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
  26 /**
  27  * do_invalidatepage - invalidate part or all of a page
  28  * @page: the page which is affected
  29  * @offset: the index of the truncation point
  30  *
  31  * do_invalidatepage() is called when all or part of the page has become
  32  * invalidated by a truncate operation.
  33  *
  34  * do_invalidatepage() does not have to release all buffers, but it must
  35  * ensure that no dirty buffer is left outside @offset and that no I/O
  36  * is underway against any of the blocks which are outside the truncation
  37  * point.  Because the caller is about to free (and possibly reuse) those
  38  * blocks on-disk.
  39  */
  40 void do_invalidatepage(struct page *page, unsigned long offset)
  41 {
  42         void (*invalidatepage)(struct page *, unsigned long);
  43         invalidatepage = page->mapping->a_ops->invalidatepage;
  44 #ifdef CONFIG_BLOCK
  45         if (!invalidatepage)
  46                 invalidatepage = block_invalidatepage;
  47 #endif
  48         if (invalidatepage)
  49                 (*invalidatepage)(page, offset);
  50 }
  51
  52 static inline void truncate_partial_page(struct page *page, unsigned partial)
  53 {
  54         zero_user_segment(page, partial, PAGE_CACHE_SIZE);
  55         cleancache_invalidate_page(page->mapping, page);
  56         if (page_has_private(page))
  57                 do_invalidatepage(page, partial);
  58 }
  59
  60 /*
  61  * This cancels just the dirty bit on the kernel page itself, it
  62  * does NOT actually remove dirty bits on any mmap's that may be
  63  * around. It also leaves the page tagged dirty, so any sync
  64  * activity will still find it on the dirty lists, and in particular,
  65  * clear_page_dirty_for_io() will still look at the dirty bits in
  66  * the VM.
  67  *
  68  * Doing this should *normally* only ever be done when a page
  69  * is truncated, and is not actually mapped anywhere at all. However,
  70  * fs/buffer.c does this when it notices that somebody has cleaned
  71  * out all the buffers on a page without actually doing it through
  72  * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
  73  */
  74 void cancel_dirty_page(struct page *page, unsigned int account_size)
  75 {
  76         if (TestClearPageDirty(page)) {
  77                 struct address_space *mapping = page->mapping;
  78                 if (mapping && mapping_cap_account_dirty(mapping)) {
  79                         dec_zone_page_state(page, NR_FILE_DIRTY);
  80                         dec_bdi_stat(mapping->backing_dev_info,
  81                                         BDI_RECLAIMABLE);
  82                         if (account_size)
  83                                 task_io_account_cancelled_write(account_size);
  84                 }
  85         }
  86 }
  87 EXPORT_SYMBOL(cancel_dirty_page);
  88
  89 /*
  90  * If truncate cannot remove the fs-private metadata from the page, the page
  91  * becomes orphaned.  It will be left on the LRU and may even be mapped into
  92  * user pagetables if we're racing with filemap_fault().
  93  *
  94  * We need to bale out if page->mapping is no longer equal to the original
  95  * mapping.  This happens a) when the VM reclaimed the page while we waited on
  96  * its lock, b) when a concurrent invalidate_mapping_pages got there first and
  97  * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
  98  */
  99 static int
 100 truncate_complete_page(struct address_space *mapping, struct page *page)
 101 {
 102         if (page->mapping != mapping)
 103                 return -EIO;
 104
 105         if (page_has_private(page))
 106                 do_invalidatepage(page, 0);
 107
 108         cancel_dirty_page(page, PAGE_CACHE_SIZE);
 109
 110         ClearPageMappedToDisk(page);
 111         delete_from_page_cache(page);
 112         return 0;
 113 }
 114
 115 /*
 116  * This is for invalidate_mapping_pages().  That function can be called at
 117  * any time, and is not supposed to throw away dirty pages.  But pages can
 118  * be marked dirty at any time too, so use remove_mapping which safely
 119  * discards clean, unused pages.
 120  *
 121  * Returns non-zero if the page was successfully invalidated.
