mm/huge_memory.c

   1 /*
   2  *  Copyright (C) 2009  Red Hat, Inc.
   3  *
   4  *  This work is licensed under the terms of the GNU GPL, version 2. See
   5  *  the COPYING file in the top-level directory.
   6  */
   7
   8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9
  10 #include <linux/mm.h>
  11 #include <linux/sched.h>
  12 #include <linux/sched/coredump.h>
  13 #include <linux/sched/numa_balancing.h>
  14 #include <linux/highmem.h>
  15 #include <linux/hugetlb.h>
  16 #include <linux/mmu_notifier.h>
  17 #include <linux/rmap.h>
  18 #include <linux/swap.h>
  19 #include <linux/shrinker.h>
  20 #include <linux/mm_inline.h>
  21 #include <linux/swapops.h>
  22 #include <linux/dax.h>
  23 #include <linux/khugepaged.h>
  24 #include <linux/freezer.h>
  25 #include <linux/pfn_t.h>
  26 #include <linux/mman.h>
  27 #include <linux/memremap.h>
  28 #include <linux/pagemap.h>
  29 #include <linux/debugfs.h>
  30 #include <linux/migrate.h>
  31 #include <linux/hashtable.h>
  32 #include <linux/userfaultfd_k.h>
  33 #include <linux/page_idle.h>
  34 #include <linux/shmem_fs.h>
  35 #include <linux/oom.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 static struct page *get_huge_zero_page(void)
  66 {
  67         struct page *zero_page;
  68 retry:
  69         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
  70                 return READ_ONCE(huge_zero_page);
  71
  72         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
  73                         HPAGE_PMD_ORDER);
  74         if (!zero_page) {
  75                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
  76                 return NULL;
  77         }
  78         count_vm_event(THP_ZERO_PAGE_ALLOC);
  79         preempt_disable();
  80         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
  81                 preempt_enable();
  82                 __free_pages(zero_page, compound_order(zero_page));
  83                 goto retry;
  84         }
  85
  86         /* We take additional reference here. It will be put back by shrinker */
  87         atomic_set(&huge_zero_refcount, 2);
  88         preempt_enable();
  89         return READ_ONCE(huge_zero_page);
  90 }
  91
  92 static void put_huge_zero_page(void)
  93 {
  94         /*
  95          * Counter should never go to zero here. Only shrinker can put
  96          * last reference.
  97          */
  98         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
  99 }
 100
 101 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
 102 {
 103         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 104                 return READ_ONCE(huge_zero_page);
 105
 106         if (!get_huge_zero_page())
 107                 return NULL;
 108
 109         if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 110                 put_huge_zero_page();
 111
 112         return READ_ONCE(huge_zero_page);
 113 }
 114
 115 void mm_put_huge_zero_page(struct mm_struct *mm)
 116 {
 117         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 118                 put_huge_zero_page();
 119 }
 120
 121 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
 122                                         struct shrink_control *sc)
 123 {
 124         /* we can free zero page only if last reference remains */
 125         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 126 }
 127
 128 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 129                                        struct shrink_control *sc)
 130 {
 131         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 132                 struct page *zero_page = xchg(&huge_zero_page, NULL);
 133                 BUG_ON(zero_page == NULL);
 134                 __free_pages(zero_page, compound_order(zero_page));
 135                 return HPAGE_PMD_NR;
 136         }
 137
 138         return 0;
 139 }
 140
 141 static struct shrinker huge_zero_page_shrinker = {
 142         .count_objects = shrink_huge_zero_page_count,
 143         .scan_objects = shrink_huge_zero_page_scan,
 144         .seeks = DEFAULT_SEEKS,
 145 };
 146
 147 #ifdef CONFIG_SYSFS
 148 static ssize_t enabled_show(struct kobject *kobj,
 149                             struct kobj_attribute *attr, char *buf)
 150 {
 151         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
 152                 return sprintf(buf, "[always] madvise never\n");
 153         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
 154                 return sprintf(buf, "always [madvise] never\n");
 155         else
 156                 return sprintf(buf, "always madvise [never]\n");
 157 }
 158
 159 static ssize_t enabled_store(struct kobject *kobj,
 160                              struct kobj_attribute *attr,
 161                              const char *buf, size_t count)
 162 {
 163         ssize_t ret = count;
 164
 165         if (!memcmp("always", buf,
 166                     min(sizeof("always")-1, count))) {
 167                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 168                 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 169         } else if (!memcmp("madvise", buf,
 170                            min(sizeof("madvise")-1, count))) {
 171                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 172                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 173         } else if (!memcmp("never", buf,
 174                            min(sizeof("never")-1, count))) {
 175                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 176                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 177         } else
 178                 ret = -EINVAL;
 179
 180         if (ret > 0) {
 181                 int err = start_stop_khugepaged();
 182                 if (err)
 183                         ret = err;
 184         }
 185         return ret;
 186 }
 187 static struct kobj_attribute enabled_attr =
 188         __ATTR(enabled, 0644, enabled_show, enabled_store);
 189
 190 ssize_t single_hugepage_flag_show(struct kobject *kobj,
 191                                 struct kobj_attribute *attr, char *buf,
 192                                 enum transparent_hugepage_flag flag)
 193 {
 194         return sprintf(buf, "%d\n",
 195                        !!test_bit(flag, &transparent_hugepage_flags));
 196 }
 197
 198 ssize_t single_hugepage_flag_store(struct kobject *kobj,
 199                                  struct kobj_attribute *attr,
 200                                  const char *buf, size_t count,
 201                                  enum transparent_hugepage_flag flag)
 202 {
 203         unsigned long value;
 204         int ret;
 205
 206         ret = kstrtoul(buf, 10, &value);
 207         if (ret < 0)
 208                 return ret;
 209         if (value > 1)
 210                 return -EINVAL;
 211
 212         if (value)
 213                 set_bit(flag, &transparent_hugepage_flags);
 214         else
 215                 clear_bit(flag, &transparent_hugepage_flags);
 216
 217         return count;
 218 }
 219
 220 static ssize_t defrag_show(struct kobject *kobj,
 221                            struct kobj_attribute *attr, char *buf)
 222 {
 223         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 224                 return sprintf(buf, "[always] defer defer+madvise madvise never\n");
 225         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 226                 return sprintf(buf, "always [defer] defer+madvise madvise never\n");
 227         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 228                 return sprintf(buf, "always defer [defer+madvise] madvise never\n");
 229         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 230                 return sprintf(buf, "always defer defer+madvise [madvise] never\n");
 231         return sprintf(buf, "always defer defer+madvise madvise [never]\n");
 232 }
 233
 234 static ssize_t defrag_store(struct kobject *kobj,
 235                             struct kobj_attribute *attr,
 236                             const char *buf, size_t count)
 237 {
 238         if (!memcmp("always", buf,
 239                     min(sizeof("always")-1, count))) {
 240                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 241                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 242                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 243                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 244         } else if (!memcmp("defer+madvise", buf,
 245                     min(sizeof("defer+madvise")-1, count))) {
 246                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 247                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 248                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 249                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 250         } else if (!memcmp("defer", buf,
 251                     min(sizeof("defer")-1, count))) {
 252                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 253                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 254                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 255                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 256         } else if (!memcmp("madvise", buf,
 257                            min(sizeof("madvise")-1, count))) {
 258                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 259                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 260                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 261                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 262         } else if (!memcmp("never", buf,
 263                            min(sizeof("never")-1, count))) {
 264                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 265                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 266                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 267                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 268         } else
 269                 return -EINVAL;
 270
 271         return count;
 272 }
 273 static struct kobj_attribute defrag_attr =
 274         __ATTR(defrag, 0644, defrag_show, defrag_store);
 275
 276 static ssize_t use_zero_page_show(struct kobject *kobj,
 277                 struct kobj_attribute *attr, char *buf)
 278 {
 279         return single_hugepage_flag_show(kobj, attr, buf,
 280                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 281 }
 282 static ssize_t use_zero_page_store(struct kobject *kobj,
 283                 struct kobj_attribute *attr, const char *buf, size_t count)
 284 {
 285         return single_hugepage_flag_store(kobj, attr, buf, count,
 286                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 287 }
 288 static struct kobj_attribute use_zero_page_attr =
 289         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 290
 291 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
 292                 struct kobj_attribute *attr, char *buf)
 293 {
 294         return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
 295 }
 296 static struct kobj_attribute hpage_pmd_size_attr =
 297         __ATTR_RO(hpage_pmd_size);
 298
 299 #ifdef CONFIG_DEBUG_VM
 300 static ssize_t debug_cow_show(struct kobject *kobj,
 301                                 struct kobj_attribute *attr, char *buf)
 302 {
 303         return single_hugepage_flag_show(kobj, attr, buf,
 304                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 305 }
 306 static ssize_t debug_cow_store(struct kobject *kobj,
 307                                struct kobj_attribute *attr,
 308                                const char *buf, size_t count)
 309 {
 310         return single_hugepage_flag_store(kobj, attr, buf, count,
 311                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 312 }
 313 static struct kobj_attribute debug_cow_attr =
 314         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 315 #endif /* CONFIG_DEBUG_VM */
 316
 317 static struct attribute *hugepage_attr[] = {
 318         &enabled_attr.attr,
 319         &defrag_attr.attr,
 320         &use_zero_page_attr.attr,
 321         &hpage_pmd_size_attr.attr,
 322 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
 323         &shmem_enabled_attr.attr,
 324 #endif
 325 #ifdef CONFIG_DEBUG_VM
 326         &debug_cow_attr.attr,
 327 #endif
 328         NULL,
 329 };
 330
 331 static const struct attribute_group hugepage_attr_group = {
 332         .attrs = hugepage_attr,
 333 };
 334
 335 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 336 {
 337         int err;
 338
 339         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 340         if (unlikely(!*hugepage_kobj)) {
 341                 pr_err("failed to create transparent hugepage kobject\n");
 342                 return -ENOMEM;
 343         }
 344
 345         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 346         if (err) {
 347                 pr_err("failed to register transparent hugepage group\n");
 348                 goto delete_obj;
 349         }
 350
 351         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 352         if (err) {
 353                 pr_err("failed to register transparent hugepage group\n");
 354                 goto remove_hp_group;
 355         }
 356
 357         return 0;
 358
 359 remove_hp_group:
 360         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 361 delete_obj:
 362         kobject_put(*hugepage_kobj);
 363         return err;
 364 }
 365
 366 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 367 {
 368         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 369         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 370         kobject_put(hugepage_kobj);
 371 }
 372 #else
 373 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 374 {
 375         return 0;
 376 }
 377
 378 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 379 {
 380 }
 381 #endif /* CONFIG_SYSFS */
 382
 383 static int __init hugepage_init(void)
 384 {
 385         int err;
 386         struct kobject *hugepage_kobj;
 387
 388         if (!has_transparent_hugepage()) {
 389                 transparent_hugepage_flags = 0;
 390                 return -EINVAL;
 391         }
 392
 393         /*
 394          * hugepages can't be allocated by the buddy allocator
 395          */
 396         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
 397         /*
 398          * we use page->mapping and page->index in second tail page
 399          * as list_head: assuming THP order >= 2
 400          */
 401         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
 402
 403         err = hugepage_init_sysfs(&hugepage_kobj);
 404         if (err)
 405                 goto err_sysfs;
 406
 407         err = khugepaged_init();
 408         if (err)
 409                 goto err_slab;
 410
 411         err = register_shrinker(&huge_zero_page_shrinker);
 412         if (err)
 413                 goto err_hzp_shrinker;
 414         err = register_shrinker(&deferred_split_shrinker);
 415         if (err)
 416                 goto err_split_shrinker;
 417
 418         /*
 419          * By default disable transparent hugepages on smaller systems,
 420          * where the extra memory used could hurt more than TLB overhead
 421          * is likely to save.  The admin can still enable it through /sys.
