mm/truncate.c

   1 /*
   2  * mm/truncate.c - code for taking down pages from address_spaces
   3  *
   4  * Copyright (C) 2002, Linus Torvalds
   5  *
   6  * 10Sep2002    Andrew Morton
   7  *              Initial version.
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/backing-dev.h>
  12 #include <linux/gfp.h>
  13 #include <linux/mm.h>
  14 #include <linux/swap.h>
  15 #include <linux/export.h>
  16 #include <linux/pagemap.h>
  17 #include <linux/highmem.h>
  18 #include <linux/pagevec.h>
  19 #include <linux/task_io_accounting_ops.h>
  20 #include <linux/buffer_head.h>  /* grr. try_to_release_page,
  21                                    do_invalidatepage */
  22 #include <linux/cleancache.h>
  23 #include "internal.h"
  24
  25 static void clear_exceptional_entry(struct address_space *mapping,
  26                                     pgoff_t index, void *entry)
  27 {
  28         /* Handled by shmem itself */
  29         if (shmem_mapping(mapping))
  30                 return;
  31
  32         spin_lock_irq(&mapping->tree_lock);
  33         /*
  34          * Regular page slots are stabilized by the page lock even
  35          * without the tree itself locked.  These unlocked entries
  36          * need verification under the tree lock.
  37          */
  38         if (radix_tree_delete_item(&mapping->page_tree, index, entry) == entry)
  39                 mapping->nrshadows--;
  40         spin_unlock_irq(&mapping->tree_lock);
  41 }
  42
  43 /**
  44  * do_invalidatepage - invalidate part or all of a page
  45  * @page: the page which is affected
  46  * @offset: start of the range to invalidate
  47  * @length: length of the range to invalidate
  48  *
  49  * do_invalidatepage() is called when all or part of the page has become
  50  * invalidated by a truncate operation.
  51  *
  52  * do_invalidatepage() does not have to release all buffers, but it must
  53  * ensure that no dirty buffer is left outside @offset and that no I/O
  54  * is underway against any of the blocks which are outside the truncation
  55  * point.  Because the caller is about to free (and possibly reuse) those
  56  * blocks on-disk.
  57  */
  58 void do_invalidatepage(struct page *page, unsigned int offset,
  59                        unsigned int length)
  60 {
  61         void (*invalidatepage)(struct page *, unsigned int, unsigned int);
  62
  63         invalidatepage = page->mapping->a_ops->invalidatepage;
  64 #ifdef CONFIG_BLOCK
  65         if (!invalidatepage)
  66                 invalidatepage = block_invalidatepage;
  67 #endif
  68         if (invalidatepage)
  69                 (*invalidatepage)(page, offset, length);
  70 }
  71
  72 /*
  73  * This cancels just the dirty bit on the kernel page itself, it
  74  * does NOT actually remove dirty bits on any mmap's that may be
  75  * around. It also leaves the page tagged dirty, so any sync
  76  * activity will still find it on the dirty lists, and in particular,
  77  * clear_page_dirty_for_io() will still look at the dirty bits in
  78  * the VM.
  79  *
  80  * Doing this should *normally* only ever be done when a page
  81  * is truncated, and is not actually mapped anywhere at all. However,
  82  * fs/buffer.c does this when it notices that somebody has cleaned
  83  * out all the buffers on a page without actually doing it through
  84  * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
  85  */
  86 void cancel_dirty_page(struct page *page, unsigned int account_size)
  87 {
  88         if (TestClearPageDirty(page)) {
  89                 struct address_space *mapping = page->mapping;
  90                 if (mapping && mapping_cap_account_dirty(mapping)) {
  91                         dec_zone_page_state(page, NR_FILE_DIRTY);
  92                         dec_bdi_stat(mapping->backing_dev_info,
  93                                         BDI_RECLAIMABLE);
  94                         if (account_size)
  95                                 task_io_account_cancelled_write(account_size);
  96                 }
  97         }
  98 }
  99 EXPORT_SYMBOL(cancel_dirty_page);
 100
 101 /*
 102  * If truncate cannot remove the fs-private metadata from the page, the page
 103  * becomes orphaned.  It will be left on the LRU and may even be mapped into
 104  * user pagetables if we're racing with filemap_fault().
