e2fsprogs/lib/ext2fs/openfs.c - nest-cam/4320010/e2fsprogs - Git at Google

 /*
  * openfs.c --- open an ext2 filesystem
  *
  * Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o.
  *
  * %Begin-Header%
  * This file may be redistributed under the terms of the GNU Library
  * General Public License, version 2.
  * %End-Header%
  */

 #include <stdio.h>
 #include <string.h>
 #if HAVE_UNISTD_H
 #include <unistd.h>
 #endif
 #include <fcntl.h>
 #include <time.h>
 #if HAVE_SYS_STAT_H
 #include <sys/stat.h>
 #endif
 #if HAVE_SYS_TYPES_H
 #include <sys/types.h>
 #endif
 #ifdef HAVE_ERRNO_H
 #include <errno.h>
 #endif

 #include "ext2_fs.h"


 #include "ext2fs.h"
 #include "e2image.h"

 blk64_t ext2fs_descriptor_block_loc2(ext2_filsys fs, blk64_t group_block,
 				     dgrp_t i)
 {
 	int	bg;
 	int	has_super = 0;
 	blk64_t	ret_blk;

 	if (!(fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG) ||
 	    (i < fs->super->s_first_meta_bg))
 		return (group_block + i + 1);

 	bg = EXT2_DESC_PER_BLOCK(fs->super) * i;
 	if (ext2fs_bg_has_super(fs, bg))
 		has_super = 1;
 	ret_blk = ext2fs_group_first_block2(fs, bg) + has_super;
 	/*
 	 * If group_block is not the normal value, we're trying to use
 	 * the backup group descriptors and superblock --- so use the
 	 * alternate location of the second block group in the
 	 * metablock group.  Ideally we should be testing each bg
 	 * descriptor block individually for correctness, but we don't
 	 * have the infrastructure in place to do that.
 	 */
 	if (group_block != fs->super->s_first_data_block &&
 	    ((ret_blk + fs->super->s_blocks_per_group) <
 	     ext2fs_blocks_count(fs->super)))
 		ret_blk += fs->super->s_blocks_per_group;
 	return ret_blk;
 }

 blk_t ext2fs_descriptor_block_loc(ext2_filsys fs, blk_t group_block, dgrp_t i)
 {
 	return ext2fs_descriptor_block_loc2(fs, group_block, i);
 }

 errcode_t ext2fs_open(const char *name, int flags, int superblock,
 		      unsigned int block_size, io_manager manager,
 		      ext2_filsys *ret_fs)
 {
 	return ext2fs_open2(name, 0, flags, superblock, block_size,
 			    manager, ret_fs);
 }

 /*
  *  Note: if superblock is non-zero, block-size must also be non-zero.
  * 	Superblock and block_size can be zero to use the default size.
  *
  * Valid flags for ext2fs_open()
  *
  * 	EXT2_FLAG_RW	- Open the filesystem for read/write.
  * 	EXT2_FLAG_FORCE - Open the filesystem even if some of the
  *				features aren't supported.
  *	EXT2_FLAG_JOURNAL_DEV_OK - Open an ext3 journal device
  *	EXT2_FLAG_SKIP_MMP - Open without multi-mount protection check.
  *	EXT2_FLAG_64BITS - Allow 64-bit bitfields (needed for large
  *				filesystems)
  */
 errcode_t ext2fs_open2(const char *name, const char *io_options,
 		       int flags, int superblock,
 		       unsigned int block_size, io_manager manager,
 		       ext2_filsys *ret_fs)
 {
 	ext2_filsys	fs;
 	errcode_t	retval;
 	unsigned long	i, first_meta_bg;
 	__u32		features;
 	unsigned int	blocks_per_group, io_flags;
 	blk64_t		group_block, blk;
 	char		*dest, *cp;
 #ifdef WORDS_BIGENDIAN
 	unsigned int	groups_per_block;
 	struct ext2_group_desc *gdp;
 	int		j;
 #endif

