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 spin_unlock(new_ptl); 1486 spin_unlock(old_ptl); 1487 } 1488 out: 1489 return ret; 1490 } 1491 1492 /* 1493 * Returns 1494 * - 0 if PMD could not be locked 1495 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary 1496 * - HPAGE_PMD_NR is protections changed and TLB flush necessary 1497 */ 1498 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1499 unsigned long addr, pgprot_t newprot, int prot_numa) 1500 { 1501 struct mm_struct *mm = vma->vm_mm; 1502 spinlock_t *ptl; 1503 int ret = 0; 1504 1505 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { 1506 pmd_t entry; 1507 ret = 1; 1508 if (!prot_numa) { 1509 entry = pmdp_get_and_clear(mm, addr, pmd); 1510 entry = pmd_modify(entry, newprot); 1511 ret = HPAGE_PMD_NR; 1512 BUG_ON(pmd_write(entry)); 1513 } else { 1514 struct page *page = pmd_page(*pmd); 1515 1516 /* 1517 * Do not trap faults against the zero page. The 1518 * read-only data is likely to be read-cached on the 1519 * local CPU cache and it is less useful to know about 1520 * local vs remote hits on the zero page. 1521 */ 1522 if (!is_huge_zero_page(page) && 1523 !pmd_numa(*pmd)) { 1524 entry = pmdp_get_and_clear(mm, addr, pmd); 1525 entry = pmd_mknuma(entry); 1526 ret = HPAGE_PMD_NR; 1527 } 1528 } 1529 1530 /* Set PMD if cleared earlier */ 1531 if (ret == HPAGE_PMD_NR) 1532 set_pmd_at(mm, addr, pmd, entry); 1533 1534 spin_unlock(ptl); 1535 } 1536 1537 return ret; 1538 } 1539 1540 /* 1541 * Returns 1 if a given pmd maps a stable (not under splitting) thp. 1542 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise. 1543 * 1544 * Note that if it returns 1, this routine returns without unlocking page 1545 * table locks. So callers must unlock them. 1546 */ 1547 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma, 1548 spinlock_t **ptl) 1549 { 1550 *ptl = pmd_lock(vma->vm_mm, pmd); 1551 if (likely(pmd_trans_huge(*pmd))) { 1552 if (unlikely(pmd_trans_splitting(*pmd))) { 1553 spin_unlock(*ptl); 1554 wait_split_huge_page(vma->anon_vma, pmd); 1555 return -1; 1556 } else { 1557 /* Thp mapped by 'pmd' is stable, so we can 1558 * handle it as it is. */ 1559 return 1; 1560 } 1561 } 1562 spin_unlock(*ptl); 1563 return 0; 1564 } 1565 1566 /* 1567 * This function returns whether a given @page is mapped onto the @address 1568 * in the virtual space of @mm. 1569 * 1570 * When it's true, this function returns *pmd with holding the page table lock 1571 * and passing it back to the caller via @ptl. 1572 * If it's false, returns NULL without holding the page table lock. 1573 */ 1574 pmd_t *page_check_address_pmd(struct page *page, 1575 struct mm_struct *mm, 1576 unsigned long address, 1577 enum page_check_address_pmd_flag flag, 1578 spinlock_t **ptl) 1579 { 1580 pmd_t *pmd; 1581 1582 if (address & ~HPAGE_PMD_MASK) 1583 return NULL; 1584 1585 pmd = mm_find_pmd(mm, address); 1586 if (!pmd) 1587 return NULL; 1588 *ptl = pmd_lock(mm, pmd); 1589 if (pmd_none(*pmd)) 1590 goto unlock; 1591 if (pmd_page(*pmd) != page) 1592 goto unlock; 1593 /* 1594 * split_vma() may create temporary aliased mappings. There is 1595 * no risk as long as all huge pmd are found and have their 1596 * splitting bit set before __split_huge_page_refcount 1597 * runs. Finding the same huge pmd more than once during the 1598 * same rmap walk is not a problem. 1599 */ 1600 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && 1601 pmd_trans_splitting(*pmd)) 1602 goto unlock; 1603 if (pmd_trans_huge(*pmd)) { 1604 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && 1605 !pmd_trans_splitting(*pmd)); 1606 return pmd; 1607 } 1608 unlock: 1609 spin_unlock(*ptl); 1610 return NULL; 1611 } 1612 1613 static int __split_huge_page_splitting(struct page *page, 1614 struct vm_area_struct *vma, 1615 unsigned long address) 1616 { 1617 struct mm_struct *mm = vma->vm_mm; 1618 spinlock_t *ptl; 1619 pmd_t *pmd; 1620 int ret = 0; 1621 /* For mmu_notifiers */ 1622 const unsigned long mmun_start = address; 1623 const unsigned long mmun_end = address + HPAGE_PMD_SIZE; 1624 1625 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1626 pmd = page_check_address_pmd(page, mm, address, 1627 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG, &ptl); 1628 if (pmd) { 1629 /* 1630 * We can't temporarily set the pmd to null in order 1631 * to split it, the pmd must remain marked huge at all 1632 * times or the VM won't take the pmd_trans_huge paths 1633 * and it won't wait on the anon_vma->root->rwsem to 1634 * serialize against split_huge_page*. 1635 */ 1636 pmdp_splitting_flush(vma, address, pmd); 1637 ret = 1; 1638 spin_unlock(ptl); 1639 } 1640 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1641 1642 return ret; 1643 } 1644 1645 static void __split_huge_page_refcount(struct page *page, 1646 struct list_head *list) 1647 { 1648 int i; 1649 struct zone *zone = page_zone(page); 1650 struct lruvec *lruvec; 1651 int tail_count = 0; 1652 1653 /* prevent PageLRU to go away from under us, and freeze lru stats */ 1654 spin_lock_irq(&zone->lru_lock); 1655 lruvec = mem_cgroup_page_lruvec(page, zone); 1656 1657 compound_lock(page); 1658 /* complete memcg works before add pages to LRU */ 1659 mem_cgroup_split_huge_fixup(page); 1660 1661 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 1662 struct page *page_tail = page + i; 1663 1664 /* tail_page->_mapcount cannot change */ 1665 BUG_ON(page_mapcount(page_tail) < 0); 1666 tail_count += page_mapcount(page_tail); 1667 /* check for overflow */ 1668 BUG_ON(tail_count < 0); 1669 BUG_ON(atomic_read(&page_tail->_count) != 0); 1670 /* 1671 * tail_page->_count is zero and not changing from 1672 * under us. But get_page_unless_zero() may be running 1673 * from under us on the tail_page. If we used 1674 * atomic_set() below instead of atomic_add(), we 1675 * would then run atomic_set() concurrently with 1676 * get_page_unless_zero(), and atomic_set() is 1677 * implemented in C not using locked ops. spin_unlock 1678 * on x86 sometime uses locked ops because of PPro 1679 * errata 66, 92, so unless somebody can guarantee 1680 * atomic_set() here would be safe on all archs (and 1681 * not only on x86), it's safer to use atomic_add(). 