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