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 bool is_transparent_hugepage(struct page *page)
 531 {
 532         if (!PageCompound(page))
 533                 return 0;
 534
 535         page = compound_head(page);
 536         return is_huge_zero_page(page) ||
 537                page[1].compound_dtor == TRANSHUGE_PAGE_DTOR;
 538 }
 539 EXPORT_SYMBOL_GPL(is_transparent_hugepage);
 540
 541 static unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
 542                 loff_t off, unsigned long flags, unsigned long size)
 543 {
 544         unsigned long addr;
 545         loff_t off_end = off + len;
 546         loff_t off_align = round_up(off, size);
 547         unsigned long len_pad;
 548
 549         if (off_end <= off_align || (off_end - off_align) < size)
 550                 return 0;
 551
 552         len_pad = len + size;
 553         if (len_pad < len || (off + len_pad) < off)
 554                 return 0;
 555
 556         addr = current->mm->get_unmapped_area(filp, 0, len_pad,
 557                                               off >> PAGE_SHIFT, flags);
 558         if (IS_ERR_VALUE(addr))
 559                 return 0;
 560
 561         addr += (off - addr) & (size - 1);
 562         return addr;
 563 }
 564
 565 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 566                 unsigned long len, unsigned long pgoff, unsigned long flags)
 567 {
 568         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 569
 570         if (addr)
 571                 goto out;
 572         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
 573                 goto out;
 574
 575         addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
 576         if (addr)
 577                 return addr;
 578
 579  out:
 580         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 581 }
 582 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 583
 584 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
 585                         struct page *page, gfp_t gfp)
 586 {
 587         struct vm_area_struct *vma = vmf->vma;
 588         struct mem_cgroup *memcg;
 589         pgtable_t pgtable;
 590         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 591         vm_fault_t ret = 0;
 592
 593         VM_BUG_ON_PAGE(!PageCompound(page), page);
 594
 595         if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
 596                 put_page(page);
 597                 count_vm_event(THP_FAULT_FALLBACK);
 598                 return VM_FAULT_FALLBACK;
 599         }
 600
 601         pgtable = pte_alloc_one(vma->vm_mm);
 602         if (unlikely(!pgtable)) {
 603                 ret = VM_FAULT_OOM;
 604                 goto release;
 605         }
 606
 607         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
 608         /*
 609          * The memory barrier inside __SetPageUptodate makes sure that
 610          * clear_huge_page writes become visible before the set_pmd_at()
 611          * write.
 612          */
 613         __SetPageUptodate(page);
 614
 615         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 616         if (unlikely(!pmd_none(*vmf->pmd))) {
 617                 goto unlock_release;
 618         } else {
 619                 pmd_t entry;
 620
 621                 ret = check_stable_address_space(vma->vm_mm);
 622                 if (ret)
 623                         goto unlock_release;
 624
 625                 /* Deliver the page fault to userland */
 626                 if (userfaultfd_missing(vma)) {
 627                         vm_fault_t ret2;
 628
 629                         spin_unlock(vmf->ptl);
 630                         mem_cgroup_cancel_charge(page, memcg, true);
 631                         put_page(page);
 632                         pte_free(vma->vm_mm, pgtable);
 633                         ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
 634                         VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
 635                         return ret2;
 636                 }
 637
 638                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 639                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 640                 page_add_new_anon_rmap(page, vma, haddr, true);
 641                 mem_cgroup_commit_charge(page, memcg, false, true);
 642                 lru_cache_add_active_or_unevictable(page, vma);
 643                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 644                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 645                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 646                 mm_inc_nr_ptes(vma->vm_mm);
 647                 spin_unlock(vmf->ptl);
 648                 count_vm_event(THP_FAULT_ALLOC);
 649                 count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
 650         }
 651
 652         return 0;
 653 unlock_release:
 654         spin_unlock(vmf->ptl);
 655 release:
 656         if (pgtable)
 657                 pte_free(vma->vm_mm, pgtable);
 658         mem_cgroup_cancel_charge(page, memcg, true);
 659         put_page(page);
 660         return ret;
 661
 662 }
 663
 664 /*
 665  * always: directly stall for all thp allocations
 666  * defer: wake kswapd and fail if not immediately available
 667  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
 668  *                fail if not immediately available
 669  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
 670  *          available
 671  * never: never stall for any thp allocation
 672  */
 673 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
 674 {
 675         const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
 676
 677         /* Always do synchronous compaction */
 678         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 679                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
 680
 681         /* Kick kcompactd and fail quickly */
 682         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 683                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
 684
 685         /* Synchronous compaction if madvised, otherwise kick kcompactd */
 686         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 687                 return GFP_TRANSHUGE_LIGHT |
 688                         (vma_madvised ? __GFP_DIRECT_RECLAIM :
 689                                         __GFP_KSWAPD_RECLAIM);
 690
 691         /* Only do synchronous compaction if madvised */
 692         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 693                 return GFP_TRANSHUGE_LIGHT |
 694                        (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
 695
 696         return GFP_TRANSHUGE_LIGHT;
 697 }
 698
 699 /* Caller must hold page table lock. */
 700 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 701                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 702                 struct page *zero_page)
 703 {
 704         pmd_t entry;
 705         if (!pmd_none(*pmd))
 706                 return false;
 707         entry = mk_pmd(zero_page, vma->vm_page_prot);
 708         entry = pmd_mkhuge(entry);
 709         if (pgtable)
 710                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 711         set_pmd_at(mm, haddr, pmd, entry);
 712         mm_inc_nr_ptes(mm);
 713         return true;
 714 }
 715
 716 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 717 {
 718         struct vm_area_struct *vma = vmf->vma;
 719         gfp_t gfp;
 720         struct page *page;
 721         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 722
 723         if (!transhuge_vma_suitable(vma, haddr))
 724                 return VM_FAULT_FALLBACK;
 725         if (unlikely(anon_vma_prepare(vma)))
 726                 return VM_FAULT_OOM;
 727         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 728                 return VM_FAULT_OOM;
 729         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
 730                         !mm_forbids_zeropage(vma->vm_mm) &&
 731                         transparent_hugepage_use_zero_page()) {
 732                 pgtable_t pgtable;
 733                 struct page *zero_page;
 734                 bool set;
 735                 vm_fault_t ret;
 736                 pgtable = pte_alloc_one(vma->vm_mm);
 737                 if (unlikely(!pgtable))
 738                         return VM_FAULT_OOM;
 739                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
 740                 if (unlikely(!zero_page)) {
 741                         pte_free(vma->vm_mm, pgtable);
 742                         count_vm_event(THP_FAULT_FALLBACK);
 743                         return VM_FAULT_FALLBACK;
 744                 }
 745                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 746                 ret = 0;
 747                 set = false;
 748                 if (pmd_none(*vmf->pmd)) {
 749                         ret = check_stable_address_space(vma->vm_mm);
 750                         if (ret) {
 751                                 spin_unlock(vmf->ptl);
 752                         } else if (userfaultfd_missing(vma)) {
 753                                 spin_unlock(vmf->ptl);
 754                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
 755                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 756                         } else {
 757                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
 758                                                    haddr, vmf->pmd, zero_page);
 759                                 spin_unlock(vmf->ptl);
 760                                 set = true;
 761                         }
 762                 } else
 763                         spin_unlock(vmf->ptl);
 764                 if (!set)
 765                         pte_free(vma->vm_mm, pgtable);
 766                 return ret;
 767         }
 768         gfp = alloc_hugepage_direct_gfpmask(vma);
 769         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 770         if (unlikely(!page)) {
 771                 count_vm_event(THP_FAULT_FALLBACK);
 772                 return VM_FAULT_FALLBACK;
 773         }
 774         prep_transhuge_page(page);
 775         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
 776 }
 777
 778 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 779                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
 780                 pgtable_t pgtable)
 781 {
 782         struct mm_struct *mm = vma->vm_mm;
 783         pmd_t entry;
 784         spinlock_t *ptl;
 785
 786         ptl = pmd_lock(mm, pmd);
 787         if (!pmd_none(*pmd)) {
 788                 if (write) {
 789                         if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
 790                                 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
 791                                 goto out_unlock;
 792                         }
 793                         entry = pmd_mkyoung(*pmd);
 794                         entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 795                         if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
 796                                 update_mmu_cache_pmd(vma, addr, pmd);
 797                 }
 798
 799                 goto out_unlock;
 800         }
 801
 802         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 803         if (pfn_t_devmap(pfn))
 804                 entry = pmd_mkdevmap(entry);
 805         if (write) {
 806                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 807                 entry = maybe_pmd_mkwrite(entry, vma);
 808         }
 809
 810         if (pgtable) {
 811                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 812                 mm_inc_nr_ptes(mm);
 813                 pgtable = NULL;
 814         }
 815
 816         set_pmd_at(mm, addr, pmd, entry);
 817         update_mmu_cache_pmd(vma, addr, pmd);
 818
 819 out_unlock:
 820         spin_unlock(ptl);
 821         if (pgtable)
 822                 pte_free(mm, pgtable);
 823 }
 824
 825 vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write)
 826 {
 827         unsigned long addr = vmf->address & PMD_MASK;
 828         struct vm_area_struct *vma = vmf->vma;
 829         pgprot_t pgprot = vma->vm_page_prot;
 830         pgtable_t pgtable = NULL;
 831
 832         /*
 833          * If we had pmd_special, we could avoid all these restrictions,
 834          * but we need to be consistent with PTEs and architectures that
 835          * can't support a 'special' bit.