 122  */
 123 static int
 124 invalidate_complete_page(struct address_space *mapping, struct page *page)
 125 {
 126         int ret;
 127
 128         if (page->mapping != mapping)
 129                 return 0;
 130
 131         if (page_has_private(page) && !try_to_release_page(page, 0))
 132                 return 0;
 133
 134         ret = remove_mapping(mapping, page);
 135
 136         return ret;
 137 }
 138
 139 int truncate_inode_page(struct address_space *mapping, struct page *page)
 140 {
 141         if (page_mapped(page)) {
 142                 unmap_mapping_range(mapping,
 143                                    (loff_t)page->index << PAGE_CACHE_SHIFT,
 144                                    PAGE_CACHE_SIZE, 0);
 145         }
 146         return truncate_complete_page(mapping, page);
 147 }
 148
 149 /*
 150  * Used to get rid of pages on hardware memory corruption.
 151  */
 152 int generic_error_remove_page(struct address_space *mapping, struct page *page)
 153 {
 154         if (!mapping)
 155                 return -EINVAL;
 156         /*
 157          * Only punch for normal data pages for now.
 158          * Handling other types like directories would need more auditing.
 159          */
 160         if (!S_ISREG(mapping->host->i_mode))
 161                 return -EIO;
 162         return truncate_inode_page(mapping, page);
 163 }
 164 EXPORT_SYMBOL(generic_error_remove_page);
 165
 166 /*
 167  * Safely invalidate one page from its pagecache mapping.
 168  * It only drops clean, unused pages. The page must be locked.
 169  *
 170  * Returns 1 if the page is successfully invalidated, otherwise 0.
 171  */
 172 int invalidate_inode_page(struct page *page)
 173 {
 174         struct address_space *mapping = page_mapping(page);
 175         if (!mapping)
 176                 return 0;
 177         if (PageDirty(page) || PageWriteback(page))
 178                 return 0;
 179         if (page_mapped(page))
 180                 return 0;
 181         return invalidate_complete_page(mapping, page);
 182 }
 183
 184 /**
 185  * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
 186  * @mapping: mapping to truncate
 187  * @lstart: offset from which to truncate
 188  * @lend: offset to which to truncate
 189  *
 190  * Truncate the page cache, removing the pages that are between
 191  * specified offsets (and zeroing out partial page
 192  * (if lstart is not page aligned)).
 193  *
 194  * Truncate takes two passes - the first pass is nonblocking.  It will not
 195  * block on page locks and it will not block on writeback.  The second pass
 196  * will wait.  This is to prevent as much IO as possible in the affected region.
 197  * The first pass will remove most pages, so the search cost of the second pass
 198  * is low.
 199  *
 200  * We pass down the cache-hot hint to the page freeing code.  Even if the
 201  * mapping is large, it is probably the case that the final pages are the most
 202  * recently touched, and freeing happens in ascending file offset order.
 203  */
 204 void truncate_inode_pages_range(struct address_space *mapping,
 205                                 loff_t lstart, loff_t lend)
 206 {
 207         const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
 208         const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
 209         struct pagevec pvec;
 210         pgoff_t index;
 211         pgoff_t end;
 212         int i;
 213
 214         cleancache_invalidate_inode(mapping);
 215         if (mapping->nrpages == 0)
 216                 return;
 217
 218         BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
 219         end = (lend >> PAGE_CACHE_SHIFT);
 220
 221         pagevec_init(&pvec, 0);
 222         index = start;
 223         while (index <= end && pagevec_lookup(&pvec, mapping, index,
 224                         min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 225                 mem_cgroup_uncharge_start();
 226                 for (i = 0; i < pagevec_count(&pvec); i++) {
 227                         struct page *page = pvec.pages[i];
 228
 229                         /* We rely upon deletion not changing page->index */
 230                         index = page->index;
 231                         if (index > end)
 232                                 break;
 233
 234                         if (!trylock_page(page))
 235                                 continue;
 236                         WARN_ON(page->index != index);
 237                         if (PageWriteback(page)) {
 238                                 unlock_page(page);
 239                                 continue;
 240                         }
 241                         truncate_inode_page(mapping, page);
 242                         unlock_page(page);
 243                 }
 244                 pagevec_release(&pvec);
 245                 mem_cgroup_uncharge_end();
 246                 cond_resched();
 247                 index++;
 248         }
 249
 250         if (partial) {
 251                 struct page *page = find_lock_page(mapping, start - 1);
 252                 if (page) {
 253                         wait_on_page_writeback(page);
 254                         truncate_partial_page(page, partial);
 255                         unlock_page(page);
 256                         page_cache_release(page);
