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/dax.h>
  13 #include <linux/gfp.h>
  14 #include <linux/mm.h>
  15 #include <linux/swap.h>
  16 #include <linux/export.h>
  17 #include <linux/pagemap.h>
  18 #include <linux/highmem.h>
  19 #include <linux/pagevec.h>
  20 #include <linux/task_io_accounting_ops.h>
  21 #include <linux/buffer_head.h>  /* grr. try_to_release_page,
  22                                    do_invalidatepage */
  23 #include <linux/cleancache.h>
  24 #include <linux/rmap.h>
  25 #include "internal.h"
  26
  27 static void clear_exceptional_entry(struct address_space *mapping,
  28                                     pgoff_t index, void *entry)
  29 {
  30         struct radix_tree_node *node;
  31         void **slot;
  32
  33         /* Handled by shmem itself */
  34         if (shmem_mapping(mapping))
  35                 return;
  36
  37         if (dax_mapping(mapping)) {
  38                 dax_delete_mapping_entry(mapping, index);
  39                 return;
  40         }
  41         spin_lock_irq(&mapping->tree_lock);
  42         /*
  43          * Regular page slots are stabilized by the page lock even
  44          * without the tree itself locked.  These unlocked entries
  45          * need verification under the tree lock.
  46          */
  47         if (!__radix_tree_lookup(&mapping->page_tree, index, &node,
  48                                 &slot))
  49                 goto unlock;
  50         if (*slot != entry)
  51                 goto unlock;
  52         radix_tree_replace_slot(slot, NULL);
  53         mapping->nrexceptional--;
  54         if (!node)
  55                 goto unlock;
  56         workingset_node_shadows_dec(node);
  57         /*
  58          * Don't track node without shadow entries.
  59          *
  60          * Avoid acquiring the list_lru lock if already untracked.
  61          * The list_empty() test is safe as node->private_list is
  62          * protected by mapping->tree_lock.
  63          */
  64         if (!workingset_node_shadows(node) &&
  65             !list_empty(&node->private_list))
  66                 list_lru_del(&workingset_shadow_nodes,
  67                                 &node->private_list);
  68         __radix_tree_delete_node(&mapping->page_tree, node);
  69 unlock:
  70         spin_unlock_irq(&mapping->tree_lock);
  71 }
  72
  73 /**
  74  * do_invalidatepage - invalidate part or all of a page
  75  * @page: the page which is affected
  76  * @offset: start of the range to invalidate
  77  * @length: length of the range to invalidate
  78  *
  79  * do_invalidatepage() is called when all or part of the page has become
  80  * invalidated by a truncate operation.
  81  *
  82  * do_invalidatepage() does not have to release all buffers, but it must
  83  * ensure that no dirty buffer is left outside @offset and that no I/O
  84  * is underway against any of the blocks which are outside the truncation
  85  * point.  Because the caller is about to free (and possibly reuse) those
  86  * blocks on-disk.
  87  */
  88 void do_invalidatepage(struct page *page, unsigned int offset,
  89                        unsigned int length)
  90 {
  91         void (*invalidatepage)(struct page *, unsigned int, unsigned int);
  92
  93         invalidatepage = page->mapping->a_ops->invalidatepage;
  94 #ifdef CONFIG_BLOCK
  95         if (!invalidatepage)
  96                 invalidatepage = block_invalidatepage;
  97 #endif
  98         if (invalidatepage)
  99                 (*invalidatepage)(page, offset, length);
 100 }
 101
 102 /*
 103  * If truncate cannot remove the fs-private metadata from the page, the page
 104  * becomes orphaned.  It will be left on the LRU and may even be mapped into
 105  * user pagetables if we're racing with filemap_fault().
 106  *
 107  * We need to bale out if page->mapping is no longer equal to the original
 108  * mapping.  This happens a) when the VM reclaimed the page while we waited on
 109  * its lock, b) when a concurrent invalidate_mapping_pages got there first and
 110  * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
 111  */
 112 static int
 113 truncate_complete_page(struct address_space *mapping, struct page *page)
 114 {
 115         if (page->mapping != mapping)
 116                 return -EIO;
 117
 118         if (page_has_private(page))
 119                 do_invalidatepage(page, 0, PAGE_SIZE);
 120
 121         /*
 122          * Some filesystems seem to re-dirty the page even after
 123          * the VM has canceled the dirty bit (eg ext3 journaling).
