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/export.h>
  13#include <linux/compiler.h>
  14#include <linux/fs.h>
  15#include <linux/uaccess.h>
  16#include <linux/aio.h>
  17#include <linux/capability.h>
  18#include <linux/kernel_stat.h>
  19#include <linux/gfp.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/cpuset.h>
  33#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
  34#include <linux/memcontrol.h>
  35#include <linux/cleancache.h>
  36#include "internal.h"
  37
  38#define CREATE_TRACE_POINTS
  39#include <trace/events/filemap.h>
  40
  41/*
  42 * FIXME: remove all knowledge of the buffer layer from the core VM
  43 */
  44#include <linux/buffer_head.h> /* for try_to_free_buffers */
  45
  46#include <asm/mman.h>
  47
  48/*
  49 * Shared mappings implemented 30.11.1994. It's not fully working yet,
  50 * though.
  51 *
  52 * Shared mappings now work. 15.8.1995  Bruno.
  53 *
  54 * finished 'unifying' the page and buffer cache and SMP-threaded the
  55 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
  56 *
  57 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
  58 */
  59
  60/*
  61 * Lock ordering:
  62 *
  63 *  ->i_mmap_mutex              (truncate_pagecache)
  64 *    ->private_lock            (__free_pte->__set_page_dirty_buffers)
  65 *      ->swap_lock             (exclusive_swap_page, others)
  66 *        ->mapping->tree_lock
  67 *
  68 *  ->i_mutex
  69 *    ->i_mmap_mutex            (truncate->unmap_mapping_range)
  70 *
  71 *  ->mmap_sem
  72 *    ->i_mmap_mutex
  73 *      ->page_table_lock or pte_lock   (various, mainly in memory.c)
  74 *        ->mapping->tree_lock  (arch-dependent flush_dcache_mmap_lock)
  75 *
  76 *  ->mmap_sem
  77 *    ->lock_page               (access_process_vm)
  78 *
  79 *  ->i_mutex                   (generic_file_buffered_write)
  80 *    ->mmap_sem                (fault_in_pages_readable->do_page_fault)
  81 *
  82 *  bdi->wb.list_lock
  83 *    sb_lock                   (fs/fs-writeback.c)
  84 *    ->mapping->tree_lock      (__sync_single_inode)
  85 *
  86 *  ->i_mmap_mutex
  87 *    ->anon_vma.lock           (vma_adjust)
  88 *
  89 *  ->anon_vma.lock
  90 *    ->page_table_lock or pte_lock     (anon_vma_prepare and various)
  91 *
  92 *  ->page_table_lock or pte_lock
  93 *    ->swap_lock               (try_to_unmap_one)
  94 *    ->private_lock            (try_to_unmap_one)
  95 *    ->tree_lock               (try_to_unmap_one)
  96 *    ->zone.lru_lock           (follow_page->mark_page_accessed)
  97 *    ->zone.lru_lock           (check_pte_range->isolate_lru_page)
  98 *    ->private_lock            (page_remove_rmap->set_page_dirty)
  99 *    ->tree_lock               (page_remove_rmap->set_page_dirty)
 100 *    bdi.wb->list_lock         (page_remove_rmap->set_page_dirty)
 101 *    ->inode->i_lock           (page_remove_rmap->set_page_dirty)
 102 *    bdi.wb->list_lock         (zap_pte_range->set_page_dirty)
 103 *    ->inode->i_lock           (zap_pte_range->set_page_dirty)
 104 *    ->private_lock            (zap_pte_range->__set_page_dirty_buffers)
 105 *
 106 * ->i_mmap_mutex
 107 *   ->tasklist_lock            (memory_failure, collect_procs_ao)
 108 */
 109
 110/*
 111 * Delete 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 __delete_from_page_cache(struct page *page)
 116{
 117        struct address_space *mapping = page->mapping;
 118
 119        trace_mm_filemap_delete_from_page_cache(page);
 120        /*
 121         * if we're uptodate, flush out into the cleancache, otherwise
 122         * invalidate any existing cleancache entries.  We can't leave
 123         * stale data around in the cleancache once our page is gone
 124         */
 125        if (PageUptodate(page) && PageMappedToDisk(page))
 126                cleancache_put_page(page);
 127        else
 128                cleancache_invalidate_page(mapping, page);
 129
 130        radix_tree_delete(&mapping->page_tree, page->index);
 131        page->mapping = NULL;
 132        /* Leave page->index set: truncation lookup relies upon it */
 133        mapping->nrpages--;
 134        __dec_zone_page_state(page, NR_FILE_PAGES);
 135        if (PageSwapBacked(page))
 136                __dec_zone_page_state(page, NR_SHMEM);
 137        BUG_ON(page_mapped(page));
 138
 139        /*
 140         * Some filesystems seem to re-dirty the page even after
 141         * the VM has canceled the dirty bit (eg ext3 journaling).
 142         *
 143         * Fix it up by doing a final dirty accounting check after
 144         * having removed the page entirely.
 145         */
 146        if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
 147                dec_zone_page_state(page, NR_FILE_DIRTY);
 148                dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
 149        }
 150}
 151
 152/**
 153 * delete_from_page_cache - delete page from page cache
 154 * @page: the page which the kernel is trying to remove from page cache
 155 *
 156 * This must be called only on pages that have been verified to be in the page
 157 * cache and locked.  It will never put the page into the free list, the caller
 158 * has a reference on the page.
 159 */
 160void delete_from_page_cache(struct page *page)
 161{
 162        struct address_space *mapping = page->mapping;
 163        void (*freepage)(struct page *);
 164
 165        BUG_ON(!PageLocked(page));
 166
 167        freepage = mapping->a_ops->freepage;
 168        spin_lock_irq(&mapping->tree_lock);
 169        __delete_from_page_cache(page);
 170        spin_unlock_irq(&mapping->tree_lock);
 171        mem_cgroup_uncharge_cache_page(page);
 172
 173        if (freepage)
 174                freepage(page);
 175        page_cache_release(page);
 176}
 177EXPORT_SYMBOL(delete_from_page_cache);
 178
 179static int sleep_on_page(void *word)
 180{
 181        io_schedule();
 182        return 0;
 183}
 184
 185static int sleep_on_page_killable(void *word)
 186{
 187        sleep_on_page(word);
 188        return fatal_signal_pending(current) ? -EINTR : 0;
 189}
 190
 191static int filemap_check_errors(struct address_space *mapping)
 192{
 193        int ret = 0;
 194        /* Check for outstanding write errors */
 195        if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
 196                ret = -ENOSPC;
 197        if (test_and_clear_bit(AS_EIO, &mapping->flags))
 198                ret = -EIO;
 199        return ret;
 200}
 201
 202/**
 203 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
 204 * @mapping:    address space structure to write
 205 * @start:      offset in bytes where the range starts
 206 * @end:        offset in bytes where the range ends (inclusive)
 207 * @sync_mode:  enable synchronous operation
 208 *
 209 * Start writeback against all of a mapping's dirty pages that lie
 210 * within the byte offsets <start, end> inclusive.
 211 *
 212 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
 213 * opposed to a regular memory cleansing writeback.  The difference between
 214 * these two operations is that if a dirty page/buffer is encountered, it must
 215 * be waited upon, and not just skipped over.
 216 */
 217int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 218                                loff_t end, int sync_mode)
 219{
 220        int ret;
 221        struct writeback_control wbc = {
 222                .sync_mode = sync_mode,
 223                .nr_to_write = LONG_MAX,
 224                .range_start = start,
 225                .range_end = end,
 226        };
 227
 228        if (!mapping_cap_writeback_dirty(mapping))
 229                return 0;
 230
 231        ret = do_writepages(mapping, &wbc);
 232        return ret;
 233}
 234
 235static inline int __filemap_fdatawrite(struct address_space *mapping,
 236        int sync_mode)
 237{
 238        return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
 239}
 240
 241int filemap_fdatawrite(struct address_space *mapping)
 242{
 243        return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
 244}
 245EXPORT_SYMBOL(filemap_fdatawrite);
 246
 247int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 248                                loff_t end)
 249{
 250        return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
 251}
 252EXPORT_SYMBOL(filemap_fdatawrite_range);
 253
 254/**
 255 * filemap_flush - mostly a non-blocking flush
 256 * @mapping:    target address_space
 257 *
 258 * This is a mostly non-blocking flush.  Not suitable for data-integrity
 259 * purposes - I/O may not be started against all dirty pages.
 260 */
 261int filemap_flush(struct address_space *mapping)
 262{
 263        return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
 264}
 265EXPORT_SYMBOL(filemap_flush);
 266
 267/**
 268 * filemap_fdatawait_range - wait for writeback to complete
 269 * @mapping:            address space structure to wait for
 270 * @start_byte:         offset in bytes where the range starts
 271 * @end_byte:           offset in bytes where the range ends (inclusive)
 272 *
 273 * Walk the list of under-writeback pages of the given address space
 274 * in the given range and wait for all of them.
 275 */
 276int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
 277                            loff_t end_byte)
 278{
 279        pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
 280        pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
 281        struct pagevec pvec;
 282        int nr_pages;
 283        int ret2, ret = 0;
 284
 285        if (end_byte < start_byte)
 286                goto out;
 287
 288        pagevec_init(&pvec, 0);
 289        while ((index <= end) &&
 290                        (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
 291                        PAGECACHE_TAG_WRITEBACK,
 292                        min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
 293                unsigned i;
 294
 295                for (i = 0; i < nr_pages; i++) {
 296                        struct page *page = pvec.pages[i];
 297
 298                        /* until radix tree lookup accepts end_index */
 299                        if (page->index > end)
 300                                continue;
 301
 302                        wait_on_page_writeback(page);
 303                        if (TestClearPageError(page))
 304                                ret = -EIO;
 305                }
 306                pagevec_release(&pvec);
 307                cond_resched();
 308        }
 309out:
 310        ret2 = filemap_check_errors(mapping);
 311        if (!ret)
 312                ret = ret2;
 313
 314        return ret;
 315}
 316EXPORT_SYMBOL(filemap_fdatawait_range);
 317
 318/**
 319 * filemap_fdatawait - wait for all under-writeback pages to complete
 320 * @mapping: address space structure to wait for
 321 *
 322 * Walk the list of under-writeback pages of the given address space
 323 * and wait for all of them.
