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/coredump.h> 11 #include <linux/sched/numa_balancing.h> 12 #include <linux/highmem.h> 13 #include <linux/hugetlb.h> 14 #include <linux/mmu_notifier.h> 15 #include <linux/rmap.h> 16 #include <linux/swap.h> 17 #include <linux/shrinker.h> 18 #include <linux/mm_inline.h> 19 #include <linux/swapops.h> 20 #include <linux/dax.h> 21 #include <linux/khugepaged.h> 22 #include <linux/freezer.h> 23 #include <linux/pfn_t.h> 24 #include <linux/mman.h> 25 #include <linux/memremap.h> 26 #include <linux/pagemap.h> 27 #include <linux/debugfs.h> 28 #include <linux/migrate.h> 29 #include <linux/hashtable.h> 30 #include <linux/userfaultfd_k.h> 31 #include <linux/page_idle.h> 32 #include <linux/shmem_fs.h> 33 #include <linux/oom.h> 34 #include <linux/numa.h> 35 #include <linux/page_owner.h> 36 37 #include <asm/tlb.h> 38 #include <asm/pgalloc.h> 39 #include "internal.h" 40 41 /* 42 * By default, transparent hugepage support is disabled in order to avoid 43 * risking an increased memory footprint for applications that are not 44 * guaranteed to benefit from it. When transparent hugepage support is 45 * enabled, it is for all mappings, and khugepaged scans all mappings. 46 * Defrag is invoked by khugepaged hugepage allocations and by page faults 47 * for all hugepage allocations. 48 */ 49 unsigned long transparent_hugepage_flags __read_mostly = 50 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS 51 (1<<TRANSPARENT_HUGEPAGE_FLAG)| 52 #endif 53 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE 54 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| 55 #endif 56 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)| 57 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)| 58 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 59 60 static struct shrinker deferred_split_shrinker; 61 62 static atomic_t huge_zero_refcount; 63 struct page *huge_zero_page __read_mostly; 64 65 bool transparent_hugepage_enabled(struct vm_area_struct *vma) 66 { 67 /* The addr is used to check if the vma size fits */ 68 unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE; 69 70 if (!transhuge_vma_suitable(vma, addr)) 71 return false; 72 if (vma_is_anonymous(vma)) 73 return __transparent_hugepage_enabled(vma); 74 if (vma_is_shmem(vma)) 75 return shmem_huge_enabled(vma); 76 77 return false; 78 } 79 80 static struct page *get_huge_zero_page(void) 81 { 82 struct page *zero_page; 83 retry: 84 if (likely(atomic_inc_not_zero(&huge_zero_refcount))) 85 return READ_ONCE(huge_zero_page); 86 87 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, 88 HPAGE_PMD_ORDER); 89 if (!zero_page) { 90 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); 91 return NULL; 92 } 93 count_vm_event(THP_ZERO_PAGE_ALLOC); 94 preempt_disable(); 95 if (cmpxchg(&huge_zero_page, NULL, zero_page)) { 96 preempt_enable(); 97 __free_pages(zero_page, compound_order(zero_page)); 98 goto retry; 99 } 100 101 /* We take additional reference here. It will be put back by shrinker */ 102 atomic_set(&huge_zero_refcount, 2); 103 preempt_enable(); 104 return READ_ONCE(huge_zero_page); 105 } 106 107 static void put_huge_zero_page(void) 108 { 109 /* 110 * Counter should never go to zero here. Only shrinker can put 111 * last reference. 112 */ 113 BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); 114 } 115 116 struct page *mm_get_huge_zero_page(struct mm_struct *mm) 117 { 118 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) 119 return READ_ONCE(huge_zero_page); 120 121 if (!get_huge_zero_page()) 122 return NULL; 123 124 if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) 125 put_huge_zero_page(); 126 127 return READ_ONCE(huge_zero_page); 128 } 129 130 void mm_put_huge_zero_page(struct mm_struct *mm) 131 { 132 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) 133 put_huge_zero_page(); 134 } 135 136 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, 137 struct shrink_control *sc) 138 { 139 /* we can free zero page only if last reference remains */ 140 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; 141 } 142 143 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, 144 struct shrink_control *sc) 145 { 146 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { 147 struct page *zero_page = xchg(&huge_zero_page, NULL); 148 BUG_ON(zero_page == NULL); 149 __free_pages(zero_page, compound_order(zero_page)); 150 return HPAGE_PMD_NR; 151 } 152 153 return 0; 154 } 155 156 static struct shrinker huge_zero_page_shrinker = { 157 .count_objects = shrink_huge_zero_page_count, 158 .scan_objects = shrink_huge_zero_page_scan, 159 .seeks = DEFAULT_SEEKS, 160 }; 161 162 #ifdef CONFIG_SYSFS 163 static ssize_t enabled_show(struct kobject *kobj, 164 struct kobj_attribute *attr, char *buf) 165 { 166 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags)) 167 return sprintf(buf, "[always] madvise never\n"); 168 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags)) 169 return sprintf(buf, "always [madvise] never\n"); 170 else 171 return sprintf(buf, "always madvise [never]\n"); 172 } 173 174 static ssize_t enabled_store(struct kobject *kobj, 175 struct kobj_attribute *attr, 176 const char *buf, size_t count) 177 { 178 ssize_t ret = count; 179 180 if (sysfs_streq(buf, "always")) { 181 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); 182 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); 183 } else if (sysfs_streq(buf, "madvise")) { 184 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); 185 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); 186 } else if (sysfs_streq(buf, "never")) { 187 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); 188 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); 189 } else 190 ret = -EINVAL; 191 192 if (ret > 0) { 193 int err = start_stop_khugepaged(); 194 if (err) 195 ret = err; 196 } 197 return ret; 198 } 199 static struct kobj_attribute enabled_attr = 200 __ATTR(enabled, 0644, enabled_show, enabled_store); 201 202 ssize_t single_hugepage_flag_show(struct kobject *kobj, 203 struct kobj_attribute *attr, char *buf, 204 enum transparent_hugepage_flag flag) 205 { 206 return sprintf(buf, "%d\n", 207 !!test_bit(flag, &transparent_hugepage_flags)); 208 } 209 210 ssize_t single_hugepage_flag_store(struct kobject *kobj, 211 struct kobj_attribute *attr, 212 const char *buf, size_t count, 213 enum transparent_hugepage_flag flag) 214 { 215 unsigned long value; 216 int ret; 217 218 ret = kstrtoul(buf, 10, &value); 219 if (ret < 0) 220 return ret; 221 if (value > 1) 222 return -EINVAL; 223 224 if (value) 225 set_bit(flag, &transparent_hugepage_flags); 226 else 227 clear_bit(flag, &transparent_hugepage_flags); 228 229 return count; 230 } 231 232 static ssize_t defrag_show(struct kobject *kobj, 233 struct kobj_attribute *attr, char *buf) 234 { 235 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) 236 return sprintf(buf, "[always] defer defer+madvise madvise never\n"); 237 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) 238 return sprintf(buf, "always [defer] defer+madvise madvise never\n"); 239 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags)) 240 return sprintf(buf, "always defer [defer+madvise] madvise never\n"); 241 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) 242 return sprintf(buf, "always defer defer+madvise [madvise] never\n"); 243 return sprintf(buf, "always defer defer+madvise madvise [never]\n"); 244 } 245 246 static ssize_t defrag_store(struct kobject *kobj, 247 struct kobj_attribute *attr, 248 const char *buf, size_t count) 249 { 250 if (sysfs_streq(buf, "always")) { 251 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 252 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 253 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 254 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 255 } else if (sysfs_streq(buf, "defer+madvise")) { 256 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 257 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 258 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 259 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 260 } else if (sysfs_streq(buf, "defer")) { 261 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 262 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 263 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 264 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 265 } else if (sysfs_streq(buf, "madvise")) { 266 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 267 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 268 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 269 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 270 } else if (sysfs_streq(buf, "never")) { 271 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 272 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 273 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 274 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 275 } else 276 return -EINVAL; 277 278 return count; 279 } 280 static struct kobj_attribute defrag_attr = 281 __ATTR(defrag, 0644, defrag_show, defrag_store); 282 283 static ssize_t use_zero_page_show(struct kobject *kobj, 284 struct kobj_attribute *attr, char *buf) 285 { 286 return single_hugepage_flag_show(kobj, attr, buf, 287 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 288 } 289 static ssize_t use_zero_page_store(struct kobject *kobj, 290 struct kobj_attribute *attr, const char *buf, size_t count) 291 { 292 return single_hugepage_flag_store(kobj, attr, buf, count, 293 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 294 } 295 static struct kobj_attribute use_zero_page_attr = 296 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); 297 298 static ssize_t hpage_pmd_size_show(struct kobject *kobj, 299 struct kobj_attribute *attr, char *buf) 300 { 301 return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE); 302 } 303 static struct kobj_attribute hpage_pmd_size_attr = 304 __ATTR_RO(hpage_pmd_size); 305 306 #ifdef CONFIG_DEBUG_VM 307 static ssize_t debug_cow_show(struct kobject *kobj, 308 struct kobj_attribute *attr, char *buf) 309 { 310 return single_hugepage_flag_show(kobj, attr, buf, 311 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 312 } 313 static ssize_t debug_cow_store(struct kobject *kobj, 314 struct kobj_attribute *attr, 315 const char *buf, size_t count) 316 { 317 return single_hugepage_flag_store(kobj, attr, buf, count, 318 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 319 } 320 static struct kobj_attribute debug_cow_attr = 321 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 322 #endif /* CONFIG_DEBUG_VM */ 323 324 static struct attribute *hugepage_attr[] = { 325 &enabled_attr.attr, 326 &defrag_attr.attr, 327 &use_zero_page_attr.attr, 328 &hpage_pmd_size_attr.attr, 329 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) 330 &shmem_enabled_attr.attr, 331 #endif 332 #ifdef CONFIG_DEBUG_VM 333 &debug_cow_attr.attr, 334 #endif 335 NULL, 336 }; 337 338 static const struct attribute_group hugepage_attr_group = { 339 .attrs = hugepage_attr, 340 }; 341 342 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) 343 { 344 int err; 345 346 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 347 if (unlikely(!