filemap.c 66.5 KB
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/*
 *	linux/mm/filemap.c
 *
 * Copyright (C) 1994-1999  Linus Torvalds
 */

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

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

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

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

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

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

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

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

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

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

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

	if (!mapping_cap_writeback_dirty(mapping))
		return 0;

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

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

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

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

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

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	if (end_byte < start_byte)
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		return 0;

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

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

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

			wait_on_page_writeback(page);
			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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EXPORT_SYMBOL(filemap_fdatawait_range);

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

	if (i_size == 0)
		return 0;

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

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

	VM_BUG_ON(!PageLocked(page));

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

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

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

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

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

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

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

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

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

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

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

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

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

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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
545 546
 * 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
547
 */
H
Harvey Harrison 已提交
548
void unlock_page(struct page *page)
L
Linus Torvalds 已提交
549
{
N
Nick Piggin 已提交
550 551 552
	VM_BUG_ON(!PageLocked(page));
	clear_bit_unlock(PG_locked, &page->flags);
	smp_mb__after_clear_bit();
L
Linus Torvalds 已提交
553 554 555 556
	wake_up_page(page, PG_locked);
}
EXPORT_SYMBOL(unlock_page);

557 558 559
/**
 * end_page_writeback - end writeback against a page
 * @page: the page
L
Linus Torvalds 已提交
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 */
void end_page_writeback(struct page *page)
{
563 564 565 566 567 568
	if (TestClearPageReclaim(page))
		rotate_reclaimable_page(page);

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

L
Linus Torvalds 已提交
569 570 571 572 573
	smp_mb__after_clear_bit();
	wake_up_page(page, PG_writeback);
}
EXPORT_SYMBOL(end_page_writeback);

574 575 576
/**
 * __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
577
 *
578
 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary.  If some
L
Linus Torvalds 已提交
579 580 581 582
 * 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
583
void __lock_page(struct page *page)
L
Linus Torvalds 已提交
584 585 586 587 588 589 590 591
{
	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
592
int __lock_page_killable(struct page *page)
M
Matthew Wilcox 已提交
593 594 595 596 597 598
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);

	return __wait_on_bit_lock(page_waitqueue(page), &wait,
					sync_page_killable, TASK_KILLABLE);
}
599
EXPORT_SYMBOL_GPL(__lock_page_killable);
M
Matthew Wilcox 已提交
600

601 602 603 604
/**
 * __lock_page_nosync - get a lock on the page, without calling sync_page()
 * @page: the page to lock
 *
605 606 607
 * 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
608
void __lock_page_nosync(struct page *page)
609 610 611 612 613 614
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
	__wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
							TASK_UNINTERRUPTIBLE);
}

615 616 617 618 619 620 621 622 623 624 625 626 627
int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
			 unsigned int flags)
{
	if (!(flags & FAULT_FLAG_ALLOW_RETRY)) {
		__lock_page(page);
		return 1;
	} else {
		up_read(&mm->mmap_sem);
		wait_on_page_locked(page);
		return 0;
	}
}

628 629 630 631 632
/**
 * 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
633 634
 * 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
635
 */
N
Nick Piggin 已提交
636
struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
L
Linus Torvalds 已提交
637
{
N
Nick Piggin 已提交
638
	void **pagep;
L
Linus Torvalds 已提交
639 640
	struct page *page;

N
Nick Piggin 已提交
641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664
	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
665 666 667 668 669 670
	return page;
}
EXPORT_SYMBOL(find_get_page);

/**
 * find_lock_page - locate, pin and lock a pagecache page
671 672
 * @mapping: the address_space to search
 * @offset: the page index
L
Linus Torvalds 已提交
673 674 675 676 677 678
 *
 * 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
679
struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
L
Linus Torvalds 已提交
680 681 682 683
{
	struct page *page;

repeat:
N
Nick Piggin 已提交
684
	page = find_get_page(mapping, offset);
L
Linus Torvalds 已提交
685
	if (page) {
N
Nick Piggin 已提交
686 687 688 689 690 691
		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
692
		}
N
Nick Piggin 已提交
693
		VM_BUG_ON(page->index != offset);
L
Linus Torvalds 已提交
694 695 696 697 698 699 700
	}
	return page;
}
EXPORT_SYMBOL(find_lock_page);

/**
 * find_or_create_page - locate or add a pagecache page
701 702 703
 * @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
704 705 706 707 708 709 710 711 712 713 714 715 716
 *
 * 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,
717
		pgoff_t index, gfp_t gfp_mask)
L
Linus Torvalds 已提交
718
{
N
Nick Piggin 已提交
719
	struct page *page;
L
Linus Torvalds 已提交
720 721 722 723
	int err;
repeat:
	page = find_lock_page(mapping, index);
	if (!page) {
N
Nick Piggin 已提交
724 725 726
		page = __page_cache_alloc(gfp_mask);
		if (!page)
			return NULL;
N
Nick Piggin 已提交
727 728 729 730 731 732 733 734
		/*
		 * 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
735 736 737 738 739
		if (unlikely(err)) {
			page_cache_release(page);
			page = NULL;
			if (err == -EEXIST)
				goto repeat;
L
Linus Torvalds 已提交
740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766
		}
	}
	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
767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794
	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
795