 324 */
 325int filemap_fdatawait(struct address_space *mapping)
 326{
 327        loff_t i_size = i_size_read(mapping->host);
 328
 329        if (i_size == 0)
 330                return 0;
 331
 332        return filemap_fdatawait_range(mapping, 0, i_size - 1);
 333}
 334EXPORT_SYMBOL(filemap_fdatawait);
 335
 336int filemap_write_and_wait(struct address_space *mapping)
 337{
 338        int err = 0;
 339
 340        if (mapping->nrpages) {
 341                err = filemap_fdatawrite(mapping);
 342                /*
 343                 * Even if the above returned error, the pages may be
 344                 * written partially (e.g. -ENOSPC), so we wait for it.
 345                 * But the -EIO is special case, it may indicate the worst
 346                 * thing (e.g. bug) happened, so we avoid waiting for it.
 347                 */
 348                if (err != -EIO) {
 349                        int err2 = filemap_fdatawait(mapping);
 350                        if (!err)
 351                                err = err2;
 352                }
 353        } else {
 354                err = filemap_check_errors(mapping);
 355        }
 356        return err;
 357}
 358EXPORT_SYMBOL(filemap_write_and_wait);
 359
 360/**
 361 * filemap_write_and_wait_range - write out & wait on a file range
 362 * @mapping:    the address_space for the pages
 363 * @lstart:     offset in bytes where the range starts
 364 * @lend:       offset in bytes where the range ends (inclusive)
 365 *
 366 * Write out and wait upon file offsets lstart->lend, inclusive.
 367 *
 368 * Note that `lend' is inclusive (describes the last byte to be written) so
 369 * that this function can be used to write to the very end-of-file (end = -1).
 370 */
 371int filemap_write_and_wait_range(struct address_space *mapping,
 372                                 loff_t lstart, loff_t lend)
 373{
 374        int err = 0;
 375
 376        if (mapping->nrpages) {
 377                err = __filemap_fdatawrite_range(mapping, lstart, lend,
 378                                                 WB_SYNC_ALL);
 379                /* See comment of filemap_write_and_wait() */
 380                if (err != -EIO) {
 381                        int err2 = filemap_fdatawait_range(mapping,
 382                                                lstart, lend);
 383                        if (!err)
 384                                err = err2;
 385                }
 386        } else {
 387                err = filemap_check_errors(mapping);
 388        }
 389        return err;
 390}
 391EXPORT_SYMBOL(filemap_write_and_wait_range);
 392
 393/**
 394 * replace_page_cache_page - replace a pagecache page with a new one
 395 * @old:        page to be replaced
 396 * @new:        page to replace with
 397 * @gfp_mask:   allocation mode
 398 *
 399 * This function replaces a page in the pagecache with a new one.  On
 400 * success it acquires the pagecache reference for the new page and
 401 * drops it for the old page.  Both the old and new pages must be
 402 * locked.  This function does not add the new page to the LRU, the
 403 * caller must do that.
 404 *
 405 * The remove + add is atomic.  The only way this function can fail is
 406 * memory allocation failure.
 407 */
 408int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 409{
 410        int error;
 411
 412        VM_BUG_ON(!PageLocked(old));
 413        VM_BUG_ON(!PageLocked(new));
 414        VM_BUG_ON(new->mapping);
 415
 416        error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
 417        if (!error) {
 418                struct address_space *mapping = old->mapping;
 419                void (*freepage)(struct page *);
 420
 421                pgoff_t offset = old->index;
 422                freepage = mapping->a_ops->freepage;
 423
 424                page_cache_get(new);
 425                new->mapping = mapping;
 426                new->index = offset;
 427
 428                spin_lock_irq(&mapping->tree_lock);
 429                __delete_from_page_cache(old);
 430                error = radix_tree_insert(&mapping->page_tree, offset, new);
 431                BUG_ON(error);
 432                mapping->nrpages++;
 433                __inc_zone_page_state(new, NR_FILE_PAGES);
 434                if (PageSwapBacked(new))
 435                        __inc_zone_page_state(new, NR_SHMEM);
 436                spin_unlock_irq(&mapping->tree_lock);
 437                /* mem_cgroup codes must not be called under tree_lock */
 438                mem_cgroup_replace_page_cache(old, new);
 439                radix_tree_preload_end();
 440                if (freepage)
 441                        freepage(old);
 442                page_cache_release(old);
 443        }
 444
 445        return error;
 446}
 447EXPORT_SYMBOL_GPL(replace_page_cache_page);
 448
 449/**
 450 * add_to_page_cache_locked - add a locked page to the pagecache
 451 * @page:       page to add
 452 * @mapping:    the page's address_space
 453 * @offset:     page index
 454 * @gfp_mask:   page allocation mode
 455 *
 456 * This function is used to add a page to the pagecache. It must be locked.
 457 * This function does not add the page to the LRU.  The caller must do that.
 458 */
 459int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
 460                pgoff_t offset, gfp_t gfp_mask)
 461{
 462        int error;
 463
 464        VM_BUG_ON(!PageLocked(page));
 465        VM_BUG_ON(PageSwapBacked(page));
 466
 467        error = mem_cgroup_cache_charge(page, current->mm,
 468                                        gfp_mask & GFP_RECLAIM_MASK);
 469        if (error)
 470                return error;
 471
 472        error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
 473        if (error) {
 474                mem_cgroup_uncharge_cache_page(page);
 475                return error;
 476        }
 477
 478        page_cache_get(page);
 479        page->mapping = mapping;
 480        page->index = offset;
 481
 482        spin_lock_irq(&mapping->tree_lock);
 483        error = radix_tree_insert(&mapping->page_tree, offset, page);
 484        radix_tree_preload_end();
 485        if (unlikely(error))
 486                goto err_insert;
 487        mapping->nrpages++;
 488        __inc_zone_page_state(page, NR_FILE_PAGES);
 489        spin_unlock_irq(&mapping->tree_lock);
 490        trace_mm_filemap_add_to_page_cache(page);
 491        return 0;
 492err_insert:
 493        page->mapping = NULL;
 494        /* Leave page->index set: truncation relies upon it */
 495        spin_unlock_irq(&mapping->tree_lock);
 496        mem_cgroup_uncharge_cache_page(page);
 497        page_cache_release(page);
 498        return error;
 499}
 500EXPORT_SYMBOL(add_to_page_cache_locked);
 501
 502int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 503                                pgoff_t offset, gfp_t gfp_mask)
 504{
 505        int ret;
 506
 507        ret = add_to_page_cache(page, mapping, offset, gfp_mask);
 508        if (ret == 0)
 509                lru_cache_add_file(page);
 510        return ret;
 511}
 512EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
 513
 514#ifdef CONFIG_NUMA
 515struct page *__page_cache_alloc(gfp_t gfp)
 516{
 517        int n;
 518        struct page *page;
 519
 520        if (cpuset_do_page_mem_spread()) {
 521                unsigned int cpuset_mems_cookie;
 522                do {
 523                        cpuset_mems_cookie = get_mems_allowed();
 524                        n = cpuset_mem_spread_node();
 525                        page = alloc_pages_exact_node(n, gfp, 0);
 526                } while (!put_mems_allowed(cpuset_mems_cookie) && !page);
 527
 528                return page;
 529        }
 530        return alloc_pages(gfp, 0);
 531}
 532EXPORT_SYMBOL(__page_cache_alloc);
 533#endif
 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, sleep_on_page,
 563                                                        TASK_UNINTERRUPTIBLE);
 564}
 565EXPORT_SYMBOL(wait_on_page_bit);
 566
 567int wait_on_page_bit_killable(struct page *page, int bit_nr)
 568{
 569        DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
 570
 571        if (!test_bit(bit_nr, &page->flags))
 572                return 0;
 573
 574        return __wait_on_bit(page_waitqueue(page), &wait,
 575                             sleep_on_page_killable, TASK_KILLABLE);
 576}
 577
 578/**
 579 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
 580 * @page: Page defining the wait queue of interest
 581 * @waiter: Waiter to add to the queue
 582 *
 583 * Add an arbitrary @waiter to the wait queue for the nominated @page.
 584 */
 585void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
 586{
 587        wait_queue_head_t *q = page_waitqueue(page);
 588        unsigned long flags;
 589
 590        spin_lock_irqsave(&q->lock, flags);
 591        __add_wait_queue(q, waiter);
 592        spin_unlock_irqrestore(&q->lock, flags);
 593}
 594EXPORT_SYMBOL_GPL(add_page_wait_queue);
 595
 596/**
 597 * unlock_page - unlock a locked page
 598 * @page: the page
 599 *
 600 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
 601 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
 602 * mechananism between PageLocked pages and PageWriteback pages is shared.
 603 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
 604 *
 605 * The mb is necessary to enforce ordering between the clear_bit and the read
 606 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
 607 */
 608void unlock_page(struct page *page)
 609{
 610        VM_BUG_ON(!PageLocked(page));
 611        clear_bit_unlock(PG_locked, &page->flags);
 612        smp_mb__after_clear_bit();
 613        wake_up_page(page, PG_locked);
 614}
 615EXPORT_SYMBOL(unlock_page);
 616
 617/**
 618 * end_page_writeback - end writeback against a page
 619 * @page: the page
 620 */
 621void end_page_writeback(struct page *page)
 622{
 623        if (TestClearPageReclaim(page))
 624                rotate_reclaimable_page(page);
 625
 626        if (!test_clear_page_writeback(page))
 627                BUG();
 628
 629        smp_mb__after_clear_bit();
 630        wake_up_page(page, PG_writeback);
 631}
 632EXPORT_SYMBOL(end_page_writeback);
 633
 634/**
 635 * __lock_page - get a lock on the page, assuming we need to sleep to get it
 636 * @page: the page to lock
 637 */
 638void __lock_page(struct page *page)
 639{
 640        DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 641
 642        __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
 643                                                        TASK_UNINTERRUPTIBLE);
 644}
 645EXPORT_SYMBOL(__lock_page);
 646
 647int __lock_page_killable(struct page *page)
 648{
 649        DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 650
 651        return __wait_on_bit_lock(page_waitqueue(page), &wait,
 652                                        sleep_on_page_killable, TASK_KILLABLE);
 653}
 654EXPORT_SYMBOL_GPL(__lock_page_killable);
 655
 656int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
 657                         unsigned int flags)
 658{
 659        if (flags & FAULT_FLAG_ALLOW_RETRY) {
 660                /*
 661                 * CAUTION! In this case, mmap_sem is not released
 662                 * even though return 0.
