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 enabled for all mappings 31 * and khugepaged scans all mappings. Defrag is only invoked by 32 * khugepaged hugepage allocations and by page faults inside 33 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived 34 * allocations. 35 */ 36 unsigned long transparent_hugepage_flags __read_mostly = 37 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS 38 (1<<TRANSPARENT_HUGEPAGE_FLAG)| 39 #endif 40 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE 41 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| 42 #endif 43 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)| 44 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)| 45 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 46 47 /* default scan 8*512 pte (or vmas) every 30 second */ 48 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8; 49 static unsigned int khugepaged_pages_collapsed; 50 static unsigned int khugepaged_full_scans; 51 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 52 /* during fragmentation poll the hugepage allocator once every minute */ 53 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 54 static struct task_struct *khugepaged_thread __read_mostly; 55 static DEFINE_MUTEX(khugepaged_mutex); 56 static DEFINE_SPINLOCK(khugepaged_mm_lock); 57 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 58 /* 59 * default collapse hugepages if there is at least one pte mapped like 60 * it would have happened if the vma was large enough during page 61 * fault. 62 */ 63 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1; 64 65 static int khugepaged(void *none); 66 static int khugepaged_slab_init(void); 67 68 #define MM_SLOTS_HASH_BITS 10 69 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); 70 71 static struct kmem_cache *mm_slot_cache __read_mostly; 72 73 /** 74 * struct mm_slot - hash lookup from mm to mm_slot 75 * @hash: hash collision list 76 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 77 * @mm: the mm that this information is valid for 78 */ 79 struct mm_slot { 80 struct hlist_node hash; 81 struct list_head mm_node; 82 struct mm_struct *mm; 83 }; 84 85 /** 86 * struct khugepaged_scan - cursor for scanning 87 * @mm_head: the head of the mm list to scan 88 * @mm_slot: the current mm_slot we are scanning 89 * @address: the next address inside that to be scanned 90 * 91 * There is only the one khugepaged_scan instance of this cursor structure. 92 */ 93 struct khugepaged_scan { 94 struct list_head mm_head; 95 struct mm_slot *mm_slot; 96 unsigned long address; 97 }; 98 static struct khugepaged_scan khugepaged_scan = { 99 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 100 }; 101 102 103 static int set_recommended_min_free_kbytes(void) 104 { 105 struct zone *zone; 106 int nr_zones = 0; 107 unsigned long recommended_min; 108 109 if (!khugepaged_enabled()) 110 return 0; 111 112 for_each_populated_zone(zone) 113 nr_zones++; 114 115 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */ 116 recommended_min = pageblock_nr_pages * nr_zones * 2; 117 118 /* 119 * Make sure that on average at least two pageblocks are almost free 120 * of another type, one for a migratetype to fall back to and a 121 * second to avoid subsequent fallbacks of other types There are 3 122 * MIGRATE_TYPES we care about. 123 */ 124 recommended_min += pageblock_nr_pages * nr_zones * 125 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; 126 127 /* don't ever allow to reserve more than 5% of the lowmem */ 128 recommended_min = min(recommended_min, 129 (unsigned long) nr_free_buffer_pages() / 20); 130 recommended_min <<= (PAGE_SHIFT-10); 131 132 if (recommended_min > min_free_kbytes) 133 min_free_kbytes = recommended_min; 134 setup_per_zone_wmarks(); 135 return 0; 136 } 137 late_initcall(set_recommended_min_free_kbytes); 138 139 static int start_khugepaged(void) 140 { 141 int err = 0; 142 if (khugepaged_enabled()) { 143 if (!khugepaged_thread) 144 khugepaged_thread = kthread_run(khugepaged, NULL, 145 "khugepaged"); 146 if (unlikely(IS_ERR(khugepaged_thread))) { 147 printk(KERN_ERR 148 "khugepaged: kthread_run(khugepaged) failed\n"); 149 err = PTR_ERR(khugepaged_thread); 150 khugepaged_thread = NULL; 151 } 152 153 if (!list_empty(&khugepaged_scan.mm_head)) 154 wake_up_interruptible(&khugepaged_wait); 155 156 set_recommended_min_free_kbytes(); 157 } else if (khugepaged_thread) { 158 kthread_stop(khugepaged_thread); 159 khugepaged_thread = NULL; 160 } 161 162 return err; 163 } 164 165 static atomic_t huge_zero_refcount; 166 static struct page *huge_zero_page __read_mostly; 167 168 static inline bool is_huge_zero_page(struct page *page) 169 { 170 return ACCESS_ONCE(huge_zero_page) == page; 171 } 172 173 static inline bool is_huge_zero_pmd(pmd_t pmd) 174 { 175 return is_huge_zero_page(pmd_page(pmd)); 176 } 177 178 static struct page *get_huge_zero_page(void) 179 { 180 struct page *zero_page; 181 retry: 182 if (likely(atomic_inc_not_zero(&huge_zero_refcount))) 183 return ACCESS_ONCE(huge_zero_page); 184 185 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, 186 HPAGE_PMD_ORDER); 187 if (!zero_page) { 188 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); 189 return NULL; 190 } 191 count_vm_event(THP_ZERO_PAGE_ALLOC); 192 preempt_disable(); 193 if (cmpxchg(&huge_zero_page, NULL, zero_page)) { 194 preempt_enable(); 195 __free_page(zero_page); 196 goto retry; 197 } 198 199 /* We take additional reference here. It will be put back by shrinker */ 200 atomic_set(&huge_zero_refcount, 2); 201 preempt_enable(); 202 return ACCESS_ONCE(huge_zero_page); 203 } 204 205 static void put_huge_zero_page(void) 206 { 207 /* 208 * Counter should never go to zero here. Only shrinker can put 209 * last reference. 210 */ 211 BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); 212 } 213 214 static int shrink_huge_zero_page(struct shrinker *shrink, 215 struct shrink_control *sc) 216 { 217 if (!sc->nr_to_scan) 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 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { 222 struct page *zero_page = xchg(&huge_zero_page, NULL); 223 BUG_ON(zero_page == NULL); 224 __free_page(zero_page); 225 } 226 227 return 0; 228 } 229 230 static struct shrinker huge_zero_page_shrinker = { 231 .shrink = shrink_huge_zero_page, 232 .seeks = DEFAULT_SEEKS, 233 }; 234 235 #ifdef CONFIG_SYSFS 236 237 static ssize_t double_flag_show(struct kobject *kobj, 238 struct kobj_attribute *attr, char *buf, 239 enum transparent_hugepage_flag enabled, 240 enum transparent_hugepage_flag req_madv) 241 { 242 if (test_bit(enabled, &transparent_hugepage_flags)) { 243 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); 244 return sprintf(buf, "[always] madvise never\n"); 245 } else if (test_bit(req_madv, &transparent_hugepage_flags)) 246 return sprintf(buf, "always [madvise] never\n"); 247 else 248 return sprintf(buf, "always madvise [never]\n"); 249 } 250 static ssize_t double_flag_store(struct kobject *kobj, 251 struct kobj_attribute *attr, 252 const char *buf, size_t count, 253 enum transparent_hugepage_flag enabled, 254 enum transparent_hugepage_flag req_madv) 255 { 256 if (!memcmp("always", buf, 257 min(sizeof("always")-1, count))) { 258 set_bit(enabled, &transparent_hugepage_flags); 259 clear_bit(req_madv, &transparent_hugepage_flags); 260 } else if (!memcmp("madvise", buf, 261 min(sizeof("madvise")-1, count))) { 262 clear_bit(enabled, &transparent_hugepage_flags); 263 set_bit(req_madv, &transparent_hugepage_flags); 264 } else if (!memcmp("never", buf, 265 min(sizeof("never")-1, count))) { 266 clear_bit(enabled, &transparent_hugepage_flags); 267 clear_bit(req_madv, &transparent_hugepage_flags); 268 } else 269 return -EINVAL; 270 271 return count; 272 } 273 274 static ssize_t enabled_show(struct kobject *kobj, 275 struct kobj_attribute *attr, char *buf) 276 { 277 return double_flag_show(kobj, attr, buf, 278 TRANSPARENT_HUGEPAGE_FLAG, 279 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 280 } 281 static ssize_t enabled_store(struct kobject *kobj, 282 struct kobj_attribute *attr, 283 const char *buf, size_t count) 284 { 285 ssize_t ret; 286 287 ret = double_flag_store(kobj, attr, buf, count, 288 TRANSPARENT_HUGEPAGE_FLAG, 289 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 290 291 if (ret > 0) { 292 int err; 293 294 mutex_lock(&khugepaged_mutex); 295 err = start_khugepaged(); 296 mutex_unlock(&khugepaged_mutex); 297 298 if (err) 299 ret = err; 300 } 301 302 return ret; 303 } 304 static struct kobj_attribute enabled_attr = 305 __ATTR(enabled, 0644, enabled_show, enabled_store); 306 307 static ssize_t single_flag_show(struct kobject *kobj, 308 struct kobj_attribute *attr, char *buf, 309 enum transparent_hugepage_flag flag) 310 { 311 return sprintf(buf, "%d\n", 312 !!test_bit(flag, &transparent_hugepage_flags)); 313 } 314 315 static ssize_t single_flag_store(struct kobject *kobj, 316 struct kobj_attribute *attr, 317 const char *buf, size_t count, 318 enum transparent_hugepage_flag flag) 319 { 320 unsigned long value; 321 int ret; 322 323 ret = kstrtoul(buf, 10, &value); 324 if (ret < 0) 325 return ret; 326 if (value > 1) 327 return -EINVAL; 328 329 if (value) 330 set_bit(flag, &transparent_hugepage_flags); 331 else 332 clear_bit(flag, &transparent_hugepage_flags); 333 334 return count; 335 } 336 337 /* 338 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind 339 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of 340 * memory just to allocate one more hugepage. 