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/syscalls.h>
  33#include <linux/cpuset.h>
  34#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
  35#include <linux/memcontrol.h>
  36#include <linux/cleancache.h>
  37#include "internal.h"
  38
  39/*
  40 * FIXME: remove all knowledge of the buffer layer from the core VM
  41 */
  42#include <linux/buffer_head.h> /* for try_to_free_buffers */
  43
  44#include <asm/mman.h>
  45
  46/*
  47 * Shared mappings implemented 30.11.1994. It's not fully working yet,
  48 * though.
  49 *
  50 * Shared mappings now work. 15.8.1995  Bruno.
  51 *
  52 * finished 'unifying' the page and buffer cache and SMP-threaded the
  53 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
  54 *
  55 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
  56 */
  57
  58/*
  59 * Lock ordering:
  60 *
  61 *  ->i_mmap_mutex              (truncate_pagecache)
  62 *    ->private_lock            (__free_pte->__set_page_dirty_buffers)
  63 *      ->swap_lock             (exclusive_swap_page, others)
  64 *        ->mapping->tree_lock
  65 *
  66 *  ->i_mutex
  67 *    ->i_mmap_mutex            (truncate->unmap_mapping_range)
  68 *
  69 *  ->mmap_sem
  70 *    ->i_mmap_mutex
  71 *      ->page_table_lock or pte_lock   (various, mainly in memory.c)
  72 *        ->mapping->tree_lock  (arch-dependent flush_dcache_mmap_lock)
  73 *
  74 *  ->mmap_sem
  75 *    ->lock_page               (access_process_vm)
  76 *
  77 *  ->i_mutex                   (generic_file_buffered_write)
  78 *    ->mmap_sem                (fault_in_pages_readable->do_page_fault)
  79 *
  80 *  bdi->wb.list_lock
  81 *    sb_lock                   (fs/fs-writeback.c)
  82 *    ->mapping->tree_lock      (__sync_single_inode)
  83 *
  84 *  ->i_mmap_mutex
  85 *    ->anon_vma.lock           (vma_adjust)
  86 *
  87 *  ->anon_vma.lock
  88 *    ->page_table_lock or pte_lock     (anon_vma_prepare and various)
  89 *
  90 *  ->page_table_lock or pte_lock
  91 *    ->swap_lock               (try_to_unmap_one)
  92 *    ->private_lock            (try_to_unmap_one)
  93 *    ->tree_lock               (try_to_unmap_one)
  94 *    ->zone.lru_lock           (follow_page->mark_page_accessed)
  95 *    ->zone.lru_lock           (check_pte_range->isolate_lru_page)
  96 *    ->private_lock            (page_remove_rmap->set_page_dirty)
  97 *    ->tree_lock               (page_remove_rmap->set_page_dirty)
  98 *    bdi.wb->list_lock         (page_remove_rmap->set_page_dirty)
  99 *    ->inode->i_lock           (page_remove_rmap->set_page_dirty)
 100 *    bdi.wb->list_lock         (zap_pte_range->set_page_dirty)
 101 *    ->inode->i_lock           (zap_pte_range->set_page_dirty)
 102 *    ->private_lock            (zap_pte_range->__set_page_dirty_buffers)
 103 *
 104 *  (code doesn't rely on that order, so you could switch it around)
 105 *  ->tasklist_lock             (memory_failure, collect_procs_ao)
 106 *    ->i_mmap_mutex
 107 */
 108
 109/*
 110 * Delete a page from the page cache and free it. Caller has to make
 111 * sure the page is locked and that nobody else uses it - or that usage
 112 * is safe.  The caller must hold the mapping's tree_lock.
 113 */
 114void __delete_from_page_cache(struct page *page)
 115{
 116        struct address_space *mapping = page->mapping;
 117
 118        /*
 119         * if we're uptodate, flush out into the cleancache, otherwise
 120         * invalidate any existing cleancache entries.  We can't leave
 121         * stale data around in the cleancache once our page is gone
 122         */
 123        if (PageUptodate(page) && PageMappedToDisk(page))
 124                cleancache_put_page(page);
 125        else
 126                cleancache_flush_page(mapping, page);
 127
 128        radix_tree_delete(&mapping->page_tree, page->index);
 129        page->mapping = NULL;
 130        /* Leave page->index set: truncation lookup relies upon it */
 131        mapping->nrpages--;
 132        __dec_zone_page_state(page, NR_FILE_PAGES);
 133        if (PageSwapBacked(page))
 134                __dec_zone_page_state(page, NR_SHMEM);
 135        BUG_ON(page_mapped(page));
 136
 137        /*
 138         * Some filesystems seem to re-dirty the page even after
 139         * the VM has canceled the dirty bit (eg ext3 journaling).
 140         *
 141         * Fix it up by doing a final dirty accounting check after
 142         * having removed the page entirely.
 143         */
 144        if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
 145                dec_zone_page_state(page, NR_FILE_DIRTY);
 146                dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
 147        }
 148}
 149
 150/**
 151 * delete_from_page_cache - delete page from page cache
 152 * @page: the page which the kernel is trying to remove from page cache
 153 *
 154 * This must be called only on pages that have been verified to be in the page
 155 * cache and locked.  It will never put the page into the free list, the caller
 156 * has a reference on the page.
 157 */
 158void delete_from_page_cache(struct page *page)
 159{
 160        struct address_space *mapping = page->mapping;
 161        void (*freepage)(struct page *);
 162
 163        BUG_ON(!PageLocked(page));
 164
 165        freepage = mapping->a_ops->freepage;
 166        spin_lock_irq(&mapping->tree_lock);
 167        __delete_from_page_cache(page);
 168        spin_unlock_irq(&mapping->tree_lock);
 169        mem_cgroup_uncharge_cache_page(page);
 170
 171        if (freepage)
 172                freepage(page);
 173        page_cache_release(page);
 174}
 175EXPORT_SYMBOL(delete_from_page_cache);
 176
 177static int sleep_on_page(void *word)
 178{
 179        io_schedule();
 180        return 0;
 181}
 182
 183static int sleep_on_page_killable(void *word)
 184{
 185        sleep_on_page(word);
 186        return fatal_signal_pending(current) ? -EINTR : 0;
 187}
 188
 189/**
 190 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
 191 * @mapping:    address space structure to write
 192 * @start:      offset in bytes where the range starts
 193 * @end:        offset in bytes where the range ends (inclusive)
 194 * @sync_mode:  enable synchronous operation
 195 *
 196 * Start writeback against all of a mapping's dirty pages that lie
 197 * within the byte offsets <start, end> inclusive.
 198 *
 199 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
 200 * opposed to a regular memory cleansing writeback.  The difference between
 201 * these two operations is that if a dirty page/buffer is encountered, it must
 202 * be waited upon, and not just skipped over.
 203 */
 204int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 205                                loff_t end, int sync_mode)
 206{
 207        int ret;
 208        struct writeback_control wbc = {
 209                .sync_mode = sync_mode,
 210                .nr_to_write = LONG_MAX,
 211                .range_start = start,
 212                .range_end = end,
 213        };
 214
 215        if (!mapping_cap_writeback_dirty(mapping))
 216                return 0;
 217
 218        ret = do_writepages(mapping, &wbc);
 219        return ret;
 220}
 221
 222static inline int __filemap_fdatawrite(struct address_space *mapping,
 223        int sync_mode)
 224{
 225        return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
 226}
 227
 228int filemap_fdatawrite(struct address_space *mapping)
 229{
 230        return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
 231}
 232EXPORT_SYMBOL(filemap_fdatawrite);
 233
 234int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 235                                loff_t end)
 236{
 237        return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
 238}
 239EXPORT_SYMBOL(filemap_fdatawrite_range);
 240
 241/**
 242 * filemap_flush - mostly a non-blocking flush
 243 * @mapping:    target address_space
 244 *
 245 * This is a mostly non-blocking flush.  Not suitable for data-integrity
 246 * purposes - I/O may not be started against all dirty pages.
 247 */
 248int filemap_flush(struct address_space *mapping)
 249{
 250        return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
 251}
 252EXPORT_SYMBOL(filemap_flush);
 253
 254/**
 255 * filemap_fdatawait_range - wait for writeback to complete
 256 * @mapping:            address space structure to wait for
 257 * @start_byte:         offset in bytes where the range starts
 258 * @end_byte:           offset in bytes where the range ends (inclusive)
 259 *
 260 * Walk the list of under-writeback pages of the given address space
 261 * in the given range and wait for all of them.
 262 */
 263int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
 264                            loff_t end_byte)
 265{
 266        pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
 267        pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
 268        struct pagevec pvec;
 269        int nr_pages;
 270        int ret = 0;
 271
 272        if (end_byte < start_byte)
 273                return 0;
 274
 275        pagevec_init(&pvec, 0);
 276        while ((index <= end) &&
 277                        (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
 278                        PAGECACHE_TAG_WRITEBACK,
 279                        min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
 280                unsigned i;
 281
 282                for (i = 0; i < nr_pages; i++) {
 283                        struct page *page = pvec.pages[i];
 284
 285                        /* until radix tree lookup accepts end_index */
 286                        if (page->index > end)
 287                                continue;
 288
 289                        wait_on_page_writeback(page);
 290                        if (TestClearPageError(page))
 291                                ret = -EIO;
 292                }
 293                pagevec_release(&pvec);
 294                cond_resched();
 295        }
 296
 297        /* Check for outstanding write errors */
 298        if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
 299                ret = -ENOSPC;
 300        if (test_and_clear_bit(AS_EIO, &mapping->flags))
 301                ret = -EIO;
 302
 303        return ret;
 304}
 305EXPORT_SYMBOL(filemap_fdatawait_range);
 306
 307/**
 308 * filemap_fdatawait - wait for all under-writeback pages to complete
 309 * @mapping: address space structure to wait for
 310 *
 311 * Walk the list of under-writeback pages of the given address space
 312 * and wait for all of them.
 313 */
 314int filemap_fdatawait(struct address_space *mapping)
 315{
 316        loff_t i_size = i_size_read(mapping->host);
 317
 318        if (i_size == 0)
 319                return 0;
 320
 321        return filemap_fdatawait_range(mapping, 0, i_size - 1);
 322}
 323EXPORT_SYMBOL(filemap_fdatawait);
 324
 325int filemap_write_and_wait(struct address_space *mapping)
 326{
 327        int err = 0;
 328
 329        if (mapping->nrpages) {
 330                err = filemap_fdatawrite(mapping);
 331                /*
 332                 * Even if the above returned error, the pages may be
 333                 * written partially (e.g. -ENOSPC), so we wait for it.
