219 } else { 2220 src_page = pte_page(pteval); 2221 copy_user_highpage(page, src_page, address, vma); 2222 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); 2223 release_pte_page(src_page); 2224 /* 2225 * ptl mostly unnecessary, but preempt has to 2226 * be disabled to update the per-cpu stats 2227 * inside page_remove_rmap(). 2228 */ 2229 spin_lock(ptl); 2230 /* 2231 * paravirt calls inside pte_clear here are 2232 * superfluous. 2233 */ 2234 pte_clear(vma->vm_mm, address, _pte); 2235 page_remove_rmap(src_page); 2236 spin_unlock(ptl); 2237 free_page_and_swap_cache(src_page); 2238 } 2239 2240 address += PAGE_SIZE; 2241 page++; 2242 } 2243 } 2244 2245 static void khugepaged_alloc_sleep(void) 2246 { 2247 wait_event_freezable_timeout(khugepaged_wait, false, 2248 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 2249 } 2250 2251 static int khugepaged_node_load[MAX_NUMNODES]; 2252 2253 static bool khugepaged_scan_abort(int nid) 2254 { 2255 int i; 2256 2257 /* 2258 * If zone_reclaim_mode is disabled, then no extra effort is made to 2259 * allocate memory locally. 2260 */ 2261 if (!zone_reclaim_mode) 2262 return false; 2263 2264 /* If there is a count for this node already, it must be acceptable */ 2265 if (khugepaged_node_load[nid]) 2266 return false; 2267 2268 for (i = 0; i < MAX_NUMNODES; i++) { 2269 if (!khugepaged_node_load[i]) 2270 continue; 2271 if (node_distance(nid, i) > RECLAIM_DISTANCE) 2272 return true; 2273 } 2274 return false; 2275 } 2276 2277 #ifdef CONFIG_NUMA 2278 static int khugepaged_find_target_node(void) 2279 { 2280 static int last_khugepaged_target_node = NUMA_NO_NODE; 2281 int nid, target_node = 0, max_value = 0; 2282 2283 /* find first node with max normal pages hit */ 2284 for (nid = 0; nid < MAX_NUMNODES; nid++) 2285 if (khugepaged_node_load[nid] > max_value) { 2286 max_value = khugepaged_node_load[nid]; 2287 target_node = nid; 2288 } 2289 2290 /* do some balance if several nodes have the same hit record */ 2291 if (target_node <= last_khugepaged_target_node) 2292 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; 2293 nid++) 2294 if (max_value == khugepaged_node_load[nid]) { 2295 target_node = nid; 2296 break; 2297 } 2298 2299 last_khugepaged_target_node = target_node; 2300 return target_node; 2301 } 2302 2303 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2304 { 2305 if (IS_ERR(*hpage)) { 2306 if (!*wait) 2307 return false; 2308 2309 *wait = false; 2310 *hpage = NULL; 2311 khugepaged_alloc_sleep(); 2312 } else if (*hpage) { 2313 put_page(*hpage); 2314 *hpage = NULL; 2315 } 2316 2317 return true; 2318 } 2319 2320 static struct page 2321 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 2322 struct vm_area_struct *vma, unsigned long address, 2323 int node) 2324 { 2325 VM_BUG_ON_PAGE(*hpage, *hpage); 2326 2327 /* 2328 * Before allocating the hugepage, release the mmap_sem read lock. 2329 * The allocation can take potentially a long time if it involves 2330 * sync compaction, and we do not need to hold the mmap_sem during 2331 * that. We will recheck the vma after taking it again in write mode. 2332 */ 2333 up_read(&mm->mmap_sem); 2334 2335 *hpage = alloc_pages_exact_node(node, alloc_hugepage_gfpmask( 2336 khugepaged_defrag(), __GFP_OTHER_NODE), HPAGE_PMD_ORDER); 2337 if (unlikely(!