filemap.c 64.9 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>
#include <linux/security.h>
#include <linux/syscalls.h>
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#include <linux/cpuset.h>
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#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
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#include <linux/memcontrol.h>
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#include <linux/mm_inline.h> /* for page_is_file_cache() */
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#include "internal.h"

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

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

/*
 * Lock ordering:
 *
 *  ->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
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 * is safe.  The caller must hold the mapping's tree_lock.
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 */
void __remove_from_page_cache(struct page *page)
{
	struct address_space *mapping = page->mapping;

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

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

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	BUG_ON(!PageLocked(page));
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	spin_lock_irq(&mapping->tree_lock);
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	__remove_from_page_cache(page);
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	spin_unlock_irq(&mapping->tree_lock);
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	mem_cgroup_uncharge_cache_page(page);
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}

static int sync_page(void *word)
{
	struct address_space *mapping;
	struct page *page;

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

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

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

	if (!mapping_cap_writeback_dirty(mapping))
		return 0;

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

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

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

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

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/**
 * 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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/**
 * filemap_fdatawait_range - wait for all under-writeback pages to complete in a given range
 * @mapping: address space structure to wait for
 * @start:	offset in bytes where the range starts
 * @end:	offset in bytes where the range ends (inclusive)
 *
 * Walk the list of under-writeback pages of the given address space
 * in the given range and wait for all of them.
 *
 * This is just a simple wrapper so that callers don't have to convert offsets
 * to page indexes themselves
 */
int filemap_fdatawait_range(struct address_space *mapping, loff_t start,
			    loff_t end)
{
	return wait_on_page_writeback_range(mapping, start >> PAGE_CACHE_SHIFT,
					    end >> PAGE_CACHE_SHIFT);
}
EXPORT_SYMBOL(filemap_fdatawait_range);

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

	if (i_size == 0)
		return 0;

	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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EXPORT_SYMBOL(filemap_write_and_wait_range);
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/**
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 * add_to_page_cache_locked - add a locked page to the pagecache
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 * @page:	page to add
 * @mapping:	the page's address_space
 * @offset:	page index
 * @gfp_mask:	page allocation mode
 *
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 * This function is used to add a page to the pagecache. It must be locked.
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 * This function does not add the page to the LRU.  The caller must do that.
 */
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int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
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		pgoff_t offset, gfp_t gfp_mask)
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{
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	int error;

	VM_BUG_ON(!PageLocked(page));

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

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

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

	ret = add_to_page_cache(page, mapping, offset, gfp_mask);
	if (ret == 0) {
		if (page_is_file_cache(page))
			lru_cache_add_file(page);
		else
			lru_cache_add_active_anon(page);
	}
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	return ret;
}
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EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
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#ifdef CONFIG_NUMA
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struct page *__page_cache_alloc(gfp_t gfp)
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{
	if (cpuset_do_page_mem_spread()) {
		int n = cpuset_mem_spread_node();
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		return alloc_pages_exact_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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/**
 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
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 * @page: Page defining the wait queue of interest
 * @waiter: Waiter to add to the queue
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 *
 * Add an arbitrary @waiter to the wait queue for the nominated @page.
 */
void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
{
	wait_queue_head_t *q = page_waitqueue(page);
	unsigned long flags;

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

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/**
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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.
 *
N
Nick Piggin 已提交
555 556
 * The mb is necessary to enforce ordering between the clear_bit and the read
 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
L
Linus Torvalds 已提交
557
 */
H
Harvey Harrison 已提交
558
void unlock_page(struct page *page)
L
Linus Torvalds 已提交
559
{
N
Nick Piggin 已提交
560 561 562
	VM_BUG_ON(!PageLocked(page));
	clear_bit_unlock(PG_locked, &page->flags);
	smp_mb__after_clear_bit();
L
Linus Torvalds 已提交
563 564 565 566
	wake_up_page(page, PG_locked);
}
EXPORT_SYMBOL(unlock_page);

567 568 569
/**
 * end_page_writeback - end writeback against a page
 * @page: the page
L
Linus Torvalds 已提交
570 571 572
 */
void end_page_writeback(struct page *page)
{
573 574 575 576 577 578
	if (TestClearPageReclaim(page))
		rotate_reclaimable_page(page);

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

L
Linus Torvalds 已提交
579 580 581 582 583
	smp_mb__after_clear_bit();
	wake_up_page(page, PG_writeback);
}
EXPORT_SYMBOL(end_page_writeback);

584 585 586
/**
 * __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
587
 *
588
 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary.  If some
L
Linus Torvalds 已提交
589 590 591 592
 * 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
593
void __lock_page(struct page *page)
L
Linus Torvalds 已提交
594 595 596 597 598 599 600 601
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);

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

H
Harvey Harrison 已提交
602
int __lock_page_killable(struct page *page)
M
Matthew Wilcox 已提交
603 604 605 606 607 608
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);

	return __wait_on_bit_lock(page_waitqueue(page), &wait,
					sync_page_killable, TASK_KILLABLE);
}
609
EXPORT_SYMBOL_GPL(__lock_page_killable);
M
Matthew Wilcox 已提交
610

611 612 613 614
/**
 * __lock_page_nosync - get a lock on the page, without calling sync_page()
 * @page: the page to lock
 *
615 616 617
 * 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
618
void __lock_page_nosync(struct page *page)
619 620 621 622 623 624
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
	__wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
							TASK_UNINTERRUPTIBLE);
}

625 626 627 628 629
/**
 * 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
630 631
 * 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
632
 */
N
Nick Piggin 已提交
633
struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
L
Linus Torvalds 已提交
634
{
N
Nick Piggin 已提交
635
	void **pagep;
L
Linus Torvalds 已提交
636 637
	struct page *page;

N
Nick Piggin 已提交
638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661
	rcu_read_lock();
repeat:
	page = NULL;
	pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
	if (pagep) {
		page = radix_tree_deref_slot(pagep);
		if (unlikely(!page || page == RADIX_TREE_RETRY))
			goto repeat;

		if (!page_cache_get_speculative(page))
			goto repeat;

