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 vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
 545                         struct page *page, 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         vm_fault_t ret = 0;
 552
 553         VM_BUG_ON_PAGE(!PageCompound(page), page);
 554
 555         if (mem_cgroup_try_charge_delay(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                         vm_fault_t ret2;
 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                         ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
 594                         VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
 595                         return ret2;
 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 vm_fault_t 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                 vm_fault_t 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                         !pfn_t_devmap(pfn));
 767         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 768                                                 (VM_PFNMAP|VM_MIXEDMAP));
 769         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 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 vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1122                         pmd_t orig_pmd, 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 i;
1130         vm_fault_t ret = 0;
1131         struct page **pages;
1132         unsigned long mmun_start;       /* For mmu_notifiers */
1133         unsigned long mmun_end;         /* For mmu_notifiers */
1134
1135         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1136                               GFP_KERNEL);
1137         if (unlikely(!pages)) {
1138                 ret |= VM_FAULT_OOM;
1139                 goto out;
1140         }
1141
1142         for (i = 0; i < HPAGE_PMD_NR; i++) {
1143                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1144                                                vmf->address, page_to_nid(page));
1145                 if (unlikely(!pages[i] ||
1146                              mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1147                                      GFP_KERNEL, &memcg, false))) {
1148                         if (pages[i])
1149                                 put_page(pages[i]);
1150                         while (--i >= 0) {
1151                                 memcg = (void *)page_private(pages[i]);
1152                                 set_page_private(pages[i], 0);
1153                                 mem_cgroup_cancel_charge(pages[i], memcg,
1154                                                 false);
1155                                 put_page(pages[i]);
1156                         }
1157                         kfree(pages);
1158                         ret |= VM_FAULT_OOM;
1159                         goto out;
1160                 }
1161                 set_page_private(pages[i], (unsigned long)memcg);
1162         }
1163
1164         for (i = 0; i < HPAGE_PMD_NR; i++) {
1165                 copy_user_highpage(pages[i], page + i,
1166                                    haddr + PAGE_SIZE * i, vma);
1167                 __SetPageUptodate(pages[i]);
1168                 cond_resched();
1169         }
1170
1171         mmun_start = haddr;
1172         mmun_end   = haddr + HPAGE_PMD_SIZE;
1173         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1174
1175         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1176         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1177                 goto out_free_pages;
1178         VM_BUG_ON_PAGE(!PageHead(page), page);
1179
1180         /*
1181          * Leave pmd empty until pte is filled note we must notify here as
1182          * concurrent CPU thread might write to new page before the call to
1183          * mmu_notifier_invalidate_range_end() happens which can lead to a
1184          * device seeing memory write in different order than CPU.
1185          *
1186          * See Documentation/vm/mmu_notifier.rst
1187          */
1188         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1189
1190         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1191         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1192
1193         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1194                 pte_t entry;
1195                 entry = mk_pte(pages[i], vma->vm_page_prot);
1196                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1197                 memcg = (void *)page_private(pages[i]);
1198                 set_page_private(pages[i], 0);
1199                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1200                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1201                 lru_cache_add_active_or_unevictable(pages[i], vma);
1202                 vmf->pte = pte_offset_map(&_pmd, haddr);
1203                 VM_BUG_ON(!pte_none(*vmf->pte));
1204                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1205                 pte_unmap(vmf->pte);
1206         }
1207         kfree(pages);
1208
1209         smp_wmb(); /* make pte visible before pmd */
1210         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1211         page_remove_rmap(page, true);
1212         spin_unlock(vmf->ptl);
1213
1214         /*
1215          * No need to double call mmu_notifier->invalidate_range() callback as
1216          * the above pmdp_huge_clear_flush_notify() did already call it.
1217          */
1218         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1219                                                 mmun_end);
1220
1221         ret |= VM_FAULT_WRITE;
1222         put_page(page);
1223
1224 out:
1225         return ret;
1226
1227 out_free_pages:
1228         spin_unlock(vmf->ptl);
1229         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1230         for (i = 0; i < HPAGE_PMD_NR; i++) {
1231                 memcg = (void *)page_private(pages[i]);
1232                 set_page_private(pages[i], 0);
1233                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1234                 put_page(pages[i]);
1235         }
1236         kfree(pages);
1237         goto out;
1238 }
1239
1240 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1241 {
1242         struct vm_area_struct *vma = vmf->vma;
1243         struct page *page = NULL, *new_page;
1244         struct mem_cgroup *memcg;
1245         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1246         unsigned long mmun_start;       /* For mmu_notifiers */
1247         unsigned long mmun_end;         /* For mmu_notifiers */
1248         gfp_t huge_gfp;                 /* for allocation and charge */
1249         vm_fault_t ret = 0;
1250
1251         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1252         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1253         if (is_huge_zero_pmd(orig_pmd))
1254                 goto alloc;
1255         spin_lock(vmf->ptl);
1256         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1257                 goto out_unlock;
1258
1259         page = pmd_page(orig_pmd);
1260         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1261         /*
1262          * We can only reuse the page if nobody else maps the huge page or it's
1263          * part.
1264          */
1265         if (!trylock_page(page)) {
1266                 get_page(page);
1267                 spin_unlock(vmf->ptl);
1268                 lock_page(page);
1269                 spin_lock(vmf->ptl);
1270                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1271                         unlock_page(page);
1272                         put_page(page);
1273                         goto out_unlock;
1274                 }
1275                 put_page(page);
1276         }
1277         if (reuse_swap_page(page, NULL)) {
1278                 pmd_t entry;
1279                 entry = pmd_mkyoung(orig_pmd);
1280                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1281                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1282                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1283                 ret |= VM_FAULT_WRITE;
1284                 unlock_page(page);
1285                 goto out_unlock;
1286         }
1287         unlock_page(page);
1288         get_page(page);
1289         spin_unlock(vmf->ptl);
1290 alloc:
1291         if (transparent_hugepage_enabled(vma) &&
1292             !transparent_hugepage_debug_cow()) {
1293                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1294                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1295         } else
1296                 new_page = NULL;
1297
1298         if (likely(new_page)) {
1299                 prep_transhuge_page(new_page);
1300         } else {
1301                 if (!page) {
1302                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1303                         ret |= VM_FAULT_FALLBACK;
1304                 } else {
1305                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1306                         if (ret & VM_FAULT_OOM) {
1307                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1308                                 ret |= VM_FAULT_FALLBACK;
1309                         }
1310                         put_page(page);
1311                 }
1312                 count_vm_event(THP_FAULT_FALLBACK);
1313                 goto out;
1314         }
1315
1316         if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1317                                         huge_gfp, &memcg, true))) {
1318                 put_page(new_page);
1319                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1320                 if (page)
1321                         put_page(page);
1322                 ret |= VM_FAULT_FALLBACK;
1323                 count_vm_event(THP_FAULT_FALLBACK);
1324                 goto out;
1325         }
1326
1327         count_vm_event(THP_FAULT_ALLOC);
1328
1329         if (!page)
1330                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1331         else
1332                 copy_user_huge_page(new_page, page, vmf->address,
1333                                     vma, HPAGE_PMD_NR);
1334         __SetPageUptodate(new_page);
1335
1336         mmun_start = haddr;
1337         mmun_end   = haddr + HPAGE_PMD_SIZE;
1338         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1339
1340         spin_lock(vmf->ptl);
1341         if (page)
1342                 put_page(page);
1343         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1344                 spin_unlock(vmf->ptl);
1345                 mem_cgroup_cancel_charge(new_page, memcg, true);
1346                 put_page(new_page);
1347                 goto out_mn;
1348         } else {
1349                 pmd_t entry;
1350                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1351                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1352                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1353                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1354                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1355                 lru_cache_add_active_or_unevictable(new_page, vma);
1356                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1357                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1358                 if (!page) {
1359                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1360                 } else {
1361                         VM_BUG_ON_PAGE(!PageHead(page), page);
1362                         page_remove_rmap(page, true);
1363                         put_page(page);
1364                 }
1365                 ret |= VM_FAULT_WRITE;
1366         }
1367         spin_unlock(vmf->ptl);
1368 out_mn:
1369         /*
1370          * No need to double call mmu_notifier->invalidate_range() callback as
1371          * the above pmdp_huge_clear_flush_notify() did already call it.
