linux/mm/filemap.c
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   1/*
   2 *      linux/mm/filemap.c
   3 *
   4 * Copyright (C) 1994-1999  Linus Torvalds
   5 */
   6
   7/*
   8 * This file handles the generic file mmap semantics used by
   9 * most "normal" filesystems (but you don't /have/ to use this:
  10 * the NFS filesystem used to do this differently, for example)
  11 */
  12#include <linux/module.h>
  13#include <linux/slab.h>
  14#include <linux/compiler.h>
  15#include <linux/fs.h>
  16#include <linux/uaccess.h>
  17#include <linux/aio.h>
  18#include <linux/capability.h>
  19#include <linux/kernel_stat.h>
  20#include <linux/mm.h>
  21#include <linux/swap.h>
  22#include <linux/mman.h>
  23#include <linux/pagemap.h>
  24#include <linux/file.h>
  25#include <linux/uio.h>
  26#include <linux/hash.h>
  27#include <linux/writeback.h>
  28#include <linux/backing-dev.h>
  29#include <linux/pagevec.h>
  30#include <linux/blkdev.h>
  31#include <linux/security.h>
  32#include <linux/syscalls.h>
  33#include <linux/cpuset.h>
  34#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
  35#include <linux/memcontrol.h>
  36#include <linux/mm_inline.h> /* for page_is_file_cache() */
  37#include "internal.h"
  38
  39/*
  40 * FIXME: remove all knowledge of the buffer layer from the core VM
  41 */
  42#include <linux/buffer_head.h> /* for generic_osync_inode */
  43
  44#include <asm/mman.h>
  45
  46
  47/*
  48 * Shared mappings implemented 30.11.1994. It's not fully working yet,
  49 * though.
  50 *
  51 * Shared mappings now work. 15.8.1995  Bruno.
  52 *
  53 * finished 'unifying' the page and buffer cache and SMP-threaded the
  54 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
  55 *
  56 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
  57 */
  58
  59/*
  60 * Lock ordering:
  61 *
  62 *  ->i_mmap_lock               (vmtruncate)
  63 *    ->private_lock            (__free_pte->__set_page_dirty_buffers)
  64 *      ->swap_lock             (exclusive_swap_page, others)
  65 *        ->mapping->tree_lock
  66 *
  67 *  ->i_mutex
  68 *    ->i_mmap_lock             (truncate->unmap_mapping_range)
  69 *
  70 *  ->mmap_sem
  71 *    ->i_mmap_lock
  72 *      ->page_table_lock or pte_lock   (various, mainly in memory.c)
  73 *        ->mapping->tree_lock  (arch-dependent flush_dcache_mmap_lock)
  74 *
  75 *  ->mmap_sem
  76 *    ->lock_page               (access_process_vm)
  77 *
  78 *  ->i_mutex                   (generic_file_buffered_write)
  79 *    ->mmap_sem                (fault_in_pages_readable->do_page_fault)
  80 *
  81 *  ->i_mutex
  82 *    ->i_alloc_sem             (various)
  83 *
  84 *  ->inode_lock
  85 *    ->sb_lock                 (fs/fs-writeback.c)
  86 *    ->mapping->tree_lock      (__sync_single_inode)
  87 *
  88 *  ->i_mmap_lock
  89 *    ->anon_vma.lock           (vma_adjust)
  90 *
  91 *  ->anon_vma.lock
  92 *    ->page_table_lock or pte_lock     (anon_vma_prepare and various)
  93 *
  94 *  ->page_table_lock or pte_lock
  95 *    ->swap_lock               (try_to_unmap_one)
  96 *    ->private_lock            (try_to_unmap_one)
  97 *    ->tree_lock               (try_to_unmap_one)
  98 *    ->zone.lru_lock           (follow_page->mark_page_accessed)
  99 *    ->zone.lru_lock           (check_pte_range->isolate_lru_page)
 100 *    ->private_lock            (page_remove_rmap->set_page_dirty)
 101 *    ->tree_lock               (page_remove_rmap->set_page_dirty)
 102 *    ->inode_lock              (page_remove_rmap->set_page_dirty)
 103 *    ->inode_lock              (zap_pte_range->set_page_dirty)
 104 *    ->private_lock            (zap_pte_range->__set_page_dirty_buffers)
 105 *
 106 *  ->task->proc_lock
 107 *    ->dcache_lock             (proc_pid_lookup)
 108 */
 109
 110/*
 111 * Remove a page from the page cache and free it. Caller has to make
 112 * sure the page is locked and that nobody else uses it - or that usage
 113 * is safe.  The caller must hold the mapping's tree_lock.
 114 */
 115void __remove_from_page_cache(struct page *page)
 116{
 117        struct address_space *mapping = page->mapping;
 118
 119        radix_tree_delete(&mapping->page_tree, page->index);
 120        page->mapping = NULL;
 121        mapping->nrpages--;
 122        __dec_zone_page_state(page, NR_FILE_PAGES);
 123        BUG_ON(page_mapped(page));
 124        mem_cgroup_uncharge_cache_page(page);
 125
 126        /*
 127         * Some filesystems seem to re-dirty the page even after
 128         * the VM has canceled the dirty bit (eg ext3 journaling).
 129         *
 130         * Fix it up by doing a final dirty accounting check after
 131         * having removed the page entirely.
 132         */
 133        if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
 134                dec_zone_page_state(page, NR_FILE_DIRTY);
 135                dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
 136        }
 137}
 138
 139void remove_from_page_cache(struct page *page)
 140{
 141        struct address_space *mapping = page->mapping;
 142
 143        BUG_ON(!PageLocked(page));
 144
 145        spin_lock_irq(&mapping->tree_lock);
 146        __remove_from_page_cache(page);
 147        spin_unlock_irq(&mapping->tree_lock);
 148}
 149
 150static int sync_page(void *word)
 151{
 152        struct address_space *mapping;
 153        struct page *page;
 154
 155        page = container_of((unsigned long *)word, struct page, flags);
 156
 157        /*
 158         * page_mapping() is being called without PG_locked held.
 159         * Some knowledge of the state and use of the page is used to
 160         * reduce the requirements down to a memory barrier.
 161         * The danger here is of a stale page_mapping() return value
 162         * indicating a struct address_space different from the one it's
 163         * associated with when it is associated with one.
 164         * After smp_mb(), it's either the correct page_mapping() for
 165         * the page, or an old page_mapping() and the page's own
 166         * page_mapping() has gone NULL.
 167         * The ->sync_page() address_space operation must tolerate
 168         * page_mapping() going NULL. By an amazing coincidence,
 169         * this comes about because none of the users of the page
 170         * in the ->sync_page() methods make essential use of the
 171         * page_mapping(), merely passing the page down to the backing
 172         * device's unplug functions when it's non-NULL, which in turn
 173         * ignore it for all cases but swap, where only page_private(page) is
 174         * of interest. When page_mapping() does go NULL, the entire
 175         * call stack gracefully ignores the page and returns.
 176         * -- wli
 177         */
 178        smp_mb();
 179        mapping = page_mapping(page);
 180        if (mapping && mapping->a_ops && mapping->a_ops->sync_page)
 181                mapping->a_ops->sync_page(page);
 182        io_schedule();
 183        return 0;
 184}
 185
 186static int sync_page_killable(void *word)
 187{
 188        sync_page(word);
 189        return fatal_signal_pending(current) ? -EINTR : 0;
 190}
 191
 192/**
 193 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
 194 * @mapping:    address space structure to write
 195 * @start:      offset in bytes where the range starts
 196 * @end:        offset in bytes where the range ends (inclusive)
 197 * @sync_mode:  enable synchronous operation
 198 *
 199 * Start writeback against all of a mapping's dirty pages that lie
 200 * within the byte offsets <start, end> inclusive.
 201 *
 202 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
 203 * opposed to a regular memory cleansing writeback.  The difference between
 204 * these two operations is that if a dirty page/buffer is encountered, it must
 205 * be waited upon, and not just skipped over.
 206 */
 207int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 208                                loff_t end, int sync_mode)
 209{
 210        int ret;
 211        struct writeback_control wbc = {
 212                .sync_mode = sync_mode,
 213                .nr_to_write = mapping->nrpages * 2,
 214                .range_start = start,
 215                .range_end = end,
 216        };
 217
 218        if (!mapping_cap_writeback_dirty(mapping))
 219                return 0;
 220
 221        ret = do_writepages(mapping, &wbc);
 222        return ret;
 223}
 224
 225static inline int __filemap_fdatawrite(struct address_space *mapping,
 226        int sync_mode)
 227{
 228        return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
 229}
 230
 231int filemap_fdatawrite(struct address_space *mapping)
 232{
 233        return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
 234}
 235EXPORT_SYMBOL(filemap_fdatawrite);
 236
 237int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 238                                loff_t end)
 239{
 240        return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
 241}
 242EXPORT_SYMBOL(filemap_fdatawrite_range);
 243
 244/**
 245 * filemap_flush - mostly a non-blocking flush
 246 * @mapping:    target address_space
 247 *
 248 * This is a mostly non-blocking flush.  Not suitable for data-integrity
 249 * purposes - I/O may not be started against all dirty pages.
