mm/huge_memory.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  Copyright (C) 2009  Red Hat, Inc.
   4  */
   5
   6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   7
   8 #include <linux/mm.h>
   9 #include <linux/sched.h>
  10 #include <linux/sched/mm.h>
  11 #include <linux/sched/coredump.h>
  12 #include <linux/sched/numa_balancing.h>
  13 #include <linux/highmem.h>
  14 #include <linux/hugetlb.h>
  15 #include <linux/mmu_notifier.h>
  16 #include <linux/rmap.h>
  17 #include <linux/swap.h>
  18 #include <linux/shrinker.h>
  19 #include <linux/mm_inline.h>
  20 #include <linux/swapops.h>
  21 #include <linux/dax.h>
  22 #include <linux/khugepaged.h>
  23 #include <linux/freezer.h>
  24 #include <linux/pfn_t.h>
  25 #include <linux/mman.h>
  26 #include <linux/memremap.h>
  27 #include <linux/pagemap.h>
  28 #include <linux/debugfs.h>
  29 #include <linux/migrate.h>
  30 #include <linux/hashtable.h>
  31 #include <linux/userfaultfd_k.h>
  32 #include <linux/page_idle.h>
  33 #include <linux/shmem_fs.h>
  34 #include <linux/oom.h>
  35 #include <linux/numa.h>
  36 #include <linux/page_owner.h>
  37 #include <linux/sched/sysctl.h>
  38
  39 #include <asm/tlb.h>
  40 #include <asm/pgalloc.h>
  41 #include "internal.h"
  42 #include "swap.h"
  43
  44 #define CREATE_TRACE_POINTS
  45 #include <trace/events/thp.h>
  46
  47 /*
  48  * By default, transparent hugepage support is disabled in order to avoid
  49  * risking an increased memory footprint for applications that are not
  50  * guaranteed to benefit from it. When transparent hugepage support is
  51  * enabled, it is for all mappings, and khugepaged scans all mappings.
  52  * Defrag is invoked by khugepaged hugepage allocations and by page faults
  53  * for all hugepage allocations.
  54  */
  55 unsigned long transparent_hugepage_flags __read_mostly =
  56 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  57         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  58 #endif
  59 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  60         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  61 #endif
  62         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
  63         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
  64         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
  65
  66 static struct shrinker deferred_split_shrinker;
  67
  68 static atomic_t huge_zero_refcount;
  69 struct page *huge_zero_page __read_mostly;
  70 unsigned long huge_zero_pfn __read_mostly = ~0UL;
  71
  72 bool transparent_hugepage_active(struct vm_area_struct *vma)
  73 {
  74         /* The addr is used to check if the vma size fits */
  75         unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE;
  76
  77         if (!transhuge_vma_suitable(vma, addr))
  78                 return false;
  79         if (vma_is_anonymous(vma))
  80                 return __transparent_hugepage_enabled(vma);
  81         if (vma_is_shmem(vma))
  82                 return shmem_huge_enabled(vma);
  83         if (transhuge_vma_enabled(vma, vma->vm_flags) && file_thp_enabled(vma))
  84                 return true;
  85
  86         return false;
  87 }
  88
  89 static bool get_huge_zero_page(void)
  90 {
  91         struct page *zero_page;
  92 retry:
  93         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
  94                 return true;
  95
  96         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
  97                         HPAGE_PMD_ORDER);
  98         if (!zero_page) {
  99                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
 100                 return false;
 101         }
 102         count_vm_event(THP_ZERO_PAGE_ALLOC);
 103         preempt_disable();
 104         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
 105                 preempt_enable();
 106                 __free_pages(zero_page, compound_order(zero_page));
 107                 goto retry;
 108         }
 109         WRITE_ONCE(huge_zero_pfn, page_to_pfn(zero_page));
 110
 111         /* We take additional reference here. It will be put back by shrinker */
 112         atomic_set(&huge_zero_refcount, 2);
 113         preempt_enable();
 114         return true;
 115 }
 116
 117 static void put_huge_zero_page(void)
 118 {
 119         /*
 120          * Counter should never go to zero here. Only shrinker can put
 121          * last reference.
 122          */
 123         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
 124 }
 125
 126 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
 127 {
 128         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 129                 return READ_ONCE(huge_zero_page);
 130
 131         if (!get_huge_zero_page())
 132                 return NULL;
 133
 134         if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 135                 put_huge_zero_page();
 136
 137         return READ_ONCE(huge_zero_page);
 138 }
 139
 140 void mm_put_huge_zero_page(struct mm_struct *mm)
 141 {
 142         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 143                 put_huge_zero_page();
 144 }
 145
 146 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
 147                                         struct shrink_control *sc)
 148 {
 149         /* we can free zero page only if last reference remains */
 150         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 151 }
 152
 153 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 154                                        struct shrink_control *sc)
 155 {
 156         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 157                 struct page *zero_page = xchg(&huge_zero_page, NULL);
 158                 BUG_ON(zero_page == NULL);
 159                 WRITE_ONCE(huge_zero_pfn, ~0UL);
 160                 __free_pages(zero_page, compound_order(zero_page));
 161                 return HPAGE_PMD_NR;
 162         }
 163
 164         return 0;
 165 }
 166
 167 static struct shrinker huge_zero_page_shrinker = {
 168         .count_objects = shrink_huge_zero_page_count,
 169         .scan_objects = shrink_huge_zero_page_scan,
 170         .seeks = DEFAULT_SEEKS,
 171 };
 172
 173 #ifdef CONFIG_SYSFS
 174 static ssize_t enabled_show(struct kobject *kobj,
 175                             struct kobj_attribute *attr, char *buf)
 176 {
 177         const char *output;
 178
 179         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
 180                 output = "[always] madvise never";
 181         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 182                           &transparent_hugepage_flags))
 183                 output = "always [madvise] never";
 184         else
 185                 output = "always madvise [never]";
 186
 187         return sysfs_emit(buf, "%s\n", output);
 188 }
 189
 190 static ssize_t enabled_store(struct kobject *kobj,
 191                              struct kobj_attribute *attr,
 192                              const char *buf, size_t count)
 193 {
 194         ssize_t ret = count;
 195
 196         if (sysfs_streq(buf, "always")) {
 197                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 198                 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 199         } else if (sysfs_streq(buf, "madvise")) {
 200                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 201                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 202         } else if (sysfs_streq(buf, "never")) {
 203                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 204                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 205         } else
 206                 ret = -EINVAL;
 207
 208         if (ret > 0) {
 209                 int err = start_stop_khugepaged();
 210                 if (err)
 211                         ret = err;
 212         }
 213         return ret;
 214 }
 215 static struct kobj_attribute enabled_attr =
 216         __ATTR(enabled, 0644, enabled_show, enabled_store);
 217
 218 ssize_t single_hugepage_flag_show(struct kobject *kobj,
 219                                   struct kobj_attribute *attr, char *buf,
 220                                   enum transparent_hugepage_flag flag)
 221 {
 222         return sysfs_emit(buf, "%d\n",
 223                           !!test_bit(flag, &transparent_hugepage_flags));
 224 }
 225
 226 ssize_t single_hugepage_flag_store(struct kobject *kobj,
 227                                  struct kobj_attribute *attr,
 228                                  const char *buf, size_t count,
 229                                  enum transparent_hugepage_flag flag)
 230 {
 231         unsigned long value;
 232         int ret;
 233
 234         ret = kstrtoul(buf, 10, &value);
 235         if (ret < 0)
 236                 return ret;
 237         if (value > 1)
 238                 return -EINVAL;
 239
 240         if (value)
 241                 set_bit(flag, &transparent_hugepage_flags);
 242         else
 243                 clear_bit(flag, &transparent_hugepage_flags);
 244
 245         return count;
 246 }
 247
 248 static ssize_t defrag_show(struct kobject *kobj,
 249                            struct kobj_attribute *attr, char *buf)
 250 {
 251         const char *output;
 252
 253         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
 254                      &transparent_hugepage_flags))
 255                 output = "[always] defer defer+madvise madvise never";
 256         else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
 257                           &transparent_hugepage_flags))
 258                 output = "always [defer] defer+madvise madvise never";
 259         else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG,
 260                           &transparent_hugepage_flags))
 261                 output = "always defer [defer+madvise] madvise never";
 262         else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
 263                           &transparent_hugepage_flags))
 264                 output = "always defer defer+madvise [madvise] never";
 265         else
 266                 output = "always defer defer+madvise madvise [never]";
 267
 268         return sysfs_emit(buf, "%s\n", output);
 269 }
 270
 271 static ssize_t defrag_store(struct kobject *kobj,
 272                             struct kobj_attribute *attr,
 273                             const char *buf, size_t count)
 274 {
 275         if (sysfs_streq(buf, "always")) {
 276                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 277                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 278                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 279                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 280         } else if (sysfs_streq(buf, "defer+madvise")) {
 281                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 282                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 283                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 284                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 285         } else if (sysfs_streq(buf, "defer")) {
 286                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 287                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 288                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 289                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 290         } else if (sysfs_streq(buf, "madvise")) {
 291                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 292                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 293                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 294                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 295         } else if (sysfs_streq(buf, "never")) {
 296                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 297                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 298                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 299                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 300         } else
 301                 return -EINVAL;
 302
 303         return count;
 304 }
 305 static struct kobj_attribute defrag_attr =
 306         __ATTR(defrag, 0644, defrag_show, defrag_store);
 307
 308 static ssize_t use_zero_page_show(struct kobject *kobj,
 309                                   struct kobj_attribute *attr, char *buf)
 310 {
 311         return single_hugepage_flag_show(kobj, attr, buf,
 312                                          TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 313 }
 314 static ssize_t use_zero_page_store(struct kobject *kobj,
 315                 struct kobj_attribute *attr, const char *buf, size_t count)
 316 {
 317         return single_hugepage_flag_store(kobj, attr, buf, count,
 318                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 319 }
 320 static struct kobj_attribute use_zero_page_attr =
 321         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 322
 323 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
 324                                    struct kobj_attribute *attr, char *buf)
 325 {
 326         return sysfs_emit(buf, "%lu\n", HPAGE_PMD_SIZE);
 327 }
 328 static struct kobj_attribute hpage_pmd_size_attr =
 329         __ATTR_RO(hpage_pmd_size);
 330
 331 static struct attribute *hugepage_attr[] = {
 332         &enabled_attr.attr,
 333         &defrag_attr.attr,
 334         &use_zero_page_attr.attr,
 335         &hpage_pmd_size_attr.attr,
 336 #ifdef CONFIG_SHMEM
 337         &shmem_enabled_attr.attr,
 338 #endif
 339         NULL,
 340 };
 341
 342 static const struct attribute_group hugepage_attr_group = {
 343         .attrs = hugepage_attr,
 344 };
 345
 346 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 347 {
 348         int err;
 349
 350         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 351         if (unlikely(!*hugepage_kobj)) {
 352                 pr_err("failed to create transparent hugepage kobject\n");
 353                 return -ENOMEM;
 354         }
 355
 356         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 357         if (err) {
 358                 pr_err("failed to register transparent hugepage group\n");
 359                 goto delete_obj;
 360         }
 361
 362         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 363         if (err) {
 364                 pr_err("failed to register transparent hugepage group\n");
 365                 goto remove_hp_group;
 366         }
 367
 368         return 0;
 369
 370 remove_hp_group:
 371         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 372 delete_obj:
 373         kobject_put(*hugepage_kobj);
 374         return err;
 375 }
 376
 377 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 378 {
 379         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 380         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 381         kobject_put(hugepage_kobj);
 382 }
 383 #else
 384 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 385 {
 386         return 0;
 387 }
 388
 389 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 390 {
 391 }
 392 #endif /* CONFIG_SYSFS */
 393
 394 static int __init hugepage_init(void)
 395 {
 396         int err;
 397         struct kobject *hugepage_kobj;
 398
 399         if (!has_transparent_hugepage()) {
 400                 /*
 401                  * Hardware doesn't support hugepages, hence disable
 402                  * DAX PMD support.
 403                  */
 404                 transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_NEVER_DAX;
 405                 return -EINVAL;
 406         }
 407
 408         /*
 409          * hugepages can't be allocated by the buddy allocator
 410          */
 411         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
 412         /*
 413          * we use page->mapping and page->index in second tail page
 414          * as list_head: assuming THP order >= 2
 415          */
 416         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
 417
 418         err = hugepage_init_sysfs(&hugepage_kobj);
 419         if (err)
 420                 goto err_sysfs;
 421
 422         err = khugepaged_init();
 423         if (err)
 424                 goto err_slab;
 425
 426         err = register_shrinker(&huge_zero_page_shrinker);
 427         if (err)
 428                 goto err_hzp_shrinker;
 429         err = register_shrinker(&deferred_split_shrinker);
 430         if (err)
 431                 goto err_split_shrinker;
 432
 433         /*
 434          * By default disable transparent hugepages on smaller systems,
 435          * where the extra memory used could hurt more than TLB overhead
 436          * is likely to save.  The admin can still enable it through /sys.
