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/mm_inline.h> 16 #include <linux/kthread.h> 17 #include <linux/khugepaged.h> 18 #include <linux/freezer.h> 19 #include <linux/mman.h> 20 #include <asm/tlb.h> 21 #include <asm/pgalloc.h> 22 #include "internal.h" 23 24 /* 25 * By default transparent hugepage support is enabled for all mappings 26 * and khugepaged scans all mappings. Defrag is only invoked by 27 * khugepaged hugepage allocations and by page faults inside 28 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived 29 * allocations. 30 */ 31 unsigned long transparent_hugepage_flags __read_mostly = 32 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS 33 (1<<TRANSPARENT_HUGEPAGE_FLAG)| 34 #endif 35 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE 36 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| 37 #endif 38 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)| 39 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 40 41 /* default scan 8*512 pte (or vmas) every 30 second */ 42 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8; 43 static unsigned int khugepaged_pages_collapsed; 44 static unsigned int khugepaged_full_scans; 45 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 46 /* during fragmentation poll the hugepage allocator once every minute */ 47 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 48 static struct task_struct *khugepaged_thread __read_mostly; 49 static DEFINE_MUTEX(khugepaged_mutex); 50 static DEFINE_SPINLOCK(khugepaged_mm_lock); 51 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 52 /* 53 * default collapse hugepages if there is at least one pte mapped like 54 * it would have happened if the vma was large enough during page 55 * fault. 56 */ 57 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1; 58 59 static int khugepaged(void *none); 60 static int mm_slots_hash_init(void); 61 static int khugepaged_slab_init(void); 62 static void khugepaged_slab_free(void); 63 64 #define MM_SLOTS_HASH_HEADS 1024 65 static struct hlist_head *mm_slots_hash __read_mostly; 66 static struct kmem_cache *mm_slot_cache __read_mostly; 67 68 /** 69 * struct mm_slot - hash lookup from mm to mm_slot 70 * @hash: hash collision list 71 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 72 * @mm: the mm that this information is valid for 73 */ 74 struct mm_slot { 75 struct hlist_node hash; 76 struct list_head mm_node; 77 struct mm_struct *mm; 78 }; 79 80 /** 81 * struct khugepaged_scan - cursor for scanning 82 * @mm_head: the head of the mm list to scan 83 * @mm_slot: the current mm_slot we are scanning 84 * @address: the next address inside that to be scanned 85 * 86 * There is only the one khugepaged_scan instance of this cursor structure. 87 */ 88 struct khugepaged_scan { 89 struct list_head mm_head; 90 struct mm_slot *mm_slot; 91 unsigned long address; 92 }; 93 static struct khugepaged_scan khugepaged_scan = { 94 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 95 }; 96 97 98 static int set_recommended_min_free_kbytes(void) 99 { 100 struct zone *zone; 101 int nr_zones = 0; 102 unsigned long recommended_min; 103 extern int min_free_kbytes; 104 105 if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG, 106 &transparent_hugepage_flags) && 107 !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 108 &transparent_hugepage_flags)) 109 return 0; 110 111 for_each_populated_zone(zone) 112 nr_zones++; 113 114 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */ 115 recommended_min = pageblock_nr_pages * nr_zones * 2; 116 117 /* 118 * Make sure that on average at least two pageblocks are almost free 119 * of another type, one for a migratetype to fall back to and a 120 * second to avoid subsequent fallbacks of other types There are 3 121 * MIGRATE_TYPES we care about. 122 */ 123 recommended_min += pageblock_nr_pages * nr_zones * 124 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; 125 126 /* don't ever allow to reserve more than 5% of the lowmem */ 127 recommended_min = min(recommended_min, 128 (unsigned long) nr_free_buffer_pages() / 20); 129 recommended_min <<= (PAGE_SHIFT-10); 130 131 if (recommended_min > min_free_kbytes) 132 min_free_kbytes = recommended_min; 133 setup_per_zone_wmarks(); 134 return 0; 135 } 136 late_initcall(set_recommended_min_free_kbytes); 137 138 static int start_khugepaged(void) 139 { 140 int err = 0; 141 if (khugepaged_enabled()) { 142 int wakeup; 143 if (unlikely(!mm_slot_cache || !mm_slots_hash)) { 144 err = -ENOMEM; 145 goto out; 146 } 147 mutex_lock(&khugepaged_mutex); 148 if (!khugepaged_thread) 149 khugepaged_thread = kthread_run(khugepaged, NULL, 150 "khugepaged"); 151 if (unlikely(IS_ERR(khugepaged_thread))) { 152 printk(KERN_ERR 153 "khugepaged: kthread_run(khugepaged) failed\n"); 154 err = PTR_ERR(khugepaged_thread); 155 khugepaged_thread = NULL; 156 } 157 wakeup = !list_empty(&khugepaged_scan.mm_head); 158 mutex_unlock(&khugepaged_mutex); 159 if (wakeup) 160 wake_up_interruptible(&khugepaged_wait); 161 162 set_recommended_min_free_kbytes(); 163 } else 164 /* wakeup to exit */ 165 wake_up_interruptible(&khugepaged_wait); 166 out: 167 return err; 168 } 169 170 #ifdef CONFIG_SYSFS 171 172 static ssize_t double_flag_show(struct kobject *kobj, 173 struct kobj_attribute *attr, char *buf, 174 enum transparent_hugepage_flag enabled, 175 enum transparent_hugepage_flag req_madv) 176 { 177 if (test_bit(enabled, &transparent_hugepage_flags)) { 178 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); 179 return sprintf(buf, "[always] madvise never\n"); 180 } else if (test_bit(req_madv, &transparent_hugepage_flags)) 181 return sprintf(buf, "always [madvise] never\n"); 182 else 183 return sprintf(buf, "always madvise [never]\n"); 184 } 185 static ssize_t double_flag_store(struct kobject *kobj, 186 struct kobj_attribute *attr, 187 const char *buf, size_t count, 188 enum transparent_hugepage_flag enabled, 189 enum transparent_hugepage_flag req_madv) 190 { 191 if (!memcmp("always", buf, 192 min(sizeof("always")-1, count))) { 193 set_bit(enabled, &transparent_hugepage_flags); 194 clear_bit(req_madv, &transparent_hugepage_flags); 195 } else if (!memcmp("madvise", buf, 196 min(sizeof("madvise")-1, count))) { 197 clear_bit(enabled, &transparent_hugepage_flags); 198 set_bit(req_madv, &transparent_hugepage_flags); 199 } else if (!memcmp("never", buf, 200 min(sizeof("never")-1, count))) { 201 clear_bit(enabled, &transparent_hugepage_flags); 202 clear_bit(req_madv, &transparent_hugepage_flags); 203 } else 204 return -EINVAL; 205 206 return count; 207 } 208 209 static ssize_t enabled_show(struct kobject *kobj, 210 struct kobj_attribute *attr, char *buf) 211 { 212 return double_flag_show(kobj, attr, buf, 213 TRANSPARENT_HUGEPAGE_FLAG, 214 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 215 } 216 static ssize_t enabled_store(struct kobject *kobj, 217 struct kobj_attribute *attr, 218 const char *buf, size_t count) 219 { 220 ssize_t ret; 221 222 ret = double_flag_store(kobj, attr, buf, count, 223 TRANSPARENT_HUGEPAGE_FLAG, 224 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 225 226 if (ret > 0) { 227 int err = start_khugepaged(); 228 if (err) 229 ret = err; 230 } 231 232 if (ret > 0 && 233 (test_bit(TRANSPARENT_HUGEPAGE_FLAG, 234 &transparent_hugepage_flags) || 235 test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 236 &transparent_hugepage_flags))) 237 set_recommended_min_free_kbytes(); 238 239 return ret; 240 } 241 static struct kobj_attribute enabled_attr = 242 __ATTR(enabled, 0644, enabled_show, enabled_store); 243 244 static ssize_t single_flag_show(struct kobject *kobj, 245 struct kobj_attribute *attr, char *buf, 246 enum transparent_hugepage_flag flag) 247 { 248 return sprintf(buf, "%d\n", 249 !!test_bit(flag, &transparent_hugepage_flags)); 250 } 251 252 static ssize_t single_flag_store(struct kobject *kobj, 253 struct kobj_attribute *attr, 254 const char *buf, size_t count, 255 enum transparent_hugepage_flag flag) 256 { 257 unsigned long value; 258 int ret; 259 260 ret = kstrtoul(buf, 10, &value); 261 if (ret < 0) 262 return ret; 263 if (value > 1) 264 return -EINVAL; 265 266 if (value) 267 set_bit(flag, &transparent_hugepage_flags); 268 else 269 clear_bit(flag, &transparent_hugepage_flags); 270 271 return count; 272 } 273 274 /* 275 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind 276 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of 277 * memory just to allocate one more hugepage. 