mm/huge_memory.c

   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 (!memcmp("always", buf,
 181                     min(sizeof("always")-1, count))) {
 182                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 183                 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 184         } else if (!memcmp("madvise", buf,
 185                            min(sizeof("madvise")-1, count))) {
 186                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 187                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 188         } else if (!memcmp("never", buf,
 189                            min(sizeof("never")-1, count))) {
 190                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 191                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 192         } else
 193                 ret = -EINVAL;
 194
 195         if (ret > 0) {
 196                 int err = start_stop_khugepaged();
 197                 if (err)
 198                         ret = err;
 199         }
 200         return ret;
 201 }
 202 static struct kobj_attribute enabled_attr =
 203         __ATTR(enabled, 0644, enabled_show, enabled_store);
 204
 205 ssize_t single_hugepage_flag_show(struct kobject *kobj,
 206                                 struct kobj_attribute *attr, char *buf,
 207                                 enum transparent_hugepage_flag flag)
 208 {
 209         return sprintf(buf, "%d\n",
 210                        !!test_bit(flag, &transparent_hugepage_flags));
 211 }
 212
 213 ssize_t single_hugepage_flag_store(struct kobject *kobj,
 214                                  struct kobj_attribute *attr,
 215                                  const char *buf, size_t count,
 216                                  enum transparent_hugepage_flag flag)
 217 {
 218         unsigned long value;
 219         int ret;
 220
 221         ret = kstrtoul(buf, 10, &value);
 222         if (ret < 0)
 223                 return ret;
 224         if (value > 1)
 225                 return -EINVAL;
 226
 227         if (value)
 228                 set_bit(flag, &transparent_hugepage_flags);
 229         else
 230                 clear_bit(flag, &transparent_hugepage_flags);
 231
 232         return count;
 233 }
 234
 235 static ssize_t defrag_show(struct kobject *kobj,
 236                            struct kobj_attribute *attr, char *buf)
 237 {
 238         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 239                 return sprintf(buf, "[always] defer defer+madvise madvise never\n");
 240         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 241                 return sprintf(buf, "always [defer] defer+madvise madvise never\n");
 242         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 243                 return sprintf(buf, "always defer [defer+madvise] madvise never\n");
 244         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 245                 return sprintf(buf, "always defer defer+madvise [madvise] never\n");
 246         return sprintf(buf, "always defer defer+madvise madvise [never]\n");
 247 }
 248
 249 static ssize_t defrag_store(struct kobject *kobj,
 250                             struct kobj_attribute *attr,
 251                             const char *buf, size_t count)
 252 {
 253         if (!memcmp("always", buf,
 254                     min(sizeof("always")-1, count))) {
 255                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 256                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 257                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 258                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 259         } else if (!memcmp("defer+madvise", buf,
 260                     min(sizeof("defer+madvise")-1, count))) {
 261                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 262                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 263                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 264                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 265         } else if (!memcmp("defer", buf,
 266                     min(sizeof("defer")-1, count))) {
 267                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 268                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 269                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 270                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 271         } else if (!memcmp("madvise", buf,
 272                            min(sizeof("madvise")-1, count))) {
 273                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 274                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 275                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 276                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 277         } else if (!memcmp("never", buf,
 278                            min(sizeof("never")-1, count))) {
 279                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 280                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 281                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 282                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 283         } else
 284                 return -EINVAL;
 285
 286         return count;
 287 }
 288 static struct kobj_attribute defrag_attr =
 289         __ATTR(defrag, 0644, defrag_show, defrag_store);
 290
 291 static ssize_t use_zero_page_show(struct kobject *kobj,
 292                 struct kobj_attribute *attr, char *buf)
 293 {
 294         return single_hugepage_flag_show(kobj, attr, buf,
 295                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 296 }
 297 static ssize_t use_zero_page_store(struct kobject *kobj,
 298                 struct kobj_attribute *attr, const char *buf, size_t count)
 299 {
 300         return single_hugepage_flag_store(kobj, attr, buf, count,
 301                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 302 }
 303 static struct kobj_attribute use_zero_page_attr =
 304         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 305
 306 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
 307                 struct kobj_attribute *attr, char *buf)
 308 {
 309         return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
 310 }
 311 static struct kobj_attribute hpage_pmd_size_attr =
 312         __ATTR_RO(hpage_pmd_size);
 313
 314 #ifdef CONFIG_DEBUG_VM
 315 static ssize_t debug_cow_show(struct kobject *kobj,
 316                                 struct kobj_attribute *attr, char *buf)
 317 {
 318         return single_hugepage_flag_show(kobj, attr, buf,
 319                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 320 }
 321 static ssize_t debug_cow_store(struct kobject *kobj,
 322                                struct kobj_attribute *attr,
 323                                const char *buf, size_t count)
 324 {
 325         return single_hugepage_flag_store(kobj, attr, buf, count,
 326                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 327 }
 328 static struct kobj_attribute debug_cow_attr =
 329         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 330 #endif /* CONFIG_DEBUG_VM */
 331
 332 static struct attribute *hugepage_attr[] = {
 333         &enabled_attr.attr,
 334         &defrag_attr.attr,
 335         &use_zero_page_attr.attr,
 336         &hpage_pmd_size_attr.attr,
 337 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
 338         &shmem_enabled_attr.attr,
 339 #endif
 340 #ifdef CONFIG_DEBUG_VM
 341         &debug_cow_attr.attr,
 342 #endif
 343         NULL,
 344 };
 345
 346 static const struct attribute_group hugepage_attr_group = {
 347         .attrs = hugepage_attr,
 348 };
 349
 350 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 351 {
 352         int err;
 353
 354         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 355         if (unlikely(!*hugepage_kobj)) {
 356                 pr_err("failed to create transparent hugepage kobject\n");
 357                 return -ENOMEM;
 358         }
 359
 360         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 361         if (err) {
 362                 pr_err("failed to register transparent hugepage group\n");
 363                 goto delete_obj;
 364         }
 365
 366         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 367         if (err) {
 368                 pr_err("failed to register transparent hugepage group\n");
 369                 goto remove_hp_group;
 370         }
 371
 372         return 0;
 373
 374 remove_hp_group:
 375         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 376 delete_obj:
 377         kobject_put(*hugepage_kobj);
 378         return err;
 379 }
 380
 381 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 382 {
 383         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 384         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 385         kobject_put(hugepage_kobj);
 386 }
 387 #else
 388 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 389 {
 390         return 0;
 391 }
 392
 393 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 394 {
 395 }
 396 #endif /* CONFIG_SYSFS */
 397
 398 static int __init hugepage_init(void)
 399 {
 400         int err;
 401         struct kobject *hugepage_kobj;
 402
 403         if (!has_transparent_hugepage()) {
 404                 transparent_hugepage_flags = 0;
 405                 return -EINVAL;
 406         }
 407
 408         /*
 409          * hugepages can't be allocated by the buddy allocator
 410          */
 411         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
 412         /*
 413          * we use page->mapping and page->index in second tail page
 414          * as list_head: assuming THP order >= 2
 415          */
 416         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
 417
 418         err = hugepage_init_sysfs(&hugepage_kobj);
 419         if (err)
 420                 goto err_sysfs;
 421
 422         err = khugepaged_init();
 423         if (err)
 424                 goto err_slab;
 425
 426         err = register_shrinker(&huge_zero_page_shrinker);
 427         if (err)
 428                 goto err_hzp_shrinker;
 429         err = register_shrinker(&deferred_split_shrinker);
 430         if (err)
 431                 goto err_split_shrinker;
 432
 433         /*
 434          * By default disable transparent hugepages on smaller systems,
 435          * where the extra memory used could hurt more than TLB overhead
 436          * is likely to save.  The admin can still enable it through /sys.
 437          */
 438         if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
 439                 transparent_hugepage_flags = 0;
 440                 return 0;
 441         }
 442
 443         err = start_stop_khugepaged();
 444         if (err)
 445                 goto err_khugepaged;
 446
 447         return 0;
 448 err_khugepaged:
 449         unregister_shrinker(&deferred_split_shrinker);
 450 err_split_shrinker:
 451         unregister_shrinker(&huge_zero_page_shrinker);
 452 err_hzp_shrinker:
 453         khugepaged_destroy();
 454 err_slab:
 455         hugepage_exit_sysfs(hugepage_kobj);
 456 err_sysfs:
 457         return err;
 458 }
 459 subsys_initcall(hugepage_init);
 460
 461 static int __init setup_transparent_hugepage(char *str)
 462 {
 463         int ret = 0;
 464         if (!str)
 465                 goto out;
 466         if (!strcmp(str, "always")) {
 467                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 468                         &transparent_hugepage_flags);
 469                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 470                           &transparent_hugepage_flags);
 471                 ret = 1;
 472         } else if (!strcmp(str, "madvise")) {
 473                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 474                           &transparent_hugepage_flags);
 475                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 476                         &transparent_hugepage_flags);
 477                 ret = 1;
 478         } else if (!strcmp(str, "never")) {
 479                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 480                           &transparent_hugepage_flags);
 481                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 482                           &transparent_hugepage_flags);
 483                 ret = 1;
 484         }
 485 out:
 486         if (!ret)
 487                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
 488         return ret;
 489 }
 490 __setup("transparent_hugepage=", setup_transparent_hugepage);
 491
 492 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 493 {
 494         if (likely(vma->vm_flags & VM_WRITE))
 495                 pmd = pmd_mkwrite(pmd);
 496         return pmd;
 497 }
 498
 499 #ifdef CONFIG_MEMCG
 500 static inline struct deferred_split *get_deferred_split_queue(struct page *page)
 501 {
 502         struct mem_cgroup *memcg = compound_head(page)->mem_cgroup;
 503         struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
 504
 505         if (memcg)
 506                 return &memcg->deferred_split_queue;
 507         else
 508                 return &pgdat->deferred_split_queue;
 509 }
 510 #else
 511 static inline struct deferred_split *get_deferred_split_queue(struct page *page)
 512 {
 513         struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
 514
 515         return &pgdat->deferred_split_queue;
 516 }
 517 #endif
 518
 519 void prep_transhuge_page(struct page *page)
 520 {
 521         /*
 522          * we use page->mapping and page->indexlru in second tail page
 523          * as list_head: assuming THP order >= 2
 524          */
 525
 526         INIT_LIST_HEAD(page_deferred_list(page));
 527         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 528 }
 529
 530 static unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
 531                 loff_t off, unsigned long flags, unsigned long size)
 532 {
 533         unsigned long addr;
 534         loff_t off_end = off + len;
 535         loff_t off_align = round_up(off, size);
 536         unsigned long len_pad;
 537
 538         if (off_end <= off_align || (off_end - off_align) < size)
 539                 return 0;
 540
 541         len_pad = len + size;
 542         if (len_pad < len || (off + len_pad) < off)
 543                 return 0;
 544
 545         addr = current->mm->get_unmapped_area(filp, 0, len_pad,
 546                                               off >> PAGE_SHIFT, flags);
 547         if (IS_ERR_VALUE(addr))
 548                 return 0;
 549
 550         addr += (off - addr) & (size - 1);
 551         return addr;
 552 }
 553
 554 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 555                 unsigned long len, unsigned long pgoff, unsigned long flags)
 556 {
 557         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 558
 559         if (addr)
 560                 goto out;
 561         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
 562                 goto out;
 563
 564         addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
 565         if (addr)
 566                 return addr;
 567
 568  out:
 569         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 570 }
 571 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 572
 573 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
 574                         struct page *page, gfp_t gfp)
 575 {
 576         struct vm_area_struct *vma = vmf->vma;
 577         struct mem_cgroup *memcg;
 578         pgtable_t pgtable;
 579         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 580         vm_fault_t ret = 0;
 581
 582         VM_BUG_ON_PAGE(!PageCompound(page), page);
 583
 584         if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
 585                 put_page(page);
 586                 count_vm_event(THP_FAULT_FALLBACK);
 587                 return VM_FAULT_FALLBACK;
 588         }
 589
 590         pgtable = pte_alloc_one(vma->vm_mm);
 591         if (unlikely(!pgtable)) {
 592                 ret = VM_FAULT_OOM;
 593                 goto release;
 594         }
 595
 596         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
 597         /*
 598          * The memory barrier inside __SetPageUptodate makes sure that
 599          * clear_huge_page writes become visible before the set_pmd_at()
 600          * write.