 250 */
 251int filemap_flush(struct address_space *mapping)
 252{
 253        return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
 254}
 255EXPORT_SYMBOL(filemap_flush);
 256
 257/**
 258 * wait_on_page_writeback_range - wait for writeback to complete
 259 * @mapping:    target address_space
 260 * @start:      beginning page index
 261 * @end:        ending page index
 262 *
 263 * Wait for writeback to complete against pages indexed by start->end
 264 * inclusive
 265 */
 266int wait_on_page_writeback_range(struct address_space *mapping,
 267                                pgoff_t start, pgoff_t end)
 268{
 269        struct pagevec pvec;
 270        int nr_pages;
 271        int ret = 0;
 272        pgoff_t index;
 273
 274        if (end < start)
 275                return 0;
 276
 277        pagevec_init(&pvec, 0);
 278        index = start;
 279        while ((index <= end) &&
 280                        (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
 281                        PAGECACHE_TAG_WRITEBACK,
 282                        min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
 283                unsigned i;
 284
 285                for (i = 0; i < nr_pages; i++) {
 286                        struct page *page = pvec.pages[i];
 287
 288                        /* until radix tree lookup accepts end_index */
 289                        if (page->index > end)
 290                                continue;
 291
 292                        wait_on_page_writeback(page);
 293                        if (PageError(page))
 294                                ret = -EIO;
 295                }
 296                pagevec_release(&pvec);
 297                cond_resched();
 298        }
 299
 300        /* Check for outstanding write errors */
 301        if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
 302                ret = -ENOSPC;
 303        if (test_and_clear_bit(AS_EIO, &mapping->flags))
 304                ret = -EIO;
 305
 306        return ret;
 307}
 308
 309/**
 310 * sync_page_range - write and wait on all pages in the passed range
 311 * @inode:      target inode
 312 * @mapping:    target address_space
 313 * @pos:        beginning offset in pages to write
 314 * @count:      number of bytes to write
 315 *
 316 * Write and wait upon all the pages in the passed range.  This is a "data
 317 * integrity" operation.  It waits upon in-flight writeout before starting and
 318 * waiting upon new writeout.  If there was an IO error, return it.
 319 *
 320 * We need to re-take i_mutex during the generic_osync_inode list walk because
 321 * it is otherwise livelockable.
 322 */
 323int sync_page_range(struct inode *inode, struct address_space *mapping,
 324                        loff_t pos, loff_t count)
 325{
 326        pgoff_t start = pos >> PAGE_CACHE_SHIFT;
 327        pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
 328        int ret;
 329
 330        if (!mapping_cap_writeback_dirty(mapping) || !count)
 331                return 0;
 332        ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
 333        if (ret == 0) {
 334                mutex_lock(&inode->i_mutex);
 335                ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
 336                mutex_unlock(&inode->i_mutex);
 337        }
 338        if (ret == 0)
 339                ret = wait_on_page_writeback_range(mapping, start, end);
 340        return ret;
 341}
 342EXPORT_SYMBOL(sync_page_range);
 343
 344/**
 345 * sync_page_range_nolock - write & wait on all pages in the passed range without locking
 346 * @inode:      target inode
 347 * @mapping:    target address_space
 348 * @pos:        beginning offset in pages to write
 349 * @count:      number of bytes to write
 350 *
 351 * Note: Holding i_mutex across sync_page_range_nolock() is not a good idea
 352 * as it forces O_SYNC writers to different parts of the same file
 353 * to be serialised right until io completion.
 354 */
 355int sync_page_range_nolock(struct inode *inode, struct address_space *mapping,
 356                           loff_t pos, loff_t count)
 357{
 358        pgoff_t start = pos >> PAGE_CACHE_SHIFT;
 359        pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
 360        int ret;
 361
 362        if (!mapping_cap_writeback_dirty(mapping) || !count)
 363                return 0;
 364        ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
 365        if (ret == 0)
 366                ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
 367        if (ret == 0)
 368                ret = wait_on_page_writeback_range(mapping, start, end);
 369        return ret;
 370}
 371EXPORT_SYMBOL(sync_page_range_nolock);
 372
 373/**
 374 * filemap_fdatawait - wait for all under-writeback pages to complete
 375 * @mapping: address space structure to wait for
 376 *
 377 * Walk the list of under-writeback pages of the given address space
 378 * and wait for all of them.
 379 */
 380int filemap_fdatawait(struct address_space *mapping)
 381{
 382        loff_t i_size = i_size_read(mapping->host);
 383
 384        if (i_size == 0)
 385                return 0;
 386
 387        return wait_on_page_writeback_range(mapping, 0,
 388                                (i_size - 1) >> PAGE_CACHE_SHIFT);
 389}
 390EXPORT_SYMBOL(filemap_fdatawait);
 391
 392int filemap_write_and_wait(struct address_space *mapping)
 393{
 394        int err = 0;
 395
 396        if (mapping->nrpages) {
 397                err = filemap_fdatawrite(mapping);
 398                /*
 399                 * Even if the above returned error, the pages may be
 400                 * written partially (e.g. -ENOSPC), so we wait for it.
 401                 * But the -EIO is special case, it may indicate the worst
 402                 * thing (e.g. bug) happened, so we avoid waiting for it.
 403                 */
 404                if (err != -EIO) {
 405                        int err2 = filemap_fdatawait(mapping);
 406                        if (!err)
 407                                err = err2;
 408                }
 409        }
 410        return err;
 411}
 412EXPORT_SYMBOL(filemap_write_and_wait);
 413
 414/**
 415 * filemap_write_and_wait_range - write out & wait on a file range
 416 * @mapping:    the address_space for the pages
 417 * @lstart:     offset in bytes where the range starts
 418 * @lend:       offset in bytes where the range ends (inclusive)
 419 *
 420 * Write out and wait upon file offsets lstart->lend, inclusive.
 421 *
 422 * Note that `lend' is inclusive (describes the last byte to be written) so
 423 * that this function can be used to write to the very end-of-file (end = -1).
 424 */
 425int filemap_write_and_wait_range(struct address_space *mapping,
 426                                 loff_t lstart, loff_t lend)
 427{
 428        int err = 0;
 429
 430        if (mapping->nrpages) {
 431                err = __filemap_fdatawrite_range(mapping, lstart, lend,
 432                                                 WB_SYNC_ALL);
 433                /* See comment of filemap_write_and_wait() */
 434                if (err != -EIO) {
 435                        int err2 = wait_on_page_writeback_range(mapping,
 436                                                lstart >> PAGE_CACHE_SHIFT,
 437                                                lend >> PAGE_CACHE_SHIFT);
 438                        if (!err)
 439                                err = err2;
 440                }
 441        }
 442        return err;
 443}
 444
 445/**
 446 * add_to_page_cache_locked - add a locked page to the pagecache
 447 * @page:       page to add
 448 * @mapping:    the page's address_space
 449 * @offset:     page index
 450 * @gfp_mask:   page allocation mode
 451 *
 452 * This function is used to add a page to the pagecache. It must be locked.
 453 * This function does not add the page to the LRU.  The caller must do that.
 454 */
 455int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
 456                pgoff_t offset, gfp_t gfp_mask)
 457{
 458        int error;
 459
 460        VM_BUG_ON(!PageLocked(page));
 461
 462        error = mem_cgroup_cache_charge(page, current->mm,
 463                                        gfp_mask & ~__GFP_HIGHMEM);
 464        if (error)
 465                goto out;
 466
 467        error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
 468        if (error == 0) {
 469                page_cache_get(page);
 470                page->mapping = mapping;
 471                page->index = offset;
 472
 473                spin_lock_irq(&mapping->tree_lock);
 474                error = radix_tree_insert(&mapping->page_tree, offset, page);
 475                if (likely(!error)) {
 476                        mapping->nrpages++;
 477                        __inc_zone_page_state(page, NR_FILE_PAGES);
 478                } else {
 479                        page->mapping = NULL;
 480                        mem_cgroup_uncharge_cache_page(page);
 481                        page_cache_release(page);
 482                }
 483
 484                spin_unlock_irq(&mapping->tree_lock);
 485                radix_tree_preload_end();
 486        } else
 487                mem_cgroup_uncharge_cache_page(page);
 488out:
 489        return error;
 490}
 491EXPORT_SYMBOL(add_to_page_cache_locked);
 492
 493int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 494                                pgoff_t offset, gfp_t gfp_mask)
 495{
 496        int ret;
 497
 498        /*
 499         * Splice_read and readahead add shmem/tmpfs pages into the page cache
 500         * before shmem_readpage has a chance to mark them as SwapBacked: they
 501         * need to go on the active_anon lru below, and mem_cgroup_cache_charge
 502         * (called in add_to_page_cache) needs to know where they're going too.
 503         */
 504        if (mapping_cap_swap_backed(mapping))
 505                SetPageSwapBacked(page);
 506
 507        ret = add_to_page_cache(page, mapping, offset, gfp_mask);
 508        if (ret == 0) {
 509                if (page_is_file_cache(page))
 510                        lru_cache_add_file(page);
 511                else
 512                        lru_cache_add_active_anon(page);
 513        }
 514        return ret;
 515}
 516
 517#ifdef CONFIG_NUMA
 518struct page *__page_cache_alloc(gfp_t gfp)
 519{
 520        if (cpuset_do_page_mem_spread()) {
 521                int n = cpuset_mem_spread_node();
 522                return alloc_pages_node(n, gfp, 0);
 523        }
 524        return alloc_pages(gfp, 0);
 525}
 526EXPORT_SYMBOL(__page_cache_alloc);
 527#endif
 528
 529static int __sleep_on_page_lock(void *word)
 530{
 531        io_schedule();
 532        return 0;
 533}
 534
 535/*
 536 * In order to wait for pages to become available there must be
 537 * waitqueues associated with pages. By using a hash table of
 538 * waitqueues where the bucket discipline is to maintain all
 539 * waiters on the same queue and wake all when any of the pages
 540 * become available, and for the woken contexts to check to be
 541 * sure the appropriate page became available, this saves space
 542 * at a cost of "thundering herd" phenomena during rare hash
 543 * collisions.
 544 */
 545static wait_queue_head_t *page_waitqueue(struct page *page)
 546{
 547        const struct zone *zone = page_zone(page);
 548
 549        return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
 550}
 551
 552static inline void wake_up_page(struct page *page, int bit)
 553{
 554        __wake_up_bit(page_waitqueue(page), &page->flags, bit);
 555}
 556
 557void wait_on_page_bit(struct page *page, int bit_nr)
 558{
 559        DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
 560
 561        if (test_bit(bit_nr, &page->flags))
 562                __wait_on_bit(page_waitqueue(page), &wait, sync_page,
 563                                                        TASK_UNINTERRUPTIBLE);
 564}
 565EXPORT_SYMBOL(wait_on_page_bit);
 566
 567/**
 568 * unlock_page - unlock a locked page
 569 * @page: the page
 570 *
 571 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
 572 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
 573 * mechananism between PageLocked pages and PageWriteback pages is shared.
