filemap.c 66.7 KB
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/*
 *	linux/mm/filemap.c
 *
 * Copyright (C) 1994-1999  Linus Torvalds
 */

/*
 * This file handles the generic file mmap semantics used by
 * most "normal" filesystems (but you don't /have/ to use this:
 * the NFS filesystem used to do this differently, for example)
 */
#include <linux/module.h>
#include <linux/compiler.h>
#include <linux/fs.h>
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#include <linux/uaccess.h>
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#include <linux/aio.h>
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#include <linux/capability.h>
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#include <linux/kernel_stat.h>
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#include <linux/gfp.h>
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#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/hash.h>
#include <linux/writeback.h>
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#include <linux/backing-dev.h>
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#include <linux/pagevec.h>
#include <linux/blkdev.h>
#include <linux/security.h>
#include <linux/syscalls.h>
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#include <linux/cpuset.h>
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#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
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#include <linux/memcontrol.h>
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#include <linux/mm_inline.h> /* for page_is_file_cache() */
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#include "internal.h"

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/*
 * FIXME: remove all knowledge of the buffer layer from the core VM
 */
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#include <linux/buffer_head.h> /* for try_to_free_buffers */
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#include <asm/mman.h>

/*
 * Shared mappings implemented 30.11.1994. It's not fully working yet,
 * though.
 *
 * Shared mappings now work. 15.8.1995  Bruno.
 *
 * finished 'unifying' the page and buffer cache and SMP-threaded the
 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
 *
 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
 */

/*
 * Lock ordering:
 *
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 *  ->i_mmap_lock		(truncate_pagecache)
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 *    ->private_lock		(__free_pte->__set_page_dirty_buffers)
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 *      ->swap_lock		(exclusive_swap_page, others)
 *        ->mapping->tree_lock
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 *
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 *  ->i_mutex
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 *    ->i_mmap_lock		(truncate->unmap_mapping_range)
 *
 *  ->mmap_sem
 *    ->i_mmap_lock
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 *      ->page_table_lock or pte_lock	(various, mainly in memory.c)
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 *        ->mapping->tree_lock	(arch-dependent flush_dcache_mmap_lock)
 *
 *  ->mmap_sem
 *    ->lock_page		(access_process_vm)
 *
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 *  ->i_mutex			(generic_file_buffered_write)
 *    ->mmap_sem		(fault_in_pages_readable->do_page_fault)
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 *
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 *  ->i_mutex
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 *    ->i_alloc_sem             (various)
 *
 *  ->inode_lock
 *    ->sb_lock			(fs/fs-writeback.c)
 *    ->mapping->tree_lock	(__sync_single_inode)
 *
 *  ->i_mmap_lock
 *    ->anon_vma.lock		(vma_adjust)
 *
 *  ->anon_vma.lock
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 *    ->page_table_lock or pte_lock	(anon_vma_prepare and various)
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 *
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 *  ->page_table_lock or pte_lock
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 *    ->swap_lock		(try_to_unmap_one)
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 *    ->private_lock		(try_to_unmap_one)
 *    ->tree_lock		(try_to_unmap_one)
 *    ->zone.lru_lock		(follow_page->mark_page_accessed)
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 *    ->zone.lru_lock		(check_pte_range->isolate_lru_page)
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 *    ->private_lock		(page_remove_rmap->set_page_dirty)
 *    ->tree_lock		(page_remove_rmap->set_page_dirty)
 *    ->inode_lock		(page_remove_rmap->set_page_dirty)
 *    ->inode_lock		(zap_pte_range->set_page_dirty)
 *    ->private_lock		(zap_pte_range->__set_page_dirty_buffers)
 *
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 *  (code doesn't rely on that order, so you could switch it around)
 *  ->tasklist_lock             (memory_failure, collect_procs_ao)
 *    ->i_mmap_lock
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 */

/*
 * Remove a page from the page cache and free it. Caller has to make
 * sure the page is locked and that nobody else uses it - or that usage
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 * is safe.  The caller must hold the mapping's tree_lock.
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 */
void __remove_from_page_cache(struct page *page)
{
	struct address_space *mapping = page->mapping;

	radix_tree_delete(&mapping->page_tree, page->index);
	page->mapping = NULL;
	mapping->nrpages--;
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	__dec_zone_page_state(page, NR_FILE_PAGES);
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	if (PageSwapBacked(page))
		__dec_zone_page_state(page, NR_SHMEM);
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	BUG_ON(page_mapped(page));
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	/*
	 * Some filesystems seem to re-dirty the page even after
	 * the VM has canceled the dirty bit (eg ext3 journaling).
	 *
	 * Fix it up by doing a final dirty accounting check after
	 * having removed the page entirely.
	 */
	if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
		dec_zone_page_state(page, NR_FILE_DIRTY);
		dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
	}
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}

void remove_from_page_cache(struct page *page)
{
	struct address_space *mapping = page->mapping;
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	void (*freepage)(struct page *);
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	BUG_ON(!PageLocked(page));
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	freepage = mapping->a_ops->freepage;
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	spin_lock_irq(&mapping->tree_lock);
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	__remove_from_page_cache(page);
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	spin_unlock_irq(&mapping->tree_lock);
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	mem_cgroup_uncharge_cache_page(page);
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	if (freepage)
		freepage(page);
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}
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EXPORT_SYMBOL(remove_from_page_cache);
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static int sync_page(void *word)
{
	struct address_space *mapping;
	struct page *page;

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	page = container_of((unsigned long *)word, struct page, flags);
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	/*
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	 * page_mapping() is being called without PG_locked held.
	 * Some knowledge of the state and use of the page is used to
	 * reduce the requirements down to a memory barrier.
	 * The danger here is of a stale page_mapping() return value
	 * indicating a struct address_space different from the one it's
	 * associated with when it is associated with one.
	 * After smp_mb(), it's either the correct page_mapping() for
	 * the page, or an old page_mapping() and the page's own
	 * page_mapping() has gone NULL.
	 * The ->sync_page() address_space operation must tolerate
	 * page_mapping() going NULL. By an amazing coincidence,
	 * this comes about because none of the users of the page
	 * in the ->sync_page() methods make essential use of the
	 * page_mapping(), merely passing the page down to the backing
	 * device's unplug functions when it's non-NULL, which in turn
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	 * ignore it for all cases but swap, where only page_private(page) is
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	 * of interest. When page_mapping() does go NULL, the entire
	 * call stack gracefully ignores the page and returns.
	 * -- wli
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	 */
	smp_mb();
	mapping = page_mapping(page);
	if (mapping && mapping->a_ops && mapping->a_ops->sync_page)
		mapping->a_ops->sync_page(page);
	io_schedule();
	return 0;
}

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static int sync_page_killable(void *word)
{
	sync_page(word);
	return fatal_signal_pending(current) ? -EINTR : 0;
}

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/**
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 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
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 * @mapping:	address space structure to write
 * @start:	offset in bytes where the range starts
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 * @end:	offset in bytes where the range ends (inclusive)
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 * @sync_mode:	enable synchronous operation
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 *
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 * Start writeback against all of a mapping's dirty pages that lie
 * within the byte offsets <start, end> inclusive.
 *
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 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
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 * opposed to a regular memory cleansing writeback.  The difference between
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 * these two operations is that if a dirty page/buffer is encountered, it must
 * be waited upon, and not just skipped over.
 */
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int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
				loff_t end, int sync_mode)
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{
	int ret;
	struct writeback_control wbc = {
		.sync_mode = sync_mode,
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		.nr_to_write = LONG_MAX,
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		.range_start = start,
		.range_end = end,
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	};

	if (!mapping_cap_writeback_dirty(mapping))
		return 0;

	ret = do_writepages(mapping, &wbc);
	return ret;
}

static inline int __filemap_fdatawrite(struct address_space *mapping,
	int sync_mode)
{
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	return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
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}

int filemap_fdatawrite(struct address_space *mapping)
{
	return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
}
EXPORT_SYMBOL(filemap_fdatawrite);

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int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
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				loff_t end)
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{
	return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
}
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EXPORT_SYMBOL(filemap_fdatawrite_range);
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/**
 * filemap_flush - mostly a non-blocking flush
 * @mapping:	target address_space
 *
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 * This is a mostly non-blocking flush.  Not suitable for data-integrity
 * purposes - I/O may not be started against all dirty pages.
 */
int filemap_flush(struct address_space *mapping)
{
	return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
}
EXPORT_SYMBOL(filemap_flush);

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/**
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 * filemap_fdatawait_range - wait for writeback to complete
 * @mapping:		address space structure to wait for
 * @start_byte:		offset in bytes where the range starts
 * @end_byte:		offset in bytes where the range ends (inclusive)
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 *
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 * Walk the list of under-writeback pages of the given address space
 * in the given range and wait for all of them.
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 */
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int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
			    loff_t end_byte)
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{
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	pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
	pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
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	struct pagevec pvec;
	int nr_pages;
	int ret = 0;

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	if (end_byte < start_byte)
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		return 0;

	pagevec_init(&pvec, 0);
	while ((index <= end) &&
			(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
			PAGECACHE_TAG_WRITEBACK,
			min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
		unsigned i;

		for (i = 0; i < nr_pages; i++) {
			struct page *page = pvec.pages[i];

			/* until radix tree lookup accepts end_index */
			if (page->index > end)
				continue;

			wait_on_page_writeback(page);
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			if (TestClearPageError(page))
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				ret = -EIO;
		}
		pagevec_release(&pvec);
		cond_resched();
	}

	/* Check for outstanding write errors */
	if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
		ret = -ENOSPC;
	if (test_and_clear_bit(AS_EIO, &mapping->flags))
		ret = -EIO;

	return ret;
}
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EXPORT_SYMBOL(filemap_fdatawait_range);

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/**
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 * filemap_fdatawait - wait for all under-writeback pages to complete
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 * @mapping: address space structure to wait for
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 *
 * Walk the list of under-writeback pages of the given address space
 * and wait for all of them.
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 */
int filemap_fdatawait(struct address_space *mapping)
{
	loff_t i_size = i_size_read(mapping->host);

	if (i_size == 0)
		return 0;

