mm/madvise.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      linux/mm/madvise.c
   4  *
   5  * Copyright (C) 1999  Linus Torvalds
   6  * Copyright (C) 2002  Christoph Hellwig
   7  */
   8
   9 #include <linux/mman.h>
  10 #include <linux/pagemap.h>
  11 #include <linux/syscalls.h>
  12 #include <linux/mempolicy.h>
  13 #include <linux/page-isolation.h>
  14 #include <linux/page_idle.h>
  15 #include <linux/userfaultfd_k.h>
  16 #include <linux/hugetlb.h>
  17 #include <linux/falloc.h>
  18 #include <linux/fadvise.h>
  19 #include <linux/sched.h>
  20 #include <linux/sched/mm.h>
  21 #include <linux/mm_inline.h>
  22 #include <linux/string.h>
  23 #include <linux/uio.h>
  24 #include <linux/ksm.h>
  25 #include <linux/fs.h>
  26 #include <linux/file.h>
  27 #include <linux/blkdev.h>
  28 #include <linux/backing-dev.h>
  29 #include <linux/pagewalk.h>
  30 #include <linux/swap.h>
  31 #include <linux/swapops.h>
  32 #include <linux/shmem_fs.h>
  33 #include <linux/mmu_notifier.h>
  34
  35 #include <asm/tlb.h>
  36
  37 #include "internal.h"
  38 #include "swap.h"
  39
  40 struct madvise_walk_private {
  41         struct mmu_gather *tlb;
  42         bool pageout;
  43 };
  44
  45 /*
  46  * Any behaviour which results in changes to the vma->vm_flags needs to
  47  * take mmap_lock for writing. Others, which simply traverse vmas, need
  48  * to only take it for reading.
  49  */
  50 static int madvise_need_mmap_write(int behavior)
  51 {
  52         switch (behavior) {
  53         case MADV_REMOVE:
  54         case MADV_WILLNEED:
  55         case MADV_DONTNEED:
  56         case MADV_DONTNEED_LOCKED:
  57         case MADV_COLD:
  58         case MADV_PAGEOUT:
  59         case MADV_FREE:
  60         case MADV_POPULATE_READ:
  61         case MADV_POPULATE_WRITE:
  62                 return 0;
  63         default:
  64                 /* be safe, default to 1. list exceptions explicitly */
  65                 return 1;
  66         }
  67 }
  68
  69 #ifdef CONFIG_ANON_VMA_NAME
  70 struct anon_vma_name *anon_vma_name_alloc(const char *name)
  71 {
  72         struct anon_vma_name *anon_name;
  73         size_t count;
  74
  75         /* Add 1 for NUL terminator at the end of the anon_name->name */
  76         count = strlen(name) + 1;
  77         anon_name = kmalloc(struct_size(anon_name, name, count), GFP_KERNEL);
  78         if (anon_name) {
  79                 kref_init(&anon_name->kref);
  80                 memcpy(anon_name->name, name, count);
  81         }
  82
  83         return anon_name;
  84 }
  85
  86 void anon_vma_name_free(struct kref *kref)
  87 {
  88         struct anon_vma_name *anon_name =
  89                         container_of(kref, struct anon_vma_name, kref);
  90         kfree(anon_name);
  91 }
  92
  93 struct anon_vma_name *anon_vma_name(struct vm_area_struct *vma)
  94 {
  95         mmap_assert_locked(vma->vm_mm);
  96
  97         if (vma->vm_file)
  98                 return NULL;
  99
 100         return vma->anon_name;
 101 }
 102
 103 /* mmap_lock should be write-locked */
 104 static int replace_anon_vma_name(struct vm_area_struct *vma,
 105                                  struct anon_vma_name *anon_name)
 106 {
 107         struct anon_vma_name *orig_name = anon_vma_name(vma);
 108
 109         if (!anon_name) {
 110                 vma->anon_name = NULL;
 111                 anon_vma_name_put(orig_name);
 112                 return 0;
 113         }
 114
 115         if (anon_vma_name_eq(orig_name, anon_name))
 116                 return 0;
 117
 118         vma->anon_name = anon_vma_name_reuse(anon_name);
 119         anon_vma_name_put(orig_name);
 120
 121         return 0;
 122 }
 123 #else /* CONFIG_ANON_VMA_NAME */
 124 static int replace_anon_vma_name(struct vm_area_struct *vma,
 125                                  struct anon_vma_name *anon_name)
 126 {
 127         if (anon_name)
 128                 return -EINVAL;
 129
 130         return 0;
 131 }
 132 #endif /* CONFIG_ANON_VMA_NAME */
 133 /*
 134  * Update the vm_flags on region of a vma, splitting it or merging it as
 135  * necessary.  Must be called with mmap_sem held for writing;
 136  * Caller should ensure anon_name stability by raising its refcount even when
 137  * anon_name belongs to a valid vma because this function might free that vma.
 138  */
 139 static int madvise_update_vma(struct vm_area_struct *vma,
 140                               struct vm_area_struct **prev, unsigned long start,
 141                               unsigned long end, unsigned long new_flags,
 142                               struct anon_vma_name *anon_name)
 143 {
 144         struct mm_struct *mm = vma->vm_mm;
 145         int error;
 146         pgoff_t pgoff;
 147
 148         if (new_flags == vma->vm_flags && anon_vma_name_eq(anon_vma_name(vma), anon_name)) {
 149                 *prev = vma;
 150                 return 0;
 151         }
 152
 153         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 154         *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
 155                           vma->vm_file, pgoff, vma_policy(vma),
 156                           vma->vm_userfaultfd_ctx, anon_name);
 157         if (*prev) {
 158                 vma = *prev;
 159                 goto success;
 160         }
 161
 162         *prev = vma;
 163
 164         if (start != vma->vm_start) {
 165                 if (unlikely(mm->map_count >= sysctl_max_map_count))
 166                         return -ENOMEM;
 167                 error = __split_vma(mm, vma, start, 1);
 168                 if (error)
 169                         return error;
 170         }
 171
 172         if (end != vma->vm_end) {
 173                 if (unlikely(mm->map_count >= sysctl_max_map_count))
 174                         return -ENOMEM;
 175                 error = __split_vma(mm, vma, end, 0);
 176                 if (error)
 177                         return error;
 178         }
 179
 180 success:
 181         /*
 182          * vm_flags is protected by the mmap_lock held in write mode.
