linux/mm/truncate.c
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   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/gfp.h>
  13#include <linux/mm.h>
  14#include <linux/swap.h>
  15#include <linux/export.h>
  16#include <linux/pagemap.h>
  17#include <linux/highmem.h>
  18#include <linux/pagevec.h>
  19#include <linux/task_io_accounting_ops.h>
  20#include <linux/buffer_head.h>  /* grr. try_to_release_page,
  21                                   do_invalidatepage */
  22#include <linux/cleancache.h>
  23#include "internal.h"
  24
  25
  26/**
  27 * do_invalidatepage - invalidate part or all of a page
  28 * @page: the page which is affected
  29 * @offset: the index of the truncation point
  30 *
  31 * do_invalidatepage() is called when all or part of the page has become
  32 * invalidated by a truncate operation.
  33 *
  34 * do_invalidatepage() does not have to release all buffers, but it must
  35 * ensure that no dirty buffer is left outside @offset and that no I/O
  36 * is underway against any of the blocks which are outside the truncation
  37 * point.  Because the caller is about to free (and possibly reuse) those
  38 * blocks on-disk.
  39 */
  40void do_invalidatepage(struct page *page, unsigned long offset)
  41{
  42        void (*invalidatepage)(struct page *, unsigned long);
  43        invalidatepage = page->mapping->a_ops->invalidatepage;
  44#ifdef CONFIG_BLOCK
  45        if (!invalidatepage)
  46                invalidatepage = block_invalidatepage;
  47#endif
  48        if (invalidatepage)
  49                (*invalidatepage)(page, offset);
  50}
  51
  52static inline void truncate_partial_page(struct page *page, unsigned partial)
  53{
  54        zero_user_segment(page, partial, PAGE_CACHE_SIZE);
  55        cleancache_invalidate_page(page->mapping, page);
  56        if (page_has_private(page))
  57                do_invalidatepage(page, partial);
  58}
  59
  60/*
  61 * This cancels just the dirty bit on the kernel page itself, it
  62 * does NOT actually remove dirty bits on any mmap's that may be
  63 * around. It also leaves the page tagged dirty, so any sync
  64 * activity will still find it on the dirty lists, and in particular,
  65 * clear_page_dirty_for_io() will still look at the dirty bits in
  66 * the VM.
  67 *
  68 * Doing this should *normally* only ever be done when a page
  69 * is truncated, and is not actually mapped anywhere at all. However,
  70 * fs/buffer.c does this when it notices that somebody has cleaned
  71 * out all the buffers on a page without actually doing it through
  72 * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
  73 */
  74void cancel_dirty_page(struct page *page, unsigned int account_size)
  75{
  76        if (TestClearPageDirty(page)) {
  77                struct address_space *mapping = page->mapping;
  78                if (mapping && mapping_cap_account_dirty(mapping)) {
  79                        dec_zone_page_state(page, NR_FILE_DIRTY);
  80                        dec_bdi_stat(mapping->backing_dev_info,
  81                                        BDI_RECLAIMABLE);
  82                        if (account_size)
  83                                task_io_account_cancelled_write(account_size);
  84                }
  85        }
  86}
  87EXPORT_SYMBOL(cancel_dirty_page);
  88
  89/*
  90 * If truncate cannot remove the fs-private metadata from the page, the page
  91 * becomes orphaned.  It will be left on the LRU and may even be mapped into
  92 * user pagetables if we're racing with filemap_fault().
