mm/huge_memory.c

   1 /*
   2  *  Copyright (C) 2009  Red Hat, Inc.
   3  *
   4  *  This work is licensed under the terms of the GNU GPL, version 2. See
   5  *  the COPYING file in the top-level directory.
   6  */
   7
   8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9
  10 #include <linux/mm.h>
  11 #include <linux/sched.h>
  12 #include <linux/sched/coredump.h>
  13 #include <linux/sched/numa_balancing.h>
  14 #include <linux/highmem.h>
  15 #include <linux/hugetlb.h>
  16 #include <linux/mmu_notifier.h>
  17 #include <linux/rmap.h>
  18 #include <linux/swap.h>
  19 #include <linux/shrinker.h>
  20 #include <linux/mm_inline.h>
  21 #include <linux/swapops.h>
  22 #include <linux/dax.h>
  23 #include <linux/khugepaged.h>
  24 #include <linux/freezer.h>
  25 #include <linux/pfn_t.h>
  26 #include <linux/mman.h>
  27 #include <linux/memremap.h>
  28 #include <linux/pagemap.h>
  29 #include <linux/debugfs.h>
  30 #include <linux/migrate.h>
  31 #include <linux/hashtable.h>
  32 #include <linux/userfaultfd_k.h>
  33 #include <linux/page_idle.h>
  34 #include <linux/shmem_fs.h>
  35 #include <linux/oom.h>
  36
  37 #include <asm/tlb.h>
  38 #include <asm/pgalloc.h>
  39 #include "internal.h"
  40
  41 /*
  42  * By default, transparent hugepage support is disabled in order to avoid
  43  * risking an increased memory footprint for applications that are not
  44  * guaranteed to benefit from it. When transparent hugepage support is
  45  * enabled, it is for all mappings, and khugepaged scans all mappings.
  46  * Defrag is invoked by khugepaged hugepage allocations and by page faults
  47  * for all hugepage allocations.
  48  */
  49 unsigned long transparent_hugepage_flags __read_mostly =
  50 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  51         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  52 #endif
  53 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  54         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  55 #endif
  56         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
  57         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
  58         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
  59
  60 static struct shrinker deferred_split_shrinker;
  61
  62 static atomic_t huge_zero_refcount;
  63 struct page *huge_zero_page __read_mostly;
  64
  65 static struct page *get_huge_zero_page(void)
  66 {
  67         struct page *zero_page;
  68 retry:
  69         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
  70                 return READ_ONCE(huge_zero_page);
  71
  72         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
  73                         HPAGE_PMD_ORDER);
  74         if (!zero_page) {
  75                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
  76                 return NULL;
  77         }
  78         count_vm_event(THP_ZERO_PAGE_ALLOC);
  79         preempt_disable();
  80         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
  81                 preempt_enable();
  82                 __free_pages(zero_page, compound_order(zero_page));
  83                 goto retry;
  84         }
  85
  86         /* We take additional reference here. It will be put back by shrinker */
  87         atomic_set(&huge_zero_refcount, 2);
  88         preempt_enable();
  89         return READ_ONCE(huge_zero_page);
  90 }
  91
  92 static void put_huge_zero_page(void)
  93 {
  94         /*
  95          * Counter should never go to zero here. Only shrinker can put
  96          * last reference.
  97          */
  98         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
  99 }
 100
 101 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
 102 {
 103         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 104                 return READ_ONCE(huge_zero_page);
 105
 106         if (!get_huge_zero_page())
 107                 return NULL;
 108
 109         if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 110                 put_huge_zero_page();
 111
 112         return READ_ONCE(huge_zero_page);
 113 }
 114
 115 void mm_put_huge_zero_page(struct mm_struct *mm)
 116 {
 117         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 118                 put_huge_zero_page();
 119 }
 120
 121 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
 122                                         struct shrink_control *sc)
 123 {
 124         /* we can free zero page only if last reference remains */
 125         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 126 }
 127
 128 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 129                                        struct shrink_control *sc)
 130 {
 131         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 132                 struct page *zero_page = xchg(&huge_zero_page, NULL);
 133                 BUG_ON(zero_page == NULL);
 134                 __free_pages(zero_page, compound_order(zero_page));
 135                 return HPAGE_PMD_NR;
 136         }
 137
 138         return 0;
 139 }
 140
 141 static struct shrinker huge_zero_page_shrinker = {
 142         .count_objects = shrink_huge_zero_page_count,
 143         .scan_objects = shrink_huge_zero_page_scan,
 144         .seeks = DEFAULT_SEEKS,
 145 };
 146
 147 #ifdef CONFIG_SYSFS
 148 static ssize_t enabled_show(struct kobject *kobj,
 149                             struct kobj_attribute *attr, char *buf)
 150 {
 151         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
 152                 return sprintf(buf, "[always] madvise never\n");
 153         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
 154                 return sprintf(buf, "always [madvise] never\n");
 155         else
 156                 return sprintf(buf, "always madvise [never]\n");
 157 }
 158
 159 static ssize_t enabled_store(struct kobject *kobj,
 160                              struct kobj_attribute *attr,
 161                              const char *buf, size_t count)
 162 {
 163         ssize_t ret = count;
 164
 165         if (!memcmp("always", buf,
 166                     min(sizeof("always")-1, count))) {
 167                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 168                 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 169         } else if (!memcmp("madvise", buf,
 170                            min(sizeof("madvise")-1, count))) {
 171                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 172                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 173         } else if (!memcmp("never", buf,
 174                            min(sizeof("never")-1, count))) {
 175                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 176                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 177         } else
 178                 ret = -EINVAL;
 179
 180         if (ret > 0) {
 181                 int err = start_stop_khugepaged();
 182                 if (err)
 183                         ret = err;
 184         }
 185         return ret;
 186 }
 187 static struct kobj_attribute enabled_attr =
 188         __ATTR(enabled, 0644, enabled_show, enabled_store);
 189
 190 ssize_t single_hugepage_flag_show(struct kobject *kobj,
 191                                 struct kobj_attribute *attr, char *buf,
 192                                 enum transparent_hugepage_flag flag)
 193 {
 194         return sprintf(buf, "%d\n",
 195                        !!test_bit(flag, &transparent_hugepage_flags));
 196 }
 197
 198 ssize_t single_hugepage_flag_store(struct kobject *kobj,
 199                                  struct kobj_attribute *attr,
 200                                  const char *buf, size_t count,
 201                                  enum transparent_hugepage_flag flag)
 202 {
 203         unsigned long value;
 204         int ret;
 205
 206         ret = kstrtoul(buf, 10, &value);
 207         if (ret < 0)
 208                 return ret;
 209         if (value > 1)
 210                 return -EINVAL;
 211
 212         if (value)
 213                 set_bit(flag, &transparent_hugepage_flags);
 214         else
 215                 clear_bit(flag, &transparent_hugepage_flags);
 216
 217         return count;
 218 }
 219
 220 static ssize_t defrag_show(struct kobject *kobj,
 221                            struct kobj_attribute *attr, char *buf)
 222 {
 223         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 224                 return sprintf(buf, "[always] defer defer+madvise madvise never\n");
 225         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 226                 return sprintf(buf, "always [defer] defer+madvise madvise never\n");
 227         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 228                 return sprintf(buf, "always defer [defer+madvise] madvise never\n");
 229         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 230                 return sprintf(buf, "always defer defer+madvise [madvise] never\n");
 231         return sprintf(buf, "always defer defer+madvise madvise [never]\n");
 232 }
 233
 234 static ssize_t defrag_store(struct kobject *kobj,
 235                             struct kobj_attribute *attr,
 236                             const char *buf, size_t count)
 237 {
 238         if (!memcmp("always", buf,
 239                     min(sizeof("always")-1, count))) {
 240                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 241                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 242                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 243                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 244         } else if (!memcmp("defer+madvise", buf,
 245                     min(sizeof("defer+madvise")-1, count))) {
 246                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 247                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 248                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 249                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 250         } else if (!memcmp("defer", buf,
 251                     min(sizeof("defer")-1, count))) {
 252                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 253                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 254                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 255                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 256         } else if (!memcmp("madvise", buf,
 257                            min(sizeof("madvise")-1, count))) {
 258                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 259                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 260                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 261                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 262         } else if (!memcmp("never", buf,
 263                            min(sizeof("never")-1, count))) {
 264                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 265                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 266                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 267                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 268         } else
 269                 return -EINVAL;
 270
 271         return count;
 272 }
 273 static struct kobj_attribute defrag_attr =
 274         __ATTR(defrag, 0644, defrag_show, defrag_store);
 275
 276 static ssize_t use_zero_page_show(struct kobject *kobj,
 277                 struct kobj_attribute *attr, char *buf)
 278 {
 279         return single_hugepage_flag_show(kobj, attr, buf,
 280                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 281 }
 282 static ssize_t use_zero_page_store(struct kobject *kobj,
 283                 struct kobj_attribute *attr, const char *buf, size_t count)
 284 {
 285         return single_hugepage_flag_store(kobj, attr, buf, count,
 286                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 287 }
 288 static struct kobj_attribute use_zero_page_attr =
 289         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 290
 291 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
 292                 struct kobj_attribute *attr, char *buf)
 293 {
 294         return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
 295 }
 296 static struct kobj_attribute hpage_pmd_size_attr =
 297         __ATTR_RO(hpage_pmd_size);
 298
 299 #ifdef CONFIG_DEBUG_VM
 300 static ssize_t debug_cow_show(struct kobject *kobj,
 301                                 struct kobj_attribute *attr, char *buf)
 302 {
 303         return single_hugepage_flag_show(kobj, attr, buf,
 304                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 305 }
 306 static ssize_t debug_cow_store(struct kobject *kobj,
 307                                struct kobj_attribute *attr,
 308                                const char *buf, size_t count)
 309 {
 310         return single_hugepage_flag_store(kobj, attr, buf, count,
 311                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 312 }
 313 static struct kobj_attribute debug_cow_attr =
 314         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 315 #endif /* CONFIG_DEBUG_VM */
 316
 317 static struct attribute *hugepage_attr[] = {
 318         &enabled_attr.attr,
 319         &defrag_attr.attr,
 320         &use_zero_page_attr.attr,
 321         &hpage_pmd_size_attr.attr,
 322 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
 323         &shmem_enabled_attr.attr,
 324 #endif
 325 #ifdef CONFIG_DEBUG_VM
 326         &debug_cow_attr.attr,
 327 #endif
 328         NULL,
 329 };
 330
 331 static const struct attribute_group hugepage_attr_group = {
 332         .attrs = hugepage_attr,
 333 };
 334
 335 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 336 {
 337         int err;
 338
 339         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 340         if (unlikely(!*hugepage_kobj)) {
 341                 pr_err("failed to create transparent hugepage kobject\n");
 342                 return -ENOMEM;
 343         }
 344
 345         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 346         if (err) {
 347                 pr_err("failed to register transparent hugepage group\n");
 348                 goto delete_obj;
 349         }
 350
 351         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 352         if (err) {
 353                 pr_err("failed to register transparent hugepage group\n");
 354                 goto remove_hp_group;
 355         }
 356
 357         return 0;
 358
 359 remove_hp_group:
 360         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 361 delete_obj:
 362         kobject_put(*hugepage_kobj);
 363         return err;
 364 }
 365
 366 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 367 {
 368         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 369         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 370         kobject_put(hugepage_kobj);
 371 }
 372 #else
 373 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 374 {
 375         return 0;
 376 }
 377
 378 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 379 {
 380 }
 381 #endif /* CONFIG_SYSFS */
 382
 383 static int __init hugepage_init(void)
 384 {
 385         int err;
 386         struct kobject *hugepage_kobj;
 387
 388         if (!has_transparent_hugepage()) {
 389                 transparent_hugepage_flags = 0;
 390                 return -EINVAL;
 391         }
 392
 393         /*
 394          * hugepages can't be allocated by the buddy allocator
 395          */
 396         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
 397         /*
 398          * we use page->mapping and page->index in second tail page
 399          * as list_head: assuming THP order >= 2
 400          */
 401         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
 402
 403         err = hugepage_init_sysfs(&hugepage_kobj);
 404         if (err)
 405                 goto err_sysfs;
 406
 407         err = khugepaged_init();
 408         if (err)
 409                 goto err_slab;
 410
 411         err = register_shrinker(&huge_zero_page_shrinker);
 412         if (err)
 413                 goto err_hzp_shrinker;
 414         err = register_shrinker(&deferred_split_shrinker);
 415         if (err)
 416                 goto err_split_shrinker;
 417
 418         /*
 419          * By default disable transparent hugepages on smaller systems,
 420          * where the extra memory used could hurt more than TLB overhead
 421          * is likely to save.  The admin can still enable it through /sys.