 574 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
 575 *
 576 * The mb is necessary to enforce ordering between the clear_bit and the read
 577 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
 578 */
 579void unlock_page(struct page *page)
 580{
 581        VM_BUG_ON(!PageLocked(page));
 582        clear_bit_unlock(PG_locked, &page->flags);
 583        smp_mb__after_clear_bit();
 584        wake_up_page(page, PG_locked);
 585}
 586EXPORT_SYMBOL(unlock_page);
 587
 588/**
 589 * end_page_writeback - end writeback against a page
 590 * @page: the page
 591 */
 592void end_page_writeback(struct page *page)
 593{
 594        if (TestClearPageReclaim(page))
 595                rotate_reclaimable_page(page);
 596
 597        if (!test_clear_page_writeback(page))
 598                BUG();
 599
 600        smp_mb__after_clear_bit();
 601        wake_up_page(page, PG_writeback);
 602}
 603EXPORT_SYMBOL(end_page_writeback);
 604
 605/**
 606 * __lock_page - get a lock on the page, assuming we need to sleep to get it
 607 * @page: the page to lock
 608 *
 609 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary.  If some
 610 * random driver's requestfn sets TASK_RUNNING, we could busywait.  However
 611 * chances are that on the second loop, the block layer's plug list is empty,
 612 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
 613 */
 614void __lock_page(struct page *page)
 615{
 616        DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 617
 618        __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page,
 619                                                        TASK_UNINTERRUPTIBLE);
 620}
 621EXPORT_SYMBOL(__lock_page);
 622
 623int __lock_page_killable(struct page *page)
 624{
 625        DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 626
 627        return __wait_on_bit_lock(page_waitqueue(page), &wait,
 628                                        sync_page_killable, TASK_KILLABLE);
 629}
 630
 631/**
 632 * __lock_page_nosync - get a lock on the page, without calling sync_page()
 633 * @page: the page to lock
 634 *
 635 * Variant of lock_page that does not require the caller to hold a reference
 636 * on the page's mapping.
 637 */
 638void __lock_page_nosync(struct page *page)
 639{
 640        DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 641        __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
 642                                                        TASK_UNINTERRUPTIBLE);
 643}
 644
 645/**
 646 * find_get_page - find and get a page reference
 647 * @mapping: the address_space to search
 648 * @offset: the page index
 649 *
 650 * Is there a pagecache struct page at the given (mapping, offset) tuple?
 651 * If yes, increment its refcount and return it; if no, return NULL.
 652 */
 653struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
 654{
 655        void **pagep;
 656        struct page *page;
 657
 658        rcu_read_lock();
 659repeat:
 660        page = NULL;
 661        pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
 662        if (pagep) {
 663                page = radix_tree_deref_slot(pagep);
 664                if (unlikely(!page || page == RADIX_TREE_RETRY))
 665                        goto repeat;
 666
 667                if (!page_cache_get_speculative(page))
 668                        goto repeat;
 669
 670                /*
 671                 * Has the page moved?
 672                 * This is part of the lockless pagecache protocol. See
 673                 * include/linux/pagemap.h for details.
 674                 */
 675                if (unlikely(page != *pagep)) {
 676                        page_cache_release(page);
 677                        goto repeat;
 678                }
 679        }
 680        rcu_read_unlock();
 681
 682        return page;
 683}
 684EXPORT_SYMBOL(find_get_page);
 685
 686/**
 687 * find_lock_page - locate, pin and lock a pagecache page
 688 * @mapping: the address_space to search
 689 * @offset: the page index
 690 *
 691 * Locates the desired pagecache page, locks it, increments its reference
 692 * count and returns its address.
 693 *
 694 * Returns zero if the page was not present. find_lock_page() may sleep.
 695 */
 696struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
 697{
 698        struct page *page;
 699
 700repeat:
 701        page = find_get_page(mapping, offset);
 702        if (page) {
 703                lock_page(page);
 704                /* Has the page been truncated? */
 705                if (unlikely(page->mapping != mapping)) {
 706                        unlock_page(page);
 707                        page_cache_release(page);
 708                        goto repeat;
 709                }
 710                VM_BUG_ON(page->index != offset);
 711        }
 712        return page;
 713}
 714EXPORT_SYMBOL(find_lock_page);
 715
 716/**
 717 * find_or_create_page - locate or add a pagecache page
 718 * @mapping: the page's address_space
 719 * @index: the page's index into the mapping
 720 * @gfp_mask: page allocation mode
 721 *
 722 * Locates a page in the pagecache.  If the page is not present, a new page
 723 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
 724 * LRU list.  The returned page is locked and has its reference count
 725 * incremented.
 726 *
 727 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
 728 * allocation!
 729 *
 730 * find_or_create_page() returns the desired page's address, or zero on
 731 * memory exhaustion.
 732 */
 733struct page *find_or_create_page(struct address_space *mapping,
 734                pgoff_t index, gfp_t gfp_mask)
 735{
 736        struct page *page;
 737        int err;
 738repeat:
 739        page = find_lock_page(mapping, index);
 740        if (!page) {
 741                page = __page_cache_alloc(gfp_mask);
 742                if (!page)
 743                        return NULL;
 744                err = add_to_page_cache_lru(page, mapping, index, gfp_mask);
 745                if (unlikely(err)) {
 746                        page_cache_release(page);
 747                        page = NULL;
 748                        if (err == -EEXIST)
 749                                goto repeat;
 750                }
 751        }
 752        return page;
 753}
 754EXPORT_SYMBOL(find_or_create_page);
 755
 756/**
 757 * find_get_pages - gang pagecache lookup
 758 * @mapping:    The address_space to search
 759 * @start:      The starting page index
 760 * @nr_pages:   The maximum number of pages
 761 * @pages:      Where the resulting pages are placed
 762 *
 763 * find_get_pages() will search for and return a group of up to
 764 * @nr_pages pages in the mapping.  The pages are placed at @pages.
 765 * find_get_pages() takes a reference against the returned pages.
 766 *
 767 * The search returns a group of mapping-contiguous pages with ascending
 768 * indexes.  There may be holes in the indices due to not-present pages.
 769 *
 770 * find_get_pages() returns the number of pages which were found.
 771 */
 772unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
 773                            unsigned int nr_pages, struct page **pages)
 774{
 775        unsigned int i;
 776        unsigned int ret;
 777        unsigned int nr_found;
 778
 779        rcu_read_lock();
 780restart:
 781        nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
 782                                (void ***)pages, start, nr_pages);
 783        ret = 0;
 784        for (i = 0; i < nr_found; i++) {
 785                struct page *page;
 786repeat:
 787                page = radix_tree_deref_slot((void **)pages[i]);
 788                if (unlikely(!page))
 789                        continue;
 790                /*
 791                 * this can only trigger if nr_found == 1, making livelock
 792                 * a non issue.
 793                 */
 794                if (unlikely(page == RADIX_TREE_RETRY))
 795                        goto restart;
 796
 797                if (!page_cache_get_speculative(page))
 798                        goto repeat;
 799
 800                /* Has the page moved? */
 801                if (unlikely(page != *((void **)pages[i]))) {
 802                        page_cache_release(page);
 803                        goto repeat;
 804                }
 805
 806                pages[ret] = page;
 807                ret++;
 808        }
 809        rcu_read_unlock();
 810        return ret;
 811}
 812
 813/**
 814 * find_get_pages_contig - gang contiguous pagecache lookup
 815 * @mapping:    The address_space to search
 816 * @index:      The starting page index
 817 * @nr_pages:   The maximum number of pages
 818 * @pages:      Where the resulting pages are placed
 819 *
 820 * find_get_pages_contig() works exactly like find_get_pages(), except
 821 * that the returned number of pages are guaranteed to be contiguous.
 822 *
 823 * find_get_pages_contig() returns the number of pages which were found.
 824 */
 825unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
 826                               unsigned int nr_pages, struct page **pages)
 827{
 828        unsigned int i;
 829        unsigned int ret;
 830        unsigned int nr_found;
 831
 832        rcu_read_lock();
 833restart:
 834        nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
 835                                (void ***)pages, index, nr_pages);
 836        ret = 0;
 837        for (i = 0; i < nr_found; i++) {
 838                struct page *page;
 839repeat:
 840                page = radix_tree_deref_slot((void **)pages[i]);
 841                if (unlikely(!page))
 842                        continue;
 843                /*
 844                 * this can only trigger if nr_found == 1, making livelock
 845                 * a non issue.
 846                 */
 847                if (unlikely(page == RADIX_TREE_RETRY))
 848                        goto restart;
 849
 850                if (page->mapping == NULL || page->index != index)
 851                        break;
 852
 853                if (!page_cache_get_speculative(page))
 854                        goto repeat;
 855
 856                /* Has the page moved? */
 857                if (unlikely(page != *((void **)pages[i]))) {
 858                        page_cache_release(page);
 859                        goto repeat;
 860                }
 861
 862                pages[ret] = page;
 863                ret++;
 864                index++;
 865        }
 866        rcu_read_unlock();
 867        return ret;
 868}
 869EXPORT_SYMBOL(find_get_pages_contig);
 870
 871/**
 872 * find_get_pages_tag - find and return pages that match @tag
 873 * @mapping:    the address_space to search
 874 * @index:      the starting page index
 875 * @tag:        the tag index
 876 * @nr_pages:   the maximum number of pages
 877 * @pages:      where the resulting pages are placed
 878 *
 879 * Like find_get_pages, except we only return pages which are tagged with
 880 * @tag.   We update @index to index the next page for the traversal.
 881 */
 882unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
 883                        int tag, unsigned int nr_pages, struct page **pages)
 884{
 885        unsigned int i;
 886        unsigned int ret;
 887        unsigned int nr_found;
 888
 889        rcu_read_lock();
 890restart:
 891        nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
 892                                (void ***)pages, *index, nr_pages, tag);
 893        ret = 0;
 894        for (i = 0; i < nr_found; i++) {
 895                struct page *page;
 896repeat:
 897                page = radix_tree_deref_slot((void **)pages[i]);
 898                if (unlikely(!page))
 899                        continue;
 900                /*
 901                 * this can only trigger if nr_found == 1, making livelock
 902                 * a non issue.