  93 *
  94 * We need to bale out if page->mapping is no longer equal to the original
  95 * mapping.  This happens a) when the VM reclaimed the page while we waited on
  96 * its lock, b) when a concurrent invalidate_mapping_pages got there first and
  97 * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
  98 */
  99static int
 100truncate_complete_page(struct address_space *mapping, struct page *page)
 101{
 102        if (page->mapping != mapping)
 103                return -EIO;
 104
 105        if (page_has_private(page))
 106                do_invalidatepage(page, 0);
 107
 108        cancel_dirty_page(page, PAGE_CACHE_SIZE);
 109
 110        clear_page_mlock(page);
 111        ClearPageMappedToDisk(page);
 112        delete_from_page_cache(page);
 113        return 0;
 114}
 115
 116/*
 117 * This is for invalidate_mapping_pages().  That function can be called at
 118 * any time, and is not supposed to throw away dirty pages.  But pages can
 119 * be marked dirty at any time too, so use remove_mapping which safely
 120 * discards clean, unused pages.
 121 *
 122 * Returns non-zero if the page was successfully invalidated.
 123 */
 124static int
 125invalidate_complete_page(struct address_space *mapping, struct page *page)
 126{
 127        int ret;
 128
 129        if (page->mapping != mapping)
 130                return 0;
 131
 132        if (page_has_private(page) && !try_to_release_page(page, 0))
 133                return 0;
 134
 135        clear_page_mlock(page);
 136        ret = remove_mapping(mapping, page);
 137
 138        return ret;
 139}
 140
 141int truncate_inode_page(struct address_space *mapping, struct page *page)
 142{
 143        if (page_mapped(page)) {
 144                unmap_mapping_range(mapping,
 145                                   (loff_t)page->index << PAGE_CACHE_SHIFT,
 146                                   PAGE_CACHE_SIZE, 0);
 147        }
 148        return truncate_complete_page(mapping, page);
 149}
 150
 151/*
 152 * Used to get rid of pages on hardware memory corruption.
 153 */
 154int generic_error_remove_page(struct address_space *mapping, struct page *page)
 155{
 156        if (!mapping)
 157                return -EINVAL;
 158        /*
 159         * Only punch for normal data pages for now.
 160         * Handling other types like directories would need more auditing.
 161         */
 162        if (!S_ISREG(mapping->host->i_mode))
 163                return -EIO;
 164        return truncate_inode_page(mapping, page);
 165}
 166EXPORT_SYMBOL(generic_error_remove_page);
 167
 168/*
 169 * Safely invalidate one page from its pagecache mapping.
 170 * It only drops clean, unused pages. The page must be locked.
 171 *
 172 * Returns 1 if the page is successfully invalidated, otherwise 0.
 173 */
 174int invalidate_inode_page(struct page *page)
 175{
 176        struct address_space *mapping = page_mapping(page);
 177        if (!mapping)
 178                return 0;
 179        if (PageDirty(page) || PageWriteback(page))
 180                return 0;
 181        if (page_mapped(page))
 182                return 0;
 183        return invalidate_complete_page(mapping, page);
 184}
 185
 186/**
 187 * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
 188 * @mapping: mapping to truncate
 189 * @lstart: offset from which to truncate
 190 * @lend: offset to which to truncate
 191 *
 192 * Truncate the page cache, removing the pages that are between
 193 * specified offsets (and zeroing out partial page
 194 * (if lstart is not page aligned)).
 195 *
 196 * Truncate takes two passes - the first pass is nonblocking.  It will not
 197 * block on page locks and it will not block on writeback.  The second pass
 198 * will wait.  This is to prevent as much IO as possible in the affected region.
 199 * The first pass will remove most pages, so the search cost of the second pass
 200 * is low.
 201 *
 202 * We pass down the cache-hot hint to the page freeing code.  Even if the
 203 * mapping is large, it is probably the case that the final pages are the most
 204 * recently touched, and freeing happens in ascending file offset order.