*hpage)) { 2338 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2339 *hpage = ERR_PTR(-ENOMEM); 2340 return NULL; 2341 } 2342 2343 count_vm_event(THP_COLLAPSE_ALLOC); 2344 return *hpage; 2345 } 2346 #else 2347 static int khugepaged_find_target_node(void) 2348 { 2349 return 0; 2350 } 2351 2352 static inline struct page *alloc_hugepage(int defrag) 2353 { 2354 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), 2355 HPAGE_PMD_ORDER); 2356 } 2357 2358 static struct page *khugepaged_alloc_hugepage(bool *wait) 2359 { 2360 struct page *hpage; 2361 2362 do { 2363 hpage = alloc_hugepage(khugepaged_defrag()); 2364 if (!hpage) { 2365 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2366 if (!*wait) 2367 return NULL; 2368 2369 *wait = false; 2370 khugepaged_alloc_sleep(); 2371 } else 2372 count_vm_event(THP_COLLAPSE_ALLOC); 2373 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 2374 2375 return hpage; 2376 } 2377 2378 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2379 { 2380 if (!*hpage) 2381 *hpage = khugepaged_alloc_hugepage(wait); 2382 2383 if (unlikely(!*hpage)) 2384 return false; 2385 2386 return true; 2387 } 2388 2389 static struct page 2390 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 2391 struct vm_area_struct *vma, unsigned long address, 2392 int node) 2393 { 2394 up_read(&mm->mmap_sem); 2395 VM_BUG_ON(!*hpage); 2396 return *hpage; 2397 } 2398 #endif 2399 2400 static bool hugepage_vma_check(struct vm_area_struct *vma) 2401 { 2402 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 2403 (vma->vm_flags & VM_NOHUGEPAGE)) 2404 return false; 2405 2406 if (!vma->anon_vma || vma->vm_ops) 2407 return false; 2408 if (is_vma_temporary_stack(vma)) 2409 return false; 2410 VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma); 2411 return true; 2412 } 2413 2414 static void collapse_huge_page(struct mm_struct *mm, 2415 unsigned long address, 2416 struct page **hpage, 2417 struct vm_area_struct *vma, 2418 int node) 2419 { 2420 pmd_t *pmd, _pmd; 2421 pte_t *pte; 2422 pgtable_t pgtable; 2423 struct page *new_page; 2424 spinlock_t *pmd_ptl, *pte_ptl; 2425 int isolated; 2426 unsigned long hstart, hend; 2427 struct mem_cgroup *memcg; 2428 unsigned long mmun_start; /* For mmu_notifiers */ 2429 unsigned long mmun_end; /* For mmu_notifiers */ 2430 2431 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2432 2433 /* release the mmap_sem read lock. */ 2434 new_page = khugepaged_alloc_page(hpage, mm, vma, address, node); 2435 if (!new_page) 2436 return; 2437 2438 if (unlikely(mem_cgroup_try_charge(new_page, mm, 2439 GFP_TRANSHUGE, &memcg))) 2440 return; 2441 2442 /* 2443 * Prevent all access to pagetables with the exception of 2444 * gup_fast later hanlded by the ptep_clear_flush and the VM 2445 * handled by the anon_vma lock + PG_lock. 2446 */ 2447 down_write(&mm->mmap_sem); 2448 if (unlikely(khugepaged_test_exit(mm))) 2449 goto out; 2450 2451 vma = find_vma(mm, address); 2452 if (!vma) 2453 goto out; 2454 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2455 hend = vma->vm_end & HPAGE_PMD_MASK; 2456 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 2457 goto out; 2458 if (!hugepage_vma_check(vma)) 2459 goto out; 2460 pmd = mm_find_pmd(mm, address); 2461 if (!pmd) 2462 goto out; 2463 2464 anon_vma_lock_write(vma->anon_vma); 2465 2466 pte = pte_offset_map(pmd, address); 2467 pte_ptl = pte_lockptr(mm, pmd); 2468 2469 mmun_start = address; 2470 mmun_end = address + HPAGE_PMD_SIZE; 2471 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2472 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ 2473 /* 2474 * After this gup_fast can't run anymore. This also removes 2475 * any huge TLB entry from the CPU so we won't allow 2476 * huge and small TLB entries for the same virtual address 2477 * to avoid the risk of CPU bugs in that area. 2478 */ 2479 _pmd = pmdp_clear_flush(vma, address, pmd); 