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/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 #include "internal.h"
  22
  23
  24 /**
  25  * do_invalidatepage - invalidate part or all of a page
  26  * @page: the page which is affected
  27  * @offset: the index of the truncation point
  28  *
  29  * do_invalidatepage() is called when all or part of the page has become
  30  * invalidated by a truncate operation.
  31  *
  32  * do_invalidatepage() does not have to release all buffers, but it must
  33  * ensure that no dirty buffer is left outside @offset and that no I/O
  34  * is underway against any of the blocks which are outside the truncation
  35  * point.  Because the caller is about to free (and possibly reuse) those
  36  * blocks on-disk.
  37  */
  38 void do_invalidatepage(struct page *page, unsigned long offset)
  39 {
  40         void (*invalidatepage)(struct page *, unsigned long);
  41         invalidatepage = page->mapping->a_ops->invalidatepage;
  42 #ifdef CONFIG_BLOCK
  43         if (!invalidatepage)
  44                 invalidatepage = block_invalidatepage;
  45 #endif
  46         if (invalidatepage)
  47                 (*invalidatepage)(page, offset);
  48 }
  49
  50 static inline void truncate_partial_page(struct page *page, unsigned partial)
  51 {
  52         zero_user_segment(page, partial, PAGE_CACHE_SIZE);
  53         if (PagePrivate(page))
  54                 do_invalidatepage(page, partial);
  55 }
  56
  57 /*
  58  * This cancels just the dirty bit on the kernel page itself, it
  59  * does NOT actually remove dirty bits on any mmap's that may be
  60  * around. It also leaves the page tagged dirty, so any sync
  61  * activity will still find it on the dirty lists, and in particular,
  62  * clear_page_dirty_for_io() will still look at the dirty bits in
  63  * the VM.
  64  *
  65  * Doing this should *normally* only ever be done when a page
  66  * is truncated, and is not actually mapped anywhere at all. However,
  67  * fs/buffer.c does this when it notices that somebody has cleaned
  68  * out all the buffers on a page without actually doing it through
  69  * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
  70  */
  71 void cancel_dirty_page(struct page *page, unsigned int account_size)
  72 {
  73         if (TestClearPageDirty(page)) {
  74                 struct address_space *mapping = page->mapping;
  75                 if (mapping && mapping_cap_account_dirty(mapping)) {
  76                         dec_zone_page_state(page, NR_FILE_DIRTY);
  77                         dec_bdi_stat(mapping->backing_dev_info,
  78                                         BDI_RECLAIMABLE);
  79                         if (account_size)
  80                                 task_io_account_cancelled_write(account_size);
  81                 }
  82         }
  83 }
  84 EXPORT_SYMBOL(cancel_dirty_page);
  85
  86 /*
  87  * If truncate cannot remove the fs-private metadata from the page, the page
  88  * becomes orphaned.  It will be left on the LRU and may even be mapped into
  89  * user pagetables if we're racing with filemap_fault().
  90  *
  91  * We need to bale out if page->mapping is no longer equal to the original
  92  * mapping.  This happens a) when the VM reclaimed the page while we waited on
  93  * its lock, b) when a concurrent invalidate_mapping_pages got there first and
  94  * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
  95  */
  96 static void
  97 truncate_complete_page(struct address_space *mapping, struct page *page)
  98 {
  99         if (page->mapping != mapping)
 100                 return;
 101
 102         if (PagePrivate(page))
 103                 do_invalidatepage(page, 0);
 104
 105         cancel_dirty_page(page, PAGE_CACHE_SIZE);
 106
 107         clear_page_mlock(page);
 108         remove_from_page_cache(page);
 109         ClearPageMappedToDisk(page);
 110         page_cache_release(page);       /* pagecache ref */
 111 }
 112
 113 /*
 114  * This is for invalidate_mapping_pages().  That function can be called at
 115  * any time, and is not supposed to throw away dirty pages.  But pages can
 116  * be marked dirty at any time too, so use remove_mapping which safely
 117  * discards clean, unused pages.
 118  *
 119  * Returns non-zero if the page was successfully invalidated.