 437          */
 438         if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
 439                 transparent_hugepage_flags = 0;
 440                 return 0;
 441         }
 442
 443         err = start_stop_khugepaged();
 444         if (err)
 445                 goto err_khugepaged;
 446
 447         return 0;
 448 err_khugepaged:
 449         unregister_shrinker(&deferred_split_shrinker);
 450 err_split_shrinker:
 451         unregister_shrinker(&huge_zero_page_shrinker);
 452 err_hzp_shrinker:
 453         khugepaged_destroy();
 454 err_slab:
 455         hugepage_exit_sysfs(hugepage_kobj);
 456 err_sysfs:
 457         return err;
 458 }
 459 subsys_initcall(hugepage_init);
 460
 461 static int __init setup_transparent_hugepage(char *str)
 462 {
 463         int ret = 0;
 464         if (!str)
 465                 goto out;
 466         if (!strcmp(str, "always")) {
 467                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 468                         &transparent_hugepage_flags);
 469                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 470                           &transparent_hugepage_flags);
 471                 ret = 1;
 472         } else if (!strcmp(str, "madvise")) {
 473                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 474                           &transparent_hugepage_flags);
 475                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 476                         &transparent_hugepage_flags);
 477                 ret = 1;
 478         } else if (!strcmp(str, "never")) {
 479                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 480                           &transparent_hugepage_flags);
 481                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 482                           &transparent_hugepage_flags);
 483                 ret = 1;
 484         }
 485 out:
 486         if (!ret)
 487                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
 488         return ret;
 489 }
 490 __setup("transparent_hugepage=", setup_transparent_hugepage);
 491
 492 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 493 {
 494         if (likely(vma->vm_flags & VM_WRITE))
 495                 pmd = pmd_mkwrite(pmd);
 496         return pmd;
 497 }
 498
 499 #ifdef CONFIG_MEMCG
 500 static inline struct deferred_split *get_deferred_split_queue(struct page *page)
 501 {
 502         struct mem_cgroup *memcg = page_memcg(compound_head(page));
 503         struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
 504
 505         if (memcg)
 506                 return &memcg->deferred_split_queue;
 507         else
 508                 return &pgdat->deferred_split_queue;
 509 }
 510 #else
 511 static inline struct deferred_split *get_deferred_split_queue(struct page *page)
 512 {
 513         struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
 514
 515         return &pgdat->deferred_split_queue;
 516 }
 517 #endif
 518
 519 void prep_transhuge_page(struct page *page)
 520 {
 521         /*
 522          * we use page->mapping and page->indexlru in second tail page
 523          * as list_head: assuming THP order >= 2
 524          */
 525
 526         INIT_LIST_HEAD(page_deferred_list(page));
 527         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 528 }
 529
 530 static inline bool is_transparent_hugepage(struct page *page)
 531 {
 532         if (!PageCompound(page))
 533                 return false;
 534
 535         page = compound_head(page);
 536         return is_huge_zero_page(page) ||
 537                page[1].compound_dtor == TRANSHUGE_PAGE_DTOR;
 538 }
 539
 540 static unsigned long __thp_get_unmapped_area(struct file *filp,
 541                 unsigned long addr, unsigned long len,
 542                 loff_t off, unsigned long flags, unsigned long size)
 543 {
 544         loff_t off_end = off + len;
 545         loff_t off_align = round_up(off, size);
 546         unsigned long len_pad, ret;
 547
 548         if (off_end <= off_align || (off_end - off_align) < size)
 549                 return 0;
 550
 551         len_pad = len + size;
 552         if (len_pad < len || (off + len_pad) < off)
 553                 return 0;
 554
 555         ret = current->mm->get_unmapped_area(filp, addr, len_pad,
 556                                               off >> PAGE_SHIFT, flags);
 557
 558         /*
 559          * The failure might be due to length padding. The caller will retry
 560          * without the padding.
 561          */
 562         if (IS_ERR_VALUE(ret))
 563                 return 0;
 564
 565         /*
 566          * Do not try to align to THP boundary if allocation at the address
 567          * hint succeeds.
 568          */
 569         if (ret == addr)
 570                 return addr;
 571
 572         ret += (off - ret) & (size - 1);
 573         return ret;
 574 }
 575
 576 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 577                 unsigned long len, unsigned long pgoff, unsigned long flags)
 578 {
 579         unsigned long ret;
 580         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 581
 582         ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE);
 583         if (ret)
 584                 return ret;
 585
 586         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 587 }
 588 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 589
 590 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
 591                         struct page *page, gfp_t gfp)
 592 {
 593         struct vm_area_struct *vma = vmf->vma;
 594         pgtable_t pgtable;
 595         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 596         vm_fault_t ret = 0;
 597
 598         VM_BUG_ON_PAGE(!PageCompound(page), page);
 599
 600         if (mem_cgroup_charge(page_folio(page), vma->vm_mm, gfp)) {
 601                 put_page(page);
 602                 count_vm_event(THP_FAULT_FALLBACK);
 603                 count_vm_event(THP_FAULT_FALLBACK_CHARGE);
 604                 return VM_FAULT_FALLBACK;
 605         }
 606         cgroup_throttle_swaprate(page, gfp);
 607
 608         pgtable = pte_alloc_one(vma->vm_mm);
 609         if (unlikely(!pgtable)) {
 610                 ret = VM_FAULT_OOM;
 611                 goto release;
 612         }
 613
 614         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
 615         /*
 616          * The memory barrier inside __SetPageUptodate makes sure that
 617          * clear_huge_page writes become visible before the set_pmd_at()
 618          * write.
 619          */
 620         __SetPageUptodate(page);
 621
 622         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 623         if (unlikely(!pmd_none(*vmf->pmd))) {
 624                 goto unlock_release;
 625         } else {
 626                 pmd_t entry;
 627
 628                 ret = check_stable_address_space(vma->vm_mm);
 629                 if (ret)
 630                         goto unlock_release;
 631
 632                 /* Deliver the page fault to userland */
 633                 if (userfaultfd_missing(vma)) {
 634                         spin_unlock(vmf->ptl);
 635                         put_page(page);
 636                         pte_free(vma->vm_mm, pgtable);
 637                         ret = handle_userfault(vmf, VM_UFFD_MISSING);
 638                         VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 639                         return ret;
 640                 }
 641
 642                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 643                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 644                 page_add_new_anon_rmap(page, vma, haddr);
 645                 lru_cache_add_inactive_or_unevictable(page, vma);
 646                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 647                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 648                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
 649                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 650                 mm_inc_nr_ptes(vma->vm_mm);
 651                 spin_unlock(vmf->ptl);
 652                 count_vm_event(THP_FAULT_ALLOC);
 653                 count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC);
 654         }
 655
 656         return 0;
 657 unlock_release:
 658         spin_unlock(vmf->ptl);
 659 release:
 660         if (pgtable)
 661                 pte_free(vma->vm_mm, pgtable);
 662         put_page(page);
 663         return ret;
 664
 665 }
 666
 667 /*
 668  * always: directly stall for all thp allocations
 669  * defer: wake kswapd and fail if not immediately available
 670  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
 671  *                fail if not immediately available
 672  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
 673  *          available
 674  * never: never stall for any thp allocation
 675  */
 676 gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma)
 677 {
 678         const bool vma_madvised = vma && (vma->vm_flags & VM_HUGEPAGE);
 679
 680         /* Always do synchronous compaction */
 681         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 682                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
 683
 684         /* Kick kcompactd and fail quickly */
 685         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 686                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
 687
 688         /* Synchronous compaction if madvised, otherwise kick kcompactd */
 689         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 690                 return GFP_TRANSHUGE_LIGHT |
 691                         (vma_madvised ? __GFP_DIRECT_RECLAIM :
 692                                         __GFP_KSWAPD_RECLAIM);
 693
 694         /* Only do synchronous compaction if madvised */
 695         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 696                 return GFP_TRANSHUGE_LIGHT |
 697                        (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
 698
 699         return GFP_TRANSHUGE_LIGHT;
 700 }
 701
 702 /* Caller must hold page table lock. */
 703 static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 704                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 705                 struct page *zero_page)
 706 {
 707         pmd_t entry;
 708         if (!pmd_none(*pmd))
 709                 return;
 710         entry = mk_pmd(zero_page, vma->vm_page_prot);
 711         entry = pmd_mkhuge(entry);
 712         if (pgtable)
 713                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 714         set_pmd_at(mm, haddr, pmd, entry);
 715         mm_inc_nr_ptes(mm);
 716 }
 717
 718 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 719 {
 720         struct vm_area_struct *vma = vmf->vma;
 721         gfp_t gfp;
 722         struct folio *folio;
 723         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 724
 725         if (!transhuge_vma_suitable(vma, haddr))
 726                 return VM_FAULT_FALLBACK;
 727         if (unlikely(anon_vma_prepare(vma)))
 728                 return VM_FAULT_OOM;
 729         khugepaged_enter(vma, vma->vm_flags);
 730
 731         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
 732                         !mm_forbids_zeropage(vma->vm_mm) &&
 733                         transparent_hugepage_use_zero_page()) {
 734                 pgtable_t pgtable;
 735                 struct page *zero_page;
 736                 vm_fault_t ret;
 737                 pgtable = pte_alloc_one(vma->vm_mm);
 738                 if (unlikely(!pgtable))
 739                         return VM_FAULT_OOM;
 740                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
 741                 if (unlikely(!zero_page)) {
 742                         pte_free(vma->vm_mm, pgtable);
 743                         count_vm_event(THP_FAULT_FALLBACK);
 744                         return VM_FAULT_FALLBACK;
 745                 }
 746                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 747                 ret = 0;
 748                 if (pmd_none(*vmf->pmd)) {
 749                         ret = check_stable_address_space(vma->vm_mm);
 750                         if (ret) {
 751                                 spin_unlock(vmf->ptl);
 752                                 pte_free(vma->vm_mm, pgtable);
 753                         } else if (userfaultfd_missing(vma)) {
 754                                 spin_unlock(vmf->ptl);
 755                                 pte_free(vma->vm_mm, pgtable);
 756                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
 757                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 758                         } else {
 759                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
 760                                                    haddr, vmf->pmd, zero_page);
 761                                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
 762                                 spin_unlock(vmf->ptl);
 763                         }
 764                 } else {
 765                         spin_unlock(vmf->ptl);
 766                         pte_free(vma->vm_mm, pgtable);
 767                 }
 768                 return ret;
 769         }
 770         gfp = vma_thp_gfp_mask(vma);
 771         folio = vma_alloc_folio(gfp, HPAGE_PMD_ORDER, vma, haddr, true);
 772         if (unlikely(!folio)) {
 773                 count_vm_event(THP_FAULT_FALLBACK);
 774                 return VM_FAULT_FALLBACK;
 775         }
 776         return __do_huge_pmd_anonymous_page(vmf, &folio->page, gfp);
 777 }
 778
 779 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 780                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
 781                 pgtable_t pgtable)
 782 {
 783         struct mm_struct *mm = vma->vm_mm;
 784         pmd_t entry;
 785         spinlock_t *ptl;
 786
 787         ptl = pmd_lock(mm, pmd);
 788         if (!pmd_none(*pmd)) {
 789                 if (write) {
 790                         if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
 791                                 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
 792                                 goto out_unlock;
 793                         }
 794                         entry = pmd_mkyoung(*pmd);
 795                         entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 796                         if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
 797                                 update_mmu_cache_pmd(vma, addr, pmd);
 798                 }
 799
 800                 goto out_unlock;
 801         }
 802
 803         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 804         if (pfn_t_devmap(pfn))
 805                 entry = pmd_mkdevmap(entry);
 806         if (write) {
 807                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 808                 entry = maybe_pmd_mkwrite(entry, vma);
 809         }
 810
 811         if (pgtable) {
 812                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 813                 mm_inc_nr_ptes(mm);
 814                 pgtable = NULL;
 815         }
 816
 817         set_pmd_at(mm, addr, pmd, entry);
 818         update_mmu_cache_pmd(vma, addr, pmd);
 819
 820 out_unlock:
 821         spin_unlock(ptl);
 822         if (pgtable)
 823                 pte_free(mm, pgtable);
 824 }
 825
 826 /**
 827  * vmf_insert_pfn_pmd_prot - insert a pmd size pfn
 828  * @vmf: Structure describing the fault
 829  * @pfn: pfn to insert
 830  * @pgprot: page protection to use
 831  * @write: whether it's a write fault
 832  *
 833  * Insert a pmd size pfn. See vmf_insert_pfn() for additional info and
 834  * also consult the vmf_insert_mixed_prot() documentation when
 835  * @pgprot != @vmf->vma->vm_page_prot.
 836  *
 837  * Return: vm_fault_t value.
 838  */
 839 vm_fault_t vmf_insert_pfn_pmd_prot(struct vm_fault *vmf, pfn_t pfn,
 840                                    pgprot_t pgprot, bool write)
 841 {
 842         unsigned long addr = vmf->address & PMD_MASK;
 843         struct vm_area_struct *vma = vmf->vma;
 844         pgtable_t pgtable = NULL;
 845
 846         /*
 847          * If we had pmd_special, we could avoid all these restrictions,
 848          * but we need to be consistent with PTEs and architectures that
 849          * can't support a 'special' bit.
