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/highmem.h>
  13 #include <linux/hugetlb.h>
  14 #include <linux/mmu_notifier.h>
  15 #include <linux/rmap.h>
  16 #include <linux/swap.h>
  17 #include <linux/shrinker.h>
  18 #include <linux/mm_inline.h>
  19 #include <linux/swapops.h>
  20 #include <linux/dax.h>
  21 #include <linux/khugepaged.h>
  22 #include <linux/freezer.h>
  23 #include <linux/pfn_t.h>
  24 #include <linux/mman.h>
  25 #include <linux/memremap.h>
  26 #include <linux/pagemap.h>
  27 #include <linux/debugfs.h>
  28 #include <linux/migrate.h>
  29 #include <linux/hashtable.h>
  30 #include <linux/userfaultfd_k.h>
  31 #include <linux/page_idle.h>
  32 #include <linux/shmem_fs.h>
  33
  34 #include <asm/tlb.h>
  35 #include <asm/pgalloc.h>
  36 #include "internal.h"
  37
  38 /*
  39  * By default transparent hugepage support is disabled in order that avoid
  40  * to risk increase the memory footprint of applications without a guaranteed
  41  * benefit. When transparent hugepage support is enabled, is for all mappings,
  42  * and khugepaged scans all mappings.
  43  * Defrag is invoked by khugepaged hugepage allocations and by page faults
  44  * for all hugepage allocations.
  45  */
  46 unsigned long transparent_hugepage_flags __read_mostly =
  47 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  48         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  49 #endif
  50 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  51         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  52 #endif
  53         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
  54         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
  55         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
  56
  57 static struct shrinker deferred_split_shrinker;
  58
  59 static atomic_t huge_zero_refcount;
  60 struct page *huge_zero_page __read_mostly;
  61
  62 static struct page *get_huge_zero_page(void)
  63 {
  64         struct page *zero_page;
  65 retry:
  66         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
  67                 return READ_ONCE(huge_zero_page);
  68
  69         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
  70                         HPAGE_PMD_ORDER);
  71         if (!zero_page) {
  72                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
  73                 return NULL;
  74         }
  75         count_vm_event(THP_ZERO_PAGE_ALLOC);
  76         preempt_disable();
  77         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
  78                 preempt_enable();
  79                 __free_pages(zero_page, compound_order(zero_page));
  80                 goto retry;
  81         }
  82
  83         /* We take additional reference here. It will be put back by shrinker */
  84         atomic_set(&huge_zero_refcount, 2);
  85         preempt_enable();
  86         return READ_ONCE(huge_zero_page);
  87 }
  88
  89 static void put_huge_zero_page(void)
  90 {
  91         /*
  92          * Counter should never go to zero here. Only shrinker can put
  93          * last reference.
  94          */
  95         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
  96 }
  97
  98 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
  99 {
 100         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 101                 return READ_ONCE(huge_zero_page);
 102
 103         if (!get_huge_zero_page())
 104                 return NULL;
 105
 106         if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 107                 put_huge_zero_page();
 108
 109         return READ_ONCE(huge_zero_page);
 110 }
 111
 112 void mm_put_huge_zero_page(struct mm_struct *mm)
 113 {
 114         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 115                 put_huge_zero_page();
 116 }
 117
 118 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
 119                                         struct shrink_control *sc)
 120 {
 121         /* we can free zero page only if last reference remains */
 122         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 123 }
 124
 125 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 126                                        struct shrink_control *sc)
 127 {
 128         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 129                 struct page *zero_page = xchg(&huge_zero_page, NULL);
 130                 BUG_ON(zero_page == NULL);
 131                 __free_pages(zero_page, compound_order(zero_page));
 132                 return HPAGE_PMD_NR;
 133         }
 134
 135         return 0;
 136 }
 137
 138 static struct shrinker huge_zero_page_shrinker = {
 139         .count_objects = shrink_huge_zero_page_count,
 140         .scan_objects = shrink_huge_zero_page_scan,
 141         .seeks = DEFAULT_SEEKS,
 142 };
 143
 144 #ifdef CONFIG_SYSFS
 145
 146 static ssize_t triple_flag_store(struct kobject *kobj,
 147                                  struct kobj_attribute *attr,
 148                                  const char *buf, size_t count,
 149                                  enum transparent_hugepage_flag enabled,
 150                                  enum transparent_hugepage_flag deferred,
 151                                  enum transparent_hugepage_flag req_madv)
 152 {
 153         if (!memcmp("defer", buf,
 154                     min(sizeof("defer")-1, count))) {
 155                 if (enabled == deferred)
 156                         return -EINVAL;
 157                 clear_bit(enabled, &transparent_hugepage_flags);
 158                 clear_bit(req_madv, &transparent_hugepage_flags);
 159                 set_bit(deferred, &transparent_hugepage_flags);
 160         } else if (!memcmp("always", buf,
 161                     min(sizeof("always")-1, count))) {
 162                 clear_bit(deferred, &transparent_hugepage_flags);
 163                 clear_bit(req_madv, &transparent_hugepage_flags);
 164                 set_bit(enabled, &transparent_hugepage_flags);
 165         } else if (!memcmp("madvise", buf,
 166                            min(sizeof("madvise")-1, count))) {
 167                 clear_bit(enabled, &transparent_hugepage_flags);
 168                 clear_bit(deferred, &transparent_hugepage_flags);
 169                 set_bit(req_madv, &transparent_hugepage_flags);
 170         } else if (!memcmp("never", buf,
 171                            min(sizeof("never")-1, count))) {
 172                 clear_bit(enabled, &transparent_hugepage_flags);
 173                 clear_bit(req_madv, &transparent_hugepage_flags);
 174                 clear_bit(deferred, &transparent_hugepage_flags);
 175         } else
 176                 return -EINVAL;
 177
 178         return count;
 179 }
 180
 181 static ssize_t enabled_show(struct kobject *kobj,
 182                             struct kobj_attribute *attr, char *buf)
 183 {
 184         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
 185                 return sprintf(buf, "[always] madvise never\n");
 186         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
 187                 return sprintf(buf, "always [madvise] never\n");
 188         else
 189                 return sprintf(buf, "always madvise [never]\n");
 190 }
 191
 192 static ssize_t enabled_store(struct kobject *kobj,
 193                              struct kobj_attribute *attr,
 194                              const char *buf, size_t count)
 195 {
 196         ssize_t ret;
 197
 198         ret = triple_flag_store(kobj, attr, buf, count,
 199                                 TRANSPARENT_HUGEPAGE_FLAG,
 200                                 TRANSPARENT_HUGEPAGE_FLAG,
 201                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 202
 203         if (ret > 0) {
 204                 int err = start_stop_khugepaged();
 205                 if (err)
 206                         ret = err;
 207         }
 208
 209         return ret;
 210 }
 211 static struct kobj_attribute enabled_attr =
 212         __ATTR(enabled, 0644, enabled_show, enabled_store);
 213
 214 ssize_t single_hugepage_flag_show(struct kobject *kobj,
 215                                 struct kobj_attribute *attr, char *buf,
 216                                 enum transparent_hugepage_flag flag)
 217 {
 218         return sprintf(buf, "%d\n",
 219                        !!test_bit(flag, &transparent_hugepage_flags));
 220 }
 221
 222 ssize_t single_hugepage_flag_store(struct kobject *kobj,
 223                                  struct kobj_attribute *attr,
 224                                  const char *buf, size_t count,
 225                                  enum transparent_hugepage_flag flag)
 226 {
 227         unsigned long value;
 228         int ret;
 229
 230         ret = kstrtoul(buf, 10, &value);
 231         if (ret < 0)
 232                 return ret;
 233         if (value > 1)
 234                 return -EINVAL;
 235
 236         if (value)
 237                 set_bit(flag, &transparent_hugepage_flags);
 238         else
 239                 clear_bit(flag, &transparent_hugepage_flags);
 240
 241         return count;
 242 }
 243
 244 /*
 245  * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
 246  * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
 247  * memory just to allocate one more hugepage.