 836          */
 837         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 838                         !pfn_t_devmap(pfn));
 839         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 840                                                 (VM_PFNMAP|VM_MIXEDMAP));
 841         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 842
 843         if (addr < vma->vm_start || addr >= vma->vm_end)
 844                 return VM_FAULT_SIGBUS;
 845
 846         if (arch_needs_pgtable_deposit()) {
 847                 pgtable = pte_alloc_one(vma->vm_mm);
 848                 if (!pgtable)
 849                         return VM_FAULT_OOM;
 850         }
 851
 852         track_pfn_insert(vma, &pgprot, pfn);
 853
 854         insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
 855         return VM_FAULT_NOPAGE;
 856 }
 857 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
 858
 859 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 860 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 861 {
 862         if (likely(vma->vm_flags & VM_WRITE))
 863                 pud = pud_mkwrite(pud);
 864         return pud;
 865 }
 866
 867 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 868                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 869 {
 870         struct mm_struct *mm = vma->vm_mm;
 871         pud_t entry;
 872         spinlock_t *ptl;
 873
 874         ptl = pud_lock(mm, pud);
 875         if (!pud_none(*pud)) {
 876                 if (write) {
 877                         if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
 878                                 WARN_ON_ONCE(!is_huge_zero_pud(*pud));
 879                                 goto out_unlock;
 880                         }
 881                         entry = pud_mkyoung(*pud);
 882                         entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
 883                         if (pudp_set_access_flags(vma, addr, pud, entry, 1))
 884                                 update_mmu_cache_pud(vma, addr, pud);
 885                 }
 886                 goto out_unlock;
 887         }
 888
 889         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
 890         if (pfn_t_devmap(pfn))
 891                 entry = pud_mkdevmap(entry);
 892         if (write) {
 893                 entry = pud_mkyoung(pud_mkdirty(entry));
 894                 entry = maybe_pud_mkwrite(entry, vma);
 895         }
 896         set_pud_at(mm, addr, pud, entry);
 897         update_mmu_cache_pud(vma, addr, pud);
 898
 899 out_unlock:
 900         spin_unlock(ptl);
 901 }
 902
 903 vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
 904 {
 905         unsigned long addr = vmf->address & PUD_MASK;
 906         struct vm_area_struct *vma = vmf->vma;
 907         pgprot_t pgprot = vma->vm_page_prot;
 908
 909         /*
 910          * If we had pud_special, we could avoid all these restrictions,
 911          * but we need to be consistent with PTEs and architectures that
 912          * can't support a 'special' bit.
 913          */
 914         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 915                         !pfn_t_devmap(pfn));
 916         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 917                                                 (VM_PFNMAP|VM_MIXEDMAP));
 918         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 919
 920         if (addr < vma->vm_start || addr >= vma->vm_end)
 921                 return VM_FAULT_SIGBUS;
 922
 923         track_pfn_insert(vma, &pgprot, pfn);
 924
 925         insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
 926         return VM_FAULT_NOPAGE;
 927 }
 928 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
 929 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 930
 931 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
 932                 pmd_t *pmd, int flags)
 933 {
 934         pmd_t _pmd;
 935
 936         _pmd = pmd_mkyoung(*pmd);
 937         if (flags & FOLL_WRITE)
 938                 _pmd = pmd_mkdirty(_pmd);
 939         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 940                                 pmd, _pmd, flags & FOLL_WRITE))
 941                 update_mmu_cache_pmd(vma, addr, pmd);
 942 }
 943
 944 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 945                 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
 946 {
 947         unsigned long pfn = pmd_pfn(*pmd);
 948         struct mm_struct *mm = vma->vm_mm;
 949         struct page *page;
 950
 951         assert_spin_locked(pmd_lockptr(mm, pmd));
 952
 953         /*
 954          * When we COW a devmap PMD entry, we split it into PTEs, so we should
 955          * not be in this function with `flags & FOLL_COW` set.
 956          */
 957         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
 958
 959         if (flags & FOLL_WRITE && !pmd_write(*pmd))
 960                 return NULL;
 961
 962         if (pmd_present(*pmd) && pmd_devmap(*pmd))
 963                 /* pass */;
 964         else
 965                 return NULL;
 966
 967         if (flags & FOLL_TOUCH)
 968                 touch_pmd(vma, addr, pmd, flags);
 969
 970         /*
 971          * device mapped pages can only be returned if the
 972          * caller will manage the page reference count.
 973          */
 974         if (!(flags & FOLL_GET))
 975                 return ERR_PTR(-EEXIST);
 976
 977         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
 978         *pgmap = get_dev_pagemap(pfn, *pgmap);
 979         if (!*pgmap)
 980                 return ERR_PTR(-EFAULT);
 981         page = pfn_to_page(pfn);
 982         get_page(page);
 983
 984         return page;
 985 }
 986
 987 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 988                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 989                   struct vm_area_struct *vma)
 990 {
 991         spinlock_t *dst_ptl, *src_ptl;
 992         struct page *src_page;
 993         pmd_t pmd;
 994         pgtable_t pgtable = NULL;
 995         int ret = -ENOMEM;
 996
 997         /* Skip if can be re-fill on fault */
 998         if (!vma_is_anonymous(vma))
 999                 return 0;
1000
1001         pgtable = pte_alloc_one(dst_mm);
1002         if (unlikely(!pgtable))
1003                 goto out;
1004
1005         dst_ptl = pmd_lock(dst_mm, dst_pmd);
1006         src_ptl = pmd_lockptr(src_mm, src_pmd);
1007         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1008
1009         ret = -EAGAIN;
1010         pmd = *src_pmd;
1011
1012 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1013         if (unlikely(is_swap_pmd(pmd))) {
1014                 swp_entry_t entry = pmd_to_swp_entry(pmd);
1015
1016                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
1017                 if (is_write_migration_entry(entry)) {
1018                         make_migration_entry_read(&entry);
1019                         pmd = swp_entry_to_pmd(entry);
1020                         if (pmd_swp_soft_dirty(*src_pmd))
1021                                 pmd = pmd_swp_mksoft_dirty(pmd);
1022                         set_pmd_at(src_mm, addr, src_pmd, pmd);
1023                 }
1024                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1025                 mm_inc_nr_ptes(dst_mm);
1026                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1027                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1028                 ret = 0;
1029                 goto out_unlock;
1030         }
1031 #endif
1032
1033         if (unlikely(!pmd_trans_huge(pmd))) {
1034                 pte_free(dst_mm, pgtable);
1035                 goto out_unlock;
1036         }
1037         /*
1038          * When page table lock is held, the huge zero pmd should not be
1039          * under splitting since we don't split the page itself, only pmd to
1040          * a page table.
1041          */
1042         if (is_huge_zero_pmd(pmd)) {
1043                 struct page *zero_page;
1044                 /*
1045                  * get_huge_zero_page() will never allocate a new page here,
1046                  * since we already have a zero page to copy. It just takes a
1047                  * reference.
1048                  */
1049                 zero_page = mm_get_huge_zero_page(dst_mm);
1050                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1051                                 zero_page);
1052                 ret = 0;
1053                 goto out_unlock;
1054         }
1055
1056         src_page = pmd_page(pmd);
1057         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1058         get_page(src_page);
1059         page_dup_rmap(src_page, true);
1060         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1061         mm_inc_nr_ptes(dst_mm);
1062         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1063
1064         pmdp_set_wrprotect(src_mm, addr, src_pmd);
1065         pmd = pmd_mkold(pmd_wrprotect(pmd));
1066         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1067
1068         ret = 0;
1069 out_unlock:
1070         spin_unlock(src_ptl);
1071         spin_unlock(dst_ptl);
1072 out:
1073         return ret;
1074 }
1075
1076 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1077 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1078                 pud_t *pud, int flags)
1079 {
1080         pud_t _pud;
1081
1082         _pud = pud_mkyoung(*pud);
1083         if (flags & FOLL_WRITE)
1084                 _pud = pud_mkdirty(_pud);
1085         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1086                                 pud, _pud, flags & FOLL_WRITE))
1087                 update_mmu_cache_pud(vma, addr, pud);
1088 }
1089
1090 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1091                 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1092 {
1093         unsigned long pfn = pud_pfn(*pud);
1094         struct mm_struct *mm = vma->vm_mm;
1095         struct page *page;
1096
1097         assert_spin_locked(pud_lockptr(mm, pud));
1098
1099         if (flags & FOLL_WRITE && !pud_write(*pud))
1100                 return NULL;
1101
1102         if (pud_present(*pud) && pud_devmap(*pud))
1103                 /* pass */;
1104         else
1105                 return NULL;
1106
1107         if (flags & FOLL_TOUCH)
1108                 touch_pud(vma, addr, pud, flags);
1109
1110         /*
1111          * device mapped pages can only be returned if the
1112          * caller will manage the page reference count.
1113          */
1114         if (!(flags & FOLL_GET))
1115                 return ERR_PTR(-EEXIST);
1116
1117         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1118         *pgmap = get_dev_pagemap(pfn, *pgmap);
1119         if (!*pgmap)
1120                 return ERR_PTR(-EFAULT);
1121         page = pfn_to_page(pfn);
1122         get_page(page);
1123
1124         return page;
1125 }
1126
1127 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1128                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1129                   struct vm_area_struct *vma)
1130 {
1131         spinlock_t *dst_ptl, *src_ptl;
1132         pud_t pud;
1133         int ret;
1134
1135         dst_ptl = pud_lock(dst_mm, dst_pud);
1136         src_ptl = pud_lockptr(src_mm, src_pud);
1137         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1138
1139         ret = -EAGAIN;
1140         pud = *src_pud;
1141         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1142                 goto out_unlock;
1143
1144         /*
1145          * When page table lock is held, the huge zero pud should not be
1146          * under splitting since we don't split the page itself, only pud to
1147          * a page table.