 422          */
 423         if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
 424                 transparent_hugepage_flags = 0;
 425                 return 0;
 426         }
 427
 428         err = start_stop_khugepaged();
 429         if (err)
 430                 goto err_khugepaged;
 431
 432         return 0;
 433 err_khugepaged:
 434         unregister_shrinker(&deferred_split_shrinker);
 435 err_split_shrinker:
 436         unregister_shrinker(&huge_zero_page_shrinker);
 437 err_hzp_shrinker:
 438         khugepaged_destroy();
 439 err_slab:
 440         hugepage_exit_sysfs(hugepage_kobj);
 441 err_sysfs:
 442         return err;
 443 }
 444 subsys_initcall(hugepage_init);
 445
 446 static int __init setup_transparent_hugepage(char *str)
 447 {
 448         int ret = 0;
 449         if (!str)
 450                 goto out;
 451         if (!strcmp(str, "always")) {
 452                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 453                         &transparent_hugepage_flags);
 454                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 455                           &transparent_hugepage_flags);
 456                 ret = 1;
 457         } else if (!strcmp(str, "madvise")) {
 458                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 459                           &transparent_hugepage_flags);
 460                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 461                         &transparent_hugepage_flags);
 462                 ret = 1;
 463         } else if (!strcmp(str, "never")) {
 464                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 465                           &transparent_hugepage_flags);
 466                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 467                           &transparent_hugepage_flags);
 468                 ret = 1;
 469         }
 470 out:
 471         if (!ret)
 472                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
 473         return ret;
 474 }
 475 __setup("transparent_hugepage=", setup_transparent_hugepage);
 476
 477 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 478 {
 479         if (likely(vma->vm_flags & VM_WRITE))
 480                 pmd = pmd_mkwrite(pmd);
 481         return pmd;
 482 }
 483
 484 static inline struct list_head *page_deferred_list(struct page *page)
 485 {
 486         /* ->lru in the tail pages is occupied by compound_head. */
 487         return &page[2].deferred_list;
 488 }
 489
 490 void prep_transhuge_page(struct page *page)
 491 {
 492         /*
 493          * we use page->mapping and page->indexlru in second tail page
 494          * as list_head: assuming THP order >= 2
 495          */
 496
 497         INIT_LIST_HEAD(page_deferred_list(page));
 498         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 499 }
 500
 501 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
 502                 loff_t off, unsigned long flags, unsigned long size)
 503 {
 504         unsigned long addr;
 505         loff_t off_end = off + len;
 506         loff_t off_align = round_up(off, size);
 507         unsigned long len_pad;
 508
 509         if (off_end <= off_align || (off_end - off_align) < size)
 510                 return 0;
 511
 512         len_pad = len + size;
 513         if (len_pad < len || (off + len_pad) < off)
 514                 return 0;
 515
 516         addr = current->mm->get_unmapped_area(filp, 0, len_pad,
 517                                               off >> PAGE_SHIFT, flags);
 518         if (IS_ERR_VALUE(addr))
 519                 return 0;
 520
 521         addr += (off - addr) & (size - 1);
 522         return addr;
 523 }
 524
 525 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 526                 unsigned long len, unsigned long pgoff, unsigned long flags)
 527 {
 528         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 529
 530         if (addr)
 531                 goto out;
 532         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
 533                 goto out;
 534
 535         addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
 536         if (addr)
 537                 return addr;
 538
 539  out:
 540         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 541 }
 542 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 543
 544 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
 545                         struct page *page, gfp_t gfp)
 546 {
 547         struct vm_area_struct *vma = vmf->vma;
 548         struct mem_cgroup *memcg;
 549         pgtable_t pgtable;
 550         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 551         vm_fault_t ret = 0;
 552
 553         VM_BUG_ON_PAGE(!PageCompound(page), page);
 554
 555         if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
 556                 put_page(page);
 557                 count_vm_event(THP_FAULT_FALLBACK);
 558                 return VM_FAULT_FALLBACK;
 559         }
 560
 561         pgtable = pte_alloc_one(vma->vm_mm, haddr);
 562         if (unlikely(!pgtable)) {
 563                 ret = VM_FAULT_OOM;
 564                 goto release;
 565         }
 566
 567         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
 568         /*
 569          * The memory barrier inside __SetPageUptodate makes sure that
 570          * clear_huge_page writes become visible before the set_pmd_at()
 571          * write.
 572          */
 573         __SetPageUptodate(page);
 574
 575         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 576         if (unlikely(!pmd_none(*vmf->pmd))) {
 577                 goto unlock_release;
 578         } else {
 579                 pmd_t entry;
 580
 581                 ret = check_stable_address_space(vma->vm_mm);
 582                 if (ret)
 583                         goto unlock_release;
 584
 585                 /* Deliver the page fault to userland */
 586                 if (userfaultfd_missing(vma)) {
 587                         vm_fault_t ret2;
 588
 589                         spin_unlock(vmf->ptl);
 590                         mem_cgroup_cancel_charge(page, memcg, true);
 591                         put_page(page);
 592                         pte_free(vma->vm_mm, pgtable);
 593                         ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
 594                         VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
 595                         return ret2;
 596                 }
 597
 598                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 599                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 600                 page_add_new_anon_rmap(page, vma, haddr, true);
 601                 mem_cgroup_commit_charge(page, memcg, false, true);
 602                 lru_cache_add_active_or_unevictable(page, vma);
 603                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 604                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 605                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 606                 mm_inc_nr_ptes(vma->vm_mm);
 607                 spin_unlock(vmf->ptl);
 608                 count_vm_event(THP_FAULT_ALLOC);
 609         }
 610
 611         return 0;
 612 unlock_release:
 613         spin_unlock(vmf->ptl);
 614 release:
 615         if (pgtable)
 616                 pte_free(vma->vm_mm, pgtable);
 617         mem_cgroup_cancel_charge(page, memcg, true);
 618         put_page(page);
 619         return ret;
 620
 621 }
 622
 623 /*
 624  * always: directly stall for all thp allocations
 625  * defer: wake kswapd and fail if not immediately available
 626  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
 627  *                fail if not immediately available
 628  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
 629  *          available
 630  * never: never stall for any thp allocation
 631  */
 632 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
 633 {
 634         const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
 635
 636         /* Always do synchronous compaction */
 637         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 638                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
 639
 640         /* Kick kcompactd and fail quickly */
 641         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 642                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
 643
 644         /* Synchronous compaction if madvised, otherwise kick kcompactd */
 645         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 646                 return GFP_TRANSHUGE_LIGHT |
 647                         (vma_madvised ? __GFP_DIRECT_RECLAIM :
 648                                         __GFP_KSWAPD_RECLAIM);
 649
 650         /* Only do synchronous compaction if madvised */
 651         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 652                 return GFP_TRANSHUGE_LIGHT |
 653                        (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
 654
 655         return GFP_TRANSHUGE_LIGHT;
 656 }
 657
 658 /* Caller must hold page table lock. */
 659 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 660                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 661                 struct page *zero_page)
 662 {
 663         pmd_t entry;
 664         if (!pmd_none(*pmd))
 665                 return false;
 666         entry = mk_pmd(zero_page, vma->vm_page_prot);
 667         entry = pmd_mkhuge(entry);
 668         if (pgtable)
 669                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 670         set_pmd_at(mm, haddr, pmd, entry);
 671         mm_inc_nr_ptes(mm);
 672         return true;
 673 }
 674
 675 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 676 {
 677         struct vm_area_struct *vma = vmf->vma;
 678         gfp_t gfp;
 679         struct page *page;
 680         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 681
 682         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
 683                 return VM_FAULT_FALLBACK;
 684         if (unlikely(anon_vma_prepare(vma)))
 685                 return VM_FAULT_OOM;
 686         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 687                 return VM_FAULT_OOM;
 688         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
 689                         !mm_forbids_zeropage(vma->vm_mm) &&
 690                         transparent_hugepage_use_zero_page()) {
 691                 pgtable_t pgtable;
 692                 struct page *zero_page;
 693                 bool set;
 694                 vm_fault_t ret;
 695                 pgtable = pte_alloc_one(vma->vm_mm, haddr);
 696                 if (unlikely(!pgtable))
 697                         return VM_FAULT_OOM;
 698                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
 699                 if (unlikely(!zero_page)) {
 700                         pte_free(vma->vm_mm, pgtable);
 701                         count_vm_event(THP_FAULT_FALLBACK);
 702                         return VM_FAULT_FALLBACK;
 703                 }
 704                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 705                 ret = 0;
 706                 set = false;
 707                 if (pmd_none(*vmf->pmd)) {
 708                         ret = check_stable_address_space(vma->vm_mm);
 709                         if (ret) {
 710                                 spin_unlock(vmf->ptl);
 711                         } else if (userfaultfd_missing(vma)) {
 712                                 spin_unlock(vmf->ptl);
 713                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
 714                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 715                         } else {
 716                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
 717                                                    haddr, vmf->pmd, zero_page);
 718                                 spin_unlock(vmf->ptl);
 719                                 set = true;
 720                         }
 721                 } else
 722                         spin_unlock(vmf->ptl);
 723                 if (!set)
 724                         pte_free(vma->vm_mm, pgtable);
 725                 return ret;
 726         }
 727         gfp = alloc_hugepage_direct_gfpmask(vma);
 728         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 729         if (unlikely(!page)) {
 730                 count_vm_event(THP_FAULT_FALLBACK);
 731                 return VM_FAULT_FALLBACK;
 732         }
 733         prep_transhuge_page(page);
 734         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
 735 }
 736
 737 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 738                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
 739                 pgtable_t pgtable)
 740 {
 741         struct mm_struct *mm = vma->vm_mm;
 742         pmd_t entry;
 743         spinlock_t *ptl;
 744
 745         ptl = pmd_lock(mm, pmd);
 746         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 747         if (pfn_t_devmap(pfn))
 748                 entry = pmd_mkdevmap(entry);
 749         if (write) {
 750                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 751                 entry = maybe_pmd_mkwrite(entry, vma);
 752         }
 753
 754         if (pgtable) {
 755                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 756                 mm_inc_nr_ptes(mm);
 757         }
 758
 759         set_pmd_at(mm, addr, pmd, entry);
 760         update_mmu_cache_pmd(vma, addr, pmd);
 761         spin_unlock(ptl);
 762 }
 763
 764 vm_fault_t vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 765                         pmd_t *pmd, pfn_t pfn, bool write)
 766 {
 767         pgprot_t pgprot = vma->vm_page_prot;
 768         pgtable_t pgtable = NULL;
 769         /*
 770          * If we had pmd_special, we could avoid all these restrictions,
 771          * but we need to be consistent with PTEs and architectures that
 772          * can't support a 'special' bit.
