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/*
  39 * FIXME: remove all knowledge of the buffer layer from the core VM
  40 */
  41#include <linux/buffer_head.h> /* for try_to_free_buffers */
  42
  43#include <asm/mman.h>
  44
  45/*
  46 * Shared mappings implemented 30.11.1994. It's not fully working yet,
  47 * though.
  48 *
  49 * Shared mappings now work. 15.8.1995  Bruno.
  50 *
  51 * finished 'unifying' the page and buffer cache and SMP-threaded the
  52 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
  53 *
  54 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
  55 */
  56
  57/*
  58 * Lock ordering:
  59 *
  60 *  ->i_mmap_mutex              (truncate_pagecache)
  61 *    ->private_lock            (__free_pte->__set_page_dirty_buffers)
  62 *      ->swap_lock             (exclusive_swap_page, others)
  63 *        ->mapping->tree_lock
  64 *
  65 *  ->i_mutex
  66 *    ->i_mmap_mutex            (truncate->unmap_mapping_range)
  67 *
  68 *  ->mmap_sem
  69 *    ->i_mmap_mutex
  70 *      ->page_table_lock or pte_lock   (various, mainly in memory.c)
  71 *        ->mapping->tree_lock  (arch-dependent flush_dcache_mmap_lock)
  72 *
  73 *  ->mmap_sem
  74 *    ->lock_page               (access_process_vm)
  75 *
  76 *  ->i_mutex                   (generic_file_buffered_write)
  77 *    ->mmap_sem                (fault_in_pages_readable->do_page_fault)
  78 *
  79 *  bdi->wb.list_lock
  80 *    sb_lock                   (fs/fs-writeback.c)
  81 *    ->mapping->tree_lock      (__sync_single_inode)
  82 *
  83 *  ->i_mmap_mutex
  84 *    ->anon_vma.lock           (vma_adjust)
  85 *
  86 *  ->anon_vma.lock
  87 *    ->page_table_lock or pte_lock     (anon_vma_prepare and various)
  88 *
  89 *  ->page_table_lock or pte_lock
  90 *    ->swap_lock               (try_to_unmap_one)
  91 *    ->private_lock            (try_to_unmap_one)
  92 *    ->tree_lock               (try_to_unmap_one)
  93 *    ->zone.lru_lock           (follow_page->mark_page_accessed)
  94 *    ->zone.lru_lock           (check_pte_range->isolate_lru_page)
  95 *    ->private_lock            (page_remove_rmap->set_page_dirty)
  96 *    ->tree_lock               (page_remove_rmap->set_page_dirty)
  97 *    bdi.wb->list_lock         (page_remove_rmap->set_page_dirty)
  98 *    ->inode->i_lock           (page_remove_rmap->set_page_dirty)
  99 *    bdi.wb->list_lock         (zap_pte_range->set_page_dirty)
 100 *    ->inode->i_lock           (zap_pte_range->set_page_dirty)
 101 *    ->private_lock            (zap_pte_range->__set_page_dirty_buffers)
 102 *
 103 * ->i_mmap_mutex
 104 *   ->tasklist_lock            (memory_failure, collect_procs_ao)
 105 */
 106
 107/*
 108 * Delete a page from the page cache and free it. Caller has to make
 109 * sure the page is locked and that nobody else uses it - or that usage
 110 * is safe.  The caller must hold the mapping's tree_lock.
 111 */
 112void __delete_from_page_cache(struct page *page)
 113{
 114        struct address_space *mapping = page->mapping;
 115
 116        /*
 117         * if we're uptodate, flush out into the cleancache, otherwise
 118         * invalidate any existing cleancache entries.  We can't leave
 119         * stale data around in the cleancache once our page is gone
 120         */
 121        if (PageUptodate(page) && PageMappedToDisk(page))
 122                cleancache_put_page(page);
 123        else
 124                cleancache_invalidate_page(mapping, page);
 125
 126        radix_tree_delete(&mapping->page_tree, page->index);
 127        page->mapping = NULL;
 128        /* Leave page->index set: truncation lookup relies upon it */
 129        mapping->nrpages--;
 130        __dec_zone_page_state(page, NR_FILE_PAGES);
 131        if (PageSwapBacked(page))
 132                __dec_zone_page_state(page, NR_SHMEM);
 133        BUG_ON(page_mapped(page));
 134
 135        /*
 136         * Some filesystems seem to re-dirty the page even after
 137         * the VM has canceled the dirty bit (eg ext3 journaling).
 138         *
 139         * Fix it up by doing a final dirty accounting check after
 140         * having removed the page entirely.
 141         */
 142        if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
 143                dec_zone_page_state(page, NR_FILE_DIRTY);
 144                dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
 145        }
 146}
 147
 148/**
 149 * delete_from_page_cache - delete page from page cache
 150 * @page: the page which the kernel is trying to remove from page cache
 151 *
 152 * This must be called only on pages that have been verified to be in the page
 153 * cache and locked.  It will never put the page into the free list, the caller
 154 * has a reference on the page.
 155 */
 156void delete_from_page_cache(struct page *page)
 157{
 158        struct address_space *mapping = page->mapping;
 159        void (*freepage)(struct page *);
 160
 161        BUG_ON(!PageLocked(page));
 162
 163        freepage = mapping->a_ops->freepage;
 164        spin_lock_irq(&mapping->tree_lock);
 165        __delete_from_page_cache(page);
 166        spin_unlock_irq(&mapping->tree_lock);
 167        mem_cgroup_uncharge_cache_page(page);
 168
 169        if (freepage)
 170                freepage(page);
 171        page_cache_release(page);
 172}
 173EXPORT_SYMBOL(delete_from_page_cache);
 174
 175static int sleep_on_page(void *word)
 176{
 177        io_schedule();
 178        return 0;
 179}
 180
 181static int sleep_on_page_killable(void *word)
 182{
 183        sleep_on_page(word);
 184        return fatal_signal_pending(current) ? -EINTR : 0;
 185}
 186
 187/**
 188 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
 189 * @mapping:    address space structure to write
 190 * @start:      offset in bytes where the range starts
 191 * @end:        offset in bytes where the range ends (inclusive)
 192 * @sync_mode:  enable synchronous operation
 193 *
 194 * Start writeback against all of a mapping's dirty pages that lie
 195 * within the byte offsets <start, end> inclusive.
 196 *
 197 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
 198 * opposed to a regular memory cleansing writeback.  The difference between
 199 * these two operations is that if a dirty page/buffer is encountered, it must
 200 * be waited upon, and not just skipped over.
 201 */
 202int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 203                                loff_t end, int sync_mode)
 204{
 205        int ret;
 206        struct writeback_control wbc = {
 207                .sync_mode = sync_mode,
 208                .nr_to_write = LONG_MAX,
 209                .range_start = start,
 210                .range_end = end,
 211        };
 212
 213        if (!mapping_cap_writeback_dirty(mapping))
 214                return 0;
 215
 216        ret = do_writepages(mapping, &wbc);
 217        return ret;
 218}
 219
 220static inline int __filemap_fdatawrite(struct address_space *mapping,
 221        int sync_mode)
 222{
 223        return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
 224}
 225
 226int filemap_fdatawrite(struct address_space *mapping)
 227{
 228        return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
 229}
 230EXPORT_SYMBOL(filemap_fdatawrite);
 231
 232int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 233                                loff_t end)
 234{
 235        return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
 236}
 237EXPORT_SYMBOL(filemap_fdatawrite_range);
 238
 239/**
 240 * filemap_flush - mostly a non-blocking flush
 241 * @mapping:    target address_space
 242 *
 243 * This is a mostly non-blocking flush.  Not suitable for data-integrity
 244 * purposes - I/O may not be started against all dirty pages.
 245 */
 246int filemap_flush(struct address_space *mapping)
 247{
 248        return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
 249}
 250EXPORT_SYMBOL(filemap_flush);
 251
 252/**
 253 * filemap_fdatawait_range - wait for writeback to complete
 254 * @mapping:            address space structure to wait for
 255 * @start_byte:         offset in bytes where the range starts
 256 * @end_byte:           offset in bytes where the range ends (inclusive)
 257 *
 258 * Walk the list of under-writeback pages of the given address space
 259 * in the given range and wait for all of them.
 260 */
 261int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
 262                            loff_t end_byte)
 263{
 264        pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
 265        pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
 266        struct pagevec pvec;
 267        int nr_pages;
 268        int ret = 0;
 269
 270        if (end_byte < start_byte)
 271                return 0;
 272
 273        pagevec_init(&pvec, 0);
 274        while ((index <= end) &&
 275                        (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
 276                        PAGECACHE_TAG_WRITEBACK,
 277                        min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
 278                unsigned i;
 279
 280                for (i = 0; i < nr_pages; i++) {
 281                        struct page *page = pvec.pages[i];
 282
 283                        /* until radix tree lookup accepts end_index */
 284                        if (page->index > end)
 285                                continue;
 286
 287                        wait_on_page_writeback(page);
 288                        if (TestClearPageError(page))
 289                                ret = -EIO;
 290                }
 291                pagevec_release(&pvec);
 292                cond_resched();
 293        }
 294
 295        /* Check for outstanding write errors */
 296        if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
 297                ret = -ENOSPC;
 298        if (test_and_clear_bit(AS_EIO, &mapping->flags))
 299                ret = -EIO;
 300
 301        return ret;
 302}
 303EXPORT_SYMBOL(filemap_fdatawait_range);
 304
 305/**
 306 * filemap_fdatawait - wait for all under-writeback pages to complete
 307 * @mapping: address space structure to wait for
 308 *
 309 * Walk the list of under-writeback pages of the given address space
 310 * and wait for all of them.
 311 */
 312int filemap_fdatawait(struct address_space *mapping)
 313{
 314        loff_t i_size = i_size_read(mapping->host);
 315
 316        if (i_size == 0)
 317                return 0;
 318
 319        return filemap_fdatawait_range(mapping, 0, i_size - 1);
 320}
 321EXPORT_SYMBOL(filemap_fdatawait);
 322
 323int filemap_write_and_wait(struct address_space *mapping)
 324{
 325        int err = 0;
 326
 327        if (mapping->nrpages) {
 328                err = filemap_fdatawrite(mapping);
 329                /*
 330                 * Even if the above returned error, the pages may be
 331                 * written partially (e.g. -ENOSPC), so we wait for it.
