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/pagevec.h>
  16 #include <linux/task_io_accounting_ops.h>
  17 #include <linux/buffer_head.h>  /* grr. try_to_release_page,
  18                                    do_invalidatepage */
  19
  20
  21 /**
  22  * do_invalidatepage - invalidate part of all of a page
  23  * @page: the page which is affected
  24  * @offset: the index of the truncation point
  25  *
  26  * do_invalidatepage() is called when all or part of the page has become
  27  * invalidated by a truncate operation.
  28  *
  29  * do_invalidatepage() does not have to release all buffers, but it must
  30  * ensure that no dirty buffer is left outside @offset and that no I/O
  31  * is underway against any of the blocks which are outside the truncation
  32  * point.  Because the caller is about to free (and possibly reuse) those
  33  * blocks on-disk.
  34  */
  35 void do_invalidatepage(struct page *page, unsigned long offset)
  36 {
  37         void (*invalidatepage)(struct page *, unsigned long);
  38         invalidatepage = page->mapping->a_ops->invalidatepage;
  39 #ifdef CONFIG_BLOCK
  40         if (!invalidatepage)
  41                 invalidatepage = block_invalidatepage;
  42 #endif
  43         if (invalidatepage)
  44                 (*invalidatepage)(page, offset);
  45 }
  46
  47 static inline void truncate_partial_page(struct page *page, unsigned partial)
  48 {
  49         memclear_highpage_flush(page, partial, PAGE_CACHE_SIZE-partial);
  50         if (PagePrivate(page))
  51                 do_invalidatepage(page, partial);
  52 }
  53
  54 /*
  55  * If truncate cannot remove the fs-private metadata from the page, the page
  56  * becomes anonymous.  It will be left on the LRU and may even be mapped into
  57  * user pagetables if we're racing with filemap_nopage().
  58  *
  59  * We need to bale out if page->mapping is no longer equal to the original
  60  * mapping.  This happens a) when the VM reclaimed the page while we waited on
  61  * its lock, b) when a concurrent invalidate_inode_pages got there first and
  62  * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
  63  */
  64 static void
  65 truncate_complete_page(struct address_space *mapping, struct page *page)
  66 {
  67         if (page->mapping != mapping)
  68                 return;
  69
  70         if (PagePrivate(page))
  71                 do_invalidatepage(page, 0);
  72
  73         if (test_clear_page_dirty(page))
  74                 task_io_account_cancelled_write(PAGE_CACHE_SIZE);
  75         ClearPageUptodate(page);
  76         ClearPageMappedToDisk(page);
  77         remove_from_page_cache(page);
  78         page_cache_release(page);       /* pagecache ref */
  79 }
  80
  81 /*
  82  * This is for invalidate_inode_pages().  That function can be called at
  83  * any time, and is not supposed to throw away dirty pages.  But pages can
  84  * be marked dirty at any time too, so use remove_mapping which safely
  85  * discards clean, unused pages.
  86  *
  87  * Returns non-zero if the page was successfully invalidated.
  88  */
  89 static int
  90 invalidate_complete_page(struct address_space *mapping, struct page *page)
  91 {
  92         int ret;
  93
  94         if (page->mapping != mapping)
  95                 return 0;
  96
  97         if (PagePrivate(page) && !try_to_release_page(page, 0))
  98                 return 0;
  99
 100         ret = remove_mapping(mapping, page);
 101
 102         return ret;
 103 }
 104
 105 /**
 106  * truncate_inode_pages - truncate range of pages specified by start and
 107  * end byte offsets
 108  * @mapping: mapping to truncate
 109  * @lstart: offset from which to truncate
 110  * @lend: offset to which to truncate
 111  *
 112  * Truncate the page cache, removing the pages that are between
 113  * specified offsets (and zeroing out partial page
 114  * (if lstart is not page aligned)).
 115  *
 116  * Truncate takes two passes - the first pass is nonblocking.  It will not
 117  * block on page locks and it will not block on writeback.  The second pass
 118  * will wait.  This is to prevent as much IO as possible in the affected region.
 119  * The first pass will remove most pages, so the search cost of the second pass
 120  * is low.
 121  *
 122  * When looking at page->index outside the page lock we need to be careful to
 123  * copy it into a local to avoid races (it could change at any time).
 124  *
 125  * We pass down the cache-hot hint to the page freeing code.  Even if the
 126  * mapping is large, it is probably the case that the final pages are the most
 127  * recently touched, and freeing happens in ascending file offset order.