278 */ 279 static ssize_t defrag_show(struct kobject *kobj, 280 struct kobj_attribute *attr, char *buf) 281 { 282 return double_flag_show(kobj, attr, buf, 283 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 284 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 285 } 286 static ssize_t defrag_store(struct kobject *kobj, 287 struct kobj_attribute *attr, 288 const char *buf, size_t count) 289 { 290 return double_flag_store(kobj, attr, buf, count, 291 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 292 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 293 } 294 static struct kobj_attribute defrag_attr = 295 __ATTR(defrag, 0644, defrag_show, defrag_store); 296 297 #ifdef CONFIG_DEBUG_VM 298 static ssize_t debug_cow_show(struct kobject *kobj, 299 struct kobj_attribute *attr, char *buf) 300 { 301 return single_flag_show(kobj, attr, buf, 302 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 303 } 304 static ssize_t debug_cow_store(struct kobject *kobj, 305 struct kobj_attribute *attr, 306 const char *buf, size_t count) 307 { 308 return single_flag_store(kobj, attr, buf, count, 309 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 310 } 311 static struct kobj_attribute debug_cow_attr = 312 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 313 #endif /* CONFIG_DEBUG_VM */ 314 315 static struct attribute *hugepage_attr[] = { 316 &enabled_attr.attr, 317 &defrag_attr.attr, 318 #ifdef CONFIG_DEBUG_VM 319 &debug_cow_attr.attr, 320 #endif 321 NULL, 322 }; 323 324 static struct attribute_group hugepage_attr_group = { 325 .attrs = hugepage_attr, 326 }; 327 328 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 329 struct kobj_attribute *attr, 330 char *buf) 331 { 332 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 333 } 334 335 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 336 struct kobj_attribute *attr, 337 const char *buf, size_t count) 338 { 339 unsigned long msecs; 340 int err; 341 342 err = strict_strtoul(buf, 10, &msecs); 343 if (err || msecs > UINT_MAX) 344 return -EINVAL; 345 346 khugepaged_scan_sleep_millisecs = msecs; 347 wake_up_interruptible(&khugepaged_wait); 348 349 return count; 350 } 351 static struct kobj_attribute scan_sleep_millisecs_attr = 352 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 353 scan_sleep_millisecs_store); 354 355 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 356 struct kobj_attribute *attr, 357 char *buf) 358 { 359 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 360 } 361 362 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 363 struct kobj_attribute *attr, 364 const char *buf, size_t count) 365 { 366 unsigned long msecs; 367 int err; 368 369 err = strict_strtoul(buf, 10, &msecs); 370 if (err || msecs > UINT_MAX) 371 return -EINVAL; 372 373 khugepaged_alloc_sleep_millisecs = msecs; 374 wake_up_interruptible(&khugepaged_wait); 375 376 return count; 377 } 378 static struct kobj_attribute alloc_sleep_millisecs_attr = 379 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 380 alloc_sleep_millisecs_store); 381 382 static ssize_t pages_to_scan_show(struct kobject *kobj, 383 struct kobj_attribute *attr, 384 char *buf) 385 { 386 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 387 } 388 static ssize_t pages_to_scan_store(struct kobject *kobj, 389 struct kobj_attribute *attr, 390 const char *buf, size_t count) 391 { 392 int err; 393 unsigned long pages; 394 395 err = strict_strtoul(buf, 10, &pages); 396 if (err || !pages || pages > UINT_MAX) 397 return -EINVAL; 398 399 khugepaged_pages_to_scan = pages; 400 401 return count; 402 } 403 static struct kobj_attribute pages_to_scan_attr = 404 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 405 pages_to_scan_store); 406 407 static ssize_t pages_collapsed_show(struct kobject *kobj, 408 struct kobj_attribute *attr, 409 char *buf) 410 { 411 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 412 } 413 static struct kobj_attribute pages_collapsed_attr = 414 __ATTR_RO(pages_collapsed); 415 416 static ssize_t full_scans_show(struct kobject *kobj, 417 struct kobj_attribute *attr, 418 char *buf) 419 { 420 return sprintf(buf, "%u\n", khugepaged_full_scans); 421 } 422 static struct kobj_attribute full_scans_attr = 423 __ATTR_RO(full_scans); 424 425 static ssize_t khugepaged_defrag_show(struct kobject *kobj, 426 struct kobj_attribute *attr, char *buf) 427 { 428 return single_flag_show(kobj, attr, buf, 429 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 430 } 431 static ssize_t khugepaged_defrag_store(struct kobject *kobj, 432 struct kobj_attribute *attr, 433 const char *buf, size_t count) 434 { 435 return single_flag_store(kobj, attr, buf, count, 436 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 437 } 438 static struct kobj_attribute khugepaged_defrag_attr = 439 __ATTR(defrag, 0644, khugepaged_defrag_show, 440 khugepaged_defrag_store); 441 442 /* 443 * max_ptes_none controls if khugepaged should collapse hugepages over 444 * any unmapped ptes in turn potentially increasing the memory 445 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 446 * reduce the available free memory in the system as it 447 * runs. Increasing max_ptes_none will instead potentially reduce the 448 * free memory in the system during the khugepaged scan. 449 */ 450 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 451 struct kobj_attribute *attr, 452 char *buf) 453 { 454 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 455 } 456 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 457 struct kobj_attribute *attr, 458 const char *buf, size_t count) 459 { 460 int err; 461 unsigned long max_ptes_none; 462 463 err = strict_strtoul(buf, 10, &max_ptes_none); 464 if (err || max_ptes_none > HPAGE_PMD_NR-1) 465 return -EINVAL; 466 467 khugepaged_max_ptes_none = max_ptes_none; 468 469 return count; 470 } 471 static struct kobj_attribute khugepaged_max_ptes_none_attr = 472 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 473 khugepaged_max_ptes_none_store); 474 475 static struct attribute *khugepaged_attr[] = { 476 &khugepaged_defrag_attr.attr, 477 &khugepaged_max_ptes_none_attr.attr, 478 &pages_to_scan_attr.attr, 479 &pages_collapsed_attr.attr, 480 &full_scans_attr.attr, 481 &scan_sleep_millisecs_attr.attr, 482 &alloc_sleep_millisecs_attr.attr, 483 NULL, 484 }; 485 486 static struct attribute_group khugepaged_attr_group = { 487 .attrs = khugepaged_attr, 488 .name = "khugepaged", 489 }; 490 491 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) 492 { 493 int err; 494 495 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 496 if (unlikely(!*hugepage_kobj)) { 497 printk(KERN_ERR "hugepage: failed kobject create\n"); 498 return -ENOMEM; 499 } 500 501 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); 502 if (err) { 503 printk(KERN_ERR "hugepage: failed register hugeage group\n"); 504 goto delete_obj; 505 } 506 507 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); 508 if (err) { 509 printk(KERN_ERR "hugepage: failed register hugeage group\n"); 510 goto remove_hp_group; 511 } 512 513 return 0; 514 515 remove_hp_group: 516 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); 517 delete_obj: 518 kobject_put(*hugepage_kobj); 519 return err; 520 } 521 522 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) 523 { 524 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); 525 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); 526 kobject_put(hugepage_kobj); 527 } 528 #else 529 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) 530 { 531 return 0; 532 } 533 534 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) 535 { 536 } 537 #endif /* CONFIG_SYSFS */ 538 539 static int __init hugepage_init(void) 540 { 541 int err; 542 struct kobject *hugepage_kobj; 543 544 if (!has_transparent_hugepage()) { 545 transparent_hugepage_flags = 0; 546 return -EINVAL; 547 } 548 549 err = hugepage_init_sysfs(&hugepage_kobj); 550 if (err) 551 return err; 552 553 err = khugepaged_slab_init(); 554 if (err) 555 goto out; 556 557 err = mm_slots_hash_init(); 558 if (err) { 559 khugepaged_slab_free(); 560 goto out; 561 } 562 563 /* 564 * By default disable transparent hugepages on smaller systems, 565 * where the extra memory used could hurt more than TLB overhead 566 * is likely to save. The admin can still enable it through /sys. 567 */ 568 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) 569 transparent_hugepage_flags = 0; 570 571 start_khugepaged(); 572 573 set_recommended_min_free_kbytes(); 574 575 return 0; 576 out: 577 hugepage_exit_sysfs(hugepage_kobj); 578 return err; 579 } 580 module_init(hugepage_init) 581 582 static int __init setup_transparent_hugepage(char *str) 583 { 584 int ret = 0; 585 if (!str) 586 goto out; 587 if (!strcmp(str, "always")) { 588 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 589 &transparent_hugepage_flags); 590 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 591 &transparent_hugepage_flags); 592 ret = 1; 593 } else if (!strcmp(str, "madvise")) { 594 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 595 &transparent_hugepage_flags); 596 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 597 &transparent_hugepage_flags); 598 ret = 1; 599 } else if (!strcmp(str, "never")) { 600 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 601 &transparent_hugepage_flags); 602 