 248  */
 249 static ssize_t defrag_show(struct kobject *kobj,
 250                            struct kobj_attribute *attr, char *buf)
 251 {
 252         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 253                 return sprintf(buf, "[always] defer madvise never\n");
 254         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 255                 return sprintf(buf, "always [defer] madvise never\n");
 256         else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 257                 return sprintf(buf, "always defer [madvise] never\n");
 258         else
 259                 return sprintf(buf, "always defer madvise [never]\n");
 260
 261 }
 262 static ssize_t defrag_store(struct kobject *kobj,
 263                             struct kobj_attribute *attr,
 264                             const char *buf, size_t count)
 265 {
 266         return triple_flag_store(kobj, attr, buf, count,
 267                                  TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
 268                                  TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
 269                                  TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 270 }
 271 static struct kobj_attribute defrag_attr =
 272         __ATTR(defrag, 0644, defrag_show, defrag_store);
 273
 274 static ssize_t use_zero_page_show(struct kobject *kobj,
 275                 struct kobj_attribute *attr, char *buf)
 276 {
 277         return single_hugepage_flag_show(kobj, attr, buf,
 278                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 279 }
 280 static ssize_t use_zero_page_store(struct kobject *kobj,
 281                 struct kobj_attribute *attr, const char *buf, size_t count)
 282 {
 283         return single_hugepage_flag_store(kobj, attr, buf, count,
 284                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 285 }
 286 static struct kobj_attribute use_zero_page_attr =
 287         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 288 #ifdef CONFIG_DEBUG_VM
 289 static ssize_t debug_cow_show(struct kobject *kobj,
 290                                 struct kobj_attribute *attr, char *buf)
 291 {
 292         return single_hugepage_flag_show(kobj, attr, buf,
 293                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 294 }
 295 static ssize_t debug_cow_store(struct kobject *kobj,
 296                                struct kobj_attribute *attr,
 297                                const char *buf, size_t count)
 298 {
 299         return single_hugepage_flag_store(kobj, attr, buf, count,
 300                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 301 }
 302 static struct kobj_attribute debug_cow_attr =
 303         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 304 #endif /* CONFIG_DEBUG_VM */
 305
 306 static struct attribute *hugepage_attr[] = {
 307         &enabled_attr.attr,
 308         &defrag_attr.attr,
 309         &use_zero_page_attr.attr,
 310 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
 311         &shmem_enabled_attr.attr,
 312 #endif
 313 #ifdef CONFIG_DEBUG_VM
 314         &debug_cow_attr.attr,
 315 #endif
 316         NULL,
 317 };
 318
 319 static struct attribute_group hugepage_attr_group = {
 320         .attrs = hugepage_attr,
 321 };
 322
 323 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 324 {
 325         int err;
 326
 327         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 328         if (unlikely(!*hugepage_kobj)) {
 329                 pr_err("failed to create transparent hugepage kobject\n");
 330                 return -ENOMEM;
 331         }
 332
 333         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 334         if (err) {
 335                 pr_err("failed to register transparent hugepage group\n");
 336                 goto delete_obj;
 337         }
 338
 339         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 340         if (err) {
 341                 pr_err("failed to register transparent hugepage group\n");
 342                 goto remove_hp_group;
 343         }
 344
 345         return 0;
 346
 347 remove_hp_group:
 348         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 349 delete_obj:
 350         kobject_put(*hugepage_kobj);
 351         return err;
 352 }
 353
 354 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 355 {
 356         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 357         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 358         kobject_put(hugepage_kobj);
 359 }
 360 #else
 361 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 362 {
 363         return 0;
 364 }
 365
 366 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 367 {
 368 }
 369 #endif /* CONFIG_SYSFS */
 370
 371 static int __init hugepage_init(void)
 372 {
 373         int err;
 374         struct kobject *hugepage_kobj;
 375
 376         if (!has_transparent_hugepage()) {
 377                 transparent_hugepage_flags = 0;
 378                 return -EINVAL;
 379         }
 380
 381         /*
 382          * hugepages can't be allocated by the buddy allocator
 383          */
 384         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
 385         /*
 386          * we use page->mapping and page->index in second tail page
 387          * as list_head: assuming THP order >= 2
 388          */
 389         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
 390
 391         err = hugepage_init_sysfs(&hugepage_kobj);
 392         if (err)
 393                 goto err_sysfs;
 394
 395         err = khugepaged_init();
 396         if (err)
 397                 goto err_slab;
 398
 399         err = register_shrinker(&huge_zero_page_shrinker);
 400         if (err)
 401                 goto err_hzp_shrinker;
 402         err = register_shrinker(&deferred_split_shrinker);
 403         if (err)
 404                 goto err_split_shrinker;
 405
 406         /*
 407          * By default disable transparent hugepages on smaller systems,
 408          * where the extra memory used could hurt more than TLB overhead
 409          * is likely to save.  The admin can still enable it through /sys.
 410          */
 411         if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
 412                 transparent_hugepage_flags = 0;
 413                 return 0;
 414         }
 415
 416         err = start_stop_khugepaged();
 417         if (err)
 418                 goto err_khugepaged;
 419
 420         return 0;
 421 err_khugepaged:
 422         unregister_shrinker(&deferred_split_shrinker);
 423 err_split_shrinker:
 424         unregister_shrinker(&huge_zero_page_shrinker);
 425 err_hzp_shrinker:
 426         khugepaged_destroy();
 427 err_slab:
 428         hugepage_exit_sysfs(hugepage_kobj);
 429 err_sysfs:
 430         return err;
 431 }
 432 subsys_initcall(hugepage_init);
 433
 434 static int __init setup_transparent_hugepage(char *str)
 435 {
 436         int ret = 0;
 437         if (!str)
 438                 goto out;
 439         if (!strcmp(str, "always")) {
 440                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 441                         &transparent_hugepage_flags);
 442                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 443                           &transparent_hugepage_flags);
 444                 ret = 1;
 445         } else if (!strcmp(str, "madvise")) {
 446                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 447                           &transparent_hugepage_flags);
 448                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 449                         &transparent_hugepage_flags);
 450                 ret = 1;
 451         } else if (!strcmp(str, "never")) {
 452                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 453                           &transparent_hugepage_flags);
 454                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 455                           &transparent_hugepage_flags);
 456                 ret = 1;
 457         }
 458 out:
 459         if (!ret)
 460                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
 461         return ret;
 462 }
 463 __setup("transparent_hugepage=", setup_transparent_hugepage);
 464
 465 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 466 {
 467         if (likely(vma->vm_flags & VM_WRITE))
 468                 pmd = pmd_mkwrite(pmd);
 469         return pmd;
 470 }
 471
 472 static inline struct list_head *page_deferred_list(struct page *page)
 473 {
 474         /*
 475          * ->lru in the tail pages is occupied by compound_head.
 476          * Let's use ->mapping + ->index in the second tail page as list_head.
 477          */
 478         return (struct list_head *)&page[2].mapping;
 479 }
 480
 481 void prep_transhuge_page(struct page *page)
 482 {
 483         /*
 484          * we use page->mapping and page->indexlru in second tail page
 485          * as list_head: assuming THP order >= 2
 486          */
 487
 488         INIT_LIST_HEAD(page_deferred_list(page));
 489         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 490 }
 491
 492 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
 493                 loff_t off, unsigned long flags, unsigned long size)
 494 {
 495         unsigned long addr;
 496         loff_t off_end = off + len;
 497         loff_t off_align = round_up(off, size);
 498         unsigned long len_pad;
 499
 500         if (off_end <= off_align || (off_end - off_align) < size)
 501                 return 0;
 502
 503         len_pad = len + size;
 504         if (len_pad < len || (off + len_pad) < off)
 505                 return 0;
 506
 507         addr = current->mm->get_unmapped_area(filp, 0, len_pad,
 508                                               off >> PAGE_SHIFT, flags);
 509         if (IS_ERR_VALUE(addr))
 510                 return 0;
 511
 512         addr += (off - addr) & (size - 1);
 513         return addr;
 514 }
 515
 516 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 517                 unsigned long len, unsigned long pgoff, unsigned long flags)
 518 {
 519         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 520
 521         if (addr)
 522                 goto out;
 523         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
 524                 goto out;
 525
 526         addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
 527         if (addr)
 528                 return addr;
 529
 530  out:
 531         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 532 }
 533 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 534
 535 static int __do_huge_pmd_anonymous_page(struct fault_env *fe, struct page *page,
 536                 gfp_t gfp)
 537 {
 538         struct vm_area_struct *vma = fe->vma;
 539         struct mem_cgroup *memcg;
 540         pgtable_t pgtable;
 541         unsigned long haddr = fe->address & HPAGE_PMD_MASK;
 542
 543         VM_BUG_ON_PAGE(!PageCompound(page), page);
 544
 545         if (mem_cgroup_try_charge(page, vma->vm_mm, gfp, &memcg, true)) {
 546                 put_page(page);
 547                 count_vm_event(THP_FAULT_FALLBACK);
 548                 return VM_FAULT_FALLBACK;
 549         }
 550
 551         pgtable = pte_alloc_one(vma->vm_mm, haddr);
 552         if (unlikely(!pgtable)) {
 553                 mem_cgroup_cancel_charge(page, memcg, true);
 554                 put_page(page);
 555                 return VM_FAULT_OOM;
 556         }
 557
 558         clear_huge_page(page, haddr, HPAGE_PMD_NR);
 559         /*
 560          * The memory barrier inside __SetPageUptodate makes sure that
 561          * clear_huge_page writes become visible before the set_pmd_at()
 562          * write.
