linux/mm/filemap.c
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   1/*
   2 *      linux/mm/filemap.c
   3 *
   4 * Copyright (C) 1994-1999  Linus Torvalds
   5 */
   6
   7/*
   8 * This file handles the generic file mmap semantics used by
   9 * most "normal" filesystems (but you don't /have/ to use this:
  10 * the NFS filesystem used to do this differently, for example)
  11 */
  12#include <linux/export.h>
  13#include <linux/compiler.h>
  14#include <linux/fs.h>
  15#include <linux/uaccess.h>
  16#include <linux/aio.h>
  17#include <linux/capability.h>
  18#include <linux/kernel_stat.h>
  19#include <linux/gfp.h>
  20#include <linux/mm.h>
  21#include <linux/swap.h>
  22#include <linux/mman.h>
  23#include <linux/pagemap.h>
  24#include <linux/file.h>
  25#include <linux/uio.h>
  26#include <linux/hash.h>
  27#include <linux/writeback.h>
  28#include <linux/backing-dev.h>
  29#include <linux/pagevec.h>
  30#include <linux/blkdev.h>
  31#include <linux/security.h>
  32#include <linux/cpuset.h>
  33#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
  34#include <linux/memcontrol.h>
  35#include <linux/cleancache.h>
  36#include "internal.h"
  37
  38#define CREATE_TRACE_POINTS
  39#include <trace/events/filemap.h>
  40
  41/*
  42 * FIXME: remove all knowledge of the buffer layer from the core VM
  43 */
  44#include <linux/buffer_head.h> /* for try_to_free_buffers */
  45
  46#include <asm/mman.h>
  47
  48/*
  49 * Shared mappings implemented 30.11.1994. It's not fully working yet,
  50 * though.
  51 *
  52 * Shared mappings now work. 15.8.1995  Bruno.
  53 *
  54 * finished 'unifying' the page and buffer cache and SMP-threaded the
  55 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
  56 *
  57 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
  58 */
  59
  60/*
  61 * Lock ordering:
  62 *
  63 *  ->i_mmap_mutex              (truncate_pagecache)
  64 *    ->private_lock            (__free_pte->__set_page_dirty_buffers)
  65 *      ->swap_lock             (exclusive_swap_page, others)
  66 *        ->mapping->tree_lock
  67 *
  68 *  ->i_mutex
  69 *    ->i_mmap_mutex            (truncate->unmap_mapping_range)
  70 *
  71 *  ->mmap_sem
  72 *    ->i_mmap_mutex
  73 *      ->page_table_lock or pte_lock   (various, mainly in memory.c)
  74 *        ->mapping->tree_lock  (arch-dependent flush_dcache_mmap_lock)
  75 *
  76 *  ->mmap_sem
  77 *    ->lock_page               (access_process_vm)
  78 *
  79 *  ->i_mutex                   (generic_file_buffered_write)
  80 *    ->mmap_sem                (fault_in_pages_readable->do_page_fault)
  81 *
  82 *  bdi->wb.list_lock
  83 *    sb_lock                   (fs/fs-writeback.c)
  84 *    ->mapping->tree_lock      (__sync_single_inode)
  85 *
  86 *  ->i_mmap_mutex
  87 *    ->anon_vma.lock           (vma_adjust)
  88 *
  89 *  ->anon_vma.lock
  90 *    ->page_table_lock or pte_lock     (anon_vma_prepare and various)
  91 *
  92 *  ->page_table_lock or pte_lock
  93 *    ->swap_lock               (try_to_unmap_one)
  94 *    ->private_lock            (try_to_unmap_one)
  95 *    ->tree_lock               (try_to_unmap_one)
  96 *    ->zone.lru_lock           (follow_page->mark_page_accessed)
  97 *    ->zone.lru_lock           (check_pte_range->isolate_lru_page)
  98 *    ->private_lock            (page_remove_rmap->set_page_dirty)
  99 *    ->tree_lock               (page_remove_rmap->set_page_dirty)
 100 *    bdi.wb->list_lock         (page_remove_rmap->set_page_dirty)
 101 *    ->inode->i_lock           (page_remove_rmap->set_page_dirty)
 102 *    bdi.wb->list_lock         (zap_pte_range->set_page_dirty)
 103 *    ->inode->i_lock           (zap_pte_range->set_page_dirty)
 104 *    ->private_lock            (zap_pte_range->__set_page_dirty_buffers)
 105 *
 106 * ->i_mmap_mutex
 107 *   ->tasklist_lock            (memory_failure, collect_procs_ao)
 108 */
 109
 110/*
 111 * Delete a page from the page cache and free it. Caller has to make
 112 * sure the page is locked and that nobody else uses it - or that usage
 113 * is safe.  The caller must hold the mapping's tree_lock.
 114 */
 115void __delete_from_page_cache(struct page *page)
 116{
 117        struct address_space *mapping = page->mapping;
 118
 119        trace_mm_filemap_delete_from_page_cache(page);
 120        /*
 121         * if we're uptodate, flush out into the cleancache, otherwise
 122         * invalidate any existing cleancache entries.  We can't leave
 123         * stale data around in the cleancache once our page is gone
 124         */
 125        if (PageUptodate(page) && PageMappedToDisk(page))
 126                cleancache_put_page(page);
 127        else
 128                cleancache_invalidate_page(mapping, page);
 129
 130        radix_tree_delete(&mapping->page_tree, page->index);
 131        page->mapping = NULL;
 132        /* Leave page->index set: truncation lookup relies upon it */
 133        mapping->nrpages--;
 134        __dec_zone_page_state(page, NR_FILE_PAGES);
 135        if (PageSwapBacked(page))
 136                __dec_zone_page_state(page, NR_SHMEM);
 137        BUG_ON(page_mapped(page));
 138
 139        /*
 140         * Some filesystems seem to re-dirty the page even after
 141         * the VM has canceled the dirty bit (eg ext3 journaling).
 142         *
 143         * Fix it up by doing a final dirty accounting check after
 144         * having removed the page entirely.
 145         */
 146        if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
 147                dec_zone_page_state(page, NR_FILE_DIRTY);
 148                dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
 149        }
 150}
 151
 152/**
 153 * delete_from_page_cache - delete page from page cache
 154 * @page: the page which the kernel is trying to remove from page cache
 155 *
 156 * This must be called only on pages that have been verified to be in the page
 157 * cache and locked.  It will never put the page into the free list, the caller
 158 * has a reference on the page.
 159 */
 160void delete_from_page_cache(struct page *page)
 161{
 162        struct address_space *mapping = page->mapping;
 163        void (*freepage)(struct page *);
 164
 165        BUG_ON(!PageLocked(page));
 166
 167        freepage = mapping->a_ops->freepage;
 168        spin_lock_irq(&mapping->tree_lock);
 169        __delete_from_page_cache(page);
 170        spin_unlock_irq(&mapping->tree_lock);
 171        mem_cgroup_uncharge_cache_page(page);
 172
 173        if (freepage)
 174                freepage(page);
 175        page_cache_release(page);
 176}
 177EXPORT_SYMBOL(delete_from_page_cache);
 178
 179static int sleep_on_page(void *word)
 180{
 181        io_schedule();
 182        return 0;
 183}
 184
 185static int sleep_on_page_killable(void *word)
 186{
 187        sleep_on_page(word);
 188        return fatal_signal_pending(current) ? -EINTR : 0;
 189}
 190
 191static int filemap_check_errors(struct address_space *mapping)
 192{
 193        int ret = 0;
 194        /* Check for outstanding write errors */
 195        if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
 196                ret = -ENOSPC;
 197        if (test_and_clear_bit(AS_EIO, &mapping->flags))
 198                ret = -EIO;
 199        return ret;
 200}
 201
 202/**
 203 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
 204 * @mapping:    address space structure to write
 205 * @start:      offset in bytes where the range starts
 206 * @end:        offset in bytes where the range ends (inclusive)
 207 * @sync_mode:  enable synchronous operation
 208 *
 209 * Start writeback against all of a mapping's dirty pages that lie
 210 * within the byte offsets <start, end> inclusive.
 211 *
 212 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
 213 * opposed to a regular memory cleansing writeback.  The difference between
 214 * these two operations is that if a dirty page/buffer is encountered, it must
 215 * be waited upon, and not just skipped over.
 216 */
 217int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 218                                loff_t end, int sync_mode)
 219{
 220        int ret;
 221        struct writeback_control wbc = {
 222                .sync_mode = sync_mode,
 223                .nr_to_write = LONG_MAX,
 224                .range_start = start,
 225                .range_end = end,
 226        };
 227
 228        if (!mapping_cap_writeback_dirty(mapping))
 229                return 0;
 230
 231        ret = do_writepages(mapping, &wbc);
 232        return ret;
 233}
 234
 235static inline int __filemap_fdatawrite(struct address_space *mapping,
 236        int sync_mode)
 237{
 238        return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
 239}
 240
 241int filemap_fdatawrite(struct address_space *mapping)
 242{
 243        return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
 244}
 245EXPORT_SYMBOL(filemap_fdatawrite);
 246
 247int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 248                                loff_t end)
 249{
 250        return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
 251}
 252EXPORT_SYMBOL(filemap_fdatawrite_range);
 253
 254/**
 255 * filemap_flush - mostly a non-blocking flush
 256 * @mapping:    target address_space
 257 *
 258 * This is a mostly non-blocking flush.  Not suitable for data-integrity
 259 * purposes - I/O may not be started against all dirty pages.
 260 */
 261int filemap_flush(struct address_space *mapping)
 262{
 263        return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
 264}
 265EXPORT_SYMBOL(filemap_flush);
 266
 267/**
 268 * filemap_fdatawait_range - wait for writeback to complete
 269 * @mapping:            address space structure to wait for
 270 * @start_byte:         offset in bytes where the range starts
 271 * @end_byte:           offset in bytes where the range ends (inclusive)
 272 *
 273 * Walk the list of under-writeback pages of the given address space
 274 * in the given range and wait for all of them.