 205 */
 206void truncate_inode_pages_range(struct address_space *mapping,
 207                                loff_t lstart, loff_t lend)
 208{
 209        const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
 210        const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
 211        struct pagevec pvec;
 212        pgoff_t index;
 213        pgoff_t end;
 214        int i;
 215
 216        cleancache_invalidate_inode(mapping);
 217        if (mapping->nrpages == 0)
 218                return;
 219
 220        BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
 221        end = (lend >> PAGE_CACHE_SHIFT);
 222
 223        pagevec_init(&pvec, 0);
 224        index = start;
 225        while (index <= end && pagevec_lookup(&pvec, mapping, index,
 226                        min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 227                mem_cgroup_uncharge_start();
 228                for (i = 0; i < pagevec_count(&pvec); i++) {
 229                        struct page *page = pvec.pages[i];
 230
 231                        /* We rely upon deletion not changing page->index */
 232                        index = page->index;
 233                        if (index > end)
 234                                break;
 235
 236                        if (!trylock_page(page))
 237                                continue;
 238                        WARN_ON(page->index != index);
 239                        if (PageWriteback(page)) {
 240                                unlock_page(page);
 241                                continue;
 242                        }
 243                        truncate_inode_page(mapping, page);
 244                        unlock_page(page);
 245                }
 246                pagevec_release(&pvec);
 247                mem_cgroup_uncharge_end();
 248                cond_resched();
 249                index++;
 250        }
 251
 252        if (partial) {
 253                struct page *page = find_lock_page(mapping, start - 1);
 254                if (page) {
 255                        wait_on_page_writeback(page);
 256                        truncate_partial_page(page, partial);
 257                        unlock_page(page);
 258                        page_cache_release(page);
 259                }
 260        }
 261
 262        index = start;
 263        for ( ; ; ) {
 264                cond_resched();
 265                if (!pagevec_lookup(&pvec, mapping, index,
 266                        min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 267                        if (index == start)
 268                                break;
 269                        index = start;
 270                        continue;
 271                }
 272                if (index == start && pvec.pages[0]->index > end) {
 273                        pagevec_release(&pvec);
 274                        break;
 275                }
 276                mem_cgroup_uncharge_start();
 277                for (i = 0; i < pagevec_count(&pvec); i++) {
 278                        struct page *page = pvec.pages[i];
 279
 280                        /* We rely upon deletion not changing page->index */
 281                        index = page->index;
 282                        if (index > end)
 283                                break;
 284
 285                        lock_page(page);
 286                        WARN_ON(page->index != index);
 287                        wait_on_page_writeback(page);
 288                        truncate_inode_page(mapping, page);
 289                        unlock_page(page);
 290                }
 291                pagevec_release(&pvec);
 292                mem_cgroup_uncharge_end();
 293                index++;
 294        }
 295        cleancache_invalidate_inode(mapping);
 296}
 297EXPORT_SYMBOL(truncate_inode_pages_range);
 298
 299/**
 300 * truncate_inode_pages - truncate *all* the pages from an offset
 301 * @mapping: mapping to truncate
 302 * @lstart: offset from which to truncate
 303 *
 304 * Called under (and serialised by) inode->i_mutex.
 305 *
 306 * Note: When this function returns, there can be a page in the process of
 307 * deletion (inside __delete_from_page_cache()) in the specified range.  Thus
 308 * mapping->nrpages can be non-zero when this function returns even after
 309 * truncation of the whole mapping.
 310 */
 311void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
 312{
 313        truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
 314}
 315EXPORT_SYMBOL(truncate_inode_pages);
 316
 317/**
 318 * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
 319 * @mapping: the address_space which holds the pages to invalidate
 320 * @start: the offset 'from' which to invalidate
 321 * @end: the offset 'to' which to invalidate (inclusive)
 322 *
 323 * This function only removes the unlocked pages, if you want to
 324 * remove all the pages of one inode, you must call truncate_inode_pages.
 325 *
 326 * invalidate_mapping_pages() will not block on IO activity. It will not
 327 * invalidate pages which are dirty, locked, under writeback or mapped into
 328 * pagetables.