N
Nick Piggin 已提交
796 797 798 799
		pages[ret] = page;
		ret++;
	}
	rcu_read_unlock();
L
Linus Torvalds 已提交
800 801 802
	return ret;
}

803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819
/**
 * 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
820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838
	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;
839

N
Nick Piggin 已提交
840
		if (page->mapping == NULL || page->index != index)
841 842
			break;

N
Nick Piggin 已提交
843 844 845 846 847 848 849 850 851 852 853
		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++;
854 855
		index++;
	}
N
Nick Piggin 已提交
856 857
	rcu_read_unlock();
	return ret;
858
}
859
EXPORT_SYMBOL(find_get_pages_contig);
860

861 862 863 864 865 866 867 868
/**
 * 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
869
 * Like find_get_pages, except we only return pages which are tagged with
870
 * @tag.   We update @index to index the next page for the traversal.
L
Linus Torvalds 已提交
871 872 873 874 875 876
 */
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
877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909
	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
910 911 912

	if (ret)
		*index = pages[ret - 1]->index + 1;
N
Nick Piggin 已提交
913

L
Linus Torvalds 已提交
914 915
	return ret;
}
916
EXPORT_SYMBOL(find_get_pages_tag);
L
Linus Torvalds 已提交
917

918 919 920 921 922
/**
 * grab_cache_page_nowait - returns locked page at given index in given cache
 * @mapping: target address_space
 * @index: the page index
 *
923
 * Same as grab_cache_page(), but do not wait if the page is unavailable.
L
Linus Torvalds 已提交
924 925 926 927 928 929 930 931
 * 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 *
932
grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
L
Linus Torvalds 已提交
933 934 935 936
{
	struct page *page = find_get_page(mapping, index);

	if (page) {
N
Nick Piggin 已提交
937
		if (trylock_page(page))
L
Linus Torvalds 已提交
938 939 940 941
			return page;
		page_cache_release(page);
		return NULL;
	}
942
	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
N
Nick Piggin 已提交
943
	if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
L
Linus Torvalds 已提交
944 945 946 947 948 949 950
		page_cache_release(page);
		page = NULL;
	}
	return page;
}
EXPORT_SYMBOL(grab_cache_page_nowait);

951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971
/*
 * 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;
}

972
/**
C
Christoph Hellwig 已提交
973
 * do_generic_file_read - generic file read routine
974 975 976 977 978
 * @filp:	the file to read
 * @ppos:	current file position
 * @desc:	read_descriptor
 * @actor:	read method
 *
L
Linus Torvalds 已提交
979
 * This is a generic file read routine, and uses the
980
 * mapping->a_ops->readpage() function for the actual low-level stuff.
L
Linus Torvalds 已提交
981 982 983 984
 *
 * 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
985 986
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
987
{
C
Christoph Hellwig 已提交
988
	struct address_space *mapping = filp->f_mapping;
L
Linus Torvalds 已提交
989
	struct inode *inode = mapping->host;
C
Christoph Hellwig 已提交
990
	struct file_ra_state *ra = &filp->f_ra;
991 992 993 994
	pgoff_t index;
	pgoff_t last_index;
	pgoff_t prev_index;
	unsigned long offset;      /* offset into pagecache page */
995
	unsigned int prev_offset;
L
Linus Torvalds 已提交
996 997 998
	int error;

	index = *ppos >> PAGE_CACHE_SHIFT;
999 1000
	prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
	prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
L
Linus Torvalds 已提交
1001 1002 1003 1004 1005
	last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
	offset = *ppos & ~PAGE_CACHE_MASK;

	for (;;) {
		struct page *page;
1006
		pgoff_t end_index;
N
NeilBrown 已提交
1007
		loff_t isize;
L
Linus Torvalds 已提交
1008 1009 1010 1011 1012
		unsigned long nr, ret;

		cond_resched();
find_page:
		page = find_get_page(mapping, index);
1013
		if (!page) {
1014
			page_cache_sync_readahead(mapping,
1015
					ra, filp,
1016 1017 1018 1019 1020 1021
					index, last_index - index);
			page = find_get_page(mapping, index);
			if (unlikely(page == NULL))
				goto no_cached_page;
		}
		if (PageReadahead(page)) {
1022
			page_cache_async_readahead(mapping,
1023
					ra, filp, page,
1024
					index, last_index - index);
L
Linus Torvalds 已提交
1025
		}
1026 1027 1028 1029
		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
1030
			if (!trylock_page(page))
1031 1032 1033 1034 1035 1036
				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
1037
page_ok:
N
NeilBrown 已提交
1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063
		/*
		 * 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
1064 1065 1066 1067 1068 1069 1070 1071 1072

		/* 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);

		/*
1073 1074
		 * When a sequential read accesses a page several times,
		 * only mark it as accessed the first time.
L
Linus Torvalds 已提交
1075
		 */
1076
		if (prev_index != index || offset != prev_offset)
L
Linus Torvalds 已提交
1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093
			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
1094
		prev_offset = offset;
L
Linus Torvalds 已提交
1095 1096 1097 1098 1099 1100 1101 1102