 332                 * But the -EIO is special case, it may indicate the worst
 333                 * thing (e.g. bug) happened, so we avoid waiting for it.
 334                 */
 335                if (err != -EIO) {
 336                        int err2 = filemap_fdatawait(mapping);
 337                        if (!err)
 338                                err = err2;
 339                }
 340        }
 341        return err;
 342}
 343EXPORT_SYMBOL(filemap_write_and_wait);
 344
 345/**
 346 * filemap_write_and_wait_range - write out & wait on a file range
 347 * @mapping:    the address_space for the pages
 348 * @lstart:     offset in bytes where the range starts
 349 * @lend:       offset in bytes where the range ends (inclusive)
 350 *
 351 * Write out and wait upon file offsets lstart->lend, inclusive.
 352 *
 353 * Note that `lend' is inclusive (describes the last byte to be written) so
 354 * that this function can be used to write to the very end-of-file (end = -1).
 355 */
 356int filemap_write_and_wait_range(struct address_space *mapping,
 357                                 loff_t lstart, loff_t lend)
 358{
 359        int err = 0;
 360
 361        if (mapping->nrpages) {
 362                err = __filemap_fdatawrite_range(mapping, lstart, lend,
 363                                                 WB_SYNC_ALL);
 364                /* See comment of filemap_write_and_wait() */
 365                if (err != -EIO) {
 366                        int err2 = filemap_fdatawait_range(mapping,
 367                                                lstart, lend);
 368                        if (!err)
 369                                err = err2;
 370                }
 371        }
 372        return err;
 373}
 374EXPORT_SYMBOL(filemap_write_and_wait_range);
 375
 376/**
 377 * replace_page_cache_page - replace a pagecache page with a new one
 378 * @old:        page to be replaced
 379 * @new:        page to replace with
 380 * @gfp_mask:   allocation mode
 381 *
 382 * This function replaces a page in the pagecache with a new one.  On
 383 * success it acquires the pagecache reference for the new page and
 384 * drops it for the old page.  Both the old and new pages must be
 385 * locked.  This function does not add the new page to the LRU, the
 386 * caller must do that.
 387 *
 388 * The remove + add is atomic.  The only way this function can fail is
 389 * memory allocation failure.
 390 */
 391int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 392{
 393        int error;
 394
 395        VM_BUG_ON(!PageLocked(old));
 396        VM_BUG_ON(!PageLocked(new));
 397        VM_BUG_ON(new->mapping);
 398
 399        error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
 400        if (!error) {
 401                struct address_space *mapping = old->mapping;
 402                void (*freepage)(struct page *);
 403
 404                pgoff_t offset = old->index;
 405                freepage = mapping->a_ops->freepage;
 406
 407                page_cache_get(new);
 408                new->mapping = mapping;
 409                new->index = offset;
 410
 411                spin_lock_irq(&mapping->tree_lock);
 412                __delete_from_page_cache(old);
 413                error = radix_tree_insert(&mapping->page_tree, offset, new);
 414                BUG_ON(error);
 415                mapping->nrpages++;
 416                __inc_zone_page_state(new, NR_FILE_PAGES);
 417                if (PageSwapBacked(new))
 418                        __inc_zone_page_state(new, NR_SHMEM);
 419                spin_unlock_irq(&mapping->tree_lock);
 420                /* mem_cgroup codes must not be called under tree_lock */
 421                mem_cgroup_replace_page_cache(old, new);
 422                radix_tree_preload_end();
 423                if (freepage)
 424                        freepage(old);
 425                page_cache_release(old);
 426        }
 427
 428        return error;
 429}
 430EXPORT_SYMBOL_GPL(replace_page_cache_page);
 431
 432/**
 433 * add_to_page_cache_locked - add a locked page to the pagecache
 434 * @page:       page to add
 435 * @mapping:    the page's address_space
 436 * @offset:     page index
 437 * @gfp_mask:   page allocation mode
 438 *
 439 * This function is used to add a page to the pagecache. It must be locked.
 440 * This function does not add the page to the LRU.  The caller must do that.
 441 */
 442int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
 443                pgoff_t offset, gfp_t gfp_mask)
 444{
 445        int error;
 446
 447        VM_BUG_ON(!PageLocked(page));
 448        VM_BUG_ON(PageSwapBacked(page));
 449
 450        error = mem_cgroup_cache_charge(page, current->mm,
 451                                        gfp_mask & GFP_RECLAIM_MASK);
 452        if (error)
 453                goto out;
 454
 455        error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
 456        if (error == 0) {
 457                page_cache_get(page);
 458                page->mapping = mapping;
 459                page->index = offset;
 460
 461                spin_lock_irq(&mapping->tree_lock);
 462                error = radix_tree_insert(&mapping->page_tree, offset, page);
 463                if (likely(!error)) {
 464                        mapping->nrpages++;
 465                        __inc_zone_page_state(page, NR_FILE_PAGES);
 466                        spin_unlock_irq(&mapping->tree_lock);
 467                } else {
 468                        page->mapping = NULL;
 469                        /* Leave page->index set: truncation relies upon it */
 470                        spin_unlock_irq(&mapping->tree_lock);
 471                        mem_cgroup_uncharge_cache_page(page);
 472                        page_cache_release(page);
 473                }
 474                radix_tree_preload_end();
 475        } else
 476                mem_cgroup_uncharge_cache_page(page);
 477out:
 478        return error;
 479}
 480EXPORT_SYMBOL(add_to_page_cache_locked);
 481
 482int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 483                                pgoff_t offset, gfp_t gfp_mask)
 484{
 485        int ret;
 486
 487        ret = add_to_page_cache(page, mapping, offset, gfp_mask);
 488        if (ret == 0)
 489                lru_cache_add_file(page);
 490        return ret;
 491}
 492EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
 493
 494#ifdef CONFIG_NUMA
 495struct page *__page_cache_alloc(gfp_t gfp)
 496{
 497        int n;
 498        struct page *page;
 499
 500        if (cpuset_do_page_mem_spread()) {
 501                unsigned int cpuset_mems_cookie;
 502                do {
 503                        cpuset_mems_cookie = get_mems_allowed();
 504                        n = cpuset_mem_spread_node();
 505                        page = alloc_pages_exact_node(n, gfp, 0);
 506                } while (!put_mems_allowed(cpuset_mems_cookie) && !page);
 507
 508                return page;
 509        }
 510        return alloc_pages(gfp, 0);
 511}
 512EXPORT_SYMBOL(__page_cache_alloc);
 513#endif
 514
 515/*
 516 * In order to wait for pages to become available there must be
 517 * waitqueues associated with pages. By using a hash table of
 518 * waitqueues where the bucket discipline is to maintain all
 519 * waiters on the same queue and wake all when any of the pages
 520 * become available, and for the woken contexts to check to be
 521 * sure the appropriate page became available, this saves space
 522 * at a cost of "thundering herd" phenomena during rare hash
 523 * collisions.
 524 */
 525static wait_queue_head_t *page_waitqueue(struct page *page)
 526{
 527        const struct zone *zone = page_zone(page);
 528
 529        return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
 530}
 531
 532static inline void wake_up_page(struct page *page, int bit)
 533{
 534        __wake_up_bit(page_waitqueue(page), &page->flags, bit);
 535}
 536
 537void wait_on_page_bit(struct page *page, int bit_nr)
 538{
 539        DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
 540
 541        if (test_bit(bit_nr, &page->flags))
 542                __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
 543                                                        TASK_UNINTERRUPTIBLE);
 544}
 545EXPORT_SYMBOL(wait_on_page_bit);
 546
 547int wait_on_page_bit_killable(struct page *page, int bit_nr)
 548{
 549        DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
 550
 551        if (!test_bit(bit_nr, &page->flags))
 552                return 0;
 553
 554        return __wait_on_bit(page_waitqueue(page), &wait,
 555                             sleep_on_page_killable, TASK_KILLABLE);
 556}
 557
 558/**
 559 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
 560 * @page: Page defining the wait queue of interest
 561 * @waiter: Waiter to add to the queue
 562 *
 563 * Add an arbitrary @waiter to the wait queue for the nominated @page.
 564 */
 565void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
 566{
 567        wait_queue_head_t *q = page_waitqueue(page);
 568        unsigned long flags;
 569
 570        spin_lock_irqsave(&q->lock, flags);
 571        __add_wait_queue(q, waiter);
 572        spin_unlock_irqrestore(&q->lock, flags);
 573}
 574EXPORT_SYMBOL_GPL(add_page_wait_queue);
 575
 576/**
 577 * unlock_page - unlock a locked page
 578 * @page: the page
 579 *
 580 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
 581 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
 582 * mechananism between PageLocked pages and PageWriteback pages is shared.
 583 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
 584 *
 585 * The mb is necessary to enforce ordering between the clear_bit and the read
 586 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
 587 */
 588void unlock_page(struct page *page)
 589{
 590        VM_BUG_ON(!PageLocked(page));
 591        clear_bit_unlock(PG_locked, &page->flags);
 592        smp_mb__after_clear_bit();
 593        wake_up_page(page, PG_locked);
 594}
 595EXPORT_SYMBOL(unlock_page);
 596
 597/**
 598 * end_page_writeback - end writeback against a page
 599 * @page: the page
 600 */
 601void end_page_writeback(struct page *page)
 602{
 603        if (TestClearPageReclaim(page))
 604                rotate_reclaimable_page(page);
 605
 606        if (!test_clear_page_writeback(page))
 607                BUG();
 608
 609        smp_mb__after_clear_bit();
 610        wake_up_page(page, PG_writeback);
 611}
 612EXPORT_SYMBOL(end_page_writeback);
 613
 614/**
 615 * __lock_page - get a lock on the page, assuming we need to sleep to get it
 616 * @page: the page to lock
 617 */
 618void __lock_page(struct page *page)
 619{
 620        DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 621
 622        __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
 623                                                        TASK_UNINTERRUPTIBLE);
 624}
 625EXPORT_SYMBOL(__lock_page);
 626
 627int __lock_page_killable(struct page *page)
 628{
 629        DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 630
 631        return __wait_on_bit_lock(page_waitqueue(page), &wait,
 632                                        sleep_on_page_killable, TASK_KILLABLE);
 633}
 634EXPORT_SYMBOL_GPL(__lock_page_killable);
 635
 636int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
 637                         unsigned int flags)
 638{
 639        if (flags & FAULT_FLAG_ALLOW_RETRY) {
 640                /*
 641                 * CAUTION! In this case, mmap_sem is not released
 642                 * even though return 0.
