filemap.c 64.7 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/slab.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>
#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>
#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 "filemap.h"
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#include "internal.h"

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

#include <asm/mman.h>

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static ssize_t
generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
	loff_t offset, unsigned long nr_segs);

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/*
 * 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:
 *
 *  ->i_mmap_lock		(vmtruncate)
 *    ->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)
 *
 *  ->mmap_sem
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 *    ->i_mutex			(msync)
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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)
 *
 *  ->task->proc_lock
 *    ->dcache_lock		(proc_pid_lookup)
 */

/*
 * 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
 * is safe.  The caller must hold a write_lock on the mapping's tree_lock.
 */
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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}

void remove_from_page_cache(struct page *page)
{
	struct address_space *mapping = page->mapping;

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	BUG_ON(!PageLocked(page));
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	write_lock_irq(&mapping->tree_lock);
	__remove_from_page_cache(page);
	write_unlock_irq(&mapping->tree_lock);
}

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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 * __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,
		.nr_to_write = mapping->nrpages * 2,
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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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static int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
				loff_t end)
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{
	return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
}

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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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/**
 * wait_on_page_writeback_range - wait for writeback to complete
 * @mapping:	target address_space
 * @start:	beginning page index
 * @end:	ending page index
 *
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 * Wait for writeback to complete against pages indexed by start->end
 * inclusive
 */
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int wait_on_page_writeback_range(struct address_space *mapping,
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				pgoff_t start, pgoff_t end)
{
	struct pagevec pvec;
	int nr_pages;
	int ret = 0;
	pgoff_t index;

	if (end < start)
		return 0;

	pagevec_init(&pvec, 0);
	index = start;
	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);
			if (PageError(page))
				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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/**
 * sync_page_range - write and wait on all pages in the passed range
 * @inode:	target inode
 * @mapping:	target address_space
 * @pos:	beginning offset in pages to write
 * @count:	number of bytes to write
 *
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 * Write and wait upon all the pages in the passed range.  This is a "data
 * integrity" operation.  It waits upon in-flight writeout before starting and
 * waiting upon new writeout.  If there was an IO error, return it.
 *
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 * We need to re-take i_mutex during the generic_osync_inode list walk because
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 * it is otherwise livelockable.
 */
int sync_page_range(struct inode *inode, struct address_space *mapping,
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			loff_t pos, loff_t count)
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{
	pgoff_t start = pos >> PAGE_CACHE_SHIFT;
	pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
	int ret;

	if (!mapping_cap_writeback_dirty(mapping) || !count)
		return 0;
	ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
	if (ret == 0) {
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		mutex_lock(&inode->i_mutex);
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		ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
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		mutex_unlock(&inode->i_mutex);
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	}
	if (ret == 0)
		ret = wait_on_page_writeback_range(mapping, start, end);
	return ret;
}
EXPORT_SYMBOL(sync_page_range);

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/**
 * sync_page_range_nolock
 * @inode:	target inode
 * @mapping:	target address_space
 * @pos:	beginning offset in pages to write
 * @count:	number of bytes to write
 *
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 * Note: Holding i_mutex across sync_page_range_nolock is not a good idea
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 * as it forces O_SYNC writers to different parts of the same file
 * to be serialised right until io completion.
 */
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int sync_page_range_nolock(struct inode *inode, struct address_space *mapping,
			   loff_t pos, loff_t count)
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{
	pgoff_t start = pos >> PAGE_CACHE_SHIFT;
	pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
	int ret;

	if (!mapping_cap_writeback_dirty(mapping) || !count)
		return 0;
	ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
	if (ret == 0)
		ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
	if (ret == 0)
		ret = wait_on_page_writeback_range(mapping, start, end);
	return ret;
}
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EXPORT_SYMBOL(sync_page_range_nolock);
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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;

	return wait_on_page_writeback_range(mapping, 0,
				(i_size - 1) >> PAGE_CACHE_SHIFT);
}
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) {
			int err2 = wait_on_page_writeback_range(mapping,
						lstart >> PAGE_CACHE_SHIFT,
						lend >> PAGE_CACHE_SHIFT);
			if (!err)
				err = err2;
		}
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	}
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	return err;
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}

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/**
 * add_to_page_cache - add newly allocated pagecache pages
 * @page:	page to add
 * @mapping:	the page's address_space
 * @offset:	page index
 * @gfp_mask:	page allocation mode
 *
 * This function is used to add newly allocated pagecache pages;
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 * the page is new, so we can just run SetPageLocked() against it.
 * The other page state flags were set by rmqueue().
 *
 * This function does not add the page to the LRU.  The caller must do that.
 */
int add_to_page_cache(struct page *page, struct address_space *mapping,
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		pgoff_t offset, gfp_t gfp_mask)
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{
	int error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);

	if (error == 0) {
		write_lock_irq(&mapping->tree_lock);
		error = radix_tree_insert(&mapping->page_tree, offset, page);
		if (!error) {
			page_cache_get(page);
			SetPageLocked(page);
			page->mapping = mapping;
			page->index = offset;
			mapping->nrpages++;
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			__inc_zone_page_state(page, NR_FILE_PAGES);
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		}
		write_unlock_irq(&mapping->tree_lock);
		radix_tree_preload_end();
	}
	return error;
}
EXPORT_SYMBOL(add_to_page_cache);

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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{
	int ret = add_to_page_cache(page, mapping, offset, gfp_mask);
	if (ret == 0)
		lru_cache_add(page);
	return ret;
}

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#ifdef CONFIG_NUMA
struct page *page_cache_alloc(struct address_space *x)
{
	if (cpuset_do_page_mem_spread()) {
		int n = cpuset_mem_spread_node();
		return alloc_pages_node(n, mapping_gfp_mask(x), 0);
	}
	return alloc_pages(mapping_gfp_mask(x), 0);
}
EXPORT_SYMBOL(page_cache_alloc);

struct page *page_cache_alloc_cold(struct address_space *x)
{
	if (cpuset_do_page_mem_spread()) {
		int n = cpuset_mem_spread_node();
		return alloc_pages_node(n, mapping_gfp_mask(x)|__GFP_COLD, 0);
	}
	return alloc_pages(mapping_gfp_mask(x)|__GFP_COLD, 0);
}
EXPORT_SYMBOL(page_cache_alloc_cold);
#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);
}

void fastcall wait_on_page_bit(struct page *page, int bit_nr)
{
	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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 * unlock_page - unlock a locked page
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 * @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.
 *
 * The first mb is necessary to safely close the critical section opened by the
 * TestSetPageLocked(), the second 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()).
 */
void fastcall unlock_page(struct page *page)
{
	smp_mb__before_clear_bit();
	if (!TestClearPageLocked(page))
		BUG();
	smp_mb__after_clear_bit(); 
	wake_up_page(page, PG_locked);
}
EXPORT_SYMBOL(unlock_page);