 120  */
 121 static int
 122 invalidate_complete_page(struct address_space *mapping, struct page *page)
 123 {
 124         int ret;
 125
 126         if (page->mapping != mapping)
 127                 return 0;
 128
 129         if (PagePrivate(page) && !try_to_release_page(page, 0))
 130                 return 0;
 131
 132         clear_page_mlock(page);
 133         ret = remove_mapping(mapping, page);
 134
 135         return ret;
 136 }
 137
 138 /**
 139  * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
 140  * @mapping: mapping to truncate
 141  * @lstart: offset from which to truncate
 142  * @lend: offset to which to truncate
 143  *
 144  * Truncate the page cache, removing the pages that are between
 145  * specified offsets (and zeroing out partial page
 146  * (if lstart is not page aligned)).
 147  *
 148  * Truncate takes two passes - the first pass is nonblocking.  It will not
 149  * block on page locks and it will not block on writeback.  The second pass
 150  * will wait.  This is to prevent as much IO as possible in the affected region.
 151  * The first pass will remove most pages, so the search cost of the second pass
 152  * is low.
 153  *
 154  * When looking at page->index outside the page lock we need to be careful to
 155  * copy it into a local to avoid races (it could change at any time).
 156  *
 157  * We pass down the cache-hot hint to the page freeing code.  Even if the
 158  * mapping is large, it is probably the case that the final pages are the most
 159  * recently touched, and freeing happens in ascending file offset order.
 160  */
 161 void truncate_inode_pages_range(struct address_space *mapping,
 162                                 loff_t lstart, loff_t lend)
 163 {
 164         const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
 165         pgoff_t end;
 166         const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
 167         struct pagevec pvec;
 168         pgoff_t next;
 169         int i;
 170
 171         if (mapping->nrpages == 0)
 172                 return;
 173
 174         BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
 175         end = (lend >> PAGE_CACHE_SHIFT);
 176
 177         pagevec_init(&pvec, 0);
 178         next = start;
 179         while (next <= end &&
 180                pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 181                 for (i = 0; i < pagevec_count(&pvec); i++) {
 182                         struct page *page = pvec.pages[i];
 183                         pgoff_t page_index = page->index;
 184
 185                         if (page_index > end) {
 186                                 next = page_index;
 187                                 break;
 188                         }
 189
 190                         if (page_index > next)
 191                                 next = page_index;
 192                         next++;
 193                         if (!trylock_page(page))
 194                                 continue;
 195                         if (PageWriteback(page)) {
 196                                 unlock_page(page);
 197                                 continue;
 198                         }
 199                         if (page_mapped(page)) {
 200                                 unmap_mapping_range(mapping,
 201                                   (loff_t)page_index<<PAGE_CACHE_SHIFT,
 202                                   PAGE_CACHE_SIZE, 0);
 203                         }
 204                         truncate_complete_page(mapping, page);
 205                         unlock_page(page);
 206                 }
 207                 pagevec_release(&pvec);
 208                 cond_resched();
 209         }
 210
 211         if (partial) {
 212                 struct page *page = find_lock_page(mapping, start - 1);
 213                 if (page) {
 214                         wait_on_page_writeback(page);
 215                         truncate_partial_page(page, partial);
 216                         unlock_page(page);
 217                         page_cache_release(page);
 218                 }
 219         }
 220
 221         next = start;
 222         for ( ; ; ) {
 223                 cond_resched();
 224                 if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 225                         if (next == start)
 226                                 break;
 227                         next = start;
 228                         continue;
 229                 }
 230                 if (pvec.pages[0]->index > end) {
 231                         pagevec_release(&pvec);
 232                         break;
 233                 }
 234                 for (i = 0; i < pagevec_count(&pvec); i++) {
 235                         struct page *page = pvec.pages[i];
 236
 237                         if (page->index > end)
 238                                 break;
 239                         lock_page(page);
 240                         wait_on_page_writeback(page);
 241                         if (page_mapped(page)) {
 242                                 unmap_mapping_range(mapping,
 243                                   (loff_t)page->index<<PAGE_CACHE_SHIFT,
 244                                   PAGE_CACHE_SIZE, 0);
 245                         }
 246                         if (page->index > next)
 247                                 next = page->index;
 248                         next++;
 249                         truncate_complete_page(mapping, page);
 250                         unlock_page(page);
 251                 }
 252                 pagevec_release(&pvec);
 253         }
 254 }
 255 EXPORT_SYMBOL(truncate_inode_pages_range);
 256
 257 /**
 258  * truncate_inode_pages - truncate *all* the pages from an offset
 259  * @mapping: mapping to truncate
 260  * @lstart: offset from which to truncate
 261  *
 262  * Called under (and serialised by) inode->i_mutex.