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	return filemap_fdatawait_range(mapping, 0, i_size - 1);
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}
EXPORT_SYMBOL(filemap_fdatawait);

int filemap_write_and_wait(struct address_space *mapping)
{
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	int err = 0;
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	if (mapping->nrpages) {
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		err = filemap_fdatawrite(mapping);
		/*
		 * Even if the above returned error, the pages may be
		 * written partially (e.g. -ENOSPC), so we wait for it.
		 * But the -EIO is special case, it may indicate the worst
		 * thing (e.g. bug) happened, so we avoid waiting for it.
		 */
		if (err != -EIO) {
			int err2 = filemap_fdatawait(mapping);
			if (!err)
				err = err2;
		}
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	}
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	return err;
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}
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EXPORT_SYMBOL(filemap_write_and_wait);
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/**
 * filemap_write_and_wait_range - write out & wait on a file range
 * @mapping:	the address_space for the pages
 * @lstart:	offset in bytes where the range starts
 * @lend:	offset in bytes where the range ends (inclusive)
 *
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 * Write out and wait upon file offsets lstart->lend, inclusive.
 *
 * Note that `lend' is inclusive (describes the last byte to be written) so
 * that this function can be used to write to the very end-of-file (end = -1).
 */
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int filemap_write_and_wait_range(struct address_space *mapping,
				 loff_t lstart, loff_t lend)
{
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	int err = 0;
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	if (mapping->nrpages) {
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		err = __filemap_fdatawrite_range(mapping, lstart, lend,
						 WB_SYNC_ALL);
		/* See comment of filemap_write_and_wait() */
		if (err != -EIO) {
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			int err2 = filemap_fdatawait_range(mapping,
						lstart, lend);
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			if (!err)
				err = err2;
		}
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	}
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	return err;
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}
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EXPORT_SYMBOL(filemap_write_and_wait_range);
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/**
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 * add_to_page_cache_locked - add a locked page to the pagecache
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 * @page:	page to add
 * @mapping:	the page's address_space
 * @offset:	page index
 * @gfp_mask:	page allocation mode
 *
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 * This function is used to add a page to the pagecache. It must be locked.
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 * This function does not add the page to the LRU.  The caller must do that.
 */
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int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
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		pgoff_t offset, gfp_t gfp_mask)
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{
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	int error;

	VM_BUG_ON(!PageLocked(page));

	error = mem_cgroup_cache_charge(page, current->mm,
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					gfp_mask & GFP_RECLAIM_MASK);
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	if (error)
		goto out;
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	error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
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	if (error == 0) {
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		page_cache_get(page);
		page->mapping = mapping;
		page->index = offset;

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		spin_lock_irq(&mapping->tree_lock);
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		error = radix_tree_insert(&mapping->page_tree, offset, page);
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		if (likely(!error)) {
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			mapping->nrpages++;
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			__inc_zone_page_state(page, NR_FILE_PAGES);
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			if (PageSwapBacked(page))
				__inc_zone_page_state(page, NR_SHMEM);
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			spin_unlock_irq(&mapping->tree_lock);
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		} else {
			page->mapping = NULL;
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			spin_unlock_irq(&mapping->tree_lock);
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			mem_cgroup_uncharge_cache_page(page);
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			page_cache_release(page);
		}
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		radix_tree_preload_end();
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	} else
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		mem_cgroup_uncharge_cache_page(page);
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out:
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	return error;
}
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EXPORT_SYMBOL(add_to_page_cache_locked);
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int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
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				pgoff_t offset, gfp_t gfp_mask)
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{
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	int ret;

	/*
	 * Splice_read and readahead add shmem/tmpfs pages into the page cache
	 * before shmem_readpage has a chance to mark them as SwapBacked: they
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	 * need to go on the anon lru below, and mem_cgroup_cache_charge
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	 * (called in add_to_page_cache) needs to know where they're going too.
	 */
	if (mapping_cap_swap_backed(mapping))
		SetPageSwapBacked(page);

	ret = add_to_page_cache(page, mapping, offset, gfp_mask);
	if (ret == 0) {
		if (page_is_file_cache(page))
			lru_cache_add_file(page);
		else
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			lru_cache_add_anon(page);
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	}
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	return ret;
}
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EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
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#ifdef CONFIG_NUMA
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struct page *__page_cache_alloc(gfp_t gfp)
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{
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	int n;
	struct page *page;

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	if (cpuset_do_page_mem_spread()) {
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		get_mems_allowed();
		n = cpuset_mem_spread_node();
		page = alloc_pages_exact_node(n, gfp, 0);
		put_mems_allowed();
		return page;
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	}
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	return alloc_pages(gfp, 0);
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}
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EXPORT_SYMBOL(__page_cache_alloc);
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#endif

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static int __sleep_on_page_lock(void *word)
{
	io_schedule();
	return 0;
}

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/*
 * In order to wait for pages to become available there must be
 * waitqueues associated with pages. By using a hash table of
 * waitqueues where the bucket discipline is to maintain all
 * waiters on the same queue and wake all when any of the pages
 * become available, and for the woken contexts to check to be
 * sure the appropriate page became available, this saves space
 * at a cost of "thundering herd" phenomena during rare hash
 * collisions.
 */
static wait_queue_head_t *page_waitqueue(struct page *page)
{
	const struct zone *zone = page_zone(page);

	return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
}

static inline void wake_up_page(struct page *page, int bit)
{
	__wake_up_bit(page_waitqueue(page), &page->flags, bit);
}

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void wait_on_page_bit(struct page *page, int bit_nr)
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{
	DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);

	if (test_bit(bit_nr, &page->flags))
		__wait_on_bit(page_waitqueue(page), &wait, sync_page,
							TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(wait_on_page_bit);

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/**
 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
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 * @page: Page defining the wait queue of interest
 * @waiter: Waiter to add to the queue
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 *
 * Add an arbitrary @waiter to the wait queue for the nominated @page.
 */
void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
{
	wait_queue_head_t *q = page_waitqueue(page);
	unsigned long flags;

	spin_lock_irqsave(&q->lock, flags);
	__add_wait_queue(q, waiter);
	spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL_GPL(add_page_wait_queue);

L
Linus Torvalds 已提交
538
/**
539
 * unlock_page - unlock a locked page
L
Linus Torvalds 已提交
540 541 542 543 544 545 546
 * @page: the page
 *
 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
 * mechananism between PageLocked pages and PageWriteback pages is shared.
 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
 *
N
Nick Piggin 已提交
547 548
 * The mb is necessary to enforce ordering between the clear_bit and the read
 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
L
Linus Torvalds 已提交
549
 */
H
Harvey Harrison 已提交
550
void unlock_page(struct page *page)
L
Linus Torvalds 已提交
551
{
N
Nick Piggin 已提交
552 553 554
	VM_BUG_ON(!PageLocked(page));
	clear_bit_unlock(PG_locked, &page->flags);
	smp_mb__after_clear_bit();
L
Linus Torvalds 已提交
555 556 557 558
	wake_up_page(page, PG_locked);
}
EXPORT_SYMBOL(unlock_page);

559 560 561
/**
 * end_page_writeback - end writeback against a page
 * @page: the page
L
Linus Torvalds 已提交
562 563 564
 */
void end_page_writeback(struct page *page)
{
565 566 567 568 569 570
	if (TestClearPageReclaim(page))
		rotate_reclaimable_page(page);

	if (!test_clear_page_writeback(page))
		BUG();

L
Linus Torvalds 已提交
571 572 573 574 575
	smp_mb__after_clear_bit();
	wake_up_page(page, PG_writeback);
}
EXPORT_SYMBOL(end_page_writeback);

576 577 578
/**
 * __lock_page - get a lock on the page, assuming we need to sleep to get it
 * @page: the page to lock
L
Linus Torvalds 已提交
579
 *
580
 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary.  If some
L
Linus Torvalds 已提交
581 582 583 584
 * random driver's requestfn sets TASK_RUNNING, we could busywait.  However
 * chances are that on the second loop, the block layer's plug list is empty,
 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
 */
H
Harvey Harrison 已提交
585
void __lock_page(struct page *page)
L
Linus Torvalds 已提交
586 587 588 589 590 591 592 593
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);

	__wait_on_bit_lock(page_waitqueue(page), &wait, sync_page,
							TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(__lock_page);

H
Harvey Harrison 已提交
594
int __lock_page_killable(struct page *page)
M
Matthew Wilcox 已提交
595 596 597 598 599 600
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);

	return __wait_on_bit_lock(page_waitqueue(page), &wait,
					sync_page_killable, TASK_KILLABLE);
}
601
EXPORT_SYMBOL_GPL(__lock_page_killable);
M
Matthew Wilcox 已提交
602

603 604 605 606
/**
 * __lock_page_nosync - get a lock on the page, without calling sync_page()
 * @page: the page to lock
 *
607 608 609
 * Variant of lock_page that does not require the caller to hold a reference
 * on the page's mapping.
 */
H
Harvey Harrison 已提交
610
void __lock_page_nosync(struct page *page)
611 612 613 614 615 616
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
	__wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
							TASK_UNINTERRUPTIBLE);
}

617 618 619 620 621 622 623 624 625 626 627 628 629
int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
			 unsigned int flags)
{
	if (!(flags & FAULT_FLAG_ALLOW_RETRY)) {
		__lock_page(page);
		return 1;
	} else {
		up_read(&mm->mmap_sem);
		wait_on_page_locked(page);
		return 0;
	}
}

630 631 632 633 634
/**
 * find_get_page - find and get a page reference
 * @mapping: the address_space to search
 * @offset: the page index
 *
N
Nick Piggin 已提交
635 636
 * Is there a pagecache struct page at the given (mapping, offset) tuple?
 * If yes, increment its refcount and return it; if no, return NULL.
L
Linus Torvalds 已提交
637
 */
N
Nick Piggin 已提交
638
struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
L
Linus Torvalds 已提交
639
{
N
Nick Piggin 已提交
640
	void **pagep;
L
Linus Torvalds 已提交
641 642
	struct page *page;

N
Nick Piggin 已提交
643 644 645 646 647 648
	rcu_read_lock();
repeat:
	page = NULL;
	pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
	if (pagep) {
		page = radix_tree_deref_slot(pagep);
N
Nick Piggin 已提交
649 650 651
		if (unlikely(!page))
			goto out;
		if (radix_tree_deref_retry(page))
N
Nick Piggin 已提交
652 653 654 655 656 657 658 659 660 661 662 663 664 665 666
			goto repeat;

		if (!page_cache_get_speculative(page))
			goto repeat;

		/*
		 * Has the page moved?
		 * This is part of the lockless pagecache protocol. See
		 * include/linux/pagemap.h for details.
		 */
		if (unlikely(page != *pagep)) {
			page_cache_release(page);
			goto repeat;
		}
	}
N
Nick Piggin 已提交
667
out:
N
Nick Piggin 已提交
668 669
	rcu_read_unlock();

L
Linus Torvalds 已提交
670 671 672 673 674 675
	return page;
}
EXPORT_SYMBOL(find_get_page);

