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