linux/mm/truncate.c
<<
>>
Prefs
   1/*
   2 * mm/truncate.c - code for taking down pages from address_spaces
   3 *
   4 * Copyright (C) 2002, Linus Torvalds
   5 *
   6 * 10Sep2002    Andrew Morton
   7 *              Initial version.
   8 */
   9
  10#include <linux/kernel.h>
  11#include <linux/backing-dev.h>
  12#include <linux/mm.h>
  13#include <linux/swap.h>
  14#include <linux/module.h>
  15#include <linux/pagemap.h>
  16#include <linux/highmem.h>
  17#include <linux/pagevec.h>
  18#include <linux/task_io_accounting_ops.h>
  19#include <linux/buffer_head.h>  /* grr. try_to_release_page,
  20                                   do_invalidatepage */
  21#include "internal.h"
  22
  23
  24/**
  25 * do_invalidatepage - invalidate part or all of a page
  26 * @page: the page which is affected
  27 * @offset: the index of the truncation point
  28 *
  29 * do_invalidatepage() is called when all or part of the page has become
  30 * invalidated by a truncate operation.
  31 *
  32 * do_invalidatepage() does not have to release all buffers, but it must
  33 * ensure that no dirty buffer is left outside @offset and that no I/O
  34 * is underway against any of the blocks which are outside the truncation
  35 * point.  Because the caller is about to free (and possibly reuse) those
  36 * blocks on-disk.
  37 */
  38void do_invalidatepage(struct page *page, unsigned long offset)
  39{
  40        void (*invalidatepage)(struct page *, unsigned long);
  41        invalidatepage = page->mapping->a_ops->invalidatepage;
  42#ifdef CONFIG_BLOCK
  43        if (!invalidatepage)
  44                invalidatepage = block_invalidatepage;
  45#endif
  46        if (invalidatepage)
  47                (*invalidatepage)(page, offset);
  48}
  49
  50static inline void truncate_partial_page(struct page *page, unsigned partial)
  51{
  52        zero_user_segment(page, partial, PAGE_CACHE_SIZE);
  53        if (PagePrivate(page))
  54                do_invalidatepage(page, partial);
  55}
  56
  57/*
  58 * This cancels just the dirty bit on the kernel page itself, it
  59 * does NOT actually remove dirty bits on any mmap's that may be
  60 * around. It also leaves the page tagged dirty, so any sync
  61 * activity will still find it on the dirty lists, and in particular,
  62 * clear_page_dirty_for_io() will still look at the dirty bits in
  63 * the VM.
  64 *
  65 * Doing this should *normally* only ever be done when a page
  66 * is truncated, and is not actually mapped anywhere at all. However,
  67 * fs/buffer.c does this when it notices that somebody has cleaned
  68 * out all the buffers on a page without actually doing it through
  69 * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
  70 */
  71void cancel_dirty_page(struct page *page, unsigned int account_size)
  72{
  73        if (TestClearPageDirty(page)) {
  74                struct address_space *mapping = page->mapping;
  75                if (mapping && mapping_cap_account_dirty(mapping)) {
  76                        dec_zone_page_state(page, NR_FILE_DIRTY);
  77                        dec_bdi_stat(mapping->backing_dev_info,
  78                                        BDI_RECLAIMABLE);
  79                        if (account_size)
  80                                task_io_account_cancelled_write(account_size);
  81                }
  82        }
  83}
  84EXPORT_SYMBOL(cancel_dirty_page);
  85
  86/*
  87 * If truncate cannot remove the fs-private metadata from the page, the page
  88 * becomes orphaned.  It will be left on the LRU and may even be mapped into
  89 * user pagetables if we're racing with filemap_fault().