 601          */
 602         __SetPageUptodate(page);
 603
 604         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 605         if (unlikely(!pmd_none(*vmf->pmd))) {
 606                 goto unlock_release;
 607         } else {
 608                 pmd_t entry;
 609
 610                 ret = check_stable_address_space(vma->vm_mm);
 611                 if (ret)
 612                         goto unlock_release;
 613
 614                 /* Deliver the page fault to userland */
 615                 if (userfaultfd_missing(vma)) {
 616                         vm_fault_t ret2;
 617
 618                         spin_unlock(vmf->ptl);
 619                         mem_cgroup_cancel_charge(page, memcg, true);
 620                         put_page(page);
 621                         pte_free(vma->vm_mm, pgtable);
 622                         ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
 623                         VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
 624                         return ret2;
 625                 }
 626
 627                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 628                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 629                 page_add_new_anon_rmap(page, vma, haddr, true);
 630                 mem_cgroup_commit_charge(page, memcg, false, true);
 631                 lru_cache_add_active_or_unevictable(page, vma);
 632                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 633                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 634                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 635                 mm_inc_nr_ptes(vma->vm_mm);
 636                 spin_unlock(vmf->ptl);
 637                 count_vm_event(THP_FAULT_ALLOC);
 638                 count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
 639         }
 640
 641         return 0;
 642 unlock_release:
 643         spin_unlock(vmf->ptl);
 644 release:
 645         if (pgtable)
 646                 pte_free(vma->vm_mm, pgtable);
 647         mem_cgroup_cancel_charge(page, memcg, true);
 648         put_page(page);
 649         return ret;
 650
 651 }
 652
 653 /*
 654  * always: directly stall for all thp allocations
 655  * defer: wake kswapd and fail if not immediately available
 656  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
 657  *                fail if not immediately available
 658  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
 659  *          available
 660  * never: never stall for any thp allocation
 661  */
 662 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
 663 {
 664         const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
 665
 666         /* Always do synchronous compaction */
 667         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 668                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
 669
 670         /* Kick kcompactd and fail quickly */
 671         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 672                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
 673
 674         /* Synchronous compaction if madvised, otherwise kick kcompactd */
 675         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 676                 return GFP_TRANSHUGE_LIGHT |
 677                         (vma_madvised ? __GFP_DIRECT_RECLAIM :
 678                                         __GFP_KSWAPD_RECLAIM);
 679
 680         /* Only do synchronous compaction if madvised */
 681         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 682                 return GFP_TRANSHUGE_LIGHT |
 683                        (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
 684
 685         return GFP_TRANSHUGE_LIGHT;
 686 }
 687
 688 /* Caller must hold page table lock. */
 689 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 690                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 691                 struct page *zero_page)
 692 {
 693         pmd_t entry;
 694         if (!pmd_none(*pmd))
 695                 return false;
 696         entry = mk_pmd(zero_page, vma->vm_page_prot);
 697         entry = pmd_mkhuge(entry);
 698         if (pgtable)
 699                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 700         set_pmd_at(mm, haddr, pmd, entry);
 701         mm_inc_nr_ptes(mm);
 702         return true;
 703 }
 704
 705 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 706 {
 707         struct vm_area_struct *vma = vmf->vma;
 708         gfp_t gfp;
 709         struct page *page;
 710         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 711
 712         if (!transhuge_vma_suitable(vma, haddr))
 713                 return VM_FAULT_FALLBACK;
 714         if (unlikely(anon_vma_prepare(vma)))
 715                 return VM_FAULT_OOM;
 716         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 717                 return VM_FAULT_OOM;
 718         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
 719                         !mm_forbids_zeropage(vma->vm_mm) &&
 720                         transparent_hugepage_use_zero_page()) {
 721                 pgtable_t pgtable;
 722                 struct page *zero_page;
 723                 bool set;
 724                 vm_fault_t ret;
 725                 pgtable = pte_alloc_one(vma->vm_mm);
 726                 if (unlikely(!pgtable))
 727                         return VM_FAULT_OOM;
 728                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
 729                 if (unlikely(!zero_page)) {
 730                         pte_free(vma->vm_mm, pgtable);
 731                         count_vm_event(THP_FAULT_FALLBACK);
 732                         return VM_FAULT_FALLBACK;
 733                 }
 734                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 735                 ret = 0;
 736                 set = false;
 737                 if (pmd_none(*vmf->pmd)) {
 738                         ret = check_stable_address_space(vma->vm_mm);
 739                         if (ret) {
 740                                 spin_unlock(vmf->ptl);
 741                         } else if (userfaultfd_missing(vma)) {
 742                                 spin_unlock(vmf->ptl);
 743                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
 744                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 745                         } else {
 746                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
 747                                                    haddr, vmf->pmd, zero_page);
 748                                 spin_unlock(vmf->ptl);
 749                                 set = true;
 750                         }
 751                 } else
 752                         spin_unlock(vmf->ptl);
 753                 if (!set)
 754                         pte_free(vma->vm_mm, pgtable);
 755                 return ret;
 756         }
 757         gfp = alloc_hugepage_direct_gfpmask(vma);
 758         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 759         if (unlikely(!page)) {
 760                 count_vm_event(THP_FAULT_FALLBACK);
 761                 return VM_FAULT_FALLBACK;
 762         }
 763         prep_transhuge_page(page);
 764         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
 765 }
 766
 767 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 768                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
 769                 pgtable_t pgtable)
 770 {
 771         struct mm_struct *mm = vma->vm_mm;
 772         pmd_t entry;
 773         spinlock_t *ptl;
 774
 775         ptl = pmd_lock(mm, pmd);
 776         if (!pmd_none(*pmd)) {
 777                 if (write) {
 778                         if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
 779                                 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
 780                                 goto out_unlock;
 781                         }
 782                         entry = pmd_mkyoung(*pmd);
 783                         entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 784                         if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
 785                                 update_mmu_cache_pmd(vma, addr, pmd);
 786                 }
 787
 788                 goto out_unlock;
 789         }
 790
 791         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 792         if (pfn_t_devmap(pfn))
 793                 entry = pmd_mkdevmap(entry);
 794         if (write) {
 795                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 796                 entry = maybe_pmd_mkwrite(entry, vma);
 797         }
 798
 799         if (pgtable) {
 800                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 801                 mm_inc_nr_ptes(mm);
 802                 pgtable = NULL;
 803         }
 804
 805         set_pmd_at(mm, addr, pmd, entry);
 806         update_mmu_cache_pmd(vma, addr, pmd);
 807
 808 out_unlock:
 809         spin_unlock(ptl);
 810         if (pgtable)
 811                 pte_free(mm, pgtable);
 812 }
 813
 814 vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write)
 815 {
 816         unsigned long addr = vmf->address & PMD_MASK;
 817         struct vm_area_struct *vma = vmf->vma;
 818         pgprot_t pgprot = vma->vm_page_prot;
 819         pgtable_t pgtable = NULL;
 820
 821         /*
 822          * If we had pmd_special, we could avoid all these restrictions,
 823          * but we need to be consistent with PTEs and architectures that
 824          * can't support a 'special' bit.
 825          */
 826         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 827                         !pfn_t_devmap(pfn));
 828         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 829                                                 (VM_PFNMAP|VM_MIXEDMAP));
 830         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 831
 832         if (addr < vma->vm_start || addr >= vma->vm_end)
 833                 return VM_FAULT_SIGBUS;
 834
 835         if (arch_needs_pgtable_deposit()) {
 836                 pgtable = pte_alloc_one(vma->vm_mm);
 837                 if (!pgtable)
 838                         return VM_FAULT_OOM;
 839         }
 840
 841         track_pfn_insert(vma, &pgprot, pfn);
 842
 843         insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
 844         return VM_FAULT_NOPAGE;
 845 }
 846 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
 847
 848 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 849 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 850 {
 851         if (likely(vma->vm_flags & VM_WRITE))
 852                 pud = pud_mkwrite(pud);
 853         return pud;
 854 }
 855
 856 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 857                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 858 {
 859         struct mm_struct *mm = vma->vm_mm;
 860         pud_t entry;
 861         spinlock_t *ptl;
 862
 863         ptl = pud_lock(mm, pud);
 864         if (!pud_none(*pud)) {
 865                 if (write) {
 866                         if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
 867                                 WARN_ON_ONCE(!is_huge_zero_pud(*pud));
 868                                 goto out_unlock;
 869                         }
 870                         entry = pud_mkyoung(*pud);
 871                         entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
 872                         if (pudp_set_access_flags(vma, addr, pud, entry, 1))
 873                                 update_mmu_cache_pud(vma, addr, pud);
 874                 }
 875                 goto out_unlock;
 876         }
 877
 878         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
 879         if (pfn_t_devmap(pfn))
 880                 entry = pud_mkdevmap(entry);
 881         if (write) {
 882                 entry = pud_mkyoung(pud_mkdirty(entry));
 883                 entry = maybe_pud_mkwrite(entry, vma);
 884         }
 885         set_pud_at(mm, addr, pud, entry);
 886         update_mmu_cache_pud(vma, addr, pud);
 887
 888 out_unlock:
 889         spin_unlock(ptl);
 890 }
 891
 892 vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
 893 {
 894         unsigned long addr = vmf->address & PUD_MASK;
 895         struct vm_area_struct *vma = vmf->vma;
 896         pgprot_t pgprot = vma->vm_page_prot;
 897
 898         /*
 899          * If we had pud_special, we could avoid all these restrictions,
 900          * but we need to be consistent with PTEs and architectures that
 901          * can't support a 'special' bit.
 902          */
 903         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 904                         !pfn_t_devmap(pfn));
 905         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 906                                                 (VM_PFNMAP|VM_MIXEDMAP));
 907         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 908
 909         if (addr < vma->vm_start || addr >= vma->vm_end)
 910                 return VM_FAULT_SIGBUS;
 911
 912         track_pfn_insert(vma, &pgprot, pfn);
 913
 914         insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
 915         return VM_FAULT_NOPAGE;
 916 }
 917 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
 918 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 919
 920 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
 921                 pmd_t *pmd, int flags)
 922 {
 923         pmd_t _pmd;
 924
 925         _pmd = pmd_mkyoung(*pmd);
 926         if (flags & FOLL_WRITE)
 927                 _pmd = pmd_mkdirty(_pmd);
 928         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 929                                 pmd, _pmd, flags & FOLL_WRITE))
 930                 update_mmu_cache_pmd(vma, addr, pmd);
 931 }
 932
 933 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 934                 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
 935 {
 936         unsigned long pfn = pmd_pfn(*pmd);
 937         struct mm_struct *mm = vma->vm_mm;
 938         struct page *page;
 939
 940         assert_spin_locked(pmd_lockptr(mm, pmd));
 941
 942         /*
 943          * When we COW a devmap PMD entry, we split it into PTEs, so we should
 944          * not be in this function with `flags & FOLL_COW` set.