 275 */
 276int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
 277                            loff_t end_byte)
 278{
 279        pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
 280        pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
 281        struct pagevec pvec;
 282        int nr_pages;
 283        int ret2, ret = 0;
 284
 285        if (end_byte < start_byte)
 286                goto out;
 287
 288        pagevec_init(&pvec, 0);
 289        while ((index <= end) &&
 290                        (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
 291                        PAGECACHE_TAG_WRITEBACK,
 292                        min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
 293                unsigned i;
 294
 295                for (i = 0; i < nr_pages; i++) {
 296                        struct page *page = pvec.pages[i];
 297
 298                        /* until radix tree lookup accepts end_index */
 299                        if (page->index > end)
 300                                continue;
 301
 302                        wait_on_page_writeback(page);
 303                        if (TestClearPageError(page))
 304                                ret = -EIO;
 305                }
 306                pagevec_release(&pvec);
 307                cond_resched();
 308        }
 309out:
 310        ret2 = filemap_check_errors(mapping);
 311        if (!ret)
 312                ret = ret2;
 313
 314        return ret;
 315}
 316EXPORT_SYMBOL(filemap_fdatawait_range);
 317
 318/**
 319 * filemap_fdatawait - wait for all under-writeback pages to complete
 320 * @mapping: address space structure to wait for
 321 *
 322 * Walk the list of under-writeback pages of the given address space
 323 * and wait for all of them.
 324 */
 325int filemap_fdatawait(struct address_space *mapping)
 326{
 327        loff_t i_size = i_size_read(mapping->host);
 328
 329        if (i_size == 0)
 330                return 0;
 331
 332        return filemap_fdatawait_range(mapping, 0, i_size - 1);
 333}
 334EXPORT_SYMBOL(filemap_fdatawait);
 335
 336int filemap_write_and_wait(struct address_space *mapping)
 337{
 338        int err = 0;
 339
 340        if (mapping->nrpages) {
 341                err = filemap_fdatawrite(mapping);
 342                /*
 343                 * Even if the above returned error, the pages may be
 344                 * written partially (e.g. -ENOSPC), so we wait for it.
 345                 * But the -EIO is special case, it may indicate the worst
 346                 * thing (e.g. bug) happened, so we avoid waiting for it.
 347                 */
 348                if (err != -EIO) {
 349                        int err2 = filemap_fdatawait(mapping);
 350                        if (!err)
 351                                err = err2;
 352                }
 353        } else {
 354                err = filemap_check_errors(mapping);
 355        }
 356        return err;
 357}
 358EXPORT_SYMBOL(filemap_write_and_wait);
 359
 360/**
 361 * filemap_write_and_wait_range - write out & wait on a file range
 362 * @mapping:    the address_space for the pages
 363 * @lstart:     offset in bytes where the range starts
 364 * @lend:       offset in bytes where the range ends (inclusive)
 365 *
 366 * Write out and wait upon file offsets lstart->lend, inclusive.
 367 *
 368 * Note that `lend' is inclusive (describes the last byte to be written) so
 369 * that this function can be used to write to the very end-of-file (end = -1).
 370 */
 371int filemap_write_and_wait_range(struct address_space *mapping,
 372                                 loff_t lstart, loff_t lend)
 373{
 374        int err = 0;
 375
 376        if (mapping->nrpages) {
 377                err = __filemap_fdatawrite_range(mapping, lstart, lend,
 378                                                 WB_SYNC_ALL);
 379                /* See comment of filemap_write_and_wait() */
 380                if (err != -EIO) {
 381                        int err2 = filemap_fdatawait_range(mapping,
 382                                                lstart, lend);
 383                        if (!err)
 384                                err = err2;
 385                }
 386        } else {
 387                err = filemap_check_errors(mapping);
 388        }
 389        return err;
 390}
 391EXPORT_SYMBOL(filemap_write_and_wait_range);
 392
 393/**
 394 * replace_page_cache_page - replace a pagecache page with a new one
 395 * @old:        page to be replaced
 396 * @new:        page to replace with
 397 * @gfp_mask:   allocation mode
 398 *
 399 * This function replaces a page in the pagecache with a new one.  On
 400 * success it acquires the pagecache reference for the new page and
 401 * drops it for the old page.  Both the old and new pages must be
 402 * locked.  This function does not add the new page to the LRU, the
 403 * caller must do that.
 404 *
 405 * The remove + add is atomic.  The only way this function can fail is
 406 * memory allocation failure.
 407 */
 408int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 409{
 410        int error;
 411
 412        VM_BUG_ON(!PageLocked(old));
 413        VM_BUG_ON(!PageLocked(new));
 414        VM_BUG_ON(new->mapping);
 415
 416        error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
 417        if (!error) {
 418                struct address_space *mapping = old->mapping;
 419                void (*freepage)(struct page *);
 420
 421                pgoff_t offset = old->index;
 422                freepage = mapping->a_ops->freepage;
 423
 424                page_cache_get(new);
 425                new->mapping = mapping;
 426                new->index = offset;
 427
 428                spin_lock_irq(&mapping->tree_lock);
 429                __delete_from_page_cache(old);
 430                error = radix_tree_insert(&mapping->page_tree, offset, new);
 431                BUG_ON(error);
 432                mapping->nrpages++;
 433                __inc_zone_page_state(new, NR_FILE_PAGES);
 434                if (PageSwapBacked(new))
 435                        __inc_zone_page_state(new, NR_SHMEM);
 436                spin_unlock_irq(&mapping->tree_lock);
 437                /* mem_cgroup codes must not be called under tree_lock */
 438                mem_cgroup_replace_page_cache(old, new);
 439                radix_tree_preload_end();
 440                if (freepage)
 441                        freepage(old);
 442                page_cache_release(old);
 443        }
 444
 445        return error;
 446}
 447EXPORT_SYMBOL_GPL(replace_page_cache_page);
 448
 449/**
 450 * add_to_page_cache_locked - add a locked page to the pagecache
 451 * @page:       page to add
 452 * @mapping:    the page's address_space
 453 * @offset:     page index
 454 * @gfp_mask:   page allocation mode
 455 *
 456 * This function is used to add a page to the pagecache. It must be locked.
 457 * This function does not add the page to the LRU.  The caller must do that.
 458 */
 459int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
 460                pgoff_t offset, gfp_t gfp_mask)
 461{
 462        int error;
 463
 464        VM_BUG_ON(!PageLocked(page));
 465        VM_BUG_ON(PageSwapBacked(page));
 466
 467        error = mem_cgroup_cache_charge(page, current->mm,
 468                                        gfp_mask & GFP_RECLAIM_MASK);
 469        if (error)
 470                goto out;
 471
 472        error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
 473        if (error == 0) {
 474                page_cache_get(page);
 475                page->mapping = mapping;
 476                page->index = offset;
 477
 478                spin_lock_irq(&mapping->tree_lock);
 479                error = radix_tree_insert(&mapping->page_tree, offset, page);
 480                if (likely(!error)) {
 481                        mapping->nrpages++;
 482                        __inc_zone_page_state(page, NR_FILE_PAGES);
 483                        spin_unlock_irq(&mapping->tree_lock);
 484                        trace_mm_filemap_add_to_page_cache(page);
 485                } else {
 486                        page->mapping = NULL;
 487                        /* Leave page->index set: truncation relies upon it */
 488                        spin_unlock_irq(&mapping->tree_lock);
 489                        mem_cgroup_uncharge_cache_page(page);
 490                        page_cache_release(page);
 491                }
 492                radix_tree_preload_end();
 493        } else
 494                mem_cgroup_uncharge_cache_page(page);
 495out:
 496        return error;
 497}
 498EXPORT_SYMBOL(add_to_page_cache_locked);
 499
 500int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 501                                pgoff_t offset, gfp_t gfp_mask)
 502{
 503        int ret;
 504
 505        ret = add_to_page_cache(page, mapping, offset, gfp_mask);
 506        if (ret == 0)
 507                lru_cache_add_file(page);
 508        return ret;
 509}
 510EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
 511
 512#ifdef CONFIG_NUMA
 513struct page *__page_cache_alloc(gfp_t gfp)
 514{
 515        int n;
 516        struct page *page;
 517
 518        if (cpuset_do_page_mem_spread()) {
 519                unsigned int cpuset_mems_cookie;
 520                do {
 521                        cpuset_mems_cookie = get_mems_allowed();
 522                        n = cpuset_mem_spread_node();
 523                        page = alloc_pages_exact_node(n, gfp, 0);
 524                } while (!put_mems_allowed(cpuset_mems_cookie) && !page);
 525
 526                return page;
 527        }
 528        return alloc_pages(gfp, 0);
 529}
 530EXPORT_SYMBOL(__page_cache_alloc);
 531#endif
 532
 533/*
 534 * In order to wait for pages to become available there must be
 535 * waitqueues associated with pages. By using a hash table of
 536 * waitqueues where the bucket discipline is to maintain all
 537 * waiters on the same queue and wake all when any of the pages
 538 * become available, and for the woken contexts to check to be
 539 * sure the appropriate page became available, this saves space
 540 * at a cost of "thundering herd" phenomena during rare hash
 541 * collisions.
 542 */
 543static wait_queue_head_t *page_waitqueue(struct page *page)
 544{
 545        const struct zone *zone = page_zone(page);
 546
 547        return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
 548}
 549
 550static inline void wake_up_page(struct page *page, int bit)
 551{
 552        __wake_up_bit(page_waitqueue(page), &page->flags, bit);
 553}
 554
 555void wait_on_page_bit(struct page *page, int bit_nr)
 556{
 557        DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
 558
 559        if (test_bit(bit_nr, &page->flags))
 560                __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
 561                                                        TASK_UNINTERRUPTIBLE);
 562}
 563EXPORT_SYMBOL(wait_on_page_bit);
 564
 565int wait_on_page_bit_killable(struct page *page, int bit_nr)
 566{
 567        DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
 568
 569        if (!test_bit(bit_nr, &page->flags))
 570                return 0;
 571
 572        return __wait_on_bit(page_waitqueue(page), &wait,
 573                             sleep_on_page_killable, TASK_KILLABLE);
 574}
 575
 576/**
 577 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
 578 * @page: Page defining the wait queue of interest
 579 * @waiter: Waiter to add to the queue
 580 *
 581 * Add an arbitrary @waiter to the wait queue for the nominated @page.
 582 */
 583void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
 584{
 585        wait_queue_head_t *q = page_waitqueue(page);
 586        unsigned long flags;
 587
 588        spin_lock_irqsave(&q->lock, flags);
 589        __add_wait_queue(q, waiter);
 590        spin_unlock_irqrestore(&q->lock, flags);
 591}
 592EXPORT_SYMBOL_GPL(add_page_wait_queue);
 593
 594/**
 595 * unlock_page - unlock a locked page
 596 * @page: the page
 597 *
 598 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
 599 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
 600 * mechananism between PageLocked pages and PageWriteback pages is shared.