  90 *
  91 * We need to bale out if page->mapping is no longer equal to the original
  92 * mapping.  This happens a) when the VM reclaimed the page while we waited on
  93 * its lock, b) when a concurrent invalidate_mapping_pages got there first and
  94 * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
  95 */
  96static void
  97truncate_complete_page(struct address_space *mapping, struct page *page)
  98{
  99        if (page->mapping != mapping)
 100                return;
 101
 102        if (PagePrivate(page))
 103                do_invalidatepage(page, 0);
 104
 105        cancel_dirty_page(page, PAGE_CACHE_SIZE);
 106
 107        clear_page_mlock(page);
 108        remove_from_page_cache(page);
 109        ClearPageMappedToDisk(page);
 110        page_cache_release(page);       /* pagecache ref */
 111}
 112
 113/*
 114 * This is for invalidate_mapping_pages().  That function can be called at
 115 * any time, and is not supposed to throw away dirty pages.  But pages can
 116 * be marked dirty at any time too, so use remove_mapping which safely
 117 * discards clean, unused pages.
 118 *
 119 * Returns non-zero if the page was successfully invalidated.
 120 */
 121static int
 122invalidate_complete_page(struct address_space *mapping, struct page *page)
 123{
 124        int ret;
 125
 126        if (page->mapping != mapping)
 127                return 0;
 128
 129        if (PagePrivate(page) && !try_to_release_page(page, 0))
 130                return 0;
 131
 132        clear_page_mlock(page);
 133        ret = remove_mapping(mapping, page);
 134
 135        return ret;
 136}
 137
 138/**
 139 * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
 140 * @mapping: mapping to truncate
 141 * @lstart: offset from which to truncate
 142 * @lend: offset to which to truncate
 143 *
 144 * Truncate the page cache, removing the pages that are between
 145 * specified offsets (and zeroing out partial page
 146 * (if lstart is not page aligned)).
 147 *
 148 * Truncate takes two passes - the first pass is nonblocking.  It will not
 149 * block on page locks and it will not block on writeback.  The second pass
 150 * will wait.  This is to prevent as much IO as possible in the affected region.
 151 * The first pass will remove most pages, so the search cost of the second pass
 152 * is low.
 153 *
 154 * When looking at page->index outside the page lock we need to be careful to
 155 * copy it into a local to avoid races (it could change at any time).
 156 *
 157 * We pass down the cache-hot hint to the page freeing code.  Even if the
 158 * mapping is large, it is probably the case that the final pages are the most
 159 * recently touched, and freeing happens in ascending file offset order.
 160 */
 161void truncate_inode_pages_range(struct address_space *mapping,
 162                                loff_t lstart, loff_t lend)
 163{
 164        const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
 165        pgoff_t end;
 166        const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
 167        struct pagevec pvec;
 168        pgoff_t next;
 169        int i;
 170
 171        if (mapping->nrpages == 0)
 172                return;
 173
 174        BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
 175        end = (lend >> PAGE_CACHE_SHIFT);
 176
 177        pagevec_init(&pvec, 0);
 178        next = start;
 179        while (next <= end &&
 180               pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 181                for (i = 0; i < pagevec_count(&pvec); i++) {
 182                        struct page *page = pvec.pages[i];
 183                        pgoff_t page_index = page->index;
 184
 185                        if (page_index > end) {
 186                                next = page_index;
 187                                break;
 188                        }
 189
 190                        if (page_index > next)
 191                                next = page_index;
 192                        next++;
 193                        if (!trylock_page(page))
 194                                continue;
 195                        if (PageWriteback(page)) {
 196                                unlock_page(page);
 197                                continue;
 198                        }
 199                        if (page_mapped(page)) {
 200                                unmap_mapping_range(mapping,
 201                                  (loff_t)page_index<<PAGE_CACHE_SHIFT,
 202                                  PAGE_CACHE_SIZE, 0);
 203                        }
 204                        truncate_complete_page(mapping, page);
 205                        unlock_page(page);
 206                }
 207                pagevec_release(&pvec);
 208                cond_resched();
 209        }
 210
 211        if (partial) {
 212                struct page *page = find_lock_page(mapping, start - 1);
 213                if (page) {
 214                        wait_on_page_writeback(page);
 215                        truncate_partial_page(page, partial);
 216                        unlock_page(page);
 217                        page_cache_release(page);
 218                }
 219        }
 220
 221        next = start;
 222        for ( ; ; ) {
 223                cond_resched();
 224                if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 225                        if (next == start)
 226                                break;
 227                        next = start;
 228                        continue;
 229                }
 230                if (pvec.pages[0]->index > end) {
 231                        pagevec_release(&pvec);
 232                        break;
 233                }
 234                for (i = 0; i < pagevec_count(&pvec); i++) {
 235                        struct page *page = pvec.pages[i];
 236
 237                        if (page->index > end)
 238                                break;
 239                        lock_page(page);
 240                        wait_on_page_writeback(page);
 241                        if (page_mapped(page)) {
 242                                unmap_mapping_range(mapping,
 243                                  (loff_t)page->index<<PAGE_CACHE_SHIFT,
 244                                  PAGE_CACHE_SIZE, 0);
 245                        }
 246                        if (page->index > next)
 247                                next = page->index;
 248                        next++;
 249                        truncate_complete_page(mapping, page);
 250                        unlock_page(page);
 251                }
 252                pagevec_release(&pvec);
 253        }
 254}
 255EXPORT_SYMBOL(truncate_inode_pages_range);
 256
 257/**
 258 * truncate_inode_pages - truncate *all* the pages from an offset
 259 * @mapping: mapping to truncate
 260 * @lstart: offset from which to truncate
 261 *
 262 * Called under (and serialised by) inode->i_mutex.
