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 if (user_min_free_kbytes >= 0) 135 pr_info("raising min_free_kbytes from %d to %lu " 136 "to help transparent hugepage allocations\n", 137 min_free_kbytes, recommended_min); 138 139 min_free_kbytes = recommended_min; 140 } 141 setup_per_zone_wmarks(); 142 return 0; 143 } 144 late_initcall(set_recommended_min_free_kbytes); 145 146 static int start_khugepaged(void) 147 { 148 int err = 0; 149 if (khugepaged_enabled()) { 150 if (!khugepaged_thread) 151 khugepaged_thread = kthread_run(khugepaged, NULL, 152 "khugepaged"); 153 if (unlikely(IS_ERR(khugepaged_thread))) { 154 printk(KERN_ERR 155 "khugepaged: kthread_run(khugepaged) failed\n"); 156 err = PTR_ERR(khugepaged_thread); 157 khugepaged_thread = NULL; 158 } 159 160 if (!list_empty(&khugepaged_scan.mm_head)) 161 wake_up_interruptible(&khugepaged_wait); 162 163 set_recommended_min_free_kbytes(); 164 } else if (khugepaged_thread) { 165 kthread_stop(khugepaged_thread); 166 khugepaged_thread = NULL; 167 } 168 169 return err; 170 } 171 172 static atomic_t huge_zero_refcount; 173 static struct page *huge_zero_page __read_mostly; 174 175 static inline bool is_huge_zero_page(struct page *page) 176 { 177 return ACCESS_ONCE(huge_zero_page) == page; 178 } 179 180 static inline bool is_huge_zero_pmd(pmd_t pmd) 181 { 182 return is_huge_zero_page(pmd_page(pmd)); 183 } 184 185 static struct page *get_huge_zero_page(void) 186 { 187 struct page *zero_page; 188 retry: 189 if (likely(atomic_inc_not_zero(&huge_zero_refcount))) 190 return ACCESS_ONCE(huge_zero_page); 191 192 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, 193 HPAGE_PMD_ORDER); 194 if (!zero_page) { 195 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); 196 return NULL; 197 } 198 count_vm_event(THP_ZERO_PAGE_ALLOC); 199 preempt_disable(); 200 if (cmpxchg(&huge_zero_page, NULL, zero_page)) { 201 preempt_enable(); 202 __free_page(zero_page); 203 goto retry; 204 } 205 206 /* We take additional reference here. It will be put back by shrinker */ 207 atomic_set(&huge_zero_refcount, 2); 208 preempt_enable(); 209 return ACCESS_ONCE(huge_zero_page); 210 } 211 212 static void put_huge_zero_page(void) 213 { 214 /* 215 * Counter should never go to zero here. Only shrinker can put 216 * last reference. 217 */ 218 BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); 219 } 220 221 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, 222 struct shrink_control *sc) 223 { 224 /* we can free zero page only if last reference remains */ 225 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; 226 } 227 228 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, 229 struct shrink_control *sc) 230 { 231 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { 232 struct page *zero_page = xchg(&huge_zero_page, NULL); 233 BUG_ON(zero_page == NULL); 234 __free_page(zero_page); 235 return HPAGE_PMD_NR; 236 } 237 238 return 0; 239 } 240 241 static struct shrinker huge_zero_page_shrinker = { 242 .count_objects = shrink_huge_zero_page_count, 243 .scan_objects = shrink_huge_zero_page_scan, 244 .seeks = DEFAULT_SEEKS, 245 }; 246 247 #ifdef CONFIG_SYSFS 248 249 static ssize_t double_flag_show(struct kobject *kobj, 250 struct kobj_attribute *attr, char *buf, 251 enum transparent_hugepage_flag enabled, 252 enum transparent_hugepage_flag req_madv) 253 { 254 if (test_bit(enabled, &transparent_hugepage_flags)) { 255 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); 256 return sprintf(buf, "[always] madvise never\n"); 257 } else if (test_bit(req_madv, &transparent_hugepage_flags)) 258 return sprintf(buf, "always [madvise] never\n"); 259 else 260 return sprintf(buf, "always madvise [never]\n"); 261 } 262 static ssize_t double_flag_store(struct kobject *kobj, 263 struct kobj_attribute *attr, 264 const char *buf, size_t count, 265 enum transparent_hugepage_flag enabled, 266 enum transparent_hugepage_flag req_madv) 267 { 268 if (!memcmp("always", buf, 269 min(sizeof("always")-1, count))) { 270 set_bit(enabled, &transparent_hugepage_flags); 271 clear_bit(req_madv, &transparent_hugepage_flags); 272 } else if (!memcmp("madvise", buf, 273 min(sizeof("madvise")-1, count))) { 274 clear_bit(enabled, &transparent_hugepage_flags); 275 set_bit(req_madv, &transparent_hugepage_flags); 276 } else if (!memcmp("never", buf, 277 min(sizeof("never")-1, count))) { 278 clear_bit(enabled, &transparent_hugepage_flags); 279 clear_bit(req_madv, &transparent_hugepage_flags); 280 } else 281 return -EINVAL; 282 283 return count; 284 } 285 286 static ssize_t enabled_show(struct kobject *kobj, 287 struct kobj_attribute *attr, char *buf) 288 { 289 return double_flag_show(kobj, attr, buf, 290 TRANSPARENT_HUGEPAGE_FLAG, 291 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 292 } 293 static ssize_t enabled_store(struct kobject *kobj, 294 struct kobj_attribute *attr, 295 const char *buf, size_t count) 296 { 297 ssize_t ret; 298 299 ret = double_flag_store(kobj, attr, buf, count, 300 TRANSPARENT_HUGEPAGE_FLAG, 301 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 302 303 if (ret > 0) { 304 int err; 305 306 mutex_lock(&khugepaged_mutex); 307 err = start_khugepaged(); 308 mutex_unlock(&khugepaged_mutex); 309 310 if (err) 311 ret = err; 312 } 313 314 return ret; 315 } 316 static struct kobj_attribute enabled_attr = 317 __ATTR(enabled, 0644, enabled_show, enabled_store); 318 319 static ssize_t single_flag_show(struct kobject *kobj, 320 struct kobj_attribute *attr, char *buf, 321 enum transparent_hugepage_flag flag) 322 { 323 return sprintf(buf, "%d\n", 324 !!test_bit(flag, &transparent_hugepage_flags)); 325 } 326 327 static ssize_t single_flag_store(struct kobject *kobj, 328 struct kobj_attribute *attr, 329 const char *buf, size_t count, 330 enum transparent_hugepage_flag flag) 331 { 332 unsigned long value; 333 int ret; 334 335 ret = kstrtoul(buf, 10, &value); 336 if (ret < 0) 337 return ret; 338 if (value > 1) 339 return -EINVAL; 340 341 if (value) 342 set_bit(flag, &transparent_hugepage_flags); 343 else 344 clear_bit(flag, &transparent_hugepage_flags); 345 346 return count; 347 } 348 349 /* 350 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind 351 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of 352 * memory just to allocate one more hugepage. 353 */ 354 static ssize_t defrag_show(struct kobject *kobj, 355 struct kobj_attribute *attr, char *buf) 356 { 357 return double_flag_show(kobj, attr, buf, 358 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 359 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 360 } 361 static ssize_t defrag_store(struct kobject *kobj, 362 struct kobj_attribute *attr, 363 const char *buf, size_t count) 364 { 365 return double_flag_store(kobj, attr, buf, count, 366 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 367 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 368 } 369 static struct kobj_attribute defrag_attr = 370 __ATTR(defrag, 0644, defrag_show, defrag_store); 371 372 static ssize_t use_zero_page_show(struct kobject *kobj, 373 struct kobj_attribute *attr, char *buf) 374 { 375 return single_flag_show(kobj, attr, buf, 376 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 377 } 378 static ssize_t use_zero_page_store(struct kobject *kobj, 379 struct kobj_attribute *attr, const char *buf, size_t count) 380 { 381 return single_flag_store(kobj, attr, buf, count, 382 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 383 } 384 static struct kobj_attribute use_zero_page_attr = 385 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); 386 #ifdef CONFIG_DEBUG_VM 387 static ssize_t debug_cow_show(struct kobject *kobj, 388 struct kobj_attribute *attr, char *buf) 389 { 390 return single_flag_show(kobj, attr, buf, 391 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 392 } 393 static ssize_t debug_cow_store(struct kobject *kobj, 394 struct kobj_attribute *attr, 395 const char *buf, size_t count) 396 { 397 return single_flag_store(kobj, attr, buf, count, 398 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 399 } 400 static struct kobj_attribute debug_cow_attr = 401 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 402 #endif /* CONFIG_DEBUG_VM */ 403 404 static struct attribute *hugepage_attr[] = { 405 &enabled_attr.attr, 406 &defrag_attr.attr, 407 &use_zero_page_attr.attr, 408 #ifdef CONFIG_DEBUG_VM 409 &debug_cow_attr.attr, 410 #endif 411 NULL, 412 }; 413 414 static struct attribute_group hugepage_attr_group = { 415 .attrs = hugepage_attr, 416 }; 417 418 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 419 struct kobj_attribute *attr, 420 char *buf) 421 { 422 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 423 } 424 425 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 426 struct kobj_attribute *attr, 427 const char *buf, size_t count) 428 { 429 unsigned long msecs; 430 int err; 431 432 err = kstrtoul(buf, 10, &msecs); 433 if (err || msecs > UINT_MAX) 434 return -EINVAL; 435 436 khugepaged_scan_sleep_millisecs = msecs; 437 wake_up_interruptible(&khugepaged_wait); 438 439 return count; 440 } 441 static struct kobj_attribute scan_sleep_millisecs_attr = 442 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 443 scan_sleep_millisecs_store); 444 445 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 446 struct kobj_attribute *attr, 447 char *buf) 448 { 449 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 450 } 451 452 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 453 struct kobj_attribute *attr, 454 const char *buf, size_t count) 455 { 456 unsigned long msecs; 457 int err; 458 459 err = kstrtoul(buf, 10, &msecs); 460 if (err || msecs > UINT_MAX) 461 return -EINVAL; 462 463 khugepaged_alloc_sleep_millisecs = msecs; 464 wake_up_interruptible(&khugepaged_wait); 465 466 return count; 467 } 468 static struct kobj_attribute alloc_sleep_millisecs_attr = 469 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 470 alloc_sleep_millisecs_store); 471 472 static ssize_t pages_to_scan_show(struct kobject *kobj, 473 struct kobj_attribute *attr, 474 char *buf) 475 { 476 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 477 } 478 static ssize_t pages_to_scan_store(struct kobject *kobj, 479 struct kobj_attribute *attr, 480 const char *buf, size_t count) 481 { 482 int err; 483 unsigned long pages; 484 485 err = kstrtoul(buf, 10, &pages); 486 if (err || !pages || pages > UINT_MAX) 487 return -EINVAL; 488 