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