 124          * Hence dirty accounting check is placed after invalidation.
 125          */
 126         cancel_dirty_page(page);
 127         ClearPageMappedToDisk(page);
 128         delete_from_page_cache(page);
 129         return 0;
 130 }
 131
 132 /*
 133  * This is for invalidate_mapping_pages().  That function can be called at
 134  * any time, and is not supposed to throw away dirty pages.  But pages can
 135  * be marked dirty at any time too, so use remove_mapping which safely
 136  * discards clean, unused pages.
 137  *
 138  * Returns non-zero if the page was successfully invalidated.
 139  */
 140 static int
 141 invalidate_complete_page(struct address_space *mapping, struct page *page)
 142 {
 143         int ret;
 144
 145         if (page->mapping != mapping)
 146                 return 0;
 147
 148         if (page_has_private(page) && !try_to_release_page(page, 0))
 149                 return 0;
 150
 151         ret = remove_mapping(mapping, page);
 152
 153         return ret;
 154 }
 155
 156 int truncate_inode_page(struct address_space *mapping, struct page *page)
 157 {
 158         loff_t holelen;
 159         VM_BUG_ON_PAGE(PageTail(page), page);
 160
 161         holelen = PageTransHuge(page) ? HPAGE_PMD_SIZE : PAGE_SIZE;
 162         if (page_mapped(page)) {
 163                 unmap_mapping_range(mapping,
 164                                    (loff_t)page->index << PAGE_SHIFT,
 165                                    holelen, 0);
 166         }
 167         return truncate_complete_page(mapping, page);
 168 }
 169
 170 /*
 171  * Used to get rid of pages on hardware memory corruption.
 172  */
 173 int generic_error_remove_page(struct address_space *mapping, struct page *page)
 174 {
 175         if (!mapping)
 176                 return -EINVAL;
 177         /*
 178          * Only punch for normal data pages for now.
 179          * Handling other types like directories would need more auditing.
 180          */
 181         if (!S_ISREG(mapping->host->i_mode))
 182                 return -EIO;
 183         return truncate_inode_page(mapping, page);
 184 }
 185 EXPORT_SYMBOL(generic_error_remove_page);
 186
 187 /*
 188  * Safely invalidate one page from its pagecache mapping.
 189  * It only drops clean, unused pages. The page must be locked.
 190  *
 191  * Returns 1 if the page is successfully invalidated, otherwise 0.
 192  */
 193 int invalidate_inode_page(struct page *page)
 194 {
 195         struct address_space *mapping = page_mapping(page);
 196         if (!mapping)
 197                 return 0;
 198         if (PageDirty(page) || PageWriteback(page))
 199                 return 0;
 200         if (page_mapped(page))
 201                 return 0;
 202         return invalidate_complete_page(mapping, page);
 203 }
 204
 205 /**
 206  * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
 207  * @mapping: mapping to truncate
 208  * @lstart: offset from which to truncate
 209  * @lend: offset to which to truncate (inclusive)
 210  *
 211  * Truncate the page cache, removing the pages that are between
 212  * specified offsets (and zeroing out partial pages
 213  * if lstart or lend + 1 is not page aligned).
 214  *
 215  * Truncate takes two passes - the first pass is nonblocking.  It will not
 216  * block on page locks and it will not block on writeback.  The second pass
 217  * will wait.  This is to prevent as much IO as possible in the affected region.
 218  * The first pass will remove most pages, so the search cost of the second pass
 219  * is low.
 220  *
 221  * We pass down the cache-hot hint to the page freeing code.  Even if the
 222  * mapping is large, it is probably the case that the final pages are the most
 223  * recently touched, and freeing happens in ascending file offset order.
 224  *
 225  * Note that since ->invalidatepage() accepts range to invalidate
 226  * truncate_inode_pages_range is able to handle cases where lend + 1 is not
 227  * page aligned properly.
 228  */
 229 void truncate_inode_pages_range(struct address_space *mapping,
 230                                 loff_t lstart, loff_t lend)
 231 {
 232         pgoff_t         start;          /* inclusive */
 233         pgoff_t         end;            /* exclusive */
 234         unsigned int    partial_start;  /* inclusive */
 235         unsigned int    partial_end;    /* exclusive */
 236         struct pagevec  pvec;
 237         pgoff_t         indices[PAGEVEC_SIZE];
 238         pgoff_t         index;
 239         int             i;
 240
 241         cleancache_invalidate_inode(mapping);
 242         if (mapping->nrpages == 0 && mapping->nrexceptional == 0)
 243                 return;
 244
 245         /* Offsets within partial pages */
 246         partial_start = lstart & (PAGE_SIZE - 1);
 247         partial_end = (lend + 1) & (PAGE_SIZE - 1);
 248
 249         /*
 250          * 'start' and 'end' always covers the range of pages to be fully
 251          * truncated. Partial pages are covered with 'partial_start' at the
 252          * start of the range and 'partial_end' at the end of the range.