489 khugepaged_pages_to_scan = pages; 490 491 return count; 492 } 493 static struct kobj_attribute pages_to_scan_attr = 494 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 495 pages_to_scan_store); 496 497 static ssize_t pages_collapsed_show(struct kobject *kobj, 498 struct kobj_attribute *attr, 499 char *buf) 500 { 501 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 502 } 503 static struct kobj_attribute pages_collapsed_attr = 504 __ATTR_RO(pages_collapsed); 505 506 static ssize_t full_scans_show(struct kobject *kobj, 507 struct kobj_attribute *attr, 508 char *buf) 509 { 510 return sprintf(buf, "%u\n", khugepaged_full_scans); 511 } 512 static struct kobj_attribute full_scans_attr = 513 __ATTR_RO(full_scans); 514 515 static ssize_t khugepaged_defrag_show(struct kobject *kobj, 516 struct kobj_attribute *attr, char *buf) 517 { 518 return single_flag_show(kobj, attr, buf, 519 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 520 } 521 static ssize_t khugepaged_defrag_store(struct kobject *kobj, 522 struct kobj_attribute *attr, 523 const char *buf, size_t count) 524 { 525 return single_flag_store(kobj, attr, buf, count, 526 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 527 } 528 static struct kobj_attribute khugepaged_defrag_attr = 529 __ATTR(defrag, 0644, khugepaged_defrag_show, 530 khugepaged_defrag_store); 531 532 /* 533 * max_ptes_none controls if khugepaged should collapse hugepages over 534 * any unmapped ptes in turn potentially increasing the memory 535 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 536 * reduce the available free memory in the system as it 537 * runs. Increasing max_ptes_none will instead potentially reduce the 538 * free memory in the system during the khugepaged scan. 539 */ 540 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 541 struct kobj_attribute *attr, 542 char *buf) 543 { 544 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 545 } 546 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 547 struct kobj_attribute *attr, 548 const char *buf, size_t count) 549 { 550 int err; 551 unsigned long max_ptes_none; 552 553 err = kstrtoul(buf, 10, &max_ptes_none); 554 if (err || max_ptes_none > HPAGE_PMD_NR-1) 555 return -EINVAL; 556 557 khugepaged_max_ptes_none = max_ptes_none; 558 559 return count; 560 } 561 static struct kobj_attribute khugepaged_max_ptes_none_attr = 562 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 563 khugepaged_max_ptes_none_store); 564 565 static struct attribute *khugepaged_attr[] = { 566 &khugepaged_defrag_attr.attr, 567 &khugepaged_max_ptes_none_attr.attr, 568 &pages_to_scan_attr.attr, 569 &pages_collapsed_attr.attr, 570 &full_scans_attr.attr, 571 &scan_sleep_millisecs_attr.attr, 572 &alloc_sleep_millisecs_attr.attr, 573 NULL, 574 }; 575 576 static struct attribute_group khugepaged_attr_group = { 577 .attrs = khugepaged_attr, 578 .name = "khugepaged", 579 }; 580 581 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) 582 { 583 int err; 584 585 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 586 if (unlikely(!*hugepage_kobj)) { 587 printk(KERN_ERR "hugepage: failed to create transparent hugepage kobject\n"); 588 return -ENOMEM; 589 } 590 591 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); 592 if (err) { 593 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n"); 594 goto delete_obj; 595 } 596 597 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); 598 if (err) { 599 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n"); 600 goto remove_hp_group; 601 } 602 603 return 0; 604 605 remove_hp_group: 606 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); 607 delete_obj: 608 kobject_put(*hugepage_kobj); 609 return err; 610 } 611 612 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) 613 { 614 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); 615 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); 616 kobject_put(hugepage_kobj); 617 } 618 #else 619 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) 620 { 621 return 0; 622 } 623 624 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) 625 { 626 } 627 #endif /* CONFIG_SYSFS */ 628 629 static int __init hugepage_init(void) 630 { 631 int err; 632 struct kobject *hugepage_kobj; 633 634 if (!has_transparent_hugepage()) { 635 transparent_hugepage_flags = 0; 636 return -EINVAL; 637 } 638 639 err = hugepage_init_sysfs(&hugepage_kobj); 640 if (err) 641 return err; 642 643 err = khugepaged_slab_init(); 644 if (err) 645 goto out; 646 647 register_shrinker(&huge_zero_page_shrinker); 648 649 /* 650 * By default disable transparent hugepages on smaller systems, 651 * where the extra memory used could hurt more than TLB overhead 652 * is likely to save. The admin can still enable it through /sys. 653 */ 654 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) 655 transparent_hugepage_flags = 0; 656 657 start_khugepaged(); 658 659 return 0; 660 out: 661 hugepage_exit_sysfs(hugepage_kobj); 662 return err; 663 } 664 subsys_initcall(hugepage_init); 665 666 static int __init setup_transparent_hugepage(char *str) 667 { 668 int ret = 0; 669 if (!str) 670 goto out; 671 if (!strcmp(str, "always")) { 672 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 673 &transparent_hugepage_flags); 674 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 675 &transparent_hugepage_flags); 676 ret = 1; 677 } else if (!strcmp(str, "madvise")) { 678 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 679 &transparent_hugepage_flags); 680 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 681 &transparent_hugepage_flags); 682 ret = 1; 683 } else if (!strcmp(str, "never")) { 684 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 685 &transparent_hugepage_flags); 686 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 687 &transparent_hugepage_flags); 688 ret = 1; 689 } 690 out: 691 if (!ret) 692 printk(KERN_WARNING 693 "transparent_hugepage= cannot parse, ignored\n"); 694 return ret; 695 } 696 __setup("transparent_hugepage=", setup_transparent_hugepage); 697 698 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 699 { 700 if (likely(vma->vm_flags & VM_WRITE)) 701 pmd = pmd_mkwrite(pmd); 702 return pmd; 703 } 704 705 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot) 706 { 707 pmd_t entry; 708 entry = mk_pmd(page, prot); 709 entry = pmd_mkhuge(entry); 710 return entry; 711 } 712 713 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, 714 struct vm_area_struct *vma, 715 unsigned long haddr, pmd_t *pmd, 716 struct page *page) 717 { 718 pgtable_t pgtable; 719 spinlock_t *ptl; 720 721 VM_BUG_ON_PAGE(!PageCompound(page), page); 722 pgtable = pte_alloc_one(mm, haddr); 723 if (unlikely(!pgtable)) 724 return VM_FAULT_OOM; 725 726 clear_huge_page(page, haddr, HPAGE_PMD_NR); 727 /* 728 * The memory barrier inside __SetPageUptodate makes sure that 729 * clear_huge_page writes become visible before the set_pmd_at() 730 * write. 731 */ 732 __SetPageUptodate(page); 733 734 ptl = pmd_lock(mm, pmd); 735 if (unlikely(!pmd_none(*pmd))) { 736 spin_unlock(ptl); 737 mem_cgroup_uncharge_page(page); 738 put_page(page); 739 pte_free(mm, pgtable); 740 } else { 741 pmd_t entry; 742 entry = mk_huge_pmd(page, vma->vm_page_prot); 743 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 744 page_add_new_anon_rmap(page, vma, haddr); 745 pgtable_trans_huge_deposit(mm, pmd, pgtable); 746 set_pmd_at(mm, haddr, pmd, entry); 747 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 748 atomic_long_inc(&mm->nr_ptes); 749 spin_unlock(ptl); 750 } 751 752 return 0; 753 } 754 755 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) 756 { 757 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; 758 } 759 760 static inline struct page *alloc_hugepage_vma(int defrag, 761 struct vm_area_struct *vma, 762 unsigned long haddr, int nd, 763 gfp_t extra_gfp) 764 { 765 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp), 766 HPAGE_PMD_ORDER, vma, haddr, nd); 767 } 768 769 /* Caller must hold page table lock. */ 770 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, 771 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, 772 struct page *zero_page) 773 { 774 pmd_t entry; 775 if (!pmd_none(*pmd)) 776 return false; 777 entry = mk_pmd(zero_page, vma->vm_page_prot); 778 entry = pmd_wrprotect(entry); 779 entry = pmd_mkhuge(entry); 780 pgtable_trans_huge_deposit(mm, pmd, pgtable); 781 set_pmd_at(mm, haddr, pmd, entry); 782 atomic_long_inc(&mm->nr_ptes); 783 return true; 784 } 785 786 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 787 unsigned long address, pmd_t *pmd, 788 unsigned int flags) 789 { 790 struct page *page; 791 unsigned long haddr = address & HPAGE_PMD_MASK; 792 793 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end) 794 return VM_FAULT_FALLBACK; 795 if (unlikely(anon_vma_prepare(vma))) 796 return VM_FAULT_OOM; 797 if (unlikely(khugepaged_enter(vma))) 798 return VM_FAULT_OOM; 799 if (!(flags & FAULT_FLAG_WRITE) && 800 transparent_hugepage_use_zero_page()) { 801 spinlock_t *ptl; 802 pgtable_t pgtable; 803 struct page *zero_page; 804 bool set; 805 pgtable = pte_alloc_one(mm, haddr); 806 if (unlikely(!pgtable)) 807 return VM_FAULT_OOM; 808 zero_page = get_huge_zero_page(); 809 if (unlikely(!zero_page)) { 810 pte_free(mm, pgtable); 811 count_vm_event(THP_FAULT_FALLBACK); 812 return VM_FAULT_FALLBACK; 813 } 814 ptl = pmd_lock(mm, pmd); 815 set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, 816 zero_page); 817 spin_unlock(ptl); 818 if (!set) { 819 pte_free(mm, pgtable); 820 put_huge_zero_page(); 821 } 822 return 0; 823 } 824 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 825 vma, haddr, numa_node_id(), 0); 826 if (unlikely(!page)) { 827 count_vm_event(THP_FAULT_FALLBACK); 828 return VM_FAULT_FALLBACK; 829 } 830 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) { 831 put_page(page); 832 count_vm_event(THP_FAULT_FALLBACK); 833 return VM_FAULT_FALLBACK; 834 } 835 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page))) { 836 mem_cgroup_uncharge_page(page); 837 put_page(page); 838 count_vm_event(THP_FAULT_FALLBACK); 839 return VM_FAULT_FALLBACK; 840 } 841 842 count_vm_event(THP_FAULT_ALLOC); 843 return 0; 844 } 845 846 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 847 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 848 struct vm_area_struct *vma) 849 { 850 spinlock_t *dst_ptl, *src_ptl; 851 struct page *src_page; 852 pmd_t pmd; 853 pgtable_t pgtable; 854 int ret; 855 856 ret = -ENOMEM; 857 pgtable = pte_alloc_one(dst_mm, addr); 858 if (unlikely(!pgtable)) 859 goto out; 860 861 dst_ptl = pmd_lock(dst_mm, dst_pmd); 862 src_ptl = pmd_lockptr(src_mm, src_pmd); 863 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); 864 865 ret = -EAGAIN; 866 pmd = *src_pmd; 867 if (unlikely(!pmd_trans_huge(pmd))) { 868 pte_free(dst_mm, pgtable); 869 goto out_unlock; 870 } 871 /* 872 * When page table lock is held, the huge zero pmd should not be 873 * under splitting since we don't split the page itself, only pmd to 874 * a page table. 