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    akpm@zip.com.au
   7  *              Initial version.
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/backing-dev.h>
  12 #include <linux/mm.h>
  13 #include <linux/swap.h>
  14 #include <linux/module.h>
  15 #include <linux/pagemap.h>
  16 #include <linux/highmem.h>
  17 #include <linux/pagevec.h>
  18 #include <linux/task_io_accounting_ops.h>
  19 #include <linux/buffer_head.h>  /* grr. try_to_release_page,
  20                                    do_invalidatepage */
  21
  22
  23 /**
  24  * do_invalidatepage - invalidate part or all of a page
  25  * @page: the page which is affected
  26  * @offset: the index of the truncation point
  27  *
  28  * do_invalidatepage() is called when all or part of the page has become
  29  * invalidated by a truncate operation.
  30  *
  31  * do_invalidatepage() does not have to release all buffers, but it must
  32  * ensure that no dirty buffer is left outside @offset and that no I/O
  33  * is underway against any of the blocks which are outside the truncation
  34  * point.  Because the caller is about to free (and possibly reuse) those
  35  * blocks on-disk.
  36  */
  37 void do_invalidatepage(struct page *page, unsigned long offset)
  38 {
  39         void (*invalidatepage)(struct page *, unsigned long);
  40         invalidatepage = page->mapping->a_ops->invalidatepage;
  41 #ifdef CONFIG_BLOCK
  42         if (!invalidatepage)
  43                 invalidatepage = block_invalidatepage;
  44 #endif
  45         if (invalidatepage)
  46                 (*invalidatepage)(page, offset);
  47 }
  48
  49 static inline void truncate_partial_page(struct page *page, unsigned partial)
  50 {
  51         zero_user_segment(page, partial, PAGE_CACHE_SIZE);
  52         if (PagePrivate(page))
  53                 do_invalidatepage(page, partial);
  54 }
  55
  56 /*
  57  * This cancels just the dirty bit on the kernel page itself, it
  58  * does NOT actually remove dirty bits on any mmap's that may be
  59  * around. It also leaves the page tagged dirty, so any sync
  60  * activity will still find it on the dirty lists, and in particular,
  61  * clear_page_dirty_for_io() will still look at the dirty bits in
  62  * the VM.
  63  *
  64  * Doing this should *normally* only ever be done when a page
  65  * is truncated, and is not actually mapped anywhere at all. However,
  66  * fs/buffer.c does this when it notices that somebody has cleaned
  67  * out all the buffers on a page without actually doing it through
  68  * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
  69  */
  70 void cancel_dirty_page(struct page *page, unsigned int account_size)
  71 {
  72         if (TestClearPageDirty(page)) {
  73                 struct address_space *mapping = page->mapping;
  74                 if (mapping && mapping_cap_account_dirty(mapping)) {
  75                         dec_zone_page_state(page, NR_FILE_DIRTY);
  76                         dec_bdi_stat(mapping->backing_dev_info,
  77                                         BDI_RECLAIMABLE);
  78                         if (account_size)
  79                                 task_io_account_cancelled_write(account_size);
  80                 }
  81         }
  82 }
  83 EXPORT_SYMBOL(cancel_dirty_page);
  84
  85 /*
  86  * If truncate cannot remove the fs-private metadata from the page, the page
  87  * becomes orphaned.  It will be left on the LRU and may even be mapped into
  88  * user pagetables if we're racing with filemap_fault().
  89  *
  90  * We need to bale out if page->mapping is no longer equal to the original
  91  * mapping.  This happens a) when the VM reclaimed the page while we waited on
  92  * its lock, b) when a concurrent invalidate_mapping_pages got there first and
  93  * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
  94  */
  95 static void
  96 truncate_complete_page(struct address_space *mapping, struct page *page)
  97 {
  98         if (page->mapping != mapping)
  99                 return;
 100
 101         if (PagePrivate(page))
 102                 do_invalidatepage(page, 0);
 103
 104         cancel_dirty_page(page, PAGE_CACHE_SIZE);
 105
 106         remove_from_page_cache(page);
 107         ClearPageMappedToDisk(page);
 108         page_cache_release(page);       /* pagecache ref */
 109 }
 110
 111 /*
 112  * This is for invalidate_mapping_pages().  That function can be called at
 113  * any time, and is not supposed to throw away dirty pages.  But pages can
 114  * be marked dirty at any time too, so use remove_mapping which safely
 115  * discards clean, unused pages.
