mm/madvise.c

   1 /*
   2  *      linux/mm/madvise.c
   3  *
   4  * Copyright (C) 1999  Linus Torvalds
   5  * Copyright (C) 2002  Christoph Hellwig
   6  */
   7
   8 #include <linux/mman.h>
   9 #include <linux/pagemap.h>
  10 #include <linux/syscalls.h>
  11 #include <linux/mempolicy.h>
  12 #include <linux/page-isolation.h>
  13 #include <linux/hugetlb.h>
  14 #include <linux/falloc.h>
  15 #include <linux/sched.h>
  16 #include <linux/ksm.h>
  17 #include <linux/fs.h>
  18 #include <linux/file.h>
  19 #include <linux/blkdev.h>
  20 #include <linux/backing-dev.h>
  21 #include <linux/swap.h>
  22 #include <linux/swapops.h>
  23
  24 /*
  25  * Any behaviour which results in changes to the vma->vm_flags needs to
  26  * take mmap_sem for writing. Others, which simply traverse vmas, need
  27  * to only take it for reading.
  28  */
  29 static int madvise_need_mmap_write(int behavior)
  30 {
  31         switch (behavior) {
  32         case MADV_REMOVE:
  33         case MADV_WILLNEED:
  34         case MADV_DONTNEED:
  35                 return 0;
  36         default:
  37                 /* be safe, default to 1. list exceptions explicitly */
  38                 return 1;
  39         }
  40 }
  41
  42 /*
  43  * We can potentially split a vm area into separate
  44  * areas, each area with its own behavior.
  45  */
  46 static long madvise_behavior(struct vm_area_struct *vma,
  47                      struct vm_area_struct **prev,
  48                      unsigned long start, unsigned long end, int behavior)
  49 {
  50         struct mm_struct *mm = vma->vm_mm;
  51         int error = 0;
  52         pgoff_t pgoff;
  53         unsigned long new_flags = vma->vm_flags;
  54
  55         switch (behavior) {
  56         case MADV_NORMAL:
  57                 new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
  58                 break;
  59         case MADV_SEQUENTIAL:
  60                 new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
  61                 break;
  62         case MADV_RANDOM:
  63                 new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
  64                 break;
  65         case MADV_DONTFORK:
  66                 new_flags |= VM_DONTCOPY;
  67                 break;
  68         case MADV_DOFORK:
  69                 if (vma->vm_flags & VM_IO) {
  70                         error = -EINVAL;
  71                         goto out;
  72                 }
  73                 new_flags &= ~VM_DONTCOPY;
  74                 break;
  75         case MADV_DONTDUMP:
  76                 new_flags |= VM_DONTDUMP;
  77                 break;
  78         case MADV_DODUMP:
  79                 if (new_flags & VM_SPECIAL) {
  80                         error = -EINVAL;
  81                         goto out;
  82                 }
  83                 new_flags &= ~VM_DONTDUMP;
  84                 break;
  85         case MADV_MERGEABLE:
  86         case MADV_UNMERGEABLE:
  87                 error = ksm_madvise(vma, start, end, behavior, &new_flags);
  88                 if (error)
  89                         goto out;
  90                 break;
  91         case MADV_HUGEPAGE:
  92         case MADV_NOHUGEPAGE:
  93                 error = hugepage_madvise(vma, &new_flags, behavior);
  94                 if (error)
  95                         goto out;
  96                 break;
  97         }
  98
  99         if (new_flags == vma->vm_flags) {
 100                 *prev = vma;
 101                 goto out;
 102         }
 103
 104         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 105         *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
 106                                 vma->vm_file, pgoff, vma_policy(vma));
 107         if (*prev) {
 108                 vma = *prev;
 109                 goto success;
 110         }
 111
 112         *prev = vma;
 113
 114         if (start != vma->vm_start) {
 115                 error = split_vma(mm, vma, start, 1);
 116                 if (error)
 117                         goto out;
 118         }
 119
 120         if (end != vma->vm_end) {
 121                 error = split_vma(mm, vma, end, 0);
 122                 if (error)
 123                         goto out;
 124         }
 125
 126 success:
 127         /*
 128          * vm_flags is protected by the mmap_sem held in write mode.