 128  */
 129 void truncate_inode_pages_range(struct address_space *mapping,
 130                                 loff_t lstart, loff_t lend)
 131 {
 132         const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
 133         pgoff_t end;
 134         const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
 135         struct pagevec pvec;
 136         pgoff_t next;
 137         int i;
 138
 139         if (mapping->nrpages == 0)
 140                 return;
 141
 142         BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
 143         end = (lend >> PAGE_CACHE_SHIFT);
 144
 145         pagevec_init(&pvec, 0);
 146         next = start;
 147         while (next <= end &&
 148                pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 149                 for (i = 0; i < pagevec_count(&pvec); i++) {
 150                         struct page *page = pvec.pages[i];
 151                         pgoff_t page_index = page->index;
 152
 153                         if (page_index > end) {
 154                                 next = page_index;
 155                                 break;
 156                         }
 157
 158                         if (page_index > next)
 159                                 next = page_index;
 160                         next++;
 161                         if (TestSetPageLocked(page))
 162                                 continue;
 163                         if (PageWriteback(page)) {
 164                                 unlock_page(page);
 165                                 continue;
 166                         }
 167                         truncate_complete_page(mapping, page);
 168                         unlock_page(page);
 169                 }
 170                 pagevec_release(&pvec);
 171                 cond_resched();
 172         }
 173
 174         if (partial) {
 175                 struct page *page = find_lock_page(mapping, start - 1);
 176                 if (page) {
 177                         wait_on_page_writeback(page);
 178                         truncate_partial_page(page, partial);
 179                         unlock_page(page);
 180                         page_cache_release(page);
 181                 }
 182         }
 183
 184         next = start;
 185         for ( ; ; ) {
 186                 cond_resched();
 187                 if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 188                         if (next == start)
 189                                 break;
 190                         next = start;
 191                         continue;
 192                 }
 193                 if (pvec.pages[0]->index > end) {
 194                         pagevec_release(&pvec);
 195                         break;
 196                 }
 197                 for (i = 0; i < pagevec_count(&pvec); i++) {
 198                         struct page *page = pvec.pages[i];
 199
 200                         if (page->index > end)
 201                                 break;
 202                         lock_page(page);
 203                         wait_on_page_writeback(page);
 204                         if (page->index > next)
 205                                 next = page->index;
 206                         next++;
 207                         truncate_complete_page(mapping, page);
 208                         unlock_page(page);
 209                 }
 210                 pagevec_release(&pvec);
 211         }
 212 }
 213 EXPORT_SYMBOL(truncate_inode_pages_range);
 214
 215 /**
 216  * truncate_inode_pages - truncate *all* the pages from an offset
 217  * @mapping: mapping to truncate
 218  * @lstart: offset from which to truncate
 219  *
 220  * Called under (and serialised by) inode->i_mutex.
 221  */
 222 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
 223 {
 224         truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
 225 }
 226 EXPORT_SYMBOL(truncate_inode_pages);
 227
 228 /**
 229  * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
 230  * @mapping: the address_space which holds the pages to invalidate
 231  * @start: the offset 'from' which to invalidate
 232  * @end: the offset 'to' which to invalidate (inclusive)
 233  *
 234  * This function only removes the unlocked pages, if you want to
 235  * remove all the pages of one inode, you must call truncate_inode_pages.
 236  *
 237  * invalidate_mapping_pages() will not block on IO activity. It will not
 238  * invalidate pages which are dirty, locked, under writeback or mapped into
 239  * pagetables.
 240  */
 241 unsigned long invalidate_mapping_pages(struct address_space *mapping,
 242                                 pgoff_t start, pgoff_t end)
 243 {
 244         struct pagevec pvec;
 245         pgoff_t next = start;
 246         unsigned long ret = 0;
 247         int i;
 248
 249         pagevec_init(&pvec, 0);
 250         while (next <= end &&
 251                         pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 252                 for (i = 0; i < pagevec_count(&pvec); i++) {
 253                         struct page *page = pvec.pages[i];
 254                         pgoff_t index;
 255                         int lock_failed;
 256
 257                         lock_failed = TestSetPageLocked(page);
 258
 259                         /*
 260                          * We really shouldn't be looking at the ->index of an
 261                          * unlocked page.  But we're not allowed to lock these
 262                          * pages.  So we rely upon nobody altering the ->index
 263                          * of this (pinned-by-us) page.
 264                          */
 265                         index = page->index;
 266                         if (index > next)
 267                                 next = index;
 268                         next++;
 269                         if (lock_failed)
 270                                 continue;
 271
 272                         if (PageDirty(page) || PageWriteback(page))
 273                                 goto unlock;
 274                         if (page_mapped(page))
 275                                 goto unlock;
 276                         ret += invalidate_complete_page(mapping, page);
 277 unlock:
 278                         unlock_page(page);
 279                         if (next > end)
 280                                 break;
 281                 }
 282                 pagevec_release(&pvec);
 283         }
 284         return ret;
 285 }
 286
 287 unsigned long invalidate_inode_pages(struct address_space *mapping)
 288 {
 289         return invalidate_mapping_pages(mapping, 0, ~0UL);
 290 }
 291 EXPORT_SYMBOL(invalidate_inode_pages);
 292
 293 /*
 294  * This is like invalidate_complete_page(), except it ignores the page's
 295  * refcount.  We do this because invalidate_inode_pages2() needs stronger
 296  * invalidation guarantees, and cannot afford to leave pages behind because
 297  * shrink_list() has a temp ref on them, or because they're transiently sitting
 298  * in the lru_cache_add() pagevecs.