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 603 &transparent_hugepage_flags); 604 ret = 1; 605 } 606 out: 607 if (!ret) 608 printk(KERN_WARNING 609 "transparent_hugepage= cannot parse, ignored\n"); 610 return ret; 611 } 612 __setup("transparent_hugepage=", setup_transparent_hugepage); 613 614 static void prepare_pmd_huge_pte(pgtable_t pgtable, 615 struct mm_struct *mm) 616 { 617 assert_spin_locked(&mm->page_table_lock); 618 619 /* FIFO */ 620 if (!mm->pmd_huge_pte) 621 INIT_LIST_HEAD(&pgtable->lru); 622 else 623 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru); 624 mm->pmd_huge_pte = pgtable; 625 } 626 627 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 628 { 629 if (likely(vma->vm_flags & VM_WRITE)) 630 pmd = pmd_mkwrite(pmd); 631 return pmd; 632 } 633 634 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, 635 struct vm_area_struct *vma, 636 unsigned long haddr, pmd_t *pmd, 637 struct page *page) 638 { 639 int ret = 0; 640 pgtable_t pgtable; 641 642 VM_BUG_ON(!PageCompound(page)); 643 pgtable = pte_alloc_one(mm, haddr); 644 if (unlikely(!pgtable)) { 645 mem_cgroup_uncharge_page(page); 646 put_page(page); 647 return VM_FAULT_OOM; 648 } 649 650 clear_huge_page(page, haddr, HPAGE_PMD_NR); 651 __SetPageUptodate(page); 652 653 spin_lock(&mm->page_table_lock); 654 if (unlikely(!pmd_none(*pmd))) { 655 spin_unlock(&mm->page_table_lock); 656 mem_cgroup_uncharge_page(page); 657 put_page(page); 658 pte_free(mm, pgtable); 659 } else { 660 pmd_t entry; 661 entry = mk_pmd(page, vma->vm_page_prot); 662 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 663 entry = pmd_mkhuge(entry); 664 /* 665 * The spinlocking to take the lru_lock inside 666 * page_add_new_anon_rmap() acts as a full memory 667 * barrier to be sure clear_huge_page writes become 668 * visible after the set_pmd_at() write. 669 */ 670 page_add_new_anon_rmap(page, vma, haddr); 671 set_pmd_at(mm, haddr, pmd, entry); 672 prepare_pmd_huge_pte(pgtable, mm); 673 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 674 mm->nr_ptes++; 675 spin_unlock(&mm->page_table_lock); 676 } 677 678 return ret; 679 } 680 681 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) 682 { 683 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; 684 } 685 686 static inline struct page *alloc_hugepage_vma(int defrag, 687 struct vm_area_struct *vma, 688 unsigned long haddr, int nd, 689 gfp_t extra_gfp) 690 { 691 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp), 692 HPAGE_PMD_ORDER, vma, haddr, nd); 693 } 694 695 #ifndef CONFIG_NUMA 696 static inline struct page *alloc_hugepage(int defrag) 697 { 698 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), 699 HPAGE_PMD_ORDER); 700 } 701 #endif 702 703 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 704 unsigned long address, pmd_t *pmd, 705 unsigned int flags) 706 { 707 struct page *page; 708 unsigned long haddr = address & HPAGE_PMD_MASK; 709 pte_t *pte; 710 711 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) { 712 if (unlikely(anon_vma_prepare(vma))) 713 return VM_FAULT_OOM; 714 if (unlikely(khugepaged_enter(vma))) 715 return VM_FAULT_OOM; 716 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 717 vma, haddr, numa_node_id(), 0); 718 if (unlikely(!page)) { 719 count_vm_event(THP_FAULT_FALLBACK); 720 goto out; 721 } 722 count_vm_event(THP_FAULT_ALLOC); 723 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) { 724 put_page(page); 725 goto out; 726 } 727 728 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page); 729 } 730 out: 731 /* 732 * Use __pte_alloc instead of pte_alloc_map, because we can't 733 * run pte_offset_map on the pmd, if an huge pmd could 734 * materialize from under us from a different thread. 735 */ 736 if (unlikely(__pte_alloc(mm, vma, pmd, address))) 737 return VM_FAULT_OOM; 738 /* if an huge pmd materialized from under us just retry later */ 739 if (unlikely(pmd_trans_huge(*pmd))) 740 return 0; 741 /* 742 * A regular pmd is established and it can't morph into a huge pmd 743 * from under us anymore at this point because we hold the mmap_sem 744 * read mode and khugepaged takes it in write mode. So now it's 745 * safe to run pte_offset_map(). 746 */ 747 pte = pte_offset_map(pmd, address); 748 return handle_pte_fault(mm, vma, address, pte, pmd, flags); 749 } 750 751 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 752 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 753 struct vm_area_struct *vma) 754 { 755 struct page *src_page; 756 pmd_t pmd; 757 pgtable_t pgtable; 758 int ret; 759 760 ret = -ENOMEM; 761 pgtable = pte_alloc_one(dst_mm, addr); 762 if (unlikely(!pgtable)) 763 goto out; 764 765 spin_lock(&dst_mm->page_table_lock); 766 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING); 767 768 ret = -EAGAIN; 769 pmd = *src_pmd; 770 if (unlikely(!pmd_trans_huge(pmd))) { 771 pte_free(dst_mm, pgtable); 772 goto out_unlock; 773 } 774 if (unlikely(pmd_trans_splitting(pmd))) { 775 /* split huge page running from under us */ 776 spin_unlock(&src_mm->page_table_lock); 777 spin_unlock(&dst_mm->page_table_lock); 778 pte_free(dst_mm, pgtable); 779 780 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ 781 goto out; 782 } 783 src_page = pmd_page(pmd); 784 VM_BUG_ON(!PageHead(src_page)); 785 get_page(src_page); 786 page_dup_rmap(src_page); 787 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 788 789 pmdp_set_wrprotect(src_mm, addr, src_pmd); 790 pmd = pmd_mkold(pmd_wrprotect(pmd)); 791 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 792 prepare_pmd_huge_pte(pgtable, dst_mm); 793 dst_mm->nr_ptes++; 794 795 ret = 0; 796 out_unlock: 797 spin_unlock(&src_mm->page_table_lock); 798 spin_unlock(&dst_mm->page_table_lock); 799 out: 800 return ret; 801 } 802 803 /* no "address" argument so destroys page coloring of some arch */ 804 pgtable_t get_pmd_huge_pte(struct mm_struct *mm) 805 { 806 pgtable_t pgtable; 807 808 assert_spin_locked(&mm->page_table_lock); 809 810 /* FIFO */ 811 pgtable = mm->pmd_huge_pte; 812 if (list_empty(&pgtable->lru)) 813 mm->pmd_huge_pte = NULL; 814 else { 815 mm->pmd_huge_pte = list_entry(pgtable->lru.next, 816 struct page, lru); 817 list_del(&pgtable->lru); 818 } 819 return pgtable; 820 } 821 822 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, 823 struct vm_area_struct *vma, 824 unsigned long address, 825 pmd_t *pmd, pmd_t orig_pmd, 826 struct page *page, 827 unsigned long haddr) 828 { 829 pgtable_t pgtable; 830 pmd_t _pmd; 831 int ret = 0, i; 832 struct page **pages; 833 834 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 835 GFP_KERNEL); 836 if (unlikely(!pages)) { 837 ret |= VM_FAULT_OOM; 838 goto out; 839 } 840 841 for (i = 0; i < HPAGE_PMD_NR; i++) { 842 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | 843 __GFP_OTHER_NODE, 844 vma, address, page_to_nid(page)); 845 if (unlikely(!pages[i] || 846 mem_cgroup_newpage_charge(pages[i], mm, 847 GFP_KERNEL))) { 848 if (pages[i]) 849 put_page(pages[i]); 850 mem_cgroup_uncharge_start(); 851 while (--i >= 0) { 852 mem_cgroup_uncharge_page(pages[i]); 853 put_page(pages[i]); 854 } 855 mem_cgroup_uncharge_end(); 856 kfree(pages); 857 ret |= VM_FAULT_OOM; 858 goto out; 859 } 860 } 861 862 for (i = 0; i < HPAGE_PMD_NR; i++) { 863 copy_user_highpage(pages[i], page + i, 864 haddr + PAGE_SIZE * i, vma); 865 __SetPageUptodate(pages[i]); 866 cond_resched(); 867 } 868 869 spin_lock(&mm->page_table_lock); 870 if (unlikely(!pmd_same(*pmd, orig_pmd))) 871 goto out_free_pages; 872 VM_BUG_ON(!PageHead(page)); 873 874 pmdp_clear_flush_notify(vma, haddr, pmd); 875 /* leave pmd empty until pte is filled */ 876 877 pgtable = get_pmd_huge_pte(mm); 878 pmd_populate(mm, &_pmd, pgtable); 879 880 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 881 pte_t *pte, entry; 882 entry = mk_pte(pages[i], vma->vm_page_prot); 883 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 884 page_add_new_anon_rmap(pages[i], vma, haddr); 885 pte = pte_offset_map(&_pmd, haddr); 886 VM_BUG_ON(!pte_none(*pte)); 887 set_pte_at(mm, haddr, pte, entry); 888 pte_unmap(pte); 889 } 890 kfree(pages); 891 892 smp_wmb(); /* make pte visible before pmd */ 893 pmd_populate(mm, pmd, pgtable); 894 page_remove_rmap(page); 895 spin_unlock(&mm->page_table_lock); 896 897 ret |= VM_FAULT_WRITE; 898 put_page(page); 899 900 out: 901 return ret; 902 903 out_free_pages: 904 spin_unlock(&mm->page_table_lock); 905 mem_cgroup_uncharge_start(); 906 for (i = 0; i < HPAGE_PMD_NR; i++) { 907 mem_cgroup_uncharge_page(pages[i]); 908 put_page(pages[i]); 909 } 910 mem_cgroup_uncharge_end(); 911 kfree(pages); 912 goto out; 913 } 914 915 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 916 unsigned long address, pmd_t *pmd, pmd_t orig_pmd) 917 { 918 int ret = 0; 919 struct page *page, *new_page; 920 unsigned long haddr; 921 922 VM_BUG_ON(!vma->anon_vma); 923 spin_lock(&mm->page_table_lock); 924 if (unlikely(!pmd_same(*pmd, orig_pmd))) 925 goto out_unlock; 926 927 