		/*
		 * Has the page moved?
		 * This is part of the lockless pagecache protocol. See
		 * include/linux/pagemap.h for details.
		 */
		if (unlikely(page != *pagep)) {
			page_cache_release(page);
			goto repeat;
		}
	}
	rcu_read_unlock();

L
Linus Torvalds 已提交
662 663 664 665 666 667
	return page;
}
EXPORT_SYMBOL(find_get_page);

/**
 * find_lock_page - locate, pin and lock a pagecache page
668 669
 * @mapping: the address_space to search
 * @offset: the page index
L
Linus Torvalds 已提交
670 671 672 673 674 675
 *
 * Locates the desired pagecache page, locks it, increments its reference
 * count and returns its address.
 *
 * Returns zero if the page was not present. find_lock_page() may sleep.
 */
N
Nick Piggin 已提交
676
struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
L
Linus Torvalds 已提交
677 678 679 680
{
	struct page *page;

repeat:
N
Nick Piggin 已提交
681
	page = find_get_page(mapping, offset);
L
Linus Torvalds 已提交
682
	if (page) {
N
Nick Piggin 已提交
683 684 685 686 687 688
		lock_page(page);
		/* Has the page been truncated? */
		if (unlikely(page->mapping != mapping)) {
			unlock_page(page);
			page_cache_release(page);
			goto repeat;
L
Linus Torvalds 已提交
689
		}
N
Nick Piggin 已提交
690
		VM_BUG_ON(page->index != offset);
L
Linus Torvalds 已提交
691 692 693 694 695 696 697
	}
	return page;
}
EXPORT_SYMBOL(find_lock_page);

/**
 * find_or_create_page - locate or add a pagecache page
698 699 700
 * @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
701 702 703 704 705 706 707 708 709 710 711 712 713
 *
 * 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,
714
		pgoff_t index, gfp_t gfp_mask)
L
Linus Torvalds 已提交
715
{
N
Nick Piggin 已提交
716
	struct page *page;
L
Linus Torvalds 已提交
717 718 719 720
	int err;
repeat:
	page = find_lock_page(mapping, index);
	if (!page) {
N
Nick Piggin 已提交
721 722 723
		page = __page_cache_alloc(gfp_mask);
		if (!page)
			return NULL;
N
Nick Piggin 已提交
724 725 726 727 728 729 730 731
		/*
		 * We want a regular kernel memory (not highmem or DMA etc)
		 * allocation for the radix tree nodes, but we need to honour
		 * the context-specific requirements the caller has asked for.
		 * GFP_RECLAIM_MASK collects those requirements.
		 */
		err = add_to_page_cache_lru(page, mapping, index,
			(gfp_mask & GFP_RECLAIM_MASK));
N
Nick Piggin 已提交
732 733 734 735 736
		if (unlikely(err)) {
			page_cache_release(page);
			page = NULL;
			if (err == -EEXIST)
				goto repeat;
L
Linus Torvalds 已提交
737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763
		}
	}
	return page;
}
EXPORT_SYMBOL(find_or_create_page);

/**
 * find_get_pages - gang pagecache lookup
 * @mapping:	The address_space to search
 * @start:	The starting page index
 * @nr_pages:	The maximum number of pages
 * @pages:	Where the resulting pages are placed
 *
 * find_get_pages() will search for and return a group of up to
 * @nr_pages pages in the mapping.  The pages are placed at @pages.
 * find_get_pages() takes a reference against the returned pages.
 *
 * The search returns a group of mapping-contiguous pages with ascending
 * indexes.  There may be holes in the indices due to not-present pages.
 *
 * find_get_pages() returns the number of pages which were found.
 */
unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
			    unsigned int nr_pages, struct page **pages)
{
	unsigned int i;
	unsigned int ret;
N
Nick Piggin 已提交
764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791
	unsigned int nr_found;

	rcu_read_lock();
restart:
	nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
				(void ***)pages, start, nr_pages);
	ret = 0;
	for (i = 0; i < nr_found; i++) {
		struct page *page;
repeat:
		page = radix_tree_deref_slot((void **)pages[i]);
		if (unlikely(!page))
			continue;
		/*
		 * this can only trigger if nr_found == 1, making livelock
		 * a non issue.
		 */
		if (unlikely(page == RADIX_TREE_RETRY))
			goto restart;

		if (!page_cache_get_speculative(page))
			goto repeat;

		/* Has the page moved? */
		if (unlikely(page != *((void **)pages[i]))) {
			page_cache_release(page);
			goto repeat;
		}
L
Linus Torvalds 已提交
792

N
Nick Piggin 已提交
793 794 795 796
		pages[ret] = page;
		ret++;
	}
	rcu_read_unlock();
L
Linus Torvalds 已提交
797 798 799
	return ret;
}

800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816
/**
 * find_get_pages_contig - gang contiguous pagecache lookup
 * @mapping:	The address_space to search
 * @index:	The starting page index
 * @nr_pages:	The maximum number of pages
 * @pages:	Where the resulting pages are placed
 *
 * find_get_pages_contig() works exactly like find_get_pages(), except
 * that the returned number of pages are guaranteed to be contiguous.
 *
 * find_get_pages_contig() returns the number of pages which were found.
 */
unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
			       unsigned int nr_pages, struct page **pages)
{
	unsigned int i;
	unsigned int ret;
N
Nick Piggin 已提交
817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835
	unsigned int nr_found;

	rcu_read_lock();
restart:
	nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
				(void ***)pages, index, nr_pages);
	ret = 0;
	for (i = 0; i < nr_found; i++) {
		struct page *page;
repeat:
		page = radix_tree_deref_slot((void **)pages[i]);
		if (unlikely(!page))
			continue;
		/*
		 * this can only trigger if nr_found == 1, making livelock
		 * a non issue.
		 */
		if (unlikely(page == RADIX_TREE_RETRY))
			goto restart;
836