1682 */ 1683 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, 1684 &page_tail->_count); 1685 1686 /* after clearing PageTail the gup refcount can be released */ 1687 smp_mb(); 1688 1689 /* 1690 * retain hwpoison flag of the poisoned tail page: 1691 * fix for the unsuitable process killed on Guest Machine(KVM) 1692 * by the memory-failure. 1693 */ 1694 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON; 1695 page_tail->flags |= (page->flags & 1696 ((1L << PG_referenced) | 1697 (1L << PG_swapbacked) | 1698 (1L << PG_mlocked) | 1699 (1L << PG_uptodate) | 1700 (1L << PG_active) | 1701 (1L << PG_unevictable))); 1702 page_tail->flags |= (1L << PG_dirty); 1703 1704 /* clear PageTail before overwriting first_page */ 1705 smp_wmb(); 1706 1707 /* 1708 * __split_huge_page_splitting() already set the 1709 * splitting bit in all pmd that could map this 1710 * hugepage, that will ensure no CPU can alter the 1711 * mapcount on the head page. The mapcount is only 1712 * accounted in the head page and it has to be 1713 * transferred to all tail pages in the below code. So 1714 * for this code to be safe, the split the mapcount 1715 * can't change. But that doesn't mean userland can't 1716 * keep changing and reading the page contents while 1717 * we transfer the mapcount, so the pmd splitting 1718 * status is achieved setting a reserved bit in the 1719 * pmd, not by clearing the present bit. 1720 */ 1721 page_tail->_mapcount = page->_mapcount; 1722 1723 BUG_ON(page_tail->mapping); 1724 page_tail->mapping = page->mapping; 1725 1726 page_tail->index = page->index + i; 1727 page_cpupid_xchg_last(page_tail, page_cpupid_last(page)); 1728 1729 BUG_ON(!PageAnon(page_tail)); 1730 BUG_ON(!PageUptodate(page_tail)); 1731 BUG_ON(!PageDirty(page_tail)); 1732 BUG_ON(!PageSwapBacked(page_tail)); 1733 1734 lru_add_page_tail(page, page_tail, lruvec, list); 1735 } 1736 atomic_sub(tail_count, &page->_count); 1737 BUG_ON(atomic_read(&page->_count) <= 0); 1738 1739 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1); 1740 1741 ClearPageCompound(page); 1742 compound_unlock(page); 1743 spin_unlock_irq(&zone->lru_lock); 1744 1745 for (i = 1; i < HPAGE_PMD_NR; i++) { 1746 struct page *page_tail = page + i; 1747 BUG_ON(page_count(page_tail) <= 0); 1748 /* 1749 * Tail pages may be freed if there wasn't any mapping 1750 * like if add_to_swap() is running on a lru page that 1751 * had its mapping zapped. And freeing these pages 1752 * requires taking the lru_lock so we do the put_page 1753 * of the tail pages after the split is complete. 1754 */ 1755 put_page(page_tail); 1756 } 1757 1758 /* 1759 * Only the head page (now become a regular page) is required 1760 * to be pinned by the caller. 1761 */ 1762 BUG_ON(page_count(page) <= 0); 1763 } 1764 1765 static int __split_huge_page_map(struct page *page, 1766 struct vm_area_struct *vma, 1767 unsigned long address) 1768 { 1769 struct mm_struct *mm = vma->vm_mm; 1770 spinlock_t *ptl; 1771 pmd_t *pmd, _pmd; 1772 int ret = 0, i; 1773 pgtable_t pgtable; 1774 unsigned long haddr; 1775 1776 pmd = page_check_address_pmd(page, mm, address, 1777 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl); 1778 if (pmd) { 1779 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1780 pmd_populate(mm, &_pmd, pgtable); 1781 1782 haddr = address; 1783 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1784 pte_t *pte, entry; 1785 BUG_ON(PageCompound(page+i)); 1786 entry = mk_pte(page + i, vma->vm_page_prot); 1787 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1788 if (!pmd_write(*pmd)) 1789 entry = pte_wrprotect(entry); 1790 else 1791 BUG_ON(page_mapcount(page) != 1); 1792 if (!pmd_young(*pmd)) 1793 entry = pte_mkold(entry); 1794 if (pmd_numa(*pmd)) 1795 entry = pte_mknuma(entry); 1796 pte = pte_offset_map(&_pmd, haddr); 1797 BUG_ON(!pte_none(*pte)); 1798 set_pte_at(mm, haddr, pte, entry); 1799 pte_unmap(pte); 1800 } 1801 1802 smp_wmb(); /* make pte visible before pmd */ 1803 /* 1804 * Up to this point the pmd is present and huge and 1805 * userland has the whole access to the hugepage 1806 * during the split (which happens in place). If we 1807 * overwrite the pmd with the not-huge version 1808 * pointing to the pte here (which of course we could 1809 * if all CPUs were bug free), userland could trigger 1810 * a small page size TLB miss on the small sized TLB 1811 * while the hugepage TLB entry is still established 1812 * in the huge TLB. Some CPU doesn't like that. See 1813 * http://support.amd.com/us/Processor_TechDocs/41322.pdf, 1814 * Erratum 383 on page 93. Intel should be safe but is 1815 * also warns that it's only safe if the permission 1816 * and cache attributes of the two entries loaded in 1817 * the two TLB is identical (which should be the case 1818 * here). But it is generally safer to never allow 1819 * small and huge TLB entries for the same virtual 1820 * address to be loaded simultaneously. So instead of 1821 * doing "pmd_populate(); flush_tlb_range();" we first 1822 * mark the current pmd notpresent (atomically because 1823 * here the pmd_trans_huge and pmd_trans_splitting 1824 * must remain set at all times on the pmd until the 1825 * split is complete for this pmd), then we flush the 1826 * SMP TLB and finally we write the non-huge version 1827 * of the pmd entry with pmd_populate. 