 253          * Note that 'end' is exclusive while 'lend' is inclusive.
 254          */
 255         start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
 256         if (lend == -1)
 257                 /*
 258                  * lend == -1 indicates end-of-file so we have to set 'end'
 259                  * to the highest possible pgoff_t and since the type is
 260                  * unsigned we're using -1.
 261                  */
 262                 end = -1;
 263         else
 264                 end = (lend + 1) >> PAGE_SHIFT;
 265
 266         pagevec_init(&pvec, 0);
 267         index = start;
 268         while (index < end && pagevec_lookup_entries(&pvec, mapping, index,
 269                         min(end - index, (pgoff_t)PAGEVEC_SIZE),
 270                         indices)) {
 271                 for (i = 0; i < pagevec_count(&pvec); i++) {
 272                         struct page *page = pvec.pages[i];
 273
 274                         /* We rely upon deletion not changing page->index */
 275                         index = indices[i];
 276                         if (index >= end)
 277                                 break;
 278
 279                         if (radix_tree_exceptional_entry(page)) {
 280                                 clear_exceptional_entry(mapping, index, page);
 281                                 continue;
 282                         }
 283
 284                         if (!trylock_page(page))
 285                                 continue;
 286                         WARN_ON(page_to_pgoff(page) != index);
 287                         if (PageWriteback(page)) {
 288                                 unlock_page(page);
 289                                 continue;
 290                         }
 291                         truncate_inode_page(mapping, page);
 292                         unlock_page(page);
 293                 }
 294                 pagevec_remove_exceptionals(&pvec);
 295                 pagevec_release(&pvec);
 296                 cond_resched();
 297                 index++;
 298         }
 299
 300         if (partial_start) {
 301                 struct page *page = find_lock_page(mapping, start - 1);
 302                 if (page) {
 303                         unsigned int top = PAGE_SIZE;
 304                         if (start > end) {
 305                                 /* Truncation within a single page */
 306                                 top = partial_end;
 307                                 partial_end = 0;
 308                         }
 309                         wait_on_page_writeback(page);
 310                         zero_user_segment(page, partial_start, top);
 311                         cleancache_invalidate_page(mapping, page);
 312                         if (page_has_private(page))
 313                                 do_invalidatepage(page, partial_start,
 314                                                   top - partial_start);
 315                         unlock_page(page);
 316                         put_page(page);
 317                 }
 318         }
 319         if (partial_end) {
 320                 struct page *page = find_lock_page(mapping, end);
 321                 if (page) {
 322                         wait_on_page_writeback(page);
 323                         zero_user_segment(page, 0, partial_end);
 324                         cleancache_invalidate_page(mapping, page);
 325                         if (page_has_private(page))
 326                                 do_invalidatepage(page, 0,
 327                                                   partial_end);
 328                         unlock_page(page);
 329                         put_page(page);
 330                 }
 331         }
 332         /*
 333          * If the truncation happened within a single page no pages
 334          * will be released, just zeroed, so we can bail out now.
