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/userfaultfd_k.h>
  15 #include <linux/hugetlb.h>
  16 #include <linux/falloc.h>
  17 #include <linux/sched.h>
  18 #include <linux/ksm.h>
  19 #include <linux/fs.h>
  20 #include <linux/file.h>
  21 #include <linux/blkdev.h>
  22 #include <linux/backing-dev.h>
  23 #include <linux/swap.h>
  24 #include <linux/swapops.h>
  25 #include <linux/shmem_fs.h>
  26 #include <linux/mmu_notifier.h>
  27
  28 #include <asm/tlb.h>
  29
  30 #include "internal.h"
  31
  32 /*
  33  * Any behaviour which results in changes to the vma->vm_flags needs to
  34  * take mmap_sem for writing. Others, which simply traverse vmas, need
  35  * to only take it for reading.
  36  */
  37 static int madvise_need_mmap_write(int behavior)
  38 {
  39         switch (behavior) {
  40         case MADV_REMOVE:
  41         case MADV_WILLNEED:
  42         case MADV_DONTNEED:
  43         case MADV_FREE:
  44                 return 0;
  45         default:
  46                 /* be safe, default to 1. list exceptions explicitly */
  47                 return 1;
  48         }
  49 }
  50
  51 /*
  52  * We can potentially split a vm area into separate
  53  * areas, each area with its own behavior.
  54  */
  55 static long madvise_behavior(struct vm_area_struct *vma,
  56                      struct vm_area_struct **prev,
  57                      unsigned long start, unsigned long end, int behavior)
  58 {
  59         struct mm_struct *mm = vma->vm_mm;
  60         int error = 0;
  61         pgoff_t pgoff;
  62         unsigned long new_flags = vma->vm_flags;
  63
  64         switch (behavior) {
  65         case MADV_NORMAL:
  66                 new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
  67                 break;
  68         case MADV_SEQUENTIAL:
  69                 new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
  70                 break;
  71         case MADV_RANDOM:
  72                 new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
  73                 break;
  74         case MADV_DONTFORK:
  75                 new_flags |= VM_DONTCOPY;
  76                 break;
  77         case MADV_DOFORK:
  78                 if (vma->vm_flags & VM_IO) {
  79                         error = -EINVAL;
  80                         goto out;
  81                 }
  82                 new_flags &= ~VM_DONTCOPY;
  83                 break;
  84         case MADV_WIPEONFORK:
  85                 /* MADV_WIPEONFORK is only supported on anonymous memory. */
  86                 if (vma->vm_file || vma->vm_flags & VM_SHARED) {
  87                         error = -EINVAL;
  88                         goto out;
  89                 }
  90                 new_flags |= VM_WIPEONFORK;
  91                 break;
  92         case MADV_KEEPONFORK:
  93                 new_flags &= ~VM_WIPEONFORK;
  94                 break;
  95         case MADV_DONTDUMP:
  96                 new_flags |= VM_DONTDUMP;
  97                 break;
  98         case MADV_DODUMP:
  99                 if (new_flags & VM_SPECIAL) {
 100                         error = -EINVAL;
 101                         goto out;
 102                 }
 103                 new_flags &= ~VM_DONTDUMP;
 104                 break;
 105         case MADV_MERGEABLE:
 106         case MADV_UNMERGEABLE:
 107                 error = ksm_madvise(vma, start, end, behavior, &new_flags);
 108                 if (error) {
 109                         /*
 110                          * madvise() returns EAGAIN if kernel resources, such as
 111                          * slab, are temporarily unavailable.
 112                          */
 113                         if (error == -ENOMEM)
 114                                 error = -EAGAIN;
 115                         goto out;
 116                 }
 117                 break;
 118         case MADV_HUGEPAGE:
 119         case MADV_NOHUGEPAGE:
 120                 error = hugepage_madvise(vma, &new_flags, behavior);
 121                 if (error) {
 122                         /*
 123                          * madvise() returns EAGAIN if kernel resources, such as
 124                          * slab, are temporarily unavailable.
