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 pgtable_t pgtable; 640 641 VM_BUG_ON(!PageCompound(page)); 642 pgtable = pte_alloc_one(mm, haddr); 643 if (unlikely(!pgtable)) 644 return VM_FAULT_OOM; 645 646 clear_huge_page(page, haddr, HPAGE_PMD_NR); 647 __SetPageUptodate(page); 648 649 spin_lock(&mm->page_table_lock); 650 if (unlikely(!pmd_none(*pmd))) { 651 spin_unlock(&mm->page_table_lock); 652 mem_cgroup_uncharge_page(page); 653 put_page(page); 654 pte_free(mm, pgtable); 655 } else { 656 pmd_t entry; 657 entry = mk_pmd(page, vma->vm_page_prot); 658 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 659 entry = pmd_mkhuge(entry); 660 /* 661 * The spinlocking to take the lru_lock inside 662 * page_add_new_anon_rmap() acts as a full memory 663 * barrier to be sure clear_huge_page writes become 664 * visible after the set_pmd_at() write. 665 */ 666 page_add_new_anon_rmap(page, vma, haddr); 667 set_pmd_at(mm, haddr, pmd, entry); 668 prepare_pmd_huge_pte(pgtable, mm); 669 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 670 mm->nr_ptes++; 671 spin_unlock(&mm->page_table_lock); 672 } 673 674 return 0; 675 } 676 677 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) 678 { 679 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; 680 } 681 682 static inline struct page *alloc_hugepage_vma(int defrag, 683 struct vm_area_struct *vma, 684 unsigned long haddr, int nd, 685 gfp_t extra_gfp) 686 { 687 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp), 688 HPAGE_PMD_ORDER, vma, haddr, nd); 689 } 690 691 #ifndef CONFIG_NUMA 692 static inline struct page *alloc_hugepage(int defrag) 693 { 694 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), 695 HPAGE_PMD_ORDER); 696 } 697 #endif 698 699 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 700 unsigned long address, pmd_t *pmd, 701 unsigned int flags) 702 { 703 struct page *page; 704 unsigned long haddr = address & HPAGE_PMD_MASK; 705 pte_t *pte; 706 707 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) { 708 if (unlikely(anon_vma_prepare(vma))) 709 return VM_FAULT_OOM; 710 if (unlikely(khugepaged_enter(vma))) 711 return VM_FAULT_OOM; 712 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 713 vma, haddr, numa_node_id(), 0); 714 if (unlikely(!page)) { 715 count_vm_event(THP_FAULT_FALLBACK); 716 goto out; 717 } 718 count_vm_event(THP_FAULT_ALLOC); 719 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) { 720 put_page(page); 721 goto out; 722 } 723 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, 724 page))) { 725 mem_cgroup_uncharge_page(page); 726 put_page(page); 727 goto out; 728 } 729 730 return 0; 731 } 732 out: 733 /* 734 * Use __pte_alloc instead of pte_alloc_map, because we can't 735 * run pte_offset_map on the pmd, if an huge pmd could 736 * materialize from under us from a different thread. 737 */ 738 if (unlikely(__pte_alloc(mm, vma, pmd, address))) 739 return VM_FAULT_OOM; 740 /* if an huge pmd materialized from under us just retry later */ 741 if (unlikely(pmd_trans_huge(*pmd))) 742 return 0; 743 /* 744 * A regular pmd is established and it can't morph into a huge pmd 745 * from under us anymore at this point because we hold the mmap_sem 746 * read mode and khugepaged takes it in write mode. So now it's 747 * safe to run pte_offset_map(). 748 */ 749 pte = pte_offset_map(pmd, address); 750 return handle_pte_fault(mm, vma, address, pte, pmd, flags); 751 } 752 753 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 754 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 755 struct vm_area_struct *vma) 756 { 757 struct page *src_page; 758 pmd_t pmd; 759 pgtable_t pgtable; 760 int ret; 761 762 ret = -ENOMEM; 763 pgtable = pte_alloc_one(dst_mm, addr); 764 if (unlikely(!pgtable)) 765 goto out; 766 767 spin_lock(&dst_mm->page_table_lock); 768 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING); 769 770 ret = -EAGAIN; 771 pmd = *src_pmd; 772 if (unlikely(!pmd_trans_huge(pmd))) { 773 pte_free(dst_mm, pgtable); 774 goto out_unlock; 775 } 776 if (unlikely(pmd_trans_splitting(pmd))) { 777 /* split huge page running from under us */ 778 spin_unlock(&src_mm->page_table_lock); 779 spin_unlock(&dst_mm->page_table_lock); 780 pte_free(dst_mm, pgtable); 781 782 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ 783 goto out; 784 } 785 src_page = pmd_page(pmd); 786 VM_BUG_ON(!PageHead(src_page)); 787 get_page(src_page); 788 page_dup_rmap(src_page); 789 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 790 791 pmdp_set_wrprotect(src_mm, addr, src_pmd); 792 pmd = pmd_mkold(pmd_wrprotect(pmd)); 793 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 794 prepare_pmd_huge_pte(pgtable, dst_mm); 795 dst_mm->nr_ptes++; 796 797 ret = 0; 798 out_unlock: 799 spin_unlock(&src_mm->page_table_lock); 800 spin_unlock(&dst_mm->page_table_lock); 801 out: 802 return ret; 803 } 804 805 /* no "address" argument so destroys page coloring of some arch */ 806 pgtable_t get_pmd_huge_pte(struct mm_struct *mm) 807 { 808 pgtable_t pgtable; 809 810 assert_spin_locked(&mm->page_table_lock); 811 812 /* FIFO */ 813 pgtable = mm->pmd_huge_pte; 814 if (list_empty(&pgtable->lru)) 815 mm->pmd_huge_pte = NULL; 816 else { 817 mm->pmd_huge_pte = list_entry(pgtable->lru.next, 818 struct page, lru); 819 list_del(&pgtable->lru); 820 } 821 return pgtable; 822 } 823 824 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, 825 struct vm_area_struct *vma, 826 unsigned long address, 827 pmd_t *pmd, pmd_t orig_pmd, 828 struct page *page, 829 unsigned long haddr) 830 { 831 pgtable_t pgtable; 832 pmd_t _pmd; 833 int ret = 0, i; 834 struct page **pages; 835 836 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 837 GFP_KERNEL); 838 if (unlikely(!pages)) { 839 ret |= VM_FAULT_OOM; 840 goto out; 841 } 842 843 for (i = 0; i < HPAGE_PMD_NR; i++) { 844 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | 845 __GFP_OTHER_NODE, 846 vma, address, page_to_nid(page)); 847 if (unlikely(!pages[i] || 848 mem_cgroup_newpage_charge(pages[i], mm, 849 GFP_KERNEL))) { 850 if (pages[i]) 851 put_page(pages[i]); 852 mem_cgroup_uncharge_start(); 853 while (--i >= 0) { 854 mem_cgroup_uncharge_page(pages[i]); 855 put_page(pages[i]); 856 } 857 mem_cgroup_uncharge_end(); 858 kfree(pages); 859 ret |= VM_FAULT_OOM; 860 goto out; 861 } 862 } 863 864 for (i = 0; i < HPAGE_PMD_NR; i++) { 865 copy_user_highpage(pages[i], page + i, 866 haddr + PAGE_SIZE * i, vma); 867 __SetPageUptodate(pages[i]); 868 cond_resched(); 869 } 870 871 spin_lock(&mm->page_table_lock); 872 if (unlikely(!pmd_same(*pmd, orig_pmd))) 873 goto out_free_pages; 874 