/**
 * find_lock_page - locate, pin and lock a pagecache page
676 677
 * @mapping: the address_space to search
 * @offset: the page index
L
Linus Torvalds 已提交
678 679 680 681 682 683
 *
 * Locates the desired pagecache page, locks it, increments its reference
 * count and returns its address.
 *
 * Returns zero if the page was not present. find_lock_page() may sleep.
 */
N
Nick Piggin 已提交
684
struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
L
Linus Torvalds 已提交
685 686 687 688
{
	struct page *page;

repeat:
N
Nick Piggin 已提交
689
	page = find_get_page(mapping, offset);
L
Linus Torvalds 已提交
690
	if (page) {
N
Nick Piggin 已提交
691 692 693 694 695 696
		lock_page(page);
		/* Has the page been truncated? */
		if (unlikely(page->mapping != mapping)) {
			unlock_page(page);
			page_cache_release(page);
			goto repeat;
L
Linus Torvalds 已提交
697
		}
N
Nick Piggin 已提交
698
		VM_BUG_ON(page->index != offset);
L
Linus Torvalds 已提交
699 700 701 702 703 704 705
	}
	return page;
}
EXPORT_SYMBOL(find_lock_page);

/**
 * find_or_create_page - locate or add a pagecache page
706 707 708
 * @mapping: the page's address_space
 * @index: the page's index into the mapping
 * @gfp_mask: page allocation mode
L
Linus Torvalds 已提交
709 710 711 712 713 714 715 716 717 718 719 720 721
 *
 * Locates a page in the pagecache.  If the page is not present, a new page
 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
 * LRU list.  The returned page is locked and has its reference count
 * incremented.
 *
 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
 * allocation!
 *
 * find_or_create_page() returns the desired page's address, or zero on
 * memory exhaustion.
 */
struct page *find_or_create_page(struct address_space *mapping,
722
		pgoff_t index, gfp_t gfp_mask)
L
Linus Torvalds 已提交
723
{
N
Nick Piggin 已提交
724
	struct page *page;
L
Linus Torvalds 已提交
725 726 727 728
	int err;
repeat:
	page = find_lock_page(mapping, index);
	if (!page) {
N
Nick Piggin 已提交
729 730 731
		page = __page_cache_alloc(gfp_mask);
		if (!page)
			return NULL;
N
Nick Piggin 已提交
732 733 734 735 736 737 738 739
		/*
		 * We want a regular kernel memory (not highmem or DMA etc)
		 * allocation for the radix tree nodes, but we need to honour
		 * the context-specific requirements the caller has asked for.
		 * GFP_RECLAIM_MASK collects those requirements.
		 */
		err = add_to_page_cache_lru(page, mapping, index,
			(gfp_mask & GFP_RECLAIM_MASK));
N
Nick Piggin 已提交
740 741 742 743 744
		if (unlikely(err)) {
			page_cache_release(page);
			page = NULL;
			if (err == -EEXIST)
				goto repeat;
L
Linus Torvalds 已提交
745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771
		}
	}
	return page;
}
EXPORT_SYMBOL(find_or_create_page);

/**
 * find_get_pages - gang pagecache lookup
 * @mapping:	The address_space to search
 * @start:	The starting page index
 * @nr_pages:	The maximum number of pages
 * @pages:	Where the resulting pages are placed
 *
 * find_get_pages() will search for and return a group of up to
 * @nr_pages pages in the mapping.  The pages are placed at @pages.
 * find_get_pages() takes a reference against the returned pages.
 *
 * The search returns a group of mapping-contiguous pages with ascending
 * indexes.  There may be holes in the indices due to not-present pages.
 *
 * find_get_pages() returns the number of pages which were found.
 */
unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
			    unsigned int nr_pages, struct page **pages)
{
	unsigned int i;
	unsigned int ret;
N
Nick Piggin 已提交
772 773 774 775 776 777 778 779 780 781 782 783 784
	unsigned int nr_found;

	rcu_read_lock();
restart:
	nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
				(void ***)pages, start, nr_pages);
	ret = 0;
	for (i = 0; i < nr_found; i++) {
		struct page *page;
repeat:
		page = radix_tree_deref_slot((void **)pages[i]);
		if (unlikely(!page))
			continue;
N
Nick Piggin 已提交
785 786 787
		if (radix_tree_deref_retry(page)) {
			if (ret)
				start = pages[ret-1]->index;
N
Nick Piggin 已提交
788
			goto restart;
N
Nick Piggin 已提交
789
		}
N
Nick Piggin 已提交
790 791 792 793 794 795 796 797 798

		if (!page_cache_get_speculative(page))
			goto repeat;

		/* Has the page moved? */
		if (unlikely(page != *((void **)pages[i]))) {
			page_cache_release(page);
			goto repeat;
		}
L
Linus Torvalds 已提交
799

N
Nick Piggin 已提交
800 801 802 803
		pages[ret] = page;
		ret++;
	}
	rcu_read_unlock();
L
Linus Torvalds 已提交
804 805 806
	return ret;
}

807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823
/**
 * find_get_pages_contig - gang contiguous pagecache lookup
 * @mapping:	The address_space to search
 * @index:	The starting page index
 * @nr_pages:	The maximum number of pages
 * @pages:	Where the resulting pages are placed
 *
 * find_get_pages_contig() works exactly like find_get_pages(), except
 * that the returned number of pages are guaranteed to be contiguous.
 *
 * find_get_pages_contig() returns the number of pages which were found.
 */
unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
			       unsigned int nr_pages, struct page **pages)
{
	unsigned int i;
	unsigned int ret;
N
Nick Piggin 已提交
824 825 826 827 828 829 830 831 832 833 834 835 836
	unsigned int nr_found;

	rcu_read_lock();
restart:
	nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
				(void ***)pages, index, nr_pages);
	ret = 0;
	for (i = 0; i < nr_found; i++) {
		struct page *page;
repeat:
		page = radix_tree_deref_slot((void **)pages[i]);
		if (unlikely(!page))
			continue;
N
Nick Piggin 已提交
837
		if (radix_tree_deref_retry(page))
N
Nick Piggin 已提交
838
			goto restart;
839

N
Nick Piggin 已提交
840 841 842 843 844 845 846 847 848
		if (!page_cache_get_speculative(page))
			goto repeat;

		/* Has the page moved? */
		if (unlikely(page != *((void **)pages[i]))) {
			page_cache_release(page);
			goto repeat;
		}

N
Nick Piggin 已提交
849 850 851 852 853 854 855 856 857 858
		/*
		 * must check mapping and index after taking the ref.
		 * otherwise we can get both false positives and false
		 * negatives, which is just confusing to the caller.
		 */
		if (page->mapping == NULL || page->index != index) {
			page_cache_release(page);
			break;
		}

N
Nick Piggin 已提交
859 860
		pages[ret] = page;
		ret++;
861 862
		index++;
	}
N
Nick Piggin 已提交
863 864
	rcu_read_unlock();
	return ret;
865
}
866
EXPORT_SYMBOL(find_get_pages_contig);
867

868 869 870 871 872 873 874 875
/**
 * find_get_pages_tag - find and return pages that match @tag
 * @mapping:	the address_space to search
 * @index:	the starting page index
 * @tag:	the tag index
 * @nr_pages:	the maximum number of pages
 * @pages:	where the resulting pages are placed
 *
L
Linus Torvalds 已提交
876
 * Like find_get_pages, except we only return pages which are tagged with
877
 * @tag.   We update @index to index the next page for the traversal.
L
Linus Torvalds 已提交
878 879 880 881 882 883
 */
unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
			int tag, unsigned int nr_pages, struct page **pages)
{
	unsigned int i;
	unsigned int ret;
N
Nick Piggin 已提交
884 885 886 887 888 889 890 891 892 893 894 895 896
	unsigned int nr_found;

	rcu_read_lock();
restart:
	nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
				(void ***)pages, *index, nr_pages, tag);
	ret = 0;
	for (i = 0; i < nr_found; i++) {
		struct page *page;
repeat:
		page = radix_tree_deref_slot((void **)pages[i]);
		if (unlikely(!page))
			continue;
N
Nick Piggin 已提交
897
		if (radix_tree_deref_retry(page))
N
Nick Piggin 已提交
898 899 900 901 902 903 904 905 906 907 908 909 910 911 912
			goto restart;

		if (!page_cache_get_speculative(page))
			goto repeat;

		/* Has the page moved? */
		if (unlikely(page != *((void **)pages[i]))) {
			page_cache_release(page);
			goto repeat;
		}

		pages[ret] = page;
		ret++;
	}
	rcu_read_unlock();
L
Linus Torvalds 已提交
913 914 915

	if (ret)
		*index = pages[ret - 1]->index + 1;
N
Nick Piggin 已提交
916

L
Linus Torvalds 已提交
917 918
	return ret;
}
919
EXPORT_SYMBOL(find_get_pages_tag);
L
Linus Torvalds 已提交
920

921 922 923 924 925
/**
 * grab_cache_page_nowait - returns locked page at given index in given cache
 * @mapping: target address_space
 * @index: the page index
 *
926
 * Same as grab_cache_page(), but do not wait if the page is unavailable.
L
Linus Torvalds 已提交
927 928 929 930 931 932 933 934
 * This is intended for speculative data generators, where the data can
 * be regenerated if the page couldn't be grabbed.  This routine should
 * be safe to call while holding the lock for another page.
 *
 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
 * and deadlock against the caller's locked page.
 */
struct page *
935
grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
L
Linus Torvalds 已提交
936 937 938 939
{
	struct page *page = find_get_page(mapping, index);

	if (page) {
N
Nick Piggin 已提交
940
		if (trylock_page(page))
L
Linus Torvalds 已提交
941 942 943 944
			return page;
		page_cache_release(page);
		return NULL;
	}
945
	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
N
Nick Piggin 已提交
946
	if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
L
Linus Torvalds 已提交
947 948 949 950 951 952 953
		page_cache_release(page);
		page = NULL;
	}
	return page;
}
EXPORT_SYMBOL(grab_cache_page_nowait);

954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974
/*
 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
 * a _large_ part of the i/o request. Imagine the worst scenario:
 *
 *      ---R__________________________________________B__________
 *         ^ reading here                             ^ bad block(assume 4k)
 *
 * read(R) => miss => readahead(R...B) => media error => frustrating retries
 * => failing the whole request => read(R) => read(R+1) =>
 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
 *
 * It is going insane. Fix it by quickly scaling down the readahead size.
 */
static void shrink_readahead_size_eio(struct file *filp,
					struct file_ra_state *ra)
{
	ra->ra_pages /= 4;
}