 125                          */
 126                         if (error == -ENOMEM)
 127                                 error = -EAGAIN;
 128                         goto out;
 129                 }
 130                 break;
 131         }
 132
 133         if (new_flags == vma->vm_flags) {
 134                 *prev = vma;
 135                 goto out;
 136         }
 137
 138         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 139         *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
 140                           vma->vm_file, pgoff, vma_policy(vma),
 141                           vma->vm_userfaultfd_ctx);
 142         if (*prev) {
 143                 vma = *prev;
 144                 goto success;
 145         }
 146
 147         *prev = vma;
 148
 149         if (start != vma->vm_start) {
 150                 if (unlikely(mm->map_count >= sysctl_max_map_count)) {
 151                         error = -ENOMEM;
 152                         goto out;
 153                 }
 154                 error = __split_vma(mm, vma, start, 1);
 155                 if (error) {
 156                         /*
 157                          * madvise() returns EAGAIN if kernel resources, such as
 158                          * slab, are temporarily unavailable.
 159                          */
 160                         if (error == -ENOMEM)
 161                                 error = -EAGAIN;
 162                         goto out;
 163                 }
 164         }
 165
 166         if (end != vma->vm_end) {
 167                 if (unlikely(mm->map_count >= sysctl_max_map_count)) {
 168                         error = -ENOMEM;
 169                         goto out;
 170                 }
 171                 error = __split_vma(mm, vma, end, 0);
 172                 if (error) {
 173                         /*
 174                          * madvise() returns EAGAIN if kernel resources, such as
 175                          * slab, are temporarily unavailable.
 176                          */
 177                         if (error == -ENOMEM)
 178                                 error = -EAGAIN;
 179                         goto out;
 180                 }
 181         }
 182
 183 success:
 184         /*
 185          * vm_flags is protected by the mmap_sem held in write mode.
 186          */
 187         vma->vm_flags = new_flags;
 188 out:
 189         return error;
 190 }
 191
 192 #ifdef CONFIG_SWAP
 193 static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
 194         unsigned long end, struct mm_walk *walk)
 195 {
 196         pte_t *orig_pte;
 197         struct vm_area_struct *vma = walk->private;
 198         unsigned long index;
 199
 200         if (pmd_none_or_trans_huge_or_clear_bad(pmd))
 201                 return 0;
 202
 203         for (index = start; index != end; index += PAGE_SIZE) {
 204                 pte_t pte;
 205                 swp_entry_t entry;
 206                 struct page *page;
 207                 spinlock_t *ptl;
 208
 209                 orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
 210                 pte = *(orig_pte + ((index - start) / PAGE_SIZE));
 211                 pte_unmap_unlock(orig_pte, ptl);
 212
 213                 if (pte_present(pte) || pte_none(pte))
 214                         continue;
 215                 entry = pte_to_swp_entry(pte);
 216                 if (unlikely(non_swap_entry(entry)))
 217                         continue;
 218
 219                 page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
 220                                                         vma, index, false);
 221                 if (page)
 222                         put_page(page);
 223         }
 224
 225         return 0;
 226 }
 227
 228 static void force_swapin_readahead(struct vm_area_struct *vma,
 229                 unsigned long start, unsigned long end)
 230 {
 231         struct mm_walk walk = {
 232                 .mm = vma->vm_mm,
 233                 .pmd_entry = swapin_walk_pmd_entry,
 234                 .private = vma,
 235         };
 236
 237         walk_page_range(start, end, &walk);
 238
 239         lru_add_drain();        /* Push any new pages onto the LRU now */
 240 }
 241
 242 static void force_shm_swapin_readahead(struct vm_area_struct *vma,
 243                 unsigned long start, unsigned long end,
 244                 struct address_space *mapping)
 245 {
 246         pgoff_t index;
 247         struct page *page;
 248         swp_entry_t swap;
 249
 250         for (; start < end; start += PAGE_SIZE) {
 251                 index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 252
 253                 page = find_get_entry(mapping, index);
 254                 if (!radix_tree_exceptional_entry(page)) {
 255                         if (page)
 256                                 put_page(page);
 257                         continue;
 258                 }
 259                 swap = radix_to_swp_entry(page);
 260                 page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
 261                                                         NULL, 0, false);
 262                 if (page)
 263                         put_page(page);
 264         }
 265
 266         lru_add_drain();        /* Push any new pages onto the LRU now */
 267 }
 268 #endif          /* CONFIG_SWAP */
 269
 270 /*
 271  * Schedule all required I/O operations.  Do not wait for completion.