 563          */
 564         __SetPageUptodate(page);
 565
 566         fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
 567         if (unlikely(!pmd_none(*fe->pmd))) {
 568                 spin_unlock(fe->ptl);
 569                 mem_cgroup_cancel_charge(page, memcg, true);
 570                 put_page(page);
 571                 pte_free(vma->vm_mm, pgtable);
 572         } else {
 573                 pmd_t entry;
 574
 575                 /* Deliver the page fault to userland */
 576                 if (userfaultfd_missing(vma)) {
 577                         int ret;
 578
 579                         spin_unlock(fe->ptl);
 580                         mem_cgroup_cancel_charge(page, memcg, true);
 581                         put_page(page);
 582                         pte_free(vma->vm_mm, pgtable);
 583                         ret = handle_userfault(fe, VM_UFFD_MISSING);
 584                         VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 585                         return ret;
 586                 }
 587
 588                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 589                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 590                 page_add_new_anon_rmap(page, vma, haddr, true);
 591                 mem_cgroup_commit_charge(page, memcg, false, true);
 592                 lru_cache_add_active_or_unevictable(page, vma);
 593                 pgtable_trans_huge_deposit(vma->vm_mm, fe->pmd, pgtable);
 594                 set_pmd_at(vma->vm_mm, haddr, fe->pmd, entry);
 595                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 596                 atomic_long_inc(&vma->vm_mm->nr_ptes);
 597                 spin_unlock(fe->ptl);
 598                 count_vm_event(THP_FAULT_ALLOC);
 599         }
 600
 601         return 0;
 602 }
 603
 604 /*
 605  * If THP defrag is set to always then directly reclaim/compact as necessary
 606  * If set to defer then do only background reclaim/compact and defer to khugepaged
 607  * If set to madvise and the VMA is flagged then directly reclaim/compact
 608  * When direct reclaim/compact is allowed, don't retry except for flagged VMA's
 609  */
 610 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
 611 {
 612         bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
 613
 614         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
 615                                 &transparent_hugepage_flags) && vma_madvised)
 616                 return GFP_TRANSHUGE;
 617         else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
 618                                                 &transparent_hugepage_flags))
 619                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
 620         else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
 621                                                 &transparent_hugepage_flags))
 622                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
 623
 624         return GFP_TRANSHUGE_LIGHT;
 625 }
 626
 627 /* Caller must hold page table lock. */
 628 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 629                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 630                 struct page *zero_page)
 631 {
 632         pmd_t entry;
 633         if (!pmd_none(*pmd))
 634                 return false;
 635         entry = mk_pmd(zero_page, vma->vm_page_prot);
 636         entry = pmd_mkhuge(entry);
 637         if (pgtable)
 638                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 639         set_pmd_at(mm, haddr, pmd, entry);
 640         atomic_long_inc(&mm->nr_ptes);
 641         return true;
 642 }
 643
 644 int do_huge_pmd_anonymous_page(struct fault_env *fe)
 645 {
 646         struct vm_area_struct *vma = fe->vma;
 647         gfp_t gfp;
 648         struct page *page;
 649         unsigned long haddr = fe->address & HPAGE_PMD_MASK;
 650
 651         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
 652                 return VM_FAULT_FALLBACK;
 653         if (unlikely(anon_vma_prepare(vma)))
 654                 return VM_FAULT_OOM;
 655         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 656                 return VM_FAULT_OOM;
 657         if (!(fe->flags & FAULT_FLAG_WRITE) &&
 658                         !mm_forbids_zeropage(vma->vm_mm) &&
 659                         transparent_hugepage_use_zero_page()) {
 660                 pgtable_t pgtable;
 661                 struct page *zero_page;
 662                 bool set;
 663                 int ret;
 664                 pgtable = pte_alloc_one(vma->vm_mm, haddr);
 665                 if (unlikely(!pgtable))
 666                         return VM_FAULT_OOM;
 667                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
 668                 if (unlikely(!zero_page)) {
 669                         pte_free(vma->vm_mm, pgtable);
 670                         count_vm_event(THP_FAULT_FALLBACK);
 671                         return VM_FAULT_FALLBACK;
 672                 }
 673                 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
 674                 ret = 0;
 675                 set = false;
 676                 if (pmd_none(*fe->pmd)) {
 677                         if (userfaultfd_missing(vma)) {
 678                                 spin_unlock(fe->ptl);
 679                                 ret = handle_userfault(fe, VM_UFFD_MISSING);
 680                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 681                         } else {
 682                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
 683                                                    haddr, fe->pmd, zero_page);
 684                                 spin_unlock(fe->ptl);
 685                                 set = true;
 686                         }
 687                 } else
 688                         spin_unlock(fe->ptl);
 689                 if (!set)
 690                         pte_free(vma->vm_mm, pgtable);
 691                 return ret;
 692         }
 693         gfp = alloc_hugepage_direct_gfpmask(vma);
 694         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 695         if (unlikely(!page)) {
 696                 count_vm_event(THP_FAULT_FALLBACK);
 697                 return VM_FAULT_FALLBACK;
 698         }
 699         prep_transhuge_page(page);
 700         return __do_huge_pmd_anonymous_page(fe, page, gfp);
 701 }
 702
 703 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 704                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write)
 705 {
 706         struct mm_struct *mm = vma->vm_mm;
 707         pmd_t entry;
 708         spinlock_t *ptl;
 709
 710         ptl = pmd_lock(mm, pmd);
 711         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 712         if (pfn_t_devmap(pfn))
 713                 entry = pmd_mkdevmap(entry);
 714         if (write) {
 715                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 716                 entry = maybe_pmd_mkwrite(entry, vma);
 717         }
 718         set_pmd_at(mm, addr, pmd, entry);
 719         update_mmu_cache_pmd(vma, addr, pmd);
 720         spin_unlock(ptl);
 721 }
 722
 723 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 724                         pmd_t *pmd, pfn_t pfn, bool write)
 725 {
 726         pgprot_t pgprot = vma->vm_page_prot;
 727         /*
 728          * If we had pmd_special, we could avoid all these restrictions,
 729          * but we need to be consistent with PTEs and architectures that
 730          * can't support a 'special' bit.
 731          */
 732         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
 733         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 734                                                 (VM_PFNMAP|VM_MIXEDMAP));
 735         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 736         BUG_ON(!pfn_t_devmap(pfn));
 737
 738         if (addr < vma->vm_start || addr >= vma->vm_end)
 739                 return VM_FAULT_SIGBUS;
 740         if (track_pfn_insert(vma, &pgprot, pfn))
 741                 return VM_FAULT_SIGBUS;
 742         insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
 743         return VM_FAULT_NOPAGE;
 744 }
 745 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
 746
 747 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
 748                 pmd_t *pmd)
 749 {
 750         pmd_t _pmd;
 751
 752         /*
 753          * We should set the dirty bit only for FOLL_WRITE but for now
 754          * the dirty bit in the pmd is meaningless.  And if the dirty
 755          * bit will become meaningful and we'll only set it with
 756          * FOLL_WRITE, an atomic set_bit will be required on the pmd to
 757          * set the young bit, instead of the current set_pmd_at.
 758          */
 759         _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
 760         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 761                                 pmd, _pmd,  1))
 762                 update_mmu_cache_pmd(vma, addr, pmd);
 763 }
 764
 765 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 766                 pmd_t *pmd, int flags)
 767 {
 768         unsigned long pfn = pmd_pfn(*pmd);
 769         struct mm_struct *mm = vma->vm_mm;
 770         struct dev_pagemap *pgmap;
 771         struct page *page;
 772
 773         assert_spin_locked(pmd_lockptr(mm, pmd));
 774
 775         /*
 776          * When we COW a devmap PMD entry, we split it into PTEs, so we should
 777          * not be in this function with `flags & FOLL_COW` set.
 778          */
 779         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
 780
 781         if (flags & FOLL_WRITE && !pmd_write(*pmd))
 782                 return NULL;
 783
 784         if (pmd_present(*pmd) && pmd_devmap(*pmd))
 785                 /* pass */;
 786         else
 787                 return NULL;
 788
 789         if (flags & FOLL_TOUCH)
 790                 touch_pmd(vma, addr, pmd);
 791
 792         /*
 793          * device mapped pages can only be returned if the
 794          * caller will manage the page reference count.
 795          */
 796         if (!(flags & FOLL_GET))
 797                 return ERR_PTR(-EEXIST);
 798
 799         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
 800         pgmap = get_dev_pagemap(pfn, NULL);
 801         if (!pgmap)
 802                 return ERR_PTR(-EFAULT);
 803         page = pfn_to_page(pfn);
 804         get_page(page);
 805         put_dev_pagemap(pgmap);
 806
 807         return page;
 808 }
 809
 810 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 811                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 812                   struct vm_area_struct *vma)
 813 {
 814         spinlock_t *dst_ptl, *src_ptl;
 815         struct page *src_page;
 816         pmd_t pmd;
 817         pgtable_t pgtable = NULL;
 818         int ret = -ENOMEM;
 819
 820         /* Skip if can be re-fill on fault */
 821         if (!vma_is_anonymous(vma))
 822                 return 0;
 823
 824         pgtable = pte_alloc_one(dst_mm, addr);
 825         if (unlikely(!pgtable))
 826                 goto out;
 827
 828         dst_ptl = pmd_lock(dst_mm, dst_pmd);
 829         src_ptl = pmd_lockptr(src_mm, src_pmd);
 830         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 831
 832         ret = -EAGAIN;
 833         pmd = *src_pmd;
 834         if (unlikely(!pmd_trans_huge(pmd))) {
 835                 pte_free(dst_mm, pgtable);
 836                 goto out_unlock;
 837         }
 838         /*
 839          * When page table lock is held, the huge zero pmd should not be
 840          * under splitting since we don't split the page itself, only pmd to
 841          * a page table.
 842          */
 843         if (is_huge_zero_pmd(pmd)) {
 844                 struct page *zero_page;
 845                 /*
 846                  * get_huge_zero_page() will never allocate a new page here,
 847                  * since we already have a zero page to copy. It just takes a
 848                  * reference.