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/**
 * end_page_writeback - end writeback against a page
 * @page: the page
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 */
void end_page_writeback(struct page *page)
{
	if (!TestClearPageReclaim(page) || rotate_reclaimable_page(page)) {
		if (!test_clear_page_writeback(page))
			BUG();
	}
	smp_mb__after_clear_bit();
	wake_up_page(page, PG_writeback);
}
EXPORT_SYMBOL(end_page_writeback);

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/**
 * __lock_page - get a lock on the page, assuming we need to sleep to get it
 * @page: the page to lock
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 *
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 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary.  If some
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 * 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.
 */
void fastcall __lock_page(struct page *page)
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);

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

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/*
 * Variant of lock_page that does not require the caller to hold a reference
 * on the page's mapping.
 */
void fastcall __lock_page_nosync(struct page *page)
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
	__wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
							TASK_UNINTERRUPTIBLE);
}

597 598 599 600 601
/**
 * find_get_page - find and get a page reference
 * @mapping: the address_space to search
 * @offset: the page index
 *
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 * Is there a pagecache struct page at the given (mapping, offset) tuple?
 * If yes, increment its refcount and return it; if no, return NULL.
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 */
struct page * find_get_page(struct address_space *mapping, unsigned long offset)
{
	struct page *page;

	read_lock_irq(&mapping->tree_lock);
	page = radix_tree_lookup(&mapping->page_tree, offset);
	if (page)
		page_cache_get(page);
	read_unlock_irq(&mapping->tree_lock);
	return page;
}
EXPORT_SYMBOL(find_get_page);

618 619 620 621 622 623
/**
 * find_trylock_page - find and lock a page
 * @mapping: the address_space to search
 * @offset: the page index
 *
 * Same as find_get_page(), but trylock it instead of incrementing the count.
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 */
struct page *find_trylock_page(struct address_space *mapping, unsigned long offset)
{
	struct page *page;

	read_lock_irq(&mapping->tree_lock);
	page = radix_tree_lookup(&mapping->page_tree, offset);
	if (page && TestSetPageLocked(page))
		page = NULL;
	read_unlock_irq(&mapping->tree_lock);
	return page;
}
EXPORT_SYMBOL(find_trylock_page);

/**
 * find_lock_page - locate, pin and lock a pagecache page
640 641
 * @mapping: the address_space to search
 * @offset: the page index
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 *
 * 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.
 */
struct page *find_lock_page(struct address_space *mapping,
				unsigned long offset)
{
	struct page *page;

	read_lock_irq(&mapping->tree_lock);
repeat:
	page = radix_tree_lookup(&mapping->page_tree, offset);
	if (page) {
		page_cache_get(page);
		if (TestSetPageLocked(page)) {
			read_unlock_irq(&mapping->tree_lock);
660
			__lock_page(page);
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			read_lock_irq(&mapping->tree_lock);

			/* Has the page been truncated while we slept? */
664 665
			if (unlikely(page->mapping != mapping ||
				     page->index != offset)) {
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				unlock_page(page);
				page_cache_release(page);
				goto repeat;
			}
		}
	}
	read_unlock_irq(&mapping->tree_lock);
	return page;
}
EXPORT_SYMBOL(find_lock_page);

/**
 * find_or_create_page - locate or add a pagecache page
679 680 681
 * @mapping: the page's address_space
 * @index: the page's index into the mapping
 * @gfp_mask: page allocation mode
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 *
 * 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,
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		unsigned long index, gfp_t gfp_mask)
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{
	struct page *page, *cached_page = NULL;
	int err;
repeat:
	page = find_lock_page(mapping, index);
	if (!page) {
		if (!cached_page) {
			cached_page = alloc_page(gfp_mask);
			if (!cached_page)
				return NULL;
		}
		err = add_to_page_cache_lru(cached_page, mapping,
					index, gfp_mask);
		if (!err) {
			page = cached_page;
			cached_page = NULL;
		} else if (err == -EEXIST)
			goto repeat;
	}
	if (cached_page)
		page_cache_release(cached_page);
	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;

	read_lock_irq(&mapping->tree_lock);
	ret = radix_tree_gang_lookup(&mapping->page_tree,
				(void **)pages, start, nr_pages);
	for (i = 0; i < ret; i++)
		page_cache_get(pages[i]);
	read_unlock_irq(&mapping->tree_lock);
	return ret;
}

752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783
/**
 * 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;

	read_lock_irq(&mapping->tree_lock);
	ret = radix_tree_gang_lookup(&mapping->page_tree,
				(void **)pages, index, nr_pages);
	for (i = 0; i < ret; i++) {
		if (pages[i]->mapping == NULL || pages[i]->index != index)
			break;

		page_cache_get(pages[i]);
		index++;
	}
	read_unlock_irq(&mapping->tree_lock);
	return i;
}

784 785 786 787 788 789 790 791
/**
 * 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
 *
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 * Like find_get_pages, except we only return pages which are tagged with
793
 * @tag.   We update @index to index the next page for the traversal.
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 */
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;

	read_lock_irq(&mapping->tree_lock);
	ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
				(void **)pages, *index, nr_pages, tag);
	for (i = 0; i < ret; i++)
		page_cache_get(pages[i]);
	if (ret)
		*index = pages[ret - 1]->index + 1;
	read_unlock_irq(&mapping->tree_lock);
	return ret;
}

