filemap.c 69.4 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)
 */
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#include <linux/export.h>
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#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/cleancache.h>
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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_mutex		(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_mutex		(truncate->unmap_mapping_range)
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 *
 *  ->mmap_sem
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 *    ->i_mmap_mutex
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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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 *  bdi->wb.list_lock
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 *    sb_lock			(fs/fs-writeback.c)
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 *    ->mapping->tree_lock	(__sync_single_inode)
 *
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 *  ->i_mmap_mutex
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 *    ->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)
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 *    bdi.wb->list_lock		(page_remove_rmap->set_page_dirty)
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 *    ->inode->i_lock		(page_remove_rmap->set_page_dirty)
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 *    bdi.wb->list_lock		(zap_pte_range->set_page_dirty)
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 *    ->inode->i_lock		(zap_pte_range->set_page_dirty)
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 *    ->private_lock		(zap_pte_range->__set_page_dirty_buffers)
 *
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 * ->i_mmap_mutex
 *   ->tasklist_lock            (memory_failure, collect_procs_ao)
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 */

/*
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 * Delete a page from the page cache and free it. Caller has to make
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 * 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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 */
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void __delete_from_page_cache(struct page *page)
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{
	struct address_space *mapping = page->mapping;

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	/*
	 * if we're uptodate, flush out into the cleancache, otherwise
	 * invalidate any existing cleancache entries.  We can't leave
	 * stale data around in the cleancache once our page is gone
	 */
	if (PageUptodate(page) && PageMappedToDisk(page))
		cleancache_put_page(page);
	else
		cleancache_flush_page(mapping, page);

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	radix_tree_delete(&mapping->page_tree, page->index);
	page->mapping = NULL;
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	/* Leave page->index set: truncation lookup relies upon it */
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	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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}

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/**
 * delete_from_page_cache - delete page from page cache
 * @page: the page which the kernel is trying to remove from page cache
 *
 * This must be called only on pages that have been verified to be in the page
 * cache and locked.  It will never put the page into the free list, the caller
 * has a reference on the page.
 */
void delete_from_page_cache(struct page *page)
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{
	struct address_space *mapping = page->mapping;
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	void (*freepage)(struct page *);
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	BUG_ON(!PageLocked(page));
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	freepage = mapping->a_ops->freepage;
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	spin_lock_irq(&mapping->tree_lock);
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	__delete_from_page_cache(page);
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	spin_unlock_irq(&mapping->tree_lock);
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	mem_cgroup_uncharge_cache_page(page);
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	if (freepage)
		freepage(page);
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	page_cache_release(page);
}
EXPORT_SYMBOL(delete_from_page_cache);

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

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

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

	if (!mapping_cap_writeback_dirty(mapping))
		return 0;

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

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

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

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

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

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	if (end_byte < start_byte)
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		return 0;

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

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

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

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

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

	return ret;
}
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EXPORT_SYMBOL(filemap_fdatawait_range);

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

	if (i_size == 0)
		return 0;

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

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

	VM_BUG_ON(!PageLocked(old));
	VM_BUG_ON(!PageLocked(new));
	VM_BUG_ON(new->mapping);

	error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
	if (!error) {
		struct address_space *mapping = old->mapping;
		void (*freepage)(struct page *);

		pgoff_t offset = old->index;
		freepage = mapping->a_ops->freepage;

		page_cache_get(new);
		new->mapping = mapping;
		new->index = offset;

		spin_lock_irq(&mapping->tree_lock);
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		__delete_from_page_cache(old);
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		error = radix_tree_insert(&mapping->page_tree, offset, new);
		BUG_ON(error);
		mapping->nrpages++;
		__inc_zone_page_state(new, NR_FILE_PAGES);
		if (PageSwapBacked(new))
			__inc_zone_page_state(new, NR_SHMEM);
		spin_unlock_irq(&mapping->tree_lock);
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		/* mem_cgroup codes must not be called under tree_lock */
		mem_cgroup_replace_page_cache(old, new);
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		radix_tree_preload_end();
		if (freepage)
			freepage(old);
		page_cache_release(old);
	}

	return error;
}
EXPORT_SYMBOL_GPL(replace_page_cache_page);

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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));
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	VM_BUG_ON(PageSwapBacked(page));
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	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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			spin_unlock_irq(&mapping->tree_lock);
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		} else {
			page->mapping = NULL;
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			/* Leave page->index set: truncation relies upon it */
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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;

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

H
Harvey Harrison 已提交
535
void wait_on_page_bit(struct page *page, int bit_nr)
L
Linus Torvalds 已提交
536 537 538 539
{
	DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);

	if (test_bit(bit_nr, &page->flags))
J
Jens Axboe 已提交
540
		__wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
L
Linus Torvalds 已提交
541 542 543 544
							TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(wait_on_page_bit);

545 546 547 548 549 550 551 552 553 554 555
int wait_on_page_bit_killable(struct page *page, int bit_nr)
{
	DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);

	if (!test_bit(bit_nr, &page->flags))
		return 0;

	return __wait_on_bit(page_waitqueue(page), &wait,
			     sleep_on_page_killable, TASK_KILLABLE);
}

556 557
/**
 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
R
Randy Dunlap 已提交
558 559
 * @page: Page defining the wait queue of interest
 * @waiter: Waiter to add to the queue
560 561 562 563 564 565 566 567 568 569 570 571 572 573
 *
 * Add an arbitrary @waiter to the wait queue for the nominated @page.
 */
void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
{
	wait_queue_head_t *q = page_waitqueue(page);
	unsigned long flags;

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

L
Linus Torvalds 已提交
574
/**
575
 * unlock_page - unlock a locked page
L
Linus Torvalds 已提交
576 577 578 579 580 581 582
 * @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
583 584
 * 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
585
 */
H
Harvey Harrison 已提交
586
void unlock_page(struct page *page)
L
Linus Torvalds 已提交
587
{
N
Nick Piggin 已提交
588 589 590
	VM_BUG_ON(!PageLocked(page));
	clear_bit_unlock(PG_locked, &page->flags);
	smp_mb__after_clear_bit();
L
Linus Torvalds 已提交
591 592 593 594
	wake_up_page(page, PG_locked);
}
EXPORT_SYMBOL(unlock_page);

