path: root/fs/fat/inode.c

/*
 *  linux/fs/fat/inode.c
 *
 *  Written 1992,1993 by Werner Almesberger
 *  VFAT extensions by Gordon Chaffee, merged with msdos fs by Henrik Storner
 *  Rewritten for the constant inumbers support by Al Viro
 *
 *  Fixes:
 *
 *	Max Cohan: Fixed invalid FSINFO offset when info_sector is 0
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/pagemap.h>
#include <linux/mpage.h>
#include <linux/buffer_head.h>
#include <linux/exportfs.h>
#include <linux/mount.h>
#include <linux/vfs.h>
#include <linux/parser.h>
#include <linux/uio.h>
#include <linux/writeback.h>
#include <linux/log2.h>
#include <linux/hash.h>
#include <asm/unaligned.h>
#include "fat.h"

#ifndef CONFIG_FAT_DEFAULT_IOCHARSET
/* if user don't select VFAT, this is undefined. */
#define CONFIG_FAT_DEFAULT_IOCHARSET	""
#endif

static int fat_default_codepage = CONFIG_FAT_DEFAULT_CODEPAGE;
static char fat_default_iocharset[] = CONFIG_FAT_DEFAULT_IOCHARSET;


static int fat_add_cluster(struct inode *inode)
{
	int err, cluster;

	err = fat_alloc_clusters(inode, &cluster, 1);
	if (err)
		return err;
	/* FIXME: this cluster should be added after data of this
	 * cluster is writed */
	err = fat_chain_add(inode, cluster, 1);
	if (err)
		fat_free_clusters(inode, cluster);
	return err;
}

static inline int __fat_get_block(struct inode *inode, sector_t iblock,
				  unsigned long *max_blocks,
				  struct buffer_head *bh_result, int create)
{
	struct super_block *sb = inode->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	unsigned long mapped_blocks;
	sector_t phys;
	int err, offset;

	err = fat_bmap(inode, iblock, &phys, &mapped_blocks, create);
	if (err)
		return err;
	if (phys) {
		map_bh(bh_result, sb, phys);
		*max_blocks = min(mapped_blocks, *max_blocks);
		return 0;
	}
	if (!create)
		return 0;

	if (iblock != MSDOS_I(inode)->mmu_private >> sb->s_blocksize_bits) {
		fat_fs_error(sb, "corrupted file size (i_pos %lld, %lld)",
			MSDOS_I(inode)->i_pos, MSDOS_I(inode)->mmu_private);
		return -EIO;
	}

	offset = (unsigned long)iblock & (sbi->sec_per_clus - 1);
	if (!offset) {
		/* TODO: multiple cluster allocation would be desirable. */
		err = fat_add_cluster(inode);
		if (err)
			return err;
	}
	/* available blocks on this cluster */
	mapped_blocks = sbi->sec_per_clus - offset;

	*max_blocks = min(mapped_blocks, *max_blocks);
	MSDOS_I(inode)->mmu_private += *max_blocks << sb->s_blocksize_bits;

	err = fat_bmap(inode, iblock, &phys, &mapped_blocks, create);
	if (err)
		return err;

	BUG_ON(!phys);
	BUG_ON(*max_blocks != mapped_blocks);
	set_buffer_new(bh_result);
	map_bh(bh_result, sb, phys);

	return 0;
}

static int fat_get_block(struct inode *inode, sector_t iblock,
			 struct buffer_head *bh_result, int create)
{
	struct super_block *sb = inode->i_sb;
	unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;
	int err;

	err = __fat_get_block(inode, iblock, &max_blocks, bh_result, create);
	if (err)
		return err;
	bh_result->b_size = max_blocks << sb->s_blocksize_bits;
	return 0;
}

static int fat_writepage(struct page *page, struct writeback_control *wbc)
{
	return block_write_full_page(page, fat_get_block, wbc);
}

static int fat_writepages(struct address_space *mapping,
			  struct writeback_control *wbc)
{
	return mpage_writepages(mapping, wbc, fat_get_block);
}

static int fat_readpage(struct file *file, struct page *page)
{
	return mpage_readpage(page, fat_get_block);
}

static int fat_readpages(struct file *file, struct address_space *mapping,
			 struct list_head *pages, unsigned nr_pages)
{
	return mpage_readpages(mapping, pages, nr_pages, fat_get_block);
}

static void fat_write_failed(struct address_space *mapping, loff_t to)
{
	struct inode *inode = mapping->host;

	if (to > inode->i_size) {
		truncate_pagecache(inode, to, inode->i_size);
		fat_truncate_blocks(inode, inode->i_size);
	}
}

static int fat_write_begin(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata)
{
	int err;

	*pagep = NULL;
	err = cont_write_begin(file, mapping, pos, len, flags,
				pagep, fsdata, fat_get_block,
				&MSDOS_I(mapping->host)->mmu_private);
	if (err < 0)
		fat_write_failed(mapping, pos + len);
	return err;
}

static int fat_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *pagep, void *fsdata)
{
	struct inode *inode = mapping->host;