VM_BUG_ON(!PageHead(page)); 875 876 pmdp_clear_flush_notify(vma, haddr, pmd); 877 /* leave pmd empty until pte is filled */ 878 879 pgtable = get_pmd_huge_pte(mm); 880 pmd_populate(mm, &_pmd, pgtable); 881 882 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 883 pte_t *pte, entry; 884 entry = mk_pte(pages[i], vma->vm_page_prot); 885 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 886 page_add_new_anon_rmap(pages[i], vma, haddr); 887 pte = pte_offset_map(&_pmd, haddr); 888 VM_BUG_ON(!pte_none(*pte)); 889 set_pte_at(mm, haddr, pte, entry); 890 pte_unmap(pte); 891 } 892 kfree(pages); 893 894 smp_wmb(); /* make pte visible before pmd */ 895 pmd_populate(mm, pmd, pgtable); 896 page_remove_rmap(page); 897 spin_unlock(&mm->page_table_lock); 898 899 ret |= VM_FAULT_WRITE; 900 put_page(page); 901 902 out: 903 return ret; 904 905 out_free_pages: 906 spin_unlock(&mm->page_table_lock); 907 mem_cgroup_uncharge_start(); 908 for (i = 0; i < HPAGE_PMD_NR; i++) { 909 mem_cgroup_uncharge_page(pages[i]); 910 put_page(pages[i]); 911 } 912 mem_cgroup_uncharge_end(); 913 kfree(pages); 914 goto out; 915 } 916 917 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 918 unsigned long address, pmd_t *pmd, pmd_t orig_pmd) 919 { 920 int ret = 0; 921 struct page *page, *new_page; 922 unsigned long haddr; 923 924 VM_BUG_ON(!vma->anon_vma); 925 spin_lock(&mm->page_table_lock); 926 if (unlikely(!pmd_same(*pmd, orig_pmd))) 927 goto out_unlock; 928 929 page = pmd_page(orig_pmd); 930 VM_BUG_ON(!PageCompound(page) || !PageHead(page)); 931 haddr = address & HPAGE_PMD_MASK; 932 if (page_mapcount(page) == 1) { 933 pmd_t entry; 934 entry = pmd_mkyoung(orig_pmd); 935 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 936 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 937 update_mmu_cache(vma, address, entry); 938 ret |= VM_FAULT_WRITE; 939 goto out_unlock; 940 } 941 get_page(page); 942 spin_unlock(&mm->page_table_lock); 943 944 if (transparent_hugepage_enabled(vma) && 945 !transparent_hugepage_debug_cow()) 946 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 947 vma, haddr, numa_node_id(), 0); 948 else 949 new_page = NULL; 950 951 if (unlikely(!new_page)) { 952 count_vm_event(THP_FAULT_FALLBACK); 953 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 954 pmd, orig_pmd, page, haddr); 955 if (ret & VM_FAULT_OOM) 956 split_huge_page(page); 957 put_page(page); 958 goto out; 959 } 960 count_vm_event(THP_FAULT_ALLOC); 961 962 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 963 put_page(new_page); 964 split_huge_page(page); 965 put_page(page); 966 ret |= VM_FAULT_OOM; 967 goto out; 968 } 969 970 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 971 __SetPageUptodate(new_page); 972 973 spin_lock(&mm->page_table_lock); 974 put_page(page); 975 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 976 spin_unlock(&mm->page_table_lock); 977 mem_cgroup_uncharge_page(new_page); 978 put_page(new_page); 979 goto out; 980 } else { 981 pmd_t entry; 982 VM_BUG_ON(!PageHead(page)); 983 entry = mk_pmd(new_page, vma->vm_page_prot); 984 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 985 entry = pmd_mkhuge(entry); 986 pmdp_clear_flush_notify(vma, haddr, pmd); 987 page_add_new_anon_rmap(new_page, vma, haddr); 988 set_pmd_at(mm, haddr, pmd, entry); 989 update_mmu_cache(vma, address, entry); 990 page_remove_rmap(page); 991 put_page(page); 992 ret |= VM_FAULT_WRITE; 993 } 994 out_unlock: 995 spin_unlock(&mm->page_table_lock); 996 out: 997 return ret; 998 } 999 1000 struct page *follow_trans_huge_pmd(struct mm_struct *mm, 1001 unsigned long addr, 1002 pmd_t *pmd, 1003 unsigned int flags) 1004 { 1005 struct page *page = NULL; 1006 1007 assert_spin_locked(&mm->page_table_lock); 1008 1009 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 1010 goto out; 1011 1012 page = pmd_page(*pmd); 1013 VM_BUG_ON(!PageHead(page)); 1014 if (flags & FOLL_TOUCH) { 1015 pmd_t _pmd; 1016 /* 1017 * We should set the dirty bit only for FOLL_WRITE but 1018 * for now the dirty bit in the pmd is meaningless. 1019 * And if the dirty bit will become meaningful and 1020 * we'll only set it with FOLL_WRITE, an atomic 1021 * set_bit will be required on the pmd to set the 1022 * young bit, instead of the current set_pmd_at. 1023 */ 1024 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 1025 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd); 1026 } 1027 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1028 VM_BUG_ON(!PageCompound(page)); 1029 if (flags & FOLL_GET) 1030 get_page_foll(page); 1031 1032 out: 1033 return page; 1034 } 1035 1036 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1037 pmd_t *pmd, unsigned long addr) 1038 { 1039 int ret = 0; 1040 1041 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1042 struct page *page; 1043 pgtable_t pgtable; 1044 pgtable = get_pmd_huge_pte(tlb->mm); 1045 page = pmd_page(*pmd); 1046 pmd_clear(pmd); 1047 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1048 page_remove_rmap(page); 1049 VM_BUG_ON(page_mapcount(page) < 0); 1050 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1051 VM_BUG_ON(!PageHead(page)); 1052 tlb->mm->nr_ptes--; 1053 spin_unlock(&tlb->mm->page_table_lock); 1054 tlb_remove_page(tlb, page); 1055 pte_free(tlb->mm, pgtable); 1056 ret = 1; 1057 } 1058 return ret; 1059 } 1060 1061 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1062 unsigned long addr, unsigned long end, 1063 unsigned char *vec) 1064 { 1065 int ret = 0; 1066 1067 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1068 /* 1069 * All logical pages in the range are present 1070 * if backed by a huge page. 1071 */ 1072 spin_unlock(&vma->vm_mm->page_table_lock); 1073 memset(vec, 1, (end - addr) >> PAGE_SHIFT); 1074 ret = 1; 1075 } 1076 1077 return ret; 1078 } 1079 1080 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, 1081 unsigned long old_addr, 1082 unsigned long new_addr, unsigned long old_end, 1083 pmd_t *old_pmd, pmd_t *new_pmd) 1084 { 1085 int ret = 0; 1086 pmd_t pmd; 1087 1088 struct mm_struct *mm = vma->vm_mm; 1089 1090 if ((old_addr & ~HPAGE_PMD_MASK) || 1091 (new_addr & ~HPAGE_PMD_MASK) || 1092 old_end - old_addr < HPAGE_PMD_SIZE || 1093 (new_vma->vm_flags & VM_NOHUGEPAGE)) 1094 goto out; 1095 1096 /* 1097 * The destination pmd shouldn't be established, free_pgtables() 1098 * should have release it. 1099 */ 1100 if (WARN_ON(!pmd_none(*new_pmd))) { 1101 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1102 goto out; 1103 } 1104 1105 ret = __pmd_trans_huge_lock(old_pmd, vma); 1106 if (ret == 1) { 1107 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); 