 422          */
 423         if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
 424                 transparent_hugepage_flags = 0;
 425                 return 0;
 426         }
 427
 428         err = start_stop_khugepaged();
 429         if (err)
 430                 goto err_khugepaged;
 431
 432         return 0;
 433 err_khugepaged:
 434         unregister_shrinker(&deferred_split_shrinker);
 435 err_split_shrinker:
 436         unregister_shrinker(&huge_zero_page_shrinker);
 437 err_hzp_shrinker:
 438         khugepaged_destroy();
 439 err_slab:
 440         hugepage_exit_sysfs(hugepage_kobj);
 441 err_sysfs:
 442         return err;
 443 }
 444 subsys_initcall(hugepage_init);
 445
 446 static int __init setup_transparent_hugepage(char *str)
 447 {
 448         int ret = 0;
 449         if (!str)
 450                 goto out;
 451         if (!strcmp(str, "always")) {
 452                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 453                         &transparent_hugepage_flags);
 454                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 455                           &transparent_hugepage_flags);
 456                 ret = 1;
 457         } else if (!strcmp(str, "madvise")) {
 458                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 459                           &transparent_hugepage_flags);
 460                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 461                         &transparent_hugepage_flags);
 462                 ret = 1;
 463         } else if (!strcmp(str, "never")) {
 464                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 465                           &transparent_hugepage_flags);
 466                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 467                           &transparent_hugepage_flags);
 468                 ret = 1;
 469         }
 470 out:
 471         if (!ret)
 472                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
 473         return ret;
 474 }
 475 __setup("transparent_hugepage=", setup_transparent_hugepage);
 476
 477 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 478 {
 479         if (likely(vma->vm_flags & VM_WRITE))
 480                 pmd = pmd_mkwrite(pmd);
 481         return pmd;
 482 }
 483
 484 static inline struct list_head *page_deferred_list(struct page *page)
 485 {
 486         /* ->lru in the tail pages is occupied by compound_head. */
 487         return &page[2].deferred_list;
 488 }
 489
 490 void prep_transhuge_page(struct page *page)
 491 {
 492         /*
 493          * we use page->mapping and page->indexlru in second tail page
 494          * as list_head: assuming THP order >= 2
 495          */
 496
 497         INIT_LIST_HEAD(page_deferred_list(page));
 498         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 499 }
 500
 501 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
 502                 loff_t off, unsigned long flags, unsigned long size)
 503 {
 504         unsigned long addr;
 505         loff_t off_end = off + len;
 506         loff_t off_align = round_up(off, size);
 507         unsigned long len_pad;
 508
 509         if (off_end <= off_align || (off_end - off_align) < size)
 510                 return 0;
 511
 512         len_pad = len + size;
 513         if (len_pad < len || (off + len_pad) < off)
 514                 return 0;
 515
 516         addr = current->mm->get_unmapped_area(filp, 0, len_pad,
 517                                               off >> PAGE_SHIFT, flags);
 518         if (IS_ERR_VALUE(addr))
 519                 return 0;
 520
 521         addr += (off - addr) & (size - 1);
 522         return addr;
 523 }
 524
 525 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 526                 unsigned long len, unsigned long pgoff, unsigned long flags)
 527 {
 528         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 529
 530         if (addr)
 531                 goto out;
 532         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
 533                 goto out;
 534
 535         addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
 536         if (addr)
 537                 return addr;
 538
 539  out:
 540         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 541 }
 542 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 543
 544 static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page,
 545                 gfp_t gfp)
 546 {
 547         struct vm_area_struct *vma = vmf->vma;
 548         struct mem_cgroup *memcg;
 549         pgtable_t pgtable;
 550         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 551         int ret = 0;
 552
 553         VM_BUG_ON_PAGE(!PageCompound(page), page);
 554
 555         if (mem_cgroup_try_charge(page, vma->vm_mm, gfp, &memcg, true)) {
 556                 put_page(page);
 557                 count_vm_event(THP_FAULT_FALLBACK);
 558                 return VM_FAULT_FALLBACK;
 559         }
 560
 561         pgtable = pte_alloc_one(vma->vm_mm, haddr);
 562         if (unlikely(!pgtable)) {
 563                 ret = VM_FAULT_OOM;
 564                 goto release;
 565         }
 566
 567         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
 568         /*
 569          * The memory barrier inside __SetPageUptodate makes sure that
 570          * clear_huge_page writes become visible before the set_pmd_at()
 571          * write.
 572          */
 573         __SetPageUptodate(page);
 574
 575         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 576         if (unlikely(!pmd_none(*vmf->pmd))) {
 577                 goto unlock_release;
 578         } else {
 579                 pmd_t entry;
 580
 581                 ret = check_stable_address_space(vma->vm_mm);
 582                 if (ret)
 583                         goto unlock_release;
 584
 585                 /* Deliver the page fault to userland */
 586                 if (userfaultfd_missing(vma)) {
 587                         int ret;
 588
 589                         spin_unlock(vmf->ptl);
 590                         mem_cgroup_cancel_charge(page, memcg, true);
 591                         put_page(page);
 592                         pte_free(vma->vm_mm, pgtable);
 593                         ret = handle_userfault(vmf, VM_UFFD_MISSING);
 594                         VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 595                         return ret;
 596                 }
 597
 598                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 599                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 600                 page_add_new_anon_rmap(page, vma, haddr, true);
 601                 mem_cgroup_commit_charge(page, memcg, false, true);
 602                 lru_cache_add_active_or_unevictable(page, vma);
 603                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 604                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 605                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 606                 mm_inc_nr_ptes(vma->vm_mm);
 607                 spin_unlock(vmf->ptl);
 608                 count_vm_event(THP_FAULT_ALLOC);
 609         }
 610
 611         return 0;
 612 unlock_release:
 613         spin_unlock(vmf->ptl);
 614 release:
 615         if (pgtable)
 616                 pte_free(vma->vm_mm, pgtable);
 617         mem_cgroup_cancel_charge(page, memcg, true);
 618         put_page(page);
 619         return ret;
 620
 621 }
 622
 623 /*
 624  * always: directly stall for all thp allocations
 625  * defer: wake kswapd and fail if not immediately available
 626  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
 627  *                fail if not immediately available
 628  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
 629  *          available
 630  * never: never stall for any thp allocation
 631  */
 632 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
 633 {
 634         const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
 635
 636         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 637                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
 638         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 639                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
 640         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 641                 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
 642                                                              __GFP_KSWAPD_RECLAIM);
 643         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 644                 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
 645                                                              0);
 646         return GFP_TRANSHUGE_LIGHT;
 647 }
 648
 649 /* Caller must hold page table lock. */
 650 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 651                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 652                 struct page *zero_page)
 653 {
 654         pmd_t entry;
 655         if (!pmd_none(*pmd))
 656                 return false;
 657         entry = mk_pmd(zero_page, vma->vm_page_prot);
 658         entry = pmd_mkhuge(entry);
 659         if (pgtable)
 660                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 661         set_pmd_at(mm, haddr, pmd, entry);
 662         mm_inc_nr_ptes(mm);
 663         return true;
 664 }
 665
 666 int do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 667 {
 668         struct vm_area_struct *vma = vmf->vma;
 669         gfp_t gfp;
 670         struct page *page;
 671         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 672
 673         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
 674                 return VM_FAULT_FALLBACK;
 675         if (unlikely(anon_vma_prepare(vma)))
 676                 return VM_FAULT_OOM;
 677         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 678                 return VM_FAULT_OOM;
 679         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
 680                         !mm_forbids_zeropage(vma->vm_mm) &&
 681                         transparent_hugepage_use_zero_page()) {
 682                 pgtable_t pgtable;
 683                 struct page *zero_page;
 684                 bool set;
 685                 int ret;
 686                 pgtable = pte_alloc_one(vma->vm_mm, haddr);
 687                 if (unlikely(!pgtable))
 688                         return VM_FAULT_OOM;
 689                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
 690                 if (unlikely(!zero_page)) {
 691                         pte_free(vma->vm_mm, pgtable);
 692                         count_vm_event(THP_FAULT_FALLBACK);
 693                         return VM_FAULT_FALLBACK;
 694                 }
 695                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 696                 ret = 0;
 697                 set = false;
 698                 if (pmd_none(*vmf->pmd)) {
 699                         ret = check_stable_address_space(vma->vm_mm);
 700                         if (ret) {
 701                                 spin_unlock(vmf->ptl);
 702                         } else if (userfaultfd_missing(vma)) {
 703                                 spin_unlock(vmf->ptl);
 704                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
 705                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 706                         } else {
 707                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
 708                                                    haddr, vmf->pmd, zero_page);
 709                                 spin_unlock(vmf->ptl);
 710                                 set = true;
 711                         }
 712                 } else
 713                         spin_unlock(vmf->ptl);
 714                 if (!set)
 715                         pte_free(vma->vm_mm, pgtable);
 716                 return ret;
 717         }
 718         gfp = alloc_hugepage_direct_gfpmask(vma);
 719         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 720         if (unlikely(!page)) {
 721                 count_vm_event(THP_FAULT_FALLBACK);
 722                 return VM_FAULT_FALLBACK;
 723         }
 724         prep_transhuge_page(page);
 725         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
 726 }
 727
 728 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 729                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
 730                 pgtable_t pgtable)
 731 {
 732         struct mm_struct *mm = vma->vm_mm;
 733         pmd_t entry;
 734         spinlock_t *ptl;
 735
 736         ptl = pmd_lock(mm, pmd);
 737         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 738         if (pfn_t_devmap(pfn))
 739                 entry = pmd_mkdevmap(entry);
 740         if (write) {
 741                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 742                 entry = maybe_pmd_mkwrite(entry, vma);
 743         }
 744
 745         if (pgtable) {
 746                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 747                 mm_inc_nr_ptes(mm);
 748         }
 749
 750         set_pmd_at(mm, addr, pmd, entry);
 751         update_mmu_cache_pmd(vma, addr, pmd);
 752         spin_unlock(ptl);
 753 }
 754
 755 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 756                         pmd_t *pmd, pfn_t pfn, bool write)
 757 {
 758         pgprot_t pgprot = vma->vm_page_prot;
 759         pgtable_t pgtable = NULL;
 760         /*
 761          * If we had pmd_special, we could avoid all these restrictions,
 762          * but we need to be consistent with PTEs and architectures that
 763          * can't support a 'special' bit.
