filemap.c 68.2 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>
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#include <linux/backing-dev.h>
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#include <linux/pagevec.h>
#include <linux/blkdev.h>
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#include <linux/backing-dev.h>
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#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 "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)
 *
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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)
 *
 *  ->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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	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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	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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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,
		.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
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struct page *__page_cache_alloc(gfp_t gfp)
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{
	if (cpuset_do_page_mem_spread()) {
		int n = cpuset_mem_spread_node();
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		return alloc_pages_node(n, gfp, 0);
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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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 * 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()).
 */
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void unlock_page(struct page *page)
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{
	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);

579 580 581
/**
 * __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
582
 *
583
 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary.  If some
L
Linus Torvalds 已提交
584 585 586 587
 * 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
588
void __lock_page(struct page *page)
L
Linus Torvalds 已提交
589 590 591 592 593 594 595 596
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);

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

M
Matthew Wilcox 已提交
597 598 599 600 601 602 603 604
int fastcall __lock_page_killable(struct page *page)
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);

	return __wait_on_bit_lock(page_waitqueue(page), &wait,
					sync_page_killable, TASK_KILLABLE);
}

605 606 607 608
/*
 * 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
609
void __lock_page_nosync(struct page *page)
610 611 612 613 614 615
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
	__wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
							TASK_UNINTERRUPTIBLE);
}

616 617 618 619 620
/**
 * 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
621 622
 * 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
623
 */
624
struct page * find_get_page(struct address_space *mapping, pgoff_t offset)
L
Linus Torvalds 已提交
625 626 627 628 629 630 631 632 633 634 635 636 637 638
{
	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);

/**
 * find_lock_page - locate, pin and lock a pagecache page
639 640
 * @mapping: the address_space to search
 * @offset: the page index
L
Linus Torvalds 已提交
641 642 643 644 645 646 647
 *
 * 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,
648
				pgoff_t offset)
L
Linus Torvalds 已提交
649 650 651 652
{
	struct page *page;

repeat:
N
Nick Piggin 已提交
653
	read_lock_irq(&mapping->tree_lock);
L
Linus Torvalds 已提交
654 655 656 657 658
	page = radix_tree_lookup(&mapping->page_tree, offset);
	if (page) {
		page_cache_get(page);
		if (TestSetPageLocked(page)) {
			read_unlock_irq(&mapping->tree_lock);
659
			__lock_page(page);
L
Linus Torvalds 已提交
660 661

			/* Has the page been truncated while we slept? */
N
Nick Piggin 已提交
662
			if (unlikely(page->mapping != mapping)) {
L
Linus Torvalds 已提交
663 664 665 666
				unlock_page(page);
				page_cache_release(page);
				goto repeat;
			}
N
Nick Piggin 已提交
667 668
			VM_BUG_ON(page->index != offset);
			goto out;
L
Linus Torvalds 已提交
669 670 671
		}
	}
	read_unlock_irq(&mapping->tree_lock);
N
Nick Piggin 已提交
672
out:
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Linus Torvalds 已提交
673 674 675 676 677 678
	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
L
Linus Torvalds 已提交
682 683 684 685 686 687 688 689 690 691 692 693 694
 *
 * 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,
695
		pgoff_t index, gfp_t gfp_mask)
L
Linus Torvalds 已提交
696
{
N
Nick Piggin 已提交
697
	struct page *page;
L
Linus Torvalds 已提交
698 699 700 701
	int err;
repeat:
	page = find_lock_page(mapping, index);
	if (!page) {
N
Nick Piggin 已提交
702 703 704 705 706 707 708 709 710
		page = __page_cache_alloc(gfp_mask);
		if (!page)
			return NULL;
		err = add_to_page_cache_lru(page, mapping, index, gfp_mask);
		if (unlikely(err)) {
			page_cache_release(page);
			page = NULL;
			if (err == -EEXIST)
				goto repeat;
L
Linus Torvalds 已提交
711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747
		}
	}
	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;
}

748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778
/**
 * 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;
}
779
EXPORT_SYMBOL(find_get_pages_contig);
780

781 782 783 784 785 786 787 788
/**
 * 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
789
 * Like find_get_pages, except we only return pages which are tagged with
790
 * @tag.   We update @index to index the next page for the traversal.
L
Linus Torvalds 已提交
791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807
 */
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;
}
808
EXPORT_SYMBOL(find_get_pages_tag);
L
Linus Torvalds 已提交
809

810 811 812 813 814
/**
 * grab_cache_page_nowait - returns locked page at given index in given cache
 * @mapping: target address_space
 * @index: the page index
 *
815
 * Same as grab_cache_page(), but do not wait if the page is unavailable.
L
Linus Torvalds 已提交
816 817 818 819 820 821 822 823
 * 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 *
824
grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
L
Linus Torvalds 已提交
825 826 827 828 829 830 831 832 833
{
	struct page *page = find_get_page(mapping, index);

	if (page) {
		if (!TestSetPageLocked(page))
			return page;
		page_cache_release(page);
		return NULL;
	}
834 835
	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
	if (page && add_to_page_cache_lru(page, mapping, index, GFP_KERNEL)) {
L
Linus Torvalds 已提交
836 837 838 839 840 841 842
		page_cache_release(page);
		page = NULL;
	}
	return page;
}
EXPORT_SYMBOL(grab_cache_page_nowait);

843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866
/*
 * 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;
}