341 */ 342 static ssize_t defrag_show(struct kobject *kobj, 343 struct kobj_attribute *attr, char *buf) 344 { 345 return double_flag_show(kobj, attr, buf, 346 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 347 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 348 } 349 static ssize_t defrag_store(struct kobject *kobj, 350 struct kobj_attribute *attr, 351 const char *buf, size_t count) 352 { 353 return double_flag_store(kobj, attr, buf, count, 354 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 355 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 356 } 357 static struct kobj_attribute defrag_attr = 358 __ATTR(defrag, 0644, defrag_show, defrag_store); 359 360 static ssize_t use_zero_page_show(struct kobject *kobj, 361 struct kobj_attribute *attr, char *buf) 362 { 363 return single_flag_show(kobj, attr, buf, 364 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 365 } 366 static ssize_t use_zero_page_store(struct kobject *kobj, 367 struct kobj_attribute *attr, const char *buf, size_t count) 368 { 369 return single_flag_store(kobj, attr, buf, count, 370 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 371 } 372 static struct kobj_attribute use_zero_page_attr = 373 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); 374 #ifdef CONFIG_DEBUG_VM 375 static ssize_t debug_cow_show(struct kobject *kobj, 376 struct kobj_attribute *attr, char *buf) 377 { 378 return single_flag_show(kobj, attr, buf, 379 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 380 } 381 static ssize_t debug_cow_store(struct kobject *kobj, 382 struct kobj_attribute *attr, 383 const char *buf, size_t count) 384 { 385 return single_flag_store(kobj, attr, buf, count, 386 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 387 } 388 static struct kobj_attribute debug_cow_attr = 389 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 390 #endif /* CONFIG_DEBUG_VM */ 391 392 static struct attribute *hugepage_attr[] = { 393 &enabled_attr.attr, 394 &defrag_attr.attr, 395 &use_zero_page_attr.attr, 396 #ifdef CONFIG_DEBUG_VM 397 &debug_cow_attr.attr, 398 #endif 399 NULL, 400 }; 401 402 static struct attribute_group hugepage_attr_group = { 403 .attrs = hugepage_attr, 404 }; 405 406 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 407 struct kobj_attribute *attr, 408 char *buf) 409 { 410 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 411 } 412 413 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 414 struct kobj_attribute *attr, 415 const char *buf, size_t count) 416 { 417 unsigned long msecs; 418 int err; 419 420 err = strict_strtoul(buf, 10, &msecs); 421 if (err || msecs > UINT_MAX) 422 return -EINVAL; 423 424 khugepaged_scan_sleep_millisecs = msecs; 425 wake_up_interruptible(&khugepaged_wait); 426 427 return count; 428 } 429 static struct kobj_attribute scan_sleep_millisecs_attr = 430 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 431 scan_sleep_millisecs_store); 432 433 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 434 struct kobj_attribute *attr, 435 char *buf) 436 { 437 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 438 } 439 440 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 441 struct kobj_attribute *attr, 442 const char *buf, size_t count) 443 { 444 unsigned long msecs; 445 int err; 446 447 err = strict_strtoul(buf, 10, &msecs); 448 if (err || msecs > UINT_MAX) 449 return -EINVAL; 450 451 khugepaged_alloc_sleep_millisecs = msecs; 452 wake_up_interruptible(&khugepaged_wait); 453 454 return count; 455 } 456 static struct kobj_attribute alloc_sleep_millisecs_attr = 457 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 458 alloc_sleep_millisecs_store); 459 460 static ssize_t pages_to_scan_show(struct kobject *kobj, 461 struct kobj_attribute *attr, 462 char *buf) 463 { 464 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 465 } 466 static ssize_t pages_to_scan_store(struct kobject *kobj, 467 struct kobj_attribute *attr, 468 const char *buf, size_t count) 469 { 470 int err; 471 unsigned long pages; 472 473 err = strict_strtoul(buf, 10, &pages); 474 if (err || !pages || pages > UINT_MAX) 475 return -EINVAL; 476 477 khugepaged_pages_to_scan = pages; 478 479 return count; 480 } 481 static struct kobj_attribute pages_to_scan_attr = 482 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 483 pages_to_scan_store); 484 485 static ssize_t pages_collapsed_show(struct kobject *kobj, 486 struct kobj_attribute *attr, 487 char *buf) 488 { 489 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 490 } 491 static struct kobj_attribute pages_collapsed_attr = 492 __ATTR_RO(pages_collapsed); 493 494 static ssize_t full_scans_show(struct kobject *kobj, 495 struct kobj_attribute *attr, 496 char *buf) 497 { 498 return sprintf(buf, "%u\n", khugepaged_full_scans); 499 } 500 static struct kobj_attribute full_scans_attr = 501 __ATTR_RO(full_scans); 502 503 static ssize_t khugepaged_defrag_show(struct kobject *kobj, 504 struct kobj_attribute *attr, char *buf) 505 { 506 return single_flag_show(kobj, attr, buf, 507 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 508 } 509 static ssize_t khugepaged_defrag_store(struct kobject *kobj, 510 struct kobj_attribute *attr, 511 const char *buf, size_t count) 512 { 513 return single_flag_store(kobj, attr, buf, count, 514 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 515 } 516 static struct kobj_attribute khugepaged_defrag_attr = 517 __ATTR(defrag, 0644, khugepaged_defrag_show, 518 khugepaged_defrag_store); 519 520 /* 521 * max_ptes_none controls if khugepaged should collapse hugepages over 522 * any unmapped ptes in turn potentially increasing the memory 523 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 524 * reduce the available free memory in the system as it 525 * runs. Increasing max_ptes_none will instead potentially reduce the 526 * free memory in the system during the khugepaged scan. 527 */ 528 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 529 struct kobj_attribute *attr, 530 char *buf) 531 { 532 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 533 } 534 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 535 struct kobj_attribute *attr, 536 const char *buf, size_t count) 537 { 538 int err; 539 unsigned long max_ptes_none; 540 541 err = strict_strtoul(buf, 10, &max_ptes_none); 542 if (err || max_ptes_none > HPAGE_PMD_NR-1) 543 return -EINVAL; 544 545 khugepaged_max_ptes_none = max_ptes_none; 546 547 return count; 548 } 549 static struct kobj_attribute khugepaged_max_ptes_none_attr = 550 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 551 khugepaged_max_ptes_none_store); 552 553 static struct attribute *khugepaged_attr[] = { 554 &khugepaged_defrag_attr.attr, 555 &khugepaged_max_ptes_none_attr.attr, 556 &pages_to_scan_attr.attr, 557 &pages_collapsed_attr.attr, 558 &full_scans_attr.attr, 559 &scan_sleep_millisecs_attr.attr, 560 &alloc_sleep_millisecs_attr.attr, 561 NULL, 562 }; 563 564 static struct attribute_group khugepaged_attr_group = { 565 .attrs = khugepaged_attr, 566 .name = "khugepaged", 567 }; 568 569 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) 570 { 571 int err; 572 573 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 574 if (unlikely(!*hugepage_kobj)) { 575 printk(KERN_ERR "hugepage: failed to create transparent hugepage kobject\n"); 576 return -ENOMEM; 577 } 578 579 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); 580 if (err) { 581 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n"); 582 goto delete_obj; 583 } 584 585 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); 586 if (err) { 587 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n"); 588 goto remove_hp_group; 589 } 590 591 return 0; 592 593 remove_hp_group: 594 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); 595 delete_obj: 596 kobject_put(*hugepage_kobj); 597 return err; 598 } 599 600 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) 601 { 602 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); 603 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); 604 kobject_put(hugepage_kobj); 605 } 606 #else 607 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) 608 { 609 return 0; 610 } 611 612 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) 613 { 614 } 615 #endif /* CONFIG_SYSFS */ 616 617 static int __init hugepage_init(void) 618 { 619 int err; 620 struct kobject *hugepage_kobj; 621 622 if (!has_transparent_hugepage()) { 623 transparent_hugepage_flags = 0; 624 return -EINVAL; 625 } 626 627 err = hugepage_init_sysfs(&hugepage_kobj); 628 if (err) 629 return err; 630 631 err = khugepaged_slab_init(); 632 if (err) 633 goto out; 634 635 register_shrinker(&huge_zero_page_shrinker); 636 637 /* 638 * By default disable transparent hugepages on smaller systems, 639 * where the extra memory used could hurt more than TLB overhead 640 * is likely to save. The admin can still enable it through /sys. 641 */ 642 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) 643 transparent_hugepage_flags = 0; 644 645 start_khugepaged(); 646 647 return 0; 648 out: 649 hugepage_exit_sysfs(hugepage_kobj); 650 return err; 651 } 652 module_init(hugepage_init) 653 654 static int __init setup_transparent_hugepage(char *str) 655 { 656 int ret = 0; 657 if (!str) 658 goto out; 659 if (!strcmp(str, "always")) { 660 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 661 &transparent_hugepage_flags); 662 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 663 &transparent_hugepage_flags); 664 ret = 1; 665 } else if (!strcmp(str, "madvise")) { 666 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 667 &transparent_hugepage_flags); 668 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 669 &transparent_hugepage_flags); 670 ret = 1; 671 } else if (!strcmp(str, "never")) { 672 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 673 &transparent_hugepage_flags); 674 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 675 &transparent_hugepage_flags); 676 ret = 1; 677 } 678 out: 679 if (!ret) 680 printk(KERN_WARNING 681 "transparent_hugepage= cannot parse, ignored\n"); 682 return ret; 683 } 684 __setup("transparent_hugepage=", setup_transparent_hugepage); 685 686 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 687 { 688 if (likely(vma->vm_flags & VM_WRITE)) 689 pmd = pmd_mkwrite(pmd); 690 return pmd; 691 } 692 693 static inline pmd_t mk_huge_pmd(struct page *page, struct vm_area_struct *vma) 694 { 695 pmd_t entry; 696 entry = mk_pmd(page, vma->vm_page_prot); 697 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 698 entry = pmd_mkhuge(entry); 699 return entry; 700 } 701 702 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, 703 struct vm_area_struct *vma, 704 unsigned long haddr, pmd_t *pmd, 705 struct page *page) 706 { 707 pgtable_t pgtable; 708 709 VM_BUG_ON(!PageCompound(page)); 710 pgtable = pte_alloc_one(mm, haddr); 711 if (unlikely(!pgtable)) 712 return VM_FAULT_OOM; 713 714 clear_huge_page(page, haddr, HPAGE_PMD_NR); 715 /* 716 * The memory barrier inside __SetPageUptodate makes sure that 717 * clear_huge_page writes become visible before the set_pmd_at() 718 * write. 