 105  *
 106  * We need to bale out if page->mapping is no longer equal to the original
 107  * mapping.  This happens a) when the VM reclaimed the page while we waited on
 108  * its lock, b) when a concurrent invalidate_mapping_pages got there first and
 109  * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
 110  */
 111 static int
 112 truncate_complete_page(struct address_space *mapping, struct page *page)
 113 {
 114         if (page->mapping != mapping)
 115                 return -EIO;
 116
 117         if (page_has_private(page))
 118                 do_invalidatepage(page, 0, PAGE_CACHE_SIZE);
 119
 120         cancel_dirty_page(page, PAGE_CACHE_SIZE);
 121
 122         ClearPageMappedToDisk(page);
 123         delete_from_page_cache(page);
 124         return 0;
 125 }
 126
 127 /*
 128  * This is for invalidate_mapping_pages().  That function can be called at
 129  * any time, and is not supposed to throw away dirty pages.  But pages can
 130  * be marked dirty at any time too, so use remove_mapping which safely
 131  * discards clean, unused pages.
 132  *
 133  * Returns non-zero if the page was successfully invalidated.
 134  */
 135 static int
 136 invalidate_complete_page(struct address_space *mapping, struct page *page)
 137 {
 138         int ret;
 139
 140         if (page->mapping != mapping)
 141                 return 0;
 142
 143         if (page_has_private(page) && !try_to_release_page(page, 0))
 144                 return 0;
 145
 146         ret = remove_mapping(mapping, page);
 147
 148         return ret;
 149 }
 150
 151 int truncate_inode_page(struct address_space *mapping, struct page *page)
 152 {
 153         if (page_mapped(page)) {
 154                 unmap_mapping_range(mapping,
 155                                    (loff_t)page->index << PAGE_CACHE_SHIFT,
 156                                    PAGE_CACHE_SIZE, 0);
 157         }
 158         return truncate_complete_page(mapping, page);
 159 }
 160
 161 /*
 162  * Used to get rid of pages on hardware memory corruption.
 163  */
 164 int generic_error_remove_page(struct address_space *mapping, struct page *page)
 165 {
 166         if (!mapping)
 167                 return -EINVAL;
 168         /*
 169          * Only punch for normal data pages for now.
 170          * Handling other types like directories would need more auditing.
 171          */
 172         if (!S_ISREG(mapping->host->i_mode))
 173                 return -EIO;
 174         return truncate_inode_page(mapping, page);
 175 }
 176 EXPORT_SYMBOL(generic_error_remove_page);
 177
 178 /*
 179  * Safely invalidate one page from its pagecache mapping.
 180  * It only drops clean, unused pages. The page must be locked.
 181  *
 182  * Returns 1 if the page is successfully invalidated, otherwise 0.
 183  */
 184 int invalidate_inode_page(struct page *page)
 185 {
 186         struct address_space *mapping = page_mapping(page);
 187         if (!mapping)
 188                 return 0;
 189         if (PageDirty(page) || PageWriteback(page))
 190                 return 0;
 191         if (page_mapped(page))
 192                 return 0;
 193         return invalidate_complete_page(mapping, page);
 194 }
 195
 196 /**
 197  * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
 198  * @mapping: mapping to truncate
 199  * @lstart: offset from which to truncate
 200  * @lend: offset to which to truncate (inclusive)
 201  *
 202  * Truncate the page cache, removing the pages that are between
 203  * specified offsets (and zeroing out partial pages
 204  * if lstart or lend + 1 is not page aligned).
 205  *
 206  * Truncate takes two passes - the first pass is nonblocking.  It will not
 207  * block on page locks and it will not block on writeback.  The second pass
 208  * will wait.  This is to prevent as much IO as possible in the affected region.
 209  * The first pass will remove most pages, so the search cost of the second pass
 210  * is low.
 211  *
 212  * We pass down the cache-hot hint to the page freeing code.  Even if the
 213  * mapping is large, it is probably the case that the final pages are the most
 214  * recently touched, and freeing happens in ascending file offset order.