875 */ 876 if (is_huge_zero_pmd(pmd)) { 877 struct page *zero_page; 878 bool set; 879 /* 880 * get_huge_zero_page() will never allocate a new page here, 881 * since we already have a zero page to copy. It just takes a 882 * reference. 883 */ 884 zero_page = get_huge_zero_page(); 885 set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, 886 zero_page); 887 BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */ 888 ret = 0; 889 goto out_unlock; 890 } 891 892 if (unlikely(pmd_trans_splitting(pmd))) { 893 /* split huge page running from under us */ 894 spin_unlock(src_ptl); 895 spin_unlock(dst_ptl); 896 pte_free(dst_mm, pgtable); 897 898 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ 899 goto out; 900 } 901 src_page = pmd_page(pmd); 902 VM_BUG_ON_PAGE(!PageHead(src_page), src_page); 903 get_page(src_page); 904 page_dup_rmap(src_page); 905 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 906 907 pmdp_set_wrprotect(src_mm, addr, src_pmd); 908 pmd = pmd_mkold(pmd_wrprotect(pmd)); 909 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); 910 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 911 atomic_long_inc(&dst_mm->nr_ptes); 912 913 ret = 0; 914 out_unlock: 915 spin_unlock(src_ptl); 916 spin_unlock(dst_ptl); 917 out: 918 return ret; 919 } 920 921 void huge_pmd_set_accessed(struct mm_struct *mm, 922 struct vm_area_struct *vma, 923 unsigned long address, 924 pmd_t *pmd, pmd_t orig_pmd, 925 int dirty) 926 { 927 spinlock_t *ptl; 928 pmd_t entry; 929 unsigned long haddr; 930 931 ptl = pmd_lock(mm, pmd); 932 if (unlikely(!pmd_same(*pmd, orig_pmd))) 933 goto unlock; 934 935 entry = pmd_mkyoung(orig_pmd); 936 haddr = address & HPAGE_PMD_MASK; 937 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty)) 938 update_mmu_cache_pmd(vma, address, pmd); 939 940 unlock: 941 spin_unlock(ptl); 942 } 943 944 static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, 945 struct vm_area_struct *vma, unsigned long address, 946 pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr) 947 { 948 spinlock_t *ptl; 949 pgtable_t pgtable; 950 pmd_t _pmd; 951 struct page *page; 952 int i, ret = 0; 953 unsigned long mmun_start; /* For mmu_notifiers */ 954 unsigned long mmun_end; /* For mmu_notifiers */ 955 956 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); 957 if (!page) { 958 ret |= VM_FAULT_OOM; 959 goto out; 960 } 961 962 if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) { 963 put_page(page); 964 ret |= VM_FAULT_OOM; 965 goto out; 966 } 967 968 clear_user_highpage(page, address); 969 __SetPageUptodate(page); 970 971 mmun_start = haddr; 972 mmun_end = haddr + HPAGE_PMD_SIZE; 973 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 974 975 ptl = pmd_lock(mm, pmd); 976 if (unlikely(!pmd_same(*pmd, orig_pmd))) 977 goto out_free_page; 978 979 pmdp_clear_flush(vma, haddr, pmd); 980 /* leave pmd empty until pte is filled */ 981 982 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 983 pmd_populate(mm, &_pmd, pgtable); 984 985 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 986 pte_t *pte, entry; 987 if (haddr == (address & PAGE_MASK)) { 988 entry = mk_pte(page, vma->vm_page_prot); 989 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 990 page_add_new_anon_rmap(page, vma, haddr); 991 } else { 992 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 993 entry = pte_mkspecial(entry); 994 } 995 pte = pte_offset_map(&_pmd, haddr); 996 VM_BUG_ON(!pte_none(*pte)); 997 set_pte_at(mm, haddr, pte, entry); 998 pte_unmap(pte); 999 } 1000 smp_wmb(); /* make pte visible before pmd */ 1001 pmd_populate(mm, pmd, pgtable); 1002 spin_unlock(ptl); 1003 put_huge_zero_page(); 1004 inc_mm_counter(mm, MM_ANONPAGES); 1005 1006 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1007 1008 ret |= VM_FAULT_WRITE; 1009 out: 1010 return ret; 1011 out_free_page: 1012 spin_unlock(ptl); 1013 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1014 mem_cgroup_uncharge_page(page); 1015 put_page(page); 1016 goto out; 1017 } 1018 1019 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, 1020 struct vm_area_struct *vma, 1021 unsigned long address, 1022 pmd_t *pmd, pmd_t orig_pmd, 1023 struct page *page, 1024 unsigned long haddr) 1025 { 1026 spinlock_t *ptl; 1027 pgtable_t pgtable; 1028 pmd_t _pmd; 1029 int ret = 0, i; 1030 struct page **pages; 1031 unsigned long mmun_start; /* For mmu_notifiers */ 1032 unsigned long mmun_end; /* For mmu_notifiers */ 1033 1034 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 1035 GFP_KERNEL); 1036 if (unlikely(!pages)) { 1037 ret |= VM_FAULT_OOM; 1038 goto out; 1039 } 1040 1041 for (i = 0; i < HPAGE_PMD_NR; i++) { 1042 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | 1043 __GFP_OTHER_NODE, 1044 vma, address, page_to_nid(page)); 1045 if (unlikely(!pages[i] || 1046 mem_cgroup_newpage_charge(pages[i], mm, 1047 GFP_KERNEL))) { 1048 if (pages[i]) 1049 put_page(pages[i]); 1050 mem_cgroup_uncharge_start(); 1051 while (--i >= 0) { 1052 mem_cgroup_uncharge_page(pages[i]); 1053 put_page(pages[i]); 1054 } 1055 mem_cgroup_uncharge_end(); 1056 kfree(pages); 1057 ret |= VM_FAULT_OOM; 1058 goto out; 1059 } 1060 } 1061 1062 for (i = 0; i < HPAGE_PMD_NR; i++) { 1063 copy_user_highpage(pages[i], page + i, 1064 haddr + PAGE_SIZE * i, vma); 1065 __SetPageUptodate(pages[i]); 1066 cond_resched(); 1067 } 1068 1069 mmun_start = haddr; 1070 mmun_end = haddr + HPAGE_PMD_SIZE; 1071 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1072 1073 ptl = pmd_lock(mm, pmd); 1074 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1075 goto out_free_pages; 1076 VM_BUG_ON_PAGE(!PageHead(page), page); 1077 1078 pmdp_clear_flush(vma, haddr, pmd); 1079 /* leave pmd empty until pte is filled */ 1080 1081 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1082 pmd_populate(mm, &_pmd, pgtable); 1083 1084 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1085 pte_t *pte, entry; 1086 entry = mk_pte(pages[i], vma->vm_page_prot); 1087 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1088 page_add_new_anon_rmap(pages[i], vma, haddr); 1089 pte = pte_offset_map(&_pmd, haddr); 1090 VM_BUG_ON(!pte_none(*pte)); 1091 set_pte_at(mm, haddr, pte, entry); 1092 pte_unmap(pte); 1093 } 1094 kfree(pages); 1095 1096 smp_wmb(); /* make pte visible before pmd */ 1097 pmd_populate(mm, pmd, pgtable); 1098 page_remove_rmap(page); 1099 spin_unlock(ptl); 1100 1101 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1102 1103 ret |= VM_FAULT_WRITE; 1104 put_page(page); 1105 1106 out: 1107 return ret; 1108 1109 out_free_pages: 1110 spin_unlock(ptl); 1111 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1112 mem_cgroup_uncharge_start(); 1113 for (i = 0; i < HPAGE_PMD_NR; i++) { 1114 mem_cgroup_uncharge_page(pages[i]); 1115 put_page(pages[i]); 1116 } 1117 mem_cgroup_uncharge_end(); 1118 kfree(pages); 1119 goto out; 1120 } 1121 1122 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 1123 unsigned long address, pmd_t *pmd, pmd_t orig_pmd) 1124 { 1125 spinlock_t *ptl; 1126 int ret = 0; 1127 struct page *page = NULL, *new_page; 1128 unsigned long haddr; 1129 unsigned long mmun_start; /* For mmu_notifiers */ 1130 unsigned long mmun_end; /* For mmu_notifiers */ 1131 1132 ptl = pmd_lockptr(mm, pmd); 1133 VM_BUG_ON(!vma->anon_vma); 1134 haddr = address & HPAGE_PMD_MASK; 1135 if (is_huge_zero_pmd(orig_pmd)) 1136 goto alloc; 1137 spin_lock(ptl); 1138 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1139 goto out_unlock; 1140 1141 page = pmd_page(orig_pmd); 1142 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); 1143 if (page_mapcount(page) == 1) { 1144 pmd_t entry; 1145 entry = pmd_mkyoung(orig_pmd); 1146 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1147 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 1148 update_mmu_cache_pmd(vma, address, pmd); 1149 ret |= VM_FAULT_WRITE; 1150 goto out_unlock; 1151 } 1152 get_page(page); 1153 spin_unlock(ptl); 1154 alloc: 1155 if (transparent_hugepage_enabled(vma) && 1156 !transparent_hugepage_debug_cow()) 1157 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 1158 vma, haddr, numa_node_id(), 0); 1159 else 1160 new_page = NULL; 1161 1162 if (unlikely(!new_page)) { 1163 if (!page) { 1164 ret = do_huge_pmd_wp_zero_page_fallback(mm, vma, 1165 address, pmd, orig_pmd, haddr); 1166 } else { 1167 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 1168 pmd, orig_pmd, page, haddr); 1169 if (ret & VM_FAULT_OOM) 1170 split_huge_page(page); 1171 put_page(page); 1172 } 1173 count_vm_event(THP_FAULT_FALLBACK); 1174 goto out; 1175 } 1176 1177 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 1178 put_page(new_page); 1179 if (page) { 1180 split_huge_page(page); 1181 put_page(page); 1182 } 1183 count_vm_event(THP_FAULT_FALLBACK); 1184 ret |= VM_FAULT_OOM; 1185 goto out; 1186 } 1187 1188 count_vm_event(THP_FAULT_ALLOC); 1189 1190 if (!page) 1191 clear_huge_page(new_page, haddr, HPAGE_PMD_NR); 1192 else 1193 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 1194 __SetPageUptodate(new_page); 1195 1196 mmun_start = haddr; 1197 mmun_end = haddr + HPAGE_PMD_SIZE; 1198 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1199 1200 spin_lock(ptl); 1201 if (page) 1202 put_page(page); 1203 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 1204 spin_unlock(ptl); 1205 mem_cgroup_uncharge_page(new_page); 1206 put_page(new_page); 1207 goto out_mn; 1208 } else { 1209 pmd_t entry; 1210 entry = mk_huge_pmd(new_page, vma->vm_page_prot); 1211 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1212 pmdp_clear_flush(vma, haddr, pmd); 1213 page_add_new_anon_rmap(new_page, vma, haddr); 1214 set_pmd_at(mm, haddr, pmd, entry); 1215 update_mmu_cache_pmd(vma, address, pmd); 1216 if (!page) { 1217 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 1218 put_huge_zero_page(); 1219 } else { 1220 VM_BUG_ON_PAGE(!PageHead(page), page); 1221 page_remove_rmap(page); 1222 put_page(page); 1223 } 1224 ret |= VM_FAULT_WRITE; 1225 } 1226 spin_unlock(ptl); 1227 out_mn: 1228 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1229 out: 1230 return ret; 1231 out_unlock: 1232 spin_unlock(ptl); 1233 return ret; 1234 } 1235 1236 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1237 unsigned long addr, 1238 pmd_t *pmd, 1239 unsigned int flags) 1240 { 1241 struct mm_struct *mm = vma->vm_mm; 1242 struct page *page = NULL; 1243 1244 assert_spin_locked(pmd_lockptr(mm, pmd)); 1245 1246 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 1247 goto out; 1248 1249 /* Avoid dumping huge zero page */ 1250 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) 1251 return ERR_PTR(-EFAULT); 1252 1253 /* Full NUMA hinting faults to serialise migration in fault paths */ 1254 if ((flags & FOLL_NUMA) && pmd_numa(*pmd)) 1255 goto out; 1256 1257 page = pmd_page(*pmd); 1258 VM_BUG_ON_PAGE(!PageHead(page), page); 1259 if (flags & FOLL_TOUCH) { 1260 pmd_t _pmd; 1261 /* 1262 * We should set the dirty bit only for FOLL_WRITE but 1263 * for now the dirty bit in the pmd is meaningless. 