 601 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
 602 *
 603 * The mb is necessary to enforce ordering between the clear_bit and the read
 604 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
 605 */
 606void unlock_page(struct page *page)
 607{
 608        VM_BUG_ON(!PageLocked(page));
 609        clear_bit_unlock(PG_locked, &page->flags);
 610        smp_mb__after_clear_bit();
 611        wake_up_page(page, PG_locked);
 612}
 613EXPORT_SYMBOL(unlock_page);
 614
 615/**
 616 * end_page_writeback - end writeback against a page
 617 * @page: the page
 618 */
 619void end_page_writeback(struct page *page)
 620{
 621        if (TestClearPageReclaim(page))
 622                rotate_reclaimable_page(page);
 623
 624        if (!test_clear_page_writeback(page))
 625                BUG();
 626
 627        smp_mb__after_clear_bit();
 628        wake_up_page(page, PG_writeback);
 629}
 630EXPORT_SYMBOL(end_page_writeback);
 631
 632/**
 633 * __lock_page - get a lock on the page, assuming we need to sleep to get it
 634 * @page: the page to lock
 635 */
 636void __lock_page(struct page *page)
 637{
 638        DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 639
 640        __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
 641                                                        TASK_UNINTERRUPTIBLE);
 642}
 643EXPORT_SYMBOL(__lock_page);
 644
 645int __lock_page_killable(struct page *page)
 646{
 647        DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 648
 649        return __wait_on_bit_lock(page_waitqueue(page), &wait,
 650                                        sleep_on_page_killable, TASK_KILLABLE);
 651}
 652EXPORT_SYMBOL_GPL(__lock_page_killable);
 653
 654int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
 655                         unsigned int flags)
 656{
 657        if (flags & FAULT_FLAG_ALLOW_RETRY) {
 658                /*
 659                 * CAUTION! In this case, mmap_sem is not released
 660                 * even though return 0.
 661                 */
 662                if (flags & FAULT_FLAG_RETRY_NOWAIT)
 663                        return 0;
 664
 665                up_read(&mm->mmap_sem);
 666                if (flags & FAULT_FLAG_KILLABLE)
 667                        wait_on_page_locked_killable(page);
 668                else
 669                        wait_on_page_locked(page);
 670                return 0;
 671        } else {
 672                if (flags & FAULT_FLAG_KILLABLE) {
 673                        int ret;
 674
 675                        ret = __lock_page_killable(page);
 676                        if (ret) {
 677                                up_read(&mm->mmap_sem);
 678                                return 0;
 679                        }
 680                } else
 681                        __lock_page(page);
 682                return 1;
 683        }
 684}
 685
 686/**
 687 * find_get_page - find and get a page reference
 688 * @mapping: the address_space to search
 689 * @offset: the page index
 690 *
 691 * Is there a pagecache struct page at the given (mapping, offset) tuple?
 692 * If yes, increment its refcount and return it; if no, return NULL.
 693 */
 694struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
 695{
 696        void **pagep;
 697        struct page *page;
 698
 699        rcu_read_lock();
 700repeat:
 701        page = NULL;
 702        pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
 703        if (pagep) {
 704                page = radix_tree_deref_slot(pagep);
 705                if (unlikely(!page))
 706                        goto out;
 707                if (radix_tree_exception(page)) {
 708                        if (radix_tree_deref_retry(page))
 709                                goto repeat;
 710                        /*
 711                         * Otherwise, shmem/tmpfs must be storing a swap entry
 712                         * here as an exceptional entry: so return it without
 713                         * attempting to raise page count.
 714                         */
 715                        goto out;
 716                }
 717                if (!page_cache_get_speculative(page))
 718                        goto repeat;
 719
 720                /*
 721                 * Has the page moved?
 722                 * This is part of the lockless pagecache protocol. See
 723                 * include/linux/pagemap.h for details.
 724                 */
 725                if (unlikely(page != *pagep)) {
 726                        page_cache_release(page);
 727                        goto repeat;
 728                }
 729        }
 730out:
 731        rcu_read_unlock();
 732
 733        return page;
 734}
 735EXPORT_SYMBOL(find_get_page);
 736
 737/**
 738 * find_lock_page - locate, pin and lock a pagecache page
 739 * @mapping: the address_space to search
 740 * @offset: the page index
 741 *
 742 * Locates the desired pagecache page, locks it, increments its reference
 743 * count and returns its address.
 744 *
 745 * Returns zero if the page was not present. find_lock_page() may sleep.
 746 */
 747struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
 748{
 749        struct page *page;
 750
 751repeat:
 752        page = find_get_page(mapping, offset);
 753        if (page && !radix_tree_exception(page)) {
 754                lock_page(page);
 755                /* Has the page been truncated? */
 756                if (unlikely(page->mapping != mapping)) {
 757                        unlock_page(page);
 758                        page_cache_release(page);
 759                        goto repeat;
 760                }
 761                VM_BUG_ON(page->index != offset);
 762        }
 763        return page;
 764}
 765EXPORT_SYMBOL(find_lock_page);
 766
 767/**
 768 * find_or_create_page - locate or add a pagecache page
 769 * @mapping: the page's address_space
 770 * @index: the page's index into the mapping
 771 * @gfp_mask: page allocation mode
 772 *
 773 * Locates a page in the pagecache.  If the page is not present, a new page
 774 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
 775 * LRU list.  The returned page is locked and has its reference count
 776 * incremented.
 777 *
 778 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
 779 * allocation!
 780 *
 781 * find_or_create_page() returns the desired page's address, or zero on
 782 * memory exhaustion.
 783 */
 784struct page *find_or_create_page(struct address_space *mapping,
 785                pgoff_t index, gfp_t gfp_mask)
 786{
 787        struct page *page;
 788        int err;
 789repeat:
 790        page = find_lock_page(mapping, index);
 791        if (!page) {
 792                page = __page_cache_alloc(gfp_mask);
 793                if (!page)
 794                        return NULL;
 795                /*
 796                 * We want a regular kernel memory (not highmem or DMA etc)
 797                 * allocation for the radix tree nodes, but we need to honour
 798                 * the context-specific requirements the caller has asked for.
 799                 * GFP_RECLAIM_MASK collects those requirements.
 800                 */
 801                err = add_to_page_cache_lru(page, mapping, index,
 802                        (gfp_mask & GFP_RECLAIM_MASK));
 803                if (unlikely(err)) {
 804                        page_cache_release(page);
 805                        page = NULL;
 806                        if (err == -EEXIST)
 807                                goto repeat;
 808                }
 809        }
 810        return page;
 811}
 812EXPORT_SYMBOL(find_or_create_page);
 813
 814/**
 815 * find_get_pages - gang pagecache lookup
 816 * @mapping:    The address_space to search
 817 * @start:      The starting page index
 818 * @nr_pages:   The maximum number of pages
 819 * @pages:      Where the resulting pages are placed
 820 *
 821 * find_get_pages() will search for and return a group of up to
 822 * @nr_pages pages in the mapping.  The pages are placed at @pages.
 823 * find_get_pages() takes a reference against the returned pages.
 824 *
 825 * The search returns a group of mapping-contiguous pages with ascending
 826 * indexes.  There may be holes in the indices due to not-present pages.
 827 *
 828 * find_get_pages() returns the number of pages which were found.
 829 */
 830unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
 831                            unsigned int nr_pages, struct page **pages)
 832{
 833        struct radix_tree_iter iter;
 834        void **slot;
 835        unsigned ret = 0;
 836
 837        if (unlikely(!nr_pages))
 838                return 0;
 839
 840        rcu_read_lock();
 841restart:
 842        radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
 843                struct page *page;
 844repeat:
 845                page = radix_tree_deref_slot(slot);
 846                if (unlikely(!page))
 847                        continue;
 848
 849                if (radix_tree_exception(page)) {
 850                        if (radix_tree_deref_retry(page)) {
 851                                /*
 852                                 * Transient condition which can only trigger
 853                                 * when entry at index 0 moves out of or back
 854                                 * to root: none yet gotten, safe to restart.
 855                                 */
 856                                WARN_ON(iter.index);
 857                                goto restart;
 858                        }
 859                        /*
 860                         * Otherwise, shmem/tmpfs must be storing a swap entry
 861                         * here as an exceptional entry: so skip over it -
 862                         * we only reach this from invalidate_mapping_pages().
 863                         */
 864                        continue;
 865                }
 866
 867                if (!page_cache_get_speculative(page))
 868                        goto repeat;
 869
 870                /* Has the page moved? */
 871                if (unlikely(page != *slot)) {
 872                        page_cache_release(page);
 873                        goto repeat;
 874                }
 875
 876                pages[ret] = page;
 877                if (++ret == nr_pages)
 878                        break;
 879        }
 880
 881        rcu_read_unlock();
 882        return ret;
 883}
 884
 885/**
 886 * find_get_pages_contig - gang contiguous pagecache lookup
 887 * @mapping:    The address_space to search
 888 * @index:      The starting page index
 889 * @nr_pages:   The maximum number of pages
 890 * @pages:      Where the resulting pages are placed
 891 *
 892 * find_get_pages_contig() works exactly like find_get_pages(), except
 893 * that the returned number of pages are guaranteed to be contiguous.
 894 *
 895 * find_get_pages_contig() returns the number of pages which were found.
 896 */
 897unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
 898                               unsigned int nr_pages, struct page **pages)
 899{
 900        struct radix_tree_iter iter;
 901        void **slot;
 902        unsigned int ret = 0;
 903
 904        if (unlikely(!nr_pages))
 905                return 0;
 906
 907        rcu_read_lock();
 908restart:
 909        radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
 910                struct page *page;
 911repeat:
 912                page = radix_tree_deref_slot(slot);
 913                /* The hole, there no reason to continue */
 914                if (unlikely(!page))
 915                        break;
 916
 917                if (radix_tree_exception(page)) {
 918                        if (radix_tree_deref_retry(page)) {
 919                                /*
 920                                 * Transient condition which can only trigger
 921                                 * when entry at index 0 moves out of or back
 922                                 * to root: none yet gotten, safe to restart.
 923                                 */
 924                                goto restart;
 925                        }
 926                        /*
 927                         * Otherwise, shmem/tmpfs must be storing a swap entry
 928                         * here as an exceptional entry: so stop looking for
 929                         * contiguous pages.
 930                         */
 931                        break;
 932                }
 933
 934                if (!page_cache_get_speculative(page))
 935                        goto repeat;
 936
 937                /* Has the page moved? */
 938                if (unlikely(page != *slot)) {
 939                        page_cache_release(page);
 940                        goto repeat;
 941                }
 942
 943                /*
 944                 * must check mapping and index after taking the ref.