 129          */
 130         vma->vm_flags = new_flags;
 131
 132 out:
 133         if (error == -ENOMEM)
 134                 error = -EAGAIN;
 135         return error;
 136 }
 137
 138 #ifdef CONFIG_SWAP
 139 static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
 140         unsigned long end, struct mm_walk *walk)
 141 {
 142         pte_t *orig_pte;
 143         struct vm_area_struct *vma = walk->private;
 144         unsigned long index;
 145
 146         if (pmd_none_or_trans_huge_or_clear_bad(pmd))
 147                 return 0;
 148
 149         for (index = start; index != end; index += PAGE_SIZE) {
 150                 pte_t pte;
 151                 swp_entry_t entry;
 152                 struct page *page;
 153                 spinlock_t *ptl;
 154
 155                 orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
 156                 pte = *(orig_pte + ((index - start) / PAGE_SIZE));
 157                 pte_unmap_unlock(orig_pte, ptl);
 158
 159                 if (pte_present(pte) || pte_none(pte))
 160                         continue;
 161                 entry = pte_to_swp_entry(pte);
 162                 if (unlikely(non_swap_entry(entry)))
 163                         continue;
 164
 165                 page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
 166                                                                 vma, index);
 167                 if (page)
 168                         page_cache_release(page);
 169         }
 170
 171         return 0;
 172 }
 173
 174 static void force_swapin_readahead(struct vm_area_struct *vma,
 175                 unsigned long start, unsigned long end)
 176 {
 177         struct mm_walk walk = {
 178                 .mm = vma->vm_mm,
 179                 .pmd_entry = swapin_walk_pmd_entry,
 180                 .private = vma,
 181         };
 182
 183         walk_page_range(start, end, &walk);
 184
 185         lru_add_drain();        /* Push any new pages onto the LRU now */
 186 }
 187
 188 static void force_shm_swapin_readahead(struct vm_area_struct *vma,
 189                 unsigned long start, unsigned long end,
 190                 struct address_space *mapping)
 191 {
 192         pgoff_t index;
 193         struct page *page;
 194         swp_entry_t swap;
 195
 196         for (; start < end; start += PAGE_SIZE) {
 197                 index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 198
 199                 page = find_get_entry(mapping, index);
 200                 if (!radix_tree_exceptional_entry(page)) {
 201                         if (page)
 202                                 page_cache_release(page);
 203                         continue;
 204                 }
 205                 swap = radix_to_swp_entry(page);
 206                 page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
 207                                                                 NULL, 0);
 208                 if (page)
 209                         page_cache_release(page);
 210         }
 211
 212         lru_add_drain();        /* Push any new pages onto the LRU now */
 213 }
 214 #endif          /* CONFIG_SWAP */
 215
 216 /*
 217  * Schedule all required I/O operations.  Do not wait for completion.
 218  */
 219 static long madvise_willneed(struct vm_area_struct *vma,
 220                              struct vm_area_struct **prev,
 221                              unsigned long start, unsigned long end)
 222 {
 223         struct file *file = vma->vm_file;
 224
 225 #ifdef CONFIG_SWAP
 226         if (!file) {
 227                 *prev = vma;
 228                 force_swapin_readahead(vma, start, end);
 229                 return 0;
 230         }
 231
 232         if (shmem_mapping(file->f_mapping)) {
 233                 *prev = vma;
 234                 force_shm_swapin_readahead(vma, start, end,
 235                                         file->f_mapping);
 236                 return 0;
 237         }
 238 #else
 239         if (!file)
 240                 return -EBADF;
 241 #endif
 242
 243         if (IS_DAX(file_inode(file))) {
 244                 /* no bad return value, but ignore advice */
 245                 return 0;
 246         }
 247
 248         *prev = vma;
 249         start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 250         if (end > vma->vm_end)
 251                 end = vma->vm_end;
 252         end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 253
 254         force_page_cache_readahead(file->f_mapping, file, start, end - start);
 255         return 0;
 256 }
 257
 258 /*
 259  * Application no longer needs these pages.  If the pages are dirty,
 260  * it's OK to just throw them away.  The app will be more careful about
 261  * data it wants to keep.  Be sure to free swap resources too.  The
 262  * zap_page_range call sets things up for shrink_active_list to actually free
 263  * these pages later if no one else has touched them in the meantime,
 264  * although we could add these pages to a global reuse list for
 265  * shrink_active_list to pick up before reclaiming other pages.
 266  *
 267  * NB: This interface discards data rather than pushes it out to swap,
 268  * as some implementations do.  This has performance implications for
 269  * applications like large transactional databases which want to discard
 270  * pages in anonymous maps after committing to backing store the data
 271  * that was kept in them.  There is no reason to write this data out to
 272  * the swap area if the application is discarding it.
 273  *
 274  * An interface that causes the system to free clean pages and flush
 275  * dirty pages is already available as msync(MS_INVALIDATE).
 276  */
 277 static long madvise_dontneed(struct vm_area_struct *vma,
 278                              struct vm_area_struct **prev,
 279                              unsigned long start, unsigned long end)
 280 {
 281         *prev = vma;
 282         if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
 283                 return -EINVAL;
 284
 285         zap_page_range(vma, start, end - start, NULL);
 286         return 0;
 287 }
 288
 289 /*
 290  * Application wants to free up the pages and associated backing store.