 334                 * But the -EIO is special case, it may indicate the worst
 335                 * thing (e.g. bug) happened, so we avoid waiting for it.
 336                 */
 337                if (err != -EIO) {
 338                        int err2 = filemap_fdatawait(mapping);
 339                        if (!err)
 340                                err = err2;
 341                }
 342        }
 343        return err;
 344}
 345EXPORT_SYMBOL(filemap_write_and_wait);
 346
 347/**
 348 * filemap_write_and_wait_range - write out & wait on a file range
 349 * @mapping:    the address_space for the pages
 350 * @lstart:     offset in bytes where the range starts
 351 * @lend:       offset in bytes where the range ends (inclusive)
 352 *
 353 * Write out and wait upon file offsets lstart->lend, inclusive.
 354 *
 355 * Note that `lend' is inclusive (describes the last byte to be written) so
 356 * that this function can be used to write to the very end-of-file (end = -1).
 357 */
 358int filemap_write_and_wait_range(struct address_space *mapping,
 359                                 loff_t lstart, loff_t lend)
 360{
 361        int err = 0;
 362
 363        if (mapping->nrpages) {
 364                err = __filemap_fdatawrite_range(mapping, lstart, lend,
 365                                                 WB_SYNC_ALL);
 366                /* See comment of filemap_write_and_wait() */
 367                if (err != -EIO) {
 368                        int err2 = filemap_fdatawait_range(mapping,
 369                                                lstart, lend);
 370                        if (!err)
 371                                err = err2;
 372                }
 373        }
 374        return err;
 375}
 376EXPORT_SYMBOL(filemap_write_and_wait_range);
 377
 378/**
 379 * replace_page_cache_page - replace a pagecache page with a new one
 380 * @old:        page to be replaced
 381 * @new:        page to replace with
 382 * @gfp_mask:   allocation mode
 383 *
 384 * This function replaces a page in the pagecache with a new one.  On
 385 * success it acquires the pagecache reference for the new page and
 386 * drops it for the old page.  Both the old and new pages must be
 387 * locked.  This function does not add the new page to the LRU, the
 388 * caller must do that.
 389 *
 390 * The remove + add is atomic.  The only way this function can fail is
 391 * memory allocation failure.
 392 */
 393int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 394{
 395        int error;
 396
 397        VM_BUG_ON(!PageLocked(old));
 398        VM_BUG_ON(!PageLocked(new));
 399        VM_BUG_ON(new->mapping);
 400
 401        error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
 402        if (!error) {
 403                struct address_space *mapping = old->mapping;
 404                void (*freepage)(struct page *);
 405
 406                pgoff_t offset = old->index;
 407                freepage = mapping->a_ops->freepage;
 408
 409                page_cache_get(new);
 410                new->mapping = mapping;
 411                new->index = offset;
 412
 413                spin_lock_irq(&mapping->tree_lock);
 414                __delete_from_page_cache(old);
 415                error = radix_tree_insert(&mapping->page_tree, offset, new);
 416                BUG_ON(error);
 417                mapping->nrpages++;
 418                __inc_zone_page_state(new, NR_FILE_PAGES);
 419                if (PageSwapBacked(new))
 420                        __inc_zone_page_state(new, NR_SHMEM);
 421                spin_unlock_irq(&mapping->tree_lock);
 422                /* mem_cgroup codes must not be called under tree_lock */
 423                mem_cgroup_replace_page_cache(old, new);
 424                radix_tree_preload_end();
 425                if (freepage)
 426                        freepage(old);
 427                page_cache_release(old);
 428        }
 429
 430        return error;
 431}
 432EXPORT_SYMBOL_GPL(replace_page_cache_page);
 433
 434/**
 435 * add_to_page_cache_locked - add a locked page to the pagecache
 436 * @page:       page to add
 437 * @mapping:    the page's address_space
 438 * @offset:     page index
 439 * @gfp_mask:   page allocation mode
 440 *
 441 * This function is used to add a page to the pagecache. It must be locked.
 442 * This function does not add the page to the LRU.  The caller must do that.
 443 */
 444int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
 445                pgoff_t offset, gfp_t gfp_mask)
 446{
 447        int error;
 448
 449        VM_BUG_ON(!PageLocked(page));
 450        VM_BUG_ON(PageSwapBacked(page));
 451
 452        error = mem_cgroup_cache_charge(page, current->mm,
 453                                        gfp_mask & GFP_RECLAIM_MASK);
 454        if (error)
 455                goto out;
 456
 457        error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
 458        if (error == 0) {
 459                page_cache_get(page);
 460                page->mapping = mapping;
 461                page->index = offset;
 462
 463                spin_lock_irq(&mapping->tree_lock);
 464                error = radix_tree_insert(&mapping->page_tree, offset, page);
 465                if (likely(!error)) {
 466                        mapping->nrpages++;
 467                        __inc_zone_page_state(page, NR_FILE_PAGES);
 468                        spin_unlock_irq(&mapping->tree_lock);
 469                } else {
 470                        page->mapping = NULL;
 471                        /* Leave page->index set: truncation relies upon it */
 472                        spin_unlock_irq(&mapping->tree_lock);
 473                        mem_cgroup_uncharge_cache_page(page);
 474                        page_cache_release(page);
 475                }
 476                radix_tree_preload_end();
 477        } else
 478                mem_cgroup_uncharge_cache_page(page);
 479out:
 480        return error;
 481}
 482EXPORT_SYMBOL(add_to_page_cache_locked);
 483
 484int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 485                                pgoff_t offset, gfp_t gfp_mask)
 486{
 487        int ret;
 488
 489        ret = add_to_page_cache(page, mapping, offset, gfp_mask);
 490        if (ret == 0)
 491                lru_cache_add_file(page);
 492        return ret;
 493}
 494EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
 495
 496#ifdef CONFIG_NUMA
 497struct page *__page_cache_alloc(gfp_t gfp)
 498{
 499        int n;
 500        struct page *page;
 501
 502        if (cpuset_do_page_mem_spread()) {
 503                get_mems_allowed();
 504                n = cpuset_mem_spread_node();
 505                page = alloc_pages_exact_node(n, gfp, 0);
 506                put_mems_allowed();
 507                return page;
 508        }
 509        return alloc_pages(gfp, 0);
 510}
 511EXPORT_SYMBOL(__page_cache_alloc);
 512#endif
 513
 514/*
 515 * In order to wait for pages to become available there must be
 516 * waitqueues associated with pages. By using a hash table of
 517 * waitqueues where the bucket discipline is to maintain all
 518 * waiters on the same queue and wake all when any of the pages
 519 * become available, and for the woken contexts to check to be
 520 * sure the appropriate page became available, this saves space
 521 * at a cost of "thundering herd" phenomena during rare hash
 522 * collisions.
 523 */
 524static wait_queue_head_t *page_waitqueue(struct page *page)
 525{
 526        const struct zone *zone = page_zone(page);
 527
 528        return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
 529}
 530
 531static inline void wake_up_page(struct page *page, int bit)
 532{
 533        __wake_up_bit(page_waitqueue(page), &page->flags, bit);
 534}
 535
 536void wait_on_page_bit(struct page *page, int bit_nr)
 537{
 538        DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
 539
 540        if (test_bit(bit_nr, &page->flags))
 541                __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
 542                                                        TASK_UNINTERRUPTIBLE);
 543}
 544EXPORT_SYMBOL(wait_on_page_bit);
 545
 546int wait_on_page_bit_killable(struct page *page, int bit_nr)
 547{
 548        DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
 549
 550        if (!test_bit(bit_nr, &page->flags))
 551                return 0;
 552
 553        return __wait_on_bit(page_waitqueue(page), &wait,
 554                             sleep_on_page_killable, TASK_KILLABLE);
 555}
 556
 557/**
 558 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
 559 * @page: Page defining the wait queue of interest
 560 * @waiter: Waiter to add to the queue
 561 *
 562 * Add an arbitrary @waiter to the wait queue for the nominated @page.
 563 */
 564void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
 565{
 566        wait_queue_head_t *q = page_waitqueue(page);
 567        unsigned long flags;
 568
 569        spin_lock_irqsave(&q->lock, flags);
 570        __add_wait_queue(q, waiter);
 571        spin_unlock_irqrestore(&q->lock, flags);
 572}
 573EXPORT_SYMBOL_GPL(add_page_wait_queue);
 574
 575/**
 576 * unlock_page - unlock a locked page
 577 * @page: the page
 578 *
 579 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
 580 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
 581 * mechananism between PageLocked pages and PageWriteback pages is shared.
 582 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
 583 *
 584 * The mb is necessary to enforce ordering between the clear_bit and the read
 585 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
 586 */
 587void unlock_page(struct page *page)
 588{
 589        VM_BUG_ON(!PageLocked(page));
 590        clear_bit_unlock(PG_locked, &page->flags);
 591        smp_mb__after_clear_bit();
 592        wake_up_page(page, PG_locked);
 593}
 594EXPORT_SYMBOL(unlock_page);
 595
 596/**
 597 * end_page_writeback - end writeback against a page
 598 * @page: the page
 599 */
 600void end_page_writeback(struct page *page)
 601{
 602        if (TestClearPageReclaim(page))
 603                rotate_reclaimable_page(page);
 604
 605        if (!test_clear_page_writeback(page))
 606                BUG();
 607
 608        smp_mb__after_clear_bit();
 609        wake_up_page(page, PG_writeback);
 610}
 611EXPORT_SYMBOL(end_page_writeback);
 612
 613/**
 614 * __lock_page - get a lock on the page, assuming we need to sleep to get it
 615 * @page: the page to lock
 616 */
 617void __lock_page(struct page *page)
 618{
 619        DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 620
 621        __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
 622                                                        TASK_UNINTERRUPTIBLE);
 623}
 624EXPORT_SYMBOL(__lock_page);
 625
 626int __lock_page_killable(struct page *page)
 627{
 628        DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 629
 630        return __wait_on_bit_lock(page_waitqueue(page), &wait,
 631                                        sleep_on_page_killable, TASK_KILLABLE);
 632}
 633EXPORT_SYMBOL_GPL(__lock_page_killable);
 634
 635int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
 636                         unsigned int flags)
 637{
 638        if (flags & FAULT_FLAG_ALLOW_RETRY) {
 639                /*
 640                 * CAUTION! In this case, mmap_sem is not released
 641                 * even though return 0.