1108 VM_BUG_ON(!pmd_none(*new_pmd)); 1109 set_pmd_at(mm, new_addr, new_pmd, pmd); 1110 spin_unlock(&mm->page_table_lock); 1111 } 1112 out: 1113 return ret; 1114 } 1115 1116 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1117 unsigned long addr, pgprot_t newprot) 1118 { 1119 struct mm_struct *mm = vma->vm_mm; 1120 int ret = 0; 1121 1122 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1123 pmd_t entry; 1124 entry = pmdp_get_and_clear(mm, addr, pmd); 1125 entry = pmd_modify(entry, newprot); 1126 set_pmd_at(mm, addr, pmd, entry); 1127 spin_unlock(&vma->vm_mm->page_table_lock); 1128 ret = 1; 1129 } 1130 1131 return ret; 1132 } 1133 1134 /* 1135 * Returns 1 if a given pmd maps a stable (not under splitting) thp. 1136 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise. 1137 * 1138 * Note that if it returns 1, this routine returns without unlocking page 1139 * table locks. So callers must unlock them. 1140 */ 1141 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) 1142 { 1143 spin_lock(&vma->vm_mm->page_table_lock); 1144 if (likely(pmd_trans_huge(*pmd))) { 1145 if (unlikely(pmd_trans_splitting(*pmd))) { 1146 spin_unlock(&vma->vm_mm->page_table_lock); 1147 wait_split_huge_page(vma->anon_vma, pmd); 1148 return -1; 1149 } else { 1150 /* Thp mapped by 'pmd' is stable, so we can 1151 * handle it as it is. */ 1152 return 1; 1153 } 1154 } 1155 spin_unlock(&vma->vm_mm->page_table_lock); 1156 return 0; 1157 } 1158 1159 pmd_t *page_check_address_pmd(struct page *page, 1160 struct mm_struct *mm, 1161 unsigned long address, 1162 enum page_check_address_pmd_flag flag) 1163 { 1164 pgd_t *pgd; 1165 pud_t *pud; 1166 pmd_t *pmd, *ret = NULL; 1167 1168 if (address & ~HPAGE_PMD_MASK) 1169 goto out; 1170 1171 pgd = pgd_offset(mm, address); 1172 if (!pgd_present(*pgd)) 1173 goto out; 1174 1175 pud = pud_offset(pgd, address); 1176 if (!pud_present(*pud)) 1177 goto out; 1178 1179 pmd = pmd_offset(pud, address); 1180 if (pmd_none(*pmd)) 1181 goto out; 1182 if (pmd_page(*pmd) != page) 1183 goto out; 1184 /* 1185 * split_vma() may create temporary aliased mappings. There is 1186 * no risk as long as all huge pmd are found and have their 1187 * splitting bit set before __split_huge_page_refcount 1188 * runs. Finding the same huge pmd more than once during the 1189 * same rmap walk is not a problem. 1190 */ 1191 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && 1192 pmd_trans_splitting(*pmd)) 1193 goto out; 1194 if (pmd_trans_huge(*pmd)) { 1195 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && 1196 !pmd_trans_splitting(*pmd)); 1197 ret = pmd; 1198 } 1199 out: 1200 return ret; 1201 } 1202 1203 static int __split_huge_page_splitting(struct page *page, 1204 struct vm_area_struct *vma, 1205 unsigned long address) 1206 { 1207 struct mm_struct *mm = vma->vm_mm; 1208 pmd_t *pmd; 1209 int ret = 0; 1210 1211 spin_lock(&mm->page_table_lock); 1212 pmd = page_check_address_pmd(page, mm, address, 1213 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG); 1214 if (pmd) { 1215 /* 1216 * We can't temporarily set the pmd to null in order 1217 * to split it, the pmd must remain marked huge at all 1218 * times or the VM won't take the pmd_trans_huge paths 1219 * and it won't wait on the anon_vma->root->mutex to 1220 * serialize against split_huge_page*. 1221 */ 1222 pmdp_splitting_flush_notify(vma, address, pmd); 1223 ret = 1; 1224 } 1225 spin_unlock(&mm->page_table_lock); 1226 1227 return ret; 1228 } 1229 1230 static void __split_huge_page_refcount(struct page *page) 1231 { 1232 int i; 1233 struct zone *zone = page_zone(page); 1234 struct lruvec *lruvec; 1235 int tail_count = 0; 1236 1237 /* prevent PageLRU to go away from under us, and freeze lru stats */ 1238 spin_lock_irq(&zone->lru_lock); 1239 lruvec = mem_cgroup_page_lruvec(page, zone); 1240 1241 compound_lock(page); 1242 /* complete memcg works before add pages to LRU */ 1243 mem_cgroup_split_huge_fixup(page); 1244 1245 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 1246 struct page *page_tail = page + i; 1247 1248 /* tail_page->_mapcount cannot change */ 1249 BUG_ON(page_mapcount(page_tail) < 0); 1250 tail_count += page_mapcount(page_tail); 1251 /* check for overflow */ 1252 BUG_ON(tail_count < 0); 1253 BUG_ON(atomic_read(&page_tail->_count) != 0); 1254 /* 1255 * tail_page->_count is zero and not changing from 1256 * under us. But get_page_unless_zero() may be running 1257 * from under us on the tail_page. If we used 1258 * atomic_set() below instead of atomic_add(), we 1259 * would then run atomic_set() concurrently with 1260 * get_page_unless_zero(), and atomic_set() is 1261 * implemented in C not using locked ops. spin_unlock 1262 * on x86 sometime uses locked ops because of PPro 1263 * errata 66, 92, so unless somebody can guarantee 1264 * atomic_set() here would be safe on all archs (and 1265 * not only on x86), it's safer to use atomic_add(). 1266 */ 1267 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, 1268 &page_tail->_count); 1269 1270 /* after clearing PageTail the gup refcount can be released */ 1271 smp_mb(); 1272 1273 /* 1274 * retain hwpoison flag of the poisoned tail page: 1275 * fix for the unsuitable process killed on Guest Machine(KVM) 1276 * by the memory-failure. 1277 */ 1278 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON; 1279 page_tail->flags |= (page->flags & 1280 ((1L << PG_referenced) | 1281 (1L << PG_swapbacked) | 1282 (1L << PG_mlocked) | 1283 (1L << PG_uptodate))); 1284 page_tail->flags |= (1L << PG_dirty); 1285 1286 /* clear PageTail before overwriting first_page */ 1287 smp_wmb(); 1288 1289 /* 1290 * __split_huge_page_splitting() already set the 1291 * splitting bit in all pmd that could map this 1292 * hugepage, that will ensure no CPU can alter the 1293 * mapcount on the head page. The mapcount is only 1294 * accounted in the head page and it has to be 1295 * transferred to all tail pages in the below code. So 1296 * for this code to be safe, the split the mapcount 1297 * can't change. But that doesn't mean userland can't 1298 * keep changing and reading the page contents while 1299 * we transfer the mapcount, so the pmd splitting 1300 * status is achieved setting a reserved bit in the 1301 * pmd, not by clearing the present bit. 1302 */ 1303 page_tail->_mapcount = page->_mapcount; 1304 1305 BUG_ON(page_tail->mapping); 1306 page_tail->mapping = page->mapping; 1307 1308 page_tail->index = page->index + i; 1309 1310 BUG_ON(!PageAnon(page_tail)); 1311 BUG_ON(!PageUptodate(page_tail)); 1312 BUG_ON(!PageDirty(page_tail)); 1313 BUG_ON(!PageSwapBacked(page_tail)); 1314 1315 lru_add_page_tail(page, page_tail, lruvec); 1316 } 1317 atomic_sub(tail_count, &page->_count); 1318 BUG_ON(atomic_read(&page->_count) <= 0); 1319 1320 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1); 1321 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR); 1322 1323 ClearPageCompound(page); 1324 compound_unlock(page); 1325 spin_unlock_irq(&zone->lru_lock); 1326 1327 for (i = 1; i < HPAGE_PMD_NR; i++) { 1328 struct page *page_tail = page + i; 1329 BUG_ON(page_count(page_tail) <= 0); 1330 /* 1331 * Tail pages may be freed if there wasn't any mapping 1332 * like if add_to_swap() is running on a lru page that 1333 * had its mapping zapped. And freeing these pages 1334 * requires taking the lru_lock so we do the put_page 1335 * of the tail pages after the split is complete. 