 257                 }
 258         }
 259
 260         index = start;
 261         for ( ; ; ) {
 262                 cond_resched();
 263                 if (!pagevec_lookup(&pvec, mapping, index,
 264                         min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 265                         if (index == start)
 266                                 break;
 267                         index = start;
 268                         continue;
 269                 }
 270                 if (index == start && pvec.pages[0]->index > end) {
 271                         pagevec_release(&pvec);
 272                         break;
 273                 }
 274                 mem_cgroup_uncharge_start();
 275                 for (i = 0; i < pagevec_count(&pvec); i++) {
 276                         struct page *page = pvec.pages[i];
 277
 278                         /* We rely upon deletion not changing page->index */
 279                         index = page->index;
 280                         if (index > end)
 281                                 break;
 282
 283                         lock_page(page);
 284                         WARN_ON(page->index != index);
 285                         wait_on_page_writeback(page);
 286                         truncate_inode_page(mapping, page);
 287                         unlock_page(page);
 288                 }
 289                 pagevec_release(&pvec);
 290                 mem_cgroup_uncharge_end();
 291                 index++;
 292         }
 293         cleancache_invalidate_inode(mapping);
 294 }
 295 EXPORT_SYMBOL(truncate_inode_pages_range);
 296
 297 /**
 298  * truncate_inode_pages - truncate *all* the pages from an offset
 299  * @mapping: mapping to truncate
 300  * @lstart: offset from which to truncate
 301  *
 302  * Called under (and serialised by) inode->i_mutex.
 303  *
 304  * Note: When this function returns, there can be a page in the process of
 305  * deletion (inside __delete_from_page_cache()) in the specified range.  Thus
 306  * mapping->nrpages can be non-zero when this function returns even after
 307  * truncation of the whole mapping.
 308  */
 309 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
 310 {
 311         truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
 312 }
 313 EXPORT_SYMBOL(truncate_inode_pages);
 314
 315 /**
 316  * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
 317  * @mapping: the address_space which holds the pages to invalidate
 318  * @start: the offset 'from' which to invalidate
 319  * @end: the offset 'to' which to invalidate (inclusive)
 320  *
 321  * This function only removes the unlocked pages, if you want to
 322  * remove all the pages of one inode, you must call truncate_inode_pages.
 323  *
 324  * invalidate_mapping_pages() will not block on IO activity. It will not
 325  * invalidate pages which are dirty, locked, under writeback or mapped into
 326  * pagetables.
 327  */
 328 unsigned long invalidate_mapping_pages(struct address_space *mapping,
 329                 pgoff_t start, pgoff_t end)
 330 {
 331         struct pagevec pvec;
 332         pgoff_t index = start;
 333         unsigned long ret;
 334         unsigned long count = 0;
 335         int i;
 336
 337         /*
 338          * Note: this function may get called on a shmem/tmpfs mapping:
 339          * pagevec_lookup() might then return 0 prematurely (because it
 340          * got a gangful of swap entries); but it's hardly worth worrying
 341          * about - it can rarely have anything to free from such a mapping
 342          * (most pages are dirty), and already skips over any difficulties.
 343          */
 344
 345         pagevec_init(&pvec, 0);
 346         while (index <= end && pagevec_lookup(&pvec, mapping, index,
 347                         min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 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 = page->index;
 354                         if (index > end)
 355                                 break;
 356
 357                         if (!trylock_page(page))
 358                                 continue;
 359                         WARN_ON(page->index != index);
 360                         ret = invalidate_inode_page(page);
 361                         unlock_page(page);
 362                         /*
 363                          * Invalidation is a hint that the page is no longer
 364                          * of interest and try to speed up its reclaim.
 365                          */
 366                         if (!ret)
 367                                 deactivate_page(page);
 368                         count += ret;
 369                 }
 370                 pagevec_release(&pvec);
 371                 mem_cgroup_uncharge_end();
 372                 cond_resched();
 373                 index++;
 374         }
 375         return count;
 376 }
 377 EXPORT_SYMBOL(invalidate_mapping_pages);
 378
 379 /*
 380  * This is like invalidate_complete_page(), except it ignores the page's
 381  * refcount.  We do this because invalidate_inode_pages2() needs stronger
 382  * invalidation guarantees, and cannot afford to leave pages behind because
 383  * shrink_page_list() has a temp ref on them, or because they're transiently
 384  * sitting in the lru_cache_add() pagevecs.
