1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2009 Red Hat, Inc. 4 */ 5 6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 7 8 #include <linux/mm.h> 9 #include <linux/sched.h> 10 #include <linux/sched/mm.h> 11 #include <linux/sched/coredump.h> 12 #include <linux/sched/numa_balancing.h> 13 #include <linux/highmem.h> 14 #include <linux/hugetlb.h> 15 #include <linux/mmu_notifier.h> 16 #include <linux/rmap.h> 17 #include <linux/swap.h> 18 #include <linux/shrinker.h> 19 #include <linux/mm_inline.h> 20 #include <linux/swapops.h> 21 #include <linux/dax.h> 22 #include <linux/khugepaged.h> 23 #include <linux/freezer.h> 24 #include <linux/pfn_t.h> 25 #include <linux/mman.h> 26 #include <linux/memremap.h> 27 #include <linux/pagemap.h> 28 #include <linux/debugfs.h> 29 #include <linux/migrate.h> 30 #include <linux/hashtable.h> 31 #include <linux/userfaultfd_k.h> 32 #include <linux/page_idle.h> 33 #include <linux/shmem_fs.h> 34 #include <linux/oom.h> 35 #include <linux/numa.h> 36 #include <linux/page_owner.h> 37 38 #include <asm/tlb.h> 39 #include <asm/pgalloc.h> 40 #include "internal.h" 41 42 /* 43 * By default, transparent hugepage support is disabled in order to avoid 44 * risking an increased memory footprint for applications that are not 45 * guaranteed to benefit from it. When transparent hugepage support is 46 * enabled, it is for all mappings, and khugepaged scans all mappings. 47 * Defrag is invoked by khugepaged hugepage allocations and by page faults 48 * for all hugepage allocations. 49 */ 50 unsigned long transparent_hugepage_flags __read_mostly = 51 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS 52 (1<<TRANSPARENT_HUGEPAGE_FLAG)| 53 #endif 54 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE 55 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| 56 #endif 57 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)| 58 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)| 59 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 60 61 static struct shrinker deferred_split_shrinker; 62 63 static atomic_t huge_zero_refcount; 64 struct page *huge_zero_page __read_mostly; 65 66 bool transparent_hugepage_enabled(struct vm_area_struct *vma) 67 { 68 /* The addr is used to check if the vma size fits */ 69 unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE; 70 71 if (!transhuge_vma_suitable(vma, addr)) 72 return false; 73 if (vma_is_anonymous(vma)) 74 return __transparent_hugepage_enabled(vma); 75 if (vma_is_shmem(vma)) 76 return shmem_huge_enabled(vma); 77 78 return false; 79 } 80 81 static bool get_huge_zero_page(void) 82 { 83 struct page *zero_page; 84 retry: 85 if (likely(atomic_inc_not_zero(&huge_zero_refcount))) 86 return true; 87 88 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, 89 HPAGE_PMD_ORDER); 90 if (!zero_page) { 91 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); 92 return false; 93 } 94 count_vm_event(THP_ZERO_PAGE_ALLOC); 95 preempt_disable(); 96 if (cmpxchg(&huge_zero_page, NULL, zero_page)) { 97 preempt_enable(); 98 __free_pages(zero_page, compound_order(zero_page)); 99 goto retry; 100 } 101 102 /* We take additional reference here. It will be put back by shrinker */ 103 atomic_set(&huge_zero_refcount, 2); 104 preempt_enable(); 105 return true; 106 } 107 108 static void put_huge_zero_page(void) 109 { 110 /* 111 * Counter should never go to zero here. Only shrinker can put 112 * last reference. 113 */ 114 BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); 115 } 116 117 struct page *mm_get_huge_zero_page(struct mm_struct *mm) 118 { 119 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) 120 return READ_ONCE(huge_zero_page); 121 122 if (!get_huge_zero_page()) 123 return NULL; 124 125 if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) 126 put_huge_zero_page(); 127 128 return READ_ONCE(huge_zero_page); 129 } 130 131 void mm_put_huge_zero_page(struct mm_struct *mm) 132 { 133 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) 134 put_huge_zero_page(); 135 } 136 137 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, 138 struct shrink_control *sc) 139 { 140 /* we can free zero page only if last reference remains */ 141 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; 142 } 143 144 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, 145 struct shrink_control *sc) 146 { 147 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { 148 struct page *zero_page = xchg(&huge_zero_page, NULL); 149 BUG_ON(zero_page == NULL); 150 __free_pages(zero_page, compound_order(zero_page)); 151 return HPAGE_PMD_NR; 152 } 153 154 return 0; 155 } 156 157 static struct shrinker huge_zero_page_shrinker = { 158 .count_objects = shrink_huge_zero_page_count, 159 .scan_objects = shrink_huge_zero_page_scan, 160 .seeks = DEFAULT_SEEKS, 161 }; 162 163 #ifdef CONFIG_SYSFS 164 static ssize_t enabled_show(struct kobject *kobj, 165 struct kobj_attribute *attr, char *buf) 166 { 167 const char *output; 168 169 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags)) 170 output = "[always] madvise never"; 171 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 172 &transparent_hugepage_flags)) 173 output = "always [madvise] never"; 174 else 175 output = "always madvise [never]"; 176 177 return sysfs_emit(buf, "%s\n", output); 178 } 179 180 static ssize_t enabled_store(struct kobject *kobj, 181 struct kobj_attribute *attr, 182 const char *buf, size_t count) 183 { 184 ssize_t ret = count; 185 186 if (sysfs_streq(buf, "always")) { 187 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); 188 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); 189 } else if (sysfs_streq(buf, "madvise")) { 190 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); 191 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); 192 } else if (sysfs_streq(buf, "never")) { 193 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); 194 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); 195 } else 196 ret = -EINVAL; 197 198 if (ret > 0) { 199 int err = start_stop_khugepaged(); 200 if (err) 201 ret = err; 202 } 203 return ret; 204 } 205 static struct kobj_attribute enabled_attr = 206 __ATTR(enabled, 0644, enabled_show, enabled_store); 207 208 ssize_t single_hugepage_flag_show(struct kobject *kobj, 209 struct kobj_attribute *attr, char *buf, 210 enum transparent_hugepage_flag flag) 211 { 212 return sysfs_emit(buf, "%d\n", 213 !!test_bit(flag, &transparent_hugepage_flags)); 214 } 215 216 ssize_t single_hugepage_flag_store(struct kobject *kobj, 217 struct kobj_attribute *attr, 218 const char *buf, size_t count, 219 enum transparent_hugepage_flag flag) 220 { 221 unsigned long value; 222 int ret; 223 224 ret = kstrtoul(buf, 10, &value); 225 if (ret < 0) 226 return ret; 227 if (value > 1) 228 return -EINVAL; 229 230 if (value) 231 set_bit(flag, &transparent_hugepage_flags); 232 else 233 clear_bit(flag, &transparent_hugepage_flags); 234 235 return count; 236 } 237 238 static ssize_t defrag_show(struct kobject *kobj, 239 struct kobj_attribute *attr, char *buf) 240 { 241 const char *output; 242 243 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, 244 &transparent_hugepage_flags)) 245 output = "[always] defer defer+madvise madvise never"; 246 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, 247 &transparent_hugepage_flags)) 248 output = "always [defer] defer+madvise madvise never"; 249 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, 250 &transparent_hugepage_flags)) 251 output = "always defer [defer+madvise] madvise never"; 252 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, 253 &transparent_hugepage_flags)) 254 output = "always defer defer+madvise [madvise] never"; 255 else 256 output = "always defer defer+madvise madvise [never]"; 257 258 return sysfs_emit(buf, "%s\n", output); 259 } 260 261 static ssize_t defrag_store(struct kobject *kobj, 262 struct kobj_attribute *attr, 263 const char *buf, size_t count) 264 { 265 if (sysfs_streq(buf, "always")) { 266 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 267 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 268 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 269 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 270 } else if (sysfs_streq(buf, "defer+madvise")) { 271 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 272 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 273 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 274 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 275 } else if (sysfs_streq(buf, "defer")) { 276 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 277 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 278 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 279 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 280 } else if (sysfs_streq(buf, "madvise")) { 281 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 282 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 283 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 284 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 285 } else if (sysfs_streq(buf, "never")) { 286 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 287 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 288 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 289 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 290 } else 291 return -EINVAL; 292 293 return count; 294 } 295 static struct kobj_attribute defrag_attr = 296 __ATTR(defrag, 0644, defrag_show, defrag_store); 297 298 static ssize_t use_zero_page_show(struct kobject *kobj, 299 struct kobj_attribute *attr, char *buf) 300 { 301 return single_hugepage_flag_show(kobj, attr, buf, 302 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 303 } 304 static ssize_t use_zero_page_store(struct kobject *kobj, 305 struct kobj_attribute *attr, const char *buf, size_t count) 306 { 307 return single_hugepage_flag_store(kobj, attr, buf, count, 308 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 309 } 310 static struct kobj_attribute use_zero_page_attr = 311 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); 312 313 static ssize_t hpage_pmd_size_show(struct kobject *kobj, 314 struct kobj_attribute *attr, char *buf) 315 { 316 return sysfs_emit(buf, "%lu\n", HPAGE_PMD_SIZE); 317 } 318 static struct kobj_attribute hpage_pmd_size_attr = 319 __ATTR_RO(hpage_pmd_size); 320 321 static struct attribute *hugepage_attr[] = { 322 &enabled_attr.attr, 323 &defrag_attr.attr, 324 &use_zero_page_attr.attr, 325 &hpage_pmd_size_attr.attr, 326 #ifdef CONFIG_SHMEM 327 &shmem_enabled_attr.attr, 328 #endif 329 NULL, 330 }; 331 332 static const struct attribute_group hugepage_attr_group = { 333 .attrs = hugepage_attr, 334 }; 335 336 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) 337 { 338 int err; 339 340 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 341 if (unlikely(!*hugepage_kobj)) { 342 pr_err("failed to create transparent hugepage kobject\n"); 343 return -ENOMEM; 344 } 345 346 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); 347 if (err) { 348 pr_err("failed to register transparent hugepage group\n"); 349 goto delete_obj; 350 } 351 352 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); 353 if (err) { 354 pr_err("failed to register transparent hugepage group\n"); 355 goto remove_hp_group; 356 } 357 358 return 0; 359 360 remove_hp_group: 361 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); 362 delete_obj: 363 kobject_put(*hugepage_kobj); 364 return err; 365 } 366 367 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) 368 { 369 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); 370 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); 371 kobject_put(hugepage_kobj); 372 } 373 #else 374 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) 375 { 376 return 0; 377 } 378 379 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) 380 { 381 } 382 #endif /* CONFIG_SYSFS */ 383 384 static int __init hugepage_init(void) 385 { 386 int err; 387 struct kobject *hugepage_kobj; 388 389 if (!has_transparent_hugepage()) { 390 /* 391 * Hardware doesn't support hugepages, hence disable 392 * DAX PMD support. 