 849                  */
 850                 zero_page = mm_get_huge_zero_page(dst_mm);
 851                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
 852                                 zero_page);
 853                 ret = 0;
 854                 goto out_unlock;
 855         }
 856
 857         src_page = pmd_page(pmd);
 858         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
 859         get_page(src_page);
 860         page_dup_rmap(src_page, true);
 861         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 862         atomic_long_inc(&dst_mm->nr_ptes);
 863         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 864
 865         pmdp_set_wrprotect(src_mm, addr, src_pmd);
 866         pmd = pmd_mkold(pmd_wrprotect(pmd));
 867         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 868
 869         ret = 0;
 870 out_unlock:
 871         spin_unlock(src_ptl);
 872         spin_unlock(dst_ptl);
 873 out:
 874         return ret;
 875 }
 876
 877 void huge_pmd_set_accessed(struct fault_env *fe, pmd_t orig_pmd)
 878 {
 879         pmd_t entry;
 880         unsigned long haddr;
 881         bool write = fe->flags & FAULT_FLAG_WRITE;
 882
 883         fe->ptl = pmd_lock(fe->vma->vm_mm, fe->pmd);
 884         if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
 885                 goto unlock;
 886
 887         entry = pmd_mkyoung(orig_pmd);
 888         if (write)
 889                 entry = pmd_mkdirty(entry);
 890         haddr = fe->address & HPAGE_PMD_MASK;
 891         if (pmdp_set_access_flags(fe->vma, haddr, fe->pmd, entry, write))
 892                 update_mmu_cache_pmd(fe->vma, fe->address, fe->pmd);
 893
 894 unlock:
 895         spin_unlock(fe->ptl);
 896 }
 897
 898 static int do_huge_pmd_wp_page_fallback(struct fault_env *fe, pmd_t orig_pmd,
 899                 struct page *page)
 900 {
 901         struct vm_area_struct *vma = fe->vma;
 902         unsigned long haddr = fe->address & HPAGE_PMD_MASK;
 903         struct mem_cgroup *memcg;
 904         pgtable_t pgtable;
 905         pmd_t _pmd;
 906         int ret = 0, i;
 907         struct page **pages;
 908         unsigned long mmun_start;       /* For mmu_notifiers */
 909         unsigned long mmun_end;         /* For mmu_notifiers */
 910
 911         pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
 912                         GFP_KERNEL);
 913         if (unlikely(!pages)) {
 914                 ret |= VM_FAULT_OOM;
 915                 goto out;
 916         }
 917
 918         for (i = 0; i < HPAGE_PMD_NR; i++) {
 919                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
 920                                                __GFP_OTHER_NODE, vma,
 921                                                fe->address, page_to_nid(page));
 922                 if (unlikely(!pages[i] ||
 923                              mem_cgroup_try_charge(pages[i], vma->vm_mm,
 924                                      GFP_KERNEL, &memcg, false))) {
 925                         if (pages[i])
 926                                 put_page(pages[i]);
 927                         while (--i >= 0) {
 928                                 memcg = (void *)page_private(pages[i]);
 929                                 set_page_private(pages[i], 0);
 930                                 mem_cgroup_cancel_charge(pages[i], memcg,
 931                                                 false);
 932                                 put_page(pages[i]);
 933                         }
 934                         kfree(pages);
 935                         ret |= VM_FAULT_OOM;
 936                         goto out;
 937                 }
 938                 set_page_private(pages[i], (unsigned long)memcg);
 939         }
 940
 941         for (i = 0; i < HPAGE_PMD_NR; i++) {
 942                 copy_user_highpage(pages[i], page + i,
 943                                    haddr + PAGE_SIZE * i, vma);
 944                 __SetPageUptodate(pages[i]);
 945                 cond_resched();
 946         }
 947
 948         mmun_start = haddr;
 949         mmun_end   = haddr + HPAGE_PMD_SIZE;
 950         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
 951
 952         fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
 953         if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
 954                 goto out_free_pages;
 955         VM_BUG_ON_PAGE(!PageHead(page), page);
 956
 957         pmdp_huge_clear_flush_notify(vma, haddr, fe->pmd);
 958         /* leave pmd empty until pte is filled */
 959
 960         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, fe->pmd);
 961         pmd_populate(vma->vm_mm, &_pmd, pgtable);
 962
 963         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
 964                 pte_t entry;
 965                 entry = mk_pte(pages[i], vma->vm_page_prot);
 966                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
 967                 memcg = (void *)page_private(pages[i]);
 968                 set_page_private(pages[i], 0);
 969                 page_add_new_anon_rmap(pages[i], fe->vma, haddr, false);
 970                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
 971                 lru_cache_add_active_or_unevictable(pages[i], vma);
 972                 fe->pte = pte_offset_map(&_pmd, haddr);
 973                 VM_BUG_ON(!pte_none(*fe->pte));
 974                 set_pte_at(vma->vm_mm, haddr, fe->pte, entry);
 975                 pte_unmap(fe->pte);
 976         }
 977         kfree(pages);
 978
 979         smp_wmb(); /* make pte visible before pmd */
 980         pmd_populate(vma->vm_mm, fe->pmd, pgtable);
 981         page_remove_rmap(page, true);
 982         spin_unlock(fe->ptl);
 983
 984         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
 985
 986         ret |= VM_FAULT_WRITE;
 987         put_page(page);
 988
 989 out:
 990         return ret;
 991
 992 out_free_pages:
 993         spin_unlock(fe->ptl);
 994         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
 995         for (i = 0; i < HPAGE_PMD_NR; i++) {
 996                 memcg = (void *)page_private(pages[i]);
 997                 set_page_private(pages[i], 0);
 998                 mem_cgroup_cancel_charge(pages[i], memcg, false);
 999                 put_page(pages[i]);
1000         }
1001         kfree(pages);
1002         goto out;
1003 }
1004
1005 int do_huge_pmd_wp_page(struct fault_env *fe, pmd_t orig_pmd)
1006 {
1007         struct vm_area_struct *vma = fe->vma;
1008         struct page *page = NULL, *new_page;
1009         struct mem_cgroup *memcg;
1010         unsigned long haddr = fe->address & HPAGE_PMD_MASK;
1011         unsigned long mmun_start;       /* For mmu_notifiers */
1012         unsigned long mmun_end;         /* For mmu_notifiers */
1013         gfp_t huge_gfp;                 /* for allocation and charge */
1014         int ret = 0;
1015
1016         fe->ptl = pmd_lockptr(vma->vm_mm, fe->pmd);
1017         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1018         if (is_huge_zero_pmd(orig_pmd))
1019                 goto alloc;
1020         spin_lock(fe->ptl);
1021         if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
1022                 goto out_unlock;
1023
1024         page = pmd_page(orig_pmd);
1025         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1026         /*
1027          * We can only reuse the page if nobody else maps the huge page or it's
1028          * part.
1029          */
1030         if (page_trans_huge_mapcount(page, NULL) == 1) {
1031                 pmd_t entry;
1032                 entry = pmd_mkyoung(orig_pmd);
1033                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1034                 if (pmdp_set_access_flags(vma, haddr, fe->pmd, entry,  1))
1035                         update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1036                 ret |= VM_FAULT_WRITE;
1037                 goto out_unlock;
1038         }
1039         get_page(page);
1040         spin_unlock(fe->ptl);
1041 alloc:
1042         if (transparent_hugepage_enabled(vma) &&
1043             !transparent_hugepage_debug_cow()) {
1044                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1045                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1046         } else
1047                 new_page = NULL;
1048
1049         if (likely(new_page)) {
1050                 prep_transhuge_page(new_page);
1051         } else {
1052                 if (!page) {
1053                         split_huge_pmd(vma, fe->pmd, fe->address);
1054                         ret |= VM_FAULT_FALLBACK;
1055                 } else {
1056                         ret = do_huge_pmd_wp_page_fallback(fe, orig_pmd, page);
1057                         if (ret & VM_FAULT_OOM) {
1058                                 split_huge_pmd(vma, fe->pmd, fe->address);
1059                                 ret |= VM_FAULT_FALLBACK;
1060                         }
1061                         put_page(page);
1062                 }
1063                 count_vm_event(THP_FAULT_FALLBACK);
1064                 goto out;
1065         }
1066
1067         if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm,
1068                                         huge_gfp, &memcg, true))) {
1069                 put_page(new_page);
1070                 split_huge_pmd(vma, fe->pmd, fe->address);
1071                 if (page)
1072                         put_page(page);
1073                 ret |= VM_FAULT_FALLBACK;
1074                 count_vm_event(THP_FAULT_FALLBACK);
1075                 goto out;
1076         }
1077
1078         count_vm_event(THP_FAULT_ALLOC);
1079
1080         if (!page)
1081                 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1082         else
1083                 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1084         __SetPageUptodate(new_page);
1085
1086         mmun_start = haddr;
1087         mmun_end   = haddr + HPAGE_PMD_SIZE;
1088         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1089
1090         spin_lock(fe->ptl);
1091         if (page)
1092                 put_page(page);
1093         if (unlikely(!pmd_same(*fe->pmd, orig_pmd))) {
1094                 spin_unlock(fe->ptl);
1095                 mem_cgroup_cancel_charge(new_page, memcg, true);
1096                 put_page(new_page);
1097                 goto out_mn;
1098         } else {
1099                 pmd_t entry;
1100                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1101                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1102                 pmdp_huge_clear_flush_notify(vma, haddr, fe->pmd);
1103                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1104                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1105                 lru_cache_add_active_or_unevictable(new_page, vma);
1106                 set_pmd_at(vma->vm_mm, haddr, fe->pmd, entry);
1107                 update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1108                 if (!page) {
1109                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1110                 } else {
1111                         VM_BUG_ON_PAGE(!PageHead(page), page);
1112                         page_remove_rmap(page, true);
1113                         put_page(page);
1114                 }
1115                 ret |= VM_FAULT_WRITE;
1116         }
1117         spin_unlock(fe->ptl);
1118 out_mn:
1119         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1120 out:
1121         return ret;
1122 out_unlock:
1123         spin_unlock(fe->ptl);
1124         return ret;
1125 }
1126
1127 /*
1128  * FOLL_FORCE can write to even unwritable pmd's, but only
1129  * after we've gone through a COW cycle and they are dirty.
1130  */
1131 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1132 {
1133         return pmd_write(pmd) ||
1134                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1135 }
1136
1137 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1138                                    unsigned long addr,
1139                                    pmd_t *pmd,
1140                                    unsigned int flags)
1141 {
1142         struct mm_struct *mm = vma->vm_mm;
1143         struct page *page = NULL;
1144
1145         assert_spin_locked(pmd_lockptr(mm, pmd));
1146
1147         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1148                 goto out;
1149
1150         /* Avoid dumping huge zero page */
1151         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1152                 return ERR_PTR(-EFAULT);
1153
1154         /* Full NUMA hinting faults to serialise migration in fault paths */
1155         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1156                 goto out;
1157
1158         page = pmd_page(*pmd);
1159         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1160         if (flags & FOLL_TOUCH)
1161                 touch_pmd(vma, addr, pmd);
1162         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1163                 /*
1164                  * We don't mlock() pte-mapped THPs. This way we can avoid
1165                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1166                  *
1167                  * For anon THP:
1168                  *
1169                  * In most cases the pmd is the only mapping of the page as we
1170                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1171                  * writable private mappings in populate_vma_page_range().
1172                  *
1173                  * The only scenario when we have the page shared here is if we
1174                  * mlocking read-only mapping shared over fork(). We skip
1175                  * mlocking such pages.