 263  */
 264 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
 265 {
 266         truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
 267 }
 268 EXPORT_SYMBOL(truncate_inode_pages);
 269
 270 unsigned long __invalidate_mapping_pages(struct address_space *mapping,
 271                                 pgoff_t start, pgoff_t end, bool be_atomic)
 272 {
 273         struct pagevec pvec;
 274         pgoff_t next = start;
 275         unsigned long ret = 0;
 276         int i;
 277
 278         pagevec_init(&pvec, 0);
 279         while (next <= end &&
 280                         pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 281                 for (i = 0; i < pagevec_count(&pvec); i++) {
 282                         struct page *page = pvec.pages[i];
 283                         pgoff_t index;
 284                         int lock_failed;
 285
 286                         lock_failed = !trylock_page(page);
 287
 288                         /*
 289                          * We really shouldn't be looking at the ->index of an
 290                          * unlocked page.  But we're not allowed to lock these
 291                          * pages.  So we rely upon nobody altering the ->index
 292                          * of this (pinned-by-us) page.
 293                          */
 294                         index = page->index;
 295                         if (index > next)
 296                                 next = index;
 297                         next++;
 298                         if (lock_failed)
 299                                 continue;
 300
 301                         if (PageDirty(page) || PageWriteback(page))
 302                                 goto unlock;
 303                         if (page_mapped(page))
 304                                 goto unlock;
 305                         ret += invalidate_complete_page(mapping, page);
 306 unlock:
 307                         unlock_page(page);
 308                         if (next > end)
 309                                 break;
 310                 }
 311                 pagevec_release(&pvec);
 312                 if (likely(!be_atomic))
 313                         cond_resched();
 314         }
 315         return ret;
 316 }
 317
 318 /**
 319  * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
 320  * @mapping: the address_space which holds the pages to invalidate
 321  * @start: the offset 'from' which to invalidate
 322  * @end: the offset 'to' which to invalidate (inclusive)
 323  *
 324  * This function only removes the unlocked pages, if you want to
 325  * remove all the pages of one inode, you must call truncate_inode_pages.
 326  *
 327  * invalidate_mapping_pages() will not block on IO activity. It will not
 328  * invalidate pages which are dirty, locked, under writeback or mapped into
 329  * pagetables.
 330  */
 331 unsigned long invalidate_mapping_pages(struct address_space *mapping,
 332                                 pgoff_t start, pgoff_t end)
 333 {
 334         return __invalidate_mapping_pages(mapping, start, end, false);
 335 }
 336 EXPORT_SYMBOL(invalidate_mapping_pages);
 337
 338 /*
 339  * This is like invalidate_complete_page(), except it ignores the page's
 340  * refcount.  We do this because invalidate_inode_pages2() needs stronger
 341  * invalidation guarantees, and cannot afford to leave pages behind because
 342  * shrink_page_list() has a temp ref on them, or because they're transiently
 343  * sitting in the lru_cache_add() pagevecs.
