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