*hugepage_kobj)) { 348 pr_err("failed to create transparent hugepage kobject\n"); 349 return -ENOMEM; 350 } 351 352 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); 353 if (err) { 354 pr_err("failed to register transparent hugepage group\n"); 355 goto delete_obj; 356 } 357 358 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); 359 if (err) { 360 pr_err("failed to register transparent hugepage group\n"); 361 goto remove_hp_group; 362 } 363 364 return 0; 365 366 remove_hp_group: 367 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); 368 delete_obj: 369 kobject_put(*hugepage_kobj); 370 return err; 371 } 372 373 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) 374 { 375 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); 376 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); 377 kobject_put(hugepage_kobj); 378 } 379 #else 380 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) 381 { 382 return 0; 383 } 384 385 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) 386 { 387 } 388 #endif /* CONFIG_SYSFS */ 389 390 static int __init hugepage_init(void) 391 { 392 int err; 393 struct kobject *hugepage_kobj; 394 395 if (!has_transparent_hugepage()) { 396 transparent_hugepage_flags = 0; 397 return -EINVAL; 398 } 399 400 /* 401 * hugepages can't be allocated by the buddy allocator 402 */ 403 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER); 404 /* 405 * we use page->mapping and page->index in second tail page 406 * as list_head: assuming THP order >= 2 407 */ 408 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2); 409 410 err = hugepage_init_sysfs(&hugepage_kobj); 411 if (err) 412 goto err_sysfs; 413 414 err = khugepaged_init(); 415 if (err) 416 goto err_slab; 417 418 err = register_shrinker(&huge_zero_page_shrinker); 419 if (err) 420 goto err_hzp_shrinker; 421 err = register_shrinker(&deferred_split_shrinker); 422 if (err) 423 goto err_split_shrinker; 424 425 /* 426 * By default disable transparent hugepages on smaller systems, 427 * where the extra memory used could hurt more than TLB overhead 428 * is likely to save. The admin can still enable it through /sys. 429 */ 430 if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) { 431 transparent_hugepage_flags = 0; 432 return 0; 433 } 434 435 err = start_stop_khugepaged(); 436 if (err) 437 goto err_khugepaged; 438 439 return 0; 440 err_khugepaged: 441 unregister_shrinker(&deferred_split_shrinker); 442 err_split_shrinker: 443 unregister_shrinker(&huge_zero_page_shrinker); 444 err_hzp_shrinker: 445 khugepaged_destroy(); 446 err_slab: 447 hugepage_exit_sysfs(hugepage_kobj); 448 err_sysfs: 449 return err; 450 } 451 subsys_initcall(hugepage_init); 452 453 static int __init setup_transparent_hugepage(char *str) 454 { 455 int ret = 0; 456 if (!str) 457 goto out; 458 if (!strcmp(str, "always")) { 459 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 460 &transparent_hugepage_flags); 461 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 462 &transparent_hugepage_flags); 463 ret = 1; 464 } else if (!strcmp(str, "madvise")) { 465 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 466 &transparent_hugepage_flags); 467 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 468 &transparent_hugepage_flags); 469 ret = 1; 470 } else if (!strcmp(str, "never")) { 471 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 472 &transparent_hugepage_flags); 473 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 474 &transparent_hugepage_flags); 475 ret = 1; 476 } 477 out: 478 if (!ret) 479 pr_warn("transparent_hugepage= cannot parse, ignored\n"); 480 return ret; 481 } 482 __setup("transparent_hugepage=", setup_transparent_hugepage); 483 484 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 485 { 486 if (likely(vma->vm_flags & VM_WRITE)) 487 pmd = pmd_mkwrite(pmd); 488 return pmd; 489 } 490 491 #ifdef CONFIG_MEMCG 492 static inline struct deferred_split *get_deferred_split_queue(struct page *page) 493 { 494 struct mem_cgroup *memcg = compound_head(page)->mem_cgroup; 495 struct pglist_data *pgdat = NODE_DATA(page_to_nid(page)); 496 497 if (memcg) 498 return &memcg->deferred_split_queue; 499 else 500 return &pgdat->deferred_split_queue; 501 } 502 #else 503 static inline struct deferred_split *get_deferred_split_queue(struct page *page) 504 { 505 struct pglist_data *pgdat = NODE_DATA(page_to_nid(page)); 506 507 return &pgdat->deferred_split_queue; 508 } 509 #endif 510 511 void prep_transhuge_page(struct page *page) 512 { 513 /* 514 * we use page->mapping and page->indexlru in second tail page 515 * as list_head: assuming THP order >= 2 516 */ 517 518 INIT_LIST_HEAD(page_deferred_list(page)); 519 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR); 520 } 521 522 bool is_transparent_hugepage(struct page *page) 523 { 524 if (!PageCompound(page)) 525 return 0; 526 527 page = compound_head(page); 528 return is_huge_zero_page(page) || 529 page[1].compound_dtor == TRANSHUGE_PAGE_DTOR; 530 } 531 EXPORT_SYMBOL_GPL(is_transparent_hugepage); 532 533 static unsigned long __thp_get_unmapped_area(struct file *filp, 534 unsigned long addr, unsigned long len, 535 loff_t off, unsigned long flags, unsigned long size) 536 { 537 loff_t off_end = off + len; 538 loff_t off_align = round_up(off, size); 539 unsigned long len_pad, ret; 540 541 if (off_end <= off_align || (off_end - off_align) < size) 542 return 0; 543 544 len_pad = len + size; 545 if (len_pad < len || (off + len_pad) < off) 546 return 0; 547 548 ret = current->mm->get_unmapped_area(filp, addr, len_pad, 549 off >> PAGE_SHIFT, flags); 550 551 /* 552 * The failure might be due to length padding. The caller will retry 553 * without the padding. 554 */ 555 if (IS_ERR_VALUE(ret)) 556 return 0; 557 558 /* 559 * Do not try to align to THP boundary if allocation at the address 560 * hint succeeds. 561 */ 562 if (ret == addr) 563 return addr; 564 565 ret += (off - ret) & (size - 1); 566 return ret; 567 } 568 569 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr, 570 unsigned long len, unsigned long pgoff, unsigned long flags) 571 { 572 unsigned long ret; 573 loff_t off = (loff_t)pgoff << PAGE_SHIFT; 574 575 if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD)) 576 goto out; 577 578 ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE); 579 if (ret) 580 return ret; 581 out: 582 return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags); 583 } 584 EXPORT_SYMBOL_GPL(thp_get_unmapped_area); 585 586 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf, 587 struct page *page, gfp_t gfp) 588 { 589 struct vm_area_struct *vma = vmf->vma; 590 struct mem_cgroup *memcg; 591 pgtable_t pgtable; 592 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 593 vm_fault_t ret = 0; 594 595 VM_BUG_ON_PAGE(!PageCompound(page), page); 596 597 if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) { 598 put_page(page); 599 count_vm_event(THP_FAULT_FALLBACK); 600 return VM_FAULT_FALLBACK; 601 } 602 603 pgtable = pte_alloc_one(vma->vm_mm); 604 if (unlikely(!pgtable)) { 605 ret = VM_FAULT_OOM; 606 goto release; 607 } 608 609 clear_huge_page(page, vmf->address, HPAGE_PMD_NR); 610 /* 611 * The memory barrier inside __SetPageUptodate makes sure that 612 * clear_huge_page writes become visible before the set_pmd_at() 613 * write. 614 */ 615 __SetPageUptodate(page); 616 617 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 618 if (unlikely(!pmd_none(*vmf->pmd))) { 619 goto unlock_release; 620 } else { 621 pmd_t entry; 622 623 ret = check_stable_address_space(vma->vm_mm); 624 if (ret) 625 goto unlock_release; 626 627 /* Deliver the page fault to userland */ 628 if (userfaultfd_missing(vma)) { 629 vm_fault_t ret2; 630 631 spin_unlock(vmf->ptl); 632 mem_cgroup_cancel_charge(page, memcg, true); 633 put_page(page); 634 pte_free(vma->vm_mm, pgtable); 635 ret2 = handle_userfault(vmf, VM_UFFD_MISSING); 636 VM_BUG_ON(ret2 & VM_FAULT_FALLBACK); 637 return ret2; 638 } 639 640 entry = mk_huge_pmd(page, vma->vm_page_prot); 641 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 642 page_add_new_anon_rmap(page, vma, haddr, true); 643 mem_cgroup_commit_charge(page, memcg, false, true); 644 lru_cache_add_active_or_unevictable(page, vma); 645 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable); 646 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); 647 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); 648 mm_inc_nr_ptes(vma->vm_mm); 649 spin_unlock(vmf->ptl); 650 count_vm_event(THP_FAULT_ALLOC); 651 count_memcg_events(memcg, THP_FAULT_ALLOC, 1); 652 } 653 654 return 0; 655 unlock_release: 656 spin_unlock(vmf->ptl); 657 release: 658 if (pgtable) 659 pte_free(vma->vm_mm, pgtable); 660 mem_cgroup_cancel_charge(page, memcg, true); 661 put_page(page); 662 return ret; 663 664 } 665 666 /* 667 * always: directly stall for all thp allocations 668 * defer: wake kswapd and fail if not immediately available 669 * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise 670 * fail if not immediately available 671 * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately 672 * available 673 * never: never stall for any thp allocation 674 */ 675 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma) 676 { 677 const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE); 678 679 /* Always do synchronous compaction */ 680 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) 681 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY); 682 683 /* Kick kcompactd and fail quickly */ 684 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) 685 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM; 686 687 /* Synchronous compaction if madvised, otherwise kick kcompactd */ 688 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags)) 689 return GFP_TRANSHUGE_LIGHT | 690 (vma_madvised ? __GFP_DIRECT_RECLAIM : 691 __GFP_KSWAPD_RECLAIM); 692 693 /* Only do synchronous compaction if madvised */ 694 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) 695 return GFP_TRANSHUGE_LIGHT | 696 (vma_madvised ? __GFP_DIRECT_RECLAIM : 0); 697 698 return GFP_TRANSHUGE_LIGHT; 699 } 700 701 /* Caller must hold page table lock. */ 702 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, 703 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, 704 struct page *zero_page) 705 { 706 pmd_t entry; 707 if (!pmd_none(*pmd)) 708 return false; 709 entry = mk_pmd(zero_page, vma->vm_page_prot); 710 entry = pmd_mkhuge(entry); 711 if (pgtable) 712 pgtable_trans_huge_deposit(mm, pmd, pgtable); 713 set_pmd_at(mm, haddr, pmd, entry); 714 mm_inc_nr_ptes(mm); 715 return true; 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 page *page; 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 if (unlikely(khugepaged_enter(vma, vma->vm_flags))) 730 return VM_FAULT_OOM; 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 bool set; 737 vm_fault_t ret; 738 pgtable = pte_alloc_one(vma->vm_mm); 739 if (unlikely(!pgtable)) 740 return VM_FAULT_OOM; 741 zero_page = mm_get_huge_zero_page(vma->vm_mm); 742 if (unlikely(!zero_page)) { 743 pte_free(vma->vm_mm, pgtable); 744 count_vm_event(THP_FAULT_FALLBACK); 745 return VM_FAULT_FALLBACK; 746 } 747 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 748 ret = 0; 749 set = false; 750 if (pmd_none(*vmf->pmd)) { 751 ret = check_stable_address_space(vma->vm_mm); 752 if (ret) { 753 spin_unlock(vmf->ptl); 754 } else if (userfaultfd_missing(vma)) { 755 spin_unlock(vmf->ptl); 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 spin_unlock(vmf->ptl); 762 set = true; 763 } 764 } else 765 spin_unlock(vmf->ptl); 766 if (!set) 767 pte_free(vma->vm_mm, pgtable); 768 return ret; 769 } 770 gfp = alloc_hugepage_direct_gfpmask(vma); 771 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER); 772 if (unlikely(!page)) { 773 count_vm_event(THP_FAULT_FALLBACK); 774 return VM_FAULT_FALLBACK; 775 } 776 prep_transhuge_page(page); 777 return __do_huge_pmd_anonymous_page(vmf, page, gfp); 778 } 779 780 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, 781 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write, 782 pgtable_t pgtable) 783 { 784 struct mm_struct *mm = vma->vm_mm; 785 pmd_t entry; 786 spinlock_t *ptl; 787 788 ptl = pmd_lock(mm, pmd); 789 if (!pmd_none(*pmd)) { 790 if (write) { 791 if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) { 792 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd)); 793 goto out_unlock; 794 } 795 entry = pmd_mkyoung(*pmd); 796 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 797 if (pmdp_set_access_flags(vma, addr, pmd, entry, 