 215  *
 216  * Note that since ->invalidatepage() accepts range to invalidate
 217  * truncate_inode_pages_range is able to handle cases where lend + 1 is not
 218  * page aligned properly.
 219  */
 220 void truncate_inode_pages_range(struct address_space *mapping,
 221                                 loff_t lstart, loff_t lend)
 222 {
 223         pgoff_t         start;          /* inclusive */
 224         pgoff_t         end;            /* exclusive */
 225         unsigned int    partial_start;  /* inclusive */
 226         unsigned int    partial_end;    /* exclusive */
 227         struct pagevec  pvec;
 228         pgoff_t         indices[PAGEVEC_SIZE];
 229         pgoff_t         index;
 230         int             i;
 231
 232         cleancache_invalidate_inode(mapping);
 233         if (mapping->nrpages == 0 && mapping->nrshadows == 0)
 234                 return;
 235
 236         /* Offsets within partial pages */
 237         partial_start = lstart & (PAGE_CACHE_SIZE - 1);
 238         partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
 239
 240         /*
 241          * 'start' and 'end' always covers the range of pages to be fully
 242          * truncated. Partial pages are covered with 'partial_start' at the
 243          * start of the range and 'partial_end' at the end of the range.
 244          * Note that 'end' is exclusive while 'lend' is inclusive.
 245          */
 246         start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 247         if (lend == -1)
 248                 /*
 249                  * lend == -1 indicates end-of-file so we have to set 'end'
 250                  * to the highest possible pgoff_t and since the type is
 251                  * unsigned we're using -1.
 252                  */
 253                 end = -1;
 254         else
 255                 end = (lend + 1) >> PAGE_CACHE_SHIFT;
 256
 257         pagevec_init(&pvec, 0);
 258         index = start;
 259         while (index < end && pagevec_lookup_entries(&pvec, mapping, index,
 260                         min(end - index, (pgoff_t)PAGEVEC_SIZE),
 261                         indices)) {
 262                 mem_cgroup_uncharge_start();
 263                 for (i = 0; i < pagevec_count(&pvec); i++) {
 264                         struct page *page = pvec.pages[i];
 265
 266                         /* We rely upon deletion not changing page->index */
 267                         index = indices[i];
 268                         if (index >= end)
 269                                 break;
 270
 271                         if (radix_tree_exceptional_entry(page)) {
 272                                 clear_exceptional_entry(mapping, index, page);
 273                                 continue;
 274                         }
 275
 276                         if (!trylock_page(page))
 277                                 continue;
 278                         WARN_ON(page->index != index);
 279                         if (PageWriteback(page)) {
 280                                 unlock_page(page);
 281                                 continue;
 282                         }
 283                         truncate_inode_page(mapping, page);
 284                         unlock_page(page);
 285                 }
 286                 pagevec_remove_exceptionals(&pvec);
 287                 pagevec_release(&pvec);
 288                 mem_cgroup_uncharge_end();
 289                 cond_resched();
 290                 index++;
 291         }
 292
 293         if (partial_start) {
 294                 struct page *page = find_lock_page(mapping, start - 1);
 295                 if (page) {
 296                         unsigned int top = PAGE_CACHE_SIZE;
 297                         if (start > end) {
 298                                 /* Truncation within a single page */
 299                                 top = partial_end;
 300                                 partial_end = 0;
 301                         }
 302                         wait_on_page_writeback(page);
 303                         zero_user_segment(page, partial_start, top);
 304                         cleancache_invalidate_page(mapping, page);
 305                         if (page_has_private(page))
 306                                 do_invalidatepage(page, partial_start,
 307                                                   top - partial_start);
 308                         unlock_page(page);
 309                         page_cache_release(page);
 310                 }
 311         }
 312         if (partial_end) {
 313                 struct page *page = find_lock_page(mapping, end);
 314                 if (page) {
 315                         wait_on_page_writeback(page);
 316                         zero_user_segment(page, 0, partial_end);
 317                         cleancache_invalidate_page(mapping, page);
 318                         if (page_has_private(page))
 319                                 do_invalidatepage(page, 0,
 320                                                   partial_end);
 321                         unlock_page(page);
 322                         page_cache_release(page);
 323                 }
 324         }
 325         /*
 326          * If the truncation happened within a single page no pages
 327          * will be released, just zeroed, so we can bail out now.