 116  *
 117  * Returns non-zero if the page was successfully invalidated.
 118  */
 119 static int
 120 invalidate_complete_page(struct address_space *mapping, struct page *page)
 121 {
 122         int ret;
 123
 124         if (page->mapping != mapping)
 125                 return 0;
 126
 127         if (PagePrivate(page) && !try_to_release_page(page, 0))
 128                 return 0;
 129
 130         ret = remove_mapping(mapping, page);
 131
 132         return ret;
 133 }
 134
 135 /**
 136  * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
 137  * @mapping: mapping to truncate
 138  * @lstart: offset from which to truncate
 139  * @lend: offset to which to truncate
 140  *
 141  * Truncate the page cache, removing the pages that are between
 142  * specified offsets (and zeroing out partial page
 143  * (if lstart is not page aligned)).
 144  *
 145  * Truncate takes two passes - the first pass is nonblocking.  It will not
 146  * block on page locks and it will not block on writeback.  The second pass
 147  * will wait.  This is to prevent as much IO as possible in the affected region.
 148  * The first pass will remove most pages, so the search cost of the second pass
 149  * is low.
 150  *
 151  * When looking at page->index outside the page lock we need to be careful to
 152  * copy it into a local to avoid races (it could change at any time).
 153  *
 154  * We pass down the cache-hot hint to the page freeing code.  Even if the
 155  * mapping is large, it is probably the case that the final pages are the most
 156  * recently touched, and freeing happens in ascending file offset order.
 157  */
 158 void truncate_inode_pages_range(struct address_space *mapping,
 159                                 loff_t lstart, loff_t lend)
 160 {
 161         const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
 162         pgoff_t end;
 163         const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
 164         struct pagevec pvec;
 165         pgoff_t next;
 166         int i;
 167
 168         if (mapping->nrpages == 0)
 169                 return;
 170
 171         BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
 172         end = (lend >> PAGE_CACHE_SHIFT);
 173
 174         pagevec_init(&pvec, 0);
 175         next = start;
 176         while (next <= end &&
 177                pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 178                 for (i = 0; i < pagevec_count(&pvec); i++) {
 179                         struct page *page = pvec.pages[i];
 180                         pgoff_t page_index = page->index;
 181
 182                         if (page_index > end) {
 183                                 next = page_index;
 184                                 break;
 185                         }
 186
 187                         if (page_index > next)
 188                                 next = page_index;
 189                         next++;
 190                         if (!trylock_page(page))
 191                                 continue;
 192                         if (PageWriteback(page)) {
 193                                 unlock_page(page);
 194                                 continue;
 195                         }
 196                         if (page_mapped(page)) {
 197                                 unmap_mapping_range(mapping,
 198                                   (loff_t)page_index<<PAGE_CACHE_SHIFT,
 199                                   PAGE_CACHE_SIZE, 0);
 200                         }
 201                         truncate_complete_page(mapping, page);
 202                         unlock_page(page);
 203                 }
 204                 pagevec_release(&pvec);
 205                 cond_resched();
 206         }
 207
 208         if (partial) {
 209                 struct page *page = find_lock_page(mapping, start - 1);
 210                 if (page) {
 211                         wait_on_page_writeback(page);
 212                         truncate_partial_page(page, partial);
 213                         unlock_page(page);
 214                         page_cache_release(page);
 215                 }
 216         }
 217
 218         next = start;
 219         for ( ; ; ) {
 220                 cond_resched();
 221                 if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 222                         if (next == start)