1)) 798 update_mmu_cache_pmd(vma, addr, pmd); 799 } 800 801 goto out_unlock; 802 } 803 804 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot)); 805 if (pfn_t_devmap(pfn)) 806 entry = pmd_mkdevmap(entry); 807 if (write) { 808 entry = pmd_mkyoung(pmd_mkdirty(entry)); 809 entry = maybe_pmd_mkwrite(entry, vma); 810 } 811 812 if (pgtable) { 813 pgtable_trans_huge_deposit(mm, pmd, pgtable); 814 mm_inc_nr_ptes(mm); 815 pgtable = NULL; 816 } 817 818 set_pmd_at(mm, addr, pmd, entry); 819 update_mmu_cache_pmd(vma, addr, pmd); 820 821 out_unlock: 822 spin_unlock(ptl); 823 if (pgtable) 824 pte_free(mm, pgtable); 825 } 826 827 vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write) 828 { 829 unsigned long addr = vmf->address & PMD_MASK; 830 struct vm_area_struct *vma = vmf->vma; 831 pgprot_t pgprot = vma->vm_page_prot; 832 pgtable_t pgtable = NULL; 833 834 /* 835 * If we had pmd_special, we could avoid all these restrictions, 836 * but we need to be consistent with PTEs and architectures that 837 * can't support a 'special' bit. 838 */ 839 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) && 840 !pfn_t_devmap(pfn)); 841 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == 842 (VM_PFNMAP|VM_MIXEDMAP)); 843 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); 844 845 if (addr < vma->vm_start || addr >= vma->vm_end) 846 return VM_FAULT_SIGBUS; 847 848 if (arch_needs_pgtable_deposit()) { 849 pgtable = pte_alloc_one(vma->vm_mm); 850 if (!pgtable) 851 return VM_FAULT_OOM; 852 } 853 854 track_pfn_insert(vma, &pgprot, pfn); 855 856 insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable); 857 return VM_FAULT_NOPAGE; 858 } 859 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd); 860 861 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 862 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma) 863 { 864 if (likely(vma->vm_flags & VM_WRITE)) 865 pud = pud_mkwrite(pud); 866 return pud; 867 } 868 869 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr, 870 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write) 871 { 872 struct mm_struct *mm = vma->vm_mm; 873 pud_t entry; 874 spinlock_t *ptl; 875 876 ptl = pud_lock(mm, pud); 877 if (!pud_none(*pud)) { 878 if (write) { 879 if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) { 880 WARN_ON_ONCE(!is_huge_zero_pud(*pud)); 881 goto out_unlock; 882 } 883 entry = pud_mkyoung(*pud); 884 entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma); 885 if (pudp_set_access_flags(vma, addr, pud, entry, 1)) 886 update_mmu_cache_pud(vma, addr, pud); 887 } 888 goto out_unlock; 889 } 890 891 entry = pud_mkhuge(pfn_t_pud(pfn, prot)); 892 if (pfn_t_devmap(pfn)) 893 entry = pud_mkdevmap(entry); 894 if (write) { 895 entry = pud_mkyoung(pud_mkdirty(entry)); 896 entry = maybe_pud_mkwrite(entry, vma); 897 } 898 set_pud_at(mm, addr, pud, entry); 899 update_mmu_cache_pud(vma, addr, pud); 900 901 out_unlock: 902 spin_unlock(ptl); 903 } 904 905 vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write) 906 { 907 unsigned long addr = vmf->address & PUD_MASK; 908 struct vm_area_struct *vma = vmf->vma; 909 pgprot_t pgprot = vma->vm_page_prot; 910 911 /* 912 * If we had pud_special, we could avoid all these restrictions, 913 * but we need to be consistent with PTEs and architectures that 914 * can't support a 'special' bit. 915 */ 916 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) && 917 !pfn_t_devmap(pfn)); 918 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == 919 (VM_PFNMAP|VM_MIXEDMAP)); 920 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); 921 922 if (addr < vma->vm_start || addr >= vma->vm_end) 923 return VM_FAULT_SIGBUS; 924 925 track_pfn_insert(vma, &pgprot, pfn); 926 927 insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write); 928 return VM_FAULT_NOPAGE; 929 } 930 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud); 931 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ 932 933 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr, 934 pmd_t *pmd, int flags) 935 { 936 pmd_t _pmd; 937 938 _pmd = pmd_mkyoung(*pmd); 939 if (flags & FOLL_WRITE) 940 _pmd = pmd_mkdirty(_pmd); 941 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, 942 pmd, _pmd, flags & FOLL_WRITE)) 943 update_mmu_cache_pmd(vma, addr, pmd); 944 } 945 946 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, 947 pmd_t *pmd, int flags, struct dev_pagemap **pgmap) 948 { 949 unsigned long pfn = pmd_pfn(*pmd); 950 struct mm_struct *mm = vma->vm_mm; 951 struct page *page; 952 953 assert_spin_locked(pmd_lockptr(mm, pmd)); 954 955 /* 956 * When we COW a devmap PMD entry, we split it into PTEs, so we should 957 * not be in this function with `flags & FOLL_COW` set. 958 */ 959 WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set"); 960 961 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 962 return NULL; 963 964 if (pmd_present(*pmd) && pmd_devmap(*pmd)) 965 /* pass */; 966 else 967 return NULL; 968 969 if (flags & FOLL_TOUCH) 970 touch_pmd(vma, addr, pmd, flags); 971 972 /* 973 * device mapped pages can only be returned if the 974 * caller will manage the page reference count. 975 */ 976 if (!(flags & FOLL_GET)) 977 return ERR_PTR(-EEXIST); 978 979 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT; 980 *pgmap = get_dev_pagemap(pfn, *pgmap); 981 if (!*pgmap) 982 return ERR_PTR(-EFAULT); 983 page = pfn_to_page(pfn); 984 get_page(page); 985 986 return page; 987 } 988 989 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 990 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 991 struct vm_area_struct *vma) 992 { 993 spinlock_t *dst_ptl, *src_ptl; 994 struct page *src_page; 995 pmd_t pmd; 996 pgtable_t pgtable = NULL; 997 int ret = -ENOMEM; 998 999 /* Skip if can be re-fill on fault */ 1000 if (!vma_is_anonymous(vma)) 1001 return 0; 1002 1003 pgtable = pte_alloc_one(dst_mm); 1004 if (unlikely(!pgtable)) 1005 goto out; 1006 1007 dst_ptl = pmd_lock(dst_mm, dst_pmd); 1008 src_ptl = pmd_lockptr(src_mm, src_pmd); 1009 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); 1010 1011 ret = -EAGAIN; 1012 pmd = *src_pmd; 1013 1014 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 1015 if (unlikely(is_swap_pmd(pmd))) { 1016 swp_entry_t entry = pmd_to_swp_entry(pmd); 1017 1018 VM_BUG_ON(!is_pmd_migration_entry(pmd)); 1019 if (is_write_migration_entry(entry)) { 1020 make_migration_entry_read(&entry); 1021 pmd = swp_entry_to_pmd(entry); 1022 if (pmd_swp_soft_dirty(*src_pmd)) 1023 pmd = pmd_swp_mksoft_dirty(pmd); 1024 set_pmd_at(src_mm, addr, src_pmd, pmd); 1025 } 1026 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 1027 mm_inc_nr_ptes(dst_mm); 1028 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); 1029 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 1030 ret = 0; 1031 goto out_unlock; 1032 } 1033 #endif 1034 1035 if (unlikely(!pmd_trans_huge(pmd))) { 1036 pte_free(dst_mm, pgtable); 1037 goto out_unlock; 1038 } 1039 /* 1040 * When page table lock is held, the huge zero pmd should not be 1041 * under splitting since we don't split the page itself, only pmd to 1042 * a page table. 1043 */ 1044 if (is_huge_zero_pmd(pmd)) { 1045 struct page *zero_page; 1046 /* 1047 * get_huge_zero_page() will never allocate a new page here, 1048 * since we already have a zero page to copy. It just takes a 1049 * reference. 1050 */ 1051 zero_page = mm_get_huge_zero_page(dst_mm); 1052 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, 1053 zero_page); 1054 ret = 0; 1055 goto out_unlock; 1056 } 1057 1058 src_page = pmd_page(pmd); 1059 VM_BUG_ON_PAGE(!PageHead(src_page), src_page); 1060 get_page(src_page); 1061 page_dup_rmap(src_page, true); 1062 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 1063 mm_inc_nr_ptes(dst_mm); 1064 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); 1065 1066 pmdp_set_wrprotect(src_mm, addr, src_pmd); 1067 pmd = pmd_mkold(pmd_wrprotect(pmd)); 1068 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 1069 1070 ret = 0; 1071 out_unlock: 1072 spin_unlock(src_ptl); 1073 spin_unlock(dst_ptl); 1074 out: 1075 return ret; 1076 } 1077 1078 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 1079 static void touch_pud(struct vm_area_struct *vma, unsigned long addr, 1080 pud_t *pud, int flags) 1081 { 1082 pud_t _pud; 1083 1084 _pud = pud_mkyoung(*pud); 1085 if (flags & FOLL_WRITE) 1086 _pud = pud_mkdirty(_pud); 1087 if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK, 1088 pud, _pud, flags & FOLL_WRITE)) 1089 update_mmu_cache_pud(vma, addr, pud); 1090 } 1091 1092 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr, 1093 pud_t *pud, int flags, struct dev_pagemap **pgmap) 1094 { 1095 unsigned long pfn = pud_pfn(*pud); 1096 struct mm_struct *mm = vma->vm_mm; 1097 struct page *page; 1098 1099 assert_spin_locked(pud_lockptr(mm, pud)); 1100 1101 if (flags & FOLL_WRITE && !pud_write(*pud)) 1102 return NULL; 1103 1104 if (pud_present(*pud) && pud_devmap(*pud)) 1105 /* pass */; 1106 else 1107 return NULL; 1108 1109 if (flags & FOLL_TOUCH) 1110 touch_pud(vma, addr, pud, flags); 1111 1112 /* 1113 * device mapped pages can only be returned if the 1114 * caller will manage the page reference count. 1115 */ 1116 if (!(flags & FOLL_GET)) 1117 return ERR_PTR(-EEXIST); 1118 1119 pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT; 1120 *pgmap = get_dev_pagemap(pfn, *pgmap); 1121 if (!*pgmap) 1122 return ERR_PTR(-EFAULT); 1123 page = pfn_to_page(pfn); 1124 get_page(page); 1125 1126 return page; 1127 } 1128 1129 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm, 1130 pud_t *dst_pud, pud_t *src_pud, unsigned long addr, 1131 struct vm_area_struct *vma) 1132 { 1133 spinlock_t *dst_ptl, *src_ptl; 1134 pud_t pud; 1135 int ret; 1136 1137 dst_ptl = pud_lock(dst_mm, dst_pud); 1138 src_ptl = pud_lockptr(src_mm, src_pud); 1139 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); 1140 1141 ret = -EAGAIN; 1142 pud = *src_pud; 1143 if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud))) 1144 goto out_unlock; 1145 1146 /* 1147 * When page table lock is held, the huge zero pud should not be 1148 * under splitting since we don't split the page itself, only pud to 1149 * a page table. 