719 */ 720 __SetPageUptodate(page); 721 722 spin_lock(&mm->page_table_lock); 723 if (unlikely(!pmd_none(*pmd))) { 724 spin_unlock(&mm->page_table_lock); 725 mem_cgroup_uncharge_page(page); 726 put_page(page); 727 pte_free(mm, pgtable); 728 } else { 729 pmd_t entry; 730 entry = mk_huge_pmd(page, vma); 731 page_add_new_anon_rmap(page, vma, haddr); 732 pgtable_trans_huge_deposit(mm, pmd, pgtable); 733 set_pmd_at(mm, haddr, pmd, entry); 734 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 735 mm->nr_ptes++; 736 spin_unlock(&mm->page_table_lock); 737 } 738 739 return 0; 740 } 741 742 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) 743 { 744 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; 745 } 746 747 static inline struct page *alloc_hugepage_vma(int defrag, 748 struct vm_area_struct *vma, 749 unsigned long haddr, int nd, 750 gfp_t extra_gfp) 751 { 752 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp), 753 HPAGE_PMD_ORDER, vma, haddr, nd); 754 } 755 756 #ifndef CONFIG_NUMA 757 static inline struct page *alloc_hugepage(int defrag) 758 { 759 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), 760 HPAGE_PMD_ORDER); 761 } 762 #endif 763 764 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 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 pte_t *pte; 787 788 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) { 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 pgtable_t pgtable; 796 struct page *zero_page; 797 bool set; 798 pgtable = pte_alloc_one(mm, haddr); 799 if (unlikely(!pgtable)) 800 return VM_FAULT_OOM; 801 zero_page = get_huge_zero_page(); 802 if (unlikely(!zero_page)) { 803 pte_free(mm, pgtable); 804 count_vm_event(THP_FAULT_FALLBACK); 805 goto out; 806 } 807 spin_lock(&mm->page_table_lock); 808 set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, 809 zero_page); 810 spin_unlock(&mm->page_table_lock); 811 if (!set) { 812 pte_free(mm, pgtable); 813 put_huge_zero_page(); 814 } 815 return 0; 816 } 817 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 818 vma, haddr, numa_node_id(), 0); 819 if (unlikely(!page)) { 820 count_vm_event(THP_FAULT_FALLBACK); 821 goto out; 822 } 823 count_vm_event(THP_FAULT_ALLOC); 824 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) { 825 put_page(page); 826 goto out; 827 } 828 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, 829 page))) { 830 mem_cgroup_uncharge_page(page); 831 put_page(page); 832 goto out; 833 } 834 835 return 0; 836 } 837 out: 838 /* 839 * Use __pte_alloc instead of pte_alloc_map, because we can't 840 * run pte_offset_map on the pmd, if an huge pmd could 841 * materialize from under us from a different thread. 842 */ 843 if (unlikely(pmd_none(*pmd)) && 844 unlikely(__pte_alloc(mm, vma, pmd, address))) 845 return VM_FAULT_OOM; 846 /* if an huge pmd materialized from under us just retry later */ 847 if (unlikely(pmd_trans_huge(*pmd))) 848 return 0; 849 /* 850 * A regular pmd is established and it can't morph into a huge pmd 851 * from under us anymore at this point because we hold the mmap_sem 852 * read mode and khugepaged takes it in write mode. So now it's 853 * safe to run pte_offset_map(). 854 */ 855 pte = pte_offset_map(pmd, address); 856 return handle_pte_fault(mm, vma, address, pte, pmd, flags); 857 } 858 859 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 860 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 861 struct vm_area_struct *vma) 862 { 863 struct page *src_page; 864 pmd_t pmd; 865 pgtable_t pgtable; 866 int ret; 867 868 ret = -ENOMEM; 869 pgtable = pte_alloc_one(dst_mm, addr); 870 if (unlikely(!pgtable)) 871 goto out; 872 873 spin_lock(&dst_mm->page_table_lock); 874 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING); 875 876 ret = -EAGAIN; 877 pmd = *src_pmd; 878 if (unlikely(!pmd_trans_huge(pmd))) { 879 pte_free(dst_mm, pgtable); 880 goto out_unlock; 881 } 882 /* 883 * mm->page_table_lock is enough to be sure that huge zero pmd is not 884 * under splitting since we don't split the page itself, only pmd to 885 * a page table. 886 */ 887 if (is_huge_zero_pmd(pmd)) { 888 struct page *zero_page; 889 bool set; 890 /* 891 * get_huge_zero_page() will never allocate a new page here, 892 * since we already have a zero page to copy. It just takes a 893 * reference. 894 */ 895 zero_page = get_huge_zero_page(); 896 set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, 897 zero_page); 898 BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */ 899 ret = 0; 900 goto out_unlock; 901 } 902 if (unlikely(pmd_trans_splitting(pmd))) { 903 /* split huge page running from under us */ 904 spin_unlock(&src_mm->page_table_lock); 905 spin_unlock(&dst_mm->page_table_lock); 906 pte_free(dst_mm, pgtable); 907 908 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ 909 goto out; 910 } 911 src_page = pmd_page(pmd); 912 VM_BUG_ON(!PageHead(src_page)); 913 get_page(src_page); 914 page_dup_rmap(src_page); 915 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 916 917 pmdp_set_wrprotect(src_mm, addr, src_pmd); 918 pmd = pmd_mkold(pmd_wrprotect(pmd)); 919 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); 920 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 921 dst_mm->nr_ptes++; 922 923 ret = 0; 924 out_unlock: 925 spin_unlock(&src_mm->page_table_lock); 926 spin_unlock(&dst_mm->page_table_lock); 927 out: 928 return ret; 929 } 930 931 void huge_pmd_set_accessed(struct mm_struct *mm, 932 struct vm_area_struct *vma, 933 unsigned long address, 934 pmd_t *pmd, pmd_t orig_pmd, 935 int dirty) 936 { 937 pmd_t entry; 938 unsigned long haddr; 939 940 spin_lock(&mm->page_table_lock); 941 if (unlikely(!pmd_same(*pmd, orig_pmd))) 942 goto unlock; 943 944 entry = pmd_mkyoung(orig_pmd); 945 haddr = address & HPAGE_PMD_MASK; 946 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty)) 947 update_mmu_cache_pmd(vma, address, pmd); 948 949 unlock: 950 spin_unlock(&mm->page_table_lock); 951 } 952 953 static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, 954 struct vm_area_struct *vma, unsigned long address, 955 pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr) 956 { 957 pgtable_t pgtable; 958 pmd_t _pmd; 959 struct page *page; 960 int i, ret = 0; 961 unsigned long mmun_start; /* For mmu_notifiers */ 962 unsigned long mmun_end; /* For mmu_notifiers */ 963 964 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); 965 if (!page) { 966 ret |= VM_FAULT_OOM; 967 goto out; 968 } 969 970 if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) { 971 put_page(page); 972 ret |= VM_FAULT_OOM; 973 goto out; 974 } 975 976 clear_user_highpage(page, address); 977 __SetPageUptodate(page); 978 979 mmun_start = haddr; 980 mmun_end = haddr + HPAGE_PMD_SIZE; 981 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 982 983 spin_lock(&mm->page_table_lock); 984 if (unlikely(!pmd_same(*pmd, orig_pmd))) 985 goto out_free_page; 986 987 pmdp_clear_flush(vma, haddr, pmd); 988 /* leave pmd empty until pte is filled */ 989 990 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 991 pmd_populate(mm, &_pmd, pgtable); 992 993 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 994 pte_t *pte, entry; 995 if (haddr == (address & PAGE_MASK)) { 996 entry = mk_pte(page, vma->vm_page_prot); 997 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 998 page_add_new_anon_rmap(page, vma, haddr); 999 } else { 1000 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 1001 entry = pte_mkspecial(entry); 1002 } 1003 pte = pte_offset_map(&_pmd, haddr); 1004 VM_BUG_ON(!pte_none(*pte)); 1005 set_pte_at(mm, haddr, pte, entry); 1006 pte_unmap(pte); 1007 } 1008 smp_wmb(); /* make pte visible before pmd */ 1009 pmd_populate(mm, pmd, pgtable); 1010 spin_unlock(&mm->page_table_lock); 1011 put_huge_zero_page(); 1012 inc_mm_counter(mm, MM_ANONPAGES); 1013 1014 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1015 1016 ret |= VM_FAULT_WRITE; 1017 out: 1018 return ret; 1019 out_free_page: 1020 spin_unlock(&mm->page_table_lock); 1021 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1022 mem_cgroup_uncharge_page(page); 1023 put_page(page); 1024 goto out; 1025 } 1026 1027 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, 1028 struct vm_area_struct *vma, 1029 unsigned long address, 1030 pmd_t *pmd, pmd_t orig_pmd, 1031 struct page *page, 1032 unsigned long haddr) 1033 { 1034 pgtable_t pgtable; 1035 pmd_t _pmd; 1036 int ret = 0, i; 1037 struct page **pages; 1038 unsigned long mmun_start; /* For mmu_notifiers */ 1039 unsigned long mmun_end; /* For mmu_notifiers */ 1040 1041 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 1042 GFP_KERNEL); 1043 if (unlikely(!pages)) { 1044 ret |= VM_FAULT_OOM; 1045 goto out; 1046 } 1047 1048 for (i = 0; i < HPAGE_PMD_NR; i++) { 1049 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | 1050 __GFP_OTHER_NODE, 1051 vma, address, page_to_nid(page)); 1052 if (unlikely(!pages[i] || 1053 mem_cgroup_newpage_charge(pages[i], mm, 1054 GFP_KERNEL))) { 1055 if (pages[i]) 1056 put_page(pages[i]); 1057 mem_cgroup_uncharge_start(); 1058 while (--i >= 0) { 1059 mem_cgroup_uncharge_page(pages[i]); 1060 put_page(pages[i]); 1061 } 1062 mem_cgroup_uncharge_end(); 1063 kfree(pages); 1064 ret |= VM_FAULT_OOM; 1065 goto out; 1066 } 1067 } 1068 1069 for (i = 0; i < HPAGE_PMD_NR; i++) { 1070 copy_user_highpage(pages[i], page + i, 1071 haddr + PAGE_SIZE * i, vma); 1072 __SetPageUptodate(pages[i]); 1073 cond_resched(); 1074 } 1075 1076 mmun_start = haddr; 1077 mmun_end = haddr + HPAGE_PMD_SIZE; 1078 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1079 1080 spin_lock(&mm->page_table_lock); 1081 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1082 goto out_free_pages; 1083 VM_BUG_ON(!PageHead(page)); 1084 1085 pmdp_clear_flush(vma, haddr, pmd); 1086 /* leave pmd empty until pte is filled */ 1087 1088 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1089 pmd_populate(mm, &_pmd, pgtable); 1090 1091 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1092 