 764          */
 765         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
 766         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 767                                                 (VM_PFNMAP|VM_MIXEDMAP));
 768         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 769         BUG_ON(!pfn_t_devmap(pfn));
 770
 771         if (addr < vma->vm_start || addr >= vma->vm_end)
 772                 return VM_FAULT_SIGBUS;
 773
 774         if (arch_needs_pgtable_deposit()) {
 775                 pgtable = pte_alloc_one(vma->vm_mm, addr);
 776                 if (!pgtable)
 777                         return VM_FAULT_OOM;
 778         }
 779
 780         track_pfn_insert(vma, &pgprot, pfn);
 781
 782         insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable);
 783         return VM_FAULT_NOPAGE;
 784 }
 785 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
 786
 787 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 788 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 789 {
 790         if (likely(vma->vm_flags & VM_WRITE))
 791                 pud = pud_mkwrite(pud);
 792         return pud;
 793 }
 794
 795 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 796                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 797 {
 798         struct mm_struct *mm = vma->vm_mm;
 799         pud_t entry;
 800         spinlock_t *ptl;
 801
 802         ptl = pud_lock(mm, pud);
 803         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
 804         if (pfn_t_devmap(pfn))
 805                 entry = pud_mkdevmap(entry);
 806         if (write) {
 807                 entry = pud_mkyoung(pud_mkdirty(entry));
 808                 entry = maybe_pud_mkwrite(entry, vma);
 809         }
 810         set_pud_at(mm, addr, pud, entry);
 811         update_mmu_cache_pud(vma, addr, pud);
 812         spin_unlock(ptl);
 813 }
 814
 815 int vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 816                         pud_t *pud, pfn_t pfn, bool write)
 817 {
 818         pgprot_t pgprot = vma->vm_page_prot;
 819         /*
 820          * If we had pud_special, we could avoid all these restrictions,
 821          * but we need to be consistent with PTEs and architectures that
 822          * can't support a 'special' bit.
 823          */
 824         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
 825         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 826                                                 (VM_PFNMAP|VM_MIXEDMAP));
 827         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 828         BUG_ON(!pfn_t_devmap(pfn));
 829
 830         if (addr < vma->vm_start || addr >= vma->vm_end)
 831                 return VM_FAULT_SIGBUS;
 832
 833         track_pfn_insert(vma, &pgprot, pfn);
 834
 835         insert_pfn_pud(vma, addr, pud, pfn, pgprot, write);
 836         return VM_FAULT_NOPAGE;
 837 }
 838 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
 839 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 840
 841 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
 842                 pmd_t *pmd, int flags)
 843 {
 844         pmd_t _pmd;
 845
 846         _pmd = pmd_mkyoung(*pmd);
 847         if (flags & FOLL_WRITE)
 848                 _pmd = pmd_mkdirty(_pmd);
 849         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 850                                 pmd, _pmd, flags & FOLL_WRITE))
 851                 update_mmu_cache_pmd(vma, addr, pmd);
 852 }
 853
 854 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 855                 pmd_t *pmd, int flags)
 856 {
 857         unsigned long pfn = pmd_pfn(*pmd);
 858         struct mm_struct *mm = vma->vm_mm;
 859         struct dev_pagemap *pgmap;
 860         struct page *page;
 861
 862         assert_spin_locked(pmd_lockptr(mm, pmd));
 863
 864         /*
 865          * When we COW a devmap PMD entry, we split it into PTEs, so we should
 866          * not be in this function with `flags & FOLL_COW` set.
 867          */
 868         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
 869
 870         if (flags & FOLL_WRITE && !pmd_write(*pmd))
 871                 return NULL;
 872
 873         if (pmd_present(*pmd) && pmd_devmap(*pmd))
 874                 /* pass */;
 875         else
 876                 return NULL;
 877
 878         if (flags & FOLL_TOUCH)
 879                 touch_pmd(vma, addr, pmd, flags);
 880
 881         /*
 882          * device mapped pages can only be returned if the
 883          * caller will manage the page reference count.
 884          */
 885         if (!(flags & FOLL_GET))
 886                 return ERR_PTR(-EEXIST);
 887
 888         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
 889         pgmap = get_dev_pagemap(pfn, NULL);
 890         if (!pgmap)
 891                 return ERR_PTR(-EFAULT);
 892         page = pfn_to_page(pfn);
 893         get_page(page);
 894         put_dev_pagemap(pgmap);
 895
 896         return page;
 897 }
 898
 899 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 900                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 901                   struct vm_area_struct *vma)
 902 {
 903         spinlock_t *dst_ptl, *src_ptl;
 904         struct page *src_page;
 905         pmd_t pmd;
 906         pgtable_t pgtable = NULL;
 907         int ret = -ENOMEM;
 908
 909         /* Skip if can be re-fill on fault */
 910         if (!vma_is_anonymous(vma))
 911                 return 0;
 912
 913         pgtable = pte_alloc_one(dst_mm, addr);
 914         if (unlikely(!pgtable))
 915                 goto out;
 916
 917         dst_ptl = pmd_lock(dst_mm, dst_pmd);
 918         src_ptl = pmd_lockptr(src_mm, src_pmd);
 919         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 920
 921         ret = -EAGAIN;
 922         pmd = *src_pmd;
 923
 924 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
 925         if (unlikely(is_swap_pmd(pmd))) {
 926                 swp_entry_t entry = pmd_to_swp_entry(pmd);
 927
 928                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
 929                 if (is_write_migration_entry(entry)) {
 930                         make_migration_entry_read(&entry);
 931                         pmd = swp_entry_to_pmd(entry);
 932                         if (pmd_swp_soft_dirty(*src_pmd))
 933                                 pmd = pmd_swp_mksoft_dirty(pmd);
 934                         set_pmd_at(src_mm, addr, src_pmd, pmd);
 935                 }
 936                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 937                 mm_inc_nr_ptes(dst_mm);
 938                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 939                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 940                 ret = 0;
 941                 goto out_unlock;
 942         }
 943 #endif
 944
 945         if (unlikely(!pmd_trans_huge(pmd))) {
 946                 pte_free(dst_mm, pgtable);
 947                 goto out_unlock;
 948         }
 949         /*
 950          * When page table lock is held, the huge zero pmd should not be
 951          * under splitting since we don't split the page itself, only pmd to
 952          * a page table.
 953          */
 954         if (is_huge_zero_pmd(pmd)) {
 955                 struct page *zero_page;
 956                 /*
 957                  * get_huge_zero_page() will never allocate a new page here,
 958                  * since we already have a zero page to copy. It just takes a
 959                  * reference.
 960                  */
 961                 zero_page = mm_get_huge_zero_page(dst_mm);
 962                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
 963                                 zero_page);
 964                 ret = 0;
 965                 goto out_unlock;
 966         }
 967
 968         src_page = pmd_page(pmd);
 969         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
 970         get_page(src_page);
 971         page_dup_rmap(src_page, true);
 972         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 973         mm_inc_nr_ptes(dst_mm);
 974         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 975
 976         pmdp_set_wrprotect(src_mm, addr, src_pmd);
 977         pmd = pmd_mkold(pmd_wrprotect(pmd));
 978         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 979
 980         ret = 0;
 981 out_unlock:
 982         spin_unlock(src_ptl);
 983         spin_unlock(dst_ptl);
 984 out:
 985         return ret;
 986 }
 987
 988 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 989 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
 990                 pud_t *pud, int flags)
 991 {
 992         pud_t _pud;
 993
 994         _pud = pud_mkyoung(*pud);
 995         if (flags & FOLL_WRITE)
 996                 _pud = pud_mkdirty(_pud);
 997         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
 998                                 pud, _pud, flags & FOLL_WRITE))
 999                 update_mmu_cache_pud(vma, addr, pud);
1000 }
1001
1002 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1003                 pud_t *pud, int flags)
1004 {
1005         unsigned long pfn = pud_pfn(*pud);
1006         struct mm_struct *mm = vma->vm_mm;
1007         struct dev_pagemap *pgmap;
1008         struct page *page;
1009
1010         assert_spin_locked(pud_lockptr(mm, pud));
1011
1012         if (flags & FOLL_WRITE && !pud_write(*pud))
1013                 return NULL;
1014
1015         if (pud_present(*pud) && pud_devmap(*pud))
1016                 /* pass */;
1017         else
1018                 return NULL;
1019
1020         if (flags & FOLL_TOUCH)
1021                 touch_pud(vma, addr, pud, flags);
1022
1023         /*
1024          * device mapped pages can only be returned if the
1025          * caller will manage the page reference count.
1026          */
1027         if (!(flags & FOLL_GET))
1028                 return ERR_PTR(-EEXIST);
1029
1030         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1031         pgmap = get_dev_pagemap(pfn, NULL);
1032         if (!pgmap)
1033                 return ERR_PTR(-EFAULT);
1034         page = pfn_to_page(pfn);
1035         get_page(page);
1036         put_dev_pagemap(pgmap);
1037
1038         return page;
1039 }
1040
1041 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1042                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1043                   struct vm_area_struct *vma)
1044 {
1045         spinlock_t *dst_ptl, *src_ptl;
1046         pud_t pud;
1047         int ret;
1048
1049         dst_ptl = pud_lock(dst_mm, dst_pud);
1050         src_ptl = pud_lockptr(src_mm, src_pud);
1051         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1052
1053         ret = -EAGAIN;
1054         pud = *src_pud;
1055         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1056                 goto out_unlock;
1057
1058         /*
1059          * When page table lock is held, the huge zero pud should not be
1060          * under splitting since we don't split the page itself, only pud to
1061          * a page table.
1062          */
1063         if (is_huge_zero_pud(pud)) {
1064                 /* No huge zero pud yet */
1065         }
1066
1067         pudp_set_wrprotect(src_mm, addr, src_pud);
1068         pud = pud_mkold(pud_wrprotect(pud));
1069         set_pud_at(dst_mm, addr, dst_pud, pud);
1070
1071         ret = 0;
1072 out_unlock:
1073         spin_unlock(src_ptl);
1074         spin_unlock(dst_ptl);
1075         return ret;
1076 }
1077
1078 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1079 {
1080         pud_t entry;
1081         unsigned long haddr;
1082         bool write = vmf->flags & FAULT_FLAG_WRITE;
1083
1084         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1085         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1086                 goto unlock;
1087
1088         entry = pud_mkyoung(orig_pud);
1089         if (write)
1090                 entry = pud_mkdirty(entry);
1091         haddr = vmf->address & HPAGE_PUD_MASK;
1092         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1093                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1094
1095 unlock:
1096         spin_unlock(vmf->ptl);
1097 }
1098 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1099
1100 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1101 {
1102         pmd_t entry;
1103         unsigned long haddr;
1104         bool write = vmf->flags & FAULT_FLAG_WRITE;
1105
1106         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1107         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1108                 goto unlock;
1109
1110         entry = pmd_mkyoung(orig_pmd);
1111         if (write)
1112                 entry = pmd_mkdirty(entry);
1113         haddr = vmf->address & HPAGE_PMD_MASK;
1114         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1115                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1116
1117 unlock:
1118         spin_unlock(vmf->ptl);
1119 }
1120
1121 static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd,
1122                 struct page *page)
1123 {
1124         struct vm_area_struct *vma = vmf->vma;
1125         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1126         struct mem_cgroup *memcg;
1127         pgtable_t pgtable;
1128         pmd_t _pmd;
1129         int ret = 0, i;
1130         struct page **pages;
1131         unsigned long mmun_start;       /* For mmu_notifiers */
1132         unsigned long mmun_end;         /* For mmu_notifiers */
1133
1134         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1135                               GFP_KERNEL);
1136         if (unlikely(!pages)) {
1137                 ret |= VM_FAULT_OOM;
1138                 goto out;
1139         }
1140
1141         for (i = 0; i < HPAGE_PMD_NR; i++) {
1142                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1143                                                vmf->address, page_to_nid(page));
1144                 if (unlikely(!pages[i] ||
1145                              mem_cgroup_try_charge(pages[i], vma->vm_mm,
1146                                      GFP_KERNEL, &memcg, false))) {
1147                         if (pages[i])
1148                                 put_page(pages[i]);
1149                         while (--i >= 0) {
1150                                 memcg = (void *)page_private(pages[i]);
1151                                 set_page_private(pages[i], 0);
1152                                 mem_cgroup_cancel_charge(pages[i], memcg,
1153                                                 false);
1154                                 put_page(pages[i]);
1155                         }
1156                         kfree(pages);
1157                         ret |= VM_FAULT_OOM;
1158                         goto out;
1159                 }
1160                 set_page_private(pages[i], (unsigned long)memcg);
1161         }
1162
1163         for (i = 0; i < HPAGE_PMD_NR; i++) {
1164                 copy_user_highpage(pages[i], page + i,
1165                                    haddr + PAGE_SIZE * i, vma);
1166                 __SetPageUptodate(pages[i]);
1167                 cond_resched();
1168         }
1169
1170         mmun_start = haddr;
1171         mmun_end   = haddr + HPAGE_PMD_SIZE;
1172         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1173
1174         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1175         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1176                 goto out_free_pages;
1177         VM_BUG_ON_PAGE(!PageHead(page), page);
1178
1179         /*
1180          * Leave pmd empty until pte is filled note we must notify here as
1181          * concurrent CPU thread might write to new page before the call to
1182          * mmu_notifier_invalidate_range_end() happens which can lead to a
1183          * device seeing memory write in different order than CPU.