page = pmd_page(orig_pmd); 928 VM_BUG_ON(!PageCompound(page) || !PageHead(page)); 929 haddr = address & HPAGE_PMD_MASK; 930 if (page_mapcount(page) == 1) { 931 pmd_t entry; 932 entry = pmd_mkyoung(orig_pmd); 933 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 934 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 935 update_mmu_cache(vma, address, entry); 936 ret |= VM_FAULT_WRITE; 937 goto out_unlock; 938 } 939 get_page(page); 940 spin_unlock(&mm->page_table_lock); 941 942 if (transparent_hugepage_enabled(vma) && 943 !transparent_hugepage_debug_cow()) 944 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 945 vma, haddr, numa_node_id(), 0); 946 else 947 new_page = NULL; 948 949 if (unlikely(!new_page)) { 950 count_vm_event(THP_FAULT_FALLBACK); 951 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 952 pmd, orig_pmd, page, haddr); 953 put_page(page); 954 goto out; 955 } 956 count_vm_event(THP_FAULT_ALLOC); 957 958 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 959 put_page(new_page); 960 put_page(page); 961 ret |= VM_FAULT_OOM; 962 goto out; 963 } 964 965 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 966 __SetPageUptodate(new_page); 967 968 spin_lock(&mm->page_table_lock); 969 put_page(page); 970 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 971 mem_cgroup_uncharge_page(new_page); 972 put_page(new_page); 973 } else { 974 pmd_t entry; 975 VM_BUG_ON(!PageHead(page)); 976 entry = mk_pmd(new_page, vma->vm_page_prot); 977 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 978 entry = pmd_mkhuge(entry); 979 pmdp_clear_flush_notify(vma, haddr, pmd); 980 page_add_new_anon_rmap(new_page, vma, haddr); 981 set_pmd_at(mm, haddr, pmd, entry); 982 update_mmu_cache(vma, address, entry); 983 page_remove_rmap(page); 984 put_page(page); 985 ret |= VM_FAULT_WRITE; 986 } 987 out_unlock: 988 spin_unlock(&mm->page_table_lock); 989 out: 990 return ret; 991 } 992 993 struct page *follow_trans_huge_pmd(struct mm_struct *mm, 994 unsigned long addr, 995 pmd_t *pmd, 996 unsigned int flags) 997 { 998 struct page *page = NULL; 999 1000 assert_spin_locked(&mm->page_table_lock); 1001 1002 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 1003 goto out; 1004 1005 page = pmd_page(*pmd); 1006 VM_BUG_ON(!PageHead(page)); 1007 if (flags & FOLL_TOUCH) { 1008 pmd_t _pmd; 1009 /* 1010 * We should set the dirty bit only for FOLL_WRITE but 1011 * for now the dirty bit in the pmd is meaningless. 1012 * And if the dirty bit will become meaningful and 1013 * we'll only set it with FOLL_WRITE, an atomic 1014 * set_bit will be required on the pmd to set the 1015 * young bit, instead of the current set_pmd_at. 1016 */ 1017 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 1018 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd); 1019 } 1020 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1021 VM_BUG_ON(!PageCompound(page)); 1022 if (flags & FOLL_GET) 1023 get_page_foll(page); 1024 1025 out: 1026 return page; 1027 } 1028 1029 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1030 pmd_t *pmd, unsigned long addr) 1031 { 1032 int ret = 0; 1033 1034 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1035 struct page *page; 1036 pgtable_t pgtable; 1037 pgtable = get_pmd_huge_pte(tlb->mm); 1038 page = pmd_page(*pmd); 1039 pmd_clear(pmd); 1040 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1041 page_remove_rmap(page); 1042 VM_BUG_ON(page_mapcount(page) < 0); 1043 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1044 VM_BUG_ON(!PageHead(page)); 1045 tlb->mm->nr_ptes--; 1046 spin_unlock(&tlb->mm->page_table_lock); 1047 tlb_remove_page(tlb, page); 1048 pte_free(tlb->mm, pgtable); 1049 ret = 1; 1050 } 1051 return ret; 1052 } 1053 1054 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1055 unsigned long addr, unsigned long end, 1056 unsigned char *vec) 1057 { 1058 int ret = 0; 1059 1060 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1061 /* 1062 * All logical pages in the range are present 1063 * if backed by a huge page. 1064 */ 1065 spin_unlock(&vma->vm_mm->page_table_lock); 1066 memset(vec, 1, (end - addr) >> PAGE_SHIFT); 1067 ret = 1; 1068 } 1069 1070 return ret; 1071 } 1072 1073 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, 1074 unsigned long old_addr, 1075 unsigned long new_addr, unsigned long old_end, 1076 pmd_t *old_pmd, pmd_t *new_pmd) 1077 { 1078 int ret = 0; 1079 pmd_t pmd; 1080 1081 struct mm_struct *mm = vma->vm_mm; 1082 1083 if ((old_addr & ~HPAGE_PMD_MASK) || 1084 (new_addr & ~HPAGE_PMD_MASK) || 1085 old_end - old_addr < HPAGE_PMD_SIZE || 1086 (new_vma->vm_flags & VM_NOHUGEPAGE)) 1087 goto out; 1088 1089 /* 1090 * The destination pmd shouldn't be established, free_pgtables() 1091 * should have release it. 1092 */ 1093 if (WARN_ON(!pmd_none(*new_pmd))) { 1094 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1095 goto out; 1096 } 1097 1098 ret = __pmd_trans_huge_lock(old_pmd, vma); 1099 if (ret == 1) { 1100 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); 1101 VM_BUG_ON(!pmd_none(*new_pmd)); 1102 set_pmd_at(mm, new_addr, new_pmd, pmd); 1103 spin_unlock(&mm->page_table_lock); 1104 } 1105 out: 1106 return ret; 1107 } 1108 1109 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1110 unsigned long addr, pgprot_t newprot) 1111 { 1112 struct mm_struct *mm = vma->vm_mm; 1113 int ret = 0; 1114 1115 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1116 pmd_t entry; 1117 entry = pmdp_get_and_clear(mm, addr, pmd); 1118 entry = pmd_modify(entry, newprot); 1119 set_pmd_at(mm, addr, pmd, entry); 1120 spin_unlock(&vma->vm_mm->page_table_lock); 1121 ret = 1; 1122 } 1123 1124 return ret; 1125 } 1126 1127 /* 1128 * Returns 1 if a given pmd maps a stable (not under splitting) thp. 1129 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise. 1130 * 1131 * Note that if it returns 1, this routine returns without unlocking page 1132 * table locks. So callers must unlock them. 1133 */ 1134 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) 1135 { 1136 spin_lock(&vma->vm_mm->page_table_lock); 1137 if (likely(pmd_trans_huge(*pmd))) { 1138 if (unlikely(pmd_trans_splitting(*pmd))) { 1139 spin_unlock(&vma->vm_mm->page_table_lock); 1140 wait_split_huge_page(vma->anon_vma, pmd); 1141 return -1; 1142 } else { 1143 /* Thp mapped by 'pmd' is stable, so we can 1144 * handle it as it is. */ 1145 return 1; 1146 } 1147 } 1148 spin_unlock(&vma->vm_mm->page_table_lock); 1149 return 0; 1150 } 1151 1152 pmd_t *page_check_address_pmd(struct page *page, 1153 struct mm_struct *mm, 1154 unsigned long address, 1155 enum page_check_address_pmd_flag flag) 1156 { 1157 pgd_t *pgd; 1158 pud_t *pud; 1159 pmd_t *pmd, *ret = NULL; 1160 1161 if (address & ~HPAGE_PMD_MASK) 1162 goto out; 1163 1164 pgd = pgd_offset(mm, address); 1165 if (!pgd_present(*pgd)) 1166 goto out; 1167 1168 pud = pud_offset(pgd, address); 1169 if (!pud_present(*pud)) 1170 goto out; 1171 1172 pmd = pmd_offset(pud, address); 1173 if (pmd_none(*pmd)) 1174 goto out; 1175 if (pmd_page(*pmd) != page) 1176 goto out; 1177 /* 1178 * split_vma() may create temporary aliased mappings. There is 1179 * no risk as long as all huge pmd are found and have their 1180 * splitting bit set before __split_huge_page_refcount 1181 * runs. Finding the same huge pmd more than once during the 1182 * same rmap walk is not a problem. 1183 */ 1184 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && 1185 pmd_trans_splitting(*pmd)) 1186 goto out; 1187 if (pmd_trans_huge(*pmd)) { 1188 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && 1189 !pmd_trans_splitting(*pmd)); 1190 ret = pmd; 1191 } 1192 out: 1193 return ret; 1194 } 1195 1196 static int __split_huge_page_splitting(struct page *page, 1197 struct vm_area_struct *vma, 1198 unsigned long address) 1199 { 1200 struct mm_struct *mm = vma->vm_mm; 1201 pmd_t *pmd; 1202 int ret = 0; 1203 1204 spin_lock(&mm->page_table_lock); 1205 pmd = page_check_address_pmd(page, mm, address, 1206 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG); 1207 if (pmd) { 1208 /* 1209 * We can't temporarily set the pmd to null in order 1210 * to split it, the pmd must remain marked huge at all 1211 * times or the VM won't take the pmd_trans_huge paths 1212 * and it won't wait on the anon_vma->root->mutex to 1213 * serialize against split_huge_page*. 