1148          */
1149         if (is_huge_zero_pud(pud)) {
1150                 /* No huge zero pud yet */
1151         }
1152
1153         pudp_set_wrprotect(src_mm, addr, src_pud);
1154         pud = pud_mkold(pud_wrprotect(pud));
1155         set_pud_at(dst_mm, addr, dst_pud, pud);
1156
1157         ret = 0;
1158 out_unlock:
1159         spin_unlock(src_ptl);
1160         spin_unlock(dst_ptl);
1161         return ret;
1162 }
1163
1164 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1165 {
1166         pud_t entry;
1167         unsigned long haddr;
1168         bool write = vmf->flags & FAULT_FLAG_WRITE;
1169
1170         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1171         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1172                 goto unlock;
1173
1174         entry = pud_mkyoung(orig_pud);
1175         if (write)
1176                 entry = pud_mkdirty(entry);
1177         haddr = vmf->address & HPAGE_PUD_MASK;
1178         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1179                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1180
1181 unlock:
1182         spin_unlock(vmf->ptl);
1183 }
1184 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1185
1186 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1187 {
1188         pmd_t entry;
1189         unsigned long haddr;
1190         bool write = vmf->flags & FAULT_FLAG_WRITE;
1191
1192         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1193         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1194                 goto unlock;
1195
1196         entry = pmd_mkyoung(orig_pmd);
1197         if (write)
1198                 entry = pmd_mkdirty(entry);
1199         haddr = vmf->address & HPAGE_PMD_MASK;
1200         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1201                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1202
1203 unlock:
1204         spin_unlock(vmf->ptl);
1205 }
1206
1207 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1208                         pmd_t orig_pmd, struct page *page)
1209 {
1210         struct vm_area_struct *vma = vmf->vma;
1211         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1212         struct mem_cgroup *memcg;
1213         pgtable_t pgtable;
1214         pmd_t _pmd;
1215         int i;
1216         vm_fault_t ret = 0;
1217         struct page **pages;
1218         struct mmu_notifier_range range;
1219
1220         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1221                               GFP_KERNEL);
1222         if (unlikely(!pages)) {
1223                 ret |= VM_FAULT_OOM;
1224                 goto out;
1225         }
1226
1227         for (i = 0; i < HPAGE_PMD_NR; i++) {
1228                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1229                                                vmf->address, page_to_nid(page));
1230                 if (unlikely(!pages[i] ||
1231                              mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1232                                      GFP_KERNEL, &memcg, false))) {
1233                         if (pages[i])
1234                                 put_page(pages[i]);
1235                         while (--i >= 0) {
1236                                 memcg = (void *)page_private(pages[i]);
1237                                 set_page_private(pages[i], 0);
1238                                 mem_cgroup_cancel_charge(pages[i], memcg,
1239                                                 false);
1240                                 put_page(pages[i]);
1241                         }
1242                         kfree(pages);
1243                         ret |= VM_FAULT_OOM;
1244                         goto out;
1245                 }
1246                 set_page_private(pages[i], (unsigned long)memcg);
1247         }
1248
1249         for (i = 0; i < HPAGE_PMD_NR; i++) {
1250                 copy_user_highpage(pages[i], page + i,
1251                                    haddr + PAGE_SIZE * i, vma);
1252                 __SetPageUptodate(pages[i]);
1253                 cond_resched();
1254         }
1255
1256         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1257                                 haddr, haddr + HPAGE_PMD_SIZE);
1258         mmu_notifier_invalidate_range_start(&range);
1259
1260         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1261         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1262                 goto out_free_pages;
1263         VM_BUG_ON_PAGE(!PageHead(page), page);
1264
1265         /*
1266          * Leave pmd empty until pte is filled note we must notify here as
1267          * concurrent CPU thread might write to new page before the call to
1268          * mmu_notifier_invalidate_range_end() happens which can lead to a
1269          * device seeing memory write in different order than CPU.
1270          *
1271          * See Documentation/vm/mmu_notifier.rst
1272          */
1273         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1274
1275         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1276         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1277
1278         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1279                 pte_t entry;
1280                 entry = mk_pte(pages[i], vma->vm_page_prot);
1281                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1282                 memcg = (void *)page_private(pages[i]);
1283                 set_page_private(pages[i], 0);
1284                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1285                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1286                 lru_cache_add_active_or_unevictable(pages[i], vma);
1287                 vmf->pte = pte_offset_map(&_pmd, haddr);
1288                 VM_BUG_ON(!pte_none(*vmf->pte));
1289                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1290                 pte_unmap(vmf->pte);
1291         }
1292         kfree(pages);
1293
1294         smp_wmb(); /* make pte visible before pmd */
1295         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1296         page_remove_rmap(page, true);
1297         spin_unlock(vmf->ptl);
1298
1299         /*
1300          * No need to double call mmu_notifier->invalidate_range() callback as
1301          * the above pmdp_huge_clear_flush_notify() did already call it.
1302          */
1303         mmu_notifier_invalidate_range_only_end(&range);
1304
1305         ret |= VM_FAULT_WRITE;
1306         put_page(page);
1307
1308 out:
1309         return ret;
1310
1311 out_free_pages:
1312         spin_unlock(vmf->ptl);
1313         mmu_notifier_invalidate_range_end(&range);
1314         for (i = 0; i < HPAGE_PMD_NR; i++) {
1315                 memcg = (void *)page_private(pages[i]);
1316                 set_page_private(pages[i], 0);
1317                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1318                 put_page(pages[i]);
1319         }
1320         kfree(pages);
1321         goto out;
1322 }
1323
1324 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1325 {
1326         struct vm_area_struct *vma = vmf->vma;
1327         struct page *page = NULL, *new_page;
1328         struct mem_cgroup *memcg;
1329         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1330         struct mmu_notifier_range range;
1331         gfp_t huge_gfp;                 /* for allocation and charge */
1332         vm_fault_t ret = 0;
1333
1334         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1335         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1336         if (is_huge_zero_pmd(orig_pmd))
1337                 goto alloc;
1338         spin_lock(vmf->ptl);
1339         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1340                 goto out_unlock;
1341
1342         page = pmd_page(orig_pmd);
1343         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1344         /*
1345          * We can only reuse the page if nobody else maps the huge page or it's
1346          * part.
1347          */
1348         if (!trylock_page(page)) {
1349                 get_page(page);
1350                 spin_unlock(vmf->ptl);
1351                 lock_page(page);
1352                 spin_lock(vmf->ptl);
1353                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1354                         unlock_page(page);
1355                         put_page(page);
1356                         goto out_unlock;
1357                 }
1358                 put_page(page);
1359         }
1360         if (reuse_swap_page(page, NULL)) {
1361                 pmd_t entry;
1362                 entry = pmd_mkyoung(orig_pmd);
1363                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1364                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1365                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1366                 ret |= VM_FAULT_WRITE;
1367                 unlock_page(page);
1368                 goto out_unlock;
1369         }
1370         unlock_page(page);
1371         get_page(page);
1372         spin_unlock(vmf->ptl);
1373 alloc:
1374         if (__transparent_hugepage_enabled(vma) &&
1375             !transparent_hugepage_debug_cow()) {
1376                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1377                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1378         } else
1379                 new_page = NULL;
1380
1381         if (likely(new_page)) {
1382                 prep_transhuge_page(new_page);
1383         } else {
1384                 if (!page) {
1385                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1386                         ret |= VM_FAULT_FALLBACK;
1387                 } else {
1388                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1389                         if (ret & VM_FAULT_OOM) {
1390                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1391                                 ret |= VM_FAULT_FALLBACK;
1392                         }
1393                         put_page(page);
1394                 }
1395                 count_vm_event(THP_FAULT_FALLBACK);
1396                 goto out;
1397         }
1398
1399         if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1400                                         huge_gfp, &memcg, true))) {
1401                 put_page(new_page);
1402                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1403                 if (page)
1404                         put_page(page);
1405                 ret |= VM_FAULT_FALLBACK;
1406                 count_vm_event(THP_FAULT_FALLBACK);
1407                 goto out;
1408         }
1409
1410         count_vm_event(THP_FAULT_ALLOC);
1411         count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
1412
1413         if (!page)
1414                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1415         else
1416                 copy_user_huge_page(new_page, page, vmf->address,
1417                                     vma, HPAGE_PMD_NR);
1418         __SetPageUptodate(new_page);
1419
1420         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1421                                 haddr, haddr + HPAGE_PMD_SIZE);
1422         mmu_notifier_invalidate_range_start(&range);
1423
1424         spin_lock(vmf->ptl);
1425         if (page)
1426                 put_page(page);
1427         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1428                 spin_unlock(vmf->ptl);
1429                 mem_cgroup_cancel_charge(new_page, memcg, true);
1430                 put_page(new_page);
1431                 goto out_mn;
1432         } else {
1433                 pmd_t entry;
1434                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1435                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1436                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1437                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1438                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1439                 lru_cache_add_active_or_unevictable(new_page, vma);
1440                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1441                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1442                 if (!page) {
1443                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1444                 } else {
1445                         VM_BUG_ON_PAGE(!PageHead(page), page);
1446                         page_remove_rmap(page, true);
1447                         put_page(page);
1448                 }
1449                 ret |= VM_FAULT_WRITE;
1450         }
1451         spin_unlock(vmf->ptl);
1452 out_mn:
1453         /*
1454          * No need to double call mmu_notifier->invalidate_range() callback as
1455          * the above pmdp_huge_clear_flush_notify() did already call it.
1456          */
1457         mmu_notifier_invalidate_range_only_end(&range);
1458 out:
1459         return ret;
1460 out_unlock:
1461         spin_unlock(vmf->ptl);
1462         return ret;
1463 }
1464
1465 /*
1466  * FOLL_FORCE can write to even unwritable pmd's, but only
1467  * after we've gone through a COW cycle and they are dirty.
1468  */
1469 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1470 {
1471         return pmd_write(pmd) ||
1472                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1473 }
1474
1475 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1476                                    unsigned long addr,
1477                                    pmd_t *pmd,
1478                                    unsigned int flags)
1479 {
1480         struct mm_struct *mm = vma->vm_mm;
1481         struct page *page = NULL;
1482
1483         assert_spin_locked(pmd_lockptr(mm, pmd));
1484
1485         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1486                 goto out;
1487
1488         /* Avoid dumping huge zero page */
1489         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1490                 return ERR_PTR(-EFAULT);
1491
1492         /* Full NUMA hinting faults to serialise migration in fault paths */
1493         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1494                 goto out;
1495
1496         page = pmd_page(*pmd);
1497         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1498         if (flags & FOLL_TOUCH)
1499                 touch_pmd(vma, addr, pmd, flags);
1500         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1501                 /*
1502                  * We don't mlock() pte-mapped THPs. This way we can avoid
1503                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1504                  *
1505                  * For anon THP:
1506                  *
1507                  * In most cases the pmd is the only mapping of the page as we
1508                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1509                  * writable private mappings in populate_vma_page_range().
1510                  *
1511                  * The only scenario when we have the page shared here is if we
1512                  * mlocking read-only mapping shared over fork(). We skip
1513                  * mlocking such pages.
1514                  *
1515                  * For file THP:
1516                  *
1517                  * We can expect PageDoubleMap() to be stable under page lock:
1518                  * for file pages we set it in page_add_file_rmap(), which
1519                  * requires page to be locked.