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/**
 * grab_cache_page_nowait - returns locked page at given index in given cache
 * @mapping: target address_space
 * @index: the page index
 *
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 * Same as grab_cache_page, but do not wait if the page is unavailable.
 * 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 *
grab_cache_page_nowait(struct address_space *mapping, unsigned long index)
{
	struct page *page = find_get_page(mapping, index);
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	gfp_t gfp_mask;
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	if (page) {
		if (!TestSetPageLocked(page))
			return page;
		page_cache_release(page);
		return NULL;
	}
	gfp_mask = mapping_gfp_mask(mapping) & ~__GFP_FS;
	page = alloc_pages(gfp_mask, 0);
	if (page && add_to_page_cache_lru(page, mapping, index, gfp_mask)) {
		page_cache_release(page);
		page = NULL;
	}
	return page;
}
EXPORT_SYMBOL(grab_cache_page_nowait);

847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870
/*
 * 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)
{
	if (!ra->ra_pages)
		return;

	ra->ra_pages /= 4;
}

871 872 873 874 875 876 877 878 879
/**
 * do_generic_mapping_read - generic file read routine
 * @mapping:	address_space to be read
 * @_ra:	file's readahead state
 * @filp:	the file to read
 * @ppos:	current file position
 * @desc:	read_descriptor
 * @actor:	read method
 *
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 * This is a generic file read routine, and uses the
881
 * mapping->a_ops->readpage() function for the actual low-level stuff.
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 *
 * This is really ugly. But the goto's actually try to clarify some
 * of the logic when it comes to error handling etc.
 *
886 887
 * Note the struct file* is only passed for the use of readpage.
 * It may be NULL.
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 */
void do_generic_mapping_read(struct address_space *mapping,
			     struct file_ra_state *_ra,
			     struct file *filp,
			     loff_t *ppos,
			     read_descriptor_t *desc,
			     read_actor_t actor)
{
	struct inode *inode = mapping->host;
	unsigned long index;
	unsigned long end_index;
	unsigned long offset;
	unsigned long last_index;
	unsigned long next_index;
	unsigned long prev_index;
	loff_t isize;
	struct page *cached_page;
	int error;
	struct file_ra_state ra = *_ra;

	cached_page = NULL;
	index = *ppos >> PAGE_CACHE_SHIFT;
	next_index = index;
	prev_index = ra.prev_page;
	last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
	offset = *ppos & ~PAGE_CACHE_MASK;

	isize = i_size_read(inode);
	if (!isize)
		goto out;

	end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
	for (;;) {
		struct page *page;
		unsigned long nr, ret;

		/* nr is the maximum number of bytes to copy from this page */
		nr = PAGE_CACHE_SIZE;
		if (index >= end_index) {
			if (index > end_index)
				goto out;
			nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
			if (nr <= offset) {
				goto out;
			}
		}
		nr = nr - offset;

		cond_resched();
		if (index == next_index)
			next_index = page_cache_readahead(mapping, &ra, filp,
					index, last_index - index);

find_page:
		page = find_get_page(mapping, index);
		if (unlikely(page == NULL)) {
			handle_ra_miss(mapping, &ra, index);
			goto no_cached_page;
		}
		if (!PageUptodate(page))
			goto page_not_up_to_date;
page_ok:

		/* 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);

		/*
		 * When (part of) the same page is read multiple times
		 * in succession, only mark it as accessed the first time.
		 */
		if (prev_index != index)
			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;

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

page_not_up_to_date:
		/* Get exclusive access to the page ... */
		lock_page(page);

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		/* Did it get truncated before we got the lock? */
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		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:
		/* Start the actual read. The read will unlock the page. */
		error = mapping->a_ops->readpage(filp, page);

1007 1008 1009 1010 1011
		if (unlikely(error)) {
			if (error == AOP_TRUNCATED_PAGE) {
				page_cache_release(page);
				goto find_page;
			}
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			goto readpage_error;
1013
		}
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		if (!PageUptodate(page)) {
			lock_page(page);
			if (!PageUptodate(page)) {
				if (page->mapping == NULL) {
					/*
					 * invalidate_inode_pages got it
					 */
					unlock_page(page);
					page_cache_release(page);
					goto find_page;
				}
				unlock_page(page);
				error = -EIO;
1028
				shrink_readahead_size_eio(filp, &ra);
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				goto readpage_error;
			}
			unlock_page(page);
		}

		/*
		 * i_size must be checked after we have done ->readpage.
		 *
		 * Checking i_size after the readpage 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;
		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..
		 */
		if (!cached_page) {
			cached_page = page_cache_alloc_cold(mapping);
			if (!cached_page) {
				desc->error = -ENOMEM;
				goto out;
			}
		}
		error = add_to_page_cache_lru(cached_page, mapping,
						index, GFP_KERNEL);
		if (error) {
			if (error == -EEXIST)
				goto find_page;
			desc->error = error;
			goto out;
		}
		page = cached_page;
		cached_page = NULL;
		goto readpage;
	}

out:
	*_ra = ra;

	*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
	if (cached_page)
		page_cache_release(cached_page);
	if (filp)
		file_accessed(filp);
}
EXPORT_SYMBOL(do_generic_mapping_read);

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;
}

1141 1142 1143 1144 1145 1146 1147
/**
 * __generic_file_aio_read - generic filesystem read routine
 * @iocb:	kernel I/O control block
 * @iov:	io vector request
 * @nr_segs:	number of segments in the iovec
 * @ppos:	current file position
 *
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 * This is the "read()" routine for all filesystems
 * that can use the page cache directly.
 */
ssize_t
__generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t *ppos)
{
	struct file *filp = iocb->ki_filp;
	ssize_t retval;
	unsigned long seg;
	size_t count;

	count = 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.
		 */
		count += iv->iov_len;
		if (unlikely((ssize_t)(count|iv->iov_len) < 0))
			return -EINVAL;
		if (access_ok(VERIFY_WRITE, iv->iov_base, iv->iov_len))
			continue;
		if (seg == 0)
			return -EFAULT;
		nr_segs = seg;
		count -= iv->iov_len;	/* This segment is no good */
		break;
	}