 183          */
 184         vma->vm_flags = new_flags;
 185         if (!vma->vm_file) {
 186                 error = replace_anon_vma_name(vma, anon_name);
 187                 if (error)
 188                         return error;
 189         }
 190
 191         return 0;
 192 }
 193
 194 #ifdef CONFIG_SWAP
 195 static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
 196         unsigned long end, struct mm_walk *walk)
 197 {
 198         struct vm_area_struct *vma = walk->private;
 199         unsigned long index;
 200         struct swap_iocb *splug = NULL;
 201
 202         if (pmd_none_or_trans_huge_or_clear_bad(pmd))
 203                 return 0;
 204
 205         for (index = start; index != end; index += PAGE_SIZE) {
 206                 pte_t pte;
 207                 swp_entry_t entry;
 208                 struct page *page;
 209                 spinlock_t *ptl;
 210                 pte_t *ptep;
 211
 212                 ptep = pte_offset_map_lock(vma->vm_mm, pmd, index, &ptl);
 213                 pte = *ptep;
 214                 pte_unmap_unlock(ptep, ptl);
 215
 216                 if (!is_swap_pte(pte))
 217                         continue;
 218                 entry = pte_to_swp_entry(pte);
 219                 if (unlikely(non_swap_entry(entry)))
 220                         continue;
 221
 222                 page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
 223                                              vma, index, false, &splug);
 224                 if (page)
 225                         put_page(page);
 226         }
 227         swap_read_unplug(splug);
 228
 229         return 0;
 230 }
 231
 232 static const struct mm_walk_ops swapin_walk_ops = {
 233         .pmd_entry              = swapin_walk_pmd_entry,
 234 };
 235
 236 static void force_shm_swapin_readahead(struct vm_area_struct *vma,
 237                 unsigned long start, unsigned long end,
 238                 struct address_space *mapping)
 239 {
 240         XA_STATE(xas, &mapping->i_pages, linear_page_index(vma, start));
 241         pgoff_t end_index = linear_page_index(vma, end + PAGE_SIZE - 1);
 242         struct page *page;
 243         struct swap_iocb *splug = NULL;
 244
 245         rcu_read_lock();
 246         xas_for_each(&xas, page, end_index) {
 247                 swp_entry_t swap;
 248
 249                 if (!xa_is_value(page))
 250                         continue;
 251                 swap = radix_to_swp_entry(page);
 252                 /* There might be swapin error entries in shmem mapping. */
 253                 if (non_swap_entry(swap))
 254                         continue;
 255                 xas_pause(&xas);
 256                 rcu_read_unlock();
 257
 258                 page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
 259                                              NULL, 0, false, &splug);
 260                 if (page)
 261                         put_page(page);
 262
 263                 rcu_read_lock();
 264         }
 265         rcu_read_unlock();
 266         swap_read_unplug(splug);
 267
 268         lru_add_drain();        /* Push any new pages onto the LRU now */
 269 }
 270 #endif          /* CONFIG_SWAP */
 271
 272 /*
 273  * Schedule all required I/O operations.  Do not wait for completion.
 274  */
 275 static long madvise_willneed(struct vm_area_struct *vma,
 276                              struct vm_area_struct **prev,
 277                              unsigned long start, unsigned long end)
 278 {
 279         struct mm_struct *mm = vma->vm_mm;
 280         struct file *file = vma->vm_file;
 281         loff_t offset;
 282
 283         *prev = vma;
 284 #ifdef CONFIG_SWAP
 285         if (!file) {
 286                 walk_page_range(vma->vm_mm, start, end, &swapin_walk_ops, vma);
 287                 lru_add_drain(); /* Push any new pages onto the LRU now */
 288                 return 0;
 289         }
 290
 291         if (shmem_mapping(file->f_mapping)) {
 292                 force_shm_swapin_readahead(vma, start, end,
 293                                         file->f_mapping);
 294                 return 0;
 295         }
 296 #else
 297         if (!file)
 298                 return -EBADF;
 299 #endif
 300
 301         if (IS_DAX(file_inode(file))) {
 302                 /* no bad return value, but ignore advice */
 303                 return 0;
 304         }
 305
 306         /*
 307          * Filesystem's fadvise may need to take various locks.  We need to
 308          * explicitly grab a reference because the vma (and hence the
 309          * vma's reference to the file) can go away as soon as we drop
 310          * mmap_lock.
 311          */
 312         *prev = NULL;   /* tell sys_madvise we drop mmap_lock */
 313         get_file(file);
 314         offset = (loff_t)(start - vma->vm_start)
 315                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 316         mmap_read_unlock(mm);
 317         vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED);
 318         fput(file);
 319         mmap_read_lock(mm);
 320         return 0;
 321 }
 322
 323 static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
 324                                 unsigned long addr, unsigned long end,
 325                                 struct mm_walk *walk)
 326 {
 327         struct madvise_walk_private *private = walk->private;
 328         struct mmu_gather *tlb = private->tlb;
 329         bool pageout = private->pageout;
 330         struct mm_struct *mm = tlb->mm;
 331         struct vm_area_struct *vma = walk->vma;
 332         pte_t *orig_pte, *pte, ptent;
 333         spinlock_t *ptl;
 334         struct page *page = NULL;
 335         LIST_HEAD(page_list);
 336
 337         if (fatal_signal_pending(current))
 338                 return -EINTR;
 339
 340 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 341         if (pmd_trans_huge(*pmd)) {
 342                 pmd_t orig_pmd;
 343                 unsigned long next = pmd_addr_end(addr, end);
 344
 345                 tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
 346                 ptl = pmd_trans_huge_lock(pmd, vma);
 347                 if (!ptl)
 348                         return 0;
 349
 350                 orig_pmd = *pmd;
 351                 if (is_huge_zero_pmd(orig_pmd))
 352                         goto huge_unlock;
 353
 354                 if (unlikely(!pmd_present(orig_pmd))) {
 355                         VM_BUG_ON(thp_migration_supported() &&
 356                                         !is_pmd_migration_entry(orig_pmd));
 357                         goto huge_unlock;
 358                 }
 359
 360                 page = pmd_page(orig_pmd);
 361
 362                 /* Do not interfere with other mappings of this page */
 363                 if (page_mapcount(page) != 1)
 364                         goto huge_unlock;
 365
 366                 if (next - addr != HPAGE_PMD_SIZE) {
 367                         int err;
 368
 369                         get_page(page);
 370                         spin_unlock(ptl);
 371                         lock_page(page);
 372                         err = split_huge_page(page);
 373                         unlock_page(page);
 374                         put_page(page);
 375                         if (!err)
 376                                 goto regular_page;
 377                         return 0;
 378                 }
 379
 380                 if (pmd_young(orig_pmd)) {
 381                         pmdp_invalidate(vma, addr, pmd);
 382                         orig_pmd = pmd_mkold(orig_pmd);
 383
 384                         set_pmd_at(mm, addr, pmd, orig_pmd);
 385                         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
 386                 }
 387
 388                 ClearPageReferenced(page);
 389                 test_and_clear_page_young(page);
 390                 if (pageout) {
 391                         if (!isolate_lru_page(page)) {
 392                                 if (PageUnevictable(page))
 393                                         putback_lru_page(page);
 394                                 else
 395                                         list_add(&page->lru, &page_list);
 396                         }
 397                 } else
 398                         deactivate_page(page);
 399 huge_unlock:
 400                 spin_unlock(ptl);
 401                 if (pageout)
 402                         reclaim_pages(&page_list);
 403                 return 0;
 404         }
 405
 406 regular_page:
 407         if (pmd_trans_unstable(pmd))
 408                 return 0;
 409 #endif
 410         tlb_change_page_size(tlb, PAGE_SIZE);
 411         orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 412         flush_tlb_batched_pending(mm);
 413         arch_enter_lazy_mmu_mode();
 414         for (; addr < end; pte++, addr += PAGE_SIZE) {
 415                 ptent = *pte;
 416
 417                 if (pte_none(ptent))
 418                         continue;
 419
 420                 if (!pte_present(ptent))
 421                         continue;
 422
 423                 page = vm_normal_page(vma, addr, ptent);
 424                 if (!page || is_zone_device_page(page))
 425                         continue;
 426
 427                 /*
 428                  * Creating a THP page is expensive so split it only if we
 429                  * are sure it's worth. Split it if we are only owner.