1176                  *
1177                  * For file THP:
1178                  *
1179                  * We can expect PageDoubleMap() to be stable under page lock:
1180                  * for file pages we set it in page_add_file_rmap(), which
1181                  * requires page to be locked.
1182                  */
1183
1184                 if (PageAnon(page) && compound_mapcount(page) != 1)
1185                         goto skip_mlock;
1186                 if (PageDoubleMap(page) || !page->mapping)
1187                         goto skip_mlock;
1188                 if (!trylock_page(page))
1189                         goto skip_mlock;
1190                 lru_add_drain();
1191                 if (page->mapping && !PageDoubleMap(page))
1192                         mlock_vma_page(page);
1193                 unlock_page(page);
1194         }
1195 skip_mlock:
1196         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1197         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1198         if (flags & FOLL_GET)
1199                 get_page(page);
1200
1201 out:
1202         return page;
1203 }
1204
1205 /* NUMA hinting page fault entry point for trans huge pmds */
1206 int do_huge_pmd_numa_page(struct fault_env *fe, pmd_t pmd)
1207 {
1208         struct vm_area_struct *vma = fe->vma;
1209         struct anon_vma *anon_vma = NULL;
1210         struct page *page;
1211         unsigned long haddr = fe->address & HPAGE_PMD_MASK;
1212         int page_nid = -1, this_nid = numa_node_id();
1213         int target_nid, last_cpupid = -1;
1214         bool page_locked;
1215         bool migrated = false;
1216         bool was_writable;
1217         int flags = 0;
1218
1219         fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
1220         if (unlikely(!pmd_same(pmd, *fe->pmd)))
1221                 goto out_unlock;
1222
1223         /*
1224          * If there are potential migrations, wait for completion and retry
1225          * without disrupting NUMA hinting information. Do not relock and
1226          * check_same as the page may no longer be mapped.
1227          */
1228         if (unlikely(pmd_trans_migrating(*fe->pmd))) {
1229                 page = pmd_page(*fe->pmd);
1230                 if (!get_page_unless_zero(page))
1231                         goto out_unlock;
1232                 spin_unlock(fe->ptl);
1233                 wait_on_page_locked(page);
1234                 put_page(page);
1235                 goto out;
1236         }
1237
1238         page = pmd_page(pmd);
1239         BUG_ON(is_huge_zero_page(page));
1240         page_nid = page_to_nid(page);
1241         last_cpupid = page_cpupid_last(page);
1242         count_vm_numa_event(NUMA_HINT_FAULTS);
1243         if (page_nid == this_nid) {
1244                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1245                 flags |= TNF_FAULT_LOCAL;
1246         }
1247
1248         /* See similar comment in do_numa_page for explanation */
1249         if (!pmd_write(pmd))
1250                 flags |= TNF_NO_GROUP;
1251
1252         /*
1253          * Acquire the page lock to serialise THP migrations but avoid dropping
1254          * page_table_lock if at all possible
1255          */
1256         page_locked = trylock_page(page);
1257         target_nid = mpol_misplaced(page, vma, haddr);
1258         if (target_nid == -1) {
1259                 /* If the page was locked, there are no parallel migrations */
1260                 if (page_locked)
1261                         goto clear_pmdnuma;
1262         }
1263
1264         /* Migration could have started since the pmd_trans_migrating check */
1265         if (!page_locked) {
1266                 if (!get_page_unless_zero(page))
1267                         goto out_unlock;
1268                 spin_unlock(fe->ptl);
1269                 wait_on_page_locked(page);
1270                 put_page(page);
1271                 page_nid = -1;
1272                 goto out;
1273         }
1274
1275         /*
1276          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1277          * to serialises splits
1278          */
1279         get_page(page);
1280         spin_unlock(fe->ptl);
1281         anon_vma = page_lock_anon_vma_read(page);
1282
1283         /* Confirm the PMD did not change while page_table_lock was released */
1284         spin_lock(fe->ptl);
1285         if (unlikely(!pmd_same(pmd, *fe->pmd))) {
1286                 unlock_page(page);
1287                 put_page(page);
1288                 page_nid = -1;
1289                 goto out_unlock;
1290         }
1291
1292         /* Bail if we fail to protect against THP splits for any reason */
1293         if (unlikely(!anon_vma)) {
1294                 put_page(page);
1295                 page_nid = -1;
1296                 goto clear_pmdnuma;
1297         }
1298
1299         /*
1300          * Migrate the THP to the requested node, returns with page unlocked
1301          * and access rights restored.
1302          */
1303         spin_unlock(fe->ptl);
1304         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1305                                 fe->pmd, pmd, fe->address, page, target_nid);
1306         if (migrated) {
1307                 flags |= TNF_MIGRATED;
1308                 page_nid = target_nid;
1309         } else
1310                 flags |= TNF_MIGRATE_FAIL;
1311
1312         goto out;
1313 clear_pmdnuma:
1314         BUG_ON(!PageLocked(page));
1315         was_writable = pmd_write(pmd);
1316         pmd = pmd_modify(pmd, vma->vm_page_prot);
1317         pmd = pmd_mkyoung(pmd);
1318         if (was_writable)
1319                 pmd = pmd_mkwrite(pmd);
1320         set_pmd_at(vma->vm_mm, haddr, fe->pmd, pmd);
1321         update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1322         unlock_page(page);
1323 out_unlock:
1324         spin_unlock(fe->ptl);
1325
1326 out:
1327         if (anon_vma)
1328                 page_unlock_anon_vma_read(anon_vma);
1329
1330         if (page_nid != -1)
1331                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, fe->flags);
1332
1333         return 0;
1334 }
1335
1336 /*
1337  * Return true if we do MADV_FREE successfully on entire pmd page.
1338  * Otherwise, return false.
1339  */
1340 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1341                 pmd_t *pmd, unsigned long addr, unsigned long next)
1342 {
1343         spinlock_t *ptl;
1344         pmd_t orig_pmd;
1345         struct page *page;
1346         struct mm_struct *mm = tlb->mm;
1347         bool ret = false;
1348
1349         ptl = pmd_trans_huge_lock(pmd, vma);
1350         if (!ptl)
1351                 goto out_unlocked;
1352
1353         orig_pmd = *pmd;
1354         if (is_huge_zero_pmd(orig_pmd))
1355                 goto out;
1356
1357         page = pmd_page(orig_pmd);
1358         /*
1359          * If other processes are mapping this page, we couldn't discard
1360          * the page unless they all do MADV_FREE so let's skip the page.
1361          */
1362         if (page_mapcount(page) != 1)
1363                 goto out;
1364
1365         if (!trylock_page(page))
1366                 goto out;
1367
1368         /*
1369          * If user want to discard part-pages of THP, split it so MADV_FREE
1370          * will deactivate only them.
1371          */
1372         if (next - addr != HPAGE_PMD_SIZE) {
1373                 get_page(page);
1374                 spin_unlock(ptl);
1375                 split_huge_page(page);
1376                 put_page(page);
1377                 unlock_page(page);
1378                 goto out_unlocked;
1379         }
1380
1381         if (PageDirty(page))
1382                 ClearPageDirty(page);
1383         unlock_page(page);
1384
1385         if (PageActive(page))
1386                 deactivate_page(page);
1387
1388         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1389                 pmdp_invalidate(vma, addr, pmd);
1390                 orig_pmd = pmd_mkold(orig_pmd);
1391                 orig_pmd = pmd_mkclean(orig_pmd);
1392
1393                 set_pmd_at(mm, addr, pmd, orig_pmd);
1394                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1395         }
1396         ret = true;
1397 out:
1398         spin_unlock(ptl);
1399 out_unlocked:
1400         return ret;
1401 }
1402
1403 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1404                  pmd_t *pmd, unsigned long addr)
1405 {
1406         pmd_t orig_pmd;
1407         spinlock_t *ptl;
1408
1409         ptl = __pmd_trans_huge_lock(pmd, vma);
1410         if (!ptl)
1411                 return 0;
1412         /*
1413          * For architectures like ppc64 we look at deposited pgtable
1414          * when calling pmdp_huge_get_and_clear. So do the
1415          * pgtable_trans_huge_withdraw after finishing pmdp related
1416          * operations.
1417          */
1418         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1419                         tlb->fullmm);
1420         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1421         if (vma_is_dax(vma)) {
1422                 spin_unlock(ptl);
1423                 if (is_huge_zero_pmd(orig_pmd))
1424                         tlb_remove_page(tlb, pmd_page(orig_pmd));
1425         } else if (is_huge_zero_pmd(orig_pmd)) {
1426                 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1427                 atomic_long_dec(&tlb->mm->nr_ptes);
1428                 spin_unlock(ptl);
1429                 tlb_remove_page(tlb, pmd_page(orig_pmd));
1430         } else {
1431                 struct page *page = pmd_page(orig_pmd);
1432                 page_remove_rmap(page, true);
1433                 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1434                 VM_BUG_ON_PAGE(!PageHead(page), page);
1435                 if (PageAnon(page)) {
1436                         pgtable_t pgtable;
1437                         pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
1438                         pte_free(tlb->mm, pgtable);
1439                         atomic_long_dec(&tlb->mm->nr_ptes);
1440                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1441                 } else {
1442                         add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1443                 }
1444                 spin_unlock(ptl);
1445                 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1446         }
1447         return 1;
1448 }
1449
1450 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1451                   unsigned long new_addr, unsigned long old_end,
1452                   pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush)
1453 {
1454         spinlock_t *old_ptl, *new_ptl;
1455         pmd_t pmd;
1456         struct mm_struct *mm = vma->vm_mm;
1457         bool force_flush = false;
1458
1459         if ((old_addr & ~HPAGE_PMD_MASK) ||
1460             (new_addr & ~HPAGE_PMD_MASK) ||
1461             old_end - old_addr < HPAGE_PMD_SIZE)
1462                 return false;
1463
1464         /*
1465          * The destination pmd shouldn't be established, free_pgtables()
1466          * should have release it.