 642                 */
 643                if (flags & FAULT_FLAG_RETRY_NOWAIT)
 644                        return 0;
 645
 646                up_read(&mm->mmap_sem);
 647                if (flags & FAULT_FLAG_KILLABLE)
 648                        wait_on_page_locked_killable(page);
 649                else
 650                        wait_on_page_locked(page);
 651                return 0;
 652        } else {
 653                if (flags & FAULT_FLAG_KILLABLE) {
 654                        int ret;
 655
 656                        ret = __lock_page_killable(page);
 657                        if (ret) {
 658                                up_read(&mm->mmap_sem);
 659                                return 0;
 660                        }
 661                } else
 662                        __lock_page(page);
 663                return 1;
 664        }
 665}
 666
 667/**
 668 * find_get_page - find and get a page reference
 669 * @mapping: the address_space to search
 670 * @offset: the page index
 671 *
 672 * Is there a pagecache struct page at the given (mapping, offset) tuple?
 673 * If yes, increment its refcount and return it; if no, return NULL.
 674 */
 675struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
 676{
 677        void **pagep;
 678        struct page *page;
 679
 680        rcu_read_lock();
 681repeat:
 682        page = NULL;
 683        pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
 684        if (pagep) {
 685                page = radix_tree_deref_slot(pagep);
 686                if (unlikely(!page))
 687                        goto out;
 688                if (radix_tree_exception(page)) {
 689                        if (radix_tree_deref_retry(page))
 690                                goto repeat;
 691                        /*
 692                         * Otherwise, shmem/tmpfs must be storing a swap entry
 693                         * here as an exceptional entry: so return it without
 694                         * attempting to raise page count.
 695                         */
 696                        goto out;
 697                }
 698                if (!page_cache_get_speculative(page))
 699                        goto repeat;
 700
 701                /*
 702                 * Has the page moved?
 703                 * This is part of the lockless pagecache protocol. See
 704                 * include/linux/pagemap.h for details.
 705                 */
 706                if (unlikely(page != *pagep)) {
 707                        page_cache_release(page);
 708                        goto repeat;
 709                }
 710        }
 711out:
 712        rcu_read_unlock();
 713
 714        return page;
 715}
 716EXPORT_SYMBOL(find_get_page);
 717
 718/**
 719 * find_lock_page - locate, pin and lock a pagecache page
 720 * @mapping: the address_space to search
 721 * @offset: the page index
 722 *
 723 * Locates the desired pagecache page, locks it, increments its reference
 724 * count and returns its address.
 725 *
 726 * Returns zero if the page was not present. find_lock_page() may sleep.
 727 */
 728struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
 729{
 730        struct page *page;
 731
 732repeat:
 733        page = find_get_page(mapping, offset);
 734        if (page && !radix_tree_exception(page)) {
 735                lock_page(page);
 736                /* Has the page been truncated? */
 737                if (unlikely(page->mapping != mapping)) {
 738                        unlock_page(page);
 739                        page_cache_release(page);
 740                        goto repeat;
 741                }
 742                VM_BUG_ON(page->index != offset);
 743        }
 744        return page;
 745}
 746EXPORT_SYMBOL(find_lock_page);
 747
 748/**
 749 * find_or_create_page - locate or add a pagecache page
 750 * @mapping: the page's address_space
 751 * @index: the page's index into the mapping
 752 * @gfp_mask: page allocation mode
 753 *
 754 * Locates a page in the pagecache.  If the page is not present, a new page
 755 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
 756 * LRU list.  The returned page is locked and has its reference count
 757 * incremented.
 758 *
 759 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
 760 * allocation!
 761 *
 762 * find_or_create_page() returns the desired page's address, or zero on
 763 * memory exhaustion.
 764 */
 765struct page *find_or_create_page(struct address_space *mapping,
 766                pgoff_t index, gfp_t gfp_mask)
 767{
 768        struct page *page;
 769        int err;
 770repeat:
 771        page = find_lock_page(mapping, index);
 772        if (!page) {
 773                page = __page_cache_alloc(gfp_mask);
 774                if (!page)
 775                        return NULL;
 776                /*
 777                 * We want a regular kernel memory (not highmem or DMA etc)
 778                 * allocation for the radix tree nodes, but we need to honour
 779                 * the context-specific requirements the caller has asked for.
 780                 * GFP_RECLAIM_MASK collects those requirements.
 781                 */
 782                err = add_to_page_cache_lru(page, mapping, index,
 783                        (gfp_mask & GFP_RECLAIM_MASK));
 784                if (unlikely(err)) {
 785                        page_cache_release(page);
 786                        page = NULL;
 787                        if (err == -EEXIST)
 788                                goto repeat;
 789                }
 790        }
 791        return page;
 792}
 793EXPORT_SYMBOL(find_or_create_page);
 794
 795/**
 796 * find_get_pages - gang pagecache lookup
 797 * @mapping:    The address_space to search
 798 * @start:      The starting page index
 799 * @nr_pages:   The maximum number of pages
 800 * @pages:      Where the resulting pages are placed
 801 *
 802 * find_get_pages() will search for and return a group of up to
 803 * @nr_pages pages in the mapping.  The pages are placed at @pages.
 804 * find_get_pages() takes a reference against the returned pages.
 805 *
 806 * The search returns a group of mapping-contiguous pages with ascending
 807 * indexes.  There may be holes in the indices due to not-present pages.
 808 *
 809 * find_get_pages() returns the number of pages which were found.
 810 */
 811unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
 812                            unsigned int nr_pages, struct page **pages)
 813{
 814        unsigned int i;
 815        unsigned int ret;
 816        unsigned int nr_found, nr_skip;
 817
 818        rcu_read_lock();
 819restart:
 820        nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
 821                                (void ***)pages, NULL, start, nr_pages);
 822        ret = 0;
 823        nr_skip = 0;
 824        for (i = 0; i < nr_found; i++) {
 825                struct page *page;
 826repeat:
 827                page = radix_tree_deref_slot((void **)pages[i]);
 828                if (unlikely(!page))
 829                        continue;
 830
 831                if (radix_tree_exception(page)) {
 832                        if (radix_tree_deref_retry(page)) {
 833                                /*
 834                                 * Transient condition which can only trigger
 835                                 * when entry at index 0 moves out of or back
 836                                 * to root: none yet gotten, safe to restart.
 837                                 */
 838                                WARN_ON(start | i);
 839                                goto restart;
 840                        }
 841                        /*
 842                         * Otherwise, shmem/tmpfs must be storing a swap entry
 843                         * here as an exceptional entry: so skip over it -
 844                         * we only reach this from invalidate_mapping_pages().
 845                         */
 846                        nr_skip++;
 847                        continue;
 848                }
 849
 850                if (!page_cache_get_speculative(page))
 851                        goto repeat;
 852
 853                /* Has the page moved? */
 854                if (unlikely(page != *((void **)pages[i]))) {
 855                        page_cache_release(page);
 856                        goto repeat;
 857                }
 858
 859                pages[ret] = page;
 860                ret++;
 861        }
 862
 863        /*
 864         * If all entries were removed before we could secure them,
 865         * try again, because callers stop trying once 0 is returned.
 866         */
 867        if (unlikely(!ret && nr_found > nr_skip))
 868                goto restart;
 869        rcu_read_unlock();
 870        return ret;
 871}
 872
 873/**
 874 * find_get_pages_contig - gang contiguous pagecache lookup
 875 * @mapping:    The address_space to search
 876 * @index:      The starting page index
 877 * @nr_pages:   The maximum number of pages
 878 * @pages:      Where the resulting pages are placed
 879 *
 880 * find_get_pages_contig() works exactly like find_get_pages(), except
 881 * that the returned number of pages are guaranteed to be contiguous.
 882 *
 883 * find_get_pages_contig() returns the number of pages which were found.
 884 */
 885unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
 886                               unsigned int nr_pages, struct page **pages)
 887{
 888        unsigned int i;
 889        unsigned int ret;
 890        unsigned int nr_found;
 891
 892        rcu_read_lock();
 893restart:
 894        nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
 895                                (void ***)pages, NULL, index, nr_pages);
 896        ret = 0;
 897        for (i = 0; i < nr_found; i++) {
 898                struct page *page;
 899repeat:
 900                page = radix_tree_deref_slot((void **)pages[i]);
 901                if (unlikely(!page))
 902                        continue;
 903
 904                if (radix_tree_exception(page)) {
 905                        if (radix_tree_deref_retry(page)) {
 906                                /*
 907                                 * Transient condition which can only trigger
 908                                 * when entry at index 0 moves out of or back
 909                                 * to root: none yet gotten, safe to restart.
 910                                 */
 911                                goto restart;
 912                        }
 913                        /*
 914                         * Otherwise, shmem/tmpfs must be storing a swap entry
 915                         * here as an exceptional entry: so stop looking for
 916                         * contiguous pages.
 917                         */
 918                        break;
 919                }
 920
 921                if (!page_cache_get_speculative(page))
 922                        goto repeat;
 923
 924                /* Has the page moved? */
 925                if (unlikely(page != *((void **)pages[i]))) {
 926                        page_cache_release(page);
 927                        goto repeat;
 928                }
 929
 930                /*
 931                 * must check mapping and index after taking the ref.
 932                 * otherwise we can get both false positives and false
 933                 * negatives, which is just confusing to the caller.
 934                 */
 935                if (page->mapping == NULL || page->index != index) {
 936                        page_cache_release(page);
 937                        break;
 938                }
 939
 940                pages[ret] = page;
 941                ret++;
 942                index++;
 943        }
 944        rcu_read_unlock();
 945        return ret;
 946}
 947EXPORT_SYMBOL(find_get_pages_contig);
 948
 949/**
 950 * find_get_pages_tag - find and return pages that match @tag
 951 * @mapping:    the address_space to search
 952 * @index:      the starting page index
 953 * @tag:        the tag index
 954 * @nr_pages:   the maximum number of pages
 955 * @pages:      where the resulting pages are placed
 956 *
 957 * Like find_get_pages, except we only return pages which are tagged with
 958 * @tag.   We update @index to index the next page for the traversal.
 959 */
 960unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
 961                        int tag, unsigned int nr_pages, struct page **pages)
 962{
 963        unsigned int i;
 964        unsigned int ret;
 965        unsigned int nr_found;
 966
 967        rcu_read_lock();
 968restart:
 969        nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
 970                                (void ***)pages, *index, nr_pages, tag);
 971        ret = 0;
 972        for (i = 0; i < nr_found; i++) {
 973                struct page *page;
 974repeat:
 975                page = radix_tree_deref_slot((void **)pages[i]);
 976                if (unlikely(!page))
 977                        continue;
 978
 979                if (radix_tree_exception(page)) {
 980                        if (radix_tree_deref_retry(page)) {
 981                                /*
 982                                 * Transient condition which can only trigger
 983                                 * when entry at index 0 moves out of or back
 984                                 * to root: none yet gotten, safe to restart.