 335          */
 336         if (start >= end)
 337                 return;
 338
 339         index = start;
 340         for ( ; ; ) {
 341                 cond_resched();
 342                 if (!pagevec_lookup_entries(&pvec, mapping, index,
 343                         min(end - index, (pgoff_t)PAGEVEC_SIZE), indices)) {
 344                         /* If all gone from start onwards, we're done */
 345                         if (index == start)
 346                                 break;
 347                         /* Otherwise restart to make sure all gone */
 348                         index = start;
 349                         continue;
 350                 }
 351                 if (index == start && indices[0] >= end) {
 352                         /* All gone out of hole to be punched, we're done */
 353                         pagevec_remove_exceptionals(&pvec);
 354                         pagevec_release(&pvec);
 355                         break;
 356                 }
 357                 for (i = 0; i < pagevec_count(&pvec); i++) {
 358                         struct page *page = pvec.pages[i];
 359
 360                         /* We rely upon deletion not changing page->index */
 361                         index = indices[i];
 362                         if (index >= end) {
 363                                 /* Restart punch to make sure all gone */
 364                                 index = start - 1;
 365                                 break;
 366                         }
 367
 368                         if (radix_tree_exceptional_entry(page)) {
 369                                 clear_exceptional_entry(mapping, index, page);
 370                                 continue;
 371                         }
 372
 373                         lock_page(page);
 374                         WARN_ON(page_to_pgoff(page) != index);
 375                         wait_on_page_writeback(page);
 376                         truncate_inode_page(mapping, page);
 377                         unlock_page(page);
 378                 }
 379                 pagevec_remove_exceptionals(&pvec);
 380                 pagevec_release(&pvec);
 381                 index++;
 382         }
 383         cleancache_invalidate_inode(mapping);
 384 }
 385 EXPORT_SYMBOL(truncate_inode_pages_range);
 386
 387 /**
 388  * truncate_inode_pages - truncate *all* the pages from an offset
 389  * @mapping: mapping to truncate
 390  * @lstart: offset from which to truncate
 391  *
 392  * Called under (and serialised by) inode->i_mutex.
 393  *
 394  * Note: When this function returns, there can be a page in the process of
 395  * deletion (inside __delete_from_page_cache()) in the specified range.  Thus
 396  * mapping->nrpages can be non-zero when this function returns even after
 397  * truncation of the whole mapping.
 398  */
 399 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
 400 {
 401         truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
 402 }
 403 EXPORT_SYMBOL(truncate_inode_pages);
 404
 405 /**
 406  * truncate_inode_pages_final - truncate *all* pages before inode dies
 407  * @mapping: mapping to truncate
 408  *
 409  * Called under (and serialized by) inode->i_mutex.
 410  *
 411  * Filesystems have to use this in the .evict_inode path to inform the
 412  * VM that this is the final truncate and the inode is going away.
 413  */
 414 void truncate_inode_pages_final(struct address_space *mapping)
 415 {
 416         unsigned long nrexceptional;
 417         unsigned long nrpages;
 418
 419         /*
 420          * Page reclaim can not participate in regular inode lifetime
 421          * management (can't call iput()) and thus can race with the
 422          * inode teardown.  Tell it when the address space is exiting,
 423          * so that it does not install eviction information after the
 424          * final truncate has begun.
 425          */
 426         mapping_set_exiting(mapping);
 427
 428         /*
 429          * When reclaim installs eviction entries, it increases
 430          * nrexceptional first, then decreases nrpages.  Make sure we see
 431          * this in the right order or we might miss an entry.
 432          */
 433         nrpages = mapping->nrpages;
 434         smp_rmb();
 435         nrexceptional = mapping->nrexceptional;
 436
 437         if (nrpages || nrexceptional) {
 438                 /*
 439                  * As truncation uses a lockless tree lookup, cycle
 440                  * the tree lock to make sure any ongoing tree
 441                  * modification that does not see AS_EXITING is
 442                  * completed before starting the final truncate.
 443                  */
 444                 spin_lock_irq(&mapping->tree_lock);
 445                 spin_unlock_irq(&mapping->tree_lock);
 446
 447                 truncate_inode_pages(mapping, 0);
 448         }
 449 }
 450 EXPORT_SYMBOL(truncate_inode_pages_final);
 451
 452 /**
 453  * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
 454  * @mapping: the address_space which holds the pages to invalidate
 455  * @start: the offset 'from' which to invalidate
 456  * @end: the offset 'to' which to invalidate (inclusive)
 457  *
 458  * This function only removes the unlocked pages, if you want to
 459  * remove all the pages of one inode, you must call truncate_inode_pages.
 460  *
 461  * invalidate_mapping_pages() will not block on IO activity. It will not
 462  * invalidate pages which are dirty, locked, under writeback or mapped into
 463  * pagetables.