1214 */ 1215 pmdp_splitting_flush_notify(vma, address, pmd); 1216 ret = 1; 1217 } 1218 spin_unlock(&mm->page_table_lock); 1219 1220 return ret; 1221 } 1222 1223 static void __split_huge_page_refcount(struct page *page) 1224 { 1225 int i; 1226 struct zone *zone = page_zone(page); 1227 int tail_count = 0; 1228 1229 /* prevent PageLRU to go away from under us, and freeze lru stats */ 1230 spin_lock_irq(&zone->lru_lock); 1231 compound_lock(page); 1232 /* complete memcg works before add pages to LRU */ 1233 mem_cgroup_split_huge_fixup(page); 1234 1235 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 1236 struct page *page_tail = page + i; 1237 1238 /* tail_page->_mapcount cannot change */ 1239 BUG_ON(page_mapcount(page_tail) < 0); 1240 tail_count += page_mapcount(page_tail); 1241 /* check for overflow */ 1242 BUG_ON(tail_count < 0); 1243 BUG_ON(atomic_read(&page_tail->_count) != 0); 1244 /* 1245 * tail_page->_count is zero and not changing from 1246 * under us. But get_page_unless_zero() may be running 1247 * from under us on the tail_page. If we used 1248 * atomic_set() below instead of atomic_add(), we 1249 * would then run atomic_set() concurrently with 1250 * get_page_unless_zero(), and atomic_set() is 1251 * implemented in C not using locked ops. spin_unlock 1252 * on x86 sometime uses locked ops because of PPro 1253 * errata 66, 92, so unless somebody can guarantee 1254 * atomic_set() here would be safe on all archs (and 1255 * not only on x86), it's safer to use atomic_add(). 1256 */ 1257 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, 1258 &page_tail->_count); 1259 1260 /* after clearing PageTail the gup refcount can be released */ 1261 smp_mb(); 1262 1263 /* 1264 * retain hwpoison flag of the poisoned tail page: 1265 * fix for the unsuitable process killed on Guest Machine(KVM) 1266 * by the memory-failure. 1267 */ 1268 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON; 1269 page_tail->flags |= (page->flags & 1270 ((1L << PG_referenced) | 1271 (1L << PG_swapbacked) | 1272 (1L << PG_mlocked) | 1273 (1L << PG_uptodate))); 1274 page_tail->flags |= (1L << PG_dirty); 1275 1276 /* clear PageTail before overwriting first_page */ 1277 smp_wmb(); 1278 1279 /* 1280 * __split_huge_page_splitting() already set the 1281 * splitting bit in all pmd that could map this 1282 * hugepage, that will ensure no CPU can alter the 1283 * mapcount on the head page. The mapcount is only 1284 * accounted in the head page and it has to be 1285 * transferred to all tail pages in the below code. So 1286 * for this code to be safe, the split the mapcount 1287 * can't change. But that doesn't mean userland can't 1288 * keep changing and reading the page contents while 1289 * we transfer the mapcount, so the pmd splitting 1290 * status is achieved setting a reserved bit in the 1291 * pmd, not by clearing the present bit. 1292 */ 1293 page_tail->_mapcount = page->_mapcount; 1294 1295 BUG_ON(page_tail->mapping); 1296 page_tail->mapping = page->mapping; 1297 1298 page_tail->index = page->index + i; 1299 1300 BUG_ON(!PageAnon(page_tail)); 1301 BUG_ON(!PageUptodate(page_tail)); 1302 BUG_ON(!PageDirty(page_tail)); 1303 BUG_ON(!PageSwapBacked(page_tail)); 1304 1305 1306 lru_add_page_tail(zone, page, page_tail); 1307 } 1308 atomic_sub(tail_count, &page->_count); 1309 BUG_ON(atomic_read(&page->_count) <= 0); 1310 1311 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); 1312 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR); 1313 1314 ClearPageCompound(page); 1315 compound_unlock(page); 1316 spin_unlock_irq(&zone->lru_lock); 1317 1318 for (i = 1; i < HPAGE_PMD_NR; i++) { 1319 struct page *page_tail = page + i; 1320 BUG_ON(page_count(page_tail) <= 0); 1321 /* 1322 * Tail pages may be freed if there wasn't any mapping 1323 * like if add_to_swap() is running on a lru page that 1324 * had its mapping zapped. And freeing these pages 1325 * requires taking the lru_lock so we do the put_page 1326 * of the tail pages after the split is complete. 1327 */ 1328 put_page(page_tail); 1329 } 1330 1331 /* 1332 * Only the head page (now become a regular page) is required 1333 * to be pinned by the caller. 1334 */ 1335 BUG_ON(page_count(page) <= 0); 1336 } 1337 1338 static int __split_huge_page_map(struct page *page, 1339 struct vm_area_struct *vma, 1340 unsigned long address) 1341 { 1342 struct mm_struct *mm = vma->vm_mm; 1343 pmd_t *pmd, _pmd; 1344 int ret = 0, i; 1345 pgtable_t pgtable; 1346 unsigned long haddr; 1347 1348 spin_lock(&mm->page_table_lock); 1349 pmd = page_check_address_pmd(page, mm, address, 1350 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG); 1351 if (pmd) { 1352 pgtable = get_pmd_huge_pte(mm); 1353 pmd_populate(mm, &_pmd, pgtable); 1354 1355 for (i = 0, haddr = address; i < HPAGE_PMD_NR; 1356 i++, haddr += PAGE_SIZE) { 1357 pte_t *pte, entry; 1358 BUG_ON(PageCompound(page+i)); 1359 entry = mk_pte(page + i, vma->vm_page_prot); 1360 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1361 if (!pmd_write(*pmd)) 1362 entry = pte_wrprotect(entry); 1363 else 1364 BUG_ON(page_mapcount(page) != 1); 1365 if (!pmd_young(*pmd)) 1366 entry = pte_mkold(entry); 1367 pte = pte_offset_map(&_pmd, haddr); 1368 BUG_ON(!pte_none(*pte)); 1369 set_pte_at(mm, haddr, pte, entry); 1370 pte_unmap(pte); 1371 } 1372 1373 smp_wmb(); /* make pte visible before pmd */ 1374 /* 1375 * Up to this point the pmd is present and huge and 1376 * userland has the whole access to the hugepage 1377 * during the split (which happens in place). If we 1378 * overwrite the pmd with the not-huge version 1379 * pointing to the pte here (which of course we could 1380 * if all CPUs were bug free), userland could trigger 1381 * a small page size TLB miss on the small sized TLB 1382 * while the hugepage TLB entry is still established 1383 * in the huge TLB. Some CPU doesn't like that. See 1384 * http://support.amd.com/us/Processor_TechDocs/41322.pdf, 1385 * Erratum 383 on page 93. Intel should be safe but is 1386 * also warns that it's only safe if the permission 1387 * and cache attributes of the two entries loaded in 1388 * the two TLB is identical (which should be the case 1389 * here). But it is generally safer to never allow 1390 * small and huge TLB entries for the same virtual 1391 * address to be loaded simultaneously. So instead of 1392 * doing "pmd_populate(); flush_tlb_range();" we first 1393 * mark the current pmd notpresent (atomically because 1394 * here the pmd_trans_huge and pmd_trans_splitting 1395 * must remain set at all times on the pmd until the 1396 * split is complete for this pmd), then we flush the 1397 * SMP TLB and finally we write the non-huge version 1398 * of the pmd entry with pmd_populate. 1399 */ 1400 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd)); 1401 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE); 1402 pmd_populate(mm, pmd, pgtable); 1403 ret = 1; 1404 } 1405 spin_unlock(&mm->page_table_lock); 1406 1407 return ret; 1408 } 1409 1410 /* must be called with anon_vma->root->mutex hold */ 1411 static void __split_huge_page(struct page *page, 1412 struct anon_vma *anon_vma) 1413 { 1414 int mapcount, mapcount2; 1415 struct anon_vma_chain *avc; 1416 1417 BUG_ON(!PageHead(page)); 1418 BUG_ON(PageTail(page)); 1419 1420 mapcount = 0; 1421 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { 1422 struct vm_area_struct *vma = avc->vma; 1423 unsigned long addr = vma_address(page, vma); 1424 BUG_ON(is_vma_temporary_stack(vma)); 1425 if (addr == -EFAULT) 1426 continue; 1427 mapcount += __split_huge_page_splitting(page, vma, addr); 1428 } 1429 /* 1430 * It is critical that new vmas are added to the tail of the 1431 * anon_vma list. This guarantes that if copy_huge_pmd() runs 1432 * and establishes a child pmd before 1433 * __split_huge_page_splitting() freezes the parent pmd (so if 1434 * we fail to prevent copy_huge_pmd() from running until the 1435 * whole __split_huge_page() is complete), we will still see 1436 * the newly established pmd of the child later during the 1437 * walk, to be able to set it as pmd_trans_splitting too. 1438 */ 1439 if (mapcount != page_mapcount(page)) 1440 printk(KERN_ERR "mapcount %d page_mapcount %d\n", 1441 mapcount, page_mapcount(page)); 1442 BUG_ON(mapcount != page_mapcount(page)); 1443 1444 __split_huge_page_refcount(page); 1445 1446 mapcount2 = 0; 1447 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { 1448 struct vm_area_struct *vma = avc->vma; 1449 unsigned long addr = vma_address(page, vma); 1450 BUG_ON(is_vma_temporary_stack(vma)); 1451 if (addr == -EFAULT) 1452 continue; 1453 mapcount2 += __split_huge_page_map(page, vma, addr); 1454 } 1455 if (mapcount != mapcount2) 1456 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n", 1457 mapcount, mapcount2, page_mapcount(page)); 1458 BUG_ON(mapcount != mapcount2); 1459 } 1460 1461 int split_huge_page(struct page *page) 1462 { 1463 struct anon_vma *anon_vma; 1464 int ret = 1; 1465 1466 BUG_ON(!PageAnon(page)); 1467 anon_vma = page_lock_anon_vma(page); 1468 if (!anon_vma) 1469 goto out; 1470 ret = 0; 1471 if (!PageCompound(page)) 1472 goto out_unlock; 1473 1474 BUG_ON(!PageSwapBacked(page)); 1475 __split_huge_page(page, anon_vma); 1476 count_vm_event(THP_SPLIT); 1477 1478 BUG_ON(PageCompound(page)); 1479 out_unlock: 1480 page_unlock_anon_vma(anon_vma); 1481 out: 1482 return ret; 1483 } 1484 1485 #define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \ 1486 VM_HUGETLB|VM_SHARED|VM_MAYSHARE) 1487 1488 int hugepage_madvise(struct