 272  */
 273 static long madvise_willneed(struct vm_area_struct *vma,
 274                              struct vm_area_struct **prev,
 275                              unsigned long start, unsigned long end)
 276 {
 277         struct file *file = vma->vm_file;
 278
 279 #ifdef CONFIG_SWAP
 280         if (!file) {
 281                 *prev = vma;
 282                 force_swapin_readahead(vma, start, end);
 283                 return 0;
 284         }
 285
 286         if (shmem_mapping(file->f_mapping)) {
 287                 *prev = vma;
 288                 force_shm_swapin_readahead(vma, start, end,
 289                                         file->f_mapping);
 290                 return 0;
 291         }
 292 #else
 293         if (!file)
 294                 return -EBADF;
 295 #endif
 296
 297         if (IS_DAX(file_inode(file))) {
 298                 /* no bad return value, but ignore advice */
 299                 return 0;
 300         }
 301
 302         *prev = vma;
 303         start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 304         if (end > vma->vm_end)
 305                 end = vma->vm_end;
 306         end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 307
 308         force_page_cache_readahead(file->f_mapping, file, start, end - start);
 309         return 0;
 310 }
 311
 312 static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 313                                 unsigned long end, struct mm_walk *walk)
 314
 315 {
 316         struct mmu_gather *tlb = walk->private;
 317         struct mm_struct *mm = tlb->mm;
 318         struct vm_area_struct *vma = walk->vma;
 319         spinlock_t *ptl;
 320         pte_t *orig_pte, *pte, ptent;
 321         struct page *page;
 322         int nr_swap = 0;
 323         unsigned long next;
 324
 325         next = pmd_addr_end(addr, end);
 326         if (pmd_trans_huge(*pmd))
 327                 if (madvise_free_huge_pmd(tlb, vma, pmd, addr, next))
 328                         goto next;
 329
 330         if (pmd_trans_unstable(pmd))
 331                 return 0;
 332
 333         tlb_remove_check_page_size_change(tlb, PAGE_SIZE);
 334         orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 335         flush_tlb_batched_pending(mm);
 336         arch_enter_lazy_mmu_mode();
 337         for (; addr != end; pte++, addr += PAGE_SIZE) {
 338                 ptent = *pte;
 339
 340                 if (pte_none(ptent))
 341                         continue;
 342                 /*
 343                  * If the pte has swp_entry, just clear page table to
 344                  * prevent swap-in which is more expensive rather than
 345                  * (page allocation + zeroing).
 346                  */
 347                 if (!pte_present(ptent)) {
 348                         swp_entry_t entry;
 349
 350                         entry = pte_to_swp_entry(ptent);
 351                         if (non_swap_entry(entry))
 352                                 continue;
 353                         nr_swap--;
 354                         free_swap_and_cache(entry);
 355                         pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
 356                         continue;
 357                 }
 358
 359                 page = _vm_normal_page(vma, addr, ptent, true);
 360                 if (!page)
 361                         continue;
 362
 363                 /*
 364                  * If pmd isn't transhuge but the page is THP and
 365                  * is owned by only this process, split it and
 366                  * deactivate all pages.