pte_t *pte, entry; 1093 entry = mk_pte(pages[i], vma->vm_page_prot); 1094 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1095 page_add_new_anon_rmap(pages[i], vma, haddr); 1096 pte = pte_offset_map(&_pmd, haddr); 1097 VM_BUG_ON(!pte_none(*pte)); 1098 set_pte_at(mm, haddr, pte, entry); 1099 pte_unmap(pte); 1100 } 1101 kfree(pages); 1102 1103 smp_wmb(); /* make pte visible before pmd */ 1104 pmd_populate(mm, pmd, pgtable); 1105 page_remove_rmap(page); 1106 spin_unlock(&mm->page_table_lock); 1107 1108 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1109 1110 ret |= VM_FAULT_WRITE; 1111 put_page(page); 1112 1113 out: 1114 return ret; 1115 1116 out_free_pages: 1117 spin_unlock(&mm->page_table_lock); 1118 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1119 mem_cgroup_uncharge_start(); 1120 for (i = 0; i < HPAGE_PMD_NR; i++) { 1121 mem_cgroup_uncharge_page(pages[i]); 1122 put_page(pages[i]); 1123 } 1124 mem_cgroup_uncharge_end(); 1125 kfree(pages); 1126 goto out; 1127 } 1128 1129 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 1130 unsigned long address, pmd_t *pmd, pmd_t orig_pmd) 1131 { 1132 int ret = 0; 1133 struct page *page = NULL, *new_page; 1134 unsigned long haddr; 1135 unsigned long mmun_start; /* For mmu_notifiers */ 1136 unsigned long mmun_end; /* For mmu_notifiers */ 1137 1138 VM_BUG_ON(!vma->anon_vma); 1139 haddr = address & HPAGE_PMD_MASK; 1140 if (is_huge_zero_pmd(orig_pmd)) 1141 goto alloc; 1142 spin_lock(&mm->page_table_lock); 1143 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1144 goto out_unlock; 1145 1146 page = pmd_page(orig_pmd); 1147 VM_BUG_ON(!PageCompound(page) || !PageHead(page)); 1148 if (page_mapcount(page) == 1) { 1149 pmd_t entry; 1150 entry = pmd_mkyoung(orig_pmd); 1151 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1152 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 1153 update_mmu_cache_pmd(vma, address, pmd); 1154 ret |= VM_FAULT_WRITE; 1155 goto out_unlock; 1156 } 1157 get_page(page); 1158 spin_unlock(&mm->page_table_lock); 1159 alloc: 1160 if (transparent_hugepage_enabled(vma) && 1161 !transparent_hugepage_debug_cow()) 1162 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 1163 vma, haddr, numa_node_id(), 0); 1164 else 1165 new_page = NULL; 1166 1167 if (unlikely(!new_page)) { 1168 count_vm_event(THP_FAULT_FALLBACK); 1169 if (is_huge_zero_pmd(orig_pmd)) { 1170 ret = do_huge_pmd_wp_zero_page_fallback(mm, vma, 1171 address, pmd, orig_pmd, haddr); 1172 } else { 1173 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 1174 pmd, orig_pmd, page, haddr); 1175 if (ret & VM_FAULT_OOM) 1176 split_huge_page(page); 1177 put_page(page); 1178 } 1179 goto out; 1180 } 1181 count_vm_event(THP_FAULT_ALLOC); 1182 1183 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 1184 put_page(new_page); 1185 if (page) { 1186 split_huge_page(page); 1187 put_page(page); 1188 } 1189 ret |= VM_FAULT_OOM; 1190 goto out; 1191 } 1192 1193 if (is_huge_zero_pmd(orig_pmd)) 1194 clear_huge_page(new_page, haddr, HPAGE_PMD_NR); 1195 else 1196 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 1197 __SetPageUptodate(new_page); 1198 1199 mmun_start = haddr; 1200 mmun_end = haddr + HPAGE_PMD_SIZE; 1201 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1202 1203 spin_lock(&mm->page_table_lock); 1204 if (page) 1205 put_page(page); 1206 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 1207 spin_unlock(&mm->page_table_lock); 1208 mem_cgroup_uncharge_page(new_page); 1209 put_page(new_page); 1210 goto out_mn; 1211 } else { 1212 pmd_t entry; 1213 entry = mk_huge_pmd(new_page, vma); 1214 pmdp_clear_flush(vma, haddr, pmd); 1215 page_add_new_anon_rmap(new_page, vma, haddr); 1216 set_pmd_at(mm, haddr, pmd, entry); 1217 update_mmu_cache_pmd(vma, address, pmd); 1218 if (is_huge_zero_pmd(orig_pmd)) { 1219 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 1220 put_huge_zero_page(); 1221 } else { 1222 VM_BUG_ON(!PageHead(page)); 1223 page_remove_rmap(page); 1224 put_page(page); 1225 } 1226 ret |= VM_FAULT_WRITE; 1227 } 1228 spin_unlock(&mm->page_table_lock); 1229 out_mn: 1230 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1231 out: 1232 return ret; 1233 out_unlock: 1234 spin_unlock(&mm->page_table_lock); 1235 return ret; 1236 } 1237 1238 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1239 unsigned long addr, 1240 pmd_t *pmd, 1241 unsigned int flags) 1242 { 1243 struct mm_struct *mm = vma->vm_mm; 1244 struct page *page = NULL; 1245 1246 assert_spin_locked(&mm->page_table_lock); 1247 1248 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 1249 goto out; 1250 1251 /* Avoid dumping huge zero page */ 1252 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) 1253 return ERR_PTR(-EFAULT); 1254 1255 page = pmd_page(*pmd); 1256 VM_BUG_ON(!PageHead(page)); 1257 if (flags & FOLL_TOUCH) { 1258 pmd_t _pmd; 1259 /* 1260 * We should set the dirty bit only for FOLL_WRITE but 1261 * for now the dirty bit in the pmd is meaningless. 1262 * And if the dirty bit will become meaningful and 1263 * we'll only set it with FOLL_WRITE, an atomic 1264 * set_bit will be required on the pmd to set the 1265 * young bit, instead of the current set_pmd_at. 1266 */ 1267 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 1268 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, 1269 pmd, _pmd, 1)) 1270 update_mmu_cache_pmd(vma, addr, pmd); 1271 } 1272 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 1273 if (page->mapping && trylock_page(page)) { 1274 lru_add_drain(); 1275 if (page->mapping) 1276 mlock_vma_page(page); 1277 unlock_page(page); 1278 } 1279 } 1280 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1281 VM_BUG_ON(!PageCompound(page)); 1282 if (flags & FOLL_GET) 1283 get_page_foll(page); 1284 1285 out: 1286 return page; 1287 } 1288 1289 /* NUMA hinting page fault entry point for trans huge pmds */ 1290 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, 1291 unsigned long addr, pmd_t pmd, pmd_t *pmdp) 1292 { 1293 struct page *page; 1294 unsigned long haddr = addr & HPAGE_PMD_MASK; 1295 int target_nid; 1296 int current_nid = -1; 1297 bool migrated; 1298 1299 spin_lock(&mm->page_table_lock); 1300 if (unlikely(!pmd_same(pmd, *pmdp))) 1301 goto out_unlock; 1302 1303 page = pmd_page(pmd); 1304 get_page(page); 1305 current_nid = page_to_nid(page); 1306 count_vm_numa_event(NUMA_HINT_FAULTS); 1307 if (current_nid == numa_node_id()) 1308 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); 1309 1310 target_nid = mpol_misplaced(page, vma, haddr); 1311 if (target_nid == -1) { 1312 put_page(page); 1313 goto clear_pmdnuma; 1314 } 1315 1316 /* Acquire the page lock to serialise THP migrations */ 1317 spin_unlock(&mm->page_table_lock); 1318 lock_page(page); 1319 1320 /* Confirm the PTE did not while locked */ 1321 spin_lock(&mm->page_table_lock); 1322 if (unlikely(!pmd_same(pmd, *pmdp))) { 1323 unlock_page(page); 1324 put_page(page); 1325 goto out_unlock; 1326 } 1327 spin_unlock(&mm->page_table_lock); 1328 1329 /* Migrate the THP to the requested node */ 1330 migrated = migrate_misplaced_transhuge_page(mm, vma, 1331 pmdp, pmd, addr, page, target_nid); 1332 if (!migrated) 1333 goto check_same; 1334 1335 task_numa_fault(target_nid, HPAGE_PMD_NR, true); 1336 return 0; 1337 1338 check_same: 1339 spin_lock(&mm->page_table_lock); 1340 if (unlikely(!pmd_same(pmd, *pmdp))) 1341 goto out_unlock; 1342 clear_pmdnuma: 1343 pmd = pmd_mknonnuma(pmd); 1344 set_pmd_at(mm, haddr, pmdp, pmd); 1345 VM_BUG_ON(pmd_numa(*pmdp)); 1346 update_mmu_cache_pmd(vma, addr, pmdp); 1347 out_unlock: 1348 spin_unlock(&mm->page_table_lock); 1349 if (current_nid != -1) 1350 task_numa_fault(current_nid, HPAGE_PMD_NR, false); 1351 return 0; 1352 } 1353 1354 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1355 pmd_t *pmd, unsigned long addr) 1356 { 1357 int ret = 0; 1358 1359 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1360 struct page *page; 1361 pgtable_t pgtable; 1362 pmd_t orig_pmd; 1363 /* 1364 * For architectures like ppc64 we look at deposited pgtable 1365 * when calling pmdp_get_and_clear. So do the 1366 * pgtable_trans_huge_withdraw after finishing pmdp related 1367 * operations. 1368 */ 1369 orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd); 1370 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1371 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd); 1372 if (is_huge_zero_pmd(orig_pmd)) { 1373 tlb->mm->nr_ptes--; 1374 spin_unlock(&tlb->mm->page_table_lock); 1375 put_huge_zero_page(); 1376 } else { 1377 page = pmd_page(orig_pmd); 1378 page_remove_rmap(page); 1379 VM_BUG_ON(page_mapcount(page) < 0); 1380 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1381 VM_BUG_ON(!PageHead(page)); 1382 tlb->mm->nr_ptes--; 1383 spin_unlock(&tlb->mm->page_table_lock); 1384 tlb_remove_page(tlb, page); 1385 } 1386 pte_free(tlb->mm, pgtable); 1387 ret = 1; 1388 } 1389 return ret; 1390 } 1391 1392 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1393 unsigned long addr, unsigned long end, 1394 unsigned char *vec) 1395 { 1396 int ret = 0; 1397 1398 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1399 /* 1400 * All logical pages in the range are present 1401 * if backed by a huge page. 1402 */ 1403 spin_unlock(&vma->vm_mm->page_table_lock); 1404 memset(vec, 1, (end - addr) >> PAGE_SHIFT); 1405 ret = 1; 1406 } 1407 1408 return ret; 1409 } 1410 1411 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, 1412 unsigned long old_addr, 1413 unsigned long new_addr, unsigned long old_end, 1414 pmd_t *old_pmd, pmd_t *new_pmd) 1415 { 1416 int ret = 0; 1417 pmd_t pmd; 1418 1419 struct mm_struct *mm = vma->vm_mm; 1420 1421 if ((old_addr & ~HPAGE_PMD_MASK) || 1422 (new_addr & ~HPAGE_PMD_MASK) || 1423 old_end - old_addr < HPAGE_PMD_SIZE || 1424 (new_vma->vm_flags & VM_NOHUGEPAGE)) 1425 goto out; 1426 1427 /* 1428 * The destination pmd shouldn't be established, free_pgtables() 1429 * should have release it. 1430 */ 1431 if (WARN_ON(!pmd_none(*new_pmd))) { 1432 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1433 goto out; 1434 } 1435 1436 ret = __pmd_trans_huge_lock(old_pmd, vma); 1437 if (ret == 1) { 1438 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); 1439 