393 */ 394 transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_NEVER_DAX; 395 return -EINVAL; 396 } 397 398 /* 399 * hugepages can't be allocated by the buddy allocator 400 */ 401 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER); 402 /* 403 * we use page->mapping and page->index in second tail page 404 * as list_head: assuming THP order >= 2 405 */ 406 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2); 407 408 err = hugepage_init_sysfs(&hugepage_kobj); 409 if (err) 410 goto err_sysfs; 411 412 err = khugepaged_init(); 413 if (err) 414 goto err_slab; 415 416 err = register_shrinker(&huge_zero_page_shrinker); 417 if (err) 418 goto err_hzp_shrinker; 419 err = register_shrinker(&deferred_split_shrinker); 420 if (err) 421 goto err_split_shrinker; 422 423 /* 424 * By default disable transparent hugepages on smaller systems, 425 * where the extra memory used could hurt more than TLB overhead 426 * is likely to save. The admin can still enable it through /sys. 427 */ 428 if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) { 429 transparent_hugepage_flags = 0; 430 return 0; 431 } 432 433 err = start_stop_khugepaged(); 434 if (err) 435 goto err_khugepaged; 436 437 return 0; 438 err_khugepaged: 439 unregister_shrinker(&deferred_split_shrinker); 440 err_split_shrinker: 441 unregister_shrinker(&huge_zero_page_shrinker); 442 err_hzp_shrinker: 443 khugepaged_destroy(); 444 err_slab: 445 hugepage_exit_sysfs(hugepage_kobj); 446 err_sysfs: 447 return err; 448 } 449 subsys_initcall(hugepage_init); 450 451 static int __init setup_transparent_hugepage(char *str) 452 { 453 int ret = 0; 454 if (!str) 455 goto out; 456 if (!strcmp(str, "always")) { 457 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 458 &transparent_hugepage_flags); 459 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 460 &transparent_hugepage_flags); 461 ret = 1; 462 } else if (!strcmp(str, "madvise")) { 463 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 464 &transparent_hugepage_flags); 465 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 466 &transparent_hugepage_flags); 467 ret = 1; 468 } else if (!strcmp(str, "never")) { 469 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 470 &transparent_hugepage_flags); 471 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 472 &transparent_hugepage_flags); 473 ret = 1; 474 } 475 out: 476 if (!ret) 477 pr_warn("transparent_hugepage= cannot parse, ignored\n"); 478 return ret; 479 } 480 __setup("transparent_hugepage=", setup_transparent_hugepage); 481 482 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 483 { 484 if (likely(vma->vm_flags & VM_WRITE)) 485 pmd = pmd_mkwrite(pmd); 486 return pmd; 487 } 488 489 #ifdef CONFIG_MEMCG 490 static inline struct deferred_split *get_deferred_split_queue(struct page *page) 491 { 492 struct mem_cgroup *memcg = page_memcg(compound_head(page)); 493 struct pglist_data *pgdat = NODE_DATA(page_to_nid(page)); 494 495 if (memcg) 496 return &memcg->deferred_split_queue; 497 else 498 return &pgdat->deferred_split_queue; 499 } 500 #else 501 static inline struct deferred_split *get_deferred_split_queue(struct page *page) 502 { 503 struct pglist_data *pgdat = NODE_DATA(page_to_nid(page)); 504 505 return &pgdat->deferred_split_queue; 506 } 507 #endif 508 509 void prep_transhuge_page(struct page *page) 510 { 511 /* 512 * we use page->mapping and page->indexlru in second tail page 513 * as list_head: assuming THP order >= 2 514 */ 515 516 INIT_LIST_HEAD(page_deferred_list(page)); 517 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR); 518 } 519 520 bool is_transparent_hugepage(struct page *page) 521 { 522 if (!PageCompound(page)) 523 return false; 524 525 page = compound_head(page); 526 return is_huge_zero_page(page) || 527 page[1].compound_dtor == TRANSHUGE_PAGE_DTOR; 528 } 529 EXPORT_SYMBOL_GPL(is_transparent_hugepage); 530 531 static unsigned long __thp_get_unmapped_area(struct file *filp, 532 unsigned long addr, unsigned long len, 533 loff_t off, unsigned long flags, unsigned long size) 534 { 535 loff_t off_end = off + len; 536 loff_t off_align = round_up(off, size); 537 unsigned long len_pad, ret; 538 539 if (off_end <= off_align || (off_end - off_align) < size) 540 return 0; 541 542 len_pad = len + size; 543 if (len_pad < len || (off + len_pad) < off) 544 return 0; 545 546 ret = current->mm->get_unmapped_area(filp, addr, len_pad, 547 off >> PAGE_SHIFT, flags); 548 549 /* 550 * The failure might be due to length padding. The caller will retry 551 * without the padding. 552 */ 553 if (IS_ERR_VALUE(ret)) 554 return 0; 555 556 /* 557 * Do not try to align to THP boundary if allocation at the address 558 * hint succeeds. 559 */ 560 if (ret == addr) 561 return addr; 562 563 ret += (off - ret) & (size - 1); 564 return ret; 565 } 566 567 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr, 568 unsigned long len, unsigned long pgoff, unsigned long flags) 569 { 570 unsigned long ret; 571 loff_t off = (loff_t)pgoff << PAGE_SHIFT; 572 573 if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD)) 574 goto out; 575 576 ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE); 577 if (ret) 578 return ret; 579 out: 580 return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags); 581 } 582 EXPORT_SYMBOL_GPL(thp_get_unmapped_area); 583 584 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf, 585 struct page *page, gfp_t gfp) 586 { 587 struct vm_area_struct *vma = vmf->vma; 588 pgtable_t pgtable; 589 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 590 vm_fault_t ret = 0; 591 592 VM_BUG_ON_PAGE(!PageCompound(page), page); 593 594 if (mem_cgroup_charge(page, vma->vm_mm, gfp)) { 595 put_page(page); 596 count_vm_event(THP_FAULT_FALLBACK); 597 count_vm_event(THP_FAULT_FALLBACK_CHARGE); 598 return VM_FAULT_FALLBACK; 599 } 600 cgroup_throttle_swaprate(page, gfp); 601 602 pgtable = pte_alloc_one(vma->vm_mm); 603 if (unlikely(!pgtable)) { 604 ret = VM_FAULT_OOM; 605 goto release; 606 } 607 608 clear_huge_page(page, vmf->address, HPAGE_PMD_NR); 609 /* 610 * The memory barrier inside __SetPageUptodate makes sure that 611 * clear_huge_page writes become visible before the set_pmd_at() 612 * write. 613 */ 614 __SetPageUptodate(page); 615 616 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 617 if (unlikely(!pmd_none(*vmf->pmd))) { 618 goto unlock_release; 619 } else { 620 pmd_t entry; 621 622 ret = check_stable_address_space(vma->vm_mm); 623 if (ret) 624 goto unlock_release; 625 626 /* Deliver the page fault to userland */ 627 if (userfaultfd_missing(vma)) { 628 spin_unlock(vmf->ptl); 629 put_page(page); 630 pte_free(vma->vm_mm, pgtable); 631 ret = handle_userfault(vmf, VM_UFFD_MISSING); 632 VM_BUG_ON(ret & VM_FAULT_FALLBACK); 633 return ret; 634 } 635 636 entry = mk_huge_pmd(page, vma->vm_page_prot); 637 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 638 page_add_new_anon_rmap(page, vma, haddr, true); 639 lru_cache_add_inactive_or_unevictable(page, vma); 640 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable); 641 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); 642 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 643 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); 644 mm_inc_nr_ptes(vma->vm_mm); 645 spin_unlock(vmf->ptl); 646 count_vm_event(THP_FAULT_ALLOC); 647 count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC); 648 } 649 650 return 0; 651 unlock_release: 652 spin_unlock(vmf->ptl); 653 release: 654 if (pgtable) 655 pte_free(vma->vm_mm, pgtable); 656 put_page(page); 657 return ret; 658 659 } 660 661 /* 662 * always: directly stall for all thp allocations 663 * defer: wake kswapd and fail if not immediately available 664 * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise 665 * fail if not immediately available 666 * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately 667 * available 668 * never: never stall for any thp allocation 669 */ 670 gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma) 671 { 672 const bool vma_madvised = vma && (vma->vm_flags & VM_HUGEPAGE); 673 674 /* Always do synchronous compaction */ 675 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) 676 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY); 677 678 /* Kick kcompactd and fail quickly */ 679 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) 680 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM; 681 682 /* Synchronous compaction if madvised, otherwise kick kcompactd */ 683 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags)) 684 return GFP_TRANSHUGE_LIGHT | 685 (vma_madvised ? __GFP_DIRECT_RECLAIM : 686 __GFP_KSWAPD_RECLAIM); 687 688 /* Only do synchronous compaction if madvised */ 689 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) 690 return GFP_TRANSHUGE_LIGHT | 691 (vma_madvised ? __GFP_DIRECT_RECLAIM : 0); 692 693 return GFP_TRANSHUGE_LIGHT; 694 } 695 696 /* Caller must hold page table lock. */ 697 static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, 698 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, 699 struct page *zero_page) 700 { 701 pmd_t entry; 702 if (!pmd_none(*pmd)) 703 return; 704 entry = mk_pmd(zero_page, vma->vm_page_prot); 705 entry = pmd_mkhuge(entry); 706 if (pgtable) 707 pgtable_trans_huge_deposit(mm, pmd, pgtable); 708 set_pmd_at(mm, haddr, pmd, entry); 709 mm_inc_nr_ptes(mm); 710 } 711 712 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf) 713 { 714 struct vm_area_struct *vma = vmf->vma; 715 gfp_t gfp; 716 struct page *page; 717 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 718 719 if (!transhuge_vma_suitable(vma, haddr)) 720 return VM_FAULT_FALLBACK; 721 if (unlikely(anon_vma_prepare(vma))) 722 return VM_FAULT_OOM; 723 if (unlikely(khugepaged_enter(vma, vma->vm_flags))) 724 return VM_FAULT_OOM; 725 if (!(vmf->flags & FAULT_FLAG_WRITE) && 726 !mm_forbids_zeropage(vma->vm_mm) && 727 transparent_hugepage_use_zero_page()) { 728 pgtable_t pgtable; 729 struct page *zero_page; 730 vm_fault_t ret; 731 pgtable = pte_alloc_one(vma->vm_mm); 732 if (unlikely(!pgtable)) 733 return VM_FAULT_OOM; 734 zero_page = mm_get_huge_zero_page(vma->vm_mm); 735 if (unlikely(!zero_page)) { 736 pte_free(vma->vm_mm, pgtable); 737 count_vm_event(THP_FAULT_FALLBACK); 738 return VM_FAULT_FALLBACK; 739 } 740 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 741 ret = 0; 742 if (pmd_none(*vmf->pmd)) { 743 ret = check_stable_address_space(vma->vm_mm); 744 if (ret) { 745 spin_unlock(vmf->ptl); 746 pte_free(vma->vm_mm, pgtable); 747 } else if (userfaultfd_missing(vma)) { 748 spin_unlock(vmf->ptl); 749 pte_free(vma->vm_mm, pgtable); 750 ret = handle_userfault(vmf, VM_UFFD_MISSING); 751 VM_BUG_ON(ret & VM_FAULT_FALLBACK); 752 } else { 753 set_huge_zero_page(pgtable, vma->vm_mm, vma, 754 haddr, vmf->pmd, zero_page); 755 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 756 spin_unlock(vmf->ptl); 757 } 758 } else { 759 spin_unlock(vmf->ptl); 760 pte_free(vma->vm_mm, pgtable); 761 } 762 return ret; 763 } 764 gfp = vma_thp_gfp_mask(vma); 765 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER); 766 if (unlikely(!page)) { 767 count_vm_event(THP_FAULT_FALLBACK); 768 return VM_FAULT_FALLBACK; 769 } 770 prep_transhuge_page(page); 771 return __do_huge_pmd_anonymous_page(vmf, page, gfp); 772 } 773 774 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, 775 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write, 776 pgtable_t pgtable) 777 { 778 struct mm_struct *mm = vma->vm_mm; 779 pmd_t entry; 780 spinlock_t *ptl; 781 782 ptl = pmd_lock(mm, pmd); 783 if (!pmd_none(*pmd)) { 784 if (write) { 785 if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) { 786 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd)); 787 goto out_unlock; 788 } 789 entry = pmd_mkyoung(*pmd); 790 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 791 if (pmdp_set_access_flags(vma, addr, pmd, entry, 1)) 792 update_mmu_cache_pmd(vma, addr, pmd); 793 } 794 795 goto out_unlock; 796 } 797 798 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot)); 799 if (pfn_t_devmap(pfn)) 800 entry = pmd_mkdevmap(entry); 801 if (write) { 802 entry = pmd_mkyoung(pmd_mkdirty(entry)); 803 entry = maybe_pmd_mkwrite(entry, vma); 804 } 805 806 if (pgtable) { 807 pgtable_trans_huge_deposit(mm, pmd, pgtable); 808 mm_inc_nr_ptes(mm); 809 pgtable = NULL; 810 } 811 812 set_pmd_at(mm, addr, pmd, entry); 813 update_mmu_cache_pmd(vma, addr, pmd); 814 815 out_unlock: 816 spin_unlock(ptl); 817 if (pgtable) 818 pte_free(mm, pgtable); 819 } 820 821 /** 822 * vmf_insert_pfn_pmd_prot - insert a pmd size pfn 823 * @vmf: Structure describing the fault 824 * @pfn: pfn to insert 825 * @pgprot: page protection to use 826 * @write: whether it's a write fault 827 * 828 * Insert a pmd size pfn. See vmf_insert_pfn() for additional info and 829 * also consult the vmf_insert_mixed_prot() documentation when 830 * @pgprot != @vmf->vma->vm_page_prot. 831 * 832 * Return: vm_fault_t value. 