1372          */
1373         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1374                                                mmun_end);
1375 out:
1376         return ret;
1377 out_unlock:
1378         spin_unlock(vmf->ptl);
1379         return ret;
1380 }
1381
1382 /*
1383  * FOLL_FORCE can write to even unwritable pmd's, but only
1384  * after we've gone through a COW cycle and they are dirty.
1385  */
1386 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1387 {
1388         return pmd_write(pmd) ||
1389                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1390 }
1391
1392 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1393                                    unsigned long addr,
1394                                    pmd_t *pmd,
1395                                    unsigned int flags)
1396 {
1397         struct mm_struct *mm = vma->vm_mm;
1398         struct page *page = NULL;
1399
1400         assert_spin_locked(pmd_lockptr(mm, pmd));
1401
1402         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1403                 goto out;
1404
1405         /* Avoid dumping huge zero page */
1406         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1407                 return ERR_PTR(-EFAULT);
1408
1409         /* Full NUMA hinting faults to serialise migration in fault paths */
1410         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1411                 goto out;
1412
1413         page = pmd_page(*pmd);
1414         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1415         if (flags & FOLL_TOUCH)
1416                 touch_pmd(vma, addr, pmd, flags);
1417         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1418                 /*
1419                  * We don't mlock() pte-mapped THPs. This way we can avoid
1420                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1421                  *
1422                  * For anon THP:
1423                  *
1424                  * In most cases the pmd is the only mapping of the page as we
1425                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1426                  * writable private mappings in populate_vma_page_range().
1427                  *
1428                  * The only scenario when we have the page shared here is if we
1429                  * mlocking read-only mapping shared over fork(). We skip
1430                  * mlocking such pages.
1431                  *
1432                  * For file THP:
1433                  *
1434                  * We can expect PageDoubleMap() to be stable under page lock:
1435                  * for file pages we set it in page_add_file_rmap(), which
1436                  * requires page to be locked.
1437                  */
1438
1439                 if (PageAnon(page) && compound_mapcount(page) != 1)
1440                         goto skip_mlock;
1441                 if (PageDoubleMap(page) || !page->mapping)
1442                         goto skip_mlock;
1443                 if (!trylock_page(page))
1444                         goto skip_mlock;
1445                 lru_add_drain();
1446                 if (page->mapping && !PageDoubleMap(page))
1447                         mlock_vma_page(page);
1448                 unlock_page(page);
1449         }
1450 skip_mlock:
1451         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1452         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1453         if (flags & FOLL_GET)
1454                 get_page(page);
1455
1456 out:
1457         return page;
1458 }
1459
1460 /* NUMA hinting page fault entry point for trans huge pmds */
1461 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1462 {
1463         struct vm_area_struct *vma = vmf->vma;
1464         struct anon_vma *anon_vma = NULL;
1465         struct page *page;
1466         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1467         int page_nid = -1, this_nid = numa_node_id();
1468         int target_nid, last_cpupid = -1;
1469         bool page_locked;
1470         bool migrated = false;
1471         bool was_writable;
1472         int flags = 0;
1473
1474         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1475         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1476                 goto out_unlock;
1477
1478         /*
1479          * If there are potential migrations, wait for completion and retry
1480          * without disrupting NUMA hinting information. Do not relock and
1481          * check_same as the page may no longer be mapped.
1482          */
1483         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1484                 page = pmd_page(*vmf->pmd);
1485                 if (!get_page_unless_zero(page))
1486                         goto out_unlock;
1487                 spin_unlock(vmf->ptl);
1488                 wait_on_page_locked(page);
1489                 put_page(page);
1490                 goto out;
1491         }
1492
1493         page = pmd_page(pmd);
1494         BUG_ON(is_huge_zero_page(page));
1495         page_nid = page_to_nid(page);
1496         last_cpupid = page_cpupid_last(page);
1497         count_vm_numa_event(NUMA_HINT_FAULTS);
1498         if (page_nid == this_nid) {
1499                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1500                 flags |= TNF_FAULT_LOCAL;
1501         }
1502
1503         /* See similar comment in do_numa_page for explanation */
1504         if (!pmd_savedwrite(pmd))
1505                 flags |= TNF_NO_GROUP;
1506
1507         /*
1508          * Acquire the page lock to serialise THP migrations but avoid dropping
1509          * page_table_lock if at all possible
1510          */
1511         page_locked = trylock_page(page);
1512         target_nid = mpol_misplaced(page, vma, haddr);
1513         if (target_nid == -1) {
1514                 /* If the page was locked, there are no parallel migrations */
1515                 if (page_locked)
1516                         goto clear_pmdnuma;
1517         }
1518
1519         /* Migration could have started since the pmd_trans_migrating check */
1520         if (!page_locked) {
1521                 page_nid = -1;
1522                 if (!get_page_unless_zero(page))
1523                         goto out_unlock;
1524                 spin_unlock(vmf->ptl);
1525                 wait_on_page_locked(page);
1526                 put_page(page);
1527                 goto out;
1528         }
1529
1530         /*
1531          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1532          * to serialises splits
1533          */
1534         get_page(page);
1535         spin_unlock(vmf->ptl);
1536         anon_vma = page_lock_anon_vma_read(page);
1537
1538         /* Confirm the PMD did not change while page_table_lock was released */
1539         spin_lock(vmf->ptl);
1540         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1541                 unlock_page(page);
1542                 put_page(page);
1543                 page_nid = -1;
1544                 goto out_unlock;
1545         }
1546
1547         /* Bail if we fail to protect against THP splits for any reason */
1548         if (unlikely(!anon_vma)) {
1549                 put_page(page);
1550                 page_nid = -1;
1551                 goto clear_pmdnuma;
1552         }
1553
1554         /*
1555          * Since we took the NUMA fault, we must have observed the !accessible
1556          * bit. Make sure all other CPUs agree with that, to avoid them
1557          * modifying the page we're about to migrate.
1558          *
1559          * Must be done under PTL such that we'll observe the relevant
1560          * inc_tlb_flush_pending().
1561          *
1562          * We are not sure a pending tlb flush here is for a huge page
1563          * mapping or not. Hence use the tlb range variant
1564          */
1565         if (mm_tlb_flush_pending(vma->vm_mm))
1566                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1567
1568         /*
1569          * Migrate the THP to the requested node, returns with page unlocked
1570          * and access rights restored.