1184          *
1185          * See Documentation/vm/mmu_notifier.rst
1186          */
1187         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1188
1189         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1190         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1191
1192         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1193                 pte_t entry;
1194                 entry = mk_pte(pages[i], vma->vm_page_prot);
1195                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1196                 memcg = (void *)page_private(pages[i]);
1197                 set_page_private(pages[i], 0);
1198                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1199                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1200                 lru_cache_add_active_or_unevictable(pages[i], vma);
1201                 vmf->pte = pte_offset_map(&_pmd, haddr);
1202                 VM_BUG_ON(!pte_none(*vmf->pte));
1203                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1204                 pte_unmap(vmf->pte);
1205         }
1206         kfree(pages);
1207
1208         smp_wmb(); /* make pte visible before pmd */
1209         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1210         page_remove_rmap(page, true);
1211         spin_unlock(vmf->ptl);
1212
1213         /*
1214          * No need to double call mmu_notifier->invalidate_range() callback as
1215          * the above pmdp_huge_clear_flush_notify() did already call it.
1216          */
1217         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1218                                                 mmun_end);
1219
1220         ret |= VM_FAULT_WRITE;
1221         put_page(page);
1222
1223 out:
1224         return ret;
1225
1226 out_free_pages:
1227         spin_unlock(vmf->ptl);
1228         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1229         for (i = 0; i < HPAGE_PMD_NR; i++) {
1230                 memcg = (void *)page_private(pages[i]);
1231                 set_page_private(pages[i], 0);
1232                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1233                 put_page(pages[i]);
1234         }
1235         kfree(pages);
1236         goto out;
1237 }
1238
1239 int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1240 {
1241         struct vm_area_struct *vma = vmf->vma;
1242         struct page *page = NULL, *new_page;
1243         struct mem_cgroup *memcg;
1244         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1245         unsigned long mmun_start;       /* For mmu_notifiers */
1246         unsigned long mmun_end;         /* For mmu_notifiers */
1247         gfp_t huge_gfp;                 /* for allocation and charge */
1248         int ret = 0;
1249
1250         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1251         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1252         if (is_huge_zero_pmd(orig_pmd))
1253                 goto alloc;
1254         spin_lock(vmf->ptl);
1255         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1256                 goto out_unlock;
1257
1258         page = pmd_page(orig_pmd);
1259         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1260         /*
1261          * We can only reuse the page if nobody else maps the huge page or it's
1262          * part.
1263          */
1264         if (!trylock_page(page)) {
1265                 get_page(page);
1266                 spin_unlock(vmf->ptl);
1267                 lock_page(page);
1268                 spin_lock(vmf->ptl);
1269                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1270                         unlock_page(page);
1271                         put_page(page);
1272                         goto out_unlock;
1273                 }
1274                 put_page(page);
1275         }
1276         if (reuse_swap_page(page, NULL)) {
1277                 pmd_t entry;
1278                 entry = pmd_mkyoung(orig_pmd);
1279                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1280                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1281                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1282                 ret |= VM_FAULT_WRITE;
1283                 unlock_page(page);
1284                 goto out_unlock;
1285         }
1286         unlock_page(page);
1287         get_page(page);
1288         spin_unlock(vmf->ptl);
1289 alloc:
1290         if (transparent_hugepage_enabled(vma) &&
1291             !transparent_hugepage_debug_cow()) {
1292                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1293                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1294         } else
1295                 new_page = NULL;
1296
1297         if (likely(new_page)) {
1298                 prep_transhuge_page(new_page);
1299         } else {
1300                 if (!page) {
1301                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1302                         ret |= VM_FAULT_FALLBACK;
1303                 } else {
1304                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1305                         if (ret & VM_FAULT_OOM) {
1306                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1307                                 ret |= VM_FAULT_FALLBACK;
1308                         }
1309                         put_page(page);
1310                 }
1311                 count_vm_event(THP_FAULT_FALLBACK);
1312                 goto out;
1313         }
1314
1315         if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm,
1316                                         huge_gfp, &memcg, true))) {
1317                 put_page(new_page);
1318                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1319                 if (page)
1320                         put_page(page);
1321                 ret |= VM_FAULT_FALLBACK;
1322                 count_vm_event(THP_FAULT_FALLBACK);
1323                 goto out;
1324         }
1325
1326         count_vm_event(THP_FAULT_ALLOC);
1327
1328         if (!page)
1329                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1330         else
1331                 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1332         __SetPageUptodate(new_page);
1333
1334         mmun_start = haddr;
1335         mmun_end   = haddr + HPAGE_PMD_SIZE;
1336         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1337
1338         spin_lock(vmf->ptl);
1339         if (page)
1340                 put_page(page);
1341         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1342                 spin_unlock(vmf->ptl);
1343                 mem_cgroup_cancel_charge(new_page, memcg, true);
1344                 put_page(new_page);
1345                 goto out_mn;
1346         } else {
1347                 pmd_t entry;
1348                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1349                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1350                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1351                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1352                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1353                 lru_cache_add_active_or_unevictable(new_page, vma);
1354                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1355                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1356                 if (!page) {
1357                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1358                 } else {
1359                         VM_BUG_ON_PAGE(!PageHead(page), page);
1360                         page_remove_rmap(page, true);
1361                         put_page(page);
1362                 }
1363                 ret |= VM_FAULT_WRITE;
1364         }
1365         spin_unlock(vmf->ptl);
1366 out_mn:
1367         /*
1368          * No need to double call mmu_notifier->invalidate_range() callback as
1369          * the above pmdp_huge_clear_flush_notify() did already call it.
1370          */
1371         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1372                                                mmun_end);
1373 out:
1374         return ret;
1375 out_unlock:
1376         spin_unlock(vmf->ptl);
1377         return ret;
1378 }
1379
1380 /*
1381  * FOLL_FORCE can write to even unwritable pmd's, but only
1382  * after we've gone through a COW cycle and they are dirty.
1383  */
1384 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1385 {
1386         return pmd_write(pmd) ||
1387                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1388 }
1389
1390 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1391                                    unsigned long addr,
1392                                    pmd_t *pmd,
1393                                    unsigned int flags)
1394 {
1395         struct mm_struct *mm = vma->vm_mm;
1396         struct page *page = NULL;
1397
1398         assert_spin_locked(pmd_lockptr(mm, pmd));
1399
1400         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1401                 goto out;
1402
1403         /* Avoid dumping huge zero page */
1404         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1405                 return ERR_PTR(-EFAULT);
1406
1407         /* Full NUMA hinting faults to serialise migration in fault paths */
1408         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1409                 goto out;
1410
1411         page = pmd_page(*pmd);
1412         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1413         if (flags & FOLL_TOUCH)
1414                 touch_pmd(vma, addr, pmd, flags);
1415         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1416                 /*
1417                  * We don't mlock() pte-mapped THPs. This way we can avoid
1418                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1419                  *
1420                  * For anon THP:
1421                  *
1422                  * In most cases the pmd is the only mapping of the page as we
1423                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1424                  * writable private mappings in populate_vma_page_range().
1425                  *
1426                  * The only scenario when we have the page shared here is if we
1427                  * mlocking read-only mapping shared over fork(). We skip
1428                  * mlocking such pages.
1429                  *
1430                  * For file THP:
1431                  *
1432                  * We can expect PageDoubleMap() to be stable under page lock:
1433                  * for file pages we set it in page_add_file_rmap(), which
1434                  * requires page to be locked.
1435                  */
1436
1437                 if (PageAnon(page) && compound_mapcount(page) != 1)
1438                         goto skip_mlock;
1439                 if (PageDoubleMap(page) || !page->mapping)
1440                         goto skip_mlock;
1441                 if (!trylock_page(page))
1442                         goto skip_mlock;
1443                 lru_add_drain();
1444                 if (page->mapping && !PageDoubleMap(page))
1445                         mlock_vma_page(page);
1446                 unlock_page(page);
1447         }
1448 skip_mlock:
1449         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1450         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1451         if (flags & FOLL_GET)
1452                 get_page(page);
1453
1454 out:
1455         return page;
1456 }
1457
1458 /* NUMA hinting page fault entry point for trans huge pmds */
1459 int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1460 {
1461         struct vm_area_struct *vma = vmf->vma;
1462         struct anon_vma *anon_vma = NULL;
1463         struct page *page;
1464         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1465         int page_nid = -1, this_nid = numa_node_id();
1466         int target_nid, last_cpupid = -1;
1467         bool page_locked;
1468         bool migrated = false;
1469         bool was_writable;
1470         int flags = 0;
1471
1472         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1473         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1474                 goto out_unlock;
1475
1476         /*
1477          * If there are potential migrations, wait for completion and retry
1478          * without disrupting NUMA hinting information. Do not relock and
1479          * check_same as the page may no longer be mapped.
1480          */
1481         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1482                 page = pmd_page(*vmf->pmd);
1483                 if (!get_page_unless_zero(page))
1484                         goto out_unlock;
1485                 spin_unlock(vmf->ptl);
1486                 wait_on_page_locked(page);
1487                 put_page(page);
1488                 goto out;
1489         }
1490
1491         page = pmd_page(pmd);
1492         BUG_ON(is_huge_zero_page(page));
1493         page_nid = page_to_nid(page);
1494         last_cpupid = page_cpupid_last(page);
1495         count_vm_numa_event(NUMA_HINT_FAULTS);
1496         if (page_nid == this_nid) {
1497                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1498                 flags |= TNF_FAULT_LOCAL;
1499         }
1500
1501         /* See similar comment in do_numa_page for explanation */
1502         if (!pmd_savedwrite(pmd))
1503                 flags |= TNF_NO_GROUP;
1504
1505         /*
1506          * Acquire the page lock to serialise THP migrations but avoid dropping
1507          * page_table_lock if at all possible
1508          */
1509         page_locked = trylock_page(page);
1510         target_nid = mpol_misplaced(page, vma, haddr);
1511         if (target_nid == -1) {
1512                 /* If the page was locked, there are no parallel migrations */
1513                 if (page_locked)
1514                         goto clear_pmdnuma;
1515         }
1516
1517         /* Migration could have started since the pmd_trans_migrating check */
1518         if (!page_locked) {
1519                 page_nid = -1;
1520                 if (!get_page_unless_zero(page))
1521                         goto out_unlock;
1522                 spin_unlock(vmf->ptl);
1523                 wait_on_page_locked(page);
1524                 put_page(page);
1525                 goto out;
1526         }
1527
1528         /*
1529          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1530          * to serialises splits
1531          */
1532         get_page(page);
1533         spin_unlock(vmf->ptl);
1534         anon_vma = page_lock_anon_vma_read(page);
1535
1536         /* Confirm the PMD did not change while page_table_lock was released */
1537         spin_lock(vmf->ptl);
1538         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1539                 unlock_page(page);
1540                 put_page(page);
1541                 page_nid = -1;
1542                 goto out_unlock;
1543         }
1544
1545         /* Bail if we fail to protect against THP splits for any reason */
1546         if (unlikely(!anon_vma)) {
1547                 put_page(page);
1548                 page_nid = -1;
1549                 goto clear_pmdnuma;
1550         }
1551
1552         /*
1553          * Since we took the NUMA fault, we must have observed the !accessible
1554          * bit. Make sure all other CPUs agree with that, to avoid them
1555          * modifying the page we're about to migrate.