 663                 */
 664                if (flags & FAULT_FLAG_RETRY_NOWAIT)
 665                        return 0;
 666
 667                up_read(&mm->mmap_sem);
 668                if (flags & FAULT_FLAG_KILLABLE)
 669                        wait_on_page_locked_killable(page);
 670                else
 671                        wait_on_page_locked(page);
 672                return 0;
 673        } else {
 674                if (flags & FAULT_FLAG_KILLABLE) {
 675                        int ret;
 676
 677                        ret = __lock_page_killable(page);
 678                        if (ret) {
 679                                up_read(&mm->mmap_sem);
 680                                return 0;
 681                        }
 682                } else
 683                        __lock_page(page);
 684                return 1;
 685        }
 686}
 687
 688/**
 689 * find_get_page - find and get a page reference
 690 * @mapping: the address_space to search
 691 * @offset: the page index
 692 *
 693 * Is there a pagecache struct page at the given (mapping, offset) tuple?
 694 * If yes, increment its refcount and return it; if no, return NULL.
 695 */
 696struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
 697{
 698        void **pagep;
 699        struct page *page;
 700
 701        rcu_read_lock();
 702repeat:
 703        page = NULL;
 704        pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
 705        if (pagep) {
 706                page = radix_tree_deref_slot(pagep);
 707                if (unlikely(!page))
 708                        goto out;
 709                if (radix_tree_exception(page)) {
 710                        if (radix_tree_deref_retry(page))
 711                                goto repeat;
 712                        /*
 713                         * Otherwise, shmem/tmpfs must be storing a swap entry
 714                         * here as an exceptional entry: so return it without
 715                         * attempting to raise page count.
 716                         */
 717                        goto out;
 718                }
 719                if (!page_cache_get_speculative(page))
 720                        goto repeat;
 721
 722                /*
 723                 * Has the page moved?
 724                 * This is part of the lockless pagecache protocol. See
 725                 * include/linux/pagemap.h for details.
 726                 */
 727                if (unlikely(page != *pagep)) {
 728                        page_cache_release(page);
 729                        goto repeat;
 730                }
 731        }
 732out:
 733        rcu_read_unlock();
 734
 735        return page;
 736}
 737EXPORT_SYMBOL(find_get_page);
 738
 739/**
 740 * find_lock_page - locate, pin and lock a pagecache page
 741 * @mapping: the address_space to search
 742 * @offset: the page index
 743 *
 744 * Locates the desired pagecache page, locks it, increments its reference
 745 * count and returns its address.
 746 *
 747 * Returns zero if the page was not present. find_lock_page() may sleep.
 748 */
 749struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
 750{
 751        struct page *page;
 752
 753repeat:
 754        page = find_get_page(mapping, offset);
 755        if (page && !radix_tree_exception(page)) {
 756                lock_page(page);
 757                /* Has the page been truncated? */
 758                if (unlikely(page->mapping != mapping)) {
 759                        unlock_page(page);
 760                        page_cache_release(page);
 761                        goto repeat;
 762                }
 763                VM_BUG_ON(page->index != offset);
 764        }
 765        return page;
 766}
 767EXPORT_SYMBOL(find_lock_page);
 768
 769/**
 770 * find_or_create_page - locate or add a pagecache page
 771 * @mapping: the page's address_space
 772 * @index: the page's index into the mapping
 773 * @gfp_mask: page allocation mode
 774 *
 775 * Locates a page in the pagecache.  If the page is not present, a new page
 776 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
 777 * LRU list.  The returned page is locked and has its reference count
 778 * incremented.
 779 *
 780 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
 781 * allocation!
 782 *
 783 * find_or_create_page() returns the desired page's address, or zero on
 784 * memory exhaustion.
 785 */
 786struct page *find_or_create_page(struct address_space *mapping,
 787                pgoff_t index, gfp_t gfp_mask)
 788{
 789        struct page *page;
 790        int err;
 791repeat:
 792        page = find_lock_page(mapping, index);
 793        if (!page) {
 794                page = __page_cache_alloc(gfp_mask);
 795                if (!page)
 796                        return NULL;
 797                /*
 798                 * We want a regular kernel memory (not highmem or DMA etc)
 799                 * allocation for the radix tree nodes, but we need to honour
 800                 * the context-specific requirements the caller has asked for.
 801                 * GFP_RECLAIM_MASK collects those requirements.
 802                 */
 803                err = add_to_page_cache_lru(page, mapping, index,
 804                        (gfp_mask & GFP_RECLAIM_MASK));
 805                if (unlikely(err)) {
 806                        page_cache_release(page);
 807                        page = NULL;
 808                        if (err == -EEXIST)
 809                                goto repeat;
 810                }
 811        }
 812        return page;
 813}
 814EXPORT_SYMBOL(find_or_create_page);
 815
 816/**
 817 * find_get_pages - gang pagecache lookup
 818 * @mapping:    The address_space to search
 819 * @start:      The starting page index
 820 * @nr_pages:   The maximum number of pages
 821 * @pages:      Where the resulting pages are placed
 822 *
 823 * find_get_pages() will search for and return a group of up to
 824 * @nr_pages pages in the mapping.  The pages are placed at @pages.
 825 * find_get_pages() takes a reference against the returned pages.
 826 *
 827 * The search returns a group of mapping-contiguous pages with ascending
 828 * indexes.  There may be holes in the indices due to not-present pages.
 829 *
 830 * find_get_pages() returns the number of pages which were found.
 831 */
 832unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
 833                            unsigned int nr_pages, struct page **pages)
 834{
 835        struct radix_tree_iter iter;
 836        void **slot;
 837        unsigned ret = 0;
 838
 839        if (unlikely(!nr_pages))
 840                return 0;
 841
 842        rcu_read_lock();
 843restart:
 844        radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
 845                struct page *page;
 846repeat:
 847                page = radix_tree_deref_slot(slot);
 848                if (unlikely(!page))
 849                        continue;
 850
 851                if (radix_tree_exception(page)) {
 852                        if (radix_tree_deref_retry(page)) {
 853                                /*
 854                                 * Transient condition which can only trigger
 855                                 * when entry at index 0 moves out of or back
 856                                 * to root: none yet gotten, safe to restart.
 857                                 */
 858                                WARN_ON(iter.index);
 859                                goto restart;
 860                        }
 861                        /*
 862                         * Otherwise, shmem/tmpfs must be storing a swap entry
 863                         * here as an exceptional entry: so skip over it -
 864                         * we only reach this from invalidate_mapping_pages().
 865                         */
 866                        continue;
 867                }
 868
 869                if (!page_cache_get_speculative(page))
 870                        goto repeat;
 871
 872                /* Has the page moved? */
 873                if (unlikely(page != *slot)) {
 874                        page_cache_release(page);
 875                        goto repeat;
 876                }
 877
 878                pages[ret] = page;
 879                if (++ret == nr_pages)
 880                        break;
 881        }
 882
 883        rcu_read_unlock();
 884        return ret;
 885}
 886
 887/**
 888 * find_get_pages_contig - gang contiguous pagecache lookup
 889 * @mapping:    The address_space to search
 890 * @index:      The starting page index
 891 * @nr_pages:   The maximum number of pages
 892 * @pages:      Where the resulting pages are placed
 893 *
 894 * find_get_pages_contig() works exactly like find_get_pages(), except
 895 * that the returned number of pages are guaranteed to be contiguous.
 896 *
 897 * find_get_pages_contig() returns the number of pages which were found.
 898 */
 899unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
 900                               unsigned int nr_pages, struct page **pages)
 901{
 902        struct radix_tree_iter iter;
 903        void **slot;
 904        unsigned int ret = 0;
 905
 906        if (unlikely(!nr_pages))
 907                return 0;
 908
 909        rcu_read_lock();
 910restart:
 911        radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
 912                struct page *page;
 913repeat:
 914                page = radix_tree_deref_slot(slot);
 915                /* The hole, there no reason to continue */
 916                if (unlikely(!page))
 917                        break;
 918
 919                if (radix_tree_exception(page)) {
 920                        if (radix_tree_deref_retry(page)) {
 921                                /*
 922                                 * Transient condition which can only trigger
 923                                 * when entry at index 0 moves out of or back
 924                                 * to root: none yet gotten, safe to restart.
 925                                 */
 926                                goto restart;
 927                        }
 928                        /*
 929                         * Otherwise, shmem/tmpfs must be storing a swap entry
 930                         * here as an exceptional entry: so stop looking for
 931                         * contiguous pages.
 932                         */
 933                        break;
 934                }
 935
 936                if (!page_cache_get_speculative(page))
 937                        goto repeat;
 938
 939                /* Has the page moved? */
 940                if (unlikely(page != *slot)) {
 941                        page_cache_release(page);
 942                        goto repeat;
 943                }
 944
 945                /*
 946                 * must check mapping and index after taking the ref.
 947                 * otherwise we can get both false positives and false
 948                 * negatives, which is just confusing to the caller.
 949                 */
 950                if (page->mapping == NULL || page->index != iter.index) {
 951                        page_cache_release(page);
 952                        break;
 953                }
 954
 955                pages[ret] = page;
 956                if (++ret == nr_pages)
 957                        break;
 958        }
 959        rcu_read_unlock();
 960        return ret;
 961}
 962EXPORT_SYMBOL(find_get_pages_contig);
 963
 964/**
 965 * find_get_pages_tag - find and return pages that match @tag
 966 * @mapping:    the address_space to search
 967 * @index:      the starting page index
 968 * @tag:        the tag index
 969 * @nr_pages:   the maximum number of pages
 970 * @pages:      where the resulting pages are placed
 971 *
 972 * Like find_get_pages, except we only return pages which are tagged with
 973 * @tag.   We update @index to index the next page for the traversal.