 773          */
 774         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 775                         !pfn_t_devmap(pfn));
 776         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 777                                                 (VM_PFNMAP|VM_MIXEDMAP));
 778         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 779
 780         if (addr < vma->vm_start || addr >= vma->vm_end)
 781                 return VM_FAULT_SIGBUS;
 782
 783         if (arch_needs_pgtable_deposit()) {
 784                 pgtable = pte_alloc_one(vma->vm_mm, addr);
 785                 if (!pgtable)
 786                         return VM_FAULT_OOM;
 787         }
 788
 789         track_pfn_insert(vma, &pgprot, pfn);
 790
 791         insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable);
 792         return VM_FAULT_NOPAGE;
 793 }
 794 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
 795
 796 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 797 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 798 {
 799         if (likely(vma->vm_flags & VM_WRITE))
 800                 pud = pud_mkwrite(pud);
 801         return pud;
 802 }
 803
 804 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 805                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 806 {
 807         struct mm_struct *mm = vma->vm_mm;
 808         pud_t entry;
 809         spinlock_t *ptl;
 810
 811         ptl = pud_lock(mm, pud);
 812         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
 813         if (pfn_t_devmap(pfn))
 814                 entry = pud_mkdevmap(entry);
 815         if (write) {
 816                 entry = pud_mkyoung(pud_mkdirty(entry));
 817                 entry = maybe_pud_mkwrite(entry, vma);
 818         }
 819         set_pud_at(mm, addr, pud, entry);
 820         update_mmu_cache_pud(vma, addr, pud);
 821         spin_unlock(ptl);
 822 }
 823
 824 vm_fault_t vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 825                         pud_t *pud, pfn_t pfn, bool write)
 826 {
 827         pgprot_t pgprot = vma->vm_page_prot;
 828         /*
 829          * If we had pud_special, we could avoid all these restrictions,
 830          * but we need to be consistent with PTEs and architectures that
 831          * can't support a 'special' bit.
 832          */
 833         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 834                         !pfn_t_devmap(pfn));
 835         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 836                                                 (VM_PFNMAP|VM_MIXEDMAP));
 837         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 838
 839         if (addr < vma->vm_start || addr >= vma->vm_end)
 840                 return VM_FAULT_SIGBUS;
 841
 842         track_pfn_insert(vma, &pgprot, pfn);
 843
 844         insert_pfn_pud(vma, addr, pud, pfn, pgprot, write);
 845         return VM_FAULT_NOPAGE;
 846 }
 847 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
 848 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 849
 850 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
 851                 pmd_t *pmd, int flags)
 852 {
 853         pmd_t _pmd;
 854
 855         _pmd = pmd_mkyoung(*pmd);
 856         if (flags & FOLL_WRITE)
 857                 _pmd = pmd_mkdirty(_pmd);
 858         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 859                                 pmd, _pmd, flags & FOLL_WRITE))
 860                 update_mmu_cache_pmd(vma, addr, pmd);
 861 }
 862
 863 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 864                 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
 865 {
 866         unsigned long pfn = pmd_pfn(*pmd);
 867         struct mm_struct *mm = vma->vm_mm;
 868         struct page *page;
 869
 870         assert_spin_locked(pmd_lockptr(mm, pmd));
 871
 872         /*
 873          * When we COW a devmap PMD entry, we split it into PTEs, so we should
 874          * not be in this function with `flags & FOLL_COW` set.
 875          */
 876         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
 877
 878         if (flags & FOLL_WRITE && !pmd_write(*pmd))
 879                 return NULL;
 880
 881         if (pmd_present(*pmd) && pmd_devmap(*pmd))
 882                 /* pass */;
 883         else
 884                 return NULL;
 885
 886         if (flags & FOLL_TOUCH)
 887                 touch_pmd(vma, addr, pmd, flags);
 888
 889         /*
 890          * device mapped pages can only be returned if the
 891          * caller will manage the page reference count.
 892          */
 893         if (!(flags & FOLL_GET))
 894                 return ERR_PTR(-EEXIST);
 895
 896         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
 897         *pgmap = get_dev_pagemap(pfn, *pgmap);
 898         if (!*pgmap)
 899                 return ERR_PTR(-EFAULT);
 900         page = pfn_to_page(pfn);
 901         get_page(page);
 902
 903         return page;
 904 }
 905
 906 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 907                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 908                   struct vm_area_struct *vma)
 909 {
 910         spinlock_t *dst_ptl, *src_ptl;
 911         struct page *src_page;
 912         pmd_t pmd;
 913         pgtable_t pgtable = NULL;
 914         int ret = -ENOMEM;
 915
 916         /* Skip if can be re-fill on fault */
 917         if (!vma_is_anonymous(vma))
 918                 return 0;
 919
 920         pgtable = pte_alloc_one(dst_mm, addr);
 921         if (unlikely(!pgtable))
 922                 goto out;
 923
 924         dst_ptl = pmd_lock(dst_mm, dst_pmd);
 925         src_ptl = pmd_lockptr(src_mm, src_pmd);
 926         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 927
 928         ret = -EAGAIN;
 929         pmd = *src_pmd;
 930
 931 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
 932         if (unlikely(is_swap_pmd(pmd))) {
 933                 swp_entry_t entry = pmd_to_swp_entry(pmd);
 934
 935                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
 936                 if (is_write_migration_entry(entry)) {
 937                         make_migration_entry_read(&entry);
 938                         pmd = swp_entry_to_pmd(entry);
 939                         if (pmd_swp_soft_dirty(*src_pmd))
 940                                 pmd = pmd_swp_mksoft_dirty(pmd);
 941                         set_pmd_at(src_mm, addr, src_pmd, pmd);
 942                 }
 943                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 944                 mm_inc_nr_ptes(dst_mm);
 945                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 946                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 947                 ret = 0;
 948                 goto out_unlock;
 949         }
 950 #endif
 951
 952         if (unlikely(!pmd_trans_huge(pmd))) {
 953                 pte_free(dst_mm, pgtable);
 954                 goto out_unlock;
 955         }
 956         /*
 957          * When page table lock is held, the huge zero pmd should not be
 958          * under splitting since we don't split the page itself, only pmd to
 959          * a page table.
 960          */
 961         if (is_huge_zero_pmd(pmd)) {
 962                 struct page *zero_page;
 963                 /*
 964                  * get_huge_zero_page() will never allocate a new page here,
 965                  * since we already have a zero page to copy. It just takes a
 966                  * reference.
 967                  */
 968                 zero_page = mm_get_huge_zero_page(dst_mm);
 969                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
 970                                 zero_page);
 971                 ret = 0;
 972                 goto out_unlock;
 973         }
 974
 975         src_page = pmd_page(pmd);
 976         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
 977         get_page(src_page);
 978         page_dup_rmap(src_page, true);
 979         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 980         mm_inc_nr_ptes(dst_mm);
 981         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 982
 983         pmdp_set_wrprotect(src_mm, addr, src_pmd);
 984         pmd = pmd_mkold(pmd_wrprotect(pmd));
 985         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 986
 987         ret = 0;
 988 out_unlock:
 989         spin_unlock(src_ptl);
 990         spin_unlock(dst_ptl);
 991 out:
 992         return ret;
 993 }
 994
 995 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 996 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
 997                 pud_t *pud, int flags)
 998 {
 999         pud_t _pud;
1000
1001         _pud = pud_mkyoung(*pud);
1002         if (flags & FOLL_WRITE)
1003                 _pud = pud_mkdirty(_pud);
1004         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1005                                 pud, _pud, flags & FOLL_WRITE))
1006                 update_mmu_cache_pud(vma, addr, pud);
1007 }
1008
1009 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1010                 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1011 {
1012         unsigned long pfn = pud_pfn(*pud);
1013         struct mm_struct *mm = vma->vm_mm;
1014         struct page *page;
1015
1016         assert_spin_locked(pud_lockptr(mm, pud));
1017
1018         if (flags & FOLL_WRITE && !pud_write(*pud))
1019                 return NULL;
1020
1021         if (pud_present(*pud) && pud_devmap(*pud))
1022                 /* pass */;
1023         else
1024                 return NULL;
1025
1026         if (flags & FOLL_TOUCH)
1027                 touch_pud(vma, addr, pud, flags);
1028
1029         /*
1030          * device mapped pages can only be returned if the
1031          * caller will manage the page reference count.
1032          */
1033         if (!(flags & FOLL_GET))
1034                 return ERR_PTR(-EEXIST);
1035
1036         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1037         *pgmap = get_dev_pagemap(pfn, *pgmap);
1038         if (!*pgmap)
1039                 return ERR_PTR(-EFAULT);
1040         page = pfn_to_page(pfn);
1041         get_page(page);
1042
1043         return page;
1044 }
1045
1046 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1047                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1048                   struct vm_area_struct *vma)
1049 {
1050         spinlock_t *dst_ptl, *src_ptl;
1051         pud_t pud;
1052         int ret;
1053
1054         dst_ptl = pud_lock(dst_mm, dst_pud);
1055         src_ptl = pud_lockptr(src_mm, src_pud);
1056         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1057
1058         ret = -EAGAIN;
1059         pud = *src_pud;
1060         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1061                 goto out_unlock;
1062
1063         /*
1064          * When page table lock is held, the huge zero pud should not be
1065          * under splitting since we don't split the page itself, only pud to
1066          * a page table.
1067          */
1068         if (is_huge_zero_pud(pud)) {
1069                 /* No huge zero pud yet */
1070         }
1071
1072         pudp_set_wrprotect(src_mm, addr, src_pud);
1073         pud = pud_mkold(pud_wrprotect(pud));
1074         set_pud_at(dst_mm, addr, dst_pud, pud);
1075
1076         ret = 0;
1077 out_unlock:
1078         spin_unlock(src_ptl);
1079         spin_unlock(dst_ptl);
1080         return ret;
1081 }
1082
1083 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1084 {
1085         pud_t entry;
1086         unsigned long haddr;
1087         bool write = vmf->flags & FAULT_FLAG_WRITE;
1088
1089         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1090         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1091                 goto unlock;
1092
1093         entry = pud_mkyoung(orig_pud);
1094         if (write)
1095                 entry = pud_mkdirty(entry);
1096         haddr = vmf->address & HPAGE_PUD_MASK;
1097         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1098                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1099
1100 unlock:
1101         spin_unlock(vmf->ptl);
1102 }
1103 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1104
1105 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1106 {
1107         pmd_t entry;
1108         unsigned long haddr;
1109         bool write = vmf->flags & FAULT_FLAG_WRITE;
1110
1111         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1112         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1113                 goto unlock;
1114
1115         entry = pmd_mkyoung(orig_pmd);
1116         if (write)
1117                 entry = pmd_mkdirty(entry);
1118         haddr = vmf->address & HPAGE_PMD_MASK;
1119         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1120                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1121
1122 unlock:
1123         spin_unlock(vmf->ptl);
1124 }
1125
1126 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1127                         pmd_t orig_pmd, struct page *page)
1128 {
1129         struct vm_area_struct *vma = vmf->vma;
1130         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1131         struct mem_cgroup *memcg;
1132         pgtable_t pgtable;
1133         pmd_t _pmd;
1134         int i;
1135         vm_fault_t ret = 0;
1136         struct page **pages;
1137         unsigned long mmun_start;       /* For mmu_notifiers */
1138         unsigned long mmun_end;         /* For mmu_notifiers */
1139
1140         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1141                               GFP_KERNEL);
1142         if (unlikely(!pages)) {
1143                 ret |= VM_FAULT_OOM;
1144                 goto out;
1145         }
1146
1147         for (i = 0; i < HPAGE_PMD_NR; i++) {
1148                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1149                                                vmf->address, page_to_nid(page));
1150                 if (unlikely(!pages[i] ||
1151                              mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1152                                      GFP_KERNEL, &memcg, false))) {
1153                         if (pages[i])
1154                                 put_page(pages[i]);
1155                         while (--i >= 0) {
1156                                 memcg = (void *)page_private(pages[i]);
1157                                 set_page_private(pages[i], 0);
1158                                 mem_cgroup_cancel_charge(pages[i], memcg,
1159                                                 false);
1160                                 put_page(pages[i]);
1161                         }
1162                         kfree(pages);
1163                         ret |= VM_FAULT_OOM;
1164                         goto out;
1165                 }
1166                 set_page_private(pages[i], (unsigned long)memcg);
1167         }
1168
1169         for (i = 0; i < HPAGE_PMD_NR; i++) {
1170                 copy_user_highpage(pages[i], page + i,
1171                                    haddr + PAGE_SIZE * i, vma);
1172                 __SetPageUptodate(pages[i]);
1173                 cond_resched();
1174         }
1175
1176         mmun_start = haddr;
1177         mmun_end   = haddr + HPAGE_PMD_SIZE;
1178         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1179
1180         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1181         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1182                 goto out_free_pages;
1183         VM_BUG_ON_PAGE(!PageHead(page), page);
1184
1185         /*
1186          * Leave pmd empty until pte is filled note we must notify here as
1187          * concurrent CPU thread might write to new page before the call to
1188          * mmu_notifier_invalidate_range_end() happens which can lead to a
1189          * device seeing memory write in different order than CPU.