 643                 */
 644                if (flags & FAULT_FLAG_RETRY_NOWAIT)
 645                        return 0;
 646
 647                up_read(&mm->mmap_sem);
 648                if (flags & FAULT_FLAG_KILLABLE)
 649                        wait_on_page_locked_killable(page);
 650                else
 651                        wait_on_page_locked(page);
 652                return 0;
 653        } else {
 654                if (flags & FAULT_FLAG_KILLABLE) {
 655                        int ret;
 656
 657                        ret = __lock_page_killable(page);
 658                        if (ret) {
 659                                up_read(&mm->mmap_sem);
 660                                return 0;
 661                        }
 662                } else
 663                        __lock_page(page);
 664                return 1;
 665        }
 666}
 667
 668/**
 669 * find_get_page - find and get a page reference
 670 * @mapping: the address_space to search
 671 * @offset: the page index
 672 *
 673 * Is there a pagecache struct page at the given (mapping, offset) tuple?
 674 * If yes, increment its refcount and return it; if no, return NULL.
 675 */
 676struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
 677{
 678        void **pagep;
 679        struct page *page;
 680
 681        rcu_read_lock();
 682repeat:
 683        page = NULL;
 684        pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
 685        if (pagep) {
 686                page = radix_tree_deref_slot(pagep);
 687                if (unlikely(!page))
 688                        goto out;
 689                if (radix_tree_exception(page)) {
 690                        if (radix_tree_deref_retry(page))
 691                                goto repeat;
 692                        /*
 693                         * Otherwise, shmem/tmpfs must be storing a swap entry
 694                         * here as an exceptional entry: so return it without
 695                         * attempting to raise page count.
 696                         */
 697                        goto out;
 698                }
 699                if (!page_cache_get_speculative(page))
 700                        goto repeat;
 701
 702                /*
 703                 * Has the page moved?
 704                 * This is part of the lockless pagecache protocol. See
 705                 * include/linux/pagemap.h for details.
 706                 */
 707                if (unlikely(page != *pagep)) {
 708                        page_cache_release(page);
 709                        goto repeat;
 710                }
 711        }
 712out:
 713        rcu_read_unlock();
 714
 715        return page;
 716}
 717EXPORT_SYMBOL(find_get_page);
 718
 719/**
 720 * find_lock_page - locate, pin and lock a pagecache page
 721 * @mapping: the address_space to search
 722 * @offset: the page index
 723 *
 724 * Locates the desired pagecache page, locks it, increments its reference
 725 * count and returns its address.
 726 *
 727 * Returns zero if the page was not present. find_lock_page() may sleep.
 728 */
 729struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
 730{
 731        struct page *page;
 732
 733repeat:
 734        page = find_get_page(mapping, offset);
 735        if (page && !radix_tree_exception(page)) {
 736                lock_page(page);
 737                /* Has the page been truncated? */
 738                if (unlikely(page->mapping != mapping)) {
 739                        unlock_page(page);
 740                        page_cache_release(page);
 741                        goto repeat;
 742                }
 743                VM_BUG_ON(page->index != offset);
 744        }
 745        return page;
 746}
 747EXPORT_SYMBOL(find_lock_page);
 748
 749/**
 750 * find_or_create_page - locate or add a pagecache page
 751 * @mapping: the page's address_space
 752 * @index: the page's index into the mapping
 753 * @gfp_mask: page allocation mode
 754 *
 755 * Locates a page in the pagecache.  If the page is not present, a new page
 756 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
 757 * LRU list.  The returned page is locked and has its reference count
 758 * incremented.
 759 *
 760 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
 761 * allocation!
 762 *
 763 * find_or_create_page() returns the desired page's address, or zero on
 764 * memory exhaustion.
 765 */
 766struct page *find_or_create_page(struct address_space *mapping,
 767                pgoff_t index, gfp_t gfp_mask)
 768{
 769        struct page *page;
 770        int err;
 771repeat:
 772        page = find_lock_page(mapping, index);
 773        if (!page) {
 774                page = __page_cache_alloc(gfp_mask);
 775                if (!page)
 776                        return NULL;
 777                /*
 778                 * We want a regular kernel memory (not highmem or DMA etc)
 779                 * allocation for the radix tree nodes, but we need to honour
 780                 * the context-specific requirements the caller has asked for.
 781                 * GFP_RECLAIM_MASK collects those requirements.
 782                 */
 783                err = add_to_page_cache_lru(page, mapping, index,
 784                        (gfp_mask & GFP_RECLAIM_MASK));
 785                if (unlikely(err)) {
 786                        page_cache_release(page);
 787                        page = NULL;
 788                        if (err == -EEXIST)
 789                                goto repeat;
 790                }
 791        }
 792        return page;
 793}
 794EXPORT_SYMBOL(find_or_create_page);
 795
 796/**
 797 * find_get_pages - gang pagecache lookup
 798 * @mapping:    The address_space to search
 799 * @start:      The starting page index
 800 * @nr_pages:   The maximum number of pages
 801 * @pages:      Where the resulting pages are placed
 802 *
 803 * find_get_pages() will search for and return a group of up to
 804 * @nr_pages pages in the mapping.  The pages are placed at @pages.
 805 * find_get_pages() takes a reference against the returned pages.
 806 *
 807 * The search returns a group of mapping-contiguous pages with ascending
 808 * indexes.  There may be holes in the indices due to not-present pages.
 809 *
 810 * find_get_pages() returns the number of pages which were found.
 811 */
 812unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
 813                            unsigned int nr_pages, struct page **pages)
 814{
 815        struct radix_tree_iter iter;
 816        void **slot;
 817        unsigned ret = 0;
 818
 819        if (unlikely(!nr_pages))
 820                return 0;
 821
 822        rcu_read_lock();
 823restart:
 824        radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
 825                struct page *page;
 826repeat:
 827                page = radix_tree_deref_slot(slot);
 828                if (unlikely(!page))
 829                        continue;
 830
 831                if (radix_tree_exception(page)) {
 832                        if (radix_tree_deref_retry(page)) {
 833                                /*
 834                                 * Transient condition which can only trigger
 835                                 * when entry at index 0 moves out of or back
 836                                 * to root: none yet gotten, safe to restart.
 837                                 */
 838                                WARN_ON(iter.index);
 839                                goto restart;
 840                        }
 841                        /*
 842                         * Otherwise, shmem/tmpfs must be storing a swap entry
 843                         * here as an exceptional entry: so skip over it -
 844                         * we only reach this from invalidate_mapping_pages().
 845                         */
 846                        continue;
 847                }
 848
 849                if (!page_cache_get_speculative(page))
 850                        goto repeat;
 851
 852                /* Has the page moved? */
 853                if (unlikely(page != *slot)) {
 854                        page_cache_release(page);
 855                        goto repeat;
 856                }
 857
 858                pages[ret] = page;
 859                if (++ret == nr_pages)
 860                        break;
 861        }
 862
 863        rcu_read_unlock();
 864        return ret;
 865}
 866
 867/**
 868 * find_get_pages_contig - gang contiguous pagecache lookup
 869 * @mapping:    The address_space to search
 870 * @index:      The starting page index
 871 * @nr_pages:   The maximum number of pages
 872 * @pages:      Where the resulting pages are placed
 873 *
 874 * find_get_pages_contig() works exactly like find_get_pages(), except
 875 * that the returned number of pages are guaranteed to be contiguous.
 876 *
 877 * find_get_pages_contig() returns the number of pages which were found.
 878 */
 879unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
 880                               unsigned int nr_pages, struct page **pages)
 881{
 882        struct radix_tree_iter iter;
 883        void **slot;
 884        unsigned int ret = 0;
 885
 886        if (unlikely(!nr_pages))
 887                return 0;
 888
 889        rcu_read_lock();
 890restart:
 891        radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
 892                struct page *page;
 893repeat:
 894                page = radix_tree_deref_slot(slot);
 895                /* The hole, there no reason to continue */
 896                if (unlikely(!page))
 897                        break;
 898
 899                if (radix_tree_exception(page)) {
 900                        if (radix_tree_deref_retry(page)) {
 901                                /*
 902                                 * Transient condition which can only trigger
 903                                 * when entry at index 0 moves out of or back
 904                                 * to root: none yet gotten, safe to restart.
 905                                 */
 906                                goto restart;
 907                        }
 908                        /*
 909                         * Otherwise, shmem/tmpfs must be storing a swap entry
 910                         * here as an exceptional entry: so stop looking for
 911                         * contiguous pages.
 912                         */
 913                        break;
 914                }
 915
 916                if (!page_cache_get_speculative(page))
 917                        goto repeat;
 918
 919                /* Has the page moved? */
 920                if (unlikely(page != *slot)) {
 921                        page_cache_release(page);
 922                        goto repeat;
 923                }
 924
 925                /*
 926                 * must check mapping and index after taking the ref.
 927                 * otherwise we can get both false positives and false
 928                 * negatives, which is just confusing to the caller.
 929                 */
 930                if (page->mapping == NULL || page->index != iter.index) {
 931                        page_cache_release(page);
 932                        break;
 933                }
 934
 935                pages[ret] = page;
 936                if (++ret == nr_pages)
 937                        break;
 938        }
 939        rcu_read_unlock();
 940        return ret;
 941}
 942EXPORT_SYMBOL(find_get_pages_contig);
 943
 944/**
 945 * find_get_pages_tag - find and return pages that match @tag
 946 * @mapping:    the address_space to search
 947 * @index:      the starting page index
 948 * @tag:        the tag index
 949 * @nr_pages:   the maximum number of pages
 950 * @pages:      where the resulting pages are placed
 951 *
 952 * Like find_get_pages, except we only return pages which are tagged with
 953 * @tag.   We update @index to index the next page for the traversal.