1571          */
1572         spin_unlock(vmf->ptl);
1573
1574         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1575                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1576         if (migrated) {
1577                 flags |= TNF_MIGRATED;
1578                 page_nid = target_nid;
1579         } else
1580                 flags |= TNF_MIGRATE_FAIL;
1581
1582         goto out;
1583 clear_pmdnuma:
1584         BUG_ON(!PageLocked(page));
1585         was_writable = pmd_savedwrite(pmd);
1586         pmd = pmd_modify(pmd, vma->vm_page_prot);
1587         pmd = pmd_mkyoung(pmd);
1588         if (was_writable)
1589                 pmd = pmd_mkwrite(pmd);
1590         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1591         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1592         unlock_page(page);
1593 out_unlock:
1594         spin_unlock(vmf->ptl);
1595
1596 out:
1597         if (anon_vma)
1598                 page_unlock_anon_vma_read(anon_vma);
1599
1600         if (page_nid != -1)
1601                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1602                                 flags);
1603
1604         return 0;
1605 }
1606
1607 /*
1608  * Return true if we do MADV_FREE successfully on entire pmd page.
1609  * Otherwise, return false.
1610  */
1611 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1612                 pmd_t *pmd, unsigned long addr, unsigned long next)
1613 {
1614         spinlock_t *ptl;
1615         pmd_t orig_pmd;
1616         struct page *page;
1617         struct mm_struct *mm = tlb->mm;
1618         bool ret = false;
1619
1620         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1621
1622         ptl = pmd_trans_huge_lock(pmd, vma);
1623         if (!ptl)
1624                 goto out_unlocked;
1625
1626         orig_pmd = *pmd;
1627         if (is_huge_zero_pmd(orig_pmd))
1628                 goto out;
1629
1630         if (unlikely(!pmd_present(orig_pmd))) {
1631                 VM_BUG_ON(thp_migration_supported() &&
1632                                   !is_pmd_migration_entry(orig_pmd));
1633                 goto out;
1634         }
1635
1636         page = pmd_page(orig_pmd);
1637         /*
1638          * If other processes are mapping this page, we couldn't discard
1639          * the page unless they all do MADV_FREE so let's skip the page.
1640          */
1641         if (page_mapcount(page) != 1)
1642                 goto out;
1643
1644         if (!trylock_page(page))
1645                 goto out;
1646
1647         /*
1648          * If user want to discard part-pages of THP, split it so MADV_FREE
1649          * will deactivate only them.
1650          */
1651         if (next - addr != HPAGE_PMD_SIZE) {
1652                 get_page(page);
1653                 spin_unlock(ptl);
1654                 split_huge_page(page);
1655                 unlock_page(page);
1656                 put_page(page);
1657                 goto out_unlocked;
1658         }
1659
1660         if (PageDirty(page))
1661                 ClearPageDirty(page);
1662         unlock_page(page);
1663
1664         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1665                 pmdp_invalidate(vma, addr, pmd);
1666                 orig_pmd = pmd_mkold(orig_pmd);
1667                 orig_pmd = pmd_mkclean(orig_pmd);
1668
1669                 set_pmd_at(mm, addr, pmd, orig_pmd);
1670                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1671         }
1672
1673         mark_page_lazyfree(page);
1674         ret = true;
1675 out:
1676         spin_unlock(ptl);
1677 out_unlocked:
1678         return ret;
1679 }
1680
1681 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1682 {
1683         pgtable_t pgtable;
1684
1685         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1686         pte_free(mm, pgtable);
1687         mm_dec_nr_ptes(mm);
1688 }
1689
1690 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1691                  pmd_t *pmd, unsigned long addr)
1692 {
1693         pmd_t orig_pmd;
1694         spinlock_t *ptl;
1695
1696         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1697
1698         ptl = __pmd_trans_huge_lock(pmd, vma);
1699         if (!ptl)
1700                 return 0;
1701         /*
1702          * For architectures like ppc64 we look at deposited pgtable
1703          * when calling pmdp_huge_get_and_clear. So do the
1704          * pgtable_trans_huge_withdraw after finishing pmdp related
1705          * operations.
1706          */
1707         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1708                         tlb->fullmm);
1709         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1710         if (vma_is_dax(vma)) {
1711                 if (arch_needs_pgtable_deposit())
1712                         zap_deposited_table(tlb->mm, pmd);
1713                 spin_unlock(ptl);
1714                 if (is_huge_zero_pmd(orig_pmd))
1715                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1716         } else if (is_huge_zero_pmd(orig_pmd)) {
1717                 zap_deposited_table(tlb->mm, pmd);
1718                 spin_unlock(ptl);
1719                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1720         } else {
1721                 struct page *page = NULL;
1722                 int flush_needed = 1;
1723
1724                 if (pmd_present(orig_pmd)) {
1725                         page = pmd_page(orig_pmd);
1726                         page_remove_rmap(page, true);
1727                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1728                         VM_BUG_ON_PAGE(!PageHead(page), page);
1729                 } else if (thp_migration_supported()) {
1730                         swp_entry_t entry;
1731
1732                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1733                         entry = pmd_to_swp_entry(orig_pmd);
1734                         page = pfn_to_page(swp_offset(entry));
1735                         flush_needed = 0;
1736                 } else
1737                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1738
1739                 if (PageAnon(page)) {
1740                         zap_deposited_table(tlb->mm, pmd);
1741                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1742                 } else {
1743                         if (arch_needs_pgtable_deposit())
1744                                 zap_deposited_table(tlb->mm, pmd);
1745                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1746                 }
1747
1748                 spin_unlock(ptl);
1749                 if (flush_needed)
1750                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1751         }
1752         return 1;
1753 }
1754
1755 #ifndef pmd_move_must_withdraw
1756 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1757                                          spinlock_t *old_pmd_ptl,
1758                                          struct vm_area_struct *vma)
1759 {
1760         /*
1761          * With split pmd lock we also need to move preallocated
1762          * PTE page table if new_pmd is on different PMD page table.
1763          *
1764          * We also don't deposit and withdraw tables for file pages.
1765          */
1766         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1767 }
1768 #endif
1769
1770 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1771 {
1772 #ifdef CONFIG_MEM_SOFT_DIRTY
1773         if (unlikely(is_pmd_migration_entry(pmd)))
1774                 pmd = pmd_swp_mksoft_dirty(pmd);
1775         else if (pmd_present(pmd))
1776                 pmd = pmd_mksoft_dirty(pmd);
1777 #endif
1778         return pmd;
1779 }
1780
1781 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1782                   unsigned long new_addr, unsigned long old_end,
1783                   pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush)
1784 {
1785         spinlock_t *old_ptl, *new_ptl;
1786         pmd_t pmd;
1787         struct mm_struct *mm = vma->vm_mm;
1788         bool force_flush = false;
1789
1790         if ((old_addr & ~HPAGE_PMD_MASK) ||
1791             (new_addr & ~HPAGE_PMD_MASK) ||
1792             old_end - old_addr < HPAGE_PMD_SIZE)
1793                 return false;
1794
1795         /*
1796          * The destination pmd shouldn't be established, free_pgtables()
1797          * should have release it.
1798          */
1799         if (WARN_ON(!pmd_none(*new_pmd))) {
1800                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1801                 return false;
1802         }
1803
1804         /*
1805          * We don't have to worry about the ordering of src and dst
1806          * ptlocks because exclusive mmap_sem prevents deadlock.