1520                  */
1521
1522                 if (PageAnon(page) && compound_mapcount(page) != 1)
1523                         goto skip_mlock;
1524                 if (PageDoubleMap(page) || !page->mapping)
1525                         goto skip_mlock;
1526                 if (!trylock_page(page))
1527                         goto skip_mlock;
1528                 lru_add_drain();
1529                 if (page->mapping && !PageDoubleMap(page))
1530                         mlock_vma_page(page);
1531                 unlock_page(page);
1532         }
1533 skip_mlock:
1534         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1535         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1536         if (flags & FOLL_GET)
1537                 get_page(page);
1538
1539 out:
1540         return page;
1541 }
1542
1543 /* NUMA hinting page fault entry point for trans huge pmds */
1544 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1545 {
1546         struct vm_area_struct *vma = vmf->vma;
1547         struct anon_vma *anon_vma = NULL;
1548         struct page *page;
1549         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1550         int page_nid = NUMA_NO_NODE, this_nid = numa_node_id();
1551         int target_nid, last_cpupid = -1;
1552         bool page_locked;
1553         bool migrated = false;
1554         bool was_writable;
1555         int flags = 0;
1556
1557         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1558         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1559                 goto out_unlock;
1560
1561         /*
1562          * If there are potential migrations, wait for completion and retry
1563          * without disrupting NUMA hinting information. Do not relock and
1564          * check_same as the page may no longer be mapped.
1565          */
1566         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1567                 page = pmd_page(*vmf->pmd);
1568                 if (!get_page_unless_zero(page))
1569                         goto out_unlock;
1570                 spin_unlock(vmf->ptl);
1571                 put_and_wait_on_page_locked(page);
1572                 goto out;
1573         }
1574
1575         page = pmd_page(pmd);
1576         BUG_ON(is_huge_zero_page(page));
1577         page_nid = page_to_nid(page);
1578         last_cpupid = page_cpupid_last(page);
1579         count_vm_numa_event(NUMA_HINT_FAULTS);
1580         if (page_nid == this_nid) {
1581                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1582                 flags |= TNF_FAULT_LOCAL;
1583         }
1584
1585         /* See similar comment in do_numa_page for explanation */
1586         if (!pmd_savedwrite(pmd))
1587                 flags |= TNF_NO_GROUP;
1588
1589         /*
1590          * Acquire the page lock to serialise THP migrations but avoid dropping
1591          * page_table_lock if at all possible
1592          */
1593         page_locked = trylock_page(page);
1594         target_nid = mpol_misplaced(page, vma, haddr);
1595         if (target_nid == NUMA_NO_NODE) {
1596                 /* If the page was locked, there are no parallel migrations */
1597                 if (page_locked)
1598                         goto clear_pmdnuma;
1599         }
1600
1601         /* Migration could have started since the pmd_trans_migrating check */
1602         if (!page_locked) {
1603                 page_nid = NUMA_NO_NODE;
1604                 if (!get_page_unless_zero(page))
1605                         goto out_unlock;
1606                 spin_unlock(vmf->ptl);
1607                 put_and_wait_on_page_locked(page);
1608                 goto out;
1609         }
1610
1611         /*
1612          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1613          * to serialises splits
1614          */
1615         get_page(page);
1616         spin_unlock(vmf->ptl);
1617         anon_vma = page_lock_anon_vma_read(page);
1618
1619         /* Confirm the PMD did not change while page_table_lock was released */
1620         spin_lock(vmf->ptl);
1621         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1622                 unlock_page(page);
1623                 put_page(page);
1624                 page_nid = NUMA_NO_NODE;
1625                 goto out_unlock;
1626         }
1627
1628         /* Bail if we fail to protect against THP splits for any reason */
1629         if (unlikely(!anon_vma)) {
1630                 put_page(page);
1631                 page_nid = NUMA_NO_NODE;
1632                 goto clear_pmdnuma;
1633         }
1634
1635         /*
1636          * Since we took the NUMA fault, we must have observed the !accessible
1637          * bit. Make sure all other CPUs agree with that, to avoid them
1638          * modifying the page we're about to migrate.
1639          *
1640          * Must be done under PTL such that we'll observe the relevant
1641          * inc_tlb_flush_pending().
1642          *
1643          * We are not sure a pending tlb flush here is for a huge page
1644          * mapping or not. Hence use the tlb range variant
1645          */
1646         if (mm_tlb_flush_pending(vma->vm_mm)) {
1647                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1648                 /*
1649                  * change_huge_pmd() released the pmd lock before
1650                  * invalidating the secondary MMUs sharing the primary
1651                  * MMU pagetables (with ->invalidate_range()). The
1652                  * mmu_notifier_invalidate_range_end() (which
1653                  * internally calls ->invalidate_range()) in
1654                  * change_pmd_range() will run after us, so we can't
1655                  * rely on it here and we need an explicit invalidate.
1656                  */
1657                 mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1658                                               haddr + HPAGE_PMD_SIZE);
1659         }
1660
1661         /*
1662          * Migrate the THP to the requested node, returns with page unlocked
1663          * and access rights restored.
1664          */
1665         spin_unlock(vmf->ptl);
1666
1667         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1668                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1669         if (migrated) {
1670                 flags |= TNF_MIGRATED;
1671                 page_nid = target_nid;
1672         } else
1673                 flags |= TNF_MIGRATE_FAIL;
1674
1675         goto out;
1676 clear_pmdnuma:
1677         BUG_ON(!PageLocked(page));
1678         was_writable = pmd_savedwrite(pmd);
1679         pmd = pmd_modify(pmd, vma->vm_page_prot);
1680         pmd = pmd_mkyoung(pmd);
1681         if (was_writable)
1682                 pmd = pmd_mkwrite(pmd);
1683         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1684         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1685         unlock_page(page);
1686 out_unlock:
1687         spin_unlock(vmf->ptl);
1688
1689 out:
1690         if (anon_vma)
1691                 page_unlock_anon_vma_read(anon_vma);
1692
1693         if (page_nid != NUMA_NO_NODE)
1694                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1695                                 flags);
1696
1697         return 0;
1698 }
1699
1700 /*
1701  * Return true if we do MADV_FREE successfully on entire pmd page.
1702  * Otherwise, return false.
1703  */
1704 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1705                 pmd_t *pmd, unsigned long addr, unsigned long next)
1706 {
1707         spinlock_t *ptl;
1708         pmd_t orig_pmd;
1709         struct page *page;
1710         struct mm_struct *mm = tlb->mm;
1711         bool ret = false;
1712
1713         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1714
1715         ptl = pmd_trans_huge_lock(pmd, vma);
1716         if (!ptl)
1717                 goto out_unlocked;
1718
1719         orig_pmd = *pmd;
1720         if (is_huge_zero_pmd(orig_pmd))
1721                 goto out;
1722
1723         if (unlikely(!pmd_present(orig_pmd))) {
1724                 VM_BUG_ON(thp_migration_supported() &&
1725                                   !is_pmd_migration_entry(orig_pmd));
1726                 goto out;
1727         }
1728
1729         page = pmd_page(orig_pmd);
1730         /*
1731          * If other processes are mapping this page, we couldn't discard
1732          * the page unless they all do MADV_FREE so let's skip the page.
1733          */
1734         if (page_mapcount(page) != 1)
1735                 goto out;
1736
1737         if (!trylock_page(page))
1738                 goto out;
1739
1740         /*
1741          * If user want to discard part-pages of THP, split it so MADV_FREE
1742          * will deactivate only them.
1743          */
1744         if (next - addr != HPAGE_PMD_SIZE) {
1745                 get_page(page);
1746                 spin_unlock(ptl);
1747                 split_huge_page(page);
1748                 unlock_page(page);
1749                 put_page(page);
1750                 goto out_unlocked;
1751         }
1752
1753         if (PageDirty(page))
1754                 ClearPageDirty(page);
1755         unlock_page(page);
1756
1757         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1758                 pmdp_invalidate(vma, addr, pmd);
1759                 orig_pmd = pmd_mkold(orig_pmd);
1760                 orig_pmd = pmd_mkclean(orig_pmd);
1761
1762                 set_pmd_at(mm, addr, pmd, orig_pmd);
1763                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1764         }
1765
1766         mark_page_lazyfree(page);
1767         ret = true;
1768 out:
1769         spin_unlock(ptl);
1770 out_unlocked:
1771         return ret;
1772 }
1773
1774 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1775 {
1776         pgtable_t pgtable;
1777
1778         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1779         pte_free(mm, pgtable);
1780         mm_dec_nr_ptes(mm);
1781 }
1782
1783 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1784                  pmd_t *pmd, unsigned long addr)
1785 {
1786         pmd_t orig_pmd;
1787         spinlock_t *ptl;
1788
1789         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1790
1791         ptl = __pmd_trans_huge_lock(pmd, vma);
1792         if (!ptl)
1793                 return 0;
1794         /*
1795          * For architectures like ppc64 we look at deposited pgtable
1796          * when calling pmdp_huge_get_and_clear. So do the
1797          * pgtable_trans_huge_withdraw after finishing pmdp related
1798          * operations.
1799          */
1800         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1801                         tlb->fullmm);
1802         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1803         if (vma_is_dax(vma)) {
1804                 if (arch_needs_pgtable_deposit())
1805                         zap_deposited_table(tlb->mm, pmd);
1806                 spin_unlock(ptl);
1807                 if (is_huge_zero_pmd(orig_pmd))
1808                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1809         } else if (is_huge_zero_pmd(orig_pmd)) {
1810                 zap_deposited_table(tlb->mm, pmd);
1811                 spin_unlock(ptl);
1812                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1813         } else {
1814                 struct page *page = NULL;
1815                 int flush_needed = 1;
1816
1817                 if (pmd_present(orig_pmd)) {
1818                         page = pmd_page(orig_pmd);
1819                         page_remove_rmap(page, true);
1820                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1821                         VM_BUG_ON_PAGE(!PageHead(page), page);
1822                 } else if (thp_migration_supported()) {
1823                         swp_entry_t entry;
1824
1825                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1826                         entry = pmd_to_swp_entry(orig_pmd);
1827                         page = pfn_to_page(swp_offset(entry));
1828                         flush_needed = 0;
1829                 } else
1830                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1831
1832                 if (PageAnon(page)) {
1833                         zap_deposited_table(tlb->mm, pmd);
1834                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1835                 } else {
1836                         if (arch_needs_pgtable_deposit())
1837                                 zap_deposited_table(tlb->mm, pmd);
1838                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1839                 }
1840
1841                 spin_unlock(ptl);
1842                 if (flush_needed)
1843                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1844         }
1845         return 1;
1846 }
1847
1848 #ifndef pmd_move_must_withdraw
1849 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1850                                          spinlock_t *old_pmd_ptl,
1851                                          struct vm_area_struct *vma)
1852 {
1853         /*
1854          * With split pmd lock we also need to move preallocated
1855          * PTE page table if new_pmd is on different PMD page table.