 954 */
 955unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
 956                        int tag, unsigned int nr_pages, struct page **pages)
 957{
 958        struct radix_tree_iter iter;
 959        void **slot;
 960        unsigned ret = 0;
 961
 962        if (unlikely(!nr_pages))
 963                return 0;
 964
 965        rcu_read_lock();
 966restart:
 967        radix_tree_for_each_tagged(slot, &mapping->page_tree,
 968                                   &iter, *index, tag) {
 969                struct page *page;
 970repeat:
 971                page = radix_tree_deref_slot(slot);
 972                if (unlikely(!page))
 973                        continue;
 974
 975                if (radix_tree_exception(page)) {
 976                        if (radix_tree_deref_retry(page)) {
 977                                /*
 978                                 * Transient condition which can only trigger
 979                                 * when entry at index 0 moves out of or back
 980                                 * to root: none yet gotten, safe to restart.
 981                                 */
 982                                goto restart;
 983                        }
 984                        /*
 985                         * This function is never used on a shmem/tmpfs
 986                         * mapping, so a swap entry won't be found here.
 987                         */
 988                        BUG();
 989                }
 990
 991                if (!page_cache_get_speculative(page))
 992                        goto repeat;
 993
 994                /* Has the page moved? */
 995                if (unlikely(page != *slot)) {
 996                        page_cache_release(page);
 997                        goto repeat;
 998                }
 999
1000                pages[ret] = page;
1001                if (++ret == nr_pages)
1002                        break;
1003        }
1004
1005        rcu_read_unlock();
1006
1007        if (ret)
1008                *index = pages[ret - 1]->index + 1;
1009
1010        return ret;
1011}
1012EXPORT_SYMBOL(find_get_pages_tag);
1013
1014/**
1015 * grab_cache_page_nowait - returns locked page at given index in given cache
1016 * @mapping: target address_space
1017 * @index: the page index
1018 *
1019 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1020 * This is intended for speculative data generators, where the data can
1021 * be regenerated if the page couldn't be grabbed.  This routine should
1022 * be safe to call while holding the lock for another page.
1023 *
1024 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1025 * and deadlock against the caller's locked page.
1026 */
1027struct page *
1028grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
1029{
1030        struct page *page = find_get_page(mapping, index);
1031
1032        if (page) {
1033                if (trylock_page(page))
1034                        return page;
1035                page_cache_release(page);
1036                return NULL;
1037        }
1038        page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1039        if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1040                page_cache_release(page);
1041                page = NULL;
1042        }
1043        return page;
1044}
1045EXPORT_SYMBOL(grab_cache_page_nowait);
1046
1047/*
1048 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1049 * a _large_ part of the i/o request. Imagine the worst scenario:
1050 *
1051 *      ---R__________________________________________B__________
1052 *         ^ reading here                             ^ bad block(assume 4k)
1053 *
1054 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1055 * => failing the whole request => read(R) => read(R+1) =>
1056 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1057 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1058 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1059 *
1060 * It is going insane. Fix it by quickly scaling down the readahead size.
1061 */
1062static void shrink_readahead_size_eio(struct file *filp,
1063                                        struct file_ra_state *ra)
1064{
1065        ra->ra_pages /= 4;
1066}
1067
1068/**
1069 * do_generic_file_read - generic file read routine
1070 * @filp:       the file to read
1071 * @ppos:       current file position
1072 * @desc:       read_descriptor
1073 * @actor:      read method
1074 *
1075 * This is a generic file read routine, and uses the
1076 * mapping->a_ops->readpage() function for the actual low-level stuff.
1077 *
1078 * This is really ugly. But the goto's actually try to clarify some
1079 * of the logic when it comes to error handling etc.
1080 */
1081static void do_generic_file_read(struct file *filp, loff_t *ppos,
1082                read_descriptor_t *desc, read_actor_t actor)
1083{
1084        struct address_space *mapping = filp->f_mapping;
1085        struct inode *inode = mapping->host;
1086        struct file_ra_state *ra = &filp->f_ra;
1087        pgoff_t index;
1088        pgoff_t last_index;
1089        pgoff_t prev_index;
1090        unsigned long offset;      /* offset into pagecache page */
1091        unsigned int prev_offset;
1092        int error;
1093
1094        index = *ppos >> PAGE_CACHE_SHIFT;
1095        prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1096        prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1097        last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1098        offset = *ppos & ~PAGE_CACHE_MASK;
1099
1100        for (;;) {
1101                struct page *page;
1102                pgoff_t end_index;
1103                loff_t isize;
1104                unsigned long nr, ret;
1105
1106                cond_resched();
1107find_page:
1108                page = find_get_page(mapping, index);
1109                if (!page) {
1110                        page_cache_sync_readahead(mapping,
1111                                        ra, filp,
1112                                        index, last_index - index);
1113                        page = find_get_page(mapping, index);
1114                        if (unlikely(page == NULL))
1115                                goto no_cached_page;
1116                }
1117                if (PageReadahead(page)) {
1118                        page_cache_async_readahead(mapping,
1119                                        ra, filp, page,
1120                                        index, last_index - index);
1121                }
1122                if (!PageUptodate(page)) {
1123                        if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1124                                        !mapping->a_ops->is_partially_uptodate)
1125                                goto page_not_up_to_date;
1126                        if (!trylock_page(page))
1127                                goto page_not_up_to_date;
1128                        /* Did it get truncated before we got the lock? */
1129                        if (!page->mapping)
1130                                goto page_not_up_to_date_locked;
1131                        if (!mapping->a_ops->is_partially_uptodate(page,
1132                                                                desc, offset))
1133                                goto page_not_up_to_date_locked;
1134                        unlock_page(page);
1135                }
1136page_ok:
1137                /*
1138                 * i_size must be checked after we know the page is Uptodate.
1139                 *
1140                 * Checking i_size after the check allows us to calculate
1141                 * the correct value for "nr", which means the zero-filled
1142                 * part of the page is not copied back to userspace (unless
1143                 * another truncate extends the file - this is desired though).
1144                 */
1145
1146                isize = i_size_read(inode);
1147                end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1148                if (unlikely(!isize || index > end_index)) {
1149                        page_cache_release(page);
1150                        goto out;
1151                }
1152
1153                /* nr is the maximum number of bytes to copy from this page */
1154                nr = PAGE_CACHE_SIZE;
1155                if (index == end_index) {
1156                        nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1157                        if (nr <= offset) {
1158                                page_cache_release(page);
1159                                goto out;
1160                        }
1161                }
1162                nr = nr - offset;
1163
1164                /* If users can be writing to this page using arbitrary
1165                 * virtual addresses, take care about potential aliasing
1166                 * before reading the page on the kernel side.
1167                 */
1168                if (mapping_writably_mapped(mapping))
1169                        flush_dcache_page(page);
1170
1171                /*
1172                 * When a sequential read accesses a page several times,
1173                 * only mark it as accessed the first time.
1174                 */
1175                if (prev_index != index || offset != prev_offset)
1176                        mark_page_accessed(page);
1177                prev_index = index;
1178
1179                /*
1180                 * Ok, we have the page, and it's up-to-date, so
1181                 * now we can copy it to user space...
1182                 *
1183                 * The actor routine returns how many bytes were actually used..
1184                 * NOTE! This may not be the same as how much of a user buffer
1185                 * we filled up (we may be padding etc), so we can only update
1186                 * "pos" here (the actor routine has to update the user buffer
1187                 * pointers and the remaining count).
1188                 */
1189                ret = actor(desc, page, offset, nr);
1190                offset += ret;
1191                index += offset >> PAGE_CACHE_SHIFT;
1192                offset &= ~PAGE_CACHE_MASK;
1193                prev_offset = offset;
1194
1195                page_cache_release(page);
1196                if (ret == nr && desc->count)
1197                        continue;
1198                goto out;
1199
1200page_not_up_to_date:
1201                /* Get exclusive access to the page ... */
1202                error = lock_page_killable(page);
1203                if (unlikely(error))
1204                        goto readpage_error;
1205
1206page_not_up_to_date_locked:
1207                /* Did it get truncated before we got the lock? */
1208                if (!page->mapping) {
1209                        unlock_page(page);
1210                        page_cache_release(page);
1211                        continue;
1212                }
1213
1214                /* Did somebody else fill it already? */
1215                if (PageUptodate(page)) {
1216                        unlock_page(page);
1217                        goto page_ok;
1218                }
1219
1220readpage:
1221                /*
1222                 * A previous I/O error may have been due to temporary
1223                 * failures, eg. multipath errors.
1224                 * PG_error will be set again if readpage fails.
1225                 */
1226                ClearPageError(page);
1227                /* Start the actual read. The read will unlock the page. */
1228                error = mapping->a_ops->readpage(filp, page);
1229
1230                if (unlikely(error)) {
1231                        if (error == AOP_TRUNCATED_PAGE) {
1232                                page_cache_release(page);
1233                                goto find_page;
1234                        }
1235                        goto readpage_error;
1236                }
1237
1238                if (!PageUptodate(page)) {
1239                        error = lock_page_killable(page);
1240                        if (unlikely(error))
1241                                goto readpage_error;
1242                        if (!PageUptodate(page)) {
1243                                if (page->mapping == NULL) {
1244                                        /*
1245                                         * invalidate_mapping_pages got it
1246                                         */
1247                                        unlock_page(page);
1248                                        page_cache_release(page);
1249                                        goto find_page;
1250                                }
1251                                unlock_page(page);
1252                                shrink_readahead_size_eio(filp, ra);
1253                                error = -EIO;
1254                                goto readpage_error;
1255                        }
1256                        unlock_page(page);
1257                }
1258
1259                goto page_ok;
1260
1261readpage_error:
1262                /* UHHUH! A synchronous read error occurred. Report it */
1263                desc->error = error;
1264                page_cache_release(page);
1265                goto out;
1266
1267no_cached_page:
1268                /*
1269                 * Ok, it wasn't cached, so we need to create a new
1270                 * page..