2480 spin_unlock(pmd_ptl); 2481 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2482 2483 spin_lock(pte_ptl); 2484 isolated = __collapse_huge_page_isolate(vma, address, pte); 2485 spin_unlock(pte_ptl); 2486 2487 if (unlikely(!isolated)) { 2488 pte_unmap(pte); 2489 spin_lock(pmd_ptl); 2490 BUG_ON(!pmd_none(*pmd)); 2491 /* 2492 * We can only use set_pmd_at when establishing 2493 * hugepmds and never for establishing regular pmds that 2494 * points to regular pagetables. Use pmd_populate for that 2495 */ 2496 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 2497 spin_unlock(pmd_ptl); 2498 anon_vma_unlock_write(vma->anon_vma); 2499 goto out; 2500 } 2501 2502 /* 2503 * All pages are isolated and locked so anon_vma rmap 2504 * can't run anymore. 2505 */ 2506 anon_vma_unlock_write(vma->anon_vma); 2507 2508 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); 2509 pte_unmap(pte); 2510 __SetPageUptodate(new_page); 2511 pgtable = pmd_pgtable(_pmd); 2512 2513 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); 2514 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 2515 2516 /* 2517 * spin_lock() below is not the equivalent of smp_wmb(), so 2518 * this is needed to avoid the copy_huge_page writes to become 2519 * visible after the set_pmd_at() write. 2520 */ 2521 smp_wmb(); 2522 2523 spin_lock(pmd_ptl); 2524 BUG_ON(!pmd_none(*pmd)); 2525 page_add_new_anon_rmap(new_page, vma, address); 2526 mem_cgroup_commit_charge(new_page, memcg, false); 2527 lru_cache_add_active_or_unevictable(new_page, vma); 2528 pgtable_trans_huge_deposit(mm, pmd, pgtable); 2529 set_pmd_at(mm, address, pmd, _pmd); 2530 update_mmu_cache_pmd(vma, address, pmd); 2531 spin_unlock(pmd_ptl); 2532 2533 *hpage = NULL; 2534 2535 khugepaged_pages_collapsed++; 2536 out_up_write: 2537 up_write(&mm->mmap_sem); 2538 return; 2539 2540 out: 2541 mem_cgroup_cancel_charge(new_page, memcg); 2542 goto out_up_write; 2543 } 2544 2545 static int khugepaged_scan_pmd(struct mm_struct *mm, 2546 struct vm_area_struct *vma, 2547 unsigned long address, 2548 struct page **hpage) 2549 { 2550 pmd_t *pmd; 2551 pte_t *pte, *_pte; 2552 int ret = 0, referenced = 0, none = 0; 2553 struct page *page; 2554 unsigned long _address; 2555 spinlock_t *ptl; 2556 int node = NUMA_NO_NODE; 2557 2558 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2559 2560 pmd = mm_find_pmd(mm, address); 2561 if (!pmd) 2562 goto out; 2563 2564 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 2565 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2566 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2567 _pte++, _address += PAGE_SIZE) { 2568 pte_t pteval = *_pte; 2569 if (pte_none(pteval)) { 2570 if (++none <= khugepaged_max_ptes_none) 2571 continue; 2572 else 2573 goto out_unmap; 2574 } 2575 if (!pte_present(pteval) || !pte_write(pteval)) 2576 goto out_unmap; 2577 page = vm_normal_page(vma, _address, pteval); 2578 if (unlikely(!page)) 2579 goto out_unmap; 2580 /* 2581 * Record which node the original page is from and save this 2582 * information to khugepaged_node_load[]. 2583 * Khupaged will allocate hugepage from the node has the max 2584 * hit record. 