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