 903                 */
 904                if (unlikely(page == RADIX_TREE_RETRY))
 905                        goto restart;
 906
 907                if (!page_cache_get_speculative(page))
 908                        goto repeat;
 909
 910                /* Has the page moved? */
 911                if (unlikely(page != *((void **)pages[i]))) {
 912                        page_cache_release(page);
 913                        goto repeat;
 914                }
 915
 916                pages[ret] = page;
 917                ret++;
 918        }
 919        rcu_read_unlock();
 920
 921        if (ret)
 922                *index = pages[ret - 1]->index + 1;
 923
 924        return ret;
 925}
 926EXPORT_SYMBOL(find_get_pages_tag);
 927
 928/**
 929 * grab_cache_page_nowait - returns locked page at given index in given cache
 930 * @mapping: target address_space
 931 * @index: the page index
 932 *
 933 * Same as grab_cache_page(), but do not wait if the page is unavailable.
 934 * This is intended for speculative data generators, where the data can
 935 * be regenerated if the page couldn't be grabbed.  This routine should
 936 * be safe to call while holding the lock for another page.
 937 *
 938 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
 939 * and deadlock against the caller's locked page.
 940 */
 941struct page *
 942grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
 943{
 944        struct page *page = find_get_page(mapping, index);
 945
 946        if (page) {
 947                if (trylock_page(page))
 948                        return page;
 949                page_cache_release(page);
 950                return NULL;
 951        }
 952        page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
 953        if (page && add_to_page_cache_lru(page, mapping, index, GFP_KERNEL)) {
 954                page_cache_release(page);
 955                page = NULL;
 956        }
 957        return page;
 958}
 959EXPORT_SYMBOL(grab_cache_page_nowait);
 960
 961/*
 962 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
 963 * a _large_ part of the i/o request. Imagine the worst scenario:
 964 *
 965 *      ---R__________________________________________B__________
 966 *         ^ reading here                             ^ bad block(assume 4k)
 967 *
 968 * read(R) => miss => readahead(R...B) => media error => frustrating retries
 969 * => failing the whole request => read(R) => read(R+1) =>
 970 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
 971 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
 972 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
 973 *
 974 * It is going insane. Fix it by quickly scaling down the readahead size.
 975 */
 976static void shrink_readahead_size_eio(struct file *filp,
 977                                        struct file_ra_state *ra)
 978{
 979        if (!ra->ra_pages)
 980                return;
 981
 982        ra->ra_pages /= 4;
 983}
 984
 985/**
 986 * do_generic_file_read - generic file read routine
 987 * @filp:       the file to read
 988 * @ppos:       current file position
 989 * @desc:       read_descriptor
 990 * @actor:      read method
 991 *
 992 * This is a generic file read routine, and uses the
 993 * mapping->a_ops->readpage() function for the actual low-level stuff.
 994 *
 995 * This is really ugly. But the goto's actually try to clarify some
 996 * of the logic when it comes to error handling etc.
 997 */
 998static void do_generic_file_read(struct file *filp, loff_t *ppos,
 999                read_descriptor_t *desc, read_actor_t actor)
1000{
1001        struct address_space *mapping = filp->f_mapping;
1002        struct inode *inode = mapping->host;
1003        struct file_ra_state *ra = &filp->f_ra;
1004        pgoff_t index;
1005        pgoff_t last_index;
1006        pgoff_t prev_index;
1007        unsigned long offset;      /* offset into pagecache page */
1008        unsigned int prev_offset;
1009        int error;
1010
1011        index = *ppos >> PAGE_CACHE_SHIFT;
1012        prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1013        prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1014        last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1015        offset = *ppos & ~PAGE_CACHE_MASK;
1016
1017        for (;;) {
1018                struct page *page;
1019                pgoff_t end_index;
1020                loff_t isize;
1021                unsigned long nr, ret;
1022
1023                cond_resched();
1024find_page:
1025                page = find_get_page(mapping, index);
1026                if (!page) {
1027                        page_cache_sync_readahead(mapping,
1028                                        ra, filp,
1029                                        index, last_index - index);
1030                        page = find_get_page(mapping, index);
1031                        if (unlikely(page == NULL))
1032                                goto no_cached_page;
1033                }
1034                if (PageReadahead(page)) {
1035                        page_cache_async_readahead(mapping,
1036                                        ra, filp, page,
1037                                        index, last_index - index);
1038                }
1039                if (!PageUptodate(page)) {
1040                        if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1041                                        !mapping->a_ops->is_partially_uptodate)
1042                                goto page_not_up_to_date;
1043                        if (!trylock_page(page))
1044                                goto page_not_up_to_date;
1045                        if (!mapping->a_ops->is_partially_uptodate(page,
1046                                                                desc, offset))
1047                                goto page_not_up_to_date_locked;
1048                        unlock_page(page);
1049                }
1050page_ok:
1051                /*
1052                 * i_size must be checked after we know the page is Uptodate.
1053                 *
1054                 * Checking i_size after the check allows us to calculate
1055                 * the correct value for "nr", which means the zero-filled
1056                 * part of the page is not copied back to userspace (unless
1057                 * another truncate extends the file - this is desired though).
1058                 */
1059
1060                isize = i_size_read(inode);
1061                end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1062                if (unlikely(!isize || index > end_index)) {
1063                        page_cache_release(page);
1064                        goto out;
1065                }
1066
1067                /* nr is the maximum number of bytes to copy from this page */
1068                nr = PAGE_CACHE_SIZE;
1069                if (index == end_index) {
1070                        nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1071                        if (nr <= offset) {
1072                                page_cache_release(page);
1073                                goto out;
1074                        }
1075                }
1076                nr = nr - offset;
1077
1078                /* If users can be writing to this page using arbitrary
1079                 * virtual addresses, take care about potential aliasing
1080                 * before reading the page on the kernel side.
1081                 */
1082                if (mapping_writably_mapped(mapping))
1083                        flush_dcache_page(page);
1084
1085                /*
1086                 * When a sequential read accesses a page several times,
1087                 * only mark it as accessed the first time.
1088                 */
1089                if (prev_index != index || offset != prev_offset)
1090                        mark_page_accessed(page);
1091                prev_index = index;
1092
1093                /*
1094                 * Ok, we have the page, and it's up-to-date, so
1095                 * now we can copy it to user space...
1096                 *
1097                 * The actor routine returns how many bytes were actually used..
1098                 * NOTE! This may not be the same as how much of a user buffer
1099                 * we filled up (we may be padding etc), so we can only update
1100                 * "pos" here (the actor routine has to update the user buffer
1101                 * pointers and the remaining count).
1102                 */
1103                ret = actor(desc, page, offset, nr);
1104                offset += ret;
1105                index += offset >> PAGE_CACHE_SHIFT;
1106                offset &= ~PAGE_CACHE_MASK;
1107                prev_offset = offset;
1108
1109                page_cache_release(page);
1110                if (ret == nr && desc->count)
1111                        continue;
1112                goto out;
1113
1114page_not_up_to_date:
1115                /* Get exclusive access to the page ... */
1116                error = lock_page_killable(page);
1117                if (unlikely(error))
1118                        goto readpage_error;
1119
1120page_not_up_to_date_locked:
1121                /* Did it get truncated before we got the lock? */
1122                if (!page->mapping) {
1123                        unlock_page(page);
1124                        page_cache_release(page);
1125                        continue;
1126                }
1127
1128                /* Did somebody else fill it already? */
1129                if (PageUptodate(page)) {
1130                        unlock_page(page);
1131                        goto page_ok;
1132                }
1133
1134readpage:
1135                /* Start the actual read. The read will unlock the page. */
1136                error = mapping->a_ops->readpage(filp, page);
1137
1138                if (unlikely(error)) {
1139                        if (error == AOP_TRUNCATED_PAGE) {
1140                                page_cache_release(page);
1141                                goto find_page;
1142                        }
1143                        goto readpage_error;
1144                }
1145
1146                if (!PageUptodate(page)) {
1147                        error = lock_page_killable(page);
1148                        if (unlikely(error))
1149                                goto readpage_error;
1150                        if (!PageUptodate(page)) {
1151                                if (page->mapping == NULL) {
1152                                        /*
1153                                         * invalidate_inode_pages got it
1154                                         */
1155                                        unlock_page(page);
1156                                        page_cache_release(page);
1157                                        goto find_page;
1158                                }
1159                                unlock_page(page);
1160                                shrink_readahead_size_eio(filp, ra);
1161                                error = -EIO;
1162                                goto readpage_error;
1163                        }
1164                        unlock_page(page);
1165                }
1166
1167                goto page_ok;
1168
1169readpage_error:
1170                /* UHHUH! A synchronous read error occurred. Report it */
1171                desc->error = error;
1172                page_cache_release(page);
1173                goto out;
1174
1175no_cached_page:
1176                /*
1177                 * Ok, it wasn't cached, so we need to create a new
1178                 * page..
1179                 */
1180                page = page_cache_alloc_cold(mapping);
1181                if (!page) {
1182                        desc->error = -ENOMEM;
1183                        goto out;
1184                }
1185                error = add_to_page_cache_lru(page, mapping,
1186                                                index, GFP_KERNEL);
1187                if (error) {
1188                        page_cache_release(page);
1189                        if (error == -EEXIST)
1190                                goto find_page;
1191                        desc->error = error;
1192                        goto out;
1193                }
1194                goto readpage;
1195        }
1196
1197out:
1198        ra->prev_pos = prev_index;
1199        ra->prev_pos <<= PAGE_CACHE_SHIFT;
1200        ra->prev_pos |= prev_offset;
1201
1202        *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1203        file_accessed(filp);
1204}
1205
1206int file_read_actor(read_descriptor_t *desc, struct page *page,
1207                        unsigned long offset, unsigned long size)
1208{
1209        char *kaddr;
1210        unsigned long left, count = desc->count;
1211
1212        if (size > count)
1213                size = count;
1214
1215        /*
1216         * Faults on the destination of a read are common, so do it before
1217         * taking the kmap.