 945                 * otherwise we can get both false positives and false
 946                 * negatives, which is just confusing to the caller.
 947                 */
 948                if (page->mapping == NULL || page->index != iter.index) {
 949                        page_cache_release(page);
 950                        break;
 951                }
 952
 953                pages[ret] = page;
 954                if (++ret == nr_pages)
 955                        break;
 956        }
 957        rcu_read_unlock();
 958        return ret;
 959}
 960EXPORT_SYMBOL(find_get_pages_contig);
 961
 962/**
 963 * find_get_pages_tag - find and return pages that match @tag
 964 * @mapping:    the address_space to search
 965 * @index:      the starting page index
 966 * @tag:        the tag index
 967 * @nr_pages:   the maximum number of pages
 968 * @pages:      where the resulting pages are placed
 969 *
 970 * Like find_get_pages, except we only return pages which are tagged with
 971 * @tag.   We update @index to index the next page for the traversal.
 972 */
 973unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
 974                        int tag, unsigned int nr_pages, struct page **pages)
 975{
 976        struct radix_tree_iter iter;
 977        void **slot;
 978        unsigned ret = 0;
 979
 980        if (unlikely(!nr_pages))
 981                return 0;
 982
 983        rcu_read_lock();
 984restart:
 985        radix_tree_for_each_tagged(slot, &mapping->page_tree,
 986                                   &iter, *index, tag) {
 987                struct page *page;
 988repeat:
 989                page = radix_tree_deref_slot(slot);
 990                if (unlikely(!page))
 991                        continue;
 992
 993                if (radix_tree_exception(page)) {
 994                        if (radix_tree_deref_retry(page)) {
 995                                /*
 996                                 * Transient condition which can only trigger
 997                                 * when entry at index 0 moves out of or back
 998                                 * to root: none yet gotten, safe to restart.
 999                                 */
1000                                goto restart;
1001                        }
1002                        /*
1003                         * This function is never used on a shmem/tmpfs
1004                         * mapping, so a swap entry won't be found here.
1005                         */
1006                        BUG();
1007                }
1008
1009                if (!page_cache_get_speculative(page))
1010                        goto repeat;
1011
1012                /* Has the page moved? */
1013                if (unlikely(page != *slot)) {
1014                        page_cache_release(page);
1015                        goto repeat;
1016                }
1017
1018                pages[ret] = page;
1019                if (++ret == nr_pages)
1020                        break;
1021        }
1022
1023        rcu_read_unlock();
1024
1025        if (ret)
1026                *index = pages[ret - 1]->index + 1;
1027
1028        return ret;
1029}
1030EXPORT_SYMBOL(find_get_pages_tag);
1031
1032/**
1033 * grab_cache_page_nowait - returns locked page at given index in given cache
1034 * @mapping: target address_space
1035 * @index: the page index
1036 *
1037 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1038 * This is intended for speculative data generators, where the data can
1039 * be regenerated if the page couldn't be grabbed.  This routine should
1040 * be safe to call while holding the lock for another page.
1041 *
1042 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1043 * and deadlock against the caller's locked page.
1044 */
1045struct page *
1046grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
1047{
1048        struct page *page = find_get_page(mapping, index);
1049
1050        if (page) {
1051                if (trylock_page(page))
1052                        return page;
1053                page_cache_release(page);
1054                return NULL;
1055        }
1056        page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1057        if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1058                page_cache_release(page);
1059                page = NULL;
1060        }
1061        return page;
1062}
1063EXPORT_SYMBOL(grab_cache_page_nowait);
1064
1065/*
1066 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1067 * a _large_ part of the i/o request. Imagine the worst scenario:
1068 *
1069 *      ---R__________________________________________B__________
1070 *         ^ reading here                             ^ bad block(assume 4k)
1071 *
1072 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1073 * => failing the whole request => read(R) => read(R+1) =>
1074 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1075 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1076 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1077 *
1078 * It is going insane. Fix it by quickly scaling down the readahead size.
1079 */
1080static void shrink_readahead_size_eio(struct file *filp,
1081                                        struct file_ra_state *ra)
1082{
1083        ra->ra_pages /= 4;
1084}
1085
1086/**
1087 * do_generic_file_read - generic file read routine
1088 * @filp:       the file to read
1089 * @ppos:       current file position
1090 * @desc:       read_descriptor
1091 * @actor:      read method
1092 *
1093 * This is a generic file read routine, and uses the
1094 * mapping->a_ops->readpage() function for the actual low-level stuff.
1095 *
1096 * This is really ugly. But the goto's actually try to clarify some
1097 * of the logic when it comes to error handling etc.
1098 */
1099static void do_generic_file_read(struct file *filp, loff_t *ppos,
1100                read_descriptor_t *desc, read_actor_t actor)
1101{
1102        struct address_space *mapping = filp->f_mapping;
1103        struct inode *inode = mapping->host;
1104        struct file_ra_state *ra = &filp->f_ra;
1105        pgoff_t index;
1106        pgoff_t last_index;
1107        pgoff_t prev_index;
1108        unsigned long offset;      /* offset into pagecache page */
1109        unsigned int prev_offset;
1110        int error;
1111
1112        index = *ppos >> PAGE_CACHE_SHIFT;
1113        prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1114        prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1115        last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1116        offset = *ppos & ~PAGE_CACHE_MASK;
1117
1118        for (;;) {
1119                struct page *page;
1120                pgoff_t end_index;
1121                loff_t isize;
1122                unsigned long nr, ret;
1123
1124                cond_resched();
1125find_page:
1126                page = find_get_page(mapping, index);
1127                if (!page) {
1128                        page_cache_sync_readahead(mapping,
1129                                        ra, filp,
1130                                        index, last_index - index);
1131                        page = find_get_page(mapping, index);
1132                        if (unlikely(page == NULL))
1133                                goto no_cached_page;
1134                }
1135                if (PageReadahead(page)) {
1136                        page_cache_async_readahead(mapping,
1137                                        ra, filp, page,
1138                                        index, last_index - index);
1139                }
1140                if (!PageUptodate(page)) {
1141                        if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1142                                        !mapping->a_ops->is_partially_uptodate)
1143                                goto page_not_up_to_date;
1144                        if (!trylock_page(page))
1145                                goto page_not_up_to_date;
1146                        /* Did it get truncated before we got the lock? */
1147                        if (!page->mapping)
1148                                goto page_not_up_to_date_locked;
1149                        if (!mapping->a_ops->is_partially_uptodate(page,
1150                                                                desc, offset))
1151                                goto page_not_up_to_date_locked;
1152                        unlock_page(page);
1153                }
1154page_ok:
1155                /*
1156                 * i_size must be checked after we know the page is Uptodate.
1157                 *
1158                 * Checking i_size after the check allows us to calculate
1159                 * the correct value for "nr", which means the zero-filled
1160                 * part of the page is not copied back to userspace (unless
1161                 * another truncate extends the file - this is desired though).
1162                 */
1163
1164                isize = i_size_read(inode);
1165                end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1166                if (unlikely(!isize || index > end_index)) {
1167                        page_cache_release(page);
1168                        goto out;
1169                }
1170
1171                /* nr is the maximum number of bytes to copy from this page */
1172                nr = PAGE_CACHE_SIZE;
1173                if (index == end_index) {
1174                        nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1175                        if (nr <= offset) {
1176                                page_cache_release(page);
1177                                goto out;
1178                        }
1179                }
1180                nr = nr - offset;
1181
1182                /* If users can be writing to this page using arbitrary
1183                 * virtual addresses, take care about potential aliasing
1184                 * before reading the page on the kernel side.
1185                 */
1186                if (mapping_writably_mapped(mapping))
1187                        flush_dcache_page(page);
1188
1189                /*
1190                 * When a sequential read accesses a page several times,
1191                 * only mark it as accessed the first time.
1192                 */
1193                if (prev_index != index || offset != prev_offset)
1194                        mark_page_accessed(page);
1195                prev_index = index;
1196
1197                /*
1198                 * Ok, we have the page, and it's up-to-date, so
1199                 * now we can copy it to user space...
1200                 *
1201                 * The actor routine returns how many bytes were actually used..
1202                 * NOTE! This may not be the same as how much of a user buffer
1203                 * we filled up (we may be padding etc), so we can only update
1204                 * "pos" here (the actor routine has to update the user buffer
1205                 * pointers and the remaining count).
1206                 */
1207                ret = actor(desc, page, offset, nr);
1208                offset += ret;
1209                index += offset >> PAGE_CACHE_SHIFT;
1210                offset &= ~PAGE_CACHE_MASK;
1211                prev_offset = offset;
1212
1213                page_cache_release(page);
1214                if (ret == nr && desc->count)
1215                        continue;
1216                goto out;
1217
1218page_not_up_to_date:
1219                /* Get exclusive access to the page ... */
1220                error = lock_page_killable(page);
1221                if (unlikely(error))
1222                        goto readpage_error;
1223
1224page_not_up_to_date_locked:
1225                /* Did it get truncated before we got the lock? */
1226                if (!page->mapping) {
1227                        unlock_page(page);
1228                        page_cache_release(page);
1229                        continue;
1230                }
1231
1232                /* Did somebody else fill it already? */
1233                if (PageUptodate(page)) {
1234                        unlock_page(page);
1235                        goto page_ok;
1236                }
1237
1238readpage:
1239                /*
1240                 * A previous I/O error may have been due to temporary
1241                 * failures, eg. multipath errors.
1242                 * PG_error will be set again if readpage fails.
1243                 */
1244                ClearPageError(page);
1245                /* Start the actual read. The read will unlock the page. */
1246                error = mapping->a_ops->readpage(filp, page);
1247
1248                if (unlikely(error)) {
1249                        if (error == AOP_TRUNCATED_PAGE) {
1250                                page_cache_release(page);
1251                                goto find_page;
1252                        }
1253                        goto readpage_error;
1254                }
1255
1256                if (!PageUptodate(page)) {
1257                        error = lock_page_killable(page);
1258                        if (unlikely(error))
1259                                goto readpage_error;
1260                        if (!PageUptodate(page)) {
1261                                if (page->mapping == NULL) {
1262                                        /*
1263                                         * invalidate_mapping_pages got it
1264                                         */
1265                                        unlock_page(page);
1266                                        page_cache_release(page);
1267                                        goto find_page;
1268                                }
1269                                unlock_page(page);
1270                                shrink_readahead_size_eio(filp, ra);
1271                                error = -EIO;
1272                                goto readpage_error;
1273                        }
1274                        unlock_page(page);
1275                }
1276
1277                goto page_ok;
1278
1279readpage_error:
1280                /* UHHUH! A synchronous read error occurred. Report it */
1281                desc->error = error;
1282                page_cache_release(page);
1283                goto out;
1284
1285no_cached_page:
1286                /*
1287                 * Ok, it wasn't cached, so we need to create a new
1288                 * page..