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

page_not_up_to_date:
		/* Get exclusive access to the page ... */
1103 1104 1105
		error = lock_page_killable(page);
		if (unlikely(error))
			goto readpage_error;
L
Linus Torvalds 已提交
1106

1107
page_not_up_to_date_locked:
N
Nick Piggin 已提交
1108
		/* Did it get truncated before we got the lock? */
L
Linus Torvalds 已提交
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:
1122 1123 1124 1125 1126 1127
		/*
		 * A previous I/O error may have been due to temporary
		 * failures, eg. multipath errors.
		 * PG_error will be set again if readpage fails.
		 */
		ClearPageError(page);
L
Linus Torvalds 已提交
1128 1129 1130
		/* Start the actual read. The read will unlock the page. */
		error = mapping->a_ops->readpage(filp, page);

1131 1132 1133 1134 1135
		if (unlikely(error)) {
			if (error == AOP_TRUNCATED_PAGE) {
				page_cache_release(page);
				goto find_page;
			}
L
Linus Torvalds 已提交
1136
			goto readpage_error;
1137
		}
L
Linus Torvalds 已提交
1138 1139

		if (!PageUptodate(page)) {
1140 1141 1142
			error = lock_page_killable(page);
			if (unlikely(error))
				goto readpage_error;
L
Linus Torvalds 已提交
1143 1144 1145
			if (!PageUptodate(page)) {
				if (page->mapping == NULL) {
					/*
1146
					 * invalidate_mapping_pages got it
L
Linus Torvalds 已提交
1147 1148 1149 1150 1151 1152
					 */
					unlock_page(page);
					page_cache_release(page);
					goto find_page;
				}
				unlock_page(page);
1153
				shrink_readahead_size_eio(filp, ra);
1154 1155
				error = -EIO;
				goto readpage_error;
L
Linus Torvalds 已提交
1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172
			}
			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
1173 1174 1175 1176
		page = page_cache_alloc_cold(mapping);
		if (!page) {
			desc->error = -ENOMEM;
			goto out;
L
Linus Torvalds 已提交
1177
		}
N
Nick Piggin 已提交
1178
		error = add_to_page_cache_lru(page, mapping,
L
Linus Torvalds 已提交
1179 1180
						index, GFP_KERNEL);
		if (error) {
N
Nick Piggin 已提交
1181
			page_cache_release(page);
L
Linus Torvalds 已提交
1182 1183 1184 1185 1186 1187 1188 1189 1190
			if (error == -EEXIST)
				goto find_page;
			desc->error = error;
			goto out;
		}
		goto readpage;
	}

out:
1191 1192 1193
	ra->prev_pos = prev_index;
	ra->prev_pos <<= PAGE_CACHE_SHIFT;
	ra->prev_pos |= prev_offset;
L
Linus Torvalds 已提交
1194

1195
	*ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1196
	file_accessed(filp);
L
Linus Torvalds 已提交
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 1228 1229 1230 1231 1232 1233 1234 1235 1236
}

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;
}

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 1267 1268 1269 1270 1271 1272 1273 1274 1275
/*
 * 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);

1276
/**
H
Henrik Kretzschmar 已提交
1277
 * generic_file_aio_read - generic filesystem read routine
1278 1279 1280
 * @iocb:	kernel I/O control block
 * @iov:	io vector request
 * @nr_segs:	number of segments in the iovec
H
Henrik Kretzschmar 已提交
1281
 * @pos:	current file position
1282
 *
L
Linus Torvalds 已提交
1283 1284 1285 1286
 * This is the "read()" routine for all filesystems
 * that can use the page cache directly.
 */
ssize_t
1287 1288
generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos)
L
Linus Torvalds 已提交
1289 1290 1291
{
	struct file *filp = iocb->ki_filp;
	ssize_t retval;
1292
	unsigned long seg = 0;
L
Linus Torvalds 已提交
1293
	size_t count;
1294
	loff_t *ppos = &iocb->ki_pos;
L
Linus Torvalds 已提交
1295 1296

	count = 0;
1297 1298 1299
	retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
	if (retval)
		return retval;
L
Linus Torvalds 已提交
1300 1301 1302

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (filp->f_flags & O_DIRECT) {
1303
		loff_t size;
L
Linus Torvalds 已提交
1304 1305 1306 1307 1308 1309 1310 1311 1312
		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) {
1313 1314
			retval = filemap_write_and_wait_range(mapping, pos,
					pos + iov_length(iov, nr_segs) - 1);
1315 1316 1317 1318
			if (!retval) {
				retval = mapping->a_ops->direct_IO(READ, iocb,
							iov, pos, nr_segs);
			}
1319
			if (retval > 0) {
L
Linus Torvalds 已提交
1320
				*ppos = pos + retval;
1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332
				count -= retval;
			}

			/*
			 * Btrfs can have a short DIO read if we encounter
			 * compressed extents, so if there was an error, or if
			 * we've already read everything we wanted to, or if
			 * there was a short read because we hit EOF, go ahead
			 * and return.  Otherwise fallthrough to buffered io for
			 * the rest of the read.
			 */
			if (retval < 0 || !count || *ppos >= size) {
H
Hugh Dickins 已提交
1333 1334 1335
				file_accessed(filp);
				goto out;
			}
1336
		}
L
Linus Torvalds 已提交
1337 1338
	}