1190          *
1191          * See Documentation/vm/mmu_notifier.rst
1192          */
1193         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1194
1195         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1196         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1197
1198         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1199                 pte_t entry;
1200                 entry = mk_pte(pages[i], vma->vm_page_prot);
1201                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1202                 memcg = (void *)page_private(pages[i]);
1203                 set_page_private(pages[i], 0);
1204                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1205                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1206                 lru_cache_add_active_or_unevictable(pages[i], vma);
1207                 vmf->pte = pte_offset_map(&_pmd, haddr);
1208                 VM_BUG_ON(!pte_none(*vmf->pte));
1209                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1210                 pte_unmap(vmf->pte);
1211         }
1212         kfree(pages);
1213
1214         smp_wmb(); /* make pte visible before pmd */
1215         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1216         page_remove_rmap(page, true);
1217         spin_unlock(vmf->ptl);
1218
1219         /*
1220          * No need to double call mmu_notifier->invalidate_range() callback as
1221          * the above pmdp_huge_clear_flush_notify() did already call it.
1222          */
1223         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1224                                                 mmun_end);
1225
1226         ret |= VM_FAULT_WRITE;
1227         put_page(page);
1228
1229 out:
1230         return ret;
1231
1232 out_free_pages:
1233         spin_unlock(vmf->ptl);
1234         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1235         for (i = 0; i < HPAGE_PMD_NR; i++) {
1236                 memcg = (void *)page_private(pages[i]);
1237                 set_page_private(pages[i], 0);
1238                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1239                 put_page(pages[i]);
1240         }
1241         kfree(pages);
1242         goto out;
1243 }
1244
1245 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1246 {
1247         struct vm_area_struct *vma = vmf->vma;
1248         struct page *page = NULL, *new_page;
1249         struct mem_cgroup *memcg;
1250         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1251         unsigned long mmun_start;       /* For mmu_notifiers */
1252         unsigned long mmun_end;         /* For mmu_notifiers */
1253         gfp_t huge_gfp;                 /* for allocation and charge */
1254         vm_fault_t ret = 0;
1255
1256         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1257         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1258         if (is_huge_zero_pmd(orig_pmd))
1259                 goto alloc;
1260         spin_lock(vmf->ptl);
1261         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1262                 goto out_unlock;
1263
1264         page = pmd_page(orig_pmd);
1265         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1266         /*
1267          * We can only reuse the page if nobody else maps the huge page or it's
1268          * part.
1269          */
1270         if (!trylock_page(page)) {
1271                 get_page(page);
1272                 spin_unlock(vmf->ptl);
1273                 lock_page(page);
1274                 spin_lock(vmf->ptl);
1275                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1276                         unlock_page(page);
1277                         put_page(page);
1278                         goto out_unlock;
1279                 }
1280                 put_page(page);
1281         }
1282         if (reuse_swap_page(page, NULL)) {
1283                 pmd_t entry;
1284                 entry = pmd_mkyoung(orig_pmd);
1285                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1286                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1287                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1288                 ret |= VM_FAULT_WRITE;
1289                 unlock_page(page);
1290                 goto out_unlock;
1291         }
1292         unlock_page(page);
1293         get_page(page);
1294         spin_unlock(vmf->ptl);
1295 alloc:
1296         if (transparent_hugepage_enabled(vma) &&
1297             !transparent_hugepage_debug_cow()) {
1298                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1299                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1300         } else
1301                 new_page = NULL;
1302
1303         if (likely(new_page)) {
1304                 prep_transhuge_page(new_page);
1305         } else {
1306                 if (!page) {
1307                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1308                         ret |= VM_FAULT_FALLBACK;
1309                 } else {
1310                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1311                         if (ret & VM_FAULT_OOM) {
1312                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1313                                 ret |= VM_FAULT_FALLBACK;
1314                         }
1315                         put_page(page);
1316                 }
1317                 count_vm_event(THP_FAULT_FALLBACK);
1318                 goto out;
1319         }
1320
1321         if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1322                                         huge_gfp, &memcg, true))) {
1323                 put_page(new_page);
1324                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1325                 if (page)
1326                         put_page(page);
1327                 ret |= VM_FAULT_FALLBACK;
1328                 count_vm_event(THP_FAULT_FALLBACK);
1329                 goto out;
1330         }
1331
1332         count_vm_event(THP_FAULT_ALLOC);
1333
1334         if (!page)
1335                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1336         else
1337                 copy_user_huge_page(new_page, page, vmf->address,
1338                                     vma, HPAGE_PMD_NR);
1339         __SetPageUptodate(new_page);
1340
1341         mmun_start = haddr;
1342         mmun_end   = haddr + HPAGE_PMD_SIZE;
1343         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1344
1345         spin_lock(vmf->ptl);
1346         if (page)
1347                 put_page(page);
1348         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1349                 spin_unlock(vmf->ptl);
1350                 mem_cgroup_cancel_charge(new_page, memcg, true);
1351                 put_page(new_page);
1352                 goto out_mn;
1353         } else {
1354                 pmd_t entry;
1355                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1356                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1357                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1358                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1359                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1360                 lru_cache_add_active_or_unevictable(new_page, vma);
1361                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1362                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1363                 if (!page) {
1364                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1365                 } else {
1366                         VM_BUG_ON_PAGE(!PageHead(page), page);
1367                         page_remove_rmap(page, true);
1368                         put_page(page);
1369                 }
1370                 ret |= VM_FAULT_WRITE;
1371         }
1372         spin_unlock(vmf->ptl);
1373 out_mn:
1374         /*
1375          * No need to double call mmu_notifier->invalidate_range() callback as
1376          * the above pmdp_huge_clear_flush_notify() did already call it.
1377          */
1378         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1379                                                mmun_end);
1380 out:
1381         return ret;
1382 out_unlock:
1383         spin_unlock(vmf->ptl);
1384         return ret;
1385 }
1386
1387 /*
1388  * FOLL_FORCE can write to even unwritable pmd's, but only
1389  * after we've gone through a COW cycle and they are dirty.
1390  */
1391 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1392 {
1393         return pmd_write(pmd) ||
1394                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1395 }
1396
1397 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1398                                    unsigned long addr,
1399                                    pmd_t *pmd,
1400                                    unsigned int flags)
1401 {
1402         struct mm_struct *mm = vma->vm_mm;
1403         struct page *page = NULL;
1404
1405         assert_spin_locked(pmd_lockptr(mm, pmd));
1406
1407         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1408                 goto out;
1409
1410         /* Avoid dumping huge zero page */
1411         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1412                 return ERR_PTR(-EFAULT);
1413
1414         /* Full NUMA hinting faults to serialise migration in fault paths */
1415         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1416                 goto out;
1417
1418         page = pmd_page(*pmd);
1419         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1420         if (flags & FOLL_TOUCH)
1421                 touch_pmd(vma, addr, pmd, flags);
1422         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1423                 /*
1424                  * We don't mlock() pte-mapped THPs. This way we can avoid
1425                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1426                  *
1427                  * For anon THP:
1428                  *
1429                  * In most cases the pmd is the only mapping of the page as we
1430                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1431                  * writable private mappings in populate_vma_page_range().
1432                  *
1433                  * The only scenario when we have the page shared here is if we
1434                  * mlocking read-only mapping shared over fork(). We skip
1435                  * mlocking such pages.
1436                  *
1437                  * For file THP:
1438                  *
1439                  * We can expect PageDoubleMap() to be stable under page lock:
1440                  * for file pages we set it in page_add_file_rmap(), which
1441                  * requires page to be locked.
1442                  */
1443
1444                 if (PageAnon(page) && compound_mapcount(page) != 1)
1445                         goto skip_mlock;
1446                 if (PageDoubleMap(page) || !page->mapping)
1447                         goto skip_mlock;
1448                 if (!trylock_page(page))
1449                         goto skip_mlock;
1450                 lru_add_drain();
1451                 if (page->mapping && !PageDoubleMap(page))
1452                         mlock_vma_page(page);
1453                 unlock_page(page);
1454         }
1455 skip_mlock:
1456         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1457         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1458         if (flags & FOLL_GET)
1459                 get_page(page);
1460
1461 out:
1462         return page;
1463 }
1464
1465 /* NUMA hinting page fault entry point for trans huge pmds */
1466 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1467 {
1468         struct vm_area_struct *vma = vmf->vma;
1469         struct anon_vma *anon_vma = NULL;
1470         struct page *page;
1471         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1472         int page_nid = -1, this_nid = numa_node_id();
1473         int target_nid, last_cpupid = -1;
1474         bool page_locked;
1475         bool migrated = false;
1476         bool was_writable;
1477         int flags = 0;
1478
1479         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1480         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1481                 goto out_unlock;
1482
1483         /*
1484          * If there are potential migrations, wait for completion and retry
1485          * without disrupting NUMA hinting information. Do not relock and
1486          * check_same as the page may no longer be mapped.