1289                 */
1290                page = page_cache_alloc_cold(mapping);
1291                if (!page) {
1292                        desc->error = -ENOMEM;
1293                        goto out;
1294                }
1295                error = add_to_page_cache_lru(page, mapping,
1296                                                index, GFP_KERNEL);
1297                if (error) {
1298                        page_cache_release(page);
1299                        if (error == -EEXIST)
1300                                goto find_page;
1301                        desc->error = error;
1302                        goto out;
1303                }
1304                goto readpage;
1305        }
1306
1307out:
1308        ra->prev_pos = prev_index;
1309        ra->prev_pos <<= PAGE_CACHE_SHIFT;
1310        ra->prev_pos |= prev_offset;
1311
1312        *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1313        file_accessed(filp);
1314}
1315
1316int file_read_actor(read_descriptor_t *desc, struct page *page,
1317                        unsigned long offset, unsigned long size)
1318{
1319        char *kaddr;
1320        unsigned long left, count = desc->count;
1321
1322        if (size > count)
1323                size = count;
1324
1325        /*
1326         * Faults on the destination of a read are common, so do it before
1327         * taking the kmap.
1328         */
1329        if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1330                kaddr = kmap_atomic(page);
1331                left = __copy_to_user_inatomic(desc->arg.buf,
1332                                                kaddr + offset, size);
1333                kunmap_atomic(kaddr);
1334                if (left == 0)
1335                        goto success;
1336        }
1337
1338        /* Do it the slow way */
1339        kaddr = kmap(page);
1340        left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1341        kunmap(page);
1342
1343        if (left) {
1344                size -= left;
1345                desc->error = -EFAULT;
1346        }
1347success:
1348        desc->count = count - size;
1349        desc->written += size;
1350        desc->arg.buf += size;
1351        return size;
1352}
1353
1354/*
1355 * Performs necessary checks before doing a write
1356 * @iov:        io vector request
1357 * @nr_segs:    number of segments in the iovec
1358 * @count:      number of bytes to write
1359 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1360 *
1361 * Adjust number of segments and amount of bytes to write (nr_segs should be
1362 * properly initialized first). Returns appropriate error code that caller
1363 * should return or zero in case that write should be allowed.
1364 */
1365int generic_segment_checks(const struct iovec *iov,
1366                        unsigned long *nr_segs, size_t *count, int access_flags)
1367{
1368        unsigned long   seg;
1369        size_t cnt = 0;
1370        for (seg = 0; seg < *nr_segs; seg++) {
1371                const struct iovec *iv = &iov[seg];
1372
1373                /*
1374                 * If any segment has a negative length, or the cumulative
1375                 * length ever wraps negative then return -EINVAL.
1376                 */
1377                cnt += iv->iov_len;
1378                if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1379                        return -EINVAL;
1380                if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1381                        continue;
1382                if (seg == 0)
1383                        return -EFAULT;
1384                *nr_segs = seg;
1385                cnt -= iv->iov_len;     /* This segment is no good */
1386                break;
1387        }
1388        *count = cnt;
1389        return 0;
1390}
1391EXPORT_SYMBOL(generic_segment_checks);
1392
1393/**
1394 * generic_file_aio_read - generic filesystem read routine
1395 * @iocb:       kernel I/O control block
1396 * @iov:        io vector request
1397 * @nr_segs:    number of segments in the iovec
1398 * @pos:        current file position
1399 *
1400 * This is the "read()" routine for all filesystems
1401 * that can use the page cache directly.
1402 */
1403ssize_t
1404generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1405                unsigned long nr_segs, loff_t pos)
1406{
1407        struct file *filp = iocb->ki_filp;
1408        ssize_t retval;
1409        unsigned long seg = 0;
1410        size_t count;
1411        loff_t *ppos = &iocb->ki_pos;
1412
1413        count = 0;
1414        retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1415        if (retval)
1416                return retval;
1417
1418        /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1419        if (filp->f_flags & O_DIRECT) {
1420                loff_t size;
1421                struct address_space *mapping;
1422                struct inode *inode;
1423
1424                mapping = filp->f_mapping;
1425                inode = mapping->host;
1426                if (!count)
1427                        goto out; /* skip atime */
1428                size = i_size_read(inode);
1429                if (pos < size) {
1430                        retval = filemap_write_and_wait_range(mapping, pos,
1431                                        pos + iov_length(iov, nr_segs) - 1);
1432                        if (!retval) {
1433                                retval = mapping->a_ops->direct_IO(READ, iocb,
1434                                                        iov, pos, nr_segs);
1435                        }
1436                        if (retval > 0) {
1437                                *ppos = pos + retval;
1438                                count -= retval;
1439                        }
1440
1441                        /*
1442                         * Btrfs can have a short DIO read if we encounter
1443                         * compressed extents, so if there was an error, or if
1444                         * we've already read everything we wanted to, or if
1445                         * there was a short read because we hit EOF, go ahead
1446                         * and return.  Otherwise fallthrough to buffered io for
1447                         * the rest of the read.
1448                         */
1449                        if (retval < 0 || !count || *ppos >= size) {
1450                                file_accessed(filp);
1451                                goto out;
1452                        }
1453                }
1454        }
1455
1456        count = retval;
1457        for (seg = 0; seg < nr_segs; seg++) {
1458                read_descriptor_t desc;
1459                loff_t offset = 0;
1460
1461                /*
1462                 * If we did a short DIO read we need to skip the section of the
1463                 * iov that we've already read data into.
1464                 */
1465                if (count) {
1466                        if (count > iov[seg].iov_len) {
1467                                count -= iov[seg].iov_len;
1468                                continue;
1469                        }
1470                        offset = count;
1471                        count = 0;
1472                }
1473
1474                desc.written = 0;
1475                desc.arg.buf = iov[seg].iov_base + offset;
1476                desc.count = iov[seg].iov_len - offset;
1477                if (desc.count == 0)
1478                        continue;
1479                desc.error = 0;
1480                do_generic_file_read(filp, ppos, &desc, file_read_actor);
1481                retval += desc.written;
1482                if (desc.error) {
1483                        retval = retval ?: desc.error;
1484                        break;
1485                }
1486                if (desc.count > 0)
1487                        break;
1488        }
1489out:
1490        return retval;
1491}
1492EXPORT_SYMBOL(generic_file_aio_read);
1493
1494#ifdef CONFIG_MMU
1495/**
1496 * page_cache_read - adds requested page to the page cache if not already there
1497 * @file:       file to read
1498 * @offset:     page index
1499 *
1500 * This adds the requested page to the page cache if it isn't already there,
1501 * and schedules an I/O to read in its contents from disk.
1502 */
1503static int page_cache_read(struct file *file, pgoff_t offset)
1504{
1505        struct address_space *mapping = file->f_mapping;
1506        struct page *page; 
1507        int ret;
1508
1509        do {
1510                page = page_cache_alloc_cold(mapping);
1511                if (!page)
1512                        return -ENOMEM;
1513
1514                ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1515                if (ret == 0)
1516                        ret = mapping->a_ops->readpage(file, page);
1517                else if (ret == -EEXIST)
1518                        ret = 0; /* losing race to add is OK */
1519
1520                page_cache_release(page);
1521
1522        } while (ret == AOP_TRUNCATED_PAGE);
1523                
1524        return ret;
1525}
1526
1527#define MMAP_LOTSAMISS  (100)
1528
1529/*
1530 * Synchronous readahead happens when we don't even find
1531 * a page in the page cache at all.
1532 */
1533static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1534                                   struct file_ra_state *ra,
1535                                   struct file *file,
1536                                   pgoff_t offset)
1537{
1538        unsigned long ra_pages;
1539        struct address_space *mapping = file->f_mapping;
1540
1541        /* If we don't want any read-ahead, don't bother */
1542        if (vma->vm_flags & VM_RAND_READ)
1543                return;
1544        if (!ra->ra_pages)
1545                return;
1546
1547        if (vma->vm_flags & VM_SEQ_READ) {
1548                page_cache_sync_readahead(mapping, ra, file, offset,
1549                                          ra->ra_pages);
1550                return;
1551        }
1552
1553        /* Avoid banging the cache line if not needed */
1554        if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1555                ra->mmap_miss++;
1556
1557        /*
1558         * Do we miss much more than hit in this file? If so,
1559         * stop bothering with read-ahead. It will only hurt.
1560         */
1561        if (ra->mmap_miss > MMAP_LOTSAMISS)
1562                return;
1563
1564        /*
1565         * mmap read-around
1566         */
1567        ra_pages = max_sane_readahead(ra->ra_pages);
1568        ra->start = max_t(long, 0, offset - ra_pages / 2);
1569        ra->size = ra_pages;
1570        ra->async_size = ra_pages / 4;
1571        ra_submit(ra, mapping, file);
1572}
1573
1574/*
1575 * Asynchronous readahead happens when we find the page and PG_readahead,
1576 * so we want to possibly extend the readahead further..
1577 */
1578static void do_async_mmap_readahead(struct vm_area_struct *vma,
1579                                    struct file_ra_state *ra,
1580                                    struct file *file,
1581                                    struct page *page,
1582                                    pgoff_t offset)
1583{
1584        struct address_space *mapping = file->f_mapping;
1585
1586        /* If we don't want any read-ahead, don't bother */
1587        if (vma->vm_flags & VM_RAND_READ)
1588                return;
1589        if (ra->mmap_miss > 0)
1590                ra->mmap_miss--;
1591        if (PageReadahead(page))
1592                page_cache_async_readahead(mapping, ra, file,
1593                                           page, offset, ra->ra_pages);
1594}
1595
1596/**
1597 * filemap_fault - read in file data for page fault handling
1598 * @vma:        vma in which the fault was taken
1599 * @vmf:        struct vm_fault containing details of the fault
1600 *
1601 * filemap_fault() is invoked via the vma operations vector for a
1602 * mapped memory region to read in file data during a page fault.
1603 *
1604 * The goto's are kind of ugly, but this streamlines the normal case of having
1605 * it in the page cache, and handles the special cases reasonably without
1606 * having a lot of duplicated code.