1856          *
1857          * We also don't deposit and withdraw tables for file pages.
1858          */
1859         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1860 }
1861 #endif
1862
1863 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1864 {
1865 #ifdef CONFIG_MEM_SOFT_DIRTY
1866         if (unlikely(is_pmd_migration_entry(pmd)))
1867                 pmd = pmd_swp_mksoft_dirty(pmd);
1868         else if (pmd_present(pmd))
1869                 pmd = pmd_mksoft_dirty(pmd);
1870 #endif
1871         return pmd;
1872 }
1873
1874 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1875                   unsigned long new_addr, unsigned long old_end,
1876                   pmd_t *old_pmd, pmd_t *new_pmd)
1877 {
1878         spinlock_t *old_ptl, *new_ptl;
1879         pmd_t pmd;
1880         struct mm_struct *mm = vma->vm_mm;
1881         bool force_flush = false;
1882
1883         if ((old_addr & ~HPAGE_PMD_MASK) ||
1884             (new_addr & ~HPAGE_PMD_MASK) ||
1885             old_end - old_addr < HPAGE_PMD_SIZE)
1886                 return false;
1887
1888         /*
1889          * The destination pmd shouldn't be established, free_pgtables()
1890          * should have release it.
1891          */
1892         if (WARN_ON(!pmd_none(*new_pmd))) {
1893                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1894                 return false;
1895         }
1896
1897         /*
1898          * We don't have to worry about the ordering of src and dst
1899          * ptlocks because exclusive mmap_sem prevents deadlock.
1900          */
1901         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1902         if (old_ptl) {
1903                 new_ptl = pmd_lockptr(mm, new_pmd);
1904                 if (new_ptl != old_ptl)
1905                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1906                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1907                 if (pmd_present(pmd))
1908                         force_flush = true;
1909                 VM_BUG_ON(!pmd_none(*new_pmd));
1910
1911                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1912                         pgtable_t pgtable;
1913                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1914                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1915                 }
1916                 pmd = move_soft_dirty_pmd(pmd);
1917                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1918                 if (force_flush)
1919                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1920                 if (new_ptl != old_ptl)
1921                         spin_unlock(new_ptl);
1922                 spin_unlock(old_ptl);
1923                 return true;
1924         }
1925         return false;
1926 }
1927
1928 /*
1929  * Returns
1930  *  - 0 if PMD could not be locked
1931  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1932  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1933  */
1934 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1935                 unsigned long addr, pgprot_t newprot, int prot_numa)
1936 {
1937         struct mm_struct *mm = vma->vm_mm;
1938         spinlock_t *ptl;
1939         pmd_t entry;
1940         bool preserve_write;
1941         int ret;
1942
1943         ptl = __pmd_trans_huge_lock(pmd, vma);
1944         if (!ptl)
1945                 return 0;
1946
1947         preserve_write = prot_numa && pmd_write(*pmd);
1948         ret = 1;
1949
1950 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1951         if (is_swap_pmd(*pmd)) {
1952                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1953
1954                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1955                 if (is_write_migration_entry(entry)) {
1956                         pmd_t newpmd;
1957                         /*
1958                          * A protection check is difficult so
1959                          * just be safe and disable write
1960                          */
1961                         make_migration_entry_read(&entry);
1962                         newpmd = swp_entry_to_pmd(entry);
1963                         if (pmd_swp_soft_dirty(*pmd))
1964                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1965                         set_pmd_at(mm, addr, pmd, newpmd);
1966                 }
1967                 goto unlock;
1968         }
1969 #endif
1970
1971         /*
1972          * Avoid trapping faults against the zero page. The read-only
1973          * data is likely to be read-cached on the local CPU and
1974          * local/remote hits to the zero page are not interesting.
1975          */
1976         if (prot_numa && is_huge_zero_pmd(*pmd))
1977                 goto unlock;
1978
1979         if (prot_numa && pmd_protnone(*pmd))
1980                 goto unlock;
1981
1982         /*
1983          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1984          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1985          * which is also under down_read(mmap_sem):
1986          *
1987          *      CPU0:                           CPU1:
1988          *                              change_huge_pmd(prot_numa=1)
1989          *                               pmdp_huge_get_and_clear_notify()
1990          * madvise_dontneed()
1991          *  zap_pmd_range()
1992          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1993          *   // skip the pmd
1994          *                               set_pmd_at();
1995          *                               // pmd is re-established
1996          *
1997          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1998          * which may break userspace.
1999          *
2000          * pmdp_invalidate() is required to make sure we don't miss
2001          * dirty/young flags set by hardware.
2002          */
2003         entry = pmdp_invalidate(vma, addr, pmd);
2004
2005         entry = pmd_modify(entry, newprot);
2006         if (preserve_write)
2007                 entry = pmd_mk_savedwrite(entry);
2008         ret = HPAGE_PMD_NR;
2009         set_pmd_at(mm, addr, pmd, entry);
2010         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
2011 unlock:
2012         spin_unlock(ptl);
2013         return ret;
2014 }
2015
2016 /*
2017  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
2018  *
2019  * Note that if it returns page table lock pointer, this routine returns without
2020  * unlocking page table lock. So callers must unlock it.
2021  */
2022 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
2023 {
2024         spinlock_t *ptl;
2025         ptl = pmd_lock(vma->vm_mm, pmd);
2026         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
2027                         pmd_devmap(*pmd)))
2028                 return ptl;
2029         spin_unlock(ptl);
2030         return NULL;
2031 }
2032
2033 /*
2034  * Returns true if a given pud maps a thp, false otherwise.
2035  *
2036  * Note that if it returns true, this routine returns without unlocking page
2037  * table lock. So callers must unlock it.
2038  */
2039 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
2040 {
2041         spinlock_t *ptl;
2042
2043         ptl = pud_lock(vma->vm_mm, pud);
2044         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
2045                 return ptl;
2046         spin_unlock(ptl);
2047         return NULL;
2048 }
2049
2050 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
2051 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
2052                  pud_t *pud, unsigned long addr)
2053 {
2054         spinlock_t *ptl;
2055
2056         ptl = __pud_trans_huge_lock(pud, vma);
2057         if (!ptl)
2058                 return 0;
2059         /*
2060          * For architectures like ppc64 we look at deposited pgtable
2061          * when calling pudp_huge_get_and_clear. So do the
2062          * pgtable_trans_huge_withdraw after finishing pudp related
2063          * operations.
2064          */
2065         pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
2066         tlb_remove_pud_tlb_entry(tlb, pud, addr);
2067         if (vma_is_dax(vma)) {
2068                 spin_unlock(ptl);
2069                 /* No zero page support yet */
2070         } else {
2071                 /* No support for anonymous PUD pages yet */
2072                 BUG();
2073         }
2074         return 1;
2075 }
2076
2077 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2078                 unsigned long haddr)
2079 {
2080         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2081         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2082         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2083         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2084
2085         count_vm_event(THP_SPLIT_PUD);
2086
2087         pudp_huge_clear_flush_notify(vma, haddr, pud);
2088 }
2089
2090 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2091                 unsigned long address)
2092 {
2093         spinlock_t *ptl;
2094         struct mmu_notifier_range range;
2095
2096         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2097                                 address & HPAGE_PUD_MASK,
2098                                 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
2099         mmu_notifier_invalidate_range_start(&range);
2100         ptl = pud_lock(vma->vm_mm, pud);
2101         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2102                 goto out;
2103         __split_huge_pud_locked(vma, pud, range.start);
2104
2105 out:
2106         spin_unlock(ptl);
2107         /*
2108          * No need to double call mmu_notifier->invalidate_range() callback as
2109          * the above pudp_huge_clear_flush_notify() did already call it.
2110          */
2111         mmu_notifier_invalidate_range_only_end(&range);
2112 }
2113 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2114
2115 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2116                 unsigned long haddr, pmd_t *pmd)
2117 {
2118         struct mm_struct *mm = vma->vm_mm;
2119         pgtable_t pgtable;
2120         pmd_t _pmd;
2121         int i;
2122
2123         /*
2124          * Leave pmd empty until pte is filled note that it is fine to delay
2125          * notification until mmu_notifier_invalidate_range_end() as we are
2126          * replacing a zero pmd write protected page with a zero pte write
2127          * protected page.
2128          *
2129          * See Documentation/vm/mmu_notifier.rst
2130          */
2131         pmdp_huge_clear_flush(vma, haddr, pmd);
2132
2133         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2134         pmd_populate(mm, &_pmd, pgtable);
2135
2136         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2137                 pte_t *pte, entry;
2138                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2139                 entry = pte_mkspecial(entry);
2140                 pte = pte_offset_map(&_pmd, haddr);
2141                 VM_BUG_ON(!pte_none(*pte));
2142                 set_pte_at(mm, haddr, pte, entry);
2143                 pte_unmap(pte);
2144         }
2145         smp_wmb(); /* make pte visible before pmd */
2146         pmd_populate(mm, pmd, pgtable);
2147 }
2148
2149 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2150                 unsigned long haddr, bool freeze)
2151 {
2152         struct mm_struct *mm = vma->vm_mm;
2153         struct page *page;
2154         pgtable_t pgtable;
2155         pmd_t old_pmd, _pmd;
2156         bool young, write, soft_dirty, pmd_migration = false;
2157         unsigned long addr;
2158         int i;
2159
2160         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2161         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2162         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2163         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2164                                 && !pmd_devmap(*pmd));
2165
2166         count_vm_event(THP_SPLIT_PMD);
2167
2168         if (!vma_is_anonymous(vma)) {
2169                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2170                 /*
2171                  * We are going to unmap this huge page. So
2172                  * just go ahead and zap it
2173                  */
2174                 if (arch_needs_pgtable_deposit())
2175                         zap_deposited_table(mm, pmd);
2176                 if (vma_is_dax(vma))
2177                         return;
2178                 page = pmd_page(_pmd);
2179                 if (!PageDirty(page) && pmd_dirty(_pmd))
2180                         set_page_dirty(page);
2181                 if (!PageReferenced(page) && pmd_young(_pmd))
2182                         SetPageReferenced(page);
2183                 page_remove_rmap(page, true);
2184                 put_page(page);
2185                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2186                 return;
2187         } else if (is_huge_zero_pmd(*pmd)) {
2188                 /*
2189                  * FIXME: Do we want to invalidate secondary mmu by calling
2190                  * mmu_notifier_invalidate_range() see comments below inside
2191                  * __split_huge_pmd() ?