867 868 869
/**
 * do_generic_mapping_read - generic file read routine
 * @mapping:	address_space to be read
870
 * @ra:		file's readahead state
871 872 873 874 875
 * @filp:	the file to read
 * @ppos:	current file position
 * @desc:	read_descriptor
 * @actor:	read method
 *
L
Linus Torvalds 已提交
876
 * This is a generic file read routine, and uses the
877
 * mapping->a_ops->readpage() function for the actual low-level stuff.
L
Linus Torvalds 已提交
878 879 880 881
 *
 * This is really ugly. But the goto's actually try to clarify some
 * of the logic when it comes to error handling etc.
 *
882 883
 * Note the struct file* is only passed for the use of readpage.
 * It may be NULL.
L
Linus Torvalds 已提交
884 885
 */
void do_generic_mapping_read(struct address_space *mapping,
886
			     struct file_ra_state *ra,
L
Linus Torvalds 已提交
887 888 889 890 891 892
			     struct file *filp,
			     loff_t *ppos,
			     read_descriptor_t *desc,
			     read_actor_t actor)
{
	struct inode *inode = mapping->host;
893 894 895 896
	pgoff_t index;
	pgoff_t last_index;
	pgoff_t prev_index;
	unsigned long offset;      /* offset into pagecache page */
897
	unsigned int prev_offset;
L
Linus Torvalds 已提交
898 899 900
	int error;

	index = *ppos >> PAGE_CACHE_SHIFT;
901 902
	prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
	prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
L
Linus Torvalds 已提交
903 904 905 906 907
	last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
	offset = *ppos & ~PAGE_CACHE_MASK;

	for (;;) {
		struct page *page;
908
		pgoff_t end_index;
N
NeilBrown 已提交
909
		loff_t isize;
L
Linus Torvalds 已提交
910 911 912 913 914
		unsigned long nr, ret;

		cond_resched();
find_page:
		page = find_get_page(mapping, index);
915
		if (!page) {
916
			page_cache_sync_readahead(mapping,
917
					ra, filp,
918 919 920 921 922 923
					index, last_index - index);
			page = find_get_page(mapping, index);
			if (unlikely(page == NULL))
				goto no_cached_page;
		}
		if (PageReadahead(page)) {
924
			page_cache_async_readahead(mapping,
925
					ra, filp, page,
926
					index, last_index - index);
L
Linus Torvalds 已提交
927 928 929 930
		}
		if (!PageUptodate(page))
			goto page_not_up_to_date;
page_ok:
N
NeilBrown 已提交
931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956
		/*
		 * 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
957 958 959 960 961 962 963 964 965

		/* 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);

		/*
966 967
		 * When a sequential read accesses a page several times,
		 * only mark it as accessed the first time.
L
Linus Torvalds 已提交
968
		 */
969
		if (prev_index != index || offset != prev_offset)
L
Linus Torvalds 已提交
970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986
			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
987
		prev_offset = offset;
L
Linus Torvalds 已提交
988 989 990 991 992 993 994 995

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

page_not_up_to_date:
		/* Get exclusive access to the page ... */
M
Matthew Wilcox 已提交
996 997
		if (lock_page_killable(page))
			goto readpage_eio;
L
Linus Torvalds 已提交
998

N
Nick Piggin 已提交
999
		/* Did it get truncated before we got the lock? */
L
Linus Torvalds 已提交
1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015
		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);

1016 1017 1018 1019 1020
		if (unlikely(error)) {
			if (error == AOP_TRUNCATED_PAGE) {
				page_cache_release(page);
				goto find_page;
			}
L
Linus Torvalds 已提交
1021
			goto readpage_error;
1022
		}
L
Linus Torvalds 已提交
1023 1024

		if (!PageUptodate(page)) {
M
Matthew Wilcox 已提交
1025 1026
			if (lock_page_killable(page))
				goto readpage_eio;
L
Linus Torvalds 已提交
1027 1028 1029 1030 1031 1032 1033 1034 1035 1036
			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);
1037
				shrink_readahead_size_eio(filp, ra);
M
Matthew Wilcox 已提交
1038
				goto readpage_eio;
L
Linus Torvalds 已提交
1039 1040 1041 1042 1043 1044
			}
			unlock_page(page);
		}

		goto page_ok;

M
Matthew Wilcox 已提交
1045 1046
readpage_eio:
		error = -EIO;
L
Linus Torvalds 已提交
1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057
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
1058 1059 1060 1061
		page = page_cache_alloc_cold(mapping);
		if (!page) {
			desc->error = -ENOMEM;
			goto out;
L
Linus Torvalds 已提交
1062
		}
N
Nick Piggin 已提交
1063
		error = add_to_page_cache_lru(page, mapping,
L
Linus Torvalds 已提交
1064 1065
						index, GFP_KERNEL);
		if (error) {
N
Nick Piggin 已提交
1066
			page_cache_release(page);
L
Linus Torvalds 已提交
1067 1068 1069 1070 1071 1072 1073 1074 1075
			if (error == -EEXIST)
				goto find_page;
			desc->error = error;
			goto out;
		}
		goto readpage;
	}

out:
1076 1077 1078
	ra->prev_pos = prev_index;
	ra->prev_pos <<= PAGE_CACHE_SHIFT;
	ra->prev_pos |= prev_offset;
L
Linus Torvalds 已提交
1079

1080
	*ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
L
Linus Torvalds 已提交
1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123
	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;
}

1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162
/*
 * 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);