 430                  */
 431                 if (PageTransCompound(page)) {
 432                         if (page_mapcount(page) != 1)
 433                                 break;
 434                         get_page(page);
 435                         if (!trylock_page(page)) {
 436                                 put_page(page);
 437                                 break;
 438                         }
 439                         pte_unmap_unlock(orig_pte, ptl);
 440                         if (split_huge_page(page)) {
 441                                 unlock_page(page);
 442                                 put_page(page);
 443                                 orig_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 444                                 break;
 445                         }
 446                         unlock_page(page);
 447                         put_page(page);
 448                         orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 449                         pte--;
 450                         addr -= PAGE_SIZE;
 451                         continue;
 452                 }
 453
 454                 /* Do not interfere with other mappings of this page */
 455                 if (page_mapcount(page) != 1)
 456                         continue;
 457
 458                 VM_BUG_ON_PAGE(PageTransCompound(page), page);
 459
 460                 if (pte_young(ptent)) {
 461                         ptent = ptep_get_and_clear_full(mm, addr, pte,
 462                                                         tlb->fullmm);
 463                         ptent = pte_mkold(ptent);
 464                         set_pte_at(mm, addr, pte, ptent);
 465                         tlb_remove_tlb_entry(tlb, pte, addr);
 466                 }
 467
 468                 /*
 469                  * We are deactivating a page for accelerating reclaiming.
 470                  * VM couldn't reclaim the page unless we clear PG_young.
 471                  * As a side effect, it makes confuse idle-page tracking
 472                  * because they will miss recent referenced history.
 473                  */
 474                 ClearPageReferenced(page);
 475                 test_and_clear_page_young(page);
 476                 if (pageout) {
 477                         if (!isolate_lru_page(page)) {
 478                                 if (PageUnevictable(page))
 479                                         putback_lru_page(page);
 480                                 else
 481                                         list_add(&page->lru, &page_list);
 482                         }
 483                 } else
 484                         deactivate_page(page);
 485         }
 486
 487         arch_leave_lazy_mmu_mode();
 488         pte_unmap_unlock(orig_pte, ptl);
 489         if (pageout)
 490                 reclaim_pages(&page_list);
 491         cond_resched();
 492
 493         return 0;
 494 }
 495
 496 static const struct mm_walk_ops cold_walk_ops = {
 497         .pmd_entry = madvise_cold_or_pageout_pte_range,
 498 };
 499
 500 static void madvise_cold_page_range(struct mmu_gather *tlb,
 501                              struct vm_area_struct *vma,
 502                              unsigned long addr, unsigned long end)
 503 {
 504         struct madvise_walk_private walk_private = {
 505                 .pageout = false,
 506                 .tlb = tlb,
 507         };
 508
 509         tlb_start_vma(tlb, vma);
 510         walk_page_range(vma->vm_mm, addr, end, &cold_walk_ops, &walk_private);
 511         tlb_end_vma(tlb, vma);
 512 }
 513
 514 static inline bool can_madv_lru_vma(struct vm_area_struct *vma)
 515 {
 516         return !(vma->vm_flags & (VM_LOCKED|VM_PFNMAP|VM_HUGETLB));
 517 }
 518
 519 static long madvise_cold(struct vm_area_struct *vma,
 520                         struct vm_area_struct **prev,
 521                         unsigned long start_addr, unsigned long end_addr)
 522 {
 523         struct mm_struct *mm = vma->vm_mm;
 524         struct mmu_gather tlb;
 525
 526         *prev = vma;
 527         if (!can_madv_lru_vma(vma))
 528                 return -EINVAL;
 529
 530         lru_add_drain();
 531         tlb_gather_mmu(&tlb, mm);
 532         madvise_cold_page_range(&tlb, vma, start_addr, end_addr);
 533         tlb_finish_mmu(&tlb);
 534
 535         return 0;
 536 }
 537
 538 static void madvise_pageout_page_range(struct mmu_gather *tlb,
 539                              struct vm_area_struct *vma,
 540                              unsigned long addr, unsigned long end)
 541 {
 542         struct madvise_walk_private walk_private = {
 543                 .pageout = true,
 544                 .tlb = tlb,
 545         };
 546
 547         tlb_start_vma(tlb, vma);
 548         walk_page_range(vma->vm_mm, addr, end, &cold_walk_ops, &walk_private);
 549         tlb_end_vma(tlb, vma);
 550 }
 551
 552 static inline bool can_do_pageout(struct vm_area_struct *vma)
 553 {
 554         if (vma_is_anonymous(vma))
 555                 return true;
 556         if (!vma->vm_file)
 557                 return false;
 558         /*
 559          * paging out pagecache only for non-anonymous mappings that correspond
 560          * to the files the calling process could (if tried) open for writing;
 561          * otherwise we'd be including shared non-exclusive mappings, which
 562          * opens a side channel.