1218         */
1219        if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1220                kaddr = kmap_atomic(page, KM_USER0);
1221                left = __copy_to_user_inatomic(desc->arg.buf,
1222                                                kaddr + offset, size);
1223                kunmap_atomic(kaddr, KM_USER0);
1224                if (left == 0)
1225                        goto success;
1226        }
1227
1228        /* Do it the slow way */
1229        kaddr = kmap(page);
1230        left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1231        kunmap(page);
1232
1233        if (left) {
1234                size -= left;
1235                desc->error = -EFAULT;
1236        }
1237success:
1238        desc->count = count - size;
1239        desc->written += size;
1240        desc->arg.buf += size;
1241        return size;
1242}
1243
1244/*
1245 * Performs necessary checks before doing a write
1246 * @iov:        io vector request
1247 * @nr_segs:    number of segments in the iovec
1248 * @count:      number of bytes to write
1249 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1250 *
1251 * Adjust number of segments and amount of bytes to write (nr_segs should be
1252 * properly initialized first). Returns appropriate error code that caller
1253 * should return or zero in case that write should be allowed.
1254 */
1255int generic_segment_checks(const struct iovec *iov,
1256                        unsigned long *nr_segs, size_t *count, int access_flags)
1257{
1258        unsigned long   seg;
1259        size_t cnt = 0;
1260        for (seg = 0; seg < *nr_segs; seg++) {
1261                const struct iovec *iv = &iov[seg];
1262
1263                /*
1264                 * If any segment has a negative length, or the cumulative
1265                 * length ever wraps negative then return -EINVAL.
1266                 */
1267                cnt += iv->iov_len;
1268                if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1269                        return -EINVAL;
1270                if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1271                        continue;
1272                if (seg == 0)
1273                        return -EFAULT;
1274                *nr_segs = seg;
1275                cnt -= iv->iov_len;     /* This segment is no good */
1276                break;
1277        }
1278        *count = cnt;
1279        return 0;
1280}
1281EXPORT_SYMBOL(generic_segment_checks);
1282
1283/**
1284 * generic_file_aio_read - generic filesystem read routine
1285 * @iocb:       kernel I/O control block
1286 * @iov:        io vector request
1287 * @nr_segs:    number of segments in the iovec
1288 * @pos:        current file position
1289 *
1290 * This is the "read()" routine for all filesystems
1291 * that can use the page cache directly.
1292 */
1293ssize_t
1294generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1295                unsigned long nr_segs, loff_t pos)
1296{
1297        struct file *filp = iocb->ki_filp;
1298        ssize_t retval;
1299        unsigned long seg;
1300        size_t count;
1301        loff_t *ppos = &iocb->ki_pos;
1302
1303        count = 0;
1304        retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1305        if (retval)
1306                return retval;
1307
1308        /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1309        if (filp->f_flags & O_DIRECT) {
1310                loff_t size;
1311                struct address_space *mapping;
1312                struct inode *inode;
1313
1314                mapping = filp->f_mapping;
1315                inode = mapping->host;
1316                if (!count)
1317                        goto out; /* skip atime */
1318                size = i_size_read(inode);
1319                if (pos < size) {
1320                        retval = filemap_write_and_wait(mapping);
1321                        if (!retval) {
1322                                retval = mapping->a_ops->direct_IO(READ, iocb,
1323                                                        iov, pos, nr_segs);
1324                        }
1325                        if (retval > 0)
1326                                *ppos = pos + retval;
1327                        if (retval) {
1328                                file_accessed(filp);
1329                                goto out;
1330                        }
1331                }
1332        }
1333
1334        for (seg = 0; seg < nr_segs; seg++) {
1335                read_descriptor_t desc;
1336
1337                desc.written = 0;
1338                desc.arg.buf = iov[seg].iov_base;
1339                desc.count = iov[seg].iov_len;
1340                if (desc.count == 0)
1341                        continue;
1342                desc.error = 0;
1343                do_generic_file_read(filp, ppos, &desc, file_read_actor);
1344                retval += desc.written;
1345                if (desc.error) {
1346                        retval = retval ?: desc.error;
1347                        break;
1348                }
1349                if (desc.count > 0)
1350                        break;
1351        }
1352out:
1353        return retval;
1354}
1355EXPORT_SYMBOL(generic_file_aio_read);
1356
1357static ssize_t
1358do_readahead(struct address_space *mapping, struct file *filp,
1359             pgoff_t index, unsigned long nr)
1360{
1361        if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1362                return -EINVAL;
1363
1364        force_page_cache_readahead(mapping, filp, index,
1365                                        max_sane_readahead(nr));
1366        return 0;
1367}
1368
1369asmlinkage ssize_t sys_readahead(int fd, loff_t offset, size_t count)
1370{
1371        ssize_t ret;
1372        struct file *file;
1373
1374        ret = -EBADF;
1375        file = fget(fd);
1376        if (file) {
1377                if (file->f_mode & FMODE_READ) {
1378                        struct address_space *mapping = file->f_mapping;
1379                        pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1380                        pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1381                        unsigned long len = end - start + 1;
1382                        ret = do_readahead(mapping, file, start, len);
1383                }
1384                fput(file);
1385        }
1386        return ret;
1387}
1388
1389#ifdef CONFIG_MMU
1390/**
1391 * page_cache_read - adds requested page to the page cache if not already there
1392 * @file:       file to read
1393 * @offset:     page index
1394 *
1395 * This adds the requested page to the page cache if it isn't already there,
1396 * and schedules an I/O to read in its contents from disk.
1397 */
1398static int page_cache_read(struct file *file, pgoff_t offset)
1399{
1400        struct address_space *mapping = file->f_mapping;
1401        struct page *page; 
1402        int ret;
1403
1404        do {
1405                page = page_cache_alloc_cold(mapping);
1406                if (!page)
1407                        return -ENOMEM;
1408
1409                ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1410                if (ret == 0)
1411                        ret = mapping->a_ops->readpage(file, page);
1412                else if (ret == -EEXIST)
1413                        ret = 0; /* losing race to add is OK */
1414
1415                page_cache_release(page);
1416
1417        } while (ret == AOP_TRUNCATED_PAGE);
1418                
1419        return ret;
1420}
1421
1422#define MMAP_LOTSAMISS  (100)
1423
1424/**
1425 * filemap_fault - read in file data for page fault handling
1426 * @vma:        vma in which the fault was taken
1427 * @vmf:        struct vm_fault containing details of the fault
1428 *
1429 * filemap_fault() is invoked via the vma operations vector for a
1430 * mapped memory region to read in file data during a page fault.
1431 *
1432 * The goto's are kind of ugly, but this streamlines the normal case of having
1433 * it in the page cache, and handles the special cases reasonably without
1434 * having a lot of duplicated code.
1435 */
1436int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1437{
1438        int error;
1439        struct file *file = vma->vm_file;
1440        struct address_space *mapping = file->f_mapping;
1441        struct file_ra_state *ra = &file->f_ra;
1442        struct inode *inode = mapping->host;
1443        struct page *page;
1444        pgoff_t size;
1445        int did_readaround = 0;
1446        int ret = 0;
1447
1448        size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1449        if (vmf->pgoff >= size)
1450                return VM_FAULT_SIGBUS;
1451
1452        /* If we don't want any read-ahead, don't bother */
1453        if (VM_RandomReadHint(vma))
1454                goto no_cached_page;
1455
1456        /*
1457         * Do we have something in the page cache already?
1458         */
1459retry_find:
1460        page = find_lock_page(mapping, vmf->pgoff);
1461        /*
1462         * For sequential accesses, we use the generic readahead logic.
1463         */
1464        if (VM_SequentialReadHint(vma)) {
1465                if (!page) {
1466                        page_cache_sync_readahead(mapping, ra, file,
1467                                                           vmf->pgoff, 1);
1468                        page = find_lock_page(mapping, vmf->pgoff);
1469                        if (!page)
1470                                goto no_cached_page;
1471                }
1472                if (PageReadahead(page)) {
1473                        page_cache_async_readahead(mapping, ra, file, page,
1474                                                           vmf->pgoff, 1);
1475                }
1476        }
1477
1478        if (!page) {
1479                unsigned long ra_pages;
1480
1481                ra->mmap_miss++;
1482
1483                /*
1484                 * Do we miss much more than hit in this file? If so,
1485                 * stop bothering with read-ahead. It will only hurt.
1486                 */
1487                if (ra->mmap_miss > MMAP_LOTSAMISS)
1488                        goto no_cached_page;
1489
1490                /*
1491                 * To keep the pgmajfault counter straight, we need to
1492                 * check did_readaround, as this is an inner loop.
1493                 */
1494                if (!did_readaround) {
1495                        ret = VM_FAULT_MAJOR;
1496                        count_vm_event(PGMAJFAULT);
1497                }
1498                did_readaround = 1;
1499                ra_pages = max_sane_readahead(file->f_ra.ra_pages);
1500                if (ra_pages) {
1501                        pgoff_t start = 0;
1502
1503                        if (vmf->pgoff > ra_pages / 2)
1504                                start = vmf->pgoff - ra_pages / 2;
1505                        do_page_cache_readahead(mapping, file, start, ra_pages);
1506                }
1507                page = find_lock_page(mapping, vmf->pgoff);
1508                if (!page)
1509                        goto no_cached_page;
1510        }
1511
1512        if (!did_readaround)
1513                ra->mmap_miss--;
1514
1515        /*
1516         * We have a locked page in the page cache, now we need to check
1517         * that it's up-to-date. If not, it is going to be due to an error.
1518         */
1519        if (unlikely(!PageUptodate(page)))
1520                goto page_not_uptodate;
1521
1522        /* Must recheck i_size under page lock */
1523        size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1524        if (unlikely(vmf->pgoff >= size)) {
1525                unlock_page(page);
1526                page_cache_release(page);
1527                return VM_FAULT_SIGBUS;
1528        }
1529
1530        /*
1531         * Found the page and have a reference on it.
1532         */
1533        mark_page_accessed(page);
1534        ra->prev_pos = (loff_t)page->index << PAGE_CACHE_SHIFT;
1535        vmf->page = page;
1536        return ret | VM_FAULT_LOCKED;
1537
1538no_cached_page:
1539        /*
1540         * We're only likely to ever get here if MADV_RANDOM is in
1541         * effect.