1163
/**
H
Henrik Kretzschmar 已提交
1164
 * generic_file_aio_read - generic filesystem read routine
1165 1166 1167
 * @iocb:	kernel I/O control block
 * @iov:	io vector request
 * @nr_segs:	number of segments in the iovec
H
Henrik Kretzschmar 已提交
1168
 * @pos:	current file position
1169
 *
L
Linus Torvalds 已提交
1170 1171 1172 1173
 * This is the "read()" routine for all filesystems
 * that can use the page cache directly.
 */
ssize_t
1174 1175
generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos)
L
Linus Torvalds 已提交
1176 1177 1178 1179 1180
{
	struct file *filp = iocb->ki_filp;
	ssize_t retval;
	unsigned long seg;
	size_t count;
1181
	loff_t *ppos = &iocb->ki_pos;
L
Linus Torvalds 已提交
1182 1183

	count = 0;
1184 1185 1186
	retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
	if (retval)
		return retval;
L
Linus Torvalds 已提交
1187 1188 1189

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (filp->f_flags & O_DIRECT) {
1190
		loff_t size;
L
Linus Torvalds 已提交
1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205
		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);
			if (retval > 0)
				*ppos = pos + retval;
		}
1206
		if (likely(retval != 0)) {
1207
			file_accessed(filp);
S
Steven Whitehouse 已提交
1208
			goto out;
1209
		}
L
Linus Torvalds 已提交
1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224
	}

	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;
1225 1226
			if (desc.error) {
				retval = retval ?: desc.error;
L
Linus Torvalds 已提交
1227 1228
				break;
			}
1229 1230
			if (desc.count > 0)
				break;
L
Linus Torvalds 已提交
1231 1232 1233 1234 1235 1236 1237 1238 1239
		}
	}
out:
	return retval;
}
EXPORT_SYMBOL(generic_file_aio_read);

static ssize_t
do_readahead(struct address_space *mapping, struct file *filp,
1240
	     pgoff_t index, unsigned long nr)
L
Linus Torvalds 已提交
1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259
{
	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;
1260 1261
			pgoff_t start = offset >> PAGE_CACHE_SHIFT;
			pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
L
Linus Torvalds 已提交
1262 1263 1264 1265 1266 1267 1268 1269 1270
			unsigned long len = end - start + 1;
			ret = do_readahead(mapping, file, start, len);
		}
		fput(file);
	}
	return ret;
}

#ifdef CONFIG_MMU
1271 1272 1273 1274 1275
/**
 * 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
1276 1277 1278
 * 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
1279
static int page_cache_read(struct file *file, pgoff_t offset)
L
Linus Torvalds 已提交
1280 1281 1282
{
	struct address_space *mapping = file->f_mapping;
	struct page *page; 
1283
	int ret;
L
Linus Torvalds 已提交
1284

1285 1286 1287 1288 1289 1290 1291 1292 1293 1294
	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
1295 1296 1297

		page_cache_release(page);

1298 1299 1300
	} while (ret == AOP_TRUNCATED_PAGE);
		
	return ret;
L
Linus Torvalds 已提交
1301 1302 1303 1304
}

#define MMAP_LOTSAMISS  (100)

1305
/**
1306
 * filemap_fault - read in file data for page fault handling
N
Nick Piggin 已提交
1307 1308
 * @vma:	vma in which the fault was taken
 * @vmf:	struct vm_fault containing details of the fault
1309
 *
1310
 * filemap_fault() is invoked via the vma operations vector for a
L
Linus Torvalds 已提交
1311 1312 1313 1314 1315 1316
 * 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
1317
int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
L
Linus Torvalds 已提交
1318 1319
{
	int error;
1320
	struct file *file = vma->vm_file;
L
Linus Torvalds 已提交
1321 1322 1323 1324
	struct address_space *mapping = file->f_mapping;
	struct file_ra_state *ra = &file->f_ra;
	struct inode *inode = mapping->host;
	struct page *page;
1325 1326
	unsigned long size;
	int did_readaround = 0;
N
Nick Piggin 已提交
1327
	int ret = 0;
L
Linus Torvalds 已提交
1328 1329

	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
N
Nick Piggin 已提交
1330
	if (vmf->pgoff >= size)
1331
		return VM_FAULT_SIGBUS;
L
Linus Torvalds 已提交
1332 1333

	/* If we don't want any read-ahead, don't bother */
1334
	if (VM_RandomReadHint(vma))
L
Linus Torvalds 已提交
1335 1336 1337 1338 1339 1340
		goto no_cached_page;

	/*
	 * Do we have something in the page cache already?
	 */
retry_find:
N
Nick Piggin 已提交
1341
	page = find_lock_page(mapping, vmf->pgoff);
1342 1343 1344 1345 1346
	/*
	 * For sequential accesses, we use the generic readahead logic.
	 */
	if (VM_SequentialReadHint(vma)) {
		if (!page) {
1347
			page_cache_sync_readahead(mapping, ra, file,
1348 1349 1350 1351 1352 1353
							   vmf->pgoff, 1);
			page = find_lock_page(mapping, vmf->pgoff);
			if (!page)
				goto no_cached_page;
		}
		if (PageReadahead(page)) {
1354
			page_cache_async_readahead(mapping, ra, file, page,
1355 1356 1357 1358
							   vmf->pgoff, 1);
		}
	}

L
Linus Torvalds 已提交
1359 1360 1361 1362 1363 1364 1365 1366 1367
	if (!page) {
		unsigned long ra_pages;

		ra->mmap_miss++;