1487          */
1488         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1489                 page = pmd_page(*vmf->pmd);
1490                 if (!get_page_unless_zero(page))
1491                         goto out_unlock;
1492                 spin_unlock(vmf->ptl);
1493                 wait_on_page_locked(page);
1494                 put_page(page);
1495                 goto out;
1496         }
1497
1498         page = pmd_page(pmd);
1499         BUG_ON(is_huge_zero_page(page));
1500         page_nid = page_to_nid(page);
1501         last_cpupid = page_cpupid_last(page);
1502         count_vm_numa_event(NUMA_HINT_FAULTS);
1503         if (page_nid == this_nid) {
1504                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1505                 flags |= TNF_FAULT_LOCAL;
1506         }
1507
1508         /* See similar comment in do_numa_page for explanation */
1509         if (!pmd_savedwrite(pmd))
1510                 flags |= TNF_NO_GROUP;
1511
1512         /*
1513          * Acquire the page lock to serialise THP migrations but avoid dropping
1514          * page_table_lock if at all possible
1515          */
1516         page_locked = trylock_page(page);
1517         target_nid = mpol_misplaced(page, vma, haddr);
1518         if (target_nid == -1) {
1519                 /* If the page was locked, there are no parallel migrations */
1520                 if (page_locked)
1521                         goto clear_pmdnuma;
1522         }
1523
1524         /* Migration could have started since the pmd_trans_migrating check */
1525         if (!page_locked) {
1526                 page_nid = -1;
1527                 if (!get_page_unless_zero(page))
1528                         goto out_unlock;
1529                 spin_unlock(vmf->ptl);
1530                 wait_on_page_locked(page);
1531                 put_page(page);
1532                 goto out;
1533         }
1534
1535         /*
1536          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1537          * to serialises splits
1538          */
1539         get_page(page);
1540         spin_unlock(vmf->ptl);
1541         anon_vma = page_lock_anon_vma_read(page);
1542
1543         /* Confirm the PMD did not change while page_table_lock was released */
1544         spin_lock(vmf->ptl);
1545         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1546                 unlock_page(page);
1547                 put_page(page);
1548                 page_nid = -1;
1549                 goto out_unlock;
1550         }
1551
1552         /* Bail if we fail to protect against THP splits for any reason */
1553         if (unlikely(!anon_vma)) {
1554                 put_page(page);
1555                 page_nid = -1;
1556                 goto clear_pmdnuma;
1557         }
1558
1559         /*
1560          * Since we took the NUMA fault, we must have observed the !accessible
1561          * bit. Make sure all other CPUs agree with that, to avoid them
1562          * modifying the page we're about to migrate.
1563          *
1564          * Must be done under PTL such that we'll observe the relevant
1565          * inc_tlb_flush_pending().
1566          *
1567          * We are not sure a pending tlb flush here is for a huge page
1568          * mapping or not. Hence use the tlb range variant
1569          */
1570         if (mm_tlb_flush_pending(vma->vm_mm)) {
1571                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1572                 /*
1573                  * change_huge_pmd() released the pmd lock before
1574                  * invalidating the secondary MMUs sharing the primary
1575                  * MMU pagetables (with ->invalidate_range()). The
1576                  * mmu_notifier_invalidate_range_end() (which
1577                  * internally calls ->invalidate_range()) in
1578                  * change_pmd_range() will run after us, so we can't
1579                  * rely on it here and we need an explicit invalidate.
1580                  */
1581                 mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1582                                               haddr + HPAGE_PMD_SIZE);
1583         }
1584
1585         /*
1586          * Migrate the THP to the requested node, returns with page unlocked
1587          * and access rights restored.
1588          */
1589         spin_unlock(vmf->ptl);
1590
1591         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1592                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1593         if (migrated) {
1594                 flags |= TNF_MIGRATED;
1595                 page_nid = target_nid;
1596         } else
1597                 flags |= TNF_MIGRATE_FAIL;
1598
1599         goto out;
1600 clear_pmdnuma:
1601         BUG_ON(!PageLocked(page));
1602         was_writable = pmd_savedwrite(pmd);
1603         pmd = pmd_modify(pmd, vma->vm_page_prot);
1604         pmd = pmd_mkyoung(pmd);
1605         if (was_writable)
1606                 pmd = pmd_mkwrite(pmd);
1607         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1608         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1609         unlock_page(page);
1610 out_unlock:
1611         spin_unlock(vmf->ptl);
1612
1613 out:
1614         if (anon_vma)
1615                 page_unlock_anon_vma_read(anon_vma);
1616
1617         if (page_nid != -1)
1618                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1619                                 flags);
1620
1621         return 0;
1622 }
1623
1624 /*
1625  * Return true if we do MADV_FREE successfully on entire pmd page.
1626  * Otherwise, return false.
1627  */
1628 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1629                 pmd_t *pmd, unsigned long addr, unsigned long next)
1630 {
1631         spinlock_t *ptl;
1632         pmd_t orig_pmd;
1633         struct page *page;
1634         struct mm_struct *mm = tlb->mm;
1635         bool ret = false;
1636
1637         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1638
1639         ptl = pmd_trans_huge_lock(pmd, vma);
1640         if (!ptl)
1641                 goto out_unlocked;
1642
1643         orig_pmd = *pmd;
1644         if (is_huge_zero_pmd(orig_pmd))
1645                 goto out;
1646
1647         if (unlikely(!pmd_present(orig_pmd))) {
1648                 VM_BUG_ON(thp_migration_supported() &&
1649                                   !is_pmd_migration_entry(orig_pmd));
1650                 goto out;
1651         }
1652
1653         page = pmd_page(orig_pmd);
1654         /*
1655          * If other processes are mapping this page, we couldn't discard
1656          * the page unless they all do MADV_FREE so let's skip the page.
1657          */
1658         if (page_mapcount(page) != 1)
1659                 goto out;
1660
1661         if (!trylock_page(page))
1662                 goto out;
1663
1664         /*
1665          * If user want to discard part-pages of THP, split it so MADV_FREE
1666          * will deactivate only them.
1667          */
1668         if (next - addr != HPAGE_PMD_SIZE) {
1669                 get_page(page);
1670                 spin_unlock(ptl);
1671                 split_huge_page(page);
1672                 unlock_page(page);
1673                 put_page(page);
1674                 goto out_unlocked;
1675         }
1676
1677         if (PageDirty(page))
1678                 ClearPageDirty(page);
1679         unlock_page(page);
1680
1681         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1682                 pmdp_invalidate(vma, addr, pmd);
1683                 orig_pmd = pmd_mkold(orig_pmd);
1684                 orig_pmd = pmd_mkclean(orig_pmd);
1685
1686                 set_pmd_at(mm, addr, pmd, orig_pmd);
1687                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1688         }
1689
1690         mark_page_lazyfree(page);
1691         ret = true;
1692 out:
1693         spin_unlock(ptl);
1694 out_unlocked:
1695         return ret;
1696 }
1697
1698 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1699 {
1700         pgtable_t pgtable;
1701
1702         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1703         pte_free(mm, pgtable);
1704         mm_dec_nr_ptes(mm);
1705 }
1706
1707 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1708                  pmd_t *pmd, unsigned long addr)
1709 {
1710         pmd_t orig_pmd;
1711         spinlock_t *ptl;
1712
1713         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1714
1715         ptl = __pmd_trans_huge_lock(pmd, vma);
1716         if (!ptl)
1717                 return 0;
1718         /*
1719          * For architectures like ppc64 we look at deposited pgtable
1720          * when calling pmdp_huge_get_and_clear. So do the
1721          * pgtable_trans_huge_withdraw after finishing pmdp related
1722          * operations.
1723          */
1724         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1725                         tlb->fullmm);
1726         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1727         if (vma_is_dax(vma)) {
1728                 if (arch_needs_pgtable_deposit())
1729                         zap_deposited_table(tlb->mm, pmd);
1730                 spin_unlock(ptl);
1731                 if (is_huge_zero_pmd(orig_pmd))
1732                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1733         } else if (is_huge_zero_pmd(orig_pmd)) {
1734                 zap_deposited_table(tlb->mm, pmd);
1735                 spin_unlock(ptl);
1736                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1737         } else {
1738                 struct page *page = NULL;
1739                 int flush_needed = 1;
1740
1741                 if (pmd_present(orig_pmd)) {
1742                         page = pmd_page(orig_pmd);
1743                         page_remove_rmap(page, true);
1744                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1745                         VM_BUG_ON_PAGE(!PageHead(page), page);
1746                 } else if (thp_migration_supported()) {
1747                         swp_entry_t entry;
1748
1749                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1750                         entry = pmd_to_swp_entry(orig_pmd);
1751                         page = pfn_to_page(swp_offset(entry));
1752                         flush_needed = 0;
1753                 } else
1754                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1755
1756                 if (PageAnon(page)) {
1757                         zap_deposited_table(tlb->mm, pmd);
1758                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1759                 } else {
1760                         if (arch_needs_pgtable_deposit())
1761                                 zap_deposited_table(tlb->mm, pmd);
1762                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1763                 }
1764
1765                 spin_unlock(ptl);
1766                 if (flush_needed)
1767                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1768         }
1769         return 1;
1770 }
1771
1772 #ifndef pmd_move_must_withdraw
1773 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1774                                          spinlock_t *old_pmd_ptl,
1775                                          struct vm_area_struct *vma)
1776 {
1777         /*
1778          * With split pmd lock we also need to move preallocated
1779          * PTE page table if new_pmd is on different PMD page table.
1780          *
1781          * We also don't deposit and withdraw tables for file pages.
1782          */
1783         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1784 }
1785 #endif
1786
1787 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1788 {
1789 #ifdef CONFIG_MEM_SOFT_DIRTY
1790         if (unlikely(is_pmd_migration_entry(pmd)))
1791                 pmd = pmd_swp_mksoft_dirty(pmd);
1792         else if (pmd_present(pmd))
1793                 pmd = pmd_mksoft_dirty(pmd);
1794 #endif
1795         return pmd;
1796 }
1797
1798 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1799                   unsigned long new_addr, unsigned long old_end,
1800                   pmd_t *old_pmd, pmd_t *new_pmd)
1801 {
1802         spinlock_t *old_ptl, *new_ptl;
1803         pmd_t pmd;
1804         struct mm_struct *mm = vma->vm_mm;
1805         bool force_flush = false;
1806
1807         if ((old_addr & ~HPAGE_PMD_MASK) ||
1808             (new_addr & ~HPAGE_PMD_MASK) ||
1809             old_end - old_addr < HPAGE_PMD_SIZE)
1810                 return false;
1811
1812         /*
1813          * The destination pmd shouldn't be established, free_pgtables()
1814          * should have release it.
1815          */
1816         if (WARN_ON(!pmd_none(*new_pmd))) {
1817                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1818                 return false;
1819         }
1820
1821         /*
1822          * We don't have to worry about the ordering of src and dst
1823          * ptlocks because exclusive mmap_sem prevents deadlock.
1824          */
1825         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1826         if (old_ptl) {
1827                 new_ptl = pmd_lockptr(mm, new_pmd);
1828                 if (new_ptl != old_ptl)
1829                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1830                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1831                 if (pmd_present(pmd))
1832                         force_flush = true;
1833                 VM_BUG_ON(!pmd_none(*new_pmd));
1834
1835                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1836                         pgtable_t pgtable;
1837                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1838                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1839                 }
1840                 pmd = move_soft_dirty_pmd(pmd);
1841                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1842                 if (force_flush)
1843                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1844                 if (new_ptl != old_ptl)
1845                         spin_unlock(new_ptl);
1846                 spin_unlock(old_ptl);
1847                 return true;
1848         }
1849         return false;
1850 }
1851
1852 /*
1853  * Returns
1854  *  - 0 if PMD could not be locked
1855  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1856  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1857  */
1858 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1859                 unsigned long addr, pgprot_t newprot, int prot_numa)
1860 {
1861         struct mm_struct *mm = vma->vm_mm;
1862         spinlock_t *ptl;
1863         pmd_t entry;
1864         bool preserve_write;
1865         int ret;
1866
1867         ptl = __pmd_trans_huge_lock(pmd, vma);
1868         if (!ptl)
1869                 return 0;
1870
1871         preserve_write = prot_numa && pmd_write(*pmd);
1872         ret = 1;
1873
1874 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1875         if (is_swap_pmd(*pmd)) {
1876                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1877
1878                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1879                 if (is_write_migration_entry(entry)) {
1880                         pmd_t newpmd;
1881                         /*
1882                          * A protection check is difficult so
1883                          * just be safe and disable write
1884                          */
1885                         make_migration_entry_read(&entry);
1886                         newpmd = swp_entry_to_pmd(entry);
1887                         if (pmd_swp_soft_dirty(*pmd))
1888                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1889                         set_pmd_at(mm, addr, pmd, newpmd);
1890                 }
1891                 goto unlock;
1892         }
1893 #endif
1894
1895         /*
1896          * Avoid trapping faults against the zero page. The read-only
1897          * data is likely to be read-cached on the local CPU and
1898          * local/remote hits to the zero page are not interesting.