1339
	count = retval;
H
Hugh Dickins 已提交
1340 1341
	for (seg = 0; seg < nr_segs; seg++) {
		read_descriptor_t desc;
1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355
		loff_t offset = 0;

		/*
		 * If we did a short DIO read we need to skip the section of the
		 * iov that we've already read data into.
		 */
		if (count) {
			if (count > iov[seg].iov_len) {
				count -= iov[seg].iov_len;
				continue;
			}
			offset = count;
			count = 0;
		}
L
Linus Torvalds 已提交
1356

H
Hugh Dickins 已提交
1357
		desc.written = 0;
1358 1359
		desc.arg.buf = iov[seg].iov_base + offset;
		desc.count = iov[seg].iov_len - offset;
H
Hugh Dickins 已提交
1360 1361 1362 1363 1364 1365 1366 1367
		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
1368
		}
H
Hugh Dickins 已提交
1369 1370
		if (desc.count > 0)
			break;
L
Linus Torvalds 已提交
1371 1372 1373 1374 1375 1376 1377 1378
	}
out:
	return retval;
}
EXPORT_SYMBOL(generic_file_aio_read);

static ssize_t
do_readahead(struct address_space *mapping, struct file *filp,
1379
	     pgoff_t index, unsigned long nr)
L
Linus Torvalds 已提交
1380 1381 1382 1383
{
	if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
		return -EINVAL;

1384
	force_page_cache_readahead(mapping, filp, index, nr);
L
Linus Torvalds 已提交
1385 1386 1387
	return 0;
}

1388
SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
L
Linus Torvalds 已提交
1389 1390 1391 1392 1393 1394 1395 1396 1397
{
	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;
1398 1399
			pgoff_t start = offset >> PAGE_CACHE_SHIFT;
			pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
L
Linus Torvalds 已提交
1400 1401 1402 1403 1404 1405 1406
			unsigned long len = end - start + 1;
			ret = do_readahead(mapping, file, start, len);
		}
		fput(file);
	}
	return ret;
}
1407 1408 1409 1410 1411 1412 1413
#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
1414 1415

#ifdef CONFIG_MMU
1416 1417 1418 1419 1420
/**
 * 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
1421 1422 1423
 * 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
1424
static int page_cache_read(struct file *file, pgoff_t offset)
L
Linus Torvalds 已提交
1425 1426 1427
{
	struct address_space *mapping = file->f_mapping;
	struct page *page; 
1428
	int ret;
L
Linus Torvalds 已提交
1429

1430 1431 1432 1433 1434 1435 1436 1437 1438 1439
	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
1440 1441 1442

		page_cache_release(page);

1443 1444 1445
	} while (ret == AOP_TRUNCATED_PAGE);
		
	return ret;
L
Linus Torvalds 已提交
1446 1447 1448 1449
}

#define MMAP_LOTSAMISS  (100)

1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465
/*
 * 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;

1466 1467
	if (VM_SequentialReadHint(vma) ||
			offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) {
1468 1469
		page_cache_sync_readahead(mapping, ra, file, offset,
					  ra->ra_pages);
1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482
		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;

1483 1484 1485
	/*
	 * mmap read-around
	 */
1486 1487
	ra_pages = max_sane_readahead(ra->ra_pages);
	if (ra_pages) {
1488 1489 1490 1491
		ra->start = max_t(long, 0, offset - ra_pages/2);
		ra->size = ra_pages;
		ra->async_size = 0;
		ra_submit(ra, mapping, file);
1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512
	}
}

/*
 * 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))
1513 1514
		page_cache_async_readahead(mapping, ra, file,
					   page, offset, ra->ra_pages);
1515 1516
}

1517
/**
1518
 * filemap_fault - read in file data for page fault handling
N
Nick Piggin 已提交
1519 1520
 * @vma:	vma in which the fault was taken
 * @vmf:	struct vm_fault containing details of the fault
1521
 *
1522
 * filemap_fault() is invoked via the vma operations vector for a
L
Linus Torvalds 已提交
1523 1524 1525 1526 1527 1528
 * 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
1529
int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
L
Linus Torvalds 已提交
1530 1531
{
	int error;
1532
	struct file *file = vma->vm_file;
L
Linus Torvalds 已提交
1533 1534 1535
	struct address_space *mapping = file->f_mapping;
	struct file_ra_state *ra = &file->f_ra;
	struct inode *inode = mapping->host;
1536
	pgoff_t offset = vmf->pgoff;
L
Linus Torvalds 已提交
1537
	struct page *page;
J
Jan Kara 已提交
1538
	pgoff_t size;
N
Nick Piggin 已提交
1539
	int ret = 0;
L
Linus Torvalds 已提交
1540 1541

	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1542
	if (offset >= size)
1543
		return VM_FAULT_SIGBUS;
L
Linus Torvalds 已提交
1544 1545 1546 1547