1336 */ 1337 put_page(page_tail); 1338 } 1339 1340 /* 1341 * Only the head page (now become a regular page) is required 1342 * to be pinned by the caller. 1343 */ 1344 BUG_ON(page_count(page) <= 0); 1345 } 1346 1347 static int __split_huge_page_map(struct page *page, 1348 struct vm_area_struct *vma, 1349 unsigned long address) 1350 { 1351 struct mm_struct *mm = vma->vm_mm; 1352 pmd_t *pmd, _pmd; 1353 int ret = 0, i; 1354 pgtable_t pgtable; 1355 unsigned long haddr; 1356 1357 spin_lock(&mm->page_table_lock); 1358 pmd = page_check_address_pmd(page, mm, address, 1359 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG); 1360 if (pmd) { 1361 pgtable = get_pmd_huge_pte(mm); 1362 pmd_populate(mm, &_pmd, pgtable); 1363 1364 for (i = 0, haddr = address; i < HPAGE_PMD_NR; 1365 i++, haddr += PAGE_SIZE) { 1366 pte_t *pte, entry; 1367 BUG_ON(PageCompound(page+i)); 1368 entry = mk_pte(page + i, vma->vm_page_prot); 1369 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1370 if (!pmd_write(*pmd)) 1371 entry = pte_wrprotect(entry); 1372 else 1373 BUG_ON(page_mapcount(page) != 1); 1374 if (!pmd_young(*pmd)) 1375 entry = pte_mkold(entry); 1376 pte = pte_offset_map(&_pmd, haddr); 1377 BUG_ON(!pte_none(*pte)); 1378 set_pte_at(mm, haddr, pte, entry); 1379 pte_unmap(pte); 1380 } 1381 1382 smp_wmb(); /* make pte visible before pmd */ 1383 /* 1384 * Up to this point the pmd is present and huge and 1385 * userland has the whole access to the hugepage 1386 * during the split (which happens in place). If we 1387 * overwrite the pmd with the not-huge version 1388 * pointing to the pte here (which of course we could 1389 * if all CPUs were bug free), userland could trigger 1390 * a small page size TLB miss on the small sized TLB 1391 * while the hugepage TLB entry is still established 1392 * in the huge TLB. Some CPU doesn't like that. See 1393 * http://support.amd.com/us/Processor_TechDocs/41322.pdf, 1394 * Erratum 383 on page 93. Intel should be safe but is 1395 * also warns that it's only safe if the permission 1396 * and cache attributes of the two entries loaded in 1397 * the two TLB is identical (which should be the case 1398 * here). But it is generally safer to never allow 1399 * small and huge TLB entries for the same virtual 1400 * address to be loaded simultaneously. So instead of 1401 * doing "pmd_populate(); flush_tlb_range();" we first 1402 * mark the current pmd notpresent (atomically because 1403 * here the pmd_trans_huge and pmd_trans_splitting 1404 * must remain set at all times on the pmd until the 1405 * split is complete for this pmd), then we flush the 1406 * SMP TLB and finally we write the non-huge version 1407 * of the pmd entry with pmd_populate. 1408 */ 1409 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd)); 1410 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE); 1411 pmd_populate(mm, pmd, pgtable); 1412 ret = 1; 1413 } 1414 spin_unlock(&mm->page_table_lock); 1415 1416 return ret; 1417 } 1418 1419 /* must be called with anon_vma->root->mutex hold */ 1420 static void __split_huge_page(struct page *page, 1421 struct anon_vma *anon_vma) 1422 { 1423 int mapcount, mapcount2; 1424 struct anon_vma_chain *avc; 1425 1426 BUG_ON(!PageHead(page)); 1427 BUG_ON(PageTail(page)); 1428 1429 mapcount = 0; 1430 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { 1431 struct vm_area_struct *vma = avc->vma; 1432 unsigned long addr = vma_address(page, vma); 1433 BUG_ON(is_vma_temporary_stack(vma)); 1434 if (addr == -EFAULT) 1435 continue; 1436 mapcount += __split_huge_page_splitting(page, vma, addr); 1437 } 1438 /* 1439 * It is critical that new vmas are added to the tail of the 1440 * anon_vma list. This guarantes that if copy_huge_pmd() runs 1441 * and establishes a child pmd before 1442 * __split_huge_page_splitting() freezes the parent pmd (so if 1443 * we fail to prevent copy_huge_pmd() from running until the 1444 * whole __split_huge_page() is complete), we will still see 1445 * the newly established pmd of the child later during the 1446 * walk, to be able to set it as pmd_trans_splitting too. 1447 */ 1448 if (mapcount != page_mapcount(page)) 1449 printk(KERN_ERR "mapcount %d page_mapcount %d\n", 1450 mapcount, page_mapcount(page)); 1451 BUG_ON(mapcount != page_mapcount(page)); 1452 1453 __split_huge_page_refcount(page); 1454 1455 mapcount2 = 0; 1456 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { 1457 struct vm_area_struct *vma = avc->vma; 1458 unsigned long addr = vma_address(page, vma); 1459 BUG_ON(is_vma_temporary_stack(vma)); 1460 if (addr == -EFAULT) 1461 continue; 1462 mapcount2 += __split_huge_page_map(page, vma, addr); 1463 } 1464 if (mapcount != mapcount2) 1465 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n", 1466 mapcount, mapcount2, page_mapcount(page)); 1467 BUG_ON(mapcount != mapcount2); 1468 } 1469 1470 int split_huge_page(struct page *page) 1471 { 1472 struct anon_vma *anon_vma; 1473 int ret = 1; 1474 1475 BUG_ON(!PageAnon(page)); 1476 anon_vma = page_lock_anon_vma(page); 1477 if (!anon_vma) 1478 goto out; 1479 ret = 0; 1480 if (!PageCompound(page)) 1481 goto out_unlock; 1482 1483 BUG_ON(!PageSwapBacked(page)); 1484 __split_huge_page(page, anon_vma); 1485 count_vm_event(THP_SPLIT); 1486 1487 BUG_ON(PageCompound(page)); 1488 out_unlock: 1489 page_unlock_anon_vma(anon_vma); 1490 out: 1491 return ret; 1492 } 1493 1494 #define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \ 1495 VM_HUGETLB|VM_SHARED|VM_MAYSHARE) 1496 1497 int hugepage_madvise(struct vm_area_struct *vma, 1498 unsigned long *vm_flags, int advice) 1499 { 1500 switch (advice) { 1501 case MADV_HUGEPAGE: 1502 /* 1503 * Be somewhat over-protective like KSM for now! 1504 */ 1505 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) 1506 return -EINVAL; 1507 *vm_flags &= ~VM_NOHUGEPAGE; 