 850          */
 851         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 852                         !pfn_t_devmap(pfn));
 853         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 854                                                 (VM_PFNMAP|VM_MIXEDMAP));
 855         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 856
 857         if (addr < vma->vm_start || addr >= vma->vm_end)
 858                 return VM_FAULT_SIGBUS;
 859
 860         if (arch_needs_pgtable_deposit()) {
 861                 pgtable = pte_alloc_one(vma->vm_mm);
 862                 if (!pgtable)
 863                         return VM_FAULT_OOM;
 864         }
 865
 866         track_pfn_insert(vma, &pgprot, pfn);
 867
 868         insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
 869         return VM_FAULT_NOPAGE;
 870 }
 871 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd_prot);
 872
 873 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 874 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 875 {
 876         if (likely(vma->vm_flags & VM_WRITE))
 877                 pud = pud_mkwrite(pud);
 878         return pud;
 879 }
 880
 881 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 882                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 883 {
 884         struct mm_struct *mm = vma->vm_mm;
 885         pud_t entry;
 886         spinlock_t *ptl;
 887
 888         ptl = pud_lock(mm, pud);
 889         if (!pud_none(*pud)) {
 890                 if (write) {
 891                         if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
 892                                 WARN_ON_ONCE(!is_huge_zero_pud(*pud));
 893                                 goto out_unlock;
 894                         }
 895                         entry = pud_mkyoung(*pud);
 896                         entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
 897                         if (pudp_set_access_flags(vma, addr, pud, entry, 1))
 898                                 update_mmu_cache_pud(vma, addr, pud);
 899                 }
 900                 goto out_unlock;
 901         }
 902
 903         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
 904         if (pfn_t_devmap(pfn))
 905                 entry = pud_mkdevmap(entry);
 906         if (write) {
 907                 entry = pud_mkyoung(pud_mkdirty(entry));
 908                 entry = maybe_pud_mkwrite(entry, vma);
 909         }
 910         set_pud_at(mm, addr, pud, entry);
 911         update_mmu_cache_pud(vma, addr, pud);
 912
 913 out_unlock:
 914         spin_unlock(ptl);
 915 }
 916
 917 /**
 918  * vmf_insert_pfn_pud_prot - insert a pud size pfn
 919  * @vmf: Structure describing the fault
 920  * @pfn: pfn to insert
 921  * @pgprot: page protection to use
 922  * @write: whether it's a write fault
 923  *
 924  * Insert a pud size pfn. See vmf_insert_pfn() for additional info and
 925  * also consult the vmf_insert_mixed_prot() documentation when
 926  * @pgprot != @vmf->vma->vm_page_prot.
 927  *
 928  * Return: vm_fault_t value.
 929  */
 930 vm_fault_t vmf_insert_pfn_pud_prot(struct vm_fault *vmf, pfn_t pfn,
 931                                    pgprot_t pgprot, bool write)
 932 {
 933         unsigned long addr = vmf->address & PUD_MASK;
 934         struct vm_area_struct *vma = vmf->vma;
 935
 936         /*
 937          * If we had pud_special, we could avoid all these restrictions,
 938          * but we need to be consistent with PTEs and architectures that
 939          * can't support a 'special' bit.
 940          */
 941         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 942                         !pfn_t_devmap(pfn));
 943         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 944                                                 (VM_PFNMAP|VM_MIXEDMAP));
 945         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 946
 947         if (addr < vma->vm_start || addr >= vma->vm_end)
 948                 return VM_FAULT_SIGBUS;
 949
 950         track_pfn_insert(vma, &pgprot, pfn);
 951
 952         insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
 953         return VM_FAULT_NOPAGE;
 954 }
 955 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud_prot);
 956 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 957
 958 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
 959                 pmd_t *pmd, int flags)
 960 {
 961         pmd_t _pmd;
 962
 963         _pmd = pmd_mkyoung(*pmd);
 964         if (flags & FOLL_WRITE)
 965                 _pmd = pmd_mkdirty(_pmd);
 966         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 967                                 pmd, _pmd, flags & FOLL_WRITE))
 968                 update_mmu_cache_pmd(vma, addr, pmd);
 969 }
 970
 971 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 972                 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
 973 {
 974         unsigned long pfn = pmd_pfn(*pmd);
 975         struct mm_struct *mm = vma->vm_mm;
 976         struct page *page;
 977
 978         assert_spin_locked(pmd_lockptr(mm, pmd));
 979
 980         /*
 981          * When we COW a devmap PMD entry, we split it into PTEs, so we should
 982          * not be in this function with `flags & FOLL_COW` set.
 983          */
 984         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
 985
 986         /* FOLL_GET and FOLL_PIN are mutually exclusive. */
 987         if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
 988                          (FOLL_PIN | FOLL_GET)))
 989                 return NULL;
 990
 991         if (flags & FOLL_WRITE && !pmd_write(*pmd))
 992                 return NULL;
 993
 994         if (pmd_present(*pmd) && pmd_devmap(*pmd))
 995                 /* pass */;
 996         else
 997                 return NULL;
 998
 999         if (flags & FOLL_TOUCH)
1000                 touch_pmd(vma, addr, pmd, flags);
1001
1002         /*
1003          * device mapped pages can only be returned if the
1004          * caller will manage the page reference count.
1005          */
1006         if (!(flags & (FOLL_GET | FOLL_PIN)))
1007                 return ERR_PTR(-EEXIST);
1008
1009         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1010         *pgmap = get_dev_pagemap(pfn, *pgmap);
1011         if (!*pgmap)
1012                 return ERR_PTR(-EFAULT);
1013         page = pfn_to_page(pfn);
1014         if (!try_grab_page(page, flags))
1015                 page = ERR_PTR(-ENOMEM);
1016
1017         return page;
1018 }
1019
1020 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1021                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1022                   struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma)
1023 {
1024         spinlock_t *dst_ptl, *src_ptl;
1025         struct page *src_page;
1026         pmd_t pmd;
1027         pgtable_t pgtable = NULL;
1028         int ret = -ENOMEM;
1029
1030         /* Skip if can be re-fill on fault */
1031         if (!vma_is_anonymous(dst_vma))
1032                 return 0;
1033
1034         pgtable = pte_alloc_one(dst_mm);
1035         if (unlikely(!pgtable))
1036                 goto out;
1037
1038         dst_ptl = pmd_lock(dst_mm, dst_pmd);
1039         src_ptl = pmd_lockptr(src_mm, src_pmd);
1040         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1041
1042         ret = -EAGAIN;
1043         pmd = *src_pmd;
1044
1045 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1046         if (unlikely(is_swap_pmd(pmd))) {
1047                 swp_entry_t entry = pmd_to_swp_entry(pmd);
1048
1049                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
1050                 if (!is_readable_migration_entry(entry)) {
1051                         entry = make_readable_migration_entry(
1052                                                         swp_offset(entry));
1053                         pmd = swp_entry_to_pmd(entry);
1054                         if (pmd_swp_soft_dirty(*src_pmd))
1055                                 pmd = pmd_swp_mksoft_dirty(pmd);
1056                         if (pmd_swp_uffd_wp(*src_pmd))
1057                                 pmd = pmd_swp_mkuffd_wp(pmd);
1058                         set_pmd_at(src_mm, addr, src_pmd, pmd);
1059                 }
1060                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1061                 mm_inc_nr_ptes(dst_mm);
1062                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1063                 if (!userfaultfd_wp(dst_vma))
1064                         pmd = pmd_swp_clear_uffd_wp(pmd);
1065                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1066                 ret = 0;
1067                 goto out_unlock;
1068         }
1069 #endif
1070
1071         if (unlikely(!pmd_trans_huge(pmd))) {
1072                 pte_free(dst_mm, pgtable);
1073                 goto out_unlock;
1074         }
1075         /*
1076          * When page table lock is held, the huge zero pmd should not be
1077          * under splitting since we don't split the page itself, only pmd to
1078          * a page table.
1079          */
1080         if (is_huge_zero_pmd(pmd)) {
1081                 /*
1082                  * get_huge_zero_page() will never allocate a new page here,
1083                  * since we already have a zero page to copy. It just takes a
1084                  * reference.
1085                  */
1086                 mm_get_huge_zero_page(dst_mm);
1087                 goto out_zero_page;
1088         }
1089
1090         src_page = pmd_page(pmd);
1091         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1092
1093         get_page(src_page);
1094         if (unlikely(page_try_dup_anon_rmap(src_page, true, src_vma))) {
1095                 /* Page maybe pinned: split and retry the fault on PTEs. */
1096                 put_page(src_page);
1097                 pte_free(dst_mm, pgtable);
1098                 spin_unlock(src_ptl);
1099                 spin_unlock(dst_ptl);
1100                 __split_huge_pmd(src_vma, src_pmd, addr, false, NULL);
1101                 return -EAGAIN;
1102         }
1103         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1104 out_zero_page:
1105         mm_inc_nr_ptes(dst_mm);
1106         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1107         pmdp_set_wrprotect(src_mm, addr, src_pmd);
1108         if (!userfaultfd_wp(dst_vma))
1109                 pmd = pmd_clear_uffd_wp(pmd);
1110         pmd = pmd_mkold(pmd_wrprotect(pmd));
1111         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1112
1113         ret = 0;
1114 out_unlock:
1115         spin_unlock(src_ptl);
1116         spin_unlock(dst_ptl);
1117 out:
1118         return ret;
1119 }
1120
1121 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1122 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1123                 pud_t *pud, int flags)
1124 {
1125         pud_t _pud;
1126
1127         _pud = pud_mkyoung(*pud);
1128         if (flags & FOLL_WRITE)
1129                 _pud = pud_mkdirty(_pud);
1130         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1131                                 pud, _pud, flags & FOLL_WRITE))
1132                 update_mmu_cache_pud(vma, addr, pud);
1133 }
1134
1135 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1136                 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1137 {
1138         unsigned long pfn = pud_pfn(*pud);
1139         struct mm_struct *mm = vma->vm_mm;
1140         struct page *page;
1141
1142         assert_spin_locked(pud_lockptr(mm, pud));
1143
1144         if (flags & FOLL_WRITE && !pud_write(*pud))
1145                 return NULL;
1146
1147         /* FOLL_GET and FOLL_PIN are mutually exclusive. */
1148         if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
1149                          (FOLL_PIN | FOLL_GET)))
1150                 return NULL;
1151
1152         if (pud_present(*pud) && pud_devmap(*pud))
1153                 /* pass */;
1154         else
1155                 return NULL;
1156
1157         if (flags & FOLL_TOUCH)
1158                 touch_pud(vma, addr, pud, flags);
1159
1160         /*
1161          * device mapped pages can only be returned if the
1162          * caller will manage the page reference count.
1163          *
1164          * At least one of FOLL_GET | FOLL_PIN must be set, so assert that here:
1165          */
1166         if (!(flags & (FOLL_GET | FOLL_PIN)))
1167                 return ERR_PTR(-EEXIST);
1168
1169         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1170         *pgmap = get_dev_pagemap(pfn, *pgmap);
1171         if (!*pgmap)
1172                 return ERR_PTR(-EFAULT);
1173         page = pfn_to_page(pfn);
1174         if (!try_grab_page(page, flags))
1175                 page = ERR_PTR(-ENOMEM);
1176
1177         return page;
1178 }
1179
1180 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1181                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1182                   struct vm_area_struct *vma)
1183 {
1184         spinlock_t *dst_ptl, *src_ptl;
1185         pud_t pud;
1186         int ret;
1187
1188         dst_ptl = pud_lock(dst_mm, dst_pud);
1189         src_ptl = pud_lockptr(src_mm, src_pud);
1190         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1191
1192         ret = -EAGAIN;
1193         pud = *src_pud;
1194         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1195                 goto out_unlock;
1196
1197         /*
1198          * When page table lock is held, the huge zero pud should not be
1199          * under splitting since we don't split the page itself, only pud to
1200          * a page table.
1201          */
1202         if (is_huge_zero_pud(pud)) {
1203                 /* No huge zero pud yet */
1204         }
1205
1206         /*
1207          * TODO: once we support anonymous pages, use page_try_dup_anon_rmap()
1208          * and split if duplicating fails.