1828 */ 1829 pmdp_invalidate(vma, address, pmd); 1830 pmd_populate(mm, pmd, pgtable); 1831 ret = 1; 1832 spin_unlock(ptl); 1833 } 1834 1835 return ret; 1836 } 1837 1838 /* must be called with anon_vma->root->rwsem held */ 1839 static void __split_huge_page(struct page *page, 1840 struct anon_vma *anon_vma, 1841 struct list_head *list) 1842 { 1843 int mapcount, mapcount2; 1844 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 1845 struct anon_vma_chain *avc; 1846 1847 BUG_ON(!PageHead(page)); 1848 BUG_ON(PageTail(page)); 1849 1850 mapcount = 0; 1851 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1852 struct vm_area_struct *vma = avc->vma; 1853 unsigned long addr = vma_address(page, vma); 1854 BUG_ON(is_vma_temporary_stack(vma)); 1855 mapcount += __split_huge_page_splitting(page, vma, addr); 1856 } 1857 /* 1858 * It is critical that new vmas are added to the tail of the 1859 * anon_vma list. This guarantes that if copy_huge_pmd() runs 1860 * and establishes a child pmd before 1861 * __split_huge_page_splitting() freezes the parent pmd (so if 1862 * we fail to prevent copy_huge_pmd() from running until the 1863 * whole __split_huge_page() is complete), we will still see 1864 * the newly established pmd of the child later during the 1865 * walk, to be able to set it as pmd_trans_splitting too. 1866 */ 1867 if (mapcount != page_mapcount(page)) 1868 printk(KERN_ERR "mapcount %d page_mapcount %d\n", 1869 mapcount, page_mapcount(page)); 1870 BUG_ON(mapcount != page_mapcount(page)); 1871 1872 __split_huge_page_refcount(page, list); 1873 1874 mapcount2 = 0; 1875 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1876 struct vm_area_struct *vma = avc->vma; 1877 unsigned long addr = vma_address(page, vma); 1878 BUG_ON(is_vma_temporary_stack(vma)); 1879 mapcount2 += __split_huge_page_map(page, vma, addr); 1880 } 1881 if (mapcount != mapcount2) 1882 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n", 1883 mapcount, mapcount2, page_mapcount(page)); 1884 BUG_ON(mapcount != mapcount2); 1885 } 1886 1887 /* 1888 * Split a hugepage into normal pages. This doesn't change the position of head 1889 * page. If @list is null, tail pages will be added to LRU list, otherwise, to 1890 * @list. Both head page and tail pages will inherit mapping, flags, and so on 1891 * from the hugepage. 1892 * Return 0 if the hugepage is split successfully otherwise return 1. 1893 */ 1894 int split_huge_page_to_list(struct page *page, struct list_head *list) 1895 { 1896 struct anon_vma *anon_vma; 1897 int ret = 1; 1898 1899 BUG_ON(is_huge_zero_page(page)); 1900 BUG_ON(!PageAnon(page)); 1901 1902 /* 1903 * The caller does not necessarily hold an mmap_sem that would prevent 1904 * the anon_vma disappearing so we first we take a reference to it 1905 * and then lock the anon_vma for write. This is similar to 1906 * page_lock_anon_vma_read except the write lock is taken to serialise 1907 * against parallel split or collapse operations. 1908 */ 1909 anon_vma = page_get_anon_vma(page); 1910 if (!anon_vma) 1911 goto out; 1912 anon_vma_lock_write(anon_vma); 1913 1914 ret = 0; 1915 if (!PageCompound(page)) 1916 goto out_unlock; 1917 1918 BUG_ON(!PageSwapBacked(page)); 1919 __split_huge_page(page, anon_vma, list); 1920 count_vm_event(THP_SPLIT); 1921 1922 BUG_ON(PageCompound(page)); 1923 out_unlock: 1924 anon_vma_unlock_write(anon_vma); 1925 put_anon_vma(anon_vma); 1926 out: 1927 return ret; 1928 } 1929 1930 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE) 1931 1932 int hugepage_madvise(struct vm_area_struct *vma, 1933 unsigned long *vm_flags, int advice) 1934 { 1935 struct mm_struct *mm = vma->vm_mm; 1936 1937 switch (advice) { 1938 case MADV_HUGEPAGE: 1939 /* 1940 * Be somewhat over-protective like KSM for now! 1941 */ 1942 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) 1943 return -EINVAL; 1944 if (mm->def_flags & VM_NOHUGEPAGE) 1945 return -EINVAL; 1946 *vm_flags &= ~VM_NOHUGEPAGE; 1947 *vm_flags |= VM_HUGEPAGE; 1948 /* 1949 * If the vma become good for khugepaged to scan, 1950 * register it here without waiting a page fault that 1951 * may not happen any time soon. 1952 */ 1953 if (unlikely(khugepaged_enter_vma_merge(vma))) 1954 return -ENOMEM; 1955 break; 1956 case MADV_NOHUGEPAGE: 1957 /* 1958 * Be somewhat over-protective like KSM for now! 1959 */ 1960 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) 1961 return -EINVAL; 1962 *vm_flags &= ~VM_HUGEPAGE; 1963 *vm_flags |= VM_NOHUGEPAGE; 1964 /* 1965 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1966 * this vma even if we leave the mm registered in khugepaged if 1967 * it got registered before VM_NOHUGEPAGE was