595 596 597
/**
 * end_page_writeback - end writeback against a page
 * @page: the page
L
Linus Torvalds 已提交
598 599 600
 */
void end_page_writeback(struct page *page)
{
601 602 603 604 605 606
	if (TestClearPageReclaim(page))
		rotate_reclaimable_page(page);

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

L
Linus Torvalds 已提交
607 608 609 610 611
	smp_mb__after_clear_bit();
	wake_up_page(page, PG_writeback);
}
EXPORT_SYMBOL(end_page_writeback);

612 613 614
/**
 * __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
615
 */
H
Harvey Harrison 已提交
616
void __lock_page(struct page *page)
L
Linus Torvalds 已提交
617 618 619
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);

J
Jens Axboe 已提交
620
	__wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
L
Linus Torvalds 已提交
621 622 623 624
							TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(__lock_page);

H
Harvey Harrison 已提交
625
int __lock_page_killable(struct page *page)
M
Matthew Wilcox 已提交
626 627 628 629
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);

	return __wait_on_bit_lock(page_waitqueue(page), &wait,
J
Jens Axboe 已提交
630
					sleep_on_page_killable, TASK_KILLABLE);
M
Matthew Wilcox 已提交
631
}
632
EXPORT_SYMBOL_GPL(__lock_page_killable);
M
Matthew Wilcox 已提交
633

634 635 636
int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
			 unsigned int flags)
{
637 638 639 640 641 642 643 644 645 646 647 648
	if (flags & FAULT_FLAG_ALLOW_RETRY) {
		/*
		 * CAUTION! In this case, mmap_sem is not released
		 * even though return 0.
		 */
		if (flags & FAULT_FLAG_RETRY_NOWAIT)
			return 0;

		up_read(&mm->mmap_sem);
		if (flags & FAULT_FLAG_KILLABLE)
			wait_on_page_locked_killable(page);
		else
649
			wait_on_page_locked(page);
650
		return 0;
651 652 653 654 655 656 657 658 659 660 661 662
	} else {
		if (flags & FAULT_FLAG_KILLABLE) {
			int ret;

			ret = __lock_page_killable(page);
			if (ret) {
				up_read(&mm->mmap_sem);
				return 0;
			}
		} else
			__lock_page(page);
		return 1;
663 664 665
	}
}

666 667 668 669 670
/**
 * 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
671 672
 * 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
673
 */
N
Nick Piggin 已提交
674
struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
L
Linus Torvalds 已提交
675
{
N
Nick Piggin 已提交
676
	void **pagep;
L
Linus Torvalds 已提交
677 678
	struct page *page;

N
Nick Piggin 已提交
679 680 681 682 683 684
	rcu_read_lock();
repeat:
	page = NULL;
	pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
	if (pagep) {
		page = radix_tree_deref_slot(pagep);
N
Nick Piggin 已提交
685 686
		if (unlikely(!page))
			goto out;
687
		if (radix_tree_exception(page)) {
688 689 690 691 692 693 694 695
			if (radix_tree_deref_retry(page))
				goto repeat;
			/*
			 * Otherwise, shmem/tmpfs must be storing a swap entry
			 * here as an exceptional entry: so return it without
			 * attempting to raise page count.
			 */
			goto out;
696
		}
N
Nick Piggin 已提交
697 698 699 700 701 702 703 704 705 706 707 708 709
		if (!page_cache_get_speculative(page))
			goto repeat;

		/*
		 * Has the page moved?
		 * This is part of the lockless pagecache protocol. See
		 * include/linux/pagemap.h for details.
		 */
		if (unlikely(page != *pagep)) {
			page_cache_release(page);
			goto repeat;
		}
	}
N
Nick Piggin 已提交
710
out:
N
Nick Piggin 已提交
711 712
	rcu_read_unlock();

L
Linus Torvalds 已提交
713 714 715 716 717 718
	return page;
}
EXPORT_SYMBOL(find_get_page);

/**
 * find_lock_page - locate, pin and lock a pagecache page
719 720
 * @mapping: the address_space to search
 * @offset: the page index
L
Linus Torvalds 已提交
721 722 723 724 725 726
 *
 * 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
727
struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
L
Linus Torvalds 已提交
728 729 730 731
{
	struct page *page;

repeat:
N
Nick Piggin 已提交
732
	page = find_get_page(mapping, offset);
733
	if (page && !radix_tree_exception(page)) {
N
Nick Piggin 已提交
734 735 736 737 738 739
		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
740
		}
N
Nick Piggin 已提交
741
		VM_BUG_ON(page->index != offset);
L
Linus Torvalds 已提交
742 743 744 745 746 747 748
	}
	return page;
}
EXPORT_SYMBOL(find_lock_page);

/**
 * find_or_create_page - locate or add a pagecache page
749 750 751
 * @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
752 753 754 755 756 757 758 759 760 761 762 763 764
 *
 * 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,
765
		pgoff_t index, gfp_t gfp_mask)
L
Linus Torvalds 已提交
766
{
N
Nick Piggin 已提交
767
	struct page *page;
L
Linus Torvalds 已提交
768 769 770 771
	int err;
repeat:
	page = find_lock_page(mapping, index);
	if (!page) {
N
Nick Piggin 已提交
772 773 774
		page = __page_cache_alloc(gfp_mask);
		if (!page)
			return NULL;
N
Nick Piggin 已提交
775 776 777 778 779 780 781 782
		/*
		 * 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
783 784 785 786 787
		if (unlikely(err)) {
			page_cache_release(page);
			page = NULL;
			if (err == -EEXIST)
				goto repeat;
L
Linus Torvalds 已提交
788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814
		}
	}
	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;
815
	unsigned int nr_found, nr_skip;
N
Nick Piggin 已提交
816 817 818 819

	rcu_read_lock();
restart:
	nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
820
				(void ***)pages, NULL, start, nr_pages);
N
Nick Piggin 已提交
821
	ret = 0;
822
	nr_skip = 0;
N
Nick Piggin 已提交
823 824 825 826 827 828
	for (i = 0; i < nr_found; i++) {
		struct page *page;
repeat:
		page = radix_tree_deref_slot((void **)pages[i]);
		if (unlikely(!page))
			continue;
829