	/*
	 * Do we have something in the page cache already?
	 */
1548 1549
	page = find_get_page(mapping, offset);
	if (likely(page)) {
L
Linus Torvalds 已提交
1550
		/*
1551 1552
		 * We found the page, so try async readahead before
		 * waiting for the lock.
L
Linus Torvalds 已提交
1553
		 */
1554 1555 1556 1557 1558 1559 1560
		do_async_mmap_readahead(vma, ra, file, page, offset);
	} else {
		/* No page in the page cache at all */
		do_sync_mmap_readahead(vma, ra, file, offset);
		count_vm_event(PGMAJFAULT);
		ret = VM_FAULT_MAJOR;
retry_find:
1561
		page = find_get_page(mapping, offset);
L
Linus Torvalds 已提交
1562 1563 1564 1565
		if (!page)
			goto no_cached_page;
	}

1566 1567
	if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags))
		return ret | VM_FAULT_RETRY;
1568 1569 1570 1571 1572 1573 1574 1575 1576

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

L
Linus Torvalds 已提交
1577
	/*
1578 1579
	 * 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
1580
	 */
1581
	if (unlikely(!PageUptodate(page)))
L
Linus Torvalds 已提交
1582 1583
		goto page_not_uptodate;

1584 1585 1586 1587
	/*
	 * Found the page and have a reference on it.
	 * We must recheck i_size under page lock.
	 */
1588
	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1589
	if (unlikely(offset >= size)) {
1590
		unlock_page(page);
1591
		page_cache_release(page);
1592
		return VM_FAULT_SIGBUS;
1593 1594
	}

1595
	ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT;
N
Nick Piggin 已提交
1596
	vmf->page = page;
N
Nick Piggin 已提交
1597
	return ret | VM_FAULT_LOCKED;
L
Linus Torvalds 已提交
1598 1599 1600 1601 1602 1603

no_cached_page:
	/*
	 * We're only likely to ever get here if MADV_RANDOM is in
	 * effect.
	 */
1604
	error = page_cache_read(file, offset);
L
Linus Torvalds 已提交
1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619

	/*
	 * 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
1620 1621
		return VM_FAULT_OOM;
	return VM_FAULT_SIGBUS;
L
Linus Torvalds 已提交
1622 1623 1624 1625 1626 1627 1628 1629 1630

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);
1631
	error = mapping->a_ops->readpage(file, page);
1632 1633 1634 1635 1636
	if (!error) {
		wait_on_page_locked(page);
		if (!PageUptodate(page))
			error = -EIO;
	}
1637 1638 1639
	page_cache_release(page);

	if (!error || error == AOP_TRUNCATED_PAGE)
1640
		goto retry_find;
L
Linus Torvalds 已提交
1641

1642
	/* Things didn't work out. Return zero to tell the mm layer so. */
1643
	shrink_readahead_size_eio(file, ra);
N
Nick Piggin 已提交
1644
	return VM_FAULT_SIGBUS;
1645 1646 1647
}
EXPORT_SYMBOL(filemap_fault);

1648
const struct vm_operations_struct generic_file_vm_ops = {
1649
	.fault		= filemap_fault,
L
Linus Torvalds 已提交
1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661
};

/* 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
1662
	vma->vm_flags |= VM_CAN_NONLINEAR;
L
Linus Torvalds 已提交
1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688
	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);

1689
static struct page *__read_cache_page(struct address_space *mapping,
1690
				pgoff_t index,
L
Linus Torvalds 已提交
1691
				int (*filler)(void *,struct page*),
1692 1693
				void *data,
				gfp_t gfp)
L
Linus Torvalds 已提交
1694
{
N
Nick Piggin 已提交
1695
	struct page *page;
L
Linus Torvalds 已提交
1696 1697 1698 1699
	int err;
repeat:
	page = find_get_page(mapping, index);
	if (!page) {
1700
		page = __page_cache_alloc(gfp | __GFP_COLD);
N
Nick Piggin 已提交
1701 1702 1703 1704 1705 1706 1707
		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
1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719
			/* 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;
}

1720
static struct page *do_read_cache_page(struct address_space *mapping,
1721
				pgoff_t index,
L
Linus Torvalds 已提交
1722
				int (*filler)(void *,struct page*),
1723 1724 1725
				void *data,
				gfp_t gfp)

L
Linus Torvalds 已提交
1726 1727 1728 1729 1730
{
	struct page *page;
	int err;

retry:
1731
	page = __read_cache_page(mapping, index, filler, data, gfp);
L
Linus Torvalds 已提交
1732
	if (IS_ERR(page))
1733
		return page;
L
Linus Torvalds 已提交
1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749
	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);
1750
		return ERR_PTR(err);
L
Linus Torvalds 已提交
1751
	}
1752
out:
1753 1754 1755
	mark_page_accessed(page);
	return page;
}
1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778

/**
 * read_cache_page_async - read into page cache, fill it if needed
 * @mapping:	the page's address_space
 * @index:	the page index
 * @filler:	function to perform the read
 * @data:	destination for read data
 *
 * Same as read_cache_page, but don't wait for page to become unlocked
 * after submitting it to the filler.
 *
 * Read into the page cache. If a page already exists, and PageUptodate() is
 * not set, try to fill the page but don't wait for it to become unlocked.
 *
 * If the page does not get brought uptodate, return -EIO.
 */
struct page *read_cache_page_async(struct address_space *mapping,
				pgoff_t index,
				int (*filler)(void *,struct page*),
				void *data)
{
	return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
}
1779 1780
EXPORT_SYMBOL(read_cache_page_async);