1807          */
1808         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1809         if (old_ptl) {
1810                 new_ptl = pmd_lockptr(mm, new_pmd);
1811                 if (new_ptl != old_ptl)
1812                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1813                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1814                 if (pmd_present(pmd) && pmd_dirty(pmd))
1815                         force_flush = true;
1816                 VM_BUG_ON(!pmd_none(*new_pmd));
1817
1818                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1819                         pgtable_t pgtable;
1820                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1821                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1822                 }
1823                 pmd = move_soft_dirty_pmd(pmd);
1824                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1825                 if (new_ptl != old_ptl)
1826                         spin_unlock(new_ptl);
1827                 if (force_flush)
1828                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1829                 else
1830                         *need_flush = true;
1831                 spin_unlock(old_ptl);
1832                 return true;
1833         }
1834         return false;
1835 }
1836
1837 /*
1838  * Returns
1839  *  - 0 if PMD could not be locked
1840  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1841  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1842  */
1843 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1844                 unsigned long addr, pgprot_t newprot, int prot_numa)
1845 {
1846         struct mm_struct *mm = vma->vm_mm;
1847         spinlock_t *ptl;
1848         pmd_t entry;
1849         bool preserve_write;
1850         int ret;
1851
1852         ptl = __pmd_trans_huge_lock(pmd, vma);
1853         if (!ptl)
1854                 return 0;
1855
1856         preserve_write = prot_numa && pmd_write(*pmd);
1857         ret = 1;
1858
1859 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1860         if (is_swap_pmd(*pmd)) {
1861                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1862
1863                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1864                 if (is_write_migration_entry(entry)) {
1865                         pmd_t newpmd;
1866                         /*
1867                          * A protection check is difficult so
1868                          * just be safe and disable write
1869                          */
1870                         make_migration_entry_read(&entry);
1871                         newpmd = swp_entry_to_pmd(entry);
1872                         if (pmd_swp_soft_dirty(*pmd))
1873                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1874                         set_pmd_at(mm, addr, pmd, newpmd);
1875                 }
1876                 goto unlock;
1877         }
1878 #endif
1879
1880         /*
1881          * Avoid trapping faults against the zero page. The read-only
1882          * data is likely to be read-cached on the local CPU and
1883          * local/remote hits to the zero page are not interesting.
1884          */
1885         if (prot_numa && is_huge_zero_pmd(*pmd))
1886                 goto unlock;
1887
1888         if (prot_numa && pmd_protnone(*pmd))
1889                 goto unlock;
1890
1891         /*
1892          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1893          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1894          * which is also under down_read(mmap_sem):
1895          *
1896          *      CPU0:                           CPU1:
1897          *                              change_huge_pmd(prot_numa=1)
1898          *                               pmdp_huge_get_and_clear_notify()
1899          * madvise_dontneed()
1900          *  zap_pmd_range()
1901          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1902          *   // skip the pmd
1903          *                               set_pmd_at();
1904          *                               // pmd is re-established
1905          *
1906          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1907          * which may break userspace.
1908          *
1909          * pmdp_invalidate() is required to make sure we don't miss
1910          * dirty/young flags set by hardware.
1911          */
1912         entry = pmdp_invalidate(vma, addr, pmd);
1913
1914         entry = pmd_modify(entry, newprot);
1915         if (preserve_write)
1916                 entry = pmd_mk_savedwrite(entry);
1917         ret = HPAGE_PMD_NR;
1918         set_pmd_at(mm, addr, pmd, entry);
1919         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1920 unlock:
1921         spin_unlock(ptl);
1922         return ret;
1923 }
1924
1925 /*
1926  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1927  *
1928  * Note that if it returns page table lock pointer, this routine returns without
1929  * unlocking page table lock. So callers must unlock it.
1930  */
1931 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1932 {
1933         spinlock_t *ptl;
1934         ptl = pmd_lock(vma->vm_mm, pmd);
1935         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1936                         pmd_devmap(*pmd)))
1937                 return ptl;
1938         spin_unlock(ptl);
1939         return NULL;
1940 }
1941
1942 /*
1943  * Returns true if a given pud maps a thp, false otherwise.
1944  *
1945  * Note that if it returns true, this routine returns without unlocking page
1946  * table lock. So callers must unlock it.
1947  */
1948 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1949 {
1950         spinlock_t *ptl;
1951
1952         ptl = pud_lock(vma->vm_mm, pud);
1953         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1954                 return ptl;
1955         spin_unlock(ptl);
1956         return NULL;
1957 }
1958
1959 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1960 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1961                  pud_t *pud, unsigned long addr)
1962 {
1963         pud_t orig_pud;
1964         spinlock_t *ptl;
1965
1966         ptl = __pud_trans_huge_lock(pud, vma);
1967         if (!ptl)
1968                 return 0;
1969         /*
1970          * For architectures like ppc64 we look at deposited pgtable
1971          * when calling pudp_huge_get_and_clear. So do the
1972          * pgtable_trans_huge_withdraw after finishing pudp related
1973          * operations.
1974          */
1975         orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1976                         tlb->fullmm);
1977         tlb_remove_pud_tlb_entry(tlb, pud, addr);
1978         if (vma_is_dax(vma)) {
1979                 spin_unlock(ptl);
1980                 /* No zero page support yet */
1981         } else {
1982                 /* No support for anonymous PUD pages yet */
1983                 BUG();
1984         }
1985         return 1;
1986 }
1987
1988 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
1989                 unsigned long haddr)
1990 {
1991         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
1992         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1993         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
1994         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
1995
1996         count_vm_event(THP_SPLIT_PUD);
1997
1998         pudp_huge_clear_flush_notify(vma, haddr, pud);
1999 }
2000
2001 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2002                 unsigned long address)
2003 {
2004         spinlock_t *ptl;
2005         struct mm_struct *mm = vma->vm_mm;
2006         unsigned long haddr = address & HPAGE_PUD_MASK;
2007
2008         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
2009         ptl = pud_lock(mm, pud);
2010         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2011                 goto out;
2012         __split_huge_pud_locked(vma, pud, haddr);
2013
2014 out:
2015         spin_unlock(ptl);
2016         /*
2017          * No need to double call mmu_notifier->invalidate_range() callback as
2018          * the above pudp_huge_clear_flush_notify() did already call it.
2019          */
2020         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2021                                                HPAGE_PUD_SIZE);
2022 }
2023 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2024
2025 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2026                 unsigned long haddr, pmd_t *pmd)
2027 {
2028         struct mm_struct *mm = vma->vm_mm;
2029         pgtable_t pgtable;
2030         pmd_t _pmd;
2031         int i;
2032
2033         /*
2034          * Leave pmd empty until pte is filled note that it is fine to delay
2035          * notification until mmu_notifier_invalidate_range_end() as we are
2036          * replacing a zero pmd write protected page with a zero pte write
2037          * protected page.
