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                 goto failed;
  73         if (page_count(page) != 2)      /* caller's ref + pagecache ref */
  74                 goto failed;
  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 failed:
  83         write_unlock_irq(&mapping->tree_lock);
  84         return 0;
  85 }
  86
  87 /**
  88  * truncate_inode_pages - truncate range of pages specified by start and
  89  * end byte offsets
  90  * @mapping: mapping to truncate
  91  * @lstart: offset from which to truncate
  92  * @lend: offset to which to truncate
  93  *
  94  * Truncate the page cache, removing the pages that are between
  95  * specified offsets (and zeroing out partial page
  96  * (if lstart is not page aligned)).
  97  *
  98  * Truncate takes two passes - the first pass is nonblocking.  It will not
  99  * block on page locks and it will not block on writeback.  The second pass
 100  * will wait.  This is to prevent as much IO as possible in the affected region.
 101  * The first pass will remove most pages, so the search cost of the second pass
 102  * is low.
 103  *
 104  * When looking at page->index outside the page lock we need to be careful to
 105  * copy it into a local to avoid races (it could change at any time).
 106  *
 107  * We pass down the cache-hot hint to the page freeing code.  Even if the
 108  * mapping is large, it is probably the case that the final pages are the most
 109  * recently touched, and freeing happens in ascending file offset order.
 110  */
 111 void truncate_inode_pages_range(struct address_space *mapping,
 112                                 loff_t lstart, loff_t lend)
 113 {
 114         const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
 115         pgoff_t end;
 116         const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
 117         struct pagevec pvec;
 118         pgoff_t next;
 119         int i;
 120
 121         if (mapping->nrpages == 0)
 122                 return;
 123
 124         BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
 125         end = (lend >> PAGE_CACHE_SHIFT);
 126
 127         pagevec_init(&pvec, 0);
 128         next = start;
 129         while (next <= end &&
 130                pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 131                 for (i = 0; i < pagevec_count(&pvec); i++) {
 132                         struct page *page = pvec.pages[i];
 133                         pgoff_t page_index = page->index;
 134
 135                         if (page_index > end) {
 136                                 next = page_index;
 137                                 break;
 138                         }
 139
 140                         if (page_index > next)
 141                                 next = page_index;
 142                         next++;
 143                         if (TestSetPageLocked(page))
 144                                 continue;
 145                         if (PageWriteback(page)) {
 146                                 unlock_page(page);
 147                                 continue;
 148                         }
 149                         truncate_complete_page(mapping, page);
 150                         unlock_page(page);
 151                 }
 152                 pagevec_release(&pvec);
 153                 cond_resched();
 154         }
 155
 156         if (partial) {
 157                 struct page *page = find_lock_page(mapping, start - 1);
 158                 if (page) {
 159                         wait_on_page_writeback(page);
 160                         truncate_partial_page(page, partial);
 161                         unlock_page(page);
 162                         page_cache_release(page);
 163                 }
 164         }
 165
 166         next = start;
 167         for ( ; ; ) {
 168                 cond_resched();
 169                 if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 170                         if (next == start)
 171                                 break;
 172                         next = start;
 173                         continue;
 174                 }
 175                 if (pvec.pages[0]->index > end) {
 176                         pagevec_release(&pvec);
 177                         break;
 178                 }
 179                 for (i = 0; i < pagevec_count(&pvec); i++) {
 180                         struct page *page = pvec.pages[i];
 181
 182                         if (page->index > end)
 183                                 break;
 184                         lock_page(page);
 185                         wait_on_page_writeback(page);
 186                         if (page->index > next)
 187                                 next = page->index;
 188                         next++;
 189                         truncate_complete_page(mapping, page);
 190                         unlock_page(page);
 191                 }
 192                 pagevec_release(&pvec);
 193         }
 194 }
 195 EXPORT_SYMBOL(truncate_inode_pages_range);
 196
 197 /**
 198  * truncate_inode_pages - truncate *all* the pages from an offset
 199  * @mapping: mapping to truncate
 200  * @lstart: offset from which to truncate
 201  *
 202  * Called under (and serialised by) inode->i_mutex.
 203  */
 204 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
 205 {
 206         truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
 207 }
 208 EXPORT_SYMBOL(truncate_inode_pages);
 209
 210 /**
 211  * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
 212  * @mapping: the address_space which holds the pages to invalidate
 213  * @start: the offset 'from' which to invalidate
 214  * @end: the offset 'to' which to invalidate (inclusive)
 215  *
 216  * This function only removes the unlocked pages, if you want to
 217  * remove all the pages of one inode, you must call truncate_inode_pages.
 218  *
 219  * invalidate_mapping_pages() will not block on IO activity. It will not
 220  * invalidate pages which are dirty, locked, under writeback or mapped into
 221  * pagetables.
 222  */
 223 unsigned long invalidate_mapping_pages(struct address_space *mapping,
 224                                 pgoff_t start, pgoff_t end)
 225 {
 226         struct pagevec pvec;
 227         pgoff_t next = start;
 228         unsigned long ret = 0;
 229         int i;
 230
 231         pagevec_init(&pvec, 0);
 232         while (next <= end &&
 233                         pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 234                 for (i = 0; i < pagevec_count(&pvec); i++) {
 235                         struct page *page = pvec.pages[i];
 236                         pgoff_t index;
 237                         int lock_failed;
 238
 239                         lock_failed = TestSetPageLocked(page);
 240
 241                         /*
 242                          * We really shouldn't be looking at the ->index of an
 243                          * unlocked page.  But we're not allowed to lock these
 244                          * pages.  So we rely upon nobody altering the ->index
 245                          * of this (pinned-by-us) page.