1542         */
1543        error = page_cache_read(file, vmf->pgoff);
1544
1545        /*
1546         * The page we want has now been added to the page cache.
1547         * In the unlikely event that someone removed it in the
1548         * meantime, we'll just come back here and read it again.
1549         */
1550        if (error >= 0)
1551                goto retry_find;
1552
1553        /*
1554         * An error return from page_cache_read can result if the
1555         * system is low on memory, or a problem occurs while trying
1556         * to schedule I/O.
1557         */
1558        if (error == -ENOMEM)
1559                return VM_FAULT_OOM;
1560        return VM_FAULT_SIGBUS;
1561
1562page_not_uptodate:
1563        /* IO error path */
1564        if (!did_readaround) {
1565                ret = VM_FAULT_MAJOR;
1566                count_vm_event(PGMAJFAULT);
1567        }
1568
1569        /*
1570         * Umm, take care of errors if the page isn't up-to-date.
1571         * Try to re-read it _once_. We do this synchronously,
1572         * because there really aren't any performance issues here
1573         * and we need to check for errors.
1574         */
1575        ClearPageError(page);
1576        error = mapping->a_ops->readpage(file, page);
1577        if (!error) {
1578                wait_on_page_locked(page);
1579                if (!PageUptodate(page))
1580                        error = -EIO;
1581        }
1582        page_cache_release(page);
1583
1584        if (!error || error == AOP_TRUNCATED_PAGE)
1585                goto retry_find;
1586
1587        /* Things didn't work out. Return zero to tell the mm layer so. */
1588        shrink_readahead_size_eio(file, ra);
1589        return VM_FAULT_SIGBUS;
1590}
1591EXPORT_SYMBOL(filemap_fault);
1592
1593struct vm_operations_struct generic_file_vm_ops = {
1594        .fault          = filemap_fault,
1595};
1596
1597/* This is used for a general mmap of a disk file */
1598
1599int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1600{
1601        struct address_space *mapping = file->f_mapping;
1602
1603        if (!mapping->a_ops->readpage)
1604                return -ENOEXEC;
1605        file_accessed(file);
1606        vma->vm_ops = &generic_file_vm_ops;
1607        vma->vm_flags |= VM_CAN_NONLINEAR;
1608        return 0;
1609}
1610
1611/*
1612 * This is for filesystems which do not implement ->writepage.
1613 */
1614int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1615{
1616        if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1617                return -EINVAL;
1618        return generic_file_mmap(file, vma);
1619}
1620#else
1621int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1622{
1623        return -ENOSYS;
1624}
1625int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1626{
1627        return -ENOSYS;
1628}
1629#endif /* CONFIG_MMU */
1630
1631EXPORT_SYMBOL(generic_file_mmap);
1632EXPORT_SYMBOL(generic_file_readonly_mmap);
1633
1634static struct page *__read_cache_page(struct address_space *mapping,
1635                                pgoff_t index,
1636                                int (*filler)(void *,struct page*),
1637                                void *data)
1638{
1639        struct page *page;
1640        int err;
1641repeat:
1642        page = find_get_page(mapping, index);
1643        if (!page) {
1644                page = page_cache_alloc_cold(mapping);
1645                if (!page)
1646                        return ERR_PTR(-ENOMEM);
1647                err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
1648                if (unlikely(err)) {
1649                        page_cache_release(page);
1650                        if (err == -EEXIST)
1651                                goto repeat;
1652                        /* Presumably ENOMEM for radix tree node */
1653                        return ERR_PTR(err);
1654                }
1655                err = filler(data, page);
1656                if (err < 0) {
1657                        page_cache_release(page);
1658                        page = ERR_PTR(err);
1659                }
1660        }
1661        return page;
1662}
1663
1664/**
1665 * read_cache_page_async - read into page cache, fill it if needed
1666 * @mapping:    the page's address_space
1667 * @index:      the page index
1668 * @filler:     function to perform the read
1669 * @data:       destination for read data
1670 *
1671 * Same as read_cache_page, but don't wait for page to become unlocked
1672 * after submitting it to the filler.
1673 *
1674 * Read into the page cache. If a page already exists, and PageUptodate() is
1675 * not set, try to fill the page but don't wait for it to become unlocked.
1676 *
1677 * If the page does not get brought uptodate, return -EIO.
1678 */
1679struct page *read_cache_page_async(struct address_space *mapping,
1680                                pgoff_t index,
1681                                int (*filler)(void *,struct page*),
1682                                void *data)
1683{
1684        struct page *page;
1685        int err;
1686
1687retry:
1688        page = __read_cache_page(mapping, index, filler, data);
1689        if (IS_ERR(page))
1690                return page;
1691        if (PageUptodate(page))
1692                goto out;
1693
1694        lock_page(page);
1695        if (!page->mapping) {
1696                unlock_page(page);
1697                page_cache_release(page);
1698                goto retry;
1699        }
1700        if (PageUptodate(page)) {
1701                unlock_page(page);
1702                goto out;
1703        }
1704        err = filler(data, page);
1705        if (err < 0) {
1706                page_cache_release(page);
1707                return ERR_PTR(err);
1708        }
1709out:
1710        mark_page_accessed(page);
1711        return page;
1712}
1713EXPORT_SYMBOL(read_cache_page_async);
1714
1715/**
1716 * read_cache_page - read into page cache, fill it if needed
1717 * @mapping:    the page's address_space
1718 * @index:      the page index
1719 * @filler:     function to perform the read
1720 * @data:       destination for read data
1721 *
1722 * Read into the page cache. If a page already exists, and PageUptodate() is
1723 * not set, try to fill the page then wait for it to become unlocked.
1724 *
1725 * If the page does not get brought uptodate, return -EIO.
1726 */
1727struct page *read_cache_page(struct address_space *mapping,
1728                                pgoff_t index,
1729                                int (*filler)(void *,struct page*),
1730                                void *data)
1731{
1732        struct page *page;
1733
1734        page = read_cache_page_async(mapping, index, filler, data);
1735        if (IS_ERR(page))
1736                goto out;
1737        wait_on_page_locked(page);
1738        if (!PageUptodate(page)) {
1739                page_cache_release(page);
1740                page = ERR_PTR(-EIO);
1741        }
1742 out:
1743        return page;
1744}
1745EXPORT_SYMBOL(read_cache_page);
1746
1747/*
1748 * The logic we want is
1749 *
1750 *      if suid or (sgid and xgrp)
1751 *              remove privs
1752 */
1753int should_remove_suid(struct dentry *dentry)
1754{
1755        mode_t mode = dentry->d_inode->i_mode;
1756        int kill = 0;
1757
1758        /* suid always must be killed */
1759        if (unlikely(mode & S_ISUID))
1760                kill = ATTR_KILL_SUID;
1761
1762        /*
1763         * sgid without any exec bits is just a mandatory locking mark; leave
1764         * it alone.  If some exec bits are set, it's a real sgid; kill it.
1765         */
1766        if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1767                kill |= ATTR_KILL_SGID;
1768
1769        if (unlikely(kill && !capable(CAP_FSETID)))
1770                return kill;
1771
1772        return 0;
1773}
1774EXPORT_SYMBOL(should_remove_suid);
1775
1776static int __remove_suid(struct dentry *dentry, int kill)
1777{
1778        struct iattr newattrs;
1779
1780        newattrs.ia_valid = ATTR_FORCE | kill;
1781        return notify_change(dentry, &newattrs);
1782}
1783
1784int file_remove_suid(struct file *file)
1785{
1786        struct dentry *dentry = file->f_path.dentry;
1787        int killsuid = should_remove_suid(dentry);
1788        int killpriv = security_inode_need_killpriv(dentry);
1789        int error = 0;
1790
1791        if (killpriv < 0)
1792                return killpriv;
1793        if (killpriv)
1794                error = security_inode_killpriv(dentry);
1795        if (!error && killsuid)
1796                error = __remove_suid(dentry, killsuid);
1797
1798        return error;
1799}
1800EXPORT_SYMBOL(file_remove_suid);
1801
1802static size_t __iovec_copy_from_user_inatomic(char *vaddr,
1803                        const struct iovec *iov, size_t base, size_t bytes)
1804{
1805        size_t copied = 0, left = 0;
1806
1807        while (bytes) {
1808                char __user *buf = iov->iov_base + base;
1809                int copy = min(bytes, iov->iov_len - base);
1810
1811                base = 0;
1812                left = __copy_from_user_inatomic_nocache(vaddr, buf, copy);
1813                copied += copy;
1814                bytes -= copy;
1815                vaddr += copy;
1816                iov++;
1817
1818                if (unlikely(left))
1819                        break;
1820        }
1821        return copied - left;
1822}
1823
1824/*
1825 * Copy as much as we can into the page and return the number of bytes which
1826 * were sucessfully copied.  If a fault is encountered then return the number of
1827 * bytes which were copied.
1828 */
1829size_t iov_iter_copy_from_user_atomic(struct page *page,
1830                struct iov_iter *i, unsigned long offset, size_t bytes)
1831{
1832        char *kaddr;
1833        size_t copied;
1834
1835        BUG_ON(!in_atomic());
1836        kaddr = kmap_atomic(page, KM_USER0);
1837        if (likely(i->nr_segs == 1)) {
1838                int left;
1839                char __user *buf = i->iov->iov_base + i->iov_offset;
1840                left = __copy_from_user_inatomic_nocache(kaddr + offset,
1841                                                        buf, bytes);
1842                copied = bytes - left;
1843        } else {
1844                copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1845                                                i->iov, i->iov_offset, bytes);
1846        }
1847        kunmap_atomic(kaddr, KM_USER0);
1848
1849        return copied;
1850}
1851EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
1852
1853/*
1854 * This has the same sideeffects and return value as
1855 * iov_iter_copy_from_user_atomic().
1856 * The difference is that it attempts to resolve faults.
1857 * Page must not be locked.