1899          */
1900         if (prot_numa && is_huge_zero_pmd(*pmd))
1901                 goto unlock;
1902
1903         if (prot_numa && pmd_protnone(*pmd))
1904                 goto unlock;
1905
1906         /*
1907          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1908          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1909          * which is also under down_read(mmap_sem):
1910          *
1911          *      CPU0:                           CPU1:
1912          *                              change_huge_pmd(prot_numa=1)
1913          *                               pmdp_huge_get_and_clear_notify()
1914          * madvise_dontneed()
1915          *  zap_pmd_range()
1916          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1917          *   // skip the pmd
1918          *                               set_pmd_at();
1919          *                               // pmd is re-established
1920          *
1921          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1922          * which may break userspace.
1923          *
1924          * pmdp_invalidate() is required to make sure we don't miss
1925          * dirty/young flags set by hardware.
1926          */
1927         entry = pmdp_invalidate(vma, addr, pmd);
1928
1929         entry = pmd_modify(entry, newprot);
1930         if (preserve_write)
1931                 entry = pmd_mk_savedwrite(entry);
1932         ret = HPAGE_PMD_NR;
1933         set_pmd_at(mm, addr, pmd, entry);
1934         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1935 unlock:
1936         spin_unlock(ptl);
1937         return ret;
1938 }
1939
1940 /*
1941  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1942  *
1943  * Note that if it returns page table lock pointer, this routine returns without
1944  * unlocking page table lock. So callers must unlock it.
1945  */
1946 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1947 {
1948         spinlock_t *ptl;
1949         ptl = pmd_lock(vma->vm_mm, pmd);
1950         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1951                         pmd_devmap(*pmd)))
1952                 return ptl;
1953         spin_unlock(ptl);
1954         return NULL;
1955 }
1956
1957 /*
1958  * Returns true if a given pud maps a thp, false otherwise.
1959  *
1960  * Note that if it returns true, this routine returns without unlocking page
1961  * table lock. So callers must unlock it.
1962  */
1963 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1964 {
1965         spinlock_t *ptl;
1966
1967         ptl = pud_lock(vma->vm_mm, pud);
1968         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1969                 return ptl;
1970         spin_unlock(ptl);
1971         return NULL;
1972 }
1973
1974 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1975 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1976                  pud_t *pud, unsigned long addr)
1977 {
1978         pud_t orig_pud;
1979         spinlock_t *ptl;
1980
1981         ptl = __pud_trans_huge_lock(pud, vma);
1982         if (!ptl)
1983                 return 0;
1984         /*
1985          * For architectures like ppc64 we look at deposited pgtable
1986          * when calling pudp_huge_get_and_clear. So do the
1987          * pgtable_trans_huge_withdraw after finishing pudp related
1988          * operations.
1989          */
1990         orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1991                         tlb->fullmm);
1992         tlb_remove_pud_tlb_entry(tlb, pud, addr);
1993         if (vma_is_dax(vma)) {
1994                 spin_unlock(ptl);
1995                 /* No zero page support yet */
1996         } else {
1997                 /* No support for anonymous PUD pages yet */
1998                 BUG();
1999         }
2000         return 1;
2001 }
2002
2003 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2004                 unsigned long haddr)
2005 {
2006         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2007         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2008         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2009         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2010
2011         count_vm_event(THP_SPLIT_PUD);
2012
2013         pudp_huge_clear_flush_notify(vma, haddr, pud);
2014 }
2015
2016 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2017                 unsigned long address)
2018 {
2019         spinlock_t *ptl;
2020         struct mm_struct *mm = vma->vm_mm;
2021         unsigned long haddr = address & HPAGE_PUD_MASK;
2022
2023         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
2024         ptl = pud_lock(mm, pud);
2025         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2026                 goto out;
2027         __split_huge_pud_locked(vma, pud, haddr);
2028
2029 out:
2030         spin_unlock(ptl);
2031         /*
2032          * No need to double call mmu_notifier->invalidate_range() callback as
2033          * the above pudp_huge_clear_flush_notify() did already call it.
2034          */
2035         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2036                                                HPAGE_PUD_SIZE);
2037 }
2038 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2039
2040 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2041                 unsigned long haddr, pmd_t *pmd)
2042 {
2043         struct mm_struct *mm = vma->vm_mm;
2044         pgtable_t pgtable;
2045         pmd_t _pmd;
2046         int i;
2047
2048         /*
2049          * Leave pmd empty until pte is filled note that it is fine to delay
2050          * notification until mmu_notifier_invalidate_range_end() as we are
2051          * replacing a zero pmd write protected page with a zero pte write
2052          * protected page.
2053          *
2054          * See Documentation/vm/mmu_notifier.rst
2055          */
2056         pmdp_huge_clear_flush(vma, haddr, pmd);
2057
2058         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2059         pmd_populate(mm, &_pmd, pgtable);
2060
2061         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2062                 pte_t *pte, entry;
2063                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2064                 entry = pte_mkspecial(entry);
2065                 pte = pte_offset_map(&_pmd, haddr);
2066                 VM_BUG_ON(!pte_none(*pte));
2067                 set_pte_at(mm, haddr, pte, entry);
2068                 pte_unmap(pte);
2069         }
2070         smp_wmb(); /* make pte visible before pmd */
2071         pmd_populate(mm, pmd, pgtable);
2072 }
2073
2074 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2075                 unsigned long haddr, bool freeze)
2076 {
2077         struct mm_struct *mm = vma->vm_mm;
2078         struct page *page;
2079         pgtable_t pgtable;
2080         pmd_t old_pmd, _pmd;
2081         bool young, write, soft_dirty, pmd_migration = false;
2082         unsigned long addr;
2083         int i;
2084
2085         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2086         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2087         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2088         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2089                                 && !pmd_devmap(*pmd));
2090
2091         count_vm_event(THP_SPLIT_PMD);
2092
2093         if (!vma_is_anonymous(vma)) {
2094                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2095                 /*
2096                  * We are going to unmap this huge page. So
2097                  * just go ahead and zap it
2098                  */
2099                 if (arch_needs_pgtable_deposit())
2100                         zap_deposited_table(mm, pmd);
2101                 if (vma_is_dax(vma))
2102                         return;
2103                 page = pmd_page(_pmd);
2104                 if (!PageDirty(page) && pmd_dirty(_pmd))
2105                         set_page_dirty(page);
2106                 if (!PageReferenced(page) && pmd_young(_pmd))
2107                         SetPageReferenced(page);
2108                 page_remove_rmap(page, true);
2109                 put_page(page);
2110                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2111                 return;
2112         } else if (is_huge_zero_pmd(*pmd)) {
2113                 /*
2114                  * FIXME: Do we want to invalidate secondary mmu by calling
2115                  * mmu_notifier_invalidate_range() see comments below inside
2116                  * __split_huge_pmd() ?
2117                  *
2118                  * We are going from a zero huge page write protected to zero
2119                  * small page also write protected so it does not seems useful
2120                  * to invalidate secondary mmu at this time.
2121                  */
2122                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2123         }
2124
2125         /*
2126          * Up to this point the pmd is present and huge and userland has the
2127          * whole access to the hugepage during the split (which happens in
2128          * place). If we overwrite the pmd with the not-huge version pointing
2129          * to the pte here (which of course we could if all CPUs were bug
2130          * free), userland could trigger a small page size TLB miss on the
2131          * small sized TLB while the hugepage TLB entry is still established in
2132          * the huge TLB. Some CPU doesn't like that.
2133          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2134          * 383 on page 93. Intel should be safe but is also warns that it's
2135          * only safe if the permission and cache attributes of the two entries
2136          * loaded in the two TLB is identical (which should be the case here).
2137          * But it is generally safer to never allow small and huge TLB entries
2138          * for the same virtual address to be loaded simultaneously. So instead
2139          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2140          * current pmd notpresent (atomically because here the pmd_trans_huge
2141          * must remain set at all times on the pmd until the split is complete
2142          * for this pmd), then we flush the SMP TLB and finally we write the
2143          * non-huge version of the pmd entry with pmd_populate.
2144          */
2145         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2146
2147         pmd_migration = is_pmd_migration_entry(old_pmd);
2148         if (unlikely(pmd_migration)) {
2149                 swp_entry_t entry;
2150
2151                 entry = pmd_to_swp_entry(old_pmd);
2152                 page = pfn_to_page(swp_offset(entry));
2153                 write = is_write_migration_entry(entry);
2154                 young = false;
2155                 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2156         } else {
2157                 page = pmd_page(old_pmd);
2158                 if (pmd_dirty(old_pmd))
2159                         SetPageDirty(page);
2160                 write = pmd_write(old_pmd);
2161                 young = pmd_young(old_pmd);
2162                 soft_dirty = pmd_soft_dirty(old_pmd);
2163         }
2164         VM_BUG_ON_PAGE(!page_count(page), page);
2165         page_ref_add(page, HPAGE_PMD_NR - 1);
2166
2167         /*
2168          * Withdraw the table only after we mark the pmd entry invalid.
2169          * This's critical for some architectures (Power).
2170          */
2171         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2172         pmd_populate(mm, &_pmd, pgtable);
2173
2174         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2175                 pte_t entry, *pte;
2176                 /*
2177                  * Note that NUMA hinting access restrictions are not
2178                  * transferred to avoid any possibility of altering
2179                  * permissions across VMAs.
2180                  */
2181                 if (freeze || pmd_migration) {
2182                         swp_entry_t swp_entry;
2183                         swp_entry = make_migration_entry(page + i, write);
2184                         entry = swp_entry_to_pte(swp_entry);
2185                         if (soft_dirty)
2186                                 entry = pte_swp_mksoft_dirty(entry);
2187                 } else {
2188                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2189                         entry = maybe_mkwrite(entry, vma);
2190                         if (!write)
2191                                 entry = pte_wrprotect(entry);
2192                         if (!young)
2193                                 entry = pte_mkold(entry);
2194                         if (soft_dirty)
2195                                 entry = pte_mksoft_dirty(entry);
2196                 }
2197                 pte = pte_offset_map(&_pmd, addr);
2198                 BUG_ON(!pte_none(*pte));
2199                 set_pte_at(mm, addr, pte, entry);
2200                 atomic_inc(&page[i]._mapcount);
2201                 pte_unmap(pte);
2202         }
2203
2204         /*
2205          * Set PG_double_map before dropping compound_mapcount to avoid
2206          * false-negative page_mapped().
2207          */
2208         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2209                 for (i = 0; i < HPAGE_PMD_NR; i++)
2210                         atomic_inc(&page[i]._mapcount);
2211         }
2212
2213         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2214                 /* Last compound_mapcount is gone. */
2215                 __dec_node_page_state(page, NR_ANON_THPS);
2216                 if (TestClearPageDoubleMap(page)) {
2217                         /* No need in mapcount reference anymore */
2218                         for (i = 0; i < HPAGE_PMD_NR; i++)
2219                                 atomic_dec(&page[i]._mapcount);
2220                 }
2221         }
2222
2223         smp_wmb(); /* make pte visible before pmd */
2224         pmd_populate(mm, pmd, pgtable);
2225
2226         if (freeze) {
2227                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2228                         page_remove_rmap(page + i, false);
2229                         put_page(page + i);
2230                 }
2231         }
2232 }
2233
2234 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2235                 unsigned long address, bool freeze, struct page *page)
2236 {
2237         spinlock_t *ptl;
2238         struct mm_struct *mm = vma->vm_mm;
2239         unsigned long haddr = address & HPAGE_PMD_MASK;
2240
2241         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2242         ptl = pmd_lock(mm, pmd);
2243
2244         /*
2245          * If caller asks to setup a migration entries, we need a page to check
2246          * pmd against. Otherwise we can end up replacing wrong page.