 328          */
 329         if (start >= end)
 330                 return;
 331
 332         index = start;
 333         for ( ; ; ) {
 334                 cond_resched();
 335                 if (!pagevec_lookup_entries(&pvec, mapping, index,
 336                         min(end - index, (pgoff_t)PAGEVEC_SIZE),
 337                         indices)) {
 338                         if (index == start)
 339                                 break;
 340                         index = start;
 341                         continue;
 342                 }
 343                 if (index == start && indices[0] >= end) {
 344                         pagevec_remove_exceptionals(&pvec);
 345                         pagevec_release(&pvec);
 346                         break;
 347                 }
 348                 mem_cgroup_uncharge_start();
 349                 for (i = 0; i < pagevec_count(&pvec); i++) {
 350                         struct page *page = pvec.pages[i];
 351
 352                         /* We rely upon deletion not changing page->index */
 353                         index = indices[i];
 354                         if (index >= end)
 355                                 break;
 356
 357                         if (radix_tree_exceptional_entry(page)) {
 358                                 clear_exceptional_entry(mapping, index, page);
 359                                 continue;
 360                         }
 361
 362                         lock_page(page);
 363                         WARN_ON(page->index != index);
 364                         wait_on_page_writeback(page);
 365                         truncate_inode_page(mapping, page);
 366                         unlock_page(page);
 367                 }
 368                 pagevec_remove_exceptionals(&pvec);
 369                 pagevec_release(&pvec);
 370                 mem_cgroup_uncharge_end();
 371                 index++;
 372         }
 373         cleancache_invalidate_inode(mapping);
 374 }
 375 EXPORT_SYMBOL(truncate_inode_pages_range);
 376
 377 /**
 378  * truncate_inode_pages - truncate *all* the pages from an offset
 379  * @mapping: mapping to truncate
 380  * @lstart: offset from which to truncate
 381  *
 382  * Called under (and serialised by) inode->i_mutex.
 383  *
 384  * Note: When this function returns, there can be a page in the process of
 385  * deletion (inside __delete_from_page_cache()) in the specified range.  Thus
 386  * mapping->nrpages can be non-zero when this function returns even after
 387  * truncation of the whole mapping.
 388  */
 389 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
 390 {
 391         truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
 392 }
 393 EXPORT_SYMBOL(truncate_inode_pages);
 394
 395 /**
 396  * truncate_inode_pages_final - truncate *all* pages before inode dies
 397  * @mapping: mapping to truncate
 398  *
 399  * Called under (and serialized by) inode->i_mutex.
 400  *
 401  * Filesystems have to use this in the .evict_inode path to inform the
 402  * VM that this is the final truncate and the inode is going away.
 403  */
 404 void truncate_inode_pages_final(struct address_space *mapping)
 405 {
 406         unsigned long nrshadows;
 407         unsigned long nrpages;
 408
 409         /*
 410          * Page reclaim can not participate in regular inode lifetime
 411          * management (can't call iput()) and thus can race with the
 412          * inode teardown.  Tell it when the address space is exiting,
 413          * so that it does not install eviction information after the
 414          * final truncate has begun.
 415          */
 416         mapping_set_exiting(mapping);
 417
 418         /*
 419          * When reclaim installs eviction entries, it increases
 420          * nrshadows first, then decreases nrpages.  Make sure we see
 421          * this in the right order or we might miss an entry.
 422          */
 423         nrpages = mapping->nrpages;
 424         smp_rmb();
 425         nrshadows = mapping->nrshadows;
 426
 427         if (nrpages || nrshadows) {
 428                 /*
 429                  * As truncation uses a lockless tree lookup, cycle
 430                  * the tree lock to make sure any ongoing tree
 431                  * modification that does not see AS_EXITING is
 432                  * completed before starting the final truncate.