 945          */
 946         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
 947
 948         if (flags & FOLL_WRITE && !pmd_write(*pmd))
 949                 return NULL;
 950
 951         if (pmd_present(*pmd) && pmd_devmap(*pmd))
 952                 /* pass */;
 953         else
 954                 return NULL;
 955
 956         if (flags & FOLL_TOUCH)
 957                 touch_pmd(vma, addr, pmd, flags);
 958
 959         /*
 960          * device mapped pages can only be returned if the
 961          * caller will manage the page reference count.
 962          */
 963         if (!(flags & FOLL_GET))
 964                 return ERR_PTR(-EEXIST);
 965
 966         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
 967         *pgmap = get_dev_pagemap(pfn, *pgmap);
 968         if (!*pgmap)
 969                 return ERR_PTR(-EFAULT);
 970         page = pfn_to_page(pfn);
 971         get_page(page);
 972
 973         return page;
 974 }
 975
 976 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 977                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 978                   struct vm_area_struct *vma)
 979 {
 980         spinlock_t *dst_ptl, *src_ptl;
 981         struct page *src_page;
 982         pmd_t pmd;
 983         pgtable_t pgtable = NULL;
 984         int ret = -ENOMEM;
 985
 986         /* Skip if can be re-fill on fault */
 987         if (!vma_is_anonymous(vma))
 988                 return 0;
 989
 990         pgtable = pte_alloc_one(dst_mm);
 991         if (unlikely(!pgtable))
 992                 goto out;
 993
 994         dst_ptl = pmd_lock(dst_mm, dst_pmd);
 995         src_ptl = pmd_lockptr(src_mm, src_pmd);
 996         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 997
 998         ret = -EAGAIN;
 999         pmd = *src_pmd;
1000
1001 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1002         if (unlikely(is_swap_pmd(pmd))) {
1003                 swp_entry_t entry = pmd_to_swp_entry(pmd);
1004
1005                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
1006                 if (is_write_migration_entry(entry)) {
1007                         make_migration_entry_read(&entry);
1008                         pmd = swp_entry_to_pmd(entry);
1009                         if (pmd_swp_soft_dirty(*src_pmd))
1010                                 pmd = pmd_swp_mksoft_dirty(pmd);
1011                         set_pmd_at(src_mm, addr, src_pmd, pmd);
1012                 }
1013                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1014                 mm_inc_nr_ptes(dst_mm);
1015                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1016                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1017                 ret = 0;
1018                 goto out_unlock;
1019         }
1020 #endif
1021
1022         if (unlikely(!pmd_trans_huge(pmd))) {
1023                 pte_free(dst_mm, pgtable);
1024                 goto out_unlock;
1025         }
1026         /*
1027          * When page table lock is held, the huge zero pmd should not be
1028          * under splitting since we don't split the page itself, only pmd to
1029          * a page table.
1030          */
1031         if (is_huge_zero_pmd(pmd)) {
1032                 struct page *zero_page;
1033                 /*
1034                  * get_huge_zero_page() will never allocate a new page here,
1035                  * since we already have a zero page to copy. It just takes a
1036                  * reference.
1037                  */
1038                 zero_page = mm_get_huge_zero_page(dst_mm);
1039                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1040                                 zero_page);
1041                 ret = 0;
1042                 goto out_unlock;
1043         }
1044
1045         src_page = pmd_page(pmd);
1046         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1047         get_page(src_page);
1048         page_dup_rmap(src_page, true);
1049         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1050         mm_inc_nr_ptes(dst_mm);
1051         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1052
1053         pmdp_set_wrprotect(src_mm, addr, src_pmd);
1054         pmd = pmd_mkold(pmd_wrprotect(pmd));
1055         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1056
1057         ret = 0;
1058 out_unlock:
1059         spin_unlock(src_ptl);
1060         spin_unlock(dst_ptl);
1061 out:
1062         return ret;
1063 }
1064
1065 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1066 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1067                 pud_t *pud, int flags)
1068 {
1069         pud_t _pud;
1070
1071         _pud = pud_mkyoung(*pud);
1072         if (flags & FOLL_WRITE)
1073                 _pud = pud_mkdirty(_pud);
1074         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1075                                 pud, _pud, flags & FOLL_WRITE))
1076                 update_mmu_cache_pud(vma, addr, pud);
1077 }
1078
1079 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1080                 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1081 {
1082         unsigned long pfn = pud_pfn(*pud);
1083         struct mm_struct *mm = vma->vm_mm;
1084         struct page *page;
1085
1086         assert_spin_locked(pud_lockptr(mm, pud));
1087
1088         if (flags & FOLL_WRITE && !pud_write(*pud))
1089                 return NULL;
1090
1091         if (pud_present(*pud) && pud_devmap(*pud))
1092                 /* pass */;
1093         else
1094                 return NULL;
1095
1096         if (flags & FOLL_TOUCH)
1097                 touch_pud(vma, addr, pud, flags);
1098
1099         /*
1100          * device mapped pages can only be returned if the
1101          * caller will manage the page reference count.
1102          */
1103         if (!(flags & FOLL_GET))
1104                 return ERR_PTR(-EEXIST);
1105
1106         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1107         *pgmap = get_dev_pagemap(pfn, *pgmap);
1108         if (!*pgmap)
1109                 return ERR_PTR(-EFAULT);
1110         page = pfn_to_page(pfn);
1111         get_page(page);
1112
1113         return page;
1114 }
1115
1116 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1117                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1118                   struct vm_area_struct *vma)
1119 {
1120         spinlock_t *dst_ptl, *src_ptl;
1121         pud_t pud;
1122         int ret;
1123
1124         dst_ptl = pud_lock(dst_mm, dst_pud);
1125         src_ptl = pud_lockptr(src_mm, src_pud);
1126         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1127
1128         ret = -EAGAIN;
1129         pud = *src_pud;
1130         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1131                 goto out_unlock;
1132
1133         /*
1134          * When page table lock is held, the huge zero pud should not be
1135          * under splitting since we don't split the page itself, only pud to
1136          * a page table.
1137          */
1138         if (is_huge_zero_pud(pud)) {
1139                 /* No huge zero pud yet */
1140         }
1141
1142         pudp_set_wrprotect(src_mm, addr, src_pud);
1143         pud = pud_mkold(pud_wrprotect(pud));
1144         set_pud_at(dst_mm, addr, dst_pud, pud);
1145
1146         ret = 0;
1147 out_unlock:
1148         spin_unlock(src_ptl);
1149         spin_unlock(dst_ptl);
1150         return ret;
1151 }
1152
1153 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1154 {
1155         pud_t entry;
1156         unsigned long haddr;
1157         bool write = vmf->flags & FAULT_FLAG_WRITE;
1158
1159         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1160         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1161                 goto unlock;
1162
1163         entry = pud_mkyoung(orig_pud);
1164         if (write)
1165                 entry = pud_mkdirty(entry);
1166         haddr = vmf->address & HPAGE_PUD_MASK;
1167         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1168                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1169
1170 unlock:
1171         spin_unlock(vmf->ptl);
1172 }
1173 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1174
1175 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1176 {
1177         pmd_t entry;
1178         unsigned long haddr;
1179         bool write = vmf->flags & FAULT_FLAG_WRITE;
1180
1181         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1182         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1183                 goto unlock;
1184
1185         entry = pmd_mkyoung(orig_pmd);
1186         if (write)
1187                 entry = pmd_mkdirty(entry);
1188         haddr = vmf->address & HPAGE_PMD_MASK;
1189         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1190                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1191
1192 unlock:
1193         spin_unlock(vmf->ptl);
1194 }
1195
1196 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1197                         pmd_t orig_pmd, struct page *page)
1198 {
1199         struct vm_area_struct *vma = vmf->vma;
1200         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1201         struct mem_cgroup *memcg;
1202         pgtable_t pgtable;
1203         pmd_t _pmd;
1204         int i;
1205         vm_fault_t ret = 0;
1206         struct page **pages;
1207         struct mmu_notifier_range range;
1208
1209         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1210                               GFP_KERNEL);
1211         if (unlikely(!pages)) {
1212                 ret |= VM_FAULT_OOM;
1213                 goto out;
1214         }
1215
1216         for (i = 0; i < HPAGE_PMD_NR; i++) {
1217                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1218                                                vmf->address, page_to_nid(page));
1219                 if (unlikely(!pages[i] ||
1220                              mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1221                                      GFP_KERNEL, &memcg, false))) {
1222                         if (pages[i])
1223                                 put_page(pages[i]);
1224                         while (--i >= 0) {
1225                                 memcg = (void *)page_private(pages[i]);
1226                                 set_page_private(pages[i], 0);
1227                                 mem_cgroup_cancel_charge(pages[i], memcg,
1228                                                 false);
1229                                 put_page(pages[i]);
1230                         }
1231                         kfree(pages);
1232                         ret |= VM_FAULT_OOM;
1233                         goto out;
1234                 }
1235                 set_page_private(pages[i], (unsigned long)memcg);
1236         }
1237
1238         for (i = 0; i < HPAGE_PMD_NR; i++) {
1239                 copy_user_highpage(pages[i], page + i,
1240                                    haddr + PAGE_SIZE * i, vma);
1241                 __SetPageUptodate(pages[i]);
1242                 cond_resched();
1243         }
1244
1245         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1246                                 haddr, haddr + HPAGE_PMD_SIZE);
1247         mmu_notifier_invalidate_range_start(&range);
1248
1249         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1250         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1251                 goto out_free_pages;
1252         VM_BUG_ON_PAGE(!PageHead(page), page);
1253
1254         /*
1255          * Leave pmd empty until pte is filled note we must notify here as
1256          * concurrent CPU thread might write to new page before the call to
1257          * mmu_notifier_invalidate_range_end() happens which can lead to a
1258          * device seeing memory write in different order than CPU.
1259          *
1260          * See Documentation/vm/mmu_notifier.rst
1261          */
1262         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1263
1264         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1265         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1266
1267         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1268                 pte_t entry;
1269                 entry = mk_pte(pages[i], vma->vm_page_prot);
1270                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1271                 memcg = (void *)page_private(pages[i]);
1272                 set_page_private(pages[i], 0);
1273                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1274                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1275                 lru_cache_add_active_or_unevictable(pages[i], vma);
1276                 vmf->pte = pte_offset_map(&_pmd, haddr);
1277                 VM_BUG_ON(!pte_none(*vmf->pte));
1278                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1279                 pte_unmap(vmf->pte);
1280         }
1281         kfree(pages);
1282
1283         smp_wmb(); /* make pte visible before pmd */
1284         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1285         page_remove_rmap(page, true);
1286         spin_unlock(vmf->ptl);
1287
1288         /*
1289          * No need to double call mmu_notifier->invalidate_range() callback as
1290          * the above pmdp_huge_clear_flush_notify() did already call it.
