mm/huge_memory.c

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