vm_area_struct *vma, 1489 unsigned long *vm_flags, int advice) 1490 { 1491 switch (advice) { 1492 case MADV_HUGEPAGE: 1493 /* 1494 * Be somewhat over-protective like KSM for now! 1495 */ 1496 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) 1497 return -EINVAL; 1498 *vm_flags &= ~VM_NOHUGEPAGE; 1499 *vm_flags |= VM_HUGEPAGE; 1500 /* 1501 * If the vma become good for khugepaged to scan, 1502 * register it here without waiting a page fault that 1503 * may not happen any time soon. 1504 */ 1505 if (unlikely(khugepaged_enter_vma_merge(vma))) 1506 return -ENOMEM; 1507 break; 1508 case MADV_NOHUGEPAGE: 1509 /* 1510 * Be somewhat over-protective like KSM for now! 1511 */ 1512 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) 1513 return -EINVAL; 1514 *vm_flags &= ~VM_HUGEPAGE; 1515 *vm_flags |= VM_NOHUGEPAGE; 1516 /* 1517 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1518 * this vma even if we leave the mm registered in khugepaged if 1519 * it got registered before VM_NOHUGEPAGE was set. 1520 */ 1521 break; 1522 } 1523 1524 return 0; 1525 } 1526 1527 static int __init khugepaged_slab_init(void) 1528 { 1529 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1530 sizeof(struct mm_slot), 1531 __alignof__(struct mm_slot), 0, NULL); 1532 if (!mm_slot_cache) 1533 return -ENOMEM; 1534 1535 return 0; 1536 } 1537 1538 static void __init khugepaged_slab_free(void) 1539 { 1540 kmem_cache_destroy(mm_slot_cache); 1541 mm_slot_cache = NULL; 1542 } 1543 1544 static inline struct mm_slot *alloc_mm_slot(void) 1545 { 1546 if (!mm_slot_cache) /* initialization failed */ 1547 return NULL; 1548 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 1549 } 1550 1551 static inline void free_mm_slot(struct mm_slot *mm_slot) 1552 { 1553 kmem_cache_free(mm_slot_cache, mm_slot); 1554 } 1555 1556 static int __init mm_slots_hash_init(void) 1557 { 1558 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), 1559 GFP_KERNEL); 1560 if (!mm_slots_hash) 1561 return -ENOMEM; 1562 return 0; 1563 } 1564 1565 #if 0 1566 static void __init mm_slots_hash_free(void) 1567 { 1568 kfree(mm_slots_hash); 1569 mm_slots_hash = NULL; 1570 } 1571 #endif 1572 1573 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 1574 { 1575 struct mm_slot *mm_slot; 1576 struct hlist_head *bucket; 1577 struct hlist_node *node; 1578 1579 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1580 % MM_SLOTS_HASH_HEADS]; 1581 hlist_for_each_entry(mm_slot, node, bucket, hash) { 1582 if (mm == mm_slot->mm) 1583 return mm_slot; 1584 } 1585 return NULL; 1586 } 1587 1588 static void insert_to_mm_slots_hash(struct mm_struct *mm, 1589 struct mm_slot *mm_slot) 1590 { 1591 struct hlist_head *bucket; 1592 1593 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1594 % MM_SLOTS_HASH_HEADS]; 1595 mm_slot->mm = mm; 1596 hlist_add_head(&mm_slot->hash, bucket); 1597 } 1598 1599 static inline int khugepaged_test_exit(struct mm_struct *mm) 1600 { 1601 return atomic_read(&mm->mm_users) == 0; 1602 } 1603 1604 int __khugepaged_enter(struct mm_struct *mm) 1605 { 1606 struct mm_slot *mm_slot; 1607 int wakeup; 1608 1609 mm_slot = alloc_mm_slot(); 1610 if (!mm_slot) 1611 return -ENOMEM; 1612 1613 /* __khugepaged_exit() must not run from under us */ 1614 VM_BUG_ON(khugepaged_test_exit(mm)); 1615 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 1616 free_mm_slot(mm_slot); 1617 return 0; 1618 } 1619 1620 spin_lock(&khugepaged_mm_lock); 1621 insert_to_mm_slots_hash(mm, mm_slot); 1622 /* 1623 * Insert just behind the scanning cursor, to let the area settle 1624 * down a little. 1625 */ 1626 wakeup = list_empty(&khugepaged_scan.mm_head); 1627 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 1628 spin_unlock(&khugepaged_mm_lock); 1629 1630 atomic_inc(&mm->mm_count); 1631 if (wakeup) 1632 wake_up_interruptible(&khugepaged_wait); 1633 1634 return 0; 1635 } 1636 1637 int khugepaged_enter_vma_merge(struct vm_area_struct *vma) 1638 { 1639 unsigned long hstart, hend; 1640 if (!vma->anon_vma) 1641 /* 1642 * Not yet faulted in so we will register later in the 1643 * page fault if needed. 1644 */ 1645 return 0; 1646 if (vma->vm_ops) 1647 /* khugepaged not yet working on file or special mappings */ 1648 return 0; 1649 /* 1650 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be 1651 * true too, verify it here. 1652 */ 1653 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP); 1654 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1655 hend = vma->vm_end & HPAGE_PMD_MASK; 1656 if (hstart < hend) 1657 return khugepaged_enter(vma); 1658 return 0; 1659 } 1660 1661 void __khugepaged_exit(struct mm_struct *mm) 1662 { 1663 struct mm_slot *mm_slot; 1664 int free = 0; 1665 1666 spin_lock(&khugepaged_mm_lock); 1667 mm_slot = get_mm_slot(mm); 1668 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 1669 hlist_del(&mm_slot->hash); 1670 list_del(&mm_slot->mm_node); 1671 free = 1; 1672 } 1673 spin_unlock(&khugepaged_mm_lock); 1674 1675 if (free) { 1676 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1677 free_mm_slot(mm_slot); 1678 mmdrop(mm); 1679 } else if (mm_slot) { 1680 /* 1681 * This is required to serialize against 1682 * khugepaged_test_exit() (which is guaranteed to run 1683 * under mmap sem read mode). Stop here (after we 1684 * return all pagetables will be destroyed) until 1685 * khugepaged has finished working on the pagetables 1686 * under the mmap_sem. 1687 */ 1688 down_write(&mm->mmap_sem); 1689 up_write(&mm->mmap_sem); 1690 } 1691 } 1692 1693 static void release_pte_page(struct page *page) 1694 { 1695 /* 0 stands for page_is_file_cache(page) == false */ 1696 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 1697 unlock_page(page); 1698 putback_lru_page(page); 1699 } 1700 1701 static void release_pte_pages(pte_t *pte, pte_t *_pte) 1702 { 1703 while (--_pte >= pte) { 1704 pte_t pteval = *_pte; 1705 if (!pte_none(pteval)) 1706 release_pte_page(pte_page(pteval)); 1707 } 1708 } 1709 1710 static void release_all_pte_pages(pte_t *pte) 1711 { 1712 release_pte_pages(pte, pte + HPAGE_PMD_NR); 1713 } 1714 1715 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 1716 unsigned long address, 1717 pte_t *pte) 1718 { 1719 struct page *page; 1720 pte_t *_pte; 1721 int referenced = 0, isolated = 0, none = 0; 1722 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 1723 _pte++, address += PAGE_SIZE) { 1724 pte_t pteval = *_pte; 1725 if (pte_none(pteval)) { 1726 if (++none <= khugepaged_max_ptes_none) 1727 continue; 1728 else { 1729 release_pte_pages(pte, _pte); 1730 goto out; 1731 } 1732 } 1733 if (!pte_present(pteval) || !pte_write(pteval)) { 1734 release_pte_pages(pte, _pte); 1735 goto out; 1736 } 1737 page = vm_normal_page(vma, address, pteval); 1738 if (unlikely(!page)) { 1739 release_pte_pages(pte, _pte); 1740 goto out; 1741 } 1742 VM_BUG_ON(PageCompound(page)); 1743 BUG_ON(!PageAnon(page)); 1744 VM_BUG_ON(!PageSwapBacked(page)); 1745 1746 /* cannot use mapcount: can't collapse if there's a gup pin */ 1747 if (page_count(page) != 1) { 1748 release_pte_pages(pte, _pte); 1749 goto out; 1750 } 1751 /* 1752 * We can do it before isolate_lru_page because the 1753 * page can't be freed from under us. NOTE: PG_lock 1754 * is needed to serialize against split_huge_page 1755 * when invoked from the VM. 1756 */ 1757 if (!trylock_page(page)) { 1758 release_pte_pages(pte, _pte); 1759 goto out; 1760 } 1761 /* 1762 * Isolate the page to avoid collapsing an hugepage 1763 * currently in use by the VM. 1764 */ 1765 if (isolate_lru_page(page)) { 1766 unlock_page(page); 1767 release_pte_pages(pte, _pte); 1768 goto out; 1769 } 1770 /* 0 stands for page_is_file_cache(page) == false */ 1771 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 1772 VM_BUG_ON(!PageLocked(page)); 1773 VM_BUG_ON(PageLRU(page)); 1774 1775 /* If there is no mapped pte young don't collapse the page */ 1776 if (pte_young(pteval) || PageReferenced(page) || 1777 mmu_notifier_test_young(vma->vm_mm, address)) 1778 referenced = 1; 1779 } 1780 if (unlikely(!referenced)) 1781 release_all_pte_pages(pte); 1782 else 1783 isolated = 1; 1784 out: 1785 return isolated; 1786 } 1787 1788 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 1789 struct vm_area_struct *vma, 1790 unsigned long address, 1791 spinlock_t *ptl) 1792 { 1793 pte_t *_pte; 1794 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 1795 pte_t pteval = *_pte; 1796 struct page *src_page; 1797 1798 if (pte_none(pteval)) { 1799 clear_user_highpage(page, address); 1800 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 1801 } else { 1802 src_page = pte_page(pteval); 1803 copy_user_highpage(page, src_page, address, vma); 1804 VM_BUG_ON(page_mapcount(src_page) != 1); 1805 VM_BUG_ON(page_count(src_page) != 2); 1806 release_pte_page(src_page); 1807 /* 1808 * ptl mostly unnecessary, but preempt has to 1809 * be disabled to update the per-cpu stats 1810 * inside page_remove_rmap(). 