1271                 */
1272                page = page_cache_alloc_cold(mapping);
1273                if (!page) {
1274                        desc->error = -ENOMEM;
1275                        goto out;
1276                }
1277                error = add_to_page_cache_lru(page, mapping,
1278                                                index, GFP_KERNEL);
1279                if (error) {
1280                        page_cache_release(page);
1281                        if (error == -EEXIST)
1282                                goto find_page;
1283                        desc->error = error;
1284                        goto out;
1285                }
1286                goto readpage;
1287        }
1288
1289out:
1290        ra->prev_pos = prev_index;
1291        ra->prev_pos <<= PAGE_CACHE_SHIFT;
1292        ra->prev_pos |= prev_offset;
1293
1294        *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1295        file_accessed(filp);
1296}
1297
1298int file_read_actor(read_descriptor_t *desc, struct page *page,
1299                        unsigned long offset, unsigned long size)
1300{
1301        char *kaddr;
1302        unsigned long left, count = desc->count;
1303
1304        if (size > count)
1305                size = count;
1306
1307        /*
1308         * Faults on the destination of a read are common, so do it before
1309         * taking the kmap.
1310         */
1311        if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1312                kaddr = kmap_atomic(page);
1313                left = __copy_to_user_inatomic(desc->arg.buf,
1314                                                kaddr + offset, size);
1315                kunmap_atomic(kaddr);
1316                if (left == 0)
1317                        goto success;
1318        }
1319
1320        /* Do it the slow way */
1321        kaddr = kmap(page);
1322        left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1323        kunmap(page);
1324
1325        if (left) {
1326                size -= left;
1327                desc->error = -EFAULT;
1328        }
1329success:
1330        desc->count = count - size;
1331        desc->written += size;
1332        desc->arg.buf += size;
1333        return size;
1334}
1335
1336/*
1337 * Performs necessary checks before doing a write
1338 * @iov:        io vector request
1339 * @nr_segs:    number of segments in the iovec
1340 * @count:      number of bytes to write
1341 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1342 *
1343 * Adjust number of segments and amount of bytes to write (nr_segs should be
1344 * properly initialized first). Returns appropriate error code that caller
1345 * should return or zero in case that write should be allowed.
1346 */
1347int generic_segment_checks(const struct iovec *iov,
1348                        unsigned long *nr_segs, size_t *count, int access_flags)
1349{
1350        unsigned long   seg;
1351        size_t cnt = 0;
1352        for (seg = 0; seg < *nr_segs; seg++) {
1353                const struct iovec *iv = &iov[seg];
1354
1355                /*
1356                 * If any segment has a negative length, or the cumulative
1357                 * length ever wraps negative then return -EINVAL.
1358                 */
1359                cnt += iv->iov_len;
1360                if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1361                        return -EINVAL;
1362                if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1363                        continue;
1364                if (seg == 0)
1365                        return -EFAULT;
1366                *nr_segs = seg;
1367                cnt -= iv->iov_len;     /* This segment is no good */
1368                break;
1369        }
1370        *count = cnt;
1371        return 0;
1372}
1373EXPORT_SYMBOL(generic_segment_checks);
1374
1375/**
1376 * generic_file_aio_read - generic filesystem read routine
1377 * @iocb:       kernel I/O control block
1378 * @iov:        io vector request
1379 * @nr_segs:    number of segments in the iovec
1380 * @pos:        current file position
1381 *
1382 * This is the "read()" routine for all filesystems
1383 * that can use the page cache directly.
1384 */
1385ssize_t
1386generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1387                unsigned long nr_segs, loff_t pos)
1388{
1389        struct file *filp = iocb->ki_filp;
1390        ssize_t retval;
1391        unsigned long seg = 0;
1392        size_t count;
1393        loff_t *ppos = &iocb->ki_pos;
1394
1395        count = 0;
1396        retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1397        if (retval)
1398                return retval;
1399
1400        /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1401        if (filp->f_flags & O_DIRECT) {
1402                loff_t size;
1403                struct address_space *mapping;
1404                struct inode *inode;
1405
1406                mapping = filp->f_mapping;
1407                inode = mapping->host;
1408                if (!count)
1409                        goto out; /* skip atime */
1410                size = i_size_read(inode);
1411                if (pos < size) {
1412                        retval = filemap_write_and_wait_range(mapping, pos,
1413                                        pos + iov_length(iov, nr_segs) - 1);
1414                        if (!retval) {
1415                                struct blk_plug plug;
1416
1417                                blk_start_plug(&plug);
1418                                retval = mapping->a_ops->direct_IO(READ, iocb,
1419                                                        iov, pos, nr_segs);
1420                                blk_finish_plug(&plug);
1421                        }
1422                        if (retval > 0) {
1423                                *ppos = pos + retval;
1424                                count -= retval;
1425                        }
1426
1427                        /*
1428                         * Btrfs can have a short DIO read if we encounter
1429                         * compressed extents, so if there was an error, or if
1430                         * we've already read everything we wanted to, or if
1431                         * there was a short read because we hit EOF, go ahead
1432                         * and return.  Otherwise fallthrough to buffered io for
1433                         * the rest of the read.
1434                         */
1435                        if (retval < 0 || !count || *ppos >= size) {
1436                                file_accessed(filp);
1437                                goto out;
1438                        }
1439                }
1440        }
1441
1442        count = retval;
1443        for (seg = 0; seg < nr_segs; seg++) {
1444                read_descriptor_t desc;
1445                loff_t offset = 0;
1446
1447                /*
1448                 * If we did a short DIO read we need to skip the section of the
1449                 * iov that we've already read data into.
1450                 */
1451                if (count) {
1452                        if (count > iov[seg].iov_len) {
1453                                count -= iov[seg].iov_len;
1454                                continue;
1455                        }
1456                        offset = count;
1457                        count = 0;
1458                }
1459
1460                desc.written = 0;
1461                desc.arg.buf = iov[seg].iov_base + offset;
1462                desc.count = iov[seg].iov_len - offset;
1463                if (desc.count == 0)
1464                        continue;
1465                desc.error = 0;
1466                do_generic_file_read(filp, ppos, &desc, file_read_actor);
1467                retval += desc.written;
1468                if (desc.error) {
1469                        retval = retval ?: desc.error;
1470                        break;
1471                }
1472                if (desc.count > 0)
1473                        break;
1474        }
1475out:
1476        return retval;
1477}
1478EXPORT_SYMBOL(generic_file_aio_read);
1479
1480#ifdef CONFIG_MMU
1481/**
1482 * page_cache_read - adds requested page to the page cache if not already there
1483 * @file:       file to read
1484 * @offset:     page index
1485 *
1486 * This adds the requested page to the page cache if it isn't already there,
1487 * and schedules an I/O to read in its contents from disk.
1488 */
1489static int page_cache_read(struct file *file, pgoff_t offset)
1490{
1491        struct address_space *mapping = file->f_mapping;
1492        struct page *page; 
1493        int ret;
1494
1495        do {
1496                page = page_cache_alloc_cold(mapping);
1497                if (!page)
1498                        return -ENOMEM;
1499
1500                ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1501                if (ret == 0)
1502                        ret = mapping->a_ops->readpage(file, page);
1503                else if (ret == -EEXIST)
1504                        ret = 0; /* losing race to add is OK */
1505
1506                page_cache_release(page);
1507
1508        } while (ret == AOP_TRUNCATED_PAGE);
1509                
1510        return ret;
1511}
1512
1513#define MMAP_LOTSAMISS  (100)
1514
1515/*
1516 * Synchronous readahead happens when we don't even find
1517 * a page in the page cache at all.
1518 */
1519static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1520                                   struct file_ra_state *ra,
1521                                   struct file *file,
1522                                   pgoff_t offset)
1523{
1524        unsigned long ra_pages;
1525        struct address_space *mapping = file->f_mapping;
1526
1527        /* If we don't want any read-ahead, don't bother */
1528        if (VM_RandomReadHint(vma))
1529                return;
1530        if (!ra->ra_pages)
1531                return;
1532
1533        if (VM_SequentialReadHint(vma)) {
1534                page_cache_sync_readahead(mapping, ra, file, offset,
1535                                          ra->ra_pages);
1536                return;
1537        }
1538
1539        /* Avoid banging the cache line if not needed */
1540        if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1541                ra->mmap_miss++;
1542
1543        /*
1544         * Do we miss much more than hit in this file? If so,
1545         * stop bothering with read-ahead. It will only hurt.
1546         */
1547        if (ra->mmap_miss > MMAP_LOTSAMISS)
1548                return;
1549
1550        /*
1551         * mmap read-around
1552         */
1553        ra_pages = max_sane_readahead(ra->ra_pages);
1554        ra->start = max_t(long, 0, offset - ra_pages / 2);
1555        ra->size = ra_pages;
1556        ra->async_size = ra_pages / 4;
1557        ra_submit(ra, mapping, file);
1558}
1559
1560/*
1561 * Asynchronous readahead happens when we find the page and PG_readahead,
1562 * so we want to possibly extend the readahead further..
1563 */
1564static void do_async_mmap_readahead(struct vm_area_struct *vma,
1565                                    struct file_ra_state *ra,
1566                                    struct file *file,
1567                                    struct page *page,
1568                                    pgoff_t offset)
1569{
1570        struct address_space *mapping = file->f_mapping;
1571
1572        /* If we don't want any read-ahead, don't bother */
1573        if (VM_RandomReadHint(vma))
1574                return;
1575        if (ra->mmap_miss > 0)
1576                ra->mmap_miss--;
1577        if (PageReadahead(page))
1578                page_cache_async_readahead(mapping, ra, file,
1579                                           page, offset, ra->ra_pages);
1580}
1581
1582/**
1583 * filemap_fault - read in file data for page fault handling
1584 * @vma:        vma in which the fault was taken
1585 * @vmf:        struct vm_fault containing details of the fault
1586 *
1587 * filemap_fault() is invoked via the vma operations vector for a
1588 * mapped memory region to read in file data during a page fault.
1589 *
1590 * The goto's are kind of ugly, but this streamlines the normal case of having
1591 * it in the page cache, and handles the special cases reasonably without
1592 * having a lot of duplicated code.
1593 */
1594int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1595{
1596        int error;
1597        struct file *file = vma->vm_file;
1598        struct address_space *mapping = file->f_mapping;
1599        struct file_ra_state *ra = &file->f_ra;
1600        struct inode *inode = mapping->host;
1601        pgoff_t offset = vmf->pgoff;
1602        struct page *page;
1603        pgoff_t size;
1604        int ret = 0;
1605
1606        size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1607        if (offset >= size)
1608                return VM_FAULT_SIGBUS;
1609
1610        /*
1611         * Do we have something in the page cache already?