VM_BUG_ON(!pmd_none(*new_pmd)); 1440 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd)); 1441 spin_unlock(&mm->page_table_lock); 1442 } 1443 out: 1444 return ret; 1445 } 1446 1447 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1448 unsigned long addr, pgprot_t newprot, int prot_numa) 1449 { 1450 struct mm_struct *mm = vma->vm_mm; 1451 int ret = 0; 1452 1453 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1454 pmd_t entry; 1455 entry = pmdp_get_and_clear(mm, addr, pmd); 1456 if (!prot_numa) { 1457 entry = pmd_modify(entry, newprot); 1458 BUG_ON(pmd_write(entry)); 1459 } else { 1460 struct page *page = pmd_page(*pmd); 1461 1462 /* only check non-shared pages */ 1463 if (page_mapcount(page) == 1 && 1464 !pmd_numa(*pmd)) { 1465 entry = pmd_mknuma(entry); 1466 } 1467 } 1468 set_pmd_at(mm, addr, pmd, entry); 1469 spin_unlock(&vma->vm_mm->page_table_lock); 1470 ret = 1; 1471 } 1472 1473 return ret; 1474 } 1475 1476 /* 1477 * Returns 1 if a given pmd maps a stable (not under splitting) thp. 1478 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise. 1479 * 1480 * Note that if it returns 1, this routine returns without unlocking page 1481 * table locks. So callers must unlock them. 1482 */ 1483 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) 1484 { 1485 spin_lock(&vma->vm_mm->page_table_lock); 1486 if (likely(pmd_trans_huge(*pmd))) { 1487 if (unlikely(pmd_trans_splitting(*pmd))) { 1488 spin_unlock(&vma->vm_mm->page_table_lock); 1489 wait_split_huge_page(vma->anon_vma, pmd); 1490 return -1; 1491 } else { 1492 /* Thp mapped by 'pmd' is stable, so we can 1493 * handle it as it is. */ 1494 return 1; 1495 } 1496 } 1497 spin_unlock(&vma->vm_mm->page_table_lock); 1498 return 0; 1499 } 1500 1501 pmd_t *page_check_address_pmd(struct page *page, 1502 struct mm_struct *mm, 1503 unsigned long address, 1504 enum page_check_address_pmd_flag flag) 1505 { 1506 pmd_t *pmd, *ret = NULL; 1507 1508 if (address & ~HPAGE_PMD_MASK) 1509 goto out; 1510 1511 pmd = mm_find_pmd(mm, address); 1512 if (!pmd) 1513 goto out; 1514 if (pmd_none(*pmd)) 1515 goto out; 1516 if (pmd_page(*pmd) != page) 1517 goto out; 1518 /* 1519 * split_vma() may create temporary aliased mappings. There is 1520 * no risk as long as all huge pmd are found and have their 1521 * splitting bit set before __split_huge_page_refcount 1522 * runs. Finding the same huge pmd more than once during the 1523 * same rmap walk is not a problem. 1524 */ 1525 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && 1526 pmd_trans_splitting(*pmd)) 1527 goto out; 1528 if (pmd_trans_huge(*pmd)) { 1529 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && 1530 !pmd_trans_splitting(*pmd)); 1531 ret = pmd; 1532 } 1533 out: 1534 return ret; 1535 } 1536 1537 static int __split_huge_page_splitting(struct page *page, 1538 struct vm_area_struct *vma, 1539 unsigned long address) 1540 { 1541 struct mm_struct *mm = vma->vm_mm; 1542 pmd_t *pmd; 1543 int ret = 0; 1544 /* For mmu_notifiers */ 1545 const unsigned long mmun_start = address; 1546 const unsigned long mmun_end = address + HPAGE_PMD_SIZE; 1547 1548 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1549 spin_lock(&mm->page_table_lock); 1550 pmd = page_check_address_pmd(page, mm, address, 1551 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG); 1552 if (pmd) { 1553 /* 1554 * We can't temporarily set the pmd to null in order 1555 * to split it, the pmd must remain marked huge at all 1556 * times or the VM won't take the pmd_trans_huge paths 1557 * and it won't wait on the anon_vma->root->rwsem to 1558 * serialize against split_huge_page*. 1559 */ 1560 pmdp_splitting_flush(vma, address, pmd); 1561 ret = 1; 1562 } 1563 spin_unlock(&mm->page_table_lock); 1564 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1565 1566 return ret; 1567 } 1568 1569 static void __split_huge_page_refcount(struct page *page, 1570 struct list_head *list) 1571 { 1572 int i; 1573 struct zone *zone = page_zone(page); 1574 struct lruvec *lruvec; 1575 int tail_count = 0; 1576 1577 /* prevent PageLRU to go away from under us, and freeze lru stats */ 1578 spin_lock_irq(&zone->lru_lock); 1579 lruvec = mem_cgroup_page_lruvec(page, zone); 1580 1581 compound_lock(page); 1582 /* complete memcg works before add pages to LRU */ 1583 mem_cgroup_split_huge_fixup(page); 1584 1585 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 1586 struct page *page_tail = page + i; 1587 1588 /* tail_page->_mapcount cannot change */ 1589 BUG_ON(page_mapcount(page_tail) < 0); 1590 tail_count += page_mapcount(page_tail); 1591 /* check for overflow */ 1592 BUG_ON(tail_count < 0); 1593 BUG_ON(atomic_read(&page_tail->_count) != 0); 1594 /* 1595 * tail_page->_count is zero and not changing from 1596 * under us. But get_page_unless_zero() may be running 1597 * from under us on the tail_page. If we used 1598 * atomic_set() below instead of atomic_add(), we 1599 * would then run atomic_set() concurrently with 1600 * get_page_unless_zero(), and atomic_set() is 1601 * implemented in C not using locked ops. spin_unlock 1602 * on x86 sometime uses locked ops because of PPro 1603 * errata 66, 92, so unless somebody can guarantee 1604 * atomic_set() here would be safe on all archs (and 1605 * not only on x86), it's safer to use atomic_add(). 1606 */ 1607 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, 1608 &page_tail->_count); 1609 1610 /* after clearing PageTail the gup refcount can be released */ 1611 smp_mb(); 1612 1613 /* 1614 * retain hwpoison flag of the poisoned tail page: 1615 * fix for the unsuitable process killed on Guest Machine(KVM) 1616 * by the memory-failure. 1617 */ 1618 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON; 1619 page_tail->flags |= (page->flags & 1620 ((1L << PG_referenced) | 1621 (1L << PG_swapbacked) | 1622 (1L << PG_mlocked) | 1623 (1L << PG_uptodate) | 1624 (1L << PG_active) | 1625 (1L << PG_unevictable))); 1626 page_tail->flags |= (1L << PG_dirty); 1627 1628 /* clear PageTail before overwriting first_page */ 1629 smp_wmb(); 1630 1631 /* 1632 * __split_huge_page_splitting() already set the 1633 * splitting bit in all pmd that could map this 1634 * hugepage, that will ensure no CPU can alter the 1635 * mapcount on the head page. The mapcount is only 1636 * accounted in the head page and it has to be 1637 * transferred to all tail pages in the below code. So 1638 * for this code to be safe, the split the mapcount 1639 * can't change. But that doesn't mean userland can't 1640 * keep changing and reading the page contents while 1641 * we transfer the mapcount, so the pmd splitting 1642 * status is achieved setting a reserved bit in the 1643 * pmd, not by clearing the present bit. 1644 */ 1645 page_tail->_mapcount = page->_mapcount; 1646 1647 BUG_ON(page_tail->mapping); 1648 page_tail->mapping = page->mapping; 1649 1650 page_tail->index = page->index + i; 1651 page_nid_xchg_last(page_tail, page_nid_last(page)); 1652 1653 BUG_ON(!PageAnon(page_tail)); 1654 BUG_ON(!PageUptodate(page_tail)); 1655 BUG_ON(!PageDirty(page_tail)); 1656 BUG_ON(!PageSwapBacked(page_tail)); 1657 1658 lru_add_page_tail(page, page_tail, lruvec, list); 1659 } 1660 atomic_sub(tail_count, &page->_count); 1661 BUG_ON(atomic_read(&page->_count) <= 0); 1662 1663 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1); 1664 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR); 1665 1666 ClearPageCompound(page); 1667 compound_unlock(page); 1668 spin_unlock_irq(&zone->lru_lock); 1669 1670 for (i = 1; i < HPAGE_PMD_NR; i++) { 1671 struct page *page_tail = page + i; 1672 BUG_ON(page_count(page_tail) <= 0); 1673 /* 1674 * Tail pages may be freed if there wasn't any mapping 1675 * like if add_to_swap() is running on a lru page that 1676 * had its mapping zapped. And freeing these pages 1677 * requires taking the lru_lock so we do the put_page 1678 * of the tail pages after the split is complete. 1679 */ 1680 put_page(page_tail); 1681 } 1682 1683 /* 1684 * Only the head page (now become a regular page) is required 1685 * to be pinned by the caller. 1686 */ 1687 BUG_ON(page_count(page) <= 0); 1688 } 1689 1690 static int __split_huge_page_map(struct page *page, 1691 struct vm_area_struct *vma, 1692 unsigned long address) 1693 { 1694 struct mm_struct *mm = vma->vm_mm; 1695 pmd_t *pmd, _pmd; 1696 int ret = 0, i; 1697 pgtable_t pgtable; 1698 unsigned long haddr; 1699 1700 spin_lock(&mm->page_table_lock); 1701 pmd = page_check_address_pmd(page, mm, address, 1702 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG); 1703 if (pmd) { 1704 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1705 pmd_populate(mm, &_pmd, pgtable); 1706 1707 haddr = address; 1708 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1709 pte_t *pte, entry; 1710 BUG_ON(PageCompound(page+i)); 1711 entry = mk_pte(page + i, vma->vm_page_prot); 1712 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1713 if (!pmd_write(*pmd)) 1714 entry = pte_wrprotect(entry); 1715 else 1716 BUG_ON(page_mapcount(page) != 1); 1717 if (!pmd_young(*pmd)) 1718 entry = pte_mkold(entry); 1719 if (pmd_numa(*pmd)) 1720 entry = pte_mknuma(entry); 1721 pte = pte_offset_map(&_pmd, haddr); 1722 BUG_ON(!pte_none(*pte)); 1723 set_pte_at(mm, haddr, pte, entry); 1724 pte_unmap(pte); 1725 } 1726 1727 smp_wmb(); /* make pte visible before pmd */ 1728 /* 1729 * Up to this point the pmd is present and huge and 1730 * userland has the whole access to the hugepage 1731 * during the split (which happens in place). If we 1732 * overwrite the pmd with the not-huge version 1733 * pointing to the pte here (which of course we could 1734 * if all CPUs were bug free), userland could trigger 1735 * a small page size TLB miss on the small sized TLB 1736 * while the hugepage TLB entry is still established 1737 * in the huge TLB. Some CPU doesn't like that. See 1738 * http://support.amd.com/us/Processor_TechDocs/41322.pdf, 1739 * Erratum 383 on page 93. Intel should be safe but is 1740 * also warns that it's only safe if the permission 1741 * and cache attributes of the two entries loaded in 1742 * the two TLB is identical (which should be the case 1743 * here). But it is generally safer to never allow 1744 * small and huge TLB entries for the same virtual 1745 * address to be loaded simultaneously. So instead of 1746 * doing "pmd_populate(); flush_tlb_range();" we first 1747 * mark the current pmd notpresent (atomically because 1748 * here the pmd_trans_huge and pmd_trans_splitting 1749 * must remain set at all times on the pmd until the 1750 * split is complete for this pmd), then we flush the 1751 * SMP TLB and finally we write the non-huge version 1752 * of the pmd entry with pmd_populate. 