833 */ 834 vm_fault_t vmf_insert_pfn_pmd_prot(struct vm_fault *vmf, pfn_t pfn, 835 pgprot_t pgprot, bool write) 836 { 837 unsigned long addr = vmf->address & PMD_MASK; 838 struct vm_area_struct *vma = vmf->vma; 839 pgtable_t pgtable = NULL; 840 841 /* 842 * If we had pmd_special, we could avoid all these restrictions, 843 * but we need to be consistent with PTEs and architectures that 844 * can't support a 'special' bit. 845 */ 846 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) && 847 !pfn_t_devmap(pfn)); 848 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == 849 (VM_PFNMAP|VM_MIXEDMAP)); 850 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); 851 852 if (addr < vma->vm_start || addr >= vma->vm_end) 853 return VM_FAULT_SIGBUS; 854 855 if (arch_needs_pgtable_deposit()) { 856 pgtable = pte_alloc_one(vma->vm_mm); 857 if (!pgtable) 858 return VM_FAULT_OOM; 859 } 860 861 track_pfn_insert(vma, &pgprot, pfn); 862 863 insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable); 864 return VM_FAULT_NOPAGE; 865 } 866 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd_prot); 867 868 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 869 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma) 870 { 871 if (likely(vma->vm_flags & VM_WRITE)) 872 pud = pud_mkwrite(pud); 873 return pud; 874 } 875 876 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr, 877 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write) 878 { 879 struct mm_struct *mm = vma->vm_mm; 880 pud_t entry; 881 spinlock_t *ptl; 882 883 ptl = pud_lock(mm, pud); 884 if (!pud_none(*pud)) { 885 if (write) { 886 if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) { 887 WARN_ON_ONCE(!is_huge_zero_pud(*pud)); 888 goto out_unlock; 889 } 890 entry = pud_mkyoung(*pud); 891 entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma); 892 if (pudp_set_access_flags(vma, addr, pud, entry, 1)) 893 update_mmu_cache_pud(vma, addr, pud); 894 } 895 goto out_unlock; 896 } 897 898 entry = pud_mkhuge(pfn_t_pud(pfn, prot)); 899 if (pfn_t_devmap(pfn)) 900 entry = pud_mkdevmap(entry); 901 if (write) { 902 entry = pud_mkyoung(pud_mkdirty(entry)); 903 entry = maybe_pud_mkwrite(entry, vma); 904 } 905 set_pud_at(mm, addr, pud, entry); 906 update_mmu_cache_pud(vma, addr, pud); 907 908 out_unlock: 909 spin_unlock(ptl); 910 } 911 912 /** 913 * vmf_insert_pfn_pud_prot - insert a pud size pfn 914 * @vmf: Structure describing the fault 915 * @pfn: pfn to insert 916 * @pgprot: page protection to use 917 * @write: whether it's a write fault 918 * 919 * Insert a pud size pfn. See vmf_insert_pfn() for additional info and 920 * also consult the vmf_insert_mixed_prot() documentation when 921 * @pgprot != @vmf->vma->vm_page_prot. 922 * 923 * Return: vm_fault_t value. 924 */ 925 vm_fault_t vmf_insert_pfn_pud_prot(struct vm_fault *vmf, pfn_t pfn, 926 pgprot_t pgprot, bool write) 927 { 928 unsigned long addr = vmf->address & PUD_MASK; 929 struct vm_area_struct *vma = vmf->vma; 930 931 /* 932 * If we had pud_special, we could avoid all these restrictions, 933 * but we need to be consistent with PTEs and architectures that 934 * can't support a 'special' bit. 935 */ 936 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) && 937 !pfn_t_devmap(pfn)); 938 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == 939 (VM_PFNMAP|VM_MIXEDMAP)); 940 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); 941 942 if (addr < vma->vm_start || addr >= vma->vm_end) 943 return VM_FAULT_SIGBUS; 944 945 track_pfn_insert(vma, &pgprot, pfn); 946 947 insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write); 948 return VM_FAULT_NOPAGE; 949 } 950 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud_prot); 951 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ 952 953 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr, 954 pmd_t *pmd, int flags) 955 { 956 pmd_t _pmd; 957 958 _pmd = pmd_mkyoung(*pmd); 959 if (flags & FOLL_WRITE) 960 _pmd = pmd_mkdirty(_pmd); 961 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, 962 pmd, _pmd, flags & FOLL_WRITE)) 963 update_mmu_cache_pmd(vma, addr, pmd); 964 } 965 966 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, 967 pmd_t *pmd, int flags, struct dev_pagemap **pgmap) 968 { 969 unsigned long pfn = pmd_pfn(*pmd); 970 struct mm_struct *mm = vma->vm_mm; 971 struct page *page; 972 973 assert_spin_locked(pmd_lockptr(mm, pmd)); 974 975 /* 976 * When we COW a devmap PMD entry, we split it into PTEs, so we should 977 * not be in this function with `flags & FOLL_COW` set. 978 */ 979 WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set"); 980 981 /* FOLL_GET and FOLL_PIN are mutually exclusive. */ 982 if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == 983 (FOLL_PIN | FOLL_GET))) 984 return NULL; 985 986 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 987 return NULL; 988 989 if (pmd_present(*pmd) && pmd_devmap(*pmd)) 990 /* pass */; 991 else 992 return NULL; 993 994 if (flags & FOLL_TOUCH) 995 touch_pmd(vma, addr, pmd, flags); 996 997 /* 998 * device mapped pages can only be returned if the 999 * caller will manage the page reference count. 1000 */ 1001 if (!(flags & (FOLL_GET | FOLL_PIN))) 1002 return ERR_PTR(-EEXIST); 1003 1004 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT; 1005 *pgmap = get_dev_pagemap(pfn, *pgmap); 1006 if (!*pgmap) 1007 return ERR_PTR(-EFAULT); 1008 page = pfn_to_page(pfn); 1009 if (!try_grab_page(page, flags)) 1010 page = ERR_PTR(-ENOMEM); 1011 1012 return page; 1013 } 1014 1015 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 1016 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 1017 struct vm_area_struct *vma) 1018 { 1019 spinlock_t *dst_ptl, *src_ptl; 1020 struct page *src_page; 1021 pmd_t pmd; 1022 pgtable_t pgtable = NULL; 1023 int ret = -ENOMEM; 1024 1025 /* Skip if can be re-fill on fault */ 1026 if (!vma_is_anonymous(vma)) 1027 return 0; 1028 1029 pgtable = pte_alloc_one(dst_mm); 1030 if (unlikely(!pgtable)) 1031 goto out; 1032 1033 dst_ptl = pmd_lock(dst_mm, dst_pmd); 1034 src_ptl = pmd_lockptr(src_mm, src_pmd); 1035 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); 1036 1037 ret = -EAGAIN; 1038 pmd = *src_pmd; 1039 1040 /* 1041 * Make sure the _PAGE_UFFD_WP bit is cleared if the new VMA 1042 * does not have the VM_UFFD_WP, which means that the uffd 1043 * fork event is not enabled. 1044 */ 1045 if (!(vma->vm_flags & VM_UFFD_WP)) 1046 pmd = pmd_clear_uffd_wp(pmd); 1047 1048 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 1049 if (unlikely(is_swap_pmd(pmd))) { 1050 swp_entry_t entry = pmd_to_swp_entry(pmd); 1051 1052 VM_BUG_ON(!is_pmd_migration_entry(pmd)); 1053 if (is_write_migration_entry(entry)) { 1054 make_migration_entry_read(&entry); 1055 pmd = swp_entry_to_pmd(entry); 1056 if (pmd_swp_soft_dirty(*src_pmd)) 1057 pmd = pmd_swp_mksoft_dirty(pmd); 1058 set_pmd_at(src_mm, addr, src_pmd, pmd); 1059 } 1060 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 1061 mm_inc_nr_ptes(dst_mm); 1062 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); 1063 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 1064 ret = 0; 1065 goto out_unlock; 1066 } 1067 #endif 1068 1069 if (unlikely(!pmd_trans_huge(pmd))) { 1070 pte_free(dst_mm, pgtable); 1071 goto out_unlock; 1072 } 1073 /* 1074 * When page table lock is held, the huge zero pmd should not be 1075 * under splitting since we don't split the page itself, only pmd to 1076 * a page table. 1077 */ 1078 if (is_huge_zero_pmd(pmd)) { 1079 struct page *zero_page; 1080 /* 1081 * get_huge_zero_page() will never allocate a new page here, 1082 * since we already have a zero page to copy. It just takes a 1083 * reference. 1084 */ 1085 zero_page = mm_get_huge_zero_page(dst_mm); 1086 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, 1087 zero_page); 1088 ret = 0; 1089 goto out_unlock; 1090 } 1091 1092 src_page = pmd_page(pmd); 1093 VM_BUG_ON_PAGE(!PageHead(src_page), src_page); 1094 1095 /* 1096 * If this page is a potentially pinned page, split and retry the fault 1097 * with smaller page size. Normally this should not happen because the 1098 * userspace should use MADV_DONTFORK upon pinned regions. This is a 1099 * best effort that the pinned pages won't be replaced by another 1100 * random page during the coming copy-on-write. 1101 */ 1102 if (unlikely(page_needs_cow_for_dma(vma, src_page))) { 1103 pte_free(dst_mm, pgtable); 1104 spin_unlock(src_ptl); 1105 spin_unlock(dst_ptl); 1106 __split_huge_pmd(vma, src_pmd, addr, false, NULL); 1107 return -EAGAIN; 1108 } 1109 1110 get_page(src_page); 1111 page_dup_rmap(src_page, true); 1112 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 1113 mm_inc_nr_ptes(dst_mm); 1114 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); 1115 1116 pmdp_set_wrprotect(src_mm, addr, src_pmd); 1117 pmd = pmd_mkold(pmd_wrprotect(pmd)); 1118 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 1119 1120 ret = 0; 1121 out_unlock: 1122 spin_unlock(src_ptl); 1123 spin_unlock(dst_ptl); 1124 out: 1125 return ret; 1126 } 1127 1128 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 1129 static void touch_pud(struct vm_area_struct *vma, unsigned long addr, 1130 pud_t *pud, int flags) 1131 { 1132 pud_t _pud; 1133 1134 _pud = pud_mkyoung(*pud); 1135 if (flags & FOLL_WRITE) 1136 _pud = pud_mkdirty(_pud); 1137 if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK, 1138 pud, _pud, flags & FOLL_WRITE)) 1139 update_mmu_cache_pud(vma, addr, pud); 1140 } 1141 1142 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr, 1143 pud_t *pud, int flags, struct dev_pagemap **pgmap) 1144 { 1145 unsigned long pfn = pud_pfn(*pud); 1146 struct mm_struct *mm = vma->vm_mm; 1147 struct page *page; 1148 1149 assert_spin_locked(pud_lockptr(mm, pud)); 1150 1151 if (flags & FOLL_WRITE && !pud_write(*pud)) 1152 return NULL; 1153 1154 /* FOLL_GET and FOLL_PIN are mutually exclusive. */ 1155 if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == 1156 (FOLL_PIN | FOLL_GET))) 1157 return NULL; 1158 1159 if (pud_present(*pud) && pud_devmap(*pud)) 1160 /* pass */; 1161 else 1162 return NULL; 1163 1164 if (flags & FOLL_TOUCH) 1165 touch_pud(vma, addr, pud, flags); 1166 1167 /* 1168 * device mapped pages can only be returned if the 1169 * caller will manage the page reference count. 1170 * 1171 * At least one of FOLL_GET | FOLL_PIN must be set, so assert that here: 1172 */ 1173 if (!(flags & (FOLL_GET | FOLL_PIN))) 1174 return ERR_PTR(-EEXIST); 1175 1176 pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT; 1177 *pgmap = get_dev_pagemap(pfn, *pgmap); 1178 if (!*pgmap) 1179 return ERR_PTR(-EFAULT); 1180 page = pfn_to_page(pfn); 1181 if (!try_grab_page(page, flags)) 1182 page = ERR_PTR(-ENOMEM); 1183 1184 return page; 1185 } 1186 1187 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm, 1188 pud_t *dst_pud, pud_t *src_pud, unsigned long addr, 1189 struct vm_area_struct *vma) 1190 { 1191 spinlock_t *dst_ptl, *src_ptl; 1192 pud_t pud; 1193 int ret; 1194 1195 dst_ptl = pud_lock(dst_mm, dst_pud); 1196 src_ptl = pud_lockptr(src_mm, src_pud); 1197 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); 1198 1199 ret = -EAGAIN; 1200 pud = *src_pud; 1201 if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud))) 1202 goto out_unlock; 1203 1204 /* 1205 * When page table lock is held, the huge zero pud should not be 1206 * under splitting since we don't split the page itself, only pud to 1207 * a page table. 