1150 */ 1151 if (is_huge_zero_pud(pud)) { 1152 /* No huge zero pud yet */ 1153 } 1154 1155 pudp_set_wrprotect(src_mm, addr, src_pud); 1156 pud = pud_mkold(pud_wrprotect(pud)); 1157 set_pud_at(dst_mm, addr, dst_pud, pud); 1158 1159 ret = 0; 1160 out_unlock: 1161 spin_unlock(src_ptl); 1162 spin_unlock(dst_ptl); 1163 return ret; 1164 } 1165 1166 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud) 1167 { 1168 pud_t entry; 1169 unsigned long haddr; 1170 bool write = vmf->flags & FAULT_FLAG_WRITE; 1171 1172 vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud); 1173 if (unlikely(!pud_same(*vmf->pud, orig_pud))) 1174 goto unlock; 1175 1176 entry = pud_mkyoung(orig_pud); 1177 if (write) 1178 entry = pud_mkdirty(entry); 1179 haddr = vmf->address & HPAGE_PUD_MASK; 1180 if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write)) 1181 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud); 1182 1183 unlock: 1184 spin_unlock(vmf->ptl); 1185 } 1186 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ 1187 1188 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd) 1189 { 1190 pmd_t entry; 1191 unsigned long haddr; 1192 bool write = vmf->flags & FAULT_FLAG_WRITE; 1193 1194 vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); 1195 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) 1196 goto unlock; 1197 1198 entry = pmd_mkyoung(orig_pmd); 1199 if (write) 1200 entry = pmd_mkdirty(entry); 1201 haddr = vmf->address & HPAGE_PMD_MASK; 1202 if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write)) 1203 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd); 1204 1205 unlock: 1206 spin_unlock(vmf->ptl); 1207 } 1208 1209 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, 1210 pmd_t orig_pmd, struct page *page) 1211 { 1212 struct vm_area_struct *vma = vmf->vma; 1213 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 1214 struct mem_cgroup *memcg; 1215 pgtable_t pgtable; 1216 pmd_t _pmd; 1217 int i; 1218 vm_fault_t ret = 0; 1219 struct page **pages; 1220 struct mmu_notifier_range range; 1221 1222 pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *), 1223 GFP_KERNEL); 1224 if (unlikely(!pages)) { 1225 ret |= VM_FAULT_OOM; 1226 goto out; 1227 } 1228 1229 for (i = 0; i < HPAGE_PMD_NR; i++) { 1230 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma, 1231 vmf->address, page_to_nid(page)); 1232 if (unlikely(!pages[i] || 1233 mem_cgroup_try_charge_delay(pages[i], vma->vm_mm, 1234 GFP_KERNEL, &memcg, false))) { 1235 if (pages[i]) 1236 put_page(pages[i]); 1237 while (--i >= 0) { 1238 memcg = (void *)page_private(pages[i]); 1239 set_page_private(pages[i], 0); 1240 mem_cgroup_cancel_charge(pages[i], memcg, 1241 false); 1242 put_page(pages[i]); 1243 } 1244 kfree(pages); 1245 ret |= VM_FAULT_OOM; 1246 goto out; 1247 } 1248 set_page_private(pages[i], (unsigned long)memcg); 1249 } 1250 1251 for (i = 0; i < HPAGE_PMD_NR; i++) { 1252 copy_user_highpage(pages[i], page + i, 1253 haddr + PAGE_SIZE * i, vma); 1254 __SetPageUptodate(pages[i]); 1255 cond_resched(); 1256 } 1257 1258 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, 1259 haddr, haddr + HPAGE_PMD_SIZE); 1260 mmu_notifier_invalidate_range_start(&range); 1261 1262 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 1263 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) 1264 goto out_free_pages; 1265 VM_BUG_ON_PAGE(!PageHead(page), page); 1266 1267 /* 1268 * Leave pmd empty until pte is filled note we must notify here as 1269 * concurrent CPU thread might write to new page before the call to 1270 * mmu_notifier_invalidate_range_end() happens which can lead to a 1271 * device seeing memory write in different order than CPU. 1272 * 1273 * See Documentation/vm/mmu_notifier.rst 1274 */ 1275 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd); 1276 1277 pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd); 1278 pmd_populate(vma->vm_mm, &_pmd, pgtable); 1279 1280 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1281 pte_t entry; 1282 entry = mk_pte(pages[i], vma->vm_page_prot); 1283 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1284 memcg = (void *)page_private(pages[i]); 1285 set_page_private(pages[i], 0); 1286 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false); 1287 mem_cgroup_commit_charge(pages[i], memcg, false, false); 1288 lru_cache_add_active_or_unevictable(pages[i], vma); 1289 vmf->pte = pte_offset_map(&_pmd, haddr); 1290 VM_BUG_ON(!pte_none(*vmf->pte)); 1291 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry); 1292 pte_unmap(vmf->pte); 1293 } 1294 kfree(pages); 1295 1296 smp_wmb(); /* make pte visible before pmd */ 1297 pmd_populate(vma->vm_mm, vmf->pmd, pgtable); 1298 page_remove_rmap(page, true); 1299 spin_unlock(vmf->ptl); 1300 1301 /* 1302 * No need to double call mmu_notifier->invalidate_range() callback as 1303 * the above pmdp_huge_clear_flush_notify() did already call it. 1304 */ 1305 mmu_notifier_invalidate_range_only_end(&range); 1306 1307 ret |= VM_FAULT_WRITE; 1308 put_page(page); 1309 1310 out: 1311 return ret; 1312 1313 out_free_pages: 1314 spin_unlock(vmf->ptl); 1315 mmu_notifier_invalidate_range_end(&range); 1316 for (i = 0; i < HPAGE_PMD_NR; i++) { 1317 memcg = (void *)page_private(pages[i]); 1318 set_page_private(pages[i], 0); 1319 mem_cgroup_cancel_charge(pages[i], memcg, false); 1320 put_page(pages[i]); 1321 } 1322 kfree(pages); 1323 goto out; 1324 } 1325 1326 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd) 1327 { 1328 struct vm_area_struct *vma = vmf->vma; 1329 struct page *page = NULL, *new_page; 1330 struct mem_cgroup *memcg; 1331 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 1332 struct mmu_notifier_range range; 1333 gfp_t huge_gfp; /* for allocation and charge */ 1334 vm_fault_t ret = 0; 1335 1336 vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd); 1337 VM_BUG_ON_VMA(!vma->anon_vma, vma); 1338 if (is_huge_zero_pmd(orig_pmd)) 1339 goto alloc; 1340 spin_lock(vmf->ptl); 1341 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) 1342 goto out_unlock; 1343 1344 page = pmd_page(orig_pmd); 1345 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); 1346 /* 1347 * We can only reuse the page if nobody else maps the huge page or it's 1348 * part. 1349 */ 1350 if (!trylock_page(page)) { 1351 get_page(page); 1352 spin_unlock(vmf->ptl); 1353 lock_page(page); 1354 spin_lock(vmf->ptl); 1355 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { 1356 unlock_page(page); 1357 put_page(page); 1358 goto out_unlock; 1359 } 1360 put_page(page); 1361 } 1362 if (reuse_swap_page(page, NULL)) { 1363 pmd_t entry; 1364 entry = pmd_mkyoung(orig_pmd); 1365 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1366 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1)) 1367 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 1368 ret |= VM_FAULT_WRITE; 1369 unlock_page(page); 1370 goto out_unlock; 1371 } 1372 unlock_page(page); 1373 get_page(page); 1374 spin_unlock(vmf->ptl); 1375 alloc: 1376 if (__transparent_hugepage_enabled(vma) && 1377 !transparent_hugepage_debug_cow()) { 1378 huge_gfp = alloc_hugepage_direct_gfpmask(vma); 1379 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER); 1380 } else 1381 new_page = NULL; 1382 1383 if (likely(new_page)) { 1384 prep_transhuge_page(new_page); 1385 } else { 1386 if (!page) { 1387 split_huge_pmd(vma, vmf->pmd, vmf->address); 1388 ret |= VM_FAULT_FALLBACK; 1389 } else { 1390 ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page); 1391 if (ret & VM_FAULT_OOM) { 1392 split_huge_pmd(vma, vmf->pmd, vmf->address); 1393 ret |= VM_FAULT_FALLBACK; 1394 } 1395 put_page(page); 1396 } 1397 count_vm_event(THP_FAULT_FALLBACK); 1398 goto out; 1399 } 1400 1401 if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm, 1402 huge_gfp, &memcg, true))) { 1403 put_page(new_page); 1404 split_huge_pmd(vma, vmf->pmd, vmf->address); 1405 if (page) 1406 put_page(page); 1407 ret |= VM_FAULT_FALLBACK; 1408 count_vm_event(THP_FAULT_FALLBACK); 1409 goto out; 1410 } 1411 1412 count_vm_event(THP_FAULT_ALLOC); 1413 count_memcg_events(memcg, THP_FAULT_ALLOC, 1); 1414 1415 if (!page) 1416 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR); 1417 else 1418 copy_user_huge_page(new_page, page, vmf->address, 1419 vma, HPAGE_PMD_NR); 1420 __SetPageUptodate(new_page); 1421 1422 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, 1423 haddr, haddr + HPAGE_PMD_SIZE); 1424 mmu_notifier_invalidate_range_start(&range); 1425 1426 spin_lock(vmf->ptl); 1427 if (page) 1428 put_page(page); 1429 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { 1430 spin_unlock(vmf->ptl); 1431 mem_cgroup_cancel_charge(new_page, memcg, true); 1432 put_page(new_page); 1433 goto out_mn; 1434 } else { 1435 pmd_t entry; 1436 entry = mk_huge_pmd(new_page, vma->vm_page_prot); 1437 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1438 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd); 1439 page_add_new_anon_rmap(new_page, vma, haddr, true); 1440 mem_cgroup_commit_charge(new_page, memcg, false, true); 1441 lru_cache_add_active_or_unevictable(new_page, vma); 1442 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); 1443 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 1444 if (!page) { 1445 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); 1446 } else { 1447 VM_BUG_ON_PAGE(!PageHead(page), page); 1448 page_remove_rmap(page, true); 1449 put_page(page); 1450 } 1451 ret |= VM_FAULT_WRITE; 1452 } 1453 spin_unlock(vmf->ptl); 1454 out_mn: 1455 /* 1456 * No need to double call mmu_notifier->invalidate_range() callback as 1457 * the above pmdp_huge_clear_flush_notify() did already call it. 1458 */ 1459 mmu_notifier_invalidate_range_only_end(&range); 1460 out: 1461 return ret; 1462 out_unlock: 1463 spin_unlock(vmf->ptl); 1464 return ret; 1465 } 1466 1467 /* 1468 * FOLL_FORCE can write to even unwritable pmd's, but only 1469 * after we've gone through a COW cycle and they are dirty. 1470 */ 1471 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags) 1472 { 1473 return pmd_write(pmd) || 1474 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd)); 1475 } 1476 1477 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1478 unsigned long addr, 1479 pmd_t *pmd, 1480 unsigned int flags) 1481 { 1482 struct mm_struct *mm = vma->vm_mm; 1483 struct page *page = NULL; 1484 1485 assert_spin_locked(pmd_lockptr(mm, pmd)); 1486 1487 if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags)) 1488 goto out; 1489 1490 /* Avoid dumping huge zero page */ 1491 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) 1492 return ERR_PTR(-EFAULT); 1493 1494 /* Full NUMA hinting faults to serialise migration in fault paths */ 1495 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) 1496 goto out; 1497 1498 page = pmd_page(*pmd); 1499 VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page); 1500 if (flags & FOLL_TOUCH) 1501 touch_pmd(vma, addr, pmd, flags); 1502 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 1503 /* 1504 * We don't mlock() pte-mapped THPs. This way we can avoid 1505 * leaking mlocked pages into non-VM_LOCKED VMAs. 1506 * 1507 * For anon THP: 1508 * 1509 * In most cases the pmd is the only mapping of the page as we 1510 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for 1511 * writable private mappings in populate_vma_page_range(). 1512 * 1513 * The only scenario when we have the page shared here is if we 1514 * mlocking read-only mapping shared over fork(). We skip 1515 * mlocking such pages. 1516 * 1517 * For file THP: 1518 * 1519 * We can expect PageDoubleMap() to be stable under page lock: 1520 * for file pages we set it in page_add_file_rmap(), which 1521 * requires page to be locked. 1522 */ 1523 1524 if (PageAnon(page) && compound_mapcount(page) != 1) 1525 goto skip_mlock; 1526 if (PageDoubleMap(page) || !page->mapping) 1527 goto skip_mlock; 1528 if (!trylock_page(page)) 1529 goto skip_mlock; 1530 lru_add_drain(); 1531 if (page->mapping && !PageDoubleMap(page)) 1532 mlock_vma_page(page); 1533 unlock_page(page); 1534 } 1535 skip_mlock: 1536 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1537 VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page); 1538 if (flags & FOLL_GET) 1539 get_page(page); 1540 1541 out: 1542 return page; 1543 } 1544 1545 /* NUMA hinting page fault entry point for trans huge pmds */ 1546 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) 1547 { 1548 struct vm_area_struct *vma = vmf->vma; 1549 struct anon_vma *anon_vma = NULL; 1550 struct page *page; 1551 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 1552 int page_nid = NUMA_NO_NODE, this_nid = numa_node_id(); 1553 int target_nid, last_cpupid = -1; 1554 bool page_locked; 1555 bool migrated = false; 1556 bool was_writable; 1557 int flags = 0; 1558 1559 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 1560 if (unlikely(!pmd_same(pmd, *vmf->pmd))) 1561 goto out_unlock; 1562 1563 /* 1564 * If there are potential migrations, wait for completion and retry 1565 * without disrupting NUMA hinting information. Do not relock and 1566 * check_same as the page may no longer be mapped. 