2192                  *
2193                  * We are going from a zero huge page write protected to zero
2194                  * small page also write protected so it does not seems useful
2195                  * to invalidate secondary mmu at this time.
2196                  */
2197                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2198         }
2199
2200         /*
2201          * Up to this point the pmd is present and huge and userland has the
2202          * whole access to the hugepage during the split (which happens in
2203          * place). If we overwrite the pmd with the not-huge version pointing
2204          * to the pte here (which of course we could if all CPUs were bug
2205          * free), userland could trigger a small page size TLB miss on the
2206          * small sized TLB while the hugepage TLB entry is still established in
2207          * the huge TLB. Some CPU doesn't like that.
2208          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2209          * 383 on page 93. Intel should be safe but is also warns that it's
2210          * only safe if the permission and cache attributes of the two entries
2211          * loaded in the two TLB is identical (which should be the case here).
2212          * But it is generally safer to never allow small and huge TLB entries
2213          * for the same virtual address to be loaded simultaneously. So instead
2214          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2215          * current pmd notpresent (atomically because here the pmd_trans_huge
2216          * must remain set at all times on the pmd until the split is complete
2217          * for this pmd), then we flush the SMP TLB and finally we write the
2218          * non-huge version of the pmd entry with pmd_populate.
2219          */
2220         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2221
2222         pmd_migration = is_pmd_migration_entry(old_pmd);
2223         if (unlikely(pmd_migration)) {
2224                 swp_entry_t entry;
2225
2226                 entry = pmd_to_swp_entry(old_pmd);
2227                 page = pfn_to_page(swp_offset(entry));
2228                 write = is_write_migration_entry(entry);
2229                 young = false;
2230                 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2231         } else {
2232                 page = pmd_page(old_pmd);
2233                 if (pmd_dirty(old_pmd))
2234                         SetPageDirty(page);
2235                 write = pmd_write(old_pmd);
2236                 young = pmd_young(old_pmd);
2237                 soft_dirty = pmd_soft_dirty(old_pmd);
2238         }
2239         VM_BUG_ON_PAGE(!page_count(page), page);
2240         page_ref_add(page, HPAGE_PMD_NR - 1);
2241
2242         /*
2243          * Withdraw the table only after we mark the pmd entry invalid.
2244          * This's critical for some architectures (Power).
2245          */
2246         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2247         pmd_populate(mm, &_pmd, pgtable);
2248
2249         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2250                 pte_t entry, *pte;
2251                 /*
2252                  * Note that NUMA hinting access restrictions are not
2253                  * transferred to avoid any possibility of altering
2254                  * permissions across VMAs.
2255                  */
2256                 if (freeze || pmd_migration) {
2257                         swp_entry_t swp_entry;
2258                         swp_entry = make_migration_entry(page + i, write);
2259                         entry = swp_entry_to_pte(swp_entry);
2260                         if (soft_dirty)
2261                                 entry = pte_swp_mksoft_dirty(entry);
2262                 } else {
2263                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2264                         entry = maybe_mkwrite(entry, vma);
2265                         if (!write)
2266                                 entry = pte_wrprotect(entry);
2267                         if (!young)
2268                                 entry = pte_mkold(entry);
2269                         if (soft_dirty)
2270                                 entry = pte_mksoft_dirty(entry);
2271                 }
2272                 pte = pte_offset_map(&_pmd, addr);
2273                 BUG_ON(!pte_none(*pte));
2274                 set_pte_at(mm, addr, pte, entry);
2275                 atomic_inc(&page[i]._mapcount);
2276                 pte_unmap(pte);
2277         }
2278
2279         /*
2280          * Set PG_double_map before dropping compound_mapcount to avoid
2281          * false-negative page_mapped().
2282          */
2283         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2284                 for (i = 0; i < HPAGE_PMD_NR; i++)
2285                         atomic_inc(&page[i]._mapcount);
2286         }
2287
2288         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2289                 /* Last compound_mapcount is gone. */
2290                 __dec_node_page_state(page, NR_ANON_THPS);
2291                 if (TestClearPageDoubleMap(page)) {
2292                         /* No need in mapcount reference anymore */
2293                         for (i = 0; i < HPAGE_PMD_NR; i++)
2294                                 atomic_dec(&page[i]._mapcount);
2295                 }
2296         }
2297
2298         smp_wmb(); /* make pte visible before pmd */
2299         pmd_populate(mm, pmd, pgtable);
2300
2301         if (freeze) {
2302                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2303                         page_remove_rmap(page + i, false);
2304                         put_page(page + i);
2305                 }
2306         }
2307 }
2308
2309 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2310                 unsigned long address, bool freeze, struct page *page)
2311 {
2312         spinlock_t *ptl;
2313         struct mmu_notifier_range range;
2314
2315         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2316                                 address & HPAGE_PMD_MASK,
2317                                 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2318         mmu_notifier_invalidate_range_start(&range);
2319         ptl = pmd_lock(vma->vm_mm, pmd);
2320
2321         /*
2322          * If caller asks to setup a migration entries, we need a page to check
2323          * pmd against. Otherwise we can end up replacing wrong page.
2324          */
2325         VM_BUG_ON(freeze && !page);
2326         if (page && page != pmd_page(*pmd))
2327                 goto out;
2328
2329         if (pmd_trans_huge(*pmd)) {
2330                 page = pmd_page(*pmd);
2331                 if (PageMlocked(page))
2332                         clear_page_mlock(page);
2333         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2334                 goto out;
2335         __split_huge_pmd_locked(vma, pmd, range.start, freeze);
2336 out:
2337         spin_unlock(ptl);
2338         /*
2339          * No need to double call mmu_notifier->invalidate_range() callback.
2340          * They are 3 cases to consider inside __split_huge_pmd_locked():
2341          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2342          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2343          *    fault will trigger a flush_notify before pointing to a new page
2344          *    (it is fine if the secondary mmu keeps pointing to the old zero
2345          *    page in the meantime)
2346          *  3) Split a huge pmd into pte pointing to the same page. No need
2347          *     to invalidate secondary tlb entry they are all still valid.
2348          *     any further changes to individual pte will notify. So no need
2349          *     to call mmu_notifier->invalidate_range()
2350          */
2351         mmu_notifier_invalidate_range_only_end(&range);
2352 }
2353
2354 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2355                 bool freeze, struct page *page)
2356 {
2357         pgd_t *pgd;
2358         p4d_t *p4d;
2359         pud_t *pud;
2360         pmd_t *pmd;
2361
2362         pgd = pgd_offset(vma->vm_mm, address);
2363         if (!pgd_present(*pgd))
2364                 return;
2365
2366         p4d = p4d_offset(pgd, address);
2367         if (!p4d_present(*p4d))
2368                 return;
2369
2370         pud = pud_offset(p4d, address);
2371         if (!pud_present(*pud))
2372                 return;
2373
2374         pmd = pmd_offset(pud, address);
2375
2376         __split_huge_pmd(vma, pmd, address, freeze, page);
2377 }
2378
2379 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2380                              unsigned long start,
2381                              unsigned long end,
2382                              long adjust_next)
2383 {
2384         /*
2385          * If the new start address isn't hpage aligned and it could
2386          * previously contain an hugepage: check if we need to split
2387          * an huge pmd.
2388          */
2389         if (start & ~HPAGE_PMD_MASK &&
2390             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2391             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2392                 split_huge_pmd_address(vma, start, false, NULL);
2393
2394         /*
2395          * If the new end address isn't hpage aligned and it could
2396          * previously contain an hugepage: check if we need to split
2397          * an huge pmd.
2398          */
2399         if (end & ~HPAGE_PMD_MASK &&
2400             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2401             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2402                 split_huge_pmd_address(vma, end, false, NULL);
2403
2404         /*
2405          * If we're also updating the vma->vm_next->vm_start, if the new
2406          * vm_next->vm_start isn't page aligned and it could previously
2407          * contain an hugepage: check if we need to split an huge pmd.
2408          */
2409         if (adjust_next > 0) {
2410                 struct vm_area_struct *next = vma->vm_next;
2411                 unsigned long nstart = next->vm_start;
2412                 nstart += adjust_next << PAGE_SHIFT;
2413                 if (nstart & ~HPAGE_PMD_MASK &&
2414                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2415                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2416                         split_huge_pmd_address(next, nstart, false, NULL);
2417         }
2418 }
2419
2420 static void unmap_page(struct page *page)
2421 {
2422         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2423                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2424         bool unmap_success;
2425
2426         VM_BUG_ON_PAGE(!PageHead(page), page);
2427
2428         if (PageAnon(page))
2429                 ttu_flags |= TTU_SPLIT_FREEZE;
2430
2431         unmap_success = try_to_unmap(page, ttu_flags);
2432         VM_BUG_ON_PAGE(!unmap_success, page);
2433 }
2434
2435 static void remap_page(struct page *page)
2436 {
2437         int i;
2438         if (PageTransHuge(page)) {
2439                 remove_migration_ptes(page, page, true);
2440         } else {
2441                 for (i = 0; i < HPAGE_PMD_NR; i++)
2442                         remove_migration_ptes(page + i, page + i, true);
2443         }
2444 }
2445
2446 static void __split_huge_page_tail(struct page *head, int tail,
2447                 struct lruvec *lruvec, struct list_head *list)
2448 {
2449         struct page *page_tail = head + tail;
2450
2451         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2452
2453         /*
2454          * Clone page flags before unfreezing refcount.
2455          *
2456          * After successful get_page_unless_zero() might follow flags change,
2457          * for exmaple lock_page() which set PG_waiters.
2458          */
2459         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2460         page_tail->flags |= (head->flags &
2461                         ((1L << PG_referenced) |
2462                          (1L << PG_swapbacked) |
2463                          (1L << PG_swapcache) |
2464                          (1L << PG_mlocked) |
2465                          (1L << PG_uptodate) |
2466                          (1L << PG_active) |
2467                          (1L << PG_workingset) |
2468                          (1L << PG_locked) |
2469                          (1L << PG_unevictable) |
2470                          (1L << PG_dirty)));
2471
2472         /* ->mapping in first tail page is compound_mapcount */
2473         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2474                         page_tail);
2475         page_tail->mapping = head->mapping;
2476         page_tail->index = head->index + tail;
2477
2478         /* Page flags must be visible before we make the page non-compound. */
2479         smp_wmb();
2480
2481         /*
2482          * Clear PageTail before unfreezing page refcount.