1753 */ 1754 pmdp_invalidate(vma, address, pmd); 1755 pmd_populate(mm, pmd, pgtable); 1756 ret = 1; 1757 } 1758 spin_unlock(&mm->page_table_lock); 1759 1760 return ret; 1761 } 1762 1763 /* must be called with anon_vma->root->rwsem held */ 1764 static void __split_huge_page(struct page *page, 1765 struct anon_vma *anon_vma, 1766 struct list_head *list) 1767 { 1768 int mapcount, mapcount2; 1769 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 1770 struct anon_vma_chain *avc; 1771 1772 BUG_ON(!PageHead(page)); 1773 BUG_ON(PageTail(page)); 1774 1775 mapcount = 0; 1776 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1777 struct vm_area_struct *vma = avc->vma; 1778 unsigned long addr = vma_address(page, vma); 1779 BUG_ON(is_vma_temporary_stack(vma)); 1780 mapcount += __split_huge_page_splitting(page, vma, addr); 1781 } 1782 /* 1783 * It is critical that new vmas are added to the tail of the 1784 * anon_vma list. This guarantes that if copy_huge_pmd() runs 1785 * and establishes a child pmd before 1786 * __split_huge_page_splitting() freezes the parent pmd (so if 1787 * we fail to prevent copy_huge_pmd() from running until the 1788 * whole __split_huge_page() is complete), we will still see 1789 * the newly established pmd of the child later during the 1790 * walk, to be able to set it as pmd_trans_splitting too. 1791 */ 1792 if (mapcount != page_mapcount(page)) 1793 printk(KERN_ERR "mapcount %d page_mapcount %d\n", 1794 mapcount, page_mapcount(page)); 1795 BUG_ON(mapcount != page_mapcount(page)); 1796 1797 __split_huge_page_refcount(page, list); 1798 1799 mapcount2 = 0; 1800 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1801 struct vm_area_struct *vma = avc->vma; 1802 unsigned long addr = vma_address(page, vma); 1803 BUG_ON(is_vma_temporary_stack(vma)); 1804 mapcount2 += __split_huge_page_map(page, vma, addr); 1805 } 1806 if (mapcount != mapcount2) 1807 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n", 1808 mapcount, mapcount2, page_mapcount(page)); 1809 BUG_ON(mapcount != mapcount2); 1810 } 1811 1812 /* 1813 * Split a hugepage into normal pages. This doesn't change the position of head 1814 * page. If @list is null, tail pages will be added to LRU list, otherwise, to 1815 * @list. Both head page and tail pages will inherit mapping, flags, and so on 1816 * from the hugepage. 1817 * Return 0 if the hugepage is split successfully otherwise return 1. 1818 */ 1819 int split_huge_page_to_list(struct page *page, struct list_head *list) 1820 { 1821 struct anon_vma *anon_vma; 1822 int ret = 1; 1823 1824 BUG_ON(is_huge_zero_page(page)); 1825 BUG_ON(!PageAnon(page)); 1826 1827 /* 1828 * The caller does not necessarily hold an mmap_sem that would prevent 1829 * the anon_vma disappearing so we first we take a reference to it 1830 * and then lock the anon_vma for write. This is similar to 1831 * page_lock_anon_vma_read except the write lock is taken to serialise 1832 * against parallel split or collapse operations. 1833 */ 1834 anon_vma = page_get_anon_vma(page); 1835 if (!anon_vma) 1836 goto out; 1837 anon_vma_lock_write(anon_vma); 1838 1839 ret = 0; 1840 if (!PageCompound(page)) 1841 goto out_unlock; 1842 1843 BUG_ON(!PageSwapBacked(page)); 1844 __split_huge_page(page, anon_vma, list); 1845 count_vm_event(THP_SPLIT); 1846 1847 BUG_ON(PageCompound(page)); 1848 out_unlock: 1849 anon_vma_unlock_write(anon_vma); 1850 put_anon_vma(anon_vma); 1851 out: 1852 return ret; 1853 } 1854 1855 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE) 1856 1857 int hugepage_madvise(struct vm_area_struct *vma, 1858 unsigned long *vm_flags, int advice) 1859 { 1860 struct mm_struct *mm = vma->vm_mm; 1861 1862 switch (advice) { 1863 case MADV_HUGEPAGE: 1864 /* 1865 * Be somewhat over-protective like KSM for now! 1866 */ 1867 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) 1868 return -EINVAL; 1869 if (mm->def_flags & VM_NOHUGEPAGE) 1870 return -EINVAL; 1871 *vm_flags &= ~VM_NOHUGEPAGE; 1872 *vm_flags |= VM_HUGEPAGE; 1873 /* 1874 * If the vma become good for khugepaged to scan, 1875 * register it here without waiting a page fault that 1876 * may not happen any time soon. 1877 */ 1878 if (unlikely(khugepaged_enter_vma_merge(vma))) 1879 return -ENOMEM; 1880 break; 1881 case MADV_NOHUGEPAGE: 1882 /* 1883 * Be somewhat over-protective like KSM for now! 1884 */ 1885 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) 1886 return -EINVAL; 1887 *vm_flags &= ~VM_HUGEPAGE; 1888 *vm_flags |= VM_NOHUGEPAGE; 1889 /* 1890 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1891 * this vma even if we leave the mm registered in khugepaged if 1892 * it got registered before VM_NOHUGEPAGE was set. 1893 */ 1894 break; 1895 } 1896 1897 return 0; 1898 } 1899 1900 static int __init khugepaged_slab_init(void) 1901 { 1902 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1903 sizeof(struct mm_slot), 1904 __alignof__(struct mm_slot), 0, NULL); 1905 if (!mm_slot_cache) 1906 return -ENOMEM; 1907 1908 return 0; 1909 } 1910 1911 static inline struct mm_slot *alloc_mm_slot(void) 1912 { 1913 if (!mm_slot_cache) /* initialization failed */ 1914 return NULL; 1915 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 1916 } 1917 1918 static inline void free_mm_slot(struct mm_slot *mm_slot) 1919 { 1920 kmem_cache_free(mm_slot_cache, mm_slot); 1921 } 1922 1923 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 1924 { 1925 struct mm_slot *mm_slot; 1926 1927 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) 1928 if (mm == mm_slot->mm) 1929 return mm_slot; 1930 1931 return NULL; 1932 } 1933 1934 static void insert_to_mm_slots_hash(struct mm_struct *mm, 1935 struct mm_slot *mm_slot) 1936 { 1937 mm_slot->mm = mm; 1938 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); 1939 } 1940 1941 static inline int khugepaged_test_exit(struct mm_struct *mm) 1942 { 1943 return atomic_read(&mm->mm_users) == 0; 1944 } 1945 1946 int __khugepaged_enter(struct mm_struct *mm) 1947 { 1948 struct mm_slot *mm_slot; 1949 int wakeup; 1950 1951 mm_slot = alloc_mm_slot(); 1952 if (!mm_slot) 1953 return -ENOMEM; 1954 1955 /* __khugepaged_exit() must not run from under us */ 1956 VM_BUG_ON(khugepaged_test_exit(mm)); 1957 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 1958 free_mm_slot(mm_slot); 1959 return 0; 1960 } 1961 1962 spin_lock(&khugepaged_mm_lock); 1963 insert_to_mm_slots_hash(mm, mm_slot); 1964 /* 1965 * Insert just behind the scanning cursor, to let the area settle 1966 * down a little. 1967 */ 1968 wakeup = list_empty(&khugepaged_scan.mm_head); 1969 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 1970 spin_unlock(&khugepaged_mm_lock); 1971 1972 atomic_inc(&mm->mm_count); 1973 if (wakeup) 1974 wake_up_interruptible(&khugepaged_wait); 1975 1976 return 0; 1977 } 1978 1979 int khugepaged_enter_vma_merge(struct vm_area_struct *vma) 1980 { 1981 unsigned long hstart, hend; 1982 if (!vma->anon_vma) 1983 /* 1984 * Not yet faulted in so we will register later in the 1985 * page fault if needed. 1986 */ 1987 return 0; 1988 if (vma->vm_ops) 1989 /* khugepaged not yet working on file or special mappings */ 1990 return 0; 1991 VM_BUG_ON(vma->vm_flags & VM_NO_THP); 1992 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1993 hend = vma->vm_end & HPAGE_PMD_MASK; 1994 if (hstart < hend) 1995 return khugepaged_enter(vma); 1996 return 0; 1997 } 1998 1999 void __khugepaged_exit(struct mm_struct *mm) 2000 { 2001 struct mm_slot *mm_slot; 2002 int free = 0; 2003 2004 spin_lock(&khugepaged_mm_lock); 2005 mm_slot = get_mm_slot(mm); 2006 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 2007 hash_del(&mm_slot->hash); 2008 list_del(&mm_slot->mm_node); 2009 free = 1; 2010 } 2011 spin_unlock(&khugepaged_mm_lock); 2012 2013 if (free) { 2014 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2015 free_mm_slot(mm_slot); 2016 mmdrop(mm); 2017 } else if (mm_slot) { 2018 /* 2019 * This is required to serialize against 2020 * khugepaged_test_exit() (which is guaranteed to run 2021 * under mmap sem read mode). Stop here (after we 2022 * return all pagetables will be destroyed) until 2023 * khugepaged has finished working on the pagetables 2024 * under the mmap_sem. 2025 */ 2026 down_write(&mm->mmap_sem); 2027 up_write(&mm->mmap_sem); 2028 } 2029 } 2030 2031 static void release_pte_page(struct page *page) 2032 { 2033 /* 0 stands for page_is_file_cache(page) == false */ 2034 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 2035 unlock_page(page); 2036 putback_lru_page(page); 2037 } 2038 2039 static void release_pte_pages(pte_t *pte, pte_t *_pte) 2040 { 2041 while (--_pte >= pte) { 2042 pte_t pteval = *_pte; 2043 if (!pte_none(pteval)) 2044 release_pte_page(pte_page(pteval)); 2045 } 2046 } 2047 2048 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 2049 unsigned long address, 2050 pte_t *pte) 2051 { 2052 struct page *page; 2053 pte_t *_pte; 2054 int referenced = 0, none = 0; 2055 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 2056 _pte++, address += PAGE_SIZE) { 2057 pte_t pteval = *_pte; 2058 if (pte_none(pteval)) { 2059 if (++none <= khugepaged_max_ptes_none) 2060 continue; 2061 else 2062 goto out; 2063 } 2064 if (!pte_present(pteval) || !pte_write(pteval)) 2065 goto out; 2066 page = vm_normal_page(vma, address, pteval); 2067 if (unlikely(!page)) 2068 goto out; 2069 2070 VM_BUG_ON(PageCompound(page)); 2071 BUG_ON(!PageAnon(page)); 2072 VM_BUG_ON(!PageSwapBacked(page)); 2073 2074 /* cannot use mapcount: can't collapse if there's a gup pin */ 2075 if (page_count(page) != 1) 2076 goto out; 2077 /* 2078 * We can do it before isolate_lru_page because the 2079 * page can't be freed from under us. NOTE: PG_lock 2080 * is needed to serialize against split_huge_page 2081 * when invoked from the VM. 2082 */ 2083 if (!trylock_page(page)) 2084 goto out; 2085 /* 2086 * Isolate the page to avoid collapsing an hugepage 2087 * currently in use by the VM. 2088 */ 2089 if (isolate_lru_page(page)) { 2090 unlock_page(page); 2091 goto out; 2092 } 2093 /* 0 stands for page_is_file_cache(page) == false */ 2094 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 2095 VM_BUG_ON(!PageLocked(page)); 2096 VM_BUG_ON(PageLRU(page)); 2097 2098 /* If there is no mapped pte young don't collapse the page */ 2099 if (pte_young(pteval) || PageReferenced(page) || 2100 mmu_notifier_test_young(vma->vm_mm, address)) 2101 referenced = 1; 2102 } 2103 if (likely(referenced)) 2104 return 1; 2105 out: 2106 release_pte_pages(pte, _pte); 2107 return 0; 2108 } 2109 2110 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 2111 struct vm_area_struct *vma, 2112 unsigned long address, 2113 spinlock_t *ptl) 2114 { 2115 pte_t *_pte; 2116 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 2117 pte_t pteval = *_pte; 2118 struct page *src_page; 2119 2120 if (pte_none(pteval)) { 2121 clear_user_highpage(page, address); 2122 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 2123 } else { 2124 src_page = pte_page(pteval); 2125 copy_user_highpage(page, src_page, address, vma); 2126 VM_BUG_ON(page_mapcount(src_page) != 1); 2127 release_pte_page(src_page); 2128 /* 2129 * ptl mostly unnecessary, but preempt has to 2130 * be disabled to update the per-cpu stats 2131 * inside page_remove_rmap(). 