N
Nick Piggin 已提交
837
		if (page->mapping == NULL || page->index != index)
838 839
			break;

N
Nick Piggin 已提交
840 841 842 843 844 845 846 847 848 849 850
		if (!page_cache_get_speculative(page))
			goto repeat;

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

		pages[ret] = page;
		ret++;
851 852
		index++;
	}
N
Nick Piggin 已提交
853 854
	rcu_read_unlock();
	return ret;
855
}
856
EXPORT_SYMBOL(find_get_pages_contig);
857

858 859 860 861 862 863 864 865
/**
 * 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
866
 * Like find_get_pages, except we only return pages which are tagged with
867
 * @tag.   We update @index to index the next page for the traversal.
L
Linus Torvalds 已提交
868 869 870 871 872 873
 */
unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
			int tag, unsigned int nr_pages, struct page **pages)
{
	unsigned int i;
	unsigned int ret;
N
Nick Piggin 已提交
874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906
	unsigned int nr_found;

	rcu_read_lock();
restart:
	nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
				(void ***)pages, *index, nr_pages, tag);
	ret = 0;
	for (i = 0; i < nr_found; i++) {
		struct page *page;
repeat:
		page = radix_tree_deref_slot((void **)pages[i]);
		if (unlikely(!page))
			continue;
		/*
		 * this can only trigger if nr_found == 1, making livelock
		 * a non issue.
		 */
		if (unlikely(page == RADIX_TREE_RETRY))
			goto restart;

		if (!page_cache_get_speculative(page))
			goto repeat;

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

		pages[ret] = page;
		ret++;
	}
	rcu_read_unlock();
L
Linus Torvalds 已提交
907 908 909

	if (ret)
		*index = pages[ret - 1]->index + 1;
N
Nick Piggin 已提交
910

L
Linus Torvalds 已提交
911 912
	return ret;
}
913
EXPORT_SYMBOL(find_get_pages_tag);
L
Linus Torvalds 已提交
914

915 916 917 918 919
/**
 * grab_cache_page_nowait - returns locked page at given index in given cache
 * @mapping: target address_space
 * @index: the page index
 *
920
 * Same as grab_cache_page(), but do not wait if the page is unavailable.
L
Linus Torvalds 已提交
921 922 923 924 925 926 927 928
 * 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 *
929
grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
L
Linus Torvalds 已提交
930 931 932 933
{
	struct page *page = find_get_page(mapping, index);

	if (page) {
N
Nick Piggin 已提交
934
		if (trylock_page(page))
L
Linus Torvalds 已提交
935 936 937 938
			return page;
		page_cache_release(page);
		return NULL;
	}
939
	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
N
Nick Piggin 已提交
940
	if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
L
Linus Torvalds 已提交
941 942 943 944 945 946 947
		page_cache_release(page);
		page = NULL;
	}
	return page;
}
EXPORT_SYMBOL(grab_cache_page_nowait);

948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968
/*
 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
 * a _large_ part of the i/o request. Imagine the worst scenario:
 *
 *      ---R__________________________________________B__________
 *         ^ reading here                             ^ bad block(assume 4k)
 *
 * read(R) => miss => readahead(R...B) => media error => frustrating retries
 * => failing the whole request => read(R) => read(R+1) =>
 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
 *
 * It is going insane. Fix it by quickly scaling down the readahead size.
 */
static void shrink_readahead_size_eio(struct file *filp,
					struct file_ra_state *ra)
{
	ra->ra_pages /= 4;
}

969
/**
C
Christoph Hellwig 已提交
970
 * do_generic_file_read - generic file read routine
971 972 973 974 975
 * @filp:	the file to read
 * @ppos:	current file position
 * @desc:	read_descriptor
 * @actor:	read method
 *
L
Linus Torvalds 已提交
976
 * This is a generic file read routine, and uses the
977
 * mapping->a_ops->readpage() function for the actual low-level stuff.
L
Linus Torvalds 已提交
978 979 980 981
 *
 * This is really ugly. But the goto's actually try to clarify some
 * of the logic when it comes to error handling etc.
 */
C
Christoph Hellwig 已提交
982 983
static void do_generic_file_read(struct file *filp, loff_t *ppos,
		read_descriptor_t *desc, read_actor_t actor)
L
Linus Torvalds 已提交
984
{
C
Christoph Hellwig 已提交
985
	struct address_space *mapping = filp->f_mapping;
L
Linus Torvalds 已提交
986
	struct inode *inode = mapping->host;
C
Christoph Hellwig 已提交
987
	struct file_ra_state *ra = &filp->f_ra;
988 989 990 991
	pgoff_t index;
	pgoff_t last_index;
	pgoff_t prev_index;
	unsigned long offset;      /* offset into pagecache page */
992
	unsigned int prev_offset;
L
Linus Torvalds 已提交
993 994 995
	int error;

	index = *ppos >> PAGE_CACHE_SHIFT;
996 997
	prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
	prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
L
Linus Torvalds 已提交
998 999 1000 1001 1002
	last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
	offset = *ppos & ~PAGE_CACHE_MASK;

	for (;;) {
		struct page *page;
1003
		pgoff_t end_index;
N
NeilBrown 已提交
1004
		loff_t isize;
L
Linus Torvalds 已提交
1005 1006 1007 1008 1009
		unsigned long nr, ret;

		cond_resched();
find_page:
		page = find_get_page(mapping, index);
1010
		if (!page) {
1011
			page_cache_sync_readahead(mapping,
1012
					ra, filp,
1013 1014 1015 1016 1017 1018
					index, last_index - index);
			page = find_get_page(mapping, index);
			if (unlikely(page == NULL))
				goto no_cached_page;
		}
		if (PageReadahead(page)) {
1019
			page_cache_async_readahead(mapping,
1020
					ra, filp, page,
1021
					index, last_index - index);
L
Linus Torvalds 已提交
1022
		}
1023 1024 1025 1026
		if (!PageUptodate(page)) {
			if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
					!mapping->a_ops->is_partially_uptodate)
				goto page_not_up_to_date;
N
Nick Piggin 已提交
1027
			if (!trylock_page(page))
1028 1029 1030 1031 1032 1033
				goto page_not_up_to_date;
			if (!mapping->a_ops->is_partially_uptodate(page,
								desc, offset))
				goto page_not_up_to_date_locked;
			unlock_page(page);
		}
L
Linus Torvalds 已提交
1034
page_ok:
N
NeilBrown 已提交
1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060
		/*
		 * 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
1061 1062 1063 1064 1065 1066 1067 1068 1069