1291          */
1292         mmu_notifier_invalidate_range_only_end(&range);
1293
1294         ret |= VM_FAULT_WRITE;
1295         put_page(page);
1296
1297 out:
1298         return ret;
1299
1300 out_free_pages:
1301         spin_unlock(vmf->ptl);
1302         mmu_notifier_invalidate_range_end(&range);
1303         for (i = 0; i < HPAGE_PMD_NR; i++) {
1304                 memcg = (void *)page_private(pages[i]);
1305                 set_page_private(pages[i], 0);
1306                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1307                 put_page(pages[i]);
1308         }
1309         kfree(pages);
1310         goto out;
1311 }
1312
1313 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1314 {
1315         struct vm_area_struct *vma = vmf->vma;
1316         struct page *page = NULL, *new_page;
1317         struct mem_cgroup *memcg;
1318         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1319         struct mmu_notifier_range range;
1320         gfp_t huge_gfp;                 /* for allocation and charge */
1321         vm_fault_t ret = 0;
1322
1323         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1324         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1325         if (is_huge_zero_pmd(orig_pmd))
1326                 goto alloc;
1327         spin_lock(vmf->ptl);
1328         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1329                 goto out_unlock;
1330
1331         page = pmd_page(orig_pmd);
1332         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1333         /*
1334          * We can only reuse the page if nobody else maps the huge page or it's
1335          * part.
1336          */
1337         if (!trylock_page(page)) {
1338                 get_page(page);
1339                 spin_unlock(vmf->ptl);
1340                 lock_page(page);
1341                 spin_lock(vmf->ptl);
1342                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1343                         unlock_page(page);
1344                         put_page(page);
1345                         goto out_unlock;
1346                 }
1347                 put_page(page);
1348         }
1349         if (reuse_swap_page(page, NULL)) {
1350                 pmd_t entry;
1351                 entry = pmd_mkyoung(orig_pmd);
1352                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1353                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1354                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1355                 ret |= VM_FAULT_WRITE;
1356                 unlock_page(page);
1357                 goto out_unlock;
1358         }
1359         unlock_page(page);
1360         get_page(page);
1361         spin_unlock(vmf->ptl);
1362 alloc:
1363         if (__transparent_hugepage_enabled(vma) &&
1364             !transparent_hugepage_debug_cow()) {
1365                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1366                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1367         } else
1368                 new_page = NULL;
1369
1370         if (likely(new_page)) {
1371                 prep_transhuge_page(new_page);
1372         } else {
1373                 if (!page) {
1374                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1375                         ret |= VM_FAULT_FALLBACK;
1376                 } else {
1377                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1378                         if (ret & VM_FAULT_OOM) {
1379                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1380                                 ret |= VM_FAULT_FALLBACK;
1381                         }
1382                         put_page(page);
1383                 }
1384                 count_vm_event(THP_FAULT_FALLBACK);
1385                 goto out;
1386         }
1387
1388         if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1389                                         huge_gfp, &memcg, true))) {
1390                 put_page(new_page);
1391                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1392                 if (page)
1393                         put_page(page);
1394                 ret |= VM_FAULT_FALLBACK;
1395                 count_vm_event(THP_FAULT_FALLBACK);
1396                 goto out;
1397         }
1398
1399         count_vm_event(THP_FAULT_ALLOC);
1400         count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
1401
1402         if (!page)
1403                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1404         else
1405                 copy_user_huge_page(new_page, page, vmf->address,
1406                                     vma, HPAGE_PMD_NR);
1407         __SetPageUptodate(new_page);
1408
1409         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1410                                 haddr, haddr + HPAGE_PMD_SIZE);
1411         mmu_notifier_invalidate_range_start(&range);
1412
1413         spin_lock(vmf->ptl);
1414         if (page)
1415                 put_page(page);
1416         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1417                 spin_unlock(vmf->ptl);
1418                 mem_cgroup_cancel_charge(new_page, memcg, true);
1419                 put_page(new_page);
1420                 goto out_mn;
1421         } else {
1422                 pmd_t entry;
1423                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1424                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1425                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1426                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1427                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1428                 lru_cache_add_active_or_unevictable(new_page, vma);
1429                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1430                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1431                 if (!page) {
1432                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1433                 } else {
1434                         VM_BUG_ON_PAGE(!PageHead(page), page);
1435                         page_remove_rmap(page, true);
1436                         put_page(page);
1437                 }
1438                 ret |= VM_FAULT_WRITE;
1439         }
1440         spin_unlock(vmf->ptl);
1441 out_mn:
1442         /*
1443          * No need to double call mmu_notifier->invalidate_range() callback as
1444          * the above pmdp_huge_clear_flush_notify() did already call it.
1445          */
1446         mmu_notifier_invalidate_range_only_end(&range);
1447 out:
1448         return ret;
1449 out_unlock:
1450         spin_unlock(vmf->ptl);
1451         return ret;
1452 }
1453
1454 /*
1455  * FOLL_FORCE can write to even unwritable pmd's, but only
1456  * after we've gone through a COW cycle and they are dirty.
1457  */
1458 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1459 {
1460         return pmd_write(pmd) ||
1461                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1462 }
1463
1464 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1465                                    unsigned long addr,
1466                                    pmd_t *pmd,
1467                                    unsigned int flags)
1468 {
1469         struct mm_struct *mm = vma->vm_mm;
1470         struct page *page = NULL;
1471
1472         assert_spin_locked(pmd_lockptr(mm, pmd));
1473
1474         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1475                 goto out;
1476
1477         /* Avoid dumping huge zero page */
1478         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1479                 return ERR_PTR(-EFAULT);
1480
1481         /* Full NUMA hinting faults to serialise migration in fault paths */
1482         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1483                 goto out;
1484
1485         page = pmd_page(*pmd);
1486         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1487         if (flags & FOLL_TOUCH)
1488                 touch_pmd(vma, addr, pmd, flags);
1489         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1490                 /*
1491                  * We don't mlock() pte-mapped THPs. This way we can avoid
1492                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1493                  *
1494                  * For anon THP:
1495                  *
1496                  * In most cases the pmd is the only mapping of the page as we
1497                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1498                  * writable private mappings in populate_vma_page_range().
1499                  *
1500                  * The only scenario when we have the page shared here is if we
1501                  * mlocking read-only mapping shared over fork(). We skip
1502                  * mlocking such pages.
1503                  *
1504                  * For file THP:
1505                  *
1506                  * We can expect PageDoubleMap() to be stable under page lock:
1507                  * for file pages we set it in page_add_file_rmap(), which
1508                  * requires page to be locked.
1509                  */
1510
1511                 if (PageAnon(page) && compound_mapcount(page) != 1)
1512                         goto skip_mlock;
1513                 if (PageDoubleMap(page) || !page->mapping)
1514                         goto skip_mlock;
1515                 if (!trylock_page(page))
1516                         goto skip_mlock;
1517                 lru_add_drain();
1518                 if (page->mapping && !PageDoubleMap(page))
1519                         mlock_vma_page(page);
1520                 unlock_page(page);
1521         }
1522 skip_mlock:
1523         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1524         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1525         if (flags & FOLL_GET)
1526                 get_page(page);
1527
1528 out:
1529         return page;
1530 }
1531
1532 /* NUMA hinting page fault entry point for trans huge pmds */
1533 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1534 {
1535         struct vm_area_struct *vma = vmf->vma;
1536         struct anon_vma *anon_vma = NULL;
1537         struct page *page;
1538         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1539         int page_nid = NUMA_NO_NODE, this_nid = numa_node_id();
1540         int target_nid, last_cpupid = -1;
1541         bool page_locked;
1542         bool migrated = false;
1543         bool was_writable;
1544         int flags = 0;
1545
1546         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1547         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1548                 goto out_unlock;
1549
1550         /*
1551          * If there are potential migrations, wait for completion and retry
1552          * without disrupting NUMA hinting information. Do not relock and
1553          * check_same as the page may no longer be mapped.
1554          */
1555         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1556                 page = pmd_page(*vmf->pmd);
1557                 if (!get_page_unless_zero(page))
1558                         goto out_unlock;
1559                 spin_unlock(vmf->ptl);
1560                 put_and_wait_on_page_locked(page);
1561                 goto out;
1562         }
1563
1564         page = pmd_page(pmd);
1565         BUG_ON(is_huge_zero_page(page));
1566         page_nid = page_to_nid(page);
1567         last_cpupid = page_cpupid_last(page);
1568         count_vm_numa_event(NUMA_HINT_FAULTS);
1569         if (page_nid == this_nid) {
1570                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1571                 flags |= TNF_FAULT_LOCAL;
1572         }
1573
1574         /* See similar comment in do_numa_page for explanation */
1575         if (!pmd_savedwrite(pmd))
1576                 flags |= TNF_NO_GROUP;
1577
1578         /*
1579          * Acquire the page lock to serialise THP migrations but avoid dropping
1580          * page_table_lock if at all possible
1581          */
1582         page_locked = trylock_page(page);
1583         target_nid = mpol_misplaced(page, vma, haddr);
1584         if (target_nid == NUMA_NO_NODE) {
1585                 /* If the page was locked, there are no parallel migrations */
1586                 if (page_locked)
1587                         goto clear_pmdnuma;
1588         }
1589
1590         /* Migration could have started since the pmd_trans_migrating check */
1591         if (!page_locked) {
1592                 page_nid = NUMA_NO_NODE;
1593                 if (!get_page_unless_zero(page))
1594                         goto out_unlock;
1595                 spin_unlock(vmf->ptl);
1596                 put_and_wait_on_page_locked(page);
1597                 goto out;
1598         }
1599
1600         /*
1601          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1602          * to serialises splits
1603          */
1604         get_page(page);
1605         spin_unlock(vmf->ptl);
1606         anon_vma = page_lock_anon_vma_read(page);
1607
1608         /* Confirm the PMD did not change while page_table_lock was released */
1609         spin_lock(vmf->ptl);
1610         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1611                 unlock_page(page);
1612                 put_page(page);
1613                 page_nid = NUMA_NO_NODE;
1614                 goto out_unlock;
1615         }
1616
1617         /* Bail if we fail to protect against THP splits for any reason */
1618         if (unlikely(!anon_vma)) {
1619                 put_page(page);
1620                 page_nid = NUMA_NO_NODE;
1621                 goto clear_pmdnuma;
1622         }
1623
1624         /*
1625          * Since we took the NUMA fault, we must have observed the !accessible
1626          * bit. Make sure all other CPUs agree with that, to avoid them
1627          * modifying the page we're about to migrate.
1628          *
1629          * Must be done under PTL such that we'll observe the relevant
1630          * inc_tlb_flush_pending().
1631          *
1632          * We are not sure a pending tlb flush here is for a huge page
1633          * mapping or not. Hence use the tlb range variant
1634          */
1635         if (mm_tlb_flush_pending(vma->vm_mm)) {
1636                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1637                 /*
1638                  * change_huge_pmd() released the pmd lock before
1639                  * invalidating the secondary MMUs sharing the primary
1640                  * MMU pagetables (with ->invalidate_range()). The
1641                  * mmu_notifier_invalidate_range_end() (which
1642                  * internally calls ->invalidate_range()) in
1643                  * change_pmd_range() will run after us, so we can't
1644                  * rely on it here and we need an explicit invalidate.
1645                  */
1646                 mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1647                                               haddr + HPAGE_PMD_SIZE);
1648         }
1649
1650         /*
1651          * Migrate the THP to the requested node, returns with page unlocked
1652          * and access rights restored.
1653          */
1654         spin_unlock(vmf->ptl);
1655
1656         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1657                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1658         if (migrated) {
1659                 flags |= TNF_MIGRATED;
1660                 page_nid = target_nid;
1661         } else
1662                 flags |= TNF_MIGRATE_FAIL;
1663
1664         goto out;
1665 clear_pmdnuma:
1666         BUG_ON(!PageLocked(page));
1667         was_writable = pmd_savedwrite(pmd);
1668         pmd = pmd_modify(pmd, vma->vm_page_prot);
1669         pmd = pmd_mkyoung(pmd);
1670         if (was_writable)
1671                 pmd = pmd_mkwrite(pmd);
1672         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1673         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1674         unlock_page(page);
1675 out_unlock:
1676         spin_unlock(vmf->ptl);
1677
1678 out:
1679         if (anon_vma)
1680                 page_unlock_anon_vma_read(anon_vma);
1681
1682         if (page_nid != NUMA_NO_NODE)
1683                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1684                                 flags);
1685
1686         return 0;
1687 }
1688
1689 /*
1690  * Return true if we do MADV_FREE successfully on entire pmd page.