1508 *vm_flags |= VM_HUGEPAGE; 1509 /* 1510 * If the vma become good for khugepaged to scan, 1511 * register it here without waiting a page fault that 1512 * may not happen any time soon. 1513 */ 1514 if (unlikely(khugepaged_enter_vma_merge(vma))) 1515 return -ENOMEM; 1516 break; 1517 case MADV_NOHUGEPAGE: 1518 /* 1519 * Be somewhat over-protective like KSM for now! 1520 */ 1521 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) 1522 return -EINVAL; 1523 *vm_flags &= ~VM_HUGEPAGE; 1524 *vm_flags |= VM_NOHUGEPAGE; 1525 /* 1526 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1527 * this vma even if we leave the mm registered in khugepaged if 1528 * it got registered before VM_NOHUGEPAGE was set. 1529 */ 1530 break; 1531 } 1532 1533 return 0; 1534 } 1535 1536 static int __init khugepaged_slab_init(void) 1537 { 1538 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1539 sizeof(struct mm_slot), 1540 __alignof__(struct mm_slot), 0, NULL); 1541 if (!mm_slot_cache) 1542 return -ENOMEM; 1543 1544 return 0; 1545 } 1546 1547 static void __init khugepaged_slab_free(void) 1548 { 1549 kmem_cache_destroy(mm_slot_cache); 1550 mm_slot_cache = NULL; 1551 } 1552 1553 static inline struct mm_slot *alloc_mm_slot(void) 1554 { 1555 if (!mm_slot_cache) /* initialization failed */ 1556 return NULL; 1557 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 1558 } 1559 1560 static inline void free_mm_slot(struct mm_slot *mm_slot) 1561 { 1562 kmem_cache_free(mm_slot_cache, mm_slot); 1563 } 1564 1565 static int __init mm_slots_hash_init(void) 1566 { 1567 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), 1568 GFP_KERNEL); 1569 if (!mm_slots_hash) 1570 return -ENOMEM; 1571 return 0; 1572 } 1573 1574 #if 0 1575 static void __init mm_slots_hash_free(void) 1576 { 1577 kfree(mm_slots_hash); 1578 mm_slots_hash = NULL; 1579 } 1580 #endif 1581 1582 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 1583 { 1584 struct mm_slot *mm_slot; 1585 struct hlist_head *bucket; 1586 struct hlist_node *node; 1587 1588 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1589 % MM_SLOTS_HASH_HEADS]; 1590 hlist_for_each_entry(mm_slot, node, bucket, hash) { 1591 if (mm == mm_slot->mm) 1592 return mm_slot; 1593 } 1594 return NULL; 1595 } 1596 1597 static void insert_to_mm_slots_hash(struct mm_struct *mm, 1598 struct mm_slot *mm_slot) 1599 { 1600 struct hlist_head *bucket; 1601 1602 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1603 % MM_SLOTS_HASH_HEADS]; 1604 mm_slot->mm = mm; 1605 hlist_add_head(&mm_slot->hash, bucket); 1606 } 1607 1608 static inline int khugepaged_test_exit(struct mm_struct *mm) 1609 { 1610 return atomic_read(&mm->mm_users) == 0; 1611 } 1612 1613 int __khugepaged_enter(struct mm_struct *mm) 1614 { 1615 struct mm_slot *mm_slot; 1616 int wakeup; 1617 1618 mm_slot = alloc_mm_slot(); 1619 if (!mm_slot) 1620 return -ENOMEM; 1621 1622 /* __khugepaged_exit() must not run from under us */ 1623 VM_BUG_ON(khugepaged_test_exit(mm)); 1624 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 1625 free_mm_slot(mm_slot); 1626 return 0; 1627 } 1628 1629 spin_lock(&khugepaged_mm_lock); 1630 insert_to_mm_slots_hash(mm, mm_slot); 1631 /* 1632 * Insert just behind the scanning cursor, to let the area settle 1633 * down a little. 1634 */ 1635 wakeup = list_empty(&khugepaged_scan.mm_head); 1636 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 1637 spin_unlock(&khugepaged_mm_lock); 1638 1639 atomic_inc(&mm->mm_count); 1640 if (wakeup) 1641 wake_up_interruptible(&khugepaged_wait); 1642 1643 return 0; 1644 } 1645 1646 int khugepaged_enter_vma_merge(struct vm_area_struct *vma) 1647 { 1648 unsigned long hstart, hend; 1649 if (!vma->anon_vma) 1650 /* 1651 * Not yet faulted in so we will register later in the 1652 * page fault if needed. 1653 */ 1654 return 0; 1655 if (vma->vm_ops) 1656 /* khugepaged not yet working on file or special mappings */ 1657 return 0; 1658 /* 1659 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be 1660 * true too, verify it here. 1661 */ 1662 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP); 1663 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1664 hend = vma->vm_end & HPAGE_PMD_MASK; 1665 if (hstart < hend) 1666 return khugepaged_enter(vma); 1667 return 0; 1668 } 1669 1670 void __khugepaged_exit(struct mm_struct *mm) 1671 { 1672 struct mm_slot *mm_slot; 1673 int free = 0; 1674 1675 spin_lock(&khugepaged_mm_lock); 1676 mm_slot = get_mm_slot(mm); 1677 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 1678 hlist_del(&mm_slot->hash); 1679 list_del(&mm_slot->mm_node); 1680 free = 1; 1681 } 1682 spin_unlock(&khugepaged_mm_lock); 1683 1684 if (free) { 1685 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1686 free_mm_slot(mm_slot); 1687 mmdrop(mm); 1688 } else if (mm_slot) { 1689 /* 1690 * This is required to serialize against 1691 * khugepaged_test_exit() (which is guaranteed to run 1692 * under mmap sem read mode). Stop here (after we 1693 * return all pagetables will be destroyed) until 1694 * khugepaged has finished working on the pagetables 1695 * under the mmap_sem. 1696 */ 1697 down_write(&mm->mmap_sem); 1698 up_write(&mm->mmap_sem); 1699 } 1700 } 1701 1702 static void release_pte_page(struct page *page) 1703 { 1704 /* 0 stands for page_is_file_cache(page) == false */ 1705 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 1706 unlock_page(page); 1707 putback_lru_page(page); 1708 } 1709 1710 static void release_pte_pages(pte_t *pte, pte_t *_pte) 1711 { 1712 while (--_pte >= pte) { 1713 pte_t pteval = *_pte; 1714 if (!pte_none(pteval)) 1715 release_pte_page(pte_page(pteval)); 1716 } 1717 } 1718 1719 static void release_all_pte_pages(pte_t *pte) 1720 { 1721 release_pte_pages(pte, pte + HPAGE_PMD_NR); 1722 } 1723 1724 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 1725 unsigned long address, 1726 pte_t *pte) 1727 { 1728 struct page *page; 1729 pte_t *_pte; 1730 int referenced = 0, isolated = 0, none = 0; 1731 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 1732 _pte++, address += PAGE_SIZE) { 1733 pte_t pteval = *_pte; 1734 if (pte_none(pteval)) { 1735 if (++none <= khugepaged_max_ptes_none) 1736 continue; 1737 else { 1738 release_pte_pages(pte, _pte); 1739 goto out; 1740 } 1741 } 1742 if (!pte_present(pteval) || !pte_write(pteval)) { 1743 release_pte_pages(pte, _pte); 1744 goto out; 1745 } 1746 page = vm_normal_page(vma, address, pteval); 1747 if (unlikely(!page)) { 1748 release_pte_pages(pte, _pte); 1749 goto out; 1750 } 1751 VM_BUG_ON(PageCompound(page)); 1752 BUG_ON(!PageAnon(page)); 1753 VM_BUG_ON(!PageSwapBacked(page)); 