		/* 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);

		/*
1070 1071
		 * When a sequential read accesses a page several times,
		 * only mark it as accessed the first time.
L
Linus Torvalds 已提交
1072
		 */
1073
		if (prev_index != index || offset != prev_offset)
L
Linus Torvalds 已提交
1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090
			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
1091
		prev_offset = offset;
L
Linus Torvalds 已提交
1092 1093 1094 1095 1096 1097 1098 1099

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

page_not_up_to_date:
		/* Get exclusive access to the page ... */
1100 1101 1102
		error = lock_page_killable(page);
		if (unlikely(error))
			goto readpage_error;
L
Linus Torvalds 已提交
1103

1104
page_not_up_to_date_locked:
N
Nick Piggin 已提交
1105
		/* Did it get truncated before we got the lock? */
L
Linus Torvalds 已提交
1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121
		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);

1122 1123 1124 1125 1126
		if (unlikely(error)) {
			if (error == AOP_TRUNCATED_PAGE) {
				page_cache_release(page);
				goto find_page;
			}
L
Linus Torvalds 已提交
1127
			goto readpage_error;
1128
		}
L
Linus Torvalds 已提交
1129 1130

		if (!PageUptodate(page)) {
1131 1132 1133
			error = lock_page_killable(page);
			if (unlikely(error))
				goto readpage_error;
L
Linus Torvalds 已提交
1134 1135 1136 1137 1138 1139 1140 1141 1142 1143
			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);
1144
				shrink_readahead_size_eio(filp, ra);
1145 1146
				error = -EIO;
				goto readpage_error;
L
Linus Torvalds 已提交
1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163
			}
			unlock_page(page);
		}

		goto page_ok;

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

no_cached_page:
		/*
		 * Ok, it wasn't cached, so we need to create a new
		 * page..
		 */
N
Nick Piggin 已提交
1164 1165 1166 1167
		page = page_cache_alloc_cold(mapping);
		if (!page) {
			desc->error = -ENOMEM;
			goto out;
L
Linus Torvalds 已提交
1168
		}
N
Nick Piggin 已提交
1169
		error = add_to_page_cache_lru(page, mapping,
L
Linus Torvalds 已提交
1170 1171
						index, GFP_KERNEL);
		if (error) {
N
Nick Piggin 已提交
1172
			page_cache_release(page);
L
Linus Torvalds 已提交
1173 1174 1175 1176 1177 1178 1179 1180 1181
			if (error == -EEXIST)
				goto find_page;
			desc->error = error;
			goto out;
		}
		goto readpage;
	}

out:
1182 1183 1184
	ra->prev_pos = prev_index;
	ra->prev_pos <<= PAGE_CACHE_SHIFT;
	ra->prev_pos |= prev_offset;
L
Linus Torvalds 已提交
1185

1186
	*ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1187
	file_accessed(filp);
L
Linus Torvalds 已提交
1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227
}

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;
}

1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266
/*
 * 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);

1267
/**
H
Henrik Kretzschmar 已提交
1268
 * generic_file_aio_read - generic filesystem read routine
1269 1270 1271
 * @iocb:	kernel I/O control block
 * @iov:	io vector request
 * @nr_segs:	number of segments in the iovec
H
Henrik Kretzschmar 已提交
1272
 * @pos:	current file position
1273
 *
L
Linus Torvalds 已提交
1274 1275 1276 1277
 * This is the "read()" routine for all filesystems
 * that can use the page cache directly.
 */
ssize_t
1278 1279
generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos)
L
Linus Torvalds 已提交
1280 1281 1282 1283 1284
{
	struct file *filp = iocb->ki_filp;
	ssize_t retval;
	unsigned long seg;
	size_t count;
1285
	loff_t *ppos = &iocb->ki_pos;
L
Linus Torvalds 已提交
1286 1287

	count = 0;
1288 1289 1290
	retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
	if (retval)
		return retval;
L
Linus Torvalds 已提交
1291 1292 1293

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (filp->f_flags & O_DIRECT) {
1294
		loff_t size;
L
Linus Torvalds 已提交
1295 1296 1297 1298 1299 1300 1301 1302 1303
		struct address_space *mapping;
		struct inode *inode;

		mapping = filp->f_mapping;
		inode = mapping->host;
		if (!count)
			goto out; /* skip atime */
		size = i_size_read(inode);
		if (pos < size) {
1304 1305
			retval = filemap_write_and_wait_range(mapping, pos,
					pos + iov_length(iov, nr_segs) - 1);
1306 1307 1308 1309
			if (!retval) {
				retval = mapping->a_ops->direct_IO(READ, iocb,
							iov, pos, nr_segs);
			}
L
Linus Torvalds 已提交
1310 1311
			if (retval > 0)
				*ppos = pos + retval;
H
Hugh Dickins 已提交
1312 1313 1314 1315
			if (retval) {
				file_accessed(filp);
				goto out;
			}
1316
		}
L
Linus Torvalds 已提交
1317 1318
	}

H
Hugh Dickins 已提交
1319 1320
	for (seg = 0; seg < nr_segs; seg++) {
		read_descriptor_t desc;
L
Linus Torvalds 已提交
1321