1556          *
1557          * Must be done under PTL such that we'll observe the relevant
1558          * inc_tlb_flush_pending().
1559          *
1560          * We are not sure a pending tlb flush here is for a huge page
1561          * mapping or not. Hence use the tlb range variant
1562          */
1563         if (mm_tlb_flush_pending(vma->vm_mm))
1564                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1565
1566         /*
1567          * Migrate the THP to the requested node, returns with page unlocked
1568          * and access rights restored.
1569          */
1570         spin_unlock(vmf->ptl);
1571
1572         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1573                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1574         if (migrated) {
1575                 flags |= TNF_MIGRATED;
1576                 page_nid = target_nid;
1577         } else
1578                 flags |= TNF_MIGRATE_FAIL;
1579
1580         goto out;
1581 clear_pmdnuma:
1582         BUG_ON(!PageLocked(page));
1583         was_writable = pmd_savedwrite(pmd);
1584         pmd = pmd_modify(pmd, vma->vm_page_prot);
1585         pmd = pmd_mkyoung(pmd);
1586         if (was_writable)
1587                 pmd = pmd_mkwrite(pmd);
1588         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1589         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1590         unlock_page(page);
1591 out_unlock:
1592         spin_unlock(vmf->ptl);
1593
1594 out:
1595         if (anon_vma)
1596                 page_unlock_anon_vma_read(anon_vma);
1597
1598         if (page_nid != -1)
1599                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1600                                 flags);
1601
1602         return 0;
1603 }
1604
1605 /*
1606  * Return true if we do MADV_FREE successfully on entire pmd page.
1607  * Otherwise, return false.
1608  */
1609 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1610                 pmd_t *pmd, unsigned long addr, unsigned long next)
1611 {
1612         spinlock_t *ptl;
1613         pmd_t orig_pmd;
1614         struct page *page;
1615         struct mm_struct *mm = tlb->mm;
1616         bool ret = false;
1617
1618         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1619
1620         ptl = pmd_trans_huge_lock(pmd, vma);
1621         if (!ptl)
1622                 goto out_unlocked;
1623
1624         orig_pmd = *pmd;
1625         if (is_huge_zero_pmd(orig_pmd))
1626                 goto out;
1627
1628         if (unlikely(!pmd_present(orig_pmd))) {
1629                 VM_BUG_ON(thp_migration_supported() &&
1630                                   !is_pmd_migration_entry(orig_pmd));
1631                 goto out;
1632         }
1633
1634         page = pmd_page(orig_pmd);
1635         /*
1636          * If other processes are mapping this page, we couldn't discard
1637          * the page unless they all do MADV_FREE so let's skip the page.
1638          */
1639         if (page_mapcount(page) != 1)
1640                 goto out;
1641
1642         if (!trylock_page(page))
1643                 goto out;
1644
1645         /*
1646          * If user want to discard part-pages of THP, split it so MADV_FREE
1647          * will deactivate only them.
1648          */
1649         if (next - addr != HPAGE_PMD_SIZE) {
1650                 get_page(page);
1651                 spin_unlock(ptl);
1652                 split_huge_page(page);
1653                 unlock_page(page);
1654                 put_page(page);
1655                 goto out_unlocked;
1656         }
1657
1658         if (PageDirty(page))
1659                 ClearPageDirty(page);
1660         unlock_page(page);
1661
1662         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1663                 pmdp_invalidate(vma, addr, pmd);
1664                 orig_pmd = pmd_mkold(orig_pmd);
1665                 orig_pmd = pmd_mkclean(orig_pmd);
1666
1667                 set_pmd_at(mm, addr, pmd, orig_pmd);
1668                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1669         }
1670
1671         mark_page_lazyfree(page);
1672         ret = true;
1673 out:
1674         spin_unlock(ptl);
1675 out_unlocked:
1676         return ret;
1677 }
1678
1679 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1680 {
1681         pgtable_t pgtable;
1682
1683         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1684         pte_free(mm, pgtable);
1685         mm_dec_nr_ptes(mm);
1686 }
1687
1688 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1689                  pmd_t *pmd, unsigned long addr)
1690 {
1691         pmd_t orig_pmd;
1692         spinlock_t *ptl;
1693
1694         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1695
1696         ptl = __pmd_trans_huge_lock(pmd, vma);
1697         if (!ptl)
1698                 return 0;
1699         /*
1700          * For architectures like ppc64 we look at deposited pgtable
1701          * when calling pmdp_huge_get_and_clear. So do the
1702          * pgtable_trans_huge_withdraw after finishing pmdp related
1703          * operations.
1704          */
1705         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1706                         tlb->fullmm);
1707         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1708         if (vma_is_dax(vma)) {
1709                 if (arch_needs_pgtable_deposit())
1710                         zap_deposited_table(tlb->mm, pmd);
1711                 spin_unlock(ptl);
1712                 if (is_huge_zero_pmd(orig_pmd))
1713                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1714         } else if (is_huge_zero_pmd(orig_pmd)) {
1715                 zap_deposited_table(tlb->mm, pmd);
1716                 spin_unlock(ptl);
1717                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1718         } else {
1719                 struct page *page = NULL;
1720                 int flush_needed = 1;
1721
1722                 if (pmd_present(orig_pmd)) {
1723                         page = pmd_page(orig_pmd);
1724                         page_remove_rmap(page, true);
1725                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1726                         VM_BUG_ON_PAGE(!PageHead(page), page);
1727                 } else if (thp_migration_supported()) {
1728                         swp_entry_t entry;
1729
1730                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1731                         entry = pmd_to_swp_entry(orig_pmd);
1732                         page = pfn_to_page(swp_offset(entry));
1733                         flush_needed = 0;
1734                 } else
1735                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1736
1737                 if (PageAnon(page)) {
1738                         zap_deposited_table(tlb->mm, pmd);
1739                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1740                 } else {
1741                         if (arch_needs_pgtable_deposit())
1742                                 zap_deposited_table(tlb->mm, pmd);
1743                         add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1744                 }
1745
1746                 spin_unlock(ptl);
1747                 if (flush_needed)
1748                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1749         }
1750         return 1;
1751 }
1752
1753 #ifndef pmd_move_must_withdraw
1754 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1755                                          spinlock_t *old_pmd_ptl,
1756                                          struct vm_area_struct *vma)
1757 {
1758         /*
1759          * With split pmd lock we also need to move preallocated
1760          * PTE page table if new_pmd is on different PMD page table.
1761          *
1762          * We also don't deposit and withdraw tables for file pages.
1763          */
1764         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1765 }
1766 #endif
1767
1768 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1769 {
1770 #ifdef CONFIG_MEM_SOFT_DIRTY
1771         if (unlikely(is_pmd_migration_entry(pmd)))
1772                 pmd = pmd_swp_mksoft_dirty(pmd);
1773         else if (pmd_present(pmd))
1774                 pmd = pmd_mksoft_dirty(pmd);
1775 #endif
1776         return pmd;
1777 }
1778
1779 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1780                   unsigned long new_addr, unsigned long old_end,
1781                   pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush)
1782 {
1783         spinlock_t *old_ptl, *new_ptl;
1784         pmd_t pmd;
1785         struct mm_struct *mm = vma->vm_mm;
1786         bool force_flush = false;
1787
1788         if ((old_addr & ~HPAGE_PMD_MASK) ||
1789             (new_addr & ~HPAGE_PMD_MASK) ||
1790             old_end - old_addr < HPAGE_PMD_SIZE)
1791                 return false;
1792
1793         /*
1794          * The destination pmd shouldn't be established, free_pgtables()
1795          * should have release it.
1796          */
1797         if (WARN_ON(!pmd_none(*new_pmd))) {
1798                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1799                 return false;
1800         }
1801
1802         /*
1803          * We don't have to worry about the ordering of src and dst
1804          * ptlocks because exclusive mmap_sem prevents deadlock.
1805          */
1806         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1807         if (old_ptl) {
1808                 new_ptl = pmd_lockptr(mm, new_pmd);
1809                 if (new_ptl != old_ptl)
1810                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1811                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1812                 if (pmd_present(pmd) && pmd_dirty(pmd))
1813                         force_flush = true;
1814                 VM_BUG_ON(!pmd_none(*new_pmd));
1815
1816                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1817                         pgtable_t pgtable;
1818                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1819                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1820                 }
1821                 pmd = move_soft_dirty_pmd(pmd);
1822                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1823                 if (new_ptl != old_ptl)
1824                         spin_unlock(new_ptl);
1825                 if (force_flush)
1826                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1827                 else
1828                         *need_flush = true;
1829                 spin_unlock(old_ptl);
1830                 return true;
1831         }
1832         return false;
1833 }
1834
1835 /*
1836  * Returns
1837  *  - 0 if PMD could not be locked
1838  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1839  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1840  */
1841 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1842                 unsigned long addr, pgprot_t newprot, int prot_numa)
1843 {
1844         struct mm_struct *mm = vma->vm_mm;
1845         spinlock_t *ptl;
1846         pmd_t entry;
1847         bool preserve_write;
1848         int ret;
1849
1850         ptl = __pmd_trans_huge_lock(pmd, vma);
1851         if (!ptl)
1852                 return 0;
1853
1854         preserve_write = prot_numa && pmd_write(*pmd);
1855         ret = 1;
1856
1857 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1858         if (is_swap_pmd(*pmd)) {
1859                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1860
1861                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1862                 if (is_write_migration_entry(entry)) {
1863                         pmd_t newpmd;
1864                         /*
1865                          * A protection check is difficult so
1866                          * just be safe and disable write
1867                          */
1868                         make_migration_entry_read(&entry);
1869                         newpmd = swp_entry_to_pmd(entry);
1870                         if (pmd_swp_soft_dirty(*pmd))
1871                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1872                         set_pmd_at(mm, addr, pmd, newpmd);
1873                 }
1874                 goto unlock;
1875         }
1876 #endif
1877
1878         /*
1879          * Avoid trapping faults against the zero page. The read-only
1880          * data is likely to be read-cached on the local CPU and
1881          * local/remote hits to the zero page are not interesting.
1882          */
1883         if (prot_numa && is_huge_zero_pmd(*pmd))
1884                 goto unlock;
1885
1886         if (prot_numa && pmd_protnone(*pmd))
1887                 goto unlock;
1888
1889         /*
1890          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1891          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1892          * which is also under down_read(mmap_sem):
1893          *
1894          *      CPU0:                           CPU1:
1895          *                              change_huge_pmd(prot_numa=1)
1896          *                               pmdp_huge_get_and_clear_notify()
1897          * madvise_dontneed()
1898          *  zap_pmd_range()
1899          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1900          *   // skip the pmd
1901          *                               set_pmd_at();
1902          *                               // pmd is re-established
1903          *
1904          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1905          * which may break userspace.