1811 */ 1812 spin_lock(ptl); 1813 /* 1814 * paravirt calls inside pte_clear here are 1815 * superfluous. 1816 */ 1817 pte_clear(vma->vm_mm, address, _pte); 1818 page_remove_rmap(src_page); 1819 spin_unlock(ptl); 1820 free_page_and_swap_cache(src_page); 1821 } 1822 1823 address += PAGE_SIZE; 1824 page++; 1825 } 1826 } 1827 1828 static void collapse_huge_page(struct mm_struct *mm, 1829 unsigned long address, 1830 struct page **hpage, 1831 struct vm_area_struct *vma, 1832 int node) 1833 { 1834 pgd_t *pgd; 1835 pud_t *pud; 1836 pmd_t *pmd, _pmd; 1837 pte_t *pte; 1838 pgtable_t pgtable; 1839 struct page *new_page; 1840 spinlock_t *ptl; 1841 int isolated; 1842 unsigned long hstart, hend; 1843 1844 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1845 #ifndef CONFIG_NUMA 1846 up_read(&mm->mmap_sem); 1847 VM_BUG_ON(!*hpage); 1848 new_page = *hpage; 1849 #else 1850 VM_BUG_ON(*hpage); 1851 /* 1852 * Allocate the page while the vma is still valid and under 1853 * the mmap_sem read mode so there is no memory allocation 1854 * later when we take the mmap_sem in write mode. This is more 1855 * friendly behavior (OTOH it may actually hide bugs) to 1856 * filesystems in userland with daemons allocating memory in 1857 * the userland I/O paths. Allocating memory with the 1858 * mmap_sem in read mode is good idea also to allow greater 1859 * scalability. 1860 */ 1861 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address, 1862 node, __GFP_OTHER_NODE); 1863 1864 /* 1865 * After allocating the hugepage, release the mmap_sem read lock in 1866 * preparation for taking it in write mode. 1867 */ 1868 up_read(&mm->mmap_sem); 1869 if (unlikely(!new_page)) { 1870 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 1871 *hpage = ERR_PTR(-ENOMEM); 1872 return; 1873 } 1874 #endif 1875 1876 count_vm_event(THP_COLLAPSE_ALLOC); 1877 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 1878 #ifdef CONFIG_NUMA 1879 put_page(new_page); 1880 #endif 1881 return; 1882 } 1883 1884 /* 1885 * Prevent all access to pagetables with the exception of 1886 * gup_fast later hanlded by the ptep_clear_flush and the VM 1887 * handled by the anon_vma lock + PG_lock. 1888 */ 1889 down_write(&mm->mmap_sem); 1890 if (unlikely(khugepaged_test_exit(mm))) 1891 goto out; 1892 1893 vma = find_vma(mm, address); 1894 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1895 hend = vma->vm_end & HPAGE_PMD_MASK; 1896 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 1897 goto out; 1898 1899 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 1900 (vma->vm_flags & VM_NOHUGEPAGE)) 1901 goto out; 1902 1903 if (!vma->anon_vma || vma->vm_ops) 1904 goto out; 1905 if (is_vma_temporary_stack(vma)) 1906 goto out; 1907 /* 1908 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be 1909 * true too, verify it here. 1910 */ 1911 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP); 1912 1913 pgd = pgd_offset(mm, address); 1914 if (!pgd_present(*pgd)) 1915 goto out; 1916 1917 pud = pud_offset(pgd, address); 1918 if (!pud_present(*pud)) 1919 goto out; 1920 1921 pmd = pmd_offset(pud, address); 1922 /* pmd can't go away or become huge under us */ 1923 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd)) 1924 goto out; 1925 1926 anon_vma_lock(vma->anon_vma); 1927 1928 pte = pte_offset_map(pmd, address); 1929 ptl = pte_lockptr(mm, pmd); 1930 1931 spin_lock(&mm->page_table_lock); /* probably unnecessary */ 1932 /* 1933 * After this gup_fast can't run anymore. This also removes 1934 * any huge TLB entry from the CPU so we won't allow 1935 * huge and small TLB entries for the same virtual address 1936 * to avoid the risk of CPU bugs in that area. 1937 */ 1938 _pmd = pmdp_clear_flush_notify(vma, address, pmd); 1939 spin_unlock(&mm->page_table_lock); 1940 1941 spin_lock(ptl); 1942 isolated = __collapse_huge_page_isolate(vma, address, pte); 1943 spin_unlock(ptl); 1944 1945 if (unlikely(!isolated)) { 1946 pte_unmap(pte); 1947 spin_lock(&mm->page_table_lock); 1948 BUG_ON(!pmd_none(*pmd)); 1949 set_pmd_at(mm, address, pmd, _pmd); 1950 spin_unlock(&mm->page_table_lock); 1951 anon_vma_unlock(vma->anon_vma); 1952 goto out; 1953 } 1954 1955 /* 1956 * All pages are isolated and locked so anon_vma rmap 1957 * can't run anymore. 1958 */ 1959 anon_vma_unlock(vma->anon_vma); 1960 1961 __collapse_huge_page_copy(pte, new_page, vma, address, ptl); 1962 pte_unmap(pte); 1963 __SetPageUptodate(new_page); 1964 pgtable = pmd_pgtable(_pmd); 1965 VM_BUG_ON(page_count(pgtable) != 1); 1966 VM_BUG_ON(page_mapcount(pgtable) != 0); 1967 1968 _pmd = mk_pmd(new_page, vma->vm_page_prot); 1969 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 1970 _pmd = pmd_mkhuge(_pmd); 1971 1972 /* 1973 * spin_lock() below is not the equivalent of smp_wmb(), so 1974 * this is needed to avoid the copy_huge_page writes to become 1975 * visible after the set_pmd_at() write. 1976 */ 1977 smp_wmb(); 1978 1979 spin_lock(&mm->page_table_lock); 1980 BUG_ON(!pmd_none(*pmd)); 1981 page_add_new_anon_rmap(new_page, vma, address); 1982 set_pmd_at(mm, address, pmd, _pmd); 1983 update_mmu_cache(vma, address, _pmd); 1984 prepare_pmd_huge_pte(pgtable, mm); 1985 spin_unlock(&mm->page_table_lock); 1986 1987 #ifndef CONFIG_NUMA 1988 *hpage = NULL; 1989 #endif 1990 khugepaged_pages_collapsed++; 1991 out_up_write: 1992 up_write(&mm->mmap_sem); 1993 return; 1994 1995 out: 1996 mem_cgroup_uncharge_page(new_page); 1997 #ifdef CONFIG_NUMA 1998 put_page(new_page); 1999 #endif 2000 goto out_up_write; 2001 } 2002 2003 static int khugepaged_scan_pmd(struct mm_struct *mm, 2004 struct vm_area_struct *vma, 2005 unsigned long address, 2006 struct page **hpage) 2007 { 2008 pgd_t *pgd; 2009 pud_t *pud; 2010 pmd_t *pmd; 2011 pte_t *pte, *_pte; 2012 int ret = 0, referenced = 0, none = 0; 2013 struct page *page; 2014 unsigned long _address; 2015 spinlock_t *ptl; 2016 int node = -1; 2017 2018 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2019 2020 pgd = pgd_offset(mm, address); 2021 if (!pgd_present(*pgd)) 2022 goto out; 2023 2024 pud = pud_offset(pgd, address); 2025 if (!pud_present(*pud)) 2026 goto out; 2027 2028 pmd = pmd_offset(pud, address); 2029 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd)) 2030 goto out; 2031 2032 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2033 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2034 _pte++, _address += PAGE_SIZE) { 2035 pte_t pteval = *_pte; 2036 if (pte_none(pteval)) { 2037 if (++none <= khugepaged_max_ptes_none) 2038 continue; 2039 else 2040 goto out_unmap; 2041 } 2042 if (!pte_present(pteval) || !pte_write(pteval)) 2043 goto out_unmap; 2044 page = vm_normal_page(vma, _address, pteval); 2045 if (unlikely(!page)) 2046 goto out_unmap; 2047 /* 2048 * Chose the node of the first page. This could 2049 * be more sophisticated and look at more pages, 2050 * but isn't for now. 2051 */ 2052 if (node == -1) 2053 node = page_to_nid(page); 2054 VM_BUG_ON(PageCompound(page)); 2055 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) 2056 goto out_unmap; 2057 /* cannot use mapcount: can't collapse if there's a gup pin */ 2058 if (page_count(page) != 1) 2059 goto out_unmap; 2060 if (pte_young(pteval) || PageReferenced(page) || 2061 mmu_notifier_test_young(vma->vm_mm, address)) 2062 referenced = 1; 2063 } 2064 if (referenced) 2065 ret = 1; 2066 out_unmap: 2067 pte_unmap_unlock(pte, ptl); 2068 if (ret) 2069 /* collapse_huge_page will return with the mmap_sem released */ 2070 collapse_huge_page(mm, address, hpage, vma, node); 2071 out: 2072 return ret; 2073 } 2074 2075 static void collect_mm_slot(struct mm_slot *mm_slot) 2076 { 2077 struct mm_struct *mm = mm_slot->mm; 2078 2079 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2080 2081 if (khugepaged_test_exit(mm)) { 2082 /* free mm_slot */ 2083 hlist_del(&mm_slot->hash); 2084 list_del(&mm_slot->mm_node); 2085 2086 /* 2087 * Not strictly needed because the mm exited already. 2088 * 2089 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2090 */ 2091 2092 /* khugepaged_mm_lock actually not necessary for the below */ 2093 free_mm_slot(mm_slot); 2094 mmdrop(mm); 2095 } 2096 } 2097 2098 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2099 struct page **hpage) 2100 __releases(&khugepaged_mm_lock) 2101 __acquires(&khugepaged_mm_lock) 2102 { 2103 struct mm_slot *mm_slot; 2104 struct mm_struct *mm; 2105 struct vm_area_struct *vma; 2106 int progress = 0; 2107 2108 VM_BUG_ON(!pages); 2109 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2110 2111 if (khugepaged_scan.mm_slot) 2112 mm_slot = khugepaged_scan.mm_slot; 2113 else { 2114 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2115 struct mm_slot, mm_node); 2116 khugepaged_scan.address = 0; 2117 khugepaged_scan.mm_slot = mm_slot; 2118 } 2119 spin_unlock(&khugepaged_mm_lock); 2120 2121 mm = mm_slot->mm; 2122 down_read(&mm->mmap_sem); 2123 if (unlikely(khugepaged_test_exit(mm))) 2124 vma = NULL; 2125 else 2126 vma = find_vma(mm, khugepaged_scan.address); 2127 2128 progress++; 2129 for (; vma; vma = vma->vm_next) { 2130 unsigned long hstart, hend; 2131 2132 cond_resched(); 2133 if (unlikely(khugepaged_test_exit(mm))) { 2134 progress++; 2135 break; 2136 } 2137 2138 if ((!