1691  * Otherwise, return false.
1692  */
1693 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1694                 pmd_t *pmd, unsigned long addr, unsigned long next)
1695 {
1696         spinlock_t *ptl;
1697         pmd_t orig_pmd;
1698         struct page *page;
1699         struct mm_struct *mm = tlb->mm;
1700         bool ret = false;
1701
1702         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1703
1704         ptl = pmd_trans_huge_lock(pmd, vma);
1705         if (!ptl)
1706                 goto out_unlocked;
1707
1708         orig_pmd = *pmd;
1709         if (is_huge_zero_pmd(orig_pmd))
1710                 goto out;
1711
1712         if (unlikely(!pmd_present(orig_pmd))) {
1713                 VM_BUG_ON(thp_migration_supported() &&
1714                                   !is_pmd_migration_entry(orig_pmd));
1715                 goto out;
1716         }
1717
1718         page = pmd_page(orig_pmd);
1719         /*
1720          * If other processes are mapping this page, we couldn't discard
1721          * the page unless they all do MADV_FREE so let's skip the page.
1722          */
1723         if (page_mapcount(page) != 1)
1724                 goto out;
1725
1726         if (!trylock_page(page))
1727                 goto out;
1728
1729         /*
1730          * If user want to discard part-pages of THP, split it so MADV_FREE
1731          * will deactivate only them.
1732          */
1733         if (next - addr != HPAGE_PMD_SIZE) {
1734                 get_page(page);
1735                 spin_unlock(ptl);
1736                 split_huge_page(page);
1737                 unlock_page(page);
1738                 put_page(page);
1739                 goto out_unlocked;
1740         }
1741
1742         if (PageDirty(page))
1743                 ClearPageDirty(page);
1744         unlock_page(page);
1745
1746         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1747                 pmdp_invalidate(vma, addr, pmd);
1748                 orig_pmd = pmd_mkold(orig_pmd);
1749                 orig_pmd = pmd_mkclean(orig_pmd);
1750
1751                 set_pmd_at(mm, addr, pmd, orig_pmd);
1752                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1753         }
1754
1755         mark_page_lazyfree(page);
1756         ret = true;
1757 out:
1758         spin_unlock(ptl);
1759 out_unlocked:
1760         return ret;
1761 }
1762
1763 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1764 {
1765         pgtable_t pgtable;
1766
1767         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1768         pte_free(mm, pgtable);
1769         mm_dec_nr_ptes(mm);
1770 }
1771
1772 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1773                  pmd_t *pmd, unsigned long addr)
1774 {
1775         pmd_t orig_pmd;
1776         spinlock_t *ptl;
1777
1778         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1779
1780         ptl = __pmd_trans_huge_lock(pmd, vma);
1781         if (!ptl)
1782                 return 0;
1783         /*
1784          * For architectures like ppc64 we look at deposited pgtable
1785          * when calling pmdp_huge_get_and_clear. So do the
1786          * pgtable_trans_huge_withdraw after finishing pmdp related
1787          * operations.
1788          */
1789         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1790                         tlb->fullmm);
1791         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1792         if (vma_is_dax(vma)) {
1793                 if (arch_needs_pgtable_deposit())
1794                         zap_deposited_table(tlb->mm, pmd);
1795                 spin_unlock(ptl);
1796                 if (is_huge_zero_pmd(orig_pmd))
1797                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1798         } else if (is_huge_zero_pmd(orig_pmd)) {
1799                 zap_deposited_table(tlb->mm, pmd);
1800                 spin_unlock(ptl);
1801                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1802         } else {
1803                 struct page *page = NULL;
1804                 int flush_needed = 1;
1805
1806                 if (pmd_present(orig_pmd)) {
1807                         page = pmd_page(orig_pmd);
1808                         page_remove_rmap(page, true);
1809                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1810                         VM_BUG_ON_PAGE(!PageHead(page), page);
1811                 } else if (thp_migration_supported()) {
1812                         swp_entry_t entry;
1813
1814                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1815                         entry = pmd_to_swp_entry(orig_pmd);
1816                         page = pfn_to_page(swp_offset(entry));
1817                         flush_needed = 0;
1818                 } else
1819                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1820
1821                 if (PageAnon(page)) {
1822                         zap_deposited_table(tlb->mm, pmd);
1823                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1824                 } else {
1825                         if (arch_needs_pgtable_deposit())
1826                                 zap_deposited_table(tlb->mm, pmd);
1827                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1828                 }
1829
1830                 spin_unlock(ptl);
1831                 if (flush_needed)
1832                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1833         }
1834         return 1;
1835 }
1836
1837 #ifndef pmd_move_must_withdraw
1838 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1839                                          spinlock_t *old_pmd_ptl,
1840                                          struct vm_area_struct *vma)
1841 {
1842         /*
1843          * With split pmd lock we also need to move preallocated
1844          * PTE page table if new_pmd is on different PMD page table.
1845          *
1846          * We also don't deposit and withdraw tables for file pages.
1847          */
1848         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1849 }
1850 #endif
1851
1852 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1853 {
1854 #ifdef CONFIG_MEM_SOFT_DIRTY
1855         if (unlikely(is_pmd_migration_entry(pmd)))
1856                 pmd = pmd_swp_mksoft_dirty(pmd);
1857         else if (pmd_present(pmd))
1858                 pmd = pmd_mksoft_dirty(pmd);
1859 #endif
1860         return pmd;
1861 }
1862
1863 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1864                   unsigned long new_addr, unsigned long old_end,
1865                   pmd_t *old_pmd, pmd_t *new_pmd)
1866 {
1867         spinlock_t *old_ptl, *new_ptl;
1868         pmd_t pmd;
1869         struct mm_struct *mm = vma->vm_mm;
1870         bool force_flush = false;
1871
1872         if ((old_addr & ~HPAGE_PMD_MASK) ||
1873             (new_addr & ~HPAGE_PMD_MASK) ||
1874             old_end - old_addr < HPAGE_PMD_SIZE)
1875                 return false;
1876
1877         /*
1878          * The destination pmd shouldn't be established, free_pgtables()
1879          * should have release it.
1880          */
1881         if (WARN_ON(!pmd_none(*new_pmd))) {
1882                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1883                 return false;
1884         }
1885
1886         /*
1887          * We don't have to worry about the ordering of src and dst
1888          * ptlocks because exclusive mmap_sem prevents deadlock.
1889          */
1890         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1891         if (old_ptl) {
1892                 new_ptl = pmd_lockptr(mm, new_pmd);
1893                 if (new_ptl != old_ptl)
1894                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1895                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1896                 if (pmd_present(pmd))
1897                         force_flush = true;
1898                 VM_BUG_ON(!pmd_none(*new_pmd));
1899
1900                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1901                         pgtable_t pgtable;
1902                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1903                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1904                 }
1905                 pmd = move_soft_dirty_pmd(pmd);
1906                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1907                 if (force_flush)
1908                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1909                 if (new_ptl != old_ptl)
1910                         spin_unlock(new_ptl);
1911                 spin_unlock(old_ptl);
1912                 return true;
1913         }
1914         return false;
1915 }
1916
1917 /*
1918  * Returns
1919  *  - 0 if PMD could not be locked
1920  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1921  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1922  */
1923 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1924                 unsigned long addr, pgprot_t newprot, int prot_numa)
1925 {
1926         struct mm_struct *mm = vma->vm_mm;
1927         spinlock_t *ptl;
1928         pmd_t entry;
1929         bool preserve_write;
1930         int ret;
1931
1932         ptl = __pmd_trans_huge_lock(pmd, vma);
1933         if (!ptl)
1934                 return 0;
1935
1936         preserve_write = prot_numa && pmd_write(*pmd);
1937         ret = 1;
1938
1939 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1940         if (is_swap_pmd(*pmd)) {
1941                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1942
1943                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1944                 if (is_write_migration_entry(entry)) {
1945                         pmd_t newpmd;
1946                         /*
1947                          * A protection check is difficult so
1948                          * just be safe and disable write
1949                          */
1950                         make_migration_entry_read(&entry);
1951                         newpmd = swp_entry_to_pmd(entry);
1952                         if (pmd_swp_soft_dirty(*pmd))
1953                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1954                         set_pmd_at(mm, addr, pmd, newpmd);
1955                 }
1956                 goto unlock;
1957         }
1958 #endif
1959
1960         /*
1961          * Avoid trapping faults against the zero page. The read-only
1962          * data is likely to be read-cached on the local CPU and
1963          * local/remote hits to the zero page are not interesting.
1964          */
1965         if (prot_numa && is_huge_zero_pmd(*pmd))
1966                 goto unlock;
1967
1968         if (prot_numa && pmd_protnone(*pmd))
1969                 goto unlock;
1970
1971         /*
1972          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1973          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1974          * which is also under down_read(mmap_sem):
1975          *
1976          *      CPU0:                           CPU1:
1977          *                              change_huge_pmd(prot_numa=1)
1978          *                               pmdp_huge_get_and_clear_notify()
1979          * madvise_dontneed()
1980          *  zap_pmd_range()
1981          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1982          *   // skip the pmd
1983          *                               set_pmd_at();
1984          *                               // pmd is re-established
1985          *
1986          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1987          * which may break userspace.
1988          *
1989          * pmdp_invalidate() is required to make sure we don't miss
1990          * dirty/young flags set by hardware.
1991          */
1992         entry = pmdp_invalidate(vma, addr, pmd);
1993
1994         entry = pmd_modify(entry, newprot);
1995         if (preserve_write)
1996                 entry = pmd_mk_savedwrite(entry);
1997         ret = HPAGE_PMD_NR;
1998         set_pmd_at(mm, addr, pmd, entry);
1999         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
2000 unlock:
2001         spin_unlock(ptl);
2002         return ret;
2003 }
2004
2005 /*
2006  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
2007  *
2008  * Note that if it returns page table lock pointer, this routine returns without
2009  * unlocking page table lock. So callers must unlock it.
2010  */
2011 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
2012 {
2013         spinlock_t *ptl;
2014         ptl = pmd_lock(vma->vm_mm, pmd);
2015         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
2016                         pmd_devmap(*pmd)))
2017                 return ptl;
2018         spin_unlock(ptl);
2019         return NULL;
2020 }
2021
2022 /*
2023  * Returns true if a given pud maps a thp, false otherwise.
2024  *
2025  * Note that if it returns true, this routine returns without unlocking page
2026  * table lock. So callers must unlock it.
2027  */
2028 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
2029 {
2030         spinlock_t *ptl;
2031
2032         ptl = pud_lock(vma->vm_mm, pud);
2033         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
2034                 return ptl;
2035         spin_unlock(ptl);
2036         return NULL;
2037 }
2038
2039 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
2040 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
2041                  pud_t *pud, unsigned long addr)
2042 {
2043         spinlock_t *ptl;
2044
2045         ptl = __pud_trans_huge_lock(pud, vma);
2046         if (!ptl)
2047                 return 0;
2048         /*
2049          * For architectures like ppc64 we look at deposited pgtable
2050          * when calling pudp_huge_get_and_clear. So do the
2051          * pgtable_trans_huge_withdraw after finishing pudp related
2052          * operations.