 563          */
 564         return inode_owner_or_capable(&init_user_ns,
 565                                       file_inode(vma->vm_file)) ||
 566                file_permission(vma->vm_file, MAY_WRITE) == 0;
 567 }
 568
 569 static long madvise_pageout(struct vm_area_struct *vma,
 570                         struct vm_area_struct **prev,
 571                         unsigned long start_addr, unsigned long end_addr)
 572 {
 573         struct mm_struct *mm = vma->vm_mm;
 574         struct mmu_gather tlb;
 575
 576         *prev = vma;
 577         if (!can_madv_lru_vma(vma))
 578                 return -EINVAL;
 579
 580         if (!can_do_pageout(vma))
 581                 return 0;
 582
 583         lru_add_drain();
 584         tlb_gather_mmu(&tlb, mm);
 585         madvise_pageout_page_range(&tlb, vma, start_addr, end_addr);
 586         tlb_finish_mmu(&tlb);
 587
 588         return 0;
 589 }
 590
 591 static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 592                                 unsigned long end, struct mm_walk *walk)
 593
 594 {
 595         struct mmu_gather *tlb = walk->private;
 596         struct mm_struct *mm = tlb->mm;
 597         struct vm_area_struct *vma = walk->vma;
 598         spinlock_t *ptl;
 599         pte_t *orig_pte, *pte, ptent;
 600         struct page *page;
 601         int nr_swap = 0;
 602         unsigned long next;
 603
 604         next = pmd_addr_end(addr, end);
 605         if (pmd_trans_huge(*pmd))
 606                 if (madvise_free_huge_pmd(tlb, vma, pmd, addr, next))
 607                         goto next;
 608
 609         if (pmd_trans_unstable(pmd))
 610                 return 0;
 611
 612         tlb_change_page_size(tlb, PAGE_SIZE);
 613         orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 614         flush_tlb_batched_pending(mm);
 615         arch_enter_lazy_mmu_mode();
 616         for (; addr != end; pte++, addr += PAGE_SIZE) {
 617                 ptent = *pte;
 618
 619                 if (pte_none(ptent))
 620                         continue;
 621                 /*
 622                  * If the pte has swp_entry, just clear page table to
 623                  * prevent swap-in which is more expensive rather than
 624                  * (page allocation + zeroing).
 625                  */
 626                 if (!pte_present(ptent)) {
 627                         swp_entry_t entry;
 628
 629                         entry = pte_to_swp_entry(ptent);
 630                         if (!non_swap_entry(entry)) {
 631                                 nr_swap--;
 632                                 free_swap_and_cache(entry);
 633                                 pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
 634                         } else if (is_hwpoison_entry(entry) ||
 635                                    is_swapin_error_entry(entry)) {
 636                                 pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
 637                         }
 638                         continue;
 639                 }
 640
 641                 page = vm_normal_page(vma, addr, ptent);
 642                 if (!page || is_zone_device_page(page))
 643                         continue;
 644
 645                 /*
 646                  * If pmd isn't transhuge but the page is THP and
 647                  * is owned by only this process, split it and
 648                  * deactivate all pages.
 649                  */
 650                 if (PageTransCompound(page)) {
 651                         if (page_mapcount(page) != 1)
 652                                 goto out;
 653                         get_page(page);
 654                         if (!trylock_page(page)) {
 655                                 put_page(page);
 656                                 goto out;
 657                         }
 658                         pte_unmap_unlock(orig_pte, ptl);
 659                         if (split_huge_page(page)) {
 660                                 unlock_page(page);
 661                                 put_page(page);
 662                                 orig_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 663                                 goto out;
 664                         }
 665                         unlock_page(page);
 666                         put_page(page);
 667                         orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 668                         pte--;
 669                         addr -= PAGE_SIZE;
 670                         continue;
 671                 }
 672
 673                 VM_BUG_ON_PAGE(PageTransCompound(page), page);
 674
 675                 if (PageSwapCache(page) || PageDirty(page)) {
 676                         if (!trylock_page(page))
 677                                 continue;
 678                         /*
 679                          * If page is shared with others, we couldn't clear
 680                          * PG_dirty of the page.
 681                          */
 682                         if (page_mapcount(page) != 1) {
 683                                 unlock_page(page);
 684                                 continue;
 685                         }
 686
 687                         if (PageSwapCache(page) && !try_to_free_swap(page)) {
 688                                 unlock_page(page);
 689                                 continue;
 690                         }
 691
 692                         ClearPageDirty(page);
 693                         unlock_page(page);
 694                 }
 695
 696                 if (pte_young(ptent) || pte_dirty(ptent)) {
 697                         /*
 698                          * Some of architecture(ex, PPC) don't update TLB
 699                          * with set_pte_at and tlb_remove_tlb_entry so for
 700                          * the portability, remap the pte with old|clean
 701                          * after pte clearing.
 702                          */
 703                         ptent = ptep_get_and_clear_full(mm, addr, pte,
 704                                                         tlb->fullmm);
 705
 706                         ptent = pte_mkold(ptent);
 707                         ptent = pte_mkclean(ptent);
 708                         set_pte_at(mm, addr, pte, ptent);
 709                         tlb_remove_tlb_entry(tlb, pte, addr);
 710                 }
 711                 mark_page_lazyfree(page);
 712         }
 713 out:
 714         if (nr_swap) {
 715                 if (current->mm == mm)
 716                         sync_mm_rss(mm);
 717
 718                 add_mm_counter(mm, MM_SWAPENTS, nr_swap);
 719         }
 720         arch_leave_lazy_mmu_mode();
 721         pte_unmap_unlock(orig_pte, ptl);
 722         cond_resched();
 723 next:
 724         return 0;
 725 }
 726
 727 static const struct mm_walk_ops madvise_free_walk_ops = {
 728         .pmd_entry              = madvise_free_pte_range,
 729 };
 730
 731 static int madvise_free_single_vma(struct vm_area_struct *vma,
 732                         unsigned long start_addr, unsigned long end_addr)
 733 {
 734         struct mm_struct *mm = vma->vm_mm;
 735         struct mmu_notifier_range range;
 736         struct mmu_gather tlb;
 737
 738         /* MADV_FREE works for only anon vma at the moment */
 739         if (!vma_is_anonymous(vma))
 740                 return -EINVAL;
 741
 742         range.start = max(vma->vm_start, start_addr);
 743         if (range.start >= vma->vm_end)
 744                 return -EINVAL;
 745         range.end = min(vma->vm_end, end_addr);
 746         if (range.end <= vma->vm_start)
 747                 return -EINVAL;
 748         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm,
 749                                 range.start, range.end);
 750
 751         lru_add_drain();
 752         tlb_gather_mmu(&tlb, mm);
 753         update_hiwater_rss(mm);
 754
 755         mmu_notifier_invalidate_range_start(&range);
 756         tlb_start_vma(&tlb, vma);
 757         walk_page_range(vma->vm_mm, range.start, range.end,
 758                         &madvise_free_walk_ops, &tlb);
 759         tlb_end_vma(&tlb, vma);
 760         mmu_notifier_invalidate_range_end(&range);
 761         tlb_finish_mmu(&tlb);
 762
 763         return 0;
 764 }
 765
 766 /*
 767  * Application no longer needs these pages.  If the pages are dirty,
 768  * it's OK to just throw them away.  The app will be more careful about
 769  * data it wants to keep.  Be sure to free swap resources too.  The
 770  * zap_page_range call sets things up for shrink_active_list to actually free
 771  * these pages later if no one else has touched them in the meantime,
 772  * although we could add these pages to a global reuse list for
 773  * shrink_active_list to pick up before reclaiming other pages.