 329 */
 330unsigned long invalidate_mapping_pages(struct address_space *mapping,
 331                pgoff_t start, pgoff_t end)
 332{
 333        struct pagevec pvec;
 334        pgoff_t index = start;
 335        unsigned long ret;
 336        unsigned long count = 0;
 337        int i;
 338
 339        /*
 340         * Note: this function may get called on a shmem/tmpfs mapping:
 341         * pagevec_lookup() might then return 0 prematurely (because it
 342         * got a gangful of swap entries); but it's hardly worth worrying
 343         * about - it can rarely have anything to free from such a mapping
 344         * (most pages are dirty), and already skips over any difficulties.
 345         */
 346
 347        pagevec_init(&pvec, 0);
 348        while (index <= end && pagevec_lookup(&pvec, mapping, index,
 349                        min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 350                mem_cgroup_uncharge_start();
 351                for (i = 0; i < pagevec_count(&pvec); i++) {
 352                        struct page *page = pvec.pages[i];
 353
 354                        /* We rely upon deletion not changing page->index */
 355                        index = page->index;
 356                        if (index > end)
 357                                break;
 358
 359                        if (!trylock_page(page))
 360                                continue;
 361                        WARN_ON(page->index != index);
 362                        ret = invalidate_inode_page(page);
 363                        unlock_page(page);
 364                        /*
 365                         * Invalidation is a hint that the page is no longer
 366                         * of interest and try to speed up its reclaim.
 367                         */
 368                        if (!ret)
 369                                deactivate_page(page);
 370                        count += ret;
 371                }
 372                pagevec_release(&pvec);
 373                mem_cgroup_uncharge_end();
 374                cond_resched();
 375                index++;
 376        }
 377        return count;
 378}
 379EXPORT_SYMBOL(invalidate_mapping_pages);
 380
 381/*
 382 * This is like invalidate_complete_page(), except it ignores the page's
 383 * refcount.  We do this because invalidate_inode_pages2() needs stronger
 384 * invalidation guarantees, and cannot afford to leave pages behind because
 385 * shrink_page_list() has a temp ref on them, or because they're transiently
 386 * sitting in the lru_cache_add() pagevecs.
 387 */
 388static int
 389invalidate_complete_page2(struct address_space *mapping, struct page *page)
 390{
 391        if (page->mapping != mapping)
 392                return 0;
 393
 394        if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
 395                return 0;
 396
 397        clear_page_mlock(page);
 398
 399        spin_lock_irq(&mapping->tree_lock);
 400        if (PageDirty(page))
 401                goto failed;
 402
 403        BUG_ON(page_has_private(page));
 404        __delete_from_page_cache(page);
 405        spin_unlock_irq(&mapping->tree_lock);
 406        mem_cgroup_uncharge_cache_page(page);
 407
 408        if (mapping->a_ops->freepage)
 409                mapping->a_ops->freepage(page);
 410
 411        page_cache_release(page);       /* pagecache ref */
 412        return 1;
 413failed:
 414        spin_unlock_irq(&mapping->tree_lock);
 415        return 0;
 416}
 417
 418static int do_launder_page(struct address_space *mapping, struct page *page)
 419{
 420        if (!PageDirty(page))
 421                return 0;
 422        if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
 423                return 0;
 424        return mapping->a_ops->launder_page(page);
 425}
 426
 427/**
 428 * invalidate_inode_pages2_range - remove range of pages from an address_space
 429 * @mapping: the address_space
 430 * @start: the page offset 'from' which to invalidate
 431 * @end: the page offset 'to' which to invalidate (inclusive)
 432 *
 433 * Any pages which are found to be mapped into pagetables are unmapped prior to
 434 * invalidation.
 435 *
 436 * Returns -EBUSY if any pages could not be invalidated.
