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