 974 */
 975unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
 976                        int tag, unsigned int nr_pages, struct page **pages)
 977{
 978        struct radix_tree_iter iter;
 979        void **slot;
 980        unsigned ret = 0;
 981
 982        if (unlikely(!nr_pages))
 983                return 0;
 984
 985        rcu_read_lock();
 986restart:
 987        radix_tree_for_each_tagged(slot, &mapping->page_tree,
 988                                   &iter, *index, tag) {
 989                struct page *page;
 990repeat:
 991                page = radix_tree_deref_slot(slot);
 992                if (unlikely(!page))
 993                        continue;
 994
 995                if (radix_tree_exception(page)) {
 996                        if (radix_tree_deref_retry(page)) {
 997                                /*
 998                                 * Transient condition which can only trigger
 999                                 * when entry at index 0 moves out of or back
1000                                 * to root: none yet gotten, safe to restart.
1001                                 */
1002                                goto restart;
1003                        }
1004                        /*
1005                         * This function is never used on a shmem/tmpfs
1006                         * mapping, so a swap entry won't be found here.
1007                         */
1008                        BUG();
1009                }
1010
1011                if (!page_cache_get_speculative(page))
1012                        goto repeat;
1013
1014                /* Has the page moved? */
1015                if (unlikely(page != *slot)) {
1016                        page_cache_release(page);
1017                        goto repeat;
1018                }
1019
1020                pages[ret] = page;
1021                if (++ret == nr_pages)
1022                        break;
1023        }
1024
1025        rcu_read_unlock();
1026
1027        if (ret)
1028                *index = pages[ret - 1]->index + 1;
1029
1030        return ret;
1031}
1032EXPORT_SYMBOL(find_get_pages_tag);
1033
1034/**
1035 * grab_cache_page_nowait - returns locked page at given index in given cache
1036 * @mapping: target address_space
1037 * @index: the page index
1038 *
1039 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1040 * This is intended for speculative data generators, where the data can
1041 * be regenerated if the page couldn't be grabbed.  This routine should
1042 * be safe to call while holding the lock for another page.
1043 *
1044 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1045 * and deadlock against the caller's locked page.
1046 */
1047struct page *
1048grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
1049{
1050        struct page *page = find_get_page(mapping, index);
1051
1052        if (page) {
1053                if (trylock_page(page))
1054                        return page;
1055                page_cache_release(page);
1056                return NULL;
1057        }
1058        page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1059        if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1060                page_cache_release(page);
1061                page = NULL;
1062        }
1063        return page;
1064}
1065EXPORT_SYMBOL(grab_cache_page_nowait);
1066
1067/*
1068 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1069 * a _large_ part of the i/o request. Imagine the worst scenario:
1070 *
1071 *      ---R__________________________________________B__________
1072 *         ^ reading here                             ^ bad block(assume 4k)
1073 *
1074 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1075 * => failing the whole request => read(R) => read(R+1) =>
1076 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1077 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1078 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1079 *
1080 * It is going insane. Fix it by quickly scaling down the readahead size.
1081 */
1082static void shrink_readahead_size_eio(struct file *filp,
1083                                        struct file_ra_state *ra)
1084{
1085        ra->ra_pages /= 4;
1086}
1087
1088/**
1089 * do_generic_file_read - generic file read routine
1090 * @filp:       the file to read
1091 * @ppos:       current file position
1092 * @desc:       read_descriptor
1093 * @actor:      read method
1094 *
1095 * This is a generic file read routine, and uses the
1096 * mapping->a_ops->readpage() function for the actual low-level stuff.
1097 *
1098 * This is really ugly. But the goto's actually try to clarify some
1099 * of the logic when it comes to error handling etc.
1100 */
1101static void do_generic_file_read(struct file *filp, loff_t *ppos,
1102                read_descriptor_t *desc, read_actor_t actor)
1103{
1104        struct address_space *mapping = filp->f_mapping;
1105        struct inode *inode = mapping->host;
1106        struct file_ra_state *ra = &filp->f_ra;
1107        pgoff_t index;
1108        pgoff_t last_index;
1109        pgoff_t prev_index;
1110        unsigned long offset;      /* offset into pagecache page */
1111        unsigned int prev_offset;
1112        int error;
1113
1114        index = *ppos >> PAGE_CACHE_SHIFT;
1115        prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1116        prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1117        last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1118        offset = *ppos & ~PAGE_CACHE_MASK;
1119
1120        for (;;) {
1121                struct page *page;
1122                pgoff_t end_index;
1123                loff_t isize;
1124                unsigned long nr, ret;
1125
1126                cond_resched();
1127find_page:
1128                page = find_get_page(mapping, index);
1129                if (!page) {
1130                        page_cache_sync_readahead(mapping,
1131                                        ra, filp,
1132                                        index, last_index - index);
1133                        page = find_get_page(mapping, index);
1134                        if (unlikely(page == NULL))
1135                                goto no_cached_page;
1136                }
1137                if (PageReadahead(page)) {
1138                        page_cache_async_readahead(mapping,
1139                                        ra, filp, page,
1140                                        index, last_index - index);
1141                }
1142                if (!PageUptodate(page)) {
1143                        if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1144                                        !mapping->a_ops->is_partially_uptodate)
1145                                goto page_not_up_to_date;
1146                        if (!trylock_page(page))
1147                                goto page_not_up_to_date;
1148                        /* Did it get truncated before we got the lock? */
1149                        if (!page->mapping)
1150                                goto page_not_up_to_date_locked;
1151                        if (!mapping->a_ops->is_partially_uptodate(page,
1152                                                                desc, offset))
1153                                goto page_not_up_to_date_locked;
1154                        unlock_page(page);
1155                }
1156page_ok:
1157                /*
1158                 * i_size must be checked after we know the page is Uptodate.
1159                 *
1160                 * Checking i_size after the check allows us to calculate
1161                 * the correct value for "nr", which means the zero-filled
1162                 * part of the page is not copied back to userspace (unless
1163                 * another truncate extends the file - this is desired though).
1164                 */
1165
1166                isize = i_size_read(inode);
1167                end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1168                if (unlikely(!isize || index > end_index)) {
1169                        page_cache_release(page);
1170                        goto out;
1171                }
1172
1173                /* nr is the maximum number of bytes to copy from this page */
1174                nr = PAGE_CACHE_SIZE;
1175                if (index == end_index) {
1176                        nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1177                        if (nr <= offset) {
1178                                page_cache_release(page);
1179                                goto out;
1180                        }
1181                }
1182                nr = nr - offset;
1183
1184                /* If users can be writing to this page using arbitrary
1185                 * virtual addresses, take care about potential aliasing
1186                 * before reading the page on the kernel side.
1187                 */
1188                if (mapping_writably_mapped(mapping))
1189                        flush_dcache_page(page);
1190
1191                /*
1192                 * When a sequential read accesses a page several times,
1193                 * only mark it as accessed the first time.
1194                 */
1195                if (prev_index != index || offset != prev_offset)
1196                        mark_page_accessed(page);
1197                prev_index = index;
1198
1199                /*
1200                 * Ok, we have the page, and it's up-to-date, so
1201                 * now we can copy it to user space...
1202                 *
1203                 * The actor routine returns how many bytes were actually used..
1204                 * NOTE! This may not be the same as how much of a user buffer
1205                 * we filled up (we may be padding etc), so we can only update
1206                 * "pos" here (the actor routine has to update the user buffer
1207                 * pointers and the remaining count).
1208                 */
1209                ret = actor(desc, page, offset, nr);
1210                offset += ret;
1211                index += offset >> PAGE_CACHE_SHIFT;
1212                offset &= ~PAGE_CACHE_MASK;
1213                prev_offset = offset;
1214
1215                page_cache_release(page);
1216                if (ret == nr && desc->count)
1217                        continue;
1218                goto out;
1219
1220page_not_up_to_date:
1221                /* Get exclusive access to the page ... */
1222                error = lock_page_killable(page);
1223                if (unlikely(error))
1224                        goto readpage_error;
1225
1226page_not_up_to_date_locked:
1227                /* Did it get truncated before we got the lock? */
1228                if (!page->mapping) {
1229                        unlock_page(page);
1230                        page_cache_release(page);
1231                        continue;
1232                }
1233
1234                /* Did somebody else fill it already? */
1235                if (PageUptodate(page)) {
1236                        unlock_page(page);
1237                        goto page_ok;
1238                }
1239
1240readpage:
1241                /*
1242                 * A previous I/O error may have been due to temporary
1243                 * failures, eg. multipath errors.
1244                 * PG_error will be set again if readpage fails.
1245                 */
1246                ClearPageError(page);
1247                /* Start the actual read. The read will unlock the page. */
1248                error = mapping->a_ops->readpage(filp, page);
1249
1250                if (unlikely(error)) {
1251                        if (error == AOP_TRUNCATED_PAGE) {
1252                                page_cache_release(page);
1253                                goto find_page;
1254                        }
1255                        goto readpage_error;
1256                }
1257
1258                if (!PageUptodate(page)) {
1259                        error = lock_page_killable(page);
1260                        if (unlikely(error))
1261                                goto readpage_error;
1262                        if (!PageUptodate(page)) {
1263                                if (page->mapping == NULL) {
1264                                        /*
1265                                         * invalidate_mapping_pages got it
1266                                         */
1267                                        unlock_page(page);
1268                                        page_cache_release(page);
1269                                        goto find_page;
1270                                }
1271                                unlock_page(page);
1272                                shrink_readahead_size_eio(filp, ra);
1273                                error = -EIO;
1274                                goto readpage_error;
1275                        }
1276                        unlock_page(page);
1277                }
1278
1279                goto page_ok;
1280
1281readpage_error:
1282                /* UHHUH! A synchronous read error occurred. Report it */
1283                desc->error = error;
1284                page_cache_release(page);
1285                goto out;
1286
1287no_cached_page:
1288                /*
1289                 * Ok, it wasn't cached, so we need to create a new
1290                 * page..
1291                 */
1292                page = page_cache_alloc_cold(mapping);
1293                if (!page) {
1294                        desc->error = -ENOMEM;
1295                        goto out;
1296                }
1297                error = add_to_page_cache_lru(page, mapping,
1298                                                index, GFP_KERNEL);
1299                if (error) {
1300                        page_cache_release(page);
1301                        if (error == -EEXIST)
1302                                goto find_page;
1303                        desc->error = error;
1304                        goto out;
1305                }
1306                goto readpage;
1307        }
1308
1309out:
1310        ra->prev_pos = prev_index;
1311        ra->prev_pos <<= PAGE_CACHE_SHIFT;
1312        ra->prev_pos |= prev_offset;
1313
1314        *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1315        file_accessed(filp);
1316}
1317
1318int file_read_actor(read_descriptor_t *desc, struct page *page,
1319                        unsigned long offset, unsigned long size)
1320{
1321        char *kaddr;
1322        unsigned long left, count = desc->count;
1323
1324        if (size > count)
1325                size = count;
1326
1327        /*
1328         * Faults on the destination of a read are common, so do it before
1329         * taking the kmap.