(vma->vm_flags & VM_HUGEPAGE) && 2139 !khugepaged_always()) || 2140 (vma->vm_flags & VM_NOHUGEPAGE)) { 2141 skip: 2142 progress++; 2143 continue; 2144 } 2145 if (!vma->anon_vma || vma->vm_ops) 2146 goto skip; 2147 if (is_vma_temporary_stack(vma)) 2148 goto skip; 2149 /* 2150 * If is_pfn_mapping() is true is_learn_pfn_mapping() 2151 * must be true too, verify it here. 2152 */ 2153 VM_BUG_ON(is_linear_pfn_mapping(vma) || 2154 vma->vm_flags & VM_NO_THP); 2155 2156 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2157 hend = vma->vm_end & HPAGE_PMD_MASK; 2158 if (hstart >= hend) 2159 goto skip; 2160 if (khugepaged_scan.address > hend) 2161 goto skip; 2162 if (khugepaged_scan.address < hstart) 2163 khugepaged_scan.address = hstart; 2164 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2165 2166 while (khugepaged_scan.address < hend) { 2167 int ret; 2168 cond_resched(); 2169 if (unlikely(khugepaged_test_exit(mm))) 2170 goto breakouterloop; 2171 2172 VM_BUG_ON(khugepaged_scan.address < hstart || 2173 khugepaged_scan.address + HPAGE_PMD_SIZE > 2174 hend); 2175 ret = khugepaged_scan_pmd(mm, vma, 2176 khugepaged_scan.address, 2177 hpage); 2178 /* move to next address */ 2179 khugepaged_scan.address += HPAGE_PMD_SIZE; 2180 progress += HPAGE_PMD_NR; 2181 if (ret) 2182 /* we released mmap_sem so break loop */ 2183 goto breakouterloop_mmap_sem; 2184 if (progress >= pages) 2185 goto breakouterloop; 2186 } 2187 } 2188 breakouterloop: 2189 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2190 breakouterloop_mmap_sem: 2191 2192 spin_lock(&khugepaged_mm_lock); 2193 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2194 /* 2195 * Release the current mm_slot if this mm is about to die, or 2196 * if we scanned all vmas of this mm. 2197 */ 2198 if (khugepaged_test_exit(mm) || !vma) { 2199 /* 2200 * Make sure that if mm_users is reaching zero while 2201 * khugepaged runs here, khugepaged_exit will find 2202 * mm_slot not pointing to the exiting mm. 2203 */ 2204 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2205 khugepaged_scan.mm_slot = list_entry( 2206 mm_slot->mm_node.next, 2207 struct mm_slot, mm_node); 2208 khugepaged_scan.address = 0; 2209 } else { 2210 khugepaged_scan.mm_slot = NULL; 2211 khugepaged_full_scans++; 2212 } 2213 2214 collect_mm_slot(mm_slot); 2215 } 2216 2217 return progress; 2218 } 2219 2220 static int khugepaged_has_work(void) 2221 { 2222 return !list_empty(&khugepaged_scan.mm_head) && 2223 khugepaged_enabled(); 2224 } 2225 2226 static int khugepaged_wait_event(void) 2227 { 2228 return !list_empty(&khugepaged_scan.mm_head) || 2229 !khugepaged_enabled(); 2230 } 2231 2232 static void khugepaged_do_scan(struct page **hpage) 2233 { 2234 unsigned int progress = 0, pass_through_head = 0; 2235 unsigned int pages = khugepaged_pages_to_scan; 2236 2237 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2238 2239 while (progress < pages) { 2240 cond_resched(); 2241 2242 #ifndef CONFIG_NUMA 2243 if (!*hpage) { 2244 *hpage = alloc_hugepage(khugepaged_defrag()); 2245 if (unlikely(!*hpage)) { 2246 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2247 break; 2248 } 2249 count_vm_event(THP_COLLAPSE_ALLOC); 2250 } 2251 #else 2252 if (IS_ERR(*hpage)) 2253 break; 2254 #endif 2255 2256 if (unlikely(kthread_should_stop() || freezing(current))) 2257 break; 2258 2259 spin_lock(&khugepaged_mm_lock); 2260 if (!khugepaged_scan.mm_slot) 2261 pass_through_head++; 2262 if (khugepaged_has_work() && 2263 pass_through_head < 2) 2264 progress += khugepaged_scan_mm_slot(pages - progress, 2265 hpage); 2266 else 2267 progress = pages; 2268 spin_unlock(&khugepaged_mm_lock); 2269 } 2270 } 2271 2272 static void khugepaged_alloc_sleep(void) 2273 { 2274 wait_event_freezable_timeout(khugepaged_wait, false, 2275 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 2276 } 2277 2278 #ifndef CONFIG_NUMA 2279 static struct page *khugepaged_alloc_hugepage(void) 2280 { 2281 struct page *hpage; 2282 2283 do { 2284 hpage = alloc_hugepage(khugepaged_defrag()); 2285 if (!hpage) { 2286 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2287 khugepaged_alloc_sleep(); 2288 } else 2289 count_vm_event(THP_COLLAPSE_ALLOC); 2290 } while (unlikely(!hpage) && 2291 likely(khugepaged_enabled())); 2292 return hpage; 2293 } 2294 #endif 2295 2296 static void khugepaged_loop(void) 2297 { 2298 struct page *hpage; 2299 2300 #ifdef CONFIG_NUMA 2301 hpage = NULL; 2302 #endif 2303 while (likely(khugepaged_enabled())) { 2304 #ifndef CONFIG_NUMA 2305 hpage = khugepaged_alloc_hugepage(); 2306 if (unlikely(!hpage)) 2307 break; 2308 #else 2309 if (IS_ERR(hpage)) { 2310 khugepaged_alloc_sleep(); 2311 hpage = NULL; 2312 } 2313 #endif 2314 2315 khugepaged_do_scan(&hpage); 2316 #ifndef CONFIG_NUMA 2317 if (hpage) 2318 put_page(hpage); 2319 #endif 2320 try_to_freeze(); 2321 if (unlikely(kthread_should_stop())) 2322 break; 2323 if (khugepaged_has_work()) { 2324 if (!khugepaged_scan_sleep_millisecs) 2325 continue; 2326 wait_event_freezable_timeout(khugepaged_wait, false, 2327 msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); 2328 } else if (khugepaged_enabled()) 2329 wait_event_freezable(khugepaged_wait, 2330 khugepaged_wait_event()); 2331 } 2332 } 2333 2334 static int khugepaged(void *none) 2335 { 2336 struct mm_slot *mm_slot; 2337 2338 set_freezable(); 2339 set_user_nice(current, 19); 2340 2341 /* serialize with start_khugepaged() */ 2342 mutex_lock(&khugepaged_mutex); 2343 2344 for (;;) { 2345 mutex_unlock(&khugepaged_mutex); 2346 VM_BUG_ON(khugepaged_thread != current); 2347 khugepaged_loop(); 2348 VM_BUG_ON(khugepaged_thread != current); 2349 2350 mutex_lock(&khugepaged_mutex); 2351 if (!khugepaged_enabled()) 2352 break; 2353 if (unlikely(kthread_should_stop())) 2354 break; 2355 } 2356 2357 spin_lock(&khugepaged_mm_lock); 2358 mm_slot = khugepaged_scan.mm_slot; 2359 khugepaged_scan.mm_slot = NULL; 2360 if (mm_slot) 2361 collect_mm_slot(mm_slot); 2362 spin_unlock(&khugepaged_mm_lock); 2363 2364 khugepaged_thread = NULL; 2365 mutex_unlock(&khugepaged_mutex); 2366 2367 return 0; 2368 } 2369 2370 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd) 2371 { 2372 struct page *page; 2373 2374 spin_lock(&mm->page_table_lock); 2375 if (unlikely(!pmd_trans_huge(*pmd))) { 2376 spin_unlock(&mm->page_table_lock); 2377 return; 2378 } 2379 page = pmd_page(*pmd); 2380 VM_BUG_ON(!page_count(page)); 2381 get_page(page); 2382 spin_unlock(&mm->page_table_lock); 2383 2384 split_huge_page(page); 2385 2386 put_page(page); 2387 BUG_ON(pmd_trans_huge(*pmd)); 2388 } 2389 2390 static void split_huge_page_address(struct mm_struct *mm, 2391 unsigned long address) 2392 { 2393 pgd_t *pgd; 2394 pud_t *pud; 2395 pmd_t *pmd; 2396 2397 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); 2398 2399 pgd = pgd_offset(mm, address); 2400 if (!pgd_present(*pgd)) 2401 return; 2402 2403 pud = pud_offset(pgd, address); 2404 if (!pud_present(*pud)) 2405 return; 2406 2407 pmd = pmd_offset(pud, address); 2408 if (!pmd_present(*pmd)) 2409 return; 2410 /* 2411 * Caller holds the mmap_sem write mode, so a huge pmd cannot 2412 * materialize from under us. 2413 */ 2414 split_huge_page_pmd(mm, pmd); 2415 } 2416 2417 void __vma_adjust_trans_huge(struct vm_area_struct *vma, 2418 unsigned long start, 2419 unsigned long end, 2420 long adjust_next) 2421 { 2422 /* 2423 * If the new start address isn't hpage aligned and it could 2424 * previously contain an hugepage: check if we need to split 2425 * an huge pmd. 2426 */ 2427 if (start & ~HPAGE_PMD_MASK && 2428 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2429 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2430 split_huge_page_address(vma->vm_mm, start); 2431 2432 /* 2433 * If the new end address isn't hpage aligned and it could 2434 * previously contain an hugepage: check if we need to split 2435 * an huge pmd. 2436 */ 2437 if (end & ~HPAGE_PMD_MASK && 2438 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2439 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2440 split_huge_page_address(vma->vm_mm, end); 2441 2442 /* 2443 * If we're also updating the vma->vm_next->vm_start, if the new 2444 * vm_next->vm_start isn't page aligned and it could previously 2445 * contain an hugepage: check if we need to split an huge pmd. 2446 */ 2447 if (adjust_next > 0) { 2448 struct vm_area_struct *next = vma->vm_next; 2449 unsigned long nstart = next->vm_start; 2450 nstart += adjust_next << PAGE_SHIFT; 2451 if (nstart & ~HPAGE_PMD_MASK && 2452 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2453 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2454 split_huge_page_address(next->vm_mm, nstart); 2455 } 2456 } 2457