1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816
static struct page *wait_on_page_read(struct page *page)
{
	if (!IS_ERR(page)) {
		wait_on_page_locked(page);
		if (!PageUptodate(page)) {
			page_cache_release(page);
			page = ERR_PTR(-EIO);
		}
	}
	return page;
}

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

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

1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829
/**
 * read_cache_page - read into page cache, fill it if needed
 * @mapping:	the page's address_space
 * @index:	the page index
 * @filler:	function to perform the read
 * @data:	destination for read data
 *
 * 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,
1830
				pgoff_t index,
1831 1832 1833
				int (*filler)(void *,struct page*),
				void *data)
{
1834
	return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
L
Linus Torvalds 已提交
1835 1836 1837 1838 1839 1840 1841 1842 1843
}
EXPORT_SYMBOL(read_cache_page);

/*
 * The logic we want is
 *
 *	if suid or (sgid and xgrp)
 *		remove privs
 */
1844
int should_remove_suid(struct dentry *dentry)
L
Linus Torvalds 已提交
1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859
{
	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;

1860
	if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1861
		return kill;
L
Linus Torvalds 已提交
1862

1863 1864
	return 0;
}
M
Mark Fasheh 已提交
1865
EXPORT_SYMBOL(should_remove_suid);
1866

1867
static int __remove_suid(struct dentry *dentry, int kill)
1868 1869 1870 1871 1872 1873 1874
{
	struct iattr newattrs;

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

1875
int file_remove_suid(struct file *file)
1876
{
1877
	struct dentry *dentry = file->f_path.dentry;
1878 1879 1880
	int killsuid = should_remove_suid(dentry);
	int killpriv = security_inode_need_killpriv(dentry);
	int error = 0;
1881

1882 1883 1884 1885 1886 1887
	if (killpriv < 0)
		return killpriv;
	if (killpriv)
		error = security_inode_killpriv(dentry);
	if (!error && killsuid)
		error = __remove_suid(dentry, killsuid);
1888

1889
	return error;
L
Linus Torvalds 已提交
1890
}
1891
EXPORT_SYMBOL(file_remove_suid);
L
Linus Torvalds 已提交
1892

N
Nick Piggin 已提交
1893
static size_t __iovec_copy_from_user_inatomic(char *vaddr,
L
Linus Torvalds 已提交
1894 1895
			const struct iovec *iov, size_t base, size_t bytes)
{
1896
	size_t copied = 0, left = 0;
L
Linus Torvalds 已提交
1897 1898 1899 1900 1901 1902

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

		base = 0;
1903
		left = __copy_from_user_inatomic(vaddr, buf, copy);
L
Linus Torvalds 已提交
1904 1905 1906 1907 1908
		copied += copy;
		bytes -= copy;
		vaddr += copy;
		iov++;

1909
		if (unlikely(left))
L
Linus Torvalds 已提交
1910 1911 1912 1913 1914
			break;
	}
	return copied - left;
}

N
Nick Piggin 已提交
1915 1916
/*
 * Copy as much as we can into the page and return the number of bytes which
1917
 * were successfully copied.  If a fault is encountered then return the number of
N
Nick Piggin 已提交
1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930
 * 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;
1931
		left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
N
Nick Piggin 已提交
1932 1933 1934 1935 1936 1937 1938 1939 1940
		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
1941
EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
N
Nick Piggin 已提交
1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958

/*
 * 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;
1959
		left = __copy_from_user(kaddr + offset, buf, bytes);
N
Nick Piggin 已提交
1960 1961 1962 1963 1964 1965 1966 1967
		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
1968
EXPORT_SYMBOL(iov_iter_copy_from_user);
N
Nick Piggin 已提交
1969

N
Nick Piggin 已提交
1970
void iov_iter_advance(struct iov_iter *i, size_t bytes)
N
Nick Piggin 已提交
1971
{
N
Nick Piggin 已提交
1972 1973
	BUG_ON(i->count < bytes);

N
Nick Piggin 已提交
1974 1975
	if (likely(i->nr_segs == 1)) {
		i->iov_offset += bytes;
N
Nick Piggin 已提交
1976
		i->count -= bytes;
N
Nick Piggin 已提交
1977 1978 1979 1980
	} else {
		const struct iovec *iov = i->iov;
		size_t base = i->iov_offset;

1981 1982
		/*
		 * The !iov->iov_len check ensures we skip over unlikely
N
Nick Piggin 已提交
1983
		 * zero-length segments (without overruning the iovec).
1984
		 */
1985
		while (bytes || unlikely(i->count && !iov->iov_len)) {
N
Nick Piggin 已提交
1986
			int copy;
N
Nick Piggin 已提交
1987

N
Nick Piggin 已提交
1988 1989 1990
			copy = min(bytes, iov->iov_len - base);
			BUG_ON(!i->count || i->count < copy);
			i->count -= copy;
N
Nick Piggin 已提交
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001
			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
2002
EXPORT_SYMBOL(iov_iter_advance);
N
Nick Piggin 已提交
2003