1607 */
1608int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1609{
1610        int error;
1611        struct file *file = vma->vm_file;
1612        struct address_space *mapping = file->f_mapping;
1613        struct file_ra_state *ra = &file->f_ra;
1614        struct inode *inode = mapping->host;
1615        pgoff_t offset = vmf->pgoff;
1616        struct page *page;
1617        pgoff_t size;
1618        int ret = 0;
1619
1620        size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1621        if (offset >= size)
1622                return VM_FAULT_SIGBUS;
1623
1624        /*
1625         * Do we have something in the page cache already?
1626         */
1627        page = find_get_page(mapping, offset);
1628        if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
1629                /*
1630                 * We found the page, so try async readahead before
1631                 * waiting for the lock.
1632                 */
1633                do_async_mmap_readahead(vma, ra, file, page, offset);
1634        } else if (!page) {
1635                /* No page in the page cache at all */
1636                do_sync_mmap_readahead(vma, ra, file, offset);
1637                count_vm_event(PGMAJFAULT);
1638                mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1639                ret = VM_FAULT_MAJOR;
1640retry_find:
1641                page = find_get_page(mapping, offset);
1642                if (!page)
1643                        goto no_cached_page;
1644        }
1645
1646        if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1647                page_cache_release(page);
1648                return ret | VM_FAULT_RETRY;
1649        }
1650
1651        /* Did it get truncated? */
1652        if (unlikely(page->mapping != mapping)) {
1653                unlock_page(page);
1654                put_page(page);
1655                goto retry_find;
1656        }
1657        VM_BUG_ON(page->index != offset);
1658
1659        /*
1660         * We have a locked page in the page cache, now we need to check
1661         * that it's up-to-date. If not, it is going to be due to an error.
1662         */
1663        if (unlikely(!PageUptodate(page)))
1664                goto page_not_uptodate;
1665
1666        /*
1667         * Found the page and have a reference on it.
1668         * We must recheck i_size under page lock.
1669         */
1670        size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1671        if (unlikely(offset >= size)) {
1672                unlock_page(page);
1673                page_cache_release(page);
1674                return VM_FAULT_SIGBUS;
1675        }
1676
1677        vmf->page = page;
1678        return ret | VM_FAULT_LOCKED;
1679
1680no_cached_page:
1681        /*
1682         * We're only likely to ever get here if MADV_RANDOM is in
1683         * effect.
1684         */
1685        error = page_cache_read(file, offset);
1686
1687        /*
1688         * The page we want has now been added to the page cache.
1689         * In the unlikely event that someone removed it in the
1690         * meantime, we'll just come back here and read it again.
1691         */
1692        if (error >= 0)
1693                goto retry_find;
1694
1695        /*
1696         * An error return from page_cache_read can result if the
1697         * system is low on memory, or a problem occurs while trying
1698         * to schedule I/O.
1699         */
1700        if (error == -ENOMEM)
1701                return VM_FAULT_OOM;
1702        return VM_FAULT_SIGBUS;
1703
1704page_not_uptodate:
1705        /*
1706         * Umm, take care of errors if the page isn't up-to-date.
1707         * Try to re-read it _once_. We do this synchronously,
1708         * because there really aren't any performance issues here
1709         * and we need to check for errors.
1710         */
1711        ClearPageError(page);
1712        error = mapping->a_ops->readpage(file, page);
1713        if (!error) {
1714                wait_on_page_locked(page);
1715                if (!PageUptodate(page))
1716                        error = -EIO;
1717        }
1718        page_cache_release(page);
1719
1720        if (!error || error == AOP_TRUNCATED_PAGE)
1721                goto retry_find;
1722
1723        /* Things didn't work out. Return zero to tell the mm layer so. */
1724        shrink_readahead_size_eio(file, ra);
1725        return VM_FAULT_SIGBUS;
1726}
1727EXPORT_SYMBOL(filemap_fault);
1728
1729int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
1730{
1731        struct page *page = vmf->page;
1732        struct inode *inode = file_inode(vma->vm_file);
1733        int ret = VM_FAULT_LOCKED;
1734
1735        sb_start_pagefault(inode->i_sb);
1736        file_update_time(vma->vm_file);
1737        lock_page(page);
1738        if (page->mapping != inode->i_mapping) {
1739                unlock_page(page);
1740                ret = VM_FAULT_NOPAGE;
1741                goto out;
1742        }
1743        /*
1744         * We mark the page dirty already here so that when freeze is in
1745         * progress, we are guaranteed that writeback during freezing will
1746         * see the dirty page and writeprotect it again.
1747         */
1748        set_page_dirty(page);
1749        wait_for_stable_page(page);
1750out:
1751        sb_end_pagefault(inode->i_sb);
1752        return ret;
1753}
1754EXPORT_SYMBOL(filemap_page_mkwrite);
1755
1756const struct vm_operations_struct generic_file_vm_ops = {
1757        .fault          = filemap_fault,
1758        .page_mkwrite   = filemap_page_mkwrite,
1759        .remap_pages    = generic_file_remap_pages,
1760};
1761
1762/* This is used for a general mmap of a disk file */
1763
1764int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1765{
1766        struct address_space *mapping = file->f_mapping;
1767
1768        if (!mapping->a_ops->readpage)
1769                return -ENOEXEC;
1770        file_accessed(file);
1771        vma->vm_ops = &generic_file_vm_ops;
1772        return 0;
1773}
1774
1775/*
1776 * This is for filesystems which do not implement ->writepage.
1777 */
1778int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1779{
1780        if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1781                return -EINVAL;
1782        return generic_file_mmap(file, vma);
1783}
1784#else
1785int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1786{
1787        return -ENOSYS;
1788}
1789int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1790{
1791        return -ENOSYS;
1792}
1793#endif /* CONFIG_MMU */
1794
1795EXPORT_SYMBOL(generic_file_mmap);
1796EXPORT_SYMBOL(generic_file_readonly_mmap);
1797
1798static struct page *__read_cache_page(struct address_space *mapping,
1799                                pgoff_t index,
1800                                int (*filler)(void *, struct page *),
1801                                void *data,
1802                                gfp_t gfp)
1803{
1804        struct page *page;
1805        int err;
1806repeat:
1807        page = find_get_page(mapping, index);
1808        if (!page) {
1809                page = __page_cache_alloc(gfp | __GFP_COLD);
1810                if (!page)
1811                        return ERR_PTR(-ENOMEM);
1812                err = add_to_page_cache_lru(page, mapping, index, gfp);
1813                if (unlikely(err)) {
1814                        page_cache_release(page);
1815                        if (err == -EEXIST)
1816                                goto repeat;
1817                        /* Presumably ENOMEM for radix tree node */
1818                        return ERR_PTR(err);
1819                }
1820                err = filler(data, page);
1821                if (err < 0) {
1822                        page_cache_release(page);
1823                        page = ERR_PTR(err);
1824                }
1825        }
1826        return page;
1827}
1828
1829static struct page *do_read_cache_page(struct address_space *mapping,
1830                                pgoff_t index,
1831                                int (*filler)(void *, struct page *),
1832                                void *data,
1833                                gfp_t gfp)
1834
1835{
1836        struct page *page;
1837        int err;
1838
1839retry:
1840        page = __read_cache_page(mapping, index, filler, data, gfp);
1841        if (IS_ERR(page))
1842                return page;
1843        if (PageUptodate(page))
1844                goto out;
1845
1846        lock_page(page);
1847        if (!page->mapping) {
1848                unlock_page(page);
1849                page_cache_release(page);
1850                goto retry;
1851        }
1852        if (PageUptodate(page)) {
1853                unlock_page(page);
1854                goto out;
1855        }
1856        err = filler(data, page);
1857        if (err < 0) {
1858                page_cache_release(page);
1859                return ERR_PTR(err);
1860        }
1861out:
1862        mark_page_accessed(page);
1863        return page;
1864}
1865
1866/**
1867 * read_cache_page_async - read into page cache, fill it if needed
1868 * @mapping:    the page's address_space
1869 * @index:      the page index
1870 * @filler:     function to perform the read
1871 * @data:       first arg to filler(data, page) function, often left as NULL
1872 *
1873 * Same as read_cache_page, but don't wait for page to become unlocked
1874 * after submitting it to the filler.
1875 *
1876 * Read into the page cache. If a page already exists, and PageUptodate() is
1877 * not set, try to fill the page but don't wait for it to become unlocked.
1878 *
1879 * If the page does not get brought uptodate, return -EIO.
1880 */
1881struct page *read_cache_page_async(struct address_space *mapping,
1882                                pgoff_t index,
1883                                int (*filler)(void *, struct page *),
1884                                void *data)
1885{
1886        return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1887}
1888EXPORT_SYMBOL(read_cache_page_async);
1889
1890static struct page *wait_on_page_read(struct page *page)
1891{
1892        if (!IS_ERR(page)) {
1893                wait_on_page_locked(page);
1894                if (!PageUptodate(page)) {
1895                        page_cache_release(page);
1896                        page = ERR_PTR(-EIO);
1897                }
1898        }
1899        return page;
1900}
1901
1902/**
1903 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1904 * @mapping:    the page's address_space
1905 * @index:      the page index
1906 * @gfp:        the page allocator flags to use if allocating
1907 *
1908 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1909 * any new page allocations done using the specified allocation flags.
1910 *
1911 * If the page does not get brought uptodate, return -EIO.
1912 */
1913struct page *read_cache_page_gfp(struct address_space *mapping,
1914                                pgoff_t index,
1915                                gfp_t gfp)
1916{
1917        filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1918
1919        return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1920}
1921EXPORT_SYMBOL(read_cache_page_gfp);
1922
1923/**
1924 * read_cache_page - read into page cache, fill it if needed
1925 * @mapping:    the page's address_space
1926 * @index:      the page index
1927 * @filler:     function to perform the read
1928 * @data:       first arg to filler(data, page) function, often left as NULL
1929 *
1930 * Read into the page cache. If a page already exists, and PageUptodate() is
1931 * not set, try to fill the page then wait for it to become unlocked.
1932 *
1933 * If the page does not get brought uptodate, return -EIO.
1934 */
1935struct page *read_cache_page(struct address_space *mapping,
1936                                pgoff_t index,
1937                                int (*filler)(void *, struct page *),
1938                                void *data)
1939{
1940        return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
1941}
1942EXPORT_SYMBOL(read_cache_page);
1943
1944static size_t __iovec_copy_from_user_inatomic(char *vaddr,
1945                        const struct iovec *iov, size_t base, size_t bytes)
1946{
1947        size_t copied = 0, left = 0;
1948
1949        while (bytes) {
1950                char __user *buf = iov->iov_base + base;
1951                int copy = min(bytes, iov->iov_len - base);
1952
1953                base = 0;
1954                left = __copy_from_user_inatomic(vaddr, buf, copy);
1955                copied += copy;
1956                bytes -= copy;
1957                vaddr += copy;
1958                iov++;
1959
1960                if (unlikely(left))
1961                        break;
1962        }
1963        return copied - left;
1964}
1965
1966/*
1967 * Copy as much as we can into the page and return the number of bytes which
1968 * were successfully copied.  If a fault is encountered then return the number of
1969 * bytes which were copied.