H
Hugh Dickins 已提交
1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332
		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;
		if (desc.error) {
			retval = retval ?: desc.error;
			break;
L
Linus Torvalds 已提交
1333
		}
H
Hugh Dickins 已提交
1334 1335
		if (desc.count > 0)
			break;
L
Linus Torvalds 已提交
1336 1337 1338 1339 1340 1341 1342 1343
	}
out:
	return retval;
}
EXPORT_SYMBOL(generic_file_aio_read);

static ssize_t
do_readahead(struct address_space *mapping, struct file *filp,
1344
	     pgoff_t index, unsigned long nr)
L
Linus Torvalds 已提交
1345 1346 1347 1348
{
	if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
		return -EINVAL;

1349
	force_page_cache_readahead(mapping, filp, index, nr);
L
Linus Torvalds 已提交
1350 1351 1352
	return 0;
}

1353
SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
L
Linus Torvalds 已提交
1354 1355 1356 1357 1358 1359 1360 1361 1362
{
	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;
1363 1364
			pgoff_t start = offset >> PAGE_CACHE_SHIFT;
			pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
L
Linus Torvalds 已提交
1365 1366 1367 1368 1369 1370 1371
			unsigned long len = end - start + 1;
			ret = do_readahead(mapping, file, start, len);
		}
		fput(file);
	}
	return ret;
}
1372 1373 1374 1375 1376 1377 1378
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
asmlinkage long SyS_readahead(long fd, loff_t offset, long count)
{
	return SYSC_readahead((int) fd, offset, (size_t) count);
}
SYSCALL_ALIAS(sys_readahead, SyS_readahead);
#endif
L
Linus Torvalds 已提交
1379 1380

#ifdef CONFIG_MMU
1381 1382 1383 1384 1385
/**
 * 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
1386 1387 1388
 * 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
1389
static int page_cache_read(struct file *file, pgoff_t offset)
L
Linus Torvalds 已提交
1390 1391 1392
{
	struct address_space *mapping = file->f_mapping;
	struct page *page; 
1393
	int ret;
L
Linus Torvalds 已提交
1394

1395 1396 1397 1398 1399 1400 1401 1402 1403 1404
	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
1405 1406 1407

		page_cache_release(page);

1408 1409 1410
	} while (ret == AOP_TRUNCATED_PAGE);
		
	return ret;
L
Linus Torvalds 已提交
1411 1412 1413 1414
}

#define MMAP_LOTSAMISS  (100)

1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430
/*
 * Synchronous readahead happens when we don't even find
 * a page in the page cache at all.
 */
static void do_sync_mmap_readahead(struct vm_area_struct *vma,
				   struct file_ra_state *ra,
				   struct file *file,
				   pgoff_t offset)
{
	unsigned long ra_pages;
	struct address_space *mapping = file->f_mapping;

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

1431 1432
	if (VM_SequentialReadHint(vma) ||
			offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) {
1433 1434
		page_cache_sync_readahead(mapping, ra, file, offset,
					  ra->ra_pages);
1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447
		return;
	}

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

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

1448 1449 1450
	/*
	 * mmap read-around
	 */
1451 1452
	ra_pages = max_sane_readahead(ra->ra_pages);
	if (ra_pages) {
1453 1454 1455 1456
		ra->start = max_t(long, 0, offset - ra_pages/2);
		ra->size = ra_pages;
		ra->async_size = 0;
		ra_submit(ra, mapping, file);
1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477
	}
}

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

	/* If we don't want any read-ahead, don't bother */
	if (VM_RandomReadHint(vma))
		return;
	if (ra->mmap_miss > 0)
		ra->mmap_miss--;
	if (PageReadahead(page))
1478 1479
		page_cache_async_readahead(mapping, ra, file,
					   page, offset, ra->ra_pages);
1480 1481
}

1482
/**
1483
 * filemap_fault - read in file data for page fault handling
N
Nick Piggin 已提交
1484 1485
 * @vma:	vma in which the fault was taken
 * @vmf:	struct vm_fault containing details of the fault
1486
 *
1487
 * filemap_fault() is invoked via the vma operations vector for a
L
Linus Torvalds 已提交
1488 1489 1490 1491 1492 1493
 * 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
1494
int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
L
Linus Torvalds 已提交
1495 1496
{
	int error;
1497
	struct file *file = vma->vm_file;
L
Linus Torvalds 已提交
1498 1499 1500
	struct address_space *mapping = file->f_mapping;
	struct file_ra_state *ra = &file->f_ra;
	struct inode *inode = mapping->host;
1501
	pgoff_t offset = vmf->pgoff;
L
Linus Torvalds 已提交
1502
	struct page *page;
J
Jan Kara 已提交
1503
	pgoff_t size;
N
Nick Piggin 已提交
1504
	int ret = 0;
L
Linus Torvalds 已提交
1505 1506

	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1507
	if (offset >= size)
1508
		return VM_FAULT_SIGBUS;
L
Linus Torvalds 已提交
1509 1510 1511 1512

	/*
	 * Do we have something in the page cache already?
	 */
1513 1514
	page = find_get_page(mapping, offset);
	if (likely(page)) {
L
Linus Torvalds 已提交
1515
		/*
1516 1517
		 * We found the page, so try async readahead before
		 * waiting for the lock.
L
Linus Torvalds 已提交
1518
		 */
1519 1520
		do_async_mmap_readahead(vma, ra, file, page, offset);
		lock_page(page);
L
Linus Torvalds 已提交
1521

1522 1523 1524 1525 1526
		/* Did it get truncated? */
		if (unlikely(page->mapping != mapping)) {
			unlock_page(page);
			put_page(page);
			goto no_cached_page;
L
Linus Torvalds 已提交
1527
		}
1528 1529 1530 1531 1532 1533 1534
	} else {
		/* No page in the page cache at all */
		do_sync_mmap_readahead(vma, ra, file, offset);
		count_vm_event(PGMAJFAULT);
		ret = VM_FAULT_MAJOR;
retry_find:
		page = find_lock_page(mapping, offset);
L
Linus Torvalds 已提交
1535 1536 1537 1538 1539
		if (!page)
			goto no_cached_page;
	}