		/*
		 * Do we miss much more than hit in this file? If so,
		 * stop bothering with read-ahead. It will only hurt.
		 */
1368
		if (ra->mmap_miss > MMAP_LOTSAMISS)
L
Linus Torvalds 已提交
1369 1370 1371 1372 1373 1374 1375
			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) {
N
Nick Piggin 已提交
1376
			ret = VM_FAULT_MAJOR;
1377
			count_vm_event(PGMAJFAULT);
L
Linus Torvalds 已提交
1378 1379 1380 1381 1382 1383
		}
		did_readaround = 1;
		ra_pages = max_sane_readahead(file->f_ra.ra_pages);
		if (ra_pages) {
			pgoff_t start = 0;

N
Nick Piggin 已提交
1384 1385
			if (vmf->pgoff > ra_pages / 2)
				start = vmf->pgoff - ra_pages / 2;
L
Linus Torvalds 已提交
1386 1387
			do_page_cache_readahead(mapping, file, start, ra_pages);
		}
N
Nick Piggin 已提交
1388
		page = find_lock_page(mapping, vmf->pgoff);
L
Linus Torvalds 已提交
1389 1390 1391 1392 1393
		if (!page)
			goto no_cached_page;
	}

	if (!did_readaround)
1394
		ra->mmap_miss--;
L
Linus Torvalds 已提交
1395 1396

	/*
1397 1398
	 * 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
1399
	 */
1400
	if (unlikely(!PageUptodate(page)))
L
Linus Torvalds 已提交
1401 1402
		goto page_not_uptodate;

1403 1404
	/* Must recheck i_size under page lock */
	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
N
Nick Piggin 已提交
1405
	if (unlikely(vmf->pgoff >= size)) {
1406
		unlock_page(page);
1407
		page_cache_release(page);
1408
		return VM_FAULT_SIGBUS;
1409 1410
	}

L
Linus Torvalds 已提交
1411 1412 1413 1414
	/*
	 * Found the page and have a reference on it.
	 */
	mark_page_accessed(page);
1415
	ra->prev_pos = (loff_t)page->index << PAGE_CACHE_SHIFT;
N
Nick Piggin 已提交
1416
	vmf->page = page;
N
Nick Piggin 已提交
1417
	return ret | VM_FAULT_LOCKED;
L
Linus Torvalds 已提交
1418 1419 1420 1421 1422 1423

no_cached_page:
	/*
	 * We're only likely to ever get here if MADV_RANDOM is in
	 * effect.
	 */
N
Nick Piggin 已提交
1424
	error = page_cache_read(file, vmf->pgoff);
L
Linus Torvalds 已提交
1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439

	/*
	 * 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
1440 1441
		return VM_FAULT_OOM;
	return VM_FAULT_SIGBUS;
L
Linus Torvalds 已提交
1442 1443

page_not_uptodate:
1444
	/* IO error path */
L
Linus Torvalds 已提交
1445
	if (!did_readaround) {
N
Nick Piggin 已提交
1446
		ret = VM_FAULT_MAJOR;
1447
		count_vm_event(PGMAJFAULT);
L
Linus Torvalds 已提交
1448 1449 1450 1451 1452 1453 1454 1455 1456
	}

	/*
	 * 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);
1457
	error = mapping->a_ops->readpage(file, page);
1458 1459 1460
	page_cache_release(page);

	if (!error || error == AOP_TRUNCATED_PAGE)
1461
		goto retry_find;
L
Linus Torvalds 已提交
1462

1463
	/* Things didn't work out. Return zero to tell the mm layer so. */
1464
	shrink_readahead_size_eio(file, ra);
N
Nick Piggin 已提交
1465
	return VM_FAULT_SIGBUS;
1466 1467 1468
}
EXPORT_SYMBOL(filemap_fault);

L
Linus Torvalds 已提交
1469
struct vm_operations_struct generic_file_vm_ops = {
1470
	.fault		= filemap_fault,
L
Linus Torvalds 已提交
1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482
};

/* 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
1483
	vma->vm_flags |= VM_CAN_NONLINEAR;
L
Linus Torvalds 已提交
1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509
	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);

1510
static struct page *__read_cache_page(struct address_space *mapping,
1511
				pgoff_t index,
L
Linus Torvalds 已提交
1512 1513 1514
				int (*filler)(void *,struct page*),
				void *data)
{
N
Nick Piggin 已提交
1515
	struct page *page;
L
Linus Torvalds 已提交
1516 1517 1518 1519
	int err;
repeat:
	page = find_get_page(mapping, index);
	if (!page) {
N
Nick Piggin 已提交
1520 1521 1522 1523 1524 1525 1526 1527
		page = page_cache_alloc_cold(mapping);
		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
1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539
			/* 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;
}

1540 1541 1542
/*
 * Same as read_cache_page, but don't wait for page to become unlocked
 * after submitting it to the filler.
L
Linus Torvalds 已提交
1543
 */
1544
struct page *read_cache_page_async(struct address_space *mapping,
1545
				pgoff_t index,
L
Linus Torvalds 已提交
1546 1547 1548 1549 1550 1551 1552 1553 1554
				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))
1555
		return page;
L
Linus Torvalds 已提交
1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571
	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);
1572
		return ERR_PTR(err);
L
Linus Torvalds 已提交
1573
	}
1574
out:
1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592
	mark_page_accessed(page);
	return page;
}
EXPORT_SYMBOL(read_cache_page_async);