1264 * And if the dirty bit will become meaningful and 1265 * we'll only set it with FOLL_WRITE, an atomic 1266 * set_bit will be required on the pmd to set the 1267 * young bit, instead of the current set_pmd_at. 1268 */ 1269 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 1270 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, 1271 pmd, _pmd, 1)) 1272 update_mmu_cache_pmd(vma, addr, pmd); 1273 } 1274 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 1275 if (page->mapping && trylock_page(page)) { 1276 lru_add_drain(); 1277 if (page->mapping) 1278 mlock_vma_page(page); 1279 unlock_page(page); 1280 } 1281 } 1282 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1283 VM_BUG_ON_PAGE(!PageCompound(page), page); 1284 if (flags & FOLL_GET) 1285 get_page_foll(page); 1286 1287 out: 1288 return page; 1289 } 1290 1291 /* NUMA hinting page fault entry point for trans huge pmds */ 1292 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, 1293 unsigned long addr, pmd_t pmd, pmd_t *pmdp) 1294 { 1295 spinlock_t *ptl; 1296 struct anon_vma *anon_vma = NULL; 1297 struct page *page; 1298 unsigned long haddr = addr & HPAGE_PMD_MASK; 1299 int page_nid = -1, this_nid = numa_node_id(); 1300 int target_nid, last_cpupid = -1; 1301 bool page_locked; 1302 bool migrated = false; 1303 int flags = 0; 1304 1305 ptl = pmd_lock(mm, pmdp); 1306 if (unlikely(!pmd_same(pmd, *pmdp))) 1307 goto out_unlock; 1308 1309 /* 1310 * If there are potential migrations, wait for completion and retry 1311 * without disrupting NUMA hinting information. Do not relock and 1312 * check_same as the page may no longer be mapped. 1313 */ 1314 if (unlikely(pmd_trans_migrating(*pmdp))) { 1315 spin_unlock(ptl); 1316 wait_migrate_huge_page(vma->anon_vma, pmdp); 1317 goto out; 1318 } 1319 1320 page = pmd_page(pmd); 1321 BUG_ON(is_huge_zero_page(page)); 1322 page_nid = page_to_nid(page); 1323 last_cpupid = page_cpupid_last(page); 1324 count_vm_numa_event(NUMA_HINT_FAULTS); 1325 if (page_nid == this_nid) { 1326 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); 1327 flags |= TNF_FAULT_LOCAL; 1328 } 1329 1330 /* 1331 * Avoid grouping on DSO/COW pages in specific and RO pages 1332 * in general, RO pages shouldn't hurt as much anyway since 1333 * they can be in shared cache state. 1334 */ 1335 if (!pmd_write(pmd)) 1336 flags |= TNF_NO_GROUP; 1337 1338 /* 1339 * Acquire the page lock to serialise THP migrations but avoid dropping 1340 * page_table_lock if at all possible 1341 */ 1342 page_locked = trylock_page(page); 1343 target_nid = mpol_misplaced(page, vma, haddr); 1344 if (target_nid == -1) { 1345 /* If the page was locked, there are no parallel migrations */ 1346 if (page_locked) 1347 goto clear_pmdnuma; 1348 } 1349 1350 /* Migration could have started since the pmd_trans_migrating check */ 1351 if (!page_locked) { 1352 spin_unlock(ptl); 1353 wait_on_page_locked(page); 1354 page_nid = -1; 1355 goto out; 1356 } 1357 1358 /* 1359 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma 1360 * to serialises splits 1361 */ 1362 get_page(page); 1363 spin_unlock(ptl); 1364 anon_vma = page_lock_anon_vma_read(page); 1365 1366 /* Confirm the PMD did not change while page_table_lock was released */ 1367 spin_lock(ptl); 1368 if (unlikely(!pmd_same(pmd, *pmdp))) { 1369 unlock_page(page); 1370 put_page(page); 1371 page_nid = -1; 1372 goto out_unlock; 1373 } 1374 1375 /* Bail if we fail to protect against THP splits for any reason */ 1376 if (unlikely(!anon_vma)) { 1377 put_page(page); 1378 page_nid = -1; 1379 goto clear_pmdnuma; 1380 } 1381 1382 /* 1383 * Migrate the THP to the requested node, returns with page unlocked 1384 * and pmd_numa cleared. 1385 */ 1386 spin_unlock(ptl); 1387 migrated = migrate_misplaced_transhuge_page(mm, vma, 1388 pmdp, pmd, addr, page, target_nid); 1389 if (migrated) { 1390 flags |= TNF_MIGRATED; 1391 page_nid = target_nid; 1392 } 1393 1394 goto out; 1395 clear_pmdnuma: 1396 BUG_ON(!PageLocked(page)); 1397 pmd = pmd_mknonnuma(pmd); 1398 set_pmd_at(mm, haddr, pmdp, pmd); 1399 VM_BUG_ON(pmd_numa(*pmdp)); 1400 update_mmu_cache_pmd(vma, addr, pmdp); 1401 unlock_page(page); 1402 out_unlock: 1403 spin_unlock(ptl); 1404 1405 out: 1406 if (anon_vma) 1407 page_unlock_anon_vma_read(anon_vma); 1408 1409 if (page_nid != -1) 1410 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags); 1411 1412 return 0; 1413 } 1414 1415 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1416 pmd_t *pmd, unsigned long addr) 1417 { 1418 spinlock_t *ptl; 1419 int ret = 0; 1420 1421 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { 1422 struct page *page; 1423 pgtable_t pgtable; 1424 pmd_t orig_pmd; 1425 /* 1426 * For architectures like ppc64 we look at deposited pgtable 1427 * when calling pmdp_get_and_clear. So do the 1428 * pgtable_trans_huge_withdraw after finishing pmdp related 1429 * operations. 1430 */ 1431 orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd); 1432 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1433 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd); 1434 if (is_huge_zero_pmd(orig_pmd)) { 1435 atomic_long_dec(&tlb->mm->nr_ptes); 1436 spin_unlock(ptl); 1437 put_huge_zero_page(); 1438 } else { 1439 page = pmd_page(orig_pmd); 1440 page_remove_rmap(page); 1441 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); 1442 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1443 VM_BUG_ON_PAGE(!PageHead(page), page); 1444 atomic_long_dec(&tlb->mm->nr_ptes); 1445 spin_unlock(ptl); 1446 tlb_remove_page(tlb, page); 1447 } 1448 pte_free(tlb->mm, pgtable); 1449 ret = 1; 1450 } 1451 return ret; 1452 } 1453 1454 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1455 unsigned long addr, unsigned long end, 1456 unsigned char *vec) 1457 { 1458 spinlock_t *ptl; 1459 int ret = 0; 1460 1461 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { 1462 /* 1463 * All logical pages in the range are present 1464 * if backed by a huge page. 1465 */ 1466 spin_unlock(ptl); 1467 memset(vec, 1, (end - addr) >> PAGE_SHIFT); 1468 ret = 1; 1469 } 1470 1471 return ret; 1472 } 1473 1474 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, 1475 unsigned long old_addr, 1476 unsigned long new_addr, unsigned long old_end, 1477 pmd_t *old_pmd, pmd_t *new_pmd) 1478 { 1479 spinlock_t *old_ptl, *new_ptl; 1480 int ret = 0; 1481 pmd_t pmd; 1482 1483 struct mm_struct *mm = vma->vm_mm; 1484 1485 if ((old_addr & ~HPAGE_PMD_MASK) || 1486 (new_addr & ~HPAGE_PMD_MASK) || 1487 old_end - old_addr < HPAGE_PMD_SIZE || 1488 (new_vma->vm_flags & VM_NOHUGEPAGE)) 1489 goto out; 1490 1491 /* 1492 * The destination pmd shouldn't be established, free_pgtables() 1493 * should have release it. 1494 */ 1495 if (WARN_ON(!pmd_none(*new_pmd))) { 1496 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1497 goto out; 1498 } 1499 1500 /* 1501 * We don't have to worry about the ordering of src and dst 1502 * ptlocks because exclusive mmap_sem prevents deadlock. 1503 */ 1504 ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl); 1505 if (ret == 1) { 1506 new_ptl = pmd_lockptr(mm, new_pmd); 1507 if (new_ptl != old_ptl) 1508 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 1509 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); 1510 VM_BUG_ON(!pmd_none(*new_pmd)); 1511 1512 if (pmd_move_must_withdraw(new_ptl, old_ptl)) { 1513 pgtable_t pgtable; 1514 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); 1515 pgtable_trans_huge_deposit(mm, new_pmd, pgtable); 1516 } 1517 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd)); 1518 if (new_ptl != old_ptl) 1519 spin_unlock(new_ptl); 1520 spin_unlock(old_ptl); 1521 } 1522 out: 1523 return ret; 1524 } 1525 1526 /* 1527 * Returns 1528 * - 0 if PMD could not be locked 1529 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary 1530 * - HPAGE_PMD_NR is protections changed and TLB flush necessary 1531 */ 1532 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1533 unsigned long addr, pgprot_t newprot, int prot_numa) 1534 { 1535 struct mm_struct *mm = vma->vm_mm; 1536 spinlock_t *ptl; 1537 int ret = 0; 1538 1539 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { 1540 pmd_t entry; 1541 ret = 1; 1542 if (!prot_numa) { 1543 entry = pmdp_get_and_clear(mm, addr, pmd); 1544 if (pmd_numa(entry)) 1545 entry = pmd_mknonnuma(entry); 1546 entry = pmd_modify(entry, newprot); 1547 ret = HPAGE_PMD_NR; 1548 BUG_ON(pmd_write(entry)); 1549 } else { 1550 struct page *page = pmd_page(*pmd); 1551 1552 /* 1553 * Do not trap faults against the zero page. The 1554 * read-only data is likely to be read-cached on the 1555 * local CPU cache and it is less useful to know about 1556 * local vs remote hits on the zero page. 1557 */ 1558 if (!is_huge_zero_page(page) && 1559 !pmd_numa(*pmd)) { 1560 entry = *pmd; 1561 entry = pmd_mknuma(entry); 1562 ret = HPAGE_PMD_NR; 1563 } 1564 } 1565 1566 /* Set PMD if cleared earlier */ 1567 if (ret == HPAGE_PMD_NR) 1568 set_pmd_at(mm, addr, pmd, entry); 1569 1570 spin_unlock(ptl); 1571 } 1572 1573 return ret; 1574 } 1575 1576 /* 1577 * Returns 1 if a given pmd maps a stable (not under splitting) thp. 1578 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise. 1579 * 1580 * Note that if it returns 1, this routine