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