 464  */
 465 unsigned long invalidate_mapping_pages(struct address_space *mapping,
 466                 pgoff_t start, pgoff_t end)
 467 {
 468         pgoff_t indices[PAGEVEC_SIZE];
 469         struct pagevec pvec;
 470         pgoff_t index = start;
 471         unsigned long ret;
 472         unsigned long count = 0;
 473         int i;
 474
 475         pagevec_init(&pvec, 0);
 476         while (index <= end && pagevec_lookup_entries(&pvec, mapping, index,
 477                         min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
 478                         indices)) {
 479                 for (i = 0; i < pagevec_count(&pvec); i++) {
 480                         struct page *page = pvec.pages[i];
 481
 482                         /* We rely upon deletion not changing page->index */
 483                         index = indices[i];
 484                         if (index > end)
 485                                 break;
 486
 487                         if (radix_tree_exceptional_entry(page)) {
 488                                 clear_exceptional_entry(mapping, index, page);
 489                                 continue;
 490                         }
 491
 492                         if (!trylock_page(page))
 493                                 continue;
 494
 495                         WARN_ON(page_to_pgoff(page) != index);
 496
 497                         /* Middle of THP: skip */
 498                         if (PageTransTail(page)) {
 499                                 unlock_page(page);
 500                                 continue;
 501                         } else if (PageTransHuge(page)) {
 502                                 index += HPAGE_PMD_NR - 1;
 503                                 i += HPAGE_PMD_NR - 1;
 504                                 /* 'end' is in the middle of THP */
 505                                 if (index ==  round_down(end, HPAGE_PMD_NR))
 506                                         continue;
 507                         }
 508
 509                         ret = invalidate_inode_page(page);
 510                         unlock_page(page);
 511                         /*
 512                          * Invalidation is a hint that the page is no longer
 513                          * of interest and try to speed up its reclaim.
 514                          */
 515                         if (!ret)
 516                                 deactivate_file_page(page);
 517                         count += ret;
 518                 }
 519                 pagevec_remove_exceptionals(&pvec);
 520                 pagevec_release(&pvec);
 521                 cond_resched();
 522                 index++;
 523         }
 524         return count;
 525 }
 526 EXPORT_SYMBOL(invalidate_mapping_pages);
 527
 528 /*
 529  * This is like invalidate_complete_page(), except it ignores the page's
 530  * refcount.  We do this because invalidate_inode_pages2() needs stronger
 531  * invalidation guarantees, and cannot afford to leave pages behind because
 532  * shrink_page_list() has a temp ref on them, or because they're transiently
 533  * sitting in the lru_cache_add() pagevecs.
 534  */
 535 static int
 536 invalidate_complete_page2(struct address_space *mapping, struct page *page)
 537 {
 538         unsigned long flags;
 539
 540         if (page->mapping != mapping)
 541                 return 0;
 542
 543         if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
 544                 return 0;
 545
 546         spin_lock_irqsave(&mapping->tree_lock, flags);
 547         if (PageDirty(page))
 548                 goto failed;
 549
 550         BUG_ON(page_has_private(page));
 551         __delete_from_page_cache(page, NULL);
 552         spin_unlock_irqrestore(&mapping->tree_lock, flags);
 553
 554         if (mapping->a_ops->freepage)
 555                 mapping->a_ops->freepage(page);
 556
 557         put_page(page); /* pagecache ref */
 558         return 1;
 559 failed:
 560         spin_unlock_irqrestore(&mapping->tree_lock, flags);
 561         return 0;
 562 }
 563
 564 static int do_launder_page(struct address_space *mapping, struct page *page)
 565 {
 566         if (!PageDirty(page))
 567                 return 0;
 568         if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
 569                 return 0;
 570         return mapping->a_ops->launder_page(page);
 571 }
 572
 573 /**
 574  * invalidate_inode_pages2_range - remove range of pages from an address_space
 575  * @mapping: the address_space
 576  * @start: the page offset 'from' which to invalidate
 577  * @end: the page offset 'to' which to invalidate (inclusive)
 578  *
 579  * Any pages which are found to be mapped into pagetables are unmapped prior to
 580  * invalidation.
 581  *
 582  * Returns -EBUSY if any pages could not be invalidated.