 367                  */
 368                 if (PageTransCompound(page)) {
 369                         if (page_mapcount(page) != 1)
 370                                 goto out;
 371                         get_page(page);
 372                         if (!trylock_page(page)) {
 373                                 put_page(page);
 374                                 goto out;
 375                         }
 376                         pte_unmap_unlock(orig_pte, ptl);
 377                         if (split_huge_page(page)) {
 378                                 unlock_page(page);
 379                                 put_page(page);
 380                                 pte_offset_map_lock(mm, pmd, addr, &ptl);
 381                                 goto out;
 382                         }
 383                         unlock_page(page);
 384                         put_page(page);
 385                         pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 386                         pte--;
 387                         addr -= PAGE_SIZE;
 388                         continue;
 389                 }
 390
 391                 VM_BUG_ON_PAGE(PageTransCompound(page), page);
 392
 393                 if (PageSwapCache(page) || PageDirty(page)) {
 394                         if (!trylock_page(page))
 395                                 continue;
 396                         /*
 397                          * If page is shared with others, we couldn't clear
 398                          * PG_dirty of the page.
 399                          */
 400                         if (page_mapcount(page) != 1) {
 401                                 unlock_page(page);
 402                                 continue;
 403                         }
 404
 405                         if (PageSwapCache(page) && !try_to_free_swap(page)) {
 406                                 unlock_page(page);
 407                                 continue;
 408                         }
 409
 410                         ClearPageDirty(page);
 411                         unlock_page(page);
 412                 }
 413
 414                 if (pte_young(ptent) || pte_dirty(ptent)) {
 415                         /*
 416                          * Some of architecture(ex, PPC) don't update TLB
 417                          * with set_pte_at and tlb_remove_tlb_entry so for
 418                          * the portability, remap the pte with old|clean
 419                          * after pte clearing.
 420                          */
 421                         ptent = ptep_get_and_clear_full(mm, addr, pte,
 422                                                         tlb->fullmm);
 423
 424                         ptent = pte_mkold(ptent);
 425                         ptent = pte_mkclean(ptent);
 426                         set_pte_at(mm, addr, pte, ptent);
 427                         tlb_remove_tlb_entry(tlb, pte, addr);
 428                 }
 429                 mark_page_lazyfree(page);
 430         }
 431 out:
 432         if (nr_swap) {
 433                 if (current->mm == mm)
 434                         sync_mm_rss(mm);
 435
 436                 add_mm_counter(mm, MM_SWAPENTS, nr_swap);
 437         }
 438         arch_leave_lazy_mmu_mode();
 439         pte_unmap_unlock(orig_pte, ptl);
 440         cond_resched();
 441 next:
 442         return 0;
 443 }
 444
 445 static void madvise_free_page_range(struct mmu_gather *tlb,
 446                              struct vm_area_struct *vma,
 447                              unsigned long addr, unsigned long end)
 448 {
 449         struct mm_walk free_walk = {
 450                 .pmd_entry = madvise_free_pte_range,
 451                 .mm = vma->vm_mm,
 452                 .private = tlb,
 453         };
 454
 455         tlb_start_vma(tlb, vma);
 456         walk_page_range(addr, end, &free_walk);
 457         tlb_end_vma(tlb, vma);
 458 }
 459
 460 static int madvise_free_single_vma(struct vm_area_struct *vma,
 461                         unsigned long start_addr, unsigned long end_addr)
 462 {
 463         unsigned long start, end;
 464         struct mm_struct *mm = vma->vm_mm;
 465         struct mmu_gather tlb;
 466
 467         /* MADV_FREE works for only anon vma at the moment */
 468         if (!vma_is_anonymous(vma))
 469                 return -EINVAL;
 470
 471         start = max(vma->vm_start, start_addr);
 472         if (start >= vma->vm_end)
 473                 return -EINVAL;
 474         end = min(vma->vm_end, end_addr);
 475         if (end <= vma->vm_start)
 476                 return -EINVAL;
 477
 478         lru_add_drain();
 479         tlb_gather_mmu(&tlb, mm, start, end);
 480         update_hiwater_rss(mm);
 481
 482         mmu_notifier_invalidate_range_start(mm, start, end);
 483         madvise_free_page_range(&tlb, vma, start, end);
 484         mmu_notifier_invalidate_range_end(mm, start, end);
 485         tlb_finish_mmu(&tlb, start, end);
 486
 487         return 0;
 488 }
 489
 490 /*
 491  * Application no longer needs these pages.  If the pages are dirty,
 492  * it's OK to just throw them away.  The app will be more careful about
 493  * data it wants to keep.  Be sure to free swap resources too.  The
 494  * zap_page_range call sets things up for shrink_active_list to actually free
 495  * these pages later if no one else has touched them in the meantime,
 496  * although we could add these pages to a global reuse list for
 497  * shrink_active_list to pick up before reclaiming other pages.