/**
 * 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,
1593
				pgoff_t index,
1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606
				int (*filler)(void *,struct page*),
				void *data)
{
	struct page *page;

	page = read_cache_page_async(mapping, index, filler, data);
	if (IS_ERR(page))
		goto out;
	wait_on_page_locked(page);
	if (!PageUptodate(page)) {
		page_cache_release(page);
		page = ERR_PTR(-EIO);
	}
L
Linus Torvalds 已提交
1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617
 out:
	return page;
}
EXPORT_SYMBOL(read_cache_page);

/*
 * The logic we want is
 *
 *	if suid or (sgid and xgrp)
 *		remove privs
 */
1618
int should_remove_suid(struct dentry *dentry)
L
Linus Torvalds 已提交
1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633
{
	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;

1634 1635
	if (unlikely(kill && !capable(CAP_FSETID)))
		return kill;
L
Linus Torvalds 已提交
1636

1637 1638
	return 0;
}
M
Mark Fasheh 已提交
1639
EXPORT_SYMBOL(should_remove_suid);
1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650

int __remove_suid(struct dentry *dentry, int kill)
{
	struct iattr newattrs;

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

int remove_suid(struct dentry *dentry)
{
1651 1652 1653
	int killsuid = should_remove_suid(dentry);
	int killpriv = security_inode_need_killpriv(dentry);
	int error = 0;
1654

1655 1656 1657 1658 1659 1660
	if (killpriv < 0)
		return killpriv;
	if (killpriv)
		error = security_inode_killpriv(dentry);
	if (!error && killsuid)
		error = __remove_suid(dentry, killsuid);
1661

1662
	return error;
L
Linus Torvalds 已提交
1663 1664 1665
}
EXPORT_SYMBOL(remove_suid);

N
Nick Piggin 已提交
1666
static size_t __iovec_copy_from_user_inatomic(char *vaddr,
L
Linus Torvalds 已提交
1667 1668 1669 1670 1671 1672 1673 1674 1675
			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;
1676
		left = __copy_from_user_inatomic_nocache(vaddr, buf, copy);
L
Linus Torvalds 已提交
1677 1678 1679 1680 1681
		copied += copy;
		bytes -= copy;
		vaddr += copy;
		iov++;

1682
		if (unlikely(left))
L
Linus Torvalds 已提交
1683 1684 1685 1686 1687
			break;
	}
	return copied - left;
}

N
Nick Piggin 已提交
1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714
/*
 * Copy as much as we can into the page and return the number of bytes which
 * were sucessfully copied.  If a fault is encountered then return the number of
 * 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;
		left = __copy_from_user_inatomic_nocache(kaddr + offset,
							buf, bytes);
		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
1715
EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
N
Nick Piggin 已提交
1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741

/*
 * 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;
		left = __copy_from_user_nocache(kaddr + offset, buf, bytes);
		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
1742
EXPORT_SYMBOL(iov_iter_copy_from_user);
N
Nick Piggin 已提交
1743 1744 1745 1746 1747 1748 1749 1750 1751

static void __iov_iter_advance_iov(struct iov_iter *i, size_t bytes)
{
	if (likely(i->nr_segs == 1)) {
		i->iov_offset += bytes;
	} else {
		const struct iovec *iov = i->iov;
		size_t base = i->iov_offset;

1752 1753 1754 1755 1756
		/*
		 * The !iov->iov_len check ensures we skip over unlikely
		 * zero-length segments.
		 */
		while (bytes || !iov->iov_len) {
N
Nick Piggin 已提交
1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777
			int copy = min(bytes, iov->iov_len - base);

			bytes -= copy;
			base += copy;
			if (iov->iov_len == base) {
				iov++;
				base = 0;
			}
		}
		i->iov = iov;
		i->iov_offset = base;
	}
}

void iov_iter_advance(struct iov_iter *i, size_t bytes)
{
	BUG_ON(i->count < bytes);

	__iov_iter_advance_iov(i, bytes);
	i->count -= bytes;
}
N
Nick Piggin 已提交
1778
EXPORT_SYMBOL(iov_iter_advance);
N
Nick Piggin 已提交
1779

1780 1781 1782 1783 1784 1785 1786 1787 1788 1789
/*
 * 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
1790 1791
{
	char __user *buf = i->iov->iov_base + i->iov_offset;
1792 1793
	bytes = min(bytes, i->iov->iov_len - i->iov_offset);
	return fault_in_pages_readable(buf, bytes);
N
Nick Piggin 已提交
1794
}
N
Nick Piggin 已提交
1795
EXPORT_SYMBOL(iov_iter_fault_in_readable);
N
Nick Piggin 已提交
1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807

/*
 * 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
1808
EXPORT_SYMBOL(iov_iter_single_seg_count);
N
Nick Piggin 已提交
1809

L
Linus Torvalds 已提交
1810 1811 1812
/*
 * Performs necessary checks before doing a write
 *
1813
 * Can adjust writing position or amount of bytes to write.
L
Linus Torvalds 已提交
1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 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
 * 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) {
			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 {
1872
#ifdef CONFIG_BLOCK
L
Linus Torvalds 已提交
1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883
		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;
1884 1885 1886
#else
		return -EPERM;
#endif
L
Linus Torvalds 已提交
1887 1888 1889 1890 1891
	}
	return 0;
}
EXPORT_SYMBOL(generic_write_checks);