2053          */
2054         pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
2055         tlb_remove_pud_tlb_entry(tlb, pud, addr);
2056         if (vma_is_dax(vma)) {
2057                 spin_unlock(ptl);
2058                 /* No zero page support yet */
2059         } else {
2060                 /* No support for anonymous PUD pages yet */
2061                 BUG();
2062         }
2063         return 1;
2064 }
2065
2066 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2067                 unsigned long haddr)
2068 {
2069         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2070         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2071         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2072         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2073
2074         count_vm_event(THP_SPLIT_PUD);
2075
2076         pudp_huge_clear_flush_notify(vma, haddr, pud);
2077 }
2078
2079 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2080                 unsigned long address)
2081 {
2082         spinlock_t *ptl;
2083         struct mmu_notifier_range range;
2084
2085         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2086                                 address & HPAGE_PUD_MASK,
2087                                 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
2088         mmu_notifier_invalidate_range_start(&range);
2089         ptl = pud_lock(vma->vm_mm, pud);
2090         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2091                 goto out;
2092         __split_huge_pud_locked(vma, pud, range.start);
2093
2094 out:
2095         spin_unlock(ptl);
2096         /*
2097          * No need to double call mmu_notifier->invalidate_range() callback as
2098          * the above pudp_huge_clear_flush_notify() did already call it.
2099          */
2100         mmu_notifier_invalidate_range_only_end(&range);
2101 }
2102 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2103
2104 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2105                 unsigned long haddr, pmd_t *pmd)
2106 {
2107         struct mm_struct *mm = vma->vm_mm;
2108         pgtable_t pgtable;
2109         pmd_t _pmd;
2110         int i;
2111
2112         /*
2113          * Leave pmd empty until pte is filled note that it is fine to delay
2114          * notification until mmu_notifier_invalidate_range_end() as we are
2115          * replacing a zero pmd write protected page with a zero pte write
2116          * protected page.
2117          *
2118          * See Documentation/vm/mmu_notifier.rst
2119          */
2120         pmdp_huge_clear_flush(vma, haddr, pmd);
2121
2122         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2123         pmd_populate(mm, &_pmd, pgtable);
2124
2125         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2126                 pte_t *pte, entry;
2127                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2128                 entry = pte_mkspecial(entry);
2129                 pte = pte_offset_map(&_pmd, haddr);
2130                 VM_BUG_ON(!pte_none(*pte));
2131                 set_pte_at(mm, haddr, pte, entry);
2132                 pte_unmap(pte);
2133         }
2134         smp_wmb(); /* make pte visible before pmd */
2135         pmd_populate(mm, pmd, pgtable);
2136 }
2137
2138 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2139                 unsigned long haddr, bool freeze)
2140 {
2141         struct mm_struct *mm = vma->vm_mm;
2142         struct page *page;
2143         pgtable_t pgtable;
2144         pmd_t old_pmd, _pmd;
2145         bool young, write, soft_dirty, pmd_migration = false;
2146         unsigned long addr;
2147         int i;
2148
2149         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2150         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2151         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2152         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2153                                 && !pmd_devmap(*pmd));
2154
2155         count_vm_event(THP_SPLIT_PMD);
2156
2157         if (!vma_is_anonymous(vma)) {
2158                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2159                 /*
2160                  * We are going to unmap this huge page. So
2161                  * just go ahead and zap it
2162                  */
2163                 if (arch_needs_pgtable_deposit())
2164                         zap_deposited_table(mm, pmd);
2165                 if (vma_is_dax(vma))
2166                         return;
2167                 page = pmd_page(_pmd);
2168                 if (!PageDirty(page) && pmd_dirty(_pmd))
2169                         set_page_dirty(page);
2170                 if (!PageReferenced(page) && pmd_young(_pmd))
2171                         SetPageReferenced(page);
2172                 page_remove_rmap(page, true);
2173                 put_page(page);
2174                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2175                 return;
2176         } else if (is_huge_zero_pmd(*pmd)) {
2177                 /*
2178                  * FIXME: Do we want to invalidate secondary mmu by calling
2179                  * mmu_notifier_invalidate_range() see comments below inside
2180                  * __split_huge_pmd() ?
2181                  *
2182                  * We are going from a zero huge page write protected to zero
2183                  * small page also write protected so it does not seems useful
2184                  * to invalidate secondary mmu at this time.
2185                  */
2186                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2187         }
2188
2189         /*
2190          * Up to this point the pmd is present and huge and userland has the
2191          * whole access to the hugepage during the split (which happens in
2192          * place). If we overwrite the pmd with the not-huge version pointing
2193          * to the pte here (which of course we could if all CPUs were bug
2194          * free), userland could trigger a small page size TLB miss on the
2195          * small sized TLB while the hugepage TLB entry is still established in
2196          * the huge TLB. Some CPU doesn't like that.
2197          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2198          * 383 on page 93. Intel should be safe but is also warns that it's
2199          * only safe if the permission and cache attributes of the two entries
2200          * loaded in the two TLB is identical (which should be the case here).
2201          * But it is generally safer to never allow small and huge TLB entries
2202          * for the same virtual address to be loaded simultaneously. So instead
2203          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2204          * current pmd notpresent (atomically because here the pmd_trans_huge
2205          * must remain set at all times on the pmd until the split is complete
2206          * for this pmd), then we flush the SMP TLB and finally we write the
2207          * non-huge version of the pmd entry with pmd_populate.
2208          */
2209         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2210
2211         pmd_migration = is_pmd_migration_entry(old_pmd);
2212         if (unlikely(pmd_migration)) {
2213                 swp_entry_t entry;
2214
2215                 entry = pmd_to_swp_entry(old_pmd);
2216                 page = pfn_to_page(swp_offset(entry));
2217                 write = is_write_migration_entry(entry);
2218                 young = false;
2219                 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2220         } else {
2221                 page = pmd_page(old_pmd);
2222                 if (pmd_dirty(old_pmd))
2223                         SetPageDirty(page);
2224                 write = pmd_write(old_pmd);
2225                 young = pmd_young(old_pmd);
2226                 soft_dirty = pmd_soft_dirty(old_pmd);
2227         }
2228         VM_BUG_ON_PAGE(!page_count(page), page);
2229         page_ref_add(page, HPAGE_PMD_NR - 1);
2230
2231         /*
2232          * Withdraw the table only after we mark the pmd entry invalid.
2233          * This's critical for some architectures (Power).
2234          */
2235         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2236         pmd_populate(mm, &_pmd, pgtable);
2237
2238         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2239                 pte_t entry, *pte;
2240                 /*
2241                  * Note that NUMA hinting access restrictions are not
2242                  * transferred to avoid any possibility of altering
2243                  * permissions across VMAs.
2244                  */
2245                 if (freeze || pmd_migration) {
2246                         swp_entry_t swp_entry;
2247                         swp_entry = make_migration_entry(page + i, write);
2248                         entry = swp_entry_to_pte(swp_entry);
2249                         if (soft_dirty)
2250                                 entry = pte_swp_mksoft_dirty(entry);
2251                 } else {
2252                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2253                         entry = maybe_mkwrite(entry, vma);
2254                         if (!write)
2255                                 entry = pte_wrprotect(entry);
2256                         if (!young)
2257                                 entry = pte_mkold(entry);
2258                         if (soft_dirty)
2259                                 entry = pte_mksoft_dirty(entry);
2260                 }
2261                 pte = pte_offset_map(&_pmd, addr);
2262                 BUG_ON(!pte_none(*pte));
2263                 set_pte_at(mm, addr, pte, entry);
2264                 atomic_inc(&page[i]._mapcount);
2265                 pte_unmap(pte);
2266         }
2267
2268         /*
2269          * Set PG_double_map before dropping compound_mapcount to avoid
2270          * false-negative page_mapped().
2271          */
2272         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2273                 for (i = 0; i < HPAGE_PMD_NR; i++)
2274                         atomic_inc(&page[i]._mapcount);
2275         }
2276
2277         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2278                 /* Last compound_mapcount is gone. */
2279                 __dec_node_page_state(page, NR_ANON_THPS);
2280                 if (TestClearPageDoubleMap(page)) {
2281                         /* No need in mapcount reference anymore */
2282                         for (i = 0; i < HPAGE_PMD_NR; i++)
2283                                 atomic_dec(&page[i]._mapcount);
2284                 }
2285         }
2286
2287         smp_wmb(); /* make pte visible before pmd */
2288         pmd_populate(mm, pmd, pgtable);
2289
2290         if (freeze) {
2291                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2292                         page_remove_rmap(page + i, false);
2293                         put_page(page + i);
2294                 }
2295         }
2296 }
2297
2298 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2299                 unsigned long address, bool freeze, struct page *page)
2300 {
2301         spinlock_t *ptl;
2302         struct mmu_notifier_range range;
2303
2304         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2305                                 address & HPAGE_PMD_MASK,
2306                                 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2307         mmu_notifier_invalidate_range_start(&range);
2308         ptl = pmd_lock(vma->vm_mm, pmd);
2309
2310         /*
2311          * If caller asks to setup a migration entries, we need a page to check
2312          * pmd against. Otherwise we can end up replacing wrong page.
2313          */
2314         VM_BUG_ON(freeze && !page);
2315         if (page && page != pmd_page(*pmd))
2316                 goto out;
2317
2318         if (pmd_trans_huge(*pmd)) {
2319                 page = pmd_page(*pmd);
2320                 if (PageMlocked(page))
2321                         clear_page_mlock(page);
2322         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2323                 goto out;
2324         __split_huge_pmd_locked(vma, pmd, range.start, freeze);
2325 out:
2326         spin_unlock(ptl);
2327         /*
2328          * No need to double call mmu_notifier->invalidate_range() callback.
2329          * They are 3 cases to consider inside __split_huge_pmd_locked():
2330          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2331          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2332          *    fault will trigger a flush_notify before pointing to a new page
2333          *    (it is fine if the secondary mmu keeps pointing to the old zero
2334          *    page in the meantime)
2335          *  3) Split a huge pmd into pte pointing to the same page. No need
2336          *     to invalidate secondary tlb entry they are all still valid.
2337          *     any further changes to individual pte will notify. So no need
2338          *     to call mmu_notifier->invalidate_range()
2339          */
2340         mmu_notifier_invalidate_range_only_end(&range);
2341 }
2342
2343 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2344                 bool freeze, struct page *page)
2345 {
2346         pgd_t *pgd;
2347         p4d_t *p4d;
2348         pud_t *pud;
2349         pmd_t *pmd;
2350
2351         pgd = pgd_offset(vma->vm_mm, address);
2352         if (!pgd_present(*pgd))
2353                 return;
2354
2355         p4d = p4d_offset(pgd, address);
2356         if (!p4d_present(*p4d))
2357                 return;
2358
2359         pud = pud_offset(p4d, address);
2360         if (!pud_present(*pud))
2361                 return;
2362
2363         pmd = pmd_offset(pud, address);
2364
2365         __split_huge_pmd(vma, pmd, address, freeze, page);
2366 }
2367
2368 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2369                              unsigned long start,
2370                              unsigned long end,
2371                              long adjust_next)
2372 {
2373         /*
2374          * If the new start address isn't hpage aligned and it could
2375          * previously contain an hugepage: check if we need to split
2376          * an huge pmd.
2377          */
2378         if (start & ~HPAGE_PMD_MASK &&
2379             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2380             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2381                 split_huge_pmd_address(vma, start, false, NULL);
2382
2383         /*
2384          * If the new end address isn't hpage aligned and it could
2385          * previously contain an hugepage: check if we need to split
2386          * an huge pmd.