2132 */ 2133 spin_lock(ptl); 2134 /* 2135 * paravirt calls inside pte_clear here are 2136 * superfluous. 2137 */ 2138 pte_clear(vma->vm_mm, address, _pte); 2139 page_remove_rmap(src_page); 2140 spin_unlock(ptl); 2141 free_page_and_swap_cache(src_page); 2142 } 2143 2144 address += PAGE_SIZE; 2145 page++; 2146 } 2147 } 2148 2149 static void khugepaged_alloc_sleep(void) 2150 { 2151 wait_event_freezable_timeout(khugepaged_wait, false, 2152 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 2153 } 2154 2155 #ifdef CONFIG_NUMA 2156 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2157 { 2158 if (IS_ERR(*hpage)) { 2159 if (!*wait) 2160 return false; 2161 2162 *wait = false; 2163 *hpage = NULL; 2164 khugepaged_alloc_sleep(); 2165 } else if (*hpage) { 2166 put_page(*hpage); 2167 *hpage = NULL; 2168 } 2169 2170 return true; 2171 } 2172 2173 static struct page 2174 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 2175 struct vm_area_struct *vma, unsigned long address, 2176 int node) 2177 { 2178 VM_BUG_ON(*hpage); 2179 /* 2180 * Allocate the page while the vma is still valid and under 2181 * the mmap_sem read mode so there is no memory allocation 2182 * later when we take the mmap_sem in write mode. This is more 2183 * friendly behavior (OTOH it may actually hide bugs) to 2184 * filesystems in userland with daemons allocating memory in 2185 * the userland I/O paths. Allocating memory with the 2186 * mmap_sem in read mode is good idea also to allow greater 2187 * scalability. 2188 */ 2189 *hpage = alloc_hugepage_vma(khugepaged_defrag(), vma, address, 2190 node, __GFP_OTHER_NODE); 2191 2192 /* 2193 * After allocating the hugepage, release the mmap_sem read lock in 2194 * preparation for taking it in write mode. 2195 */ 2196 up_read(&mm->mmap_sem); 2197 if (unlikely(!*hpage)) { 2198 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2199 *hpage = ERR_PTR(-ENOMEM); 2200 return NULL; 2201 } 2202 2203 count_vm_event(THP_COLLAPSE_ALLOC); 2204 return *hpage; 2205 } 2206 #else 2207 static struct page *khugepaged_alloc_hugepage(bool *wait) 2208 { 2209 struct page *hpage; 2210 2211 do { 2212 hpage = alloc_hugepage(khugepaged_defrag()); 2213 if (!hpage) { 2214 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2215 if (!*wait) 2216 return NULL; 2217 2218 *wait = false; 2219 khugepaged_alloc_sleep(); 2220 } else 2221 count_vm_event(THP_COLLAPSE_ALLOC); 2222 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 2223 2224 return hpage; 2225 } 2226 2227 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2228 { 2229 if (!*hpage) 2230 *hpage = khugepaged_alloc_hugepage(wait); 2231 2232 if (unlikely(!*hpage)) 2233 return false; 2234 2235 return true; 2236 } 2237 2238 static struct page 2239 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 2240 struct vm_area_struct *vma, unsigned long address, 2241 int node) 2242 { 2243 up_read(&mm->mmap_sem); 2244 VM_BUG_ON(!*hpage); 2245 return *hpage; 2246 } 2247 #endif 2248 2249 static bool hugepage_vma_check(struct vm_area_struct *vma) 2250 { 2251 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 2252 (vma->vm_flags & VM_NOHUGEPAGE)) 2253 return false; 2254 2255 if (!vma->anon_vma || vma->vm_ops) 2256 return false; 2257 if (is_vma_temporary_stack(vma)) 2258 return false; 2259 VM_BUG_ON(vma->vm_flags & VM_NO_THP); 2260 return true; 2261 } 2262 2263 static void collapse_huge_page(struct mm_struct *mm, 2264 unsigned long address, 2265 struct page **hpage, 2266 struct vm_area_struct *vma, 2267 int node) 2268 { 2269 pmd_t *pmd, _pmd; 2270 pte_t *pte; 2271 pgtable_t pgtable; 2272 struct page *new_page; 2273 spinlock_t *ptl; 2274 int isolated; 2275 unsigned long hstart, hend; 2276 unsigned long mmun_start; /* For mmu_notifiers */ 2277 unsigned long mmun_end; /* For mmu_notifiers */ 2278 2279 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2280 2281 /* release the mmap_sem read lock. */ 2282 new_page = khugepaged_alloc_page(hpage, mm, vma, address, node); 2283 if (!new_page) 2284 return; 2285 2286 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) 2287 return; 2288 2289 /* 2290 * Prevent all access to pagetables with the exception of 2291 * gup_fast later hanlded by the ptep_clear_flush and the VM 2292 * handled by the anon_vma lock + PG_lock. 2293 */ 2294 down_write(&mm->mmap_sem); 2295 if (unlikely(khugepaged_test_exit(mm))) 2296 goto out; 2297 2298 vma = find_vma(mm, address); 2299 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2300 hend = vma->vm_end & HPAGE_PMD_MASK; 2301 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 2302 goto out; 2303 if (!hugepage_vma_check(vma)) 2304 goto out; 2305 pmd = mm_find_pmd(mm, address); 2306 if (!pmd) 2307 goto out; 2308 if (pmd_trans_huge(*pmd)) 2309 goto out; 2310 2311 anon_vma_lock_write(vma->anon_vma); 2312 2313 pte = pte_offset_map(pmd, address); 2314 ptl = pte_lockptr(mm, pmd); 2315 2316 mmun_start = address; 2317 mmun_end = address + HPAGE_PMD_SIZE; 2318 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2319 spin_lock(&mm->page_table_lock); /* probably unnecessary */ 2320 /* 2321 * After this gup_fast can't run anymore. This also removes 2322 * any huge TLB entry from the CPU so we won't allow 2323 * huge and small TLB entries for the same virtual address 2324 * to avoid the risk of CPU bugs in that area. 2325 */ 2326 _pmd = pmdp_clear_flush(vma, address, pmd); 2327 spin_unlock(&mm->page_table_lock); 2328 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2329 2330 spin_lock(ptl); 2331 isolated = __collapse_huge_page_isolate(vma, address, pte); 2332 spin_unlock(ptl); 2333 2334 if (unlikely(!isolated)) { 2335 pte_unmap(pte); 2336 spin_lock(&mm->page_table_lock); 2337 BUG_ON(!pmd_none(*pmd)); 2338 /* 2339 * We can only use set_pmd_at when establishing 2340 * hugepmds and never for establishing regular pmds that 2341 * points to regular pagetables. Use pmd_populate for that 2342 */ 2343 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 2344 spin_unlock(&mm->page_table_lock); 2345 anon_vma_unlock_write(vma->anon_vma); 2346 goto out; 2347 } 2348 2349 /* 2350 * All pages are isolated and locked so anon_vma rmap 2351 * can't run anymore. 2352 */ 2353 anon_vma_unlock_write(vma->anon_vma); 2354 2355 __collapse_huge_page_copy(pte, new_page, vma, address, ptl); 2356 pte_unmap(pte); 2357 __SetPageUptodate(new_page); 2358 pgtable = pmd_pgtable(_pmd); 2359 2360 _pmd = mk_huge_pmd(new_page, vma); 2361 2362 /* 2363 * spin_lock() below is not the equivalent of smp_wmb(), so 2364 * this is needed to avoid the copy_huge_page writes to become 2365 * visible after the set_pmd_at() write. 2366 */ 2367 smp_wmb(); 2368 2369 spin_lock(&mm->page_table_lock); 2370 BUG_ON(!pmd_none(*pmd)); 2371 page_add_new_anon_rmap(new_page, vma, address); 2372 pgtable_trans_huge_deposit(mm, pmd, pgtable); 2373 set_pmd_at(mm, address, pmd, _pmd); 2374 update_mmu_cache_pmd(vma, address, pmd); 2375 spin_unlock(&mm->page_table_lock); 2376 2377 *hpage = NULL; 2378 2379 khugepaged_pages_collapsed++; 2380 out_up_write: 2381 up_write(&mm->mmap_sem); 2382 return; 2383 2384 out: 2385 mem_cgroup_uncharge_page(new_page); 2386 goto out_up_write; 2387 } 2388 2389 static int khugepaged_scan_pmd(struct mm_struct *mm, 2390 struct vm_area_struct *vma, 2391 unsigned long address, 2392 struct page **hpage) 2393 { 2394 pmd_t *pmd; 2395 pte_t *pte, *_pte; 2396 int ret = 0, referenced = 0, none = 0; 2397 struct page *page; 2398 unsigned long _address; 2399 spinlock_t *ptl; 2400 int node = NUMA_NO_NODE; 2401 2402 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2403 2404 pmd = mm_find_pmd(mm, address); 2405 if (!pmd) 2406 goto out; 2407 if (pmd_trans_huge(*pmd)) 2408 goto out; 2409 2410 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2411 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2412 _pte++, _address += PAGE_SIZE) { 2413 pte_t pteval = *_pte; 2414 if (pte_none(pteval)) { 2415 if (++none <= khugepaged_max_ptes_none) 2416 continue; 2417 else 2418 goto out_unmap; 2419 } 2420 if (!pte_present(pteval) || !pte_write(pteval)) 2421 goto out_unmap; 2422 page = vm_normal_page(vma, _address, pteval); 2423 if (unlikely(!page)) 2424 goto out_unmap; 2425 /* 2426 * Chose the node of the first page. This could 2427 * be more sophisticated and look at more pages, 2428 * but isn't for now. 2429 */ 2430 if (node == NUMA_NO_NODE) 2431 node = page_to_nid(page); 2432 VM_BUG_ON(PageCompound(page)); 2433 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) 2434 goto out_unmap; 2435 /* cannot use mapcount: can't collapse if there's a gup pin */ 2436 if (page_count(page) != 1) 2437 goto out_unmap; 2438 if (pte_young(pteval) || PageReferenced(page) || 2439 mmu_notifier_test_young(vma->vm_mm, address)) 2440 referenced = 1; 2441 } 2442 if (referenced) 2443 ret = 1; 2444 out_unmap: 2445 pte_unmap_unlock(pte, ptl); 2446 if (ret) 2447 /* collapse_huge_page will return with the mmap_sem released */ 2448 collapse_huge_page(mm, address, hpage, vma, node); 2449 out: 2450 return ret; 2451 } 2452 2453 static void collect_mm_slot(struct mm_slot *mm_slot) 2454 { 2455 struct mm_struct *mm = mm_slot->mm; 2456 2457 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2458 2459 if (khugepaged_test_exit(mm)) { 2460 /* free mm_slot */ 2461 hash_del(&mm_slot->hash); 2462 list_del(&mm_slot->mm_node); 2463 2464 /* 2465 * Not strictly needed because the mm exited already. 