 263 */
 264void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
 265{
 266        truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
 267}
 268EXPORT_SYMBOL(truncate_inode_pages);
 269
 270unsigned long __invalidate_mapping_pages(struct address_space *mapping,
 271                                pgoff_t start, pgoff_t end, bool be_atomic)
 272{
 273        struct pagevec pvec;
 274        pgoff_t next = start;
 275        unsigned long ret = 0;
 276        int i;
 277
 278        pagevec_init(&pvec, 0);
 279        while (next <= end &&
 280                        pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
 281                for (i = 0; i < pagevec_count(&pvec); i++) {
 282                        struct page *page = pvec.pages[i];
 283                        pgoff_t index;
 284                        int lock_failed;
 285
 286                        lock_failed = !trylock_page(page);
 287
 288                        /*
 289                         * We really shouldn't be looking at the ->index of an
 290                         * unlocked page.  But we're not allowed to lock these
 291                         * pages.  So we rely upon nobody altering the ->index
 292                         * of this (pinned-by-us) page.
 293                         */
 294                        index = page->index;
 295                        if (index > next)
 296                                next = index;
 297                        next++;
 298                        if (lock_failed)
 299                                continue;
 300
 301                        if (PageDirty(page) || PageWriteback(page))
 302                                goto unlock;
 303                        if (page_mapped(page))
 304                                goto unlock;
 305                        ret += invalidate_complete_page(mapping, page);
 306unlock:
 307                        unlock_page(page);
 308                        if (next > end)
 309                                break;
 310                }
 311                pagevec_release(&pvec);
 312                if (likely(!be_atomic))
 313                        cond_resched();
 314        }
 315        return ret;
 316}
 317
 318/**
 319 * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
 320 * @mapping: the address_space which holds the pages to invalidate
 321 * @start: the offset 'from' which to invalidate
 322 * @end: the offset 'to' which to invalidate (inclusive)
 323 *
 324 * This function only removes the unlocked pages, if you want to
 325 * remove all the pages of one inode, you must call truncate_inode_pages.
 326 *
 327 * invalidate_mapping_pages() will not block on IO activity. It will not
 328 * invalidate pages which are dirty, locked, under writeback or mapped into
 329 * pagetables.
 330 */
 331unsigned long invalidate_mapping_pages(struct address_space *mapping,
 332                                pgoff_t start, pgoff_t end)
 333{
 334        return __invalidate_mapping_pages(mapping, start, end, false);
 335}
 336EXPORT_SYMBOL(invalidate_mapping_pages);
 337
 338/*
 339 * This is like invalidate_complete_page(), except it ignores the page's
 340 * refcount.  We do this because invalidate_inode_pages2() needs stronger
 341 * invalidation guarantees, and cannot afford to leave pages behind because
 342 * shrink_page_list() has a temp ref on them, or because they're transiently
 343 * sitting in the lru_cache_add() pagevecs.