1970 */
1971size_t iov_iter_copy_from_user_atomic(struct page *page,
1972                struct iov_iter *i, unsigned long offset, size_t bytes)
1973{
1974        char *kaddr;
1975        size_t copied;
1976
1977        BUG_ON(!in_atomic());
1978        kaddr = kmap_atomic(page);
1979        if (likely(i->nr_segs == 1)) {
1980                int left;
1981                char __user *buf = i->iov->iov_base + i->iov_offset;
1982                left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
1983                copied = bytes - left;
1984        } else {
1985                copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1986                                                i->iov, i->iov_offset, bytes);
1987        }
1988        kunmap_atomic(kaddr);
1989
1990        return copied;
1991}
1992EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
1993
1994/*
1995 * This has the same sideeffects and return value as
1996 * iov_iter_copy_from_user_atomic().
1997 * The difference is that it attempts to resolve faults.
1998 * Page must not be locked.
1999 */
2000size_t iov_iter_copy_from_user(struct page *page,
2001                struct iov_iter *i, unsigned long offset, size_t bytes)
2002{
2003        char *kaddr;
2004        size_t copied;
2005
2006        kaddr = kmap(page);
2007        if (likely(i->nr_segs == 1)) {
2008                int left;
2009                char __user *buf = i->iov->iov_base + i->iov_offset;
2010                left = __copy_from_user(kaddr + offset, buf, bytes);
2011                copied = bytes - left;
2012        } else {
2013                copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2014                                                i->iov, i->iov_offset, bytes);
2015        }
2016        kunmap(page);
2017        return copied;
2018}
2019EXPORT_SYMBOL(iov_iter_copy_from_user);
2020
2021void iov_iter_advance(struct iov_iter *i, size_t bytes)
2022{
2023        BUG_ON(i->count < bytes);
2024
2025        if (likely(i->nr_segs == 1)) {
2026                i->iov_offset += bytes;
2027                i->count -= bytes;
2028        } else {
2029                const struct iovec *iov = i->iov;
2030                size_t base = i->iov_offset;
2031                unsigned long nr_segs = i->nr_segs;
2032
2033                /*
2034                 * The !iov->iov_len check ensures we skip over unlikely
2035                 * zero-length segments (without overruning the iovec).
2036                 */
2037                while (bytes || unlikely(i->count && !iov->iov_len)) {
2038                        int copy;
2039
2040                        copy = min(bytes, iov->iov_len - base);
2041                        BUG_ON(!i->count || i->count < copy);
2042                        i->count -= copy;
2043                        bytes -= copy;
2044                        base += copy;
2045                        if (iov->iov_len == base) {
2046                                iov++;
2047                                nr_segs--;
2048                                base = 0;
2049                        }
2050                }
2051                i->iov = iov;
2052                i->iov_offset = base;
2053                i->nr_segs = nr_segs;
2054        }
2055}
2056EXPORT_SYMBOL(iov_iter_advance);
2057
2058/*
2059 * Fault in the first iovec of the given iov_iter, to a maximum length
2060 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2061 * accessed (ie. because it is an invalid address).
2062 *
2063 * writev-intensive code may want this to prefault several iovecs -- that
2064 * would be possible (callers must not rely on the fact that _only_ the
2065 * first iovec will be faulted with the current implementation).
2066 */
2067int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2068{
2069        char __user *buf = i->iov->iov_base + i->iov_offset;
2070        bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2071        return fault_in_pages_readable(buf, bytes);
2072}
2073EXPORT_SYMBOL(iov_iter_fault_in_readable);
2074
2075/*
2076 * Return the count of just the current iov_iter segment.
2077 */
2078size_t iov_iter_single_seg_count(const struct iov_iter *i)
2079{
2080        const struct iovec *iov = i->iov;
2081        if (i->nr_segs == 1)
2082                return i->count;
2083        else
2084                return min(i->count, iov->iov_len - i->iov_offset);
2085}
2086EXPORT_SYMBOL(iov_iter_single_seg_count);
2087
2088/*
2089 * Performs necessary checks before doing a write
2090 *
2091 * Can adjust writing position or amount of bytes to write.
2092 * Returns appropriate error code that caller should return or
2093 * zero in case that write should be allowed.
2094 */
2095inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2096{
2097        struct inode *inode = file->f_mapping->host;
2098        unsigned long limit = rlimit(RLIMIT_FSIZE);
2099
2100        if (unlikely(*pos < 0))
2101                return -EINVAL;
2102
2103        if (!isblk) {
2104                /* FIXME: this is for backwards compatibility with 2.4 */
2105                if (file->f_flags & O_APPEND)
2106                        *pos = i_size_read(inode);
2107
2108                if (limit != RLIM_INFINITY) {
2109                        if (*pos >= limit) {
2110                                send_sig(SIGXFSZ, current, 0);
2111                                return -EFBIG;
2112                        }
2113                        if (*count > limit - (typeof(limit))*pos) {
2114                                *count = limit - (typeof(limit))*pos;
2115                        }
2116                }
2117        }
2118
2119        /*
2120         * LFS rule
2121         */
2122        if (unlikely(*pos + *count > MAX_NON_LFS &&
2123                                !(file->f_flags & O_LARGEFILE))) {
2124                if (*pos >= MAX_NON_LFS) {
2125                        return -EFBIG;
2126                }
2127                if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2128                        *count = MAX_NON_LFS - (unsigned long)*pos;
2129                }
2130        }
2131
2132        /*
2133         * Are we about to exceed the fs block limit ?
2134         *
2135         * If we have written data it becomes a short write.  If we have
2136         * exceeded without writing data we send a signal and return EFBIG.
2137         * Linus frestrict idea will clean these up nicely..
2138         */
2139        if (likely(!isblk)) {
2140                if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2141                        if (*count || *pos > inode->i_sb->s_maxbytes) {
2142                                return -EFBIG;
2143                        }
2144                        /* zero-length writes at ->s_maxbytes are OK */
2145                }
2146
2147                if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2148                        *count = inode->i_sb->s_maxbytes - *pos;
2149        } else {
2150#ifdef CONFIG_BLOCK
2151                loff_t isize;
2152                if (bdev_read_only(I_BDEV(inode)))
2153                        return -EPERM;
2154                isize = i_size_read(inode);
2155                if (*pos >= isize) {
2156                        if (*count || *pos > isize)
2157                                return -ENOSPC;
2158                }
2159
2160                if (*pos + *count > isize)
2161                        *count = isize - *pos;
2162#else
2163                return -EPERM;
2164#endif
2165        }
2166        return 0;
2167}
2168EXPORT_SYMBOL(generic_write_checks);
2169
2170int pagecache_write_begin(struct file *file, struct address_space *mapping,
2171                                loff_t pos, unsigned len, unsigned flags,
2172                                struct page **pagep, void **fsdata)
2173{
2174        const struct address_space_operations *aops = mapping->a_ops;
2175
2176        return aops->write_begin(file, mapping, pos, len, flags,
2177                                                        pagep, fsdata);
2178}
2179EXPORT_SYMBOL(pagecache_write_begin);
2180
2181int pagecache_write_end(struct file *file, struct address_space *mapping,
2182                                loff_t pos, unsigned len, unsigned copied,
2183                                struct page *page, void *fsdata)
2184{
2185        const struct address_space_operations *aops = mapping->a_ops;
2186
2187        mark_page_accessed(page);
2188        return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2189}
2190EXPORT_SYMBOL(pagecache_write_end);
2191
2192ssize_t
2193generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2194                unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2195                size_t count, size_t ocount)
2196{
2197        struct file     *file = iocb->ki_filp;
2198        struct address_space *mapping = file->f_mapping;
2199        struct inode    *inode = mapping->host;
2200        ssize_t         written;
2201        size_t          write_len;
2202        pgoff_t         end;
2203
2204        if (count != ocount)
2205                *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2206
2207        write_len = iov_length(iov, *nr_segs);
2208        end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2209
2210        written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2211        if (written)
2212                goto out;
2213
2214        /*
2215         * After a write we want buffered reads to be sure to go to disk to get
2216         * the new data.  We invalidate clean cached page from the region we're
2217         * about to write.  We do this *before* the write so that we can return
2218         * without clobbering -EIOCBQUEUED from ->direct_IO().
2219         */
2220        if (mapping->nrpages) {
2221                written = invalidate_inode_pages2_range(mapping,
2222                                        pos >> PAGE_CACHE_SHIFT, end);
2223                /*
2224                 * If a page can not be invalidated, return 0 to fall back
2225                 * to buffered write.
2226                 */
2227                if (written) {
2228                        if (written == -EBUSY)
2229                                return 0;
2230                        goto out;
2231                }
2232        }
2233
2234        written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2235
2236        /*
2237         * Finally, try again to invalidate clean pages which might have been
2238         * cached by non-direct readahead, or faulted in by get_user_pages()
2239         * if the source of the write was an mmap'ed region of the file
2240         * we're writing.  Either one is a pretty crazy thing to do,
2241         * so we don't support it 100%.  If this invalidation
2242         * fails, tough, the write still worked...
2243         */
2244        if (mapping->nrpages) {
2245                invalidate_inode_pages2_range(mapping,
2246                                              pos >> PAGE_CACHE_SHIFT, end);
2247        }
2248
2249        if (written > 0) {
2250                pos += written;
2251                if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2252                        i_size_write(inode, pos);
2253                        mark_inode_dirty(inode);
2254                }
2255                *ppos = pos;
2256        }
2257out:
2258        return written;
2259}
2260EXPORT_SYMBOL(generic_file_direct_write);
2261
2262/*
2263 * Find or create a page at the given pagecache position. Return the locked
2264 * page. This function is specifically for buffered writes.
