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