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (filp->f_flags & O_DIRECT) {
		loff_t pos = *ppos, size;
		struct address_space *mapping;
		struct inode *inode;

		mapping = filp->f_mapping;
		inode = mapping->host;
		retval = 0;
		if (!count)
			goto out; /* skip atime */
		size = i_size_read(inode);
		if (pos < size) {
			retval = generic_file_direct_IO(READ, iocb,
						iov, pos, nr_segs);
1195
			if (retval > 0 && !is_sync_kiocb(iocb))
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				retval = -EIOCBQUEUED;
			if (retval > 0)
				*ppos = pos + retval;
		}
		file_accessed(filp);
		goto out;
	}

	retval = 0;
	if (count) {
		for (seg = 0; seg < nr_segs; seg++) {
			read_descriptor_t desc;

			desc.written = 0;
			desc.arg.buf = iov[seg].iov_base;
			desc.count = iov[seg].iov_len;
			if (desc.count == 0)
				continue;
			desc.error = 0;
			do_generic_file_read(filp,ppos,&desc,file_read_actor);
			retval += desc.written;
1217 1218
			if (desc.error) {
				retval = retval ?: desc.error;
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				break;
			}
		}
	}
out:
	return retval;
}
EXPORT_SYMBOL(__generic_file_aio_read);

ssize_t
generic_file_aio_read(struct kiocb *iocb, char __user *buf, size_t count, loff_t pos)
{
	struct iovec local_iov = { .iov_base = buf, .iov_len = count };

	BUG_ON(iocb->ki_pos != pos);
	return __generic_file_aio_read(iocb, &local_iov, 1, &iocb->ki_pos);
}
EXPORT_SYMBOL(generic_file_aio_read);

ssize_t
generic_file_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
{
	struct iovec local_iov = { .iov_base = buf, .iov_len = count };
	struct kiocb kiocb;
	ssize_t ret;

	init_sync_kiocb(&kiocb, filp);
	ret = __generic_file_aio_read(&kiocb, &local_iov, 1, ppos);
	if (-EIOCBQUEUED == ret)
		ret = wait_on_sync_kiocb(&kiocb);
	return ret;
}
EXPORT_SYMBOL(generic_file_read);

int file_send_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size)
{
	ssize_t written;
	unsigned long count = desc->count;
	struct file *file = desc->arg.data;

	if (size > count)
		size = count;

	written = file->f_op->sendpage(file, page, offset,
				       size, &file->f_pos, size<count);
	if (written < 0) {
		desc->error = written;
		written = 0;
	}
	desc->count = count - written;
	desc->written += written;
	return written;
}

ssize_t generic_file_sendfile(struct file *in_file, loff_t *ppos,
			 size_t count, read_actor_t actor, void *target)
{
	read_descriptor_t desc;

	if (!count)
		return 0;

	desc.written = 0;
	desc.count = count;
	desc.arg.data = target;
	desc.error = 0;

	do_generic_file_read(in_file, ppos, &desc, actor);
	if (desc.written)
		return desc.written;
	return desc.error;
}
EXPORT_SYMBOL(generic_file_sendfile);

static ssize_t
do_readahead(struct address_space *mapping, struct file *filp,
	     unsigned long index, unsigned long nr)
{
	if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
		return -EINVAL;

	force_page_cache_readahead(mapping, filp, index,
					max_sane_readahead(nr));
	return 0;
}

asmlinkage ssize_t sys_readahead(int fd, loff_t offset, size_t count)
{
	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;
			unsigned long start = offset >> PAGE_CACHE_SHIFT;
			unsigned long end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
			unsigned long len = end - start + 1;
			ret = do_readahead(mapping, file, start, len);
		}
		fput(file);
	}
	return ret;
}

#ifdef CONFIG_MMU
1326 1327 1328 1329 1330 1331
static int FASTCALL(page_cache_read(struct file * file, unsigned long offset));
/**
 * page_cache_read - adds requested page to the page cache if not already there
 * @file:	file to read
 * @offset:	page index
 *
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 * 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.
 */
static int fastcall page_cache_read(struct file * file, unsigned long offset)
{
	struct address_space *mapping = file->f_mapping;
	struct page *page; 
1339
	int ret;
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1341 1342 1343 1344 1345 1346 1347 1348 1349 1350
	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 */
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		page_cache_release(page);

1354 1355 1356
	} while (ret == AOP_TRUNCATED_PAGE);
		
	return ret;
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}

#define MMAP_LOTSAMISS  (100)

1361 1362 1363 1364 1365 1366
/**
 * filemap_nopage - read in file data for page fault handling
 * @area:	the applicable vm_area
 * @address:	target address to read in
 * @type:	returned with VM_FAULT_{MINOR,MAJOR} if not %NULL
 *
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 * filemap_nopage() is invoked via the vma operations vector for a
 * 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.
 */
struct page *filemap_nopage(struct vm_area_struct *area,
				unsigned long address, int *type)
{
	int error;
	struct file *file = area->vm_file;
	struct address_space *mapping = file->f_mapping;
	struct file_ra_state *ra = &file->f_ra;
	struct inode *inode = mapping->host;
	struct page *page;
	unsigned long size, pgoff;
	int did_readaround = 0, majmin = VM_FAULT_MINOR;

	pgoff = ((address-area->vm_start) >> PAGE_CACHE_SHIFT) + area->vm_pgoff;

retry_all:
	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
	if (pgoff >= size)
		goto outside_data_content;

	/* If we don't want any read-ahead, don't bother */
	if (VM_RandomReadHint(area))
		goto no_cached_page;

	/*
	 * The readahead code wants to be told about each and every page
	 * so it can build and shrink its windows appropriately
	 *
	 * For sequential accesses, we use the generic readahead logic.
	 */
	if (VM_SequentialReadHint(area))
		page_cache_readahead(mapping, ra, file, pgoff, 1);

	/*
	 * Do we have something in the page cache already?
	 */
retry_find:
	page = find_get_page(mapping, pgoff);
	if (!page) {
		unsigned long ra_pages;

		if (VM_SequentialReadHint(area)) {
			handle_ra_miss(mapping, ra, pgoff);
			goto no_cached_page;
		}
		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 > ra->mmap_hit + MMAP_LOTSAMISS)
			goto no_cached_page;