 344 */
 345static int
 346invalidate_complete_page2(struct address_space *mapping, struct page *page)
 347{
 348        if (page->mapping != mapping)
 349                return 0;
 350
 351        if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
 352                return 0;
 353
 354        spin_lock_irq(&mapping->tree_lock);
 355        if (PageDirty(page))
 356                goto failed;
 357
 358        clear_page_mlock(page);
 359        BUG_ON(PagePrivate(page));
 360        __remove_from_page_cache(page);
 361        spin_unlock_irq(&mapping->tree_lock);
 362        page_cache_release(page);       /* pagecache ref */
 363        return 1;
 364failed:
 365        spin_unlock_irq(&mapping->tree_lock);
 366        return 0;
 367}
 368
 369static int do_launder_page(struct address_space *mapping, struct page *page)
 370{
 371        if (!PageDirty(page))
 372                return 0;
 373        if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
 374                return 0;
 375        return mapping->a_ops->launder_page(page);
 376}
 377
 378/**
 379 * invalidate_inode_pages2_range - remove range of pages from an address_space
 380 * @mapping: the address_space
 381 * @start: the page offset 'from' which to invalidate
 382 * @end: the page offset 'to' which to invalidate (inclusive)
 383 *
 384 * Any pages which are found to be mapped into pagetables are unmapped prior to
 385 * invalidation.
 386 *
 387 * Returns -EBUSY if any pages could not be invalidated.
 388 */
 389int invalidate_inode_pages2_range(struct address_space *mapping,
 390                                  pgoff_t start, pgoff_t end)
 391{
 392        struct pagevec pvec;
 393        pgoff_t next;
 394        int i;
 395        int ret = 0;
 396        int ret2 = 0;
 397        int did_range_unmap = 0;
 398        int wrapped = 0;
 399
 400        pagevec_init(&pvec, 0);
 401        next = start;
 402        while (next <= end && !wrapped &&
 403                pagevec_lookup(&pvec, mapping, next,
 404                        min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 405                for (i = 0; i < pagevec_count(&pvec); i++) {
 406                        struct page *page = pvec.pages[i];
 407                        pgoff_t page_index;
 408
 409                        lock_page(page);
 410                        if (page->mapping != mapping) {
 411                                unlock_page(page);
 412                                continue;
 413                        }
 414                        page_index = page->index;
 415                        next = page_index + 1;
 416                        if (next == 0)
 417                                wrapped = 1;
 418                        if (page_index > end) {
 419                                unlock_page(page);
 420                                break;
 421                        }
 422                        wait_on_page_writeback(page);
 423                        if (page_mapped(page)) {
 424                                if (!did_range_unmap) {
 425                                        /*
 426                                         * Zap the rest of the file in one hit.
 427                                         */
 428                                        unmap_mapping_range(mapping,
 429                                           (loff_t)page_index<<PAGE_CACHE_SHIFT,
 430                                           (loff_t)(end - page_index + 1)
 431                                                        << PAGE_CACHE_SHIFT,
 432                                            0);
 433                                        did_range_unmap = 1;
 434                                } else {
 435                                        /*
 436                                         * Just zap this page
 437                                         */
 438                                        unmap_mapping_range(mapping,
 439                                          (loff_t)page_index<<PAGE_CACHE_SHIFT,
 440                                          PAGE_CACHE_SIZE, 0);
 441                                }
 442                        }
 443                        BUG_ON(page_mapped(page));
 444                        ret2 = do_launder_page(mapping, page);
 445                        if (ret2 == 0) {
 446                                if (!invalidate_complete_page2(mapping, page))
 447                                        ret2 = -EBUSY;
 448                        }
 449                        if (ret2 < 0)
 450                                ret = ret2;
 451                        unlock_page(page);
 452                }
 453                pagevec_release(&pvec);
 454                cond_resched();
 455        }
 456        return ret;
 457}
 458EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
 459
 460/**
 461 * invalidate_inode_pages2 - remove all pages from an address_space
 462 * @mapping: the address_space
 463 *
 464 * Any pages which are found to be mapped into pagetables are unmapped prior to
 465 * invalidation.
 466 *
 467 * Returns -EIO if any pages could not be invalidated.
 468 */
 469int invalidate_inode_pages2(struct address_space *mapping)
 470{
 471        return invalidate_inode_pages2_range(mapping, 0, -1);
 472}
 473EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
 474