975
/**
C
Christoph Hellwig 已提交
976
 * do_generic_file_read - generic file read routine
977 978 979 980 981
 * @filp:	the file to read
 * @ppos:	current file position
 * @desc:	read_descriptor
 * @actor:	read method
 *
L
Linus Torvalds 已提交
982
 * This is a generic file read routine, and uses the
983
 * mapping->a_ops->readpage() function for the actual low-level stuff.
L
Linus Torvalds 已提交
984 985 986 987
 *
 * This is really ugly. But the goto's actually try to clarify some
 * of the logic when it comes to error handling etc.
 */
C
Christoph Hellwig 已提交
988 989
static void do_generic_file_read(struct file *filp, loff_t *ppos,
		read_descriptor_t *desc, read_actor_t actor)
L
Linus Torvalds 已提交
990
{
C
Christoph Hellwig 已提交
991
	struct address_space *mapping = filp->f_mapping;
L
Linus Torvalds 已提交
992
	struct inode *inode = mapping->host;
C
Christoph Hellwig 已提交
993
	struct file_ra_state *ra = &filp->f_ra;
994 995 996 997
	pgoff_t index;
	pgoff_t last_index;
	pgoff_t prev_index;
	unsigned long offset;      /* offset into pagecache page */
998
	unsigned int prev_offset;
L
Linus Torvalds 已提交
999 1000 1001
	int error;

	index = *ppos >> PAGE_CACHE_SHIFT;
1002 1003
	prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
	prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
L
Linus Torvalds 已提交
1004 1005 1006 1007 1008
	last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
	offset = *ppos & ~PAGE_CACHE_MASK;

	for (;;) {
		struct page *page;
1009
		pgoff_t end_index;
N
NeilBrown 已提交
1010
		loff_t isize;
L
Linus Torvalds 已提交
1011 1012 1013 1014 1015
		unsigned long nr, ret;

		cond_resched();
find_page:
		page = find_get_page(mapping, index);
1016
		if (!page) {
1017
			page_cache_sync_readahead(mapping,
1018
					ra, filp,
1019 1020 1021 1022 1023 1024
					index, last_index - index);
			page = find_get_page(mapping, index);
			if (unlikely(page == NULL))
				goto no_cached_page;
		}
		if (PageReadahead(page)) {
1025
			page_cache_async_readahead(mapping,
1026
					ra, filp, page,
1027
					index, last_index - index);
L
Linus Torvalds 已提交
1028
		}
1029 1030 1031 1032
		if (!PageUptodate(page)) {
			if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
					!mapping->a_ops->is_partially_uptodate)
				goto page_not_up_to_date;
N
Nick Piggin 已提交
1033
			if (!trylock_page(page))
1034
				goto page_not_up_to_date;
1035 1036 1037
			/* Did it get truncated before we got the lock? */
			if (!page->mapping)
				goto page_not_up_to_date_locked;
1038 1039 1040 1041 1042
			if (!mapping->a_ops->is_partially_uptodate(page,
								desc, offset))
				goto page_not_up_to_date_locked;
			unlock_page(page);
		}
L
Linus Torvalds 已提交
1043
page_ok:
N
NeilBrown 已提交
1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069
		/*
		 * i_size must be checked after we know the page is Uptodate.
		 *
		 * Checking i_size after the check allows us to calculate
		 * the correct value for "nr", which means the zero-filled
		 * part of the page is not copied back to userspace (unless
		 * another truncate extends the file - this is desired though).
		 */

		isize = i_size_read(inode);
		end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
		if (unlikely(!isize || index > end_index)) {
			page_cache_release(page);
			goto out;
		}

		/* nr is the maximum number of bytes to copy from this page */
		nr = PAGE_CACHE_SIZE;
		if (index == end_index) {
			nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
			if (nr <= offset) {
				page_cache_release(page);
				goto out;
			}
		}
		nr = nr - offset;
L
Linus Torvalds 已提交
1070 1071 1072 1073 1074 1075 1076 1077 1078

		/* If users can be writing to this page using arbitrary
		 * virtual addresses, take care about potential aliasing
		 * before reading the page on the kernel side.
		 */
		if (mapping_writably_mapped(mapping))
			flush_dcache_page(page);

		/*
1079 1080
		 * When a sequential read accesses a page several times,
		 * only mark it as accessed the first time.
L
Linus Torvalds 已提交
1081
		 */
1082
		if (prev_index != index || offset != prev_offset)
L
Linus Torvalds 已提交
1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099
			mark_page_accessed(page);
		prev_index = index;

		/*
		 * Ok, we have the page, and it's up-to-date, so
		 * now we can copy it to user space...
		 *
		 * The actor routine returns how many bytes were actually used..
		 * NOTE! This may not be the same as how much of a user buffer
		 * we filled up (we may be padding etc), so we can only update
		 * "pos" here (the actor routine has to update the user buffer
		 * pointers and the remaining count).
		 */
		ret = actor(desc, page, offset, nr);
		offset += ret;
		index += offset >> PAGE_CACHE_SHIFT;
		offset &= ~PAGE_CACHE_MASK;
J
Jan Kara 已提交
1100
		prev_offset = offset;
L
Linus Torvalds 已提交
1101 1102 1103 1104 1105 1106 1107 1108

		page_cache_release(page);
		if (ret == nr && desc->count)
			continue;
		goto out;

page_not_up_to_date:
		/* Get exclusive access to the page ... */
1109 1110 1111
		error = lock_page_killable(page);
		if (unlikely(error))
			goto readpage_error;
L
Linus Torvalds 已提交
1112

1113
page_not_up_to_date_locked:
N
Nick Piggin 已提交
1114
		/* Did it get truncated before we got the lock? */
L
Linus Torvalds 已提交
1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127
		if (!page->mapping) {
			unlock_page(page);
			page_cache_release(page);
			continue;
		}

		/* Did somebody else fill it already? */
		if (PageUptodate(page)) {
			unlock_page(page);
			goto page_ok;
		}

readpage:
1128 1129 1130 1131 1132 1133
		/*
		 * A previous I/O error may have been due to temporary
		 * failures, eg. multipath errors.
		 * PG_error will be set again if readpage fails.
		 */
		ClearPageError(page);
L
Linus Torvalds 已提交
1134 1135 1136
		/* Start the actual read. The read will unlock the page. */
		error = mapping->a_ops->readpage(filp, page);

1137 1138 1139 1140 1141
		if (unlikely(error)) {
			if (error == AOP_TRUNCATED_PAGE) {
				page_cache_release(page);
				goto find_page;
			}
L
Linus Torvalds 已提交
1142
			goto readpage_error;
1143
		}
L
Linus Torvalds 已提交
1144 1145

		if (!PageUptodate(page)) {
1146 1147 1148
			error = lock_page_killable(page);
			if (unlikely(error))
				goto readpage_error;
L
Linus Torvalds 已提交
1149 1150 1151
			if (!PageUptodate(page)) {
				if (page->mapping == NULL) {
					/*
1152
					 * invalidate_mapping_pages got it
L
Linus Torvalds 已提交
1153 1154 1155 1156 1157 1158
					 */
					unlock_page(page);
					page_cache_release(page);
					goto find_page;
				}
				unlock_page(page);
1159
				shrink_readahead_size_eio(filp, ra);
1160 1161
				error = -EIO;
				goto readpage_error;
L
Linus Torvalds 已提交
1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178
			}
			unlock_page(page);
		}

		goto page_ok;

readpage_error:
		/* UHHUH! A synchronous read error occurred. Report it */
		desc->error = error;
		page_cache_release(page);
		goto out;

no_cached_page:
		/*
		 * Ok, it wasn't cached, so we need to create a new
		 * page..
		 */
N
Nick Piggin 已提交
1179 1180 1181 1182
		page = page_cache_alloc_cold(mapping);
		if (!page) {
			desc->error = -ENOMEM;
			goto out;
L
Linus Torvalds 已提交
1183
		}
N
Nick Piggin 已提交
1184
		error = add_to_page_cache_lru(page, mapping,
L
Linus Torvalds 已提交
1185 1186
						index, GFP_KERNEL);
		if (error) {
N
Nick Piggin 已提交
1187
			page_cache_release(page);
L
Linus Torvalds 已提交
1188 1189 1190 1191 1192 1193 1194 1195 1196
			if (error == -EEXIST)
				goto find_page;
			desc->error = error;
			goto out;
		}
		goto readpage;
	}

out:
1197 1198 1199
	ra->prev_pos = prev_index;
	ra->prev_pos <<= PAGE_CACHE_SHIFT;
	ra->prev_pos |= prev_offset;
L
Linus Torvalds 已提交
1200

1201
	*ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1202
	file_accessed(filp);
L
Linus Torvalds 已提交
1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242
}

int file_read_actor(read_descriptor_t *desc, struct page *page,
			unsigned long offset, unsigned long size)
{
	char *kaddr;
	unsigned long left, count = desc->count;

	if (size > count)
		size = count;

	/*
	 * Faults on the destination of a read are common, so do it before
	 * taking the kmap.
	 */
	if (!fault_in_pages_writeable(desc->arg.buf, size)) {
		kaddr = kmap_atomic(page, KM_USER0);
		left = __copy_to_user_inatomic(desc->arg.buf,
						kaddr + offset, size);
		kunmap_atomic(kaddr, KM_USER0);
		if (left == 0)
			goto success;
	}

	/* Do it the slow way */
	kaddr = kmap(page);
	left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
	kunmap(page);

	if (left) {
		size -= left;
		desc->error = -EFAULT;
	}
success:
	desc->count = count - size;
	desc->written += size;
	desc->arg.buf += size;
	return size;
}

1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281
/*
 * Performs necessary checks before doing a write
 * @iov:	io vector request
 * @nr_segs:	number of segments in the iovec
 * @count:	number of bytes to write
 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
 *
 * Adjust number of segments and amount of bytes to write (nr_segs should be
 * properly initialized first). Returns appropriate error code that caller
 * should return or zero in case that write should be allowed.
 */
int generic_segment_checks(const struct iovec *iov,
			unsigned long *nr_segs, size_t *count, int access_flags)
{
	unsigned long   seg;
	size_t cnt = 0;
	for (seg = 0; seg < *nr_segs; seg++) {
		const struct iovec *iv = &iov[seg];

		/*
		 * If any segment has a negative length, or the cumulative
		 * length ever wraps negative then return -EINVAL.
		 */
		cnt += iv->iov_len;
		if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
			return -EINVAL;
		if (access_ok(access_flags, iv->iov_base, iv->iov_len))
			continue;
		if (seg == 0)
			return -EFAULT;
		*nr_segs = seg;
		cnt -= iv->iov_len;	/* This segment is no good */
		break;
	}
	*count = cnt;
	return 0;
}
EXPORT_SYMBOL(generic_segment_checks);

1282
/**
H
Henrik Kretzschmar 已提交
1283
 * generic_file_aio_read - generic filesystem read routine
1284 1285 1286
 * @iocb:	kernel I/O control block
 * @iov:	io vector request
 * @nr_segs:	number of segments in the iovec
H
Henrik Kretzschmar 已提交
1287
 * @pos:	current file position
1288
 *
L
Linus Torvalds 已提交
1289 1290 1291 1292
 * This is the "read()" routine for all filesystems
 * that can use the page cache directly.
 */
ssize_t
1293 1294
generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos)
L
Linus Torvalds 已提交
1295 1296 1297
{
	struct file *filp = iocb->ki_filp;
	ssize_t retval;
1298
	unsigned long seg = 0;
L
Linus Torvalds 已提交
1299
	size_t count;
1300
	loff_t *ppos = &iocb->ki_pos;
L
Linus Torvalds 已提交
1301 1302

	count = 0;
1303 1304 1305
	retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
	if (retval)
		return retval;
L
Linus Torvalds 已提交
1306 1307 1308

