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/mm.h>
  12 #include <linux/swap.h>
  13 #include <linux/module.h>
  14 #include <linux/pagemap.h>
  15 #include <linux/highmem.h>
  16 #include <linux/pagevec.h>
  17 #include <linux/task_io_accounting_ops.h>
  18 #include <linux/buffer_head.h>  /* grr. try_to_release_page,
  19                                    do_invalidatepage */
  20
  21
  22 /**
  23  * do_invalidatepage - invalidate part of all of a page
  24  * @page: the page which is affected
  25  * @offset: the index of the truncation point
  26  *
  27  * do_invalidatepage() is called when all or part of the page has become
  28  * invalidated by a truncate operation.
  29  *
  30  * do_invalidatepage() does not have to release all buffers, but it must
  31  * ensure that no dirty buffer is left outside @offset and that no I/O
  32  * is underway against any of the blocks which are outside the truncation
  33  * point.  Because the caller is about to free (and possibly reuse) those
  34  * blocks on-disk.
  35  */
  36 void do_invalidatepage(struct page *page, unsigned long offset)
  37 {
  38         void (*invalidatepage)(struct page *, unsigned long);
  39         invalidatepage = page->mapping->a_ops->invalidatepage;
  40 #ifdef CONFIG_BLOCK
  41         if (!invalidatepage)
  42                 invalidatepage = block_invalidatepage;
  43 #endif
  44         if (invalidatepage)
  45                 (*invalidatepage)(page, offset);
  46 }
  47
  48 static inline void truncate_partial_page(struct page *page, unsigned partial)
  49 {
  50         zero_user_page(page, partial, PAGE_CACHE_SIZE - partial, KM_USER0);
  51         if (PagePrivate(page))
  52                 do_invalidatepage(page, partial);
  53 }
  54
  55 /*
  56  * This cancels just the dirty bit on the kernel page itself, it
  57  * does NOT actually remove dirty bits on any mmap's that may be
  58  * around. It also leaves the page tagged dirty, so any sync
  59  * activity will still find it on the dirty lists, and in particular,
  60  * clear_page_dirty_for_io() will still look at the dirty bits in
  61  * the VM.
  62  *
  63  * Doing this should *normally* only ever be done when a page
  64  * is truncated, and is not actually mapped anywhere at all. However,
  65  * fs/buffer.c does this when it notices that somebody has cleaned
  66  * out all the buffers on a page without actually doing it through
  67  * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
  68  */
  69 void cancel_dirty_page(struct page *page, unsigned int account_size)
  70 {
  71         if (TestClearPageDirty(page)) {
  72                 struct address_space *mapping = page->mapping;
  73                 if (mapping && mapping_cap_account_dirty(mapping)) {
  74                         dec_zone_page_state(page, NR_FILE_DIRTY);
  75                         if (account_size)
  76                                 task_io_account_cancelled_write(account_size);
  77                 }
  78         }
  79 }
  80 EXPORT_SYMBOL(cancel_dirty_page);
  81
  82 /*
  83  * If truncate cannot remove the fs-private metadata from the page, the page
  84  * becomes anonymous.  It will be left on the LRU and may even be mapped into
  85  * user pagetables if we're racing with filemap_fault().
  86  *
  87  * We need to bale out if page->mapping is no longer equal to the original
  88  * mapping.  This happens a) when the VM reclaimed the page while we waited on
  89  * its lock, b) when a concurrent invalidate_mapping_pages got there first and
  90  * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
  91  */
  92 static void
  93 truncate_complete_page(struct address_space *mapping, struct page *page)
  94 {
  95         if (page->mapping != mapping)
  96                 return;
  97
  98         if (PagePrivate(page))
  99                 do_invalidatepage(page, 0);
 100
 101         cancel_dirty_page(page, PAGE_CACHE_SIZE);
 102
 103         remove_from_page_cache(page);
 104         ClearPageUptodate(page);
 105         ClearPageMappedToDisk(page);
 106         page_cache_release(page);       /* pagecache ref */
 107 }
 108
 109 /*
 110  * This is for invalidate_mapping_pages().  That function can be called at
 111  * any time, and is not supposed to throw away dirty pages.  But pages can
 112  * be marked dirty at any time too, so use remove_mapping which safely
 113  * discards clean, unused pages.
 114  *
 115  * Returns non-zero if the page was successfully invalidated.
 116  */
 117 static int
 118 invalidate_complete_page(struct address_space *mapping, struct page *page)
 119 {
 120         int ret;
 121
 122         if (page->mapping != mapping)
 123                 return 0;
 124
 125         if (PagePrivate(page) && !try_to_release_page(page, 0))
 126                 return 0;
 127
 128         ret = remove_mapping(mapping, page);
 129
 130         return ret;
 131 }
 132
 133 /**
 134  * truncate_inode_pages - truncate range of pages specified by start and
 135  * end byte offsets
 136  * @mapping: mapping to truncate
 137  * @lstart: offset from which to truncate
 138  * @lend: offset to which to truncate
 139  *
 140  * Truncate the page cache, removing the pages that are between
 141  * specified offsets (and zeroing out partial page
 142  * (if lstart is not page aligned)).