1467          */
1468         if (WARN_ON(!pmd_none(*new_pmd))) {
1469                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1470                 return false;
1471         }
1472
1473         /*
1474          * We don't have to worry about the ordering of src and dst
1475          * ptlocks because exclusive mmap_sem prevents deadlock.
1476          */
1477         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1478         if (old_ptl) {
1479                 new_ptl = pmd_lockptr(mm, new_pmd);
1480                 if (new_ptl != old_ptl)
1481                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1482                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1483                 if (pmd_present(pmd) && pmd_dirty(pmd))
1484                         force_flush = true;
1485                 VM_BUG_ON(!pmd_none(*new_pmd));
1486
1487                 if (pmd_move_must_withdraw(new_ptl, old_ptl) &&
1488                                 vma_is_anonymous(vma)) {
1489                         pgtable_t pgtable;
1490                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1491                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1492                 }
1493                 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1494                 if (new_ptl != old_ptl)
1495                         spin_unlock(new_ptl);
1496                 if (force_flush)
1497                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1498                 else
1499                         *need_flush = true;
1500                 spin_unlock(old_ptl);
1501                 return true;
1502         }
1503         return false;
1504 }
1505
1506 /*
1507  * Returns
1508  *  - 0 if PMD could not be locked
1509  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1510  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1511  */
1512 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1513                 unsigned long addr, pgprot_t newprot, int prot_numa)
1514 {
1515         struct mm_struct *mm = vma->vm_mm;
1516         spinlock_t *ptl;
1517         int ret = 0;
1518
1519         ptl = __pmd_trans_huge_lock(pmd, vma);
1520         if (ptl) {
1521                 pmd_t entry;
1522                 bool preserve_write = prot_numa && pmd_write(*pmd);
1523                 ret = 1;
1524
1525                 /*
1526                  * Avoid trapping faults against the zero page. The read-only
1527                  * data is likely to be read-cached on the local CPU and
1528                  * local/remote hits to the zero page are not interesting.
1529                  */
1530                 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1531                         spin_unlock(ptl);
1532                         return ret;
1533                 }
1534
1535                 if (!prot_numa || !pmd_protnone(*pmd)) {
1536                         entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
1537                         entry = pmd_modify(entry, newprot);
1538                         if (preserve_write)
1539                                 entry = pmd_mkwrite(entry);
1540                         ret = HPAGE_PMD_NR;
1541                         set_pmd_at(mm, addr, pmd, entry);
1542                         BUG_ON(vma_is_anonymous(vma) && !preserve_write &&
1543                                         pmd_write(entry));
1544                 }
1545                 spin_unlock(ptl);
1546         }
1547
1548         return ret;
1549 }
1550
1551 /*
1552  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1553  *
1554  * Note that if it returns page table lock pointer, this routine returns without
1555  * unlocking page table lock. So callers must unlock it.
1556  */
1557 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1558 {
1559         spinlock_t *ptl;
1560         ptl = pmd_lock(vma->vm_mm, pmd);
1561         if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
1562                 return ptl;
1563         spin_unlock(ptl);
1564         return NULL;
1565 }
1566
1567 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
1568                 unsigned long haddr, pmd_t *pmd)
1569 {
1570         struct mm_struct *mm = vma->vm_mm;
1571         pgtable_t pgtable;
1572         pmd_t _pmd;
1573         int i;
1574
1575         /* leave pmd empty until pte is filled */
1576         pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1577
1578         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1579         pmd_populate(mm, &_pmd, pgtable);
1580
1581         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1582                 pte_t *pte, entry;
1583                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
1584                 entry = pte_mkspecial(entry);
1585                 pte = pte_offset_map(&_pmd, haddr);
1586                 VM_BUG_ON(!pte_none(*pte));
1587                 set_pte_at(mm, haddr, pte, entry);
1588                 pte_unmap(pte);
1589         }
1590         smp_wmb(); /* make pte visible before pmd */
1591         pmd_populate(mm, pmd, pgtable);
1592 }
1593
1594 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
1595                 unsigned long haddr, bool freeze)
1596 {
1597         struct mm_struct *mm = vma->vm_mm;
1598         struct page *page;
1599         pgtable_t pgtable;
1600         pmd_t _pmd;
1601         bool young, write, dirty, soft_dirty;
1602         unsigned long addr;
1603         int i;
1604
1605         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
1606         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1607         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
1608         VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
1609
1610         count_vm_event(THP_SPLIT_PMD);
1611
1612         if (!vma_is_anonymous(vma)) {
1613                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1614                 if (vma_is_dax(vma))
1615                         return;
1616                 page = pmd_page(_pmd);
1617                 if (!PageReferenced(page) && pmd_young(_pmd))
1618                         SetPageReferenced(page);
1619                 page_remove_rmap(page, true);
1620                 put_page(page);
1621                 add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1622                 return;
1623         } else if (is_huge_zero_pmd(*pmd)) {
1624                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
1625         }
1626
1627         page = pmd_page(*pmd);
1628         VM_BUG_ON_PAGE(!page_count(page), page);
1629         page_ref_add(page, HPAGE_PMD_NR - 1);
1630         write = pmd_write(*pmd);
1631         young = pmd_young(*pmd);
1632         dirty = pmd_dirty(*pmd);
1633         soft_dirty = pmd_soft_dirty(*pmd);
1634
1635         pmdp_huge_split_prepare(vma, haddr, pmd);
1636         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1637         pmd_populate(mm, &_pmd, pgtable);
1638
1639         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
1640                 pte_t entry, *pte;
1641                 /*
1642                  * Note that NUMA hinting access restrictions are not
1643                  * transferred to avoid any possibility of altering
1644                  * permissions across VMAs.
1645                  */
1646                 if (freeze) {
1647                         swp_entry_t swp_entry;
1648                         swp_entry = make_migration_entry(page + i, write);
1649                         entry = swp_entry_to_pte(swp_entry);
1650                         if (soft_dirty)
1651                                 entry = pte_swp_mksoft_dirty(entry);
1652                 } else {
1653                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
1654                         entry = maybe_mkwrite(entry, vma);
1655                         if (!write)
1656                                 entry = pte_wrprotect(entry);
1657                         if (!young)
1658                                 entry = pte_mkold(entry);
1659                         if (soft_dirty)
1660                                 entry = pte_mksoft_dirty(entry);
1661                 }
1662                 if (dirty)
1663                         SetPageDirty(page + i);
1664                 pte = pte_offset_map(&_pmd, addr);
1665                 BUG_ON(!pte_none(*pte));
1666                 set_pte_at(mm, addr, pte, entry);
1667                 atomic_inc(&page[i]._mapcount);
1668                 pte_unmap(pte);
1669         }
1670
1671         /*
1672          * Set PG_double_map before dropping compound_mapcount to avoid
1673          * false-negative page_mapped().
1674          */
1675         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
1676                 for (i = 0; i < HPAGE_PMD_NR; i++)
1677                         atomic_inc(&page[i]._mapcount);
1678         }
1679
1680         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
1681                 /* Last compound_mapcount is gone. */
1682                 __dec_node_page_state(page, NR_ANON_THPS);
1683                 if (TestClearPageDoubleMap(page)) {
1684                         /* No need in mapcount reference anymore */
1685                         for (i = 0; i < HPAGE_PMD_NR; i++)
1686                                 atomic_dec(&page[i]._mapcount);
1687                 }
1688         }
1689
1690         smp_wmb(); /* make pte visible before pmd */
1691         /*
1692          * Up to this point the pmd is present and huge and userland has the
1693          * whole access to the hugepage during the split (which happens in
1694          * place). If we overwrite the pmd with the not-huge version pointing
1695          * to the pte here (which of course we could if all CPUs were bug
1696          * free), userland could trigger a small page size TLB miss on the
1697          * small sized TLB while the hugepage TLB entry is still established in
1698          * the huge TLB. Some CPU doesn't like that.
1699          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
1700          * 383 on page 93. Intel should be safe but is also warns that it's
1701          * only safe if the permission and cache attributes of the two entries
1702          * loaded in the two TLB is identical (which should be the case here).
1703          * But it is generally safer to never allow small and huge TLB entries
1704          * for the same virtual address to be loaded simultaneously. So instead
1705          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
1706          * current pmd notpresent (atomically because here the pmd_trans_huge
1707          * and pmd_trans_splitting must remain set at all times on the pmd
1708          * until the split is complete for this pmd), then we flush the SMP TLB
1709          * and finally we write the non-huge version of the pmd entry with
1710          * pmd_populate.
1711          */
1712         pmdp_invalidate(vma, haddr, pmd);
1713         pmd_populate(mm, pmd, pgtable);
1714
1715         if (freeze) {
1716                 for (i = 0; i < HPAGE_PMD_NR; i++) {
1717                         page_remove_rmap(page + i, false);
1718                         put_page(page + i);
1719                 }
1720         }
1721 }
1722
1723 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1724                 unsigned long address, bool freeze, struct page *page)
1725 {
1726         spinlock_t *ptl;
1727         struct mm_struct *mm = vma->vm_mm;
1728         unsigned long haddr = address & HPAGE_PMD_MASK;
1729
1730         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
1731         ptl = pmd_lock(mm, pmd);
1732
1733         /*
1734          * If caller asks to setup a migration entries, we need a page to check
1735          * pmd against. Otherwise we can end up replacing wrong page.