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (filp->f_flags & O_DIRECT) {
1309
		loff_t size;
L
Linus Torvalds 已提交
1310 1311 1312 1313 1314 1315 1316 1317 1318
		struct address_space *mapping;
		struct inode *inode;

		mapping = filp->f_mapping;
		inode = mapping->host;
		if (!count)
			goto out; /* skip atime */
		size = i_size_read(inode);
		if (pos < size) {
1319 1320
			retval = filemap_write_and_wait_range(mapping, pos,
					pos + iov_length(iov, nr_segs) - 1);
1321 1322 1323 1324
			if (!retval) {
				retval = mapping->a_ops->direct_IO(READ, iocb,
							iov, pos, nr_segs);
			}
1325
			if (retval > 0) {
L
Linus Torvalds 已提交
1326
				*ppos = pos + retval;
1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338
				count -= retval;
			}

			/*
			 * Btrfs can have a short DIO read if we encounter
			 * compressed extents, so if there was an error, or if
			 * we've already read everything we wanted to, or if
			 * there was a short read because we hit EOF, go ahead
			 * and return.  Otherwise fallthrough to buffered io for
			 * the rest of the read.
			 */
			if (retval < 0 || !count || *ppos >= size) {
H
Hugh Dickins 已提交
1339 1340 1341
				file_accessed(filp);
				goto out;
			}
1342
		}
L
Linus Torvalds 已提交
1343 1344
	}

1345
	count = retval;
H
Hugh Dickins 已提交
1346 1347
	for (seg = 0; seg < nr_segs; seg++) {
		read_descriptor_t desc;
1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361
		loff_t offset = 0;

		/*
		 * If we did a short DIO read we need to skip the section of the
		 * iov that we've already read data into.
		 */
		if (count) {
			if (count > iov[seg].iov_len) {
				count -= iov[seg].iov_len;
				continue;
			}
			offset = count;
			count = 0;
		}
L
Linus Torvalds 已提交
1362

H
Hugh Dickins 已提交
1363
		desc.written = 0;
1364 1365
		desc.arg.buf = iov[seg].iov_base + offset;
		desc.count = iov[seg].iov_len - offset;
H
Hugh Dickins 已提交
1366 1367 1368 1369 1370 1371 1372 1373
		if (desc.count == 0)
			continue;
		desc.error = 0;
		do_generic_file_read(filp, ppos, &desc, file_read_actor);
		retval += desc.written;
		if (desc.error) {
			retval = retval ?: desc.error;
			break;
L
Linus Torvalds 已提交
1374
		}
H
Hugh Dickins 已提交
1375 1376
		if (desc.count > 0)
			break;
L
Linus Torvalds 已提交
1377 1378 1379 1380 1381 1382 1383 1384
	}
out:
	return retval;
}
EXPORT_SYMBOL(generic_file_aio_read);

static ssize_t
do_readahead(struct address_space *mapping, struct file *filp,
1385
	     pgoff_t index, unsigned long nr)
L
Linus Torvalds 已提交
1386 1387 1388 1389
{
	if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
		return -EINVAL;

1390
	force_page_cache_readahead(mapping, filp, index, nr);
L
Linus Torvalds 已提交
1391 1392 1393
	return 0;
}

1394
SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
L
Linus Torvalds 已提交
1395 1396 1397 1398 1399 1400 1401 1402 1403
{
	ssize_t ret;
	struct file *file;

	ret = -EBADF;
	file = fget(fd);
	if (file) {
		if (file->f_mode & FMODE_READ) {
			struct address_space *mapping = file->f_mapping;
1404 1405
			pgoff_t start = offset >> PAGE_CACHE_SHIFT;
			pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
L
Linus Torvalds 已提交
1406 1407 1408 1409 1410 1411 1412
			unsigned long len = end - start + 1;
			ret = do_readahead(mapping, file, start, len);
		}
		fput(file);
	}
	return ret;
}
1413 1414 1415 1416 1417 1418 1419
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
asmlinkage long SyS_readahead(long fd, loff_t offset, long count)
{
	return SYSC_readahead((int) fd, offset, (size_t) count);
}
SYSCALL_ALIAS(sys_readahead, SyS_readahead);
#endif
L
Linus Torvalds 已提交
1420 1421

#ifdef CONFIG_MMU
1422 1423 1424 1425 1426
/**
 * page_cache_read - adds requested page to the page cache if not already there
 * @file:	file to read
 * @offset:	page index
 *
L
Linus Torvalds 已提交
1427 1428 1429
 * This adds the requested page to the page cache if it isn't already there,
 * and schedules an I/O to read in its contents from disk.
 */
H
Harvey Harrison 已提交
1430
static int page_cache_read(struct file *file, pgoff_t offset)
L
Linus Torvalds 已提交
1431 1432 1433
{
	struct address_space *mapping = file->f_mapping;
	struct page *page; 
1434
	int ret;
L
Linus Torvalds 已提交
1435

1436 1437 1438 1439 1440 1441 1442 1443 1444 1445
	do {
		page = page_cache_alloc_cold(mapping);
		if (!page)
			return -ENOMEM;

		ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
		if (ret == 0)
			ret = mapping->a_ops->readpage(file, page);
		else if (ret == -EEXIST)
			ret = 0; /* losing race to add is OK */
L
Linus Torvalds 已提交
1446 1447 1448

		page_cache_release(page);

1449 1450 1451
	} while (ret == AOP_TRUNCATED_PAGE);
		
	return ret;
L
Linus Torvalds 已提交
1452 1453 1454 1455
}

#define MMAP_LOTSAMISS  (100)

1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471
/*
 * Synchronous readahead happens when we don't even find
 * a page in the page cache at all.
 */
static void do_sync_mmap_readahead(struct vm_area_struct *vma,
				   struct file_ra_state *ra,
				   struct file *file,
				   pgoff_t offset)
{
	unsigned long ra_pages;
	struct address_space *mapping = file->f_mapping;

	/* If we don't want any read-ahead, don't bother */
	if (VM_RandomReadHint(vma))
		return;

1472 1473
	if (VM_SequentialReadHint(vma) ||
			offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) {
1474 1475
		page_cache_sync_readahead(mapping, ra, file, offset,
					  ra->ra_pages);
1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488
		return;
	}

	if (ra->mmap_miss < INT_MAX)
		ra->mmap_miss++;

	/*
	 * Do we miss much more than hit in this file? If so,
	 * stop bothering with read-ahead. It will only hurt.
	 */
	if (ra->mmap_miss > MMAP_LOTSAMISS)
		return;

1489 1490 1491
	/*
	 * mmap read-around
	 */
1492 1493
	ra_pages = max_sane_readahead(ra->ra_pages);
	if (ra_pages) {
1494 1495 1496 1497
		ra->start = max_t(long, 0, offset - ra_pages/2);
		ra->size = ra_pages;
		ra->async_size = 0;
		ra_submit(ra, mapping, file);
1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518
	}
}

/*
 * Asynchronous readahead happens when we find the page and PG_readahead,
 * so we want to possibly extend the readahead further..
 */
static void do_async_mmap_readahead(struct vm_area_struct *vma,
				    struct file_ra_state *ra,
				    struct file *file,
				    struct page *page,
				    pgoff_t offset)
{
	struct address_space *mapping = file->f_mapping;

	/* If we don't want any read-ahead, don't bother */
	if (VM_RandomReadHint(vma))
		return;
	if (ra->mmap_miss > 0)
		ra->mmap_miss--;
	if (PageReadahead(page))
1519 1520
		page_cache_async_readahead(mapping, ra, file,
					   page, offset, ra->ra_pages);
1521 1522
}

1523
/**
1524
 * filemap_fault - read in file data for page fault handling
N
Nick Piggin 已提交
1525 1526
 * @vma:	vma in which the fault was taken
 * @vmf:	struct vm_fault containing details of the fault
1527
 *
1528
 * filemap_fault() is invoked via the vma operations vector for a
L
Linus Torvalds 已提交
1529 1530 1531 1532 1533 1534
 * mapped memory region to read in file data during a page fault.
 *
 * The goto's are kind of ugly, but this streamlines the normal case of having
 * it in the page cache, and handles the special cases reasonably without
 * having a lot of duplicated code.
 */
N
Nick Piggin 已提交
1535
int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
L
Linus Torvalds 已提交
1536 1537
{
	int error;
1538
	struct file *file = vma->vm_file;
L
Linus Torvalds 已提交
1539 1540 1541
	struct address_space *mapping = file->f_mapping;
	struct file_ra_state *ra = &file->f_ra;
	struct inode *inode = mapping->host;
1542
	pgoff_t offset = vmf->pgoff;
L
Linus Torvalds 已提交
1543
	struct page *page;
J
Jan Kara 已提交
1544
	pgoff_t size;
N
Nick Piggin 已提交
1545
	int ret = 0;
L
Linus Torvalds 已提交
1546 1547

	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1548
	if (offset >= size)
1549
		return VM_FAULT_SIGBUS;
L
Linus Torvalds 已提交
1550 1551 1552 1553

	/*
	 * Do we have something in the page cache already?
	 */
1554 1555
	page = find_get_page(mapping, offset);
	if (likely(page)) {
L
Linus Torvalds 已提交
1556
		/*
1557 1558
		 * We found the page, so try async readahead before
		 * waiting for the lock.
L
Linus Torvalds 已提交
1559
		 */
1560 1561 1562 1563 1564 1565 1566
		do_async_mmap_readahead(vma, ra, file, page, offset);
	} else {
		/* No page in the page cache at all */
		do_sync_mmap_readahead(vma, ra, file, offset);
		count_vm_event(PGMAJFAULT);
		ret = VM_FAULT_MAJOR;
retry_find:
1567
		page = find_get_page(mapping, offset);
L
Linus Torvalds 已提交
1568 1569 1570 1571
		if (!page)
			goto no_cached_page;
	}

1572 1573
	if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
		page_cache_release(page);
1574
		return ret | VM_FAULT_RETRY;
1575
	}
1576 1577 1578 1579 1580 1581 1582 1583 1584

	/* Did it get truncated? */
	if (unlikely(page->mapping != mapping)) {
		unlock_page(page);
		put_page(page);
		goto retry_find;
	}
	VM_BUG_ON(page->index != offset);