1906          *
1907          * pmdp_invalidate() is required to make sure we don't miss
1908          * dirty/young flags set by hardware.
1909          */
1910         entry = pmdp_invalidate(vma, addr, pmd);
1911
1912         entry = pmd_modify(entry, newprot);
1913         if (preserve_write)
1914                 entry = pmd_mk_savedwrite(entry);
1915         ret = HPAGE_PMD_NR;
1916         set_pmd_at(mm, addr, pmd, entry);
1917         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1918 unlock:
1919         spin_unlock(ptl);
1920         return ret;
1921 }
1922
1923 /*
1924  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1925  *
1926  * Note that if it returns page table lock pointer, this routine returns without
1927  * unlocking page table lock. So callers must unlock it.
1928  */
1929 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1930 {
1931         spinlock_t *ptl;
1932         ptl = pmd_lock(vma->vm_mm, pmd);
1933         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1934                         pmd_devmap(*pmd)))
1935                 return ptl;
1936         spin_unlock(ptl);
1937         return NULL;
1938 }
1939
1940 /*
1941  * Returns true if a given pud maps a thp, false otherwise.
1942  *
1943  * Note that if it returns true, this routine returns without unlocking page
1944  * table lock. So callers must unlock it.
1945  */
1946 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1947 {
1948         spinlock_t *ptl;
1949
1950         ptl = pud_lock(vma->vm_mm, pud);
1951         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1952                 return ptl;
1953         spin_unlock(ptl);
1954         return NULL;
1955 }
1956
1957 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1958 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1959                  pud_t *pud, unsigned long addr)
1960 {
1961         pud_t orig_pud;
1962         spinlock_t *ptl;
1963
1964         ptl = __pud_trans_huge_lock(pud, vma);
1965         if (!ptl)
1966                 return 0;
1967         /*
1968          * For architectures like ppc64 we look at deposited pgtable
1969          * when calling pudp_huge_get_and_clear. So do the
1970          * pgtable_trans_huge_withdraw after finishing pudp related
1971          * operations.
1972          */
1973         orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1974                         tlb->fullmm);
1975         tlb_remove_pud_tlb_entry(tlb, pud, addr);
1976         if (vma_is_dax(vma)) {
1977                 spin_unlock(ptl);
1978                 /* No zero page support yet */
1979         } else {
1980                 /* No support for anonymous PUD pages yet */
1981                 BUG();
1982         }
1983         return 1;
1984 }
1985
1986 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
1987                 unsigned long haddr)
1988 {
1989         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
1990         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1991         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
1992         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
1993
1994         count_vm_event(THP_SPLIT_PUD);
1995
1996         pudp_huge_clear_flush_notify(vma, haddr, pud);
1997 }
1998
1999 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2000                 unsigned long address)
2001 {
2002         spinlock_t *ptl;
2003         struct mm_struct *mm = vma->vm_mm;
2004         unsigned long haddr = address & HPAGE_PUD_MASK;
2005
2006         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
2007         ptl = pud_lock(mm, pud);
2008         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2009                 goto out;
2010         __split_huge_pud_locked(vma, pud, haddr);
2011
2012 out:
2013         spin_unlock(ptl);
2014         /*
2015          * No need to double call mmu_notifier->invalidate_range() callback as
2016          * the above pudp_huge_clear_flush_notify() did already call it.
2017          */
2018         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2019                                                HPAGE_PUD_SIZE);
2020 }
2021 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2022
2023 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2024                 unsigned long haddr, pmd_t *pmd)
2025 {
2026         struct mm_struct *mm = vma->vm_mm;
2027         pgtable_t pgtable;
2028         pmd_t _pmd;
2029         int i;
2030
2031         /*
2032          * Leave pmd empty until pte is filled note that it is fine to delay
2033          * notification until mmu_notifier_invalidate_range_end() as we are
2034          * replacing a zero pmd write protected page with a zero pte write
2035          * protected page.
2036          *
2037          * See Documentation/vm/mmu_notifier.rst
2038          */
2039         pmdp_huge_clear_flush(vma, haddr, pmd);
2040
2041         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2042         pmd_populate(mm, &_pmd, pgtable);
2043
2044         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2045                 pte_t *pte, entry;
2046                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2047                 entry = pte_mkspecial(entry);
2048                 pte = pte_offset_map(&_pmd, haddr);
2049                 VM_BUG_ON(!pte_none(*pte));
2050                 set_pte_at(mm, haddr, pte, entry);
2051                 pte_unmap(pte);
2052         }
2053         smp_wmb(); /* make pte visible before pmd */
2054         pmd_populate(mm, pmd, pgtable);
2055 }
2056
2057 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2058                 unsigned long haddr, bool freeze)
2059 {
2060         struct mm_struct *mm = vma->vm_mm;
2061         struct page *page;
2062         pgtable_t pgtable;
2063         pmd_t old_pmd, _pmd;
2064         bool young, write, soft_dirty, pmd_migration = false;
2065         unsigned long addr;
2066         int i;
2067
2068         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2069         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2070         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2071         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2072                                 && !pmd_devmap(*pmd));
2073
2074         count_vm_event(THP_SPLIT_PMD);
2075
2076         if (!vma_is_anonymous(vma)) {
2077                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2078                 /*
2079                  * We are going to unmap this huge page. So
2080                  * just go ahead and zap it
2081                  */
2082                 if (arch_needs_pgtable_deposit())
2083                         zap_deposited_table(mm, pmd);
2084                 if (vma_is_dax(vma))
2085                         return;
2086                 page = pmd_page(_pmd);
2087                 if (!PageDirty(page) && pmd_dirty(_pmd))
2088                         set_page_dirty(page);
2089                 if (!PageReferenced(page) && pmd_young(_pmd))
2090                         SetPageReferenced(page);
2091                 page_remove_rmap(page, true);
2092                 put_page(page);
2093                 add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
2094                 return;
2095         } else if (is_huge_zero_pmd(*pmd)) {
2096                 /*
2097                  * FIXME: Do we want to invalidate secondary mmu by calling
2098                  * mmu_notifier_invalidate_range() see comments below inside
2099                  * __split_huge_pmd() ?
2100                  *
2101                  * We are going from a zero huge page write protected to zero
2102                  * small page also write protected so it does not seems useful
2103                  * to invalidate secondary mmu at this time.
2104                  */
2105                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2106         }
2107
2108         /*
2109          * Up to this point the pmd is present and huge and userland has the
2110          * whole access to the hugepage during the split (which happens in
2111          * place). If we overwrite the pmd with the not-huge version pointing
2112          * to the pte here (which of course we could if all CPUs were bug
2113          * free), userland could trigger a small page size TLB miss on the
2114          * small sized TLB while the hugepage TLB entry is still established in
2115          * the huge TLB. Some CPU doesn't like that.
2116          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2117          * 383 on page 93. Intel should be safe but is also warns that it's
2118          * only safe if the permission and cache attributes of the two entries
2119          * loaded in the two TLB is identical (which should be the case here).
2120          * But it is generally safer to never allow small and huge TLB entries
2121          * for the same virtual address to be loaded simultaneously. So instead
2122          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2123          * current pmd notpresent (atomically because here the pmd_trans_huge
2124          * must remain set at all times on the pmd until the split is complete
2125          * for this pmd), then we flush the SMP TLB and finally we write the
2126          * non-huge version of the pmd entry with pmd_populate.
2127          */
2128         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2129
2130 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2131         pmd_migration = is_pmd_migration_entry(old_pmd);
2132         if (pmd_migration) {
2133                 swp_entry_t entry;
2134
2135                 entry = pmd_to_swp_entry(old_pmd);
2136                 page = pfn_to_page(swp_offset(entry));
2137         } else
2138 #endif
2139                 page = pmd_page(old_pmd);
2140         VM_BUG_ON_PAGE(!page_count(page), page);
2141         page_ref_add(page, HPAGE_PMD_NR - 1);
2142         if (pmd_dirty(old_pmd))
2143                 SetPageDirty(page);
2144         write = pmd_write(old_pmd);
2145         young = pmd_young(old_pmd);
2146         soft_dirty = pmd_soft_dirty(old_pmd);
2147
2148         /*
2149          * Withdraw the table only after we mark the pmd entry invalid.
2150          * This's critical for some architectures (Power).
2151          */
2152         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2153         pmd_populate(mm, &_pmd, pgtable);
2154
2155         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2156                 pte_t entry, *pte;
2157                 /*
2158                  * Note that NUMA hinting access restrictions are not
2159                  * transferred to avoid any possibility of altering
2160                  * permissions across VMAs.
2161                  */
2162                 if (freeze || pmd_migration) {
2163                         swp_entry_t swp_entry;
2164                         swp_entry = make_migration_entry(page + i, write);
2165                         entry = swp_entry_to_pte(swp_entry);
2166                         if (soft_dirty)
2167                                 entry = pte_swp_mksoft_dirty(entry);
2168                 } else {
2169                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2170                         entry = maybe_mkwrite(entry, vma);
2171                         if (!write)
2172                                 entry = pte_wrprotect(entry);
2173                         if (!young)
2174                                 entry = pte_mkold(entry);
2175                         if (soft_dirty)
2176                                 entry = pte_mksoft_dirty(entry);
2177                 }
2178                 pte = pte_offset_map(&_pmd, addr);
2179                 BUG_ON(!pte_none(*pte));
2180                 set_pte_at(mm, addr, pte, entry);
2181                 atomic_inc(&page[i]._mapcount);
2182                 pte_unmap(pte);
2183         }
2184
2185         /*
2186          * Set PG_double_map before dropping compound_mapcount to avoid
2187          * false-negative page_mapped().
2188          */
2189         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2190                 for (i = 0; i < HPAGE_PMD_NR; i++)
2191                         atomic_inc(&page[i]._mapcount);
2192         }
2193
2194         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2195                 /* Last compound_mapcount is gone. */
2196                 __dec_node_page_state(page, NR_ANON_THPS);
2197                 if (TestClearPageDoubleMap(page)) {
2198                         /* No need in mapcount reference anymore */
2199                         for (i = 0; i < HPAGE_PMD_NR; i++)
2200                                 atomic_dec(&page[i]._mapcount);
2201                 }
2202         }
2203
2204         smp_wmb(); /* make pte visible before pmd */
2205         pmd_populate(mm, pmd, pgtable);
2206
2207         if (freeze) {
2208                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2209                         page_remove_rmap(page + i, false);
2210                         put_page(page + i);
2211                 }
2212         }
2213 }
2214
2215 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2216                 unsigned long address, bool freeze, struct page *page)
2217 {
2218         spinlock_t *ptl;
2219         struct mm_struct *mm = vma->vm_mm;
2220         unsigned long haddr = address & HPAGE_PMD_MASK;
2221
2222         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2223         ptl = pmd_lock(mm, pmd);
2224
2225         /*
2226          * If caller asks to setup a migration entries, we need a page to check
2227          * pmd against. Otherwise we can end up replacing wrong page.