 437 */
 438int invalidate_inode_pages2_range(struct address_space *mapping,
 439                                  pgoff_t start, pgoff_t end)
 440{
 441        struct pagevec pvec;
 442        pgoff_t index;
 443        int i;
 444        int ret = 0;
 445        int ret2 = 0;
 446        int did_range_unmap = 0;
 447
 448        cleancache_invalidate_inode(mapping);
 449        pagevec_init(&pvec, 0);
 450        index = start;
 451        while (index <= end && pagevec_lookup(&pvec, mapping, index,
 452                        min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
 453                mem_cgroup_uncharge_start();
 454                for (i = 0; i < pagevec_count(&pvec); i++) {
 455                        struct page *page = pvec.pages[i];
 456
 457                        /* We rely upon deletion not changing page->index */
 458                        index = page->index;
 459                        if (index > end)
 460                                break;
 461
 462                        lock_page(page);
 463                        WARN_ON(page->index != index);
 464                        if (page->mapping != mapping) {
 465                                unlock_page(page);
 466                                continue;
 467                        }
 468                        wait_on_page_writeback(page);
 469                        if (page_mapped(page)) {
 470                                if (!did_range_unmap) {
 471                                        /*
 472                                         * Zap the rest of the file in one hit.
 473                                         */
 474                                        unmap_mapping_range(mapping,
 475                                           (loff_t)index << PAGE_CACHE_SHIFT,
 476                                           (loff_t)(1 + end - index)
 477                                                         << PAGE_CACHE_SHIFT,
 478                                            0);
 479                                        did_range_unmap = 1;
 480                                } else {
 481                                        /*
 482                                         * Just zap this page
 483                                         */
 484                                        unmap_mapping_range(mapping,
 485                                           (loff_t)index << PAGE_CACHE_SHIFT,
 486                                           PAGE_CACHE_SIZE, 0);
 487                                }
 488                        }
 489                        BUG_ON(page_mapped(page));
 490                        ret2 = do_launder_page(mapping, page);
 491                        if (ret2 == 0) {
 492                                if (!invalidate_complete_page2(mapping, page))
 493                                        ret2 = -EBUSY;
 494                        }
 495                        if (ret2 < 0)
 496                                ret = ret2;
 497                        unlock_page(page);
 498                }
 499                pagevec_release(&pvec);
 500                mem_cgroup_uncharge_end();
 501                cond_resched();
 502                index++;
 503        }
 504        cleancache_invalidate_inode(mapping);
 505        return ret;
 506}
 507EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
 508
 509/**
 510 * invalidate_inode_pages2 - remove all pages from an address_space
 511 * @mapping: the address_space
 512 *
 513 * Any pages which are found to be mapped into pagetables are unmapped prior to
 514 * invalidation.
 515 *
 516 * Returns -EBUSY if any pages could not be invalidated.
 517 */
 518int invalidate_inode_pages2(struct address_space *mapping)
 519{
 520        return invalidate_inode_pages2_range(mapping, 0, -1);
 521}
 522EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
 523
 524/**
 525 * truncate_pagecache - unmap and remove pagecache that has been truncated
 526 * @inode: inode
 527 * @oldsize: old file size
 528 * @newsize: new file size
 529 *
 530 * inode's new i_size must already be written before truncate_pagecache
 531 * is called.
 532 *
 533 * This function should typically be called before the filesystem
 534 * releases resources associated with the freed range (eg. deallocates
 535 * blocks). This way, pagecache will always stay logically coherent
 536 * with on-disk format, and the filesystem would not have to deal with
 537 * situations such as writepage being called for a page that has already
 538 * had its underlying blocks deallocated.
 539 */
 540void truncate_pagecache(struct inode *inode, loff_t oldsize, loff_t newsize)
 541{
 542        struct address_space *mapping = inode->i_mapping;
 543        loff_t holebegin = round_up(newsize, PAGE_SIZE);
 544
 545        /*
 546         * unmap_mapping_range is called twice, first simply for
 547         * efficiency so that truncate_inode_pages does fewer
 548         * single-page unmaps.  However after this first call, and
 549         * before truncate_inode_pages finishes, it is possible for
 550         * private pages to be COWed, which remain after
 551         * truncate_inode_pages finishes, hence the second
 552         * unmap_mapping_range call must be made for correctness.