1612         */
1613        page = find_get_page(mapping, offset);
1614        if (likely(page)) {
1615                /*
1616                 * We found the page, so try async readahead before
1617                 * waiting for the lock.
1618                 */
1619                do_async_mmap_readahead(vma, ra, file, page, offset);
1620        } else {
1621                /* No page in the page cache at all */
1622                do_sync_mmap_readahead(vma, ra, file, offset);
1623                count_vm_event(PGMAJFAULT);
1624                mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1625                ret = VM_FAULT_MAJOR;
1626retry_find:
1627                page = find_get_page(mapping, offset);
1628                if (!page)
1629                        goto no_cached_page;
1630        }
1631
1632        if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1633                page_cache_release(page);
1634                return ret | VM_FAULT_RETRY;
1635        }
1636
1637        /* Did it get truncated? */
1638        if (unlikely(page->mapping != mapping)) {
1639                unlock_page(page);
1640                put_page(page);
1641                goto retry_find;
1642        }
1643        VM_BUG_ON(page->index != offset);
1644
1645        /*
1646         * We have a locked page in the page cache, now we need to check
1647         * that it's up-to-date. If not, it is going to be due to an error.
1648         */
1649        if (unlikely(!PageUptodate(page)))
1650                goto page_not_uptodate;
1651
1652        /*
1653         * Found the page and have a reference on it.
1654         * We must recheck i_size under page lock.
1655         */
1656        size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1657        if (unlikely(offset >= size)) {
1658                unlock_page(page);
1659                page_cache_release(page);
1660                return VM_FAULT_SIGBUS;
1661        }
1662
1663        vmf->page = page;
1664        return ret | VM_FAULT_LOCKED;
1665
1666no_cached_page:
1667        /*
1668         * We're only likely to ever get here if MADV_RANDOM is in
1669         * effect.
1670         */
1671        error = page_cache_read(file, offset);
1672
1673        /*
1674         * The page we want has now been added to the page cache.
1675         * In the unlikely event that someone removed it in the
1676         * meantime, we'll just come back here and read it again.
1677         */
1678        if (error >= 0)
1679                goto retry_find;
1680
1681        /*
1682         * An error return from page_cache_read can result if the
1683         * system is low on memory, or a problem occurs while trying
1684         * to schedule I/O.
1685         */
1686        if (error == -ENOMEM)
1687                return VM_FAULT_OOM;
1688        return VM_FAULT_SIGBUS;
1689
1690page_not_uptodate:
1691        /*
1692         * Umm, take care of errors if the page isn't up-to-date.
1693         * Try to re-read it _once_. We do this synchronously,
1694         * because there really aren't any performance issues here
1695         * and we need to check for errors.
1696         */
1697        ClearPageError(page);
1698        error = mapping->a_ops->readpage(file, page);
1699        if (!error) {
1700                wait_on_page_locked(page);
1701                if (!PageUptodate(page))
1702                        error = -EIO;
1703        }
1704        page_cache_release(page);
1705
1706        if (!error || error == AOP_TRUNCATED_PAGE)
1707                goto retry_find;
1708
1709        /* Things didn't work out. Return zero to tell the mm layer so. */
1710        shrink_readahead_size_eio(file, ra);
1711        return VM_FAULT_SIGBUS;
1712}
1713EXPORT_SYMBOL(filemap_fault);
1714
1715const struct vm_operations_struct generic_file_vm_ops = {
1716        .fault          = filemap_fault,
1717};
1718
1719/* This is used for a general mmap of a disk file */
1720
1721int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1722{
1723        struct address_space *mapping = file->f_mapping;
1724
1725        if (!mapping->a_ops->readpage)
1726                return -ENOEXEC;
1727        file_accessed(file);
1728        vma->vm_ops = &generic_file_vm_ops;
1729        vma->vm_flags |= VM_CAN_NONLINEAR;
1730        return 0;
1731}
1732
1733/*
1734 * This is for filesystems which do not implement ->writepage.
1735 */
1736int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1737{
1738        if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1739                return -EINVAL;
1740        return generic_file_mmap(file, vma);
1741}
1742#else
1743int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1744{
1745        return -ENOSYS;
1746}
1747int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1748{
1749        return -ENOSYS;
1750}
1751#endif /* CONFIG_MMU */
1752
1753EXPORT_SYMBOL(generic_file_mmap);
1754EXPORT_SYMBOL(generic_file_readonly_mmap);
1755
1756static struct page *__read_cache_page(struct address_space *mapping,
1757                                pgoff_t index,
1758                                int (*filler)(void *, struct page *),
1759                                void *data,
1760                                gfp_t gfp)
1761{
1762        struct page *page;
1763        int err;
1764repeat:
1765        page = find_get_page(mapping, index);
1766        if (!page) {
1767                page = __page_cache_alloc(gfp | __GFP_COLD);
1768                if (!page)
1769                        return ERR_PTR(-ENOMEM);
1770                err = add_to_page_cache_lru(page, mapping, index, gfp);
1771                if (unlikely(err)) {
1772                        page_cache_release(page);
1773                        if (err == -EEXIST)
1774                                goto repeat;
1775                        /* Presumably ENOMEM for radix tree node */
1776                        return ERR_PTR(err);
1777                }
1778                err = filler(data, page);
1779                if (err < 0) {
1780                        page_cache_release(page);
1781                        page = ERR_PTR(err);
1782                }
1783        }
1784        return page;
1785}
1786
1787static struct page *do_read_cache_page(struct address_space *mapping,
1788                                pgoff_t index,
1789                                int (*filler)(void *, struct page *),
1790                                void *data,
1791                                gfp_t gfp)
1792
1793{
1794        struct page *page;
1795        int err;
1796
1797retry:
1798        page = __read_cache_page(mapping, index, filler, data, gfp);
1799        if (IS_ERR(page))
1800                return page;
1801        if (PageUptodate(page))
1802                goto out;
1803
1804        lock_page(page);
1805        if (!page->mapping) {
1806                unlock_page(page);
1807                page_cache_release(page);
1808                goto retry;
1809        }
1810        if (PageUptodate(page)) {
1811                unlock_page(page);
1812                goto out;
1813        }
1814        err = filler(data, page);
1815        if (err < 0) {
1816                page_cache_release(page);
1817                return ERR_PTR(err);
1818        }
1819out:
1820        mark_page_accessed(page);
1821        return page;
1822}
1823
1824/**
1825 * read_cache_page_async - read into page cache, fill it if needed
1826 * @mapping:    the page's address_space
1827 * @index:      the page index
1828 * @filler:     function to perform the read
1829 * @data:       first arg to filler(data, page) function, often left as NULL
1830 *
1831 * Same as read_cache_page, but don't wait for page to become unlocked
1832 * after submitting it to the filler.
1833 *
1834 * Read into the page cache. If a page already exists, and PageUptodate() is
1835 * not set, try to fill the page but don't wait for it to become unlocked.
1836 *
1837 * If the page does not get brought uptodate, return -EIO.
1838 */
1839struct page *read_cache_page_async(struct address_space *mapping,
1840                                pgoff_t index,
1841                                int (*filler)(void *, struct page *),
1842                                void *data)
1843{
1844        return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1845}
1846EXPORT_SYMBOL(read_cache_page_async);
1847
1848static struct page *wait_on_page_read(struct page *page)
1849{
1850        if (!IS_ERR(page)) {
1851                wait_on_page_locked(page);
1852                if (!PageUptodate(page)) {
1853                        page_cache_release(page);
1854                        page = ERR_PTR(-EIO);
1855                }
1856        }
1857        return page;
1858}
1859
1860/**
1861 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1862 * @mapping:    the page's address_space
1863 * @index:      the page index
1864 * @gfp:        the page allocator flags to use if allocating
1865 *
1866 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1867 * any new page allocations done using the specified allocation flags.
1868 *
1869 * If the page does not get brought uptodate, return -EIO.
1870 */
1871struct page *read_cache_page_gfp(struct address_space *mapping,
1872                                pgoff_t index,
1873                                gfp_t gfp)
1874{
1875        filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1876
1877        return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1878}
1879EXPORT_SYMBOL(read_cache_page_gfp);
1880
1881/**
1882 * read_cache_page - read into page cache, fill it if needed
1883 * @mapping:    the page's address_space
1884 * @index:      the page index
1885 * @filler:     function to perform the read
1886 * @data:       first arg to filler(data, page) function, often left as NULL
1887 *
1888 * Read into the page cache. If a page already exists, and PageUptodate() is
1889 * not set, try to fill the page then wait for it to become unlocked.
1890 *
1891 * If the page does not get brought uptodate, return -EIO.
1892 */
1893struct page *read_cache_page(struct address_space *mapping,
1894                                pgoff_t index,
1895                                int (*filler)(void *, struct page *),
1896                                void *data)
1897{
1898        return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
1899}
1900EXPORT_SYMBOL(read_cache_page);
1901
1902static size_t __iovec_copy_from_user_inatomic(char *vaddr,
1903                        const struct iovec *iov, size_t base, size_t bytes)
1904{
1905        size_t copied = 0, left = 0;
1906
1907        while (bytes) {
1908                char __user *buf = iov->iov_base + base;
1909                int copy = min(bytes, iov->iov_len - base);
1910
1911                base = 0;
1912                left = __copy_from_user_inatomic(vaddr, buf, copy);
1913                copied += copy;
1914                bytes -= copy;
1915                vaddr += copy;
1916                iov++;
1917
1918                if (unlikely(left))
1919                        break;
1920        }
1921        return copied - left;
1922}
1923
1924/*
1925 * Copy as much as we can into the page and return the number of bytes which
1926 * were successfully copied.  If a fault is encountered then return the number of
1927 * bytes which were copied.