2247          */
2248         VM_BUG_ON(freeze && !page);
2249         if (page && page != pmd_page(*pmd))
2250                 goto out;
2251
2252         if (pmd_trans_huge(*pmd)) {
2253                 page = pmd_page(*pmd);
2254                 if (PageMlocked(page))
2255                         clear_page_mlock(page);
2256         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2257                 goto out;
2258         __split_huge_pmd_locked(vma, pmd, haddr, freeze);
2259 out:
2260         spin_unlock(ptl);
2261         /*
2262          * No need to double call mmu_notifier->invalidate_range() callback.
2263          * They are 3 cases to consider inside __split_huge_pmd_locked():
2264          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2265          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2266          *    fault will trigger a flush_notify before pointing to a new page
2267          *    (it is fine if the secondary mmu keeps pointing to the old zero
2268          *    page in the meantime)
2269          *  3) Split a huge pmd into pte pointing to the same page. No need
2270          *     to invalidate secondary tlb entry they are all still valid.
2271          *     any further changes to individual pte will notify. So no need
2272          *     to call mmu_notifier->invalidate_range()
2273          */
2274         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2275                                                HPAGE_PMD_SIZE);
2276 }
2277
2278 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2279                 bool freeze, struct page *page)
2280 {
2281         pgd_t *pgd;
2282         p4d_t *p4d;
2283         pud_t *pud;
2284         pmd_t *pmd;
2285
2286         pgd = pgd_offset(vma->vm_mm, address);
2287         if (!pgd_present(*pgd))
2288                 return;
2289
2290         p4d = p4d_offset(pgd, address);
2291         if (!p4d_present(*p4d))
2292                 return;
2293
2294         pud = pud_offset(p4d, address);
2295         if (!pud_present(*pud))
2296                 return;
2297
2298         pmd = pmd_offset(pud, address);
2299
2300         __split_huge_pmd(vma, pmd, address, freeze, page);
2301 }
2302
2303 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2304                              unsigned long start,
2305                              unsigned long end,
2306                              long adjust_next)
2307 {
2308         /*
2309          * If the new start address isn't hpage aligned and it could
2310          * previously contain an hugepage: check if we need to split
2311          * an huge pmd.
2312          */
2313         if (start & ~HPAGE_PMD_MASK &&
2314             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2315             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2316                 split_huge_pmd_address(vma, start, false, NULL);
2317
2318         /*
2319          * If the new end address isn't hpage aligned and it could
2320          * previously contain an hugepage: check if we need to split
2321          * an huge pmd.
2322          */
2323         if (end & ~HPAGE_PMD_MASK &&
2324             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2325             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2326                 split_huge_pmd_address(vma, end, false, NULL);
2327
2328         /*
2329          * If we're also updating the vma->vm_next->vm_start, if the new
2330          * vm_next->vm_start isn't page aligned and it could previously
2331          * contain an hugepage: check if we need to split an huge pmd.
2332          */
2333         if (adjust_next > 0) {
2334                 struct vm_area_struct *next = vma->vm_next;
2335                 unsigned long nstart = next->vm_start;
2336                 nstart += adjust_next << PAGE_SHIFT;
2337                 if (nstart & ~HPAGE_PMD_MASK &&
2338                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2339                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2340                         split_huge_pmd_address(next, nstart, false, NULL);
2341         }
2342 }
2343
2344 static void unmap_page(struct page *page)
2345 {
2346         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2347                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2348         bool unmap_success;
2349
2350         VM_BUG_ON_PAGE(!PageHead(page), page);
2351
2352         if (PageAnon(page))
2353                 ttu_flags |= TTU_SPLIT_FREEZE;
2354
2355         unmap_success = try_to_unmap(page, ttu_flags);
2356         VM_BUG_ON_PAGE(!unmap_success, page);
2357 }
2358
2359 static void remap_page(struct page *page)
2360 {
2361         int i;
2362         if (PageTransHuge(page)) {
2363                 remove_migration_ptes(page, page, true);
2364         } else {
2365                 for (i = 0; i < HPAGE_PMD_NR; i++)
2366                         remove_migration_ptes(page + i, page + i, true);
2367         }
2368 }
2369
2370 static void __split_huge_page_tail(struct page *head, int tail,
2371                 struct lruvec *lruvec, struct list_head *list)
2372 {
2373         struct page *page_tail = head + tail;
2374
2375         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2376
2377         /*
2378          * Clone page flags before unfreezing refcount.
2379          *
2380          * After successful get_page_unless_zero() might follow flags change,
2381          * for exmaple lock_page() which set PG_waiters.
2382          */
2383         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2384         page_tail->flags |= (head->flags &
2385                         ((1L << PG_referenced) |
2386                          (1L << PG_swapbacked) |
2387                          (1L << PG_swapcache) |
2388                          (1L << PG_mlocked) |
2389                          (1L << PG_uptodate) |
2390                          (1L << PG_active) |
2391                          (1L << PG_workingset) |
2392                          (1L << PG_locked) |
2393                          (1L << PG_unevictable) |
2394                          (1L << PG_dirty)));
2395
2396         /* ->mapping in first tail page is compound_mapcount */
2397         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2398                         page_tail);
2399         page_tail->mapping = head->mapping;
2400         page_tail->index = head->index + tail;
2401
2402         /* Page flags must be visible before we make the page non-compound. */
2403         smp_wmb();
2404
2405         /*
2406          * Clear PageTail before unfreezing page refcount.
2407          *
2408          * After successful get_page_unless_zero() might follow put_page()
2409          * which needs correct compound_head().
2410          */
2411         clear_compound_head(page_tail);
2412
2413         /* Finally unfreeze refcount. Additional reference from page cache. */
2414         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2415                                           PageSwapCache(head)));
2416
2417         if (page_is_young(head))
2418                 set_page_young(page_tail);
2419         if (page_is_idle(head))
2420                 set_page_idle(page_tail);
2421
2422         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2423
2424         /*
2425          * always add to the tail because some iterators expect new
2426          * pages to show after the currently processed elements - e.g.
2427          * migrate_pages
2428          */
2429         lru_add_page_tail(head, page_tail, lruvec, list);
2430 }
2431
2432 static void __split_huge_page(struct page *page, struct list_head *list,
2433                 pgoff_t end, unsigned long flags)
2434 {
2435         struct page *head = compound_head(page);
2436         struct zone *zone = page_zone(head);
2437         struct lruvec *lruvec;
2438         int i;
2439
2440         lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
2441
2442         /* complete memcg works before add pages to LRU */
2443         mem_cgroup_split_huge_fixup(head);
2444
2445         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2446                 __split_huge_page_tail(head, i, lruvec, list);
2447                 /* Some pages can be beyond i_size: drop them from page cache */
2448                 if (head[i].index >= end) {
2449                         ClearPageDirty(head + i);
2450                         __delete_from_page_cache(head + i, NULL);
2451                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2452                                 shmem_uncharge(head->mapping->host, 1);
2453                         put_page(head + i);
2454                 }
2455         }
2456
2457         ClearPageCompound(head);
2458         /* See comment in __split_huge_page_tail() */
2459         if (PageAnon(head)) {
2460                 /* Additional pin to swap cache */
2461                 if (PageSwapCache(head))
2462                         page_ref_add(head, 2);
2463                 else
2464                         page_ref_inc(head);
2465         } else {
2466                 /* Additional pin to page cache */
2467                 page_ref_add(head, 2);
2468                 xa_unlock(&head->mapping->i_pages);
2469         }
2470
2471         spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2472
2473         remap_page(head);
2474
2475         for (i = 0; i < HPAGE_PMD_NR; i++) {
2476                 struct page *subpage = head + i;
2477                 if (subpage == page)
2478                         continue;
2479                 unlock_page(subpage);
2480
2481                 /*
2482                  * Subpages may be freed if there wasn't any mapping
2483                  * like if add_to_swap() is running on a lru page that
2484                  * had its mapping zapped. And freeing these pages
2485                  * requires taking the lru_lock so we do the put_page
2486                  * of the tail pages after the split is complete.
2487                  */
2488                 put_page(subpage);
2489         }
2490 }
2491
2492 int total_mapcount(struct page *page)
2493 {
2494         int i, compound, ret;
2495
2496         VM_BUG_ON_PAGE(PageTail(page), page);
2497
2498         if (likely(!PageCompound(page)))
2499                 return atomic_read(&page->_mapcount) + 1;
2500
2501         compound = compound_mapcount(page);
2502         if (PageHuge(page))
2503                 return compound;
2504         ret = compound;
2505         for (i = 0; i < HPAGE_PMD_NR; i++)
2506                 ret += atomic_read(&page[i]._mapcount) + 1;
2507         /* File pages has compound_mapcount included in _mapcount */
2508         if (!PageAnon(page))
2509                 return ret - compound * HPAGE_PMD_NR;
2510         if (PageDoubleMap(page))
2511                 ret -= HPAGE_PMD_NR;
2512         return ret;
2513 }
2514
2515 /*
2516  * This calculates accurately how many mappings a transparent hugepage
2517  * has (unlike page_mapcount() which isn't fully accurate). This full
2518  * accuracy is primarily needed to know if copy-on-write faults can
2519  * reuse the page and change the mapping to read-write instead of
2520  * copying them. At the same time this returns the total_mapcount too.
2521  *
2522  * The function returns the highest mapcount any one of the subpages
2523  * has. If the return value is one, even if different processes are
2524  * mapping different subpages of the transparent hugepage, they can
2525  * all reuse it, because each process is reusing a different subpage.
2526  *
2527  * The total_mapcount is instead counting all virtual mappings of the
2528  * subpages. If the total_mapcount is equal to "one", it tells the
2529  * caller all mappings belong to the same "mm" and in turn the
2530  * anon_vma of the transparent hugepage can become the vma->anon_vma
2531  * local one as no other process may be mapping any of the subpages.
2532  *
2533  * It would be more accurate to replace page_mapcount() with
2534  * page_trans_huge_mapcount(), however we only use
2535  * page_trans_huge_mapcount() in the copy-on-write faults where we
2536  * need full accuracy to avoid breaking page pinning, because
2537  * page_trans_huge_mapcount() is slower than page_mapcount().
2538  */
2539 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2540 {
2541         int i, ret, _total_mapcount, mapcount;
2542
2543         /* hugetlbfs shouldn't call it */
2544         VM_BUG_ON_PAGE(PageHuge(page), page);
2545
2546         if (likely(!PageTransCompound(page))) {
2547                 mapcount = atomic_read(&page->_mapcount) + 1;
2548                 if (total_mapcount)
2549                         *total_mapcount = mapcount;
2550                 return mapcount;
2551         }
2552
2553         page = compound_head(page);
2554
2555         _total_mapcount = ret = 0;
2556         for (i = 0; i < HPAGE_PMD_NR; i++) {
2557                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2558                 ret = max(ret, mapcount);
2559                 _total_mapcount += mapcount;
2560         }
2561         if (PageDoubleMap(page)) {
2562                 ret -= 1;
2563                 _total_mapcount -= HPAGE_PMD_NR;
2564         }
2565         mapcount = compound_mapcount(page);
2566         ret += mapcount;
2567         _total_mapcount += mapcount;
2568         if (total_mapcount)
2569                 *total_mapcount = _total_mapcount;
2570         return ret;
2571 }
2572
2573 /* Racy check whether the huge page can be split */
2574 bool can_split_huge_page(struct page *page, int *pextra_pins)
2575 {
2576         int extra_pins;
2577
2578         /* Additional pins from page cache */
2579         if (PageAnon(page))
2580                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2581         else
2582                 extra_pins = HPAGE_PMD_NR;
2583         if (pextra_pins)
2584                 *pextra_pins = extra_pins;
2585         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2586 }
2587
2588 /*
2589  * This function splits huge page into normal pages. @page can point to any
2590  * subpage of huge page to split. Split doesn't change the position of @page.