1208 */ 1209 if (is_huge_zero_pud(pud)) { 1210 /* No huge zero pud yet */ 1211 } 1212 1213 /* Please refer to comments in copy_huge_pmd() */ 1214 if (unlikely(page_needs_cow_for_dma(vma, pud_page(pud)))) { 1215 spin_unlock(src_ptl); 1216 spin_unlock(dst_ptl); 1217 __split_huge_pud(vma, src_pud, addr); 1218 return -EAGAIN; 1219 } 1220 1221 pudp_set_wrprotect(src_mm, addr, src_pud); 1222 pud = pud_mkold(pud_wrprotect(pud)); 1223 set_pud_at(dst_mm, addr, dst_pud, pud); 1224 1225 ret = 0; 1226 out_unlock: 1227 spin_unlock(src_ptl); 1228 spin_unlock(dst_ptl); 1229 return ret; 1230 } 1231 1232 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud) 1233 { 1234 pud_t entry; 1235 unsigned long haddr; 1236 bool write = vmf->flags & FAULT_FLAG_WRITE; 1237 1238 vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud); 1239 if (unlikely(!pud_same(*vmf->pud, orig_pud))) 1240 goto unlock; 1241 1242 entry = pud_mkyoung(orig_pud); 1243 if (write) 1244 entry = pud_mkdirty(entry); 1245 haddr = vmf->address & HPAGE_PUD_MASK; 1246 if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write)) 1247 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud); 1248 1249 unlock: 1250 spin_unlock(vmf->ptl); 1251 } 1252 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ 1253 1254 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd) 1255 { 1256 pmd_t entry; 1257 unsigned long haddr; 1258 bool write = vmf->flags & FAULT_FLAG_WRITE; 1259 1260 vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); 1261 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) 1262 goto unlock; 1263 1264 entry = pmd_mkyoung(orig_pmd); 1265 if (write) 1266 entry = pmd_mkdirty(entry); 1267 haddr = vmf->address & HPAGE_PMD_MASK; 1268 if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write)) 1269 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd); 1270 1271 unlock: 1272 spin_unlock(vmf->ptl); 1273 } 1274 1275 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd) 1276 { 1277 struct vm_area_struct *vma = vmf->vma; 1278 struct page *page; 1279 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 1280 1281 vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd); 1282 VM_BUG_ON_VMA(!vma->anon_vma, vma); 1283 1284 if (is_huge_zero_pmd(orig_pmd)) 1285 goto fallback; 1286 1287 spin_lock(vmf->ptl); 1288 1289 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { 1290 spin_unlock(vmf->ptl); 1291 return 0; 1292 } 1293 1294 page = pmd_page(orig_pmd); 1295 VM_BUG_ON_PAGE(!PageHead(page), page); 1296 1297 /* Lock page for reuse_swap_page() */ 1298 if (!trylock_page(page)) { 1299 get_page(page); 1300 spin_unlock(vmf->ptl); 1301 lock_page(page); 1302 spin_lock(vmf->ptl); 1303 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { 1304 spin_unlock(vmf->ptl); 1305 unlock_page(page); 1306 put_page(page); 1307 return 0; 1308 } 1309 put_page(page); 1310 } 1311 1312 /* 1313 * We can only reuse the page if nobody else maps the huge page or it's 1314 * part. 1315 */ 1316 if (reuse_swap_page(page, NULL)) { 1317 pmd_t entry; 1318 entry = pmd_mkyoung(orig_pmd); 1319 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1320 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1)) 1321 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 1322 unlock_page(page); 1323 spin_unlock(vmf->ptl); 1324 return VM_FAULT_WRITE; 1325 } 1326 1327 unlock_page(page); 1328 spin_unlock(vmf->ptl); 1329 fallback: 1330 __split_huge_pmd(vma, vmf->pmd, vmf->address, false, NULL); 1331 return VM_FAULT_FALLBACK; 1332 } 1333 1334 /* 1335 * FOLL_FORCE can write to even unwritable pmd's, but only 1336 * after we've gone through a COW cycle and they are dirty. 1337 */ 1338 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags) 1339 { 1340 return pmd_write(pmd) || 1341 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd)); 1342 } 1343 1344 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1345 unsigned long addr, 1346 pmd_t *pmd, 1347 unsigned int flags) 1348 { 1349 struct mm_struct *mm = vma->vm_mm; 1350 struct page *page = NULL; 1351 1352 assert_spin_locked(pmd_lockptr(mm, pmd)); 1353 1354 if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags)) 1355 goto out; 1356 1357 /* Avoid dumping huge zero page */ 1358 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) 1359 return ERR_PTR(-EFAULT); 1360 1361 /* Full NUMA hinting faults to serialise migration in fault paths */ 1362 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) 1363 goto out; 1364 1365 page = pmd_page(*pmd); 1366 VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page); 1367 1368 if (!try_grab_page(page, flags)) 1369 return ERR_PTR(-ENOMEM); 1370 1371 if (flags & FOLL_TOUCH) 1372 touch_pmd(vma, addr, pmd, flags); 1373 1374 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 1375 /* 1376 * We don't mlock() pte-mapped THPs. This way we can avoid 1377 * leaking mlocked pages into non-VM_LOCKED VMAs. 1378 * 1379 * For anon THP: 1380 * 1381 * In most cases the pmd is the only mapping of the page as we 1382 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for 1383 * writable private mappings in populate_vma_page_range(). 1384 * 1385 * The only scenario when we have the page shared here is if we 1386 * mlocking read-only mapping shared over fork(). We skip 1387 * mlocking such pages. 1388 * 1389 * For file THP: 1390 * 1391 * We can expect PageDoubleMap() to be stable under page lock: 1392 * for file pages we set it in page_add_file_rmap(), which 1393 * requires page to be locked. 1394 */ 1395 1396 if (PageAnon(page) && compound_mapcount(page) != 1) 1397 goto skip_mlock; 1398 if (PageDoubleMap(page) || !page->mapping) 1399 goto skip_mlock; 1400 if (!trylock_page(page)) 1401 goto skip_mlock; 1402 if (page->mapping && !PageDoubleMap(page)) 1403 mlock_vma_page(page); 1404 unlock_page(page); 1405 } 1406 skip_mlock: 1407 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1408 VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page); 1409 1410 out: 1411 return page; 1412 } 1413 1414 /* NUMA hinting page fault entry point for trans huge pmds */ 1415 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) 1416 { 1417 struct vm_area_struct *vma = vmf->vma; 1418 struct anon_vma *anon_vma = NULL; 1419 struct page *page; 1420 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 1421 int page_nid = NUMA_NO_NODE, this_nid = numa_node_id(); 1422 int target_nid, last_cpupid = -1; 1423 bool page_locked; 1424 bool migrated = false; 1425 bool was_writable; 1426 int flags = 0; 1427 1428 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 1429 if (unlikely(!pmd_same(pmd, *vmf->pmd))) 1430 goto out_unlock; 1431 1432 /* 1433 * If there are potential migrations, wait for completion and retry 1434 * without disrupting NUMA hinting information. Do not relock and 1435 * check_same as the page may no longer be mapped. 1436 */ 1437 if (unlikely(pmd_trans_migrating(*vmf->pmd))) { 1438 page = pmd_page(*vmf->pmd); 1439 if (!get_page_unless_zero(page)) 1440 goto out_unlock; 1441 spin_unlock(vmf->ptl); 1442 put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE); 1443 goto out; 1444 } 1445 1446 page = pmd_page(pmd); 1447 BUG_ON(is_huge_zero_page(page)); 1448 page_nid = page_to_nid(page); 1449 last_cpupid = page_cpupid_last(page); 1450 count_vm_numa_event(NUMA_HINT_FAULTS); 1451 if (page_nid == this_nid) { 1452 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); 1453 flags |= TNF_FAULT_LOCAL; 1454 } 1455 1456 /* See similar comment in do_numa_page for explanation */ 1457 if (!pmd_savedwrite(pmd)) 1458 flags |= TNF_NO_GROUP; 1459 1460 /* 1461 * Acquire the page lock to serialise THP migrations but avoid dropping 1462 * page_table_lock if at all possible 1463 */ 1464 page_locked = trylock_page(page); 1465 target_nid = mpol_misplaced(page, vma, haddr); 1466 /* Migration could have started since the pmd_trans_migrating check */ 1467 if (!page_locked) { 1468 page_nid = NUMA_NO_NODE; 1469 if (!get_page_unless_zero(page)) 1470 goto out_unlock; 1471 spin_unlock(vmf->ptl); 1472 put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE); 1473 goto out; 1474 } else if (target_nid == NUMA_NO_NODE) { 1475 /* There are no parallel migrations and page is in the right 1476 * node. Clear the numa hinting info in this pmd. 1477 */ 1478 goto clear_pmdnuma; 1479 } 1480 1481 /* 1482 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma 1483 * to serialises splits 1484 */ 1485 get_page(page); 1486 spin_unlock(vmf->ptl); 1487 anon_vma = page_lock_anon_vma_read(page); 1488 1489 /* Confirm the PMD did not change while page_table_lock was released */ 1490 spin_lock(vmf->ptl); 1491 if (unlikely(!pmd_same(pmd, *vmf->pmd))) { 1492 unlock_page(page); 1493 put_page(page); 1494 page_nid = NUMA_NO_NODE; 1495 goto out_unlock; 1496 } 1497 1498 /* Bail if we fail to protect against THP splits for any reason */ 1499 if (unlikely(!anon_vma)) { 1500 put_page(page); 1501 page_nid = NUMA_NO_NODE; 1502 goto clear_pmdnuma; 1503 } 1504 1505 /* 1506 * Since we took the NUMA fault, we must have observed the !accessible 1507 * bit. Make sure all other CPUs agree with that, to avoid them 1508 * modifying the page we're about to migrate. 1509 * 1510 * Must be done under PTL such that we'll observe the relevant 1511 * inc_tlb_flush_pending(). 1512 * 1513 * We are not sure a pending tlb flush here is for a huge page 1514 * mapping or not. Hence use the tlb range variant 1515 */ 1516 if (mm_tlb_flush_pending(vma->vm_mm)) { 1517 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE); 1518 /* 1519 * change_huge_pmd() released the pmd lock before 1520 * invalidating the secondary MMUs sharing the primary 1521 * MMU pagetables (with ->invalidate_range()). The 1522 * mmu_notifier_invalidate_range_end() (which 1523 * internally calls ->invalidate_range()) in 1524 * change_pmd_range() will run after us, so we can't 1525 * rely on it here and we need an explicit invalidate. 1526 */ 1527 mmu_notifier_invalidate_range(vma->vm_mm, haddr, 1528 haddr + HPAGE_PMD_SIZE); 1529 } 1530 1531 /* 1532 * Migrate the THP to the requested node, returns with page unlocked 1533 * and access rights restored. 1534 */ 1535 spin_unlock(vmf->ptl); 1536 1537 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma, 1538 vmf->pmd, pmd, vmf->address, page, target_nid); 1539 if (migrated) { 1540 flags |= TNF_MIGRATED; 1541 page_nid = target_nid; 1542 } else 1543 flags |= TNF_MIGRATE_FAIL; 1544 1545 goto out; 1546 clear_pmdnuma: 1547 BUG_ON(!PageLocked(page)); 1548 was_writable = pmd_savedwrite(pmd); 1549 pmd = pmd_modify(pmd, vma->vm_page_prot); 1550 pmd = pmd_mkyoung(pmd); 1551 if (was_writable) 1552 pmd = pmd_mkwrite(pmd); 1553 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd); 1554 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 1555 unlock_page(page); 1556 out_unlock: 1557 spin_unlock(vmf->ptl); 1558 1559 out: 1560 if (anon_vma) 1561 page_unlock_anon_vma_read(anon_vma); 1562 1563 if (page_nid != NUMA_NO_NODE) 1564 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, 1565 flags); 1566 1567 return 0; 1568 } 1569 1570 /* 1571 * Return true if we do MADV_FREE successfully on entire pmd page. 1572 * Otherwise, return false. 1573 */ 1574 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1575 pmd_t *pmd, unsigned long addr, unsigned long next) 1576 { 1577 spinlock_t *ptl; 1578 pmd_t orig_pmd; 1579 struct page *page; 1580 struct mm_struct *mm = tlb->mm; 1581 bool ret = false; 1582 1583 tlb_change_page_size(tlb, HPAGE_PMD_SIZE); 1584 1585 ptl = pmd_trans_huge_lock(pmd, vma); 1586 if (!ptl) 1587 goto out_unlocked; 1588 1589 orig_pmd = *pmd; 1590 if (is_huge_zero_pmd(orig_pmd)) 1591 goto out; 1592 1593 if (unlikely(!pmd_present(orig_pmd))) { 1594 VM_BUG_ON(thp_migration_supported() && 1595 !is_pmd_migration_entry(orig_pmd)); 1596 goto out; 1597 } 1598 1599 page = pmd_page(orig_pmd); 1600 /* 1601 * If other processes are mapping this page, we couldn't discard 1602 * the page unless they all do MADV_FREE so let's skip the page. 1603 */ 1604 if (page_mapcount(page) != 1) 1605 goto out; 1606 1607 if (!trylock_page(page)) 1608 goto out; 1609 1610 /* 1611 * If user want to discard part-pages of THP, split it so MADV_FREE 1612 * will deactivate only them. 1613 */ 1614 if (next - addr != HPAGE_PMD_SIZE) { 1615 get_page(page); 1616 spin_unlock(ptl); 1617 split_huge_page(page); 1618 unlock_page(page); 1619 put_page(page); 1620 goto out_unlocked; 1621 } 1622 1623 if (PageDirty(page)) 1624 ClearPageDirty(page); 1625 unlock_page(page); 1626 1627 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { 1628 pmdp_invalidate(vma, addr, pmd); 1629 orig_pmd = pmd_mkold(orig_pmd); 1630 orig_pmd = pmd_mkclean(orig_pmd); 1631 1632 set_pmd_at(mm, addr, pmd, orig_pmd); 1633 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1634 } 1635 1636 mark_page_lazyfree(page); 1637 ret = true; 1638 out: 1639 spin_unlock(ptl); 1640 out_unlocked: 1641 return ret; 1642 } 1643 1644 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd) 1645 { 1646 pgtable_t pgtable; 1647 1648 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1649 pte_free(mm, pgtable); 1650 mm_dec_nr_ptes(mm); 1651 } 1652 1653 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1654 pmd_t *pmd, unsigned long addr) 1655 { 1656 pmd_t orig_pmd; 1657 spinlock_t *ptl; 1658 1659 tlb_change_page_size(tlb, HPAGE_PMD_SIZE); 1660 1661 ptl = __pmd_trans_huge_lock(pmd, vma); 1662 if (!ptl) 1663 return 0; 1664 /* 1665 * For architectures like ppc64 we look at deposited pgtable 1666 * when calling pmdp_huge_get_and_clear. So do the 1667 * pgtable_trans_huge_withdraw after finishing pmdp related 1668 * operations. 