 385  */
 386 static int
 387 invalidate_complete_page2(struct address_space *mapping, struct page *page)
 388 {
 389         if (page->mapping != mapping)
 390                 return 0;
 391
 392         if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
 393                 return 0;
 394
 395         spin_lock_irq(&mapping->tree_lock);
 396         if (PageDirty(page))
 397                 goto failed;
 398
 399         BUG_ON(page_has_private(page));
 400         __delete_from_page_cache(page);
 401         spin_unlock_irq(&mapping->tree_lock);
 402         mem_cgroup_uncharge_cache_page(page);
 403
 404         if (mapping->a_ops->freepage)
 405                 mapping->a_ops->freepage(page);
 406
 407         page_cache_release(page);       /* pagecache ref */
 408         return 1;
 409 failed:
 410         spin_unlock_irq(&mapping->tree_lock);
 411         return 0;
 412 }
 413
 414 static int do_launder_page(struct address_space *mapping, struct page *page)
 415 {
 416         if (!PageDirty(page))
 417                 return 0;
 418         if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
 419                 return 0;
 420         return mapping->a_ops->launder_page(page);
 421 }
 422
 423 /**
 424  * invalidate_inode_pages2_range - remove range of pages from an address_space
 425  * @mapping: the address_space
 426  * @start: the page offset 'from' which to invalidate
 427  * @end: the page offset 'to' which to invalidate (inclusive)
 428  *
 429  * Any pages which are found to be mapped into pagetables are unmapped prior to
 430  * invalidation.
 431  *
 432  * Returns -EBUSY if any pages could not be invalidated.
 433  */
 434 int invalidate_inode_pages2_range(struct address_space *mapping,
 435                                   pgoff_t start, pgoff_t end)
 436 {
 437         struct pagevec pvec;
 438         pgoff_t index;
 439         int i;
 440         int ret = 0;
 441         int ret2 = 0;
 442         int did_range_unmap = 0;
 443
 444         cleancache_invalidate_inode(mapping);
 445         pagevec_init(&pvec, 0);
 446         index = start;
 447         while (index <= end && pagevec_lookup(&pvec, mapping, index,
 448                         min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 449                 mem_cgroup_uncharge_start();
 450                 for (i = 0; i < pagevec_count(&pvec); i++) {
 451                         struct page *page = pvec.pages[i];
 452
 453                         /* We rely upon deletion not changing page->index */
 454                         index = page->index;
 455                         if (index > end)
 456                                 break;
 457
 458                         lock_page(page);
 459                         WARN_ON(page->index != index);
 460                         if (page->mapping != mapping) {
 461                                 unlock_page(page);
 462                                 continue;
 463                         }
 464                         wait_on_page_writeback(page);
 465                         if (page_mapped(page)) {
 466                                 if (!did_range_unmap) {
 467                                         /*
 468                                          * Zap the rest of the file in one hit.
 469                                          */
 470                                         unmap_mapping_range(mapping,
 471                                            (loff_t)index << PAGE_CACHE_SHIFT,
 472                                            (loff_t)(1 + end - index)
 473                                                          << PAGE_CACHE_SHIFT,
 474                                             0);
 475                                         did_range_unmap = 1;
 476                                 } else {
 477                                         /*
 478                                          * Just zap this page
 479                                          */
 480                                         unmap_mapping_range(mapping,
 481                                            (loff_t)index << PAGE_CACHE_SHIFT,
 482                                            PAGE_CACHE_SIZE, 0);
 483                                 }
 484                         }
 485                         BUG_ON(page_mapped(page));
 486                         ret2 = do_launder_page(mapping, page);
 487                         if (ret2 == 0) {
 488                                 if (!invalidate_complete_page2(mapping, page))
 489                                         ret2 = -EBUSY;
 490                         }
 491                         if (ret2 < 0)
 492                                 ret = ret2;
 493                         unlock_page(page);
 494                 }
 495                 pagevec_release(&pvec);
 496                 mem_cgroup_uncharge_end();
 497                 cond_resched();
 498                 index++;
 499         }
 500         cleancache_invalidate_inode(mapping);
 501         return ret;
 502 }
 503 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
 504
 505 /**
 506  * invalidate_inode_pages2 - remove all pages from an address_space
 507  * @mapping: the address_space
 508  *
 509  * Any pages which are found to be mapped into pagetables are unmapped prior to
 510  * invalidation.
 511  *
 512  * Returns -EBUSY if any pages could not be invalidated.