1330         */
1331        if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1332                kaddr = kmap_atomic(page);
1333                left = __copy_to_user_inatomic(desc->arg.buf,
1334                                                kaddr + offset, size);
1335                kunmap_atomic(kaddr);
1336                if (left == 0)
1337                        goto success;
1338        }
1339
1340        /* Do it the slow way */
1341        kaddr = kmap(page);
1342        left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1343        kunmap(page);
1344
1345        if (left) {
1346                size -= left;
1347                desc->error = -EFAULT;
1348        }
1349success:
1350        desc->count = count - size;
1351        desc->written += size;
1352        desc->arg.buf += size;
1353        return size;
1354}
1355
1356/*
1357 * Performs necessary checks before doing a write
1358 * @iov:        io vector request
1359 * @nr_segs:    number of segments in the iovec
1360 * @count:      number of bytes to write
1361 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1362 *
1363 * Adjust number of segments and amount of bytes to write (nr_segs should be
1364 * properly initialized first). Returns appropriate error code that caller
1365 * should return or zero in case that write should be allowed.
1366 */
1367int generic_segment_checks(const struct iovec *iov,
1368                        unsigned long *nr_segs, size_t *count, int access_flags)
1369{
1370        unsigned long   seg;
1371        size_t cnt = 0;
1372        for (seg = 0; seg < *nr_segs; seg++) {
1373                const struct iovec *iv = &iov[seg];
1374
1375                /*
1376                 * If any segment has a negative length, or the cumulative
1377                 * length ever wraps negative then return -EINVAL.
1378                 */
1379                cnt += iv->iov_len;
1380                if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1381                        return -EINVAL;
1382                if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1383                        continue;
1384                if (seg == 0)
1385                        return -EFAULT;
1386                *nr_segs = seg;
1387                cnt -= iv->iov_len;     /* This segment is no good */
1388                break;
1389        }
1390        *count = cnt;
1391        return 0;
1392}
1393EXPORT_SYMBOL(generic_segment_checks);
1394
1395/**
1396 * generic_file_aio_read - generic filesystem read routine
1397 * @iocb:       kernel I/O control block
1398 * @iov:        io vector request
1399 * @nr_segs:    number of segments in the iovec
1400 * @pos:        current file position
1401 *
1402 * This is the "read()" routine for all filesystems
1403 * that can use the page cache directly.
1404 */
1405ssize_t
1406generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1407                unsigned long nr_segs, loff_t pos)
1408{
1409        struct file *filp = iocb->ki_filp;
1410        ssize_t retval;
1411        unsigned long seg = 0;
1412        size_t count;
1413        loff_t *ppos = &iocb->ki_pos;
1414
1415        count = 0;
1416        retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1417        if (retval)
1418                return retval;
1419
1420        /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1421        if (filp->f_flags & O_DIRECT) {
1422                loff_t size;
1423                struct address_space *mapping;
1424                struct inode *inode;
1425
1426                mapping = filp->f_mapping;
1427                inode = mapping->host;
1428                if (!count)
1429                        goto out; /* skip atime */
1430                size = i_size_read(inode);
1431                if (pos < size) {
1432                        retval = filemap_write_and_wait_range(mapping, pos,
1433                                        pos + iov_length(iov, nr_segs) - 1);
1434                        if (!retval) {
1435                                retval = mapping->a_ops->direct_IO(READ, iocb,
1436                                                        iov, pos, nr_segs);
1437                        }
1438                        if (retval > 0) {
1439                                *ppos = pos + retval;
1440                                count -= retval;
1441                        }
1442
1443                        /*
1444                         * Btrfs can have a short DIO read if we encounter
1445                         * compressed extents, so if there was an error, or if
1446                         * we've already read everything we wanted to, or if
1447                         * there was a short read because we hit EOF, go ahead
1448                         * and return.  Otherwise fallthrough to buffered io for
1449                         * the rest of the read.
1450                         */
1451                        if (retval < 0 || !count || *ppos >= size) {
1452                                file_accessed(filp);
1453                                goto out;
1454                        }
1455                }
1456        }
1457
1458        count = retval;
1459        for (seg = 0; seg < nr_segs; seg++) {
1460                read_descriptor_t desc;
1461                loff_t offset = 0;
1462
1463                /*
1464                 * If we did a short DIO read we need to skip the section of the
1465                 * iov that we've already read data into.
1466                 */
1467                if (count) {
1468                        if (count > iov[seg].iov_len) {
1469                                count -= iov[seg].iov_len;
1470                                continue;
1471                        }
1472                        offset = count;
1473                        count = 0;
1474                }
1475
1476                desc.written = 0;
1477                desc.arg.buf = iov[seg].iov_base + offset;
1478                desc.count = iov[seg].iov_len - offset;
1479                if (desc.count == 0)
1480                        continue;
1481                desc.error = 0;
1482                do_generic_file_read(filp, ppos, &desc, file_read_actor);
1483                retval += desc.written;
1484                if (desc.error) {
1485                        retval = retval ?: desc.error;
1486                        break;
1487                }
1488                if (desc.count > 0)
1489                        break;
1490        }
1491out:
1492        return retval;
1493}
1494EXPORT_SYMBOL(generic_file_aio_read);
1495
1496#ifdef CONFIG_MMU
1497/**
1498 * page_cache_read - adds requested page to the page cache if not already there
1499 * @file:       file to read
1500 * @offset:     page index
1501 *
1502 * This adds the requested page to the page cache if it isn't already there,
1503 * and schedules an I/O to read in its contents from disk.
1504 */
1505static int page_cache_read(struct file *file, pgoff_t offset)
1506{
1507        struct address_space *mapping = file->f_mapping;
1508        struct page *page; 
1509        int ret;
1510
1511        do {
1512                page = page_cache_alloc_cold(mapping);
1513                if (!page)
1514                        return -ENOMEM;
1515
1516                ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1517                if (ret == 0)
1518                        ret = mapping->a_ops->readpage(file, page);
1519                else if (ret == -EEXIST)
1520                        ret = 0; /* losing race to add is OK */
1521
1522                page_cache_release(page);
1523
1524        } while (ret == AOP_TRUNCATED_PAGE);
1525                
1526        return ret;
1527}
1528
1529#define MMAP_LOTSAMISS  (100)
1530
1531/*
1532 * Synchronous readahead happens when we don't even find
1533 * a page in the page cache at all.
1534 */
1535static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1536                                   struct file_ra_state *ra,
1537                                   struct file *file,
1538                                   pgoff_t offset)
1539{
1540        unsigned long ra_pages;
1541        struct address_space *mapping = file->f_mapping;
1542
1543        /* If we don't want any read-ahead, don't bother */
1544        if (vma->vm_flags & VM_RAND_READ)
1545                return;
1546        if (!ra->ra_pages)
1547                return;
1548
1549        if (vma->vm_flags & VM_SEQ_READ) {
1550                page_cache_sync_readahead(mapping, ra, file, offset,
1551                                          ra->ra_pages);
1552                return;
1553        }
1554
1555        /* Avoid banging the cache line if not needed */
1556        if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1557                ra->mmap_miss++;
1558
1559        /*
1560         * Do we miss much more than hit in this file? If so,
1561         * stop bothering with read-ahead. It will only hurt.
1562         */
1563        if (ra->mmap_miss > MMAP_LOTSAMISS)
1564                return;
1565
1566        /*
1567         * mmap read-around
1568         */
1569        ra_pages = max_sane_readahead(ra->ra_pages);
1570        ra->start = max_t(long, 0, offset - ra_pages / 2);
1571        ra->size = ra_pages;
1572        ra->async_size = ra_pages / 4;
1573        ra_submit(ra, mapping, file);
1574}
1575
1576/*
1577 * Asynchronous readahead happens when we find the page and PG_readahead,
1578 * so we want to possibly extend the readahead further..
1579 */
1580static void do_async_mmap_readahead(struct vm_area_struct *vma,
1581                                    struct file_ra_state *ra,
1582                                    struct file *file,
1583                                    struct page *page,
1584                                    pgoff_t offset)
1585{
1586        struct address_space *mapping = file->f_mapping;
1587
1588        /* If we don't want any read-ahead, don't bother */
1589        if (vma->vm_flags & VM_RAND_READ)
1590                return;
1591        if (ra->mmap_miss > 0)
1592                ra->mmap_miss--;
1593        if (PageReadahead(page))
1594                page_cache_async_readahead(mapping, ra, file,
1595                                           page, offset, ra->ra_pages);
1596}
1597
1598/**
1599 * filemap_fault - read in file data for page fault handling
1600 * @vma:        vma in which the fault was taken
1601 * @vmf:        struct vm_fault containing details of the fault
1602 *
1603 * filemap_fault() is invoked via the vma operations vector for a
1604 * mapped memory region to read in file data during a page fault.
1605 *
1606 * The goto's are kind of ugly, but this streamlines the normal case of having
1607 * it in the page cache, and handles the special cases reasonably without
1608 * having a lot of duplicated code.
1609 */
1610int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1611{
1612        int error;
1613        struct file *file = vma->vm_file;
1614        struct address_space *mapping = file->f_mapping;
1615        struct file_ra_state *ra = &file->f_ra;
1616        struct inode *inode = mapping->host;
1617        pgoff_t offset = vmf->pgoff;
1618        struct page *page;
1619        pgoff_t size;
1620        int ret = 0;
1621
1622        size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1623        if (offset >= size)
1624                return VM_FAULT_SIGBUS;
1625
1626        /*
1627         * Do we have something in the page cache already?
1628         */
1629        page = find_get_page(mapping, offset);
1630        if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
1631                /*
1632                 * We found the page, so try async readahead before
1633                 * waiting for the lock.