1209          */
1210         pudp_set_wrprotect(src_mm, addr, src_pud);
1211         pud = pud_mkold(pud_wrprotect(pud));
1212         set_pud_at(dst_mm, addr, dst_pud, pud);
1213
1214         ret = 0;
1215 out_unlock:
1216         spin_unlock(src_ptl);
1217         spin_unlock(dst_ptl);
1218         return ret;
1219 }
1220
1221 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1222 {
1223         pud_t entry;
1224         unsigned long haddr;
1225         bool write = vmf->flags & FAULT_FLAG_WRITE;
1226
1227         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1228         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1229                 goto unlock;
1230
1231         entry = pud_mkyoung(orig_pud);
1232         if (write)
1233                 entry = pud_mkdirty(entry);
1234         haddr = vmf->address & HPAGE_PUD_MASK;
1235         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1236                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1237
1238 unlock:
1239         spin_unlock(vmf->ptl);
1240 }
1241 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1242
1243 void huge_pmd_set_accessed(struct vm_fault *vmf)
1244 {
1245         pmd_t entry;
1246         unsigned long haddr;
1247         bool write = vmf->flags & FAULT_FLAG_WRITE;
1248         pmd_t orig_pmd = vmf->orig_pmd;
1249
1250         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1251         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1252                 goto unlock;
1253
1254         entry = pmd_mkyoung(orig_pmd);
1255         if (write)
1256                 entry = pmd_mkdirty(entry);
1257         haddr = vmf->address & HPAGE_PMD_MASK;
1258         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1259                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1260
1261 unlock:
1262         spin_unlock(vmf->ptl);
1263 }
1264
1265 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
1266 {
1267         const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
1268         struct vm_area_struct *vma = vmf->vma;
1269         struct page *page;
1270         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1271         pmd_t orig_pmd = vmf->orig_pmd;
1272
1273         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1274         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1275
1276         VM_BUG_ON(unshare && (vmf->flags & FAULT_FLAG_WRITE));
1277         VM_BUG_ON(!unshare && !(vmf->flags & FAULT_FLAG_WRITE));
1278
1279         if (is_huge_zero_pmd(orig_pmd))
1280                 goto fallback;
1281
1282         spin_lock(vmf->ptl);
1283
1284         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1285                 spin_unlock(vmf->ptl);
1286                 return 0;
1287         }
1288
1289         page = pmd_page(orig_pmd);
1290         VM_BUG_ON_PAGE(!PageHead(page), page);
1291
1292         /* Early check when only holding the PT lock. */
1293         if (PageAnonExclusive(page))
1294                 goto reuse;
1295
1296         if (!trylock_page(page)) {
1297                 get_page(page);
1298                 spin_unlock(vmf->ptl);
1299                 lock_page(page);
1300                 spin_lock(vmf->ptl);
1301                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1302                         spin_unlock(vmf->ptl);
1303                         unlock_page(page);
1304                         put_page(page);
1305                         return 0;
1306                 }
1307                 put_page(page);
1308         }
1309
1310         /* Recheck after temporarily dropping the PT lock. */
1311         if (PageAnonExclusive(page)) {
1312                 unlock_page(page);
1313                 goto reuse;
1314         }
1315
1316         /*
1317          * See do_wp_page(): we can only reuse the page exclusively if there are
1318          * no additional references. Note that we always drain the LRU
1319          * pagevecs immediately after adding a THP.
1320          */
1321         if (page_count(page) > 1 + PageSwapCache(page) * thp_nr_pages(page))
1322                 goto unlock_fallback;
1323         if (PageSwapCache(page))
1324                 try_to_free_swap(page);
1325         if (page_count(page) == 1) {
1326                 pmd_t entry;
1327
1328                 page_move_anon_rmap(page, vma);
1329                 unlock_page(page);
1330 reuse:
1331                 if (unlikely(unshare)) {
1332                         spin_unlock(vmf->ptl);
1333                         return 0;
1334                 }
1335                 entry = pmd_mkyoung(orig_pmd);
1336                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1337                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1))
1338                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1339                 spin_unlock(vmf->ptl);
1340                 return VM_FAULT_WRITE;
1341         }
1342
1343 unlock_fallback:
1344         unlock_page(page);
1345         spin_unlock(vmf->ptl);
1346 fallback:
1347         __split_huge_pmd(vma, vmf->pmd, vmf->address, false, NULL);
1348         return VM_FAULT_FALLBACK;
1349 }
1350
1351 /*
1352  * FOLL_FORCE can write to even unwritable pmd's, but only
1353  * after we've gone through a COW cycle and they are dirty.
1354  */
1355 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1356 {
1357         return pmd_write(pmd) ||
1358                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1359 }
1360
1361 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1362                                    unsigned long addr,
1363                                    pmd_t *pmd,
1364                                    unsigned int flags)
1365 {
1366         struct mm_struct *mm = vma->vm_mm;
1367         struct page *page = NULL;
1368
1369         assert_spin_locked(pmd_lockptr(mm, pmd));
1370
1371         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1372                 goto out;
1373
1374         /* Avoid dumping huge zero page */
1375         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1376                 return ERR_PTR(-EFAULT);
1377
1378         /* Full NUMA hinting faults to serialise migration in fault paths */
1379         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1380                 goto out;
1381
1382         page = pmd_page(*pmd);
1383         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1384
1385         if (!pmd_write(*pmd) && gup_must_unshare(flags, page))
1386                 return ERR_PTR(-EMLINK);
1387
1388         VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
1389                         !PageAnonExclusive(page), page);
1390
1391         if (!try_grab_page(page, flags))
1392                 return ERR_PTR(-ENOMEM);
1393
1394         if (flags & FOLL_TOUCH)
1395                 touch_pmd(vma, addr, pmd, flags);
1396
1397         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1398         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1399
1400 out:
1401         return page;
1402 }
1403
1404 /* NUMA hinting page fault entry point for trans huge pmds */
1405 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
1406 {
1407         struct vm_area_struct *vma = vmf->vma;
1408         pmd_t oldpmd = vmf->orig_pmd;
1409         pmd_t pmd;
1410         struct page *page;
1411         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1412         int page_nid = NUMA_NO_NODE;
1413         int target_nid, last_cpupid = -1;
1414         bool migrated = false;
1415         bool was_writable = pmd_savedwrite(oldpmd);
1416         int flags = 0;
1417
1418         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1419         if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) {
1420                 spin_unlock(vmf->ptl);
1421                 goto out;
1422         }
1423
1424         pmd = pmd_modify(oldpmd, vma->vm_page_prot);
1425         page = vm_normal_page_pmd(vma, haddr, pmd);
1426         if (!page)
1427                 goto out_map;
1428
1429         /* See similar comment in do_numa_page for explanation */
1430         if (!was_writable)
1431                 flags |= TNF_NO_GROUP;
1432
1433         page_nid = page_to_nid(page);
1434         last_cpupid = page_cpupid_last(page);
1435         target_nid = numa_migrate_prep(page, vma, haddr, page_nid,
1436                                        &flags);
1437
1438         if (target_nid == NUMA_NO_NODE) {
1439                 put_page(page);
1440                 goto out_map;
1441         }
1442
1443         spin_unlock(vmf->ptl);
1444
1445         migrated = migrate_misplaced_page(page, vma, target_nid);
1446         if (migrated) {
1447                 flags |= TNF_MIGRATED;
1448                 page_nid = target_nid;
1449         } else {
1450                 flags |= TNF_MIGRATE_FAIL;
1451                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1452                 if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) {
1453                         spin_unlock(vmf->ptl);
1454                         goto out;
1455                 }
1456                 goto out_map;
1457         }
1458
1459 out:
1460         if (page_nid != NUMA_NO_NODE)
1461                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1462                                 flags);
1463
1464         return 0;
1465
1466 out_map:
1467         /* Restore the PMD */
1468         pmd = pmd_modify(oldpmd, vma->vm_page_prot);
1469         pmd = pmd_mkyoung(pmd);
1470         if (was_writable)
1471                 pmd = pmd_mkwrite(pmd);
1472         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1473         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1474         spin_unlock(vmf->ptl);
1475         goto out;
1476 }
1477
1478 /*
1479  * Return true if we do MADV_FREE successfully on entire pmd page.
1480  * Otherwise, return false.
1481  */
1482 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1483                 pmd_t *pmd, unsigned long addr, unsigned long next)
1484 {
1485         spinlock_t *ptl;
1486         pmd_t orig_pmd;
1487         struct page *page;
1488         struct mm_struct *mm = tlb->mm;
1489         bool ret = false;
1490
1491         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1492
1493         ptl = pmd_trans_huge_lock(pmd, vma);
1494         if (!ptl)
1495                 goto out_unlocked;
1496
1497         orig_pmd = *pmd;
1498         if (is_huge_zero_pmd(orig_pmd))
1499                 goto out;
1500
1501         if (unlikely(!pmd_present(orig_pmd))) {
1502                 VM_BUG_ON(thp_migration_supported() &&
1503                                   !is_pmd_migration_entry(orig_pmd));
1504                 goto out;
1505         }
1506
1507         page = pmd_page(orig_pmd);
1508         /*
1509          * If other processes are mapping this page, we couldn't discard
1510          * the page unless they all do MADV_FREE so let's skip the page.
1511          */
1512         if (total_mapcount(page) != 1)
1513                 goto out;
1514
1515         if (!trylock_page(page))
1516                 goto out;
1517
1518         /*
1519          * If user want to discard part-pages of THP, split it so MADV_FREE
1520          * will deactivate only them.
1521          */
1522         if (next - addr != HPAGE_PMD_SIZE) {
1523                 get_page(page);
1524                 spin_unlock(ptl);
1525                 split_huge_page(page);
1526                 unlock_page(page);
1527                 put_page(page);
1528                 goto out_unlocked;
1529         }
1530
1531         if (PageDirty(page))
1532                 ClearPageDirty(page);
1533         unlock_page(page);
1534
1535         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1536                 pmdp_invalidate(vma, addr, pmd);
1537                 orig_pmd = pmd_mkold(orig_pmd);
1538                 orig_pmd = pmd_mkclean(orig_pmd);
1539
1540                 set_pmd_at(mm, addr, pmd, orig_pmd);
1541                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1542         }
1543
1544         mark_page_lazyfree(page);
1545         ret = true;
1546 out:
1547         spin_unlock(ptl);
1548 out_unlocked:
1549         return ret;
1550 }
1551
1552 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1553 {
1554         pgtable_t pgtable;
1555
1556         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1557         pte_free(mm, pgtable);
1558         mm_dec_nr_ptes(mm);
1559 }
1560
1561 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1562                  pmd_t *pmd, unsigned long addr)
1563 {
1564         pmd_t orig_pmd;
1565         spinlock_t *ptl;
1566
1567         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1568
1569         ptl = __pmd_trans_huge_lock(pmd, vma);
1570         if (!ptl)
1571                 return 0;
1572         /*
1573          * For architectures like ppc64 we look at deposited pgtable
1574          * when calling pmdp_huge_get_and_clear. So do the
1575          * pgtable_trans_huge_withdraw after finishing pmdp related
1576          * operations.
1577          */
1578         orig_pmd = pmdp_huge_get_and_clear_full(vma, addr, pmd,
1579                                                 tlb->fullmm);
1580         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1581         if (vma_is_special_huge(vma)) {
1582                 if (arch_needs_pgtable_deposit())
1583                         zap_deposited_table(tlb->mm, pmd);
1584                 spin_unlock(ptl);
1585         } else if (is_huge_zero_pmd(orig_pmd)) {
1586                 zap_deposited_table(tlb->mm, pmd);
1587                 spin_unlock(ptl);
1588         } else {
1589                 struct page *page = NULL;
1590                 int flush_needed = 1;
1591
1592                 if (pmd_present(orig_pmd)) {
1593                         page = pmd_page(orig_pmd);
1594                         page_remove_rmap(page, vma, true);
1595                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1596                         VM_BUG_ON_PAGE(!PageHead(page), page);
1597                 } else if (thp_migration_supported()) {
1598                         swp_entry_t entry;
1599
1600                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1601                         entry = pmd_to_swp_entry(orig_pmd);
1602                         page = pfn_swap_entry_to_page(entry);
1603                         flush_needed = 0;
1604                 } else
1605                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1606
1607                 if (PageAnon(page)) {
1608                         zap_deposited_table(tlb->mm, pmd);
1609                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1610                 } else {
1611                         if (arch_needs_pgtable_deposit())
1612                                 zap_deposited_table(tlb->mm, pmd);
1613                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1614                 }
1615
1616                 spin_unlock(ptl);
1617                 if (flush_needed)
1618                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1619         }
1620         return 1;
1621 }
1622
1623 #ifndef pmd_move_must_withdraw
1624 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1625                                          spinlock_t *old_pmd_ptl,
1626                                          struct vm_area_struct *vma)
1627 {
1628         /*
1629          * With split pmd lock we also need to move preallocated
1630          * PTE page table if new_pmd is on different PMD page table.
1631          *
1632          * We also don't deposit and withdraw tables for file pages.
1633          */
1634         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1635 }
1636 #endif
1637
1638 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1639 {
1640 #ifdef CONFIG_MEM_SOFT_DIRTY
1641         if (unlikely(is_pmd_migration_entry(pmd)))
1642                 pmd = pmd_swp_mksoft_dirty(pmd);
1643         else if (pmd_present(pmd))
1644                 pmd = pmd_mksoft_dirty(pmd);
1645 #endif
1646         return pmd;
1647 }
1648
1649 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1650                   unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
1651 {
1652         spinlock_t *old_ptl, *new_ptl;
1653         pmd_t pmd;
1654         struct mm_struct *mm = vma->vm_mm;
1655         bool force_flush = false;
1656
1657         /*
1658          * The destination pmd shouldn't be established, free_pgtables()
1659          * should have release it.