2585 */ 2586 node = page_to_nid(page); 2587 if (khugepaged_scan_abort(node)) 2588 goto out_unmap; 2589 khugepaged_node_load[node]++; 2590 VM_BUG_ON_PAGE(PageCompound(page), page); 2591 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) 2592 goto out_unmap; 2593 /* cannot use mapcount: can't collapse if there's a gup pin */ 2594 if (page_count(page) != 1) 2595 goto out_unmap; 2596 if (pte_young(pteval) || PageReferenced(page) || 2597 mmu_notifier_test_young(vma->vm_mm, address)) 2598 referenced = 1; 2599 } 2600 if (referenced) 2601 ret = 1; 2602 out_unmap: 2603 pte_unmap_unlock(pte, ptl); 2604 if (ret) { 2605 node = khugepaged_find_target_node(); 2606 /* collapse_huge_page will return with the mmap_sem released */ 2607 collapse_huge_page(mm, address, hpage, vma, node); 2608 } 2609 out: 2610 return ret; 2611 } 2612 2613 static void collect_mm_slot(struct mm_slot *mm_slot) 2614 { 2615 struct mm_struct *mm = mm_slot->mm; 2616 2617 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2618 2619 if (khugepaged_test_exit(mm)) { 2620 /* free mm_slot */ 2621 hash_del(&mm_slot->hash); 2622 list_del(&mm_slot->mm_node); 2623 2624 /* 2625 * Not strictly needed because the mm exited already. 2626 * 2627 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2628 */ 2629 2630 /* khugepaged_mm_lock actually not necessary for the below */ 2631 free_mm_slot(mm_slot); 2632 mmdrop(mm); 2633 } 2634 } 2635 2636 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2637 struct page **hpage) 2638 __releases(&khugepaged_mm_lock) 2639 __acquires(&khugepaged_mm_lock) 2640 { 2641 struct mm_slot *mm_slot; 2642 struct mm_struct *mm; 2643 struct vm_area_struct *vma; 2644 int progress = 0; 2645 2646 VM_BUG_ON(!pages); 2647 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2648 2649 if (khugepaged_scan.mm_slot) 2650 mm_slot = khugepaged_scan.mm_slot; 2651 else { 2652 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2653 struct mm_slot, mm_node); 2654 khugepaged_scan.address = 0; 2655 khugepaged_scan.mm_slot = mm_slot; 2656 } 2657 spin_unlock(&khugepaged_mm_lock); 2658 2659 mm = mm_slot->mm; 2660 down_read(&mm->mmap_sem); 2661 if (unlikely(khugepaged_test_exit(mm))) 2662 vma = NULL; 2663 else 2664 vma = find_vma(mm, khugepaged_scan.address); 2665 2666 progress++; 2667 for (; vma; vma = vma->vm_next) { 2668 unsigned long hstart, hend; 2669 2670 cond_resched(); 2671 if (unlikely(khugepaged_test_exit(mm))) { 2672 progress++; 2673 break; 2674 } 2675 if (!hugepage_vma_check(vma)) { 2676 skip: 2677 progress++; 2678 continue; 2679 } 2680 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2681 hend = vma->vm_end & HPAGE_PMD_MASK; 2682 if (hstart >= hend) 2683 goto skip; 2684 if (khugepaged_scan.address > hend) 2685 goto skip; 2686 if (khugepaged_scan.address < hstart) 2687 khugepaged_scan.address = hstart; 2688 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2689 2690 while (khugepaged_scan.address < hend) { 2691 int ret; 2692 cond_resched(); 2693 if (unlikely(khugepaged_test_exit(mm))) 2694 goto breakouterloop; 2695 2696 VM_BUG_ON(khugepaged_scan.address < hstart || 2697 khugepaged_scan.address + HPAGE_PMD_SIZE > 2698 hend); 2699 ret = khugepaged_scan_pmd(mm, vma, 2700 khugepaged_scan.address, 2701 hpage); 2702 /* move to next address */ 2703 khugepaged_scan.address += HPAGE_PMD_SIZE; 2704 progress += HPAGE_PMD_NR; 2705 if (ret) 2706 /* we released mmap_sem so break loop */ 2707 goto breakouterloop_mmap_sem; 2708 if (progress >= pages) 2709 goto breakouterloop; 2710 } 2711 } 2712 breakouterloop: 2713 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2714 breakouterloop_mmap_sem: 2715 2716 spin_lock(&khugepaged_mm_lock); 2717 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2718 /* 2719 * Release the current mm_slot if this mm is about to die, or 2720 * if we scanned all vmas of this mm. 2721 */ 2722 if (khugepaged_test_exit(mm) || !vma) { 2723 /* 2724 * Make sure that if mm_users is reaching zero while 2725 * khugepaged runs here, khugepaged_exit