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
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;

	if (aops->write_begin) {
		return aops->write_begin(file, mapping, pos, len, flags,
							pagep, fsdata);
	} else {
		int ret;
		pgoff_t index = pos >> PAGE_CACHE_SHIFT;
		unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
		struct inode *inode = mapping->host;
		struct page *page;
again:
		page = __grab_cache_page(mapping, index);
		*pagep = page;
		if (!page)
			return -ENOMEM;

		if (flags & AOP_FLAG_UNINTERRUPTIBLE && !PageUptodate(page)) {
			/*
			 * There is no way to resolve a short write situation
			 * for a !Uptodate page (except by double copying in
			 * the caller done by generic_perform_write_2copy).
			 *
			 * Instead, we have to bring it uptodate here.
			 */
			ret = aops->readpage(file, page);
			page_cache_release(page);
			if (ret) {
				if (ret == AOP_TRUNCATED_PAGE)
					goto again;
				return ret;
			}
			goto again;
		}

		ret = aops->prepare_write(file, page, offset, offset+len);
		if (ret) {
N
Nick Piggin 已提交
1933
			unlock_page(page);
1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976
			page_cache_release(page);
			if (pos + len > inode->i_size)
				vmtruncate(inode, inode->i_size);
		}
		return ret;
	}
}
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;
	int ret;

	if (aops->write_end) {
		mark_page_accessed(page);
		ret = aops->write_end(file, mapping, pos, len, copied,
							page, fsdata);
	} else {
		unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
		struct inode *inode = mapping->host;

		flush_dcache_page(page);
		ret = aops->commit_write(file, page, offset, offset+len);
		unlock_page(page);
		mark_page_accessed(page);
		page_cache_release(page);

		if (ret < 0) {
			if (pos + len > inode->i_size)
				vmtruncate(inode, inode->i_size);
		} else if (ret > 0)
			ret = min_t(size_t, copied, ret);
		else
			ret = copied;
	}

	return ret;
}
EXPORT_SYMBOL(pagecache_write_end);

L
Linus Torvalds 已提交
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
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.
2003
	 * i_mutex is held, which protects generic_osync_inode() from
2004
	 * livelocking.  AIO O_DIRECT ops attempt to sync metadata here.
L
Linus Torvalds 已提交
2005
	 */
2006 2007
	if ((written >= 0 || written == -EIOCBQUEUED) &&
	    ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2008 2009 2010 2011
		int err = generic_osync_inode(inode, mapping, OSYNC_METADATA);
		if (err < 0)
			written = err;
	}
L
Linus Torvalds 已提交
2012 2013 2014 2015
	return written;
}
EXPORT_SYMBOL(generic_file_direct_write);

N
Nick Piggin 已提交
2016 2017 2018 2019
/*
 * Find or create a page at the given pagecache position. Return the locked
 * page. This function is specifically for buffered writes.
 */
2020
struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index)
N
Nick Piggin 已提交
2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040
{
	int status;
	struct page *page;
repeat:
	page = find_lock_page(mapping, index);
	if (likely(page))
		return page;

	page = page_cache_alloc(mapping);
	if (!page)
		return NULL;
	status = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
	if (unlikely(status)) {
		page_cache_release(page);
		if (status == -EEXIST)
			goto repeat;
		return NULL;
	}
	return page;
}
2041
EXPORT_SYMBOL(__grab_cache_page);
N
Nick Piggin 已提交
2042

2043 2044
static ssize_t generic_perform_write_2copy(struct file *file,
				struct iov_iter *i, loff_t pos)
L
Linus Torvalds 已提交
2045
{
A
Andrew Morton 已提交
2046
	struct address_space *mapping = file->f_mapping;
2047
	const struct address_space_operations *a_ops = mapping->a_ops;
2048 2049 2050
	struct inode *inode = mapping->host;
	long status = 0;
	ssize_t written = 0;
L
Linus Torvalds 已提交
2051 2052

	do {
N
Nick Piggin 已提交
2053
		struct page *src_page;
N
Nick Piggin 已提交
2054
		struct page *page;
A
Andrew Morton 已提交
2055 2056
		pgoff_t index;		/* Pagecache index for current page */
		unsigned long offset;	/* Offset into pagecache page */
N
Nick Piggin 已提交
2057
		unsigned long bytes;	/* Bytes to write to page */
A
Andrew Morton 已提交
2058
		size_t copied;		/* Bytes copied from user */
L
Linus Torvalds 已提交
2059

A
Andrew Morton 已提交
2060
		offset = (pos & (PAGE_CACHE_SIZE - 1));
L
Linus Torvalds 已提交
2061
		index = pos >> PAGE_CACHE_SHIFT;
N
Nick Piggin 已提交
2062
		bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2063
						iov_iter_count(i));
2064

N
Nick Piggin 已提交
2065 2066 2067 2068 2069 2070
		/*
		 * a non-NULL src_page indicates that we're doing the
		 * copy via get_user_pages and kmap.
		 */
		src_page = NULL;

2071 2072 2073 2074 2075
		/*
		 * 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.
N
Nick Piggin 已提交
2076 2077 2078 2079
		 *
		 * 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.
2080
		 */
2081
		if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
N
Nick Piggin 已提交
2082 2083 2084
			status = -EFAULT;
			break;
		}
N
Nick Piggin 已提交
2085 2086

		page = __grab_cache_page(mapping, index);
L
Linus Torvalds 已提交
2087 2088 2089 2090 2091
		if (!page) {
			status = -ENOMEM;
			break;
		}