1660          */
1661         if (WARN_ON(!pmd_none(*new_pmd))) {
1662                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1663                 return false;
1664         }
1665
1666         /*
1667          * We don't have to worry about the ordering of src and dst
1668          * ptlocks because exclusive mmap_lock prevents deadlock.
1669          */
1670         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1671         if (old_ptl) {
1672                 new_ptl = pmd_lockptr(mm, new_pmd);
1673                 if (new_ptl != old_ptl)
1674                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1675                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1676                 if (pmd_present(pmd))
1677                         force_flush = true;
1678                 VM_BUG_ON(!pmd_none(*new_pmd));
1679
1680                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1681                         pgtable_t pgtable;
1682                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1683                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1684                 }
1685                 pmd = move_soft_dirty_pmd(pmd);
1686                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1687                 if (force_flush)
1688                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1689                 if (new_ptl != old_ptl)
1690                         spin_unlock(new_ptl);
1691                 spin_unlock(old_ptl);
1692                 return true;
1693         }
1694         return false;
1695 }
1696
1697 /*
1698  * Returns
1699  *  - 0 if PMD could not be locked
1700  *  - 1 if PMD was locked but protections unchanged and TLB flush unnecessary
1701  *      or if prot_numa but THP migration is not supported
1702  *  - HPAGE_PMD_NR if protections changed and TLB flush necessary
1703  */
1704 int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1705                     pmd_t *pmd, unsigned long addr, pgprot_t newprot,
1706                     unsigned long cp_flags)
1707 {
1708         struct mm_struct *mm = vma->vm_mm;
1709         spinlock_t *ptl;
1710         pmd_t oldpmd, entry;
1711         bool preserve_write;
1712         int ret;
1713         bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
1714         bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
1715         bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
1716
1717         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1718
1719         if (prot_numa && !thp_migration_supported())
1720                 return 1;
1721
1722         ptl = __pmd_trans_huge_lock(pmd, vma);
1723         if (!ptl)
1724                 return 0;
1725
1726         preserve_write = prot_numa && pmd_write(*pmd);
1727         ret = 1;
1728
1729 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1730         if (is_swap_pmd(*pmd)) {
1731                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1732                 struct page *page = pfn_swap_entry_to_page(entry);
1733
1734                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1735                 if (is_writable_migration_entry(entry)) {
1736                         pmd_t newpmd;
1737                         /*
1738                          * A protection check is difficult so
1739                          * just be safe and disable write
1740                          */
1741                         if (PageAnon(page))
1742                                 entry = make_readable_exclusive_migration_entry(swp_offset(entry));
1743                         else
1744                                 entry = make_readable_migration_entry(swp_offset(entry));
1745                         newpmd = swp_entry_to_pmd(entry);
1746                         if (pmd_swp_soft_dirty(*pmd))
1747                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1748                         if (pmd_swp_uffd_wp(*pmd))
1749                                 newpmd = pmd_swp_mkuffd_wp(newpmd);
1750                         set_pmd_at(mm, addr, pmd, newpmd);
1751                 }
1752                 goto unlock;
1753         }
1754 #endif
1755
1756         if (prot_numa) {
1757                 struct page *page;
1758                 /*
1759                  * Avoid trapping faults against the zero page. The read-only
1760                  * data is likely to be read-cached on the local CPU and
1761                  * local/remote hits to the zero page are not interesting.
1762                  */
1763                 if (is_huge_zero_pmd(*pmd))
1764                         goto unlock;
1765
1766                 if (pmd_protnone(*pmd))
1767                         goto unlock;
1768
1769                 page = pmd_page(*pmd);
1770                 /*
1771                  * Skip scanning top tier node if normal numa
1772                  * balancing is disabled
1773                  */
1774                 if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) &&
1775                     node_is_toptier(page_to_nid(page)))
1776                         goto unlock;
1777         }
1778         /*
1779          * In case prot_numa, we are under mmap_read_lock(mm). It's critical
1780          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1781          * which is also under mmap_read_lock(mm):
1782          *
1783          *      CPU0:                           CPU1:
1784          *                              change_huge_pmd(prot_numa=1)
1785          *                               pmdp_huge_get_and_clear_notify()
1786          * madvise_dontneed()
1787          *  zap_pmd_range()
1788          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1789          *   // skip the pmd
1790          *                               set_pmd_at();
1791          *                               // pmd is re-established
1792          *
1793          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1794          * which may break userspace.
1795          *
1796          * pmdp_invalidate_ad() is required to make sure we don't miss
1797          * dirty/young flags set by hardware.
1798          */
1799         oldpmd = pmdp_invalidate_ad(vma, addr, pmd);
1800
1801         entry = pmd_modify(oldpmd, newprot);
1802         if (preserve_write)
1803                 entry = pmd_mk_savedwrite(entry);
1804         if (uffd_wp) {
1805                 entry = pmd_wrprotect(entry);
1806                 entry = pmd_mkuffd_wp(entry);
1807         } else if (uffd_wp_resolve) {
1808                 /*
1809                  * Leave the write bit to be handled by PF interrupt
1810                  * handler, then things like COW could be properly
1811                  * handled.
1812                  */
1813                 entry = pmd_clear_uffd_wp(entry);
1814         }
1815         ret = HPAGE_PMD_NR;
1816         set_pmd_at(mm, addr, pmd, entry);
1817
1818         if (huge_pmd_needs_flush(oldpmd, entry))
1819                 tlb_flush_pmd_range(tlb, addr, HPAGE_PMD_SIZE);
1820
1821         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1822 unlock:
1823         spin_unlock(ptl);
1824         return ret;
1825 }
1826
1827 /*
1828  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1829  *
1830  * Note that if it returns page table lock pointer, this routine returns without
1831  * unlocking page table lock. So callers must unlock it.
1832  */
1833 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1834 {
1835         spinlock_t *ptl;
1836         ptl = pmd_lock(vma->vm_mm, pmd);
1837         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1838                         pmd_devmap(*pmd)))
1839                 return ptl;
1840         spin_unlock(ptl);
1841         return NULL;
1842 }
1843
1844 /*
1845  * Returns true if a given pud maps a thp, false otherwise.
1846  *
1847  * Note that if it returns true, this routine returns without unlocking page
1848  * table lock. So callers must unlock it.
1849  */
1850 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1851 {
1852         spinlock_t *ptl;
1853
1854         ptl = pud_lock(vma->vm_mm, pud);
1855         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1856                 return ptl;
1857         spin_unlock(ptl);
1858         return NULL;
1859 }
1860
1861 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1862 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1863                  pud_t *pud, unsigned long addr)
1864 {
1865         spinlock_t *ptl;
1866
1867         ptl = __pud_trans_huge_lock(pud, vma);
1868         if (!ptl)
1869                 return 0;
1870         /*
1871          * For architectures like ppc64 we look at deposited pgtable
1872          * when calling pudp_huge_get_and_clear. So do the
1873          * pgtable_trans_huge_withdraw after finishing pudp related
1874          * operations.
1875          */
1876         pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
1877         tlb_remove_pud_tlb_entry(tlb, pud, addr);
1878         if (vma_is_special_huge(vma)) {
1879                 spin_unlock(ptl);
1880                 /* No zero page support yet */
1881         } else {
1882                 /* No support for anonymous PUD pages yet */
1883                 BUG();
1884         }
1885         return 1;
1886 }
1887
1888 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
1889                 unsigned long haddr)
1890 {
1891         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
1892         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1893         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
1894         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
1895
1896         count_vm_event(THP_SPLIT_PUD);
1897
1898         pudp_huge_clear_flush_notify(vma, haddr, pud);
1899 }
1900
1901 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
1902                 unsigned long address)
1903 {
1904         spinlock_t *ptl;
1905         struct mmu_notifier_range range;
1906
1907         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1908                                 address & HPAGE_PUD_MASK,
1909                                 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
1910         mmu_notifier_invalidate_range_start(&range);
1911         ptl = pud_lock(vma->vm_mm, pud);
1912         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
1913                 goto out;
1914         __split_huge_pud_locked(vma, pud, range.start);
1915
1916 out:
1917         spin_unlock(ptl);
1918         /*
1919          * No need to double call mmu_notifier->invalidate_range() callback as
1920          * the above pudp_huge_clear_flush_notify() did already call it.
1921          */
1922         mmu_notifier_invalidate_range_only_end(&range);
1923 }
1924 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1925
1926 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
1927                 unsigned long haddr, pmd_t *pmd)
1928 {
1929         struct mm_struct *mm = vma->vm_mm;
1930         pgtable_t pgtable;
1931         pmd_t _pmd;
1932         int i;
1933
1934         /*
1935          * Leave pmd empty until pte is filled note that it is fine to delay
1936          * notification until mmu_notifier_invalidate_range_end() as we are
1937          * replacing a zero pmd write protected page with a zero pte write
1938          * protected page.
1939          *
1940          * See Documentation/vm/mmu_notifier.rst
1941          */
1942         pmdp_huge_clear_flush(vma, haddr, pmd);
1943
1944         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1945         pmd_populate(mm, &_pmd, pgtable);
1946
1947         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1948                 pte_t *pte, entry;
1949                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
1950                 entry = pte_mkspecial(entry);
1951                 pte = pte_offset_map(&_pmd, haddr);
1952                 VM_BUG_ON(!pte_none(*pte));
1953                 set_pte_at(mm, haddr, pte, entry);
1954                 pte_unmap(pte);
1955         }
1956         smp_wmb(); /* make pte visible before pmd */
1957         pmd_populate(mm, pmd, pgtable);
1958 }
1959
1960 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
1961                 unsigned long haddr, bool freeze)
1962 {
1963         struct mm_struct *mm = vma->vm_mm;
1964         struct page *page;
1965         pgtable_t pgtable;
1966         pmd_t old_pmd, _pmd;
1967         bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false;
1968         bool anon_exclusive = false;
1969         unsigned long addr;
1970         int i;
1971
1972         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
1973         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1974         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
1975         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
1976                                 && !pmd_devmap(*pmd));
1977
1978         count_vm_event(THP_SPLIT_PMD);
1979
1980         if (!vma_is_anonymous(vma)) {
1981                 old_pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1982                 /*
1983                  * We are going to unmap this huge page. So
1984                  * just go ahead and zap it
1985                  */
1986                 if (arch_needs_pgtable_deposit())
1987                         zap_deposited_table(mm, pmd);
1988                 if (vma_is_special_huge(vma))
1989                         return;
1990                 if (unlikely(is_pmd_migration_entry(old_pmd))) {
1991                         swp_entry_t entry;
1992
1993                         entry = pmd_to_swp_entry(old_pmd);
1994                         page = pfn_swap_entry_to_page(entry);
1995                 } else {
1996                         page = pmd_page(old_pmd);
1997                         if (!PageDirty(page) && pmd_dirty(old_pmd))
1998                                 set_page_dirty(page);
1999                         if (!PageReferenced(page) && pmd_young(old_pmd))
2000                                 SetPageReferenced(page);
2001                         page_remove_rmap(page, vma, true);
2002                         put_page(page);
2003                 }
2004                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2005                 return;
2006         }
2007
2008         if (is_huge_zero_pmd(*pmd)) {
2009                 /*
2010                  * FIXME: Do we want to invalidate secondary mmu by calling
2011                  * mmu_notifier_invalidate_range() see comments below inside
2012                  * __split_huge_pmd() ?
2013                  *
2014                  * We are going from a zero huge page write protected to zero
2015                  * small page also write protected so it does not seems useful
2016                  * to invalidate secondary mmu at this time.
2017                  */
2018                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2019         }
2020
2021         /*
2022          * Up to this point the pmd is present and huge and userland has the
2023          * whole access to the hugepage during the split (which happens in
2024          * place). If we overwrite the pmd with the not-huge version pointing
2025          * to the pte here (which of course we could if all CPUs were bug
2026          * free), userland could trigger a small page size TLB miss on the
2027          * small sized TLB while the hugepage TLB entry is still established in
2028          * the huge TLB. Some CPU doesn't like that.
2029          * See http://support.amd.com/TechDocs/41322_10h_Rev_Gd.pdf, Erratum
2030          * 383 on page 105. Intel should be safe but is also warns that it's
2031          * only safe if the permission and cache attributes of the two entries
2032          * loaded in the two TLB is identical (which should be the case here).
2033          * But it is generally safer to never allow small and huge TLB entries
2034          * for the same virtual address to be loaded simultaneously. So instead
2035          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2036          * current pmd notpresent (atomically because here the pmd_trans_huge
2037          * must remain set at all times on the pmd until the split is complete
2038          * for this pmd), then we flush the SMP TLB and finally we write the
2039          * non-huge version of the pmd entry with pmd_populate.