	/*
1540 1541
	 * 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
1542
	 */
1543
	if (unlikely(!PageUptodate(page)))
L
Linus Torvalds 已提交
1544 1545
		goto page_not_uptodate;

1546 1547 1548 1549
	/*
	 * Found the page and have a reference on it.
	 * We must recheck i_size under page lock.
	 */
1550
	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1551
	if (unlikely(offset >= size)) {
1552
		unlock_page(page);
1553
		page_cache_release(page);
1554
		return VM_FAULT_SIGBUS;
1555 1556
	}

1557
	ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT;
N
Nick Piggin 已提交
1558
	vmf->page = page;
N
Nick Piggin 已提交
1559
	return ret | VM_FAULT_LOCKED;
L
Linus Torvalds 已提交
1560 1561 1562 1563 1564 1565

no_cached_page:
	/*
	 * We're only likely to ever get here if MADV_RANDOM is in
	 * effect.
	 */
1566
	error = page_cache_read(file, offset);
L
Linus Torvalds 已提交
1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581

	/*
	 * 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
1582 1583
		return VM_FAULT_OOM;
	return VM_FAULT_SIGBUS;
L
Linus Torvalds 已提交
1584 1585 1586 1587 1588 1589 1590 1591 1592

page_not_uptodate:
	/*
	 * Umm, take care of errors if the page isn't up-to-date.
	 * Try to re-read it _once_. We do this synchronously,
	 * because there really aren't any performance issues here
	 * and we need to check for errors.
	 */
	ClearPageError(page);
1593
	error = mapping->a_ops->readpage(file, page);
1594 1595 1596 1597 1598
	if (!error) {
		wait_on_page_locked(page);
		if (!PageUptodate(page))
			error = -EIO;
	}
1599 1600 1601
	page_cache_release(page);

	if (!error || error == AOP_TRUNCATED_PAGE)
1602
		goto retry_find;
L
Linus Torvalds 已提交
1603

1604
	/* Things didn't work out. Return zero to tell the mm layer so. */
1605
	shrink_readahead_size_eio(file, ra);
N
Nick Piggin 已提交
1606
	return VM_FAULT_SIGBUS;
1607 1608 1609
}
EXPORT_SYMBOL(filemap_fault);

L
Linus Torvalds 已提交
1610
struct vm_operations_struct generic_file_vm_ops = {
1611
	.fault		= filemap_fault,
L
Linus Torvalds 已提交
1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623
};

/* 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
1624
	vma->vm_flags |= VM_CAN_NONLINEAR;
L
Linus Torvalds 已提交
1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650
	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);

1651
static struct page *__read_cache_page(struct address_space *mapping,
1652
				pgoff_t index,
L
Linus Torvalds 已提交
1653 1654 1655
				int (*filler)(void *,struct page*),
				void *data)
{
N
Nick Piggin 已提交
1656
	struct page *page;
L
Linus Torvalds 已提交
1657 1658 1659 1660
	int err;
repeat:
	page = find_get_page(mapping, index);
	if (!page) {
N
Nick Piggin 已提交
1661 1662 1663 1664 1665 1666 1667 1668
		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
1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680
			/* 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;
}

1681 1682 1683 1684 1685 1686 1687
/**
 * read_cache_page_async - read into page cache, fill it if needed
 * @mapping:	the page's address_space
 * @index:	the page index
 * @filler:	function to perform the read
 * @data:	destination for read data
 *
1688 1689
 * Same as read_cache_page, but don't wait for page to become unlocked
 * after submitting it to the filler.
1690 1691 1692 1693 1694
 *
 * Read into the page cache. If a page already exists, and PageUptodate() is
 * not set, try to fill the page but don't wait for it to become unlocked.
 *
 * If the page does not get brought uptodate, return -EIO.
L
Linus Torvalds 已提交
1695
 */
1696
struct page *read_cache_page_async(struct address_space *mapping,
1697
				pgoff_t index,
L
Linus Torvalds 已提交
1698 1699 1700 1701 1702 1703 1704 1705 1706
				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))
1707
		return page;
L
Linus Torvalds 已提交
1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723
	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);
1724
		return ERR_PTR(err);
L
Linus Torvalds 已提交
1725
	}
1726
out:
1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744
	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,
1745
				pgoff_t index,
1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758
				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
1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769
 out:
	return page;
}
EXPORT_SYMBOL(read_cache_page);

/*
 * The logic we want is
 *
 *	if suid or (sgid and xgrp)
 *		remove privs
 */
1770
int should_remove_suid(struct dentry *dentry)
L
Linus Torvalds 已提交
1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785
{
	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;

1786
	if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1787
		return kill;
L
Linus Torvalds 已提交
1788

1789 1790
	return 0;
}
M
Mark Fasheh 已提交
1791
EXPORT_SYMBOL(should_remove_suid);
1792

1793
static int __remove_suid(struct dentry *dentry, int kill)
1794 1795 1796 1797 1798 1799 1800
{
	struct iattr newattrs;

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

1801
int file_remove_suid(struct file *file)
1802
{
1803
	struct dentry *dentry = file->f_path.dentry;
1804 1805 1806
	int killsuid = should_remove_suid(dentry);
	int killpriv = security_inode_need_killpriv(dentry);
	int error = 0;
1807

1808 1809 1810 1811 1812 1813
	if (killpriv < 0)
		return killpriv;
	if (killpriv)
		error = security_inode_killpriv(dentry);
	if (!error && killsuid)
		error = __remove_suid(dentry, killsuid);
1814

1815
	return error;
L
Linus Torvalds 已提交
1816
}
1817
EXPORT_SYMBOL(file_remove_suid);
L
Linus Torvalds 已提交
1818