1634                 */
1635                do_async_mmap_readahead(vma, ra, file, page, offset);
1636        } else if (!page) {
1637                /* No page in the page cache at all */
1638                do_sync_mmap_readahead(vma, ra, file, offset);
1639                count_vm_event(PGMAJFAULT);
1640                mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1641                ret = VM_FAULT_MAJOR;
1642retry_find:
1643                page = find_get_page(mapping, offset);
1644                if (!page)
1645                        goto no_cached_page;
1646        }
1647
1648        if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1649                page_cache_release(page);
1650                return ret | VM_FAULT_RETRY;
1651        }
1652
1653        /* Did it get truncated? */
1654        if (unlikely(page->mapping != mapping)) {
1655                unlock_page(page);
1656                put_page(page);
1657                goto retry_find;
1658        }
1659        VM_BUG_ON(page->index != offset);
1660
1661        /*
1662         * We have a locked page in the page cache, now we need to check
1663         * that it's up-to-date. If not, it is going to be due to an error.
1664         */
1665        if (unlikely(!PageUptodate(page)))
1666                goto page_not_uptodate;
1667
1668        /*
1669         * Found the page and have a reference on it.
1670         * We must recheck i_size under page lock.
1671         */
1672        size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1673        if (unlikely(offset >= size)) {
1674                unlock_page(page);
1675                page_cache_release(page);
1676                return VM_FAULT_SIGBUS;
1677        }
1678
1679        vmf->page = page;
1680        return ret | VM_FAULT_LOCKED;
1681
1682no_cached_page:
1683        /*
1684         * We're only likely to ever get here if MADV_RANDOM is in
1685         * effect.
1686         */
1687        error = page_cache_read(file, offset);
1688
1689        /*
1690         * The page we want has now been added to the page cache.
1691         * In the unlikely event that someone removed it in the
1692         * meantime, we'll just come back here and read it again.
1693         */
1694        if (error >= 0)
1695                goto retry_find;
1696
1697        /*
1698         * An error return from page_cache_read can result if the
1699         * system is low on memory, or a problem occurs while trying
1700         * to schedule I/O.
1701         */
1702        if (error == -ENOMEM)
1703                return VM_FAULT_OOM;
1704        return VM_FAULT_SIGBUS;
1705
1706page_not_uptodate:
1707        /*
1708         * Umm, take care of errors if the page isn't up-to-date.
1709         * Try to re-read it _once_. We do this synchronously,
1710         * because there really aren't any performance issues here
1711         * and we need to check for errors.
1712         */
1713        ClearPageError(page);
1714        error = mapping->a_ops->readpage(file, page);
1715        if (!error) {
1716                wait_on_page_locked(page);
1717                if (!PageUptodate(page))
1718                        error = -EIO;
1719        }
1720        page_cache_release(page);
1721
1722        if (!error || error == AOP_TRUNCATED_PAGE)
1723                goto retry_find;
1724
1725        /* Things didn't work out. Return zero to tell the mm layer so. */
1726        shrink_readahead_size_eio(file, ra);
1727        return VM_FAULT_SIGBUS;
1728}
1729EXPORT_SYMBOL(filemap_fault);
1730
1731int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
1732{
1733        struct page *page = vmf->page;
1734        struct inode *inode = file_inode(vma->vm_file);
1735        int ret = VM_FAULT_LOCKED;
1736
1737        sb_start_pagefault(inode->i_sb);
1738        file_update_time(vma->vm_file);
1739        lock_page(page);
1740        if (page->mapping != inode->i_mapping) {
1741                unlock_page(page);
1742                ret = VM_FAULT_NOPAGE;
1743                goto out;
1744        }
1745        /*
1746         * We mark the page dirty already here so that when freeze is in
1747         * progress, we are guaranteed that writeback during freezing will
1748         * see the dirty page and writeprotect it again.
1749         */
1750        set_page_dirty(page);
1751        wait_for_stable_page(page);
1752out:
1753        sb_end_pagefault(inode->i_sb);
1754        return ret;
1755}
1756EXPORT_SYMBOL(filemap_page_mkwrite);
1757
1758const struct vm_operations_struct generic_file_vm_ops = {
1759        .fault          = filemap_fault,
1760        .page_mkwrite   = filemap_page_mkwrite,
1761        .remap_pages    = generic_file_remap_pages,
1762};
1763
1764/* This is used for a general mmap of a disk file */
1765
1766int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1767{
1768        struct address_space *mapping = file->f_mapping;
1769
1770        if (!mapping->a_ops->readpage)
1771                return -ENOEXEC;
1772        file_accessed(file);
1773        vma->vm_ops = &generic_file_vm_ops;
1774        return 0;
1775}
1776
1777/*
1778 * This is for filesystems which do not implement ->writepage.
1779 */
1780int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1781{
1782        if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1783                return -EINVAL;
1784        return generic_file_mmap(file, vma);
1785}
1786#else
1787int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1788{
1789        return -ENOSYS;
1790}
1791int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1792{
1793        return -ENOSYS;
1794}
1795#endif /* CONFIG_MMU */
1796
1797EXPORT_SYMBOL(generic_file_mmap);
1798EXPORT_SYMBOL(generic_file_readonly_mmap);
1799
1800static struct page *__read_cache_page(struct address_space *mapping,
1801                                pgoff_t index,
1802                                int (*filler)(void *, struct page *),
1803                                void *data,
1804                                gfp_t gfp)
1805{
1806        struct page *page;
1807        int err;
1808repeat:
1809        page = find_get_page(mapping, index);
1810        if (!page) {
1811                page = __page_cache_alloc(gfp | __GFP_COLD);
1812                if (!page)
1813                        return ERR_PTR(-ENOMEM);
1814                err = add_to_page_cache_lru(page, mapping, index, gfp);
1815                if (unlikely(err)) {
1816                        page_cache_release(page);
1817                        if (err == -EEXIST)
1818                                goto repeat;
1819                        /* Presumably ENOMEM for radix tree node */
1820                        return ERR_PTR(err);
1821                }
1822                err = filler(data, page);
1823                if (err < 0) {
1824                        page_cache_release(page);
1825                        page = ERR_PTR(err);
1826                }
1827        }
1828        return page;
1829}
1830
1831static struct page *do_read_cache_page(struct address_space *mapping,
1832                                pgoff_t index,
1833                                int (*filler)(void *, struct page *),
1834                                void *data,
1835                                gfp_t gfp)
1836
1837{
1838        struct page *page;
1839        int err;
1840
1841retry:
1842        page = __read_cache_page(mapping, index, filler, data, gfp);
1843        if (IS_ERR(page))
1844                return page;
1845        if (PageUptodate(page))
1846                goto out;
1847
1848        lock_page(page);
1849        if (!page->mapping) {
1850                unlock_page(page);
1851                page_cache_release(page);
1852                goto retry;
1853        }
1854        if (PageUptodate(page)) {
1855                unlock_page(page);
1856                goto out;
1857        }
1858        err = filler(data, page);
1859        if (err < 0) {
1860                page_cache_release(page);
1861                return ERR_PTR(err);
1862        }
1863out:
1864        mark_page_accessed(page);
1865        return page;
1866}
1867
1868/**
1869 * read_cache_page_async - read into page cache, fill it if needed
1870 * @mapping:    the page's address_space
1871 * @index:      the page index
1872 * @filler:     function to perform the read
1873 * @data:       first arg to filler(data, page) function, often left as NULL
1874 *
1875 * Same as read_cache_page, but don't wait for page to become unlocked
1876 * after submitting it to the filler.
1877 *
1878 * Read into the page cache. If a page already exists, and PageUptodate() is
1879 * not set, try to fill the page but don't wait for it to become unlocked.
1880 *
1881 * If the page does not get brought uptodate, return -EIO.
1882 */
1883struct page *read_cache_page_async(struct address_space *mapping,
1884                                pgoff_t index,
1885                                int (*filler)(void *, struct page *),
1886                                void *data)
1887{
1888        return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1889}
1890EXPORT_SYMBOL(read_cache_page_async);
1891
1892static struct page *wait_on_page_read(struct page *page)
1893{
1894        if (!IS_ERR(page)) {
1895                wait_on_page_locked(page);
1896                if (!PageUptodate(page)) {
1897                        page_cache_release(page);
1898                        page = ERR_PTR(-EIO);
1899                }
1900        }
1901        return page;
1902}
1903
1904/**
1905 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1906 * @mapping:    the page's address_space
1907 * @index:      the page index
1908 * @gfp:        the page allocator flags to use if allocating
1909 *
1910 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1911 * any new page allocations done using the specified allocation flags.
1912 *
1913 * If the page does not get brought uptodate, return -EIO.
1914 */
1915struct page *read_cache_page_gfp(struct address_space *mapping,
1916                                pgoff_t index,
1917                                gfp_t gfp)
1918{
1919        filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1920
1921        return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1922}
1923EXPORT_SYMBOL(read_cache_page_gfp);
1924
1925/**
1926 * read_cache_page - read into page cache, fill it if needed
1927 * @mapping:    the page's address_space
1928 * @index:      the page index
1929 * @filler:     function to perform the read
1930 * @data:       first arg to filler(data, page) function, often left as NULL
1931 *
1932 * Read into the page cache. If a page already exists, and PageUptodate() is
1933 * not set, try to fill the page then wait for it to become unlocked.
1934 *
1935 * If the page does not get brought uptodate, return -EIO.
1936 */
1937struct page *read_cache_page(struct address_space *mapping,
1938                                pgoff_t index,
1939                                int (*filler)(void *, struct page *),
1940                                void *data)
1941{
1942        return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
1943}
1944EXPORT_SYMBOL(read_cache_page);
1945
1946static size_t __iovec_copy_from_user_inatomic(char *vaddr,
1947                        const struct iovec *iov, size_t base, size_t bytes)
1948{
1949        size_t copied = 0, left = 0;
1950
1951        while (bytes) {
1952                char __user *buf = iov->iov_base + base;
1953                int copy = min(bytes, iov->iov_len - base);
1954
1955                base = 0;
1956                left = __copy_from_user_inatomic(vaddr, buf, copy);
1957                copied += copy;
1958                bytes -= copy;
1959                vaddr += copy;
1960                iov++;
1961
1962                if (unlikely(left))
1963                        break;
1964        }
1965        return copied - left;
1966}
1967
1968/*
1969 * Copy as much as we can into the page and return the number of bytes which
1970 * were successfully copied.  If a fault is encountered then return the number of
1971 * bytes which were copied.