 583  */
 584 int invalidate_inode_pages2_range(struct address_space *mapping,
 585                                   pgoff_t start, pgoff_t end)
 586 {
 587         pgoff_t indices[PAGEVEC_SIZE];
 588         struct pagevec pvec;
 589         pgoff_t index;
 590         int i;
 591         int ret = 0;
 592         int ret2 = 0;
 593         int did_range_unmap = 0;
 594
 595         cleancache_invalidate_inode(mapping);
 596         pagevec_init(&pvec, 0);
 597         index = start;
 598         while (index <= end && pagevec_lookup_entries(&pvec, mapping, index,
 599                         min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
 600                         indices)) {
 601                 for (i = 0; i < pagevec_count(&pvec); i++) {
 602                         struct page *page = pvec.pages[i];
 603
 604                         /* We rely upon deletion not changing page->index */
 605                         index = indices[i];
 606                         if (index > end)
 607                                 break;
 608
 609                         if (radix_tree_exceptional_entry(page)) {
 610                                 clear_exceptional_entry(mapping, index, page);
 611                                 continue;
 612                         }
 613
 614                         lock_page(page);
 615                         WARN_ON(page_to_pgoff(page) != index);
 616                         if (page->mapping != mapping) {
 617                                 unlock_page(page);
 618                                 continue;
 619                         }
 620                         wait_on_page_writeback(page);
 621                         if (page_mapped(page)) {
 622                                 if (!did_range_unmap) {
 623                                         /*
 624                                          * Zap the rest of the file in one hit.
 625                                          */
 626                                         unmap_mapping_range(mapping,
 627                                            (loff_t)index << PAGE_SHIFT,
 628                                            (loff_t)(1 + end - index)
 629                                                          << PAGE_SHIFT,
 630                                                          0);
 631                                         did_range_unmap = 1;
 632                                 } else {
 633                                         /*
 634                                          * Just zap this page
 635                                          */
 636                                         unmap_mapping_range(mapping,
 637                                            (loff_t)index << PAGE_SHIFT,
 638                                            PAGE_SIZE, 0);
 639                                 }
 640                         }
 641                         BUG_ON(page_mapped(page));
 642                         ret2 = do_launder_page(mapping, page);
 643                         if (ret2 == 0) {
 644                                 if (!invalidate_complete_page2(mapping, page))
 645                                         ret2 = -EBUSY;
 646                         }
 647                         if (ret2 < 0)
 648                                 ret = ret2;
 649                         unlock_page(page);
 650                 }
 651                 pagevec_remove_exceptionals(&pvec);
 652                 pagevec_release(&pvec);
 653                 cond_resched();
 654                 index++;
 655         }
 656         cleancache_invalidate_inode(mapping);
 657         return ret;
 658 }
 659 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
 660
 661 /**
 662  * invalidate_inode_pages2 - remove all pages from an address_space
 663  * @mapping: the address_space
 664  *
 665  * Any pages which are found to be mapped into pagetables are unmapped prior to
 666  * invalidation.
 667  *
 668  * Returns -EBUSY if any pages could not be invalidated.
 669  */
 670 int invalidate_inode_pages2(struct address_space *mapping)
 671 {
 672         return invalidate_inode_pages2_range(mapping, 0, -1);
 673 }
 674 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
 675
 676 /**
 677  * truncate_pagecache - unmap and remove pagecache that has been truncated
 678  * @inode: inode
 679  * @newsize: new file size
 680  *
 681  * inode's new i_size must already be written before truncate_pagecache
 682  * is called.
 683  *
 684  * This function should typically be called before the filesystem
 685  * releases resources associated with the freed range (eg. deallocates
 686  * blocks). This way, pagecache will always stay logically coherent
 687  * with on-disk format, and the filesystem would not have to deal with
 688  * situations such as writepage being called for a page that has already
 689  * had its underlying blocks deallocated.
 690  */
 691 void truncate_pagecache(struct inode *inode, loff_t newsize)
 692 {
 693         struct address_space *mapping = inode->i_mapping;
 694         loff_t holebegin = round_up(newsize, PAGE_SIZE);
 695
 696         /*
 697          * unmap_mapping_range is called twice, first simply for
 698          * efficiency so that truncate_inode_pages does fewer
 699          * single-page unmaps.  However after this first call, and
 700          * before truncate_inode_pages finishes, it is possible for
 701          * private pages to be COWed, which remain after
 702          * truncate_inode_pages finishes, hence the second
 703          * unmap_mapping_range call must be made for correctness.
 704          */
 705         unmap_mapping_range(mapping, holebegin, 0, 1);
 706         truncate_inode_pages(mapping, newsize);
 707         unmap_mapping_range(mapping, holebegin, 0, 1);
 708 }
 709 EXPORT_SYMBOL(truncate_pagecache);
 710
 711 /**
 712  * truncate_setsize - update inode and pagecache for a new file size
 713  * @inode: inode
 714  * @newsize: new file size
 715  *
 716  * truncate_setsize updates i_size and performs pagecache truncation (if
 717  * necessary) to @newsize. It will be typically be called from the filesystem's
 718  * setattr function when ATTR_SIZE is passed in.