1567 */ 1568 if (unlikely(pmd_trans_migrating(*vmf->pmd))) { 1569 page = pmd_page(*vmf->pmd); 1570 if (!get_page_unless_zero(page)) 1571 goto out_unlock; 1572 spin_unlock(vmf->ptl); 1573 put_and_wait_on_page_locked(page); 1574 goto out; 1575 } 1576 1577 page = pmd_page(pmd); 1578 BUG_ON(is_huge_zero_page(page)); 1579 page_nid = page_to_nid(page); 1580 last_cpupid = page_cpupid_last(page); 1581 count_vm_numa_event(NUMA_HINT_FAULTS); 1582 if (page_nid == this_nid) { 1583 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); 1584 flags |= TNF_FAULT_LOCAL; 1585 } 1586 1587 /* See similar comment in do_numa_page for explanation */ 1588 if (!pmd_savedwrite(pmd)) 1589 flags |= TNF_NO_GROUP; 1590 1591 /* 1592 * Acquire the page lock to serialise THP migrations but avoid dropping 1593 * page_table_lock if at all possible 1594 */ 1595 page_locked = trylock_page(page); 1596 target_nid = mpol_misplaced(page, vma, haddr); 1597 if (target_nid == NUMA_NO_NODE) { 1598 /* If the page was locked, there are no parallel migrations */ 1599 if (page_locked) 1600 goto clear_pmdnuma; 1601 } 1602 1603 /* Migration could have started since the pmd_trans_migrating check */ 1604 if (!page_locked) { 1605 page_nid = NUMA_NO_NODE; 1606 if (!get_page_unless_zero(page)) 1607 goto out_unlock; 1608 spin_unlock(vmf->ptl); 1609 put_and_wait_on_page_locked(page); 1610 goto out; 1611 } 1612 1613 /* 1614 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma 1615 * to serialises splits 1616 */ 1617 get_page(page); 1618 spin_unlock(vmf->ptl); 1619 anon_vma = page_lock_anon_vma_read(page); 1620 1621 /* Confirm the PMD did not change while page_table_lock was released */ 1622 spin_lock(vmf->ptl); 1623 if (unlikely(!pmd_same(pmd, *vmf->pmd))) { 1624 unlock_page(page); 1625 put_page(page); 1626 page_nid = NUMA_NO_NODE; 1627 goto out_unlock; 1628 } 1629 1630 /* Bail if we fail to protect against THP splits for any reason */ 1631 if (unlikely(!anon_vma)) { 1632 put_page(page); 1633 page_nid = NUMA_NO_NODE; 1634 goto clear_pmdnuma; 1635 } 1636 1637 /* 1638 * Since we took the NUMA fault, we must have observed the !accessible 1639 * bit. Make sure all other CPUs agree with that, to avoid them 1640 * modifying the page we're about to migrate. 1641 * 1642 * Must be done under PTL such that we'll observe the relevant 1643 * inc_tlb_flush_pending(). 1644 * 1645 * We are not sure a pending tlb flush here is for a huge page 1646 * mapping or not. Hence use the tlb range variant 1647 */ 1648 if (mm_tlb_flush_pending(vma->vm_mm)) { 1649 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE); 1650 /* 1651 * change_huge_pmd() released the pmd lock before 1652 * invalidating the secondary MMUs sharing the primary 1653 * MMU pagetables (with ->invalidate_range()). The 1654 * mmu_notifier_invalidate_range_end() (which 1655 * internally calls ->invalidate_range()) in 1656 * change_pmd_range() will run after us, so we can't 1657 * rely on it here and we need an explicit invalidate. 1658 */ 1659 mmu_notifier_invalidate_range(vma->vm_mm, haddr, 1660 haddr + HPAGE_PMD_SIZE); 1661 } 1662 1663 /* 1664 * Migrate the THP to the requested node, returns with page unlocked 1665 * and access rights restored. 1666 */ 1667 spin_unlock(vmf->ptl); 1668 1669 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma, 1670 vmf->pmd, pmd, vmf->address, page, target_nid); 1671 if (migrated) { 1672 flags |= TNF_MIGRATED; 1673 page_nid = target_nid; 1674 } else 1675 flags |= TNF_MIGRATE_FAIL; 1676 1677 goto out; 1678 clear_pmdnuma: 1679 BUG_ON(!PageLocked(page)); 1680 was_writable = pmd_savedwrite(pmd); 1681 pmd = pmd_modify(pmd, vma->vm_page_prot); 1682 pmd = pmd_mkyoung(pmd); 1683 if (was_writable) 1684 pmd = pmd_mkwrite(pmd); 1685 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd); 1686 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 1687 unlock_page(page); 1688 out_unlock: 1689 spin_unlock(vmf->ptl); 1690 1691 out: 1692 if (anon_vma) 1693 page_unlock_anon_vma_read(anon_vma); 1694 1695 if (page_nid != NUMA_NO_NODE) 1696 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, 1697 flags); 1698 1699 return 0; 1700 } 1701 1702 /* 1703 * Return true if we do MADV_FREE successfully on entire pmd page. 1704 * Otherwise, return false. 1705 */ 1706 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1707 pmd_t *pmd, unsigned long addr, unsigned long next) 1708 { 1709 spinlock_t *ptl; 1710 pmd_t orig_pmd; 1711 struct page *page; 1712 struct mm_struct *mm = tlb->mm; 1713 bool ret = false; 1714 1715 tlb_change_page_size(tlb, HPAGE_PMD_SIZE); 1716 1717 ptl = pmd_trans_huge_lock(pmd, vma); 1718 if (!ptl) 1719 goto out_unlocked; 1720 1721 orig_pmd = *pmd; 1722 if (is_huge_zero_pmd(orig_pmd)) 1723 goto out; 1724 1725 if (unlikely(!pmd_present(orig_pmd))) { 1726 VM_BUG_ON(thp_migration_supported() && 1727 !is_pmd_migration_entry(orig_pmd)); 1728 goto out; 1729 } 1730 1731 page = pmd_page(orig_pmd); 1732 /* 1733 * If other processes are mapping this page, we couldn't discard 1734 * the page unless they all do MADV_FREE so let's skip the page. 1735 */ 1736 if (page_mapcount(page) != 1) 1737 goto out; 1738 1739 if (!trylock_page(page)) 1740 goto out; 1741 1742 /* 1743 * If user want to discard part-pages of THP, split it so MADV_FREE 1744 * will deactivate only them. 1745 */ 1746 if (next - addr != HPAGE_PMD_SIZE) { 1747 get_page(page); 1748 spin_unlock(ptl); 1749 split_huge_page(page); 1750 unlock_page(page); 1751 put_page(page); 1752 goto out_unlocked; 1753 } 1754 1755 if (PageDirty(page)) 1756 ClearPageDirty(page); 1757 unlock_page(page); 1758 1759 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { 1760 pmdp_invalidate(vma, addr, pmd); 1761 orig_pmd = pmd_mkold(orig_pmd); 1762 orig_pmd = pmd_mkclean(orig_pmd); 1763 1764 set_pmd_at(mm, addr, pmd, orig_pmd); 1765 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1766 } 1767 1768 mark_page_lazyfree(page); 1769 ret = true; 1770 out: 1771 spin_unlock(ptl); 1772 out_unlocked: 1773 return ret; 1774 } 1775 1776 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd) 1777 { 1778 pgtable_t pgtable; 1779 1780 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1781 pte_free(mm, pgtable); 1782 mm_dec_nr_ptes(mm); 1783 } 1784 1785 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1786 pmd_t *pmd, unsigned long addr) 1787 { 1788 pmd_t orig_pmd; 1789 spinlock_t *ptl; 1790 1791 tlb_change_page_size(tlb, HPAGE_PMD_SIZE); 1792 1793 ptl = __pmd_trans_huge_lock(pmd, vma); 1794 if (!ptl) 1795 return 0; 1796 /* 1797 * For architectures like ppc64 we look at deposited pgtable 1798 * when calling pmdp_huge_get_and_clear. So do the 1799 * pgtable_trans_huge_withdraw after finishing pmdp related 1800 * operations. 1801 */ 1802 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, 1803 tlb->fullmm); 1804 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1805 if (vma_is_dax(vma)) { 1806 if (arch_needs_pgtable_deposit()) 1807 zap_deposited_table(tlb->mm, pmd); 1808 spin_unlock(ptl); 1809 if (is_huge_zero_pmd(orig_pmd)) 1810 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); 1811 } else if (is_huge_zero_pmd(orig_pmd)) { 1812 zap_deposited_table(tlb->mm, pmd); 1813 spin_unlock(ptl); 1814 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); 1815 } else { 1816 struct page *page = NULL; 1817 int flush_needed = 1; 1818 1819 if (pmd_present(orig_pmd)) { 1820 page = pmd_page(orig_pmd); 1821 page_remove_rmap(page, true); 1822 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); 1823 VM_BUG_ON_PAGE(!PageHead(page), page); 1824 } else if (thp_migration_supported()) { 1825 swp_entry_t entry; 1826 1827 VM_BUG_ON(!is_pmd_migration_entry(orig_pmd)); 1828 entry = pmd_to_swp_entry(orig_pmd); 1829 page = pfn_to_page(swp_offset(entry)); 1830 flush_needed = 0; 1831 } else 1832 WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!"); 1833 1834 if (PageAnon(page)) { 1835 zap_deposited_table(tlb->mm, pmd); 1836 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1837 } else { 1838 if (arch_needs_pgtable_deposit()) 1839 zap_deposited_table(tlb->mm, pmd); 1840 add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR); 1841 } 1842 1843 spin_unlock(ptl); 1844 if (flush_needed) 1845 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE); 1846 } 1847 return 1; 1848 } 1849 1850 #ifndef pmd_move_must_withdraw 1851 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl, 1852 spinlock_t *old_pmd_ptl, 1853 struct vm_area_struct *vma) 1854 { 1855 /* 1856 * With split pmd lock we also need to move preallocated 1857 * PTE page table if new_pmd is on different PMD page table. 1858 * 1859 * We also don't deposit and withdraw tables for file pages. 1860 */ 1861 return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma); 1862 } 1863 #endif 1864 1865 static pmd_t move_soft_dirty_pmd(pmd_t pmd) 1866 { 1867 #ifdef CONFIG_MEM_SOFT_DIRTY 1868 if (unlikely(is_pmd_migration_entry(pmd))) 1869 pmd = pmd_swp_mksoft_dirty(pmd); 1870 else if (pmd_present(pmd)) 1871 pmd = pmd_mksoft_dirty(pmd); 1872 #endif 1873 return pmd; 1874 } 1875 1876 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr, 1877 unsigned long new_addr, unsigned long old_end, 1878 pmd_t *old_pmd, pmd_t *new_pmd) 1879 { 1880 spinlock_t *old_ptl, *new_ptl; 1881 pmd_t pmd; 1882 struct mm_struct *mm = vma->vm_mm; 1883 bool force_flush = false; 1884 1885 if ((old_addr & ~HPAGE_PMD_MASK) || 1886 (new_addr & ~HPAGE_PMD_MASK) || 1887 old_end - old_addr < HPAGE_PMD_SIZE) 1888 return false; 1889 1890 /* 1891 * The destination pmd shouldn't be established, free_pgtables() 1892 * should have release it. 1893 */ 1894 if (WARN_ON(!pmd_none(*new_pmd))) { 1895 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1896 return false; 1897 } 1898 1899 /* 1900 * We don't have to worry about the ordering of src and dst 1901 * ptlocks because exclusive mmap_sem prevents deadlock. 1902 */ 1903 old_ptl = __pmd_trans_huge_lock(old_pmd, vma); 1904 if (old_ptl) { 1905 new_ptl = pmd_lockptr(mm, new_pmd); 1906 if (new_ptl != old_ptl) 1907 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 1908 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd); 1909 if (pmd_present(pmd)) 1910 force_flush = true; 1911 VM_BUG_ON(!pmd_none(*new_pmd)); 1912 1913 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) { 1914 pgtable_t pgtable; 1915 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); 1916 pgtable_trans_huge_deposit(mm, new_pmd, pgtable); 1917 } 1918 pmd = move_soft_dirty_pmd(pmd); 1919 set_pmd_at(mm, new_addr, new_pmd, pmd); 1920 if (force_flush) 1921 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE); 1922 if (new_ptl != old_ptl) 1923 spin_unlock(new_ptl); 1924 spin_unlock(old_ptl); 1925 return true; 1926 } 1927 return false; 1928 } 1929 1930 /* 1931 * Returns 1932 * - 0 if PMD could not be locked 1933 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary 1934 * - HPAGE_PMD_NR is protections changed and TLB flush necessary 1935 */ 1936 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1937 unsigned long addr, pgprot_t newprot, int prot_numa) 1938 { 1939 struct mm_struct *mm = vma->vm_mm; 1940 spinlock_t *ptl; 1941 pmd_t entry; 1942 bool preserve_write; 1943 int ret; 1944 1945 ptl = __pmd_trans_huge_lock(pmd, vma); 1946 if (!ptl) 1947 return 0; 1948 1949 preserve_write = prot_numa && pmd_write(*pmd); 1950 ret = 1; 1951 1952 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 1953 if (is_swap_pmd(*pmd)) { 1954 swp_entry_t entry = pmd_to_swp_entry(*pmd); 1955 1956 VM_BUG_ON(!is_pmd_migration_entry(*pmd)); 1957 if (is_write_migration_entry(entry)) { 1958 pmd_t newpmd; 1959 /* 1960 * A protection check is difficult so 1961 * just be safe and disable write 1962 */ 1963 make_migration_entry_read(&entry); 1964 newpmd = swp_entry_to_pmd(entry); 1965 if (pmd_swp_soft_dirty(*pmd)) 1966 newpmd = pmd_swp_mksoft_dirty(newpmd); 1967 set_pmd_at(mm, addr, pmd, newpmd); 1968 } 1969 goto unlock; 1970 } 1971 #endif 1972 1973 /* 1974 * Avoid trapping faults against the zero page. The read-only 1975 * data is likely to be read-cached on the local CPU and 1976 * local/remote hits to the zero page are not interesting. 