returns without unlocking page 1581 * table locks. So callers must unlock them. 1582 */ 1583 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma, 1584 spinlock_t **ptl) 1585 { 1586 *ptl = pmd_lock(vma->vm_mm, pmd); 1587 if (likely(pmd_trans_huge(*pmd))) { 1588 if (unlikely(pmd_trans_splitting(*pmd))) { 1589 spin_unlock(*ptl); 1590 wait_split_huge_page(vma->anon_vma, pmd); 1591 return -1; 1592 } else { 1593 /* Thp mapped by 'pmd' is stable, so we can 1594 * handle it as it is. */ 1595 return 1; 1596 } 1597 } 1598 spin_unlock(*ptl); 1599 return 0; 1600 } 1601 1602 /* 1603 * This function returns whether a given @page is mapped onto the @address 1604 * in the virtual space of @mm. 1605 * 1606 * When it's true, this function returns *pmd with holding the page table lock 1607 * and passing it back to the caller via @ptl. 1608 * If it's false, returns NULL without holding the page table lock. 1609 */ 1610 pmd_t *page_check_address_pmd(struct page *page, 1611 struct mm_struct *mm, 1612 unsigned long address, 1613 enum page_check_address_pmd_flag flag, 1614 spinlock_t **ptl) 1615 { 1616 pmd_t *pmd; 1617 1618 if (address & ~HPAGE_PMD_MASK) 1619 return NULL; 1620 1621 pmd = mm_find_pmd(mm, address); 1622 if (!pmd) 1623 return NULL; 1624 *ptl = pmd_lock(mm, pmd); 1625 if (pmd_none(*pmd)) 1626 goto unlock; 1627 if (pmd_page(*pmd) != page) 1628 goto unlock; 1629 /* 1630 * split_vma() may create temporary aliased mappings. There is 1631 * no risk as long as all huge pmd are found and have their 1632 * splitting bit set before __split_huge_page_refcount 1633 * runs. Finding the same huge pmd more than once during the 1634 * same rmap walk is not a problem. 1635 */ 1636 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && 1637 pmd_trans_splitting(*pmd)) 1638 goto unlock; 1639 if (pmd_trans_huge(*pmd)) { 1640 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && 1641 !pmd_trans_splitting(*pmd)); 1642 return pmd; 1643 } 1644 unlock: 1645 spin_unlock(*ptl); 1646 return NULL; 1647 } 1648 1649 static int __split_huge_page_splitting(struct page *page, 1650 struct vm_area_struct *vma, 1651 unsigned long address) 1652 { 1653 struct mm_struct *mm = vma->vm_mm; 1654 spinlock_t *ptl; 1655 pmd_t *pmd; 1656 int ret = 0; 1657 /* For mmu_notifiers */ 1658 const unsigned long mmun_start = address; 1659 const unsigned long mmun_end = address + HPAGE_PMD_SIZE; 1660 1661 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1662 pmd = page_check_address_pmd(page, mm, address, 1663 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG, &ptl); 1664 if (pmd) { 1665 /* 1666 * We can't temporarily set the pmd to null in order 1667 * to split it, the pmd must remain marked huge at all 1668 * times or the VM won't take the pmd_trans_huge paths 1669 * and it won't wait on the anon_vma->root->rwsem to 1670 * serialize against split_huge_page*. 1671 */ 1672 pmdp_splitting_flush(vma, address, pmd); 1673 ret = 1; 1674 spin_unlock(ptl); 1675 } 1676 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1677 1678 return ret; 1679 } 1680 1681 static void __split_huge_page_refcount(struct page *page, 1682 struct list_head *list) 1683 { 1684 int i; 1685 struct zone *zone = page_zone(page); 1686 struct lruvec *lruvec; 1687 int tail_count = 0; 1688 1689 /* prevent PageLRU to go away from under us, and freeze lru stats */ 1690 spin_lock_irq(&zone->lru_lock); 1691 lruvec = mem_cgroup_page_lruvec(page, zone); 1692 1693 compound_lock(page); 1694 /* complete memcg works before add pages to LRU */ 1695 mem_cgroup_split_huge_fixup(page); 1696 1697 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 1698 struct page *page_tail = page + i; 1699 1700 /* tail_page->_mapcount cannot change */ 1701 BUG_ON(page_mapcount(page_tail) < 0); 1702 tail_count += page_mapcount(page_tail); 1703 /* check for overflow */ 1704 BUG_ON(tail_count < 0); 1705 BUG_ON(atomic_read(&page_tail->_count) != 0); 1706 /* 1707 * tail_page->_count is zero and not changing from 1708 * under us. But get_page_unless_zero() may be running 1709 * from under us on the tail_page. If we used 1710 * atomic_set() below instead of atomic_add(), we 1711 * would then run atomic_set() concurrently with 1712 * get_page_unless_zero(), and atomic_set() is 1713 * implemented in C not using locked ops. spin_unlock 1714 * on x86 sometime uses locked ops because of PPro 1715 * errata 66, 92, so unless somebody can guarantee 1716 * atomic_set() here would be safe on all archs (and 1717 * not only on x86), it's safer to use atomic_add(). 1718 */ 1719 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, 1720 &page_tail->_count); 1721 1722 /* after clearing PageTail the gup refcount can be released */ 1723 smp_mb(); 1724 1725 /* 1726 * retain hwpoison flag of the poisoned tail page: 1727 * fix for the unsuitable process killed on Guest Machine(KVM) 1728 * by the memory-failure. 1729 */ 1730 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON; 1731 page_tail->flags |= (page->flags & 1732 ((1L << PG_referenced) | 1733 (1L << PG_swapbacked) | 1734 (1L << PG_mlocked) | 1735 (1L << PG_uptodate) | 1736 (1L << PG_active) | 1737 (1L << PG_unevictable))); 1738 page_tail->flags |= (1L << PG_dirty); 1739 1740 /* clear PageTail before overwriting first_page */ 1741 smp_wmb(); 1742 1743 /* 1744 * __split_huge_page_splitting() already set the 1745 * splitting bit in all pmd that could map this 1746 * hugepage, that will ensure no CPU can alter the 1747 * mapcount on the head page. The mapcount is only 1748 * accounted in the head page and it has to be 1749 * transferred to all tail pages in the below code. So 1750 * for this code to be safe, the split the mapcount 1751 * can't change. But that doesn't mean userland can't 1752 * keep changing and reading the page contents while 1753 * we transfer the mapcount, so the pmd splitting 1754 * status is achieved setting a reserved bit in the 1755 * pmd, not by clearing the present bit. 1756 */ 1757 page_tail->_mapcount = page->_mapcount; 1758 1759 BUG_ON(page_tail->mapping); 1760 page_tail->mapping = page->mapping; 1761 1762 page_tail->index = page->index + i; 1763 page_cpupid_xchg_last(page_tail, page_cpupid_last(page)); 1764 1765 BUG_ON(!PageAnon(page_tail)); 1766 BUG_ON(!PageUptodate(page_tail)); 1767 BUG_ON(!PageDirty(page_tail)); 1768 BUG_ON(!PageSwapBacked(page_tail)); 1769 1770 lru_add_page_tail(page, page_tail, lruvec, list); 1771 } 1772 atomic_sub(tail_count, &page->_count); 1773 BUG_ON(atomic_read(&page->_count) <= 0); 1774 1775 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1); 1776 1777 ClearPageCompound(page); 1778 compound_unlock(page); 1779 spin_unlock_irq(&zone->lru_lock); 1780 1781 for (i = 1; i < HPAGE_PMD_NR; i++) { 1782 struct page *page_tail = page + i; 1783 BUG_ON(page_count(page_tail) <= 0); 1784 /* 1785 * Tail pages may be freed if there wasn't any mapping 1786 * like if add_to_swap() is running on a lru page that 1787 * had its mapping zapped. And freeing these pages 1788 * requires taking the lru_lock so we do the put_page 1789 * of the tail pages after the split is complete. 1790 */ 1791 put_page(page_tail); 1792 } 1793 1794 /* 1795 * Only the head page (now become a regular page) is required 1796 * to be pinned by the caller. 1797 */ 1798 BUG_ON(page_count(page) <= 0); 1799 } 1800 1801 static int __split_huge_page_map(struct page *page, 1802 struct vm_area_struct *vma, 1803 unsigned long address) 1804 { 1805 struct mm_struct *mm = vma->vm_mm; 1806 spinlock_t *ptl; 1807 pmd_t *pmd, _pmd; 1808 int ret = 0, i; 1809 pgtable_t pgtable; 1810 unsigned long haddr; 1811 1812 pmd = page_check_address_pmd(page, mm, address, 1813 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl); 1814 if (pmd) { 1815 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1816 pmd_populate(mm, &_pmd, pgtable); 1817 1818 haddr = address; 1819 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1820 pte_t *pte, entry; 1821 BUG_ON(PageCompound(page+i)); 1822 entry = mk_pte(page + i, vma->vm_page_prot); 1823 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1824 if (!pmd_write(*pmd)) 1825 entry = pte_wrprotect(entry); 1826 else 1827 BUG_ON(page_mapcount(page) != 1); 1828 if (!pmd_young(*pmd)) 1829 entry = pte_mkold(entry); 1830 if (pmd_numa(*pmd)) 1831 entry = pte_mknuma(entry); 1832 pte = pte_offset_map(&_pmd, haddr); 1833 BUG_ON(!pte_none(*pte)); 1834 set_pte_at(mm, haddr, pte, entry); 1835 pte_unmap(pte); 1836 } 1837 1838 smp_wmb(); /* make pte visible before pmd */ 1839 /* 1840 * Up to this point the pmd is present and huge and 1841 * userland has the whole access to the hugepage 1842 * during the split (which happens in place). If we 1843 * overwrite the pmd with the not-huge version 1844 * pointing to the pte here (which of course we could 1845 * if all CPUs were bug free), userland could trigger 1846 * a small page size TLB miss on the small sized TLB 1847 * while the hugepage TLB entry is still established 1848 * in the huge TLB. Some CPU doesn't like that. See 1849 * http://support.amd.com/us/Processor_TechDocs/41322.pdf, 1850 * Erratum 383 on page 93. Intel should be safe but is 1851 * also warns that it's only safe if the permission 1852 * and cache attributes of the two entries loaded in 1853 * the two TLB is identical (which should be the case 1854 * here). But it is generally safer to never allow 1855 * small and huge TLB entries for the same virtual 1856 * address to be loaded simultaneously. So instead of 1857 * doing "pmd_populate(); flush_tlb_range();" we first 1858 * mark the current pmd notpresent (atomically because 1859 * here the pmd_trans_huge and pmd_trans_splitting 1860 * must remain set at all times on the pmd until the 1861 * split is complete for this pmd), then we flush the 1862 * SMP TLB and finally we write the non-huge version 1863 * of the pmd entry with pmd_populate. 