1669 */ 1670 orig_pmd = pmdp_huge_get_and_clear_full(vma, addr, pmd, 1671 tlb->fullmm); 1672 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1673 if (vma_is_special_huge(vma)) { 1674 if (arch_needs_pgtable_deposit()) 1675 zap_deposited_table(tlb->mm, pmd); 1676 spin_unlock(ptl); 1677 if (is_huge_zero_pmd(orig_pmd)) 1678 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); 1679 } else if (is_huge_zero_pmd(orig_pmd)) { 1680 zap_deposited_table(tlb->mm, pmd); 1681 spin_unlock(ptl); 1682 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); 1683 } else { 1684 struct page *page = NULL; 1685 int flush_needed = 1; 1686 1687 if (pmd_present(orig_pmd)) { 1688 page = pmd_page(orig_pmd); 1689 page_remove_rmap(page, true); 1690 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); 1691 VM_BUG_ON_PAGE(!PageHead(page), page); 1692 } else if (thp_migration_supported()) { 1693 swp_entry_t entry; 1694 1695 VM_BUG_ON(!is_pmd_migration_entry(orig_pmd)); 1696 entry = pmd_to_swp_entry(orig_pmd); 1697 page = migration_entry_to_page(entry); 1698 flush_needed = 0; 1699 } else 1700 WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!"); 1701 1702 if (PageAnon(page)) { 1703 zap_deposited_table(tlb->mm, pmd); 1704 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1705 } else { 1706 if (arch_needs_pgtable_deposit()) 1707 zap_deposited_table(tlb->mm, pmd); 1708 add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR); 1709 } 1710 1711 spin_unlock(ptl); 1712 if (flush_needed) 1713 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE); 1714 } 1715 return 1; 1716 } 1717 1718 #ifndef pmd_move_must_withdraw 1719 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl, 1720 spinlock_t *old_pmd_ptl, 1721 struct vm_area_struct *vma) 1722 { 1723 /* 1724 * With split pmd lock we also need to move preallocated 1725 * PTE page table if new_pmd is on different PMD page table. 1726 * 1727 * We also don't deposit and withdraw tables for file pages. 1728 */ 1729 return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma); 1730 } 1731 #endif 1732 1733 static pmd_t move_soft_dirty_pmd(pmd_t pmd) 1734 { 1735 #ifdef CONFIG_MEM_SOFT_DIRTY 1736 if (unlikely(is_pmd_migration_entry(pmd))) 1737 pmd = pmd_swp_mksoft_dirty(pmd); 1738 else if (pmd_present(pmd)) 1739 pmd = pmd_mksoft_dirty(pmd); 1740 #endif 1741 return pmd; 1742 } 1743 1744 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr, 1745 unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd) 1746 { 1747 spinlock_t *old_ptl, *new_ptl; 1748 pmd_t pmd; 1749 struct mm_struct *mm = vma->vm_mm; 1750 bool force_flush = false; 1751 1752 /* 1753 * The destination pmd shouldn't be established, free_pgtables() 1754 * should have release it. 1755 */ 1756 if (WARN_ON(!pmd_none(*new_pmd))) { 1757 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1758 return false; 1759 } 1760 1761 /* 1762 * We don't have to worry about the ordering of src and dst 1763 * ptlocks because exclusive mmap_lock prevents deadlock. 1764 */ 1765 old_ptl = __pmd_trans_huge_lock(old_pmd, vma); 1766 if (old_ptl) { 1767 new_ptl = pmd_lockptr(mm, new_pmd); 1768 if (new_ptl != old_ptl) 1769 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 1770 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd); 1771 if (pmd_present(pmd)) 1772 force_flush = true; 1773 VM_BUG_ON(!pmd_none(*new_pmd)); 1774 1775 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) { 1776 pgtable_t pgtable; 1777 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); 1778 pgtable_trans_huge_deposit(mm, new_pmd, pgtable); 1779 } 1780 pmd = move_soft_dirty_pmd(pmd); 1781 set_pmd_at(mm, new_addr, new_pmd, pmd); 1782 if (force_flush) 1783 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE); 1784 if (new_ptl != old_ptl) 1785 spin_unlock(new_ptl); 1786 spin_unlock(old_ptl); 1787 return true; 1788 } 1789 return false; 1790 } 1791 1792 /* 1793 * Returns 1794 * - 0 if PMD could not be locked 1795 * - 1 if PMD was locked but protections unchanged and TLB flush unnecessary 1796 * - HPAGE_PMD_NR if protections changed and TLB flush necessary 1797 */ 1798 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1799 unsigned long addr, pgprot_t newprot, unsigned long cp_flags) 1800 { 1801 struct mm_struct *mm = vma->vm_mm; 1802 spinlock_t *ptl; 1803 pmd_t entry; 1804 bool preserve_write; 1805 int ret; 1806 bool prot_numa = cp_flags & MM_CP_PROT_NUMA; 1807 bool uffd_wp = cp_flags & MM_CP_UFFD_WP; 1808 bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; 1809 1810 ptl = __pmd_trans_huge_lock(pmd, vma); 1811 if (!ptl) 1812 return 0; 1813 1814 preserve_write = prot_numa && pmd_write(*pmd); 1815 ret = 1; 1816 1817 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 1818 if (is_swap_pmd(*pmd)) { 1819 swp_entry_t entry = pmd_to_swp_entry(*pmd); 1820 1821 VM_BUG_ON(!is_pmd_migration_entry(*pmd)); 1822 if (is_write_migration_entry(entry)) { 1823 pmd_t newpmd; 1824 /* 1825 * A protection check is difficult so 1826 * just be safe and disable write 1827 */ 1828 make_migration_entry_read(&entry); 1829 newpmd = swp_entry_to_pmd(entry); 1830 if (pmd_swp_soft_dirty(*pmd)) 1831 newpmd = pmd_swp_mksoft_dirty(newpmd); 1832 set_pmd_at(mm, addr, pmd, newpmd); 1833 } 1834 goto unlock; 1835 } 1836 #endif 1837 1838 /* 1839 * Avoid trapping faults against the zero page. The read-only 1840 * data is likely to be read-cached on the local CPU and 1841 * local/remote hits to the zero page are not interesting. 1842 */ 1843 if (prot_numa && is_huge_zero_pmd(*pmd)) 1844 goto unlock; 1845 1846 if (prot_numa && pmd_protnone(*pmd)) 1847 goto unlock; 1848 1849 /* 1850 * In case prot_numa, we are under mmap_read_lock(mm). It's critical 1851 * to not clear pmd intermittently to avoid race with MADV_DONTNEED 1852 * which is also under mmap_read_lock(mm): 1853 * 1854 * CPU0: CPU1: 1855 * change_huge_pmd(prot_numa=1) 1856 * pmdp_huge_get_and_clear_notify() 1857 * madvise_dontneed() 1858 * zap_pmd_range() 1859 * pmd_trans_huge(*pmd) == 0 (without ptl) 1860 * // skip the pmd 1861 * set_pmd_at(); 1862 * // pmd is re-established 1863 * 1864 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it 1865 * which may break userspace. 1866 * 1867 * pmdp_invalidate() is required to make sure we don't miss 1868 * dirty/young flags set by hardware. 1869 */ 1870 entry = pmdp_invalidate(vma, addr, pmd); 1871 1872 entry = pmd_modify(entry, newprot); 1873 if (preserve_write) 1874 entry = pmd_mk_savedwrite(entry); 1875 if (uffd_wp) { 1876 entry = pmd_wrprotect(entry); 1877 entry = pmd_mkuffd_wp(entry); 1878 } else if (uffd_wp_resolve) { 1879 /* 1880 * Leave the write bit to be handled by PF interrupt 1881 * handler, then things like COW could be properly 1882 * handled. 1883 */ 1884 entry = pmd_clear_uffd_wp(entry); 1885 } 1886 ret = HPAGE_PMD_NR; 1887 set_pmd_at(mm, addr, pmd, entry); 1888 BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry)); 1889 unlock: 1890 spin_unlock(ptl); 1891 return ret; 1892 } 1893 1894 /* 1895 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise. 1896 * 1897 * Note that if it returns page table lock pointer, this routine returns without 1898 * unlocking page table lock. So callers must unlock it. 1899 */ 1900 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) 1901 { 1902 spinlock_t *ptl; 1903 ptl = pmd_lock(vma->vm_mm, pmd); 1904 if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || 1905 pmd_devmap(*pmd))) 1906 return ptl; 1907 spin_unlock(ptl); 1908 return NULL; 1909 } 1910 1911 /* 1912 * Returns true if a given pud maps a thp, false otherwise. 1913 * 1914 * Note that if it returns true, this routine returns without unlocking page 1915 * table lock. So callers must unlock it. 1916 */ 1917 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma) 1918 { 1919 spinlock_t *ptl; 1920 1921 ptl = pud_lock(vma->vm_mm, pud); 1922 if (likely(pud_trans_huge(*pud) || pud_devmap(*pud))) 1923 return ptl; 1924 spin_unlock(ptl); 1925 return NULL; 1926 } 1927 1928 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 1929 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma, 1930 pud_t *pud, unsigned long addr) 1931 { 1932 spinlock_t *ptl; 1933 1934 ptl = __pud_trans_huge_lock(pud, vma); 1935 if (!ptl) 1936 return 0; 1937 /* 1938 * For architectures like ppc64 we look at deposited pgtable 1939 * when calling pudp_huge_get_and_clear. So do the 1940 * pgtable_trans_huge_withdraw after finishing pudp related 1941 * operations. 1942 */ 1943 pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm); 1944 tlb_remove_pud_tlb_entry(tlb, pud, addr); 1945 if (vma_is_special_huge(vma)) { 1946 spin_unlock(ptl); 1947 /* No zero page support yet */ 1948 } else { 1949 /* No support for anonymous PUD pages yet */ 1950 BUG(); 1951 } 1952 return 1; 1953 } 1954 1955 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud, 1956 unsigned long haddr) 1957 { 1958 VM_BUG_ON(haddr & ~HPAGE_PUD_MASK); 1959 VM_BUG_ON_VMA(vma->vm_start > haddr, vma); 1960 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma); 1961 VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud)); 1962 1963 count_vm_event(THP_SPLIT_PUD); 1964 1965 pudp_huge_clear_flush_notify(vma, haddr, pud); 1966 } 1967 1968 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud, 1969 unsigned long address) 1970 { 1971 spinlock_t *ptl; 1972 struct mmu_notifier_range range; 1973 1974 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, 1975 address & HPAGE_PUD_MASK, 1976 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE); 1977 mmu_notifier_invalidate_range_start(&range); 1978 ptl = pud_lock(vma->vm_mm, pud); 1979 if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud))) 1980 goto out; 1981 __split_huge_pud_locked(vma, pud, range.start); 1982 1983 out: 1984 spin_unlock(ptl); 1985 /* 1986 * No need to double call mmu_notifier->invalidate_range() callback as 1987 * the above pudp_huge_clear_flush_notify() did already call it. 1988 */ 1989 mmu_notifier_invalidate_range_only_end(&range); 1990 } 1991 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ 1992 1993 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 1994 unsigned long haddr, pmd_t *pmd) 1995 { 1996 struct mm_struct *mm = vma->vm_mm; 1997 pgtable_t pgtable; 1998 pmd_t _pmd; 1999 int i; 2000 2001 /* 2002 * Leave pmd empty until pte is filled note that it is fine to delay 2003 * notification until mmu_notifier_invalidate_range_end() as we are 2004 * replacing a zero pmd write protected page with a zero pte write 2005 * protected page. 2006 * 2007 * See Documentation/vm/mmu_notifier.rst 2008 */ 2009 pmdp_huge_clear_flush(vma, haddr, pmd); 2010 2011 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2012 pmd_populate(mm, &_pmd, pgtable); 2013 2014 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2015 pte_t *pte, entry; 2016 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2017 entry = pte_mkspecial(entry); 2018 pte = pte_offset_map(&_pmd, haddr); 2019 VM_BUG_ON(!pte_none(*pte)); 2020 set_pte_at(mm, haddr, pte, entry); 2021 pte_unmap(pte); 2022 } 2023 smp_wmb(); /* make pte visible before pmd */ 2024 pmd_populate(mm, pmd, pgtable); 2025 } 2026 2027 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 2028 unsigned long haddr, bool freeze) 2029 { 2030 struct mm_struct *mm = vma->vm_mm; 2031 struct page *page; 2032 pgtable_t pgtable; 2033 pmd_t old_pmd, _pmd; 2034 bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false; 2035 unsigned long addr; 2036 int i; 2037 2038 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK); 2039 VM_BUG_ON_VMA(vma->vm_start > haddr, vma); 2040 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma); 2041 VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd) 2042 && !pmd_devmap(*pmd)); 2043 2044 count_vm_event(THP_SPLIT_PMD); 2045 2046 if (!vma_is_anonymous(vma)) { 2047 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd); 2048 /* 2049 * We are going to unmap this huge page. So 2050 * just go ahead and zap it 2051 */ 2052 if (arch_needs_pgtable_deposit()) 2053 zap_deposited_table(mm, pmd); 2054 if (vma_is_special_huge(vma)) 2055 return; 2056 page = pmd_page(_pmd); 2057 if (!PageDirty(page) && pmd_dirty(_pmd)) 2058 set_page_dirty(page); 2059 if (!PageReferenced(page) && pmd_young(_pmd)) 2060 SetPageReferenced(page); 2061 page_remove_rmap(page, true); 2062 put_page(page); 2063 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR); 2064 return; 2065 } else if (pmd_trans_huge(*pmd) && is_huge_zero_pmd(*pmd)) { 2066 /* 2067 * FIXME: Do we want to invalidate secondary mmu by calling 2068 * mmu_notifier_invalidate_range() see comments below inside 2069 * __split_huge_pmd() ? 