set. 1968 */ 1969 break; 1970 } 1971 1972 return 0; 1973 } 1974 1975 static int __init khugepaged_slab_init(void) 1976 { 1977 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1978 sizeof(struct mm_slot), 1979 __alignof__(struct mm_slot), 0, NULL); 1980 if (!mm_slot_cache) 1981 return -ENOMEM; 1982 1983 return 0; 1984 } 1985 1986 static inline struct mm_slot *alloc_mm_slot(void) 1987 { 1988 if (!mm_slot_cache) /* initialization failed */ 1989 return NULL; 1990 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 1991 } 1992 1993 static inline void free_mm_slot(struct mm_slot *mm_slot) 1994 { 1995 kmem_cache_free(mm_slot_cache, mm_slot); 1996 } 1997 1998 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 1999 { 2000 struct mm_slot *mm_slot; 2001 2002 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) 2003 if (mm == mm_slot->mm) 2004 return mm_slot; 2005 2006 return NULL; 2007 } 2008 2009 static void insert_to_mm_slots_hash(struct mm_struct *mm, 2010 struct mm_slot *mm_slot) 2011 { 2012 mm_slot->mm = mm; 2013 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); 2014 } 2015 2016 static inline int khugepaged_test_exit(struct mm_struct *mm) 2017 { 2018 return atomic_read(&mm->mm_users) == 0; 2019 } 2020 2021 int __khugepaged_enter(struct mm_struct *mm) 2022 { 2023 struct mm_slot *mm_slot; 2024 int wakeup; 2025 2026 mm_slot = alloc_mm_slot(); 2027 if (!mm_slot) 2028 return -ENOMEM; 2029 2030 /* __khugepaged_exit() must not run from under us */ 2031 VM_BUG_ON(khugepaged_test_exit(mm)); 2032 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 2033 free_mm_slot(mm_slot); 2034 return 0; 2035 } 2036 2037 spin_lock(&khugepaged_mm_lock); 2038 insert_to_mm_slots_hash(mm, mm_slot); 2039 /* 2040 * Insert just behind the scanning cursor, to let the area settle 2041 * down a little. 2042 */ 2043 wakeup = list_empty(&khugepaged_scan.mm_head); 2044 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 2045 spin_unlock(&khugepaged_mm_lock); 2046 2047 atomic_inc(&mm->mm_count); 2048 if (wakeup) 2049 wake_up_interruptible(&khugepaged_wait); 2050 2051 return 0; 2052 } 2053 2054 int khugepaged_enter_vma_merge(struct vm_area_struct *vma) 2055 { 2056 unsigned long hstart, hend; 2057 if (!vma->anon_vma) 2058 /* 2059 * Not yet faulted in so we will register later in the 2060 * page fault if needed. 2061 */ 2062 return 0; 2063 if (vma->vm_ops) 2064 /* khugepaged not yet working on file or special mappings */ 2065 return 0; 2066 VM_BUG_ON(vma->vm_flags & VM_NO_THP); 2067 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2068 hend = vma->vm_end & HPAGE_PMD_MASK; 2069 if (hstart < hend) 2070 return khugepaged_enter(vma); 2071 return 0; 2072 } 2073 2074 void __khugepaged_exit(struct mm_struct *mm) 2075 { 2076 struct mm_slot *mm_slot; 2077 int free = 0; 2078 2079 spin_lock(&khugepaged_mm_lock); 2080 mm_slot = get_mm_slot(mm); 2081 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 2082 hash_del(&mm_slot->hash); 2083 list_del(&mm_slot->mm_node); 2084 free = 1; 2085 } 2086 spin_unlock(&khugepaged_mm_lock); 2087 2088 if (free) { 2089 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2090 free_mm_slot(mm_slot); 2091 mmdrop(mm); 2092 } else if (mm_slot) { 2093 /* 2094 * This is required to serialize against 2095 * khugepaged_test_exit() (which is guaranteed to run 2096 * under mmap sem read mode). Stop here (after we 2097 * return all pagetables will be destroyed) until 2098 * khugepaged has finished working on the pagetables 2099 * under the mmap_sem. 2100 */ 2101 down_write(&mm->mmap_sem); 2102 up_write(&mm->mmap_sem); 2103 } 2104 } 2105 2106 static void release_pte_page(struct page *page) 2107 { 2108 /* 0 stands for page_is_file_cache(page) == false */ 2109 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 2110 unlock_page(page); 2111 putback_lru_page(page); 2112 } 2113 2114 static void release_pte_pages(pte_t *pte, pte_t *_pte) 2115 { 2116 while (--_pte >= pte) { 2117 pte_t pteval = *_pte; 2118 if (!pte_none(pteval)) 2119 release_pte_page(pte_page(pteval)); 2120 } 2121 } 2122 2123 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 2124 unsigned long address, 2125 pte_t *pte) 2126 { 2127 struct page *page; 2128 pte_t *_pte; 2129 int referenced = 0, none = 0; 2130 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 2131 _pte++, address += PAGE_SIZE) { 2132 pte_t pteval = *_pte; 2133 if (pte_none(pteval)) { 2134 if (++none <= khugepaged_max_ptes_none) 2135 continue; 2136 else 2137 goto out; 2138 } 2139 if (!pte_present(pteval) || !pte_write(pteval)) 2140 goto out; 2141 page = vm_normal_page(vma, address, pteval); 2142 if (unlikely(!page)) 2143 goto out; 2144 2145 VM_BUG_ON(PageCompound(page)); 2146 BUG_ON(!PageAnon(page)); 2147 VM_BUG_ON(!PageSwapBacked(page)); 2148 2149 /* cannot use mapcount: can't collapse if there's a gup pin */ 2150 if (page_count(page) != 1) 2151 goto out; 2152 /* 2153 * We can do it before isolate_lru_page because the 2154 * page can't be freed from under us. NOTE: PG_lock 2155 * is needed to serialize against split_huge_page 2156 * when invoked from the VM. 2157 */ 2158 if (!trylock_page(page)) 2159 goto out; 2160 /* 2161 * Isolate the page to avoid collapsing an hugepage 2162 * currently in use by the VM. 2163 */ 2164 if (isolate_lru_page(page)) { 2165 unlock_page(page); 2166 goto out; 2167 } 2168 /* 0 stands for page_is_file_cache(page) == false */ 2169 