1864 */ 1865 pmdp_invalidate(vma, address, pmd); 1866 pmd_populate(mm, pmd, pgtable); 1867 ret = 1; 1868 spin_unlock(ptl); 1869 } 1870 1871 return ret; 1872 } 1873 1874 /* must be called with anon_vma->root->rwsem held */ 1875 static void __split_huge_page(struct page *page, 1876 struct anon_vma *anon_vma, 1877 struct list_head *list) 1878 { 1879 int mapcount, mapcount2; 1880 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 1881 struct anon_vma_chain *avc; 1882 1883 BUG_ON(!PageHead(page)); 1884 BUG_ON(PageTail(page)); 1885 1886 mapcount = 0; 1887 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1888 struct vm_area_struct *vma = avc->vma; 1889 unsigned long addr = vma_address(page, vma); 1890 BUG_ON(is_vma_temporary_stack(vma)); 1891 mapcount += __split_huge_page_splitting(page, vma, addr); 1892 } 1893 /* 1894 * It is critical that new vmas are added to the tail of the 1895 * anon_vma list. This guarantes that if copy_huge_pmd() runs 1896 * and establishes a child pmd before 1897 * __split_huge_page_splitting() freezes the parent pmd (so if 1898 * we fail to prevent copy_huge_pmd() from running until the 1899 * whole __split_huge_page() is complete), we will still see 1900 * the newly established pmd of the child later during the 1901 * walk, to be able to set it as pmd_trans_splitting too. 1902 */ 1903 if (mapcount != page_mapcount(page)) 1904 printk(KERN_ERR "mapcount %d page_mapcount %d\n", 1905 mapcount, page_mapcount(page)); 1906 BUG_ON(mapcount != page_mapcount(page)); 1907 1908 __split_huge_page_refcount(page, list); 1909 1910 mapcount2 = 0; 1911 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1912 struct vm_area_struct *vma = avc->vma; 1913 unsigned long addr = vma_address(page, vma); 1914 BUG_ON(is_vma_temporary_stack(vma)); 1915 mapcount2 += __split_huge_page_map(page, vma, addr); 1916 } 1917 if (mapcount != mapcount2) 1918 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n", 1919 mapcount, mapcount2, page_mapcount(page)); 1920 BUG_ON(mapcount != mapcount2); 1921 } 1922 1923 /* 1924 * Split a hugepage into normal pages. This doesn't change the position of head 1925 * page. If @list is null, tail pages will be added to LRU list, otherwise, to 1926 * @list. Both head page and tail pages will inherit mapping, flags, and so on 1927 * from the hugepage. 1928 * Return 0 if the hugepage is split successfully otherwise return 1. 1929 */ 1930 int split_huge_page_to_list(struct page *page, struct list_head *list) 1931 { 1932 struct anon_vma *anon_vma; 1933 int ret = 1; 1934 1935 BUG_ON(is_huge_zero_page(page)); 1936 BUG_ON(!PageAnon(page)); 1937 1938 /* 1939 * The caller does not necessarily hold an mmap_sem that would prevent 1940 * the anon_vma disappearing so we first we take a reference to it 1941 * and then lock the anon_vma for write. This is similar to 1942 * page_lock_anon_vma_read except the write lock is taken to serialise 1943 * against parallel split or collapse operations. 1944 */ 1945 anon_vma = page_get_anon_vma(page); 1946 if (!anon_vma) 1947 goto out; 1948 anon_vma_lock_write(anon_vma); 1949 1950 ret = 0; 1951 if (!PageCompound(page)) 1952 goto out_unlock; 1953 1954 BUG_ON(!PageSwapBacked(page)); 1955 __split_huge_page(page, anon_vma, list); 1956 count_vm_event(THP_SPLIT); 1957 1958 BUG_ON(PageCompound(page)); 1959 out_unlock: 1960 anon_vma_unlock_write(anon_vma); 1961 put_anon_vma(anon_vma); 1962 out: 1963 return ret; 1964 } 1965 1966 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE) 1967 1968 int hugepage_madvise(struct vm_area_struct *vma, 1969 unsigned long *vm_flags, int advice) 1970 { 1971 struct mm_struct *mm = vma->vm_mm; 1972 1973 switch (advice) { 1974 case MADV_HUGEPAGE: 1975 /* 1976 * Be somewhat over-protective like KSM for now! 1977 */ 1978 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) 1979 return -EINVAL; 1980 if (mm->def_flags & VM_NOHUGEPAGE) 1981 return -EINVAL; 1982 *vm_flags &= ~VM_NOHUGEPAGE; 1983 *vm_flags |= VM_HUGEPAGE; 1984 /* 1985 * If the vma become good for khugepaged to scan, 1986 * register it here without waiting a page fault that 1987 * may not happen any time soon. 1988 */ 1989 if (unlikely(khugepaged_enter_vma_merge(vma))) 1990 return -ENOMEM; 1991 break; 1992 case MADV_NOHUGEPAGE: 1993 /* 1994 * Be somewhat over-protective like KSM for now! 1995 */ 1996 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) 1997 return -EINVAL; 1998 *vm_flags &= ~VM_HUGEPAGE; 1999 *vm_flags |= VM_NOHUGEPAGE; 2000 /* 2001 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 2002 * this vma even if we leave the mm registered in khugepaged if 2003 * it got registered before VM_NOHUGEPAGE was set. 2004 */ 2005 break; 2006 } 2007 2008 return 0; 2009 } 2010 2011 static int __init khugepaged_slab_init(void) 2012 { 2013 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 2014 sizeof(struct mm_slot), 2015 __alignof__(struct mm_slot), 0, NULL); 2016 if (!mm_slot_cache) 2017 return -ENOMEM; 2018 2019 return 0; 2020 } 2021 2022 static inline struct mm_slot *alloc_mm_slot(void) 2023 { 2024 if (!mm_slot_cache) /* initialization failed */ 2025 return NULL; 2026 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 2027 } 2028 2029 static inline void free_mm_slot(struct mm_slot *mm_slot) 2030 { 2031 kmem_cache_free(mm_slot_cache, mm_slot); 2032 } 2033 2034 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 2035 { 2036 struct mm_slot *mm_slot; 2037 2038 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) 2039 if (mm == mm_slot->mm) 2040 return mm_slot; 2041 2042 return NULL; 2043 } 2044 2045 static void insert_to_mm_slots_hash(struct mm_struct *mm, 2046 struct mm_slot *mm_slot) 2047 { 2048 mm_slot->mm = mm; 2049 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); 2050 } 2051 2052 static inline int khugepaged_test_exit(struct mm_struct *mm) 2053 { 2054 return atomic_read(&mm->mm_users) == 0; 2055 } 2056 2057 int __khugepaged_enter(struct mm_struct *mm) 2058 { 2059 struct mm_slot *mm_slot; 2060 int wakeup; 2061 2062 mm_slot = alloc_mm_slot(); 2063 if (!mm_slot) 2064 return -ENOMEM; 2065 2066 /* __khugepaged_exit() must not run from under us */ 2067 VM_BUG_ON(khugepaged_test_exit(mm)); 2068 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 2069 free_mm_slot(mm_slot); 2070 return 0; 2071 } 2072 2073 spin_lock(&khugepaged_mm_lock); 2074 insert_to_mm_slots_hash(mm, mm_slot); 2075 /* 2076 * Insert just behind the scanning cursor, to let the area settle 2077 * down a little. 2078 */ 2079 wakeup = list_empty(&khugepaged_scan.mm_head); 2080 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 2081 spin_unlock(&khugepaged_mm_lock); 2082 2083 atomic_inc(&mm->mm_count); 2084 if (wakeup) 2085 wake_up_interruptible(&khugepaged_wait); 2086 2087 return 0; 2088 } 2089 2090 int khugepaged_enter_vma_merge(struct vm_area_struct *vma) 2091 { 2092 unsigned long hstart, hend; 2093 if (!vma->anon_vma) 2094 /* 2095 * Not yet faulted in so we will register later in the 2096 * page fault if needed. 2097 */ 2098 return 0; 2099 if (vma->vm_ops) 2100 /* khugepaged not yet working on file or special mappings */ 2101 return 0; 2102 VM_BUG_ON(vma->vm_flags & VM_NO_THP); 2103 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2104 hend = vma->vm_end & HPAGE_PMD_MASK; 2105 if (hstart < hend) 2106 return khugepaged_enter(vma); 2107 return 0; 2108 } 2109 2110 void __khugepaged_exit(struct mm_struct *mm) 2111 { 2112 struct mm_slot *mm_slot; 2113 int free = 0; 2114 2115 spin_lock(&khugepaged_mm_lock); 2116 mm_slot = get_mm_slot(mm); 2117 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 2118 hash_del(&mm_slot->hash); 2119 list_del(&mm_slot->mm_node); 2120 free = 1; 2121 } 2122 spin_unlock(&khugepaged_mm_lock); 2123 2124 if (free) { 2125 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2126 free_mm_slot(mm_slot); 2127 mmdrop(mm); 2128 } else if (mm_slot) { 2129 /* 2130 * This is required to serialize against 2131 * khugepaged_test_exit() (which is guaranteed to run 2132 * under mmap sem read mode). Stop here (after we 2133 * return all pagetables will be destroyed) until 2134 * khugepaged has finished working on the pagetables 2135 * under the mmap_sem. 2136 */ 2137 down_write(&mm->mmap_sem); 2138 up_write(&mm->mmap_sem); 2139 } 2140 } 2141 2142 static void release_pte_page(struct page *page) 2143 { 2144 /* 0 stands for page_is_file_cache(page) == false */ 2145 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 2146 unlock_page(page); 2147 putback_lru_page(page); 2148 } 2149 2150 static void release_pte_pages(pte_t *pte, pte_t *_pte) 2151 { 2152 while (--_pte >= pte) { 2153 pte_t pteval = *_pte; 2154 if (!pte_none(pteval)) 2155 release_pte_page(pte_page(pteval)); 2156 } 2157 } 2158 2159 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 2160 unsigned long address, 2161 pte_t *pte) 2162 { 2163 struct page *page; 2164 pte_t *_pte; 2165 int referenced = 0, none = 0; 2166 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 2167 _pte++, address += PAGE_SIZE) { 2168 pte_t pteval = *_pte; 2169 if (pte_none(pteval)) { 2170 if (++none <= khugepaged_max_ptes_none) 2171 continue; 2172 else 2173 goto out; 2174 } 2175 if (!pte_present(pteval) || !pte_write(pteval)) 2176 goto out; 2177 page = vm_normal_page(vma, address, pteval); 2178 if (unlikely(!page)) 2179 goto out; 2180 2181 VM_BUG_ON_PAGE(PageCompound(page), page); 2182 VM_BUG_ON_PAGE(!PageAnon(page), page); 2183 VM_BUG_ON_PAGE(!PageSwapBacked(page), page); 2184 2185 /* cannot use mapcount: can't collapse if there's a gup pin */ 2186 if (page_count(page) != 1) 2187 goto out; 2188 /* 2189 * We can do it before isolate_lru_page because the 2190 * page can't be freed from under us. NOTE: PG_lock 2191 * is needed to serialize against split_huge_page 2192 * when invoked from the VM. 2193 */ 2194 if (!trylock_page(page)) 2195 goto out; 2196 /* 2197 * Isolate the page to avoid collapsing an hugepage 2198 * currently in use by the VM. 2199 */ 2200 if (isolate_lru_page(page)) { 2201 unlock_page(page); 2202 goto out; 2203 } 2204 /* 0 stands for page_is_file_cache(page) == false */ 2205 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 2206 VM_BUG_ON_PAGE(!PageLocked(page), page); 2207 VM_BUG_ON_PAGE(PageLRU(page), page); 2208 2209 /* If there is no mapped pte young don't collapse the page */ 2210 if (pte_young(pteval) || PageReferenced(page) || 2211 mmu_notifier_test_young(vma->vm_mm, address)) 2212 referenced = 1; 2213 } 2214 if (likely(referenced)) 2215 return 1; 2216 out: 2217 release_pte_pages(pte, _pte); 2218 return 0; 2219 } 2220 2221 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 2222 struct vm_area_struct *vma, 2223 unsigned long address, 2224 spinlock_t *ptl) 2225 { 2226 pte_t *_pte; 2227 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 2228 pte_t pteval = *_pte; 2229 struct page *src_page; 2230 2231 if (pte_none(pteval)) { 2232 clear_user_highpage(page, address); 2233 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 2234 } else { 2235 src_page = pte_page(pteval); 2236 copy_user_highpage(page, src_page, address, vma); 2237 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); 2238 release_pte_page(src_page); 2239 /* 2240 * ptl mostly unnecessary, but preempt has to 2241 * be disabled to update the per-cpu stats 2242 * inside page_remove_rmap(). 