N
Nick Piggin 已提交
1819
static size_t __iovec_copy_from_user_inatomic(char *vaddr,
L
Linus Torvalds 已提交
1820 1821
			const struct iovec *iov, size_t base, size_t bytes)
{
1822
	size_t copied = 0, left = 0;
L
Linus Torvalds 已提交
1823 1824 1825 1826 1827 1828

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

		base = 0;
1829
		left = __copy_from_user_inatomic(vaddr, buf, copy);
L
Linus Torvalds 已提交
1830 1831 1832 1833 1834
		copied += copy;
		bytes -= copy;
		vaddr += copy;
		iov++;

1835
		if (unlikely(left))
L
Linus Torvalds 已提交
1836 1837 1838 1839 1840
			break;
	}
	return copied - left;
}

N
Nick Piggin 已提交
1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856
/*
 * 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;
1857
		left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
N
Nick Piggin 已提交
1858 1859 1860 1861 1862 1863 1864 1865 1866
		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
1867
EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
N
Nick Piggin 已提交
1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884

/*
 * 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;
1885
		left = __copy_from_user(kaddr + offset, buf, bytes);
N
Nick Piggin 已提交
1886 1887 1888 1889 1890 1891 1892 1893
		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
1894
EXPORT_SYMBOL(iov_iter_copy_from_user);
N
Nick Piggin 已提交
1895

N
Nick Piggin 已提交
1896
void iov_iter_advance(struct iov_iter *i, size_t bytes)
N
Nick Piggin 已提交
1897
{
N
Nick Piggin 已提交
1898 1899
	BUG_ON(i->count < bytes);

N
Nick Piggin 已提交
1900 1901
	if (likely(i->nr_segs == 1)) {
		i->iov_offset += bytes;
N
Nick Piggin 已提交
1902
		i->count -= bytes;
N
Nick Piggin 已提交
1903 1904 1905 1906
	} else {
		const struct iovec *iov = i->iov;
		size_t base = i->iov_offset;

1907 1908
		/*
		 * The !iov->iov_len check ensures we skip over unlikely
N
Nick Piggin 已提交
1909
		 * zero-length segments (without overruning the iovec).
1910
		 */
1911
		while (bytes || unlikely(i->count && !iov->iov_len)) {
N
Nick Piggin 已提交
1912
			int copy;
N
Nick Piggin 已提交
1913

N
Nick Piggin 已提交
1914 1915 1916
			copy = min(bytes, iov->iov_len - base);
			BUG_ON(!i->count || i->count < copy);
			i->count -= copy;
N
Nick Piggin 已提交
1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927
			bytes -= copy;
			base += copy;
			if (iov->iov_len == base) {
				iov++;
				base = 0;
			}
		}
		i->iov = iov;
		i->iov_offset = base;
	}
}
N
Nick Piggin 已提交
1928
EXPORT_SYMBOL(iov_iter_advance);
N
Nick Piggin 已提交
1929

1930 1931 1932 1933 1934 1935 1936 1937 1938 1939
/*
 * 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
1940 1941
{
	char __user *buf = i->iov->iov_base + i->iov_offset;
1942 1943
	bytes = min(bytes, i->iov->iov_len - i->iov_offset);
	return fault_in_pages_readable(buf, bytes);
N
Nick Piggin 已提交
1944
}
N
Nick Piggin 已提交
1945
EXPORT_SYMBOL(iov_iter_fault_in_readable);
N
Nick Piggin 已提交
1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957

/*
 * 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
1958
EXPORT_SYMBOL(iov_iter_single_seg_count);
N
Nick Piggin 已提交
1959

L
Linus Torvalds 已提交
1960 1961 1962
/*
 * Performs necessary checks before doing a write
 *
1963
 * Can adjust writing position or amount of bytes to write.
L
Linus Torvalds 已提交
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
 * 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 {
2022
#ifdef CONFIG_BLOCK
L
Linus Torvalds 已提交
2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033
		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;
2034 2035 2036
#else
		return -EPERM;
#endif
L
Linus Torvalds 已提交
2037 2038 2039 2040 2041
	}
	return 0;
}
EXPORT_SYMBOL(generic_write_checks);

2042 2043 2044 2045 2046 2047
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;

2048
	return aops->write_begin(file, mapping, pos, len, flags,
2049 2050 2051 2052 2053 2054 2055 2056 2057 2058
							pagep, fsdata);
}
EXPORT_SYMBOL(pagecache_write_begin);

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

2059 2060
	mark_page_accessed(page);
	return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2061 2062 2063
}
EXPORT_SYMBOL(pagecache_write_end);

L
Linus Torvalds 已提交
2064 2065 2066 2067 2068 2069 2070 2071 2072
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;
2073 2074
	size_t		write_len;
	pgoff_t		end;
L
Linus Torvalds 已提交
2075 2076 2077 2078

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

2079 2080 2081
	write_len = iov_length(iov, *nr_segs);
	end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;

2082
	written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2083 2084 2085 2086 2087 2088 2089
	if (written)
		goto out;

	/*
	 * After a write we want buffered reads to be sure to go to disk to get
	 * the new data.  We invalidate clean cached page from the region we're
	 * about to write.  We do this *before* the write so that we can return
2090
	 * without clobbering -EIOCBQUEUED from ->direct_IO().
2091 2092 2093 2094
	 */
	if (mapping->nrpages) {
		written = invalidate_inode_pages2_range(mapping,
					pos >> PAGE_CACHE_SHIFT, end);
2095 2096 2097 2098 2099 2100 2101
		/*
		 * If a page can not be invalidated, return 0 to fall back
		 * to buffered write.
		 */
		if (written) {
			if (written == -EBUSY)
				return 0;
2102
			goto out;
2103
		}
2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120
	}

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

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

L
Linus Torvalds 已提交
2121 2122 2123 2124 2125 2126 2127 2128
	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;
	}
2129
out:
L
Linus Torvalds 已提交
2130 2131 2132 2133
	return written;
}
EXPORT_SYMBOL(generic_file_direct_write);