 433                  */
 434                 spin_lock_irq(&mapping->tree_lock);
 435                 spin_unlock_irq(&mapping->tree_lock);
 436
 437                 truncate_inode_pages(mapping, 0);
 438         }
 439 }
 440 EXPORT_SYMBOL(truncate_inode_pages_final);
 441
 442 /**
 443  * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
 444  * @mapping: the address_space which holds the pages to invalidate
 445  * @start: the offset 'from' which to invalidate
 446  * @end: the offset 'to' which to invalidate (inclusive)
 447  *
 448  * This function only removes the unlocked pages, if you want to
 449  * remove all the pages of one inode, you must call truncate_inode_pages.
 450  *
 451  * invalidate_mapping_pages() will not block on IO activity. It will not
 452  * invalidate pages which are dirty, locked, under writeback or mapped into
 453  * pagetables.
 454  */
 455 unsigned long invalidate_mapping_pages(struct address_space *mapping,
 456                 pgoff_t start, pgoff_t end)
 457 {
 458         pgoff_t indices[PAGEVEC_SIZE];
 459         struct pagevec pvec;
 460         pgoff_t index = start;
 461         unsigned long ret;
 462         unsigned long count = 0;
 463         int i;
 464
 465         /*
 466          * Note: this function may get called on a shmem/tmpfs mapping:
 467          * pagevec_lookup() might then return 0 prematurely (because it
 468          * got a gangful of swap entries); but it's hardly worth worrying
 469          * about - it can rarely have anything to free from such a mapping
 470          * (most pages are dirty), and already skips over any difficulties.
 471          */
 472
 473         pagevec_init(&pvec, 0);
 474         while (index <= end && pagevec_lookup_entries(&pvec, mapping, index,
 475                         min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
 476                         indices)) {
 477                 mem_cgroup_uncharge_start();
 478                 for (i = 0; i < pagevec_count(&pvec); i++) {
 479                         struct page *page = pvec.pages[i];
 480
 481                         /* We rely upon deletion not changing page->index */
 482                         index = indices[i];
 483                         if (index > end)
 484                                 break;
 485
 486                         if (radix_tree_exceptional_entry(page)) {
 487                                 clear_exceptional_entry(mapping, index, page);
 488                                 continue;
 489                         }
 490
 491                         if (!trylock_page(page))
 492                                 continue;
 493                         WARN_ON(page->index != index);
 494                         ret = invalidate_inode_page(page);
 495                         unlock_page(page);
 496                         /*
 497                          * Invalidation is a hint that the page is no longer
 498                          * of interest and try to speed up its reclaim.
 499                          */
 500                         if (!ret)
 501                                 deactivate_page(page);
 502                         count += ret;
 503                 }
 504                 pagevec_remove_exceptionals(&pvec);
 505                 pagevec_release(&pvec);
 506                 mem_cgroup_uncharge_end();
 507                 cond_resched();
 508                 index++;
 509         }
 510         return count;
 511 }
 512 EXPORT_SYMBOL(invalidate_mapping_pages);
 513
 514 /*
 515  * This is like invalidate_complete_page(), except it ignores the page's
 516  * refcount.  We do this because invalidate_inode_pages2() needs stronger
 517  * invalidation guarantees, and cannot afford to leave pages behind because
 518  * shrink_page_list() has a temp ref on them, or because they're transiently
 519  * sitting in the lru_cache_add() pagevecs.
 520  */
 521 static int
 522 invalidate_complete_page2(struct address_space *mapping, struct page *page)
 523 {
 524         if (page->mapping != mapping)
 525                 return 0;
 526
 527         if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
 528                 return 0;
 529
 530         spin_lock_irq(&mapping->tree_lock);
 531         if (PageDirty(page))
 532                 goto failed;
 533
 534         BUG_ON(page_has_private(page));
 535         __delete_from_page_cache(page, NULL);
 536         spin_unlock_irq(&mapping->tree_lock);
 537         mem_cgroup_uncharge_cache_page(page);
 538
 539         if (mapping->a_ops->freepage)
 540                 mapping->a_ops->freepage(page);
 541
 542         page_cache_release(page);       /* pagecache ref */
 543         return 1;
 544 failed:
 545         spin_unlock_irq(&mapping->tree_lock);
 546         return 0;
 547 }
 548
 549 static int do_launder_page(struct address_space *mapping, struct page *page)
 550 {
 551         if (!PageDirty(page))
 552                 return 0;
 553         if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
 554                 return 0;
 555         return mapping->a_ops->launder_page(page);
 556 }
 557
 558 /**
 559  * invalidate_inode_pages2_range - remove range of pages from an address_space
 560  * @mapping: the address_space
 561  * @start: the page offset 'from' which to invalidate
 562  * @end: the page offset 'to' which to invalidate (inclusive)
 563  *
 564  * Any pages which are found to be mapped into pagetables are unmapped prior to
 565  * invalidation.