L
Linus Torvalds 已提交
1585
	/*
1586 1587
	 * We have a locked page in the page cache, now we need to check
	 * that it's up-to-date. If not, it is going to be due to an error.
L
Linus Torvalds 已提交
1588
	 */
1589
	if (unlikely(!PageUptodate(page)))
L
Linus Torvalds 已提交
1590 1591
		goto page_not_uptodate;

1592 1593 1594 1595
	/*
	 * Found the page and have a reference on it.
	 * We must recheck i_size under page lock.
	 */
1596
	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1597
	if (unlikely(offset >= size)) {
1598
		unlock_page(page);
1599
		page_cache_release(page);
1600
		return VM_FAULT_SIGBUS;
1601 1602
	}

1603
	ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT;
N
Nick Piggin 已提交
1604
	vmf->page = page;
N
Nick Piggin 已提交
1605
	return ret | VM_FAULT_LOCKED;
L
Linus Torvalds 已提交
1606 1607 1608 1609 1610 1611

no_cached_page:
	/*
	 * We're only likely to ever get here if MADV_RANDOM is in
	 * effect.
	 */
1612
	error = page_cache_read(file, offset);
L
Linus Torvalds 已提交
1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627

	/*
	 * The page we want has now been added to the page cache.
	 * In the unlikely event that someone removed it in the
	 * meantime, we'll just come back here and read it again.
	 */
	if (error >= 0)
		goto retry_find;

	/*
	 * An error return from page_cache_read can result if the
	 * system is low on memory, or a problem occurs while trying
	 * to schedule I/O.
	 */
	if (error == -ENOMEM)
N
Nick Piggin 已提交
1628 1629
		return VM_FAULT_OOM;
	return VM_FAULT_SIGBUS;
L
Linus Torvalds 已提交
1630 1631 1632 1633 1634 1635 1636 1637 1638

page_not_uptodate:
	/*
	 * Umm, take care of errors if the page isn't up-to-date.
	 * Try to re-read it _once_. We do this synchronously,
	 * because there really aren't any performance issues here
	 * and we need to check for errors.
	 */
	ClearPageError(page);
1639
	error = mapping->a_ops->readpage(file, page);
1640 1641 1642 1643 1644
	if (!error) {
		wait_on_page_locked(page);
		if (!PageUptodate(page))
			error = -EIO;
	}
1645 1646 1647
	page_cache_release(page);

	if (!error || error == AOP_TRUNCATED_PAGE)
1648
		goto retry_find;
L
Linus Torvalds 已提交
1649

1650
	/* Things didn't work out. Return zero to tell the mm layer so. */
1651
	shrink_readahead_size_eio(file, ra);
N
Nick Piggin 已提交
1652
	return VM_FAULT_SIGBUS;
1653 1654 1655
}
EXPORT_SYMBOL(filemap_fault);

1656
const struct vm_operations_struct generic_file_vm_ops = {
1657
	.fault		= filemap_fault,
L
Linus Torvalds 已提交
1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669
};

/* This is used for a general mmap of a disk file */

int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
{
	struct address_space *mapping = file->f_mapping;

	if (!mapping->a_ops->readpage)
		return -ENOEXEC;
	file_accessed(file);
	vma->vm_ops = &generic_file_vm_ops;
N
Nick Piggin 已提交
1670
	vma->vm_flags |= VM_CAN_NONLINEAR;
L
Linus Torvalds 已提交
1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696
	return 0;
}

/*
 * This is for filesystems which do not implement ->writepage.
 */
int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
{
	if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
		return -EINVAL;
	return generic_file_mmap(file, vma);
}
#else
int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
{
	return -ENOSYS;
}
int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
{
	return -ENOSYS;
}
#endif /* CONFIG_MMU */

EXPORT_SYMBOL(generic_file_mmap);
EXPORT_SYMBOL(generic_file_readonly_mmap);

1697
static struct page *__read_cache_page(struct address_space *mapping,
1698
				pgoff_t index,
L
Linus Torvalds 已提交
1699
				int (*filler)(void *,struct page*),
1700 1701
				void *data,
				gfp_t gfp)
L
Linus Torvalds 已提交
1702
{
N
Nick Piggin 已提交
1703
	struct page *page;
L
Linus Torvalds 已提交
1704 1705 1706 1707
	int err;
repeat:
	page = find_get_page(mapping, index);
	if (!page) {
1708
		page = __page_cache_alloc(gfp | __GFP_COLD);
N
Nick Piggin 已提交
1709 1710 1711 1712 1713 1714 1715
		if (!page)
			return ERR_PTR(-ENOMEM);
		err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
		if (unlikely(err)) {
			page_cache_release(page);
			if (err == -EEXIST)
				goto repeat;
L
Linus Torvalds 已提交
1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727
			/* Presumably ENOMEM for radix tree node */
			return ERR_PTR(err);
		}
		err = filler(data, page);
		if (err < 0) {
			page_cache_release(page);
			page = ERR_PTR(err);
		}
	}
	return page;
}

1728
static struct page *do_read_cache_page(struct address_space *mapping,
1729
				pgoff_t index,
L
Linus Torvalds 已提交
1730
				int (*filler)(void *,struct page*),
1731 1732 1733
				void *data,
				gfp_t gfp)

L
Linus Torvalds 已提交
1734 1735 1736 1737 1738
{
	struct page *page;
	int err;

retry:
1739
	page = __read_cache_page(mapping, index, filler, data, gfp);
L
Linus Torvalds 已提交
1740
	if (IS_ERR(page))
1741
		return page;
L
Linus Torvalds 已提交
1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757
	if (PageUptodate(page))
		goto out;

	lock_page(page);
	if (!page->mapping) {
		unlock_page(page);
		page_cache_release(page);
		goto retry;
	}
	if (PageUptodate(page)) {
		unlock_page(page);
		goto out;
	}
	err = filler(data, page);
	if (err < 0) {
		page_cache_release(page);
1758
		return ERR_PTR(err);
L
Linus Torvalds 已提交
1759
	}
1760
out:
1761 1762 1763
	mark_page_accessed(page);
	return page;
}
1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786

/**
 * read_cache_page_async - read into page cache, fill it if needed
 * @mapping:	the page's address_space
 * @index:	the page index
 * @filler:	function to perform the read
 * @data:	destination for read data
 *
 * Same as read_cache_page, but don't wait for page to become unlocked
 * after submitting it to the filler.
 *
 * Read into the page cache. If a page already exists, and PageUptodate() is
 * not set, try to fill the page but don't wait for it to become unlocked.
 *
 * If the page does not get brought uptodate, return -EIO.
 */
struct page *read_cache_page_async(struct address_space *mapping,
				pgoff_t index,
				int (*filler)(void *,struct page*),
				void *data)
{
	return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
}
1787 1788
EXPORT_SYMBOL(read_cache_page_async);

1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824
static struct page *wait_on_page_read(struct page *page)
{
	if (!IS_ERR(page)) {
		wait_on_page_locked(page);
		if (!PageUptodate(page)) {
			page_cache_release(page);
			page = ERR_PTR(-EIO);
		}
	}
	return page;
}

/**
 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
 * @mapping:	the page's address_space
 * @index:	the page index
 * @gfp:	the page allocator flags to use if allocating
 *
 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
 * any new page allocations done using the specified allocation flags. Note
 * that the Radix tree operations will still use GFP_KERNEL, so you can't
 * expect to do this atomically or anything like that - but you can pass in
 * other page requirements.
 *
 * If the page does not get brought uptodate, return -EIO.
 */
struct page *read_cache_page_gfp(struct address_space *mapping,
				pgoff_t index,
				gfp_t gfp)
{
	filler_t *filler = (filler_t *)mapping->a_ops->readpage;

	return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
}
EXPORT_SYMBOL(read_cache_page_gfp);

1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837
/**
 * read_cache_page - read into page cache, fill it if needed
 * @mapping:	the page's address_space
 * @index:	the page index
 * @filler:	function to perform the read
 * @data:	destination for read data
 *
 * Read into the page cache. If a page already exists, and PageUptodate() is
 * not set, try to fill the page then wait for it to become unlocked.
 *
 * If the page does not get brought uptodate, return -EIO.
 */
struct page *read_cache_page(struct address_space *mapping,
1838
				pgoff_t index,
1839 1840 1841
				int (*filler)(void *,struct page*),
				void *data)
{
1842
	return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
L
Linus Torvalds 已提交
1843 1844 1845 1846 1847 1848 1849 1850 1851
}
EXPORT_SYMBOL(read_cache_page);

/*
 * The logic we want is
 *
 *	if suid or (sgid and xgrp)
 *		remove privs
 */
1852
int should_remove_suid(struct dentry *dentry)
L
Linus Torvalds 已提交
1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867
{
	mode_t mode = dentry->d_inode->i_mode;
	int kill = 0;

	/* suid always must be killed */
	if (unlikely(mode & S_ISUID))
		kill = ATTR_KILL_SUID;

	/*
	 * sgid without any exec bits is just a mandatory locking mark; leave
	 * it alone.  If some exec bits are set, it's a real sgid; kill it.
	 */
	if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
		kill |= ATTR_KILL_SGID;

1868
	if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1869
		return kill;
L
Linus Torvalds 已提交
1870

1871 1872
	return 0;
}
M
Mark Fasheh 已提交
1873
EXPORT_SYMBOL(should_remove_suid);
1874

1875
static int __remove_suid(struct dentry *dentry, int kill)
1876 1877 1878 1879 1880 1881 1882
{
	struct iattr newattrs;

	newattrs.ia_valid = ATTR_FORCE | kill;
	return notify_change(dentry, &newattrs);
}

1883
int file_remove_suid(struct file *file)
1884
{
1885
	struct dentry *dentry = file->f_path.dentry;
1886 1887 1888
	int killsuid = should_remove_suid(dentry);
	int killpriv = security_inode_need_killpriv(dentry);
	int error = 0;
1889

1890 1891 1892 1893 1894 1895
	if (killpriv < 0)
		return killpriv;
	if (killpriv)
		error = security_inode_killpriv(dentry);
	if (!error && killsuid)
		error = __remove_suid(dentry, killsuid);
1896

1897
	return error;
L
Linus Torvalds 已提交
1898
}
1899
EXPORT_SYMBOL(file_remove_suid);
L
Linus Torvalds 已提交
1900

N
Nick Piggin 已提交
1901
static size_t __iovec_copy_from_user_inatomic(char *vaddr,
L
Linus Torvalds 已提交
1902 1903
			const struct iovec *iov, size_t base, size_t bytes)
{
1904
	size_t copied = 0, left = 0;
L
Linus Torvalds 已提交
1905 1906 1907 1908 1909 1910

	while (bytes) {
		char __user *buf = iov->iov_base + base;
		int copy = min(bytes, iov->iov_len - base);

		base = 0;
1911
		left = __copy_from_user_inatomic(vaddr, buf, copy);
L
Linus Torvalds 已提交
1912 1913 1914 1915 1916
		copied += copy;
		bytes -= copy;
		vaddr += copy;
		iov++;