2243 */ 2244 spin_lock(ptl); 2245 /* 2246 * paravirt calls inside pte_clear here are 2247 * superfluous. 2248 */ 2249 pte_clear(vma->vm_mm, address, _pte); 2250 page_remove_rmap(src_page); 2251 spin_unlock(ptl); 2252 free_page_and_swap_cache(src_page); 2253 } 2254 2255 address += PAGE_SIZE; 2256 page++; 2257 } 2258 } 2259 2260 static void khugepaged_alloc_sleep(void) 2261 { 2262 wait_event_freezable_timeout(khugepaged_wait, false, 2263 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 2264 } 2265 2266 static int khugepaged_node_load[MAX_NUMNODES]; 2267 2268 #ifdef CONFIG_NUMA 2269 static int khugepaged_find_target_node(void) 2270 { 2271 static int last_khugepaged_target_node = NUMA_NO_NODE; 2272 int nid, target_node = 0, max_value = 0; 2273 2274 /* find first node with max normal pages hit */ 2275 for (nid = 0; nid < MAX_NUMNODES; nid++) 2276 if (khugepaged_node_load[nid] > max_value) { 2277 max_value = khugepaged_node_load[nid]; 2278 target_node = nid; 2279 } 2280 2281 /* do some balance if several nodes have the same hit record */ 2282 if (target_node <= last_khugepaged_target_node) 2283 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; 2284 nid++) 2285 if (max_value == khugepaged_node_load[nid]) { 2286 target_node = nid; 2287 break; 2288 } 2289 2290 last_khugepaged_target_node = target_node; 2291 return target_node; 2292 } 2293 2294 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2295 { 2296 if (IS_ERR(*hpage)) { 2297 if (!*wait) 2298 return false; 2299 2300 *wait = false; 2301 *hpage = NULL; 2302 khugepaged_alloc_sleep(); 2303 } else if (*hpage) { 2304 put_page(*hpage); 2305 *hpage = NULL; 2306 } 2307 2308 return true; 2309 } 2310 2311 static struct page 2312 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 2313 struct vm_area_struct *vma, unsigned long address, 2314 int node) 2315 { 2316 VM_BUG_ON_PAGE(*hpage, *hpage); 2317 /* 2318 * Allocate the page while the vma is still valid and under 2319 * the mmap_sem read mode so there is no memory allocation 2320 * later when we take the mmap_sem in write mode. This is more 2321 * friendly behavior (OTOH it may actually hide bugs) to 2322 * filesystems in userland with daemons allocating memory in 2323 * the userland I/O paths. Allocating memory with the 2324 * mmap_sem in read mode is good idea also to allow greater 2325 * scalability. 2326 */ 2327 *hpage = alloc_pages_exact_node(node, alloc_hugepage_gfpmask( 2328 khugepaged_defrag(), __GFP_OTHER_NODE), HPAGE_PMD_ORDER); 2329 /* 2330 * After allocating the hugepage, release the mmap_sem read lock in 2331 * preparation for taking it in write mode. 2332 */ 2333 up_read(&mm->mmap_sem); 2334 if (unlikely(!*hpage)) { 2335 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2336 *hpage = ERR_PTR(-ENOMEM); 2337 return NULL; 2338 } 2339 2340 count_vm_event(THP_COLLAPSE_ALLOC); 2341 return *hpage; 2342 } 2343 #else 2344 static int khugepaged_find_target_node(void) 2345 { 2346 return 0; 2347 } 2348 2349 static inline struct page *alloc_hugepage(int defrag) 2350 { 2351 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), 2352 HPAGE_PMD_ORDER); 2353 } 2354 2355 static struct page *khugepaged_alloc_hugepage(bool *wait) 2356 { 2357 struct page *hpage; 2358 2359 do { 2360 hpage = alloc_hugepage(khugepaged_defrag()); 2361 if (!hpage) { 2362 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2363 if (!*wait) 2364 return NULL; 2365 2366 *wait = false; 2367 khugepaged_alloc_sleep(); 2368 } else 2369 count_vm_event(THP_COLLAPSE_ALLOC); 2370 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 2371 2372 return hpage; 2373 } 2374 2375 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2376 { 2377 if (!*hpage) 2378 *hpage = khugepaged_alloc_hugepage(wait); 2379 2380 if (unlikely(!*hpage)) 2381 return false; 2382 2383 return true; 2384 } 2385 2386 static struct page 2387 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 2388 struct vm_area_struct *vma, unsigned long address, 2389 int node) 2390 { 2391 up_read(&mm->mmap_sem); 2392 VM_BUG_ON(!*hpage); 2393 return *hpage; 2394 } 2395 #endif 2396 2397 static bool hugepage_vma_check(struct vm_area_struct *vma) 2398 { 2399 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 2400 (vma->vm_flags & VM_NOHUGEPAGE)) 2401 return false; 2402 2403 if (!vma->anon_vma || vma->vm_ops) 2404 return false; 2405 if (is_vma_temporary_stack(vma)) 2406 return false; 2407 VM_BUG_ON(vma->vm_flags & VM_NO_THP); 2408 return true; 2409 } 2410 2411 static void collapse_huge_page(struct mm_struct *mm, 2412 unsigned long address, 2413 struct page **hpage, 2414 struct vm_area_struct *vma, 2415 int node) 2416 { 2417 pmd_t *pmd, _pmd; 2418 pte_t *pte; 2419 pgtable_t pgtable; 2420 struct page *new_page; 2421 spinlock_t *pmd_ptl, *pte_ptl; 2422 int isolated; 2423 unsigned long hstart, hend; 2424 unsigned long mmun_start; /* For mmu_notifiers */ 2425 unsigned long mmun_end; /* For mmu_notifiers */ 2426 2427 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2428 2429 /* release the mmap_sem read lock. */ 2430 new_page = khugepaged_alloc_page(hpage, mm, vma, address, node); 2431 if (!new_page) 2432 return; 2433 2434 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) 2435 return; 2436 2437 /* 2438 * Prevent all access to pagetables with the exception of 2439 * gup_fast later hanlded by the ptep_clear_flush and the VM 2440 * handled by the anon_vma lock + PG_lock. 2441 */ 2442 down_write(&mm->mmap_sem); 2443 if (unlikely(khugepaged_test_exit(mm))) 2444 goto out; 2445 2446 vma = find_vma(mm, address); 2447 if (!vma) 2448 goto out; 2449 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2450 hend = vma->vm_end & HPAGE_PMD_MASK; 2451 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 2452 goto out; 2453 if (!hugepage_vma_check(vma)) 2454 goto out; 2455 pmd = mm_find_pmd(mm, address); 2456 if (!pmd) 2457 goto out; 2458 if (pmd_trans_huge(*pmd)) 2459 goto out; 2460 2461 anon_vma_lock_write(vma->anon_vma); 2462 2463 pte = pte_offset_map(pmd, address); 2464 pte_ptl = pte_lockptr(mm, pmd); 2465 2466 mmun_start = address; 2467 mmun_end = address + HPAGE_PMD_SIZE; 2468 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2469 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ 2470 /* 2471 * After this gup_fast can't run anymore. This also removes 2472 * any huge TLB entry from the CPU so we won't allow 2473 * huge and small TLB entries for the same virtual address 2474 * to avoid the risk of CPU bugs in that area. 2475 */ 2476 _pmd = pmdp_clear_flush(vma, address, pmd); 2477 spin_unlock(pmd_ptl); 2478 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2479 2480 spin_lock(pte_ptl); 2481 isolated = __collapse_huge_page_isolate(vma, address, pte); 2482 spin_unlock(pte_ptl); 2483 2484 if (unlikely(!isolated)) { 2485 pte_unmap(pte); 2486 spin_lock(pmd_ptl); 2487 BUG_ON(!pmd_none(*pmd)); 2488 /* 2489 * We can only use set_pmd_at when establishing 2490 * hugepmds and never for establishing regular pmds that 2491 * points to regular pagetables. Use pmd_populate for that 2492 */ 2493 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 2494 spin_unlock(pmd_ptl); 2495 anon_vma_unlock_write(vma->anon_vma); 2496 goto out; 2497 } 2498 2499 /* 2500 * All pages are isolated and locked so anon_vma rmap 2501 * can't run anymore. 2502 */ 2503 anon_vma_unlock_write(vma->anon_vma); 2504 2505 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); 2506 pte_unmap(pte); 2507 __SetPageUptodate(new_page); 2508 pgtable = pmd_pgtable(_pmd); 2509 2510 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); 2511 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 2512 2513 /* 2514 * spin_lock() below is not the equivalent of smp_wmb(), so 2515 * this is needed to avoid the copy_huge_page writes to become 2516 * visible after the set_pmd_at() write. 2517 */ 2518 smp_wmb(); 2519 2520 spin_lock(pmd_ptl); 2521 BUG_ON(!pmd_none(*pmd)); 2522 page_add_new_anon_rmap(new_page, vma, address); 2523 pgtable_trans_huge_deposit(mm, pmd, pgtable); 2524 set_pmd_at(mm, address, pmd, _pmd); 2525 update_mmu_cache_pmd(vma, address, pmd); 2526 spin_unlock(pmd_ptl); 2527 2528 *hpage = NULL; 2529 2530 khugepaged_pages_collapsed++; 2531 out_up_write: 2532 up_write(&mm->mmap_sem); 2533 return; 2534 2535 out: 2536 mem_cgroup_uncharge_page(new_page); 2537 goto out_up_write; 2538 } 2539 2540 static int khugepaged_scan_pmd(struct mm_struct *mm, 2541 struct vm_area_struct *vma, 2542 unsigned long address, 2543 struct page **hpage) 2544 { 2545 pmd_t *pmd; 2546 pte_t *pte, *_pte; 2547 int ret = 0, referenced = 0, none = 0; 2548 struct page *page; 2549 unsigned long _address; 2550 spinlock_t *ptl; 2551 int node = NUMA_NO_NODE; 2552 2553 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2554 2555 pmd = mm_find_pmd(mm, address); 2556 if (!pmd) 2557 goto out; 2558 if (pmd_trans_huge(*pmd)) 2559 goto out; 2560 2561 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 2562 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2563 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2564 _pte++, _address += PAGE_SIZE) { 2565 pte_t pteval = *_pte; 2566 if (pte_none(pteval)) { 2567 if (++none <= khugepaged_max_ptes_none) 2568 continue; 2569 else 2570 goto out_unmap; 2571 } 2572 if (!pte_present(pteval) || !pte_write(pteval)) 2573 goto out_unmap; 2574 page = vm_normal_page(vma, _address, pteval); 2575 if (unlikely(!page)) 2576 goto out_unmap; 2577 /* 2578 * Record which node the original page is from and save this 2579 * information to khugepaged_node_load[]. 2580 * Khupaged will allocate hugepage from the node has the max 2581 * hit record. 