2038          *
2039          * See Documentation/vm/mmu_notifier.rst
2040          */
2041         pmdp_huge_clear_flush(vma, haddr, pmd);
2042
2043         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2044         pmd_populate(mm, &_pmd, pgtable);
2045
2046         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2047                 pte_t *pte, entry;
2048                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2049                 entry = pte_mkspecial(entry);
2050                 pte = pte_offset_map(&_pmd, haddr);
2051                 VM_BUG_ON(!pte_none(*pte));
2052                 set_pte_at(mm, haddr, pte, entry);
2053                 pte_unmap(pte);
2054         }
2055         smp_wmb(); /* make pte visible before pmd */
2056         pmd_populate(mm, pmd, pgtable);
2057 }
2058
2059 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2060                 unsigned long haddr, bool freeze)
2061 {
2062         struct mm_struct *mm = vma->vm_mm;
2063         struct page *page;
2064         pgtable_t pgtable;
2065         pmd_t old_pmd, _pmd;
2066         bool young, write, soft_dirty, pmd_migration = false;
2067         unsigned long addr;
2068         int i;
2069
2070         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2071         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2072         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2073         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2074                                 && !pmd_devmap(*pmd));
2075
2076         count_vm_event(THP_SPLIT_PMD);
2077
2078         if (!vma_is_anonymous(vma)) {
2079                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2080                 /*
2081                  * We are going to unmap this huge page. So
2082                  * just go ahead and zap it
2083                  */
2084                 if (arch_needs_pgtable_deposit())
2085                         zap_deposited_table(mm, pmd);
2086                 if (vma_is_dax(vma))
2087                         return;
2088                 page = pmd_page(_pmd);
2089                 if (!PageDirty(page) && pmd_dirty(_pmd))
2090                         set_page_dirty(page);
2091                 if (!PageReferenced(page) && pmd_young(_pmd))
2092                         SetPageReferenced(page);
2093                 page_remove_rmap(page, true);
2094                 put_page(page);
2095                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2096                 return;
2097         } else if (is_huge_zero_pmd(*pmd)) {
2098                 /*
2099                  * FIXME: Do we want to invalidate secondary mmu by calling
2100                  * mmu_notifier_invalidate_range() see comments below inside
2101                  * __split_huge_pmd() ?
2102                  *
2103                  * We are going from a zero huge page write protected to zero
2104                  * small page also write protected so it does not seems useful
2105                  * to invalidate secondary mmu at this time.
2106                  */
2107                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2108         }
2109
2110         /*
2111          * Up to this point the pmd is present and huge and userland has the
2112          * whole access to the hugepage during the split (which happens in
2113          * place). If we overwrite the pmd with the not-huge version pointing
2114          * to the pte here (which of course we could if all CPUs were bug
2115          * free), userland could trigger a small page size TLB miss on the
2116          * small sized TLB while the hugepage TLB entry is still established in
2117          * the huge TLB. Some CPU doesn't like that.
2118          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2119          * 383 on page 93. Intel should be safe but is also warns that it's
2120          * only safe if the permission and cache attributes of the two entries
2121          * loaded in the two TLB is identical (which should be the case here).
2122          * But it is generally safer to never allow small and huge TLB entries
2123          * for the same virtual address to be loaded simultaneously. So instead
2124          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2125          * current pmd notpresent (atomically because here the pmd_trans_huge
2126          * must remain set at all times on the pmd until the split is complete
2127          * for this pmd), then we flush the SMP TLB and finally we write the
2128          * non-huge version of the pmd entry with pmd_populate.
2129          */
2130         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2131
2132 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2133         pmd_migration = is_pmd_migration_entry(old_pmd);
2134         if (pmd_migration) {
2135                 swp_entry_t entry;
2136
2137                 entry = pmd_to_swp_entry(old_pmd);
2138                 page = pfn_to_page(swp_offset(entry));
2139         } else
2140 #endif
2141                 page = pmd_page(old_pmd);
2142         VM_BUG_ON_PAGE(!page_count(page), page);
2143         page_ref_add(page, HPAGE_PMD_NR - 1);
2144         if (pmd_dirty(old_pmd))
2145                 SetPageDirty(page);
2146         write = pmd_write(old_pmd);
2147         young = pmd_young(old_pmd);
2148         soft_dirty = pmd_soft_dirty(old_pmd);
2149
2150         /*
2151          * Withdraw the table only after we mark the pmd entry invalid.
2152          * This's critical for some architectures (Power).
2153          */
2154         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2155         pmd_populate(mm, &_pmd, pgtable);
2156
2157         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2158                 pte_t entry, *pte;
2159                 /*
2160                  * Note that NUMA hinting access restrictions are not
2161                  * transferred to avoid any possibility of altering
2162                  * permissions across VMAs.
2163                  */
2164                 if (freeze || pmd_migration) {
2165                         swp_entry_t swp_entry;
2166                         swp_entry = make_migration_entry(page + i, write);
2167                         entry = swp_entry_to_pte(swp_entry);
2168                         if (soft_dirty)
2169                                 entry = pte_swp_mksoft_dirty(entry);
2170                 } else {
2171                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2172                         entry = maybe_mkwrite(entry, vma);
2173                         if (!write)
2174                                 entry = pte_wrprotect(entry);
2175                         if (!young)
2176                                 entry = pte_mkold(entry);
2177                         if (soft_dirty)
2178                                 entry = pte_mksoft_dirty(entry);
2179                 }
2180                 pte = pte_offset_map(&_pmd, addr);
2181                 BUG_ON(!pte_none(*pte));
2182                 set_pte_at(mm, addr, pte, entry);
2183                 atomic_inc(&page[i]._mapcount);
2184                 pte_unmap(pte);
2185         }
2186
2187         /*
2188          * Set PG_double_map before dropping compound_mapcount to avoid
2189          * false-negative page_mapped().
2190          */
2191         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2192                 for (i = 0; i < HPAGE_PMD_NR; i++)
2193                         atomic_inc(&page[i]._mapcount);
2194         }
2195
2196         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2197                 /* Last compound_mapcount is gone. */
2198                 __dec_node_page_state(page, NR_ANON_THPS);
2199                 if (TestClearPageDoubleMap(page)) {
2200                         /* No need in mapcount reference anymore */
2201                         for (i = 0; i < HPAGE_PMD_NR; i++)
2202                                 atomic_dec(&page[i]._mapcount);
2203                 }
2204         }
2205
2206         smp_wmb(); /* make pte visible before pmd */
2207         pmd_populate(mm, pmd, pgtable);
2208
2209         if (freeze) {
2210                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2211                         page_remove_rmap(page + i, false);
2212                         put_page(page + i);
2213                 }
2214         }
2215 }
2216
2217 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2218                 unsigned long address, bool freeze, struct page *page)
2219 {
2220         spinlock_t *ptl;
2221         struct mm_struct *mm = vma->vm_mm;
2222         unsigned long haddr = address & HPAGE_PMD_MASK;
2223
2224         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2225         ptl = pmd_lock(mm, pmd);
2226
2227         /*
2228          * If caller asks to setup a migration entries, we need a page to check
2229          * pmd against. Otherwise we can end up replacing wrong page.
2230          */
2231         VM_BUG_ON(freeze && !page);
2232         if (page && page != pmd_page(*pmd))
2233                 goto out;
2234
2235         if (pmd_trans_huge(*pmd)) {
2236                 page = pmd_page(*pmd);
2237                 if (PageMlocked(page))
2238                         clear_page_mlock(page);
2239         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2240                 goto out;
2241         __split_huge_pmd_locked(vma, pmd, haddr, freeze);
2242 out:
2243         spin_unlock(ptl);
2244         /*
2245          * No need to double call mmu_notifier->invalidate_range() callback.
2246          * They are 3 cases to consider inside __split_huge_pmd_locked():
2247          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2248          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2249          *    fault will trigger a flush_notify before pointing to a new page
2250          *    (it is fine if the secondary mmu keeps pointing to the old zero
2251          *    page in the meantime)
2252          *  3) Split a huge pmd into pte pointing to the same page. No need
2253          *     to invalidate secondary tlb entry they are all still valid.