2070 * 2071 * We are going from a zero huge page write protected to zero 2072 * small page also write protected so it does not seems useful 2073 * to invalidate secondary mmu at this time. 2074 */ 2075 return __split_huge_zero_page_pmd(vma, haddr, pmd); 2076 } 2077 2078 /* 2079 * Up to this point the pmd is present and huge and userland has the 2080 * whole access to the hugepage during the split (which happens in 2081 * place). If we overwrite the pmd with the not-huge version pointing 2082 * to the pte here (which of course we could if all CPUs were bug 2083 * free), userland could trigger a small page size TLB miss on the 2084 * small sized TLB while the hugepage TLB entry is still established in 2085 * the huge TLB. Some CPU doesn't like that. 2086 * See http://support.amd.com/TechDocs/41322_10h_Rev_Gd.pdf, Erratum 2087 * 383 on page 105. Intel should be safe but is also warns that it's 2088 * only safe if the permission and cache attributes of the two entries 2089 * loaded in the two TLB is identical (which should be the case here). 2090 * But it is generally safer to never allow small and huge TLB entries 2091 * for the same virtual address to be loaded simultaneously. So instead 2092 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the 2093 * current pmd notpresent (atomically because here the pmd_trans_huge 2094 * must remain set at all times on the pmd until the split is complete 2095 * for this pmd), then we flush the SMP TLB and finally we write the 2096 * non-huge version of the pmd entry with pmd_populate. 2097 */ 2098 old_pmd = pmdp_invalidate(vma, haddr, pmd); 2099 2100 pmd_migration = is_pmd_migration_entry(old_pmd); 2101 if (unlikely(pmd_migration)) { 2102 swp_entry_t entry; 2103 2104 entry = pmd_to_swp_entry(old_pmd); 2105 page = migration_entry_to_page(entry); 2106 write = is_write_migration_entry(entry); 2107 young = false; 2108 soft_dirty = pmd_swp_soft_dirty(old_pmd); 2109 uffd_wp = pmd_swp_uffd_wp(old_pmd); 2110 } else { 2111 page = pmd_page(old_pmd); 2112 if (pmd_dirty(old_pmd)) 2113 SetPageDirty(page); 2114 write = pmd_write(old_pmd); 2115 young = pmd_young(old_pmd); 2116 soft_dirty = pmd_soft_dirty(old_pmd); 2117 uffd_wp = pmd_uffd_wp(old_pmd); 2118 } 2119 VM_BUG_ON_PAGE(!page_count(page), page); 2120 page_ref_add(page, HPAGE_PMD_NR - 1); 2121 2122 /* 2123 * Withdraw the table only after we mark the pmd entry invalid. 2124 * This's critical for some architectures (Power). 2125 */ 2126 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2127 pmd_populate(mm, &_pmd, pgtable); 2128 2129 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { 2130 pte_t entry, *pte; 2131 /* 2132 * Note that NUMA hinting access restrictions are not 2133 * transferred to avoid any possibility of altering 2134 * permissions across VMAs. 2135 */ 2136 if (freeze || pmd_migration) { 2137 swp_entry_t swp_entry; 2138 swp_entry = make_migration_entry(page + i, write); 2139 entry = swp_entry_to_pte(swp_entry); 2140 if (soft_dirty) 2141 entry = pte_swp_mksoft_dirty(entry); 2142 if (uffd_wp) 2143 entry = pte_swp_mkuffd_wp(entry); 2144 } else { 2145 entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot)); 2146 entry = maybe_mkwrite(entry, vma); 2147 if (!write) 2148 entry = pte_wrprotect(entry); 2149 if (!young) 2150 entry = pte_mkold(entry); 2151 if (soft_dirty) 2152 entry = pte_mksoft_dirty(entry); 2153 if (uffd_wp) 2154 entry = pte_mkuffd_wp(entry); 2155 } 2156 pte = pte_offset_map(&_pmd, addr); 2157 BUG_ON(!pte_none(*pte)); 2158 set_pte_at(mm, addr, pte, entry); 2159 if (!pmd_migration) 2160 atomic_inc(&page[i]._mapcount); 2161 pte_unmap(pte); 2162 } 2163 2164 if (!pmd_migration) { 2165 /* 2166 * Set PG_double_map before dropping compound_mapcount to avoid 2167 * false-negative page_mapped(). 2168 */ 2169 if (compound_mapcount(page) > 1 && 2170 !TestSetPageDoubleMap(page)) { 2171 for (i = 0; i < HPAGE_PMD_NR; i++) 2172 atomic_inc(&page[i]._mapcount); 2173 } 2174 2175 lock_page_memcg(page); 2176 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { 2177 /* Last compound_mapcount is gone. */ 2178 __mod_lruvec_page_state(page, NR_ANON_THPS, 2179 -HPAGE_PMD_NR); 2180 if (TestClearPageDoubleMap(page)) { 2181 /* No need in mapcount reference anymore */ 2182 for (i = 0; i < HPAGE_PMD_NR; i++) 2183 atomic_dec(&page[i]._mapcount); 2184 } 2185 } 2186 unlock_page_memcg(page); 2187 } 2188 2189 smp_wmb(); /* make pte visible before pmd */ 2190 pmd_populate(mm, pmd, pgtable); 2191 2192 if (freeze) { 2193 for (i = 0; i < HPAGE_PMD_NR; i++) { 2194 page_remove_rmap(page + i, false); 2195 put_page(page + i); 2196 } 2197 } 2198 } 2199 2200 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 2201 unsigned long address, bool freeze, struct page *page) 2202 { 2203 spinlock_t *ptl; 2204 struct mmu_notifier_range range; 2205 bool do_unlock_page = false; 2206 pmd_t _pmd; 2207 2208 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, 2209 address & HPAGE_PMD_MASK, 2210 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE); 2211 mmu_notifier_invalidate_range_start(&range); 2212 ptl = pmd_lock(vma->vm_mm, pmd); 2213 2214 /* 2215 * If caller asks to setup a migration entries, we need a page to check 2216 * pmd against. Otherwise we can end up replacing wrong page. 2217 */ 2218 VM_BUG_ON(freeze && !page); 2219 if (page) { 2220 VM_WARN_ON_ONCE(!PageLocked(page)); 2221 if (page != pmd_page(*pmd)) 2222 goto out; 2223 } 2224 2225 repeat: 2226 if (pmd_trans_huge(*pmd)) { 2227 if (!page) { 2228 page = pmd_page(*pmd); 2229 /* 2230 * An anonymous page must be locked, to ensure that a 2231 * concurrent reuse_swap_page() sees stable mapcount; 2232 * but reuse_swap_page() is not used on shmem or file, 2233 * and page lock must not be taken when zap_pmd_range() 2234 * calls __split_huge_pmd() while i_mmap_lock is held. 2235 */ 2236 if (PageAnon(page)) { 2237 if (unlikely(!trylock_page(page))) { 2238 get_page(page); 2239 _pmd = *pmd; 2240 spin_unlock(ptl); 2241 lock_page(page); 2242 spin_lock(ptl); 2243 if (unlikely(!pmd_same(*pmd, _pmd))) { 2244 unlock_page(page); 2245 put_page(page); 2246 page = NULL; 2247 goto repeat; 2248 } 2249 put_page(page); 2250 } 2251 do_unlock_page = true; 2252 } 2253 } 2254 if (PageMlocked(page)) 2255 clear_page_mlock(page); 2256 } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd))) 2257 goto out; 2258 __split_huge_pmd_locked(vma, pmd, range.start, freeze); 2259 out: 2260 spin_unlock(ptl); 2261 if (do_unlock_page) 2262 unlock_page(page); 2263 /* 2264 * No need to double call mmu_notifier->invalidate_range() callback. 2265 * They are 3 cases to consider inside __split_huge_pmd_locked(): 2266 * 1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious 2267 * 2) __split_huge_zero_page_pmd() read only zero page and any write 2268 * fault will trigger a flush_notify before pointing to a new page 2269 * (it is fine if the secondary mmu keeps pointing to the old zero 2270 * page in the meantime) 2271 * 3) Split a huge pmd into pte pointing to the same page. No need 2272 * to invalidate secondary tlb entry they are all still valid. 2273 * any further changes to individual pte will notify. So no need 2274 * to call mmu_notifier->invalidate_range() 2275 */ 2276 mmu_notifier_invalidate_range_only_end(&range); 2277 } 2278 2279 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, 2280 bool freeze, struct page *page) 2281 { 2282 pgd_t *pgd; 2283 p4d_t *p4d; 2284 pud_t *pud; 2285 pmd_t *pmd; 2286 2287 pgd = pgd_offset(vma->vm_mm, address); 2288 if (!pgd_present(*pgd)) 2289 return; 2290 2291 p4d = p4d_offset(pgd, address); 2292 if (!p4d_present(*p4d)) 2293 return; 2294 2295 pud = pud_offset(p4d, address); 2296 if (!pud_present(*pud)) 2297 return; 2298 2299 pmd = pmd_offset(pud, address); 2300 2301 __split_huge_pmd(vma, pmd, address, freeze, page); 2302 } 2303 2304 static inline void split_huge_pmd_if_needed(struct vm_area_struct *vma, unsigned long address) 2305 { 2306 /* 2307 * If the new address isn't hpage aligned and it could previously 2308 * contain an hugepage: check if we need to split an huge pmd. 2309 */ 2310 if (!IS_ALIGNED(address, HPAGE_PMD_SIZE) && 2311 range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PMD_SIZE), 2312 ALIGN(address, HPAGE_PMD_SIZE))) 2313 split_huge_pmd_address(vma, address, false, NULL); 2314 } 2315 2316 void vma_adjust_trans_huge(struct vm_area_struct *vma, 2317 unsigned long start, 2318 unsigned long end, 2319 long adjust_next) 2320 { 2321 /* Check if we need to split start first. */ 2322 split_huge_pmd_if_needed(vma, start); 2323 2324 /* Check if we need to split end next. */ 2325 split_huge_pmd_if_needed(vma, end); 2326 2327 /* 2328 * If we're also updating the vma->vm_next->vm_start, 2329 * check if we need to split it. 2330 */ 2331 if (adjust_next > 0) { 2332 struct vm_area_struct *next = vma->vm_next; 2333 unsigned long nstart = next->vm_start; 2334 nstart += adjust_next; 2335 split_huge_pmd_if_needed(next, nstart); 2336 } 2337 } 2338 2339 static void unmap_page(struct page *page) 2340 { 2341 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | 2342 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD; 2343 bool unmap_success; 2344 2345 VM_BUG_ON_PAGE(!PageHead(page), page); 2346 2347 if (PageAnon(page)) 2348 ttu_flags |= TTU_SPLIT_FREEZE; 2349 2350 unmap_success = try_to_unmap(page, ttu_flags); 2351 VM_BUG_ON_PAGE(!unmap_success, page); 2352 } 2353 2354 static void remap_page(struct page *page, unsigned int nr) 2355 { 2356 int i; 2357 if (PageTransHuge(page)) { 2358 remove_migration_ptes(page, page, true); 2359 } else { 2360 for (i = 0; i < nr; i++) 2361 remove_migration_ptes(page + i, page + i, true); 2362 } 2363 } 2364 2365 static void lru_add_page_tail(struct page *head, struct page *tail, 2366 struct lruvec *lruvec, struct list_head *list) 2367 { 2368 VM_BUG_ON_PAGE(!PageHead(head), head); 2369 VM_BUG_ON_PAGE(PageCompound(tail), head); 2370 VM_BUG_ON_PAGE(PageLRU(tail), head); 2371 lockdep_assert_held(&lruvec->lru_lock); 2372 2373 if (list) { 2374 /* page reclaim is reclaiming a huge page */ 2375 VM_WARN_ON(PageLRU(head)); 2376 get_page(tail); 2377 list_add_tail(&tail->lru, list); 2378 } else { 2379 /* head is still on lru (and we have it frozen) */ 2380 VM_WARN_ON(!PageLRU(head)); 2381 SetPageLRU(tail); 2382 list_add_tail(&tail->lru, &head->lru); 2383 } 2384 } 2385 2386 static void __split_huge_page_tail(struct page *head, int tail, 2387 struct lruvec *lruvec, struct list_head *list) 2388 { 2389 struct page *page_tail = head + tail; 2390 2391 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); 2392 2393 /* 2394 * Clone page flags before unfreezing refcount. 2395 * 2396 * After successful get_page_unless_zero() might follow flags change, 2397 * for example lock_page() which set PG_waiters. 2398 */ 2399 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; 2400 page_tail->flags |= (head->flags & 2401 ((1L << PG_referenced) | 2402 (1L << PG_swapbacked) | 2403 (1L << PG_swapcache) | 2404 (1L << PG_mlocked) | 2405 (1L << PG_uptodate) | 2406 (1L << PG_active) | 2407 (1L << PG_workingset) | 2408 (1L << PG_locked) | 2409 (1L << PG_unevictable) | 2410 #ifdef CONFIG_64BIT 2411 (1L << PG_arch_2) | 2412 #endif 2413 (1L << PG_dirty))); 2414 2415 /* ->mapping in first tail page is compound_mapcount */ 2416 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING, 2417 page_tail); 2418 page_tail->mapping = head->mapping; 2419 page_tail->index = head->index + tail; 2420 2421 /* Page flags must be visible before we make the page non-compound. */ 2422 smp_wmb(); 2423 2424 /* 2425 * Clear PageTail before unfreezing page refcount. 