2040          */
2041         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2042
2043         pmd_migration = is_pmd_migration_entry(old_pmd);
2044         if (unlikely(pmd_migration)) {
2045                 swp_entry_t entry;
2046
2047                 entry = pmd_to_swp_entry(old_pmd);
2048                 page = pfn_swap_entry_to_page(entry);
2049                 write = is_writable_migration_entry(entry);
2050                 if (PageAnon(page))
2051                         anon_exclusive = is_readable_exclusive_migration_entry(entry);
2052                 young = false;
2053                 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2054                 uffd_wp = pmd_swp_uffd_wp(old_pmd);
2055         } else {
2056                 page = pmd_page(old_pmd);
2057                 if (pmd_dirty(old_pmd))
2058                         SetPageDirty(page);
2059                 write = pmd_write(old_pmd);
2060                 young = pmd_young(old_pmd);
2061                 soft_dirty = pmd_soft_dirty(old_pmd);
2062                 uffd_wp = pmd_uffd_wp(old_pmd);
2063
2064                 VM_BUG_ON_PAGE(!page_count(page), page);
2065                 page_ref_add(page, HPAGE_PMD_NR - 1);
2066
2067                 /*
2068                  * Without "freeze", we'll simply split the PMD, propagating the
2069                  * PageAnonExclusive() flag for each PTE by setting it for
2070                  * each subpage -- no need to (temporarily) clear.
2071                  *
2072                  * With "freeze" we want to replace mapped pages by
2073                  * migration entries right away. This is only possible if we
2074                  * managed to clear PageAnonExclusive() -- see
2075                  * set_pmd_migration_entry().
2076                  *
2077                  * In case we cannot clear PageAnonExclusive(), split the PMD
2078                  * only and let try_to_migrate_one() fail later.
2079                  */
2080                 anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
2081                 if (freeze && anon_exclusive && page_try_share_anon_rmap(page))
2082                         freeze = false;
2083         }
2084
2085         /*
2086          * Withdraw the table only after we mark the pmd entry invalid.
2087          * This's critical for some architectures (Power).
2088          */
2089         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2090         pmd_populate(mm, &_pmd, pgtable);
2091
2092         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2093                 pte_t entry, *pte;
2094                 /*
2095                  * Note that NUMA hinting access restrictions are not
2096                  * transferred to avoid any possibility of altering
2097                  * permissions across VMAs.
2098                  */
2099                 if (freeze || pmd_migration) {
2100                         swp_entry_t swp_entry;
2101                         if (write)
2102                                 swp_entry = make_writable_migration_entry(
2103                                                         page_to_pfn(page + i));
2104                         else if (anon_exclusive)
2105                                 swp_entry = make_readable_exclusive_migration_entry(
2106                                                         page_to_pfn(page + i));
2107                         else
2108                                 swp_entry = make_readable_migration_entry(
2109                                                         page_to_pfn(page + i));
2110                         entry = swp_entry_to_pte(swp_entry);
2111                         if (soft_dirty)
2112                                 entry = pte_swp_mksoft_dirty(entry);
2113                         if (uffd_wp)
2114                                 entry = pte_swp_mkuffd_wp(entry);
2115                 } else {
2116                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2117                         entry = maybe_mkwrite(entry, vma);
2118                         if (anon_exclusive)
2119                                 SetPageAnonExclusive(page + i);
2120                         if (!write)
2121                                 entry = pte_wrprotect(entry);
2122                         if (!young)
2123                                 entry = pte_mkold(entry);
2124                         if (soft_dirty)
2125                                 entry = pte_mksoft_dirty(entry);
2126                         if (uffd_wp)
2127                                 entry = pte_mkuffd_wp(entry);
2128                 }
2129                 pte = pte_offset_map(&_pmd, addr);
2130                 BUG_ON(!pte_none(*pte));
2131                 set_pte_at(mm, addr, pte, entry);
2132                 if (!pmd_migration)
2133                         atomic_inc(&page[i]._mapcount);
2134                 pte_unmap(pte);
2135         }
2136
2137         if (!pmd_migration) {
2138                 /*
2139                  * Set PG_double_map before dropping compound_mapcount to avoid
2140                  * false-negative page_mapped().
2141                  */
2142                 if (compound_mapcount(page) > 1 &&
2143                     !TestSetPageDoubleMap(page)) {
2144                         for (i = 0; i < HPAGE_PMD_NR; i++)
2145                                 atomic_inc(&page[i]._mapcount);
2146                 }
2147
2148                 lock_page_memcg(page);
2149                 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2150                         /* Last compound_mapcount is gone. */
2151                         __mod_lruvec_page_state(page, NR_ANON_THPS,
2152                                                 -HPAGE_PMD_NR);
2153                         if (TestClearPageDoubleMap(page)) {
2154                                 /* No need in mapcount reference anymore */
2155                                 for (i = 0; i < HPAGE_PMD_NR; i++)
2156                                         atomic_dec(&page[i]._mapcount);
2157                         }
2158                 }
2159                 unlock_page_memcg(page);
2160
2161                 /* Above is effectively page_remove_rmap(page, vma, true) */
2162                 munlock_vma_page(page, vma, true);
2163         }
2164
2165         smp_wmb(); /* make pte visible before pmd */
2166         pmd_populate(mm, pmd, pgtable);
2167
2168         if (freeze) {
2169                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2170                         page_remove_rmap(page + i, vma, false);
2171                         put_page(page + i);
2172                 }
2173         }
2174 }
2175
2176 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2177                 unsigned long address, bool freeze, struct folio *folio)
2178 {
2179         spinlock_t *ptl;
2180         struct mmu_notifier_range range;
2181
2182         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2183                                 address & HPAGE_PMD_MASK,
2184                                 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2185         mmu_notifier_invalidate_range_start(&range);
2186         ptl = pmd_lock(vma->vm_mm, pmd);
2187
2188         /*
2189          * If caller asks to setup a migration entry, we need a folio to check
2190          * pmd against. Otherwise we can end up replacing wrong folio.
2191          */
2192         VM_BUG_ON(freeze && !folio);
2193         VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
2194
2195         if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
2196             is_pmd_migration_entry(*pmd)) {
2197                 if (folio && folio != page_folio(pmd_page(*pmd)))
2198                         goto out;
2199                 __split_huge_pmd_locked(vma, pmd, range.start, freeze);
2200         }
2201
2202 out:
2203         spin_unlock(ptl);
2204         /*
2205          * No need to double call mmu_notifier->invalidate_range() callback.
2206          * They are 3 cases to consider inside __split_huge_pmd_locked():
2207          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2208          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2209          *    fault will trigger a flush_notify before pointing to a new page
2210          *    (it is fine if the secondary mmu keeps pointing to the old zero
2211          *    page in the meantime)
2212          *  3) Split a huge pmd into pte pointing to the same page. No need
2213          *     to invalidate secondary tlb entry they are all still valid.
2214          *     any further changes to individual pte will notify. So no need
2215          *     to call mmu_notifier->invalidate_range()
2216          */
2217         mmu_notifier_invalidate_range_only_end(&range);
2218 }
2219
2220 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2221                 bool freeze, struct folio *folio)
2222 {
2223         pgd_t *pgd;
2224         p4d_t *p4d;
2225         pud_t *pud;
2226         pmd_t *pmd;
2227
2228         pgd = pgd_offset(vma->vm_mm, address);
2229         if (!pgd_present(*pgd))
2230                 return;
2231
2232         p4d = p4d_offset(pgd, address);
2233         if (!p4d_present(*p4d))
2234                 return;
2235
2236         pud = pud_offset(p4d, address);
2237         if (!pud_present(*pud))
2238                 return;
2239
2240         pmd = pmd_offset(pud, address);
2241
2242         __split_huge_pmd(vma, pmd, address, freeze, folio);
2243 }
2244
2245 static inline void split_huge_pmd_if_needed(struct vm_area_struct *vma, unsigned long address)
2246 {
2247         /*
2248          * If the new address isn't hpage aligned and it could previously
2249          * contain an hugepage: check if we need to split an huge pmd.
2250          */
2251         if (!IS_ALIGNED(address, HPAGE_PMD_SIZE) &&
2252             range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PMD_SIZE),
2253                          ALIGN(address, HPAGE_PMD_SIZE)))
2254                 split_huge_pmd_address(vma, address, false, NULL);
2255 }
2256
2257 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2258                              unsigned long start,
2259                              unsigned long end,
2260                              long adjust_next)
2261 {
2262         /* Check if we need to split start first. */
2263         split_huge_pmd_if_needed(vma, start);
2264
2265         /* Check if we need to split end next. */
2266         split_huge_pmd_if_needed(vma, end);
2267
2268         /*
2269          * If we're also updating the vma->vm_next->vm_start,
2270          * check if we need to split it.
2271          */
2272         if (adjust_next > 0) {
2273                 struct vm_area_struct *next = vma->vm_next;
2274                 unsigned long nstart = next->vm_start;
2275                 nstart += adjust_next;
2276                 split_huge_pmd_if_needed(next, nstart);
2277         }
2278 }
2279
2280 static void unmap_page(struct page *page)
2281 {
2282         struct folio *folio = page_folio(page);
2283         enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD |
2284                 TTU_SYNC;
2285
2286         VM_BUG_ON_PAGE(!PageHead(page), page);
2287
2288         /*
2289          * Anon pages need migration entries to preserve them, but file
2290          * pages can simply be left unmapped, then faulted back on demand.
2291          * If that is ever changed (perhaps for mlock), update remap_page().
2292          */
2293         if (folio_test_anon(folio))
2294                 try_to_migrate(folio, ttu_flags);
2295         else
2296                 try_to_unmap(folio, ttu_flags | TTU_IGNORE_MLOCK);
2297 }
2298
2299 static void remap_page(struct folio *folio, unsigned long nr)
2300 {
2301         int i = 0;
2302
2303         /* If unmap_page() uses try_to_migrate() on file, remove this check */
2304         if (!folio_test_anon(folio))
2305                 return;
2306         for (;;) {
2307                 remove_migration_ptes(folio, folio, true);
2308                 i += folio_nr_pages(folio);
2309                 if (i >= nr)
2310                         break;
2311                 folio = folio_next(folio);
2312         }
2313 }
2314
2315 static void lru_add_page_tail(struct page *head, struct page *tail,
2316                 struct lruvec *lruvec, struct list_head *list)
2317 {
2318         VM_BUG_ON_PAGE(!PageHead(head), head);
2319         VM_BUG_ON_PAGE(PageCompound(tail), head);
2320         VM_BUG_ON_PAGE(PageLRU(tail), head);
2321         lockdep_assert_held(&lruvec->lru_lock);
2322
2323         if (list) {
2324                 /* page reclaim is reclaiming a huge page */
2325                 VM_WARN_ON(PageLRU(head));
2326                 get_page(tail);
2327                 list_add_tail(&tail->lru, list);
2328         } else {
2329                 /* head is still on lru (and we have it frozen) */
2330                 VM_WARN_ON(!PageLRU(head));
2331                 if (PageUnevictable(tail))
2332                         tail->mlock_count = 0;
2333                 else
2334                         list_add_tail(&tail->lru, &head->lru);
2335                 SetPageLRU(tail);
2336         }
2337 }
2338
2339 static void __split_huge_page_tail(struct page *head, int tail,
2340                 struct lruvec *lruvec, struct list_head *list)
2341 {
2342         struct page *page_tail = head + tail;
2343
2344         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2345
2346         /*
2347          * Clone page flags before unfreezing refcount.
2348          *
2349          * After successful get_page_unless_zero() might follow flags change,
2350          * for example lock_page() which set PG_waiters.
2351          *
2352          * Note that for mapped sub-pages of an anonymous THP,
2353          * PG_anon_exclusive has been cleared in unmap_page() and is stored in
2354          * the migration entry instead from where remap_page() will restore it.
2355          * We can still have PG_anon_exclusive set on effectively unmapped and
2356          * unreferenced sub-pages of an anonymous THP: we can simply drop
2357          * PG_anon_exclusive (-> PG_mappedtodisk) for these here.
2358          */
2359         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2360         page_tail->flags |= (head->flags &
2361                         ((1L << PG_referenced) |
2362                          (1L << PG_swapbacked) |
2363                          (1L << PG_swapcache) |
2364                          (1L << PG_mlocked) |
2365                          (1L << PG_uptodate) |
2366                          (1L << PG_active) |
2367                          (1L << PG_workingset) |
2368                          (1L << PG_locked) |
2369                          (1L << PG_unevictable) |
2370 #ifdef CONFIG_64BIT
2371                          (1L << PG_arch_2) |
2372 #endif
2373                          (1L << PG_dirty)));
2374
2375         /* ->mapping in first tail page is compound_mapcount */
2376         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2377                         page_tail);
2378         page_tail->mapping = head->mapping;
2379         page_tail->index = head->index + tail;
2380         page_tail->private = 0;
2381
2382         /* Page flags must be visible before we make the page non-compound. */
2383         smp_wmb();
2384
2385         /*
2386          * Clear PageTail before unfreezing page refcount.
2387          *
2388          * After successful get_page_unless_zero() might follow put_page()
2389          * which needs correct compound_head().