 498  *
 499  * NB: This interface discards data rather than pushes it out to swap,
 500  * as some implementations do.  This has performance implications for
 501  * applications like large transactional databases which want to discard
 502  * pages in anonymous maps after committing to backing store the data
 503  * that was kept in them.  There is no reason to write this data out to
 504  * the swap area if the application is discarding it.
 505  *
 506  * An interface that causes the system to free clean pages and flush
 507  * dirty pages is already available as msync(MS_INVALIDATE).
 508  */
 509 static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
 510                                         unsigned long start, unsigned long end)
 511 {
 512         zap_page_range(vma, start, end - start);
 513         return 0;
 514 }
 515
 516 static long madvise_dontneed_free(struct vm_area_struct *vma,
 517                                   struct vm_area_struct **prev,
 518                                   unsigned long start, unsigned long end,
 519                                   int behavior)
 520 {
 521         *prev = vma;
 522         if (!can_madv_dontneed_vma(vma))
 523                 return -EINVAL;
 524
 525         if (!userfaultfd_remove(vma, start, end)) {
 526                 *prev = NULL; /* mmap_sem has been dropped, prev is stale */
 527
 528                 down_read(&current->mm->mmap_sem);
 529                 vma = find_vma(current->mm, start);
 530                 if (!vma)
 531                         return -ENOMEM;
 532                 if (start < vma->vm_start) {
 533                         /*
 534                          * This "vma" under revalidation is the one
 535                          * with the lowest vma->vm_start where start
 536                          * is also < vma->vm_end. If start <
 537                          * vma->vm_start it means an hole materialized
 538                          * in the user address space within the
 539                          * virtual range passed to MADV_DONTNEED
 540                          * or MADV_FREE.
 541                          */
 542                         return -ENOMEM;
 543                 }
 544                 if (!can_madv_dontneed_vma(vma))
 545                         return -EINVAL;
 546                 if (end > vma->vm_end) {
 547                         /*
 548                          * Don't fail if end > vma->vm_end. If the old
 549                          * vma was splitted while the mmap_sem was
 550                          * released the effect of the concurrent
 551                          * operation may not cause madvise() to
 552                          * have an undefined result. There may be an
 553                          * adjacent next vma that we'll walk
 554                          * next. userfaultfd_remove() will generate an
 555                          * UFFD_EVENT_REMOVE repetition on the
 556                          * end-vma->vm_end range, but the manager can
 557                          * handle a repetition fine.
 558                          */
 559                         end = vma->vm_end;
 560                 }
 561                 VM_WARN_ON(start >= end);
 562         }
 563
 564         if (behavior == MADV_DONTNEED)
 565                 return madvise_dontneed_single_vma(vma, start, end);
 566         else if (behavior == MADV_FREE)
 567                 return madvise_free_single_vma(vma, start, end);
 568         else
 569                 return -EINVAL;
 570 }
 571
 572 /*
 573  * Application wants to free up the pages and associated backing store.