 291  * This is effectively punching a hole into the middle of a file.
 292  */
 293 static long madvise_remove(struct vm_area_struct *vma,
 294                                 struct vm_area_struct **prev,
 295                                 unsigned long start, unsigned long end)
 296 {
 297         loff_t offset;
 298         int error;
 299         struct file *f;
 300
 301         *prev = NULL;   /* tell sys_madvise we drop mmap_sem */
 302
 303         if (vma->vm_flags & (VM_LOCKED | VM_HUGETLB))
 304                 return -EINVAL;
 305
 306         f = vma->vm_file;
 307
 308         if (!f || !f->f_mapping || !f->f_mapping->host) {
 309                         return -EINVAL;
 310         }
 311
 312         if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
 313                 return -EACCES;
 314
 315         offset = (loff_t)(start - vma->vm_start)
 316                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 317
 318         /*
 319          * Filesystem's fallocate may need to take i_mutex.  We need to
 320          * explicitly grab a reference because the vma (and hence the
 321          * vma's reference to the file) can go away as soon as we drop
 322          * mmap_sem.
 323          */
 324         get_file(f);
 325         up_read(&current->mm->mmap_sem);
 326         error = vfs_fallocate(f,
 327                                 FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
 328                                 offset, end - start);
 329         fput(f);
 330         down_read(&current->mm->mmap_sem);
 331         return error;
 332 }
 333
 334 #ifdef CONFIG_MEMORY_FAILURE
 335 /*
 336  * Error injection support for memory error handling.
 337  */
 338 static int madvise_hwpoison(int bhv, unsigned long start, unsigned long end)
 339 {
 340         struct page *p;
 341         if (!capable(CAP_SYS_ADMIN))
 342                 return -EPERM;
 343         for (; start < end; start += PAGE_SIZE <<
 344                                 compound_order(compound_head(p))) {
 345                 int ret;
 346
 347                 ret = get_user_pages_fast(start, 1, 0, &p);
 348                 if (ret != 1)
 349                         return ret;
 350
 351                 if (PageHWPoison(p)) {
 352                         put_page(p);
 353                         continue;
 354                 }
 355                 if (bhv == MADV_SOFT_OFFLINE) {
 356                         pr_info("Soft offlining page %#lx at %#lx\n",
 357                                 page_to_pfn(p), start);
 358                         ret = soft_offline_page(p, MF_COUNT_INCREASED);
 359                         if (ret)
 360                                 return ret;
 361                         continue;
 362                 }
 363                 pr_info("Injecting memory failure for page %#lx at %#lx\n",
 364                        page_to_pfn(p), start);
 365                 /* Ignore return value for now */
 366                 memory_failure(page_to_pfn(p), 0, MF_COUNT_INCREASED);
 367         }
 368         return 0;
 369 }
 370 #endif
 371
 372 static long
 373 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 374                 unsigned long start, unsigned long end, int behavior)
 375 {
 376         switch (behavior) {
 377         case MADV_REMOVE:
 378                 return madvise_remove(vma, prev, start, end);
 379         case MADV_WILLNEED:
 380                 return madvise_willneed(vma, prev, start, end);
 381         case MADV_DONTNEED:
 382                 return madvise_dontneed(vma, prev, start, end);
 383         default:
 384                 return madvise_behavior(vma, prev, start, end, behavior);
 385         }
 386 }
 387
 388 static int
 389 madvise_behavior_valid(int behavior)
 390 {
 391         switch (behavior) {
 392         case MADV_DOFORK:
 393         case MADV_DONTFORK:
 394         case MADV_NORMAL:
 395         case MADV_SEQUENTIAL:
 396         case MADV_RANDOM:
 397         case MADV_REMOVE:
 398         case MADV_WILLNEED:
 399         case MADV_DONTNEED:
 400 #ifdef CONFIG_KSM
 401         case MADV_MERGEABLE:
 402         case MADV_UNMERGEABLE:
 403 #endif
 404 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 405         case MADV_HUGEPAGE:
 406         case MADV_NOHUGEPAGE:
 407 #endif
 408         case MADV_DONTDUMP:
 409         case MADV_DODUMP:
 410                 return 1;
 411
 412         default:
 413                 return 0;
 414         }
 415 }
 416
 417 /*
 418  * The madvise(2) system call.
 419  *
 420  * Applications can use madvise() to advise the kernel how it should
 421  * handle paging I/O in this VM area.  The idea is to help the kernel
 422  * use appropriate read-ahead and caching techniques.  The information
 423  * provided is advisory only, and can be safely disregarded by the
 424  * kernel without affecting the correct operation of the application.