2254          *     any further changes to individual pte will notify. So no need
2255          *     to call mmu_notifier->invalidate_range()
2256          */
2257         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2258                                                HPAGE_PMD_SIZE);
2259 }
2260
2261 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2262                 bool freeze, struct page *page)
2263 {
2264         pgd_t *pgd;
2265         p4d_t *p4d;
2266         pud_t *pud;
2267         pmd_t *pmd;
2268
2269         pgd = pgd_offset(vma->vm_mm, address);
2270         if (!pgd_present(*pgd))
2271                 return;
2272
2273         p4d = p4d_offset(pgd, address);
2274         if (!p4d_present(*p4d))
2275                 return;
2276
2277         pud = pud_offset(p4d, address);
2278         if (!pud_present(*pud))
2279                 return;
2280
2281         pmd = pmd_offset(pud, address);
2282
2283         __split_huge_pmd(vma, pmd, address, freeze, page);
2284 }
2285
2286 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2287                              unsigned long start,
2288                              unsigned long end,
2289                              long adjust_next)
2290 {
2291         /*
2292          * If the new start address isn't hpage aligned and it could
2293          * previously contain an hugepage: check if we need to split
2294          * an huge pmd.
2295          */
2296         if (start & ~HPAGE_PMD_MASK &&
2297             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2298             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2299                 split_huge_pmd_address(vma, start, false, NULL);
2300
2301         /*
2302          * If the new end address isn't hpage aligned and it could
2303          * previously contain an hugepage: check if we need to split
2304          * an huge pmd.
2305          */
2306         if (end & ~HPAGE_PMD_MASK &&
2307             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2308             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2309                 split_huge_pmd_address(vma, end, false, NULL);
2310
2311         /*
2312          * If we're also updating the vma->vm_next->vm_start, if the new
2313          * vm_next->vm_start isn't page aligned and it could previously
2314          * contain an hugepage: check if we need to split an huge pmd.
2315          */
2316         if (adjust_next > 0) {
2317                 struct vm_area_struct *next = vma->vm_next;
2318                 unsigned long nstart = next->vm_start;
2319                 nstart += adjust_next << PAGE_SHIFT;
2320                 if (nstart & ~HPAGE_PMD_MASK &&
2321                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2322                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2323                         split_huge_pmd_address(next, nstart, false, NULL);
2324         }
2325 }
2326
2327 static void freeze_page(struct page *page)
2328 {
2329         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2330                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2331         bool unmap_success;
2332
2333         VM_BUG_ON_PAGE(!PageHead(page), page);
2334
2335         if (PageAnon(page))
2336                 ttu_flags |= TTU_SPLIT_FREEZE;
2337
2338         unmap_success = try_to_unmap(page, ttu_flags);
2339         VM_BUG_ON_PAGE(!unmap_success, page);
2340 }
2341
2342 static void unfreeze_page(struct page *page)
2343 {
2344         int i;
2345         if (PageTransHuge(page)) {
2346                 remove_migration_ptes(page, page, true);
2347         } else {
2348                 for (i = 0; i < HPAGE_PMD_NR; i++)
2349                         remove_migration_ptes(page + i, page + i, true);
2350         }
2351 }
2352
2353 static void __split_huge_page_tail(struct page *head, int tail,
2354                 struct lruvec *lruvec, struct list_head *list)
2355 {
2356         struct page *page_tail = head + tail;
2357
2358         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2359
2360         /*
2361          * Clone page flags before unfreezing refcount.
2362          *
2363          * After successful get_page_unless_zero() might follow flags change,
2364          * for exmaple lock_page() which set PG_waiters.
2365          */
2366         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2367         page_tail->flags |= (head->flags &
2368                         ((1L << PG_referenced) |
2369                          (1L << PG_swapbacked) |
2370                          (1L << PG_swapcache) |
2371                          (1L << PG_mlocked) |
2372                          (1L << PG_uptodate) |
2373                          (1L << PG_active) |
2374                          (1L << PG_locked) |
2375                          (1L << PG_unevictable) |
2376                          (1L << PG_dirty)));
2377
2378         /* Page flags must be visible before we make the page non-compound. */
2379         smp_wmb();
2380
2381         /*
2382          * Clear PageTail before unfreezing page refcount.
2383          *
2384          * After successful get_page_unless_zero() might follow put_page()
2385          * which needs correct compound_head().
2386          */
2387         clear_compound_head(page_tail);
2388
2389         /* Finally unfreeze refcount. Additional reference from page cache. */
2390         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2391                                           PageSwapCache(head)));
2392
2393         if (page_is_young(head))
2394                 set_page_young(page_tail);
2395         if (page_is_idle(head))
2396                 set_page_idle(page_tail);
2397
2398         /* ->mapping in first tail page is compound_mapcount */
2399         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2400                         page_tail);
2401         page_tail->mapping = head->mapping;
2402
2403         page_tail->index = head->index + tail;
2404         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2405
2406         /*
2407          * always add to the tail because some iterators expect new
2408          * pages to show after the currently processed elements - e.g.
2409          * migrate_pages
2410          */
2411         lru_add_page_tail(head, page_tail, lruvec, list);
2412 }
2413
2414 static void __split_huge_page(struct page *page, struct list_head *list,
2415                 unsigned long flags)
2416 {
2417         struct page *head = compound_head(page);
2418         struct zone *zone = page_zone(head);
2419         struct lruvec *lruvec;
2420         pgoff_t end = -1;
2421         int i;
2422
2423         lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
2424
2425         /* complete memcg works before add pages to LRU */
2426         mem_cgroup_split_huge_fixup(head);
2427
2428         if (!PageAnon(page))
2429                 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE);
2430
2431         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2432                 __split_huge_page_tail(head, i, lruvec, list);
2433                 /* Some pages can be beyond i_size: drop them from page cache */
2434                 if (head[i].index >= end) {
2435                         ClearPageDirty(head + i);
2436                         __delete_from_page_cache(head + i, NULL);
2437                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2438                                 shmem_uncharge(head->mapping->host, 1);
2439                         put_page(head + i);
2440                 }
2441         }
2442
2443         ClearPageCompound(head);
2444         /* See comment in __split_huge_page_tail() */
2445         if (PageAnon(head)) {
2446                 /* Additional pin to radix tree of swap cache */
2447                 if (PageSwapCache(head))
2448                         page_ref_add(head, 2);
2449                 else
2450                         page_ref_inc(head);
2451         } else {
2452                 /* Additional pin to radix tree */
2453                 page_ref_add(head, 2);
2454                 xa_unlock(&head->mapping->i_pages);
2455         }
2456
2457         spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2458
2459         unfreeze_page(head);
2460
2461         for (i = 0; i < HPAGE_PMD_NR; i++) {
2462                 struct page *subpage = head + i;
2463                 if (subpage == page)
2464                         continue;
2465                 unlock_page(subpage);
2466
2467                 /*
2468                  * Subpages may be freed if there wasn't any mapping
2469                  * like if add_to_swap() is running on a lru page that
2470                  * had its mapping zapped. And freeing these pages
2471                  * requires taking the lru_lock so we do the put_page
2472                  * of the tail pages after the split is complete.