1858 */
1859size_t iov_iter_copy_from_user(struct page *page,
1860                struct iov_iter *i, unsigned long offset, size_t bytes)
1861{
1862        char *kaddr;
1863        size_t copied;
1864
1865        kaddr = kmap(page);
1866        if (likely(i->nr_segs == 1)) {
1867                int left;
1868                char __user *buf = i->iov->iov_base + i->iov_offset;
1869                left = __copy_from_user_nocache(kaddr + offset, buf, bytes);
1870                copied = bytes - left;
1871        } else {
1872                copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1873                                                i->iov, i->iov_offset, bytes);
1874        }
1875        kunmap(page);
1876        return copied;
1877}
1878EXPORT_SYMBOL(iov_iter_copy_from_user);
1879
1880void iov_iter_advance(struct iov_iter *i, size_t bytes)
1881{
1882        BUG_ON(i->count < bytes);
1883
1884        if (likely(i->nr_segs == 1)) {
1885                i->iov_offset += bytes;
1886                i->count -= bytes;
1887        } else {
1888                const struct iovec *iov = i->iov;
1889                size_t base = i->iov_offset;
1890
1891                /*
1892                 * The !iov->iov_len check ensures we skip over unlikely
1893                 * zero-length segments (without overruning the iovec).
1894                 */
1895                while (bytes || unlikely(i->count && !iov->iov_len)) {
1896                        int copy;
1897
1898                        copy = min(bytes, iov->iov_len - base);
1899                        BUG_ON(!i->count || i->count < copy);
1900                        i->count -= copy;
1901                        bytes -= copy;
1902                        base += copy;
1903                        if (iov->iov_len == base) {
1904                                iov++;
1905                                base = 0;
1906                        }
1907                }
1908                i->iov = iov;
1909                i->iov_offset = base;
1910        }
1911}
1912EXPORT_SYMBOL(iov_iter_advance);
1913
1914/*
1915 * Fault in the first iovec of the given iov_iter, to a maximum length
1916 * of bytes. Returns 0 on success, or non-zero if the memory could not be
1917 * accessed (ie. because it is an invalid address).
1918 *
1919 * writev-intensive code may want this to prefault several iovecs -- that
1920 * would be possible (callers must not rely on the fact that _only_ the
1921 * first iovec will be faulted with the current implementation).
1922 */
1923int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
1924{
1925        char __user *buf = i->iov->iov_base + i->iov_offset;
1926        bytes = min(bytes, i->iov->iov_len - i->iov_offset);
1927        return fault_in_pages_readable(buf, bytes);
1928}
1929EXPORT_SYMBOL(iov_iter_fault_in_readable);
1930
1931/*
1932 * Return the count of just the current iov_iter segment.
1933 */
1934size_t iov_iter_single_seg_count(struct iov_iter *i)
1935{
1936        const struct iovec *iov = i->iov;
1937        if (i->nr_segs == 1)
1938                return i->count;
1939        else
1940                return min(i->count, iov->iov_len - i->iov_offset);
1941}
1942EXPORT_SYMBOL(iov_iter_single_seg_count);
1943
1944/*
1945 * Performs necessary checks before doing a write
1946 *
1947 * Can adjust writing position or amount of bytes to write.
1948 * Returns appropriate error code that caller should return or
1949 * zero in case that write should be allowed.
1950 */
1951inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
1952{
1953        struct inode *inode = file->f_mapping->host;
1954        unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
1955
1956        if (unlikely(*pos < 0))
1957                return -EINVAL;
1958
1959        if (!isblk) {
1960                /* FIXME: this is for backwards compatibility with 2.4 */
1961                if (file->f_flags & O_APPEND)
1962                        *pos = i_size_read(inode);
1963
1964                if (limit != RLIM_INFINITY) {
1965                        if (*pos >= limit) {
1966                                send_sig(SIGXFSZ, current, 0);
1967                                return -EFBIG;
1968                        }
1969                        if (*count > limit - (typeof(limit))*pos) {
1970                                *count = limit - (typeof(limit))*pos;
1971                        }
1972                }
1973        }
1974
1975        /*
1976         * LFS rule
1977         */
1978        if (unlikely(*pos + *count > MAX_NON_LFS &&
1979                                !(file->f_flags & O_LARGEFILE))) {
1980                if (*pos >= MAX_NON_LFS) {
1981                        return -EFBIG;
1982                }
1983                if (*count > MAX_NON_LFS - (unsigned long)*pos) {
1984                        *count = MAX_NON_LFS - (unsigned long)*pos;
1985                }
1986        }
1987
1988        /*
1989         * Are we about to exceed the fs block limit ?
1990         *
1991         * If we have written data it becomes a short write.  If we have
1992         * exceeded without writing data we send a signal and return EFBIG.
1993         * Linus frestrict idea will clean these up nicely..
1994         */
1995        if (likely(!isblk)) {
1996                if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
1997                        if (*count || *pos > inode->i_sb->s_maxbytes) {
1998                                return -EFBIG;
1999                        }
2000                        /* zero-length writes at ->s_maxbytes are OK */
2001                }
2002
2003                if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2004                        *count = inode->i_sb->s_maxbytes - *pos;
2005        } else {
2006#ifdef CONFIG_BLOCK
2007                loff_t isize;
2008                if (bdev_read_only(I_BDEV(inode)))
2009                        return -EPERM;
2010                isize = i_size_read(inode);
2011                if (*pos >= isize) {
2012                        if (*count || *pos > isize)
2013                                return -ENOSPC;
2014                }
2015
2016                if (*pos + *count > isize)
2017                        *count = isize - *pos;
2018#else
2019                return -EPERM;
2020#endif
2021        }
2022        return 0;
2023}
2024EXPORT_SYMBOL(generic_write_checks);
2025
2026int pagecache_write_begin(struct file *file, struct address_space *mapping,
2027                                loff_t pos, unsigned len, unsigned flags,
2028                                struct page **pagep, void **fsdata)
2029{
2030        const struct address_space_operations *aops = mapping->a_ops;
2031
2032        return aops->write_begin(file, mapping, pos, len, flags,
2033                                                        pagep, fsdata);
2034}
2035EXPORT_SYMBOL(pagecache_write_begin);
2036
2037int pagecache_write_end(struct file *file, struct address_space *mapping,
2038                                loff_t pos, unsigned len, unsigned copied,
2039                                struct page *page, void *fsdata)
2040{
2041        const struct address_space_operations *aops = mapping->a_ops;
2042
2043        mark_page_accessed(page);
2044        return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2045}
2046EXPORT_SYMBOL(pagecache_write_end);
2047
2048ssize_t
2049generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2050                unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2051                size_t count, size_t ocount)
2052{
2053        struct file     *file = iocb->ki_filp;
2054        struct address_space *mapping = file->f_mapping;
2055        struct inode    *inode = mapping->host;
2056        ssize_t         written;
2057        size_t          write_len;
2058        pgoff_t         end;
2059
2060        if (count != ocount)
2061                *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2062
2063        /*
2064         * Unmap all mmappings of the file up-front.
2065         *
2066         * This will cause any pte dirty bits to be propagated into the
2067         * pageframes for the subsequent filemap_write_and_wait().
2068         */
2069        write_len = iov_length(iov, *nr_segs);
2070        end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2071        if (mapping_mapped(mapping))
2072                unmap_mapping_range(mapping, pos, write_len, 0);
2073
2074        written = filemap_write_and_wait(mapping);
2075        if (written)
2076                goto out;
2077
2078        /*
2079         * After a write we want buffered reads to be sure to go to disk to get
2080         * the new data.  We invalidate clean cached page from the region we're
2081         * about to write.  We do this *before* the write so that we can return
2082         * without clobbering -EIOCBQUEUED from ->direct_IO().
2083         */
2084        if (mapping->nrpages) {
2085                written = invalidate_inode_pages2_range(mapping,
2086                                        pos >> PAGE_CACHE_SHIFT, end);
2087                /*
2088                 * If a page can not be invalidated, return 0 to fall back
2089                 * to buffered write.
2090                 */
2091                if (written) {
2092                        if (written == -EBUSY)
2093                                return 0;
2094                        goto out;
2095                }
2096        }
2097
2098        written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2099
2100        /*
2101         * Finally, try again to invalidate clean pages which might have been
2102         * cached by non-direct readahead, or faulted in by get_user_pages()
2103         * if the source of the write was an mmap'ed region of the file
2104         * we're writing.  Either one is a pretty crazy thing to do,
2105         * so we don't support it 100%.  If this invalidation
2106         * fails, tough, the write still worked...
2107         */
2108        if (mapping->nrpages) {
2109                invalidate_inode_pages2_range(mapping,
2110                                              pos >> PAGE_CACHE_SHIFT, end);
2111        }
2112
2113        if (written > 0) {
2114                loff_t end = pos + written;
2115                if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2116                        i_size_write(inode,  end);
2117                        mark_inode_dirty(inode);
2118                }
2119                *ppos = end;
2120        }
2121
2122        /*
2123         * Sync the fs metadata but not the minor inode changes and
2124         * of course not the data as we did direct DMA for the IO.
2125         * i_mutex is held, which protects generic_osync_inode() from
2126         * livelocking.  AIO O_DIRECT ops attempt to sync metadata here.
2127         */
2128out:
2129        if ((written >= 0 || written == -EIOCBQUEUED) &&
2130            ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2131                int err = generic_osync_inode(inode, mapping, OSYNC_METADATA);
2132                if (err < 0)
2133                        written = err;
2134        }
2135        return written;
2136}
2137EXPORT_SYMBOL(generic_file_direct_write);
2138
2139/*
2140 * Find or create a page at the given pagecache position. Return the locked
2141 * page. This function is specifically for buffered writes.