1977 */ 1978 if (prot_numa && is_huge_zero_pmd(*pmd)) 1979 goto unlock; 1980 1981 if (prot_numa && pmd_protnone(*pmd)) 1982 goto unlock; 1983 1984 /* 1985 * In case prot_numa, we are under down_read(mmap_sem). It's critical 1986 * to not clear pmd intermittently to avoid race with MADV_DONTNEED 1987 * which is also under down_read(mmap_sem): 1988 * 1989 * CPU0: CPU1: 1990 * change_huge_pmd(prot_numa=1) 1991 * pmdp_huge_get_and_clear_notify() 1992 * madvise_dontneed() 1993 * zap_pmd_range() 1994 * pmd_trans_huge(*pmd) == 0 (without ptl) 1995 * // skip the pmd 1996 * set_pmd_at(); 1997 * // pmd is re-established 1998 * 1999 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it 2000 * which may break userspace. 2001 * 2002 * pmdp_invalidate() is required to make sure we don't miss 2003 * dirty/young flags set by hardware. 2004 */ 2005 entry = pmdp_invalidate(vma, addr, pmd); 2006 2007 entry = pmd_modify(entry, newprot); 2008 if (preserve_write) 2009 entry = pmd_mk_savedwrite(entry); 2010 ret = HPAGE_PMD_NR; 2011 set_pmd_at(mm, addr, pmd, entry); 2012 BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry)); 2013 unlock: 2014 spin_unlock(ptl); 2015 return ret; 2016 } 2017 2018 /* 2019 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise. 2020 * 2021 * Note that if it returns page table lock pointer, this routine returns without 2022 * unlocking page table lock. So callers must unlock it. 2023 */ 2024 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) 2025 { 2026 spinlock_t *ptl; 2027 ptl = pmd_lock(vma->vm_mm, pmd); 2028 if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || 2029 pmd_devmap(*pmd))) 2030 return ptl; 2031 spin_unlock(ptl); 2032 return NULL; 2033 } 2034 2035 /* 2036 * Returns true if a given pud maps a thp, false otherwise. 2037 * 2038 * Note that if it returns true, this routine returns without unlocking page 2039 * table lock. So callers must unlock it. 2040 */ 2041 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma) 2042 { 2043 spinlock_t *ptl; 2044 2045 ptl = pud_lock(vma->vm_mm, pud); 2046 if (likely(pud_trans_huge(*pud) || pud_devmap(*pud))) 2047 return ptl; 2048 spin_unlock(ptl); 2049 return NULL; 2050 } 2051 2052 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 2053 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma, 2054 pud_t *pud, unsigned long addr) 2055 { 2056 spinlock_t *ptl; 2057 2058 ptl = __pud_trans_huge_lock(pud, vma); 2059 if (!ptl) 2060 return 0; 2061 /* 2062 * For architectures like ppc64 we look at deposited pgtable 2063 * when calling pudp_huge_get_and_clear. So do the 2064 * pgtable_trans_huge_withdraw after finishing pudp related 2065 * operations. 2066 */ 2067 pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm); 2068 tlb_remove_pud_tlb_entry(tlb, pud, addr); 2069 if (vma_is_dax(vma)) { 2070 spin_unlock(ptl); 2071 /* No zero page support yet */ 2072 } else { 2073 /* No support for anonymous PUD pages yet */ 2074 BUG(); 2075 } 2076 return 1; 2077 } 2078 2079 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud, 2080 unsigned long haddr) 2081 { 2082 VM_BUG_ON(haddr & ~HPAGE_PUD_MASK); 2083 VM_BUG_ON_VMA(vma->vm_start > haddr, vma); 2084 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma); 2085 VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud)); 2086 2087 count_vm_event(THP_SPLIT_PUD); 2088 2089 pudp_huge_clear_flush_notify(vma, haddr, pud); 2090 } 2091 2092 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud, 2093 unsigned long address) 2094 { 2095 spinlock_t *ptl; 2096 struct mmu_notifier_range range; 2097 2098 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, 2099 address & HPAGE_PUD_MASK, 2100 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE); 2101 mmu_notifier_invalidate_range_start(&range); 2102 ptl = pud_lock(vma->vm_mm, pud); 2103 if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud))) 2104 goto out; 2105 __split_huge_pud_locked(vma, pud, range.start); 2106 2107 out: 2108 spin_unlock(ptl); 2109 /* 2110 * No need to double call mmu_notifier->invalidate_range() callback as 2111 * the above pudp_huge_clear_flush_notify() did already call it. 2112 */ 2113 mmu_notifier_invalidate_range_only_end(&range); 2114 } 2115 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ 2116 2117 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2118 unsigned long haddr, pmd_t *pmd) 2119 { 2120 struct mm_struct *mm = vma->vm_mm; 2121 pgtable_t pgtable; 2122 pmd_t _pmd; 2123 int i; 2124 2125 /* 2126 * Leave pmd empty until pte is filled note that it is fine to delay 2127 * notification until mmu_notifier_invalidate_range_end() as we are 2128 * replacing a zero pmd write protected page with a zero pte write 2129 * protected page. 2130 * 2131 * See Documentation/vm/mmu_notifier.rst 2132 */ 2133 pmdp_huge_clear_flush(vma, haddr, pmd); 2134 2135 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2136 pmd_populate(mm, &_pmd, pgtable); 2137 2138 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2139 pte_t *pte, entry; 2140 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2141 entry = pte_mkspecial(entry); 2142 pte = pte_offset_map(&_pmd, haddr); 2143 VM_BUG_ON(!pte_none(*pte)); 2144 set_pte_at(mm, haddr, pte, entry); 2145 pte_unmap(pte); 2146 } 2147 smp_wmb(); /* make pte visible before pmd */ 2148 pmd_populate(mm, pmd, pgtable); 2149 } 2150 2151 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 2152 unsigned long haddr, bool freeze) 2153 { 2154 struct mm_struct *mm = vma->vm_mm; 2155 struct page *page; 2156 pgtable_t pgtable; 2157 pmd_t old_pmd, _pmd; 2158 bool young, write, soft_dirty, pmd_migration = false; 2159 unsigned long addr; 2160 int i; 2161 2162 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK); 2163 VM_BUG_ON_VMA(vma->vm_start > haddr, vma); 2164 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma); 2165 VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd) 2166 && !pmd_devmap(*pmd)); 2167 2168 count_vm_event(THP_SPLIT_PMD); 2169 2170 if (!vma_is_anonymous(vma)) { 2171 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd); 2172 /* 2173 * We are going to unmap this huge page. So 2174 * just go ahead and zap it 2175 */ 2176 if (arch_needs_pgtable_deposit()) 2177 zap_deposited_table(mm, pmd); 2178 if (vma_is_dax(vma)) 2179 return; 2180 page = pmd_page(_pmd); 2181 if (!PageDirty(page) && pmd_dirty(_pmd)) 2182 set_page_dirty(page); 2183 if (!PageReferenced(page) && pmd_young(_pmd)) 2184 SetPageReferenced(page); 2185 page_remove_rmap(page, true); 2186 put_page(page); 2187 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR); 2188 return; 2189 } else if (is_huge_zero_pmd(*pmd)) { 2190 /* 2191 * FIXME: Do we want to invalidate secondary mmu by calling 2192 * mmu_notifier_invalidate_range() see comments below inside 2193 * __split_huge_pmd() ? 2194 * 2195 * We are going from a zero huge page write protected to zero 2196 * small page also write protected so it does not seems useful 2197 * to invalidate secondary mmu at this time. 2198 */ 2199 return __split_huge_zero_page_pmd(vma, haddr, pmd); 2200 } 2201 2202 /* 2203 * Up to this point the pmd is present and huge and userland has the 2204 * whole access to the hugepage during the split (which happens in 2205 * place). If we overwrite the pmd with the not-huge version pointing 2206 * to the pte here (which of course we could if all CPUs were bug 2207 * free), userland could trigger a small page size TLB miss on the 2208 * small sized TLB while the hugepage TLB entry is still established in 2209 * the huge TLB. Some CPU doesn't like that. 2210 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum 2211 * 383 on page 93. Intel should be safe but is also warns that it's 2212 * only safe if the permission and cache attributes of the two entries 2213 * loaded in the two TLB is identical (which should be the case here). 2214 * But it is generally safer to never allow small and huge TLB entries 2215 * for the same virtual address to be loaded simultaneously. So instead 2216 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the 2217 * current pmd notpresent (atomically because here the pmd_trans_huge 2218 * must remain set at all times on the pmd until the split is complete 2219 * for this pmd), then we flush the SMP TLB and finally we write the 2220 * non-huge version of the pmd entry with pmd_populate. 2221 */ 2222 old_pmd = pmdp_invalidate(vma, haddr, pmd); 2223 2224 pmd_migration = is_pmd_migration_entry(old_pmd); 2225 if (unlikely(pmd_migration)) { 2226 swp_entry_t entry; 2227 2228 entry = pmd_to_swp_entry(old_pmd); 2229 page = pfn_to_page(swp_offset(entry)); 2230 write = is_write_migration_entry(entry); 2231 young = false; 2232 soft_dirty = pmd_swp_soft_dirty(old_pmd); 2233 } else { 2234 page = pmd_page(old_pmd); 2235 if (pmd_dirty(old_pmd)) 2236 SetPageDirty(page); 2237 write = pmd_write(old_pmd); 2238 young = pmd_young(old_pmd); 2239 soft_dirty = pmd_soft_dirty(old_pmd); 2240 } 2241 VM_BUG_ON_PAGE(!page_count(page), page); 2242 page_ref_add(page, HPAGE_PMD_NR - 1); 2243 2244 /* 2245 * Withdraw the table only after we mark the pmd entry invalid. 2246 * This's critical for some architectures (Power). 2247 */ 2248 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2249 pmd_populate(mm, &_pmd, pgtable); 2250 2251 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { 2252 pte_t entry, *pte; 2253 /* 2254 * Note that NUMA hinting access restrictions are not 2255 * transferred to avoid any possibility of altering 2256 * permissions across VMAs. 2257 */ 2258 if (freeze || pmd_migration) { 2259 swp_entry_t swp_entry; 2260 swp_entry = make_migration_entry(page + i, write); 2261 entry = swp_entry_to_pte(swp_entry); 2262 if (soft_dirty) 2263 entry = pte_swp_mksoft_dirty(entry); 2264 } else { 2265 entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot)); 2266 entry = maybe_mkwrite(entry, vma); 2267 if (!write) 2268 entry = pte_wrprotect(entry); 2269 if (!young) 2270 entry = pte_mkold(entry); 2271 if (soft_dirty) 2272 entry = pte_mksoft_dirty(entry); 2273 } 2274 pte = pte_offset_map(&_pmd, addr); 2275 BUG_ON(!pte_none(*pte)); 2276 set_pte_at(mm, addr, pte, entry); 2277 atomic_inc(&page[i]._mapcount); 2278 pte_unmap(pte); 2279 } 2280 2281 /* 2282 * Set PG_double_map before dropping compound_mapcount to avoid 2283 * false-negative page_mapped(). 2284 */ 2285 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) { 2286 for (i = 0; i < HPAGE_PMD_NR; i++) 2287 atomic_inc(&page[i]._mapcount); 2288 } 2289 2290 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { 2291 /* Last compound_mapcount is gone. */ 2292 __dec_node_page_state(page, NR_ANON_THPS); 2293 if (TestClearPageDoubleMap(page)) { 2294 /* No need in mapcount reference anymore */ 2295 for (i = 0; i < HPAGE_PMD_NR; i++) 2296 atomic_dec(&page[i]._mapcount); 2297 } 2298 } 2299 2300 smp_wmb(); /* make pte visible before pmd */ 2301 pmd_populate(mm, pmd, pgtable); 2302 2303 if (freeze) { 2304 for (i = 0; i < HPAGE_PMD_NR; i++) { 2305 page_remove_rmap(page + i, false); 2306 put_page(page + i); 2307 } 2308 } 2309 } 2310 2311 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 2312 unsigned long address, bool freeze, struct page *page) 2313 { 2314 spinlock_t *ptl; 2315 struct mmu_notifier_range range; 2316 2317 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, 2318 address & HPAGE_PMD_MASK, 2319 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE); 2320 mmu_notifier_invalidate_range_start(&range); 2321 ptl = pmd_lock(vma->vm_mm, pmd); 2322 2323 /* 2324 * If caller asks to setup a migration entries, we need a page to check 2325 * pmd against. Otherwise we can end up replacing wrong page. 2326 */ 2327 VM_BUG_ON(freeze && !page); 2328 if (page && page != pmd_page(*pmd)) 2329 goto out; 2330 2331 if (pmd_trans_huge(*pmd)) { 2332 page = pmd_page(*pmd); 2333 if (PageMlocked(page)) 2334 clear_page_mlock(page); 2335 } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd))) 2336 goto out; 2337 __split_huge_pmd_locked(vma, pmd, range.start, freeze); 2338 out: 2339 spin_unlock(ptl); 2340 /* 2341 * No need to double call mmu_notifier->invalidate_range() callback. 