 774  *
 775  * NB: This interface discards data rather than pushes it out to swap,
 776  * as some implementations do.  This has performance implications for
 777  * applications like large transactional databases which want to discard
 778  * pages in anonymous maps after committing to backing store the data
 779  * that was kept in them.  There is no reason to write this data out to
 780  * the swap area if the application is discarding it.
 781  *
 782  * An interface that causes the system to free clean pages and flush
 783  * dirty pages is already available as msync(MS_INVALIDATE).
 784  */
 785 static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
 786                                         unsigned long start, unsigned long end)
 787 {
 788         zap_page_range(vma, start, end - start);
 789         return 0;
 790 }
 791
 792 static bool madvise_dontneed_free_valid_vma(struct vm_area_struct *vma,
 793                                             unsigned long start,
 794                                             unsigned long *end,
 795                                             int behavior)
 796 {
 797         if (!is_vm_hugetlb_page(vma)) {
 798                 unsigned int forbidden = VM_PFNMAP;
 799
 800                 if (behavior != MADV_DONTNEED_LOCKED)
 801                         forbidden |= VM_LOCKED;
 802
 803                 return !(vma->vm_flags & forbidden);
 804         }
 805
 806         if (behavior != MADV_DONTNEED && behavior != MADV_DONTNEED_LOCKED)
 807                 return false;
 808         if (start & ~huge_page_mask(hstate_vma(vma)))
 809                 return false;
 810
 811         *end = ALIGN(*end, huge_page_size(hstate_vma(vma)));
 812         return true;
 813 }
 814
 815 static long madvise_dontneed_free(struct vm_area_struct *vma,
 816                                   struct vm_area_struct **prev,
 817                                   unsigned long start, unsigned long end,
 818                                   int behavior)
 819 {
 820         struct mm_struct *mm = vma->vm_mm;
 821
 822         *prev = vma;
 823         if (!madvise_dontneed_free_valid_vma(vma, start, &end, behavior))
 824                 return -EINVAL;
 825
 826         if (!userfaultfd_remove(vma, start, end)) {
 827                 *prev = NULL; /* mmap_lock has been dropped, prev is stale */
 828
 829                 mmap_read_lock(mm);
 830                 vma = find_vma(mm, start);
 831                 if (!vma)
 832                         return -ENOMEM;
 833                 if (start < vma->vm_start) {
 834                         /*
 835                          * This "vma" under revalidation is the one
 836                          * with the lowest vma->vm_start where start
 837                          * is also < vma->vm_end. If start <
 838                          * vma->vm_start it means an hole materialized
 839                          * in the user address space within the
 840                          * virtual range passed to MADV_DONTNEED
 841                          * or MADV_FREE.
 842                          */
 843                         return -ENOMEM;
 844                 }
 845                 /*
 846                  * Potential end adjustment for hugetlb vma is OK as
 847                  * the check below keeps end within vma.
 848                  */
 849                 if (!madvise_dontneed_free_valid_vma(vma, start, &end,
 850                                                      behavior))
 851                         return -EINVAL;
 852                 if (end > vma->vm_end) {
 853                         /*
 854                          * Don't fail if end > vma->vm_end. If the old
 855                          * vma was split while the mmap_lock was
 856                          * released the effect of the concurrent
 857                          * operation may not cause madvise() to
 858                          * have an undefined result. There may be an
 859                          * adjacent next vma that we'll walk
 860                          * next. userfaultfd_remove() will generate an
 861                          * UFFD_EVENT_REMOVE repetition on the
 862                          * end-vma->vm_end range, but the manager can
 863                          * handle a repetition fine.
 864                          */
 865                         end = vma->vm_end;
 866                 }
 867                 VM_WARN_ON(start >= end);
 868         }
 869
 870         if (behavior == MADV_DONTNEED || behavior == MADV_DONTNEED_LOCKED)
 871                 return madvise_dontneed_single_vma(vma, start, end);
 872         else if (behavior == MADV_FREE)
 873                 return madvise_free_single_vma(vma, start, end);
 874         else
 875                 return -EINVAL;
 876 }
 877
 878 static long madvise_populate(struct vm_area_struct *vma,
 879                              struct vm_area_struct **prev,
 880                              unsigned long start, unsigned long end,
 881                              int behavior)
 882 {
 883         const bool write = behavior == MADV_POPULATE_WRITE;
 884         struct mm_struct *mm = vma->vm_mm;
 885         unsigned long tmp_end;
 886         int locked = 1;
 887         long pages;
 888
 889         *prev = vma;
 890
 891         while (start < end) {
 892                 /*
 893                  * We might have temporarily dropped the lock. For example,
 894                  * our VMA might have been split.
 895                  */
 896                 if (!vma || start >= vma->vm_end) {
 897                         vma = vma_lookup(mm, start);
 898                         if (!vma)
 899                                 return -ENOMEM;
 900                 }
 901
 902                 tmp_end = min_t(unsigned long, end, vma->vm_end);
 903                 /* Populate (prefault) page tables readable/writable. */
 904                 pages = faultin_vma_page_range(vma, start, tmp_end, write,
 905                                                &locked);
 906                 if (!locked) {
 907                         mmap_read_lock(mm);
 908                         locked = 1;
 909                         *prev = NULL;
 910                         vma = NULL;
 911                 }
 912                 if (pages < 0) {
 913                         switch (pages) {
 914                         case -EINTR:
 915                                 return -EINTR;
 916                         case -EINVAL: /* Incompatible mappings / permissions. */
 917                                 return -EINVAL;
 918                         case -EHWPOISON:
 919                                 return -EHWPOISON;
 920                         case -EFAULT: /* VM_FAULT_SIGBUS or VM_FAULT_SIGSEGV */
 921                                 return -EFAULT;
 922                         default:
 923                                 pr_warn_once("%s: unhandled return value: %ld\n",
 924                                              __func__, pages);
 925                                 fallthrough;
 926                         case -ENOMEM:
 927                                 return -ENOMEM;
 928                         }
 929                 }
 930                 start += pages * PAGE_SIZE;
 931         }
 932         return 0;
 933 }
 934
 935 /*
 936  * Application wants to free up the pages and associated backing store.
 937  * This is effectively punching a hole into the middle of a file.