2228          */
2229         VM_BUG_ON(freeze && !page);
2230         if (page && page != pmd_page(*pmd))
2231                 goto out;
2232
2233         if (pmd_trans_huge(*pmd)) {
2234                 page = pmd_page(*pmd);
2235                 if (PageMlocked(page))
2236                         clear_page_mlock(page);
2237         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2238                 goto out;
2239         __split_huge_pmd_locked(vma, pmd, haddr, freeze);
2240 out:
2241         spin_unlock(ptl);
2242         /*
2243          * No need to double call mmu_notifier->invalidate_range() callback.
2244          * They are 3 cases to consider inside __split_huge_pmd_locked():
2245          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2246          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2247          *    fault will trigger a flush_notify before pointing to a new page
2248          *    (it is fine if the secondary mmu keeps pointing to the old zero
2249          *    page in the meantime)
2250          *  3) Split a huge pmd into pte pointing to the same page. No need
2251          *     to invalidate secondary tlb entry they are all still valid.
2252          *     any further changes to individual pte will notify. So no need
2253          *     to call mmu_notifier->invalidate_range()
2254          */
2255         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2256                                                HPAGE_PMD_SIZE);
2257 }
2258
2259 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2260                 bool freeze, struct page *page)
2261 {
2262         pgd_t *pgd;
2263         p4d_t *p4d;
2264         pud_t *pud;
2265         pmd_t *pmd;
2266
2267         pgd = pgd_offset(vma->vm_mm, address);
2268         if (!pgd_present(*pgd))
2269                 return;
2270
2271         p4d = p4d_offset(pgd, address);
2272         if (!p4d_present(*p4d))
2273                 return;
2274
2275         pud = pud_offset(p4d, address);
2276         if (!pud_present(*pud))
2277                 return;
2278
2279         pmd = pmd_offset(pud, address);
2280
2281         __split_huge_pmd(vma, pmd, address, freeze, page);
2282 }
2283
2284 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2285                              unsigned long start,
2286                              unsigned long end,
2287                              long adjust_next)
2288 {
2289         /*
2290          * If the new start address isn't hpage aligned and it could
2291          * previously contain an hugepage: check if we need to split
2292          * an huge pmd.
2293          */
2294         if (start & ~HPAGE_PMD_MASK &&
2295             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2296             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2297                 split_huge_pmd_address(vma, start, false, NULL);
2298
2299         /*
2300          * If the new end address isn't hpage aligned and it could
2301          * previously contain an hugepage: check if we need to split
2302          * an huge pmd.
2303          */
2304         if (end & ~HPAGE_PMD_MASK &&
2305             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2306             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2307                 split_huge_pmd_address(vma, end, false, NULL);
2308
2309         /*
2310          * If we're also updating the vma->vm_next->vm_start, if the new
2311          * vm_next->vm_start isn't page aligned and it could previously
2312          * contain an hugepage: check if we need to split an huge pmd.
2313          */
2314         if (adjust_next > 0) {
2315                 struct vm_area_struct *next = vma->vm_next;
2316                 unsigned long nstart = next->vm_start;
2317                 nstart += adjust_next << PAGE_SHIFT;
2318                 if (nstart & ~HPAGE_PMD_MASK &&
2319                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2320                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2321                         split_huge_pmd_address(next, nstart, false, NULL);
2322         }
2323 }
2324
2325 static void freeze_page(struct page *page)
2326 {
2327         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2328                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2329         bool unmap_success;
2330
2331         VM_BUG_ON_PAGE(!PageHead(page), page);
2332
2333         if (PageAnon(page))
2334                 ttu_flags |= TTU_SPLIT_FREEZE;
2335
2336         unmap_success = try_to_unmap(page, ttu_flags);
2337         VM_BUG_ON_PAGE(!unmap_success, page);
2338 }
2339
2340 static void unfreeze_page(struct page *page)
2341 {
2342         int i;
2343         if (PageTransHuge(page)) {
2344                 remove_migration_ptes(page, page, true);
2345         } else {
2346                 for (i = 0; i < HPAGE_PMD_NR; i++)
2347                         remove_migration_ptes(page + i, page + i, true);
2348         }
2349 }
2350
2351 static void __split_huge_page_tail(struct page *head, int tail,
2352                 struct lruvec *lruvec, struct list_head *list)
2353 {
2354         struct page *page_tail = head + tail;
2355
2356         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2357
2358         /*
2359          * Clone page flags before unfreezing refcount.
2360          *
2361          * After successful get_page_unless_zero() might follow flags change,
2362          * for exmaple lock_page() which set PG_waiters.
2363          */
2364         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2365         page_tail->flags |= (head->flags &
2366                         ((1L << PG_referenced) |
2367                          (1L << PG_swapbacked) |
2368                          (1L << PG_swapcache) |
2369                          (1L << PG_mlocked) |
2370                          (1L << PG_uptodate) |
2371                          (1L << PG_active) |
2372                          (1L << PG_locked) |
2373                          (1L << PG_unevictable) |
2374                          (1L << PG_dirty)));
2375
2376         /* Page flags must be visible before we make the page non-compound. */
2377         smp_wmb();
2378
2379         /*
2380          * Clear PageTail before unfreezing page refcount.
2381          *
2382          * After successful get_page_unless_zero() might follow put_page()
2383          * which needs correct compound_head().
2384          */
2385         clear_compound_head(page_tail);
2386
2387         /* Finally unfreeze refcount. Additional reference from page cache. */
2388         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2389                                           PageSwapCache(head)));
2390
2391         if (page_is_young(head))
2392                 set_page_young(page_tail);
2393         if (page_is_idle(head))
2394                 set_page_idle(page_tail);
2395
2396         /* ->mapping in first tail page is compound_mapcount */
2397         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2398                         page_tail);
2399         page_tail->mapping = head->mapping;
2400
2401         page_tail->index = head->index + tail;
2402         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2403
2404         /*
2405          * always add to the tail because some iterators expect new
2406          * pages to show after the currently processed elements - e.g.
2407          * migrate_pages
2408          */
2409         lru_add_page_tail(head, page_tail, lruvec, list);
2410 }
2411
2412 static void __split_huge_page(struct page *page, struct list_head *list,
2413                 unsigned long flags)
2414 {
2415         struct page *head = compound_head(page);
2416         struct zone *zone = page_zone(head);
2417         struct lruvec *lruvec;
2418         pgoff_t end = -1;
2419         int i;
2420
2421         lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
2422
2423         /* complete memcg works before add pages to LRU */
2424         mem_cgroup_split_huge_fixup(head);
2425
2426         if (!PageAnon(page))
2427                 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE);
2428
2429         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2430                 __split_huge_page_tail(head, i, lruvec, list);
2431                 /* Some pages can be beyond i_size: drop them from page cache */
2432                 if (head[i].index >= end) {
2433                         ClearPageDirty(head + i);
2434                         __delete_from_page_cache(head + i, NULL);
2435                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2436                                 shmem_uncharge(head->mapping->host, 1);
2437                         put_page(head + i);
2438                 }
2439         }
2440
2441         ClearPageCompound(head);
2442         /* See comment in __split_huge_page_tail() */
2443         if (PageAnon(head)) {
2444                 /* Additional pin to radix tree of swap cache */
2445                 if (PageSwapCache(head))
2446                         page_ref_add(head, 2);
2447                 else
2448                         page_ref_inc(head);
2449         } else {
2450                 /* Additional pin to radix tree */
2451                 page_ref_add(head, 2);
2452                 xa_unlock(&head->mapping->i_pages);
2453         }
2454
2455         spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2456
2457         unfreeze_page(head);
2458
2459         for (i = 0; i < HPAGE_PMD_NR; i++) {
2460                 struct page *subpage = head + i;
2461                 if (subpage == page)
2462                         continue;
2463                 unlock_page(subpage);
2464
2465                 /*
2466                  * Subpages may be freed if there wasn't any mapping
2467                  * like if add_to_swap() is running on a lru page that
2468                  * had its mapping zapped. And freeing these pages
2469                  * requires taking the lru_lock so we do the put_page
2470                  * of the tail pages after the split is complete.
2471                  */
2472                 put_page(subpage);
2473         }
2474 }
2475
2476 int total_mapcount(struct page *page)
2477 {
2478         int i, compound, ret;
2479
2480         VM_BUG_ON_PAGE(PageTail(page), page);
2481
2482         if (likely(!PageCompound(page)))
2483                 return atomic_read(&page->_mapcount) + 1;
2484
2485         compound = compound_mapcount(page);
2486         if (PageHuge(page))
2487                 return compound;
2488         ret = compound;
2489         for (i = 0; i < HPAGE_PMD_NR; i++)
2490                 ret += atomic_read(&page[i]._mapcount) + 1;
2491         /* File pages has compound_mapcount included in _mapcount */
2492         if (!PageAnon(page))
2493                 return ret - compound * HPAGE_PMD_NR;
2494         if (PageDoubleMap(page))
2495                 ret -= HPAGE_PMD_NR;
2496         return ret;
2497 }
2498
2499 /*
2500  * This calculates accurately how many mappings a transparent hugepage
2501  * has (unlike page_mapcount() which isn't fully accurate). This full
2502  * accuracy is primarily needed to know if copy-on-write faults can
2503  * reuse the page and change the mapping to read-write instead of
2504  * copying them. At the same time this returns the total_mapcount too.
2505  *
2506  * The function returns the highest mapcount any one of the subpages
2507  * has. If the return value is one, even if different processes are
2508  * mapping different subpages of the transparent hugepage, they can
2509  * all reuse it, because each process is reusing a different subpage.
2510  *
2511  * The total_mapcount is instead counting all virtual mappings of the
2512  * subpages. If the total_mapcount is equal to "one", it tells the
2513  * caller all mappings belong to the same "mm" and in turn the
2514  * anon_vma of the transparent hugepage can become the vma->anon_vma
2515  * local one as no other process may be mapping any of the subpages.
2516  *
2517  * It would be more accurate to replace page_mapcount() with
2518  * page_trans_huge_mapcount(), however we only use
2519  * page_trans_huge_mapcount() in the copy-on-write faults where we
2520  * need full accuracy to avoid breaking page pinning, because
2521  * page_trans_huge_mapcount() is slower than page_mapcount().
2522  */
2523 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2524 {
2525         int i, ret, _total_mapcount, mapcount;
2526
2527         /* hugetlbfs shouldn't call it */
2528         VM_BUG_ON_PAGE(PageHuge(page), page);
2529
2530         if (likely(!PageTransCompound(page))) {
2531                 mapcount = atomic_read(&page->_mapcount) + 1;
2532                 if (total_mapcount)
2533                         *total_mapcount = mapcount;
2534                 return mapcount;
2535         }
2536
2537         page = compound_head(page);
2538
2539         _total_mapcount = ret = 0;
2540         for (i = 0; i < HPAGE_PMD_NR; i++) {
2541                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2542                 ret = max(ret, mapcount);
2543                 _total_mapcount += mapcount;
2544         }
2545         if (PageDoubleMap(page)) {
2546                 ret -= 1;
2547                 _total_mapcount -= HPAGE_PMD_NR;
2548         }
2549         mapcount = compound_mapcount(page);
2550         ret += mapcount;
2551         _total_mapcount += mapcount;
2552         if (total_mapcount)
2553                 *total_mapcount = _total_mapcount;
2554         return ret;
2555 }
2556
2557 /* Racy check whether the huge page can be split */
2558 bool can_split_huge_page(struct page *page, int *pextra_pins)
2559 {
2560         int extra_pins;
2561
2562         /* Additional pins from radix tree */
2563         if (PageAnon(page))
2564                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2565         else
2566                 extra_pins = HPAGE_PMD_NR;
2567         if (pextra_pins)
2568                 *pextra_pins = extra_pins;
2569         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2570 }
2571
2572 /*
2573  * This function splits huge page into normal pages. @page can point to any
2574  * subpage of huge page to split. Split doesn't change the position of @page.