 985                                 */
 986                                goto restart;
 987                        }
 988                        /*
 989                         * This function is never used on a shmem/tmpfs
 990                         * mapping, so a swap entry won't be found here.
 991                         */
 992                        BUG();
 993                }
 994
 995                if (!page_cache_get_speculative(page))
 996                        goto repeat;
 997
 998                /* Has the page moved? */
 999                if (unlikely(page != *((void **)pages[i]))) {
1000                        page_cache_release(page);
1001                        goto repeat;
1002                }
1003
1004                pages[ret] = page;
1005                ret++;
1006        }
1007
1008        /*
1009         * If all entries were removed before we could secure them,
1010         * try again, because callers stop trying once 0 is returned.
1011         */
1012        if (unlikely(!ret && nr_found))
1013                goto restart;
1014        rcu_read_unlock();
1015
1016        if (ret)
1017                *index = pages[ret - 1]->index + 1;
1018
1019        return ret;
1020}
1021EXPORT_SYMBOL(find_get_pages_tag);
1022
1023/**
1024 * grab_cache_page_nowait - returns locked page at given index in given cache
1025 * @mapping: target address_space
1026 * @index: the page index
1027 *
1028 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1029 * This is intended for speculative data generators, where the data can
1030 * be regenerated if the page couldn't be grabbed.  This routine should
1031 * be safe to call while holding the lock for another page.
1032 *
1033 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1034 * and deadlock against the caller's locked page.
1035 */
1036struct page *
1037grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
1038{
1039        struct page *page = find_get_page(mapping, index);
1040
1041        if (page) {
1042                if (trylock_page(page))
1043                        return page;
1044                page_cache_release(page);
1045                return NULL;
1046        }
1047        page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1048        if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1049                page_cache_release(page);
1050                page = NULL;
1051        }
1052        return page;
1053}
1054EXPORT_SYMBOL(grab_cache_page_nowait);
1055
1056/*
1057 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1058 * a _large_ part of the i/o request. Imagine the worst scenario:
1059 *
1060 *      ---R__________________________________________B__________
1061 *         ^ reading here                             ^ bad block(assume 4k)
1062 *
1063 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1064 * => failing the whole request => read(R) => read(R+1) =>
1065 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1066 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1067 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1068 *
1069 * It is going insane. Fix it by quickly scaling down the readahead size.
1070 */
1071static void shrink_readahead_size_eio(struct file *filp,
1072                                        struct file_ra_state *ra)
1073{
1074        ra->ra_pages /= 4;
1075}
1076
1077/**
1078 * do_generic_file_read - generic file read routine
1079 * @filp:       the file to read
1080 * @ppos:       current file position
1081 * @desc:       read_descriptor
1082 * @actor:      read method
1083 *
1084 * This is a generic file read routine, and uses the
1085 * mapping->a_ops->readpage() function for the actual low-level stuff.
1086 *
1087 * This is really ugly. But the goto's actually try to clarify some
1088 * of the logic when it comes to error handling etc.
1089 */
1090static void do_generic_file_read(struct file *filp, loff_t *ppos,
1091                read_descriptor_t *desc, read_actor_t actor)
1092{
1093        struct address_space *mapping = filp->f_mapping;
1094        struct inode *inode = mapping->host;
1095        struct file_ra_state *ra = &filp->f_ra;
1096        pgoff_t index;
1097        pgoff_t last_index;
1098        pgoff_t prev_index;
1099        unsigned long offset;      /* offset into pagecache page */
1100        unsigned int prev_offset;
1101        int error;
1102
1103        index = *ppos >> PAGE_CACHE_SHIFT;
1104        prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1105        prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1106        last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1107        offset = *ppos & ~PAGE_CACHE_MASK;
1108
1109        for (;;) {
1110                struct page *page;
1111                pgoff_t end_index;
1112                loff_t isize;
1113                unsigned long nr, ret;
1114
1115                cond_resched();
1116find_page:
1117                page = find_get_page(mapping, index);
1118                if (!page) {
1119                        page_cache_sync_readahead(mapping,
1120                                        ra, filp,
1121                                        index, last_index - index);
1122                        page = find_get_page(mapping, index);
1123                        if (unlikely(page == NULL))
1124                                goto no_cached_page;
1125                }
1126                if (PageReadahead(page)) {
1127                        page_cache_async_readahead(mapping,
1128                                        ra, filp, page,
1129                                        index, last_index - index);
1130                }
1131                if (!PageUptodate(page)) {
1132                        if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1133                                        !mapping->a_ops->is_partially_uptodate)
1134                                goto page_not_up_to_date;
1135                        if (!trylock_page(page))
1136                                goto page_not_up_to_date;
1137                        /* Did it get truncated before we got the lock? */
1138                        if (!page->mapping)
1139                                goto page_not_up_to_date_locked;
1140                        if (!mapping->a_ops->is_partially_uptodate(page,
1141                                                                desc, offset))
1142                                goto page_not_up_to_date_locked;
1143                        unlock_page(page);
1144                }
1145page_ok:
1146                /*
1147                 * i_size must be checked after we know the page is Uptodate.
1148                 *
1149                 * Checking i_size after the check allows us to calculate
1150                 * the correct value for "nr", which means the zero-filled
1151                 * part of the page is not copied back to userspace (unless
1152                 * another truncate extends the file - this is desired though).
1153                 */
1154
1155                isize = i_size_read(inode);
1156                end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1157                if (unlikely(!isize || index > end_index)) {
1158                        page_cache_release(page);
1159                        goto out;
1160                }
1161
1162                /* nr is the maximum number of bytes to copy from this page */
1163                nr = PAGE_CACHE_SIZE;
1164                if (index == end_index) {
1165                        nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1166                        if (nr <= offset) {
1167                                page_cache_release(page);
1168                                goto out;
1169                        }
1170                }
1171                nr = nr - offset;
1172
1173                /* If users can be writing to this page using arbitrary
1174                 * virtual addresses, take care about potential aliasing
1175                 * before reading the page on the kernel side.
1176                 */
1177                if (mapping_writably_mapped(mapping))
1178                        flush_dcache_page(page);
1179
1180                /*
1181                 * When a sequential read accesses a page several times,
1182                 * only mark it as accessed the first time.
1183                 */
1184                if (prev_index != index || offset != prev_offset)
1185                        mark_page_accessed(page);
1186                prev_index = index;
1187
1188                /*
1189                 * Ok, we have the page, and it's up-to-date, so
1190                 * now we can copy it to user space...
1191                 *
1192                 * The actor routine returns how many bytes were actually used..
1193                 * NOTE! This may not be the same as how much of a user buffer
1194                 * we filled up (we may be padding etc), so we can only update
1195                 * "pos" here (the actor routine has to update the user buffer
1196                 * pointers and the remaining count).
1197                 */
1198                ret = actor(desc, page, offset, nr);
1199                offset += ret;
1200                index += offset >> PAGE_CACHE_SHIFT;
1201                offset &= ~PAGE_CACHE_MASK;
1202                prev_offset = offset;
1203
1204                page_cache_release(page);
1205                if (ret == nr && desc->count)
1206                        continue;
1207                goto out;
1208
1209page_not_up_to_date:
1210                /* Get exclusive access to the page ... */
1211                error = lock_page_killable(page);
1212                if (unlikely(error))
1213                        goto readpage_error;
1214
1215page_not_up_to_date_locked:
1216                /* Did it get truncated before we got the lock? */
1217                if (!page->mapping) {
1218                        unlock_page(page);
1219                        page_cache_release(page);
1220                        continue;
1221                }
1222
1223                /* Did somebody else fill it already? */
1224                if (PageUptodate(page)) {
1225                        unlock_page(page);
1226                        goto page_ok;
1227                }
1228
1229readpage:
1230                /*
1231                 * A previous I/O error may have been due to temporary
1232                 * failures, eg. multipath errors.
1233                 * PG_error will be set again if readpage fails.
1234                 */
1235                ClearPageError(page);
1236                /* Start the actual read. The read will unlock the page. */
1237                error = mapping->a_ops->readpage(filp, page);
1238
1239                if (unlikely(error)) {
1240                        if (error == AOP_TRUNCATED_PAGE) {
1241                                page_cache_release(page);
1242                                goto find_page;
1243                        }
1244                        goto readpage_error;
1245                }
1246
1247                if (!PageUptodate(page)) {
1248                        error = lock_page_killable(page);
1249                        if (unlikely(error))
1250                                goto readpage_error;
1251                        if (!PageUptodate(page)) {
1252                                if (page->mapping == NULL) {
1253                                        /*
1254                                         * invalidate_mapping_pages got it
1255                                         */
1256                                        unlock_page(page);
1257                                        page_cache_release(page);
1258                                        goto find_page;
1259                                }
1260                                unlock_page(page);
1261                                shrink_readahead_size_eio(filp, ra);
1262                                error = -EIO;
1263                                goto readpage_error;
1264                        }
1265                        unlock_page(page);
1266                }
1267
1268                goto page_ok;
1269
1270readpage_error:
1271                /* UHHUH! A synchronous read error occurred. Report it */
1272                desc->error = error;
1273                page_cache_release(page);
1274                goto out;
1275
1276no_cached_page:
1277                /*
1278                 * Ok, it wasn't cached, so we need to create a new
1279                 * page..
1280                 */
1281                page = page_cache_alloc_cold(mapping);
1282                if (!page) {
1283                        desc->error = -ENOMEM;
1284                        goto out;
1285                }
1286                error = add_to_page_cache_lru(page, mapping,
1287                                                index, GFP_KERNEL);
1288                if (error) {
1289                        page_cache_release(page);
1290                        if (error == -EEXIST)
1291                                goto find_page;
1292                        desc->error = error;
1293                        goto out;
1294                }
1295                goto readpage;
1296        }
1297
1298out:
1299        ra->prev_pos = prev_index;
1300        ra->prev_pos <<= PAGE_CACHE_SHIFT;
1301        ra->prev_pos |= prev_offset;
1302
1303        *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1304        file_accessed(filp);
1305}
1306
1307int file_read_actor(read_descriptor_t *desc, struct page *page,
1308                        unsigned long offset, unsigned long size)
1309{
1310        char *kaddr;
1311        unsigned long left, count = desc->count;
1312
1313        if (size > count)
1314                size = count;
1315
1316        /*
1317         * Faults on the destination of a read are common, so do it before
1318         * taking the kmap.