 938  */
 939 static long madvise_remove(struct vm_area_struct *vma,
 940                                 struct vm_area_struct **prev,
 941                                 unsigned long start, unsigned long end)
 942 {
 943         loff_t offset;
 944         int error;
 945         struct file *f;
 946         struct mm_struct *mm = vma->vm_mm;
 947
 948         *prev = NULL;   /* tell sys_madvise we drop mmap_lock */
 949
 950         if (vma->vm_flags & VM_LOCKED)
 951                 return -EINVAL;
 952
 953         f = vma->vm_file;
 954
 955         if (!f || !f->f_mapping || !f->f_mapping->host) {
 956                         return -EINVAL;
 957         }
 958
 959         if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
 960                 return -EACCES;
 961
 962         offset = (loff_t)(start - vma->vm_start)
 963                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 964
 965         /*
 966          * Filesystem's fallocate may need to take i_rwsem.  We need to
 967          * explicitly grab a reference because the vma (and hence the
 968          * vma's reference to the file) can go away as soon as we drop
 969          * mmap_lock.
 970          */
 971         get_file(f);
 972         if (userfaultfd_remove(vma, start, end)) {
 973                 /* mmap_lock was not released by userfaultfd_remove() */
 974                 mmap_read_unlock(mm);
 975         }
 976         error = vfs_fallocate(f,
 977                                 FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
 978                                 offset, end - start);
 979         fput(f);
 980         mmap_read_lock(mm);
 981         return error;
 982 }
 983
 984 /*
 985  * Apply an madvise behavior to a region of a vma.  madvise_update_vma
 986  * will handle splitting a vm area into separate areas, each area with its own
 987  * behavior.
 988  */
 989 static int madvise_vma_behavior(struct vm_area_struct *vma,
 990                                 struct vm_area_struct **prev,
 991                                 unsigned long start, unsigned long end,
 992                                 unsigned long behavior)
 993 {
 994         int error;
 995         struct anon_vma_name *anon_name;
 996         unsigned long new_flags = vma->vm_flags;
 997
 998         switch (behavior) {
 999         case MADV_REMOVE:
1000                 return madvise_remove(vma, prev, start, end);
1001         case MADV_WILLNEED:
1002                 return madvise_willneed(vma, prev, start, end);
1003         case MADV_COLD:
1004                 return madvise_cold(vma, prev, start, end);
1005         case MADV_PAGEOUT:
1006                 return madvise_pageout(vma, prev, start, end);
1007         case MADV_FREE:
1008         case MADV_DONTNEED:
1009         case MADV_DONTNEED_LOCKED:
1010                 return madvise_dontneed_free(vma, prev, start, end, behavior);
1011         case MADV_POPULATE_READ:
1012         case MADV_POPULATE_WRITE:
1013                 return madvise_populate(vma, prev, start, end, behavior);
1014         case MADV_NORMAL:
1015                 new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
1016                 break;
1017         case MADV_SEQUENTIAL:
1018                 new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
1019                 break;
1020         case MADV_RANDOM:
1021                 new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
1022                 break;
1023         case MADV_DONTFORK:
1024                 new_flags |= VM_DONTCOPY;
1025                 break;
1026         case MADV_DOFORK:
1027                 if (vma->vm_flags & VM_IO)
1028                         return -EINVAL;
1029                 new_flags &= ~VM_DONTCOPY;
1030                 break;
1031         case MADV_WIPEONFORK:
1032                 /* MADV_WIPEONFORK is only supported on anonymous memory. */
1033                 if (vma->vm_file || vma->vm_flags & VM_SHARED)
1034                         return -EINVAL;
1035                 new_flags |= VM_WIPEONFORK;
1036                 break;
1037         case MADV_KEEPONFORK:
1038                 new_flags &= ~VM_WIPEONFORK;
1039                 break;
1040         case MADV_DONTDUMP:
1041                 new_flags |= VM_DONTDUMP;
1042                 break;
1043         case MADV_DODUMP:
1044                 if (!is_vm_hugetlb_page(vma) && new_flags & VM_SPECIAL)
1045                         return -EINVAL;
1046                 new_flags &= ~VM_DONTDUMP;
1047                 break;
1048         case MADV_MERGEABLE:
1049         case MADV_UNMERGEABLE:
1050                 error = ksm_madvise(vma, start, end, behavior, &new_flags);
1051                 if (error)
1052                         goto out;
1053                 break;
1054         case MADV_HUGEPAGE:
1055         case MADV_NOHUGEPAGE:
1056                 error = hugepage_madvise(vma, &new_flags, behavior);
1057                 if (error)
1058                         goto out;
1059                 break;
1060         }
1061
1062         anon_name = anon_vma_name(vma);
1063         anon_vma_name_get(anon_name);
1064         error = madvise_update_vma(vma, prev, start, end, new_flags,
1065                                    anon_name);
1066         anon_vma_name_put(anon_name);
1067
1068 out:
1069         /*
1070          * madvise() returns EAGAIN if kernel resources, such as
1071          * slab, are temporarily unavailable.
1072          */
1073         if (error == -ENOMEM)
1074                 error = -EAGAIN;
1075         return error;
1076 }
1077
1078 #ifdef CONFIG_MEMORY_FAILURE
1079 /*
1080  * Error injection support for memory error handling.
1081  */
1082 static int madvise_inject_error(int behavior,
1083                 unsigned long start, unsigned long end)
1084 {
1085         unsigned long size;
1086
1087         if (!capable(CAP_SYS_ADMIN))
1088                 return -EPERM;
1089
1090
1091         for (; start < end; start += size) {
1092                 unsigned long pfn;
1093                 struct page *page;
1094                 int ret;
1095
1096                 ret = get_user_pages_fast(start, 1, 0, &page);
1097                 if (ret != 1)
1098                         return ret;
1099                 pfn = page_to_pfn(page);
1100
1101                 /*
1102                  * When soft offlining hugepages, after migrating the page
1103                  * we dissolve it, therefore in the second loop "page" will
1104                  * no longer be a compound page.