2483          *
2484          * After successful get_page_unless_zero() might follow put_page()
2485          * which needs correct compound_head().
2486          */
2487         clear_compound_head(page_tail);
2488
2489         /* Finally unfreeze refcount. Additional reference from page cache. */
2490         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2491                                           PageSwapCache(head)));
2492
2493         if (page_is_young(head))
2494                 set_page_young(page_tail);
2495         if (page_is_idle(head))
2496                 set_page_idle(page_tail);
2497
2498         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2499
2500         /*
2501          * always add to the tail because some iterators expect new
2502          * pages to show after the currently processed elements - e.g.
2503          * migrate_pages
2504          */
2505         lru_add_page_tail(head, page_tail, lruvec, list);
2506 }
2507
2508 static void __split_huge_page(struct page *page, struct list_head *list,
2509                 pgoff_t end, unsigned long flags)
2510 {
2511         struct page *head = compound_head(page);
2512         pg_data_t *pgdat = page_pgdat(head);
2513         struct lruvec *lruvec;
2514         struct address_space *swap_cache = NULL;
2515         unsigned long offset = 0;
2516         int i;
2517
2518         lruvec = mem_cgroup_page_lruvec(head, pgdat);
2519
2520         /* complete memcg works before add pages to LRU */
2521         mem_cgroup_split_huge_fixup(head);
2522
2523         if (PageAnon(head) && PageSwapCache(head)) {
2524                 swp_entry_t entry = { .val = page_private(head) };
2525
2526                 offset = swp_offset(entry);
2527                 swap_cache = swap_address_space(entry);
2528                 xa_lock(&swap_cache->i_pages);
2529         }
2530
2531         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2532                 __split_huge_page_tail(head, i, lruvec, list);
2533                 /* Some pages can be beyond i_size: drop them from page cache */
2534                 if (head[i].index >= end) {
2535                         ClearPageDirty(head + i);
2536                         __delete_from_page_cache(head + i, NULL);
2537                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2538                                 shmem_uncharge(head->mapping->host, 1);
2539                         put_page(head + i);
2540                 } else if (!PageAnon(page)) {
2541                         __xa_store(&head->mapping->i_pages, head[i].index,
2542                                         head + i, 0);
2543                 } else if (swap_cache) {
2544                         __xa_store(&swap_cache->i_pages, offset + i,
2545                                         head + i, 0);
2546                 }
2547         }
2548
2549         ClearPageCompound(head);
2550
2551         split_page_owner(head, HPAGE_PMD_ORDER);
2552
2553         /* See comment in __split_huge_page_tail() */
2554         if (PageAnon(head)) {
2555                 /* Additional pin to swap cache */
2556                 if (PageSwapCache(head)) {
2557                         page_ref_add(head, 2);
2558                         xa_unlock(&swap_cache->i_pages);
2559                 } else {
2560                         page_ref_inc(head);
2561                 }
2562         } else {
2563                 /* Additional pin to page cache */
2564                 page_ref_add(head, 2);
2565                 xa_unlock(&head->mapping->i_pages);
2566         }
2567
2568         spin_unlock_irqrestore(&pgdat->lru_lock, flags);
2569
2570         remap_page(head);
2571
2572         for (i = 0; i < HPAGE_PMD_NR; i++) {
2573                 struct page *subpage = head + i;
2574                 if (subpage == page)
2575                         continue;
2576                 unlock_page(subpage);
2577
2578                 /*
2579                  * Subpages may be freed if there wasn't any mapping
2580                  * like if add_to_swap() is running on a lru page that
2581                  * had its mapping zapped. And freeing these pages
2582                  * requires taking the lru_lock so we do the put_page
2583                  * of the tail pages after the split is complete.
2584                  */
2585                 put_page(subpage);
2586         }
2587 }
2588
2589 int total_mapcount(struct page *page)
2590 {
2591         int i, compound, ret;
2592
2593         VM_BUG_ON_PAGE(PageTail(page), page);
2594
2595         if (likely(!PageCompound(page)))
2596                 return atomic_read(&page->_mapcount) + 1;
2597
2598         compound = compound_mapcount(page);
2599         if (PageHuge(page))
2600                 return compound;
2601         ret = compound;
2602         for (i = 0; i < HPAGE_PMD_NR; i++)
2603                 ret += atomic_read(&page[i]._mapcount) + 1;
2604         /* File pages has compound_mapcount included in _mapcount */
2605         if (!PageAnon(page))
2606                 return ret - compound * HPAGE_PMD_NR;
2607         if (PageDoubleMap(page))
2608                 ret -= HPAGE_PMD_NR;
2609         return ret;
2610 }
2611
2612 /*
2613  * This calculates accurately how many mappings a transparent hugepage
2614  * has (unlike page_mapcount() which isn't fully accurate). This full
2615  * accuracy is primarily needed to know if copy-on-write faults can
2616  * reuse the page and change the mapping to read-write instead of
2617  * copying them. At the same time this returns the total_mapcount too.
2618  *
2619  * The function returns the highest mapcount any one of the subpages
2620  * has. If the return value is one, even if different processes are
2621  * mapping different subpages of the transparent hugepage, they can
2622  * all reuse it, because each process is reusing a different subpage.
2623  *
2624  * The total_mapcount is instead counting all virtual mappings of the
2625  * subpages. If the total_mapcount is equal to "one", it tells the
2626  * caller all mappings belong to the same "mm" and in turn the
2627  * anon_vma of the transparent hugepage can become the vma->anon_vma
2628  * local one as no other process may be mapping any of the subpages.
2629  *
2630  * It would be more accurate to replace page_mapcount() with
2631  * page_trans_huge_mapcount(), however we only use
2632  * page_trans_huge_mapcount() in the copy-on-write faults where we
2633  * need full accuracy to avoid breaking page pinning, because
2634  * page_trans_huge_mapcount() is slower than page_mapcount().
2635  */
2636 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2637 {
2638         int i, ret, _total_mapcount, mapcount;
2639
2640         /* hugetlbfs shouldn't call it */
2641         VM_BUG_ON_PAGE(PageHuge(page), page);
2642
2643         if (likely(!PageTransCompound(page))) {
2644                 mapcount = atomic_read(&page->_mapcount) + 1;
2645                 if (total_mapcount)
2646                         *total_mapcount = mapcount;
2647                 return mapcount;
2648         }
2649
2650         page = compound_head(page);
2651
2652         _total_mapcount = ret = 0;
2653         for (i = 0; i < HPAGE_PMD_NR; i++) {
2654                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2655                 ret = max(ret, mapcount);
2656                 _total_mapcount += mapcount;
2657         }
2658         if (PageDoubleMap(page)) {
2659                 ret -= 1;
2660                 _total_mapcount -= HPAGE_PMD_NR;
2661         }
2662         mapcount = compound_mapcount(page);
2663         ret += mapcount;
2664         _total_mapcount += mapcount;
2665         if (total_mapcount)
2666                 *total_mapcount = _total_mapcount;
2667         return ret;
2668 }
2669
2670 /* Racy check whether the huge page can be split */
2671 bool can_split_huge_page(struct page *page, int *pextra_pins)
2672 {
2673         int extra_pins;
2674
2675         /* Additional pins from page cache */
2676         if (PageAnon(page))
2677                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2678         else
2679                 extra_pins = HPAGE_PMD_NR;
2680         if (pextra_pins)
2681                 *pextra_pins = extra_pins;
2682         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2683 }
2684
2685 /*
2686  * This function splits huge page into normal pages. @page can point to any
2687  * subpage of huge page to split. Split doesn't change the position of @page.
2688  *
2689  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2690  * The huge page must be locked.
2691  *
2692  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2693  *
2694  * Both head page and tail pages will inherit mapping, flags, and so on from
2695  * the hugepage.
2696  *
2697  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2698  * they are not mapped.
2699  *
2700  * Returns 0 if the hugepage is split successfully.
2701  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2702  * us.
2703  */
2704 int split_huge_page_to_list(struct page *page, struct list_head *list)
2705 {
2706         struct page *head = compound_head(page);
2707         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2708         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2709         struct anon_vma *anon_vma = NULL;
2710         struct address_space *mapping = NULL;
2711         int count, mapcount, extra_pins, ret;
2712         bool mlocked;
2713         unsigned long flags;
2714         pgoff_t end;
2715
2716         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2717         VM_BUG_ON_PAGE(!PageLocked(page), page);
2718         VM_BUG_ON_PAGE(!PageCompound(page), page);
2719
2720         if (PageWriteback(page))
2721                 return -EBUSY;
2722
2723         if (PageAnon(head)) {
2724                 /*
2725                  * The caller does not necessarily hold an mmap_sem that would
2726                  * prevent the anon_vma disappearing so we first we take a
2727                  * reference to it and then lock the anon_vma for write. This
2728                  * is similar to page_lock_anon_vma_read except the write lock
2729                  * is taken to serialise against parallel split or collapse
2730                  * operations.
2731                  */
2732                 anon_vma = page_get_anon_vma(head);
2733                 if (!anon_vma) {
2734                         ret = -EBUSY;
2735                         goto out;
2736                 }
2737                 end = -1;
2738                 mapping = NULL;
2739                 anon_vma_lock_write(anon_vma);
2740         } else {
2741                 mapping = head->mapping;
2742
2743                 /* Truncated ? */
2744                 if (!mapping) {
2745                         ret = -EBUSY;
2746                         goto out;
2747                 }
2748
2749                 anon_vma = NULL;
2750                 i_mmap_lock_read(mapping);
2751
2752                 /*
2753                  *__split_huge_page() may need to trim off pages beyond EOF:
2754                  * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2755                  * which cannot be nested inside the page tree lock. So note
2756                  * end now: i_size itself may be changed at any moment, but
2757                  * head page lock is good enough to serialize the trimming.