N
Nick Piggin 已提交
2092 2093 2094 2095 2096
		/*
		 * non-uptodate pages cannot cope with short copies, and we
		 * cannot take a pagefault with the destination page locked.
		 * So pin the source page to copy it.
		 */
N
Nick Piggin 已提交
2097
		if (!PageUptodate(page) && !segment_eq(get_fs(), KERNEL_DS)) {
N
Nick Piggin 已提交
2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111
			unlock_page(page);

			src_page = alloc_page(GFP_KERNEL);
			if (!src_page) {
				page_cache_release(page);
				status = -ENOMEM;
				break;
			}

			/*
			 * Cannot get_user_pages with a page locked for the
			 * same reason as we can't take a page fault with a
			 * page locked (as explained below).
			 */
2112
			copied = iov_iter_copy_from_user(src_page, i,
N
Nick Piggin 已提交
2113
								offset, bytes);
N
Nick Piggin 已提交
2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138
			if (unlikely(copied == 0)) {
				status = -EFAULT;
				page_cache_release(page);
				page_cache_release(src_page);
				break;
			}
			bytes = copied;

			lock_page(page);
			/*
			 * Can't handle the page going uptodate here, because
			 * that means we would use non-atomic usercopies, which
			 * zero out the tail of the page, which can cause
			 * zeroes to become transiently visible. We could just
			 * use a non-zeroing copy, but the APIs aren't too
			 * consistent.
			 */
			if (unlikely(!page->mapping || PageUptodate(page))) {
				unlock_page(page);
				page_cache_release(page);
				page_cache_release(src_page);
				continue;
			}
		}

L
Linus Torvalds 已提交
2139
		status = a_ops->prepare_write(file, page, offset, offset+bytes);
N
Nick Piggin 已提交
2140 2141
		if (unlikely(status))
			goto fs_write_aop_error;
2142

N
Nick Piggin 已提交
2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157
		if (!src_page) {
			/*
			 * Must not enter the pagefault handler here, because
			 * we hold the page lock, so we might recursively
			 * deadlock on the same lock, or get an ABBA deadlock
			 * against a different lock, or against the mmap_sem
			 * (which nests outside the page lock).  So increment
			 * preempt count, and use _atomic usercopies.
			 *
			 * The page is uptodate so we are OK to encounter a
			 * short copy: if unmodified parts of the page are
			 * marked dirty and written out to disk, it doesn't
			 * really matter.
			 */
			pagefault_disable();
2158
			copied = iov_iter_copy_from_user_atomic(page, i,
N
Nick Piggin 已提交
2159
								offset, bytes);
N
Nick Piggin 已提交
2160 2161 2162 2163 2164 2165 2166 2167 2168 2169
			pagefault_enable();
		} else {
			void *src, *dst;
			src = kmap_atomic(src_page, KM_USER0);
			dst = kmap_atomic(page, KM_USER1);
			memcpy(dst + offset, src + offset, bytes);
			kunmap_atomic(dst, KM_USER1);
			kunmap_atomic(src, KM_USER0);
			copied = bytes;
		}
L
Linus Torvalds 已提交
2170
		flush_dcache_page(page);
N
Nick Piggin 已提交
2171

L
Linus Torvalds 已提交
2172
		status = a_ops->commit_write(file, page, offset, offset+bytes);
N
Nick Piggin 已提交
2173
		if (unlikely(status < 0))
N
Nick Piggin 已提交
2174 2175
			goto fs_write_aop_error;
		if (unlikely(status > 0)) /* filesystem did partial write */
N
Nick Piggin 已提交
2176 2177 2178 2179 2180 2181 2182
			copied = min_t(size_t, copied, status);

		unlock_page(page);
		mark_page_accessed(page);
		page_cache_release(page);
		if (src_page)
			page_cache_release(src_page);
N
Nick Piggin 已提交
2183

2184
		iov_iter_advance(i, copied);
N
Nick Piggin 已提交
2185
		pos += copied;
2186
		written += copied;
N
Nick Piggin 已提交
2187

L
Linus Torvalds 已提交
2188 2189
		balance_dirty_pages_ratelimited(mapping);
		cond_resched();
N
Nick Piggin 已提交
2190 2191 2192
		continue;

fs_write_aop_error:
N
Nick Piggin 已提交
2193
		unlock_page(page);
N
Nick Piggin 已提交
2194
		page_cache_release(page);
N
Nick Piggin 已提交
2195 2196
		if (src_page)
			page_cache_release(src_page);
N
Nick Piggin 已提交
2197 2198 2199 2200 2201 2202 2203 2204

		/*
		 * prepare_write() may have instantiated a few blocks
		 * outside i_size.  Trim these off again. Don't need
		 * i_size_read because we hold i_mutex.
		 */
		if (pos + bytes > inode->i_size)
			vmtruncate(inode, inode->i_size);
N
Nick Piggin 已提交
2205
		break;
2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217
	} while (iov_iter_count(i));

	return written ? written : status;
}

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
Nick Piggin 已提交
2218 2219 2220 2221 2222 2223 2224
	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;
2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255

	do {
		struct page *page;
		pgoff_t index;		/* Pagecache index for current 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));
		index = pos >> PAGE_CACHE_SHIFT;
		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;
		}

N
Nick Piggin 已提交
2256
		status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273
						&page, &fsdata);
		if (unlikely(status))
			break;

		pagefault_disable();
		copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
		pagefault_enable();
		flush_dcache_page(page);

		status = a_ops->write_end(file, mapping, pos, bytes, copied,
						page, fsdata);
		if (unlikely(status < 0))
			break;
		copied = status;

		cond_resched();