 719  *
 720  * Must be called with a lock serializing truncates and writes (generally
 721  * i_mutex but e.g. xfs uses a different lock) and before all filesystem
 722  * specific block truncation has been performed.
 723  */
 724 void truncate_setsize(struct inode *inode, loff_t newsize)
 725 {
 726         loff_t oldsize = inode->i_size;
 727
 728         i_size_write(inode, newsize);
 729         if (newsize > oldsize)
 730                 pagecache_isize_extended(inode, oldsize, newsize);
 731         truncate_pagecache(inode, newsize);
 732 }
 733 EXPORT_SYMBOL(truncate_setsize);
 734
 735 /**
 736  * pagecache_isize_extended - update pagecache after extension of i_size
 737  * @inode:      inode for which i_size was extended
 738  * @from:       original inode size
 739  * @to:         new inode size
 740  *
 741  * Handle extension of inode size either caused by extending truncate or by
 742  * write starting after current i_size. We mark the page straddling current
 743  * i_size RO so that page_mkwrite() is called on the nearest write access to
 744  * the page.  This way filesystem can be sure that page_mkwrite() is called on
 745  * the page before user writes to the page via mmap after the i_size has been
 746  * changed.
 747  *
 748  * The function must be called after i_size is updated so that page fault
 749  * coming after we unlock the page will already see the new i_size.
 750  * The function must be called while we still hold i_mutex - this not only
 751  * makes sure i_size is stable but also that userspace cannot observe new
 752  * i_size value before we are prepared to store mmap writes at new inode size.
 753  */
 754 void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to)
 755 {
 756         int bsize = 1 << inode->i_blkbits;
 757         loff_t rounded_from;
 758         struct page *page;
 759         pgoff_t index;
 760
 761         WARN_ON(to > inode->i_size);
 762
 763         if (from >= to || bsize == PAGE_SIZE)
 764                 return;
 765         /* Page straddling @from will not have any hole block created? */
 766         rounded_from = round_up(from, bsize);
 767         if (to <= rounded_from || !(rounded_from & (PAGE_SIZE - 1)))
 768                 return;
 769
 770         index = from >> PAGE_SHIFT;
 771         page = find_lock_page(inode->i_mapping, index);
 772         /* Page not cached? Nothing to do */
 773         if (!page)
 774                 return;
 775         /*
 776          * See clear_page_dirty_for_io() for details why set_page_dirty()
 777          * is needed.
 778          */
 779         if (page_mkclean(page))
 780                 set_page_dirty(page);
 781         unlock_page(page);
 782         put_page(page);
 783 }
 784 EXPORT_SYMBOL(pagecache_isize_extended);
 785
 786 /**
 787  * truncate_pagecache_range - unmap and remove pagecache that is hole-punched
 788  * @inode: inode
 789  * @lstart: offset of beginning of hole
 790  * @lend: offset of last byte of hole
 791  *
 792  * This function should typically be called before the filesystem
 793  * releases resources associated with the freed range (eg. deallocates
 794  * blocks). This way, pagecache will always stay logically coherent
 795  * with on-disk format, and the filesystem would not have to deal with
 796  * situations such as writepage being called for a page that has already
 797  * had its underlying blocks deallocated.
 798  */
 799 void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
 800 {
 801         struct address_space *mapping = inode->i_mapping;
 802         loff_t unmap_start = round_up(lstart, PAGE_SIZE);
 803         loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
 804         /*
 805          * This rounding is currently just for example: unmap_mapping_range
 806          * expands its hole outwards, whereas we want it to contract the hole
 807          * inwards.  However, existing callers of truncate_pagecache_range are
 808          * doing their own page rounding first.  Note that unmap_mapping_range
 809          * allows holelen 0 for all, and we allow lend -1 for end of file.
 810          */
 811
 812         /*
 813          * Unlike in truncate_pagecache, unmap_mapping_range is called only
 814          * once (before truncating pagecache), and without "even_cows" flag:
 815          * hole-punching should not remove private COWed pages from the hole.
 816          */
 817         if ((u64)unmap_end > (u64)unmap_start)
 818                 unmap_mapping_range(mapping, unmap_start,
 819                                     1 + unmap_end - unmap_start, 0);
 820         truncate_inode_pages_range(mapping, lstart, lend);
 821 }
 822 EXPORT_SYMBOL(truncate_pagecache_range);