2387          */
2388         if (end & ~HPAGE_PMD_MASK &&
2389             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2390             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2391                 split_huge_pmd_address(vma, end, false, NULL);
2392
2393         /*
2394          * If we're also updating the vma->vm_next->vm_start, if the new
2395          * vm_next->vm_start isn't page aligned and it could previously
2396          * contain an hugepage: check if we need to split an huge pmd.
2397          */
2398         if (adjust_next > 0) {
2399                 struct vm_area_struct *next = vma->vm_next;
2400                 unsigned long nstart = next->vm_start;
2401                 nstart += adjust_next << PAGE_SHIFT;
2402                 if (nstart & ~HPAGE_PMD_MASK &&
2403                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2404                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2405                         split_huge_pmd_address(next, nstart, false, NULL);
2406         }
2407 }
2408
2409 static void unmap_page(struct page *page)
2410 {
2411         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2412                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2413         bool unmap_success;
2414
2415         VM_BUG_ON_PAGE(!PageHead(page), page);
2416
2417         if (PageAnon(page))
2418                 ttu_flags |= TTU_SPLIT_FREEZE;
2419
2420         unmap_success = try_to_unmap(page, ttu_flags);
2421         VM_BUG_ON_PAGE(!unmap_success, page);
2422 }
2423
2424 static void remap_page(struct page *page)
2425 {
2426         int i;
2427         if (PageTransHuge(page)) {
2428                 remove_migration_ptes(page, page, true);
2429         } else {
2430                 for (i = 0; i < HPAGE_PMD_NR; i++)
2431                         remove_migration_ptes(page + i, page + i, true);
2432         }
2433 }
2434
2435 static void __split_huge_page_tail(struct page *head, int tail,
2436                 struct lruvec *lruvec, struct list_head *list)
2437 {
2438         struct page *page_tail = head + tail;
2439
2440         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2441
2442         /*
2443          * Clone page flags before unfreezing refcount.
2444          *
2445          * After successful get_page_unless_zero() might follow flags change,
2446          * for exmaple lock_page() which set PG_waiters.
2447          */
2448         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2449         page_tail->flags |= (head->flags &
2450                         ((1L << PG_referenced) |
2451                          (1L << PG_swapbacked) |
2452                          (1L << PG_swapcache) |
2453                          (1L << PG_mlocked) |
2454                          (1L << PG_uptodate) |
2455                          (1L << PG_active) |
2456                          (1L << PG_workingset) |
2457                          (1L << PG_locked) |
2458                          (1L << PG_unevictable) |
2459                          (1L << PG_dirty)));
2460
2461         /* ->mapping in first tail page is compound_mapcount */
2462         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2463                         page_tail);
2464         page_tail->mapping = head->mapping;
2465         page_tail->index = head->index + tail;
2466
2467         /* Page flags must be visible before we make the page non-compound. */
2468         smp_wmb();
2469
2470         /*
2471          * Clear PageTail before unfreezing page refcount.
2472          *
2473          * After successful get_page_unless_zero() might follow put_page()
2474          * which needs correct compound_head().
2475          */
2476         clear_compound_head(page_tail);
2477
2478         /* Finally unfreeze refcount. Additional reference from page cache. */
2479         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2480                                           PageSwapCache(head)));
2481
2482         if (page_is_young(head))
2483                 set_page_young(page_tail);
2484         if (page_is_idle(head))
2485                 set_page_idle(page_tail);
2486
2487         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2488
2489         /*
2490          * always add to the tail because some iterators expect new
2491          * pages to show after the currently processed elements - e.g.
2492          * migrate_pages
2493          */
2494         lru_add_page_tail(head, page_tail, lruvec, list);
2495 }
2496
2497 static void __split_huge_page(struct page *page, struct list_head *list,
2498                 pgoff_t end, unsigned long flags)
2499 {
2500         struct page *head = compound_head(page);
2501         pg_data_t *pgdat = page_pgdat(head);
2502         struct lruvec *lruvec;
2503         struct address_space *swap_cache = NULL;
2504         unsigned long offset = 0;
2505         int i;
2506
2507         lruvec = mem_cgroup_page_lruvec(head, pgdat);
2508
2509         /* complete memcg works before add pages to LRU */
2510         mem_cgroup_split_huge_fixup(head);
2511
2512         if (PageAnon(head) && PageSwapCache(head)) {
2513                 swp_entry_t entry = { .val = page_private(head) };
2514
2515                 offset = swp_offset(entry);
2516                 swap_cache = swap_address_space(entry);
2517                 xa_lock(&swap_cache->i_pages);
2518         }
2519
2520         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2521                 __split_huge_page_tail(head, i, lruvec, list);
2522                 /* Some pages can be beyond i_size: drop them from page cache */
2523                 if (head[i].index >= end) {
2524                         ClearPageDirty(head + i);
2525                         __delete_from_page_cache(head + i, NULL);
2526                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2527                                 shmem_uncharge(head->mapping->host, 1);
2528                         put_page(head + i);
2529                 } else if (!PageAnon(page)) {
2530                         __xa_store(&head->mapping->i_pages, head[i].index,
2531                                         head + i, 0);
2532                 } else if (swap_cache) {
2533                         __xa_store(&swap_cache->i_pages, offset + i,
2534                                         head + i, 0);
2535                 }
2536         }
2537
2538         ClearPageCompound(head);
2539
2540         split_page_owner(head, HPAGE_PMD_ORDER);
2541
2542         /* See comment in __split_huge_page_tail() */
2543         if (PageAnon(head)) {
2544                 /* Additional pin to swap cache */
2545                 if (PageSwapCache(head)) {
2546                         page_ref_add(head, 2);
2547                         xa_unlock(&swap_cache->i_pages);
2548                 } else {
2549                         page_ref_inc(head);
2550                 }
2551         } else {
2552                 /* Additional pin to page cache */
2553                 page_ref_add(head, 2);
2554                 xa_unlock(&head->mapping->i_pages);
2555         }
2556
2557         spin_unlock_irqrestore(&pgdat->lru_lock, flags);
2558
2559         remap_page(head);
2560
2561         for (i = 0; i < HPAGE_PMD_NR; i++) {
2562                 struct page *subpage = head + i;
2563                 if (subpage == page)
2564                         continue;
2565                 unlock_page(subpage);
2566
2567                 /*
2568                  * Subpages may be freed if there wasn't any mapping
2569                  * like if add_to_swap() is running on a lru page that
2570                  * had its mapping zapped. And freeing these pages
2571                  * requires taking the lru_lock so we do the put_page
2572                  * of the tail pages after the split is complete.
2573                  */
2574                 put_page(subpage);
2575         }
2576 }
2577
2578 int total_mapcount(struct page *page)
2579 {
2580         int i, compound, ret;
2581
2582         VM_BUG_ON_PAGE(PageTail(page), page);
2583
2584         if (likely(!PageCompound(page)))
2585                 return atomic_read(&page->_mapcount) + 1;
2586
2587         compound = compound_mapcount(page);
2588         if (PageHuge(page))
2589                 return compound;
2590         ret = compound;
2591         for (i = 0; i < HPAGE_PMD_NR; i++)
2592                 ret += atomic_read(&page[i]._mapcount) + 1;
2593         /* File pages has compound_mapcount included in _mapcount */
2594         if (!PageAnon(page))
2595                 return ret - compound * HPAGE_PMD_NR;
2596         if (PageDoubleMap(page))
2597                 ret -= HPAGE_PMD_NR;
2598         return ret;
2599 }
2600
2601 /*
2602  * This calculates accurately how many mappings a transparent hugepage
2603  * has (unlike page_mapcount() which isn't fully accurate). This full
2604  * accuracy is primarily needed to know if copy-on-write faults can
2605  * reuse the page and change the mapping to read-write instead of
2606  * copying them. At the same time this returns the total_mapcount too.
2607  *
2608  * The function returns the highest mapcount any one of the subpages
2609  * has. If the return value is one, even if different processes are
2610  * mapping different subpages of the transparent hugepage, they can
2611  * all reuse it, because each process is reusing a different subpage.
2612  *
2613  * The total_mapcount is instead counting all virtual mappings of the
2614  * subpages. If the total_mapcount is equal to "one", it tells the
2615  * caller all mappings belong to the same "mm" and in turn the
2616  * anon_vma of the transparent hugepage can become the vma->anon_vma
2617  * local one as no other process may be mapping any of the subpages.
2618  *
2619  * It would be more accurate to replace page_mapcount() with
2620  * page_trans_huge_mapcount(), however we only use
2621  * page_trans_huge_mapcount() in the copy-on-write faults where we
2622  * need full accuracy to avoid breaking page pinning, because
2623  * page_trans_huge_mapcount() is slower than page_mapcount().
2624  */
2625 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2626 {
2627         int i, ret, _total_mapcount, mapcount;
2628
2629         /* hugetlbfs shouldn't call it */
2630         VM_BUG_ON_PAGE(PageHuge(page), page);
2631
2632         if (likely(!PageTransCompound(page))) {
2633                 mapcount = atomic_read(&page->_mapcount) + 1;
2634                 if (total_mapcount)
2635                         *total_mapcount = mapcount;
2636                 return mapcount;
2637         }
2638
2639         page = compound_head(page);
2640
2641         _total_mapcount = ret = 0;
2642         for (i = 0; i < HPAGE_PMD_NR; i++) {
2643                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2644                 ret = max(ret, mapcount);
2645                 _total_mapcount += mapcount;
2646         }
2647         if (PageDoubleMap(page)) {
2648                 ret -= 1;
2649                 _total_mapcount -= HPAGE_PMD_NR;
2650         }
2651         mapcount = compound_mapcount(page);
2652         ret += mapcount;
2653         _total_mapcount += mapcount;
2654         if (total_mapcount)
2655                 *total_mapcount = _total_mapcount;
2656         return ret;
2657 }
2658
2659 /* Racy check whether the huge page can be split */
2660 bool can_split_huge_page(struct page *page, int *pextra_pins)
2661 {
2662         int extra_pins;
2663
2664         /* Additional pins from page cache */
2665         if (PageAnon(page))
2666                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2667         else
2668                 extra_pins = HPAGE_PMD_NR;
2669         if (pextra_pins)
2670                 *pextra_pins = extra_pins;
2671         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2672 }
2673
2674 /*
2675  * This function splits huge page into normal pages. @page can point to any
2676  * subpage of huge page to split. Split doesn't change the position of @page.
2677  *
2678  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2679  * The huge page must be locked.
2680  *
2681  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2682  *
2683  * Both head page and tail pages will inherit mapping, flags, and so on from
2684  * the hugepage.
2685  *
2686  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2687  * they are not mapped.
2688  *
2689  * Returns 0 if the hugepage is split successfully.
2690  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2691  * us.
2692  */
2693 int split_huge_page_to_list(struct page *page, struct list_head *list)
2694 {
2695         struct page *head = compound_head(page);
2696         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2697         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2698         struct anon_vma *anon_vma = NULL;
2699         struct address_space *mapping = NULL;
2700         int count, mapcount, extra_pins, ret;
2701         bool mlocked;
2702         unsigned long flags;
2703         pgoff_t end;
2704
2705         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2706         VM_BUG_ON_PAGE(!PageLocked(page), page);
2707         VM_BUG_ON_PAGE(!PageCompound(page), page);
2708
2709         if (PageWriteback(page))
2710                 return -EBUSY;
2711
2712         if (PageAnon(head)) {
2713                 /*
2714                  * The caller does not necessarily hold an mmap_sem that would
2715                  * prevent the anon_vma disappearing so we first we take a
2716                  * reference to it and then lock the anon_vma for write. This
2717                  * is similar to page_lock_anon_vma_read except the write lock
2718                  * is taken to serialise against parallel split or collapse
2719                  * operations.