1319         */
1320        if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1321                kaddr = kmap_atomic(page, KM_USER0);
1322                left = __copy_to_user_inatomic(desc->arg.buf,
1323                                                kaddr + offset, size);
1324                kunmap_atomic(kaddr, KM_USER0);
1325                if (left == 0)
1326                        goto success;
1327        }
1328
1329        /* Do it the slow way */
1330        kaddr = kmap(page);
1331        left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1332        kunmap(page);
1333
1334        if (left) {
1335                size -= left;
1336                desc->error = -EFAULT;
1337        }
1338success:
1339        desc->count = count - size;
1340        desc->written += size;
1341        desc->arg.buf += size;
1342        return size;
1343}
1344
1345/*
1346 * Performs necessary checks before doing a write
1347 * @iov:        io vector request
1348 * @nr_segs:    number of segments in the iovec
1349 * @count:      number of bytes to write
1350 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1351 *
1352 * Adjust number of segments and amount of bytes to write (nr_segs should be
1353 * properly initialized first). Returns appropriate error code that caller
1354 * should return or zero in case that write should be allowed.
1355 */
1356int generic_segment_checks(const struct iovec *iov,
1357                        unsigned long *nr_segs, size_t *count, int access_flags)
1358{
1359        unsigned long   seg;
1360        size_t cnt = 0;
1361        for (seg = 0; seg < *nr_segs; seg++) {
1362                const struct iovec *iv = &iov[seg];
1363
1364                /*
1365                 * If any segment has a negative length, or the cumulative
1366                 * length ever wraps negative then return -EINVAL.
1367                 */
1368                cnt += iv->iov_len;
1369                if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1370                        return -EINVAL;
1371                if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1372                        continue;
1373                if (seg == 0)
1374                        return -EFAULT;
1375                *nr_segs = seg;
1376                cnt -= iv->iov_len;     /* This segment is no good */
1377                break;
1378        }
1379        *count = cnt;
1380        return 0;
1381}
1382EXPORT_SYMBOL(generic_segment_checks);
1383
1384/**
1385 * generic_file_aio_read - generic filesystem read routine
1386 * @iocb:       kernel I/O control block
1387 * @iov:        io vector request
1388 * @nr_segs:    number of segments in the iovec
1389 * @pos:        current file position
1390 *
1391 * This is the "read()" routine for all filesystems
1392 * that can use the page cache directly.
1393 */
1394ssize_t
1395generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1396                unsigned long nr_segs, loff_t pos)
1397{
1398        struct file *filp = iocb->ki_filp;
1399        ssize_t retval;
1400        unsigned long seg = 0;
1401        size_t count;
1402        loff_t *ppos = &iocb->ki_pos;
1403
1404        count = 0;
1405        retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1406        if (retval)
1407                return retval;
1408
1409        /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1410        if (filp->f_flags & O_DIRECT) {
1411                loff_t size;
1412                struct address_space *mapping;
1413                struct inode *inode;
1414
1415                mapping = filp->f_mapping;
1416                inode = mapping->host;
1417                if (!count)
1418                        goto out; /* skip atime */
1419                size = i_size_read(inode);
1420                if (pos < size) {
1421                        retval = filemap_write_and_wait_range(mapping, pos,
1422                                        pos + iov_length(iov, nr_segs) - 1);
1423                        if (!retval) {
1424                                struct blk_plug plug;
1425
1426                                blk_start_plug(&plug);
1427                                retval = mapping->a_ops->direct_IO(READ, iocb,
1428                                                        iov, pos, nr_segs);
1429                                blk_finish_plug(&plug);
1430                        }
1431                        if (retval > 0) {
1432                                *ppos = pos + retval;
1433                                count -= retval;
1434                        }
1435
1436                        /*
1437                         * Btrfs can have a short DIO read if we encounter
1438                         * compressed extents, so if there was an error, or if
1439                         * we've already read everything we wanted to, or if
1440                         * there was a short read because we hit EOF, go ahead
1441                         * and return.  Otherwise fallthrough to buffered io for
1442                         * the rest of the read.
1443                         */
1444                        if (retval < 0 || !count || *ppos >= size) {
1445                                file_accessed(filp);
1446                                goto out;
1447                        }
1448                }
1449        }
1450
1451        count = retval;
1452        for (seg = 0; seg < nr_segs; seg++) {
1453                read_descriptor_t desc;
1454                loff_t offset = 0;
1455
1456                /*
1457                 * If we did a short DIO read we need to skip the section of the
1458                 * iov that we've already read data into.
1459                 */
1460                if (count) {
1461                        if (count > iov[seg].iov_len) {
1462                                count -= iov[seg].iov_len;
1463                                continue;
1464                        }
1465                        offset = count;
1466                        count = 0;
1467                }
1468
1469                desc.written = 0;
1470                desc.arg.buf = iov[seg].iov_base + offset;
1471                desc.count = iov[seg].iov_len - offset;
1472                if (desc.count == 0)
1473                        continue;
1474                desc.error = 0;
1475                do_generic_file_read(filp, ppos, &desc, file_read_actor);
1476                retval += desc.written;
1477                if (desc.error) {
1478                        retval = retval ?: desc.error;
1479                        break;
1480                }
1481                if (desc.count > 0)
1482                        break;
1483        }
1484out:
1485        return retval;
1486}
1487EXPORT_SYMBOL(generic_file_aio_read);
1488
1489static ssize_t
1490do_readahead(struct address_space *mapping, struct file *filp,
1491             pgoff_t index, unsigned long nr)
1492{
1493        if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1494                return -EINVAL;
1495
1496        force_page_cache_readahead(mapping, filp, index, nr);
1497        return 0;
1498}
1499
1500SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
1501{
1502        ssize_t ret;
1503        struct file *file;
1504
1505        ret = -EBADF;
1506        file = fget(fd);
1507        if (file) {
1508                if (file->f_mode & FMODE_READ) {
1509                        struct address_space *mapping = file->f_mapping;
1510                        pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1511                        pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1512                        unsigned long len = end - start + 1;
1513                        ret = do_readahead(mapping, file, start, len);
1514                }
1515                fput(file);
1516        }
1517        return ret;
1518}
1519#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1520asmlinkage long SyS_readahead(long fd, loff_t offset, long count)
1521{
1522        return SYSC_readahead((int) fd, offset, (size_t) count);
1523}
1524SYSCALL_ALIAS(sys_readahead, SyS_readahead);
1525#endif
1526
1527#ifdef CONFIG_MMU
1528/**
1529 * page_cache_read - adds requested page to the page cache if not already there
1530 * @file:       file to read
1531 * @offset:     page index
1532 *
1533 * This adds the requested page to the page cache if it isn't already there,
1534 * and schedules an I/O to read in its contents from disk.
1535 */
1536static int page_cache_read(struct file *file, pgoff_t offset)
1537{
1538        struct address_space *mapping = file->f_mapping;
1539        struct page *page; 
1540        int ret;
1541
1542        do {
1543                page = page_cache_alloc_cold(mapping);
1544                if (!page)
1545                        return -ENOMEM;
1546
1547                ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1548                if (ret == 0)
1549                        ret = mapping->a_ops->readpage(file, page);
1550                else if (ret == -EEXIST)
1551                        ret = 0; /* losing race to add is OK */
1552
1553                page_cache_release(page);
1554
1555        } while (ret == AOP_TRUNCATED_PAGE);
1556                
1557        return ret;
1558}
1559
1560#define MMAP_LOTSAMISS  (100)
1561
1562/*
1563 * Synchronous readahead happens when we don't even find
1564 * a page in the page cache at all.
1565 */
1566static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1567                                   struct file_ra_state *ra,
1568                                   struct file *file,
1569                                   pgoff_t offset)
1570{
1571        unsigned long ra_pages;
1572        struct address_space *mapping = file->f_mapping;
1573
1574        /* If we don't want any read-ahead, don't bother */
1575        if (VM_RandomReadHint(vma))
1576                return;
1577        if (!ra->ra_pages)
1578                return;
1579
1580        if (VM_SequentialReadHint(vma)) {
1581                page_cache_sync_readahead(mapping, ra, file, offset,
1582                                          ra->ra_pages);
1583                return;
1584        }
1585
1586        /* Avoid banging the cache line if not needed */
1587        if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1588                ra->mmap_miss++;
1589
1590        /*
1591         * Do we miss much more than hit in this file? If so,
1592         * stop bothering with read-ahead. It will only hurt.
1593         */
1594        if (ra->mmap_miss > MMAP_LOTSAMISS)
1595                return;
1596
1597        /*
1598         * mmap read-around
1599         */
1600        ra_pages = max_sane_readahead(ra->ra_pages);
1601        ra->start = max_t(long, 0, offset - ra_pages / 2);
1602        ra->size = ra_pages;
1603        ra->async_size = ra_pages / 4;
1604        ra_submit(ra, mapping, file);
1605}
1606
1607/*
1608 * Asynchronous readahead happens when we find the page and PG_readahead,
1609 * so we want to possibly extend the readahead further..
1610 */
1611static void do_async_mmap_readahead(struct vm_area_struct *vma,
1612                                    struct file_ra_state *ra,
1613                                    struct file *file,
1614                                    struct page *page,
1615                                    pgoff_t offset)
1616{
1617        struct address_space *mapping = file->f_mapping;
1618
1619        /* If we don't want any read-ahead, don't bother */
1620        if (VM_RandomReadHint(vma))
1621                return;
1622        if (ra->mmap_miss > 0)
1623                ra->mmap_miss--;
1624        if (PageReadahead(page))
1625                page_cache_async_readahead(mapping, ra, file,
1626                                           page, offset, ra->ra_pages);
1627}
1628
1629/**
1630 * filemap_fault - read in file data for page fault handling
1631 * @vma:        vma in which the fault was taken
1632 * @vmf:        struct vm_fault containing details of the fault
1633 *
1634 * filemap_fault() is invoked via the vma operations vector for a
1635 * mapped memory region to read in file data during a page fault.
1636 *
1637 * The goto's are kind of ugly, but this streamlines the normal case of having
1638 * it in the page cache, and handles the special cases reasonably without
1639 * having a lot of duplicated code.
1640 */
1641int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1642{
1643        int error;
1644        struct file *file = vma->vm_file;
1645        struct address_space *mapping = file->f_mapping;
1646        struct file_ra_state *ra = &file->f_ra;
1647        struct inode *inode = mapping->host;
1648        pgoff_t offset = vmf->pgoff;
1649        struct page *page;
1650        pgoff_t size;
1651        int ret = 0;
1652
1653        size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1654        if (offset >= size)
1655                return VM_FAULT_SIGBUS;
1656
1657        /*
1658         * Do we have something in the page cache already?
1659         */
1660        page = find_get_page(mapping, offset);
1661        if (likely(page)) {
1662                /*
1663                 * We found the page, so try async readahead before
1664                 * waiting for the lock.