 	EXT2_CHECK_MAGIC(manager, EXT2_ET_MAGIC_IO_MANAGER);

 	retval = ext2fs_get_mem(sizeof(struct struct_ext2_filsys), &fs);
 	if (retval)
 		return retval;

 	memset(fs, 0, sizeof(struct struct_ext2_filsys));
 	fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
 	fs->flags = flags;
 	/* don't overwrite sb backups unless flag is explicitly cleared */
 	fs->flags |= EXT2_FLAG_MASTER_SB_ONLY;
 	fs->umask = 022;
 	retval = ext2fs_get_mem(strlen(name)+1, &fs->device_name);
 	if (retval)
 		goto cleanup;
 	strcpy(fs->device_name, name);
 	cp = strchr(fs->device_name, '?');
 	if (!io_options && cp) {
 		*cp++ = 0;
 		io_options = cp;
 	}

 	io_flags = 0;
 	if (flags & EXT2_FLAG_RW)
 		io_flags |= IO_FLAG_RW;
 	if (flags & EXT2_FLAG_EXCLUSIVE)
 		io_flags |= IO_FLAG_EXCLUSIVE;
 	if (flags & EXT2_FLAG_DIRECT_IO)
 		io_flags |= IO_FLAG_DIRECT_IO;
 	retval = manager->open(fs->device_name, io_flags, &fs->io);
 	if (retval)
 		goto cleanup;
 	if (io_options &&
 	    (retval = io_channel_set_options(fs->io, io_options)))
 		goto cleanup;
 	fs->image_io = fs->io;
 	fs->io->app_data = fs;
 	retval = io_channel_alloc_buf(fs->io, -SUPERBLOCK_SIZE, &fs->super);
 	if (retval)
 		goto cleanup;
 	if (flags & EXT2_FLAG_IMAGE_FILE) {
 		retval = ext2fs_get_mem(sizeof(struct ext2_image_hdr),
 					&fs->image_header);
 		if (retval)
 			goto cleanup;
 		retval = io_channel_read_blk(fs->io, 0,
 					     -(int)sizeof(struct ext2_image_hdr),
 					     fs->image_header);
 		if (retval)
 			goto cleanup;
 		if (fs->image_header->magic_number != EXT2_ET_MAGIC_E2IMAGE)
 			return EXT2_ET_MAGIC_E2IMAGE;
 		superblock = 1;
 		block_size = fs->image_header->fs_blocksize;
 	}

 	/*
 	 * If the user specifies a specific block # for the
 	 * superblock, then he/she must also specify the block size!
 	 * Otherwise, read the master superblock located at offset
 	 * SUPERBLOCK_OFFSET from the start of the partition.
 	 *
 	 * Note: we only save a backup copy of the superblock if we
 	 * are reading the superblock from the primary superblock location.
 	 */
 	if (superblock) {
 		if (!block_size) {
 			retval = EXT2_ET_INVALID_ARGUMENT;
 			goto cleanup;
 		}
 		io_channel_set_blksize(fs->io, block_size);
 		group_block = superblock;
 		fs->orig_super = 0;
 	} else {
 		io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
 		superblock = 1;
 		group_block = 0;
 		retval = ext2fs_get_mem(SUPERBLOCK_SIZE, &fs->orig_super);
 		if (retval)
 			goto cleanup;
 	}
 	retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
 				     fs->super);
 	if (retval)
 		goto cleanup;
 	if (fs->orig_super)
 		memcpy(fs->orig_super, fs->super, SUPERBLOCK_SIZE);

 #ifdef WORDS_BIGENDIAN
 	fs->flags |= EXT2_FLAG_SWAP_BYTES;
 	ext2fs_swap_super(fs->super);
 #else
 	if (fs->flags & EXT2_FLAG_SWAP_BYTES) {
 		retval = EXT2_ET_UNIMPLEMENTED;
 		goto cleanup;
 	}
 #endif

 	if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
 		retval = EXT2_ET_BAD_MAGIC;
 		goto cleanup;
 	}
 	if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) {
 		retval = EXT2_ET_REV_TOO_HIGH;
 		goto cleanup;
 	}