1736          */
1737         VM_BUG_ON(freeze && !page);
1738         if (page && page != pmd_page(*pmd))
1739                 goto out;
1740
1741         if (pmd_trans_huge(*pmd)) {
1742                 page = pmd_page(*pmd);
1743                 if (PageMlocked(page))
1744                         clear_page_mlock(page);
1745         } else if (!pmd_devmap(*pmd))
1746                 goto out;
1747         __split_huge_pmd_locked(vma, pmd, haddr, freeze);
1748 out:
1749         spin_unlock(ptl);
1750         mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
1751 }
1752
1753 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
1754                 bool freeze, struct page *page)
1755 {
1756         pgd_t *pgd;
1757         pud_t *pud;
1758         pmd_t *pmd;
1759
1760         pgd = pgd_offset(vma->vm_mm, address);
1761         if (!pgd_present(*pgd))
1762                 return;
1763
1764         pud = pud_offset(pgd, address);
1765         if (!pud_present(*pud))
1766                 return;
1767
1768         pmd = pmd_offset(pud, address);
1769
1770         __split_huge_pmd(vma, pmd, address, freeze, page);
1771 }
1772
1773 void vma_adjust_trans_huge(struct vm_area_struct *vma,
1774                              unsigned long start,
1775                              unsigned long end,
1776                              long adjust_next)
1777 {
1778         /*
1779          * If the new start address isn't hpage aligned and it could
1780          * previously contain an hugepage: check if we need to split
1781          * an huge pmd.
1782          */
1783         if (start & ~HPAGE_PMD_MASK &&
1784             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
1785             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
1786                 split_huge_pmd_address(vma, start, false, NULL);
1787
1788         /*
1789          * If the new end address isn't hpage aligned and it could
1790          * previously contain an hugepage: check if we need to split
1791          * an huge pmd.
1792          */
1793         if (end & ~HPAGE_PMD_MASK &&
1794             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
1795             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
1796                 split_huge_pmd_address(vma, end, false, NULL);
1797
1798         /*
1799          * If we're also updating the vma->vm_next->vm_start, if the new
1800          * vm_next->vm_start isn't page aligned and it could previously
1801          * contain an hugepage: check if we need to split an huge pmd.
1802          */
1803         if (adjust_next > 0) {
1804                 struct vm_area_struct *next = vma->vm_next;
1805                 unsigned long nstart = next->vm_start;
1806                 nstart += adjust_next << PAGE_SHIFT;
1807                 if (nstart & ~HPAGE_PMD_MASK &&
1808                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
1809                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
1810                         split_huge_pmd_address(next, nstart, false, NULL);
1811         }
1812 }
1813
1814 static void freeze_page(struct page *page)
1815 {
1816         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
1817                 TTU_RMAP_LOCKED;
1818         int i, ret;
1819
1820         VM_BUG_ON_PAGE(!PageHead(page), page);
1821
1822         if (PageAnon(page))
1823                 ttu_flags |= TTU_MIGRATION;
1824
1825         /* We only need TTU_SPLIT_HUGE_PMD once */
1826         ret = try_to_unmap(page, ttu_flags | TTU_SPLIT_HUGE_PMD);
1827         for (i = 1; !ret && i < HPAGE_PMD_NR; i++) {
1828                 /* Cut short if the page is unmapped */
1829                 if (page_count(page) == 1)
1830                         return;
1831
1832                 ret = try_to_unmap(page + i, ttu_flags);
1833         }
1834         VM_BUG_ON_PAGE(ret, page + i - 1);
1835 }
1836
1837 static void unfreeze_page(struct page *page)
1838 {
1839         int i;
1840
1841         for (i = 0; i < HPAGE_PMD_NR; i++)
1842                 remove_migration_ptes(page + i, page + i, true);
1843 }
1844
1845 static void __split_huge_page_tail(struct page *head, int tail,
1846                 struct lruvec *lruvec, struct list_head *list)
1847 {
1848         struct page *page_tail = head + tail;
1849
1850         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
1851         VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
1852
1853         /*
1854          * tail_page->_refcount is zero and not changing from under us. But
1855          * get_page_unless_zero() may be running from under us on the
1856          * tail_page. If we used atomic_set() below instead of atomic_inc() or
1857          * atomic_add(), we would then run atomic_set() concurrently with
1858          * get_page_unless_zero(), and atomic_set() is implemented in C not
1859          * using locked ops. spin_unlock on x86 sometime uses locked ops
1860          * because of PPro errata 66, 92, so unless somebody can guarantee
1861          * atomic_set() here would be safe on all archs (and not only on x86),
1862          * it's safer to use atomic_inc()/atomic_add().
1863          */
1864         if (PageAnon(head)) {
1865                 page_ref_inc(page_tail);
1866         } else {
1867                 /* Additional pin to radix tree */
1868                 page_ref_add(page_tail, 2);
1869         }
1870
1871         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
1872         page_tail->flags |= (head->flags &
1873                         ((1L << PG_referenced) |
1874                          (1L << PG_swapbacked) |
1875                          (1L << PG_mlocked) |
1876                          (1L << PG_uptodate) |
1877                          (1L << PG_active) |
1878                          (1L << PG_locked) |
1879                          (1L << PG_unevictable) |
1880                          (1L << PG_dirty)));
1881
1882         /*
1883          * After clearing PageTail the gup refcount can be released.
1884          * Page flags also must be visible before we make the page non-compound.
1885          */
1886         smp_wmb();
1887
1888         clear_compound_head(page_tail);
1889
1890         if (page_is_young(head))
1891                 set_page_young(page_tail);
1892         if (page_is_idle(head))
1893                 set_page_idle(page_tail);
1894
1895         /* ->mapping in first tail page is compound_mapcount */
1896         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
1897                         page_tail);
1898         page_tail->mapping = head->mapping;
1899
1900         page_tail->index = head->index + tail;
1901         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
1902         lru_add_page_tail(head, page_tail, lruvec, list);
1903 }
1904
1905 static void __split_huge_page(struct page *page, struct list_head *list,
1906                 unsigned long flags)
1907 {
1908         struct page *head = compound_head(page);
1909         struct zone *zone = page_zone(head);
1910         struct lruvec *lruvec;
1911         pgoff_t end = -1;
1912         int i;
1913
1914         lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
1915
1916         /* complete memcg works before add pages to LRU */
1917         mem_cgroup_split_huge_fixup(head);
1918
1919         if (!PageAnon(page))
1920                 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE);
1921
1922         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1923                 __split_huge_page_tail(head, i, lruvec, list);
1924                 /* Some pages can be beyond i_size: drop them from page cache */
1925                 if (head[i].index >= end) {
1926                         __ClearPageDirty(head + i);
1927                         __delete_from_page_cache(head + i, NULL);
1928                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
1929                                 shmem_uncharge(head->mapping->host, 1);
1930                         put_page(head + i);
1931                 }
1932         }
1933
1934         ClearPageCompound(head);
1935         /* See comment in __split_huge_page_tail() */
1936         if (PageAnon(head)) {
1937                 page_ref_inc(head);
1938         } else {
1939                 /* Additional pin to radix tree */
1940                 page_ref_add(head, 2);
1941                 spin_unlock(&head->mapping->tree_lock);
1942         }
1943
1944         spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
1945
1946         unfreeze_page(head);
1947
1948         for (i = 0; i < HPAGE_PMD_NR; i++) {
1949                 struct page *subpage = head + i;
1950                 if (subpage == page)
1951                         continue;
1952                 unlock_page(subpage);
1953
1954                 /*
1955                  * Subpages may be freed if there wasn't any mapping
1956                  * like if add_to_swap() is running on a lru page that
1957                  * had its mapping zapped. And freeing these pages
1958                  * requires taking the lru_lock so we do the put_page
1959                  * of the tail pages after the split is complete.
1960                  */
1961                 put_page(subpage);
1962         }
1963 }
1964
1965 int total_mapcount(struct page *page)
1966 {
1967         int i, compound, ret;
1968
1969         VM_BUG_ON_PAGE(PageTail(page), page);
1970
1971         if (likely(!PageCompound(page)))
1972                 return atomic_read(&page->_mapcount) + 1;
1973
1974         compound = compound_mapcount(page);
1975         if (PageHuge(page))
1976                 return compound;
1977         ret = compound;
1978         for (i = 0; i < HPAGE_PMD_NR; i++)
1979                 ret += atomic_read(&page[i]._mapcount) + 1;
1980         /* File pages has compound_mapcount included in _mapcount */
1981         if (!PageAnon(page))
1982                 return ret - compound * HPAGE_PMD_NR;
1983         if (PageDoubleMap(page))
1984                 ret -= HPAGE_PMD_NR;
1985         return ret;
1986 }
1987
1988 /*
1989  * This calculates accurately how many mappings a transparent hugepage
1990  * has (unlike page_mapcount() which isn't fully accurate). This full
1991  * accuracy is primarily needed to know if copy-on-write faults can
1992  * reuse the page and change the mapping to read-write instead of
1993  * copying them. At the same time this returns the total_mapcount too.
1994  *
1995  * The function returns the highest mapcount any one of the subpages
1996  * has. If the return value is one, even if different processes are
1997  * mapping different subpages of the transparent hugepage, they can
1998  * all reuse it, because each process is reusing a different subpage.
1999  *
2000  * The total_mapcount is instead counting all virtual mappings of the
2001  * subpages. If the total_mapcount is equal to "one", it tells the
2002  * caller all mappings belong to the same "mm" and in turn the
2003  * anon_vma of the transparent hugepage can become the vma->anon_vma
2004  * local one as no other process may be mapping any of the subpages.
2005  *
2006  * It would be more accurate to replace page_mapcount() with
2007  * page_trans_huge_mapcount(), however we only use
2008  * page_trans_huge_mapcount() in the copy-on-write faults where we
2009  * need full accuracy to avoid breaking page pinning, because
2010  * page_trans_huge_mapcount() is slower than page_mapcount().