N
Nick Piggin 已提交
2134 2135 2136 2137
/*
 * Find or create a page at the given pagecache position. Return the locked
 * page. This function is specifically for buffered writes.
 */
2138 2139
struct page *grab_cache_page_write_begin(struct address_space *mapping,
					pgoff_t index, unsigned flags)
N
Nick Piggin 已提交
2140 2141 2142
{
	int status;
	struct page *page;
2143 2144 2145
	gfp_t gfp_notmask = 0;
	if (flags & AOP_FLAG_NOFS)
		gfp_notmask = __GFP_FS;
N
Nick Piggin 已提交
2146 2147 2148 2149 2150
repeat:
	page = find_lock_page(mapping, index);
	if (likely(page))
		return page;

2151
	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
N
Nick Piggin 已提交
2152 2153
	if (!page)
		return NULL;
2154 2155
	status = add_to_page_cache_lru(page, mapping, index,
						GFP_KERNEL & ~gfp_notmask);
N
Nick Piggin 已提交
2156 2157 2158 2159 2160 2161 2162 2163
	if (unlikely(status)) {
		page_cache_release(page);
		if (status == -EEXIST)
			goto repeat;
		return NULL;
	}
	return page;
}
2164
EXPORT_SYMBOL(grab_cache_page_write_begin);
N
Nick Piggin 已提交
2165

2166 2167 2168 2169 2170 2171 2172
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
2173 2174 2175 2176 2177 2178 2179
	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;
2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210

	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
2211
		status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2212 2213 2214 2215 2216 2217 2218 2219 2220
						&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);

2221
		mark_page_accessed(page);
2222 2223 2224 2225 2226 2227 2228 2229
		status = a_ops->write_end(file, mapping, pos, bytes, copied,
						page, fsdata);
		if (unlikely(status < 0))
			break;
		copied = status;

		cond_resched();

2230
		iov_iter_advance(i, copied);
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 2256 2257 2258 2259 2260 2261 2262 2263 2264
		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;
	ssize_t status;
	struct iov_iter i;

	iov_iter_init(&i, iov, nr_segs, count, written);
2265
	status = generic_perform_write(file, &i, pos);
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	if (likely(status >= 0)) {
2268 2269
		written += status;
		*ppos = pos + status;
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  	}
	
	/*
	 * 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)
2278 2279
		status = filemap_write_and_wait_range(mapping,
					pos, pos + written - 1);
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	return written ? written : status;
}
EXPORT_SYMBOL(generic_file_buffered_write);

2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305
/**
 * __generic_file_aio_write - write data to a file
 * @iocb:	IO state structure (file, offset, etc.)
 * @iov:	vector with data to write
 * @nr_segs:	number of segments in the vector
 * @ppos:	position where to write
 *
 * This function does all the work needed for actually writing data to a
 * file. It does all basic checks, removes SUID from the file, updates
 * modification times and calls proper subroutines depending on whether we
 * do direct IO or a standard buffered write.
 *
 * It expects i_mutex to be grabbed unless we work on a block device or similar
 * object which does not need locking at all.
 *
 * This function does *not* take care of syncing data in case of O_SYNC write.
 * A caller has to handle it. This is mainly due to the fact that we want to
 * avoid syncing under i_mutex.
 */
ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
				 unsigned long nr_segs, loff_t *ppos)
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{
	struct file *file = iocb->ki_filp;
2308
	struct address_space * mapping = file->f_mapping;
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	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;
2317 2318 2319
	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;

2337
	err = file_remove_suid(file);
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	if (err)
		goto out;

2341
	file_update_time(file);
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	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (unlikely(file->f_flags & O_DIRECT)) {
2345 2346 2347 2348 2349
		loff_t endbyte;
		ssize_t written_buffered;

		written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
							ppos, count, ocount);
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		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;
2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371
		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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2373 2374 2375 2376 2377 2378
		/*
		 * 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;
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		err = do_sync_mapping_range(file->f_mapping, pos, endbyte,
					    SYNC_FILE_RANGE_WAIT_BEFORE|
					    SYNC_FILE_RANGE_WRITE|
					    SYNC_FILE_RANGE_WAIT_AFTER);
2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397
		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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out:
	current->backing_dev_info = NULL;
	return written ? written : err;
}
2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414
EXPORT_SYMBOL(__generic_file_aio_write);

/**
 * generic_file_aio_write - write data to a file
 * @iocb:	IO state structure
 * @iov:	vector with data to write
 * @nr_segs:	number of segments in the vector
 * @pos:	position in file where to write
 *
 * This is a wrapper around __generic_file_aio_write() to be used by most
 * filesystems. It takes care of syncing the file in case of O_SYNC file
 * and acquires i_mutex as needed.
 */
2415 2416
ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos)
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{
	struct file *file = iocb->ki_filp;
2419
	struct inode *inode = file->f_mapping->host;
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2420 2421 2422 2423
	ssize_t ret;

	BUG_ON(iocb->ki_pos != pos);

2424
	mutex_lock(&inode->i_mutex);
2425
	ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2426
	mutex_unlock(&inode->i_mutex);
L
Linus Torvalds 已提交
2427

2428
	if (ret > 0 || ret == -EIOCBQUEUED) {
L
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2429 2430
		ssize_t err;

2431
		err = generic_write_sync(file, pos, ret);
2432
		if (err < 0 && ret > 0)
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2433 2434 2435 2436 2437 2438
			ret = err;
	}
	return ret;
}
EXPORT_SYMBOL(generic_file_aio_write);

2439 2440 2441 2442 2443 2444 2445 2446 2447 2448
/**
 * 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.
 *
2449 2450 2451
 * This may also be called if PG_fscache is set on a page, indicating that the
 * page is known to the local caching routines.
 *
2452
 * The @gfp_mask argument specifies whether I/O may be performed to release
2453
 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469
 *
 */
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);