2390          */
2391         clear_compound_head(page_tail);
2392
2393         /* Finally unfreeze refcount. Additional reference from page cache. */
2394         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2395                                           PageSwapCache(head)));
2396
2397         if (page_is_young(head))
2398                 set_page_young(page_tail);
2399         if (page_is_idle(head))
2400                 set_page_idle(page_tail);
2401
2402         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2403
2404         /*
2405          * always add to the tail because some iterators expect new
2406          * pages to show after the currently processed elements - e.g.
2407          * migrate_pages
2408          */
2409         lru_add_page_tail(head, page_tail, lruvec, list);
2410 }
2411
2412 static void __split_huge_page(struct page *page, struct list_head *list,
2413                 pgoff_t end)
2414 {
2415         struct folio *folio = page_folio(page);
2416         struct page *head = &folio->page;
2417         struct lruvec *lruvec;
2418         struct address_space *swap_cache = NULL;
2419         unsigned long offset = 0;
2420         unsigned int nr = thp_nr_pages(head);
2421         int i;
2422
2423         /* complete memcg works before add pages to LRU */
2424         split_page_memcg(head, nr);
2425
2426         if (PageAnon(head) && PageSwapCache(head)) {
2427                 swp_entry_t entry = { .val = page_private(head) };
2428
2429                 offset = swp_offset(entry);
2430                 swap_cache = swap_address_space(entry);
2431                 xa_lock(&swap_cache->i_pages);
2432         }
2433
2434         /* lock lru list/PageCompound, ref frozen by page_ref_freeze */
2435         lruvec = folio_lruvec_lock(folio);
2436
2437         ClearPageHasHWPoisoned(head);
2438
2439         for (i = nr - 1; i >= 1; i--) {
2440                 __split_huge_page_tail(head, i, lruvec, list);
2441                 /* Some pages can be beyond EOF: drop them from page cache */
2442                 if (head[i].index >= end) {
2443                         ClearPageDirty(head + i);
2444                         __delete_from_page_cache(head + i, NULL);
2445                         if (shmem_mapping(head->mapping))
2446                                 shmem_uncharge(head->mapping->host, 1);
2447                         put_page(head + i);
2448                 } else if (!PageAnon(page)) {
2449                         __xa_store(&head->mapping->i_pages, head[i].index,
2450                                         head + i, 0);
2451                 } else if (swap_cache) {
2452                         __xa_store(&swap_cache->i_pages, offset + i,
2453                                         head + i, 0);
2454                 }
2455         }
2456
2457         ClearPageCompound(head);
2458         unlock_page_lruvec(lruvec);
2459         /* Caller disabled irqs, so they are still disabled here */
2460
2461         split_page_owner(head, nr);
2462
2463         /* See comment in __split_huge_page_tail() */
2464         if (PageAnon(head)) {
2465                 /* Additional pin to swap cache */
2466                 if (PageSwapCache(head)) {
2467                         page_ref_add(head, 2);
2468                         xa_unlock(&swap_cache->i_pages);
2469                 } else {
2470                         page_ref_inc(head);
2471                 }
2472         } else {
2473                 /* Additional pin to page cache */
2474                 page_ref_add(head, 2);
2475                 xa_unlock(&head->mapping->i_pages);
2476         }
2477         local_irq_enable();
2478
2479         remap_page(folio, nr);
2480
2481         if (PageSwapCache(head)) {
2482                 swp_entry_t entry = { .val = page_private(head) };
2483
2484                 split_swap_cluster(entry);
2485         }
2486
2487         for (i = 0; i < nr; i++) {
2488                 struct page *subpage = head + i;
2489                 if (subpage == page)
2490                         continue;
2491                 unlock_page(subpage);
2492
2493                 /*
2494                  * Subpages may be freed if there wasn't any mapping
2495                  * like if add_to_swap() is running on a lru page that
2496                  * had its mapping zapped. And freeing these pages
2497                  * requires taking the lru_lock so we do the put_page
2498                  * of the tail pages after the split is complete.
2499                  */
2500                 put_page(subpage);
2501         }
2502 }
2503
2504 /* Racy check whether the huge page can be split */
2505 bool can_split_folio(struct folio *folio, int *pextra_pins)
2506 {
2507         int extra_pins;
2508
2509         /* Additional pins from page cache */
2510         if (folio_test_anon(folio))
2511                 extra_pins = folio_test_swapcache(folio) ?
2512                                 folio_nr_pages(folio) : 0;
2513         else
2514                 extra_pins = folio_nr_pages(folio);
2515         if (pextra_pins)
2516                 *pextra_pins = extra_pins;
2517         return folio_mapcount(folio) == folio_ref_count(folio) - extra_pins - 1;
2518 }
2519
2520 /*
2521  * This function splits huge page into normal pages. @page can point to any
2522  * subpage of huge page to split. Split doesn't change the position of @page.
2523  *
2524  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2525  * The huge page must be locked.
2526  *
2527  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2528  *
2529  * Both head page and tail pages will inherit mapping, flags, and so on from
2530  * the hugepage.
2531  *
2532  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2533  * they are not mapped.
2534  *
2535  * Returns 0 if the hugepage is split successfully.
2536  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2537  * us.
2538  */
2539 int split_huge_page_to_list(struct page *page, struct list_head *list)
2540 {
2541         struct folio *folio = page_folio(page);
2542         struct page *head = &folio->page;
2543         struct deferred_split *ds_queue = get_deferred_split_queue(head);
2544         XA_STATE(xas, &head->mapping->i_pages, head->index);
2545         struct anon_vma *anon_vma = NULL;
2546         struct address_space *mapping = NULL;
2547         int extra_pins, ret;
2548         pgoff_t end;
2549         bool is_hzp;
2550
2551         VM_BUG_ON_PAGE(!PageLocked(head), head);
2552         VM_BUG_ON_PAGE(!PageCompound(head), head);
2553
2554         is_hzp = is_huge_zero_page(head);
2555         VM_WARN_ON_ONCE_PAGE(is_hzp, head);
2556         if (is_hzp)
2557                 return -EBUSY;
2558
2559         if (PageWriteback(head))
2560                 return -EBUSY;
2561
2562         if (PageAnon(head)) {
2563                 /*
2564                  * The caller does not necessarily hold an mmap_lock that would
2565                  * prevent the anon_vma disappearing so we first we take a
2566                  * reference to it and then lock the anon_vma for write. This
2567                  * is similar to folio_lock_anon_vma_read except the write lock
2568                  * is taken to serialise against parallel split or collapse
2569                  * operations.
2570                  */
2571                 anon_vma = page_get_anon_vma(head);
2572                 if (!anon_vma) {
2573                         ret = -EBUSY;
2574                         goto out;
2575                 }
2576                 end = -1;
2577                 mapping = NULL;
2578                 anon_vma_lock_write(anon_vma);
2579         } else {
2580                 mapping = head->mapping;
2581
2582                 /* Truncated ? */
2583                 if (!mapping) {
2584                         ret = -EBUSY;
2585                         goto out;
2586                 }
2587
2588                 xas_split_alloc(&xas, head, compound_order(head),
2589                                 mapping_gfp_mask(mapping) & GFP_RECLAIM_MASK);
2590                 if (xas_error(&xas)) {
2591                         ret = xas_error(&xas);
2592                         goto out;
2593                 }
2594
2595                 anon_vma = NULL;
2596                 i_mmap_lock_read(mapping);
2597
2598                 /*
2599                  *__split_huge_page() may need to trim off pages beyond EOF:
2600                  * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2601                  * which cannot be nested inside the page tree lock. So note
2602                  * end now: i_size itself may be changed at any moment, but
2603                  * head page lock is good enough to serialize the trimming.
2604                  */
2605                 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2606                 if (shmem_mapping(mapping))
2607                         end = shmem_fallocend(mapping->host, end);
2608         }
2609
2610         /*
2611          * Racy check if we can split the page, before unmap_page() will
2612          * split PMDs
2613          */
2614         if (!can_split_folio(folio, &extra_pins)) {
2615                 ret = -EBUSY;
2616                 goto out_unlock;
2617         }
2618
2619         unmap_page(head);
2620
2621         /* block interrupt reentry in xa_lock and spinlock */
2622         local_irq_disable();
2623         if (mapping) {
2624                 /*
2625                  * Check if the head page is present in page cache.
2626                  * We assume all tail are present too, if head is there.
2627                  */
2628                 xas_lock(&xas);
2629                 xas_reset(&xas);
2630                 if (xas_load(&xas) != head)
2631                         goto fail;
2632         }
2633
2634         /* Prevent deferred_split_scan() touching ->_refcount */
2635         spin_lock(&ds_queue->split_queue_lock);
2636         if (page_ref_freeze(head, 1 + extra_pins)) {
2637                 if (!list_empty(page_deferred_list(head))) {
2638                         ds_queue->split_queue_len--;
2639                         list_del(page_deferred_list(head));
2640                 }
2641                 spin_unlock(&ds_queue->split_queue_lock);
2642                 if (mapping) {
2643                         int nr = thp_nr_pages(head);
2644
2645                         xas_split(&xas, head, thp_order(head));
2646                         if (PageSwapBacked(head)) {
2647                                 __mod_lruvec_page_state(head, NR_SHMEM_THPS,
2648                                                         -nr);
2649                         } else {
2650                                 __mod_lruvec_page_state(head, NR_FILE_THPS,
2651                                                         -nr);
2652                                 filemap_nr_thps_dec(mapping);
2653                         }
2654                 }
2655
2656                 __split_huge_page(page, list, end);
2657                 ret = 0;
2658         } else {
2659                 spin_unlock(&ds_queue->split_queue_lock);
2660 fail:
2661                 if (mapping)
2662                         xas_unlock(&xas);
2663                 local_irq_enable();
2664                 remap_page(folio, folio_nr_pages(folio));
2665                 ret = -EBUSY;
2666         }
2667
2668 out_unlock:
2669         if (anon_vma) {
2670                 anon_vma_unlock_write(anon_vma);
2671                 put_anon_vma(anon_vma);
2672         }
2673         if (mapping)
2674                 i_mmap_unlock_read(mapping);
2675 out:
2676         xas_destroy(&xas);
2677         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2678         return ret;
2679 }
2680
2681 void free_transhuge_page(struct page *page)
2682 {
2683         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2684         unsigned long flags;
2685
2686         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2687         if (!list_empty(page_deferred_list(page))) {
2688                 ds_queue->split_queue_len--;
2689                 list_del(page_deferred_list(page));
2690         }
2691         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2692         free_compound_page(page);
2693 }
2694
2695 void deferred_split_huge_page(struct page *page)
2696 {
2697         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2698 #ifdef CONFIG_MEMCG
2699         struct mem_cgroup *memcg = page_memcg(compound_head(page));
2700 #endif
2701         unsigned long flags;
2702
2703         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2704
2705         /*
2706          * The try_to_unmap() in page reclaim path might reach here too,
2707          * this may cause a race condition to corrupt deferred split queue.
2708          * And, if page reclaim is already handling the same page, it is
2709          * unnecessary to handle it again in shrinker.
2710          *
2711          * Check PageSwapCache to determine if the page is being
2712          * handled by page reclaim since THP swap would add the page into
2713          * swap cache before calling try_to_unmap().
2714          */
2715         if (PageSwapCache(page))
2716                 return;
2717
2718         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2719         if (list_empty(page_deferred_list(page))) {
2720                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2721                 list_add_tail(page_deferred_list(page), &ds_queue->split_queue);
2722                 ds_queue->split_queue_len++;
2723 #ifdef CONFIG_MEMCG
2724                 if (memcg)
2725                         set_shrinker_bit(memcg, page_to_nid(page),
2726                                          deferred_split_shrinker.id);
2727 #endif
2728         }
2729         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2730 }
2731
2732 static unsigned long deferred_split_count(struct shrinker *shrink,
2733                 struct shrink_control *sc)
2734 {
2735         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2736         struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2737
2738 #ifdef CONFIG_MEMCG
2739         if (sc->memcg)
2740                 ds_queue = &sc->memcg->deferred_split_queue;
2741 #endif
2742         return READ_ONCE(ds_queue->split_queue_len);
2743 }
2744
2745 static unsigned long deferred_split_scan(struct shrinker *shrink,
2746                 struct shrink_control *sc)
2747 {
2748         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2749         struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2750         unsigned long flags;
2751         LIST_HEAD(list), *pos, *next;
2752         struct page *page;
2753         int split = 0;
2754
2755 #ifdef CONFIG_MEMCG
2756         if (sc->memcg)
2757                 ds_queue = &sc->memcg->deferred_split_queue;
2758 #endif
2759
2760         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2761         /* Take pin on all head pages to avoid freeing them under us */
2762         list_for_each_safe(pos, next, &ds_queue->split_queue) {
2763                 page = list_entry((void *)pos, struct page, deferred_list);
2764                 page = compound_head(page);
2765                 if (get_page_unless_zero(page)) {
2766                         list_move(page_deferred_list(page), &list);
2767                 } else {
2768                         /* We lost race with put_compound_page() */
2769                         list_del_init(page_deferred_list(page));
2770                         ds_queue->split_queue_len--;
2771                 }
2772                 if (!--sc->nr_to_scan)
2773                         break;
2774         }
2775         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2776
2777         list_for_each_safe(pos, next, &list) {
2778                 page = list_entry((void *)pos, struct page, deferred_list);
2779                 if (!trylock_page(page))
2780                         goto next;
2781                 /* split_huge_page() removes page from list on success */
2782                 if (!split_huge_page(page))
2783                         split++;
2784                 unlock_page(page);
2785 next:
2786                 put_page(page);
2787         }
2788
2789         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2790         list_splice_tail(&list, &ds_queue->split_queue);
2791         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2792
2793         /*
2794          * Stop shrinker if we didn't split any page, but the queue is empty.