 574  * This is effectively punching a hole into the middle of a file.
 575  */
 576 static long madvise_remove(struct vm_area_struct *vma,
 577                                 struct vm_area_struct **prev,
 578                                 unsigned long start, unsigned long end)
 579 {
 580         loff_t offset;
 581         int error;
 582         struct file *f;
 583
 584         *prev = NULL;   /* tell sys_madvise we drop mmap_sem */
 585
 586         if (vma->vm_flags & VM_LOCKED)
 587                 return -EINVAL;
 588
 589         f = vma->vm_file;
 590
 591         if (!f || !f->f_mapping || !f->f_mapping->host) {
 592                         return -EINVAL;
 593         }
 594
 595         if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
 596                 return -EACCES;
 597
 598         offset = (loff_t)(start - vma->vm_start)
 599                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 600
 601         /*
 602          * Filesystem's fallocate may need to take i_mutex.  We need to
 603          * explicitly grab a reference because the vma (and hence the
 604          * vma's reference to the file) can go away as soon as we drop
 605          * mmap_sem.
 606          */
 607         get_file(f);
 608         if (userfaultfd_remove(vma, start, end)) {
 609                 /* mmap_sem was not released by userfaultfd_remove() */
 610                 up_read(&current->mm->mmap_sem);
 611         }
 612         error = vfs_fallocate(f,
 613                                 FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
 614                                 offset, end - start);
 615         fput(f);
 616         down_read(&current->mm->mmap_sem);
 617         return error;
 618 }
 619
 620 #ifdef CONFIG_MEMORY_FAILURE
 621 /*
 622  * Error injection support for memory error handling.
 623  */
 624 static int madvise_inject_error(int behavior,
 625                 unsigned long start, unsigned long end)
 626 {
 627         struct page *page;
 628         struct zone *zone;
 629         unsigned int order;
 630
 631         if (!capable(CAP_SYS_ADMIN))
 632                 return -EPERM;
 633
 634
 635         for (; start < end; start += PAGE_SIZE << order) {
 636                 int ret;
 637
 638                 ret = get_user_pages_fast(start, 1, 0, &page);
 639                 if (ret != 1)
 640                         return ret;
 641
 642                 /*
 643                  * When soft offlining hugepages, after migrating the page
 644                  * we dissolve it, therefore in the second loop "page" will
 645                  * no longer be a compound page, and order will be 0.
 646                  */
 647                 order = compound_order(compound_head(page));
 648
 649                 if (PageHWPoison(page)) {
 650                         put_page(page);
 651                         continue;
 652                 }
 653
 654                 if (behavior == MADV_SOFT_OFFLINE) {
 655                         pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
 656                                                 page_to_pfn(page), start);
 657
 658                         ret = soft_offline_page(page, MF_COUNT_INCREASED);
 659                         if (ret)
 660                                 return ret;
 661                         continue;
 662                 }
 663                 pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
 664                                                 page_to_pfn(page), start);
 665
 666                 ret = memory_failure(page_to_pfn(page), 0, MF_COUNT_INCREASED);
 667                 if (ret)
 668                         return ret;
 669         }
 670
 671         /* Ensure that all poisoned pages are removed from per-cpu lists */
 672         for_each_populated_zone(zone)
 673                 drain_all_pages(zone);
 674
 675         return 0;
 676 }
 677 #endif
 678
 679 static long
 680 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 681                 unsigned long start, unsigned long end, int behavior)
 682 {
 683         switch (behavior) {
 684         case MADV_REMOVE:
 685                 return madvise_remove(vma, prev, start, end);
 686         case MADV_WILLNEED:
