fatent.c

/*
 *  Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version 2
 *  of the License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

/************************************************************************/
/*                                                                      */
/*  PROJECT : exFAT & FAT12/16/32 File System                           */
/*  FILE    : fatent.c                                                  */
/*  PURPOSE : exFAT FAT entry manager                                   */
/*                                                                      */
/*----------------------------------------------------------------------*/
/*  NOTES                                                               */
/*                                                                      */
/*                                                                      */
/************************************************************************/

#include <asm/unaligned.h>

#include "exfat.h"
#include "core.h"

/*----------------------------------------------------------------------*/
/*  Global Variable Definitions                                         */
/*----------------------------------------------------------------------*/
/* All buffer structures are protected w/ fsi->v_sem */

/*----------------------------------------------------------------------*/
/*  Static functions                                                    */
/*----------------------------------------------------------------------*/

/*======================================================================*/
/*  FAT Read/Write Functions                                            */
/*======================================================================*/
/* in : sb, loc
 * out: content
 * returns 0 on success, -1 on error
 */
static s32 exfat_ent_get(struct super_block *sb, u32 loc, u32 *content)
{
	u32 off, _content;
	u64 sec;
	u8 *fat_sector;
	FS_INFO_T *fsi = &(EXFAT_SB(sb)->fsi);

	sec = fsi->FAT1_start_sector + (loc >> (sb->s_blocksize_bits-2));
	off = (loc << 2) & (u32)(sb->s_blocksize - 1);

	fat_sector = fcache_getblk(sb, sec);
	if (!fat_sector)
		return -EIO;

	_content = le32_to_cpu(*(__le32 *)(&fat_sector[off]));

	/* remap reserved clusters to simplify code */
	if (_content >= CLUSTER_32(0xFFFFFFF8))
		_content = CLUS_EOF;

	*content = CLUSTER_32(_content);
	return 0;
}

static s32 exfat_ent_set(struct super_block *sb, u32 loc, u32 content)
{
	u32 off;
	u64 sec;
	u8 *fat_sector;
	__le32 *fat_entry;
	FS_INFO_T *fsi = &(EXFAT_SB(sb)->fsi);

	sec = fsi->FAT1_start_sector + (loc >> (sb->s_blocksize_bits-2));
	off = (loc << 2) & (u32)(sb->s_blocksize - 1);

	fat_sector = fcache_getblk(sb, sec);
	if (!fat_sector)
		return -EIO;

	fat_entry = (__le32 *)&(fat_sector[off]);
	*fat_entry = cpu_to_le32(content);

	return fcache_modify(sb, sec);
}

static FATENT_OPS_T exfat_ent_ops = {
	exfat_ent_get,
	exfat_ent_set
};

s32 fat_ent_ops_init(struct super_block *sb)
{
	FS_INFO_T *fsi = &(EXFAT_SB(sb)->fsi);
	fsi->fatent_ops = &exfat_ent_ops;

	return 0;
}

static inline bool is_reserved_clus(u32 clus)
{
	if (IS_CLUS_FREE(clus))
		return true;
	if (IS_CLUS_EOF(clus))
		return true;
	if (IS_CLUS_BAD(clus))
		return true;
	return false;
}

static inline bool is_valid_clus(FS_INFO_T *fsi, u32 clus)
{
	if (clus < CLUS_BASE || fsi->num_clusters <= clus)
		return false;
	return true;
}

s32 fat_ent_get(struct super_block *sb, u32 loc, u32 *content)
{
	FS_INFO_T *fsi = &(EXFAT_SB(sb)->fsi);
	s32 err;

	if (!is_valid_clus(fsi, loc)) {
		exfat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", loc);
		return -EIO;
	}

	err = fsi->fatent_ops->ent_get(sb, loc, content);
	if (err) {
		exfat_fs_error(sb, "failed to access to FAT "
				"(entry 0x%08x, err:%d)", loc, err);
		return err;
	}

	if (!is_reserved_clus(*content) && !is_valid_clus(fsi, *content)) {
		exfat_fs_error(sb, "invalid access to FAT (entry 0x%08x) "
			"bogus content (0x%08x)", loc, *content);
		return -EIO;
	}

	return 0;
}

s32 fat_ent_set(struct super_block *sb, u32 loc, u32 content)
{
	FS_INFO_T *fsi = &(EXFAT_SB(sb)->fsi);

	return fsi->fatent_ops->ent_set(sb, loc, content);
}

s32 fat_ent_get_safe(struct super_block *sb, u32 loc, u32 *content)
{
	s32 err = fat_ent_get(sb, loc, content);

	if (err)
		return err;

	if (IS_CLUS_FREE(*content)) {
		exfat_fs_error(sb, "invalid access to FAT free cluster "
				"(entry 0x%08x)", loc);
		return -EIO;
	}

	if (IS_CLUS_BAD(*content)) {
		exfat_fs_error(sb, "invalid access to FAT bad cluster "
				"(entry 0x%08x)", loc);
		return -EIO;
	}

	return 0;
}

/* end of fatent.c */