2011  */
2012 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2013 {
2014         int i, ret, _total_mapcount, mapcount;
2015
2016         /* hugetlbfs shouldn't call it */
2017         VM_BUG_ON_PAGE(PageHuge(page), page);
2018
2019         if (likely(!PageTransCompound(page))) {
2020                 mapcount = atomic_read(&page->_mapcount) + 1;
2021                 if (total_mapcount)
2022                         *total_mapcount = mapcount;
2023                 return mapcount;
2024         }
2025
2026         page = compound_head(page);
2027
2028         _total_mapcount = ret = 0;
2029         for (i = 0; i < HPAGE_PMD_NR; i++) {
2030                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2031                 ret = max(ret, mapcount);
2032                 _total_mapcount += mapcount;
2033         }
2034         if (PageDoubleMap(page)) {
2035                 ret -= 1;
2036                 _total_mapcount -= HPAGE_PMD_NR;
2037         }
2038         mapcount = compound_mapcount(page);
2039         ret += mapcount;
2040         _total_mapcount += mapcount;
2041         if (total_mapcount)
2042                 *total_mapcount = _total_mapcount;
2043         return ret;
2044 }
2045
2046 /*
2047  * This function splits huge page into normal pages. @page can point to any
2048  * subpage of huge page to split. Split doesn't change the position of @page.
2049  *
2050  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2051  * The huge page must be locked.
2052  *
2053  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2054  *
2055  * Both head page and tail pages will inherit mapping, flags, and so on from
2056  * the hugepage.
2057  *
2058  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2059  * they are not mapped.
2060  *
2061  * Returns 0 if the hugepage is split successfully.
2062  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2063  * us.
2064  */
2065 int split_huge_page_to_list(struct page *page, struct list_head *list)
2066 {
2067         struct page *head = compound_head(page);
2068         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2069         struct anon_vma *anon_vma = NULL;
2070         struct address_space *mapping = NULL;
2071         int count, mapcount, extra_pins, ret;
2072         bool mlocked;
2073         unsigned long flags;
2074
2075         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2076         VM_BUG_ON_PAGE(!PageLocked(page), page);
2077         VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2078         VM_BUG_ON_PAGE(!PageCompound(page), page);
2079
2080         if (PageAnon(head)) {
2081                 /*
2082                  * The caller does not necessarily hold an mmap_sem that would
2083                  * prevent the anon_vma disappearing so we first we take a
2084                  * reference to it and then lock the anon_vma for write. This
2085                  * is similar to page_lock_anon_vma_read except the write lock
2086                  * is taken to serialise against parallel split or collapse
2087                  * operations.
2088                  */
2089                 anon_vma = page_get_anon_vma(head);
2090                 if (!anon_vma) {
2091                         ret = -EBUSY;
2092                         goto out;
2093                 }
2094                 extra_pins = 0;
2095                 mapping = NULL;
2096                 anon_vma_lock_write(anon_vma);
2097         } else {
2098                 mapping = head->mapping;
2099
2100                 /* Truncated ? */
2101                 if (!mapping) {
2102                         ret = -EBUSY;
2103                         goto out;
2104                 }
2105
2106                 /* Addidional pins from radix tree */
2107                 extra_pins = HPAGE_PMD_NR;
2108                 anon_vma = NULL;
2109                 i_mmap_lock_read(mapping);
2110         }
2111
2112         /*
2113          * Racy check if we can split the page, before freeze_page() will
2114          * split PMDs
2115          */
2116         if (total_mapcount(head) != page_count(head) - extra_pins - 1) {
2117                 ret = -EBUSY;
2118                 goto out_unlock;
2119         }
2120
2121         mlocked = PageMlocked(page);
2122         freeze_page(head);
2123         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2124
2125         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2126         if (mlocked)
2127                 lru_add_drain();
2128
2129         /* prevent PageLRU to go away from under us, and freeze lru stats */
2130         spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2131
2132         if (mapping) {
2133                 void **pslot;
2134
2135                 spin_lock(&mapping->tree_lock);
2136                 pslot = radix_tree_lookup_slot(&mapping->page_tree,
2137                                 page_index(head));
2138                 /*
2139                  * Check if the head page is present in radix tree.
2140                  * We assume all tail are present too, if head is there.
2141                  */
2142                 if (radix_tree_deref_slot_protected(pslot,
2143                                         &mapping->tree_lock) != head)
2144                         goto fail;
2145         }
2146
2147         /* Prevent deferred_split_scan() touching ->_refcount */
2148         spin_lock(&pgdata->split_queue_lock);
2149         count = page_count(head);
2150         mapcount = total_mapcount(head);
2151         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2152                 if (!list_empty(page_deferred_list(head))) {
2153                         pgdata->split_queue_len--;
2154                         list_del(page_deferred_list(head));
2155                 }
2156                 if (mapping)
2157                         __dec_node_page_state(page, NR_SHMEM_THPS);
2158                 spin_unlock(&pgdata->split_queue_lock);
2159                 __split_huge_page(page, list, flags);
2160                 ret = 0;
2161         } else {
2162                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2163                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2164                                         mapcount, count);
2165                         if (PageTail(page))
2166                                 dump_page(head, NULL);
2167                         dump_page(page, "total_mapcount(head) > 0");
2168                         BUG();
2169                 }
2170                 spin_unlock(&pgdata->split_queue_lock);
2171 fail:           if (mapping)
2172                         spin_unlock(&mapping->tree_lock);
2173                 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2174                 unfreeze_page(head);
2175                 ret = -EBUSY;
2176         }
2177
2178 out_unlock:
2179         if (anon_vma) {
2180                 anon_vma_unlock_write(anon_vma);
2181                 put_anon_vma(anon_vma);
2182         }
2183         if (mapping)
2184                 i_mmap_unlock_read(mapping);
2185 out:
2186         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2187         return ret;
2188 }
2189
2190 void free_transhuge_page(struct page *page)
2191 {
2192         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2193         unsigned long flags;
2194
2195         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2196         if (!list_empty(page_deferred_list(page))) {
2197                 pgdata->split_queue_len--;
2198                 list_del(page_deferred_list(page));
2199         }
2200         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2201         free_compound_page(page);
2202 }
2203
2204 void deferred_split_huge_page(struct page *page)
2205 {
2206         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2207         unsigned long flags;
2208
2209         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2210
2211         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2212         if (list_empty(page_deferred_list(page))) {
2213                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2214                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2215                 pgdata->split_queue_len++;
2216         }
2217         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2218 }
2219
2220 static unsigned long deferred_split_count(struct shrinker *shrink,
2221                 struct shrink_control *sc)
2222 {
2223         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2224         return ACCESS_ONCE(pgdata->split_queue_len);
2225 }
2226
2227 static unsigned long deferred_split_scan(struct shrinker *shrink,
2228                 struct shrink_control *sc)
2229 {
2230         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2231         unsigned long flags;
2232         LIST_HEAD(list), *pos, *next;
2233         struct page *page;
2234         int split = 0;
2235
2236         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2237         /* Take pin on all head pages to avoid freeing them under us */
2238         list_for_each_safe(pos, next, &pgdata->split_queue) {
2239                 page = list_entry((void *)pos, struct page, mapping);
2240                 page = compound_head(page);
2241                 if (get_page_unless_zero(page)) {
2242                         list_move(page_deferred_list(page), &list);
2243                 } else {
2244                         /* We lost race with put_compound_page() */
2245                         list_del_init(page_deferred_list(page));
2246                         pgdata->split_queue_len--;
2247                 }
2248                 if (!--sc->nr_to_scan)
2249                         break;
2250         }
2251         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2252
2253         list_for_each_safe(pos, next, &list) {
2254                 page = list_entry((void *)pos, struct page, mapping);
2255                 lock_page(page);
2256                 /* split_huge_page() removes page from list on success */
2257                 if (!split_huge_page(page))
2258                         split++;
2259                 unlock_page(page);
2260                 put_page(page);
2261         }
2262
2263         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2264         list_splice_tail(&list, &pgdata->split_queue);
2265         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2266
2267         /*
2268          * Stop shrinker if we didn't split any page, but the queue is empty.
2269          * This can happen if pages were freed under us.
2270          */
2271         if (!split && list_empty(&pgdata->split_queue))
2272                 return SHRINK_STOP;
2273         return split;
2274 }
2275
2276 static struct shrinker deferred_split_shrinker = {
2277         .count_objects = deferred_split_count,
2278         .scan_objects = deferred_split_scan,
2279         .seeks = DEFAULT_SEEKS,
2280         .flags = SHRINKER_NUMA_AWARE,
2281 };
2282
2283 #ifdef CONFIG_DEBUG_FS
2284 static int split_huge_pages_set(void *data, u64 val)
2285 {
2286         struct zone *zone;
2287         struct page *page;
2288         unsigned long pfn, max_zone_pfn;
2289         unsigned long total = 0, split = 0;
2290
2291         if (val != 1)
2292                 return -EINVAL;
2293
2294         for_each_populated_zone(zone) {
2295                 max_zone_pfn = zone_end_pfn(zone);
2296                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2297                         if (!pfn_valid(pfn))
2298                                 continue;
2299
2300                         page = pfn_to_page(pfn);
2301                         if (!get_page_unless_zero(page))
2302                                 continue;
2303
2304                         if (zone != page_zone(page))
2305                                 goto next;
2306
2307                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2308                                 goto next;
2309
2310                         total++;
2311                         lock_page(page);
2312                         if (!split_huge_page(page))
2313                                 split++;
2314                         unlock_page(page);
2315 next:
2316                         put_page(page);
2317                 }
2318         }
2319
2320         pr_info("%lu of %lu THP split\n", split, total);
2321
2322         return 0;
2323 }
2324 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2325                 "%llu\n");
2326
2327 static int __init split_huge_pages_debugfs(void)
2328 {
2329         void *ret;
2330
2331         ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2332                         &split_huge_pages_fops);
2333         if (!ret)
2334                 pr_warn("Failed to create split_huge_pages in debugfs");
2335         return 0;
2336 }
2337 late_initcall(split_huge_pages_debugfs);
2338 #endif