1665                 */
1666                do_async_mmap_readahead(vma, ra, file, page, offset);
1667        } else {
1668                /* No page in the page cache at all */
1669                do_sync_mmap_readahead(vma, ra, file, offset);
1670                count_vm_event(PGMAJFAULT);
1671                mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1672                ret = VM_FAULT_MAJOR;
1673retry_find:
1674                page = find_get_page(mapping, offset);
1675                if (!page)
1676                        goto no_cached_page;
1677        }
1678
1679        if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1680                page_cache_release(page);
1681                return ret | VM_FAULT_RETRY;
1682        }
1683
1684        /* Did it get truncated? */
1685        if (unlikely(page->mapping != mapping)) {
1686                unlock_page(page);
1687                put_page(page);
1688                goto retry_find;
1689        }
1690        VM_BUG_ON(page->index != offset);
1691
1692        /*
1693         * We have a locked page in the page cache, now we need to check
1694         * that it's up-to-date. If not, it is going to be due to an error.
1695         */
1696        if (unlikely(!PageUptodate(page)))
1697                goto page_not_uptodate;
1698
1699        /*
1700         * Found the page and have a reference on it.
1701         * We must recheck i_size under page lock.
1702         */
1703        size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1704        if (unlikely(offset >= size)) {
1705                unlock_page(page);
1706                page_cache_release(page);
1707                return VM_FAULT_SIGBUS;
1708        }
1709
1710        vmf->page = page;
1711        return ret | VM_FAULT_LOCKED;
1712
1713no_cached_page:
1714        /*
1715         * We're only likely to ever get here if MADV_RANDOM is in
1716         * effect.
1717         */
1718        error = page_cache_read(file, offset);
1719
1720        /*
1721         * The page we want has now been added to the page cache.
1722         * In the unlikely event that someone removed it in the
1723         * meantime, we'll just come back here and read it again.
1724         */
1725        if (error >= 0)
1726                goto retry_find;
1727
1728        /*
1729         * An error return from page_cache_read can result if the
1730         * system is low on memory, or a problem occurs while trying
1731         * to schedule I/O.
1732         */
1733        if (error == -ENOMEM)
1734                return VM_FAULT_OOM;
1735        return VM_FAULT_SIGBUS;
1736
1737page_not_uptodate:
1738        /*
1739         * Umm, take care of errors if the page isn't up-to-date.
1740         * Try to re-read it _once_. We do this synchronously,
1741         * because there really aren't any performance issues here
1742         * and we need to check for errors.
1743         */
1744        ClearPageError(page);
1745        error = mapping->a_ops->readpage(file, page);
1746        if (!error) {
1747                wait_on_page_locked(page);
1748                if (!PageUptodate(page))
1749                        error = -EIO;
1750        }
1751        page_cache_release(page);
1752
1753        if (!error || error == AOP_TRUNCATED_PAGE)
1754                goto retry_find;
1755
1756        /* Things didn't work out. Return zero to tell the mm layer so. */
1757        shrink_readahead_size_eio(file, ra);
1758        return VM_FAULT_SIGBUS;
1759}
1760EXPORT_SYMBOL(filemap_fault);
1761
1762const struct vm_operations_struct generic_file_vm_ops = {
1763        .fault          = filemap_fault,
1764};
1765
1766/* This is used for a general mmap of a disk file */
1767
1768int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1769{
1770        struct address_space *mapping = file->f_mapping;
1771
1772        if (!mapping->a_ops->readpage)
1773                return -ENOEXEC;
1774        file_accessed(file);
1775        vma->vm_ops = &generic_file_vm_ops;
1776        vma->vm_flags |= VM_CAN_NONLINEAR;
1777        return 0;
1778}
1779
1780/*
1781 * This is for filesystems which do not implement ->writepage.
1782 */
1783int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1784{
1785        if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1786                return -EINVAL;
1787        return generic_file_mmap(file, vma);
1788}
1789#else
1790int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1791{
1792        return -ENOSYS;
1793}
1794int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1795{
1796        return -ENOSYS;
1797}
1798#endif /* CONFIG_MMU */
1799
1800EXPORT_SYMBOL(generic_file_mmap);
1801EXPORT_SYMBOL(generic_file_readonly_mmap);
1802
1803static struct page *__read_cache_page(struct address_space *mapping,
1804                                pgoff_t index,
1805                                int (*filler)(void *, struct page *),
1806                                void *data,
1807                                gfp_t gfp)
1808{
1809        struct page *page;
1810        int err;
1811repeat:
1812        page = find_get_page(mapping, index);
1813        if (!page) {
1814                page = __page_cache_alloc(gfp | __GFP_COLD);
1815                if (!page)
1816                        return ERR_PTR(-ENOMEM);
1817                err = add_to_page_cache_lru(page, mapping, index, gfp);
1818                if (unlikely(err)) {
1819                        page_cache_release(page);
1820                        if (err == -EEXIST)
1821                                goto repeat;
1822                        /* Presumably ENOMEM for radix tree node */
1823                        return ERR_PTR(err);
1824                }
1825                err = filler(data, page);
1826                if (err < 0) {
1827                        page_cache_release(page);
1828                        page = ERR_PTR(err);
1829                }
1830        }
1831        return page;
1832}
1833
1834static struct page *do_read_cache_page(struct address_space *mapping,
1835                                pgoff_t index,
1836                                int (*filler)(void *, struct page *),
1837                                void *data,
1838                                gfp_t gfp)
1839
1840{
1841        struct page *page;
1842        int err;
1843
1844retry:
1845        page = __read_cache_page(mapping, index, filler, data, gfp);
1846        if (IS_ERR(page))
1847                return page;
1848        if (PageUptodate(page))
1849                goto out;
1850
1851        lock_page(page);
1852        if (!page->mapping) {
1853                unlock_page(page);
1854                page_cache_release(page);
1855                goto retry;
1856        }
1857        if (PageUptodate(page)) {
1858                unlock_page(page);
1859                goto out;
1860        }
1861        err = filler(data, page);
1862        if (err < 0) {
1863                page_cache_release(page);
1864                return ERR_PTR(err);
1865        }
1866out:
1867        mark_page_accessed(page);
1868        return page;
1869}
1870
1871/**
1872 * read_cache_page_async - read into page cache, fill it if needed
1873 * @mapping:    the page's address_space
1874 * @index:      the page index
1875 * @filler:     function to perform the read
1876 * @data:       first arg to filler(data, page) function, often left as NULL
1877 *
1878 * Same as read_cache_page, but don't wait for page to become unlocked
1879 * after submitting it to the filler.
1880 *
1881 * Read into the page cache. If a page already exists, and PageUptodate() is
1882 * not set, try to fill the page but don't wait for it to become unlocked.
1883 *
1884 * If the page does not get brought uptodate, return -EIO.
1885 */
1886struct page *read_cache_page_async(struct address_space *mapping,
1887                                pgoff_t index,
1888                                int (*filler)(void *, struct page *),
1889                                void *data)
1890{
1891        return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1892}
1893EXPORT_SYMBOL(read_cache_page_async);
1894
1895static struct page *wait_on_page_read(struct page *page)
1896{
1897        if (!IS_ERR(page)) {
1898                wait_on_page_locked(page);
1899                if (!PageUptodate(page)) {
1900                        page_cache_release(page);
1901                        page = ERR_PTR(-EIO);
1902                }
1903        }
1904        return page;
1905}
1906
1907/**
1908 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1909 * @mapping:    the page's address_space
1910 * @index:      the page index
1911 * @gfp:        the page allocator flags to use if allocating
1912 *
1913 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1914 * any new page allocations done using the specified allocation flags.
1915 *
1916 * If the page does not get brought uptodate, return -EIO.
1917 */
1918struct page *read_cache_page_gfp(struct address_space *mapping,
1919                                pgoff_t index,
1920                                gfp_t gfp)
1921{
1922        filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1923
1924        return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1925}
1926EXPORT_SYMBOL(read_cache_page_gfp);
1927
1928/**
1929 * read_cache_page - read into page cache, fill it if needed
1930 * @mapping:    the page's address_space
1931 * @index:      the page index
1932 * @filler:     function to perform the read
1933 * @data:       first arg to filler(data, page) function, often left as NULL
1934 *
1935 * Read into the page cache. If a page already exists, and PageUptodate() is
1936 * not set, try to fill the page then wait for it to become unlocked.
1937 *
1938 * If the page does not get brought uptodate, return -EIO.
1939 */
1940struct page *read_cache_page(struct address_space *mapping,
1941                                pgoff_t index,
1942                                int (*filler)(void *, struct page *),
1943                                void *data)
1944{
1945        return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
1946}
1947EXPORT_SYMBOL(read_cache_page);
1948
1949/*
1950 * The logic we want is
1951 *
1952 *      if suid or (sgid and xgrp)
1953 *              remove privs
1954 */
1955int should_remove_suid(struct dentry *dentry)
1956{
1957        umode_t mode = dentry->d_inode->i_mode;
1958        int kill = 0;
1959
1960        /* suid always must be killed */
1961        if (unlikely(mode & S_ISUID))
1962                kill = ATTR_KILL_SUID;
1963
1964        /*
1965         * sgid without any exec bits is just a mandatory locking mark; leave
1966         * it alone.  If some exec bits are set, it's a real sgid; kill it.
1967         */
1968        if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1969                kill |= ATTR_KILL_SGID;
1970
1971        if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1972                return kill;
1973
1974        return 0;
1975}
1976EXPORT_SYMBOL(should_remove_suid);
1977
1978static int __remove_suid(struct dentry *dentry, int kill)
1979{
1980        struct iattr newattrs;
1981
1982        newattrs.ia_valid = ATTR_FORCE | kill;
1983        return notify_change(dentry, &newattrs);
1984}
1985
1986int file_remove_suid(struct file *file)
1987{
1988        struct dentry *dentry = file->f_path.dentry;
1989        struct inode *inode = dentry->d_inode;
1990        int killsuid;
1991        int killpriv;
1992        int error = 0;
1993
1994        /* Fast path for nothing security related */
1995        if (IS_NOSEC(inode))
1996                return 0;
1997
1998        killsuid = should_remove_suid(dentry);
1999        killpriv = security_inode_need_killpriv(dentry);
2000
2001        if (killpriv < 0)
2002                return killpriv;
2003        if (killpriv)
2004                error = security_inode_killpriv(dentry);
2005        if (!error && killsuid)
2006                error = __remove_suid(dentry, killsuid);
2007        if (!error && (inode->i_sb->s_flags & MS_NOSEC))
2008                inode->i_flags |= S_NOSEC;
2009
2010        return error;
2011}
2012EXPORT_SYMBOL(file_remove_suid);
2013
2014static size_t __iovec_copy_from_user_inatomic(char *vaddr,
2015                        const struct iovec *iov, size_t base, size_t bytes)
2016{
2017        size_t copied = 0, left = 0;
2018
2019        while (bytes) {
2020                char __user *buf = iov->iov_base + base;
2021                int copy = min(bytes, iov->iov_len - base);
2022
2023                base = 0;
2024                left = __copy_from_user_inatomic(vaddr, buf, copy);
2025                copied += copy;
2026                bytes -= copy;
2027                vaddr += copy;
2028                iov++;
2029
2030                if (unlikely(left))
2031                        break;
2032        }
2033        return copied - left;
2034}
2035
2036/*
2037 * Copy as much as we can into the page and return the number of bytes which
2038 * were successfully copied.  If a fault is encountered then return the number of
2039 * bytes which were copied.