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 2170 VM_BUG_ON(!PageLocked(page)); 2171 VM_BUG_ON(PageLRU(page)); 2172 2173 /* If there is no mapped pte young don't collapse the page */ 2174 if (pte_young(pteval) || PageReferenced(page) || 2175 mmu_notifier_test_young(vma->vm_mm, address)) 2176 referenced = 1; 2177 } 2178 if (likely(referenced)) 2179 return 1; 2180 out: 2181 release_pte_pages(pte, _pte); 2182 return 0; 2183 } 2184 2185 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 2186 struct vm_area_struct *vma, 2187 unsigned long address, 2188 spinlock_t *ptl) 2189 { 2190 pte_t *_pte; 2191 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 2192 pte_t pteval = *_pte; 2193 struct page *src_page; 2194 2195 if (pte_none(pteval)) { 2196 clear_user_highpage(page, address); 2197 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 2198 } else { 2199 src_page = pte_page(pteval); 2200 copy_user_highpage(page, src_page, address, vma); 2201 VM_BUG_ON(page_mapcount(src_page) != 1); 2202 release_pte_page(src_page); 2203 /* 2204 * ptl mostly unnecessary, but preempt has to 2205 * be disabled to update the per-cpu stats 2206 * inside page_remove_rmap(). 2207 */ 2208 spin_lock(ptl); 2209 /* 2210 * paravirt calls inside pte_clear here are 2211 * superfluous. 2212 */ 2213 pte_clear(vma->vm_mm, address, _pte); 2214 page_remove_rmap(src_page); 2215 spin_unlock(ptl); 2216 free_page_and_swap_cache(src_page); 2217 } 2218 2219 address += PAGE_SIZE; 2220 page++; 2221 } 2222 } 2223 2224 static void khugepaged_alloc_sleep(void) 2225 { 2226 wait_event_freezable_timeout(khugepaged_wait, false, 2227 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 2228 } 2229 2230 static int khugepaged_node_load[MAX_NUMNODES]; 2231 2232 #ifdef CONFIG_NUMA 2233 static int khugepaged_find_target_node(void) 2234 { 2235 static int last_khugepaged_target_node = NUMA_NO_NODE; 2236 int nid, target_node = 0, max_value = 0; 2237 2238 /* find first node with max normal pages hit */ 2239 for (nid = 0; nid < MAX_NUMNODES; nid++) 2240 if (khugepaged_node_load[nid] > max_value) { 2241 max_value = khugepaged_node_load[nid]; 2242 target_node = nid; 2243 } 2244 2245 /* do some balance if several nodes have the same hit record */ 2246 if (target_node <= last_khugepaged_target_node) 2247 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; 2248 nid++) 2249 if (max_value == khugepaged_node_load[nid]) { 2250 target_node = nid; 2251 break; 2252 } 2253 2254 last_khugepaged_target_node = target_node; 2255 return target_node; 2256 } 2257 2258 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2259 { 2260 if (IS_ERR(*hpage)) { 2261 if (!*wait) 2262 return false; 2263 2264 *wait = false; 2265 *hpage = NULL; 2266 khugepaged_alloc_sleep(); 2267 } else if (*hpage) { 2268 put_page(*hpage); 2269 *hpage = NULL; 2270 } 2271 2272 return true; 2273 } 2274 2275 static struct page 2276 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 2277 struct vm_area_struct *vma, unsigned long address, 2278 int node) 2279 { 2280 VM_BUG_ON(*hpage); 2281 /* 2282 * Allocate the page while the vma is still valid and under 2283 * the mmap_sem read mode so there is no memory allocation 2284 * later when we take the mmap_sem in write mode. This is more 2285 * friendly behavior (OTOH it may actually hide bugs) to 2286 * filesystems in userland with daemons allocating memory in 2287 * the userland I/O paths. Allocating memory with the 2288 * mmap_sem in read mode is good idea also to allow greater 2289 * scalability. 2290 */ 2291 *hpage = alloc_pages_exact_node(node, alloc_hugepage_gfpmask( 2292 khugepaged_defrag(), __GFP_OTHER_NODE), HPAGE_PMD_ORDER); 2293 /* 2294 * After allocating the hugepage, release the mmap_sem read lock in 2295 * preparation for taking it in write mode. 2296 */ 2297 up_read(&mm->mmap_sem); 2298 if (unlikely(!*hpage)) { 2299 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2300 *hpage = ERR_PTR(-ENOMEM); 2301 return NULL; 2302 } 2303 2304 count_vm_event(THP_COLLAPSE_ALLOC); 2305 return *hpage; 2306 } 2307 #else 2308 static int khugepaged_find_target_node(void) 2309 { 2310 return 0; 2311 } 2312 2313 static inline struct page *alloc_hugepage(int defrag) 2314 { 2315 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), 2316 HPAGE_PMD_ORDER); 2317 } 2318 2319 static struct page *khugepaged_alloc_hugepage(bool *wait) 2320 { 2321 struct page *hpage; 2322 2323 do { 2324 hpage = alloc_hugepage(khugepaged_defrag()); 2325 if (!hpage) { 2326 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2327 if (!*wait) 2328 return NULL; 2329 2330 *wait = false; 2331 khugepaged_alloc_sleep(); 2332 } else 2333 count_vm_event(THP_COLLAPSE_ALLOC); 2334 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 2335 2336 return hpage; 2337 } 2338 2339 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2340 { 2341 if (!*hpage) 2342 *hpage = khugepaged_alloc_hugepage(wait); 2343 2344 if (unlikely(!*hpage)) 2345 return false; 2346 2347 return true; 2348 } 2349 2350 static struct page 2351 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 2352 struct vm_area_struct *vma, unsigned long address, 2353 int node) 2354 { 2355 up_read(&mm->mmap_sem); 2356 VM_BUG_ON(!