1917
		if (unlikely(left))
L
Linus Torvalds 已提交
1918 1919 1920 1921 1922
			break;
	}
	return copied - left;
}

N
Nick Piggin 已提交
1923 1924
/*
 * Copy as much as we can into the page and return the number of bytes which
1925
 * were successfully copied.  If a fault is encountered then return the number of
N
Nick Piggin 已提交
1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938
 * bytes which were copied.
 */
size_t iov_iter_copy_from_user_atomic(struct page *page,
		struct iov_iter *i, unsigned long offset, size_t bytes)
{
	char *kaddr;
	size_t copied;

	BUG_ON(!in_atomic());
	kaddr = kmap_atomic(page, KM_USER0);
	if (likely(i->nr_segs == 1)) {
		int left;
		char __user *buf = i->iov->iov_base + i->iov_offset;
1939
		left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
N
Nick Piggin 已提交
1940 1941 1942 1943 1944 1945 1946 1947 1948
		copied = bytes - left;
	} else {
		copied = __iovec_copy_from_user_inatomic(kaddr + offset,
						i->iov, i->iov_offset, bytes);
	}
	kunmap_atomic(kaddr, KM_USER0);

	return copied;
}
N
Nick Piggin 已提交
1949
EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
N
Nick Piggin 已提交
1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966

/*
 * This has the same sideeffects and return value as
 * iov_iter_copy_from_user_atomic().
 * The difference is that it attempts to resolve faults.
 * Page must not be locked.
 */
size_t iov_iter_copy_from_user(struct page *page,
		struct iov_iter *i, unsigned long offset, size_t bytes)
{
	char *kaddr;
	size_t copied;

	kaddr = kmap(page);
	if (likely(i->nr_segs == 1)) {
		int left;
		char __user *buf = i->iov->iov_base + i->iov_offset;
1967
		left = __copy_from_user(kaddr + offset, buf, bytes);
N
Nick Piggin 已提交
1968 1969 1970 1971 1972 1973 1974 1975
		copied = bytes - left;
	} else {
		copied = __iovec_copy_from_user_inatomic(kaddr + offset,
						i->iov, i->iov_offset, bytes);
	}
	kunmap(page);
	return copied;
}
N
Nick Piggin 已提交
1976
EXPORT_SYMBOL(iov_iter_copy_from_user);
N
Nick Piggin 已提交
1977

N
Nick Piggin 已提交
1978
void iov_iter_advance(struct iov_iter *i, size_t bytes)
N
Nick Piggin 已提交
1979
{
N
Nick Piggin 已提交
1980 1981
	BUG_ON(i->count < bytes);

N
Nick Piggin 已提交
1982 1983
	if (likely(i->nr_segs == 1)) {
		i->iov_offset += bytes;
N
Nick Piggin 已提交
1984
		i->count -= bytes;
N
Nick Piggin 已提交
1985 1986 1987 1988
	} else {
		const struct iovec *iov = i->iov;
		size_t base = i->iov_offset;

1989 1990
		/*
		 * The !iov->iov_len check ensures we skip over unlikely
N
Nick Piggin 已提交
1991
		 * zero-length segments (without overruning the iovec).
1992
		 */
1993
		while (bytes || unlikely(i->count && !iov->iov_len)) {
N
Nick Piggin 已提交
1994
			int copy;
N
Nick Piggin 已提交
1995

N
Nick Piggin 已提交
1996 1997 1998
			copy = min(bytes, iov->iov_len - base);
			BUG_ON(!i->count || i->count < copy);
			i->count -= copy;
N
Nick Piggin 已提交
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
			bytes -= copy;
			base += copy;
			if (iov->iov_len == base) {
				iov++;
				base = 0;
			}
		}
		i->iov = iov;
		i->iov_offset = base;
	}
}
N
Nick Piggin 已提交
2010
EXPORT_SYMBOL(iov_iter_advance);
N
Nick Piggin 已提交
2011

2012 2013 2014 2015 2016 2017 2018 2019 2020 2021
/*
 * Fault in the first iovec of the given iov_iter, to a maximum length
 * of bytes. Returns 0 on success, or non-zero if the memory could not be
 * accessed (ie. because it is an invalid address).
 *
 * writev-intensive code may want this to prefault several iovecs -- that
 * would be possible (callers must not rely on the fact that _only_ the
 * first iovec will be faulted with the current implementation).
 */
int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
N
Nick Piggin 已提交
2022 2023
{
	char __user *buf = i->iov->iov_base + i->iov_offset;
2024 2025
	bytes = min(bytes, i->iov->iov_len - i->iov_offset);
	return fault_in_pages_readable(buf, bytes);
N
Nick Piggin 已提交
2026
}
N
Nick Piggin 已提交
2027
EXPORT_SYMBOL(iov_iter_fault_in_readable);
N
Nick Piggin 已提交
2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039

/*
 * Return the count of just the current iov_iter segment.
 */
size_t iov_iter_single_seg_count(struct iov_iter *i)
{
	const struct iovec *iov = i->iov;
	if (i->nr_segs == 1)
		return i->count;
	else
		return min(i->count, iov->iov_len - i->iov_offset);
}
N
Nick Piggin 已提交
2040
EXPORT_SYMBOL(iov_iter_single_seg_count);
N
Nick Piggin 已提交
2041

L
Linus Torvalds 已提交
2042 2043 2044
/*
 * Performs necessary checks before doing a write
 *
2045
 * Can adjust writing position or amount of bytes to write.
L
Linus Torvalds 已提交
2046 2047 2048 2049 2050 2051
 * Returns appropriate error code that caller should return or
 * zero in case that write should be allowed.
 */
inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
{
	struct inode *inode = file->f_mapping->host;
J
Jiri Slaby 已提交
2052
	unsigned long limit = rlimit(RLIMIT_FSIZE);
L
Linus Torvalds 已提交
2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103

        if (unlikely(*pos < 0))
                return -EINVAL;

	if (!isblk) {
		/* FIXME: this is for backwards compatibility with 2.4 */
		if (file->f_flags & O_APPEND)
                        *pos = i_size_read(inode);

		if (limit != RLIM_INFINITY) {
			if (*pos >= limit) {
				send_sig(SIGXFSZ, current, 0);
				return -EFBIG;
			}
			if (*count > limit - (typeof(limit))*pos) {
				*count = limit - (typeof(limit))*pos;
			}
		}
	}

	/*
	 * LFS rule
	 */
	if (unlikely(*pos + *count > MAX_NON_LFS &&
				!(file->f_flags & O_LARGEFILE))) {
		if (*pos >= MAX_NON_LFS) {
			return -EFBIG;
		}
		if (*count > MAX_NON_LFS - (unsigned long)*pos) {
			*count = MAX_NON_LFS - (unsigned long)*pos;
		}
	}

	/*
	 * Are we about to exceed the fs block limit ?
	 *
	 * If we have written data it becomes a short write.  If we have
	 * exceeded without writing data we send a signal and return EFBIG.
	 * Linus frestrict idea will clean these up nicely..
	 */
	if (likely(!isblk)) {
		if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
			if (*count || *pos > inode->i_sb->s_maxbytes) {
				return -EFBIG;
			}
			/* zero-length writes at ->s_maxbytes are OK */
		}

		if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
			*count = inode->i_sb->s_maxbytes - *pos;
	} else {
2104
#ifdef CONFIG_BLOCK
L
Linus Torvalds 已提交
2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115
		loff_t isize;
		if (bdev_read_only(I_BDEV(inode)))
			return -EPERM;
		isize = i_size_read(inode);
		if (*pos >= isize) {
			if (*count || *pos > isize)
				return -ENOSPC;
		}

		if (*pos + *count > isize)
			*count = isize - *pos;
2116 2117 2118
#else
		return -EPERM;
#endif
L
Linus Torvalds 已提交
2119 2120 2121 2122 2123
	}
	return 0;
}
EXPORT_SYMBOL(generic_write_checks);

2124 2125 2126 2127 2128 2129
int pagecache_write_begin(struct file *file, struct address_space *mapping,
				loff_t pos, unsigned len, unsigned flags,
				struct page **pagep, void **fsdata)
{
	const struct address_space_operations *aops = mapping->a_ops;

2130
	return aops->write_begin(file, mapping, pos, len, flags,
2131 2132 2133 2134 2135 2136 2137 2138 2139 2140
							pagep, fsdata);
}
EXPORT_SYMBOL(pagecache_write_begin);

int pagecache_write_end(struct file *file, struct address_space *mapping,
				loff_t pos, unsigned len, unsigned copied,
				struct page *page, void *fsdata)
{
	const struct address_space_operations *aops = mapping->a_ops;

2141 2142
	mark_page_accessed(page);
	return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2143 2144 2145
}
EXPORT_SYMBOL(pagecache_write_end);

L
Linus Torvalds 已提交
2146 2147 2148 2149 2150 2151 2152 2153 2154
ssize_t
generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
		unsigned long *nr_segs, loff_t pos, loff_t *ppos,
		size_t count, size_t ocount)
{
	struct file	*file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	struct inode	*inode = mapping->host;
	ssize_t		written;
2155 2156
	size_t		write_len;
	pgoff_t		end;
L
Linus Torvalds 已提交
2157 2158 2159 2160

	if (count != ocount)
		*nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);

2161 2162 2163
	write_len = iov_length(iov, *nr_segs);
	end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;

2164
	written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2165 2166 2167 2168 2169 2170 2171
	if (written)
		goto out;

	/*
	 * After a write we want buffered reads to be sure to go to disk to get
	 * the new data.  We invalidate clean cached page from the region we're
	 * about to write.  We do this *before* the write so that we can return
2172
	 * without clobbering -EIOCBQUEUED from ->direct_IO().
2173 2174 2175 2176
	 */
	if (mapping->nrpages) {
		written = invalidate_inode_pages2_range(mapping,
					pos >> PAGE_CACHE_SHIFT, end);
2177 2178 2179 2180 2181 2182 2183
		/*
		 * If a page can not be invalidated, return 0 to fall back
		 * to buffered write.
		 */
		if (written) {
			if (written == -EBUSY)
				return 0;
2184
			goto out;
2185
		}
2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202
	}

	written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);

	/*
	 * Finally, try again to invalidate clean pages which might have been
	 * cached by non-direct readahead, or faulted in by get_user_pages()
	 * if the source of the write was an mmap'ed region of the file
	 * we're writing.  Either one is a pretty crazy thing to do,
	 * so we don't support it 100%.  If this invalidation
	 * fails, tough, the write still worked...
	 */
	if (mapping->nrpages) {
		invalidate_inode_pages2_range(mapping,
					      pos >> PAGE_CACHE_SHIFT, end);
	}