		/*
		 * To keep the pgmajfault counter straight, we need to
		 * check did_readaround, as this is an inner loop.
		 */
		if (!did_readaround) {
			majmin = VM_FAULT_MAJOR;
1433
			count_vm_event(PGMAJFAULT);
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		}
		did_readaround = 1;
		ra_pages = max_sane_readahead(file->f_ra.ra_pages);
		if (ra_pages) {
			pgoff_t start = 0;

			if (pgoff > ra_pages / 2)
				start = pgoff - ra_pages / 2;
			do_page_cache_readahead(mapping, file, start, ra_pages);
		}
		page = find_get_page(mapping, pgoff);
		if (!page)
			goto no_cached_page;
	}

	if (!did_readaround)
		ra->mmap_hit++;

	/*
	 * Ok, found a page in the page cache, now we need to check
	 * that it's up-to-date.
	 */
	if (!PageUptodate(page))
		goto page_not_uptodate;

success:
	/*
	 * Found the page and have a reference on it.
	 */
	mark_page_accessed(page);
	if (type)
		*type = majmin;
	return page;

outside_data_content:
	/*
	 * An external ptracer can access pages that normally aren't
	 * accessible..
	 */
	if (area->vm_mm == current->mm)
1474
		return NOPAGE_SIGBUS;
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	/* Fall through to the non-read-ahead case */
no_cached_page:
	/*
	 * We're only likely to ever get here if MADV_RANDOM is in
	 * effect.
	 */
	error = page_cache_read(file, pgoff);
	grab_swap_token();

	/*
	 * 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)
		return NOPAGE_OOM;
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	return NOPAGE_SIGBUS;
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page_not_uptodate:
	if (!did_readaround) {
		majmin = VM_FAULT_MAJOR;
1504
		count_vm_event(PGMAJFAULT);
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	}
	lock_page(page);

	/* Did it get unhashed while we waited for it? */
	if (!page->mapping) {
		unlock_page(page);
		page_cache_release(page);
		goto retry_all;
	}

	/* Did somebody else get it up-to-date? */
	if (PageUptodate(page)) {
		unlock_page(page);
		goto success;
	}

1521 1522
	error = mapping->a_ops->readpage(file, page);
	if (!error) {
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		wait_on_page_locked(page);
		if (PageUptodate(page))
			goto success;
1526 1527 1528
	} else if (error == AOP_TRUNCATED_PAGE) {
		page_cache_release(page);
		goto retry_find;
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	}

	/*
	 * 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.
	 */
	lock_page(page);

	/* Somebody truncated the page on us? */
	if (!page->mapping) {
		unlock_page(page);
		page_cache_release(page);
		goto retry_all;
	}

	/* Somebody else successfully read it in? */
	if (PageUptodate(page)) {
		unlock_page(page);
		goto success;
	}
	ClearPageError(page);
1552 1553
	error = mapping->a_ops->readpage(file, page);
	if (!error) {
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		wait_on_page_locked(page);
		if (PageUptodate(page))
			goto success;
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	} else if (error == AOP_TRUNCATED_PAGE) {
		page_cache_release(page);
		goto retry_find;
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	}

	/*
	 * Things didn't work out. Return zero to tell the
	 * mm layer so, possibly freeing the page cache page first.
	 */
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	shrink_readahead_size_eio(file, ra);
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	page_cache_release(page);
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	return NOPAGE_SIGBUS;
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}
EXPORT_SYMBOL(filemap_nopage);

static struct page * filemap_getpage(struct file *file, unsigned long pgoff,
					int nonblock)
{
	struct address_space *mapping = file->f_mapping;
	struct page *page;
	int error;

	/*
	 * Do we have something in the page cache already?
	 */
retry_find:
	page = find_get_page(mapping, pgoff);
	if (!page) {
		if (nonblock)
			return NULL;
		goto no_cached_page;
	}

	/*
	 * Ok, found a page in the page cache, now we need to check
	 * that it's up-to-date.
	 */
1594 1595 1596 1597 1598
	if (!PageUptodate(page)) {
		if (nonblock) {
			page_cache_release(page);
			return NULL;
		}
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		goto page_not_uptodate;
1600
	}
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success:
	/*
	 * Found the page and have a reference on it.
	 */
	mark_page_accessed(page);
	return page;

no_cached_page:
	error = page_cache_read(file, pgoff);

	/*
	 * 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.
	 */
	return NULL;

page_not_uptodate:
	lock_page(page);

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	/* Did it get truncated while we waited for it? */
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	if (!page->mapping) {
		unlock_page(page);
		goto err;
	}

	/* Did somebody else get it up-to-date? */
	if (PageUptodate(page)) {
		unlock_page(page);
		goto success;
	}

1642 1643
	error = mapping->a_ops->readpage(file, page);
	if (!error) {
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		wait_on_page_locked(page);
		if (PageUptodate(page))
			goto success;
1647 1648 1649
	} else if (error == AOP_TRUNCATED_PAGE) {
		page_cache_release(page);
		goto retry_find;
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	}

	/*
	 * 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.
	 */
	lock_page(page);

	/* Somebody truncated the page on us? */
	if (!page->mapping) {
		unlock_page(page);
		goto err;
	}
	/* Somebody else successfully read it in? */
	if (PageUptodate(page)) {
		unlock_page(page);
		goto success;
	}

	ClearPageError(page);
1672 1673
	error = mapping->a_ops->readpage(file, page);
	if (!error) {
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		wait_on_page_locked(page);
		if (PageUptodate(page))
			goto success;
1677 1678 1679
	} else if (error == AOP_TRUNCATED_PAGE) {
		page_cache_release(page);
		goto retry_find;
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	}

	/*
	 * Things didn't work out. Return zero to tell the
	 * mm layer so, possibly freeing the page cache page first.
	 */
err:
	page_cache_release(page);

	return NULL;
}

int filemap_populate(struct vm_area_struct *vma, unsigned long addr,
		unsigned long len, pgprot_t prot, unsigned long pgoff,
		int nonblock)
{
	struct file *file = vma->vm_file;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	unsigned long size;
	struct mm_struct *mm = vma->vm_mm;
	struct page *page;
	int err;

	if (!nonblock)
		force_page_cache_readahead(mapping, vma->vm_file,
					pgoff, len >> PAGE_CACHE_SHIFT);

repeat:
	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
	if (pgoff + (len >> PAGE_CACHE_SHIFT) > size)
		return -EINVAL;

	page = filemap_getpage(file, pgoff, nonblock);
1714 1715 1716

	/* XXX: This is wrong, a filesystem I/O error may have happened. Fix that as
	 * done in shmem_populate calling shmem_getpage */
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	if (!page && !nonblock)
		return -ENOMEM;
1719