 566  *
 567  * Returns -EBUSY if any pages could not be invalidated.
 568  */
 569 int invalidate_inode_pages2_range(struct address_space *mapping,
 570                                   pgoff_t start, pgoff_t end)
 571 {
 572         pgoff_t indices[PAGEVEC_SIZE];
 573         struct pagevec pvec;
 574         pgoff_t index;
 575         int i;
 576         int ret = 0;
 577         int ret2 = 0;
 578         int did_range_unmap = 0;
 579
 580         cleancache_invalidate_inode(mapping);
 581         pagevec_init(&pvec, 0);
 582         index = start;
 583         while (index <= end && pagevec_lookup_entries(&pvec, mapping, index,
 584                         min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
 585                         indices)) {
 586                 mem_cgroup_uncharge_start();
 587                 for (i = 0; i < pagevec_count(&pvec); i++) {
 588                         struct page *page = pvec.pages[i];
 589
 590                         /* We rely upon deletion not changing page->index */
 591                         index = indices[i];
 592                         if (index > end)
 593                                 break;
 594
 595                         if (radix_tree_exceptional_entry(page)) {
 596                                 clear_exceptional_entry(mapping, index, page);
 597                                 continue;
 598                         }
 599
 600                         lock_page(page);
 601                         WARN_ON(page->index != index);
 602                         if (page->mapping != mapping) {
 603                                 unlock_page(page);
 604                                 continue;
 605                         }
 606                         wait_on_page_writeback(page);
 607                         if (page_mapped(page)) {
 608                                 if (!did_range_unmap) {
 609                                         /*
 610                                          * Zap the rest of the file in one hit.
 611                                          */
 612                                         unmap_mapping_range(mapping,
 613                                            (loff_t)index << PAGE_CACHE_SHIFT,
 614                                            (loff_t)(1 + end - index)
 615                                                          << PAGE_CACHE_SHIFT,
 616                                             0);
 617                                         did_range_unmap = 1;
 618                                 } else {
 619                                         /*
 620                                          * Just zap this page
 621                                          */
 622                                         unmap_mapping_range(mapping,
 623                                            (loff_t)index << PAGE_CACHE_SHIFT,
 624                                            PAGE_CACHE_SIZE, 0);
 625                                 }
 626                         }
 627                         BUG_ON(page_mapped(page));
 628                         ret2 = do_launder_page(mapping, page);
 629                         if (ret2 == 0) {
 630                                 if (!invalidate_complete_page2(mapping, page))
 631                                         ret2 = -EBUSY;
 632                         }
 633                         if (ret2 < 0)
 634                                 ret = ret2;
 635                         unlock_page(page);
 636                 }
 637                 pagevec_remove_exceptionals(&pvec);
 638                 pagevec_release(&pvec);
 639                 mem_cgroup_uncharge_end();
 640                 cond_resched();
 641                 index++;
 642         }
 643         cleancache_invalidate_inode(mapping);
 644         return ret;
 645 }
 646 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
 647
 648 /**
 649  * invalidate_inode_pages2 - remove all pages from an address_space
 650  * @mapping: the address_space
 651  *
 652  * Any pages which are found to be mapped into pagetables are unmapped prior to
 653  * invalidation.
 654  *
 655  * Returns -EBUSY if any pages could not be invalidated.
