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 *all* the pages from an offset
  86  * @mapping: mapping to truncate
  87  * @lstart: offset from which to truncate
  88  *
  89  * Truncate the page cache at a set offset, removing the pages that are beyond
  90  * that offset (and zeroing out partial pages).
  91  *
  92  * Truncate takes two passes - the first pass is nonblocking.  It will not
  93  * block on page locks and it will not block on writeback.  The second pass
  94  * will wait.  This is to prevent as much IO as possible in the affected region.
  95  * The first pass will remove most pages, so the search cost of the second pass
  96  * is low.
  97  *
  98  * When looking at page->index outside the page lock we need to be careful to
  99  * copy it into a local to avoid races (it could change at any time).
 100  *
 101  * We pass down the cache-hot hint to the page freeing code.  Even if the
 102  * mapping is large, it is probably the case that the final pages are the most
 103  * recently touched, and freeing happens in ascending file offset order.
 104  *
 105  * Called under (and serialised by) inode->i_sem.
 106  */
 107 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
 108 {
 109         const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
 110         const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
 111         struct pagevec pvec;
 112         pgoff_t next;
 113         int i;
 114
 115         if (mapping->nrpages == 0)
 116                 return;
 117
 118         pagevec_init(&pvec, 0);
 119         next = start;
 120         while (pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 121                 for (i = 0; i < pagevec_count(&pvec); i++) {
 122                         struct page *page = pvec.pages[i];
 123                         pgoff_t page_index = page->index;
 124
 125                         if (page_index > next)
 126                                 next = page_index;
 127                         next++;
 128                         if (TestSetPageLocked(page))
 129                                 continue;
 130                         if (PageWriteback(page)) {
 131                                 unlock_page(page);
 132                                 continue;
 133                         }
 134                         truncate_complete_page(mapping, page);
 135                         unlock_page(page);
 136                 }
 137                 pagevec_release(&pvec);
 138                 cond_resched();
 139         }
 140
 141         if (partial) {
 142                 struct page *page = find_lock_page(mapping, start - 1);
 143                 if (page) {
 144                         wait_on_page_writeback(page);
 145                         truncate_partial_page(page, partial);
 146                         unlock_page(page);
 147                         page_cache_release(page);
 148                 }
 149         }
 150
 151         next = start;
 152         for ( ; ; ) {
 153                 cond_resched();
 154                 if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 155                         if (next == start)
 156                                 break;
 157                         next = start;
 158                         continue;
 159                 }
 160                 for (i = 0; i < pagevec_count(&pvec); i++) {
 161                         struct page *page = pvec.pages[i];
 162
 163                         lock_page(page);
 164                         wait_on_page_writeback(page);
 165                         if (page->index > next)
 166                                 next = page->index;
 167                         next++;
 168                         truncate_complete_page(mapping, page);
 169                         unlock_page(page);
 170                 }
 171                 pagevec_release(&pvec);
 172         }
 173 }
 174
 175 EXPORT_SYMBOL(truncate_inode_pages);
 176
 177 /**
 178  * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
 179  * @mapping: the address_space which holds the pages to invalidate
 180  * @start: the offset 'from' which to invalidate
 181  * @end: the offset 'to' which to invalidate (inclusive)
 182  *
 183  * This function only removes the unlocked pages, if you want to
 184  * remove all the pages of one inode, you must call truncate_inode_pages.
 185  *
 186  * invalidate_mapping_pages() will not block on IO activity. It will not
 187  * invalidate pages which are dirty, locked, under writeback or mapped into
 188  * pagetables.