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	if (page) {
		err = install_page(mm, vma, addr, page, prot);
		if (err) {
			page_cache_release(page);
			return err;
		}
1726
	} else if (vma->vm_flags & VM_NONLINEAR) {
1727 1728 1729
		/* No page was found just because we can't read it in now (being
		 * here implies nonblock != 0), but the page may exist, so set
		 * the PTE to fault it in later. */
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		err = install_file_pte(mm, vma, addr, pgoff, prot);
		if (err)
			return err;
	}

	len -= PAGE_SIZE;
	addr += PAGE_SIZE;
	pgoff++;
	if (len)
		goto repeat;

	return 0;
}
1743
EXPORT_SYMBOL(filemap_populate);
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struct vm_operations_struct generic_file_vm_ops = {
	.nopage		= filemap_nopage,
	.populate	= filemap_populate,
};

/* 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;
	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);

static inline struct page *__read_cache_page(struct address_space *mapping,
				unsigned long index,
				int (*filler)(void *,struct page*),
				void *data)
{
	struct page *page, *cached_page = NULL;
	int err;
repeat:
	page = find_get_page(mapping, index);
	if (!page) {
		if (!cached_page) {
			cached_page = page_cache_alloc_cold(mapping);
			if (!cached_page)
				return ERR_PTR(-ENOMEM);
		}
		err = add_to_page_cache_lru(cached_page, mapping,
					index, GFP_KERNEL);
		if (err == -EEXIST)
			goto repeat;
		if (err < 0) {
			/* Presumably ENOMEM for radix tree node */
			page_cache_release(cached_page);
			return ERR_PTR(err);
		}
		page = cached_page;
		cached_page = NULL;
		err = filler(data, page);
		if (err < 0) {
			page_cache_release(page);
			page = ERR_PTR(err);
		}
	}
	if (cached_page)
		page_cache_release(cached_page);
	return page;
}

1823 1824 1825 1826 1827 1828 1829
/**
 * 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
 *
L
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1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935
 * Read into the page cache. If a page already exists,
 * and PageUptodate() is not set, try to fill the page.
 */
struct page *read_cache_page(struct address_space *mapping,
				unsigned long index,
				int (*filler)(void *,struct page*),
				void *data)
{
	struct page *page;
	int err;

retry:
	page = __read_cache_page(mapping, index, filler, data);
	if (IS_ERR(page))
		goto out;
	mark_page_accessed(page);
	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);
		page = ERR_PTR(err);
	}
 out:
	return page;
}
EXPORT_SYMBOL(read_cache_page);

/*
 * If the page was newly created, increment its refcount and add it to the
 * caller's lru-buffering pagevec.  This function is specifically for
 * generic_file_write().
 */
static inline struct page *
__grab_cache_page(struct address_space *mapping, unsigned long index,
			struct page **cached_page, struct pagevec *lru_pvec)
{
	int err;
	struct page *page;
repeat:
	page = find_lock_page(mapping, index);
	if (!page) {
		if (!*cached_page) {
			*cached_page = page_cache_alloc(mapping);
			if (!*cached_page)
				return NULL;
		}
		err = add_to_page_cache(*cached_page, mapping,
					index, GFP_KERNEL);
		if (err == -EEXIST)
			goto repeat;
		if (err == 0) {
			page = *cached_page;
			page_cache_get(page);
			if (!pagevec_add(lru_pvec, page))
				__pagevec_lru_add(lru_pvec);
			*cached_page = NULL;
		}
	}
	return page;
}

/*
 * The logic we want is
 *
 *	if suid or (sgid and xgrp)
 *		remove privs
 */
int remove_suid(struct dentry *dentry)
{
	mode_t mode = dentry->d_inode->i_mode;
	int kill = 0;
	int result = 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;

	if (unlikely(kill && !capable(CAP_FSETID))) {
		struct iattr newattrs;

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

1936
size_t
1937
__filemap_copy_from_user_iovec_inatomic(char *vaddr,
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Linus Torvalds 已提交
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			const struct iovec *iov, size_t base, size_t bytes)
{
	size_t copied = 0, left = 0;

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

		base = 0;
1947
		left = __copy_from_user_inatomic_nocache(vaddr, buf, copy);
L
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1948 1949 1950 1951 1952
		copied += copy;
		bytes -= copy;
		vaddr += copy;
		iov++;

1953
		if (unlikely(left))
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1954 1955 1956 1957 1958 1959 1960 1961
			break;
	}
	return copied - left;
}

/*
 * Performs necessary checks before doing a write
 *
1962
 * Can adjust writing position or amount of bytes to write.
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1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064
 * 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;
	unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;

        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) {
			send_sig(SIGXFSZ, current, 0);
			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) {
				send_sig(SIGXFSZ, current, 0);
				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 {
		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;
	}
	return 0;
}
EXPORT_SYMBOL(generic_write_checks);

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;

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

	written = generic_file_direct_IO(WRITE, iocb, iov, pos, *nr_segs);
	if (written > 0) {
		loff_t end = pos + written;
		if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
			i_size_write(inode,  end);
			mark_inode_dirty(inode);
		}
		*ppos = end;
	}

	/*
	 * Sync the fs metadata but not the minor inode changes and
	 * of course not the data as we did direct DMA for the IO.
2065
	 * i_mutex is held, which protects generic_osync_inode() from
L
Linus Torvalds 已提交
2066 2067
	 * livelocking.
	 */
2068 2069 2070 2071 2072
	if (written >= 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
		int err = generic_osync_inode(inode, mapping, OSYNC_METADATA);
		if (err < 0)
			written = err;
	}
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2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085
	if (written == count && !is_sync_kiocb(iocb))
		written = -EIOCBQUEUED;
	return written;
}
EXPORT_SYMBOL(generic_file_direct_write);