 553         */
 554        unmap_mapping_range(mapping, holebegin, 0, 1);
 555        truncate_inode_pages(mapping, newsize);
 556        unmap_mapping_range(mapping, holebegin, 0, 1);
 557}
 558EXPORT_SYMBOL(truncate_pagecache);
 559
 560/**
 561 * truncate_setsize - update inode and pagecache for a new file size
 562 * @inode: inode
 563 * @newsize: new file size
 564 *
 565 * truncate_setsize updates i_size and performs pagecache truncation (if
 566 * necessary) to @newsize. It will be typically be called from the filesystem's
 567 * setattr function when ATTR_SIZE is passed in.
 568 *
 569 * Must be called with inode_mutex held and before all filesystem specific
 570 * block truncation has been performed.
 571 */
 572void truncate_setsize(struct inode *inode, loff_t newsize)
 573{
 574        loff_t oldsize;
 575
 576        oldsize = inode->i_size;
 577        i_size_write(inode, newsize);
 578
 579        truncate_pagecache(inode, oldsize, newsize);
 580}
 581EXPORT_SYMBOL(truncate_setsize);
 582
 583/**
 584 * vmtruncate - unmap mappings "freed" by truncate() syscall
 585 * @inode: inode of the file used
 586 * @newsize: file offset to start truncating
 587 *
 588 * This function is deprecated and truncate_setsize or truncate_pagecache
 589 * should be used instead, together with filesystem specific block truncation.
 590 */
 591int vmtruncate(struct inode *inode, loff_t newsize)
 592{
 593        int error;
 594
 595        error = inode_newsize_ok(inode, newsize);
 596        if (error)
 597                return error;
 598
 599        truncate_setsize(inode, newsize);
 600        if (inode->i_op->truncate)
 601                inode->i_op->truncate(inode);
 602        return 0;
 603}
 604EXPORT_SYMBOL(vmtruncate);
 605
 606/**
 607 * truncate_pagecache_range - unmap and remove pagecache that is hole-punched
 608 * @inode: inode
 609 * @lstart: offset of beginning of hole
 610 * @lend: offset of last byte of hole
 611 *
 612 * This function should typically be called before the filesystem
 613 * releases resources associated with the freed range (eg. deallocates
 614 * blocks). This way, pagecache will always stay logically coherent
 615 * with on-disk format, and the filesystem would not have to deal with
 616 * situations such as writepage being called for a page that has already
 617 * had its underlying blocks deallocated.
 618 */
 619void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
 620{
 621        struct address_space *mapping = inode->i_mapping;
 622        loff_t unmap_start = round_up(lstart, PAGE_SIZE);
 623        loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
 624        /*
 625         * This rounding is currently just for example: unmap_mapping_range
 626         * expands its hole outwards, whereas we want it to contract the hole
 627         * inwards.  However, existing callers of truncate_pagecache_range are
 628         * doing their own page rounding first; and truncate_inode_pages_range
 629         * currently BUGs if lend is not pagealigned-1 (it handles partial
 630         * page at start of hole, but not partial page at end of hole).  Note
 631         * unmap_mapping_range allows holelen 0 for all, and we allow lend -1.
 632         */
 633
 634        /*
 635         * Unlike in truncate_pagecache, unmap_mapping_range is called only
 636         * once (before truncating pagecache), and without "even_cows" flag:
 637         * hole-punching should not remove private COWed pages from the hole.
 638         */
 639        if ((u64)unmap_end > (u64)unmap_start)
 640                unmap_mapping_range(mapping, unmap_start,
 641                                    1 + unmap_end - unmap_start, 0);
 642        truncate_inode_pages_range(mapping, lstart, lend);
 643}
 644EXPORT_SYMBOL(truncate_pagecache_range);
 645
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