1928 */
1929size_t iov_iter_copy_from_user_atomic(struct page *page,
1930                struct iov_iter *i, unsigned long offset, size_t bytes)
1931{
1932        char *kaddr;
1933        size_t copied;
1934
1935        BUG_ON(!in_atomic());
1936        kaddr = kmap_atomic(page);
1937        if (likely(i->nr_segs == 1)) {
1938                int left;
1939                char __user *buf = i->iov->iov_base + i->iov_offset;
1940                left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
1941                copied = bytes - left;
1942        } else {
1943                copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1944                                                i->iov, i->iov_offset, bytes);
1945        }
1946        kunmap_atomic(kaddr);
1947
1948        return copied;
1949}
1950EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
1951
1952/*
1953 * This has the same sideeffects and return value as
1954 * iov_iter_copy_from_user_atomic().
1955 * The difference is that it attempts to resolve faults.
1956 * Page must not be locked.
1957 */
1958size_t iov_iter_copy_from_user(struct page *page,
1959                struct iov_iter *i, unsigned long offset, size_t bytes)
1960{
1961        char *kaddr;
1962        size_t copied;
1963
1964        kaddr = kmap(page);
1965        if (likely(i->nr_segs == 1)) {
1966                int left;
1967                char __user *buf = i->iov->iov_base + i->iov_offset;
1968                left = __copy_from_user(kaddr + offset, buf, bytes);
1969                copied = bytes - left;
1970        } else {
1971                copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1972                                                i->iov, i->iov_offset, bytes);
1973        }
1974        kunmap(page);
1975        return copied;
1976}
1977EXPORT_SYMBOL(iov_iter_copy_from_user);
1978
1979void iov_iter_advance(struct iov_iter *i, size_t bytes)
1980{
1981        BUG_ON(i->count < bytes);
1982
1983        if (likely(i->nr_segs == 1)) {
1984                i->iov_offset += bytes;
1985                i->count -= bytes;
1986        } else {
1987                const struct iovec *iov = i->iov;
1988                size_t base = i->iov_offset;
1989                unsigned long nr_segs = i->nr_segs;
1990
1991                /*
1992                 * The !iov->iov_len check ensures we skip over unlikely
1993                 * zero-length segments (without overruning the iovec).
1994                 */
1995                while (bytes || unlikely(i->count && !iov->iov_len)) {
1996                        int copy;
1997
1998                        copy = min(bytes, iov->iov_len - base);
1999                        BUG_ON(!i->count || i->count < copy);
2000                        i->count -= copy;
2001                        bytes -= copy;
2002                        base += copy;
2003                        if (iov->iov_len == base) {
2004                                iov++;
2005                                nr_segs--;
2006                                base = 0;
2007                        }
2008                }
2009                i->iov = iov;
2010                i->iov_offset = base;
2011                i->nr_segs = nr_segs;
2012        }
2013}
2014EXPORT_SYMBOL(iov_iter_advance);
2015
2016/*
2017 * Fault in the first iovec of the given iov_iter, to a maximum length
2018 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2019 * accessed (ie. because it is an invalid address).
2020 *
2021 * writev-intensive code may want this to prefault several iovecs -- that
2022 * would be possible (callers must not rely on the fact that _only_ the
2023 * first iovec will be faulted with the current implementation).
2024 */
2025int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2026{
2027        char __user *buf = i->iov->iov_base + i->iov_offset;
2028        bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2029        return fault_in_pages_readable(buf, bytes);
2030}
2031EXPORT_SYMBOL(iov_iter_fault_in_readable);
2032
2033/*
2034 * Return the count of just the current iov_iter segment.
2035 */
2036size_t iov_iter_single_seg_count(struct iov_iter *i)
2037{
2038        const struct iovec *iov = i->iov;
2039        if (i->nr_segs == 1)
2040                return i->count;
2041        else
2042                return min(i->count, iov->iov_len - i->iov_offset);
2043}
2044EXPORT_SYMBOL(iov_iter_single_seg_count);
2045
2046/*
2047 * Performs necessary checks before doing a write
2048 *
2049 * Can adjust writing position or amount of bytes to write.
2050 * Returns appropriate error code that caller should return or
2051 * zero in case that write should be allowed.
2052 */
2053inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2054{
2055        struct inode *inode = file->f_mapping->host;
2056        unsigned long limit = rlimit(RLIMIT_FSIZE);
2057
2058        if (unlikely(*pos < 0))
2059                return -EINVAL;
2060
2061        if (!isblk) {
2062                /* FIXME: this is for backwards compatibility with 2.4 */
2063                if (file->f_flags & O_APPEND)
2064                        *pos = i_size_read(inode);
2065
2066                if (limit != RLIM_INFINITY) {
2067                        if (*pos >= limit) {
2068                                send_sig(SIGXFSZ, current, 0);
2069                                return -EFBIG;
2070                        }
2071                        if (*count > limit - (typeof(limit))*pos) {
2072                                *count = limit - (typeof(limit))*pos;
2073                        }
2074                }
2075        }
2076
2077        /*
2078         * LFS rule
2079         */
2080        if (unlikely(*pos + *count > MAX_NON_LFS &&
2081                                !(file->f_flags & O_LARGEFILE))) {
2082                if (*pos >= MAX_NON_LFS) {
2083                        return -EFBIG;
2084                }
2085                if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2086                        *count = MAX_NON_LFS - (unsigned long)*pos;
2087                }
2088        }
2089
2090        /*
2091         * Are we about to exceed the fs block limit ?
2092         *
2093         * If we have written data it becomes a short write.  If we have
2094         * exceeded without writing data we send a signal and return EFBIG.
2095         * Linus frestrict idea will clean these up nicely..
2096         */
2097        if (likely(!isblk)) {
2098                if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2099                        if (*count || *pos > inode->i_sb->s_maxbytes) {
2100                                return -EFBIG;
2101                        }
2102                        /* zero-length writes at ->s_maxbytes are OK */
2103                }
2104
2105                if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2106                        *count = inode->i_sb->s_maxbytes - *pos;
2107        } else {
2108#ifdef CONFIG_BLOCK
2109                loff_t isize;
2110                if (bdev_read_only(I_BDEV(inode)))
2111                        return -EPERM;
2112                isize = i_size_read(inode);
2113                if (*pos >= isize) {
2114                        if (*count || *pos > isize)
2115                                return -ENOSPC;
2116                }
2117
2118                if (*pos + *count > isize)
2119                        *count = isize - *pos;
2120#else
2121                return -EPERM;
2122#endif
2123        }
2124        return 0;
2125}
2126EXPORT_SYMBOL(generic_write_checks);
2127
2128int pagecache_write_begin(struct file *file, struct address_space *mapping,
2129                                loff_t pos, unsigned len, unsigned flags,
2130                                struct page **pagep, void **fsdata)
2131{
2132        const struct address_space_operations *aops = mapping->a_ops;
2133
2134        return aops->write_begin(file, mapping, pos, len, flags,
2135                                                        pagep, fsdata);
2136}
2137EXPORT_SYMBOL(pagecache_write_begin);
2138
2139int pagecache_write_end(struct file *file, struct address_space *mapping,
2140                                loff_t pos, unsigned len, unsigned copied,
2141                                struct page *page, void *fsdata)
2142{
2143        const struct address_space_operations *aops = mapping->a_ops;
2144
2145        mark_page_accessed(page);
2146        return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2147}
2148EXPORT_SYMBOL(pagecache_write_end);
2149
2150ssize_t
2151generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2152                unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2153                size_t count, size_t ocount)
2154{
2155        struct file     *file = iocb->ki_filp;
2156        struct address_space *mapping = file->f_mapping;
2157        struct inode    *inode = mapping->host;
2158        ssize_t         written;
2159        size_t          write_len;
2160        pgoff_t         end;
2161
2162        if (count != ocount)
2163                *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2164
2165        write_len = iov_length(iov, *nr_segs);
2166        end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2167
2168        written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2169        if (written)
2170                goto out;
2171
2172        /*
2173         * After a write we want buffered reads to be sure to go to disk to get
2174         * the new data.  We invalidate clean cached page from the region we're
2175         * about to write.  We do this *before* the write so that we can return
2176         * without clobbering -EIOCBQUEUED from ->direct_IO().
2177         */
2178        if (mapping->nrpages) {
2179                written = invalidate_inode_pages2_range(mapping,
2180                                        pos >> PAGE_CACHE_SHIFT, end);
2181                /*
2182                 * If a page can not be invalidated, return 0 to fall back
2183                 * to buffered write.
2184                 */
2185                if (written) {
2186                        if (written == -EBUSY)
2187                                return 0;
2188                        goto out;
2189                }
2190        }
2191
2192        written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2193
2194        /*
2195         * Finally, try again to invalidate clean pages which might have been
2196         * cached by non-direct readahead, or faulted in by get_user_pages()
2197         * if the source of the write was an mmap'ed region of the file
2198         * we're writing.  Either one is a pretty crazy thing to do,
2199         * so we don't support it 100%.  If this invalidation
2200         * fails, tough, the write still worked...
2201         */
2202        if (mapping->nrpages) {
2203                invalidate_inode_pages2_range(mapping,
2204                                              pos >> PAGE_CACHE_SHIFT, end);
2205        }
2206
2207        if (written > 0) {
2208                pos += written;
2209                if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2210                        i_size_write(inode, pos);
2211                        mark_inode_dirty(inode);
2212                }
2213                *ppos = pos;
2214        }
2215out:
2216        return written;
2217}
2218EXPORT_SYMBOL(generic_file_direct_write);
2219
2220/*
2221 * Find or create a page at the given pagecache position. Return the locked
2222 * page. This function is specifically for buffered writes.