 344  */
 345 static int
 346 invalidate_complete_page2(struct address_space *mapping, struct page *page)
 347 {
 348         if (page->mapping != mapping)
 349                 return 0;
 350
 351         if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
 352                 return 0;
 353
 354         spin_lock_irq(&mapping->tree_lock);
 355         if (PageDirty(page))
 356                 goto failed;
 357
 358         clear_page_mlock(page);
 359         BUG_ON(PagePrivate(page));
 360         __remove_from_page_cache(page);
 361         spin_unlock_irq(&mapping->tree_lock);
 362         page_cache_release(page);       /* pagecache ref */
 363         return 1;
 364 failed:
 365         spin_unlock_irq(&mapping->tree_lock);
 366         return 0;
 367 }
 368
 369 static int do_launder_page(struct address_space *mapping, struct page *page)
 370 {
 371         if (!PageDirty(page))
 372                 return 0;
 373         if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
 374                 return 0;
 375         return mapping->a_ops->launder_page(page);
 376 }
 377
 378 /**
 379  * invalidate_inode_pages2_range - remove range of pages from an address_space
 380  * @mapping: the address_space
 381  * @start: the page offset 'from' which to invalidate
 382  * @end: the page offset 'to' which to invalidate (inclusive)
 383  *
 384  * Any pages which are found to be mapped into pagetables are unmapped prior to
 385  * invalidation.
 386  *
 387  * Returns -EBUSY if any pages could not be invalidated.
 388  */
 389 int invalidate_inode_pages2_range(struct address_space *mapping,
 390                                   pgoff_t start, pgoff_t end)
 391 {
 392         struct pagevec pvec;
 393         pgoff_t next;
 394         int i;
 395         int ret = 0;
 396         int ret2 = 0;
 397         int did_range_unmap = 0;
 398         int wrapped = 0;
 399
 400         pagevec_init(&pvec, 0);
 401         next = start;
 402         while (next <= end && !wrapped &&
 403                 pagevec_lookup(&pvec, mapping, next,
 404                         min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 405                 for (i = 0; i < pagevec_count(&pvec); i++) {
 406                         struct page *page = pvec.pages[i];
 407                         pgoff_t page_index;
 408
 409                         lock_page(page);
 410                         if (page->mapping != mapping) {
 411                                 unlock_page(page);
 412                                 continue;
 413                         }
 414                         page_index = page->index;
 415                         next = page_index + 1;
 416                         if (next == 0)
 417                                 wrapped = 1;
 418                         if (page_index > end) {
 419                                 unlock_page(page);
 420                                 break;
 421                         }
 422                         wait_on_page_writeback(page);
 423                         if (page_mapped(page)) {
 424                                 if (!did_range_unmap) {
 425                                         /*
 426                                          * Zap the rest of the file in one hit.
 427                                          */
 428                                         unmap_mapping_range(mapping,
 429                                            (loff_t)page_index<<PAGE_CACHE_SHIFT,
 430                                            (loff_t)(end - page_index + 1)
 431                                                         << PAGE_CACHE_SHIFT,
 432                                             0);
 433                                         did_range_unmap = 1;
 434                                 } else {
 435                                         /*
 436                                          * Just zap this page
 437                                          */
 438                                         unmap_mapping_range(mapping,
 439                                           (loff_t)page_index<<PAGE_CACHE_SHIFT,
 440                                           PAGE_CACHE_SIZE, 0);
 441                                 }
 442                         }
 443                         BUG_ON(page_mapped(page));
 444                         ret2 = do_launder_page(mapping, page);
 445                         if (ret2 == 0) {
 446                                 if (!invalidate_complete_page2(mapping, page))
 447                                         ret2 = -EBUSY;
 448                         }
 449                         if (ret2 < 0)
 450                                 ret = ret2;
 451                         unlock_page(page);
 452                 }
 453                 pagevec_release(&pvec);
 454                 cond_resched();
 455         }
 456         return ret;
 457 }
 458 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
 459
 460 /**
 461  * invalidate_inode_pages2 - remove all pages from an address_space
 462  * @mapping: the address_space
 463  *
 464  * Any pages which are found to be mapped into pagetables are unmapped prior to
 465  * invalidation.
 466  *
 467  * Returns -EIO if any pages could not be invalidated.
 468  */
 469 int invalidate_inode_pages2(struct address_space *mapping)
 470 {
 471         return invalidate_inode_pages2_range(mapping, 0, -1);
 472 }
 473 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);