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