1754 1755 /* cannot use mapcount: can't collapse if there's a gup pin */ 1756 if (page_count(page) != 1) { 1757 release_pte_pages(pte, _pte); 1758 goto out; 1759 } 1760 /* 1761 * We can do it before isolate_lru_page because the 1762 * page can't be freed from under us. NOTE: PG_lock 1763 * is needed to serialize against split_huge_page 1764 * when invoked from the VM. 1765 */ 1766 if (!trylock_page(page)) { 1767 release_pte_pages(pte, _pte); 1768 goto out; 1769 } 1770 /* 1771 * Isolate the page to avoid collapsing an hugepage 1772 * currently in use by the VM. 1773 */ 1774 if (isolate_lru_page(page)) { 1775 unlock_page(page); 1776 release_pte_pages(pte, _pte); 1777 goto out; 1778 } 1779 /* 0 stands for page_is_file_cache(page) == false */ 1780 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 1781 VM_BUG_ON(!PageLocked(page)); 1782 VM_BUG_ON(PageLRU(page)); 1783 1784 /* If there is no mapped pte young don't collapse the page */ 1785 if (pte_young(pteval) || PageReferenced(page) || 1786 mmu_notifier_test_young(vma->vm_mm, address)) 1787 referenced = 1; 1788 } 1789 if (unlikely(!referenced)) 1790 release_all_pte_pages(pte); 1791 else 1792 isolated = 1; 1793 out: 1794 return isolated; 1795 } 1796 1797 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 1798 struct vm_area_struct *vma, 1799 unsigned long address, 1800 spinlock_t *ptl) 1801 { 1802 pte_t *_pte; 1803 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 1804 pte_t pteval = *_pte; 1805 struct page *src_page; 1806 1807 if (pte_none(pteval)) { 1808 clear_user_highpage(page, address); 1809 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 1810 } else { 1811 src_page = pte_page(pteval); 1812 copy_user_highpage(page, src_page, address, vma); 1813 VM_BUG_ON(page_mapcount(src_page) != 1); 1814 release_pte_page(src_page); 1815 /* 1816 * ptl mostly unnecessary, but preempt has to 1817 * be disabled to update the per-cpu stats 1818 * inside page_remove_rmap(). 1819 */ 1820 spin_lock(ptl); 1821 /* 1822 * paravirt calls inside pte_clear here are 1823 * superfluous. 1824 */ 1825 pte_clear(vma->vm_mm, address, _pte); 1826 page_remove_rmap(src_page); 1827 spin_unlock(ptl); 1828 free_page_and_swap_cache(src_page); 1829 } 1830 1831 address += PAGE_SIZE; 1832 page++; 1833 } 1834 } 1835 1836 static void collapse_huge_page(struct mm_struct *mm, 1837 unsigned long address, 1838 struct page **hpage, 1839 struct vm_area_struct *vma, 1840 int node) 1841 { 1842 pgd_t *pgd; 1843 pud_t *pud; 1844 pmd_t *pmd, _pmd; 1845 pte_t *pte; 1846 pgtable_t pgtable; 1847 struct page *new_page; 1848 spinlock_t *ptl; 1849 int isolated; 1850 unsigned long hstart, hend; 1851 1852 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1853 #ifndef CONFIG_NUMA 1854 up_read(&mm->mmap_sem); 1855 VM_BUG_ON(!*hpage); 1856 new_page = *hpage; 1857 #else 1858 VM_BUG_ON(*hpage); 1859 /* 1860 * Allocate the page while the vma is still valid and under 1861 * the mmap_sem read mode so there is no memory allocation 1862 * later when we take the mmap_sem in write mode. This is more 1863 * friendly behavior (OTOH it may actually hide bugs) to 1864 * filesystems in userland with daemons allocating memory in 1865 * the userland I/O paths. Allocating memory with the 1866 * mmap_sem in read mode is good idea also to allow greater 1867 * scalability. 1868 */ 1869 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address, 1870 node, __GFP_OTHER_NODE); 1871 1872 /* 1873 * After allocating the hugepage, release the mmap_sem read lock in 1874 * preparation for taking it in write mode. 1875 */ 1876 up_read(&mm->mmap_sem); 1877 if (unlikely(!new_page)) { 1878 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 1879 *hpage = ERR_PTR(-ENOMEM); 1880 return; 1881 } 1882 #endif 1883 1884 count_vm_event(THP_COLLAPSE_ALLOC); 1885 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 1886 #ifdef CONFIG_NUMA 1887 put_page(new_page); 1888 #endif 1889 return; 1890 } 1891 1892 /* 1893 * Prevent all access to pagetables with the exception of 1894 * gup_fast later hanlded by the ptep_clear_flush and the VM 1895 * handled by the anon_vma lock + PG_lock. 1896 */ 1897 down_write(&mm->mmap_sem); 1898 if (unlikely(khugepaged_test_exit(mm))) 1899 goto out; 1900 1901 vma = find_vma(mm, address); 1902 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1903 hend = vma->vm_end & HPAGE_PMD_MASK; 1904 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 1905 goto out; 1906 1907 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 1908 (vma->vm_flags & VM_NOHUGEPAGE)) 1909 goto out; 1910 1911 if (!vma->anon_vma || vma->vm_ops) 1912 goto out; 1913 if (is_vma_temporary_stack(vma)) 1914 goto out; 1915 /* 1916 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be 1917 * true too, verify it here. 1918 */ 1919 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP); 1920 1921 pgd = pgd_offset(mm, address); 1922 if (!pgd_present(*pgd)) 1923 goto out; 1924 1925 pud = pud_offset(pgd, address); 1926 if (!pud_present(*pud)) 1927 goto out; 1928 1929 pmd = pmd_offset(pud, address); 1930 /* pmd can't go away or become huge under us */ 1931 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd)) 1932 goto out; 1933 1934 anon_vma_lock(vma->anon_vma); 1935 1936 pte = pte_offset_map(pmd, address); 1937 ptl = pte_lockptr(mm, pmd); 1938 1939 spin_lock(&mm->page_table_lock); /* probably unnecessary */ 1940 /* 1941 * After this gup_fast can't run anymore. This also removes 1942 * any huge TLB entry from the CPU so we won't allow 1943 * huge and small TLB entries for the same virtual address 1944 * to avoid the risk of CPU bugs in that area. 1945 */ 1946 _pmd = pmdp_clear_flush_notify(vma, address, pmd); 1947 spin_unlock(&mm->page_table_lock); 1948 1949 spin_lock(ptl); 1950 isolated = __collapse_huge_page_isolate(vma, address, pte); 1951 spin_unlock(ptl); 1952 1953 if (unlikely(!isolated)) { 1954 pte_unmap(pte); 1955 spin_lock(&mm->page_table_lock); 1956 BUG_ON(!pmd_none(*pmd)); 1957 set_pmd_at(mm, address, pmd, _pmd); 1958 spin_unlock(&mm->page_table_lock); 1959 anon_vma_unlock(vma->anon_vma); 1960 goto out; 1961 } 1962 1963 /* 1964 * All pages are isolated and locked so anon_vma rmap 1965 * can't run anymore. 1966 */ 1967 anon_vma_unlock(vma->anon_vma); 1968 1969 __collapse_huge_page_copy(pte, new_page, vma, address, ptl); 1970 pte_unmap(pte); 1971 __SetPageUptodate(new_page); 1972 pgtable = pmd_pgtable(_pmd); 1973 VM_BUG_ON(page_count(pgtable) != 1); 1974 VM_BUG_ON(page_mapcount(pgtable) != 0); 1975 1976 _pmd = mk_pmd(new_page, vma->vm_page_prot); 1977 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 1978 _pmd = pmd_mkhuge(_pmd); 1979 1980 /* 1981 * spin_lock() below is not the equivalent of smp_wmb(), so 1982 * this is needed to avoid the copy_huge_page writes to become 1983 * visible after the set_pmd_at() write. 