2265 */
2266struct page *grab_cache_page_write_begin(struct address_space *mapping,
2267                                        pgoff_t index, unsigned flags)
2268{
2269        int status;
2270        gfp_t gfp_mask;
2271        struct page *page;
2272        gfp_t gfp_notmask = 0;
2273
2274        gfp_mask = mapping_gfp_mask(mapping);
2275        if (mapping_cap_account_dirty(mapping))
2276                gfp_mask |= __GFP_WRITE;
2277        if (flags & AOP_FLAG_NOFS)
2278                gfp_notmask = __GFP_FS;
2279repeat:
2280        page = find_lock_page(mapping, index);
2281        if (page)
2282                goto found;
2283
2284        page = __page_cache_alloc(gfp_mask & ~gfp_notmask);
2285        if (!page)
2286                return NULL;
2287        status = add_to_page_cache_lru(page, mapping, index,
2288                                                GFP_KERNEL & ~gfp_notmask);
2289        if (unlikely(status)) {
2290                page_cache_release(page);
2291                if (status == -EEXIST)
2292                        goto repeat;
2293                return NULL;
2294        }
2295found:
2296        wait_for_stable_page(page);
2297        return page;
2298}
2299EXPORT_SYMBOL(grab_cache_page_write_begin);
2300
2301static ssize_t generic_perform_write(struct file *file,
2302                                struct iov_iter *i, loff_t pos)
2303{
2304        struct address_space *mapping = file->f_mapping;
2305        const struct address_space_operations *a_ops = mapping->a_ops;
2306        long status = 0;
2307        ssize_t written = 0;
2308        unsigned int flags = 0;
2309
2310        /*
2311         * Copies from kernel address space cannot fail (NFSD is a big user).
2312         */
2313        if (segment_eq(get_fs(), KERNEL_DS))
2314                flags |= AOP_FLAG_UNINTERRUPTIBLE;
2315
2316        do {
2317                struct page *page;
2318                unsigned long offset;   /* Offset into pagecache page */
2319                unsigned long bytes;    /* Bytes to write to page */
2320                size_t copied;          /* Bytes copied from user */
2321                void *fsdata;
2322
2323                offset = (pos & (PAGE_CACHE_SIZE - 1));
2324                bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2325                                                iov_iter_count(i));
2326
2327again:
2328                /*
2329                 * Bring in the user page that we will copy from _first_.
2330                 * Otherwise there's a nasty deadlock on copying from the
2331                 * same page as we're writing to, without it being marked
2332                 * up-to-date.
2333                 *
2334                 * Not only is this an optimisation, but it is also required
2335                 * to check that the address is actually valid, when atomic
2336                 * usercopies are used, below.
2337                 */
2338                if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2339                        status = -EFAULT;
2340                        break;
2341                }
2342
2343                status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2344                                                &page, &fsdata);
2345                if (unlikely(status))
2346                        break;
2347
2348                if (mapping_writably_mapped(mapping))
2349                        flush_dcache_page(page);
2350
2351                pagefault_disable();
2352                copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2353                pagefault_enable();
2354                flush_dcache_page(page);
2355
2356                mark_page_accessed(page);
2357                status = a_ops->write_end(file, mapping, pos, bytes, copied,
2358                                                page, fsdata);
2359                if (unlikely(status < 0))
2360                        break;
2361                copied = status;
2362
2363                cond_resched();
2364
2365                iov_iter_advance(i, copied);
2366                if (unlikely(copied == 0)) {
2367                        /*
2368                         * If we were unable to copy any data at all, we must
2369                         * fall back to a single segment length write.
2370                         *
2371                         * If we didn't fallback here, we could livelock
2372                         * because not all segments in the iov can be copied at
2373                         * once without a pagefault.
2374                         */
2375                        bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2376                                                iov_iter_single_seg_count(i));
2377                        goto again;
2378                }
2379                pos += copied;
2380                written += copied;
2381
2382                balance_dirty_pages_ratelimited(mapping);
2383                if (fatal_signal_pending(current)) {
2384                        status = -EINTR;
2385                        break;
2386                }
2387        } while (iov_iter_count(i));
2388
2389        return written ? written : status;
2390}
2391
2392ssize_t
2393generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2394                unsigned long nr_segs, loff_t pos, loff_t *ppos,
2395                size_t count, ssize_t written)
2396{
2397        struct file *file = iocb->ki_filp;
2398        ssize_t status;
2399        struct iov_iter i;
2400
2401        iov_iter_init(&i, iov, nr_segs, count, written);
2402        status = generic_perform_write(file, &i, pos);
2403
2404        if (likely(status >= 0)) {
2405                written += status;
2406                *ppos = pos + status;
2407        }
2408        
2409        return written ? written : status;
2410}
2411EXPORT_SYMBOL(generic_file_buffered_write);
2412
2413/**
2414 * __generic_file_aio_write - write data to a file
2415 * @iocb:       IO state structure (file, offset, etc.)
2416 * @iov:        vector with data to write
2417 * @nr_segs:    number of segments in the vector
2418 * @ppos:       position where to write
2419 *
2420 * This function does all the work needed for actually writing data to a
2421 * file. It does all basic checks, removes SUID from the file, updates
2422 * modification times and calls proper subroutines depending on whether we
2423 * do direct IO or a standard buffered write.
2424 *
2425 * It expects i_mutex to be grabbed unless we work on a block device or similar
2426 * object which does not need locking at all.
2427 *
2428 * This function does *not* take care of syncing data in case of O_SYNC write.
2429 * A caller has to handle it. This is mainly due to the fact that we want to
2430 * avoid syncing under i_mutex.
2431 */
2432ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2433                                 unsigned long nr_segs, loff_t *ppos)
2434{
2435        struct file *file = iocb->ki_filp;
2436        struct address_space * mapping = file->f_mapping;
2437        size_t ocount;          /* original count */
2438        size_t count;           /* after file limit checks */
2439        struct inode    *inode = mapping->host;
2440        loff_t          pos;
2441        ssize_t         written;
2442        ssize_t         err;
2443
2444        ocount = 0;
2445        err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2446        if (err)
2447                return err;
2448
2449        count = ocount;
2450        pos = *ppos;
2451
2452        /* We can write back this queue in page reclaim */
2453        current->backing_dev_info = mapping->backing_dev_info;
2454        written = 0;
2455
2456        err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2457        if (err)
2458                goto out;
2459
2460        if (count == 0)
2461                goto out;
2462
2463        err = file_remove_suid(file);
2464        if (err)
2465                goto out;
2466
2467        err = file_update_time(file);
2468        if (err)
2469                goto out;
2470
2471        /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2472        if (unlikely(file->f_flags & O_DIRECT)) {
2473                loff_t endbyte;
2474                ssize_t written_buffered;
2475
2476                written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2477                                                        ppos, count, ocount);
2478                if (written < 0 || written == count)
2479                        goto out;
2480                /*
2481                 * direct-io write to a hole: fall through to buffered I/O
2482                 * for completing the rest of the request.
2483                 */
2484                pos += written;
2485                count -= written;
2486                written_buffered = generic_file_buffered_write(iocb, iov,
2487                                                nr_segs, pos, ppos, count,
2488                                                written);
2489                /*
2490                 * If generic_file_buffered_write() retuned a synchronous error
2491                 * then we want to return the number of bytes which were
2492                 * direct-written, or the error code if that was zero.  Note
2493                 * that this differs from normal direct-io semantics, which
2494                 * will return -EFOO even if some bytes were written.
2495                 */
2496                if (written_buffered < 0) {
2497                        err = written_buffered;
2498                        goto out;
2499                }
2500
2501                /*
2502                 * We need to ensure that the page cache pages are written to
2503                 * disk and invalidated to preserve the expected O_DIRECT
2504                 * semantics.
2505                 */
2506                endbyte = pos + written_buffered - written - 1;
2507                err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2508                if (err == 0) {
2509                        written = written_buffered;
2510                        invalidate_mapping_pages(mapping,
2511                                                 pos >> PAGE_CACHE_SHIFT,
2512                                                 endbyte >> PAGE_CACHE_SHIFT);
2513                } else {
2514                        /*
2515                         * We don't know how much we wrote, so just return
2516                         * the number of bytes which were direct-written
2517                         */
2518                }
2519        } else {
2520                written = generic_file_buffered_write(iocb, iov, nr_segs,
2521                                pos, ppos, count, written);
2522        }
2523out:
2524        current->backing_dev_info = NULL;
2525        return written ? written : err;
2526}
2527EXPORT_SYMBOL(__generic_file_aio_write);
2528
2529/**
2530 * generic_file_aio_write - write data to a file
2531 * @iocb:       IO state structure
2532 * @iov:        vector with data to write
2533 * @nr_segs:    number of segments in the vector
2534 * @pos:        position in file where to write
2535 *
2536 * This is a wrapper around __generic_file_aio_write() to be used by most
2537 * filesystems. It takes care of syncing the file in case of O_SYNC file
2538 * and acquires i_mutex as needed.
2539 */
2540ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2541                unsigned long nr_segs, loff_t pos)
2542{
2543        struct file *file = iocb->ki_filp;
2544        struct inode *inode = file->f_mapping->host;
2545        ssize_t ret;
2546
2547        BUG_ON(iocb->ki_pos != pos);
2548
2549        mutex_lock(&inode->i_mutex);
2550        ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2551        mutex_unlock(&inode->i_mutex);
2552
2553        if (ret > 0 || ret == -EIOCBQUEUED) {
2554                ssize_t err;
2555
2556                err = generic_write_sync(file, pos, ret);
2557                if (err < 0 && ret > 0)
2558                        ret = err;
2559        }
2560        return ret;
2561}
2562EXPORT_SYMBOL(generic_file_aio_write);
2563
2564/**
2565 * try_to_release_page() - release old fs-specific metadata on a page
2566 *
2567 * @page: the page which the kernel is trying to free
2568 * @gfp_mask: memory allocation flags (and I/O mode)
2569 *
2570 * The address_space is to try to release any data against the page
2571 * (presumably at page->private).  If the release was successful, return `1'.
2572 * Otherwise return zero.
2573 *
2574 * This may also be called if PG_fscache is set on a page, indicating that the
2575 * page is known to the local caching routines.
2576 *
2577 * The @gfp_mask argument specifies whether I/O may be performed to release
2578 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2579 *
2580 */
2581int try_to_release_page(struct page *page, gfp_t gfp_mask)
2582{
2583        struct address_space * const mapping = page->mapping;
2584
2585        BUG_ON(!PageLocked(page));
2586        if (PageWriteback(page))
2587                return 0;
2588
2589        if (mapping && mapping->a_ops->releasepage)
2590                return mapping->a_ops->releasepage(page, gfp_mask);
2591        return try_to_free_buffers(page);
2592}
2593
2594EXPORT_SYMBOL(try_to_release_page);
2595
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