2342 * They are 3 cases to consider inside __split_huge_pmd_locked(): 2343 * 1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious 2344 * 2) __split_huge_zero_page_pmd() read only zero page and any write 2345 * fault will trigger a flush_notify before pointing to a new page 2346 * (it is fine if the secondary mmu keeps pointing to the old zero 2347 * page in the meantime) 2348 * 3) Split a huge pmd into pte pointing to the same page. No need 2349 * to invalidate secondary tlb entry they are all still valid. 2350 * any further changes to individual pte will notify. So no need 2351 * to call mmu_notifier->invalidate_range() 2352 */ 2353 mmu_notifier_invalidate_range_only_end(&range); 2354 } 2355 2356 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, 2357 bool freeze, struct page *page) 2358 { 2359 pgd_t *pgd; 2360 p4d_t *p4d; 2361 pud_t *pud; 2362 pmd_t *pmd; 2363 2364 pgd = pgd_offset(vma->vm_mm, address); 2365 if (!pgd_present(*pgd)) 2366 return; 2367 2368 p4d = p4d_offset(pgd, address); 2369 if (!p4d_present(*p4d)) 2370 return; 2371 2372 pud = pud_offset(p4d, address); 2373 if (!pud_present(*pud)) 2374 return; 2375 2376 pmd = pmd_offset(pud, address); 2377 2378 __split_huge_pmd(vma, pmd, address, freeze, page); 2379 } 2380 2381 void vma_adjust_trans_huge(struct vm_area_struct *vma, 2382 unsigned long start, 2383 unsigned long end, 2384 long adjust_next) 2385 { 2386 /* 2387 * If the new start address isn't hpage aligned and it could 2388 * previously contain an hugepage: check if we need to split 2389 * an huge pmd. 2390 */ 2391 if (start & ~HPAGE_PMD_MASK && 2392 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2393 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2394 split_huge_pmd_address(vma, start, false, NULL); 2395 2396 /* 2397 * If the new end address isn't hpage aligned and it could 2398 * previously contain an hugepage: check if we need to split 2399 * an huge pmd. 2400 */ 2401 if (end & ~HPAGE_PMD_MASK && 2402 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2403 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2404 split_huge_pmd_address(vma, end, false, NULL); 2405 2406 /* 2407 * If we're also updating the vma->vm_next->vm_start, if the new 2408 * vm_next->vm_start isn't page aligned and it could previously 2409 * contain an hugepage: check if we need to split an huge pmd. 2410 */ 2411 if (adjust_next > 0) { 2412 struct vm_area_struct *next = vma->vm_next; 2413 unsigned long nstart = next->vm_start; 2414 nstart += adjust_next << PAGE_SHIFT; 2415 if (nstart & ~HPAGE_PMD_MASK && 2416 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2417 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2418 split_huge_pmd_address(next, nstart, false, NULL); 2419 } 2420 } 2421 2422 static void unmap_page(struct page *page) 2423 { 2424 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS | 2425 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD; 2426 bool unmap_success; 2427 2428 VM_BUG_ON_PAGE(!PageHead(page), page); 2429 2430 if (PageAnon(page)) 2431 ttu_flags |= TTU_SPLIT_FREEZE; 2432 2433 unmap_success = try_to_unmap(page, ttu_flags); 2434 VM_BUG_ON_PAGE(!unmap_success, page); 2435 } 2436 2437 static void remap_page(struct page *page) 2438 { 2439 int i; 2440 if (PageTransHuge(page)) { 2441 remove_migration_ptes(page, page, true); 2442 } else { 2443 for (i = 0; i < HPAGE_PMD_NR; i++) 2444 remove_migration_ptes(page + i, page + i, true); 2445 } 2446 } 2447 2448 static void __split_huge_page_tail(struct page *head, int tail, 2449 struct lruvec *lruvec, struct list_head *list) 2450 { 2451 struct page *page_tail = head + tail; 2452 2453 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); 2454 2455 /* 2456 * Clone page flags before unfreezing refcount. 2457 * 2458 * After successful get_page_unless_zero() might follow flags change, 2459 * for exmaple lock_page() which set PG_waiters. 2460 */ 2461 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; 2462 page_tail->flags |= (head->flags & 2463 ((1L << PG_referenced) | 2464 (1L << PG_swapbacked) | 2465 (1L << PG_swapcache) | 2466 (1L << PG_mlocked) | 2467 (1L << PG_uptodate) | 2468 (1L << PG_active) | 2469 (1L << PG_workingset) | 2470 (1L << PG_locked) | 2471 (1L << PG_unevictable) | 2472 (1L << PG_dirty))); 2473 2474 /* ->mapping in first tail page is compound_mapcount */ 2475 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING, 2476 page_tail); 2477 page_tail->mapping = head->mapping; 2478 page_tail->index = head->index + tail; 2479 2480 /* Page flags must be visible before we make the page non-compound. */ 2481 smp_wmb(); 2482 2483 /* 2484 * Clear PageTail before unfreezing page refcount. 2485 * 2486 * After successful get_page_unless_zero() might follow put_page() 2487 * which needs correct compound_head(). 2488 */ 2489 clear_compound_head(page_tail); 2490 2491 /* Finally unfreeze refcount. Additional reference from page cache. */ 2492 page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) || 2493 PageSwapCache(head))); 2494 2495 if (page_is_young(head)) 2496 set_page_young(page_tail); 2497 if (page_is_idle(head)) 2498 set_page_idle(page_tail); 2499 2500 page_cpupid_xchg_last(page_tail, page_cpupid_last(head)); 2501 2502 /* 2503 * always add to the tail because some iterators expect new 2504 * pages to show after the currently processed elements - e.g. 2505 * migrate_pages 2506 */ 2507 lru_add_page_tail(head, page_tail, lruvec, list); 2508 } 2509 2510 static void __split_huge_page(struct page *page, struct list_head *list, 2511 pgoff_t end, unsigned long flags) 2512 { 2513 struct page *head = compound_head(page); 2514 pg_data_t *pgdat = page_pgdat(head); 2515 struct lruvec *lruvec; 2516 struct address_space *swap_cache = NULL; 2517 unsigned long offset = 0; 2518 int i; 2519 2520 lruvec = mem_cgroup_page_lruvec(head, pgdat); 2521 2522 /* complete memcg works before add pages to LRU */ 2523 mem_cgroup_split_huge_fixup(head); 2524 2525 if (PageAnon(head) && PageSwapCache(head)) { 2526 swp_entry_t entry = { .val = page_private(head) }; 2527 2528 offset = swp_offset(entry); 2529 swap_cache = swap_address_space(entry); 2530 xa_lock(&swap_cache->i_pages); 2531 } 2532 2533 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 2534 __split_huge_page_tail(head, i, lruvec, list); 2535 /* Some pages can be beyond i_size: drop them from page cache */ 2536 if (head[i].index >= end) { 2537 ClearPageDirty(head + i); 2538 __delete_from_page_cache(head + i, NULL); 2539 if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head)) 2540 shmem_uncharge(head->mapping->host, 1); 2541 put_page(head + i); 2542 } else if (!PageAnon(page)) { 2543 __xa_store(&head->mapping->i_pages, head[i].index, 2544 head + i, 0); 2545 } else if (swap_cache) { 2546 __xa_store(&swap_cache->i_pages, offset + i, 2547 head + i, 0); 2548 } 2549 } 2550 2551 ClearPageCompound(head); 2552 2553 split_page_owner(head, HPAGE_PMD_ORDER); 2554 2555 /* See comment in __split_huge_page_tail() */ 2556 if (PageAnon(head)) { 2557 /* Additional pin to swap cache */ 2558 if (PageSwapCache(head)) { 2559 page_ref_add(head, 2); 2560 xa_unlock(&swap_cache->i_pages); 2561 } else { 2562 page_ref_inc(head); 2563 } 2564 } else { 2565 /* Additional pin to page cache */ 2566 page_ref_add(head, 2); 2567 xa_unlock(&head->mapping->i_pages); 2568 } 2569 2570 spin_unlock_irqrestore(&pgdat->lru_lock, flags); 2571 2572 remap_page(head); 2573 2574 for (i = 0; i < HPAGE_PMD_NR; i++) { 2575 struct page *subpage = head + i; 2576 if (subpage == page) 2577 continue; 2578 unlock_page(subpage); 2579 2580 /* 2581 * Subpages may be freed if there wasn't any mapping 2582 * like if add_to_swap() is running on a lru page that 2583 * had its mapping zapped. And freeing these pages 2584 * requires taking the lru_lock so we do the put_page 2585 * of the tail pages after the split is complete. 2586 */ 2587 put_page(subpage); 2588 } 2589 } 2590 2591 int total_mapcount(struct page *page) 2592 { 2593 int i, compound, ret; 2594 2595 VM_BUG_ON_PAGE(PageTail(page), page); 2596 2597 if (likely(!PageCompound(page))) 2598 return atomic_read(&page->_mapcount) + 1; 2599 2600 compound = compound_mapcount(page); 2601 if (PageHuge(page)) 2602 return compound; 2603 ret = compound; 2604 for (i = 0; i < HPAGE_PMD_NR; i++) 2605 ret += atomic_read(&page[i]._mapcount) + 1; 2606 /* File pages has compound_mapcount included in _mapcount */ 2607 if (!PageAnon(page)) 2608 return ret - compound * HPAGE_PMD_NR; 2609 if (PageDoubleMap(page)) 2610 ret -= HPAGE_PMD_NR; 2611 return ret; 2612 } 2613 2614 /* 2615 * This calculates accurately how many mappings a transparent hugepage 2616 * has (unlike page_mapcount() which isn't fully accurate). This full 2617 * accuracy is primarily needed to know if copy-on-write faults can 2618 * reuse the page and change the mapping to read-write instead of 2619 * copying them. At the same time this returns the total_mapcount too. 2620 * 2621 * The function returns the highest mapcount any one of the subpages 2622 * has. If the return value is one, even if different processes are 2623 * mapping different subpages of the transparent hugepage, they can 2624 * all reuse it, because each process is reusing a different subpage. 2625 * 2626 * The total_mapcount is instead counting all virtual mappings of the 2627 * subpages. If the total_mapcount is equal to "one", it tells the 2628 * caller all mappings belong to the same "mm" and in turn the 2629 * anon_vma of the transparent hugepage can become the vma->anon_vma 2630 * local one as no other process may be mapping any of the subpages. 2631 * 2632 * It would be more accurate to replace page_mapcount() with 2633 * page_trans_huge_mapcount(), however we only use 2634 * page_trans_huge_mapcount() in the copy-on-write faults where we 2635 * need full accuracy to avoid breaking page pinning, because 2636 * page_trans_huge_mapcount() is slower than page_mapcount(). 2637 */ 2638 int page_trans_huge_mapcount(struct page *page, int *total_mapcount) 2639 { 2640 int i, ret, _total_mapcount, mapcount; 2641 2642 /* hugetlbfs shouldn't call it */ 2643 VM_BUG_ON_PAGE(PageHuge(page), page); 2644 2645 if (likely(!PageTransCompound(page))) { 2646 mapcount = atomic_read(&page->_mapcount) + 1; 2647 if (total_mapcount) 2648 *total_mapcount = mapcount; 2649 return mapcount; 2650 } 2651 2652 page = compound_head(page); 2653 2654 _total_mapcount = ret = 0; 2655 for (i = 0; i < HPAGE_PMD_NR; i++) { 2656 mapcount = atomic_read(&page[i]._mapcount) + 1; 2657 ret = max(ret, mapcount); 2658 _total_mapcount += mapcount; 2659 } 2660 if (PageDoubleMap(page)) { 2661 ret -= 1; 2662 _total_mapcount -= HPAGE_PMD_NR; 2663 } 2664 mapcount = compound_mapcount(page); 2665 ret += mapcount; 2666 _total_mapcount += mapcount; 2667 if (total_mapcount) 2668 *total_mapcount = _total_mapcount; 2669 return ret; 2670 } 2671 2672 /* Racy check whether the huge page can be split */ 2673 bool can_split_huge_page(struct page *page, int *pextra_pins) 2674 { 2675 int extra_pins; 2676 2677 /* Additional pins from page cache */ 2678 if (PageAnon(page)) 2679 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0; 2680 else 2681 extra_pins = HPAGE_PMD_NR; 2682 if (pextra_pins) 2683 *pextra_pins = extra_pins; 2684 return total_mapcount(page) == page_count(page) - extra_pins - 1; 2685 } 2686 2687 /* 2688 * This function splits huge page into normal pages. @page can point to any 2689 * subpage of huge page to split. Split doesn't change the position of @page. 2690 * 2691 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY. 2692 * The huge page must be locked. 2693 * 2694 * If @list is null, tail pages will be added to LRU list, otherwise, to @list. 2695 * 2696 * Both head page and tail pages will inherit mapping, flags, and so on from 2697 * the hugepage. 2698 * 2699 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if 2700 * they are not mapped. 