2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
/*
 * 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
2014 2015
{
	char __user *buf = i->iov->iov_base + i->iov_offset;
2016 2017
	bytes = min(bytes, i->iov->iov_len - i->iov_offset);
	return fault_in_pages_readable(buf, bytes);
N
Nick Piggin 已提交
2018
}
N
Nick Piggin 已提交
2019
EXPORT_SYMBOL(iov_iter_fault_in_readable);
N
Nick Piggin 已提交
2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031

/*
 * 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
2032
EXPORT_SYMBOL(iov_iter_single_seg_count);
N
Nick Piggin 已提交
2033

L
Linus Torvalds 已提交
2034 2035 2036
/*
 * Performs necessary checks before doing a write
 *
2037
 * Can adjust writing position or amount of bytes to write.
L
Linus Torvalds 已提交
2038 2039 2040 2041 2042 2043
 * Returns appropriate error code that caller should return or
 * zero in case that write should be allowed.
 */
inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
{
	struct inode *inode = file->f_mapping->host;
J
Jiri Slaby 已提交
2044
	unsigned long limit = rlimit(RLIMIT_FSIZE);
L
Linus Torvalds 已提交
2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095

        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 {
2096
#ifdef CONFIG_BLOCK
L
Linus Torvalds 已提交
2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107
		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;
2108 2109 2110
#else
		return -EPERM;
#endif
L
Linus Torvalds 已提交
2111 2112 2113 2114 2115
	}
	return 0;
}
EXPORT_SYMBOL(generic_write_checks);

2116 2117 2118 2119 2120 2121
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;

2122
	return aops->write_begin(file, mapping, pos, len, flags,
2123 2124 2125 2126 2127 2128 2129 2130 2131 2132
							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;

2133 2134
	mark_page_accessed(page);
	return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2135 2136 2137
}
EXPORT_SYMBOL(pagecache_write_end);

L
Linus Torvalds 已提交
2138 2139 2140 2141 2142 2143 2144 2145 2146
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;
2147 2148
	size_t		write_len;
	pgoff_t		end;
L
Linus Torvalds 已提交
2149 2150 2151 2152

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

2153 2154 2155
	write_len = iov_length(iov, *nr_segs);
	end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;

2156
	written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2157 2158 2159 2160 2161 2162 2163
	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
2164
	 * without clobbering -EIOCBQUEUED from ->direct_IO().
2165 2166 2167 2168
	 */
	if (mapping->nrpages) {
		written = invalidate_inode_pages2_range(mapping,
					pos >> PAGE_CACHE_SHIFT, end);
2169 2170 2171 2172 2173 2174 2175
		/*
		 * If a page can not be invalidated, return 0 to fall back
		 * to buffered write.
		 */
		if (written) {
			if (written == -EBUSY)
				return 0;
2176
			goto out;
2177
		}
2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194
	}

	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
2195
	if (written > 0) {
2196 2197 2198
		pos += written;
		if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
			i_size_write(inode, pos);
L
Linus Torvalds 已提交
2199 2200
			mark_inode_dirty(inode);
		}
2201
		*ppos = pos;
L
Linus Torvalds 已提交
2202
	}
2203
out:
L
Linus Torvalds 已提交
2204 2205 2206 2207
	return written;
}
EXPORT_SYMBOL(generic_file_direct_write);

N
Nick Piggin 已提交
2208 2209 2210 2211
/*
 * Find or create a page at the given pagecache position. Return the locked
 * page. This function is specifically for buffered writes.
 */
2212 2213
struct page *grab_cache_page_write_begin(struct address_space *mapping,
					pgoff_t index, unsigned flags)
N
Nick Piggin 已提交
2214 2215 2216
{
	int status;
	struct page *page;
2217 2218 2219
	gfp_t gfp_notmask = 0;
	if (flags & AOP_FLAG_NOFS)
		gfp_notmask = __GFP_FS;
N
Nick Piggin 已提交
2220 2221 2222 2223 2224
repeat:
	page = find_lock_page(mapping, index);
	if (likely(page))
		return page;

2225
	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
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Nick Piggin 已提交
2226 2227
	if (!page)
		return NULL;
2228 2229
	status = add_to_page_cache_lru(page, mapping, index,
						GFP_KERNEL & ~gfp_notmask);
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Nick Piggin 已提交
2230 2231 2232 2233 2234 2235 2236 2237
	if (unlikely(status)) {
		page_cache_release(page);
		if (status == -EEXIST)
			goto repeat;
		return NULL;
	}
	return page;
}
2238
EXPORT_SYMBOL(grab_cache_page_write_begin);
N
Nick Piggin 已提交
2239

2240 2241 2242 2243 2244 2245 2246
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
2247 2248 2249 2250 2251 2252 2253
	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;
2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282

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

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

again:

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

N
Nick Piggin 已提交
2283
		status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2284 2285 2286 2287
						&page, &fsdata);
		if (unlikely(status))
			break;

2288 2289 2290
		if (mapping_writably_mapped(mapping))
			flush_dcache_page(page);

2291 2292 2293 2294 2295
		pagefault_disable();
		copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
		pagefault_enable();
		flush_dcache_page(page);

2296
		mark_page_accessed(page);
2297 2298 2299 2300 2301 2302 2303 2304
		status = a_ops->write_end(file, mapping, pos, bytes, copied,
						page, fsdata);
		if (unlikely(status < 0))
			break;
		copied = status;

		cond_resched();