830
		if (radix_tree_exception(page)) {
831 832 833 834 835 836 837 838 839
			if (radix_tree_deref_retry(page)) {
				/*
				 * Transient condition which can only trigger
				 * when entry at index 0 moves out of or back
				 * to root: none yet gotten, safe to restart.
				 */
				WARN_ON(start | i);
				goto restart;
			}
840
			/*
841 842 843
			 * Otherwise, shmem/tmpfs must be storing a swap entry
			 * here as an exceptional entry: so skip over it -
			 * we only reach this from invalidate_mapping_pages().
844
			 */
845
			nr_skip++;
846
			continue;
N
Nick Piggin 已提交
847
		}
N
Nick Piggin 已提交
848 849 850 851 852 853 854 855 856

		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
857

N
Nick Piggin 已提交
858 859 860
		pages[ret] = page;
		ret++;
	}
861 862 863 864 865

	/*
	 * If all entries were removed before we could secure them,
	 * try again, because callers stop trying once 0 is returned.
	 */
866
	if (unlikely(!ret && nr_found > nr_skip))
867
		goto restart;
N
Nick Piggin 已提交
868
	rcu_read_unlock();
L
Linus Torvalds 已提交
869 870 871
	return ret;
}

872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888
/**
 * 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
889 890 891 892 893
	unsigned int nr_found;

	rcu_read_lock();
restart:
	nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
894
				(void ***)pages, NULL, index, nr_pages);
N
Nick Piggin 已提交
895 896 897 898 899 900 901
	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;
902

903
		if (radix_tree_exception(page)) {
904 905 906 907 908 909 910 911
			if (radix_tree_deref_retry(page)) {
				/*
				 * Transient condition which can only trigger
				 * when entry at index 0 moves out of or back
				 * to root: none yet gotten, safe to restart.
				 */
				goto restart;
			}
912
			/*
913 914 915
			 * Otherwise, shmem/tmpfs must be storing a swap entry
			 * here as an exceptional entry: so stop looking for
			 * contiguous pages.
916
			 */
917
			break;
918
		}
919

N
Nick Piggin 已提交
920 921 922 923 924 925 926 927 928
		if (!page_cache_get_speculative(page))
			goto repeat;

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

N
Nick Piggin 已提交
929 930 931 932 933 934 935 936 937 938
		/*
		 * must check mapping and index after taking the ref.
		 * otherwise we can get both false positives and false
		 * negatives, which is just confusing to the caller.
		 */
		if (page->mapping == NULL || page->index != index) {
			page_cache_release(page);
			break;
		}

N
Nick Piggin 已提交
939 940
		pages[ret] = page;
		ret++;
941 942
		index++;
	}
N
Nick Piggin 已提交
943 944
	rcu_read_unlock();
	return ret;
945
}
946
EXPORT_SYMBOL(find_get_pages_contig);
947

948 949 950 951 952 953 954 955
/**
 * 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
956
 * Like find_get_pages, except we only return pages which are tagged with
957
 * @tag.   We update @index to index the next page for the traversal.
L
Linus Torvalds 已提交
958 959 960 961 962 963
 */
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
964 965 966 967 968 969 970 971 972 973 974 975 976
	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;
977

978
		if (radix_tree_exception(page)) {
979 980 981 982 983 984 985 986
			if (radix_tree_deref_retry(page)) {
				/*
				 * Transient condition which can only trigger
				 * when entry at index 0 moves out of or back
				 * to root: none yet gotten, safe to restart.
				 */
				goto restart;
			}
987
			/*
988 989
			 * This function is never used on a shmem/tmpfs
			 * mapping, so a swap entry won't be found here.
990
			 */
991
			BUG();
992
		}
N
Nick Piggin 已提交
993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005

		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++;
	}
1006 1007 1008 1009 1010 1011 1012

	/*
	 * If all entries were removed before we could secure them,
	 * try again, because callers stop trying once 0 is returned.
	 */
	if (unlikely(!ret && nr_found))
		goto restart;
N
Nick Piggin 已提交
1013
	rcu_read_unlock();
L
Linus Torvalds 已提交
1014 1015 1016

	if (ret)
		*index = pages[ret - 1]->index + 1;
N
Nick Piggin 已提交
1017

L
Linus Torvalds 已提交
1018 1019
	return ret;
}
1020
EXPORT_SYMBOL(find_get_pages_tag);
L
Linus Torvalds 已提交
1021

1022 1023 1024 1025 1026
/**
 * grab_cache_page_nowait - returns locked page at given index in given cache
 * @mapping: target address_space
 * @index: the page index
 *
1027
 * Same as grab_cache_page(), but do not wait if the page is unavailable.
L
Linus Torvalds 已提交
1028 1029 1030 1031 1032 1033 1034 1035
 * 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 *
1036
grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
L
Linus Torvalds 已提交
1037 1038 1039 1040
{
	struct page *page = find_get_page(mapping, index);

	if (page) {
N
Nick Piggin 已提交
1041
		if (trylock_page(page))
L
Linus Torvalds 已提交
1042 1043 1044 1045
			return page;
		page_cache_release(page);
		return NULL;
	}
1046
	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
N
Nick Piggin 已提交
1047
	if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
L
Linus Torvalds 已提交
1048 1049 1050 1051 1052 1053 1054
		page_cache_release(page);
		page = NULL;
	}
	return page;
}
EXPORT_SYMBOL(grab_cache_page_nowait);

1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075
/*
 * 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;
}

1076
/**
C
Christoph Hellwig 已提交
1077
 * do_generic_file_read - generic file read routine
1078 1079 1080 1081 1082
 * @filp:	the file to read
 * @ppos:	current file position
 * @desc:	read_descriptor
 * @actor:	read method
 *
L
Linus Torvalds 已提交
1083
 * This is a generic file read routine, and uses the
1084
 * mapping->a_ops->readpage() function for the actual low-level stuff.
L
Linus Torvalds 已提交
1085 1086 1087 1088
 *
 * 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
1089 1090
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
1091
{
C
Christoph Hellwig 已提交
1092
	struct address_space *mapping = filp->f_mapping;
L
Linus Torvalds 已提交
1093
	struct inode *inode = mapping->host;
C
Christoph Hellwig 已提交
1094
	struct file_ra_state *ra = &filp->f_ra;
1095 1096 1097 1098
	pgoff_t index;
	pgoff_t last_index;
	pgoff_t prev_index;
	unsigned long offset;      /* offset into pagecache page */
1099
	unsigned int prev_offset;
L
Linus Torvalds 已提交
1100 1101 1102
	int error;

