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