2720                  */
2721                 anon_vma = page_get_anon_vma(head);
2722                 if (!anon_vma) {
2723                         ret = -EBUSY;
2724                         goto out;
2725                 }
2726                 end = -1;
2727                 mapping = NULL;
2728                 anon_vma_lock_write(anon_vma);
2729         } else {
2730                 mapping = head->mapping;
2731
2732                 /* Truncated ? */
2733                 if (!mapping) {
2734                         ret = -EBUSY;
2735                         goto out;
2736                 }
2737
2738                 anon_vma = NULL;
2739                 i_mmap_lock_read(mapping);
2740
2741                 /*
2742                  *__split_huge_page() may need to trim off pages beyond EOF:
2743                  * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2744                  * which cannot be nested inside the page tree lock. So note
2745                  * end now: i_size itself may be changed at any moment, but
2746                  * head page lock is good enough to serialize the trimming.
2747                  */
2748                 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2749         }
2750
2751         /*
2752          * Racy check if we can split the page, before unmap_page() will
2753          * split PMDs
2754          */
2755         if (!can_split_huge_page(head, &extra_pins)) {
2756                 ret = -EBUSY;
2757                 goto out_unlock;
2758         }
2759
2760         mlocked = PageMlocked(page);
2761         unmap_page(head);
2762         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2763
2764         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2765         if (mlocked)
2766                 lru_add_drain();
2767
2768         /* prevent PageLRU to go away from under us, and freeze lru stats */
2769         spin_lock_irqsave(&pgdata->lru_lock, flags);
2770
2771         if (mapping) {
2772                 XA_STATE(xas, &mapping->i_pages, page_index(head));
2773
2774                 /*
2775                  * Check if the head page is present in page cache.
2776                  * We assume all tail are present too, if head is there.
2777                  */
2778                 xa_lock(&mapping->i_pages);
2779                 if (xas_load(&xas) != head)
2780                         goto fail;
2781         }
2782
2783         /* Prevent deferred_split_scan() touching ->_refcount */
2784         spin_lock(&ds_queue->split_queue_lock);
2785         count = page_count(head);
2786         mapcount = total_mapcount(head);
2787         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2788                 if (!list_empty(page_deferred_list(head))) {
2789                         ds_queue->split_queue_len--;
2790                         list_del(page_deferred_list(head));
2791                 }
2792                 if (mapping)
2793                         __dec_node_page_state(page, NR_SHMEM_THPS);
2794                 spin_unlock(&ds_queue->split_queue_lock);
2795                 __split_huge_page(page, list, end, flags);
2796                 if (PageSwapCache(head)) {
2797                         swp_entry_t entry = { .val = page_private(head) };
2798
2799                         ret = split_swap_cluster(entry);
2800                 } else
2801                         ret = 0;
2802         } else {
2803                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2804                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2805                                         mapcount, count);
2806                         if (PageTail(page))
2807                                 dump_page(head, NULL);
2808                         dump_page(page, "total_mapcount(head) > 0");
2809                         BUG();
2810                 }
2811                 spin_unlock(&ds_queue->split_queue_lock);
2812 fail:           if (mapping)
2813                         xa_unlock(&mapping->i_pages);
2814                 spin_unlock_irqrestore(&pgdata->lru_lock, flags);
2815                 remap_page(head);
2816                 ret = -EBUSY;
2817         }
2818
2819 out_unlock:
2820         if (anon_vma) {
2821                 anon_vma_unlock_write(anon_vma);
2822                 put_anon_vma(anon_vma);
2823         }
2824         if (mapping)
2825                 i_mmap_unlock_read(mapping);
2826 out:
2827         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2828         return ret;
2829 }
2830
2831 void free_transhuge_page(struct page *page)
2832 {
2833         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2834         unsigned long flags;
2835
2836         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2837         if (!list_empty(page_deferred_list(page))) {
2838                 ds_queue->split_queue_len--;
2839                 list_del(page_deferred_list(page));
2840         }
2841         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2842         free_compound_page(page);
2843 }
2844
2845 void deferred_split_huge_page(struct page *page)
2846 {
2847         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2848 #ifdef CONFIG_MEMCG
2849         struct mem_cgroup *memcg = compound_head(page)->mem_cgroup;
2850 #endif
2851         unsigned long flags;
2852
2853         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2854
2855         /*
2856          * The try_to_unmap() in page reclaim path might reach here too,
2857          * this may cause a race condition to corrupt deferred split queue.
2858          * And, if page reclaim is already handling the same page, it is
2859          * unnecessary to handle it again in shrinker.
2860          *
2861          * Check PageSwapCache to determine if the page is being
2862          * handled by page reclaim since THP swap would add the page into
2863          * swap cache before calling try_to_unmap().
2864          */
2865         if (PageSwapCache(page))
2866                 return;
2867
2868         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2869         if (list_empty(page_deferred_list(page))) {
2870                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2871                 list_add_tail(page_deferred_list(page), &ds_queue->split_queue);
2872                 ds_queue->split_queue_len++;
2873 #ifdef CONFIG_MEMCG
2874                 if (memcg)
2875                         memcg_set_shrinker_bit(memcg, page_to_nid(page),
2876                                                deferred_split_shrinker.id);
2877 #endif
2878         }
2879         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2880 }
2881
2882 static unsigned long deferred_split_count(struct shrinker *shrink,
2883                 struct shrink_control *sc)
2884 {
2885         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2886         struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2887
2888 #ifdef CONFIG_MEMCG
2889         if (sc->memcg)
2890                 ds_queue = &sc->memcg->deferred_split_queue;
2891 #endif
2892         return READ_ONCE(ds_queue->split_queue_len);
2893 }
2894
2895 static unsigned long deferred_split_scan(struct shrinker *shrink,
2896                 struct shrink_control *sc)
2897 {
2898         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2899         struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2900         unsigned long flags;
2901         LIST_HEAD(list), *pos, *next;
2902         struct page *page;
2903         int split = 0;
2904
2905 #ifdef CONFIG_MEMCG
2906         if (sc->memcg)
2907                 ds_queue = &sc->memcg->deferred_split_queue;
2908 #endif
2909
2910         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2911         /* Take pin on all head pages to avoid freeing them under us */
2912         list_for_each_safe(pos, next, &ds_queue->split_queue) {
2913                 page = list_entry((void *)pos, struct page, mapping);
2914                 page = compound_head(page);
2915                 if (get_page_unless_zero(page)) {
2916                         list_move(page_deferred_list(page), &list);
2917                 } else {
2918                         /* We lost race with put_compound_page() */
2919                         list_del_init(page_deferred_list(page));
2920                         ds_queue->split_queue_len--;
2921                 }
2922                 if (!--sc->nr_to_scan)
2923                         break;
2924         }
2925         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2926
2927         list_for_each_safe(pos, next, &list) {
2928                 page = list_entry((void *)pos, struct page, mapping);
2929                 if (!trylock_page(page))
2930                         goto next;
2931                 /* split_huge_page() removes page from list on success */
2932                 if (!split_huge_page(page))
2933                         split++;
2934                 unlock_page(page);
2935 next:
2936                 put_page(page);
2937         }
2938
2939         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2940         list_splice_tail(&list, &ds_queue->split_queue);
2941         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2942
2943         /*
2944          * Stop shrinker if we didn't split any page, but the queue is empty.
2945          * This can happen if pages were freed under us.
2946          */
2947         if (!split && list_empty(&ds_queue->split_queue))
2948                 return SHRINK_STOP;
2949         return split;
2950 }
2951
2952 static struct shrinker deferred_split_shrinker = {
2953         .count_objects = deferred_split_count,
2954         .scan_objects = deferred_split_scan,
2955         .seeks = DEFAULT_SEEKS,
2956         .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |
2957                  SHRINKER_NONSLAB,
2958 };
2959
2960 #ifdef CONFIG_DEBUG_FS
2961 static int split_huge_pages_set(void *data, u64 val)
2962 {
2963         struct zone *zone;
2964         struct page *page;
2965         unsigned long pfn, max_zone_pfn;
2966         unsigned long total = 0, split = 0;
2967
2968         if (val != 1)
2969                 return -EINVAL;
2970
2971         for_each_populated_zone(zone) {
2972                 max_zone_pfn = zone_end_pfn(zone);
2973                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2974                         if (!pfn_valid(pfn))
2975                                 continue;
2976
2977                         page = pfn_to_page(pfn);
2978                         if (!get_page_unless_zero(page))
2979                                 continue;
2980
2981                         if (zone != page_zone(page))
2982                                 goto next;
2983
2984                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2985                                 goto next;
2986
2987                         total++;
2988                         lock_page(page);
2989                         if (!split_huge_page(page))
2990                                 split++;
2991                         unlock_page(page);
2992 next:
2993                         put_page(page);
2994                 }
2995         }
2996
2997         pr_info("%lu of %lu THP split\n", split, total);
2998
2999         return 0;
3000 }
3001 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
3002                 "%llu\n");
3003
3004 static int __init split_huge_pages_debugfs(void)
3005 {
3006         debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
3007                             &split_huge_pages_fops);
3008         return 0;
3009 }
3010 late_initcall(split_huge_pages_debugfs);
3011 #endif
3012
3013 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
3014 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
3015                 struct page *page)
3016 {
3017         struct vm_area_struct *vma = pvmw->vma;
3018         struct mm_struct *mm = vma->vm_mm;
3019         unsigned long address = pvmw->address;
3020         pmd_t pmdval;
3021         swp_entry_t entry;
3022         pmd_t pmdswp;
3023
3024         if (!(pvmw->pmd && !pvmw->pte))
3025                 return;
3026
3027         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
3028         pmdval = *pvmw->pmd;
3029         pmdp_invalidate(vma, address, pvmw->pmd);
3030         if (pmd_dirty(pmdval))
3031                 set_page_dirty(page);
3032         entry = make_migration_entry(page, pmd_write(pmdval));
3033         pmdswp = swp_entry_to_pmd(entry);
3034         if (pmd_soft_dirty(pmdval))
3035                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
3036         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
3037         page_remove_rmap(page, true);
3038         put_page(page);
3039 }
3040
3041 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
3042 {
3043         struct vm_area_struct *vma = pvmw->vma;
3044         struct mm_struct *mm = vma->vm_mm;
3045         unsigned long address = pvmw->address;
3046         unsigned long mmun_start = address & HPAGE_PMD_MASK;
3047         pmd_t pmde;
3048         swp_entry_t entry;
3049
3050         if (!(pvmw->pmd && !pvmw->pte))
3051                 return;
3052
3053         entry = pmd_to_swp_entry(*pvmw->pmd);
3054         get_page(new);
3055         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
3056         if (pmd_swp_soft_dirty(*pvmw->pmd))
3057                 pmde = pmd_mksoft_dirty(pmde);
3058         if (is_write_migration_entry(entry))
3059                 pmde = maybe_pmd_mkwrite(pmde, vma);
3060
3061         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
3062         if (PageAnon(new))
3063                 page_add_anon_rmap(new, vma, mmun_start, true);
3064         else
3065                 page_add_file_rmap(new, true);
3066         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
3067         if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
3068                 mlock_vma_page(new);
3069         update_mmu_cache_pmd(vma, address, pvmw->pmd);
3070 }
3071 #endif