 143  *
 144  * Truncate takes two passes - the first pass is nonblocking.  It will not
 145  * block on page locks and it will not block on writeback.  The second pass
 146  * will wait.  This is to prevent as much IO as possible in the affected region.
 147  * The first pass will remove most pages, so the search cost of the second pass
 148  * is low.
 149  *
 150  * When looking at page->index outside the page lock we need to be careful to
 151  * copy it into a local to avoid races (it could change at any time).
 152  *
 153  * We pass down the cache-hot hint to the page freeing code.  Even if the
 154  * mapping is large, it is probably the case that the final pages are the most
 155  * recently touched, and freeing happens in ascending file offset order.
 156  */
 157 void truncate_inode_pages_range(struct address_space *mapping,
 158                                 loff_t lstart, loff_t lend)
 159 {
 160         const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
 161         pgoff_t end;
 162         const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
 163         struct pagevec pvec;
 164         pgoff_t next;
 165         int i;
 166
 167         if (mapping->nrpages == 0)
 168                 return;
 169
 170         BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
 171         end = (lend >> PAGE_CACHE_SHIFT);
 172
 173         pagevec_init(&pvec, 0);
 174         next = start;
 175         while (next <= end &&
 176                pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 177                 for (i = 0; i < pagevec_count(&pvec); i++) {
 178                         struct page *page = pvec.pages[i];
 179                         pgoff_t page_index = page->index;
 180
 181                         if (page_index > end) {
 182                                 next = page_index;
 183                                 break;
 184                         }
 185
 186                         if (page_index > next)
 187                                 next = page_index;
 188                         next++;
 189                         if (TestSetPageLocked(page))
 190                                 continue;
 191                         if (PageWriteback(page)) {
 192                                 unlock_page(page);
 193                                 continue;
 194                         }
 195                         if (page_mapped(page)) {
 196                                 unmap_mapping_range(mapping,
 197                                   (loff_t)page_index<<PAGE_CACHE_SHIFT,
 198                                   PAGE_CACHE_SIZE, 0);
 199                         }
 200                         truncate_complete_page(mapping, page);
 201                         unlock_page(page);
 202                 }
 203                 pagevec_release(&pvec);
 204                 cond_resched();
 205         }
 206
 207         if (partial) {
 208                 struct page *page = find_lock_page(mapping, start - 1);
 209                 if (page) {
 210                         wait_on_page_writeback(page);
 211                         truncate_partial_page(page, partial);
 212                         unlock_page(page);
 213                         page_cache_release(page);
 214                 }
 215         }
 216
 217         next = start;
 218         for ( ; ; ) {
 219                 cond_resched();
 220                 if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 221                         if (next == start)
 222                                 break;
 223                         next = start;
 224                         continue;
 225                 }
 226                 if (pvec.pages[0]->index > end) {
 227                         pagevec_release(&pvec);
 228                         break;
 229                 }
 230                 for (i = 0; i < pagevec_count(&pvec); i++) {
 231                         struct page *page = pvec.pages[i];
 232
 233                         if (page->index > end)
 234                                 break;
 235                         lock_page(page);
 236                         wait_on_page_writeback(page);
 237                         if (page_mapped(page)) {
 238                                 unmap_mapping_range(mapping,
 239                                   (loff_t)page->index<<PAGE_CACHE_SHIFT,
 240                                   PAGE_CACHE_SIZE, 0);
 241                         }
 242                         if (page->index > next)
 243                                 next = page->index;
 244                         next++;
 245                         truncate_complete_page(mapping, page);
 246                         unlock_page(page);
 247                 }
 248                 pagevec_release(&pvec);
 249         }
 250 }
 251 EXPORT_SYMBOL(truncate_inode_pages_range);
 252
 253 /**
 254  * truncate_inode_pages - truncate *all* the pages from an offset
 255  * @mapping: mapping to truncate
 256  * @lstart: offset from which to truncate
 257  *
 258  * Called under (and serialised by) inode->i_mutex.
 259  */
 260 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
 261 {
 262         truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
 263 }
 264 EXPORT_SYMBOL(truncate_inode_pages);
 265
 266 unsigned long __invalidate_mapping_pages(struct address_space *mapping,
 267                                 pgoff_t start, pgoff_t end, bool be_atomic)
 268 {
 269         struct pagevec pvec;
 270         pgoff_t next = start;
 271         unsigned long ret = 0;
 272         int i;
 273
 274         pagevec_init(&pvec, 0);
 275         while (next <= end &&
 276                         pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 277                 for (i = 0; i < pagevec_count(&pvec); i++) {
 278                         struct page *page = pvec.pages[i];
 279                         pgoff_t index;
 280                         int lock_failed;
 281
 282                         lock_failed = TestSetPageLocked(page);
 283
 284                         /*
 285                          * We really shouldn't be looking at the ->index of an
 286                          * unlocked page.  But we're not allowed to lock these
 287                          * pages.  So we rely upon nobody altering the ->index
 288                          * of this (pinned-by-us) page.