	index = *ppos >> PAGE_CACHE_SHIFT;
1103 1104
	prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
	prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
L
Linus Torvalds 已提交
1105 1106 1107 1108 1109
	last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
	offset = *ppos & ~PAGE_CACHE_MASK;

	for (;;) {
		struct page *page;
1110
		pgoff_t end_index;
N
NeilBrown 已提交
1111
		loff_t isize;
L
Linus Torvalds 已提交
1112 1113 1114 1115 1116
		unsigned long nr, ret;

		cond_resched();
find_page:
		page = find_get_page(mapping, index);
1117
		if (!page) {
1118
			page_cache_sync_readahead(mapping,
1119
					ra, filp,
1120 1121 1122 1123 1124 1125
					index, last_index - index);
			page = find_get_page(mapping, index);
			if (unlikely(page == NULL))
				goto no_cached_page;
		}
		if (PageReadahead(page)) {
1126
			page_cache_async_readahead(mapping,
1127
					ra, filp, page,
1128
					index, last_index - index);
L
Linus Torvalds 已提交
1129
		}
1130 1131 1132 1133
		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
1134
			if (!trylock_page(page))
1135
				goto page_not_up_to_date;
1136 1137 1138
			/* Did it get truncated before we got the lock? */
			if (!page->mapping)
				goto page_not_up_to_date_locked;
1139 1140 1141 1142 1143
			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
1144
page_ok:
N
NeilBrown 已提交
1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170
		/*
		 * 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
1171 1172 1173 1174 1175 1176 1177 1178 1179

		/* 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);

		/*
1180 1181
		 * When a sequential read accesses a page several times,
		 * only mark it as accessed the first time.
L
Linus Torvalds 已提交
1182
		 */
1183
		if (prev_index != index || offset != prev_offset)
L
Linus Torvalds 已提交
1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200
			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
1201
		prev_offset = offset;
L
Linus Torvalds 已提交
1202 1203 1204 1205 1206 1207 1208 1209

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

page_not_up_to_date:
		/* Get exclusive access to the page ... */
1210 1211 1212
		error = lock_page_killable(page);
		if (unlikely(error))
			goto readpage_error;
L
Linus Torvalds 已提交
1213

1214
page_not_up_to_date_locked:
N
Nick Piggin 已提交
1215
		/* Did it get truncated before we got the lock? */
L
Linus Torvalds 已提交
1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228
		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:
1229 1230 1231 1232 1233 1234
		/*
		 * 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
1235 1236 1237
		/* Start the actual read. The read will unlock the page. */
		error = mapping->a_ops->readpage(filp, page);

1238 1239 1240 1241 1242
		if (unlikely(error)) {
			if (error == AOP_TRUNCATED_PAGE) {
				page_cache_release(page);
				goto find_page;
			}
L
Linus Torvalds 已提交
1243
			goto readpage_error;
1244
		}
L
Linus Torvalds 已提交
1245 1246

		if (!PageUptodate(page)) {
1247 1248 1249
			error = lock_page_killable(page);
			if (unlikely(error))
				goto readpage_error;
L
Linus Torvalds 已提交
1250 1251 1252
			if (!PageUptodate(page)) {
				if (page->mapping == NULL) {
					/*
1253
					 * invalidate_mapping_pages got it
L
Linus Torvalds 已提交
1254 1255 1256 1257 1258 1259
					 */
					unlock_page(page);
					page_cache_release(page);
					goto find_page;
				}
				unlock_page(page);
1260
				shrink_readahead_size_eio(filp, ra);
1261 1262
				error = -EIO;
				goto readpage_error;
L
Linus Torvalds 已提交
1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279
			}
			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
1280 1281 1282 1283
		page = page_cache_alloc_cold(mapping);
		if (!page) {
			desc->error = -ENOMEM;
			goto out;
L
Linus Torvalds 已提交
1284
		}
N
Nick Piggin 已提交
1285
		error = add_to_page_cache_lru(page, mapping,
L
Linus Torvalds 已提交
1286 1287
						index, GFP_KERNEL);
		if (error) {
N
Nick Piggin 已提交
1288
			page_cache_release(page);
L
Linus Torvalds 已提交
1289 1290 1291 1292 1293 1294 1295 1296 1297
			if (error == -EEXIST)
				goto find_page;
			desc->error = error;
			goto out;
		}
		goto readpage;
	}

out:
1298 1299 1300
	ra->prev_pos = prev_index;
	ra->prev_pos <<= PAGE_CACHE_SHIFT;
	ra->prev_pos |= prev_offset;
L
Linus Torvalds 已提交
1301

1302
	*ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1303
	file_accessed(filp);
L
Linus Torvalds 已提交
1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319
}

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)) {
1320
		kaddr = kmap_atomic(page);
L
Linus Torvalds 已提交
1321 1322
		left = __copy_to_user_inatomic(desc->arg.buf,
						kaddr + offset, size);
1323
		kunmap_atomic(kaddr);
L
Linus Torvalds 已提交
1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343
		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;
}

1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382
/*
 * 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);

1383
/**
H
Henrik Kretzschmar 已提交
1384
 * generic_file_aio_read - generic filesystem read routine
1385 1386 1387
 * @iocb:	kernel I/O control block
 * @iov:	io vector request
 * @nr_segs:	number of segments in the iovec
H
Henrik Kretzschmar 已提交
1388
 * @pos:	current file position
1389
 *
L
Linus Torvalds 已提交
1390 1391 1392 1393
 * This is the "read()" routine for all filesystems
 * that can use the page cache directly.
 */
ssize_t
1394 1395
generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos)
L
Linus Torvalds 已提交
1396 1397 1398
{
	struct file *filp = iocb->ki_filp;
	ssize_t retval;
1399
	unsigned long seg = 0;
L
Linus Torvalds 已提交
1400
	size_t count;
1401
	loff_t *ppos = &iocb->ki_pos;
L
Linus Torvalds 已提交
1402 1403

	count = 0;
1404 1405 1406
	retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
	if (retval)
		return retval;
L
Linus Torvalds 已提交
1407 1408 1409