2466 * 2467 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2468 */ 2469 2470 /* khugepaged_mm_lock actually not necessary for the below */ 2471 free_mm_slot(mm_slot); 2472 mmdrop(mm); 2473 } 2474 } 2475 2476 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2477 struct page **hpage) 2478 __releases(&khugepaged_mm_lock) 2479 __acquires(&khugepaged_mm_lock) 2480 { 2481 struct mm_slot *mm_slot; 2482 struct mm_struct *mm; 2483 struct vm_area_struct *vma; 2484 int progress = 0; 2485 2486 VM_BUG_ON(!pages); 2487 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2488 2489 if (khugepaged_scan.mm_slot) 2490 mm_slot = khugepaged_scan.mm_slot; 2491 else { 2492 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2493 struct mm_slot, mm_node); 2494 khugepaged_scan.address = 0; 2495 khugepaged_scan.mm_slot = mm_slot; 2496 } 2497 spin_unlock(&khugepaged_mm_lock); 2498 2499 mm = mm_slot->mm; 2500 down_read(&mm->mmap_sem); 2501 if (unlikely(khugepaged_test_exit(mm))) 2502 vma = NULL; 2503 else 2504 vma = find_vma(mm, khugepaged_scan.address); 2505 2506 progress++; 2507 for (; vma; vma = vma->vm_next) { 2508 unsigned long hstart, hend; 2509 2510 cond_resched(); 2511 if (unlikely(khugepaged_test_exit(mm))) { 2512 progress++; 2513 break; 2514 } 2515 if (!hugepage_vma_check(vma)) { 2516 skip: 2517 progress++; 2518 continue; 2519 } 2520 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2521 hend = vma->vm_end & HPAGE_PMD_MASK; 2522 if (hstart >= hend) 2523 goto skip; 2524 if (khugepaged_scan.address > hend) 2525 goto skip; 2526 if (khugepaged_scan.address < hstart) 2527 khugepaged_scan.address = hstart; 2528 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2529 2530 while (khugepaged_scan.address < hend) { 2531 int ret; 2532 cond_resched(); 2533 if (unlikely(khugepaged_test_exit(mm))) 2534 goto breakouterloop; 2535 2536 VM_BUG_ON(khugepaged_scan.address < hstart || 2537 khugepaged_scan.address + HPAGE_PMD_SIZE > 2538 hend); 2539 ret = khugepaged_scan_pmd(mm, vma, 2540 khugepaged_scan.address, 2541 hpage); 2542 /* move to next address */ 2543 khugepaged_scan.address += HPAGE_PMD_SIZE; 2544 progress += HPAGE_PMD_NR; 2545 if (ret) 2546 /* we released mmap_sem so break loop */ 2547 goto breakouterloop_mmap_sem; 2548 if (progress >= pages) 2549 goto breakouterloop; 2550 } 2551 } 2552 breakouterloop: 2553 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2554 breakouterloop_mmap_sem: 2555 2556 spin_lock(&khugepaged_mm_lock); 2557 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2558 /* 2559 * Release the current mm_slot if this mm is about to die, or 2560 * if we scanned all vmas of this mm. 2561 */ 2562 if (khugepaged_test_exit(mm) || !vma) { 2563 /* 2564 * Make sure that if mm_users is reaching zero while 2565 * khugepaged runs here, khugepaged_exit will find 2566 * mm_slot not pointing to the exiting mm. 2567 */ 2568 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2569 khugepaged_scan.mm_slot = list_entry( 2570 mm_slot->mm_node.next, 2571 struct mm_slot, mm_node); 2572 khugepaged_scan.address = 0; 2573 } else { 2574 khugepaged_scan.mm_slot = NULL; 2575 khugepaged_full_scans++; 2576 } 2577 2578 collect_mm_slot(mm_slot); 2579 } 2580 2581 return progress; 2582 } 2583 2584 static int khugepaged_has_work(void) 2585 { 2586 return !list_empty(&khugepaged_scan.mm_head) && 2587 khugepaged_enabled(); 2588 } 2589 2590 static int khugepaged_wait_event(void) 2591 { 2592 return !list_empty(&khugepaged_scan.mm_head) || 2593 kthread_should_stop(); 2594 } 2595 2596 static void khugepaged_do_scan(void) 2597 { 2598 struct page *hpage = NULL; 2599 unsigned int progress = 0, pass_through_head = 0; 2600 unsigned int pages = khugepaged_pages_to_scan; 2601 bool wait = true; 2602 2603 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2604 2605 while (progress < pages) { 2606 if (!khugepaged_prealloc_page(&hpage, &wait)) 2607 break; 2608 2609 cond_resched(); 2610 2611 if (unlikely(kthread_should_stop() || freezing(current))) 2612 break; 2613 2614 spin_lock(&khugepaged_mm_lock); 2615 if (!khugepaged_scan.mm_slot) 2616 pass_through_head++; 2617 if (khugepaged_has_work() && 2618 pass_through_head < 2) 2619 progress += khugepaged_scan_mm_slot(pages - progress, 2620 &hpage); 2621 else 2622 progress = pages; 2623 spin_unlock(&khugepaged_mm_lock); 2624 } 2625 2626 if (!IS_ERR_OR_NULL(hpage)) 2627 put_page(hpage); 2628 } 2629 2630 static void khugepaged_wait_work(void) 2631 { 2632 try_to_freeze(); 2633 2634 if (khugepaged_has_work()) { 2635 if (!khugepaged_scan_sleep_millisecs) 2636 return; 2637 2638 wait_event_freezable_timeout(khugepaged_wait, 2639 kthread_should_stop(), 2640 msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); 2641 return; 2642 } 2643 2644 if (khugepaged_enabled()) 2645 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 2646 } 2647 2648 static int khugepaged(void *none) 2649 { 2650 struct mm_slot *mm_slot; 2651 2652 set_freezable(); 2653 set_user_nice(current, 19); 2654 2655 while (!kthread_should_stop()) { 2656 khugepaged_do_scan(); 2657 khugepaged_wait_work(); 2658 } 2659 2660 spin_lock(&khugepaged_mm_lock); 2661 mm_slot = khugepaged_scan.mm_slot; 2662 khugepaged_scan.mm_slot = NULL; 2663 if (mm_slot) 2664 collect_mm_slot(mm_slot); 2665 spin_unlock(&khugepaged_mm_lock); 2666 return 0; 2667 } 2668 2669 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2670 unsigned long haddr, pmd_t *pmd) 2671 { 2672 struct mm_struct *mm = vma->vm_mm; 2673 pgtable_t pgtable; 2674 pmd_t _pmd; 2675 int i; 2676 2677 pmdp_clear_flush(vma, haddr, pmd); 2678 /* leave pmd empty until pte is filled */ 2679 2680 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2681 pmd_populate(mm, &_pmd, pgtable); 2682 2683 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2684 pte_t *pte, entry; 2685 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2686 entry = pte_mkspecial(entry); 2687 pte = pte_offset_map(&_pmd, haddr); 2688 VM_BUG_ON(!pte_none(*pte)); 2689 set_pte_at(mm, haddr, pte, entry); 2690 pte_unmap(pte); 2691 } 2692 smp_wmb(); /* make pte visible before pmd */ 2693 pmd_populate(mm, pmd, pgtable); 2694 put_huge_zero_page(); 2695 } 2696 2697 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address, 2698 pmd_t *pmd) 2699 { 2700 struct page *page; 2701 struct mm_struct *mm = vma->vm_mm; 2702 unsigned long haddr = address & HPAGE_PMD_MASK; 2703 unsigned long mmun_start; /* For mmu_notifiers */ 2704 unsigned long mmun_end; /* For mmu_notifiers */ 2705 2706 BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE); 2707 2708 mmun_start = haddr; 2709 mmun_end = haddr + HPAGE_PMD_SIZE; 2710 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2711 spin_lock(&mm->page_table_lock); 2712 if (unlikely(!pmd_trans_huge(*pmd))) { 2713 spin_unlock(&mm->page_table_lock); 2714 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2715 return; 2716 } 2717 if (is_huge_zero_pmd(*pmd)) { 2718 __split_huge_zero_page_pmd(vma, haddr, pmd); 2719 spin_unlock(&mm->page_table_lock); 2720 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2721 return; 2722 } 2723 page = pmd_page(*pmd); 2724 VM_BUG_ON(!page_count(page)); 2725 get_page(page); 2726 spin_unlock(&mm->page_table_lock); 2727 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2728 2729 split_huge_page(page); 2730 2731 put_page(page); 2732 BUG_ON(pmd_trans_huge(*pmd)); 2733 } 2734 2735 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address, 2736 pmd_t *pmd) 2737 { 2738 struct vm_area_struct *vma; 2739 2740 vma = find_vma(mm, address); 2741 BUG_ON(vma == NULL); 2742 split_huge_page_pmd(vma, address, pmd); 2743 } 2744 2745 static void split_huge_page_address(struct mm_struct *mm, 2746 unsigned long address) 2747 { 2748 pmd_t *pmd; 2749 2750 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); 2751 2752 pmd = mm_find_pmd(mm, address); 2753 if (!pmd) 2754 return; 2755 /* 2756 * Caller holds the mmap_sem write mode, so a huge pmd cannot 2757 * materialize from under us. 2758 */ 2759 split_huge_page_pmd_mm(mm, address, pmd); 2760 } 2761 2762 void __vma_adjust_trans_huge(struct vm_area_struct *vma, 2763 unsigned long start, 2764 unsigned long end, 2765 long adjust_next) 2766 { 2767 /* 2768 * If the new start address isn't hpage aligned and it could 2769 * previously contain an hugepage: check if we need to split 2770 * an huge pmd. 2771 */ 2772 if (start & ~HPAGE_PMD_MASK && 2773 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2774 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2775 split_huge_page_address(vma->vm_mm, start); 2776 2777 /* 2778 * If the new end address isn't hpage aligned and it could 2779 * previously contain an hugepage: check if we need to split 2780 * an huge pmd. 2781 */ 2782 if (end & ~HPAGE_PMD_MASK && 2783 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2784 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2785 split_huge_page_address(vma->vm_mm, end); 2786 2787 /* 2788 * If we're also updating the vma->vm_next->vm_start, if the new 2789 * vm_next->vm_start isn't page aligned and it could previously 2790 * contain an hugepage: check if we need to split an huge pmd. 2791 */ 2792 if (adjust_next > 0) { 2793 struct vm_area_struct *next = vma->vm_next; 2794 unsigned long nstart = next->vm_start; 2795 nstart += adjust_next << PAGE_SHIFT; 2796 if (nstart & ~HPAGE_PMD_MASK && 2797 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2798 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2799 split_huge_page_address(next->vm_mm, nstart); 2800 } 2801 } 2802