L
Linus Torvalds 已提交
2203
	if (written > 0) {
2204 2205 2206
		pos += written;
		if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
			i_size_write(inode, pos);
L
Linus Torvalds 已提交
2207 2208
			mark_inode_dirty(inode);
		}
2209
		*ppos = pos;
L
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2210
	}
2211
out:
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2212 2213 2214 2215
	return written;
}
EXPORT_SYMBOL(generic_file_direct_write);

N
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2216 2217 2218 2219
/*
 * Find or create a page at the given pagecache position. Return the locked
 * page. This function is specifically for buffered writes.
 */
2220 2221
struct page *grab_cache_page_write_begin(struct address_space *mapping,
					pgoff_t index, unsigned flags)
N
Nick Piggin 已提交
2222 2223 2224
{
	int status;
	struct page *page;
2225 2226 2227
	gfp_t gfp_notmask = 0;
	if (flags & AOP_FLAG_NOFS)
		gfp_notmask = __GFP_FS;
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Nick Piggin 已提交
2228 2229 2230 2231 2232
repeat:
	page = find_lock_page(mapping, index);
	if (likely(page))
		return page;

2233
	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
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	if (!page)
		return NULL;
2236 2237
	status = add_to_page_cache_lru(page, mapping, index,
						GFP_KERNEL & ~gfp_notmask);
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Nick Piggin 已提交
2238 2239 2240 2241 2242 2243 2244 2245
	if (unlikely(status)) {
		page_cache_release(page);
		if (status == -EEXIST)
			goto repeat;
		return NULL;
	}
	return page;
}
2246
EXPORT_SYMBOL(grab_cache_page_write_begin);
N
Nick Piggin 已提交
2247

2248 2249 2250 2251 2252 2253 2254
static ssize_t generic_perform_write(struct file *file,
				struct iov_iter *i, loff_t pos)
{
	struct address_space *mapping = file->f_mapping;
	const struct address_space_operations *a_ops = mapping->a_ops;
	long status = 0;
	ssize_t written = 0;
N
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2255 2256 2257 2258 2259 2260 2261
	unsigned int flags = 0;

	/*
	 * Copies from kernel address space cannot fail (NFSD is a big user).
	 */
	if (segment_eq(get_fs(), KERNEL_DS))
		flags |= AOP_FLAG_UNINTERRUPTIBLE;
2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290

	do {
		struct page *page;
		unsigned long offset;	/* Offset into pagecache page */
		unsigned long bytes;	/* Bytes to write to page */
		size_t copied;		/* Bytes copied from user */
		void *fsdata;

		offset = (pos & (PAGE_CACHE_SIZE - 1));
		bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
						iov_iter_count(i));

again:

		/*
		 * Bring in the user page that we will copy from _first_.
		 * Otherwise there's a nasty deadlock on copying from the
		 * same page as we're writing to, without it being marked
		 * up-to-date.
		 *
		 * Not only is this an optimisation, but it is also required
		 * to check that the address is actually valid, when atomic
		 * usercopies are used, below.
		 */
		if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
			status = -EFAULT;
			break;
		}

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		status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2292 2293 2294 2295
						&page, &fsdata);
		if (unlikely(status))
			break;

2296 2297 2298
		if (mapping_writably_mapped(mapping))
			flush_dcache_page(page);

2299 2300 2301 2302 2303
		pagefault_disable();
		copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
		pagefault_enable();
		flush_dcache_page(page);

2304
		mark_page_accessed(page);
2305 2306 2307 2308 2309 2310 2311 2312
		status = a_ops->write_end(file, mapping, pos, bytes, copied,
						page, fsdata);
		if (unlikely(status < 0))
			break;
		copied = status;

		cond_resched();

2313
		iov_iter_advance(i, copied);
2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346
		if (unlikely(copied == 0)) {
			/*
			 * If we were unable to copy any data at all, we must
			 * fall back to a single segment length write.
			 *
			 * If we didn't fallback here, we could livelock
			 * because not all segments in the iov can be copied at
			 * once without a pagefault.
			 */
			bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
						iov_iter_single_seg_count(i));
			goto again;
		}
		pos += copied;
		written += copied;

		balance_dirty_pages_ratelimited(mapping);

	} while (iov_iter_count(i));

	return written ? written : status;
}

ssize_t
generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos, loff_t *ppos,
		size_t count, ssize_t written)
{
	struct file *file = iocb->ki_filp;
	ssize_t status;
	struct iov_iter i;

	iov_iter_init(&i, iov, nr_segs, count, written);
2347
	status = generic_perform_write(file, &i, pos);
L
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2348 2349

	if (likely(status >= 0)) {
2350 2351
		written += status;
		*ppos = pos + status;
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2352 2353 2354 2355 2356 2357
  	}
	
	return written ? written : status;
}
EXPORT_SYMBOL(generic_file_buffered_write);

2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378
/**
 * __generic_file_aio_write - write data to a file
 * @iocb:	IO state structure (file, offset, etc.)
 * @iov:	vector with data to write
 * @nr_segs:	number of segments in the vector
 * @ppos:	position where to write
 *
 * This function does all the work needed for actually writing data to a
 * file. It does all basic checks, removes SUID from the file, updates
 * modification times and calls proper subroutines depending on whether we
 * do direct IO or a standard buffered write.
 *
 * It expects i_mutex to be grabbed unless we work on a block device or similar
 * object which does not need locking at all.
 *
 * This function does *not* take care of syncing data in case of O_SYNC write.
 * A caller has to handle it. This is mainly due to the fact that we want to
 * avoid syncing under i_mutex.
 */
ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
				 unsigned long nr_segs, loff_t *ppos)
L
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2379 2380
{
	struct file *file = iocb->ki_filp;
2381
	struct address_space * mapping = file->f_mapping;
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2382 2383 2384 2385 2386 2387 2388 2389
	size_t ocount;		/* original count */
	size_t count;		/* after file limit checks */
	struct inode 	*inode = mapping->host;
	loff_t		pos;
	ssize_t		written;
	ssize_t		err;

	ocount = 0;
2390 2391 2392
	err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
	if (err)
		return err;
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2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409

	count = ocount;
	pos = *ppos;

	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);

	/* We can write back this queue in page reclaim */
	current->backing_dev_info = mapping->backing_dev_info;
	written = 0;

	err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
	if (err)
		goto out;

	if (count == 0)
		goto out;

2410
	err = file_remove_suid(file);
L
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2411 2412 2413
	if (err)
		goto out;

2414
	file_update_time(file);
L
Linus Torvalds 已提交
2415 2416 2417

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (unlikely(file->f_flags & O_DIRECT)) {
2418 2419 2420 2421 2422
		loff_t endbyte;
		ssize_t written_buffered;

		written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
							ppos, count, ocount);
L
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2423 2424 2425 2426 2427 2428 2429 2430
		if (written < 0 || written == count)
			goto out;
		/*
		 * direct-io write to a hole: fall through to buffered I/O
		 * for completing the rest of the request.
		 */
		pos += written;
		count -= written;
2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444
		written_buffered = generic_file_buffered_write(iocb, iov,
						nr_segs, pos, ppos, count,
						written);
		/*
		 * If generic_file_buffered_write() retuned a synchronous error
		 * then we want to return the number of bytes which were
		 * direct-written, or the error code if that was zero.  Note
		 * that this differs from normal direct-io semantics, which
		 * will return -EFOO even if some bytes were written.
		 */
		if (written_buffered < 0) {
			err = written_buffered;
			goto out;
		}
L
Linus Torvalds 已提交
2445

2446 2447 2448 2449 2450 2451
		/*
		 * We need to ensure that the page cache pages are written to
		 * disk and invalidated to preserve the expected O_DIRECT
		 * semantics.
		 */
		endbyte = pos + written_buffered - written - 1;
2452
		err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467
		if (err == 0) {
			written = written_buffered;
			invalidate_mapping_pages(mapping,
						 pos >> PAGE_CACHE_SHIFT,
						 endbyte >> PAGE_CACHE_SHIFT);
		} else {
			/*
			 * We don't know how much we wrote, so just return
			 * the number of bytes which were direct-written
			 */
		}
	} else {
		written = generic_file_buffered_write(iocb, iov, nr_segs,
				pos, ppos, count, written);
	}
L
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2468 2469 2470 2471
out:
	current->backing_dev_info = NULL;
	return written ? written : err;
}
2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484
EXPORT_SYMBOL(__generic_file_aio_write);

/**
 * generic_file_aio_write - write data to a file
 * @iocb:	IO state structure
 * @iov:	vector with data to write
 * @nr_segs:	number of segments in the vector
 * @pos:	position in file where to write
 *
 * This is a wrapper around __generic_file_aio_write() to be used by most
 * filesystems. It takes care of syncing the file in case of O_SYNC file
 * and acquires i_mutex as needed.
 */
2485 2486
ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos)
L
Linus Torvalds 已提交
2487 2488
{
	struct file *file = iocb->ki_filp;
2489
	struct inode *inode = file->f_mapping->host;
L
Linus Torvalds 已提交
2490 2491 2492 2493
	ssize_t ret;

	BUG_ON(iocb->ki_pos != pos);

2494
	mutex_lock(&inode->i_mutex);
2495
	ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2496
	mutex_unlock(&inode->i_mutex);
L
Linus Torvalds 已提交
2497

2498
	if (ret > 0 || ret == -EIOCBQUEUED) {
L
Linus Torvalds 已提交
2499 2500
		ssize_t err;

2501
		err = generic_write_sync(file, pos, ret);
2502
		if (err < 0 && ret > 0)
L
Linus Torvalds 已提交
2503 2504 2505 2506 2507 2508
			ret = err;
	}
	return ret;
}
EXPORT_SYMBOL(generic_file_aio_write);

2509 2510 2511 2512 2513 2514 2515 2516 2517 2518
/**
 * try_to_release_page() - release old fs-specific metadata on a page
 *
 * @page: the page which the kernel is trying to free
 * @gfp_mask: memory allocation flags (and I/O mode)
 *
 * The address_space is to try to release any data against the page
 * (presumably at page->private).  If the release was successful, return `1'.
 * Otherwise return zero.
 *
2519 2520 2521
 * This may also be called if PG_fscache is set on a page, indicating that the
 * page is known to the local caching routines.
 *
2522
 * The @gfp_mask argument specifies whether I/O may be performed to release
2523
 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539
 *
 */
int try_to_release_page(struct page *page, gfp_t gfp_mask)
{
	struct address_space * const mapping = page->mapping;

	BUG_ON(!PageLocked(page));
	if (PageWriteback(page))
		return 0;

	if (mapping && mapping->a_ops->releasepage)
		return mapping->a_ops->releasepage(page, gfp_mask);
	return try_to_free_buffers(page);
}

EXPORT_SYMBOL(try_to_release_page);