1105                  */
1106                 size = page_size(compound_head(page));
1107
1108                 if (behavior == MADV_SOFT_OFFLINE) {
1109                         pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
1110                                  pfn, start);
1111                         ret = soft_offline_page(pfn, MF_COUNT_INCREASED);
1112                 } else {
1113                         pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
1114                                  pfn, start);
1115                         ret = memory_failure(pfn, MF_COUNT_INCREASED | MF_SW_SIMULATED);
1116                         if (ret == -EOPNOTSUPP)
1117                                 ret = 0;
1118                 }
1119
1120                 if (ret)
1121                         return ret;
1122         }
1123
1124         return 0;
1125 }
1126 #endif
1127
1128 static bool
1129 madvise_behavior_valid(int behavior)
1130 {
1131         switch (behavior) {
1132         case MADV_DOFORK:
1133         case MADV_DONTFORK:
1134         case MADV_NORMAL:
1135         case MADV_SEQUENTIAL:
1136         case MADV_RANDOM:
1137         case MADV_REMOVE:
1138         case MADV_WILLNEED:
1139         case MADV_DONTNEED:
1140         case MADV_DONTNEED_LOCKED:
1141         case MADV_FREE:
1142         case MADV_COLD:
1143         case MADV_PAGEOUT:
1144         case MADV_POPULATE_READ:
1145         case MADV_POPULATE_WRITE:
1146 #ifdef CONFIG_KSM
1147         case MADV_MERGEABLE:
1148         case MADV_UNMERGEABLE:
1149 #endif
1150 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
1151         case MADV_HUGEPAGE:
1152         case MADV_NOHUGEPAGE:
1153 #endif
1154         case MADV_DONTDUMP:
1155         case MADV_DODUMP:
1156         case MADV_WIPEONFORK:
1157         case MADV_KEEPONFORK:
1158 #ifdef CONFIG_MEMORY_FAILURE
1159         case MADV_SOFT_OFFLINE:
1160         case MADV_HWPOISON:
1161 #endif
1162                 return true;
1163
1164         default:
1165                 return false;
1166         }
1167 }
1168
1169 static bool
1170 process_madvise_behavior_valid(int behavior)
1171 {
1172         switch (behavior) {
1173         case MADV_COLD:
1174         case MADV_PAGEOUT:
1175         case MADV_WILLNEED:
1176                 return true;
1177         default:
1178                 return false;
1179         }
1180 }
1181
1182 /*
1183  * Walk the vmas in range [start,end), and call the visit function on each one.
1184  * The visit function will get start and end parameters that cover the overlap
1185  * between the current vma and the original range.  Any unmapped regions in the
1186  * original range will result in this function returning -ENOMEM while still
1187  * calling the visit function on all of the existing vmas in the range.
1188  * Must be called with the mmap_lock held for reading or writing.
1189  */
1190 static
1191 int madvise_walk_vmas(struct mm_struct *mm, unsigned long start,
1192                       unsigned long end, unsigned long arg,
1193                       int (*visit)(struct vm_area_struct *vma,
1194                                    struct vm_area_struct **prev, unsigned long start,
1195                                    unsigned long end, unsigned long arg))
1196 {
1197         struct vm_area_struct *vma;
1198         struct vm_area_struct *prev;
1199         unsigned long tmp;
1200         int unmapped_error = 0;
1201
1202         /*
1203          * If the interval [start,end) covers some unmapped address
1204          * ranges, just ignore them, but return -ENOMEM at the end.
1205          * - different from the way of handling in mlock etc.
1206          */
1207         vma = find_vma_prev(mm, start, &prev);
1208         if (vma && start > vma->vm_start)
1209                 prev = vma;
1210
1211         for (;;) {
1212                 int error;
1213
1214                 /* Still start < end. */
1215                 if (!vma)
1216                         return -ENOMEM;
1217
1218                 /* Here start < (end|vma->vm_end). */
1219                 if (start < vma->vm_start) {
1220                         unmapped_error = -ENOMEM;
1221                         start = vma->vm_start;
1222                         if (start >= end)
1223                                 break;
1224                 }
1225
1226                 /* Here vma->vm_start <= start < (end|vma->vm_end) */
1227                 tmp = vma->vm_end;
1228                 if (end < tmp)
1229                         tmp = end;
1230
1231                 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
1232                 error = visit(vma, &prev, start, tmp, arg);
1233                 if (error)
1234                         return error;
1235                 start = tmp;
1236                 if (prev && start < prev->vm_end)
1237                         start = prev->vm_end;
1238                 if (start >= end)
1239                         break;
1240                 if (prev)
1241                         vma = prev->vm_next;
1242                 else    /* madvise_remove dropped mmap_lock */
1243                         vma = find_vma(mm, start);
1244         }
1245
1246         return unmapped_error;
1247 }
1248
1249 #ifdef CONFIG_ANON_VMA_NAME
1250 static int madvise_vma_anon_name(struct vm_area_struct *vma,
1251                                  struct vm_area_struct **prev,
1252                                  unsigned long start, unsigned long end,
1253                                  unsigned long anon_name)
1254 {
1255         int error;
1256
1257         /* Only anonymous mappings can be named */
1258         if (vma->vm_file)
1259                 return -EBADF;
1260
1261         error = madvise_update_vma(vma, prev, start, end, vma->vm_flags,
1262                                    (struct anon_vma_name *)anon_name);
1263
1264         /*
1265          * madvise() returns EAGAIN if kernel resources, such as
1266          * slab, are temporarily unavailable.
1267          */
1268         if (error == -ENOMEM)
1269                 error = -EAGAIN;
1270         return error;
1271 }
1272
1273 int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
1274                           unsigned long len_in, struct anon_vma_name *anon_name)
1275 {
1276         unsigned long end;
1277         unsigned long len;
1278
1279         if (start & ~PAGE_MASK)
1280                 return -EINVAL;
1281         len = (len_in + ~PAGE_MASK) & PAGE_MASK;
1282
1283         /* Check to see whether len was rounded up from small -ve to zero */
1284         if (len_in && !len)
1285                 return -EINVAL;
1286
1287         end = start + len;
1288         if (end < start)
1289                 return -EINVAL;
1290
1291         if (end == start)
1292                 return 0;
1293
1294         return madvise_walk_vmas(mm, start, end, (unsigned long)anon_name,
1295                                  madvise_vma_anon_name);
1296 }
1297 #endif /* CONFIG_ANON_VMA_NAME */
1298 /*
1299  * The madvise(2) system call.
1300  *
1301  * Applications can use madvise() to advise the kernel how it should
1302  * handle paging I/O in this VM area.  The idea is to help the kernel
1303  * use appropriate read-ahead and caching techniques.  The information
1304  * provided is advisory only, and can be safely disregarded by the
1305  * kernel without affecting the correct operation of the application.
1306  *
1307  * behavior values:
1308  *  MADV_NORMAL - the default behavior is to read clusters.  This
1309  *              results in some read-ahead and read-behind.
1310  *  MADV_RANDOM - the system should read the minimum amount of data
1311  *              on any access, since it is unlikely that the appli-
1312  *              cation will need more than what it asks for.
1313  *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
1314  *              once, so they can be aggressively read ahead, and
1315  *              can be freed soon after they are accessed.
1316  *  MADV_WILLNEED - the application is notifying the system to read
1317  *              some pages ahead.