 223                                 break;
 224                         next = start;
 225                         continue;
 226                 }
 227                 if (pvec.pages[0]->index > end) {
 228                         pagevec_release(&pvec);
 229                         break;
 230                 }
 231                 for (i = 0; i < pagevec_count(&pvec); i++) {
 232                         struct page *page = pvec.pages[i];
 233
 234                         if (page->index > end)
 235                                 break;
 236                         lock_page(page);
 237                         wait_on_page_writeback(page);
 238                         if (page_mapped(page)) {
 239                                 unmap_mapping_range(mapping,
 240                                   (loff_t)page->index<<PAGE_CACHE_SHIFT,
 241                                   PAGE_CACHE_SIZE, 0);
 242                         }
 243                         if (page->index > next)
 244                                 next = page->index;
 245                         next++;
 246                         truncate_complete_page(mapping, page);
 247                         unlock_page(page);
 248                 }
 249                 pagevec_release(&pvec);
 250         }
 251 }
 252 EXPORT_SYMBOL(truncate_inode_pages_range);
 253
 254 /**
 255  * truncate_inode_pages - truncate *all* the pages from an offset
 256  * @mapping: mapping to truncate
 257  * @lstart: offset from which to truncate
 258  *
 259  * Called under (and serialised by) inode->i_mutex.
 260  */
 261 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
 262 {
 263         truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
 264 }
 265 EXPORT_SYMBOL(truncate_inode_pages);
 266
 267 unsigned long __invalidate_mapping_pages(struct address_space *mapping,
 268                                 pgoff_t start, pgoff_t end, bool be_atomic)
 269 {
 270         struct pagevec pvec;
 271         pgoff_t next = start;
 272         unsigned long ret = 0;
 273         int i;
 274
 275         pagevec_init(&pvec, 0);
 276         while (next <= end &&
 277                         pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 278                 for (i = 0; i < pagevec_count(&pvec); i++) {
 279                         struct page *page = pvec.pages[i];
 280                         pgoff_t index;
 281                         int lock_failed;
 282
 283                         lock_failed = !trylock_page(page);
 284
 285                         /*
 286                          * We really shouldn't be looking at the ->index of an
 287                          * unlocked page.  But we're not allowed to lock these
 288                          * pages.  So we rely upon nobody altering the ->index
 289                          * of this (pinned-by-us) page.
 290                          */
 291                         index = page->index;
 292                         if (index > next)
 293                                 next = index;
 294                         next++;
 295                         if (lock_failed)
 296                                 continue;
 297
 298                         if (PageDirty(page) || PageWriteback(page))
 299                                 goto unlock;
 300                         if (page_mapped(page))
 301                                 goto unlock;
 302                         ret += invalidate_complete_page(mapping, page);
 303 unlock:
 304                         unlock_page(page);
 305                         if (next > end)
 306                                 break;
 307                 }
 308                 pagevec_release(&pvec);
 309                 if (likely(!be_atomic))
 310                         cond_resched();
 311         }
 312         return ret;
 313 }
 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         return __invalidate_mapping_pages(mapping, start, end, false);
 332 }
 333 EXPORT_SYMBOL(invalidate_mapping_pages);
 334
 335 /*
 336  * This is like invalidate_complete_page(), except it ignores the page's
 337  * refcount.  We do this because invalidate_inode_pages2() needs stronger
 338  * invalidation guarantees, and cannot afford to leave pages behind because
 339  * shrink_page_list() has a temp ref on them, or because they're transiently
 340  * sitting in the lru_cache_add() pagevecs.