 656  */
 657 int invalidate_inode_pages2(struct address_space *mapping)
 658 {
 659         return invalidate_inode_pages2_range(mapping, 0, -1);
 660 }
 661 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
 662
 663 /**
 664  * truncate_pagecache - unmap and remove pagecache that has been truncated
 665  * @inode: inode
 666  * @newsize: new file size
 667  *
 668  * inode's new i_size must already be written before truncate_pagecache
 669  * is called.
 670  *
 671  * This function should typically be called before the filesystem
 672  * releases resources associated with the freed range (eg. deallocates
 673  * blocks). This way, pagecache will always stay logically coherent
 674  * with on-disk format, and the filesystem would not have to deal with
 675  * situations such as writepage being called for a page that has already
 676  * had its underlying blocks deallocated.
 677  */
 678 void truncate_pagecache(struct inode *inode, loff_t newsize)
 679 {
 680         struct address_space *mapping = inode->i_mapping;
 681         loff_t holebegin = round_up(newsize, PAGE_SIZE);
 682
 683         /*
 684          * unmap_mapping_range is called twice, first simply for
 685          * efficiency so that truncate_inode_pages does fewer
 686          * single-page unmaps.  However after this first call, and
 687          * before truncate_inode_pages finishes, it is possible for
 688          * private pages to be COWed, which remain after
 689          * truncate_inode_pages finishes, hence the second
 690          * unmap_mapping_range call must be made for correctness.
 691          */
 692         unmap_mapping_range(mapping, holebegin, 0, 1);
 693         truncate_inode_pages(mapping, newsize);
 694         unmap_mapping_range(mapping, holebegin, 0, 1);
 695 }
 696 EXPORT_SYMBOL(truncate_pagecache);
 697
 698 /**
 699  * truncate_setsize - update inode and pagecache for a new file size
 700  * @inode: inode
 701  * @newsize: new file size
 702  *
 703  * truncate_setsize updates i_size and performs pagecache truncation (if
 704  * necessary) to @newsize. It will be typically be called from the filesystem's
 705  * setattr function when ATTR_SIZE is passed in.
 706  *
 707  * Must be called with inode_mutex held and before all filesystem specific
 708  * block truncation has been performed.
 709  */
 710 void truncate_setsize(struct inode *inode, loff_t newsize)
 711 {
 712         i_size_write(inode, newsize);
 713         truncate_pagecache(inode, newsize);
 714 }
 715 EXPORT_SYMBOL(truncate_setsize);
 716
 717 /**
 718  * truncate_pagecache_range - unmap and remove pagecache that is hole-punched
 719  * @inode: inode
 720  * @lstart: offset of beginning of hole
 721  * @lend: offset of last byte of hole
 722  *
 723  * This function should typically be called before the filesystem
 724  * releases resources associated with the freed range (eg. deallocates
 725  * blocks). This way, pagecache will always stay logically coherent
 726  * with on-disk format, and the filesystem would not have to deal with
 727  * situations such as writepage being called for a page that has already
 728  * had its underlying blocks deallocated.
 729  */
 730 void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
 731 {
 732         struct address_space *mapping = inode->i_mapping;
 733         loff_t unmap_start = round_up(lstart, PAGE_SIZE);
 734         loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
 735         /*
 736          * This rounding is currently just for example: unmap_mapping_range
 737          * expands its hole outwards, whereas we want it to contract the hole
 738          * inwards.  However, existing callers of truncate_pagecache_range are
 739          * doing their own page rounding first.  Note that unmap_mapping_range
 740          * allows holelen 0 for all, and we allow lend -1 for end of file.
 741          */
 742
 743         /*
 744          * Unlike in truncate_pagecache, unmap_mapping_range is called only
 745          * once (before truncating pagecache), and without "even_cows" flag:
 746          * hole-punching should not remove private COWed pages from the hole.
 747          */
 748         if ((u64)unmap_end > (u64)unmap_start)
 749                 unmap_mapping_range(mapping, unmap_start,
 750                                     1 + unmap_end - unmap_start, 0);
 751         truncate_inode_pages_range(mapping, lstart, lend);
 752 }
 753 EXPORT_SYMBOL(truncate_pagecache_range);