2795          * This can happen if pages were freed under us.
2796          */
2797         if (!split && list_empty(&ds_queue->split_queue))
2798                 return SHRINK_STOP;
2799         return split;
2800 }
2801
2802 static struct shrinker deferred_split_shrinker = {
2803         .count_objects = deferred_split_count,
2804         .scan_objects = deferred_split_scan,
2805         .seeks = DEFAULT_SEEKS,
2806         .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |
2807                  SHRINKER_NONSLAB,
2808 };
2809
2810 #ifdef CONFIG_DEBUG_FS
2811 static void split_huge_pages_all(void)
2812 {
2813         struct zone *zone;
2814         struct page *page;
2815         unsigned long pfn, max_zone_pfn;
2816         unsigned long total = 0, split = 0;
2817
2818         pr_debug("Split all THPs\n");
2819         for_each_populated_zone(zone) {
2820                 max_zone_pfn = zone_end_pfn(zone);
2821                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2822                         if (!pfn_valid(pfn))
2823                                 continue;
2824
2825                         page = pfn_to_page(pfn);
2826                         if (!get_page_unless_zero(page))
2827                                 continue;
2828
2829                         if (zone != page_zone(page))
2830                                 goto next;
2831
2832                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2833                                 goto next;
2834
2835                         total++;
2836                         lock_page(page);
2837                         if (!split_huge_page(page))
2838                                 split++;
2839                         unlock_page(page);
2840 next:
2841                         put_page(page);
2842                         cond_resched();
2843                 }
2844         }
2845
2846         pr_debug("%lu of %lu THP split\n", split, total);
2847 }
2848
2849 static inline bool vma_not_suitable_for_thp_split(struct vm_area_struct *vma)
2850 {
2851         return vma_is_special_huge(vma) || (vma->vm_flags & VM_IO) ||
2852                     is_vm_hugetlb_page(vma);
2853 }
2854
2855 static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
2856                                 unsigned long vaddr_end)
2857 {
2858         int ret = 0;
2859         struct task_struct *task;
2860         struct mm_struct *mm;
2861         unsigned long total = 0, split = 0;
2862         unsigned long addr;
2863
2864         vaddr_start &= PAGE_MASK;
2865         vaddr_end &= PAGE_MASK;
2866
2867         /* Find the task_struct from pid */
2868         rcu_read_lock();
2869         task = find_task_by_vpid(pid);
2870         if (!task) {
2871                 rcu_read_unlock();
2872                 ret = -ESRCH;
2873                 goto out;
2874         }
2875         get_task_struct(task);
2876         rcu_read_unlock();
2877
2878         /* Find the mm_struct */
2879         mm = get_task_mm(task);
2880         put_task_struct(task);
2881
2882         if (!mm) {
2883                 ret = -EINVAL;
2884                 goto out;
2885         }
2886
2887         pr_debug("Split huge pages in pid: %d, vaddr: [0x%lx - 0x%lx]\n",
2888                  pid, vaddr_start, vaddr_end);
2889
2890         mmap_read_lock(mm);
2891         /*
2892          * always increase addr by PAGE_SIZE, since we could have a PTE page
2893          * table filled with PTE-mapped THPs, each of which is distinct.
2894          */
2895         for (addr = vaddr_start; addr < vaddr_end; addr += PAGE_SIZE) {
2896                 struct vm_area_struct *vma = find_vma(mm, addr);
2897                 struct page *page;
2898
2899                 if (!vma || addr < vma->vm_start)
2900                         break;
2901
2902                 /* skip special VMA and hugetlb VMA */
2903                 if (vma_not_suitable_for_thp_split(vma)) {
2904                         addr = vma->vm_end;
2905                         continue;
2906                 }
2907
2908                 /* FOLL_DUMP to ignore special (like zero) pages */
2909                 page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
2910
2911                 if (IS_ERR(page))
2912                         continue;
2913                 if (!page)
2914                         continue;
2915
2916                 if (!is_transparent_hugepage(page))
2917                         goto next;
2918
2919                 total++;
2920                 if (!can_split_folio(page_folio(page), NULL))
2921                         goto next;
2922
2923                 if (!trylock_page(page))
2924                         goto next;
2925
2926                 if (!split_huge_page(page))
2927                         split++;
2928
2929                 unlock_page(page);
2930 next:
2931                 put_page(page);
2932                 cond_resched();
2933         }
2934         mmap_read_unlock(mm);
2935         mmput(mm);
2936
2937         pr_debug("%lu of %lu THP split\n", split, total);
2938
2939 out:
2940         return ret;
2941 }
2942
2943 static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
2944                                 pgoff_t off_end)
2945 {
2946         struct filename *file;
2947         struct file *candidate;
2948         struct address_space *mapping;
2949         int ret = -EINVAL;
2950         pgoff_t index;
2951         int nr_pages = 1;
2952         unsigned long total = 0, split = 0;
2953
2954         file = getname_kernel(file_path);
2955         if (IS_ERR(file))
2956                 return ret;
2957
2958         candidate = file_open_name(file, O_RDONLY, 0);
2959         if (IS_ERR(candidate))
2960                 goto out;
2961
2962         pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx]\n",
2963                  file_path, off_start, off_end);
2964
2965         mapping = candidate->f_mapping;
2966
2967         for (index = off_start; index < off_end; index += nr_pages) {
2968                 struct page *fpage = pagecache_get_page(mapping, index,
2969                                                 FGP_ENTRY | FGP_HEAD, 0);
2970
2971                 nr_pages = 1;
2972                 if (xa_is_value(fpage) || !fpage)
2973                         continue;
2974
2975                 if (!is_transparent_hugepage(fpage))
2976                         goto next;
2977
2978                 total++;
2979                 nr_pages = thp_nr_pages(fpage);
2980
2981                 if (!trylock_page(fpage))
2982                         goto next;
2983
2984                 if (!split_huge_page(fpage))
2985                         split++;
2986
2987                 unlock_page(fpage);
2988 next:
2989                 put_page(fpage);
2990                 cond_resched();
2991         }
2992
2993         filp_close(candidate, NULL);
2994         ret = 0;
2995
2996         pr_debug("%lu of %lu file-backed THP split\n", split, total);
2997 out:
2998         putname(file);
2999         return ret;
3000 }
3001
3002 #define MAX_INPUT_BUF_SZ 255
3003
3004 static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
3005                                 size_t count, loff_t *ppops)
3006 {
3007         static DEFINE_MUTEX(split_debug_mutex);
3008         ssize_t ret;
3009         /* hold pid, start_vaddr, end_vaddr or file_path, off_start, off_end */
3010         char input_buf[MAX_INPUT_BUF_SZ];
3011         int pid;
3012         unsigned long vaddr_start, vaddr_end;
3013
3014         ret = mutex_lock_interruptible(&split_debug_mutex);
3015         if (ret)
3016                 return ret;
3017
3018         ret = -EFAULT;
3019
3020         memset(input_buf, 0, MAX_INPUT_BUF_SZ);
3021         if (copy_from_user(input_buf, buf, min_t(size_t, count, MAX_INPUT_BUF_SZ)))
3022                 goto out;
3023
3024         input_buf[MAX_INPUT_BUF_SZ - 1] = '\0';
3025
3026         if (input_buf[0] == '/') {
3027                 char *tok;
3028                 char *buf = input_buf;
3029                 char file_path[MAX_INPUT_BUF_SZ];
3030                 pgoff_t off_start = 0, off_end = 0;
3031                 size_t input_len = strlen(input_buf);
3032
3033                 tok = strsep(&buf, ",");
3034                 if (tok) {
3035                         strcpy(file_path, tok);
3036                 } else {
3037                         ret = -EINVAL;
3038                         goto out;
3039                 }
3040
3041                 ret = sscanf(buf, "0x%lx,0x%lx", &off_start, &off_end);
3042                 if (ret != 2) {
3043                         ret = -EINVAL;
3044                         goto out;
3045                 }
3046                 ret = split_huge_pages_in_file(file_path, off_start, off_end);
3047                 if (!ret)
3048                         ret = input_len;
3049
3050                 goto out;
3051         }
3052
3053         ret = sscanf(input_buf, "%d,0x%lx,0x%lx", &pid, &vaddr_start, &vaddr_end);
3054         if (ret == 1 && pid == 1) {
3055                 split_huge_pages_all();
3056                 ret = strlen(input_buf);
3057                 goto out;
3058         } else if (ret != 3) {
3059                 ret = -EINVAL;
3060                 goto out;
3061         }
3062
3063         ret = split_huge_pages_pid(pid, vaddr_start, vaddr_end);
3064         if (!ret)
3065                 ret = strlen(input_buf);
3066 out:
3067         mutex_unlock(&split_debug_mutex);
3068         return ret;
3069
3070 }
3071
3072 static const struct file_operations split_huge_pages_fops = {
3073         .owner   = THIS_MODULE,
3074         .write   = split_huge_pages_write,
3075         .llseek  = no_llseek,
3076 };
3077
3078 static int __init split_huge_pages_debugfs(void)
3079 {
3080         debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
3081                             &split_huge_pages_fops);
3082         return 0;
3083 }
3084 late_initcall(split_huge_pages_debugfs);
3085 #endif
3086
3087 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
3088 int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
3089                 struct page *page)
3090 {
3091         struct vm_area_struct *vma = pvmw->vma;
3092         struct mm_struct *mm = vma->vm_mm;
3093         unsigned long address = pvmw->address;
3094         bool anon_exclusive;
3095         pmd_t pmdval;
3096         swp_entry_t entry;
3097         pmd_t pmdswp;
3098
3099         if (!(pvmw->pmd && !pvmw->pte))
3100                 return 0;
3101
3102         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
3103         pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
3104
3105         anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
3106         if (anon_exclusive && page_try_share_anon_rmap(page)) {
3107                 set_pmd_at(mm, address, pvmw->pmd, pmdval);
3108                 return -EBUSY;
3109         }
3110
3111         if (pmd_dirty(pmdval))
3112                 set_page_dirty(page);
3113         if (pmd_write(pmdval))
3114                 entry = make_writable_migration_entry(page_to_pfn(page));
3115         else if (anon_exclusive)
3116                 entry = make_readable_exclusive_migration_entry(page_to_pfn(page));
3117         else
3118                 entry = make_readable_migration_entry(page_to_pfn(page));
3119         pmdswp = swp_entry_to_pmd(entry);
3120         if (pmd_soft_dirty(pmdval))
3121                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
3122         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
3123         page_remove_rmap(page, vma, true);
3124         put_page(page);
3125         trace_set_migration_pmd(address, pmd_val(pmdswp));
3126
3127         return 0;
3128 }
3129
3130 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
3131 {
3132         struct vm_area_struct *vma = pvmw->vma;
3133         struct mm_struct *mm = vma->vm_mm;
3134         unsigned long address = pvmw->address;
3135         unsigned long mmun_start = address & HPAGE_PMD_MASK;
3136         pmd_t pmde;
3137         swp_entry_t entry;
3138
3139         if (!(pvmw->pmd && !pvmw->pte))
3140                 return;
3141
3142         entry = pmd_to_swp_entry(*pvmw->pmd);
3143         get_page(new);
3144         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
3145         if (pmd_swp_soft_dirty(*pvmw->pmd))
3146                 pmde = pmd_mksoft_dirty(pmde);
3147         if (is_writable_migration_entry(entry))
3148                 pmde = maybe_pmd_mkwrite(pmde, vma);
3149         if (pmd_swp_uffd_wp(*pvmw->pmd))
3150                 pmde = pmd_wrprotect(pmd_mkuffd_wp(pmde));
3151
3152         if (PageAnon(new)) {
3153                 rmap_t rmap_flags = RMAP_COMPOUND;
3154
3155                 if (!is_readable_migration_entry(entry))
3156                         rmap_flags |= RMAP_EXCLUSIVE;
3157
3158                 page_add_anon_rmap(new, vma, mmun_start, rmap_flags);
3159         } else {
3160                 page_add_file_rmap(new, vma, true);
3161         }
3162         VM_BUG_ON(pmd_write(pmde) && PageAnon(new) && !PageAnonExclusive(new));
3163         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
3164
3165         /* No need to invalidate - it was non-present before */
3166         update_mmu_cache_pmd(vma, address, pvmw->pmd);
3167         trace_remove_migration_pmd(address, pmd_val(pmde));
3168 }
3169 #endif