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;
	struct address_space * mapping = file->f_mapping;
2086
	const struct address_space_operations *a_ops = mapping->a_ops;
L
Linus Torvalds 已提交
2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105
	struct inode 	*inode = mapping->host;
	long		status = 0;
	struct page	*page;
	struct page	*cached_page = NULL;
	size_t		bytes;
	struct pagevec	lru_pvec;
	const struct iovec *cur_iov = iov; /* current iovec */
	size_t		iov_base = 0;	   /* offset in the current iovec */
	char __user	*buf;

	pagevec_init(&lru_pvec, 0);

	/*
	 * handle partial DIO write.  Adjust cur_iov if needed.
	 */
	if (likely(nr_segs == 1))
		buf = iov->iov_base + written;
	else {
		filemap_set_next_iovec(&cur_iov, &iov_base, written);
2106
		buf = cur_iov->iov_base + iov_base;
L
Linus Torvalds 已提交
2107 2108 2109 2110 2111 2112 2113 2114 2115 2116
	}

	do {
		unsigned long index;
		unsigned long offset;
		size_t copied;

		offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
		index = pos >> PAGE_CACHE_SHIFT;
		bytes = PAGE_CACHE_SIZE - offset;
2117 2118 2119 2120 2121 2122 2123 2124 2125 2126

		/* Limit the size of the copy to the caller's write size */
		bytes = min(bytes, count);

		/*
		 * Limit the size of the copy to that of the current segment,
		 * because fault_in_pages_readable() doesn't know how to walk
		 * segments.
		 */
		bytes = min(bytes, cur_iov->iov_len - iov_base);
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2127 2128 2129 2130 2131 2132 2133

		/*
		 * 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.
		 */
2134
		fault_in_pages_readable(buf, bytes);
L
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2135 2136 2137 2138 2139 2140 2141

		page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec);
		if (!page) {
			status = -ENOMEM;
			break;
		}

2142 2143 2144 2145 2146 2147
		if (unlikely(bytes == 0)) {
			status = 0;
			copied = 0;
			goto zero_length_segment;
		}

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2148 2149 2150
		status = a_ops->prepare_write(file, page, offset, offset+bytes);
		if (unlikely(status)) {
			loff_t isize = i_size_read(inode);
2151 2152 2153 2154 2155 2156

			if (status != AOP_TRUNCATED_PAGE)
				unlock_page(page);
			page_cache_release(page);
			if (status == AOP_TRUNCATED_PAGE)
				continue;
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Linus Torvalds 已提交
2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172
			/*
			 * prepare_write() may have instantiated a few blocks
			 * outside i_size.  Trim these off again.
			 */
			if (pos + bytes > isize)
				vmtruncate(inode, isize);
			break;
		}
		if (likely(nr_segs == 1))
			copied = filemap_copy_from_user(page, offset,
							buf, bytes);
		else
			copied = filemap_copy_from_user_iovec(page, offset,
						cur_iov, iov_base, bytes);
		flush_dcache_page(page);
		status = a_ops->commit_write(file, page, offset, offset+bytes);
2173 2174 2175 2176
		if (status == AOP_TRUNCATED_PAGE) {
			page_cache_release(page);
			continue;
		}
2177 2178
zero_length_segment:
		if (likely(copied >= 0)) {
L
Linus Torvalds 已提交
2179 2180 2181 2182 2183 2184 2185 2186
			if (!status)
				status = copied;

			if (status >= 0) {
				written += status;
				count -= status;
				pos += status;
				buf += status;
2187
				if (unlikely(nr_segs > 1)) {
L
Linus Torvalds 已提交
2188 2189
					filemap_set_next_iovec(&cur_iov,
							&iov_base, status);
2190 2191 2192
					if (count)
						buf = cur_iov->iov_base +
							iov_base;
2193 2194
				} else {
					iov_base += status;
2195
				}
L
Linus Torvalds 已提交
2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237
			}
		}
		if (unlikely(copied != bytes))
			if (status >= 0)
				status = -EFAULT;
		unlock_page(page);
		mark_page_accessed(page);
		page_cache_release(page);
		if (status < 0)
			break;
		balance_dirty_pages_ratelimited(mapping);
		cond_resched();
	} while (count);
	*ppos = pos;

	if (cached_page)
		page_cache_release(cached_page);

	/*
	 * For now, when the user asks for O_SYNC, we'll actually give O_DSYNC
	 */
	if (likely(status >= 0)) {
		if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
			if (!a_ops->writepage || !is_sync_kiocb(iocb))
				status = generic_osync_inode(inode, mapping,
						OSYNC_METADATA|OSYNC_DATA);
		}
  	}
	
	/*
	 * If we get here for O_DIRECT writes then we must have fallen through
	 * to buffered writes (block instantiation inside i_size).  So we sync
	 * the file data here, to try to honour O_DIRECT expectations.
	 */
	if (unlikely(file->f_flags & O_DIRECT) && written)
		status = filemap_write_and_wait(mapping);

	pagevec_lru_add(&lru_pvec);
	return written ? written : status;
}
EXPORT_SYMBOL(generic_file_buffered_write);

2238
static ssize_t
L
Linus Torvalds 已提交
2239 2240 2241 2242
__generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
				unsigned long nr_segs, loff_t *ppos)
{
	struct file *file = iocb->ki_filp;
2243
	const struct address_space * mapping = file->f_mapping;
L
Linus Torvalds 已提交
2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 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 2291
	size_t ocount;		/* original count */
	size_t count;		/* after file limit checks */
	struct inode 	*inode = mapping->host;
	unsigned long	seg;
	loff_t		pos;
	ssize_t		written;
	ssize_t		err;

	ocount = 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.
		 */
		ocount += iv->iov_len;
		if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
			return -EINVAL;
		if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
			continue;
		if (seg == 0)
			return -EFAULT;
		nr_segs = seg;
		ocount -= iv->iov_len;	/* This segment is no good */
		break;
	}

	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;

	err = remove_suid(file->f_dentry);
	if (err)
		goto out;