2426 * 2427 * After successful get_page_unless_zero() might follow put_page() 2428 * which needs correct compound_head(). 2429 */ 2430 clear_compound_head(page_tail); 2431 2432 /* Finally unfreeze refcount. Additional reference from page cache. */ 2433 page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) || 2434 PageSwapCache(head))); 2435 2436 if (page_is_young(head)) 2437 set_page_young(page_tail); 2438 if (page_is_idle(head)) 2439 set_page_idle(page_tail); 2440 2441 page_cpupid_xchg_last(page_tail, page_cpupid_last(head)); 2442 2443 /* 2444 * always add to the tail because some iterators expect new 2445 * pages to show after the currently processed elements - e.g. 2446 * migrate_pages 2447 */ 2448 lru_add_page_tail(head, page_tail, lruvec, list); 2449 } 2450 2451 static void __split_huge_page(struct page *page, struct list_head *list, 2452 pgoff_t end) 2453 { 2454 struct page *head = compound_head(page); 2455 struct lruvec *lruvec; 2456 struct address_space *swap_cache = NULL; 2457 unsigned long offset = 0; 2458 unsigned int nr = thp_nr_pages(head); 2459 int i; 2460 2461 /* complete memcg works before add pages to LRU */ 2462 split_page_memcg(head, nr); 2463 2464 if (PageAnon(head) && PageSwapCache(head)) { 2465 swp_entry_t entry = { .val = page_private(head) }; 2466 2467 offset = swp_offset(entry); 2468 swap_cache = swap_address_space(entry); 2469 xa_lock(&swap_cache->i_pages); 2470 } 2471 2472 /* lock lru list/PageCompound, ref frozen by page_ref_freeze */ 2473 lruvec = lock_page_lruvec(head); 2474 2475 for (i = nr - 1; i >= 1; i--) { 2476 __split_huge_page_tail(head, i, lruvec, list); 2477 /* Some pages can be beyond i_size: drop them from page cache */ 2478 if (head[i].index >= end) { 2479 ClearPageDirty(head + i); 2480 __delete_from_page_cache(head + i, NULL); 2481 if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head)) 2482 shmem_uncharge(head->mapping->host, 1); 2483 put_page(head + i); 2484 } else if (!PageAnon(page)) { 2485 __xa_store(&head->mapping->i_pages, head[i].index, 2486 head + i, 0); 2487 } else if (swap_cache) { 2488 __xa_store(&swap_cache->i_pages, offset + i, 2489 head + i, 0); 2490 } 2491 } 2492 2493 ClearPageCompound(head); 2494 unlock_page_lruvec(lruvec); 2495 /* Caller disabled irqs, so they are still disabled here */ 2496 2497 split_page_owner(head, nr); 2498 2499 /* See comment in __split_huge_page_tail() */ 2500 if (PageAnon(head)) { 2501 /* Additional pin to swap cache */ 2502 if (PageSwapCache(head)) { 2503 page_ref_add(head, 2); 2504 xa_unlock(&swap_cache->i_pages); 2505 } else { 2506 page_ref_inc(head); 2507 } 2508 } else { 2509 /* Additional pin to page cache */ 2510 page_ref_add(head, 2); 2511 xa_unlock(&head->mapping->i_pages); 2512 } 2513 local_irq_enable(); 2514 2515 remap_page(head, nr); 2516 2517 if (PageSwapCache(head)) { 2518 swp_entry_t entry = { .val = page_private(head) }; 2519 2520 split_swap_cluster(entry); 2521 } 2522 2523 for (i = 0; i < nr; i++) { 2524 struct page *subpage = head + i; 2525 if (subpage == page) 2526 continue; 2527 unlock_page(subpage); 2528 2529 /* 2530 * Subpages may be freed if there wasn't any mapping 2531 * like if add_to_swap() is running on a lru page that 2532 * had its mapping zapped. And freeing these pages 2533 * requires taking the lru_lock so we do the put_page 2534 * of the tail pages after the split is complete. 2535 */ 2536 put_page(subpage); 2537 } 2538 } 2539 2540 int total_mapcount(struct page *page) 2541 { 2542 int i, compound, nr, ret; 2543 2544 VM_BUG_ON_PAGE(PageTail(page), page); 2545 2546 if (likely(!PageCompound(page))) 2547 return atomic_read(&page->_mapcount) + 1; 2548 2549 compound = compound_mapcount(page); 2550 nr = compound_nr(page); 2551 if (PageHuge(page)) 2552 return compound; 2553 ret = compound; 2554 for (i = 0; i < nr; i++) 2555 ret += atomic_read(&page[i]._mapcount) + 1; 2556 /* File pages has compound_mapcount included in _mapcount */ 2557 if (!PageAnon(page)) 2558 return ret - compound * nr; 2559 if (PageDoubleMap(page)) 2560 ret -= nr; 2561 return ret; 2562 } 2563 2564 /* 2565 * This calculates accurately how many mappings a transparent hugepage 2566 * has (unlike page_mapcount() which isn't fully accurate). This full 2567 * accuracy is primarily needed to know if copy-on-write faults can 2568 * reuse the page and change the mapping to read-write instead of 2569 * copying them. At the same time this returns the total_mapcount too. 2570 * 2571 * The function returns the highest mapcount any one of the subpages 2572 * has. If the return value is one, even if different processes are 2573 * mapping different subpages of the transparent hugepage, they can 2574 * all reuse it, because each process is reusing a different subpage. 2575 * 2576 * The total_mapcount is instead counting all virtual mappings of the 2577 * subpages. If the total_mapcount is equal to "one", it tells the 2578 * caller all mappings belong to the same "mm" and in turn the 2579 * anon_vma of the transparent hugepage can become the vma->anon_vma 2580 * local one as no other process may be mapping any of the subpages. 2581 * 2582 * It would be more accurate to replace page_mapcount() with 2583 * page_trans_huge_mapcount(), however we only use 2584 * page_trans_huge_mapcount() in the copy-on-write faults where we 2585 * need full accuracy to avoid breaking page pinning, because 2586 * page_trans_huge_mapcount() is slower than page_mapcount(). 2587 */ 2588 int page_trans_huge_mapcount(struct page *page, int *total_mapcount) 2589 { 2590 int i, ret, _total_mapcount, mapcount; 2591 2592 /* hugetlbfs shouldn't call it */ 2593 VM_BUG_ON_PAGE(PageHuge(page), page); 2594 2595 if (likely(!PageTransCompound(page))) { 2596 mapcount = atomic_read(&page->_mapcount) + 1; 2597 if (total_mapcount) 2598 *total_mapcount = mapcount; 2599 return mapcount; 2600 } 2601 2602 page = compound_head(page); 2603 2604 _total_mapcount = ret = 0; 2605 for (i = 0; i < thp_nr_pages(page); i++) { 2606 mapcount = atomic_read(&page[i]._mapcount) + 1; 2607 ret = max(ret, mapcount); 2608 _total_mapcount += mapcount; 2609 } 2610 if (PageDoubleMap(page)) { 2611 ret -= 1; 2612 _total_mapcount -= thp_nr_pages(page); 2613 } 2614 mapcount = compound_mapcount(page); 2615 ret += mapcount; 2616 _total_mapcount += mapcount; 2617 if (total_mapcount) 2618 *total_mapcount = _total_mapcount; 2619 return ret; 2620 } 2621 2622 /* Racy check whether the huge page can be split */ 2623 bool can_split_huge_page(struct page *page, int *pextra_pins) 2624 { 2625 int extra_pins; 2626 2627 /* Additional pins from page cache */ 2628 if (PageAnon(page)) 2629 extra_pins = PageSwapCache(page) ? thp_nr_pages(page) : 0; 2630 else 2631 extra_pins = thp_nr_pages(page); 2632 if (pextra_pins) 2633 *pextra_pins = extra_pins; 2634 return total_mapcount(page) == page_count(page) - extra_pins - 1; 2635 } 2636 2637 /* 2638 * This function splits huge page into normal pages. @page can point to any 2639 * subpage of huge page to split. Split doesn't change the position of @page. 2640 * 2641 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY. 2642 * The huge page must be locked. 2643 * 2644 * If @list is null, tail pages will be added to LRU list, otherwise, to @list. 2645 * 2646 * Both head page and tail pages will inherit mapping, flags, and so on from 2647 * the hugepage. 2648 * 2649 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if 2650 * they are not mapped. 2651 * 2652 * Returns 0 if the hugepage is split successfully. 2653 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under 2654 * us. 2655 */ 2656 int split_huge_page_to_list(struct page *page, struct list_head *list) 2657 { 2658 struct page *head = compound_head(page); 2659 struct deferred_split *ds_queue = get_deferred_split_queue(head); 2660 struct anon_vma *anon_vma = NULL; 2661 struct address_space *mapping = NULL; 2662 int count, mapcount, extra_pins, ret; 2663 pgoff_t end; 2664 2665 VM_BUG_ON_PAGE(is_huge_zero_page(head), head); 2666 VM_BUG_ON_PAGE(!PageLocked(head), head); 2667 VM_BUG_ON_PAGE(!PageCompound(head), head); 2668 2669 if (PageWriteback(head)) 2670 return -EBUSY; 2671 2672 if (PageAnon(head)) { 2673 /* 2674 * The caller does not necessarily hold an mmap_lock that would 2675 * prevent the anon_vma disappearing so we first we take a 2676 * reference to it and then lock the anon_vma for write. This 2677 * is similar to page_lock_anon_vma_read except the write lock 2678 * is taken to serialise against parallel split or collapse 2679 * operations. 2680 */ 2681 anon_vma = page_get_anon_vma(head); 2682 if (!anon_vma) { 2683 ret = -EBUSY; 2684 goto out; 2685 } 2686 end = -1; 2687 mapping = NULL; 2688 anon_vma_lock_write(anon_vma); 2689 } else { 2690 mapping = head->mapping; 2691 2692 /* Truncated ? */ 2693 if (!mapping) { 2694 ret = -EBUSY; 2695 goto out; 2696 } 2697 2698 anon_vma = NULL; 2699 i_mmap_lock_read(mapping); 2700 2701 /* 2702 *__split_huge_page() may need to trim off pages beyond EOF: 2703 * but on 32-bit, i_size_read() takes an irq-unsafe seqlock, 2704 * which cannot be nested inside the page tree lock. So note 2705 * end now: i_size itself may be changed at any moment, but 2706 * head page lock is good enough to serialize the trimming. 2707 */ 2708 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); 2709 } 2710 2711 /* 2712 * Racy check if we can split the page, before unmap_page() will 2713 * split PMDs 2714 */ 2715 if (!can_split_huge_page(head, &extra_pins)) { 2716 ret = -EBUSY; 2717 goto out_unlock; 2718 } 2719 2720 unmap_page(head); 2721 VM_BUG_ON_PAGE(compound_mapcount(head), head); 2722 2723 /* block interrupt reentry in xa_lock and spinlock */ 2724 local_irq_disable(); 2725 if (mapping) { 2726 XA_STATE(xas, &mapping->i_pages, page_index(head)); 2727 2728 /* 2729 * Check if the head page is present in page cache. 2730 * We assume all tail are present too, if head is there. 2731 */ 2732 xa_lock(&mapping->i_pages); 2733 if (xas_load(&xas) != head) 2734 goto fail; 2735 } 2736 2737 /* Prevent deferred_split_scan() touching ->_refcount */ 2738 spin_lock(&ds_queue->split_queue_lock); 2739 count = page_count(head); 2740 mapcount = total_mapcount(head); 2741 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) { 2742 if (!list_empty(page_deferred_list(head))) { 2743 ds_queue->split_queue_len--; 2744 list_del(page_deferred_list(head)); 2745 } 2746 spin_unlock(&ds_queue->split_queue_lock); 2747 if (mapping) { 2748 int nr = thp_nr_pages(head); 2749 2750 if (PageSwapBacked(head)) 2751 __mod_lruvec_page_state(head, NR_SHMEM_THPS, 2752 -nr); 2753 else 2754 __mod_lruvec_page_state(head, NR_FILE_THPS, 2755 -nr); 2756 } 2757 2758 __split_huge_page(page, list, end); 2759 ret = 0; 2760 } else { 2761 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { 2762 pr_alert("total_mapcount: %u, page_count(): %u\n", 2763 mapcount, count); 2764 if (PageTail(page)) 2765 dump_page(head, NULL); 2766 dump_page(page, "total_mapcount(head) > 0"); 2767 BUG(); 2768 } 2769 spin_unlock(&ds_queue->split_queue_lock); 2770 fail: if (mapping) 2771 xa_unlock(&mapping->i_pages); 2772 local_irq_enable(); 2773 remap_page(head, thp_nr_pages(head)); 2774 ret = -EBUSY; 2775 } 2776 2777 out_unlock: 2778 if (anon_vma) { 2779 anon_vma_unlock_write(anon_vma); 2780 put_anon_vma(anon_vma); 2781 } 2782 if (mapping) 2783 i_mmap_unlock_read(mapping); 2784 out: 2785 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); 2786 return ret; 2787 } 2788 2789 void free_transhuge_page(struct page *page) 2790 { 2791 struct deferred_split *ds_queue = get_deferred_split_queue(page); 2792 unsigned long flags; 2793 2794 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 2795 if (!list_empty(page_deferred_list(page))) { 2796 ds_queue->split_queue_len--; 2797 list_del(page_deferred_list(page)); 2798 } 2799 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 2800 free_compound_page(page); 2801 } 2802 2803 void deferred_split_huge_page(struct page *page) 2804 { 2805 struct deferred_split *ds_queue = get_deferred_split_queue(page); 2806 #ifdef CONFIG_MEMCG 2807 struct mem_cgroup *memcg = page_memcg(compound_head(page)); 2808 #endif 2809 unsigned long flags; 2810 2811 VM_BUG_ON_PAGE(!PageTransHuge(page), page); 2812 2813 /* 2814 * The try_to_unmap() in page reclaim path might reach here too, 2815 * this may cause a race condition to corrupt deferred split queue. 