 246                          */
 247                         index = page->index;
 248                         if (index > next)
 249                                 next = index;
 250                         next++;
 251                         if (lock_failed)
 252                                 continue;
 253
 254                         if (PageDirty(page) || PageWriteback(page))
 255                                 goto unlock;
 256                         if (page_mapped(page))
 257                                 goto unlock;
 258                         ret += invalidate_complete_page(mapping, page);
 259 unlock:
 260                         unlock_page(page);
 261                         if (next > end)
 262                                 break;
 263                 }
 264                 pagevec_release(&pvec);
 265         }
 266         return ret;
 267 }
 268
 269 unsigned long invalidate_inode_pages(struct address_space *mapping)
 270 {
 271         return invalidate_mapping_pages(mapping, 0, ~0UL);
 272 }
 273 EXPORT_SYMBOL(invalidate_inode_pages);
 274
 275 /*
 276  * This is like invalidate_complete_page(), except it ignores the page's
 277  * refcount.  We do this because invalidate_inode_pages2() needs stronger
 278  * invalidation guarantees, and cannot afford to leave pages behind because
 279  * shrink_list() has a temp ref on them, or because they're transiently sitting
 280  * in the lru_cache_add() pagevecs.
 281  */
 282 static int
 283 invalidate_complete_page2(struct address_space *mapping, struct page *page)
 284 {
 285         if (page->mapping != mapping)
 286                 return 0;
 287
 288         if (PagePrivate(page) && !try_to_release_page(page, 0))
 289                 return 0;
 290
 291         write_lock_irq(&mapping->tree_lock);
 292         if (PageDirty(page))
 293                 goto failed;
 294
 295         BUG_ON(PagePrivate(page));
 296         __remove_from_page_cache(page);
 297         write_unlock_irq(&mapping->tree_lock);
 298         ClearPageUptodate(page);
 299         page_cache_release(page);       /* pagecache ref */
 300         return 1;
 301 failed:
 302         write_unlock_irq(&mapping->tree_lock);
 303         return 0;
 304 }
 305
 306 /**
 307  * invalidate_inode_pages2_range - remove range of pages from an address_space
 308  * @mapping: the address_space
 309  * @start: the page offset 'from' which to invalidate
 310  * @end: the page offset 'to' which to invalidate (inclusive)
 311  *
 312  * Any pages which are found to be mapped into pagetables are unmapped prior to
 313  * invalidation.
 314  *
 315  * Returns -EIO if any pages could not be invalidated.
 316  */
 317 int invalidate_inode_pages2_range(struct address_space *mapping,
 318                                   pgoff_t start, pgoff_t end)
 319 {
 320         struct pagevec pvec;
 321         pgoff_t next;
 322         int i;
 323         int ret = 0;
 324         int did_range_unmap = 0;
 325         int wrapped = 0;
 326
 327         pagevec_init(&pvec, 0);
 328         next = start;
 329         while (next <= end && !ret && !wrapped &&
 330                 pagevec_lookup(&pvec, mapping, next,
 331                         min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 332                 for (i = 0; !ret && i < pagevec_count(&pvec); i++) {
 333                         struct page *page = pvec.pages[i];
 334                         pgoff_t page_index;
 335                         int was_dirty;
 336
 337                         lock_page(page);
 338                         if (page->mapping != mapping) {
 339                                 unlock_page(page);
 340                                 continue;
 341                         }
 342                         page_index = page->index;
 343                         next = page_index + 1;
 344                         if (next == 0)
 345                                 wrapped = 1;
 346                         if (page_index > end) {
 347                                 unlock_page(page);
 348                                 break;
 349                         }
 350                         wait_on_page_writeback(page);
 351                         while (page_mapped(page)) {
 352                                 if (!did_range_unmap) {
 353                                         /*
 354                                          * Zap the rest of the file in one hit.
 355                                          */
 356                                         unmap_mapping_range(mapping,
 357                                            (loff_t)page_index<<PAGE_CACHE_SHIFT,
 358                                            (loff_t)(end - page_index + 1)
 359                                                         << PAGE_CACHE_SHIFT,
 360                                             0);
 361                                         did_range_unmap = 1;
 362                                 } else {
 363                                         /*
 364                                          * Just zap this page
 365                                          */
 366                                         unmap_mapping_range(mapping,
 367                                           (loff_t)page_index<<PAGE_CACHE_SHIFT,
 368                                           PAGE_CACHE_SIZE, 0);
 369                                 }
 370                         }
 371                         was_dirty = test_clear_page_dirty(page);
 372                         if (!invalidate_complete_page2(mapping, page)) {
 373                                 if (was_dirty)
 374                                         set_page_dirty(page);
 375                                 ret = -EIO;
 376                         }
 377                         unlock_page(page);
 378                 }
 379                 pagevec_release(&pvec);
 380                 cond_resched();
 381         }
 382         return ret;
 383 }
 384 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
 385
 386 /**
 387  * invalidate_inode_pages2 - remove all pages from an address_space
 388  * @mapping: the address_space
 389  *
 390  * Any pages which are found to be mapped into pagetables are unmapped prior to
 391  * invalidation.
 392  *
 393  * Returns -EIO if any pages could not be invalidated.
 394  */
 395 int invalidate_inode_pages2(struct address_space *mapping)
 396 {
 397         return invalidate_inode_pages2_range(mapping, 0, -1);
 398 }
 399 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);