1972 */
1973size_t iov_iter_copy_from_user_atomic(struct page *page,
1974                struct iov_iter *i, unsigned long offset, size_t bytes)
1975{
1976        char *kaddr;
1977        size_t copied;
1978
1979        BUG_ON(!in_atomic());
1980        kaddr = kmap_atomic(page);
1981        if (likely(i->nr_segs == 1)) {
1982                int left;
1983                char __user *buf = i->iov->iov_base + i->iov_offset;
1984                left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
1985                copied = bytes - left;
1986        } else {
1987                copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1988                                                i->iov, i->iov_offset, bytes);
1989        }
1990        kunmap_atomic(kaddr);
1991
1992        return copied;
1993}
1994EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
1995
1996/*
1997 * This has the same sideeffects and return value as
1998 * iov_iter_copy_from_user_atomic().
1999 * The difference is that it attempts to resolve faults.
2000 * Page must not be locked.
2001 */
2002size_t iov_iter_copy_from_user(struct page *page,
2003                struct iov_iter *i, unsigned long offset, size_t bytes)
2004{
2005        char *kaddr;
2006        size_t copied;
2007
2008        kaddr = kmap(page);
2009        if (likely(i->nr_segs == 1)) {
2010                int left;
2011                char __user *buf = i->iov->iov_base + i->iov_offset;
2012                left = __copy_from_user(kaddr + offset, buf, bytes);
2013                copied = bytes - left;
2014        } else {
2015                copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2016                                                i->iov, i->iov_offset, bytes);
2017        }
2018        kunmap(page);
2019        return copied;
2020}
2021EXPORT_SYMBOL(iov_iter_copy_from_user);
2022
2023void iov_iter_advance(struct iov_iter *i, size_t bytes)
2024{
2025        BUG_ON(i->count < bytes);
2026
2027        if (likely(i->nr_segs == 1)) {
2028                i->iov_offset += bytes;
2029                i->count -= bytes;
2030        } else {
2031                const struct iovec *iov = i->iov;
2032                size_t base = i->iov_offset;
2033                unsigned long nr_segs = i->nr_segs;
2034
2035                /*
2036                 * The !iov->iov_len check ensures we skip over unlikely
2037                 * zero-length segments (without overruning the iovec).
2038                 */
2039                while (bytes || unlikely(i->count && !iov->iov_len)) {
2040                        int copy;
2041
2042                        copy = min(bytes, iov->iov_len - base);
2043                        BUG_ON(!i->count || i->count < copy);
2044                        i->count -= copy;
2045                        bytes -= copy;
2046                        base += copy;
2047                        if (iov->iov_len == base) {
2048                                iov++;
2049                                nr_segs--;
2050                                base = 0;
2051                        }
2052                }
2053                i->iov = iov;
2054                i->iov_offset = base;
2055                i->nr_segs = nr_segs;
2056        }
2057}
2058EXPORT_SYMBOL(iov_iter_advance);
2059
2060/*
2061 * Fault in the first iovec of the given iov_iter, to a maximum length
2062 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2063 * accessed (ie. because it is an invalid address).
2064 *
2065 * writev-intensive code may want this to prefault several iovecs -- that
2066 * would be possible (callers must not rely on the fact that _only_ the
2067 * first iovec will be faulted with the current implementation).
2068 */
2069int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2070{
2071        char __user *buf = i->iov->iov_base + i->iov_offset;
2072        bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2073        return fault_in_pages_readable(buf, bytes);
2074}
2075EXPORT_SYMBOL(iov_iter_fault_in_readable);
2076
2077/*
2078 * Return the count of just the current iov_iter segment.
2079 */
2080size_t iov_iter_single_seg_count(const struct iov_iter *i)
2081{
2082        const struct iovec *iov = i->iov;
2083        if (i->nr_segs == 1)
2084                return i->count;
2085        else
2086                return min(i->count, iov->iov_len - i->iov_offset);
2087}
2088EXPORT_SYMBOL(iov_iter_single_seg_count);
2089
2090/*
2091 * Performs necessary checks before doing a write
2092 *
2093 * Can adjust writing position or amount of bytes to write.
2094 * Returns appropriate error code that caller should return or
2095 * zero in case that write should be allowed.
2096 */
2097inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2098{
2099        struct inode *inode = file->f_mapping->host;
2100        unsigned long limit = rlimit(RLIMIT_FSIZE);
2101
2102        if (unlikely(*pos < 0))
2103                return -EINVAL;
2104
2105        if (!isblk) {
2106                /* FIXME: this is for backwards compatibility with 2.4 */
2107                if (file->f_flags & O_APPEND)
2108                        *pos = i_size_read(inode);
2109
2110                if (limit != RLIM_INFINITY) {
2111                        if (*pos >= limit) {
2112                                send_sig(SIGXFSZ, current, 0);
2113                                return -EFBIG;
2114                        }
2115                        if (*count > limit - (typeof(limit))*pos) {
2116                                *count = limit - (typeof(limit))*pos;
2117                        }
2118                }
2119        }
2120
2121        /*
2122         * LFS rule
2123         */
2124        if (unlikely(*pos + *count > MAX_NON_LFS &&
2125                                !(file->f_flags & O_LARGEFILE))) {
2126                if (*pos >= MAX_NON_LFS) {
2127                        return -EFBIG;
2128                }
2129                if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2130                        *count = MAX_NON_LFS - (unsigned long)*pos;
2131                }
2132        }
2133
2134        /*
2135         * Are we about to exceed the fs block limit ?
2136         *
2137         * If we have written data it becomes a short write.  If we have
2138         * exceeded without writing data we send a signal and return EFBIG.
2139         * Linus frestrict idea will clean these up nicely..
2140         */
2141        if (likely(!isblk)) {
2142                if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2143                        if (*count || *pos > inode->i_sb->s_maxbytes) {
2144                                return -EFBIG;
2145                        }
2146                        /* zero-length writes at ->s_maxbytes are OK */
2147                }
2148
2149                if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2150                        *count = inode->i_sb->s_maxbytes - *pos;
2151        } else {
2152#ifdef CONFIG_BLOCK
2153                loff_t isize;
2154                if (bdev_read_only(I_BDEV(inode)))
2155                        return -EPERM;
2156                isize = i_size_read(inode);
2157                if (*pos >= isize) {
2158                        if (*count || *pos > isize)
2159                                return -ENOSPC;
2160                }
2161
2162                if (*pos + *count > isize)
2163                        *count = isize - *pos;
2164#else
2165                return -EPERM;
2166#endif
2167        }
2168        return 0;
2169}
2170EXPORT_SYMBOL(generic_write_checks);
2171
2172int pagecache_write_begin(struct file *file, struct address_space *mapping,
2173                                loff_t pos, unsigned len, unsigned flags,
2174                                struct page **pagep, void **fsdata)
2175{
2176        const struct address_space_operations *aops = mapping->a_ops;
2177
2178        return aops->write_begin(file, mapping, pos, len, flags,
2179                                                        pagep, fsdata);
2180}
2181EXPORT_SYMBOL(pagecache_write_begin);
2182
2183int pagecache_write_end(struct file *file, struct address_space *mapping,
2184                                loff_t pos, unsigned len, unsigned copied,
2185                                struct page *page, void *fsdata)
2186{
2187        const struct address_space_operations *aops = mapping->a_ops;
2188
2189        mark_page_accessed(page);
2190        return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2191}
2192EXPORT_SYMBOL(pagecache_write_end);
2193
2194ssize_t
2195generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2196                unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2197                size_t count, size_t ocount)
2198{
2199        struct file     *file = iocb->ki_filp;
2200        struct address_space *mapping = file->f_mapping;
2201        struct inode    *inode = mapping->host;
2202        ssize_t         written;
2203        size_t          write_len;
2204        pgoff_t         end;
2205
2206        if (count != ocount)
2207                *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2208
2209        write_len = iov_length(iov, *nr_segs);
2210        end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2211
2212        written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2213        if (written)
2214                goto out;
2215
2216        /*
2217         * After a write we want buffered reads to be sure to go to disk to get
2218         * the new data.  We invalidate clean cached page from the region we're
2219         * about to write.  We do this *before* the write so that we can return
2220         * without clobbering -EIOCBQUEUED from ->direct_IO().
2221         */
2222        if (mapping->nrpages) {
2223                written = invalidate_inode_pages2_range(mapping,
2224                                        pos >> PAGE_CACHE_SHIFT, end);
2225                /*
2226                 * If a page can not be invalidated, return 0 to fall back
2227                 * to buffered write.
2228                 */
2229                if (written) {
2230                        if (written == -EBUSY)
2231                                return 0;
2232                        goto out;
2233                }
2234        }
2235
2236        written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2237
2238        /*
2239         * Finally, try again to invalidate clean pages which might have been
2240         * cached by non-direct readahead, or faulted in by get_user_pages()
2241         * if the source of the write was an mmap'ed region of the file
2242         * we're writing.  Either one is a pretty crazy thing to do,
2243         * so we don't support it 100%.  If this invalidation
2244         * fails, tough, the write still worked...
2245         */
2246        if (mapping->nrpages) {
2247                invalidate_inode_pages2_range(mapping,
2248                                              pos >> PAGE_CACHE_SHIFT, end);
2249        }
2250
2251        if (written > 0) {
2252                pos += written;
2253                if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2254                        i_size_write(inode, pos);
2255                        mark_inode_dirty(inode);
2256                }
2257                *ppos = pos;
2258        }
2259out:
2260        return written;
2261}
2262EXPORT_SYMBOL(generic_file_direct_write);
2263
2264/*
2265 * Find or create a page at the given pagecache position. Return the locked
2266 * page. This function is specifically for buffered writes.