2292
	file_update_time(file);
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Linus Torvalds 已提交
2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (unlikely(file->f_flags & O_DIRECT)) {
		written = generic_file_direct_write(iocb, iov,
				&nr_segs, pos, ppos, count, ocount);
		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;
	}

	written = generic_file_buffered_write(iocb, iov, nr_segs,
			pos, ppos, count, written);
out:
	current->backing_dev_info = NULL;
	return written ? written : err;
}
EXPORT_SYMBOL(generic_file_aio_write_nolock);

ssize_t
generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
				unsigned long nr_segs, loff_t *ppos)
{
	struct file *file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t ret;
	loff_t pos = *ppos;

	ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs, ppos);

	if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
		int err;

		err = sync_page_range_nolock(inode, mapping, pos, ret);
		if (err < 0)
			ret = err;
	}
	return ret;
}

2338
static ssize_t
L
Linus Torvalds 已提交
2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378
__generic_file_write_nolock(struct file *file, const struct iovec *iov,
				unsigned long nr_segs, loff_t *ppos)
{
	struct kiocb kiocb;
	ssize_t ret;

	init_sync_kiocb(&kiocb, file);
	ret = __generic_file_aio_write_nolock(&kiocb, iov, nr_segs, ppos);
	if (ret == -EIOCBQUEUED)
		ret = wait_on_sync_kiocb(&kiocb);
	return ret;
}

ssize_t
generic_file_write_nolock(struct file *file, const struct iovec *iov,
				unsigned long nr_segs, loff_t *ppos)
{
	struct kiocb kiocb;
	ssize_t ret;

	init_sync_kiocb(&kiocb, file);
	ret = generic_file_aio_write_nolock(&kiocb, iov, nr_segs, ppos);
	if (-EIOCBQUEUED == ret)
		ret = wait_on_sync_kiocb(&kiocb);
	return ret;
}
EXPORT_SYMBOL(generic_file_write_nolock);

ssize_t generic_file_aio_write(struct kiocb *iocb, const char __user *buf,
			       size_t count, loff_t pos)
{
	struct file *file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t ret;
	struct iovec local_iov = { .iov_base = (void __user *)buf,
					.iov_len = count };

	BUG_ON(iocb->ki_pos != pos);

2379
	mutex_lock(&inode->i_mutex);
L
Linus Torvalds 已提交
2380 2381
	ret = __generic_file_aio_write_nolock(iocb, &local_iov, 1,
						&iocb->ki_pos);
2382
	mutex_unlock(&inode->i_mutex);
L
Linus Torvalds 已提交
2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403

	if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
		ssize_t err;

		err = sync_page_range(inode, mapping, pos, ret);
		if (err < 0)
			ret = err;
	}
	return ret;
}
EXPORT_SYMBOL(generic_file_aio_write);

ssize_t generic_file_write(struct file *file, const char __user *buf,
			   size_t count, loff_t *ppos)
{
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t	ret;
	struct iovec local_iov = { .iov_base = (void __user *)buf,
					.iov_len = count };

2404
	mutex_lock(&inode->i_mutex);
L
Linus Torvalds 已提交
2405
	ret = __generic_file_write_nolock(file, &local_iov, 1, ppos);
2406
	mutex_unlock(&inode->i_mutex);
L
Linus Torvalds 已提交
2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439

	if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
		ssize_t err;

		err = sync_page_range(inode, mapping, *ppos - ret, ret);
		if (err < 0)
			ret = err;
	}
	return ret;
}
EXPORT_SYMBOL(generic_file_write);

ssize_t generic_file_readv(struct file *filp, const struct iovec *iov,
			unsigned long nr_segs, loff_t *ppos)
{
	struct kiocb kiocb;
	ssize_t ret;

	init_sync_kiocb(&kiocb, filp);
	ret = __generic_file_aio_read(&kiocb, iov, nr_segs, ppos);
	if (-EIOCBQUEUED == ret)
		ret = wait_on_sync_kiocb(&kiocb);
	return ret;
}
EXPORT_SYMBOL(generic_file_readv);

ssize_t generic_file_writev(struct file *file, const struct iovec *iov,
			unsigned long nr_segs, loff_t *ppos)
{
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t ret;

2440
	mutex_lock(&inode->i_mutex);
L
Linus Torvalds 已提交
2441
	ret = __generic_file_write_nolock(file, iov, nr_segs, ppos);
2442
	mutex_unlock(&inode->i_mutex);
L
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2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455

	if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
		int err;

		err = sync_page_range(inode, mapping, *ppos - ret, ret);
		if (err < 0)
			ret = err;
	}
	return ret;
}
EXPORT_SYMBOL(generic_file_writev);

/*
2456
 * Called under i_mutex for writes to S_ISREG files.   Returns -EIO if something
L
Linus Torvalds 已提交
2457 2458
 * went wrong during pagecache shootdown.
 */
2459
static ssize_t
L
Linus Torvalds 已提交
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generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
	loff_t offset, unsigned long nr_segs)
{
	struct file *file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	ssize_t retval;
	size_t write_len = 0;

	/*
	 * If it's a write, unmap all mmappings of the file up-front.  This
	 * will cause any pte dirty bits to be propagated into the pageframes
	 * for the subsequent filemap_write_and_wait().
	 */
	if (rw == WRITE) {
		write_len = iov_length(iov, nr_segs);
	       	if (mapping_mapped(mapping))
			unmap_mapping_range(mapping, offset, write_len, 0);
	}

	retval = filemap_write_and_wait(mapping);
	if (retval == 0) {
		retval = mapping->a_ops->direct_IO(rw, iocb, iov,
						offset, nr_segs);
		if (rw == WRITE && mapping->nrpages) {
			pgoff_t end = (offset + write_len - 1)
						>> PAGE_CACHE_SHIFT;
			int err = invalidate_inode_pages2_range(mapping,
					offset >> PAGE_CACHE_SHIFT, end);
			if (err)
				retval = err;
		}
	}
	return retval;
}
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/**
 * 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.
 *
 * The @gfp_mask argument specifies whether I/O may be performed to release
 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT).
 *
 * NOTE: @gfp_mask may go away, and this function may become non-blocking.
 */
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);