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (filp->f_flags & O_DIRECT) {
1410
		loff_t size;
L
Linus Torvalds 已提交
1411 1412 1413 1414 1415 1416 1417 1418 1419
		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) {
1420 1421
			retval = filemap_write_and_wait_range(mapping, pos,
					pos + iov_length(iov, nr_segs) - 1);
1422
			if (!retval) {
1423 1424 1425
				struct blk_plug plug;

				blk_start_plug(&plug);
1426 1427
				retval = mapping->a_ops->direct_IO(READ, iocb,
							iov, pos, nr_segs);
1428
				blk_finish_plug(&plug);
1429
			}
1430
			if (retval > 0) {
L
Linus Torvalds 已提交
1431
				*ppos = pos + retval;
1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443
				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
1444 1445 1446
				file_accessed(filp);
				goto out;
			}
1447
		}
L
Linus Torvalds 已提交
1448 1449
	}

1450
	count = retval;
H
Hugh Dickins 已提交
1451 1452
	for (seg = 0; seg < nr_segs; seg++) {
		read_descriptor_t desc;
1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466
		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
1467

H
Hugh Dickins 已提交
1468
		desc.written = 0;
1469 1470
		desc.arg.buf = iov[seg].iov_base + offset;
		desc.count = iov[seg].iov_len - offset;
H
Hugh Dickins 已提交
1471 1472 1473 1474 1475 1476 1477 1478
		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
1479
		}
H
Hugh Dickins 已提交
1480 1481
		if (desc.count > 0)
			break;
L
Linus Torvalds 已提交
1482 1483 1484 1485 1486 1487 1488 1489
	}
out:
	return retval;
}
EXPORT_SYMBOL(generic_file_aio_read);

static ssize_t
do_readahead(struct address_space *mapping, struct file *filp,
1490
	     pgoff_t index, unsigned long nr)
L
Linus Torvalds 已提交
1491 1492 1493 1494
{
	if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
		return -EINVAL;

1495
	force_page_cache_readahead(mapping, filp, index, nr);
L
Linus Torvalds 已提交
1496 1497 1498
	return 0;
}

1499
SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
L
Linus Torvalds 已提交
1500 1501 1502 1503 1504 1505 1506 1507 1508
{
	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;
1509 1510
			pgoff_t start = offset >> PAGE_CACHE_SHIFT;
			pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
L
Linus Torvalds 已提交
1511 1512 1513 1514 1515 1516 1517
			unsigned long len = end - start + 1;
			ret = do_readahead(mapping, file, start, len);
		}
		fput(file);
	}
	return ret;
}
1518 1519 1520 1521 1522 1523 1524
#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
1525 1526

#ifdef CONFIG_MMU
1527 1528 1529 1530 1531
/**
 * 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
1532 1533 1534
 * 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
1535
static int page_cache_read(struct file *file, pgoff_t offset)
L
Linus Torvalds 已提交
1536 1537 1538
{
	struct address_space *mapping = file->f_mapping;
	struct page *page; 
1539
	int ret;
L
Linus Torvalds 已提交
1540

1541 1542 1543 1544 1545 1546 1547 1548 1549 1550
	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
1551 1552 1553

		page_cache_release(page);

1554 1555 1556
	} while (ret == AOP_TRUNCATED_PAGE);
		
	return ret;
L
Linus Torvalds 已提交
1557 1558 1559 1560
}

#define MMAP_LOTSAMISS  (100)

1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575
/*
 * 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;
1576 1577
	if (!ra->ra_pages)
		return;
1578

1579
	if (VM_SequentialReadHint(vma)) {
1580 1581
		page_cache_sync_readahead(mapping, ra, file, offset,
					  ra->ra_pages);
1582 1583 1584
		return;
	}

1585 1586
	/* Avoid banging the cache line if not needed */
	if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1587 1588 1589 1590 1591 1592 1593 1594 1595
		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;

1596 1597 1598
	/*
	 * mmap read-around
	 */
1599
	ra_pages = max_sane_readahead(ra->ra_pages);
1600 1601
	ra->start = max_t(long, 0, offset - ra_pages / 2);
	ra->size = ra_pages;
1602
	ra->async_size = ra_pages / 4;
1603
	ra_submit(ra, mapping, file);
1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623
}

/*
 * 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))
1624 1625
		page_cache_async_readahead(mapping, ra, file,
					   page, offset, ra->ra_pages);
1626 1627
}

1628
/**
1629
 * filemap_fault - read in file data for page fault handling
N
Nick Piggin 已提交
1630 1631
 * @vma:	vma in which the fault was taken
 * @vmf:	struct vm_fault containing details of the fault
1632
 *
1633
 * filemap_fault() is invoked via the vma operations vector for a
L
Linus Torvalds 已提交
1634 1635 1636 1637 1638 1639
 * 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
1640
int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
L
Linus Torvalds 已提交
1641 1642
{
	int error;
1643
	struct file *file = vma->vm_file;
L
Linus Torvalds 已提交
1644 1645 1646
	struct address_space *mapping = file->f_mapping;
	struct file_ra_state *ra = &file->f_ra;
	struct inode *inode = mapping->host;
1647
	pgoff_t offset = vmf->pgoff;
L
Linus Torvalds 已提交
1648
	struct page *page;
J
Jan Kara 已提交
1649
	pgoff_t size;
N
Nick Piggin 已提交
1650
	int ret = 0;
L
Linus Torvalds 已提交
1651 1652

	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1653
	if (offset >= size)
1654
		return VM_FAULT_SIGBUS;
L
Linus Torvalds 已提交
1655 1656 1657 1658

	/*
	 * Do we have something in the page cache already?
	 */
1659 1660
	page = find_get_page(mapping, offset);
	if (likely(page)) {
L
Linus Torvalds 已提交
1661
		/*
1662 1663
		 * We found the page, so try async readahead before
		 * waiting for the lock.
L
Linus Torvalds 已提交
1664
		 */
1665 1666 1667 1668 1669
		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);
1670
		mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1671 1672
		ret = VM_FAULT_MAJOR;
retry_find:
1673
		page = find_get_page(mapping, offset);
L
Linus Torvalds 已提交
1674 1675 1676 1677
		if (!page)
			goto no_cached_page;
	}

1678 1679
	if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
		page_cache_release(page);
1680
		return ret | VM_FAULT_RETRY;
1681
	}
1682 1683 1684 1685 1686 1687 1688 1689 1690

	/* 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
1691
	/*
1692 1693
	 * 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
1694
	 */
1695
	if (unlikely(!PageUptodate(page)))
L
Linus Torvalds 已提交
1696 1697
		goto page_not_uptodate;