2223 */
2224struct page *grab_cache_page_write_begin(struct address_space *mapping,
2225                                        pgoff_t index, unsigned flags)
2226{
2227        int status;
2228        gfp_t gfp_mask;
2229        struct page *page;
2230        gfp_t gfp_notmask = 0;
2231
2232        gfp_mask = mapping_gfp_mask(mapping);
2233        if (mapping_cap_account_dirty(mapping))
2234                gfp_mask |= __GFP_WRITE;
2235        if (flags & AOP_FLAG_NOFS)
2236                gfp_notmask = __GFP_FS;
2237repeat:
2238        page = find_lock_page(mapping, index);
2239        if (page)
2240                goto found;
2241
2242        page = __page_cache_alloc(gfp_mask & ~gfp_notmask);
2243        if (!page)
2244                return NULL;
2245        status = add_to_page_cache_lru(page, mapping, index,
2246                                                GFP_KERNEL & ~gfp_notmask);
2247        if (unlikely(status)) {
2248                page_cache_release(page);
2249                if (status == -EEXIST)
2250                        goto repeat;
2251                return NULL;
2252        }
2253found:
2254        wait_on_page_writeback(page);
2255        return page;
2256}
2257EXPORT_SYMBOL(grab_cache_page_write_begin);
2258
2259static ssize_t generic_perform_write(struct file *file,
2260                                struct iov_iter *i, loff_t pos)
2261{
2262        struct address_space *mapping = file->f_mapping;
2263        const struct address_space_operations *a_ops = mapping->a_ops;
2264        long status = 0;
2265        ssize_t written = 0;
2266        unsigned int flags = 0;
2267
2268        /*
2269         * Copies from kernel address space cannot fail (NFSD is a big user).
2270         */
2271        if (segment_eq(get_fs(), KERNEL_DS))
2272                flags |= AOP_FLAG_UNINTERRUPTIBLE;
2273
2274        do {
2275                struct page *page;
2276                unsigned long offset;   /* Offset into pagecache page */
2277                unsigned long bytes;    /* Bytes to write to page */
2278                size_t copied;          /* Bytes copied from user */
2279                void *fsdata;
2280
2281                offset = (pos & (PAGE_CACHE_SIZE - 1));
2282                bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2283                                                iov_iter_count(i));
2284
2285again:
2286                /*
2287                 * Bring in the user page that we will copy from _first_.
2288                 * Otherwise there's a nasty deadlock on copying from the
2289                 * same page as we're writing to, without it being marked
2290                 * up-to-date.
2291                 *
2292                 * Not only is this an optimisation, but it is also required
2293                 * to check that the address is actually valid, when atomic
2294                 * usercopies are used, below.
2295                 */
2296                if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2297                        status = -EFAULT;
2298                        break;
2299                }
2300
2301                status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2302                                                &page, &fsdata);
2303                if (unlikely(status))
2304                        break;
2305
2306                if (mapping_writably_mapped(mapping))
2307                        flush_dcache_page(page);
2308
2309                pagefault_disable();
2310                copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2311                pagefault_enable();
2312                flush_dcache_page(page);
2313
2314                mark_page_accessed(page);
2315                status = a_ops->write_end(file, mapping, pos, bytes, copied,
2316                                                page, fsdata);
2317                if (unlikely(status < 0))
2318                        break;
2319                copied = status;
2320
2321                cond_resched();
2322
2323                iov_iter_advance(i, copied);
2324                if (unlikely(copied == 0)) {
2325                        /*
2326                         * If we were unable to copy any data at all, we must
2327                         * fall back to a single segment length write.
2328                         *
2329                         * If we didn't fallback here, we could livelock
2330                         * because not all segments in the iov can be copied at
2331                         * once without a pagefault.
2332                         */
2333                        bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2334                                                iov_iter_single_seg_count(i));
2335                        goto again;
2336                }
2337                pos += copied;
2338                written += copied;
2339
2340                balance_dirty_pages_ratelimited(mapping);
2341                if (fatal_signal_pending(current)) {
2342                        status = -EINTR;
2343                        break;
2344                }
2345        } while (iov_iter_count(i));
2346
2347        return written ? written : status;
2348}
2349
2350ssize_t
2351generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2352                unsigned long nr_segs, loff_t pos, loff_t *ppos,
2353                size_t count, ssize_t written)
2354{
2355        struct file *file = iocb->ki_filp;
2356        ssize_t status;
2357        struct iov_iter i;
2358
2359        iov_iter_init(&i, iov, nr_segs, count, written);
2360        status = generic_perform_write(file, &i, pos);
2361
2362        if (likely(status >= 0)) {
2363                written += status;
2364                *ppos = pos + status;
2365        }
2366        
2367        return written ? written : status;
2368}
2369EXPORT_SYMBOL(generic_file_buffered_write);
2370
2371/**
2372 * __generic_file_aio_write - write data to a file
2373 * @iocb:       IO state structure (file, offset, etc.)
2374 * @iov:        vector with data to write
2375 * @nr_segs:    number of segments in the vector
2376 * @ppos:       position where to write
2377 *
2378 * This function does all the work needed for actually writing data to a
2379 * file. It does all basic checks, removes SUID from the file, updates
2380 * modification times and calls proper subroutines depending on whether we
2381 * do direct IO or a standard buffered write.
2382 *
2383 * It expects i_mutex to be grabbed unless we work on a block device or similar
2384 * object which does not need locking at all.
2385 *
2386 * This function does *not* take care of syncing data in case of O_SYNC write.
2387 * A caller has to handle it. This is mainly due to the fact that we want to
2388 * avoid syncing under i_mutex.
2389 */
2390ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2391                                 unsigned long nr_segs, loff_t *ppos)
2392{
2393        struct file *file = iocb->ki_filp;
2394        struct address_space * mapping = file->f_mapping;
2395        size_t ocount;          /* original count */
2396        size_t count;           /* after file limit checks */
2397        struct inode    *inode = mapping->host;
2398        loff_t          pos;
2399        ssize_t         written;
2400        ssize_t         err;
2401
2402        ocount = 0;
2403        err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2404        if (err)
2405                return err;
2406
2407        count = ocount;
2408        pos = *ppos;
2409
2410        vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2411
2412        /* We can write back this queue in page reclaim */
2413        current->backing_dev_info = mapping->backing_dev_info;
2414        written = 0;
2415
2416        err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2417        if (err)
2418                goto out;
2419
2420        if (count == 0)
2421                goto out;
2422
2423        err = file_remove_suid(file);
2424        if (err)
2425                goto out;
2426
2427        err = file_update_time(file);
2428        if (err)
2429                goto out;
2430
2431        /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2432        if (unlikely(file->f_flags & O_DIRECT)) {
2433                loff_t endbyte;
2434                ssize_t written_buffered;
2435
2436                written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2437                                                        ppos, count, ocount);
2438                if (written < 0 || written == count)
2439                        goto out;
2440                /*
2441                 * direct-io write to a hole: fall through to buffered I/O
2442                 * for completing the rest of the request.
2443                 */
2444                pos += written;
2445                count -= written;
2446                written_buffered = generic_file_buffered_write(iocb, iov,
2447                                                nr_segs, pos, ppos, count,
2448                                                written);
2449                /*
2450                 * If generic_file_buffered_write() retuned a synchronous error
2451                 * then we want to return the number of bytes which were
2452                 * direct-written, or the error code if that was zero.  Note
2453                 * that this differs from normal direct-io semantics, which
2454                 * will return -EFOO even if some bytes were written.
2455                 */
2456                if (written_buffered < 0) {
2457                        err = written_buffered;
2458                        goto out;
2459                }
2460
2461                /*
2462                 * We need to ensure that the page cache pages are written to
2463                 * disk and invalidated to preserve the expected O_DIRECT
2464                 * semantics.
2465                 */
2466                endbyte = pos + written_buffered - written - 1;
2467                err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2468                if (err == 0) {
2469                        written = written_buffered;
2470                        invalidate_mapping_pages(mapping,
2471                                                 pos >> PAGE_CACHE_SHIFT,
2472                                                 endbyte >> PAGE_CACHE_SHIFT);
2473                } else {
2474                        /*
2475                         * We don't know how much we wrote, so just return
2476                         * the number of bytes which were direct-written
2477                         */
2478                }
2479        } else {
2480                written = generic_file_buffered_write(iocb, iov, nr_segs,
2481                                pos, ppos, count, written);
2482        }
2483out:
2484        current->backing_dev_info = NULL;
2485        return written ? written : err;
2486}
2487EXPORT_SYMBOL(__generic_file_aio_write);
2488
2489/**
2490 * generic_file_aio_write - write data to a file
2491 * @iocb:       IO state structure
2492 * @iov:        vector with data to write
2493 * @nr_segs:    number of segments in the vector
2494 * @pos:        position in file where to write
2495 *
2496 * This is a wrapper around __generic_file_aio_write() to be used by most
2497 * filesystems. It takes care of syncing the file in case of O_SYNC file
2498 * and acquires i_mutex as needed.
2499 */
2500ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2501                unsigned long nr_segs, loff_t pos)
2502{
2503        struct file *file = iocb->ki_filp;
2504        struct inode *inode = file->f_mapping->host;
2505        struct blk_plug plug;
2506        ssize_t ret;
2507
2508        BUG_ON(iocb->ki_pos != pos);
2509
2510        mutex_lock(&inode->i_mutex);
2511        blk_start_plug(&plug);
2512        ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2513        mutex_unlock(&inode->i_mutex);
2514
2515        if (ret > 0 || ret == -EIOCBQUEUED) {
2516                ssize_t err;
2517
2518                err = generic_write_sync(file, pos, ret);
2519                if (err < 0 && ret > 0)
2520                        ret = err;
2521        }
2522        blk_finish_plug(&plug);
2523        return ret;
2524}
2525EXPORT_SYMBOL(generic_file_aio_write);
2526
2527/**
2528 * try_to_release_page() - release old fs-specific metadata on a page
2529 *
2530 * @page: the page which the kernel is trying to free
2531 * @gfp_mask: memory allocation flags (and I/O mode)
2532 *
2533 * The address_space is to try to release any data against the page
2534 * (presumably at page->private).  If the release was successful, return `1'.
2535 * Otherwise return zero.
2536 *
2537 * This may also be called if PG_fscache is set on a page, indicating that the
2538 * page is known to the local caching routines.
2539 *
2540 * The @gfp_mask argument specifies whether I/O may be performed to release
2541 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2542 *
2543 */
2544int try_to_release_page(struct page *page, gfp_t gfp_mask)
2545{
2546        struct address_space * const mapping = page->mapping;
2547
2548        BUG_ON(!PageLocked(page));
2549        if (PageWriteback(page))
2550                return 0;
2551
2552        if (mapping && mapping->a_ops->releasepage)
2553                return mapping->a_ops->releasepage(page, gfp_mask);
2554        return try_to_free_buffers(page);
2555}
2556
2557EXPORT_SYMBOL(try_to_release_page);
2558
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