2582 */ 2583 node = page_to_nid(page); 2584 khugepaged_node_load[node]++; 2585 VM_BUG_ON_PAGE(PageCompound(page), page); 2586 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) 2587 goto out_unmap; 2588 /* cannot use mapcount: can't collapse if there's a gup pin */ 2589 if (page_count(page) != 1) 2590 goto out_unmap; 2591 if (pte_young(pteval) || PageReferenced(page) || 2592 mmu_notifier_test_young(vma->vm_mm, address)) 2593 referenced = 1; 2594 } 2595 if (referenced) 2596 ret = 1; 2597 out_unmap: 2598 pte_unmap_unlock(pte, ptl); 2599 if (ret) { 2600 node = khugepaged_find_target_node(); 2601 /* collapse_huge_page will return with the mmap_sem released */ 2602 collapse_huge_page(mm, address, hpage, vma, node); 2603 } 2604 out: 2605 return ret; 2606 } 2607 2608 static void collect_mm_slot(struct mm_slot *mm_slot) 2609 { 2610 struct mm_struct *mm = mm_slot->mm; 2611 2612 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2613 2614 if (khugepaged_test_exit(mm)) { 2615 /* free mm_slot */ 2616 hash_del(&mm_slot->hash); 2617 list_del(&mm_slot->mm_node); 2618 2619 /* 2620 * Not strictly needed because the mm exited already. 2621 * 2622 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2623 */ 2624 2625 /* khugepaged_mm_lock actually not necessary for the below */ 2626 free_mm_slot(mm_slot); 2627 mmdrop(mm); 2628 } 2629 } 2630 2631 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2632 struct page **hpage) 2633 __releases(&khugepaged_mm_lock) 2634 __acquires(&khugepaged_mm_lock) 2635 { 2636 struct mm_slot *mm_slot; 2637 struct mm_struct *mm; 2638 struct vm_area_struct *vma; 2639 int progress = 0; 2640 2641 VM_BUG_ON(!pages); 2642 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2643 2644 if (khugepaged_scan.mm_slot) 2645 mm_slot = khugepaged_scan.mm_slot; 2646 else { 2647 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2648 struct mm_slot, mm_node); 2649 khugepaged_scan.address = 0; 2650 khugepaged_scan.mm_slot = mm_slot; 2651 } 2652 spin_unlock(&khugepaged_mm_lock); 2653 2654 mm = mm_slot->mm; 2655 down_read(&mm->mmap_sem); 2656 if (unlikely(khugepaged_test_exit(mm))) 2657 vma = NULL; 2658 else 2659 vma = find_vma(mm, khugepaged_scan.address); 2660 2661 progress++; 2662 for (; vma; vma = vma->vm_next) { 2663 unsigned long hstart, hend; 2664 2665 cond_resched(); 2666 if (unlikely(khugepaged_test_exit(mm))) { 2667 progress++; 2668 break; 2669 } 2670 if (!hugepage_vma_check(vma)) { 2671 skip: 2672 progress++; 2673 continue; 2674 } 2675 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2676 hend = vma->vm_end & HPAGE_PMD_MASK; 2677 if (hstart >= hend) 2678 goto skip; 2679 if (khugepaged_scan.address > hend) 2680 goto skip; 2681 if (khugepaged_scan.address < hstart) 2682 khugepaged_scan.address = hstart; 2683 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2684 2685 while (khugepaged_scan.address < hend) { 2686 int ret; 2687 cond_resched(); 2688 if (unlikely(khugepaged_test_exit(mm))) 2689 goto breakouterloop; 2690 2691 VM_BUG_ON(khugepaged_scan.address < hstart || 2692 khugepaged_scan.address + HPAGE_PMD_SIZE > 2693 hend); 2694 ret = khugepaged_scan_pmd(mm, vma, 2695 khugepaged_scan.address, 2696 hpage); 2697 /* move to next address */ 2698 khugepaged_scan.address += HPAGE_PMD_SIZE; 2699 progress += HPAGE_PMD_NR; 2700 if (ret) 2701 /* we released mmap_sem so break loop */ 2702 goto breakouterloop_mmap_sem; 2703 if (progress >= pages) 2704 goto breakouterloop; 2705 } 2706 } 2707 breakouterloop: 2708 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2709 breakouterloop_mmap_sem: 2710 2711 spin_lock(&khugepaged_mm_lock); 2712 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2713 /* 2714 * Release the current mm_slot if this mm is about to die, or 2715 * if we scanned all vmas of this mm. 2716 */ 2717 if (khugepaged_test_exit(mm) || !vma) { 2718 /* 2719 * Make sure that if mm_users is reaching zero while 2720 * khugepaged runs here, khugepaged_exit will find 2721 * mm_slot not pointing to the exiting mm. 2722 */ 2723 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2724 khugepaged_scan.mm_slot = list_entry( 2725 mm_slot->mm_node.next, 2726 struct mm_slot, mm_node); 2727 khugepaged_scan.address = 0; 2728 } else { 2729 khugepaged_scan.mm_slot = NULL; 2730 khugepaged_full_scans++; 2731 } 2732 2733 collect_mm_slot(mm_slot); 2734 } 2735 2736 return progress; 2737 } 2738 2739 static int khugepaged_has_work(void) 2740 { 2741 return !list_empty(&khugepaged_scan.mm_head) && 2742 khugepaged_enabled(); 2743 } 2744 2745 static int khugepaged_wait_event(void) 2746 { 2747 return !list_empty(&khugepaged_scan.mm_head) || 2748 kthread_should_stop(); 2749 } 2750 2751 static void khugepaged_do_scan(void) 2752 { 2753 struct page *hpage = NULL; 2754 unsigned int progress = 0, pass_through_head = 0; 2755 unsigned int pages = khugepaged_pages_to_scan; 2756 bool wait = true; 2757 2758 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2759 2760 while (progress < pages) { 2761 if (!khugepaged_prealloc_page(&hpage, &wait)) 2762 break; 2763 2764 cond_resched(); 2765 2766 if (unlikely(kthread_should_stop() || freezing(current))) 2767 break; 2768 2769 spin_lock(&khugepaged_mm_lock); 2770 if (!khugepaged_scan.mm_slot) 2771 pass_through_head++; 2772 if (khugepaged_has_work() && 2773 pass_through_head < 2) 2774 progress += khugepaged_scan_mm_slot(pages - progress, 2775 &hpage); 2776 else 2777 progress = pages; 2778 spin_unlock(&khugepaged_mm_lock); 2779 } 2780 2781 if (!IS_ERR_OR_NULL(hpage)) 2782 put_page(hpage); 2783 } 2784 2785 static void khugepaged_wait_work(void) 2786 { 2787 try_to_freeze(); 2788 2789 if (khugepaged_has_work()) { 2790 if (!khugepaged_scan_sleep_millisecs) 2791 return; 2792 2793 wait_event_freezable_timeout(khugepaged_wait, 2794 kthread_should_stop(), 2795 msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); 2796 return; 2797 } 2798 2799 if (khugepaged_enabled()) 2800 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 2801 } 2802 2803 static int khugepaged(void *none) 2804 { 2805 struct mm_slot *mm_slot; 2806 2807 set_freezable(); 2808 set_user_nice(current, 19); 2809 2810 while (!kthread_should_stop()) { 2811 khugepaged_do_scan(); 2812 khugepaged_wait_work(); 2813 } 2814 2815 spin_lock(&khugepaged_mm_lock); 2816 mm_slot = khugepaged_scan.mm_slot; 2817 khugepaged_scan.mm_slot = NULL; 2818 if (mm_slot) 2819 collect_mm_slot(mm_slot); 2820 spin_unlock(&khugepaged_mm_lock); 2821 return 0; 2822 } 2823 2824 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2825 unsigned long haddr, pmd_t *pmd) 2826 { 2827 struct mm_struct *mm = vma->vm_mm; 2828 pgtable_t pgtable; 2829 pmd_t _pmd; 2830 int i; 2831 2832 pmdp_clear_flush(vma, haddr, pmd); 2833 /* leave pmd empty until pte is filled */ 2834 2835 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2836 pmd_populate(mm, &_pmd, pgtable); 2837 2838 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2839 pte_t *pte, entry; 2840 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2841 entry = pte_mkspecial(entry); 2842 pte = pte_offset_map(&_pmd, haddr); 2843 VM_BUG_ON(!pte_none(*pte)); 2844 set_pte_at(mm, haddr, pte, entry); 2845 pte_unmap(pte); 2846 } 2847 smp_wmb(); /* make pte visible before pmd */ 2848 pmd_populate(mm, pmd, pgtable); 2849 put_huge_zero_page(); 2850 } 2851 2852 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address, 2853 pmd_t *pmd) 2854 { 2855 spinlock_t *ptl; 2856 struct page *page; 2857 struct mm_struct *mm = vma->vm_mm; 2858 unsigned long haddr = address & HPAGE_PMD_MASK; 2859 unsigned long mmun_start; /* For mmu_notifiers */ 2860 unsigned long mmun_end; /* For mmu_notifiers */ 2861 2862 BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE); 2863 2864 mmun_start = haddr; 2865 mmun_end = haddr + HPAGE_PMD_SIZE; 2866 again: 2867 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2868 ptl = pmd_lock(mm, pmd); 2869 if (unlikely(!pmd_trans_huge(*pmd))) { 2870 spin_unlock(ptl); 2871 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2872 return; 2873 } 2874 if (is_huge_zero_pmd(*pmd)) { 2875 __split_huge_zero_page_pmd(vma, haddr, pmd); 2876 spin_unlock(ptl); 2877 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2878 return; 2879 } 2880 page = pmd_page(*pmd); 2881 VM_BUG_ON_PAGE(!page_count(page), page); 2882 get_page(page); 2883 spin_unlock(ptl); 2884 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2885 2886 split_huge_page(page); 2887 2888 put_page(page); 2889 2890 /* 2891 * We don't always have down_write of mmap_sem here: a racing 2892 * do_huge_pmd_wp_page() might have copied-on-write to another 2893 * huge page before our split_huge_page() got the anon_vma lock. 2894 */ 2895 if (unlikely(pmd_trans_huge(*pmd))) 2896 goto again; 2897 } 2898 2899 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address, 2900 pmd_t *pmd) 2901 { 2902 struct vm_area_struct *vma; 2903 2904 vma = find_vma(mm, address); 2905 BUG_ON(vma == NULL); 2906 split_huge_page_pmd(vma, address, pmd); 2907 } 2908 2909 static void split_huge_page_address(struct mm_struct *mm, 2910 unsigned long address) 2911 { 2912 pmd_t *pmd; 2913 2914 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); 2915 2916 pmd = mm_find_pmd(mm, address); 2917 if (!pmd) 2918 return; 2919 /* 2920 * Caller holds the mmap_sem write mode, so a huge pmd cannot 2921 * materialize from under us. 2922 */ 2923 split_huge_page_pmd_mm(mm, address, pmd); 2924 } 2925 2926 void __vma_adjust_trans_huge(struct vm_area_struct *vma, 2927 unsigned long start, 2928 unsigned long end, 2929 long adjust_next) 2930 { 2931 /* 2932 * If the new start address isn't hpage aligned and it could 2933 * previously contain an hugepage: check if we need to split 2934 * an huge pmd. 2935 */ 2936 if (start & ~HPAGE_PMD_MASK && 2937 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2938 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2939 split_huge_page_address(vma->vm_mm, start); 2940 2941 /* 2942 * If the new end address isn't hpage aligned and it could 2943 * previously contain an hugepage: check if we need to split 2944 * an huge pmd. 2945 */ 2946 if (end & ~HPAGE_PMD_MASK && 2947 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2948 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2949 split_huge_page_address(vma->vm_mm, end); 2950 2951 /* 2952 * If we're also updating the vma->vm_next->vm_start, if the new 2953 * vm_next->vm_start isn't page aligned and it could previously 2954 * contain an hugepage: check if we need to split an huge pmd. 2955 */ 2956 if (adjust_next > 0) { 2957 struct vm_area_struct *next = vma->vm_next; 2958 unsigned long nstart = next->vm_start; 2959 nstart += adjust_next << PAGE_SHIFT; 2960 if (nstart & ~HPAGE_PMD_MASK && 2961 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2962 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2963 split_huge_page_address(next->vm_mm, nstart); 2964 } 2965 } 2966