1698 1699 1700 1701
	/*
	 * Found the page and have a reference on it.
	 * We must recheck i_size under page lock.
	 */
1702
	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1703
	if (unlikely(offset >= size)) {
1704
		unlock_page(page);
1705
		page_cache_release(page);
1706
		return VM_FAULT_SIGBUS;
1707 1708
	}

N
Nick Piggin 已提交
1709
	vmf->page = page;
N
Nick Piggin 已提交
1710
	return ret | VM_FAULT_LOCKED;
L
Linus Torvalds 已提交
1711 1712 1713 1714 1715 1716

no_cached_page:
	/*
	 * We're only likely to ever get here if MADV_RANDOM is in
	 * effect.
	 */
1717
	error = page_cache_read(file, offset);
L
Linus Torvalds 已提交
1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732

	/*
	 * 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
1733 1734
		return VM_FAULT_OOM;
	return VM_FAULT_SIGBUS;
L
Linus Torvalds 已提交
1735 1736 1737 1738 1739 1740 1741 1742 1743

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);
1744
	error = mapping->a_ops->readpage(file, page);
1745 1746 1747 1748 1749
	if (!error) {
		wait_on_page_locked(page);
		if (!PageUptodate(page))
			error = -EIO;
	}
1750 1751 1752
	page_cache_release(page);

	if (!error || error == AOP_TRUNCATED_PAGE)
1753
		goto retry_find;
L
Linus Torvalds 已提交
1754

1755
	/* Things didn't work out. Return zero to tell the mm layer so. */
1756
	shrink_readahead_size_eio(file, ra);
N
Nick Piggin 已提交
1757
	return VM_FAULT_SIGBUS;
1758 1759 1760
}
EXPORT_SYMBOL(filemap_fault);

1761
const struct vm_operations_struct generic_file_vm_ops = {
1762
	.fault		= filemap_fault,
L
Linus Torvalds 已提交
1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774
};

/* 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
1775
	vma->vm_flags |= VM_CAN_NONLINEAR;
L
Linus Torvalds 已提交
1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801
	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);

1802
static struct page *__read_cache_page(struct address_space *mapping,
1803
				pgoff_t index,
1804
				int (*filler)(void *, struct page *),
1805 1806
				void *data,
				gfp_t gfp)
L
Linus Torvalds 已提交
1807
{
N
Nick Piggin 已提交
1808
	struct page *page;
L
Linus Torvalds 已提交
1809 1810 1811 1812
	int err;
repeat:
	page = find_get_page(mapping, index);
	if (!page) {
1813
		page = __page_cache_alloc(gfp | __GFP_COLD);
N
Nick Piggin 已提交
1814 1815
		if (!page)
			return ERR_PTR(-ENOMEM);
1816
		err = add_to_page_cache_lru(page, mapping, index, gfp);
N
Nick Piggin 已提交
1817 1818 1819 1820
		if (unlikely(err)) {
			page_cache_release(page);
			if (err == -EEXIST)
				goto repeat;
L
Linus Torvalds 已提交
1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832
			/* 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;
}

1833
static struct page *do_read_cache_page(struct address_space *mapping,
1834
				pgoff_t index,
1835
				int (*filler)(void *, struct page *),
1836 1837 1838
				void *data,
				gfp_t gfp)

L
Linus Torvalds 已提交
1839 1840 1841 1842 1843
{
	struct page *page;
	int err;

retry:
1844
	page = __read_cache_page(mapping, index, filler, data, gfp);
L
Linus Torvalds 已提交
1845
	if (IS_ERR(page))
1846
		return page;
L
Linus Torvalds 已提交
1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862
	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);
1863
		return ERR_PTR(err);
L
Linus Torvalds 已提交
1864
	}
1865
out:
1866 1867 1868
	mark_page_accessed(page);
	return page;
}
1869 1870 1871 1872 1873 1874

/**
 * 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
1875
 * @data:	first arg to filler(data, page) function, often left as NULL
1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886
 *
 * 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,
1887
				int (*filler)(void *, struct page *),
1888 1889 1890 1891
				void *data)
{
	return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
}
1892 1893
EXPORT_SYMBOL(read_cache_page_async);

1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912
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
1913
 * any new page allocations done using the specified allocation flags.
1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926
 *
 * 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);

1927 1928 1929 1930 1931
/**
 * 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
1932
 * @data:	first arg to filler(data, page) function, often left as NULL
1933 1934 1935 1936 1937 1938 1939
 *
 * 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,
1940
				pgoff_t index,
1941
				int (*filler)(void *, struct page *),
1942 1943
				void *data)
{
1944
	return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
L
Linus Torvalds 已提交
1945 1946 1947 1948 1949 1950 1951 1952 1953
}
EXPORT_SYMBOL(read_cache_page);

/*
 * The logic we want is
 *
 *	if suid or (sgid and xgrp)
 *		remove privs
 */
1954
int should_remove_suid(struct dentry *dentry)
L
Linus Torvalds 已提交
1955
{
1956
	umode_t mode = dentry->d_inode->i_mode;
L
Linus Torvalds 已提交
1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969
	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;

1970
	if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1971
		return kill;
L
Linus Torvalds 已提交
1972

1973 1974
	return 0;
}
M
Mark Fasheh 已提交
1975
EXPORT_SYMBOL(should_remove_suid);
1976

1977
static int __remove_suid(struct dentry *dentry, int kill)
1978 1979 1980 1981 1982 1983 1984
{
	struct iattr newattrs;

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

1985
int file_remove_suid(struct file *file)
1986
{
1987
	struct dentry *dentry = file->f_path.dentry;
1988 1989 1990
	struct inode *inode = dentry->d_inode;
	int killsuid;
	int killpriv;
1991
	int error = 0;
1992

1993 1994 1995 1996 1997 1998 1999
	/* Fast path for nothing security related */
	if (IS_NOSEC(inode))
		return 0;

	killsuid = should_remove_suid(dentry);
	killpriv = security_inode_need_killpriv(dentry);

2000 2001 2002 2003 2004 2005
	if (killpriv < 0)
		return killpriv;
	if (killpriv)
		error = security_inode_killpriv(dentry);
	if (!error && killsuid)
		error = __remove_suid(dentry, killsuid);
A
Al Viro 已提交
2006
	if (!error && (inode->i_sb->s_flags & MS_NOSEC))
2007
		inode->i_flags |= S_NOSEC;
2008