 687                 return madvise_willneed(vma, prev, start, end);
 688         case MADV_FREE:
 689         case MADV_DONTNEED:
 690                 return madvise_dontneed_free(vma, prev, start, end, behavior);
 691         default:
 692                 return madvise_behavior(vma, prev, start, end, behavior);
 693         }
 694 }
 695
 696 static bool
 697 madvise_behavior_valid(int behavior)
 698 {
 699         switch (behavior) {
 700         case MADV_DOFORK:
 701         case MADV_DONTFORK:
 702         case MADV_NORMAL:
 703         case MADV_SEQUENTIAL:
 704         case MADV_RANDOM:
 705         case MADV_REMOVE:
 706         case MADV_WILLNEED:
 707         case MADV_DONTNEED:
 708         case MADV_FREE:
 709 #ifdef CONFIG_KSM
 710         case MADV_MERGEABLE:
 711         case MADV_UNMERGEABLE:
 712 #endif
 713 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 714         case MADV_HUGEPAGE:
 715         case MADV_NOHUGEPAGE:
 716 #endif
 717         case MADV_DONTDUMP:
 718         case MADV_DODUMP:
 719         case MADV_WIPEONFORK:
 720         case MADV_KEEPONFORK:
 721 #ifdef CONFIG_MEMORY_FAILURE
 722         case MADV_SOFT_OFFLINE:
 723         case MADV_HWPOISON:
 724 #endif
 725                 return true;
 726
 727         default:
 728                 return false;
 729         }
 730 }
 731
 732 /*
 733  * The madvise(2) system call.
 734  *
 735  * Applications can use madvise() to advise the kernel how it should
 736  * handle paging I/O in this VM area.  The idea is to help the kernel
 737  * use appropriate read-ahead and caching techniques.  The information
 738  * provided is advisory only, and can be safely disregarded by the
 739  * kernel without affecting the correct operation of the application.
 740  *
 741  * behavior values:
 742  *  MADV_NORMAL - the default behavior is to read clusters.  This
 743  *              results in some read-ahead and read-behind.
 744  *  MADV_RANDOM - the system should read the minimum amount of data
 745  *              on any access, since it is unlikely that the appli-
 746  *              cation will need more than what it asks for.
 747  *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
 748  *              once, so they can be aggressively read ahead, and
 749  *              can be freed soon after they are accessed.
 750  *  MADV_WILLNEED - the application is notifying the system to read
 751  *              some pages ahead.
 752  *  MADV_DONTNEED - the application is finished with the given range,
 753  *              so the kernel can free resources associated with it.
 754  *  MADV_FREE - the application marks pages in the given range as lazy free,
 755  *              where actual purges are postponed until memory pressure happens.
 756  *  MADV_REMOVE - the application wants to free up the given range of
 757  *              pages and associated backing store.
 758  *  MADV_DONTFORK - omit this area from child's address space when forking:
 759  *              typically, to avoid COWing pages pinned by get_user_pages().
 760  *  MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
 761  *  MADV_WIPEONFORK - present the child process with zero-filled memory in this
 762  *              range after a fork.
 763  *  MADV_KEEPONFORK - undo the effect of MADV_WIPEONFORK
 764  *  MADV_HWPOISON - trigger memory error handler as if the given memory range
 765  *              were corrupted by unrecoverable hardware memory failure.
 766  *  MADV_SOFT_OFFLINE - try to soft-offline the given range of memory.
 767  *  MADV_MERGEABLE - the application recommends that KSM try to merge pages in
 768  *              this area with pages of identical content from other such areas.
 769  *  MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
 770  *  MADV_HUGEPAGE - the application wants to back the given range by transparent
 771  *              huge pages in the future. Existing pages might be coalesced and
 772  *              new pages might be allocated as THP.
 773  *  MADV_NOHUGEPAGE - mark the given range as not worth being backed by
 774  *              transparent huge pages so the existing pages will not be
 775  *              coalesced into THP and new pages will not be allocated as THP.