*hpage); 2357 return *hpage; 2358 } 2359 #endif 2360 2361 static bool hugepage_vma_check(struct vm_area_struct *vma) 2362 { 2363 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 2364 (vma->vm_flags & VM_NOHUGEPAGE)) 2365 return false; 2366 2367 if (!vma->anon_vma || vma->vm_ops) 2368 return false; 2369 if (is_vma_temporary_stack(vma)) 2370 return false; 2371 VM_BUG_ON(vma->vm_flags & VM_NO_THP); 2372 return true; 2373 } 2374 2375 static void collapse_huge_page(struct mm_struct *mm, 2376 unsigned long address, 2377 struct page **hpage, 2378 struct vm_area_struct *vma, 2379 int node) 2380 { 2381 pmd_t *pmd, _pmd; 2382 pte_t *pte; 2383 pgtable_t pgtable; 2384 struct page *new_page; 2385 spinlock_t *pmd_ptl, *pte_ptl; 2386 int isolated; 2387 unsigned long hstart, hend; 2388 unsigned long mmun_start; /* For mmu_notifiers */ 2389 unsigned long mmun_end; /* For mmu_notifiers */ 2390 2391 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2392 2393 /* release the mmap_sem read lock. */ 2394 new_page = khugepaged_alloc_page(hpage, mm, vma, address, node); 2395 if (!new_page) 2396 return; 2397 2398 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) 2399 return; 2400 2401 /* 2402 * Prevent all access to pagetables with the exception of 2403 * gup_fast later hanlded by the ptep_clear_flush and the VM 2404 * handled by the anon_vma lock + PG_lock. 2405 */ 2406 down_write(&mm->mmap_sem); 2407 if (unlikely(khugepaged_test_exit(mm))) 2408 goto out; 2409 2410 vma = find_vma(mm, address); 2411 if (!vma) 2412 goto out; 2413 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2414 hend = vma->vm_end & HPAGE_PMD_MASK; 2415 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 2416 goto out; 2417 if (!hugepage_vma_check(vma)) 2418 goto out; 2419 pmd = mm_find_pmd(mm, address); 2420 if (!pmd) 2421 goto out; 2422 if (pmd_trans_huge(*pmd)) 2423 goto out; 2424 2425 anon_vma_lock_write(vma->anon_vma); 2426 2427 pte = pte_offset_map(pmd, address); 2428 pte_ptl = pte_lockptr(mm, pmd); 2429 2430 mmun_start = address; 2431 mmun_end = address + HPAGE_PMD_SIZE; 2432 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2433 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ 2434 /* 2435 * After this gup_fast can't run anymore. This also removes 2436 * any huge TLB entry from the CPU so we won't allow 2437 * huge and small TLB entries for the same virtual address 2438 * to avoid the risk of CPU bugs in that area. 2439 */ 2440 _pmd = pmdp_clear_flush(vma, address, pmd); 2441 spin_unlock(pmd_ptl); 2442 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2443 2444 spin_lock(pte_ptl); 2445 isolated = __collapse_huge_page_isolate(vma, address, pte); 2446 spin_unlock(pte_ptl); 2447 2448 if (unlikely(!isolated)) { 2449 pte_unmap(pte); 2450 spin_lock(pmd_ptl); 2451 BUG_ON(!pmd_none(*pmd)); 2452 /* 2453 * We can only use set_pmd_at when establishing 2454 * hugepmds and never for establishing regular pmds that 2455 * points to regular pagetables. Use pmd_populate for that 2456 */ 2457 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 2458 spin_unlock(pmd_ptl); 2459 anon_vma_unlock_write(vma->anon_vma); 2460 goto out; 2461 } 2462 2463 /* 2464 * All pages are isolated and locked so anon_vma rmap 2465 * can't run anymore. 2466 */ 2467 anon_vma_unlock_write(vma->anon_vma); 2468 2469 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); 2470 pte_unmap(pte); 2471 __SetPageUptodate(new_page); 2472 pgtable = pmd_pgtable(_pmd); 2473 2474 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); 2475 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 2476 2477 /* 2478 * spin_lock() below is not the equivalent of smp_wmb(), so 2479 * this is needed to avoid the copy_huge_page writes to become 2480 * visible after the set_pmd_at() write. 2481 */ 2482 smp_wmb(); 2483 2484 spin_lock(pmd_ptl); 2485 BUG_ON(!pmd_none(*pmd)); 2486 page_add_new_anon_rmap(new_page, vma, address); 2487 pgtable_trans_huge_deposit(mm, pmd, pgtable); 2488 set_pmd_at(mm, address, pmd, _pmd); 2489 update_mmu_cache_pmd(vma, address, pmd); 2490 spin_unlock(pmd_ptl); 2491 2492 *hpage = NULL; 2493 2494 khugepaged_pages_collapsed++; 2495 out_up_write: 2496 up_write(&mm->mmap_sem); 2497 return; 2498 2499 out: 2500 mem_cgroup_uncharge_page(new_page); 2501 goto out_up_write; 2502 } 2503 2504 static int khugepaged_scan_pmd(struct mm_struct *mm, 2505 struct vm_area_struct *vma, 2506 unsigned long address, 2507 struct page **hpage) 2508 { 2509 pmd_t *pmd; 2510 pte_t *pte, *_pte; 2511 int ret = 0, referenced = 0, none = 0; 2512 struct page *page; 2513 unsigned long _address; 2514 spinlock_t *ptl; 2515 int node = NUMA_NO_NODE; 2516 2517 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2518 2519 pmd = mm_find_pmd(mm, address); 2520 if (!pmd) 2521 goto out; 2522 if (pmd_trans_huge(*pmd)) 2523 goto out; 2524 2525 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 2526 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2527 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2528 _pte++, _address += PAGE_SIZE) { 2529 pte_t pteval = *_pte; 2530 if (pte_none(pteval)) { 2531 if (++none <= khugepaged_max_ptes_none) 2532 continue; 2533 else 2534 goto out_unmap; 2535 } 2536 if (!pte_present(pteval) || !pte_write(pteval)) 2537 goto out_unmap; 2538 page = vm_normal_page(vma, _address, pteval); 2539 if (unlikely(!page)) 2540 goto out_unmap; 2541 /* 2542 * Record which node the original page is from and save this 2543 * information to khugepaged_node_load[]. 2544 * Khupaged will allocate hugepage from the node has the max 2545 * hit record. 