2701 * 2702 * Returns 0 if the hugepage is split successfully. 2703 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under 2704 * us. 2705 */ 2706 int split_huge_page_to_list(struct page *page, struct list_head *list) 2707 { 2708 struct page *head = compound_head(page); 2709 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head)); 2710 struct deferred_split *ds_queue = get_deferred_split_queue(head); 2711 struct anon_vma *anon_vma = NULL; 2712 struct address_space *mapping = NULL; 2713 int count, mapcount, extra_pins, ret; 2714 bool mlocked; 2715 unsigned long flags; 2716 pgoff_t end; 2717 2718 VM_BUG_ON_PAGE(is_huge_zero_page(head), head); 2719 VM_BUG_ON_PAGE(!PageLocked(head), head); 2720 VM_BUG_ON_PAGE(!PageCompound(head), head); 2721 2722 if (PageWriteback(head)) 2723 return -EBUSY; 2724 2725 if (PageAnon(head)) { 2726 /* 2727 * The caller does not necessarily hold an mmap_sem that would 2728 * prevent the anon_vma disappearing so we first we take a 2729 * reference to it and then lock the anon_vma for write. This 2730 * is similar to page_lock_anon_vma_read except the write lock 2731 * is taken to serialise against parallel split or collapse 2732 * operations. 2733 */ 2734 anon_vma = page_get_anon_vma(head); 2735 if (!anon_vma) { 2736 ret = -EBUSY; 2737 goto out; 2738 } 2739 end = -1; 2740 mapping = NULL; 2741 anon_vma_lock_write(anon_vma); 2742 } else { 2743 mapping = head->mapping; 2744 2745 /* Truncated ? */ 2746 if (!mapping) { 2747 ret = -EBUSY; 2748 goto out; 2749 } 2750 2751 anon_vma = NULL; 2752 i_mmap_lock_read(mapping); 2753 2754 /* 2755 *__split_huge_page() may need to trim off pages beyond EOF: 2756 * but on 32-bit, i_size_read() takes an irq-unsafe seqlock, 2757 * which cannot be nested inside the page tree lock. So note 2758 * end now: i_size itself may be changed at any moment, but 2759 * head page lock is good enough to serialize the trimming. 2760 */ 2761 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); 2762 } 2763 2764 /* 2765 * Racy check if we can split the page, before unmap_page() will 2766 * split PMDs 2767 */ 2768 if (!can_split_huge_page(head, &extra_pins)) { 2769 ret = -EBUSY; 2770 goto out_unlock; 2771 } 2772 2773 mlocked = PageMlocked(head); 2774 unmap_page(head); 2775 VM_BUG_ON_PAGE(compound_mapcount(head), head); 2776 2777 /* Make sure the page is not on per-CPU pagevec as it takes pin */ 2778 if (mlocked) 2779 lru_add_drain(); 2780 2781 /* prevent PageLRU to go away from under us, and freeze lru stats */ 2782 spin_lock_irqsave(&pgdata->lru_lock, flags); 2783 2784 if (mapping) { 2785 XA_STATE(xas, &mapping->i_pages, page_index(head)); 2786 2787 /* 2788 * Check if the head page is present in page cache. 2789 * We assume all tail are present too, if head is there. 2790 */ 2791 xa_lock(&mapping->i_pages); 2792 if (xas_load(&xas) != head) 2793 goto fail; 2794 } 2795 2796 /* Prevent deferred_split_scan() touching ->_refcount */ 2797 spin_lock(&ds_queue->split_queue_lock); 2798 count = page_count(head); 2799 mapcount = total_mapcount(head); 2800 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) { 2801 if (!list_empty(page_deferred_list(head))) { 2802 ds_queue->split_queue_len--; 2803 list_del(page_deferred_list(head)); 2804 } 2805 spin_unlock(&ds_queue->split_queue_lock); 2806 if (mapping) { 2807 if (PageSwapBacked(head)) 2808 __dec_node_page_state(head, NR_SHMEM_THPS); 2809 else 2810 __dec_node_page_state(head, NR_FILE_THPS); 2811 } 2812 2813 __split_huge_page(page, list, end, flags); 2814 if (PageSwapCache(head)) { 2815 swp_entry_t entry = { .val = page_private(head) }; 2816 2817 ret = split_swap_cluster(entry); 2818 } else 2819 ret = 0; 2820 } else { 2821 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { 2822 pr_alert("total_mapcount: %u, page_count(): %u\n", 2823 mapcount, count); 2824 if (PageTail(page)) 2825 dump_page(head, NULL); 2826 dump_page(page, "total_mapcount(head) > 0"); 2827 BUG(); 2828 } 2829 spin_unlock(&ds_queue->split_queue_lock); 2830 fail: if (mapping) 2831 xa_unlock(&mapping->i_pages); 2832 spin_unlock_irqrestore(&pgdata->lru_lock, flags); 2833 remap_page(head); 2834 ret = -EBUSY; 2835 } 2836 2837 out_unlock: 2838 if (anon_vma) { 2839 anon_vma_unlock_write(anon_vma); 2840 put_anon_vma(anon_vma); 2841 } 2842 if (mapping) 2843 i_mmap_unlock_read(mapping); 2844 out: 2845 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); 2846 return ret; 2847 } 2848 2849 void free_transhuge_page(struct page *page) 2850 { 2851 struct deferred_split *ds_queue = get_deferred_split_queue(page); 2852 unsigned long flags; 2853 2854 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 2855 if (!list_empty(page_deferred_list(page))) { 2856 ds_queue->split_queue_len--; 2857 list_del(page_deferred_list(page)); 2858 } 2859 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 2860 free_compound_page(page); 2861 } 2862 2863 void deferred_split_huge_page(struct page *page) 2864 { 2865 struct deferred_split *ds_queue = get_deferred_split_queue(page); 2866 #ifdef CONFIG_MEMCG 2867 struct mem_cgroup *memcg = compound_head(page)->mem_cgroup; 2868 #endif 2869 unsigned long flags; 2870 2871 VM_BUG_ON_PAGE(!PageTransHuge(page), page); 2872 2873 /* 2874 * The try_to_unmap() in page reclaim path might reach here too, 2875 * this may cause a race condition to corrupt deferred split queue. 2876 * And, if page reclaim is already handling the same page, it is 2877 * unnecessary to handle it again in shrinker. 2878 * 2879 * Check PageSwapCache to determine if the page is being 2880 * handled by page reclaim since THP swap would add the page into 2881 * swap cache before calling try_to_unmap(). 2882 */ 2883 if (PageSwapCache(page)) 2884 return; 2885 2886 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 2887 if (list_empty(page_deferred_list(page))) { 2888 count_vm_event(THP_DEFERRED_SPLIT_PAGE); 2889 list_add_tail(page_deferred_list(page), &ds_queue->split_queue); 2890 ds_queue->split_queue_len++; 2891 #ifdef CONFIG_MEMCG 2892 if (memcg) 2893 memcg_set_shrinker_bit(memcg, page_to_nid(page), 2894 deferred_split_shrinker.id); 2895 #endif 2896 } 2897 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 2898 } 2899 2900 static unsigned long deferred_split_count(struct shrinker *shrink, 2901 struct shrink_control *sc) 2902 { 2903 struct pglist_data *pgdata = NODE_DATA(sc->nid); 2904 struct deferred_split *ds_queue = &pgdata->deferred_split_queue; 2905 2906 #ifdef CONFIG_MEMCG 2907 if (sc->memcg) 2908 ds_queue = &sc->memcg->deferred_split_queue; 2909 #endif 2910 return READ_ONCE(ds_queue->split_queue_len); 2911 } 2912 2913 static unsigned long deferred_split_scan(struct shrinker *shrink, 2914 struct shrink_control *sc) 2915 { 2916 struct pglist_data *pgdata = NODE_DATA(sc->nid); 2917 struct deferred_split *ds_queue = &pgdata->deferred_split_queue; 2918 unsigned long flags; 2919 LIST_HEAD(list), *pos, *next; 2920 struct page *page; 2921 int split = 0; 2922 2923 #ifdef CONFIG_MEMCG 2924 if (sc->memcg) 2925 ds_queue = &sc->memcg->deferred_split_queue; 2926 #endif 2927 2928 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 2929 /* Take pin on all head pages to avoid freeing them under us */ 2930 list_for_each_safe(pos, next, &ds_queue->split_queue) { 2931 page = list_entry((void *)pos, struct page, mapping); 2932 page = compound_head(page); 2933 if (get_page_unless_zero(page)) { 2934 list_move(page_deferred_list(page), &list); 2935 } else { 2936 /* We lost race with put_compound_page() */ 2937 list_del_init(page_deferred_list(page)); 2938 ds_queue->split_queue_len--; 2939 } 2940 if (!--sc->nr_to_scan) 2941 break; 2942 } 2943 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 2944 2945 list_for_each_safe(pos, next, &list) { 2946 page = list_entry((void *)pos, struct page, mapping); 2947 if (!trylock_page(page)) 2948 goto next; 2949 /* split_huge_page() removes page from list on success */ 2950 if (!split_huge_page(page)) 2951 split++; 2952 unlock_page(page); 2953 next: 2954 put_page(page); 2955 } 2956 2957 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 2958 list_splice_tail(&list, &ds_queue->split_queue); 2959 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 2960 2961 /* 2962 * Stop shrinker if we didn't split any page, but the queue is empty. 2963 * This can happen if pages were freed under us. 2964 */ 2965 if (!split && list_empty(&ds_queue->split_queue)) 2966 return SHRINK_STOP; 2967 return split; 2968 } 2969 2970 static struct shrinker deferred_split_shrinker = { 2971 .count_objects = deferred_split_count, 2972 .scan_objects = deferred_split_scan, 2973 .seeks = DEFAULT_SEEKS, 2974 .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE | 2975 SHRINKER_NONSLAB, 2976 }; 2977 2978 #ifdef CONFIG_DEBUG_FS 2979 static int split_huge_pages_set(void *data, u64 val) 2980 { 2981 struct zone *zone; 2982 struct page *page; 2983 unsigned long pfn, max_zone_pfn; 2984 unsigned long total = 0, split = 0; 2985 2986 if (val != 1) 2987 return -EINVAL; 2988 2989 for_each_populated_zone(zone) { 2990 max_zone_pfn = zone_end_pfn(zone); 2991 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) { 2992 if (!pfn_valid(pfn)) 2993 continue; 2994 2995 page = pfn_to_page(pfn); 2996 if (!get_page_unless_zero(page)) 2997 continue; 2998 2999 if (zone != page_zone(page)) 3000 goto next; 3001 3002 if (!PageHead(page) || PageHuge(page) || !PageLRU(page)) 3003 goto next; 3004 3005 total++; 3006 lock_page(page); 3007 if (!split_huge_page(page)) 3008 split++; 3009 unlock_page(page); 3010 next: 3011 put_page(page); 3012 } 3013 } 3014 3015 pr_info("%lu of %lu THP split\n", split, total); 3016 3017 return 0; 3018 } 3019 DEFINE_DEBUGFS_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set, 3020 "%llu\n"); 3021 3022 static int __init split_huge_pages_debugfs(void) 3023 { 3024 debugfs_create_file("split_huge_pages", 0200, NULL, NULL, 3025 &split_huge_pages_fops); 3026 return 0; 3027 } 3028 late_initcall(split_huge_pages_debugfs); 3029 #endif 3030 3031 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 3032 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw, 3033 struct page *page) 3034 { 3035 struct vm_area_struct *vma = pvmw->vma; 3036 struct mm_struct *mm = vma->vm_mm; 3037 unsigned long address = pvmw->address; 3038 pmd_t pmdval; 3039 swp_entry_t entry; 3040 pmd_t pmdswp; 3041 3042 if (!(pvmw->pmd && !pvmw->pte)) 3043 return; 3044 3045 flush_cache_range(vma, address, address + HPAGE_PMD_SIZE); 3046 pmdval = *pvmw->pmd; 3047 pmdp_invalidate(vma, address, pvmw->pmd); 3048 if (pmd_dirty(pmdval)) 3049 set_page_dirty(page); 3050 entry = make_migration_entry(page, pmd_write(pmdval)); 3051 pmdswp = swp_entry_to_pmd(entry); 3052 if (pmd_soft_dirty(pmdval)) 3053 pmdswp = pmd_swp_mksoft_dirty(pmdswp); 3054 set_pmd_at(mm, address, pvmw->pmd, pmdswp); 3055 page_remove_rmap(page, true); 3056 put_page(page); 3057 } 3058 3059 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new) 3060 { 3061 struct vm_area_struct *vma = pvmw->vma; 3062 struct mm_struct *mm = vma->vm_mm; 3063 unsigned long address = pvmw->address; 3064 unsigned long mmun_start = address & HPAGE_PMD_MASK; 3065 pmd_t pmde; 3066 swp_entry_t entry; 3067 3068 if (!(pvmw->pmd && !pvmw->pte)) 3069 return; 3070 3071 entry = pmd_to_swp_entry(*pvmw->pmd); 3072 get_page(new); 3073 pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot)); 3074 if (pmd_swp_soft_dirty(*pvmw->pmd)) 3075 pmde = pmd_mksoft_dirty(pmde); 3076 if (is_write_migration_entry(entry)) 3077 pmde = maybe_pmd_mkwrite(pmde, vma); 3078 3079 flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE); 3080 if (PageAnon(new)) 3081 page_add_anon_rmap(new, vma, mmun_start, true); 3082 else 3083 page_add_file_rmap(new, true); 3084 set_pmd_at(mm, mmun_start, pvmw->pmd, pmde); 3085 if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new)) 3086 mlock_vma_page(new); 3087 update_mmu_cache_pmd(vma, address, pvmw->pmd); 3088 } 3089 #endif 3090