 299  */
 300 static int
 301 invalidate_complete_page2(struct address_space *mapping, struct page *page)
 302 {
 303         if (page->mapping != mapping)
 304                 return 0;
 305
 306         if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
 307                 return 0;
 308
 309         write_lock_irq(&mapping->tree_lock);
 310         if (PageDirty(page))
 311                 goto failed;
 312
 313         BUG_ON(PagePrivate(page));
 314         __remove_from_page_cache(page);
 315         write_unlock_irq(&mapping->tree_lock);
 316         ClearPageUptodate(page);
 317         page_cache_release(page);       /* pagecache ref */
 318         return 1;
 319 failed:
 320         write_unlock_irq(&mapping->tree_lock);
 321         return 0;
 322 }
 323
 324 /**
 325  * invalidate_inode_pages2_range - remove range of pages from an address_space
 326  * @mapping: the address_space
 327  * @start: the page offset 'from' which to invalidate
 328  * @end: the page offset 'to' which to invalidate (inclusive)
 329  *
 330  * Any pages which are found to be mapped into pagetables are unmapped prior to
 331  * invalidation.
 332  *
 333  * Returns -EIO if any pages could not be invalidated.
 334  */
 335 int invalidate_inode_pages2_range(struct address_space *mapping,
 336                                   pgoff_t start, pgoff_t end)
 337 {
 338         struct pagevec pvec;
 339         pgoff_t next;
 340         int i;
 341         int ret = 0;
 342         int did_range_unmap = 0;
 343         int wrapped = 0;
 344
 345         pagevec_init(&pvec, 0);
 346         next = start;
 347         while (next <= end && !ret && !wrapped &&
 348                 pagevec_lookup(&pvec, mapping, next,
 349                         min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 350                 for (i = 0; !ret && i < pagevec_count(&pvec); i++) {
 351                         struct page *page = pvec.pages[i];
 352                         pgoff_t page_index;
 353                         int was_dirty;
 354
 355                         lock_page(page);
 356                         if (page->mapping != mapping) {
 357                                 unlock_page(page);
 358                                 continue;
 359                         }
 360                         page_index = page->index;
 361                         next = page_index + 1;
 362                         if (next == 0)
 363                                 wrapped = 1;
 364                         if (page_index > end) {
 365                                 unlock_page(page);
 366                                 break;
 367                         }
 368                         wait_on_page_writeback(page);
 369                         while (page_mapped(page)) {
 370                                 if (!did_range_unmap) {
 371                                         /*
 372                                          * Zap the rest of the file in one hit.
 373                                          */
 374                                         unmap_mapping_range(mapping,
 375                                            (loff_t)page_index<<PAGE_CACHE_SHIFT,
 376                                            (loff_t)(end - page_index + 1)
 377                                                         << PAGE_CACHE_SHIFT,
 378                                             0);
 379                                         did_range_unmap = 1;
 380                                 } else {
 381                                         /*
 382                                          * Just zap this page
 383                                          */
 384                                         unmap_mapping_range(mapping,
 385                                           (loff_t)page_index<<PAGE_CACHE_SHIFT,
 386                                           PAGE_CACHE_SIZE, 0);
 387                                 }
 388                         }
 389                         was_dirty = test_clear_page_dirty(page);
 390                         if (!invalidate_complete_page2(mapping, page)) {
 391                                 if (was_dirty)
 392                                         set_page_dirty(page);
 393                                 ret = -EIO;
 394                         }
 395                         unlock_page(page);
 396                 }
 397                 pagevec_release(&pvec);
 398                 cond_resched();
 399         }
 400         WARN_ON_ONCE(ret);
 401         return ret;
 402 }
 403 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
 404
 405 /**
 406  * invalidate_inode_pages2 - remove all pages from an address_space
 407  * @mapping: the address_space
 408  *
 409  * Any pages which are found to be mapped into pagetables are unmapped prior to
 410  * invalidation.
 411  *
 412  * Returns -EIO if any pages could not be invalidated.
 413  */
 414 int invalidate_inode_pages2(struct address_space *mapping)
 415 {
 416         return invalidate_inode_pages2_range(mapping, 0, -1);
 417 }
 418 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);