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