 189  */
 190 unsigned long invalidate_mapping_pages(struct address_space *mapping,
 191                                 pgoff_t start, pgoff_t end)
 192 {
 193         struct pagevec pvec;
 194         pgoff_t next = start;
 195         unsigned long ret = 0;
 196         int i;
 197
 198         pagevec_init(&pvec, 0);
 199         while (next <= end &&
 200                         pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 201                 for (i = 0; i < pagevec_count(&pvec); i++) {
 202                         struct page *page = pvec.pages[i];
 203
 204                         if (TestSetPageLocked(page)) {
 205                                 next++;
 206                                 continue;
 207                         }
 208                         if (page->index > next)
 209                                 next = page->index;
 210                         next++;
 211                         if (PageDirty(page) || PageWriteback(page))
 212                                 goto unlock;
 213                         if (page_mapped(page))
 214                                 goto unlock;
 215                         ret += invalidate_complete_page(mapping, page);
 216 unlock:
 217                         unlock_page(page);
 218                         if (next > end)
 219                                 break;
 220                 }
 221                 pagevec_release(&pvec);
 222                 cond_resched();
 223         }
 224         return ret;
 225 }
 226
 227 unsigned long invalidate_inode_pages(struct address_space *mapping)
 228 {
 229         return invalidate_mapping_pages(mapping, 0, ~0UL);
 230 }
 231
 232 EXPORT_SYMBOL(invalidate_inode_pages);
 233
 234 /**
 235  * invalidate_inode_pages2_range - remove range of pages from an address_space
 236  * @mapping: the address_space
 237  * @start: the page offset 'from' which to invalidate
 238  * @end: the page offset 'to' which to invalidate (inclusive)
 239  *
 240  * Any pages which are found to be mapped into pagetables are unmapped prior to
 241  * invalidation.
 242  *
 243  * Returns -EIO if any pages could not be invalidated.
 244  */
 245 int invalidate_inode_pages2_range(struct address_space *mapping,
 246                                   pgoff_t start, pgoff_t end)
 247 {
 248         struct pagevec pvec;
 249         pgoff_t next;
 250         int i;
 251         int ret = 0;
 252         int did_range_unmap = 0;
 253         int wrapped = 0;
 254
 255         pagevec_init(&pvec, 0);
 256         next = start;
 257         while (next <= end && !ret && !wrapped &&
 258                 pagevec_lookup(&pvec, mapping, next,
 259                         min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 260                 for (i = 0; !ret && i < pagevec_count(&pvec); i++) {
 261                         struct page *page = pvec.pages[i];
 262                         pgoff_t page_index;
 263                         int was_dirty;
 264
 265                         lock_page(page);
 266                         if (page->mapping != mapping) {
 267                                 unlock_page(page);
 268                                 continue;
 269                         }
 270                         page_index = page->index;
 271                         next = page_index + 1;
 272                         if (next == 0)
 273                                 wrapped = 1;
 274                         if (page_index > end) {
 275                                 unlock_page(page);
 276                                 break;
 277                         }
 278                         wait_on_page_writeback(page);
 279                         while (page_mapped(page)) {
 280                                 if (!did_range_unmap) {
 281                                         /*
 282                                          * Zap the rest of the file in one hit.
 283                                          */
 284                                         unmap_mapping_range(mapping,
 285                                             page_index << PAGE_CACHE_SHIFT,
 286                                             (end - page_index + 1)
 287                                                         << PAGE_CACHE_SHIFT,
 288                                             0);
 289                                         did_range_unmap = 1;
 290                                 } else {
 291                                         /*
 292                                          * Just zap this page
 293                                          */
 294                                         unmap_mapping_range(mapping,
 295                                           page_index << PAGE_CACHE_SHIFT,
 296                                           PAGE_CACHE_SIZE, 0);
 297                                 }
 298                         }
 299                         was_dirty = test_clear_page_dirty(page);
 300                         if (!invalidate_complete_page(mapping, page)) {
 301                                 if (was_dirty)
 302                                         set_page_dirty(page);
 303                                 ret = -EIO;
 304                         }
 305                         unlock_page(page);
 306                 }
 307                 pagevec_release(&pvec);
 308                 cond_resched();
 309         }
 310         return ret;
 311 }
 312 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
 313
 314 /**
 315  * invalidate_inode_pages2 - remove all pages from an address_space
 316  * @mapping: the address_space
 317  *
 318  * Any pages which are found to be mapped into pagetables are unmapped prior to
 319  * invalidation.
 320  *
 321  * Returns -EIO if any pages could not be invalidated.
 322  */
 323 int invalidate_inode_pages2(struct address_space *mapping)
 324 {
 325         return invalidate_inode_pages2_range(mapping, 0, -1);
 326 }
 327 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);