2546 */ 2547 node = page_to_nid(page); 2548 khugepaged_node_load[node]++; 2549 VM_BUG_ON(PageCompound(page)); 2550 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) 2551 goto out_unmap; 2552 /* cannot use mapcount: can't collapse if there's a gup pin */ 2553 if (page_count(page) != 1) 2554 goto out_unmap; 2555 if (pte_young(pteval) || PageReferenced(page) || 2556 mmu_notifier_test_young(vma->vm_mm, address)) 2557 referenced = 1; 2558 } 2559 if (referenced) 2560 ret = 1; 2561 out_unmap: 2562 pte_unmap_unlock(pte, ptl); 2563 if (ret) { 2564 node = khugepaged_find_target_node(); 2565 /* collapse_huge_page will return with the mmap_sem released */ 2566 collapse_huge_page(mm, address, hpage, vma, node); 2567 } 2568 out: 2569 return ret; 2570 } 2571 2572 static void collect_mm_slot(struct mm_slot *mm_slot) 2573 { 2574 struct mm_struct *mm = mm_slot->mm; 2575 2576 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2577 2578 if (khugepaged_test_exit(mm)) { 2579 /* free mm_slot */ 2580 hash_del(&mm_slot->hash); 2581 list_del(&mm_slot->mm_node); 2582 2583 /* 2584 * Not strictly needed because the mm exited already. 2585 * 2586 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2587 */ 2588 2589 /* khugepaged_mm_lock actually not necessary for the below */ 2590 free_mm_slot(mm_slot); 2591 mmdrop(mm); 2592 } 2593 } 2594 2595 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2596 struct page **hpage) 2597 __releases(&khugepaged_mm_lock) 2598 __acquires(&khugepaged_mm_lock) 2599 { 2600 struct mm_slot *mm_slot; 2601 struct mm_struct *mm; 2602 struct vm_area_struct *vma; 2603 int progress = 0; 2604 2605 VM_BUG_ON(!pages); 2606 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2607 2608 if (khugepaged_scan.mm_slot) 2609 mm_slot = khugepaged_scan.mm_slot; 2610 else { 2611 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2612 struct mm_slot, mm_node); 2613 khugepaged_scan.address = 0; 2614 khugepaged_scan.mm_slot = mm_slot; 2615 } 2616 spin_unlock(&khugepaged_mm_lock); 2617 2618 mm = mm_slot->mm; 2619 down_read(&mm->mmap_sem); 2620 if (unlikely(khugepaged_test_exit(mm))) 2621 vma = NULL; 2622 else 2623 vma = find_vma(mm, khugepaged_scan.address); 2624 2625 progress++; 2626 for (; vma; vma = vma->vm_next) { 2627 unsigned long hstart, hend; 2628 2629 cond_resched(); 2630 if (unlikely(khugepaged_test_exit(mm))) { 2631 progress++; 2632 break; 2633 } 2634 if (!hugepage_vma_check(vma)) { 2635 skip: 2636 progress++; 2637 continue; 2638 } 2639 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2640 hend = vma->vm_end & HPAGE_PMD_MASK; 2641 if (hstart >= hend) 2642 goto skip; 2643 if (khugepaged_scan.address > hend) 2644 goto skip; 2645 if (khugepaged_scan.address < hstart) 2646 khugepaged_scan.address = hstart; 2647 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2648 2649 while (khugepaged_scan.address < hend) { 2650 int ret; 2651 cond_resched(); 2652 if (unlikely(khugepaged_test_exit(mm))) 2653 goto breakouterloop; 2654 2655 VM_BUG_ON(khugepaged_scan.address < hstart || 2656 khugepaged_scan.address + HPAGE_PMD_SIZE > 2657 hend); 2658 ret = khugepaged_scan_pmd(mm, vma, 2659 khugepaged_scan.address, 2660 hpage); 2661 /* move to next address */ 2662 khugepaged_scan.address += HPAGE_PMD_SIZE; 2663 progress += HPAGE_PMD_NR; 2664 if (ret) 2665 /* we released mmap_sem so break loop */ 2666 goto breakouterloop_mmap_sem; 2667 if (progress >= pages) 2668 goto breakouterloop; 2669 } 2670 } 2671 breakouterloop: 2672 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2673 breakouterloop_mmap_sem: 2674 2675 spin_lock(&khugepaged_mm_lock); 2676 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2677 /* 2678 * Release the current mm_slot if this mm is about to die, or 2679 * if we scanned all vmas of this mm. 2680 */ 2681 if (khugepaged_test_exit(mm) || !vma) { 2682 /* 2683 * Make sure that if mm_users is reaching zero while 2684 * khugepaged runs here, khugepaged_exit will find 2685 * mm_slot not pointing to the exiting mm. 2686 */ 2687 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2688 khugepaged_scan.mm_slot = list_entry( 2689 mm_slot->mm_node.next, 2690 struct mm_slot, mm_node); 2691 khugepaged_scan.address = 0; 2692 } else { 2693 khugepaged_scan.mm_slot = NULL; 2694 khugepaged_full_scans++; 2695 } 2696 2697 collect_mm_slot(mm_slot); 2698 } 2699 2700 return progress; 2701 } 2702 2703 static int khugepaged_has_work(void) 2704 { 2705 return !list_empty(&khugepaged_scan.mm_head) && 2706 khugepaged_enabled(); 2707 } 2708 2709 static int khugepaged_wait_event(void) 2710 { 2711 return !list_empty(&khugepaged_scan.mm_head) || 2712 kthread_should_stop(); 2713 } 2714 2715 static void khugepaged_do_scan(void) 2716 { 2717 struct page *hpage = NULL; 2718 unsigned int progress = 0, pass_through_head = 0; 2719 unsigned int pages = khugepaged_pages_to_scan; 2720 bool wait = true; 2721 2722 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2723 2724 while (progress < pages) { 2725 if (!khugepaged_prealloc_page(&hpage, &wait)) 2726 break; 2727 2728 cond_resched(); 2729 2730 if (unlikely(kthread_should_stop() || freezing(current))) 2731 break; 2732 2733 spin_lock(&khugepaged_mm_lock); 2734 if (!khugepaged_scan.mm_slot) 2735 pass_through_head++; 2736 if (khugepaged_has_work() && 2737 pass_through_head < 2) 2738 progress += khugepaged_scan_mm_slot(pages - progress, 2739 &hpage); 2740 else 2741 progress = pages; 2742 spin_unlock(&khugepaged_mm_lock); 2743 } 2744 2745 if (!IS_ERR_OR_NULL(hpage)) 2746 put_page(hpage); 2747 } 2748 2749 static void khugepaged_wait_work(void) 2750 { 2751 try_to_freeze(); 2752 2753 if (khugepaged_has_work()) { 2754 if (!khugepaged_scan_sleep_millisecs) 2755 return; 2756 2757 wait_event_freezable_timeout(khugepaged_wait, 2758 kthread_should_stop(), 2759 msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); 2760 return; 2761 } 2762 2763 if (khugepaged_enabled()) 2764 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 2765 } 2766 2767 static int khugepaged(void *none) 2768 { 2769 struct mm_slot *mm_slot; 2770 2771 set_freezable(); 2772 set_user_nice(current, 19); 2773 2774 while (!kthread_should_stop()) { 2775 khugepaged_do_scan(); 2776 khugepaged_wait_work(); 2777 } 2778 2779 spin_lock(&khugepaged_mm_lock); 2780 mm_slot = khugepaged_scan.mm_slot; 2781 khugepaged_scan.mm_slot = NULL; 2782 if (mm_slot) 2783 collect_mm_slot(mm_slot); 2784 spin_unlock(&khugepaged_mm_lock); 2785 return 0; 2786 } 2787 2788 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2789 unsigned long haddr, pmd_t *pmd) 2790 { 2791 struct mm_struct *mm = vma->vm_mm; 2792 pgtable_t pgtable; 2793 pmd_t _pmd; 2794 int i; 2795 2796 pmdp_clear_flush(vma, haddr, pmd); 2797 /* leave pmd empty until pte is filled */ 2798 2799 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2800 pmd_populate(mm, &_pmd, pgtable); 2801 2802 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2803 pte_t *pte, entry; 2804 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2805 entry = pte_mkspecial(entry); 2806 pte = pte_offset_map(&_pmd, haddr); 2807 VM_BUG_ON(!pte_none(*pte)); 2808 set_pte_at(mm, haddr, pte, entry); 2809 pte_unmap(pte); 2810 } 2811 smp_wmb(); /* make pte visible before pmd */ 2812 pmd_populate(mm, pmd, pgtable); 2813 put_huge_zero_page(); 2814 } 2815 2816 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address, 2817 pmd_t *pmd) 2818 { 2819 spinlock_t *ptl; 2820 struct page *page; 2821 struct mm_struct *mm = vma->vm_mm; 2822 unsigned long haddr = address & HPAGE_PMD_MASK; 2823 unsigned long mmun_start; /* For mmu_notifiers */ 2824 unsigned long mmun_end; /* For mmu_notifiers */ 2825 2826 BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE); 2827 2828 mmun_start = haddr; 2829 mmun_end = haddr + HPAGE_PMD_SIZE; 2830 again: 2831 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2832 ptl = pmd_lock(mm, pmd); 2833 if (unlikely(!pmd_trans_huge(*pmd))) { 2834 spin_unlock(ptl); 2835 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2836 return; 2837 } 2838 if (is_huge_zero_pmd(*pmd)) { 2839 __split_huge_zero_page_pmd(vma, haddr, pmd); 2840 spin_unlock(ptl); 2841 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2842 return; 2843 } 2844 page = pmd_page(*pmd); 2845 VM_BUG_ON(!page_count(page)); 2846 get_page(page); 2847 spin_unlock(ptl); 2848 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2849 2850 split_huge_page(page); 2851 2852 put_page(page); 2853 2854 /* 2855 * We don't always have down_write of mmap_sem here: a racing 2856 * do_huge_pmd_wp_page() might have copied-on-write to another 2857 * huge page before our split_huge_page() got the anon_vma lock. 2858 */ 2859 if (unlikely(pmd_trans_huge(*pmd))) 2860 goto again; 2861 } 2862 2863 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address, 2864 pmd_t *pmd) 2865 { 2866 struct vm_area_struct *vma; 2867 2868 vma = find_vma(mm, address); 2869 BUG_ON(vma == NULL); 2870 split_huge_page_pmd(vma, address, pmd); 2871 } 2872 2873 static void split_huge_page_address(struct mm_struct *mm, 2874 unsigned long address) 2875 { 2876 pmd_t *pmd; 2877 2878 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); 2879 2880 pmd = mm_find_pmd(mm, address); 2881 if (!pmd) 2882 return; 2883 /* 2884 * Caller holds the mmap_sem write mode, so a huge pmd cannot 2885 * materialize from under us. 2886 */ 2887 split_huge_page_pmd_mm(mm, address, pmd); 2888 } 2889 2890 void __vma_adjust_trans_huge(struct vm_area_struct *vma, 2891 unsigned long start, 2892 unsigned long end, 2893 long adjust_next) 2894 { 2895 /* 2896 * If the new start address isn't hpage aligned and it could 2897 * previously contain an hugepage: check if we need to split 2898 * an huge pmd. 2899 */ 2900 if (start & ~HPAGE_PMD_MASK && 2901 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2902 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2903 split_huge_page_address(vma->vm_mm, start); 2904 2905 /* 2906 * If the new end 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 (end & ~HPAGE_PMD_MASK && 2911 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2912 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2913 split_huge_page_address(vma->vm_mm, end); 2914 2915 /* 2916 * If we're also updating the vma->vm_next->vm_start, if the new 2917 * vm_next->vm_start isn't page aligned and it could previously 2918 * contain an hugepage: check if we need to split an huge pmd. 2919 */ 2920 if (adjust_next > 0) { 2921 struct vm_area_struct *next = vma->vm_next; 2922 unsigned long nstart = next->vm_start; 2923 nstart += adjust_next << PAGE_SHIFT; 2924 if (nstart & ~HPAGE_PMD_MASK && 2925 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2926 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2927 split_huge_page_address(next->vm_mm, nstart); 2928 } 2929 } 2930