2305
		iov_iter_advance(i, copied);
2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338
		if (unlikely(copied == 0)) {
			/*
			 * If we were unable to copy any data at all, we must
			 * fall back to a single segment length write.
			 *
			 * If we didn't fallback here, we could livelock
			 * because not all segments in the iov can be copied at
			 * once without a pagefault.
			 */
			bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
						iov_iter_single_seg_count(i));
			goto again;
		}
		pos += copied;
		written += copied;

		balance_dirty_pages_ratelimited(mapping);

	} while (iov_iter_count(i));

	return written ? written : status;
}

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

	iov_iter_init(&i, iov, nr_segs, count, written);
2339
	status = generic_perform_write(file, &i, pos);
L
Linus Torvalds 已提交
2340 2341

	if (likely(status >= 0)) {
2342 2343
		written += status;
		*ppos = pos + status;
L
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2344 2345 2346 2347 2348 2349
  	}
	
	return written ? written : status;
}
EXPORT_SYMBOL(generic_file_buffered_write);

2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370
/**
 * __generic_file_aio_write - write data to a file
 * @iocb:	IO state structure (file, offset, etc.)
 * @iov:	vector with data to write
 * @nr_segs:	number of segments in the vector
 * @ppos:	position where to write
 *
 * This function does all the work needed for actually writing data to a
 * file. It does all basic checks, removes SUID from the file, updates
 * modification times and calls proper subroutines depending on whether we
 * do direct IO or a standard buffered write.
 *
 * It expects i_mutex to be grabbed unless we work on a block device or similar
 * object which does not need locking at all.
 *
 * This function does *not* take care of syncing data in case of O_SYNC write.
 * A caller has to handle it. This is mainly due to the fact that we want to
 * avoid syncing under i_mutex.
 */
ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
				 unsigned long nr_segs, loff_t *ppos)
L
Linus Torvalds 已提交
2371 2372
{
	struct file *file = iocb->ki_filp;
2373
	struct address_space * mapping = file->f_mapping;
L
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2374 2375 2376 2377 2378 2379 2380 2381
	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;
2382 2383 2384
	err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
	if (err)
		return err;
L
Linus Torvalds 已提交
2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401

	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;

2402
	err = file_remove_suid(file);
L
Linus Torvalds 已提交
2403 2404 2405
	if (err)
		goto out;

2406
	file_update_time(file);
L
Linus Torvalds 已提交
2407 2408 2409

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (unlikely(file->f_flags & O_DIRECT)) {
2410 2411 2412 2413 2414
		loff_t endbyte;
		ssize_t written_buffered;

		written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
							ppos, count, ocount);
L
Linus Torvalds 已提交
2415 2416 2417 2418 2419 2420 2421 2422
		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;
2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436
		written_buffered = generic_file_buffered_write(iocb, iov,
						nr_segs, pos, ppos, count,
						written);
		/*
		 * If generic_file_buffered_write() retuned a synchronous error
		 * then we want to return the number of bytes which were
		 * direct-written, or the error code if that was zero.  Note
		 * that this differs from normal direct-io semantics, which
		 * will return -EFOO even if some bytes were written.
		 */
		if (written_buffered < 0) {
			err = written_buffered;
			goto out;
		}
L
Linus Torvalds 已提交
2437

2438 2439 2440 2441 2442 2443
		/*
		 * 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;
2444
		err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459
		if (err == 0) {
			written = written_buffered;
			invalidate_mapping_pages(mapping,
						 pos >> PAGE_CACHE_SHIFT,
						 endbyte >> PAGE_CACHE_SHIFT);
		} else {
			/*
			 * We don't know how much we wrote, so just return
			 * the number of bytes which were direct-written
			 */
		}
	} else {
		written = generic_file_buffered_write(iocb, iov, nr_segs,
				pos, ppos, count, written);
	}
L
Linus Torvalds 已提交
2460 2461 2462 2463
out:
	current->backing_dev_info = NULL;
	return written ? written : err;
}
2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476
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.
 */
2477 2478
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
2479 2480
{
	struct file *file = iocb->ki_filp;
2481
	struct inode *inode = file->f_mapping->host;
L
Linus Torvalds 已提交
2482 2483 2484 2485
	ssize_t ret;

	BUG_ON(iocb->ki_pos != pos);

2486
	mutex_lock(&inode->i_mutex);
2487
	ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2488
	mutex_unlock(&inode->i_mutex);
L
Linus Torvalds 已提交
2489

2490
	if (ret > 0 || ret == -EIOCBQUEUED) {
L
Linus Torvalds 已提交
2491 2492
		ssize_t err;

2493
		err = generic_write_sync(file, pos, ret);
2494
		if (err < 0 && ret > 0)
L
Linus Torvalds 已提交
2495 2496 2497 2498 2499 2500
			ret = err;
	}
	return ret;
}
EXPORT_SYMBOL(generic_file_aio_write);

2501 2502 2503 2504 2505 2506 2507 2508 2509 2510
/**
 * 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.
 *
2511 2512 2513
 * This may also be called if PG_fscache is set on a page, indicating that the
 * page is known to the local caching routines.
 *
2514
 * The @gfp_mask argument specifies whether I/O may be performed to release
2515
 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531
 *
 */
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);