2591  *
2592  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2593  * The huge page must be locked.
2594  *
2595  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2596  *
2597  * Both head page and tail pages will inherit mapping, flags, and so on from
2598  * the hugepage.
2599  *
2600  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2601  * they are not mapped.
2602  *
2603  * Returns 0 if the hugepage is split successfully.
2604  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2605  * us.
2606  */
2607 int split_huge_page_to_list(struct page *page, struct list_head *list)
2608 {
2609         struct page *head = compound_head(page);
2610         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2611         struct anon_vma *anon_vma = NULL;
2612         struct address_space *mapping = NULL;
2613         int count, mapcount, extra_pins, ret;
2614         bool mlocked;
2615         unsigned long flags;
2616         pgoff_t end;
2617
2618         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2619         VM_BUG_ON_PAGE(!PageLocked(page), page);
2620         VM_BUG_ON_PAGE(!PageCompound(page), page);
2621
2622         if (PageWriteback(page))
2623                 return -EBUSY;
2624
2625         if (PageAnon(head)) {
2626                 /*
2627                  * The caller does not necessarily hold an mmap_sem that would
2628                  * prevent the anon_vma disappearing so we first we take a
2629                  * reference to it and then lock the anon_vma for write. This
2630                  * is similar to page_lock_anon_vma_read except the write lock
2631                  * is taken to serialise against parallel split or collapse
2632                  * operations.
2633                  */
2634                 anon_vma = page_get_anon_vma(head);
2635                 if (!anon_vma) {
2636                         ret = -EBUSY;
2637                         goto out;
2638                 }
2639                 end = -1;
2640                 mapping = NULL;
2641                 anon_vma_lock_write(anon_vma);
2642         } else {
2643                 mapping = head->mapping;
2644
2645                 /* Truncated ? */
2646                 if (!mapping) {
2647                         ret = -EBUSY;
2648                         goto out;
2649                 }
2650
2651                 anon_vma = NULL;
2652                 i_mmap_lock_read(mapping);
2653
2654                 /*
2655                  *__split_huge_page() may need to trim off pages beyond EOF:
2656                  * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2657                  * which cannot be nested inside the page tree lock. So note
2658                  * end now: i_size itself may be changed at any moment, but
2659                  * head page lock is good enough to serialize the trimming.
2660                  */
2661                 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2662         }
2663
2664         /*
2665          * Racy check if we can split the page, before unmap_page() will
2666          * split PMDs
2667          */
2668         if (!can_split_huge_page(head, &extra_pins)) {
2669                 ret = -EBUSY;
2670                 goto out_unlock;
2671         }
2672
2673         mlocked = PageMlocked(page);
2674         unmap_page(head);
2675         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2676
2677         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2678         if (mlocked)
2679                 lru_add_drain();
2680
2681         /* prevent PageLRU to go away from under us, and freeze lru stats */
2682         spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2683
2684         if (mapping) {
2685                 XA_STATE(xas, &mapping->i_pages, page_index(head));
2686
2687                 /*
2688                  * Check if the head page is present in page cache.
2689                  * We assume all tail are present too, if head is there.
2690                  */
2691                 xa_lock(&mapping->i_pages);
2692                 if (xas_load(&xas) != head)
2693                         goto fail;
2694         }
2695
2696         /* Prevent deferred_split_scan() touching ->_refcount */
2697         spin_lock(&pgdata->split_queue_lock);
2698         count = page_count(head);
2699         mapcount = total_mapcount(head);
2700         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2701                 if (!list_empty(page_deferred_list(head))) {
2702                         pgdata->split_queue_len--;
2703                         list_del(page_deferred_list(head));
2704                 }
2705                 if (mapping)
2706                         __dec_node_page_state(page, NR_SHMEM_THPS);
2707                 spin_unlock(&pgdata->split_queue_lock);
2708                 __split_huge_page(page, list, end, flags);
2709                 if (PageSwapCache(head)) {
2710                         swp_entry_t entry = { .val = page_private(head) };
2711
2712                         ret = split_swap_cluster(entry);
2713                 } else
2714                         ret = 0;
2715         } else {
2716                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2717                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2718                                         mapcount, count);
2719                         if (PageTail(page))
2720                                 dump_page(head, NULL);
2721                         dump_page(page, "total_mapcount(head) > 0");
2722                         BUG();
2723                 }
2724                 spin_unlock(&pgdata->split_queue_lock);
2725 fail:           if (mapping)
2726                         xa_unlock(&mapping->i_pages);
2727                 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2728                 remap_page(head);
2729                 ret = -EBUSY;
2730         }
2731
2732 out_unlock:
2733         if (anon_vma) {
2734                 anon_vma_unlock_write(anon_vma);
2735                 put_anon_vma(anon_vma);
2736         }
2737         if (mapping)
2738                 i_mmap_unlock_read(mapping);
2739 out:
2740         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2741         return ret;
2742 }
2743
2744 void free_transhuge_page(struct page *page)
2745 {
2746         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2747         unsigned long flags;
2748
2749         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2750         if (!list_empty(page_deferred_list(page))) {
2751                 pgdata->split_queue_len--;
2752                 list_del(page_deferred_list(page));
2753         }
2754         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2755         free_compound_page(page);
2756 }
2757
2758 void deferred_split_huge_page(struct page *page)
2759 {
2760         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2761         unsigned long flags;
2762
2763         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2764
2765         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2766         if (list_empty(page_deferred_list(page))) {
2767                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2768                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2769                 pgdata->split_queue_len++;
2770         }
2771         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2772 }
2773
2774 static unsigned long deferred_split_count(struct shrinker *shrink,
2775                 struct shrink_control *sc)
2776 {
2777         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2778         return READ_ONCE(pgdata->split_queue_len);
2779 }
2780
2781 static unsigned long deferred_split_scan(struct shrinker *shrink,
2782                 struct shrink_control *sc)
2783 {
2784         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2785         unsigned long flags;
2786         LIST_HEAD(list), *pos, *next;
2787         struct page *page;
2788         int split = 0;
2789
2790         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2791         /* Take pin on all head pages to avoid freeing them under us */
2792         list_for_each_safe(pos, next, &pgdata->split_queue) {
2793                 page = list_entry((void *)pos, struct page, mapping);
2794                 page = compound_head(page);
2795                 if (get_page_unless_zero(page)) {
2796                         list_move(page_deferred_list(page), &list);
2797                 } else {
2798                         /* We lost race with put_compound_page() */
2799                         list_del_init(page_deferred_list(page));
2800                         pgdata->split_queue_len--;
2801                 }
2802                 if (!--sc->nr_to_scan)
2803                         break;
2804         }
2805         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2806
2807         list_for_each_safe(pos, next, &list) {
2808                 page = list_entry((void *)pos, struct page, mapping);
2809                 if (!trylock_page(page))
2810                         goto next;
2811                 /* split_huge_page() removes page from list on success */
2812                 if (!split_huge_page(page))
2813                         split++;
2814                 unlock_page(page);
2815 next:
2816                 put_page(page);
2817         }
2818
2819         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2820         list_splice_tail(&list, &pgdata->split_queue);
2821         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2822
2823         /*
2824          * Stop shrinker if we didn't split any page, but the queue is empty.
2825          * This can happen if pages were freed under us.
2826          */
2827         if (!split && list_empty(&pgdata->split_queue))
2828                 return SHRINK_STOP;
2829         return split;
2830 }
2831
2832 static struct shrinker deferred_split_shrinker = {
2833         .count_objects = deferred_split_count,
2834         .scan_objects = deferred_split_scan,
2835         .seeks = DEFAULT_SEEKS,
2836         .flags = SHRINKER_NUMA_AWARE,
2837 };
2838
2839 #ifdef CONFIG_DEBUG_FS
2840 static int split_huge_pages_set(void *data, u64 val)
2841 {
2842         struct zone *zone;
2843         struct page *page;
2844         unsigned long pfn, max_zone_pfn;
2845         unsigned long total = 0, split = 0;
2846
2847         if (val != 1)
2848                 return -EINVAL;
2849
2850         for_each_populated_zone(zone) {
2851                 max_zone_pfn = zone_end_pfn(zone);
2852                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2853                         if (!pfn_valid(pfn))
2854                                 continue;
2855
2856                         page = pfn_to_page(pfn);
2857                         if (!get_page_unless_zero(page))
2858                                 continue;
2859
2860                         if (zone != page_zone(page))
2861                                 goto next;
2862
2863                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2864                                 goto next;
2865
2866                         total++;
2867                         lock_page(page);
2868                         if (!split_huge_page(page))
2869                                 split++;
2870                         unlock_page(page);
2871 next:
2872                         put_page(page);
2873                 }
2874         }
2875
2876         pr_info("%lu of %lu THP split\n", split, total);
2877
2878         return 0;
2879 }
2880 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2881                 "%llu\n");
2882
2883 static int __init split_huge_pages_debugfs(void)
2884 {
2885         void *ret;
2886
2887         ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2888                         &split_huge_pages_fops);
2889         if (!ret)
2890                 pr_warn("Failed to create split_huge_pages in debugfs");
2891         return 0;
2892 }
2893 late_initcall(split_huge_pages_debugfs);
2894 #endif
2895
2896 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2897 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2898                 struct page *page)
2899 {
2900         struct vm_area_struct *vma = pvmw->vma;
2901         struct mm_struct *mm = vma->vm_mm;
2902         unsigned long address = pvmw->address;
2903         pmd_t pmdval;
2904         swp_entry_t entry;
2905         pmd_t pmdswp;
2906
2907         if (!(pvmw->pmd && !pvmw->pte))
2908                 return;
2909
2910         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2911         pmdval = *pvmw->pmd;
2912         pmdp_invalidate(vma, address, pvmw->pmd);
2913         if (pmd_dirty(pmdval))
2914                 set_page_dirty(page);
2915         entry = make_migration_entry(page, pmd_write(pmdval));
2916         pmdswp = swp_entry_to_pmd(entry);
2917         if (pmd_soft_dirty(pmdval))
2918                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2919         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2920         page_remove_rmap(page, true);
2921         put_page(page);
2922 }
2923
2924 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2925 {
2926         struct vm_area_struct *vma = pvmw->vma;
2927         struct mm_struct *mm = vma->vm_mm;
2928         unsigned long address = pvmw->address;
2929         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2930         pmd_t pmde;
2931         swp_entry_t entry;
2932
2933         if (!(pvmw->pmd && !pvmw->pte))
2934                 return;
2935
2936         entry = pmd_to_swp_entry(*pvmw->pmd);
2937         get_page(new);
2938         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2939         if (pmd_swp_soft_dirty(*pvmw->pmd))
2940                 pmde = pmd_mksoft_dirty(pmde);
2941         if (is_write_migration_entry(entry))
2942                 pmde = maybe_pmd_mkwrite(pmde, vma);
2943
2944         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2945         if (PageAnon(new))
2946                 page_add_anon_rmap(new, vma, mmun_start, true);
2947         else
2948                 page_add_file_rmap(new, true);
2949         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
2950         if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
2951                 mlock_vma_page(new);
2952         update_mmu_cache_pmd(vma, address, pvmw->pmd);
2953 }
2954 #endif