 513  */
 514 int invalidate_inode_pages2(struct address_space *mapping)
 515 {
 516         return invalidate_inode_pages2_range(mapping, 0, -1);
 517 }
 518 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
 519
 520 /**
 521  * truncate_pagecache - unmap and remove pagecache that has been truncated
 522  * @inode: inode
 523  * @oldsize: old file size
 524  * @newsize: new file size
 525  *
 526  * inode's new i_size must already be written before truncate_pagecache
 527  * is called.
 528  *
 529  * This function should typically be called before the filesystem
 530  * releases resources associated with the freed range (eg. deallocates
 531  * blocks). This way, pagecache will always stay logically coherent
 532  * with on-disk format, and the filesystem would not have to deal with
 533  * situations such as writepage being called for a page that has already
 534  * had its underlying blocks deallocated.
 535  */
 536 void truncate_pagecache(struct inode *inode, loff_t oldsize, loff_t newsize)
 537 {
 538         struct address_space *mapping = inode->i_mapping;
 539         loff_t holebegin = round_up(newsize, PAGE_SIZE);
 540
 541         /*
 542          * unmap_mapping_range is called twice, first simply for
 543          * efficiency so that truncate_inode_pages does fewer
 544          * single-page unmaps.  However after this first call, and
 545          * before truncate_inode_pages finishes, it is possible for
 546          * private pages to be COWed, which remain after
 547          * truncate_inode_pages finishes, hence the second
 548          * unmap_mapping_range call must be made for correctness.
 549          */
 550         unmap_mapping_range(mapping, holebegin, 0, 1);
 551         truncate_inode_pages(mapping, newsize);
 552         unmap_mapping_range(mapping, holebegin, 0, 1);
 553 }
 554 EXPORT_SYMBOL(truncate_pagecache);
 555
 556 /**
 557  * truncate_setsize - update inode and pagecache for a new file size
 558  * @inode: inode
 559  * @newsize: new file size
 560  *
 561  * truncate_setsize updates i_size and performs pagecache truncation (if
 562  * necessary) to @newsize. It will be typically be called from the filesystem's
 563  * setattr function when ATTR_SIZE is passed in.
 564  *
 565  * Must be called with inode_mutex held and before all filesystem specific
 566  * block truncation has been performed.
 567  */
 568 void truncate_setsize(struct inode *inode, loff_t newsize)
 569 {
 570         loff_t oldsize;
 571
 572         oldsize = inode->i_size;
 573         i_size_write(inode, newsize);
 574
 575         truncate_pagecache(inode, oldsize, newsize);
 576 }
 577 EXPORT_SYMBOL(truncate_setsize);
 578
 579 /**
 580  * truncate_pagecache_range - unmap and remove pagecache that is hole-punched
 581  * @inode: inode
 582  * @lstart: offset of beginning of hole
 583  * @lend: offset of last byte of hole
 584  *
 585  * This function should typically be called before the filesystem
 586  * releases resources associated with the freed range (eg. deallocates
 587  * blocks). This way, pagecache will always stay logically coherent
 588  * with on-disk format, and the filesystem would not have to deal with
 589  * situations such as writepage being called for a page that has already
 590  * had its underlying blocks deallocated.
 591  */
 592 void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
 593 {
 594         struct address_space *mapping = inode->i_mapping;
 595         loff_t unmap_start = round_up(lstart, PAGE_SIZE);
 596         loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
 597         /*
 598          * This rounding is currently just for example: unmap_mapping_range
 599          * expands its hole outwards, whereas we want it to contract the hole
 600          * inwards.  However, existing callers of truncate_pagecache_range are
 601          * doing their own page rounding first; and truncate_inode_pages_range
 602          * currently BUGs if lend is not pagealigned-1 (it handles partial
 603          * page at start of hole, but not partial page at end of hole).  Note
 604          * unmap_mapping_range allows holelen 0 for all, and we allow lend -1.
 605          */
 606
 607         /*
 608          * Unlike in truncate_pagecache, unmap_mapping_range is called only
 609          * once (before truncating pagecache), and without "even_cows" flag:
 610          * hole-punching should not remove private COWed pages from the hole.
 611          */
 612         if ((u64)unmap_end > (u64)unmap_start)
 613                 unmap_mapping_range(mapping, unmap_start,
 614                                     1 + unmap_end - unmap_start, 0);
 615         truncate_inode_pages_range(mapping, lstart, lend);
 616 }
 617 EXPORT_SYMBOL(truncate_pagecache_range);