1318  *  MADV_DONTNEED - the application is finished with the given range,
1319  *              so the kernel can free resources associated with it.
1320  *  MADV_FREE - the application marks pages in the given range as lazy free,
1321  *              where actual purges are postponed until memory pressure happens.
1322  *  MADV_REMOVE - the application wants to free up the given range of
1323  *              pages and associated backing store.
1324  *  MADV_DONTFORK - omit this area from child's address space when forking:
1325  *              typically, to avoid COWing pages pinned by get_user_pages().
1326  *  MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
1327  *  MADV_WIPEONFORK - present the child process with zero-filled memory in this
1328  *              range after a fork.
1329  *  MADV_KEEPONFORK - undo the effect of MADV_WIPEONFORK
1330  *  MADV_HWPOISON - trigger memory error handler as if the given memory range
1331  *              were corrupted by unrecoverable hardware memory failure.
1332  *  MADV_SOFT_OFFLINE - try to soft-offline the given range of memory.
1333  *  MADV_MERGEABLE - the application recommends that KSM try to merge pages in
1334  *              this area with pages of identical content from other such areas.
1335  *  MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
1336  *  MADV_HUGEPAGE - the application wants to back the given range by transparent
1337  *              huge pages in the future. Existing pages might be coalesced and
1338  *              new pages might be allocated as THP.
1339  *  MADV_NOHUGEPAGE - mark the given range as not worth being backed by
1340  *              transparent huge pages so the existing pages will not be
1341  *              coalesced into THP and new pages will not be allocated as THP.
1342  *  MADV_DONTDUMP - the application wants to prevent pages in the given range
1343  *              from being included in its core dump.
1344  *  MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
1345  *  MADV_COLD - the application is not expected to use this memory soon,
1346  *              deactivate pages in this range so that they can be reclaimed
1347  *              easily if memory pressure happens.
1348  *  MADV_PAGEOUT - the application is not expected to use this memory soon,
1349  *              page out the pages in this range immediately.
1350  *  MADV_POPULATE_READ - populate (prefault) page tables readable by
1351  *              triggering read faults if required
1352  *  MADV_POPULATE_WRITE - populate (prefault) page tables writable by
1353  *              triggering write faults if required
1354  *
1355  * return values:
1356  *  zero    - success
1357  *  -EINVAL - start + len < 0, start is not page-aligned,
1358  *              "behavior" is not a valid value, or application
1359  *              is attempting to release locked or shared pages,
1360  *              or the specified address range includes file, Huge TLB,
1361  *              MAP_SHARED or VMPFNMAP range.
1362  *  -ENOMEM - addresses in the specified range are not currently
1363  *              mapped, or are outside the AS of the process.
1364  *  -EIO    - an I/O error occurred while paging in data.
1365  *  -EBADF  - map exists, but area maps something that isn't a file.
1366  *  -EAGAIN - a kernel resource was temporarily unavailable.
1367  */
1368 int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int behavior)
1369 {
1370         unsigned long end;
1371         int error;
1372         int write;
1373         size_t len;
1374         struct blk_plug plug;
1375
1376         start = untagged_addr(start);
1377
1378         if (!madvise_behavior_valid(behavior))
1379                 return -EINVAL;
1380
1381         if (!PAGE_ALIGNED(start))
1382                 return -EINVAL;
1383         len = PAGE_ALIGN(len_in);
1384
1385         /* Check to see whether len was rounded up from small -ve to zero */
1386         if (len_in && !len)
1387                 return -EINVAL;
1388
1389         end = start + len;
1390         if (end < start)
1391                 return -EINVAL;
1392
1393         if (end == start)
1394                 return 0;
1395
1396 #ifdef CONFIG_MEMORY_FAILURE
1397         if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
1398                 return madvise_inject_error(behavior, start, start + len_in);
1399 #endif
1400
1401         write = madvise_need_mmap_write(behavior);
1402         if (write) {
1403                 if (mmap_write_lock_killable(mm))
1404                         return -EINTR;
1405         } else {
1406                 mmap_read_lock(mm);
1407         }
1408
1409         blk_start_plug(&plug);
1410         error = madvise_walk_vmas(mm, start, end, behavior,
1411                         madvise_vma_behavior);
1412         blk_finish_plug(&plug);
1413         if (write)
1414                 mmap_write_unlock(mm);
1415         else
1416                 mmap_read_unlock(mm);
1417
1418         return error;
1419 }
1420
1421 SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
1422 {
1423         return do_madvise(current->mm, start, len_in, behavior);
1424 }
1425
1426 SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
1427                 size_t, vlen, int, behavior, unsigned int, flags)
1428 {
1429         ssize_t ret;
1430         struct iovec iovstack[UIO_FASTIOV], iovec;
1431         struct iovec *iov = iovstack;
1432         struct iov_iter iter;
1433         struct task_struct *task;
1434         struct mm_struct *mm;
1435         size_t total_len;
1436         unsigned int f_flags;
1437
1438         if (flags != 0) {
1439                 ret = -EINVAL;
1440                 goto out;
1441         }
1442
1443         ret = import_iovec(READ, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);
1444         if (ret < 0)
1445                 goto out;
1446
1447         task = pidfd_get_task(pidfd, &f_flags);
1448         if (IS_ERR(task)) {
1449                 ret = PTR_ERR(task);
1450                 goto free_iov;
1451         }
1452
1453         if (!process_madvise_behavior_valid(behavior)) {
1454                 ret = -EINVAL;
1455                 goto release_task;
1456         }
1457
1458         /* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */
1459         mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
1460         if (IS_ERR_OR_NULL(mm)) {
1461                 ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
1462                 goto release_task;
1463         }
1464
1465         /*
1466          * Require CAP_SYS_NICE for influencing process performance. Note that
1467          * only non-destructive hints are currently supported.
1468          */
1469         if (!capable(CAP_SYS_NICE)) {
1470                 ret = -EPERM;
1471                 goto release_mm;
1472         }
1473
1474         total_len = iov_iter_count(&iter);
1475
1476         while (iov_iter_count(&iter)) {
1477                 iovec = iov_iter_iovec(&iter);
1478                 ret = do_madvise(mm, (unsigned long)iovec.iov_base,
1479                                         iovec.iov_len, behavior);
1480                 if (ret < 0)
1481                         break;
1482                 iov_iter_advance(&iter, iovec.iov_len);
1483         }
1484
1485         ret = (total_len - iov_iter_count(&iter)) ? : ret;
1486
1487 release_mm:
1488         mmput(mm);
1489 release_task:
1490         put_task_struct(task);
1491 free_iov:
1492         kfree(iov);
1493 out:
1494         return ret;
1495 }