2267 */
2268struct page *grab_cache_page_write_begin(struct address_space *mapping,
2269                                        pgoff_t index, unsigned flags)
2270{
2271        int status;
2272        gfp_t gfp_mask;
2273        struct page *page;
2274        gfp_t gfp_notmask = 0;
2275
2276        gfp_mask = mapping_gfp_mask(mapping);
2277        if (mapping_cap_account_dirty(mapping))
2278                gfp_mask |= __GFP_WRITE;
2279        if (flags & AOP_FLAG_NOFS)
2280                gfp_notmask = __GFP_FS;
2281repeat:
2282        page = find_lock_page(mapping, index);
2283        if (page)
2284                goto found;
2285
2286        page = __page_cache_alloc(gfp_mask & ~gfp_notmask);
2287        if (!page)
2288                return NULL;
2289        status = add_to_page_cache_lru(page, mapping, index,
2290                                                GFP_KERNEL & ~gfp_notmask);
2291        if (unlikely(status)) {
2292                page_cache_release(page);
2293                if (status == -EEXIST)
2294                        goto repeat;
2295                return NULL;
2296        }
2297found:
2298        wait_for_stable_page(page);
2299        return page;
2300}
2301EXPORT_SYMBOL(grab_cache_page_write_begin);
2302
2303static ssize_t generic_perform_write(struct file *file,
2304                                struct iov_iter *i, loff_t pos)
2305{
2306        struct address_space *mapping = file->f_mapping;
2307        const struct address_space_operations *a_ops = mapping->a_ops;
2308        long status = 0;
2309        ssize_t written = 0;
2310        unsigned int flags = 0;
2311
2312        /*
2313         * Copies from kernel address space cannot fail (NFSD is a big user).
2314         */
2315        if (segment_eq(get_fs(), KERNEL_DS))
2316                flags |= AOP_FLAG_UNINTERRUPTIBLE;
2317
2318        do {
2319                struct page *page;
2320                unsigned long offset;   /* Offset into pagecache page */
2321                unsigned long bytes;    /* Bytes to write to page */
2322                size_t copied;          /* Bytes copied from user */
2323                void *fsdata;
2324
2325                offset = (pos & (PAGE_CACHE_SIZE - 1));
2326                bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2327                                                iov_iter_count(i));
2328
2329again:
2330                /*
2331                 * Bring in the user page that we will copy from _first_.
2332                 * Otherwise there's a nasty deadlock on copying from the
2333                 * same page as we're writing to, without it being marked
2334                 * up-to-date.
2335                 *
2336                 * Not only is this an optimisation, but it is also required
2337                 * to check that the address is actually valid, when atomic
2338                 * usercopies are used, below.
2339                 */
2340                if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2341                        status = -EFAULT;
2342                        break;
2343                }
2344
2345                status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2346                                                &page, &fsdata);
2347                if (unlikely(status))
2348                        break;
2349
2350                if (mapping_writably_mapped(mapping))
2351                        flush_dcache_page(page);
2352
2353                pagefault_disable();
2354                copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2355                pagefault_enable();
2356                flush_dcache_page(page);
2357
2358                mark_page_accessed(page);
2359                status = a_ops->write_end(file, mapping, pos, bytes, copied,
2360                                                page, fsdata);
2361                if (unlikely(status < 0))
2362                        break;
2363                copied = status;
2364
2365                cond_resched();
2366
2367                iov_iter_advance(i, copied);
2368                if (unlikely(copied == 0)) {
2369                        /*
2370                         * If we were unable to copy any data at all, we must
2371                         * fall back to a single segment length write.
2372                         *
2373                         * If we didn't fallback here, we could livelock
2374                         * because not all segments in the iov can be copied at
2375                         * once without a pagefault.
2376                         */
2377                        bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2378                                                iov_iter_single_seg_count(i));
2379                        goto again;
2380                }
2381                pos += copied;
2382                written += copied;
2383
2384                balance_dirty_pages_ratelimited(mapping);
2385                if (fatal_signal_pending(current)) {
2386                        status = -EINTR;
2387                        break;
2388                }
2389        } while (iov_iter_count(i));
2390
2391        return written ? written : status;
2392}
2393
2394ssize_t
2395generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2396                unsigned long nr_segs, loff_t pos, loff_t *ppos,
2397                size_t count, ssize_t written)
2398{
2399        struct file *file = iocb->ki_filp;
2400        ssize_t status;
2401        struct iov_iter i;
2402
2403        iov_iter_init(&i, iov, nr_segs, count, written);
2404        status = generic_perform_write(file, &i, pos);
2405
2406        if (likely(status >= 0)) {
2407                written += status;
2408                *ppos = pos + status;
2409        }
2410        
2411        return written ? written : status;
2412}
2413EXPORT_SYMBOL(generic_file_buffered_write);
2414
2415/**
2416 * __generic_file_aio_write - write data to a file
2417 * @iocb:       IO state structure (file, offset, etc.)
2418 * @iov:        vector with data to write
2419 * @nr_segs:    number of segments in the vector
2420 * @ppos:       position where to write
2421 *
2422 * This function does all the work needed for actually writing data to a
2423 * file. It does all basic checks, removes SUID from the file, updates
2424 * modification times and calls proper subroutines depending on whether we
2425 * do direct IO or a standard buffered write.
2426 *
2427 * It expects i_mutex to be grabbed unless we work on a block device or similar
2428 * object which does not need locking at all.
2429 *
2430 * This function does *not* take care of syncing data in case of O_SYNC write.
2431 * A caller has to handle it. This is mainly due to the fact that we want to
2432 * avoid syncing under i_mutex.
2433 */
2434ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2435                                 unsigned long nr_segs, loff_t *ppos)
2436{
2437        struct file *file = iocb->ki_filp;
2438        struct address_space * mapping = file->f_mapping;
2439        size_t ocount;          /* original count */
2440        size_t count;           /* after file limit checks */
2441        struct inode    *inode = mapping->host;
2442        loff_t          pos;
2443        ssize_t         written;
2444        ssize_t         err;
2445
2446        ocount = 0;
2447        err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2448        if (err)
2449                return err;
2450
2451        count = ocount;
2452        pos = *ppos;
2453
2454        /* We can write back this queue in page reclaim */
2455        current->backing_dev_info = mapping->backing_dev_info;
2456        written = 0;
2457
2458        err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2459        if (err)
2460                goto out;
2461
2462        if (count == 0)
2463                goto out;
2464
2465        err = file_remove_suid(file);
2466        if (err)
2467                goto out;
2468
2469        err = file_update_time(file);
2470        if (err)
2471                goto out;
2472
2473        /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2474        if (unlikely(file->f_flags & O_DIRECT)) {
2475                loff_t endbyte;
2476                ssize_t written_buffered;
2477
2478                written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2479                                                        ppos, count, ocount);
2480                if (written < 0 || written == count)
2481                        goto out;
2482                /*
2483                 * direct-io write to a hole: fall through to buffered I/O
2484                 * for completing the rest of the request.
2485                 */
2486                pos += written;
2487                count -= written;
2488                written_buffered = generic_file_buffered_write(iocb, iov,
2489                                                nr_segs, pos, ppos, count,
2490                                                written);
2491                /*
2492                 * If generic_file_buffered_write() retuned a synchronous error
2493                 * then we want to return the number of bytes which were
2494                 * direct-written, or the error code if that was zero.  Note
2495                 * that this differs from normal direct-io semantics, which
2496                 * will return -EFOO even if some bytes were written.
2497                 */
2498                if (written_buffered < 0) {
2499                        err = written_buffered;
2500                        goto out;
2501                }
2502
2503                /*
2504                 * We need to ensure that the page cache pages are written to
2505                 * disk and invalidated to preserve the expected O_DIRECT
2506                 * semantics.
2507                 */
2508                endbyte = pos + written_buffered - written - 1;
2509                err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2510                if (err == 0) {
2511                        written = written_buffered;
2512                        invalidate_mapping_pages(mapping,
2513                                                 pos >> PAGE_CACHE_SHIFT,
2514                                                 endbyte >> PAGE_CACHE_SHIFT);
2515                } else {
2516                        /*
2517                         * We don't know how much we wrote, so just return
2518                         * the number of bytes which were direct-written
2519                         */
2520                }
2521        } else {
2522                written = generic_file_buffered_write(iocb, iov, nr_segs,
2523                                pos, ppos, count, written);
2524        }
2525out:
2526        current->backing_dev_info = NULL;
2527        return written ? written : err;
2528}
2529EXPORT_SYMBOL(__generic_file_aio_write);
2530
2531/**
2532 * generic_file_aio_write - write data to a file
2533 * @iocb:       IO state structure
2534 * @iov:        vector with data to write
2535 * @nr_segs:    number of segments in the vector
2536 * @pos:        position in file where to write
2537 *
2538 * This is a wrapper around __generic_file_aio_write() to be used by most
2539 * filesystems. It takes care of syncing the file in case of O_SYNC file
2540 * and acquires i_mutex as needed.
2541 */
2542ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2543                unsigned long nr_segs, loff_t pos)
2544{
2545        struct file *file = iocb->ki_filp;
2546        struct inode *inode = file->f_mapping->host;
2547        ssize_t ret;
2548
2549        BUG_ON(iocb->ki_pos != pos);
2550
2551        mutex_lock(&inode->i_mutex);
2552        ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2553        mutex_unlock(&inode->i_mutex);
2554
2555        if (ret > 0) {
2556                ssize_t err;
2557
2558                err = generic_write_sync(file, pos, ret);
2559                if (err < 0 && ret > 0)
2560                        ret = err;
2561        }
2562        return ret;
2563}
2564EXPORT_SYMBOL(generic_file_aio_write);
2565
2566/**
2567 * try_to_release_page() - release old fs-specific metadata on a page
2568 *
2569 * @page: the page which the kernel is trying to free
2570 * @gfp_mask: memory allocation flags (and I/O mode)
2571 *
2572 * The address_space is to try to release any data against the page
2573 * (presumably at page->private).  If the release was successful, return `1'.
2574 * Otherwise return zero.
2575 *
2576 * This may also be called if PG_fscache is set on a page, indicating that the
2577 * page is known to the local caching routines.
2578 *
2579 * The @gfp_mask argument specifies whether I/O may be performed to release
2580 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2581 *
2582 */
2583int try_to_release_page(struct page *page, gfp_t gfp_mask)
2584{
2585        struct address_space * const mapping = page->mapping;
2586
2587        BUG_ON(!PageLocked(page));
2588        if (PageWriteback(page))
2589                return 0;
2590
2591        if (mapping && mapping->a_ops->releasepage)
2592                return mapping->a_ops->releasepage(page, gfp_mask);
2593        return try_to_free_buffers(page);
2594}
2595
2596EXPORT_SYMBOL(try_to_release_page);
2597
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