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