2473                  */
2474                 put_page(subpage);
2475         }
2476 }
2477
2478 int total_mapcount(struct page *page)
2479 {
2480         int i, compound, ret;
2481
2482         VM_BUG_ON_PAGE(PageTail(page), page);
2483
2484         if (likely(!PageCompound(page)))
2485                 return atomic_read(&page->_mapcount) + 1;
2486
2487         compound = compound_mapcount(page);
2488         if (PageHuge(page))
2489                 return compound;
2490         ret = compound;
2491         for (i = 0; i < HPAGE_PMD_NR; i++)
2492                 ret += atomic_read(&page[i]._mapcount) + 1;
2493         /* File pages has compound_mapcount included in _mapcount */
2494         if (!PageAnon(page))
2495                 return ret - compound * HPAGE_PMD_NR;
2496         if (PageDoubleMap(page))
2497                 ret -= HPAGE_PMD_NR;
2498         return ret;
2499 }
2500
2501 /*
2502  * This calculates accurately how many mappings a transparent hugepage
2503  * has (unlike page_mapcount() which isn't fully accurate). This full
2504  * accuracy is primarily needed to know if copy-on-write faults can
2505  * reuse the page and change the mapping to read-write instead of
2506  * copying them. At the same time this returns the total_mapcount too.
2507  *
2508  * The function returns the highest mapcount any one of the subpages
2509  * has. If the return value is one, even if different processes are
2510  * mapping different subpages of the transparent hugepage, they can
2511  * all reuse it, because each process is reusing a different subpage.
2512  *
2513  * The total_mapcount is instead counting all virtual mappings of the
2514  * subpages. If the total_mapcount is equal to "one", it tells the
2515  * caller all mappings belong to the same "mm" and in turn the
2516  * anon_vma of the transparent hugepage can become the vma->anon_vma
2517  * local one as no other process may be mapping any of the subpages.
2518  *
2519  * It would be more accurate to replace page_mapcount() with
2520  * page_trans_huge_mapcount(), however we only use
2521  * page_trans_huge_mapcount() in the copy-on-write faults where we
2522  * need full accuracy to avoid breaking page pinning, because
2523  * page_trans_huge_mapcount() is slower than page_mapcount().
2524  */
2525 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2526 {
2527         int i, ret, _total_mapcount, mapcount;
2528
2529         /* hugetlbfs shouldn't call it */
2530         VM_BUG_ON_PAGE(PageHuge(page), page);
2531
2532         if (likely(!PageTransCompound(page))) {
2533                 mapcount = atomic_read(&page->_mapcount) + 1;
2534                 if (total_mapcount)
2535                         *total_mapcount = mapcount;
2536                 return mapcount;
2537         }
2538
2539         page = compound_head(page);
2540
2541         _total_mapcount = ret = 0;
2542         for (i = 0; i < HPAGE_PMD_NR; i++) {
2543                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2544                 ret = max(ret, mapcount);
2545                 _total_mapcount += mapcount;
2546         }
2547         if (PageDoubleMap(page)) {
2548                 ret -= 1;
2549                 _total_mapcount -= HPAGE_PMD_NR;
2550         }
2551         mapcount = compound_mapcount(page);
2552         ret += mapcount;
2553         _total_mapcount += mapcount;
2554         if (total_mapcount)
2555                 *total_mapcount = _total_mapcount;
2556         return ret;
2557 }
2558
2559 /* Racy check whether the huge page can be split */
2560 bool can_split_huge_page(struct page *page, int *pextra_pins)
2561 {
2562         int extra_pins;
2563
2564         /* Additional pins from radix tree */
2565         if (PageAnon(page))
2566                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2567         else
2568                 extra_pins = HPAGE_PMD_NR;
2569         if (pextra_pins)
2570                 *pextra_pins = extra_pins;
2571         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2572 }
2573
2574 /*
2575  * This function splits huge page into normal pages. @page can point to any
2576  * subpage of huge page to split. Split doesn't change the position of @page.
2577  *
2578  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2579  * The huge page must be locked.
2580  *
2581  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2582  *
2583  * Both head page and tail pages will inherit mapping, flags, and so on from
2584  * the hugepage.
2585  *
2586  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2587  * they are not mapped.
2588  *
2589  * Returns 0 if the hugepage is split successfully.
2590  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2591  * us.
2592  */
2593 int split_huge_page_to_list(struct page *page, struct list_head *list)
2594 {
2595         struct page *head = compound_head(page);
2596         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2597         struct anon_vma *anon_vma = NULL;
2598         struct address_space *mapping = NULL;
2599         int count, mapcount, extra_pins, ret;
2600         bool mlocked;
2601         unsigned long flags;
2602
2603         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2604         VM_BUG_ON_PAGE(!PageLocked(page), page);
2605         VM_BUG_ON_PAGE(!PageCompound(page), page);
2606
2607         if (PageWriteback(page))
2608                 return -EBUSY;
2609
2610         if (PageAnon(head)) {
2611                 /*
2612                  * The caller does not necessarily hold an mmap_sem that would
2613                  * prevent the anon_vma disappearing so we first we take a
2614                  * reference to it and then lock the anon_vma for write. This
2615                  * is similar to page_lock_anon_vma_read except the write lock
2616                  * is taken to serialise against parallel split or collapse
2617                  * operations.
2618                  */
2619                 anon_vma = page_get_anon_vma(head);
2620                 if (!anon_vma) {
2621                         ret = -EBUSY;
2622                         goto out;
2623                 }
2624                 mapping = NULL;
2625                 anon_vma_lock_write(anon_vma);
2626         } else {
2627                 mapping = head->mapping;
2628
2629                 /* Truncated ? */
2630                 if (!mapping) {
2631                         ret = -EBUSY;
2632                         goto out;
2633                 }
2634
2635                 anon_vma = NULL;
2636                 i_mmap_lock_read(mapping);
2637         }
2638
2639         /*
2640          * Racy check if we can split the page, before freeze_page() will
2641          * split PMDs
2642          */
2643         if (!can_split_huge_page(head, &extra_pins)) {
2644                 ret = -EBUSY;
2645                 goto out_unlock;
2646         }
2647
2648         mlocked = PageMlocked(page);
2649         freeze_page(head);
2650         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2651
2652         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2653         if (mlocked)
2654                 lru_add_drain();
2655
2656         /* prevent PageLRU to go away from under us, and freeze lru stats */
2657         spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2658
2659         if (mapping) {
2660                 void **pslot;
2661
2662                 xa_lock(&mapping->i_pages);
2663                 pslot = radix_tree_lookup_slot(&mapping->i_pages,
2664                                 page_index(head));
2665                 /*
2666                  * Check if the head page is present in radix tree.
2667                  * We assume all tail are present too, if head is there.