2040 */
2041size_t iov_iter_copy_from_user_atomic(struct page *page,
2042                struct iov_iter *i, unsigned long offset, size_t bytes)
2043{
2044        char *kaddr;
2045        size_t copied;
2046
2047        BUG_ON(!in_atomic());
2048        kaddr = kmap_atomic(page, KM_USER0);
2049        if (likely(i->nr_segs == 1)) {
2050                int left;
2051                char __user *buf = i->iov->iov_base + i->iov_offset;
2052                left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
2053                copied = bytes - left;
2054        } else {
2055                copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2056                                                i->iov, i->iov_offset, bytes);
2057        }
2058        kunmap_atomic(kaddr, KM_USER0);
2059
2060        return copied;
2061}
2062EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
2063
2064/*
2065 * This has the same sideeffects and return value as
2066 * iov_iter_copy_from_user_atomic().
2067 * The difference is that it attempts to resolve faults.
2068 * Page must not be locked.
2069 */
2070size_t iov_iter_copy_from_user(struct page *page,
2071                struct iov_iter *i, unsigned long offset, size_t bytes)
2072{
2073        char *kaddr;
2074        size_t copied;
2075
2076        kaddr = kmap(page);
2077        if (likely(i->nr_segs == 1)) {
2078                int left;
2079                char __user *buf = i->iov->iov_base + i->iov_offset;
2080                left = __copy_from_user(kaddr + offset, buf, bytes);
2081                copied = bytes - left;
2082        } else {
2083                copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2084                                                i->iov, i->iov_offset, bytes);
2085        }
2086        kunmap(page);
2087        return copied;
2088}
2089EXPORT_SYMBOL(iov_iter_copy_from_user);
2090
2091void iov_iter_advance(struct iov_iter *i, size_t bytes)
2092{
2093        BUG_ON(i->count < bytes);
2094
2095        if (likely(i->nr_segs == 1)) {
2096                i->iov_offset += bytes;
2097                i->count -= bytes;
2098        } else {
2099                const struct iovec *iov = i->iov;
2100                size_t base = i->iov_offset;
2101                unsigned long nr_segs = i->nr_segs;
2102
2103                /*
2104                 * The !iov->iov_len check ensures we skip over unlikely
2105                 * zero-length segments (without overruning the iovec).
2106                 */
2107                while (bytes || unlikely(i->count && !iov->iov_len)) {
2108                        int copy;
2109
2110                        copy = min(bytes, iov->iov_len - base);
2111                        BUG_ON(!i->count || i->count < copy);
2112                        i->count -= copy;
2113                        bytes -= copy;
2114                        base += copy;
2115                        if (iov->iov_len == base) {
2116                                iov++;
2117                                nr_segs--;
2118                                base = 0;
2119                        }
2120                }
2121                i->iov = iov;
2122                i->iov_offset = base;
2123                i->nr_segs = nr_segs;
2124        }
2125}
2126EXPORT_SYMBOL(iov_iter_advance);
2127
2128/*
2129 * Fault in the first iovec of the given iov_iter, to a maximum length
2130 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2131 * accessed (ie. because it is an invalid address).
2132 *
2133 * writev-intensive code may want this to prefault several iovecs -- that
2134 * would be possible (callers must not rely on the fact that _only_ the
2135 * first iovec will be faulted with the current implementation).
2136 */
2137int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2138{
2139        char __user *buf = i->iov->iov_base + i->iov_offset;
2140        bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2141        return fault_in_pages_readable(buf, bytes);
2142}
2143EXPORT_SYMBOL(iov_iter_fault_in_readable);
2144
2145/*
2146 * Return the count of just the current iov_iter segment.
2147 */
2148size_t iov_iter_single_seg_count(struct iov_iter *i)
2149{
2150        const struct iovec *iov = i->iov;
2151        if (i->nr_segs == 1)
2152                return i->count;
2153        else
2154                return min(i->count, iov->iov_len - i->iov_offset);
2155}
2156EXPORT_SYMBOL(iov_iter_single_seg_count);
2157
2158/*
2159 * Performs necessary checks before doing a write
2160 *
2161 * Can adjust writing position or amount of bytes to write.
2162 * Returns appropriate error code that caller should return or
2163 * zero in case that write should be allowed.
2164 */
2165inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2166{
2167        struct inode *inode = file->f_mapping->host;
2168        unsigned long limit = rlimit(RLIMIT_FSIZE);
2169
2170        if (unlikely(*pos < 0))
2171                return -EINVAL;
2172
2173        if (!isblk) {
2174                /* FIXME: this is for backwards compatibility with 2.4 */
2175                if (file->f_flags & O_APPEND)
2176                        *pos = i_size_read(inode);
2177
2178                if (limit != RLIM_INFINITY) {
2179                        if (*pos >= limit) {
2180                                send_sig(SIGXFSZ, current, 0);
2181                                return -EFBIG;
2182                        }
2183                        if (*count > limit - (typeof(limit))*pos) {
2184                                *count = limit - (typeof(limit))*pos;
2185                        }
2186                }
2187        }
2188
2189        /*
2190         * LFS rule
2191         */
2192        if (unlikely(*pos + *count > MAX_NON_LFS &&
2193                                !(file->f_flags & O_LARGEFILE))) {
2194                if (*pos >= MAX_NON_LFS) {
2195                        return -EFBIG;
2196                }
2197                if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2198                        *count = MAX_NON_LFS - (unsigned long)*pos;
2199                }
2200        }
2201
2202        /*
2203         * Are we about to exceed the fs block limit ?
2204         *
2205         * If we have written data it becomes a short write.  If we have
2206         * exceeded without writing data we send a signal and return EFBIG.
2207         * Linus frestrict idea will clean these up nicely..
2208         */
2209        if (likely(!isblk)) {
2210                if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2211                        if (*count || *pos > inode->i_sb->s_maxbytes) {
2212                                return -EFBIG;
2213                        }
2214                        /* zero-length writes at ->s_maxbytes are OK */
2215                }
2216
2217                if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2218                        *count = inode->i_sb->s_maxbytes - *pos;
2219        } else {
2220#ifdef CONFIG_BLOCK
2221                loff_t isize;
2222                if (bdev_read_only(I_BDEV(inode)))
2223                        return -EPERM;
2224                isize = i_size_read(inode);
2225                if (*pos >= isize) {
2226                        if (*count || *pos > isize)
2227                                return -ENOSPC;
2228                }
2229
2230                if (*pos + *count > isize)
2231                        *count = isize - *pos;
2232#else
2233                return -EPERM;
2234#endif
2235        }
2236        return 0;
2237}
2238EXPORT_SYMBOL(generic_write_checks);
2239
2240int pagecache_write_begin(struct file *file, struct address_space *mapping,
2241                                loff_t pos, unsigned len, unsigned flags,
2242                                struct page **pagep, void **fsdata)
2243{
2244        const struct address_space_operations *aops = mapping->a_ops;
2245
2246        return aops->write_begin(file, mapping, pos, len, flags,
2247                                                        pagep, fsdata);
2248}
2249EXPORT_SYMBOL(pagecache_write_begin);
2250
2251int pagecache_write_end(struct file *file, struct address_space *mapping,
2252                                loff_t pos, unsigned len, unsigned copied,
2253                                struct page *page, void *fsdata)
2254{
2255        const struct address_space_operations *aops = mapping->a_ops;
2256
2257        mark_page_accessed(page);
2258        return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2259}
2260EXPORT_SYMBOL(pagecache_write_end);
2261
2262ssize_t
2263generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2264                unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2265                size_t count, size_t ocount)
2266{
2267        struct file     *file = iocb->ki_filp;
2268        struct address_space *mapping = file->f_mapping;
2269        struct inode    *inode = mapping->host;
2270        ssize_t         written;
2271        size_t          write_len;
2272        pgoff_t         end;
2273
2274        if (count != ocount)
2275                *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2276
2277        write_len = iov_length(iov, *nr_segs);
2278        end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2279
2280        written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2281        if (written)
2282                goto out;
2283
2284        /*
2285         * After a write we want buffered reads to be sure to go to disk to get
2286         * the new data.  We invalidate clean cached page from the region we're
2287         * about to write.  We do this *before* the write so that we can return
2288         * without clobbering -EIOCBQUEUED from ->direct_IO().
2289         */
2290        if (mapping->nrpages) {
2291                written = invalidate_inode_pages2_range(mapping,
2292                                        pos >> PAGE_CACHE_SHIFT, end);
2293                /*
2294                 * If a page can not be invalidated, return 0 to fall back
2295                 * to buffered write.
2296                 */
2297                if (written) {
2298                        if (written == -EBUSY)
2299                                return 0;
2300                        goto out;
2301                }
2302        }
2303
2304        written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2305
2306        /*
2307         * Finally, try again to invalidate clean pages which might have been
2308         * cached by non-direct readahead, or faulted in by get_user_pages()
2309         * if the source of the write was an mmap'ed region of the file
2310         * we're writing.  Either one is a pretty crazy thing to do,
2311         * so we don't support it 100%.  If this invalidation
2312         * fails, tough, the write still worked...
2313         */
2314        if (mapping->nrpages) {
2315                invalidate_inode_pages2_range(mapping,
2316                                              pos >> PAGE_CACHE_SHIFT, end);
2317        }
2318
2319        if (written > 0) {
2320                pos += written;
2321                if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2322                        i_size_write(inode, pos);
2323                        mark_inode_dirty(inode);
2324                }
2325                *ppos = pos;
2326        }
2327out:
2328        return written;
2329}
2330EXPORT_SYMBOL(generic_file_direct_write);
2331
2332/*
2333 * Find or create a page at the given pagecache position. Return the locked
2334 * page. This function is specifically for buffered writes.