2009
	return error;
L
Linus Torvalds 已提交
2010
}
2011
EXPORT_SYMBOL(file_remove_suid);
L
Linus Torvalds 已提交
2012

N
Nick Piggin 已提交
2013
static size_t __iovec_copy_from_user_inatomic(char *vaddr,
L
Linus Torvalds 已提交
2014 2015
			const struct iovec *iov, size_t base, size_t bytes)
{
2016
	size_t copied = 0, left = 0;
L
Linus Torvalds 已提交
2017 2018 2019 2020 2021 2022

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

		base = 0;
2023
		left = __copy_from_user_inatomic(vaddr, buf, copy);
L
Linus Torvalds 已提交
2024 2025 2026 2027 2028
		copied += copy;
		bytes -= copy;
		vaddr += copy;
		iov++;

2029
		if (unlikely(left))
L
Linus Torvalds 已提交
2030 2031 2032 2033 2034
			break;
	}
	return copied - left;
}

N
Nick Piggin 已提交
2035 2036
/*
 * Copy as much as we can into the page and return the number of bytes which
2037
 * were successfully copied.  If a fault is encountered then return the number of
N
Nick Piggin 已提交
2038 2039 2040 2041 2042 2043 2044 2045 2046
 * 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());
2047
	kaddr = kmap_atomic(page);
N
Nick Piggin 已提交
2048 2049 2050
	if (likely(i->nr_segs == 1)) {
		int left;
		char __user *buf = i->iov->iov_base + i->iov_offset;
2051
		left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
N
Nick Piggin 已提交
2052 2053 2054 2055 2056
		copied = bytes - left;
	} else {
		copied = __iovec_copy_from_user_inatomic(kaddr + offset,
						i->iov, i->iov_offset, bytes);
	}
2057
	kunmap_atomic(kaddr);
N
Nick Piggin 已提交
2058 2059 2060

	return copied;
}
N
Nick Piggin 已提交
2061
EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
N
Nick Piggin 已提交
2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078

/*
 * 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;
2079
		left = __copy_from_user(kaddr + offset, buf, bytes);
N
Nick Piggin 已提交
2080 2081 2082 2083 2084 2085 2086 2087
		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
2088
EXPORT_SYMBOL(iov_iter_copy_from_user);
N
Nick Piggin 已提交
2089

N
Nick Piggin 已提交
2090
void iov_iter_advance(struct iov_iter *i, size_t bytes)
N
Nick Piggin 已提交
2091
{
N
Nick Piggin 已提交
2092 2093
	BUG_ON(i->count < bytes);

N
Nick Piggin 已提交
2094 2095
	if (likely(i->nr_segs == 1)) {
		i->iov_offset += bytes;
N
Nick Piggin 已提交
2096
		i->count -= bytes;
N
Nick Piggin 已提交
2097 2098 2099
	} else {
		const struct iovec *iov = i->iov;
		size_t base = i->iov_offset;
2100
		unsigned long nr_segs = i->nr_segs;
N
Nick Piggin 已提交
2101

2102 2103
		/*
		 * The !iov->iov_len check ensures we skip over unlikely
N
Nick Piggin 已提交
2104
		 * zero-length segments (without overruning the iovec).
2105
		 */
2106
		while (bytes || unlikely(i->count && !iov->iov_len)) {
N
Nick Piggin 已提交
2107
			int copy;
N
Nick Piggin 已提交
2108

N
Nick Piggin 已提交
2109 2110 2111
			copy = min(bytes, iov->iov_len - base);
			BUG_ON(!i->count || i->count < copy);
			i->count -= copy;
N
Nick Piggin 已提交
2112 2113 2114 2115
			bytes -= copy;
			base += copy;
			if (iov->iov_len == base) {
				iov++;
2116
				nr_segs--;
N
Nick Piggin 已提交
2117 2118 2119 2120 2121
				base = 0;
			}
		}
		i->iov = iov;
		i->iov_offset = base;
2122
		i->nr_segs = nr_segs;
N
Nick Piggin 已提交
2123 2124
	}
}
N
Nick Piggin 已提交
2125
EXPORT_SYMBOL(iov_iter_advance);
N
Nick Piggin 已提交
2126

2127 2128 2129 2130 2131 2132 2133 2134 2135 2136
/*
 * 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
2137 2138
{
	char __user *buf = i->iov->iov_base + i->iov_offset;
2139 2140
	bytes = min(bytes, i->iov->iov_len - i->iov_offset);
	return fault_in_pages_readable(buf, bytes);
N
Nick Piggin 已提交
2141
}
N
Nick Piggin 已提交
2142
EXPORT_SYMBOL(iov_iter_fault_in_readable);
N
Nick Piggin 已提交
2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154

/*
 * 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
2155
EXPORT_SYMBOL(iov_iter_single_seg_count);
N
Nick Piggin 已提交
2156

L
Linus Torvalds 已提交
2157 2158 2159
/*
 * Performs necessary checks before doing a write
 *
2160
 * Can adjust writing position or amount of bytes to write.
L
Linus Torvalds 已提交
2161 2162 2163 2164 2165 2166
 * 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
2167
	unsigned long limit = rlimit(RLIMIT_FSIZE);
L
Linus Torvalds 已提交
2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218

        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 {
2219
#ifdef CONFIG_BLOCK
L
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2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230
		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;
2231 2232 2233
#else
		return -EPERM;
#endif
L
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2234 2235 2236 2237 2238
	}
	return 0;
}
EXPORT_SYMBOL(generic_write_checks);

2239 2240 2241 2242 2243 2244
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;

2245
	return aops->write_begin(file, mapping, pos, len, flags,
2246 2247 2248 2249 2250 2251 2252 2253 2254 2255
							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;

2256 2257
	mark_page_accessed(page);
	return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2258 2259 2260
}
EXPORT_SYMBOL(pagecache_write_end);

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Linus Torvalds 已提交
2261 2262 2263 2264 2265 2266 2267 2268 2269
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;
2270 2271
	size_t		write_len;
	pgoff_t		end;
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2272 2273 2274 2275

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

2276 2277 2278
	write_len = iov_length(iov, *nr_segs);
	end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;