will find 2726 * mm_slot not pointing to the exiting mm. 2727 */ 2728 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2729 khugepaged_scan.mm_slot = list_entry( 2730 mm_slot->mm_node.next, 2731 struct mm_slot, mm_node); 2732 khugepaged_scan.address = 0; 2733 } else { 2734 khugepaged_scan.mm_slot = NULL; 2735 khugepaged_full_scans++; 2736 } 2737 2738 collect_mm_slot(mm_slot); 2739 } 2740 2741 return progress; 2742 } 2743 2744 static int khugepaged_has_work(void) 2745 { 2746 return !list_empty(&khugepaged_scan.mm_head) && 2747 khugepaged_enabled(); 2748 } 2749 2750 static int khugepaged_wait_event(void) 2751 { 2752 return !list_empty(&khugepaged_scan.mm_head) || 2753 kthread_should_stop(); 2754 } 2755 2756 static void khugepaged_do_scan(void) 2757 { 2758 struct page *hpage = NULL; 2759 unsigned int progress = 0, pass_through_head = 0; 2760 unsigned int pages = khugepaged_pages_to_scan; 2761 bool wait = true; 2762 2763 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2764 2765 while (progress < pages) { 2766 if (!khugepaged_prealloc_page(&hpage, &wait)) 2767 break; 2768 2769 cond_resched(); 2770 2771 if (unlikely(kthread_should_stop() || freezing(current))) 2772 break; 2773 2774 spin_lock(&khugepaged_mm_lock); 2775 if (!khugepaged_scan.mm_slot) 2776 pass_through_head++; 2777 if (khugepaged_has_work() && 2778 pass_through_head < 2) 2779 progress += khugepaged_scan_mm_slot(pages - progress, 2780 &hpage); 2781 else 2782 progress = pages; 2783 spin_unlock(&khugepaged_mm_lock); 2784 } 2785 2786 if (!IS_ERR_OR_NULL(hpage)) 2787 put_page(hpage); 2788 } 2789 2790 static void khugepaged_wait_work(void) 2791 { 2792 try_to_freeze(); 2793 2794 if (khugepaged_has_work()) { 2795 if (!khugepaged_scan_sleep_millisecs) 2796 return; 2797 2798 wait_event_freezable_timeout(khugepaged_wait, 2799 kthread_should_stop(), 2800 msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); 2801 return; 2802 } 2803 2804 if (khugepaged_enabled()) 2805 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 2806 } 2807 2808 static int khugepaged(void *none) 2809 { 2810 struct mm_slot *mm_slot; 2811 2812 set_freezable(); 2813 set_user_nice(current, MAX_NICE); 2814 2815 while (!kthread_should_stop()) { 2816 khugepaged_do_scan(); 2817 khugepaged_wait_work(); 2818 } 2819 2820 spin_lock(&khugepaged_mm_lock); 2821 mm_slot = khugepaged_scan.mm_slot; 2822 khugepaged_scan.mm_slot = NULL; 2823 if (mm_slot) 2824 collect_mm_slot(mm_slot); 2825 spin_unlock(&khugepaged_mm_lock); 2826 return 0; 2827 } 2828 2829 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2830 unsigned long haddr, pmd_t *pmd) 2831 { 2832 struct mm_struct *mm = vma->vm_mm; 2833 pgtable_t pgtable; 2834 pmd_t _pmd; 2835 int i; 2836 2837 pmdp_clear_flush(vma, haddr, pmd); 2838 /* leave pmd empty until pte is filled */ 2839 2840 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2841 pmd_populate(mm, &_pmd, pgtable); 2842 2843 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2844 pte_t *pte, entry; 2845 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2846 entry = pte_mkspecial(entry); 2847 pte = pte_offset_map(&_pmd, haddr); 2848 VM_BUG_ON(!pte_none(*pte)); 2849 set_pte_at(mm, haddr, pte, entry); 2850 pte_unmap(pte); 2851 } 2852 smp_wmb(); /* make pte visible before pmd */ 2853 pmd_populate(mm, pmd, pgtable); 2854 put_huge_zero_page(); 2855 } 2856 2857 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address, 2858 pmd_t *pmd) 2859 { 2860 spinlock_t *ptl; 2861 struct page *page; 2862 struct mm_struct *mm = vma->vm_mm; 2863 unsigned long haddr = address & HPAGE_PMD_MASK; 