2575  *
2576  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2577  * The huge page must be locked.
2578  *
2579  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2580  *
2581  * Both head page and tail pages will inherit mapping, flags, and so on from
2582  * the hugepage.
2583  *
2584  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2585  * they are not mapped.
2586  *
2587  * Returns 0 if the hugepage is split successfully.
2588  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2589  * us.
2590  */
2591 int split_huge_page_to_list(struct page *page, struct list_head *list)
2592 {
2593         struct page *head = compound_head(page);
2594         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2595         struct anon_vma *anon_vma = NULL;
2596         struct address_space *mapping = NULL;
2597         int count, mapcount, extra_pins, ret;
2598         bool mlocked;
2599         unsigned long flags;
2600
2601         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2602         VM_BUG_ON_PAGE(!PageLocked(page), page);
2603         VM_BUG_ON_PAGE(!PageCompound(page), page);
2604
2605         if (PageWriteback(page))
2606                 return -EBUSY;
2607
2608         if (PageAnon(head)) {
2609                 /*
2610                  * The caller does not necessarily hold an mmap_sem that would
2611                  * prevent the anon_vma disappearing so we first we take a
2612                  * reference to it and then lock the anon_vma for write. This
2613                  * is similar to page_lock_anon_vma_read except the write lock
2614                  * is taken to serialise against parallel split or collapse
2615                  * operations.
2616                  */
2617                 anon_vma = page_get_anon_vma(head);
2618                 if (!anon_vma) {
2619                         ret = -EBUSY;
2620                         goto out;
2621                 }
2622                 mapping = NULL;
2623                 anon_vma_lock_write(anon_vma);
2624         } else {
2625                 mapping = head->mapping;
2626
2627                 /* Truncated ? */
2628                 if (!mapping) {
2629                         ret = -EBUSY;
2630                         goto out;
2631                 }
2632
2633                 anon_vma = NULL;
2634                 i_mmap_lock_read(mapping);
2635         }
2636
2637         /*
2638          * Racy check if we can split the page, before freeze_page() will
2639          * split PMDs
2640          */
2641         if (!can_split_huge_page(head, &extra_pins)) {
2642                 ret = -EBUSY;
2643                 goto out_unlock;
2644         }
2645
2646         mlocked = PageMlocked(page);
2647         freeze_page(head);
2648         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2649
2650         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2651         if (mlocked)
2652                 lru_add_drain();
2653
2654         /* prevent PageLRU to go away from under us, and freeze lru stats */
2655         spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2656
2657         if (mapping) {
2658                 void **pslot;
2659
2660                 xa_lock(&mapping->i_pages);
2661                 pslot = radix_tree_lookup_slot(&mapping->i_pages,
2662                                 page_index(head));
2663                 /*
2664                  * Check if the head page is present in radix tree.
2665                  * We assume all tail are present too, if head is there.
2666                  */
2667                 if (radix_tree_deref_slot_protected(pslot,
2668                                         &mapping->i_pages.xa_lock) != head)
2669                         goto fail;
2670         }
2671
2672         /* Prevent deferred_split_scan() touching ->_refcount */
2673         spin_lock(&pgdata->split_queue_lock);
2674         count = page_count(head);
2675         mapcount = total_mapcount(head);
2676         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2677                 if (!list_empty(page_deferred_list(head))) {
2678                         pgdata->split_queue_len--;
2679                         list_del(page_deferred_list(head));
2680                 }
2681                 if (mapping)
2682                         __dec_node_page_state(page, NR_SHMEM_THPS);
2683                 spin_unlock(&pgdata->split_queue_lock);
2684                 __split_huge_page(page, list, flags);
2685                 if (PageSwapCache(head)) {
2686                         swp_entry_t entry = { .val = page_private(head) };
2687
2688                         ret = split_swap_cluster(entry);
2689                 } else
2690                         ret = 0;
2691         } else {
2692                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2693                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2694                                         mapcount, count);
2695                         if (PageTail(page))
2696                                 dump_page(head, NULL);
2697                         dump_page(page, "total_mapcount(head) > 0");
2698                         BUG();
2699                 }
2700                 spin_unlock(&pgdata->split_queue_lock);
2701 fail:           if (mapping)
2702                         xa_unlock(&mapping->i_pages);
2703                 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2704                 unfreeze_page(head);
2705                 ret = -EBUSY;
2706         }
2707
2708 out_unlock:
2709         if (anon_vma) {
2710                 anon_vma_unlock_write(anon_vma);
2711                 put_anon_vma(anon_vma);
2712         }
2713         if (mapping)
2714                 i_mmap_unlock_read(mapping);
2715 out:
2716         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2717         return ret;
2718 }
2719
2720 void free_transhuge_page(struct page *page)
2721 {
2722         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2723         unsigned long flags;
2724
2725         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2726         if (!list_empty(page_deferred_list(page))) {
2727                 pgdata->split_queue_len--;
2728                 list_del(page_deferred_list(page));
2729         }
2730         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2731         free_compound_page(page);
2732 }
2733
2734 void deferred_split_huge_page(struct page *page)
2735 {
2736         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2737         unsigned long flags;
2738
2739         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2740
2741         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2742         if (list_empty(page_deferred_list(page))) {
2743                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2744                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2745                 pgdata->split_queue_len++;
2746         }
2747         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2748 }
2749
2750 static unsigned long deferred_split_count(struct shrinker *shrink,
2751                 struct shrink_control *sc)
2752 {
2753         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2754         return READ_ONCE(pgdata->split_queue_len);
2755 }
2756
2757 static unsigned long deferred_split_scan(struct shrinker *shrink,
2758                 struct shrink_control *sc)
2759 {
2760         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2761         unsigned long flags;
2762         LIST_HEAD(list), *pos, *next;
2763         struct page *page;
2764         int split = 0;
2765
2766         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2767         /* Take pin on all head pages to avoid freeing them under us */
2768         list_for_each_safe(pos, next, &pgdata->split_queue) {
2769                 page = list_entry((void *)pos, struct page, mapping);
2770                 page = compound_head(page);
2771                 if (get_page_unless_zero(page)) {
2772                         list_move(page_deferred_list(page), &list);
2773                 } else {
2774                         /* We lost race with put_compound_page() */
2775                         list_del_init(page_deferred_list(page));
2776                         pgdata->split_queue_len--;
2777                 }
2778                 if (!--sc->nr_to_scan)
2779                         break;
2780         }
2781         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2782
2783         list_for_each_safe(pos, next, &list) {
2784                 page = list_entry((void *)pos, struct page, mapping);
2785                 if (!trylock_page(page))
2786                         goto next;
2787                 /* split_huge_page() removes page from list on success */
2788                 if (!split_huge_page(page))
2789                         split++;
2790                 unlock_page(page);
2791 next:
2792                 put_page(page);
2793         }
2794
2795         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2796         list_splice_tail(&list, &pgdata->split_queue);
2797         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2798
2799         /*
2800          * Stop shrinker if we didn't split any page, but the queue is empty.
2801          * This can happen if pages were freed under us.
2802          */
2803         if (!split && list_empty(&pgdata->split_queue))
2804                 return SHRINK_STOP;
2805         return split;
2806 }
2807
2808 static struct shrinker deferred_split_shrinker = {
2809         .count_objects = deferred_split_count,
2810         .scan_objects = deferred_split_scan,
2811         .seeks = DEFAULT_SEEKS,
2812         .flags = SHRINKER_NUMA_AWARE,
2813 };
2814
2815 #ifdef CONFIG_DEBUG_FS
2816 static int split_huge_pages_set(void *data, u64 val)
2817 {
2818         struct zone *zone;
2819         struct page *page;
2820         unsigned long pfn, max_zone_pfn;
2821         unsigned long total = 0, split = 0;
2822
2823         if (val != 1)
2824                 return -EINVAL;
2825
2826         for_each_populated_zone(zone) {
2827                 max_zone_pfn = zone_end_pfn(zone);
2828                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2829                         if (!pfn_valid(pfn))
2830                                 continue;
2831
2832                         page = pfn_to_page(pfn);
2833                         if (!get_page_unless_zero(page))
2834                                 continue;
2835
2836                         if (zone != page_zone(page))
2837                                 goto next;
2838
2839                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2840                                 goto next;
2841
2842                         total++;
2843                         lock_page(page);
2844                         if (!split_huge_page(page))
2845                                 split++;
2846                         unlock_page(page);
2847 next:
2848                         put_page(page);
2849                 }
2850         }
2851
2852         pr_info("%lu of %lu THP split\n", split, total);
2853
2854         return 0;
2855 }
2856 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2857                 "%llu\n");
2858
2859 static int __init split_huge_pages_debugfs(void)
2860 {
2861         void *ret;
2862
2863         ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2864                         &split_huge_pages_fops);
2865         if (!ret)
2866                 pr_warn("Failed to create split_huge_pages in debugfs");
2867         return 0;
2868 }
2869 late_initcall(split_huge_pages_debugfs);
2870 #endif
2871
2872 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2873 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2874                 struct page *page)
2875 {
2876         struct vm_area_struct *vma = pvmw->vma;
2877         struct mm_struct *mm = vma->vm_mm;
2878         unsigned long address = pvmw->address;
2879         pmd_t pmdval;
2880         swp_entry_t entry;
2881         pmd_t pmdswp;
2882
2883         if (!(pvmw->pmd && !pvmw->pte))
2884                 return;
2885
2886         mmu_notifier_invalidate_range_start(mm, address,
2887                         address + HPAGE_PMD_SIZE);
2888
2889         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2890         pmdval = *pvmw->pmd;
2891         pmdp_invalidate(vma, address, pvmw->pmd);
2892         if (pmd_dirty(pmdval))
2893                 set_page_dirty(page);
2894         entry = make_migration_entry(page, pmd_write(pmdval));
2895         pmdswp = swp_entry_to_pmd(entry);
2896         if (pmd_soft_dirty(pmdval))
2897                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2898         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2899         page_remove_rmap(page, true);
2900         put_page(page);
2901
2902         mmu_notifier_invalidate_range_end(mm, address,
2903                         address + HPAGE_PMD_SIZE);
2904 }
2905
2906 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2907 {
2908         struct vm_area_struct *vma = pvmw->vma;
2909         struct mm_struct *mm = vma->vm_mm;
2910         unsigned long address = pvmw->address;
2911         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2912         pmd_t pmde;
2913         swp_entry_t entry;
2914
2915         if (!(pvmw->pmd && !pvmw->pte))
2916                 return;
2917
2918         entry = pmd_to_swp_entry(*pvmw->pmd);
2919         get_page(new);
2920         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2921         if (pmd_swp_soft_dirty(*pvmw->pmd))
2922                 pmde = pmd_mksoft_dirty(pmde);
2923         if (is_write_migration_entry(entry))
2924                 pmde = maybe_pmd_mkwrite(pmde, vma);
2925
2926         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2927         if (PageAnon(new))
2928                 page_add_anon_rmap(new, vma, mmun_start, true);
2929         else
2930                 page_add_file_rmap(new, true);
2931         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
2932         if (vma->vm_flags & VM_LOCKED)
2933                 mlock_vma_page(new);
2934         update_mmu_cache_pmd(vma, address, pvmw->pmd);
2935 }
2936 #endif