 425  *
 426  * behavior values:
 427  *  MADV_NORMAL - the default behavior is to read clusters.  This
 428  *              results in some read-ahead and read-behind.
 429  *  MADV_RANDOM - the system should read the minimum amount of data
 430  *              on any access, since it is unlikely that the appli-
 431  *              cation will need more than what it asks for.
 432  *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
 433  *              once, so they can be aggressively read ahead, and
 434  *              can be freed soon after they are accessed.
 435  *  MADV_WILLNEED - the application is notifying the system to read
 436  *              some pages ahead.
 437  *  MADV_DONTNEED - the application is finished with the given range,
 438  *              so the kernel can free resources associated with it.
 439  *  MADV_REMOVE - the application wants to free up the given range of
 440  *              pages and associated backing store.
 441  *  MADV_DONTFORK - omit this area from child's address space when forking:
 442  *              typically, to avoid COWing pages pinned by get_user_pages().
 443  *  MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
 444  *  MADV_MERGEABLE - the application recommends that KSM try to merge pages in
 445  *              this area with pages of identical content from other such areas.
 446  *  MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
 447  *
 448  * return values:
 449  *  zero    - success
 450  *  -EINVAL - start + len < 0, start is not page-aligned,
 451  *              "behavior" is not a valid value, or application
 452  *              is attempting to release locked or shared pages.
 453  *  -ENOMEM - addresses in the specified range are not currently
 454  *              mapped, or are outside the AS of the process.
 455  *  -EIO    - an I/O error occurred while paging in data.
 456  *  -EBADF  - map exists, but area maps something that isn't a file.
 457  *  -EAGAIN - a kernel resource was temporarily unavailable.
 458  */
 459 SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
 460 {
 461         unsigned long end, tmp;
 462         struct vm_area_struct *vma, *prev;
 463         int unmapped_error = 0;
 464         int error = -EINVAL;
 465         int write;
 466         size_t len;
 467         struct blk_plug plug;
 468
 469 #ifdef CONFIG_MEMORY_FAILURE
 470         if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
 471                 return madvise_hwpoison(behavior, start, start+len_in);
 472 #endif
 473         if (!madvise_behavior_valid(behavior))
 474                 return error;
 475
 476         if (start & ~PAGE_MASK)
 477                 return error;
 478         len = (len_in + ~PAGE_MASK) & PAGE_MASK;
 479
 480         /* Check to see whether len was rounded up from small -ve to zero */
 481         if (len_in && !len)
 482                 return error;
 483
 484         end = start + len;
 485         if (end < start)
 486                 return error;
 487
 488         error = 0;
 489         if (end == start)
 490                 return error;
 491
 492         write = madvise_need_mmap_write(behavior);
 493         if (write)
 494                 down_write(&current->mm->mmap_sem);
 495         else
 496                 down_read(&current->mm->mmap_sem);
 497
 498         /*
 499          * If the interval [start,end) covers some unmapped address
 500          * ranges, just ignore them, but return -ENOMEM at the end.
 501          * - different from the way of handling in mlock etc.
 502          */
 503         vma = find_vma_prev(current->mm, start, &prev);
 504         if (vma && start > vma->vm_start)
 505                 prev = vma;
 506
 507         blk_start_plug(&plug);
 508         for (;;) {
 509                 /* Still start < end. */
 510                 error = -ENOMEM;
 511                 if (!vma)
 512                         goto out;
 513
 514                 /* Here start < (end|vma->vm_end). */
 515                 if (start < vma->vm_start) {
 516                         unmapped_error = -ENOMEM;
 517                         start = vma->vm_start;
 518                         if (start >= end)
 519                                 goto out;
 520                 }
 521
 522                 /* Here vma->vm_start <= start < (end|vma->vm_end) */
 523                 tmp = vma->vm_end;
 524                 if (end < tmp)
 525                         tmp = end;
 526
 527                 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
 528                 error = madvise_vma(vma, &prev, start, tmp, behavior);
 529                 if (error)
 530                         goto out;
 531                 start = tmp;
 532                 if (prev && start < prev->vm_end)
 533                         start = prev->vm_end;
 534                 error = unmapped_error;
 535                 if (start >= end)
 536                         goto out;
 537                 if (prev)
 538                         vma = prev->vm_next;
 539                 else    /* madvise_remove dropped mmap_sem */
 540                         vma = find_vma(current->mm, start);
 541         }
 542 out:
 543         blk_finish_plug(&plug);
 544         if (write)
 545                 up_write(&current->mm->mmap_sem);
 546         else
 547                 up_read(&current->mm->mmap_sem);
 548
 549         return error;
 550 }