2142 */
2143struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index)
2144{
2145        int status;
2146        struct page *page;
2147repeat:
2148        page = find_lock_page(mapping, index);
2149        if (likely(page))
2150                return page;
2151
2152        page = page_cache_alloc(mapping);
2153        if (!page)
2154                return NULL;
2155        status = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
2156        if (unlikely(status)) {
2157                page_cache_release(page);
2158                if (status == -EEXIST)
2159                        goto repeat;
2160                return NULL;
2161        }
2162        return page;
2163}
2164EXPORT_SYMBOL(__grab_cache_page);
2165
2166static ssize_t generic_perform_write(struct file *file,
2167                                struct iov_iter *i, loff_t pos)
2168{
2169        struct address_space *mapping = file->f_mapping;
2170        const struct address_space_operations *a_ops = mapping->a_ops;
2171        long status = 0;
2172        ssize_t written = 0;
2173        unsigned int flags = 0;
2174
2175        /*
2176         * Copies from kernel address space cannot fail (NFSD is a big user).
2177         */
2178        if (segment_eq(get_fs(), KERNEL_DS))
2179                flags |= AOP_FLAG_UNINTERRUPTIBLE;
2180
2181        do {
2182                struct page *page;
2183                pgoff_t index;          /* Pagecache index for current page */
2184                unsigned long offset;   /* Offset into pagecache page */
2185                unsigned long bytes;    /* Bytes to write to page */
2186                size_t copied;          /* Bytes copied from user */
2187                void *fsdata;
2188
2189                offset = (pos & (PAGE_CACHE_SIZE - 1));
2190                index = pos >> PAGE_CACHE_SHIFT;
2191                bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2192                                                iov_iter_count(i));
2193
2194again:
2195
2196                /*
2197                 * Bring in the user page that we will copy from _first_.
2198                 * Otherwise there's a nasty deadlock on copying from the
2199                 * same page as we're writing to, without it being marked
2200                 * up-to-date.
2201                 *
2202                 * Not only is this an optimisation, but it is also required
2203                 * to check that the address is actually valid, when atomic
2204                 * usercopies are used, below.
2205                 */
2206                if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2207                        status = -EFAULT;
2208                        break;
2209                }
2210
2211                status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2212                                                &page, &fsdata);
2213                if (unlikely(status))
2214                        break;
2215
2216                pagefault_disable();
2217                copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2218                pagefault_enable();
2219                flush_dcache_page(page);
2220
2221                status = a_ops->write_end(file, mapping, pos, bytes, copied,
2222                                                page, fsdata);
2223                if (unlikely(status < 0))
2224                        break;
2225                copied = status;
2226
2227                cond_resched();
2228
2229                iov_iter_advance(i, copied);
2230                if (unlikely(copied == 0)) {
2231                        /*
2232                         * If we were unable to copy any data at all, we must
2233                         * fall back to a single segment length write.
2234                         *
2235                         * If we didn't fallback here, we could livelock
2236                         * because not all segments in the iov can be copied at
2237                         * once without a pagefault.
2238                         */
2239                        bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2240                                                iov_iter_single_seg_count(i));
2241                        goto again;
2242                }
2243                pos += copied;
2244                written += copied;
2245
2246                balance_dirty_pages_ratelimited(mapping);
2247
2248        } while (iov_iter_count(i));
2249
2250        return written ? written : status;
2251}
2252
2253ssize_t
2254generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2255                unsigned long nr_segs, loff_t pos, loff_t *ppos,
2256                size_t count, ssize_t written)
2257{
2258        struct file *file = iocb->ki_filp;
2259        struct address_space *mapping = file->f_mapping;
2260        const struct address_space_operations *a_ops = mapping->a_ops;
2261        struct inode *inode = mapping->host;
2262        ssize_t status;
2263        struct iov_iter i;
2264
2265        iov_iter_init(&i, iov, nr_segs, count, written);
2266        status = generic_perform_write(file, &i, pos);
2267
2268        if (likely(status >= 0)) {
2269                written += status;
2270                *ppos = pos + status;
2271
2272                /*
2273                 * For now, when the user asks for O_SYNC, we'll actually give
2274                 * O_DSYNC
2275                 */
2276                if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2277                        if (!a_ops->writepage || !is_sync_kiocb(iocb))
2278                                status = generic_osync_inode(inode, mapping,
2279                                                OSYNC_METADATA|OSYNC_DATA);
2280                }
2281        }
2282        
2283        /*
2284         * If we get here for O_DIRECT writes then we must have fallen through
2285         * to buffered writes (block instantiation inside i_size).  So we sync
2286         * the file data here, to try to honour O_DIRECT expectations.
2287         */
2288        if (unlikely(file->f_flags & O_DIRECT) && written)
2289                status = filemap_write_and_wait(mapping);
2290
2291        return written ? written : status;
2292}
2293EXPORT_SYMBOL(generic_file_buffered_write);
2294
2295static ssize_t
2296__generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
2297                                unsigned long nr_segs, loff_t *ppos)
2298{
2299        struct file *file = iocb->ki_filp;
2300        struct address_space * mapping = file->f_mapping;
2301        size_t ocount;          /* original count */
2302        size_t count;           /* after file limit checks */
2303        struct inode    *inode = mapping->host;
2304        loff_t          pos;
2305        ssize_t         written;
2306        ssize_t         err;
2307
2308        ocount = 0;
2309        err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2310        if (err)
2311                return err;
2312
2313        count = ocount;
2314        pos = *ppos;
2315
2316        vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2317
2318        /* We can write back this queue in page reclaim */
2319        current->backing_dev_info = mapping->backing_dev_info;
2320        written = 0;
2321
2322        err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2323        if (err)
2324                goto out;
2325
2326        if (count == 0)
2327                goto out;
2328
2329        err = file_remove_suid(file);
2330        if (err)
2331                goto out;
2332
2333        file_update_time(file);
2334
2335        /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2336        if (unlikely(file->f_flags & O_DIRECT)) {
2337                loff_t endbyte;
2338                ssize_t written_buffered;
2339
2340                written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2341                                                        ppos, count, ocount);
2342                if (written < 0 || written == count)
2343                        goto out;
2344                /*
2345                 * direct-io write to a hole: fall through to buffered I/O
2346                 * for completing the rest of the request.
2347                 */
2348                pos += written;
2349                count -= written;
2350                written_buffered = generic_file_buffered_write(iocb, iov,
2351                                                nr_segs, pos, ppos, count,
2352                                                written);
2353                /*
2354                 * If generic_file_buffered_write() retuned a synchronous error
2355                 * then we want to return the number of bytes which were
2356                 * direct-written, or the error code if that was zero.  Note
2357                 * that this differs from normal direct-io semantics, which
2358                 * will return -EFOO even if some bytes were written.
2359                 */
2360                if (written_buffered < 0) {
2361                        err = written_buffered;
2362                        goto out;
2363                }
2364
2365                /*
2366                 * We need to ensure that the page cache pages are written to
2367                 * disk and invalidated to preserve the expected O_DIRECT
2368                 * semantics.
2369                 */
2370                endbyte = pos + written_buffered - written - 1;
2371                err = do_sync_mapping_range(file->f_mapping, pos, endbyte,
2372                                            SYNC_FILE_RANGE_WAIT_BEFORE|
2373                                            SYNC_FILE_RANGE_WRITE|
2374                                            SYNC_FILE_RANGE_WAIT_AFTER);
2375                if (err == 0) {
2376                        written = written_buffered;
2377                        invalidate_mapping_pages(mapping,
2378                                                 pos >> PAGE_CACHE_SHIFT,
2379                                                 endbyte >> PAGE_CACHE_SHIFT);
2380                } else {
2381                        /*
2382                         * We don't know how much we wrote, so just return
2383                         * the number of bytes which were direct-written
2384                         */
2385                }
2386        } else {
2387                written = generic_file_buffered_write(iocb, iov, nr_segs,
2388                                pos, ppos, count, written);
2389        }
2390out:
2391        current->backing_dev_info = NULL;
2392        return written ? written : err;
2393}
2394
2395ssize_t generic_file_aio_write_nolock(struct kiocb *iocb,
2396                const struct iovec *iov, unsigned long nr_segs, loff_t pos)
2397{
2398        struct file *file = iocb->ki_filp;
2399        struct address_space *mapping = file->f_mapping;
2400        struct inode *inode = mapping->host;
2401        ssize_t ret;
2402
2403        BUG_ON(iocb->ki_pos != pos);
2404
2405        ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
2406                        &iocb->ki_pos);
2407
2408        if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2409                ssize_t err;
2410
2411                err = sync_page_range_nolock(inode, mapping, pos, ret);
2412                if (err < 0)
2413                        ret = err;
2414        }
2415        return ret;
2416}
2417EXPORT_SYMBOL(generic_file_aio_write_nolock);
2418
2419ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2420                unsigned long nr_segs, loff_t pos)
2421{
2422        struct file *file = iocb->ki_filp;
2423        struct address_space *mapping = file->f_mapping;
2424        struct inode *inode = mapping->host;
2425        ssize_t ret;
2426
2427        BUG_ON(iocb->ki_pos != pos);
2428
2429        mutex_lock(&inode->i_mutex);
2430        ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
2431                        &iocb->ki_pos);
2432        mutex_unlock(&inode->i_mutex);
2433
2434        if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2435                ssize_t err;
2436
2437                err = sync_page_range(inode, mapping, pos, ret);
2438                if (err < 0)
2439                        ret = err;
2440        }
2441        return ret;
2442}
2443EXPORT_SYMBOL(generic_file_aio_write);
2444
2445/**
2446 * try_to_release_page() - release old fs-specific metadata on a page
2447 *
2448 * @page: the page which the kernel is trying to free
2449 * @gfp_mask: memory allocation flags (and I/O mode)
2450 *
2451 * The address_space is to try to release any data against the page
2452 * (presumably at page->private).  If the release was successful, return `1'.
2453 * Otherwise return zero.
2454 *
2455 * The @gfp_mask argument specifies whether I/O may be performed to release
2456 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2457 *
2458 */
2459int try_to_release_page(struct page *page, gfp_t gfp_mask)
2460{
2461        struct address_space * const mapping = page->mapping;
2462
2463        BUG_ON(!PageLocked(page));
2464        if (PageWriteback(page))
2465                return 0;
2466
2467        if (mapping && mapping->a_ops->releasepage)
2468                return mapping->a_ops->releasepage(page, gfp_mask);
2469        return try_to_free_buffers(page);
2470}
2471
2472EXPORT_SYMBOL(try_to_release_page);
2473
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