 776  *  MADV_DONTDUMP - the application wants to prevent pages in the given range
 777  *              from being included in its core dump.
 778  *  MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
 779  *
 780  * return values:
 781  *  zero    - success
 782  *  -EINVAL - start + len < 0, start is not page-aligned,
 783  *              "behavior" is not a valid value, or application
 784  *              is attempting to release locked or shared pages,
 785  *              or the specified address range includes file, Huge TLB,
 786  *              MAP_SHARED or VMPFNMAP range.
 787  *  -ENOMEM - addresses in the specified range are not currently
 788  *              mapped, or are outside the AS of the process.
 789  *  -EIO    - an I/O error occurred while paging in data.
 790  *  -EBADF  - map exists, but area maps something that isn't a file.
 791  *  -EAGAIN - a kernel resource was temporarily unavailable.
 792  */
 793 SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
 794 {
 795         unsigned long end, tmp;
 796         struct vm_area_struct *vma, *prev;
 797         int unmapped_error = 0;
 798         int error = -EINVAL;
 799         int write;
 800         size_t len;
 801         struct blk_plug plug;
 802
 803         if (!madvise_behavior_valid(behavior))
 804                 return error;
 805
 806         if (start & ~PAGE_MASK)
 807                 return error;
 808         len = (len_in + ~PAGE_MASK) & PAGE_MASK;
 809
 810         /* Check to see whether len was rounded up from small -ve to zero */
 811         if (len_in && !len)
 812                 return error;
 813
 814         end = start + len;
 815         if (end < start)
 816                 return error;
 817
 818         error = 0;
 819         if (end == start)
 820                 return error;
 821
 822 #ifdef CONFIG_MEMORY_FAILURE
 823         if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
 824                 return madvise_inject_error(behavior, start, start + len_in);
 825 #endif
 826
 827         write = madvise_need_mmap_write(behavior);
 828         if (write) {
 829                 if (down_write_killable(&current->mm->mmap_sem))
 830                         return -EINTR;
 831         } else {
 832                 down_read(&current->mm->mmap_sem);
 833         }
 834
 835         /*
 836          * If the interval [start,end) covers some unmapped address
 837          * ranges, just ignore them, but return -ENOMEM at the end.
 838          * - different from the way of handling in mlock etc.
 839          */
 840         vma = find_vma_prev(current->mm, start, &prev);
 841         if (vma && start > vma->vm_start)
 842                 prev = vma;
 843
 844         blk_start_plug(&plug);
 845         for (;;) {
 846                 /* Still start < end. */
 847                 error = -ENOMEM;
 848                 if (!vma)
 849                         goto out;
 850
 851                 /* Here start < (end|vma->vm_end). */
 852                 if (start < vma->vm_start) {
 853                         unmapped_error = -ENOMEM;
 854                         start = vma->vm_start;
 855                         if (start >= end)
 856                                 goto out;
 857                 }
 858
 859                 /* Here vma->vm_start <= start < (end|vma->vm_end) */
 860                 tmp = vma->vm_end;
 861                 if (end < tmp)
 862                         tmp = end;
 863
 864                 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
 865                 error = madvise_vma(vma, &prev, start, tmp, behavior);
 866                 if (error)
 867                         goto out;
 868                 start = tmp;
 869                 if (prev && start < prev->vm_end)
 870                         start = prev->vm_end;
 871                 error = unmapped_error;
 872                 if (start >= end)
 873                         goto out;
 874                 if (prev)
 875                         vma = prev->vm_next;
 876                 else    /* madvise_remove dropped mmap_sem */
 877                         vma = find_vma(current->mm, start);
 878         }
 879 out:
 880         blk_finish_plug(&plug);
 881         if (write)
 882                 up_write(&current->mm->mmap_sem);
 883         else
 884                 up_read(&current->mm->mmap_sem);
 885
 886         return error;
 887 }