2274
		iov_iter_advance(i, copied);
2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314
		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;
	struct address_space *mapping = file->f_mapping;
	const struct address_space_operations *a_ops = mapping->a_ops;
	struct inode *inode = mapping->host;
	ssize_t status;
	struct iov_iter i;

	iov_iter_init(&i, iov, nr_segs, count, written);
	if (a_ops->write_begin)
		status = generic_perform_write(file, &i, pos);
	else
		status = generic_perform_write_2copy(file, &i, pos);
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Linus Torvalds 已提交
2315 2316

	if (likely(status >= 0)) {
2317 2318 2319 2320 2321 2322 2323
		written += status;
		*ppos = pos + status;

		/*
		 * For now, when the user asks for O_SYNC, we'll actually give
		 * O_DSYNC
		 */
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2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342
		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);

	return written ? written : status;
}
EXPORT_SYMBOL(generic_file_buffered_write);

2343
static ssize_t
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Linus Torvalds 已提交
2344 2345 2346 2347
__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;
2348
	struct address_space * mapping = file->f_mapping;
L
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2349 2350 2351 2352 2353 2354 2355 2356
	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;
2357 2358 2359
	err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
	if (err)
		return err;
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	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;

2377
	err = remove_suid(file->f_path.dentry);
L
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2378 2379 2380
	if (err)
		goto out;

2381
	file_update_time(file);
L
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2382 2383 2384

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (unlikely(file->f_flags & O_DIRECT)) {
2385 2386 2387 2388 2389
		loff_t endbyte;
		ssize_t written_buffered;

		written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
							ppos, count, ocount);
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2390 2391 2392 2393 2394 2395 2396 2397
		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;
2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411
		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;
		}
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Linus Torvalds 已提交
2412

2413 2414 2415 2416 2417 2418
		/*
		 * 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;
M
Mark Fasheh 已提交
2419 2420 2421 2422
		err = do_sync_mapping_range(file->f_mapping, pos, endbyte,
					    SYNC_FILE_RANGE_WAIT_BEFORE|
					    SYNC_FILE_RANGE_WRITE|
					    SYNC_FILE_RANGE_WAIT_AFTER);
2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437
		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);
	}
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2438 2439 2440 2441 2442
out:
	current->backing_dev_info = NULL;
	return written ? written : err;
}

2443 2444
ssize_t generic_file_aio_write_nolock(struct kiocb *iocb,
		const struct iovec *iov, unsigned long nr_segs, loff_t pos)
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2445 2446 2447 2448 2449 2450
{
	struct file *file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t ret;

2451 2452 2453 2454
	BUG_ON(iocb->ki_pos != pos);

	ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
			&iocb->ki_pos);
L
Linus Torvalds 已提交
2455 2456

	if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2457
		ssize_t err;
L
Linus Torvalds 已提交
2458 2459 2460 2461 2462 2463 2464

		err = sync_page_range_nolock(inode, mapping, pos, ret);
		if (err < 0)
			ret = err;
	}
	return ret;
}
2465
EXPORT_SYMBOL(generic_file_aio_write_nolock);
L
Linus Torvalds 已提交
2466

2467 2468
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
2469 2470 2471 2472 2473 2474 2475 2476
{
	struct file *file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t ret;

	BUG_ON(iocb->ki_pos != pos);

2477
	mutex_lock(&inode->i_mutex);
2478 2479
	ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
			&iocb->ki_pos);
2480
	mutex_unlock(&inode->i_mutex);
L
Linus Torvalds 已提交
2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493

	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);

/*
2494
 * Called under i_mutex for writes to S_ISREG files.   Returns -EIO if something
L
Linus Torvalds 已提交
2495 2496
 * went wrong during pagecache shootdown.
 */
2497
static ssize_t
L
Linus Torvalds 已提交
2498 2499 2500 2501 2502 2503
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;
2504 2505
	size_t write_len;
	pgoff_t end = 0; /* silence gcc */
L
Linus Torvalds 已提交
2506 2507 2508 2509 2510 2511 2512 2513

	/*
	 * 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);
2514
		end = (offset + write_len - 1) >> PAGE_CACHE_SHIFT;
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Linus Torvalds 已提交
2515 2516 2517 2518 2519
	       	if (mapping_mapped(mapping))
			unmap_mapping_range(mapping, offset, write_len, 0);
	}

	retval = filemap_write_and_wait(mapping);
2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530
	if (retval)
		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
	 * -EIO without clobbering -EIOCBQUEUED from ->direct_IO().
	 */
	if (rw == WRITE && mapping->nrpages) {
		retval = invalidate_inode_pages2_range(mapping,
L
Linus Torvalds 已提交
2531
					offset >> PAGE_CACHE_SHIFT, end);
2532 2533
		if (retval)
			goto out;
L
Linus Torvalds 已提交
2534
	}
2535 2536 2537 2538 2539

	retval = mapping->a_ops->direct_IO(rw, iocb, iov, offset, nr_segs);

	/*
	 * Finally, try again to invalidate clean pages which might have been
2540 2541 2542 2543 2544
	 * 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...
2545 2546
	 */
	if (rw == WRITE && mapping->nrpages) {
2547
		invalidate_inode_pages2_range(mapping, offset >> PAGE_CACHE_SHIFT, end);
2548 2549
	}
out:
L
Linus Torvalds 已提交
2550 2551
	return retval;
}
2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581

/**
 * 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);