2335 */
2336struct page *grab_cache_page_write_begin(struct address_space *mapping,
2337                                        pgoff_t index, unsigned flags)
2338{
2339        int status;
2340        gfp_t gfp_mask;
2341        struct page *page;
2342        gfp_t gfp_notmask = 0;
2343
2344        gfp_mask = mapping_gfp_mask(mapping) | __GFP_WRITE;
2345        if (flags & AOP_FLAG_NOFS)
2346                gfp_notmask = __GFP_FS;
2347repeat:
2348        page = find_lock_page(mapping, index);
2349        if (page)
2350                goto found;
2351
2352        page = __page_cache_alloc(gfp_mask & ~gfp_notmask);
2353        if (!page)
2354                return NULL;
2355        status = add_to_page_cache_lru(page, mapping, index,
2356                                                GFP_KERNEL & ~gfp_notmask);
2357        if (unlikely(status)) {
2358                page_cache_release(page);
2359                if (status == -EEXIST)
2360                        goto repeat;
2361                return NULL;
2362        }
2363found:
2364        wait_on_page_writeback(page);
2365        return page;
2366}
2367EXPORT_SYMBOL(grab_cache_page_write_begin);
2368
2369static ssize_t generic_perform_write(struct file *file,
2370                                struct iov_iter *i, loff_t pos)
2371{
2372        struct address_space *mapping = file->f_mapping;
2373        const struct address_space_operations *a_ops = mapping->a_ops;
2374        long status = 0;
2375        ssize_t written = 0;
2376        unsigned int flags = 0;
2377
2378        /*
2379         * Copies from kernel address space cannot fail (NFSD is a big user).
2380         */
2381        if (segment_eq(get_fs(), KERNEL_DS))
2382                flags |= AOP_FLAG_UNINTERRUPTIBLE;
2383
2384        do {
2385                struct page *page;
2386                unsigned long offset;   /* Offset into pagecache page */
2387                unsigned long bytes;    /* Bytes to write to page */
2388                size_t copied;          /* Bytes copied from user */
2389                void *fsdata;
2390
2391                offset = (pos & (PAGE_CACHE_SIZE - 1));
2392                bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2393                                                iov_iter_count(i));
2394
2395again:
2396                /*
2397                 * Bring in the user page that we will copy from _first_.
2398                 * Otherwise there's a nasty deadlock on copying from the
2399                 * same page as we're writing to, without it being marked
2400                 * up-to-date.
2401                 *
2402                 * Not only is this an optimisation, but it is also required
2403                 * to check that the address is actually valid, when atomic
2404                 * usercopies are used, below.
2405                 */
2406                if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2407                        status = -EFAULT;
2408                        break;
2409                }
2410
2411                status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2412                                                &page, &fsdata);
2413                if (unlikely(status))
2414                        break;
2415
2416                if (mapping_writably_mapped(mapping))
2417                        flush_dcache_page(page);
2418
2419                pagefault_disable();
2420                copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2421                pagefault_enable();
2422                flush_dcache_page(page);
2423
2424                mark_page_accessed(page);
2425                status = a_ops->write_end(file, mapping, pos, bytes, copied,
2426                                                page, fsdata);
2427                if (unlikely(status < 0))
2428                        break;
2429                copied = status;
2430
2431                cond_resched();
2432
2433                iov_iter_advance(i, copied);
2434                if (unlikely(copied == 0)) {
2435                        /*
2436                         * If we were unable to copy any data at all, we must
2437                         * fall back to a single segment length write.
2438                         *
2439                         * If we didn't fallback here, we could livelock
2440                         * because not all segments in the iov can be copied at
2441                         * once without a pagefault.
2442                         */
2443                        bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2444                                                iov_iter_single_seg_count(i));
2445                        goto again;
2446                }
2447                pos += copied;
2448                written += copied;
2449
2450                balance_dirty_pages_ratelimited(mapping);
2451                if (fatal_signal_pending(current)) {
2452                        status = -EINTR;
2453                        break;
2454                }
2455        } while (iov_iter_count(i));
2456
2457        return written ? written : status;
2458}
2459
2460ssize_t
2461generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2462                unsigned long nr_segs, loff_t pos, loff_t *ppos,
2463                size_t count, ssize_t written)
2464{
2465        struct file *file = iocb->ki_filp;
2466        ssize_t status;
2467        struct iov_iter i;
2468
2469        iov_iter_init(&i, iov, nr_segs, count, written);
2470        status = generic_perform_write(file, &i, pos);
2471
2472        if (likely(status >= 0)) {
2473                written += status;
2474                *ppos = pos + status;
2475        }
2476        
2477        return written ? written : status;
2478}
2479EXPORT_SYMBOL(generic_file_buffered_write);
2480
2481/**
2482 * __generic_file_aio_write - write data to a file
2483 * @iocb:       IO state structure (file, offset, etc.)
2484 * @iov:        vector with data to write
2485 * @nr_segs:    number of segments in the vector
2486 * @ppos:       position where to write
2487 *
2488 * This function does all the work needed for actually writing data to a
2489 * file. It does all basic checks, removes SUID from the file, updates
2490 * modification times and calls proper subroutines depending on whether we
2491 * do direct IO or a standard buffered write.
2492 *
2493 * It expects i_mutex to be grabbed unless we work on a block device or similar
2494 * object which does not need locking at all.
2495 *
2496 * This function does *not* take care of syncing data in case of O_SYNC write.
2497 * A caller has to handle it. This is mainly due to the fact that we want to
2498 * avoid syncing under i_mutex.
2499 */
2500ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2501                                 unsigned long nr_segs, loff_t *ppos)
2502{
2503        struct file *file = iocb->ki_filp;
2504        struct address_space * mapping = file->f_mapping;
2505        size_t ocount;          /* original count */
2506        size_t count;           /* after file limit checks */
2507        struct inode    *inode = mapping->host;
2508        loff_t          pos;
2509        ssize_t         written;
2510        ssize_t         err;
2511
2512        ocount = 0;
2513        err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2514        if (err)
2515                return err;
2516
2517        count = ocount;
2518        pos = *ppos;
2519
2520        vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2521
2522        /* We can write back this queue in page reclaim */
2523        current->backing_dev_info = mapping->backing_dev_info;
2524        written = 0;
2525
2526        err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2527        if (err)
2528                goto out;
2529
2530        if (count == 0)
2531                goto out;
2532
2533        err = file_remove_suid(file);
2534        if (err)
2535                goto out;
2536
2537        file_update_time(file);
2538
2539        /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2540        if (unlikely(file->f_flags & O_DIRECT)) {
2541                loff_t endbyte;
2542                ssize_t written_buffered;
2543
2544                written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2545                                                        ppos, count, ocount);
2546                if (written < 0 || written == count)
2547                        goto out;
2548                /*
2549                 * direct-io write to a hole: fall through to buffered I/O
2550                 * for completing the rest of the request.
2551                 */
2552                pos += written;
2553                count -= written;
2554                written_buffered = generic_file_buffered_write(iocb, iov,
2555                                                nr_segs, pos, ppos, count,
2556                                                written);
2557                /*
2558                 * If generic_file_buffered_write() retuned a synchronous error
2559                 * then we want to return the number of bytes which were
2560                 * direct-written, or the error code if that was zero.  Note
2561                 * that this differs from normal direct-io semantics, which
2562                 * will return -EFOO even if some bytes were written.
2563                 */
2564                if (written_buffered < 0) {
2565                        err = written_buffered;
2566                        goto out;
2567                }
2568
2569                /*
2570                 * We need to ensure that the page cache pages are written to
2571                 * disk and invalidated to preserve the expected O_DIRECT
2572                 * semantics.
2573                 */
2574                endbyte = pos + written_buffered - written - 1;
2575                err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2576                if (err == 0) {
2577                        written = written_buffered;
2578                        invalidate_mapping_pages(mapping,
2579                                                 pos >> PAGE_CACHE_SHIFT,
2580                                                 endbyte >> PAGE_CACHE_SHIFT);
2581                } else {
2582                        /*
2583                         * We don't know how much we wrote, so just return
2584                         * the number of bytes which were direct-written
2585                         */
2586                }
2587        } else {
2588                written = generic_file_buffered_write(iocb, iov, nr_segs,
2589                                pos, ppos, count, written);
2590        }
2591out:
2592        current->backing_dev_info = NULL;
2593        return written ? written : err;
2594}
2595EXPORT_SYMBOL(__generic_file_aio_write);
2596
2597/**
2598 * generic_file_aio_write - write data to a file
2599 * @iocb:       IO state structure
2600 * @iov:        vector with data to write
2601 * @nr_segs:    number of segments in the vector
2602 * @pos:        position in file where to write
2603 *
2604 * This is a wrapper around __generic_file_aio_write() to be used by most
2605 * filesystems. It takes care of syncing the file in case of O_SYNC file
2606 * and acquires i_mutex as needed.
2607 */
2608ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2609                unsigned long nr_segs, loff_t pos)
2610{
2611        struct file *file = iocb->ki_filp;
2612        struct inode *inode = file->f_mapping->host;
2613        struct blk_plug plug;
2614        ssize_t ret;
2615
2616        BUG_ON(iocb->ki_pos != pos);
2617
2618        mutex_lock(&inode->i_mutex);
2619        blk_start_plug(&plug);
2620        ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2621        mutex_unlock(&inode->i_mutex);
2622
2623        if (ret > 0 || ret == -EIOCBQUEUED) {
2624                ssize_t err;
2625
2626                err = generic_write_sync(file, pos, ret);
2627                if (err < 0 && ret > 0)
2628                        ret = err;
2629        }
2630        blk_finish_plug(&plug);
2631        return ret;
2632}
2633EXPORT_SYMBOL(generic_file_aio_write);
2634
2635/**
2636 * try_to_release_page() - release old fs-specific metadata on a page
2637 *
2638 * @page: the page which the kernel is trying to free
2639 * @gfp_mask: memory allocation flags (and I/O mode)
2640 *
2641 * The address_space is to try to release any data against the page
2642 * (presumably at page->private).  If the release was successful, return `1'.
2643 * Otherwise return zero.
2644 *
2645 * This may also be called if PG_fscache is set on a page, indicating that the
2646 * page is known to the local caching routines.
2647 *
2648 * The @gfp_mask argument specifies whether I/O may be performed to release
2649 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2650 *
2651 */
2652int try_to_release_page(struct page *page, gfp_t gfp_mask)
2653{
2654        struct address_space * const mapping = page->mapping;
2655
2656        BUG_ON(!PageLocked(page));
2657        if (PageWriteback(page))
2658                return 0;
2659
2660        if (mapping && mapping->a_ops->releasepage)
2661                return mapping->a_ops->releasepage(page, gfp_mask);
2662        return try_to_free_buffers(page);
2663}
2664
2665EXPORT_SYMBOL(try_to_release_page);
2666