1984 */ 1985 smp_wmb(); 1986 1987 spin_lock(&mm->page_table_lock); 1988 BUG_ON(!pmd_none(*pmd)); 1989 page_add_new_anon_rmap(new_page, vma, address); 1990 set_pmd_at(mm, address, pmd, _pmd); 1991 update_mmu_cache(vma, address, _pmd); 1992 prepare_pmd_huge_pte(pgtable, mm); 1993 spin_unlock(&mm->page_table_lock); 1994 1995 #ifndef CONFIG_NUMA 1996 *hpage = NULL; 1997 #endif 1998 khugepaged_pages_collapsed++; 1999 out_up_write: 2000 up_write(&mm->mmap_sem); 2001 return; 2002 2003 out: 2004 mem_cgroup_uncharge_page(new_page); 2005 #ifdef CONFIG_NUMA 2006 put_page(new_page); 2007 #endif 2008 goto out_up_write; 2009 } 2010 2011 static int khugepaged_scan_pmd(struct mm_struct *mm, 2012 struct vm_area_struct *vma, 2013 unsigned long address, 2014 struct page **hpage) 2015 { 2016 pgd_t *pgd; 2017 pud_t *pud; 2018 pmd_t *pmd; 2019 pte_t *pte, *_pte; 2020 int ret = 0, referenced = 0, none = 0; 2021 struct page *page; 2022 unsigned long _address; 2023 spinlock_t *ptl; 2024 int node = -1; 2025 2026 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2027 2028 pgd = pgd_offset(mm, address); 2029 if (!pgd_present(*pgd)) 2030 goto out; 2031 2032 pud = pud_offset(pgd, address); 2033 if (!pud_present(*pud)) 2034 goto out; 2035 2036 pmd = pmd_offset(pud, address); 2037 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd)) 2038 goto out; 2039 2040 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2041 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2042 _pte++, _address += PAGE_SIZE) { 2043 pte_t pteval = *_pte; 2044 if (pte_none(pteval)) { 2045 if (++none <= khugepaged_max_ptes_none) 2046 continue; 2047 else 2048 goto out_unmap; 2049 } 2050 if (!pte_present(pteval) || !pte_write(pteval)) 2051 goto out_unmap; 2052 page = vm_normal_page(vma, _address, pteval); 2053 if (unlikely(!page)) 2054 goto out_unmap; 2055 /* 2056 * Chose the node of the first page. This could 2057 * be more sophisticated and look at more pages, 2058 * but isn't for now. 2059 */ 2060 if (node == -1) 2061 node = page_to_nid(page); 2062 VM_BUG_ON(PageCompound(page)); 2063 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) 2064 goto out_unmap; 2065 /* cannot use mapcount: can't collapse if there's a gup pin */ 2066 if (page_count(page) != 1) 2067 goto out_unmap; 2068 if (pte_young(pteval) || PageReferenced(page) || 2069 mmu_notifier_test_young(vma->vm_mm, address)) 2070 referenced = 1; 2071 } 2072 if (referenced) 2073 ret = 1; 2074 out_unmap: 2075 pte_unmap_unlock(pte, ptl); 2076 if (ret) 2077 /* collapse_huge_page will return with the mmap_sem released */ 2078 collapse_huge_page(mm, address, hpage, vma, node); 2079 out: 2080 return ret; 2081 } 2082 2083 static void collect_mm_slot(struct mm_slot *mm_slot) 2084 { 2085 struct mm_struct *mm = mm_slot->mm; 2086 2087 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2088 2089 if (khugepaged_test_exit(mm)) { 2090 /* free mm_slot */ 2091 hlist_del(&mm_slot->hash); 2092 list_del(&mm_slot->mm_node); 2093 2094 /* 2095 * Not strictly needed because the mm exited already. 2096 * 2097 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2098 */ 2099 2100 /* khugepaged_mm_lock actually not necessary for the below */ 2101 free_mm_slot(mm_slot); 2102 mmdrop(mm); 2103 } 2104 } 2105 2106 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2107 struct page **hpage) 2108 __releases(&khugepaged_mm_lock) 2109 __acquires(&khugepaged_mm_lock) 2110 { 2111 struct mm_slot *mm_slot; 2112 struct mm_struct *mm; 2113 struct vm_area_struct *vma; 2114 int progress = 0; 2115 2116 VM_BUG_ON(!pages); 2117 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2118 2119 if (khugepaged_scan.mm_slot) 2120 mm_slot = khugepaged_scan.mm_slot; 2121 else { 2122 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2123 struct mm_slot, mm_node); 2124 khugepaged_scan.address = 0; 2125 khugepaged_scan.mm_slot = mm_slot; 2126 } 2127 spin_unlock(&khugepaged_mm_lock); 2128 2129 mm = mm_slot->mm; 2130 down_read(&mm->mmap_sem); 2131 if (unlikely(khugepaged_test_exit(mm))) 2132 vma = NULL; 2133 else 2134 vma = find_vma(mm, khugepaged_scan.address); 2135 2136 progress++; 2137 for (; vma; vma = vma->vm_next) { 2138 unsigned long hstart, hend; 2139 2140 cond_resched(); 2141 if (unlikely(khugepaged_test_exit(mm))) { 2142 progress++; 2143 break; 2144 } 2145 2146 if ((!(vma->vm_flags & VM_HUGEPAGE) && 2147 !khugepaged_always()) || 2148 (vma->vm_flags & VM_NOHUGEPAGE)) { 2149 skip: 2150 progress++; 2151 continue; 2152 } 2153 if (!vma->anon_vma || vma->vm_ops) 2154 goto skip; 2155 if (is_vma_temporary_stack(vma)) 2156 goto skip; 2157 /* 2158 * If is_pfn_mapping() is true is_learn_pfn_mapping() 2159 * must be true too, verify it here. 2160 */ 2161 VM_BUG_ON(is_linear_pfn_mapping(vma) || 2162 vma->vm_flags & VM_NO_THP); 2163 2164 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2165 hend = vma->vm_end & HPAGE_PMD_MASK; 2166 if (hstart >= hend) 2167 goto skip; 2168 if (khugepaged_scan.address > hend) 2169 goto skip; 2170 if (khugepaged_scan.address < hstart) 2171 khugepaged_scan.address = hstart; 2172 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2173 2174 while (khugepaged_scan.address < hend) { 2175 int ret; 2176 cond_resched(); 2177 if (unlikely(khugepaged_test_exit(mm))) 2178 goto breakouterloop; 2179 2180 VM_BUG_ON(khugepaged_scan.address < hstart || 2181 khugepaged_scan.address + HPAGE_PMD_SIZE > 2182 hend); 2183 ret = khugepaged_scan_pmd(mm, vma, 2184 khugepaged_scan.address, 2185 hpage); 2186 /* move to next address */ 2187 khugepaged_scan.address += HPAGE_PMD_SIZE; 2188 progress += HPAGE_PMD_NR; 2189 if (ret) 2190 /* we released mmap_sem so break loop */ 2191 goto breakouterloop_mmap_sem; 2192 if (progress >= pages) 2193 goto breakouterloop; 2194 } 2195 } 2196 breakouterloop: 2197 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2198 breakouterloop_mmap_sem: 2199 2200 spin_lock(&khugepaged_mm_lock); 2201 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2202 /* 2203 * Release the current mm_slot if this mm is about to die, or 2204 * if we scanned all vmas of this mm. 2205 */ 2206 if (khugepaged_test_exit(mm) || !vma) { 2207 /* 2208 * Make sure that if mm_users is reaching zero while 2209 * khugepaged runs here, khugepaged_exit will find 2210 * mm_slot not pointing to the exiting mm. 2211 */ 2212 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2213 khugepaged_scan.mm_slot = list_entry( 2214 mm_slot->mm_node.next, 2215 struct mm_slot, mm_node); 2216 khugepaged_scan.address = 0; 2217 } else { 2218 khugepaged_scan.mm_slot = NULL; 2219 khugepaged_full_scans++; 2220 } 2221 2222 collect_mm_slot(mm_slot); 2223 } 2224 2225 return progress; 2226 } 2227 2228 static int khugepaged_has_work(void) 2229 { 2230 return !list_empty(&khugepaged_scan.mm_head) && 2231 khugepaged_enabled(); 2232 } 2233 2234 static int khugepaged_wait_event(void) 2235 { 2236 return !list_empty(&khugepaged_scan.mm_head) || 2237 !khugepaged_enabled(); 2238 } 2239 2240 static void khugepaged_do_scan(struct page **hpage) 2241 { 2242 unsigned int progress = 0, pass_through_head = 0; 2243 unsigned int pages = khugepaged_pages_to_scan; 2244 2245 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2246 2247 while (progress < pages) { 2248 cond_resched(); 2249 2250 #ifndef CONFIG_NUMA 2251 if (!