2864 unsigned long mmun_start; /* For mmu_notifiers */ 2865 unsigned long mmun_end; /* For mmu_notifiers */ 2866 2867 BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE); 2868 2869 mmun_start = haddr; 2870 mmun_end = haddr + HPAGE_PMD_SIZE; 2871 again: 2872 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2873 ptl = pmd_lock(mm, pmd); 2874 if (unlikely(!pmd_trans_huge(*pmd))) { 2875 spin_unlock(ptl); 2876 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2877 return; 2878 } 2879 if (is_huge_zero_pmd(*pmd)) { 2880 __split_huge_zero_page_pmd(vma, haddr, pmd); 2881 spin_unlock(ptl); 2882 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2883 return; 2884 } 2885 page = pmd_page(*pmd); 2886 VM_BUG_ON_PAGE(!page_count(page), page); 2887 get_page(page); 2888 spin_unlock(ptl); 2889 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2890 2891 split_huge_page(page); 2892 2893 put_page(page); 2894 2895 /* 2896 * We don't always have down_write of mmap_sem here: a racing 2897 * do_huge_pmd_wp_page() might have copied-on-write to another 2898 * huge page before our split_huge_page() got the anon_vma lock. 2899 */ 2900 if (unlikely(pmd_trans_huge(*pmd))) 2901 goto again; 2902 } 2903 2904 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address, 2905 pmd_t *pmd) 2906 { 2907 struct vm_area_struct *vma; 2908 2909 vma = find_vma(mm, address); 2910 BUG_ON(vma == NULL); 2911 split_huge_page_pmd(vma, address, pmd); 2912 } 2913 2914 static void split_huge_page_address(struct mm_struct *mm, 2915 unsigned long address) 2916 { 2917 pgd_t *pgd; 2918 pud_t *pud; 2919 pmd_t *pmd; 2920 2921 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); 2922 2923 pgd = pgd_offset(mm, address); 2924 if (!pgd_present(*pgd)) 2925 return; 2926 2927 pud = pud_offset(pgd, address); 2928 if (!pud_present(*pud)) 2929 return; 2930 2931 pmd = pmd_offset(pud, address); 2932 if (!pmd_present(*pmd)) 2933 return; 2934 /* 2935 * Caller holds the mmap_sem write mode, so a huge pmd cannot 2936 * materialize from under us. 2937 */ 2938 split_huge_page_pmd_mm(mm, address, pmd); 2939 } 2940 2941 void __vma_adjust_trans_huge(struct vm_area_struct *vma, 2942 unsigned long start, 2943 unsigned long end, 2944 long adjust_next) 2945 { 2946 /* 2947 * If the new start address isn't hpage aligned and it could 2948 * previously contain an hugepage: check if we need to split 2949 * an huge pmd. 2950 */ 2951 if (start & ~HPAGE_PMD_MASK && 2952 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2953 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2954 split_huge_page_address(vma->vm_mm, start); 2955 2956 /* 2957 * If the new end address isn't hpage aligned and it could 2958 * previously contain an hugepage: check if we need to split 2959 * an huge pmd. 2960 */ 2961 if (end & ~HPAGE_PMD_MASK && 2962 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2963 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2964 split_huge_page_address(vma->vm_mm, end); 2965 2966 /* 2967 * If we're also updating the vma->vm_next->vm_start, if the new 2968 * vm_next->vm_start isn't page aligned and it could previously 2969 * contain an hugepage: check if we need to split an huge pmd. 2970 */ 2971 if (adjust_next > 0) { 2972 struct vm_area_struct *next = vma->vm_next; 2973 unsigned long nstart = next->vm_start; 2974 nstart += adjust_next << PAGE_SHIFT; 2975 if (nstart & ~HPAGE_PMD_MASK && 2976 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2977 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2978 split_huge_page_address(next->vm_mm, nstart); 2979 } 2980 } 2981