2758                  */
2759                 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2760         }
2761
2762         /*
2763          * Racy check if we can split the page, before unmap_page() will
2764          * split PMDs
2765          */
2766         if (!can_split_huge_page(head, &extra_pins)) {
2767                 ret = -EBUSY;
2768                 goto out_unlock;
2769         }
2770
2771         mlocked = PageMlocked(page);
2772         unmap_page(head);
2773         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2774
2775         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2776         if (mlocked)
2777                 lru_add_drain();
2778
2779         /* prevent PageLRU to go away from under us, and freeze lru stats */
2780         spin_lock_irqsave(&pgdata->lru_lock, flags);
2781
2782         if (mapping) {
2783                 XA_STATE(xas, &mapping->i_pages, page_index(head));
2784
2785                 /*
2786                  * Check if the head page is present in page cache.
2787                  * We assume all tail are present too, if head is there.
2788                  */
2789                 xa_lock(&mapping->i_pages);
2790                 if (xas_load(&xas) != head)
2791                         goto fail;
2792         }
2793
2794         /* Prevent deferred_split_scan() touching ->_refcount */
2795         spin_lock(&ds_queue->split_queue_lock);
2796         count = page_count(head);
2797         mapcount = total_mapcount(head);
2798         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2799                 if (!list_empty(page_deferred_list(head))) {
2800                         ds_queue->split_queue_len--;
2801                         list_del(page_deferred_list(head));
2802                 }
2803                 if (mapping) {
2804                         if (PageSwapBacked(page))
2805                                 __dec_node_page_state(page, NR_SHMEM_THPS);
2806                         else
2807                                 __dec_node_page_state(page, NR_FILE_THPS);
2808                 }
2809
2810                 spin_unlock(&ds_queue->split_queue_lock);
2811                 __split_huge_page(page, list, end, flags);
2812                 if (PageSwapCache(head)) {
2813                         swp_entry_t entry = { .val = page_private(head) };
2814
2815                         ret = split_swap_cluster(entry);
2816                 } else
2817                         ret = 0;
2818         } else {
2819                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2820                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2821                                         mapcount, count);
2822                         if (PageTail(page))
2823                                 dump_page(head, NULL);
2824                         dump_page(page, "total_mapcount(head) > 0");
2825                         BUG();
2826                 }
2827                 spin_unlock(&ds_queue->split_queue_lock);
2828 fail:           if (mapping)
2829                         xa_unlock(&mapping->i_pages);
2830                 spin_unlock_irqrestore(&pgdata->lru_lock, flags);
2831                 remap_page(head);
2832                 ret = -EBUSY;
2833         }
2834
2835 out_unlock:
2836         if (anon_vma) {
2837                 anon_vma_unlock_write(anon_vma);
2838                 put_anon_vma(anon_vma);
2839         }
2840         if (mapping)
2841                 i_mmap_unlock_read(mapping);
2842 out:
2843         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2844         return ret;
2845 }
2846
2847 void free_transhuge_page(struct page *page)
2848 {
2849         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2850         unsigned long flags;
2851
2852         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2853         if (!list_empty(page_deferred_list(page))) {
2854                 ds_queue->split_queue_len--;
2855                 list_del(page_deferred_list(page));
2856         }
2857         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2858         free_compound_page(page);
2859 }
2860
2861 void deferred_split_huge_page(struct page *page)
2862 {
2863         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2864 #ifdef CONFIG_MEMCG
2865         struct mem_cgroup *memcg = compound_head(page)->mem_cgroup;
2866 #endif
2867         unsigned long flags;
2868
2869         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2870
2871         /*
2872          * The try_to_unmap() in page reclaim path might reach here too,
2873          * this may cause a race condition to corrupt deferred split queue.
2874          * And, if page reclaim is already handling the same page, it is
2875          * unnecessary to handle it again in shrinker.
2876          *
2877          * Check PageSwapCache to determine if the page is being
2878          * handled by page reclaim since THP swap would add the page into
2879          * swap cache before calling try_to_unmap().
2880          */
2881         if (PageSwapCache(page))
2882                 return;
2883
2884         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2885         if (list_empty(page_deferred_list(page))) {
2886                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2887                 list_add_tail(page_deferred_list(page), &ds_queue->split_queue);
2888                 ds_queue->split_queue_len++;
2889 #ifdef CONFIG_MEMCG
2890                 if (memcg)
2891                         memcg_set_shrinker_bit(memcg, page_to_nid(page),
2892                                                deferred_split_shrinker.id);
2893 #endif
2894         }
2895         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2896 }
2897
2898 static unsigned long deferred_split_count(struct shrinker *shrink,
2899                 struct shrink_control *sc)
2900 {
2901         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2902         struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2903
2904 #ifdef CONFIG_MEMCG
2905         if (sc->memcg)
2906                 ds_queue = &sc->memcg->deferred_split_queue;
2907 #endif
2908         return READ_ONCE(ds_queue->split_queue_len);
2909 }
2910
2911 static unsigned long deferred_split_scan(struct shrinker *shrink,
2912                 struct shrink_control *sc)
2913 {
2914         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2915         struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2916         unsigned long flags;
2917         LIST_HEAD(list), *pos, *next;
2918         struct page *page;
2919         int split = 0;
2920
2921 #ifdef CONFIG_MEMCG
2922         if (sc->memcg)
2923                 ds_queue = &sc->memcg->deferred_split_queue;
2924 #endif
2925
2926         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2927         /* Take pin on all head pages to avoid freeing them under us */
2928         list_for_each_safe(pos, next, &ds_queue->split_queue) {
2929                 page = list_entry((void *)pos, struct page, mapping);
2930                 page = compound_head(page);
2931                 if (get_page_unless_zero(page)) {
2932                         list_move(page_deferred_list(page), &list);
2933                 } else {
2934                         /* We lost race with put_compound_page() */
2935                         list_del_init(page_deferred_list(page));
2936                         ds_queue->split_queue_len--;
2937                 }
2938                 if (!--sc->nr_to_scan)
2939                         break;
2940         }
2941         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2942
2943         list_for_each_safe(pos, next, &list) {
2944                 page = list_entry((void *)pos, struct page, mapping);
2945                 if (!trylock_page(page))
2946                         goto next;
2947                 /* split_huge_page() removes page from list on success */
2948                 if (!split_huge_page(page))
2949                         split++;
2950                 unlock_page(page);
2951 next:
2952                 put_page(page);
2953         }
2954
2955         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2956         list_splice_tail(&list, &ds_queue->split_queue);
2957         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2958
2959         /*
2960          * Stop shrinker if we didn't split any page, but the queue is empty.
2961          * This can happen if pages were freed under us.
2962          */
2963         if (!split && list_empty(&ds_queue->split_queue))
2964                 return SHRINK_STOP;
2965         return split;
2966 }
2967
2968 static struct shrinker deferred_split_shrinker = {
2969         .count_objects = deferred_split_count,
2970         .scan_objects = deferred_split_scan,
2971         .seeks = DEFAULT_SEEKS,
2972         .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |
2973                  SHRINKER_NONSLAB,
2974 };
2975
2976 #ifdef CONFIG_DEBUG_FS
2977 static int split_huge_pages_set(void *data, u64 val)
2978 {
2979         struct zone *zone;
2980         struct page *page;
2981         unsigned long pfn, max_zone_pfn;
2982         unsigned long total = 0, split = 0;
2983
2984         if (val != 1)
2985                 return -EINVAL;
2986
2987         for_each_populated_zone(zone) {
2988                 max_zone_pfn = zone_end_pfn(zone);
2989                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2990                         if (!pfn_valid(pfn))
2991                                 continue;
2992
2993                         page = pfn_to_page(pfn);
2994                         if (!get_page_unless_zero(page))
2995                                 continue;
2996
2997                         if (zone != page_zone(page))
2998                                 goto next;
2999
3000                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
3001                                 goto next;
3002
3003                         total++;
3004                         lock_page(page);
3005                         if (!split_huge_page(page))
3006                                 split++;
3007                         unlock_page(page);
3008 next:
3009                         put_page(page);
3010                 }
3011         }
3012
3013         pr_info("%lu of %lu THP split\n", split, total);
3014
3015         return 0;
3016 }
3017 DEFINE_DEBUGFS_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
3018                 "%llu\n");
3019
3020 static int __init split_huge_pages_debugfs(void)
3021 {
3022         debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
3023                             &split_huge_pages_fops);
3024         return 0;
3025 }
3026 late_initcall(split_huge_pages_debugfs);
3027 #endif
3028
3029 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
3030 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
3031                 struct page *page)
3032 {
3033         struct vm_area_struct *vma = pvmw->vma;
3034         struct mm_struct *mm = vma->vm_mm;
3035         unsigned long address = pvmw->address;
3036         pmd_t pmdval;
3037         swp_entry_t entry;
3038         pmd_t pmdswp;
3039
3040         if (!(pvmw->pmd && !pvmw->pte))
3041                 return;
3042
3043         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
3044         pmdval = *pvmw->pmd;
3045         pmdp_invalidate(vma, address, pvmw->pmd);
3046         if (pmd_dirty(pmdval))
3047                 set_page_dirty(page);
3048         entry = make_migration_entry(page, pmd_write(pmdval));
3049         pmdswp = swp_entry_to_pmd(entry);
3050         if (pmd_soft_dirty(pmdval))
3051                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
3052         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
3053         page_remove_rmap(page, true);
3054         put_page(page);
3055 }
3056
3057 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
3058 {
3059         struct vm_area_struct *vma = pvmw->vma;
3060         struct mm_struct *mm = vma->vm_mm;
3061         unsigned long address = pvmw->address;
3062         unsigned long mmun_start = address & HPAGE_PMD_MASK;
3063         pmd_t pmde;
3064         swp_entry_t entry;
3065
3066         if (!(pvmw->pmd && !pvmw->pte))
3067                 return;
3068
3069         entry = pmd_to_swp_entry(*pvmw->pmd);
3070         get_page(new);
3071         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
3072         if (pmd_swp_soft_dirty(*pvmw->pmd))
3073                 pmde = pmd_mksoft_dirty(pmde);
3074         if (is_write_migration_entry(entry))
3075                 pmde = maybe_pmd_mkwrite(pmde, vma);
3076
3077         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
3078         if (PageAnon(new))
3079                 page_add_anon_rmap(new, vma, mmun_start, true);
3080         else
3081                 page_add_file_rmap(new, true);
3082         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
3083         if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
3084                 mlock_vma_page(new);
3085         update_mmu_cache_pmd(vma, address, pvmw->pmd);
3086 }
3087 #endif