 341  */
 342 static int
 343 invalidate_complete_page2(struct address_space *mapping, struct page *page)
 344 {
 345         if (page->mapping != mapping)
 346                 return 0;
 347
 348         if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
 349                 return 0;
 350
 351         spin_lock_irq(&mapping->tree_lock);
 352         if (PageDirty(page))
 353                 goto failed;
 354
 355         BUG_ON(PagePrivate(page));
 356         __remove_from_page_cache(page);
 357         spin_unlock_irq(&mapping->tree_lock);
 358         page_cache_release(page);       /* pagecache ref */
 359         return 1;
 360 failed:
 361         spin_unlock_irq(&mapping->tree_lock);
 362         return 0;
 363 }
 364
 365 static int do_launder_page(struct address_space *mapping, struct page *page)
 366 {
 367         if (!PageDirty(page))
 368                 return 0;
 369         if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
 370                 return 0;
 371         return mapping->a_ops->launder_page(page);
 372 }
 373
 374 /**
 375  * invalidate_inode_pages2_range - remove range of pages from an address_space
 376  * @mapping: the address_space
 377  * @start: the page offset 'from' which to invalidate
 378  * @end: the page offset 'to' which to invalidate (inclusive)
 379  *
 380  * Any pages which are found to be mapped into pagetables are unmapped prior to
 381  * invalidation.
 382  *
 383  * Returns -EBUSY if any pages could not be invalidated.
 384  */
 385 int invalidate_inode_pages2_range(struct address_space *mapping,
 386                                   pgoff_t start, pgoff_t end)
 387 {
 388         struct pagevec pvec;
 389         pgoff_t next;
 390         int i;
 391         int ret = 0;
 392         int ret2 = 0;
 393         int did_range_unmap = 0;
 394         int wrapped = 0;
 395
 396         pagevec_init(&pvec, 0);
 397         next = start;
 398         while (next <= end && !wrapped &&
 399                 pagevec_lookup(&pvec, mapping, next,
 400                         min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 401                 for (i = 0; i < pagevec_count(&pvec); i++) {
 402                         struct page *page = pvec.pages[i];
 403                         pgoff_t page_index;
 404
 405                         lock_page(page);
 406                         if (page->mapping != mapping) {
 407                                 unlock_page(page);
 408                                 continue;
 409                         }
 410                         page_index = page->index;
 411                         next = page_index + 1;
 412                         if (next == 0)
 413                                 wrapped = 1;
 414                         if (page_index > end) {
 415                                 unlock_page(page);
 416                                 break;
 417                         }
 418                         wait_on_page_writeback(page);
 419                         if (page_mapped(page)) {
 420                                 if (!did_range_unmap) {
 421                                         /*
 422                                          * Zap the rest of the file in one hit.
 423                                          */
 424                                         unmap_mapping_range(mapping,
 425                                            (loff_t)page_index<<PAGE_CACHE_SHIFT,
 426                                            (loff_t)(end - page_index + 1)
 427                                                         << PAGE_CACHE_SHIFT,
 428                                             0);
 429                                         did_range_unmap = 1;
 430                                 } else {
 431                                         /*
 432                                          * Just zap this page
 433                                          */
 434                                         unmap_mapping_range(mapping,
 435                                           (loff_t)page_index<<PAGE_CACHE_SHIFT,
 436                                           PAGE_CACHE_SIZE, 0);
 437                                 }
 438                         }
 439                         BUG_ON(page_mapped(page));
 440                         ret2 = do_launder_page(mapping, page);
 441                         if (ret2 == 0) {
 442                                 if (!invalidate_complete_page2(mapping, page))
 443                                         ret2 = -EBUSY;
 444                         }
 445                         if (ret2 < 0)
 446                                 ret = ret2;
 447                         unlock_page(page);
 448                 }
 449                 pagevec_release(&pvec);
 450                 cond_resched();
 451         }
 452         return ret;
 453 }
 454 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
 455
 456 /**
 457  * invalidate_inode_pages2 - remove all pages from an address_space
 458  * @mapping: the address_space
 459  *
 460  * Any pages which are found to be mapped into pagetables are unmapped prior to
 461  * invalidation.
 462  *
 463  * Returns -EIO if any pages could not be invalidated.
 464  */
 465 int invalidate_inode_pages2(struct address_space *mapping)
 466 {
 467         return invalidate_inode_pages2_range(mapping, 0, -1);
 468 }
 469 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);