*hpage) { 2252 *hpage = alloc_hugepage(khugepaged_defrag()); 2253 if (unlikely(!*hpage)) { 2254 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2255 break; 2256 } 2257 count_vm_event(THP_COLLAPSE_ALLOC); 2258 } 2259 #else 2260 if (IS_ERR(*hpage)) 2261 break; 2262 #endif 2263 2264 if (unlikely(kthread_should_stop() || freezing(current))) 2265 break; 2266 2267 spin_lock(&khugepaged_mm_lock); 2268 if (!khugepaged_scan.mm_slot) 2269 pass_through_head++; 2270 if (khugepaged_has_work() && 2271 pass_through_head < 2) 2272 progress += khugepaged_scan_mm_slot(pages - progress, 2273 hpage); 2274 else 2275 progress = pages; 2276 spin_unlock(&khugepaged_mm_lock); 2277 } 2278 } 2279 2280 static void khugepaged_alloc_sleep(void) 2281 { 2282 wait_event_freezable_timeout(khugepaged_wait, false, 2283 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 2284 } 2285 2286 #ifndef CONFIG_NUMA 2287 static struct page *khugepaged_alloc_hugepage(void) 2288 { 2289 struct page *hpage; 2290 2291 do { 2292 hpage = alloc_hugepage(khugepaged_defrag()); 2293 if (!hpage) { 2294 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2295 khugepaged_alloc_sleep(); 2296 } else 2297 count_vm_event(THP_COLLAPSE_ALLOC); 2298 } while (unlikely(!hpage) && 2299 likely(khugepaged_enabled())); 2300 return hpage; 2301 } 2302 #endif 2303 2304 static void khugepaged_loop(void) 2305 { 2306 struct page *hpage; 2307 2308 #ifdef CONFIG_NUMA 2309 hpage = NULL; 2310 #endif 2311 while (likely(khugepaged_enabled())) { 2312 #ifndef CONFIG_NUMA 2313 hpage = khugepaged_alloc_hugepage(); 2314 if (unlikely(!hpage)) 2315 break; 2316 #else 2317 if (IS_ERR(hpage)) { 2318 khugepaged_alloc_sleep(); 2319 hpage = NULL; 2320 } 2321 #endif 2322 2323 khugepaged_do_scan(&hpage); 2324 #ifndef CONFIG_NUMA 2325 if (hpage) 2326 put_page(hpage); 2327 #endif 2328 try_to_freeze(); 2329 if (unlikely(kthread_should_stop())) 2330 break; 2331 if (khugepaged_has_work()) { 2332 if (!khugepaged_scan_sleep_millisecs) 2333 continue; 2334 wait_event_freezable_timeout(khugepaged_wait, false, 2335 msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); 2336 } else if (khugepaged_enabled()) 2337 wait_event_freezable(khugepaged_wait, 2338 khugepaged_wait_event()); 2339 } 2340 } 2341 2342 static int khugepaged(void *none) 2343 { 2344 struct mm_slot *mm_slot; 2345 2346 set_freezable(); 2347 set_user_nice(current, 19); 2348 2349 /* serialize with start_khugepaged() */ 2350 mutex_lock(&khugepaged_mutex); 2351 2352 for (;;) { 2353 mutex_unlock(&khugepaged_mutex); 2354 VM_BUG_ON(khugepaged_thread != current); 2355 khugepaged_loop(); 2356 VM_BUG_ON(khugepaged_thread != current); 2357 2358 mutex_lock(&khugepaged_mutex); 2359 if (!khugepaged_enabled()) 2360 break; 2361 if (unlikely(kthread_should_stop())) 2362 break; 2363 } 2364 2365 spin_lock(&khugepaged_mm_lock); 2366 mm_slot = khugepaged_scan.mm_slot; 2367 khugepaged_scan.mm_slot = NULL; 2368 if (mm_slot) 2369 collect_mm_slot(mm_slot); 2370 spin_unlock(&khugepaged_mm_lock); 2371 2372 khugepaged_thread = NULL; 2373 mutex_unlock(&khugepaged_mutex); 2374 2375 return 0; 2376 } 2377 2378 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd) 2379 { 2380 struct page *page; 2381 2382 spin_lock(&mm->page_table_lock); 2383 if (unlikely(!pmd_trans_huge(*pmd))) { 2384 spin_unlock(&mm->page_table_lock); 2385 return; 2386 } 2387 page = pmd_page(*pmd); 2388 VM_BUG_ON(!page_count(page)); 2389 get_page(page); 2390 spin_unlock(&mm->page_table_lock); 2391 2392 split_huge_page(page); 2393 2394 put_page(page); 2395 BUG_ON(pmd_trans_huge(*pmd)); 2396 } 2397 2398 static void split_huge_page_address(struct mm_struct *mm, 2399 unsigned long address) 2400 { 2401 pgd_t *pgd; 2402 pud_t *pud; 2403 pmd_t *pmd; 2404 2405 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); 2406 2407 pgd = pgd_offset(mm, address); 2408 if (!pgd_present(*pgd)) 2409 return; 2410 2411 pud = pud_offset(pgd, address); 2412 if (!pud_present(*pud)) 2413 return; 2414 2415 pmd = pmd_offset(pud, address); 2416 if (!pmd_present(*pmd)) 2417 return; 2418 /* 2419 * Caller holds the mmap_sem write mode, so a huge pmd cannot 2420 * materialize from under us. 2421 */ 2422 split_huge_page_pmd(mm, pmd); 2423 } 2424 2425 void __vma_adjust_trans_huge(struct vm_area_struct *vma, 2426 unsigned long start, 2427 unsigned long end, 2428 long adjust_next) 2429 { 2430 /* 2431 * If the new start address isn't hpage aligned and it could 2432 * previously contain an hugepage: check if we need to split 2433 * an huge pmd. 2434 */ 2435 if (start & ~HPAGE_PMD_MASK && 2436 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2437 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2438 split_huge_page_address(vma->vm_mm, start); 2439 2440 /* 2441 * If the new end address isn't hpage aligned and it could 2442 * previously contain an hugepage: check if we need to split 2443 * an huge pmd. 2444 */ 2445 if (end & ~HPAGE_PMD_MASK && 2446 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2447 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2448 split_huge_page_address(vma->vm_mm, end); 2449 2450 /* 2451 * If we're also updating the vma->vm_next->vm_start, if the new 2452 * vm_next->vm_start isn't page aligned and it could previously 2453 * contain an hugepage: check if we need to split an huge pmd. 2454 */ 2455 if (adjust_next > 0) { 2456 struct vm_area_struct *next = vma->vm_next; 2457 unsigned long nstart = next->vm_start; 2458 nstart += adjust_next << PAGE_SHIFT; 2459 if (nstart & ~HPAGE_PMD_MASK && 2460 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2461 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2462 split_huge_page_address(next->vm_mm, nstart); 2463 } 2464 } 2465