2279
	written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2280 2281 2282 2283 2284 2285 2286
	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
2287
	 * without clobbering -EIOCBQUEUED from ->direct_IO().
2288 2289 2290 2291
	 */
	if (mapping->nrpages) {
		written = invalidate_inode_pages2_range(mapping,
					pos >> PAGE_CACHE_SHIFT, end);
2292 2293 2294 2295 2296 2297 2298
		/*
		 * If a page can not be invalidated, return 0 to fall back
		 * to buffered write.
		 */
		if (written) {
			if (written == -EBUSY)
				return 0;
2299
			goto out;
2300
		}
2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317
	}

	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);
	}

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	if (written > 0) {
2319 2320 2321
		pos += written;
		if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
			i_size_write(inode, pos);
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2322 2323
			mark_inode_dirty(inode);
		}
2324
		*ppos = pos;
L
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2325
	}
2326
out:
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2327 2328 2329 2330
	return written;
}
EXPORT_SYMBOL(generic_file_direct_write);

N
Nick Piggin 已提交
2331 2332 2333 2334
/*
 * Find or create a page at the given pagecache position. Return the locked
 * page. This function is specifically for buffered writes.
 */
2335 2336
struct page *grab_cache_page_write_begin(struct address_space *mapping,
					pgoff_t index, unsigned flags)
N
Nick Piggin 已提交
2337 2338
{
	int status;
2339
	gfp_t gfp_mask;
N
Nick Piggin 已提交
2340
	struct page *page;
2341
	gfp_t gfp_notmask = 0;
2342

2343 2344 2345
	gfp_mask = mapping_gfp_mask(mapping);
	if (mapping_cap_account_dirty(mapping))
		gfp_mask |= __GFP_WRITE;
2346 2347
	if (flags & AOP_FLAG_NOFS)
		gfp_notmask = __GFP_FS;
N
Nick Piggin 已提交
2348 2349
repeat:
	page = find_lock_page(mapping, index);
2350
	if (page)
2351
		goto found;
N
Nick Piggin 已提交
2352

2353
	page = __page_cache_alloc(gfp_mask & ~gfp_notmask);
N
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2354 2355
	if (!page)
		return NULL;
2356 2357
	status = add_to_page_cache_lru(page, mapping, index,
						GFP_KERNEL & ~gfp_notmask);
N
Nick Piggin 已提交
2358 2359 2360 2361 2362 2363
	if (unlikely(status)) {
		page_cache_release(page);
		if (status == -EEXIST)
			goto repeat;
		return NULL;
	}
2364 2365
found:
	wait_on_page_writeback(page);
N
Nick Piggin 已提交
2366 2367
	return page;
}
2368
EXPORT_SYMBOL(grab_cache_page_write_begin);
N
Nick Piggin 已提交
2369

2370 2371 2372 2373 2374 2375 2376
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
2377 2378 2379 2380 2381 2382 2383
	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;
2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411

	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
2412
		status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2413 2414 2415 2416
						&page, &fsdata);
		if (unlikely(status))
			break;

2417 2418 2419
		if (mapping_writably_mapped(mapping))
			flush_dcache_page(page);

2420 2421 2422 2423 2424
		pagefault_disable();
		copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
		pagefault_enable();
		flush_dcache_page(page);

2425
		mark_page_accessed(page);
2426 2427 2428 2429 2430 2431 2432 2433
		status = a_ops->write_end(file, mapping, pos, bytes, copied,
						page, fsdata);
		if (unlikely(status < 0))
			break;
		copied = status;

		cond_resched();

2434
		iov_iter_advance(i, copied);
2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451
		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);
2452 2453 2454 2455
		if (fatal_signal_pending(current)) {
			status = -EINTR;
			break;
		}
2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470
	} 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);
2471
	status = generic_perform_write(file, &i, pos);
L
Linus Torvalds 已提交
2472 2473

	if (likely(status >= 0)) {
2474 2475
		written += status;
		*ppos = pos + status;
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2476 2477 2478 2479 2480 2481
  	}
	
	return written ? written : status;
}
EXPORT_SYMBOL(generic_file_buffered_write);

2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502
/**
 * __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
2503 2504
{
	struct file *file = iocb->ki_filp;
2505
	struct address_space * mapping = file->f_mapping;
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2506 2507 2508 2509 2510 2511 2512 2513
	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;
2514 2515 2516
	err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
	if (err)
		return err;
L
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2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533

	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;

2534
	err = file_remove_suid(file);
L
Linus Torvalds 已提交
2535 2536 2537
	if (err)
		goto out;

2538
	file_update_time(file);
L
Linus Torvalds 已提交
2539 2540 2541

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (unlikely(file->f_flags & O_DIRECT)) {
2542 2543 2544 2545 2546
		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
2547 2548 2549 2550 2551 2552 2553 2554
		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;
2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568
		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
2569

2570 2571 2572 2573 2574 2575
		/*
		 * 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;
2576
		err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591
		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
2592 2593 2594 2595
out:
	current->backing_dev_info = NULL;
	return written ? written : err;
}
2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608
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.
 */
2609 2610
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
2611 2612
{
	struct file *file = iocb->ki_filp;
2613
	struct inode *inode = file->f_mapping->host;
2614
	struct blk_plug plug;
L
Linus Torvalds 已提交
2615 2616 2617 2618
	ssize_t ret;

	BUG_ON(iocb->ki_pos != pos);

2619
	mutex_lock(&inode->i_mutex);
2620
	blk_start_plug(&plug);
2621
	ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2622
	mutex_unlock(&inode->i_mutex);
L
Linus Torvalds 已提交
2623

2624
	if (ret > 0 || ret == -EIOCBQUEUED) {
L
Linus Torvalds 已提交
2625 2626
		ssize_t err;

2627
		err = generic_write_sync(file, pos, ret);
2628
		if (err < 0 && ret > 0)
L
Linus Torvalds 已提交
2629 2630
			ret = err;
	}
2631
	blk_finish_plug(&plug);
L
Linus Torvalds 已提交
2632 2633 2634 2635
	return ret;
}
EXPORT_SYMBOL(generic_file_aio_write);

2636 2637 2638 2639 2640 2641 2642 2643 2644 2645
/**
 * 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.
 *
2646 2647 2648
 * This may also be called if PG_fscache is set on a page, indicating that the
 * page is known to the local caching routines.
 *
2649
 * The @gfp_mask argument specifies whether I/O may be performed to release
2650
 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666
 *
 */
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);