2816 * And, if page reclaim is already handling the same page, it is 2817 * unnecessary to handle it again in shrinker. 2818 * 2819 * Check PageSwapCache to determine if the page is being 2820 * handled by page reclaim since THP swap would add the page into 2821 * swap cache before calling try_to_unmap(). 2822 */ 2823 if (PageSwapCache(page)) 2824 return; 2825 2826 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 2827 if (list_empty(page_deferred_list(page))) { 2828 count_vm_event(THP_DEFERRED_SPLIT_PAGE); 2829 list_add_tail(page_deferred_list(page), &ds_queue->split_queue); 2830 ds_queue->split_queue_len++; 2831 #ifdef CONFIG_MEMCG 2832 if (memcg) 2833 set_shrinker_bit(memcg, page_to_nid(page), 2834 deferred_split_shrinker.id); 2835 #endif 2836 } 2837 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 2838 } 2839 2840 static unsigned long deferred_split_count(struct shrinker *shrink, 2841 struct shrink_control *sc) 2842 { 2843 struct pglist_data *pgdata = NODE_DATA(sc->nid); 2844 struct deferred_split *ds_queue = &pgdata->deferred_split_queue; 2845 2846 #ifdef CONFIG_MEMCG 2847 if (sc->memcg) 2848 ds_queue = &sc->memcg->deferred_split_queue; 2849 #endif 2850 return READ_ONCE(ds_queue->split_queue_len); 2851 } 2852 2853 static unsigned long deferred_split_scan(struct shrinker *shrink, 2854 struct shrink_control *sc) 2855 { 2856 struct pglist_data *pgdata = NODE_DATA(sc->nid); 2857 struct deferred_split *ds_queue = &pgdata->deferred_split_queue; 2858 unsigned long flags; 2859 LIST_HEAD(list), *pos, *next; 2860 struct page *page; 2861 int split = 0; 2862 2863 #ifdef CONFIG_MEMCG 2864 if (sc->memcg) 2865 ds_queue = &sc->memcg->deferred_split_queue; 2866 #endif 2867 2868 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 2869 /* Take pin on all head pages to avoid freeing them under us */ 2870 list_for_each_safe(pos, next, &ds_queue->split_queue) { 2871 page = list_entry((void *)pos, struct page, mapping); 2872 page = compound_head(page); 2873 if (get_page_unless_zero(page)) { 2874 list_move(page_deferred_list(page), &list); 2875 } else { 2876 /* We lost race with put_compound_page() */ 2877 list_del_init(page_deferred_list(page)); 2878 ds_queue->split_queue_len--; 2879 } 2880 if (!--sc->nr_to_scan) 2881 break; 2882 } 2883 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 2884 2885 list_for_each_safe(pos, next, &list) { 2886 page = list_entry((void *)pos, struct page, mapping); 2887 if (!trylock_page(page)) 2888 goto next; 2889 /* split_huge_page() removes page from list on success */ 2890 if (!split_huge_page(page)) 2891 split++; 2892 unlock_page(page); 2893 next: 2894 put_page(page); 2895 } 2896 2897 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 2898 list_splice_tail(&list, &ds_queue->split_queue); 2899 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 2900 2901 /* 2902 * Stop shrinker if we didn't split any page, but the queue is empty. 2903 * This can happen if pages were freed under us. 2904 */ 2905 if (!split && list_empty(&ds_queue->split_queue)) 2906 return SHRINK_STOP; 2907 return split; 2908 } 2909 2910 static struct shrinker deferred_split_shrinker = { 2911 .count_objects = deferred_split_count, 2912 .scan_objects = deferred_split_scan, 2913 .seeks = DEFAULT_SEEKS, 2914 .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE | 2915 SHRINKER_NONSLAB, 2916 }; 2917 2918 #ifdef CONFIG_DEBUG_FS 2919 static void split_huge_pages_all(void) 2920 { 2921 struct zone *zone; 2922 struct page *page; 2923 unsigned long pfn, max_zone_pfn; 2924 unsigned long total = 0, split = 0; 2925 2926 pr_debug("Split all THPs\n"); 2927 for_each_populated_zone(zone) { 2928 max_zone_pfn = zone_end_pfn(zone); 2929 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) { 2930 if (!pfn_valid(pfn)) 2931 continue; 2932 2933 page = pfn_to_page(pfn); 2934 if (!get_page_unless_zero(page)) 2935 continue; 2936 2937 if (zone != page_zone(page)) 2938 goto next; 2939 2940 if (!PageHead(page) || PageHuge(page) || !PageLRU(page)) 2941 goto next; 2942 2943 total++; 2944 lock_page(page); 2945 if (!split_huge_page(page)) 2946 split++; 2947 unlock_page(page); 2948 next: 2949 put_page(page); 2950 cond_resched(); 2951 } 2952 } 2953 2954 pr_debug("%lu of %lu THP split\n", split, total); 2955 } 2956 2957 static inline bool vma_not_suitable_for_thp_split(struct vm_area_struct *vma) 2958 { 2959 return vma_is_special_huge(vma) || (vma->vm_flags & VM_IO) || 2960 is_vm_hugetlb_page(vma); 2961 } 2962 2963 static int split_huge_pages_pid(int pid, unsigned long vaddr_start, 2964 unsigned long vaddr_end) 2965 { 2966 int ret = 0; 2967 struct task_struct *task; 2968 struct mm_struct *mm; 2969 unsigned long total = 0, split = 0; 2970 unsigned long addr; 2971 2972 vaddr_start &= PAGE_MASK; 2973 vaddr_end &= PAGE_MASK; 2974 2975 /* Find the task_struct from pid */ 2976 rcu_read_lock(); 2977 task = find_task_by_vpid(pid); 2978 if (!task) { 2979 rcu_read_unlock(); 2980 ret = -ESRCH; 2981 goto out; 2982 } 2983 get_task_struct(task); 2984 rcu_read_unlock(); 2985 2986 /* Find the mm_struct */ 2987 mm = get_task_mm(task); 2988 put_task_struct(task); 2989 2990 if (!mm) { 2991 ret = -EINVAL; 2992 goto out; 2993 } 2994 2995 pr_debug("Split huge pages in pid: %d, vaddr: [0x%lx - 0x%lx]\n", 2996 pid, vaddr_start, vaddr_end); 2997 2998 mmap_read_lock(mm); 2999 /* 3000 * always increase addr by PAGE_SIZE, since we could have a PTE page 3001 * table filled with PTE-mapped THPs, each of which is distinct. 3002 */ 3003 for (addr = vaddr_start; addr < vaddr_end; addr += PAGE_SIZE) { 3004 struct vm_area_struct *vma = find_vma(mm, addr); 3005 unsigned int follflags; 3006 struct page *page; 3007 3008 if (!vma || addr < vma->vm_start) 3009 break; 3010 3011 /* skip special VMA and hugetlb VMA */ 3012 if (vma_not_suitable_for_thp_split(vma)) { 3013 addr = vma->vm_end; 3014 continue; 3015 } 3016 3017 /* FOLL_DUMP to ignore special (like zero) pages */ 3018 follflags = FOLL_GET | FOLL_DUMP; 3019 page = follow_page(vma, addr, follflags); 3020 3021 if (IS_ERR(page)) 3022 continue; 3023 if (!page) 3024 continue; 3025 3026 if (!is_transparent_hugepage(page)) 3027 goto next; 3028 3029 total++; 3030 if (!can_split_huge_page(compound_head(page), NULL)) 3031 goto next; 3032 3033 if (!trylock_page(page)) 3034 goto next; 3035 3036 if (!split_huge_page(page)) 3037 split++; 3038 3039 unlock_page(page); 3040 next: 3041 put_page(page); 3042 cond_resched(); 3043 } 3044 mmap_read_unlock(mm); 3045 mmput(mm); 3046 3047 pr_debug("%lu of %lu THP split\n", split, total); 3048 3049 out: 3050 return ret; 3051 } 3052 3053 static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start, 3054 pgoff_t off_end) 3055 { 3056 struct filename *file; 3057 struct file *candidate; 3058 struct address_space *mapping; 3059 int ret = -EINVAL; 3060 pgoff_t index; 3061 int nr_pages = 1; 3062 unsigned long total = 0, split = 0; 3063 3064 file = getname_kernel(file_path); 3065 if (IS_ERR(file)) 3066 return ret; 3067 3068 candidate = file_open_name(file, O_RDONLY, 0); 3069 if (IS_ERR(candidate)) 3070 goto out; 3071 3072 pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx]\n", 3073 file_path, off_start, off_end); 3074 3075 mapping = candidate->f_mapping; 3076 3077 for (index = off_start; index < off_end; index += nr_pages) { 3078 struct page *fpage = pagecache_get_page(mapping, index, 3079 FGP_ENTRY | FGP_HEAD, 0); 3080 3081 nr_pages = 1; 3082 if (xa_is_value(fpage) || !fpage) 3083 continue; 3084 3085 if (!is_transparent_hugepage(fpage)) 3086 goto next; 3087 3088 total++; 3089 nr_pages = thp_nr_pages(fpage); 3090 3091 if (!trylock_page(fpage)) 3092 goto next; 3093 3094 if (!split_huge_page(fpage)) 3095 split++; 3096 3097 unlock_page(fpage); 3098 next: 3099 put_page(fpage); 3100 cond_resched(); 3101 } 3102 3103 filp_close(candidate, NULL); 3104 ret = 0; 3105 3106 pr_debug("%lu of %lu file-backed THP split\n", split, total); 3107 out: 3108 putname(file); 3109 return ret; 3110 } 3111 3112 #define MAX_INPUT_BUF_SZ 255 3113 3114 static ssize_t split_huge_pages_write(struct file *file, const char __user *buf, 3115 size_t count, loff_t *ppops) 3116 { 3117 static DEFINE_MUTEX(split_debug_mutex); 3118 ssize_t ret; 3119 /* hold pid, start_vaddr, end_vaddr or file_path, off_start, off_end */ 3120 char input_buf[MAX_INPUT_BUF_SZ]; 3121 int pid; 3122 unsigned long vaddr_start, vaddr_end; 3123 3124 ret = mutex_lock_interruptible(&split_debug_mutex); 3125 if (ret) 3126 return ret; 3127 3128 ret = -EFAULT; 3129 3130 memset(input_buf, 0, MAX_INPUT_BUF_SZ); 3131 if (copy_from_user(input_buf, buf, min_t(size_t, count, MAX_INPUT_BUF_SZ))) 3132 goto out; 3133 3134 input_buf[MAX_INPUT_BUF_SZ - 1] = '\0'; 3135 3136 if (input_buf[0] == '/') { 3137 char *tok; 3138 char *buf = input_buf; 3139 char file_path[MAX_INPUT_BUF_SZ]; 3140 pgoff_t off_start = 0, off_end = 0; 3141 size_t input_len = strlen(input_buf); 3142 3143 tok = strsep(&buf, ","); 3144 if (tok) { 3145 strncpy(file_path, tok, MAX_INPUT_BUF_SZ); 3146 } else { 3147 ret = -EINVAL; 3148 goto out; 3149 } 3150 3151 ret = sscanf(buf, "0x%lx,0x%lx", &off_start, &off_end); 3152 if (ret != 2) { 3153 ret = -EINVAL; 3154 goto out; 3155 } 3156 ret = split_huge_pages_in_file(file_path, off_start, off_end); 3157 if (!ret) 3158 ret = input_len; 3159 3160 goto out; 3161 } 3162 3163 ret = sscanf(input_buf, "%d,0x%lx,0x%lx", &pid, &vaddr_start, &vaddr_end); 3164 if (ret == 1 && pid == 1) { 3165 split_huge_pages_all(); 3166 ret = strlen(input_buf); 3167 goto out; 3168 } else if (ret != 3) { 3169 ret = -EINVAL; 3170 goto out; 3171 } 3172 3173 ret = split_huge_pages_pid(pid, vaddr_start, vaddr_end); 3174 if (!ret) 3175 ret = strlen(input_buf); 3176 out: 3177 mutex_unlock(&split_debug_mutex); 3178 return ret; 3179 3180 } 3181 3182 static const struct file_operations split_huge_pages_fops = { 3183 .owner = THIS_MODULE, 3184 .write = split_huge_pages_write, 3185 .llseek = no_llseek, 3186 }; 3187 3188 static int __init split_huge_pages_debugfs(void) 3189 { 3190 debugfs_create_file("split_huge_pages", 0200, NULL, NULL, 3191 &split_huge_pages_fops); 3192 return 0; 3193 } 3194 late_initcall(split_huge_pages_debugfs); 3195 #endif 3196 3197 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 3198 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw, 3199 struct page *page) 3200 { 3201 struct vm_area_struct *vma = pvmw->vma; 3202 struct mm_struct *mm = vma->vm_mm; 3203 unsigned long address = pvmw->address; 3204 pmd_t pmdval; 3205 swp_entry_t entry; 3206 pmd_t pmdswp; 3207 3208 if (!(pvmw->pmd && !pvmw->pte)) 3209 return; 3210 3211 flush_cache_range(vma, address, address + HPAGE_PMD_SIZE); 3212 pmdval = pmdp_invalidate(vma, address, pvmw->pmd); 3213 if (pmd_dirty(pmdval)) 3214 set_page_dirty(page); 3215 entry = make_migration_entry(page, pmd_write(pmdval)); 3216 pmdswp = swp_entry_to_pmd(entry); 3217 if (pmd_soft_dirty(pmdval)) 3218 pmdswp = pmd_swp_mksoft_dirty(pmdswp); 3219 set_pmd_at(mm, address, pvmw->pmd, pmdswp); 3220 page_remove_rmap(page, true); 3221 put_page(page); 3222 } 3223 3224 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new) 3225 { 3226 struct vm_area_struct *vma = pvmw->vma; 3227 struct mm_struct *mm = vma->vm_mm; 3228 unsigned long address = pvmw->address; 3229 unsigned long mmun_start = address & HPAGE_PMD_MASK; 3230 pmd_t pmde; 3231 swp_entry_t entry; 3232 3233 if (!(pvmw->pmd && !pvmw->pte)) 3234 return; 3235 3236 entry = pmd_to_swp_entry(*pvmw->pmd); 3237 get_page(new); 3238 pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot)); 3239 if (pmd_swp_soft_dirty(*pvmw->pmd)) 3240 pmde = pmd_mksoft_dirty(pmde); 3241 if (is_write_migration_entry(entry)) 3242 pmde = maybe_pmd_mkwrite(pmde, vma); 3243 3244 flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE); 3245 if (PageAnon(new)) 3246 page_add_anon_rmap(new, vma, mmun_start, true); 3247 else 3248 page_add_file_rmap(new, true); 3249 set_pmd_at(mm, mmun_start, pvmw->pmd, pmde); 3250 if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new)) 3251 mlock_vma_page(new); 3252 update_mmu_cache_pmd(vma, address, pvmw->pmd); 3253 } 3254 #endif 3255