 289                          */
 290                         index = page->index;
 291                         if (index > next)
 292                                 next = index;
 293                         next++;
 294                         if (lock_failed)
 295                                 continue;
 296
 297                         if (PageDirty(page) || PageWriteback(page))
 298                                 goto unlock;
 299                         if (page_mapped(page))
 300                                 goto unlock;
 301                         ret += invalidate_complete_page(mapping, page);
 302 unlock:
 303                         unlock_page(page);
 304                         if (next > end)
 305                                 break;
 306                 }
 307                 pagevec_release(&pvec);
 308                 if (likely(!be_atomic))
 309                         cond_resched();
 310         }
 311         return ret;
 312 }
 313
 314 /**
 315  * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
 316  * @mapping: the address_space which holds the pages to invalidate
 317  * @start: the offset 'from' which to invalidate
 318  * @end: the offset 'to' which to invalidate (inclusive)
 319  *
 320  * This function only removes the unlocked pages, if you want to
 321  * remove all the pages of one inode, you must call truncate_inode_pages.
 322  *
 323  * invalidate_mapping_pages() will not block on IO activity. It will not
 324  * invalidate pages which are dirty, locked, under writeback or mapped into
 325  * pagetables.
 326  */
 327 unsigned long invalidate_mapping_pages(struct address_space *mapping,
 328                                 pgoff_t start, pgoff_t end)
 329 {
 330         return __invalidate_mapping_pages(mapping, start, end, false);
 331 }
 332 EXPORT_SYMBOL(invalidate_mapping_pages);
 333
 334 /*
 335  * This is like invalidate_complete_page(), except it ignores the page's
 336  * refcount.  We do this because invalidate_inode_pages2() needs stronger
 337  * invalidation guarantees, and cannot afford to leave pages behind because
 338  * shrink_page_list() has a temp ref on them, or because they're transiently
 339  * sitting in the lru_cache_add() pagevecs.
 340  */
 341 static int
 342 invalidate_complete_page2(struct address_space *mapping, struct page *page)
 343 {
 344         if (page->mapping != mapping)
 345                 return 0;
 346
 347         if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
 348                 return 0;
 349
 350         write_lock_irq(&mapping->tree_lock);
 351         if (PageDirty(page))
 352                 goto failed;
 353
 354         BUG_ON(PagePrivate(page));
 355         __remove_from_page_cache(page);
 356         write_unlock_irq(&mapping->tree_lock);
 357         ClearPageUptodate(page);
 358         page_cache_release(page);       /* pagecache ref */
 359         return 1;
 360 failed:
 361         write_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 -EIO 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 did_range_unmap = 0;
 393         int wrapped = 0;
 394
 395         pagevec_init(&pvec, 0);
 396         next = start;
 397         while (next <= end && !wrapped &&
 398                 pagevec_lookup(&pvec, mapping, next,
 399                         min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 400                 for (i = 0; i < pagevec_count(&pvec); i++) {
 401                         struct page *page = pvec.pages[i];
 402                         pgoff_t page_index;
 403
 404                         lock_page(page);
 405                         if (page->mapping != mapping) {
 406                                 unlock_page(page);
 407                                 continue;
 408                         }
 409                         page_index = page->index;
 410                         next = page_index + 1;
 411                         if (next == 0)
 412                                 wrapped = 1;
 413                         if (page_index > end) {
 414                                 unlock_page(page);
 415                                 break;
 416                         }
 417                         wait_on_page_writeback(page);
 418                         if (page_mapped(page)) {
 419                                 if (!did_range_unmap) {
 420                                         /*
 421                                          * Zap the rest of the file in one hit.
 422                                          */
 423                                         unmap_mapping_range(mapping,
 424                                            (loff_t)page_index<<PAGE_CACHE_SHIFT,
 425                                            (loff_t)(end - page_index + 1)
 426                                                         << PAGE_CACHE_SHIFT,
 427                                             0);
 428                                         did_range_unmap = 1;
 429                                 } else {
 430                                         /*
 431                                          * Just zap this page
 432                                          */
 433                                         unmap_mapping_range(mapping,
 434                                           (loff_t)page_index<<PAGE_CACHE_SHIFT,
 435                                           PAGE_CACHE_SIZE, 0);
 436                                 }
 437                         }
 438                         BUG_ON(page_mapped(page));
 439                         ret = do_launder_page(mapping, page);
 440                         if (ret == 0 && !invalidate_complete_page2(mapping, page))
 441                                 ret = -EIO;
 442                         unlock_page(page);
 443                 }
 444                 pagevec_release(&pvec);
 445                 cond_resched();
 446         }
 447         return ret;
 448 }
 449 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
 450
 451 /**
 452  * invalidate_inode_pages2 - remove all pages from an address_space
 453  * @mapping: the address_space
 454  *
 455  * Any pages which are found to be mapped into pagetables are unmapped prior to
 456  * invalidation.
 457  *
 458  * Returns -EIO if any pages could not be invalidated.
 459  */
 460 int invalidate_inode_pages2(struct address_space *mapping)
 461 {
 462         return invalidate_inode_pages2_range(mapping, 0, -1);
 463 }
 464 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);