2668                  */
2669                 if (radix_tree_deref_slot_protected(pslot,
2670                                         &mapping->i_pages.xa_lock) != head)
2671                         goto fail;
2672         }
2673
2674         /* Prevent deferred_split_scan() touching ->_refcount */
2675         spin_lock(&pgdata->split_queue_lock);
2676         count = page_count(head);
2677         mapcount = total_mapcount(head);
2678         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2679                 if (!list_empty(page_deferred_list(head))) {
2680                         pgdata->split_queue_len--;
2681                         list_del(page_deferred_list(head));
2682                 }
2683                 if (mapping)
2684                         __dec_node_page_state(page, NR_SHMEM_THPS);
2685                 spin_unlock(&pgdata->split_queue_lock);
2686                 __split_huge_page(page, list, flags);
2687                 if (PageSwapCache(head)) {
2688                         swp_entry_t entry = { .val = page_private(head) };
2689
2690                         ret = split_swap_cluster(entry);
2691                 } else
2692                         ret = 0;
2693         } else {
2694                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2695                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2696                                         mapcount, count);
2697                         if (PageTail(page))
2698                                 dump_page(head, NULL);
2699                         dump_page(page, "total_mapcount(head) > 0");
2700                         BUG();
2701                 }
2702                 spin_unlock(&pgdata->split_queue_lock);
2703 fail:           if (mapping)
2704                         xa_unlock(&mapping->i_pages);
2705                 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2706                 unfreeze_page(head);
2707                 ret = -EBUSY;
2708         }
2709
2710 out_unlock:
2711         if (anon_vma) {
2712                 anon_vma_unlock_write(anon_vma);
2713                 put_anon_vma(anon_vma);
2714         }
2715         if (mapping)
2716                 i_mmap_unlock_read(mapping);
2717 out:
2718         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2719         return ret;
2720 }
2721
2722 void free_transhuge_page(struct page *page)
2723 {
2724         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2725         unsigned long flags;
2726
2727         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2728         if (!list_empty(page_deferred_list(page))) {
2729                 pgdata->split_queue_len--;
2730                 list_del(page_deferred_list(page));
2731         }
2732         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2733         free_compound_page(page);
2734 }
2735
2736 void deferred_split_huge_page(struct page *page)
2737 {
2738         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2739         unsigned long flags;
2740
2741         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2742
2743         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2744         if (list_empty(page_deferred_list(page))) {
2745                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2746                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2747                 pgdata->split_queue_len++;
2748         }
2749         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2750 }
2751
2752 static unsigned long deferred_split_count(struct shrinker *shrink,
2753                 struct shrink_control *sc)
2754 {
2755         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2756         return READ_ONCE(pgdata->split_queue_len);
2757 }
2758
2759 static unsigned long deferred_split_scan(struct shrinker *shrink,
2760                 struct shrink_control *sc)
2761 {
2762         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2763         unsigned long flags;
2764         LIST_HEAD(list), *pos, *next;
2765         struct page *page;
2766         int split = 0;
2767
2768         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2769         /* Take pin on all head pages to avoid freeing them under us */
2770         list_for_each_safe(pos, next, &pgdata->split_queue) {
2771                 page = list_entry((void *)pos, struct page, mapping);
2772                 page = compound_head(page);
2773                 if (get_page_unless_zero(page)) {
2774                         list_move(page_deferred_list(page), &list);
2775                 } else {
2776                         /* We lost race with put_compound_page() */
2777                         list_del_init(page_deferred_list(page));
2778                         pgdata->split_queue_len--;
2779                 }
2780                 if (!--sc->nr_to_scan)
2781                         break;
2782         }
2783         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2784
2785         list_for_each_safe(pos, next, &list) {
2786                 page = list_entry((void *)pos, struct page, mapping);
2787                 if (!trylock_page(page))
2788                         goto next;
2789                 /* split_huge_page() removes page from list on success */
2790                 if (!split_huge_page(page))
2791                         split++;
2792                 unlock_page(page);
2793 next:
2794                 put_page(page);
2795         }
2796
2797         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2798         list_splice_tail(&list, &pgdata->split_queue);
2799         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2800
2801         /*
2802          * Stop shrinker if we didn't split any page, but the queue is empty.
2803          * This can happen if pages were freed under us.
2804          */
2805         if (!split && list_empty(&pgdata->split_queue))
2806                 return SHRINK_STOP;
2807         return split;
2808 }
2809
2810 static struct shrinker deferred_split_shrinker = {
2811         .count_objects = deferred_split_count,
2812         .scan_objects = deferred_split_scan,
2813         .seeks = DEFAULT_SEEKS,
2814         .flags = SHRINKER_NUMA_AWARE,
2815 };
2816
2817 #ifdef CONFIG_DEBUG_FS
2818 static int split_huge_pages_set(void *data, u64 val)
2819 {
2820         struct zone *zone;
2821         struct page *page;
2822         unsigned long pfn, max_zone_pfn;
2823         unsigned long total = 0, split = 0;
2824
2825         if (val != 1)
2826                 return -EINVAL;
2827
2828         for_each_populated_zone(zone) {
2829                 max_zone_pfn = zone_end_pfn(zone);
2830                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2831                         if (!pfn_valid(pfn))
2832                                 continue;
2833
2834                         page = pfn_to_page(pfn);
2835                         if (!get_page_unless_zero(page))
2836                                 continue;
2837
2838                         if (zone != page_zone(page))
2839                                 goto next;
2840
2841                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2842                                 goto next;
2843
2844                         total++;
2845                         lock_page(page);
2846                         if (!split_huge_page(page))
2847                                 split++;
2848                         unlock_page(page);
2849 next:
2850                         put_page(page);
2851                 }
2852         }
2853
2854         pr_info("%lu of %lu THP split\n", split, total);
2855
2856         return 0;
2857 }
2858 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2859                 "%llu\n");
2860
2861 static int __init split_huge_pages_debugfs(void)
2862 {
2863         void *ret;
2864
2865         ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2866                         &split_huge_pages_fops);
2867         if (!ret)
2868                 pr_warn("Failed to create split_huge_pages in debugfs");
2869         return 0;
2870 }
2871 late_initcall(split_huge_pages_debugfs);
2872 #endif
2873
2874 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2875 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2876                 struct page *page)
2877 {
2878         struct vm_area_struct *vma = pvmw->vma;
2879         struct mm_struct *mm = vma->vm_mm;
2880         unsigned long address = pvmw->address;
2881         pmd_t pmdval;
2882         swp_entry_t entry;
2883         pmd_t pmdswp;
2884
2885         if (!(pvmw->pmd && !pvmw->pte))
2886                 return;
2887
2888         mmu_notifier_invalidate_range_start(mm, address,
2889                         address + HPAGE_PMD_SIZE);
2890
2891         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2892         pmdval = *pvmw->pmd;
2893         pmdp_invalidate(vma, address, pvmw->pmd);
2894         if (pmd_dirty(pmdval))
2895                 set_page_dirty(page);
2896         entry = make_migration_entry(page, pmd_write(pmdval));
2897         pmdswp = swp_entry_to_pmd(entry);
2898         if (pmd_soft_dirty(pmdval))
2899                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2900         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2901         page_remove_rmap(page, true);
2902         put_page(page);
2903
2904         mmu_notifier_invalidate_range_end(mm, address,
2905                         address + HPAGE_PMD_SIZE);
2906 }
2907
2908 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2909 {
2910         struct vm_area_struct *vma = pvmw->vma;
2911         struct mm_struct *mm = vma->vm_mm;
2912         unsigned long address = pvmw->address;
2913         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2914         pmd_t pmde;
2915         swp_entry_t entry;
2916
2917         if (!(pvmw->pmd && !pvmw->pte))
2918                 return;
2919
2920         entry = pmd_to_swp_entry(*pvmw->pmd);
2921         get_page(new);
2922         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2923         if (pmd_swp_soft_dirty(*pvmw->pmd))
2924                 pmde = pmd_mksoft_dirty(pmde);
2925         if (is_write_migration_entry(entry))
2926                 pmde = maybe_pmd_mkwrite(pmde, vma);
2927
2928         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2929         if (PageAnon(new))
2930                 page_add_anon_rmap(new, vma, mmun_start, true);
2931         else
2932                 page_add_file_rmap(new, true);
2933         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
2934         if (vma->vm_flags & VM_LOCKED)
2935                 mlock_vma_page(new);
2936         update_mmu_cache_pmd(vma, address, pvmw->pmd);
2937 }
2938 #endif