 	/*
 	 * Check for feature set incompatibility
 	 */
 	if (!(flags & EXT2_FLAG_FORCE)) {
 		features = fs->super->s_feature_incompat;
 #ifdef EXT2_LIB_SOFTSUPP_INCOMPAT
 		if (flags & EXT2_FLAG_SOFTSUPP_FEATURES)
 			features &= ~EXT2_LIB_SOFTSUPP_INCOMPAT;
 #endif
 		if (features & ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {
 			retval = EXT2_ET_UNSUPP_FEATURE;
 			goto cleanup;
 		}

 		features = fs->super->s_feature_ro_compat;
 #ifdef EXT2_LIB_SOFTSUPP_RO_COMPAT
 		if (flags & EXT2_FLAG_SOFTSUPP_FEATURES)
 			features &= ~EXT2_LIB_SOFTSUPP_RO_COMPAT;
 #endif
 		if ((flags & EXT2_FLAG_RW) &&
 		    (features & ~EXT2_LIB_FEATURE_RO_COMPAT_SUPP)) {
 			retval = EXT2_ET_RO_UNSUPP_FEATURE;
 			goto cleanup;
 		}

 		if (!(flags & EXT2_FLAG_JOURNAL_DEV_OK) &&
 		    (fs->super->s_feature_incompat &
 		     EXT3_FEATURE_INCOMPAT_JOURNAL_DEV)) {
 			retval = EXT2_ET_UNSUPP_FEATURE;
 			goto cleanup;
 		}
 	}

 	if ((fs->super->s_log_block_size + EXT2_MIN_BLOCK_LOG_SIZE) >
 	    EXT2_MAX_BLOCK_LOG_SIZE) {
 		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 		goto cleanup;
 	}

 	/*
 	 * bigalloc requires cluster-aware bitfield operations, which at the
 	 * moment means we need EXT2_FLAG_64BITS.
 	 */
 	if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
 				       EXT4_FEATURE_RO_COMPAT_BIGALLOC) &&
 	    !(flags & EXT2_FLAG_64BITS)) {
 		retval = EXT2_ET_CANT_USE_LEGACY_BITMAPS;
 		goto cleanup;
 	}

 	if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
 					EXT4_FEATURE_RO_COMPAT_BIGALLOC) &&
 	    (fs->super->s_log_block_size != fs->super->s_log_cluster_size)) {
 		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 		goto cleanup;
 	}
 	fs->fragsize = fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
 	if (EXT2_INODE_SIZE(fs->super) < EXT2_GOOD_OLD_INODE_SIZE) {
 		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 		goto cleanup;
 	}
 	fs->cluster_ratio_bits = fs->super->s_log_cluster_size -
 		fs->super->s_log_block_size;
 	if (EXT2_BLOCKS_PER_GROUP(fs->super) !=
 	    EXT2_CLUSTERS_PER_GROUP(fs->super) << fs->cluster_ratio_bits) {
 		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 		goto cleanup;
 	}
 	fs->inode_blocks_per_group = ((EXT2_INODES_PER_GROUP(fs->super) *
 				       EXT2_INODE_SIZE(fs->super) +
 				       EXT2_BLOCK_SIZE(fs->super) - 1) /
 				      EXT2_BLOCK_SIZE(fs->super));
 	if (block_size) {
 		if (block_size != fs->blocksize) {
 			retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
 			goto cleanup;
 		}
 	}
 	/*
 	 * Set the blocksize to the filesystem's blocksize.
 	 */
 	io_channel_set_blksize(fs->io, fs->blocksize);

 	/*
 	 * If this is an external journal device, don't try to read
 	 * the group descriptors, because they're not there.
 	 */
 	if (fs->super->s_feature_incompat &
 	    EXT3_FEATURE_INCOMPAT_JOURNAL_DEV) {
 		fs->group_desc_count = 0;
 		*ret_fs = fs;
 		return 0;
 	}

 	if (EXT2_INODES_PER_GROUP(fs->super) == 0) {
 		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 		goto cleanup;
 	}

 	/*
 	 * Read group descriptors
 	 */
 	blocks_per_group = EXT2_BLOCKS_PER_GROUP(fs->super);
 	if (blocks_per_group == 0 ||
 	    blocks_per_group > EXT2_MAX_BLOCKS_PER_GROUP(fs->super) ||
 	    fs->inode_blocks_per_group > EXT2_MAX_INODES_PER_GROUP(fs->super) ||
            EXT2_DESC_PER_BLOCK(fs->super) == 0 ||
            fs->super->s_first_data_block >= ext2fs_blocks_count(fs->super)) {
 		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 		goto cleanup;
 	}
 	fs->group_desc_count = ext2fs_div64_ceil(ext2fs_blocks_count(fs->super) -
 						 fs->super->s_first_data_block,
 						 blocks_per_group);
 	if (fs->group_desc_count * EXT2_INODES_PER_GROUP(fs->super) !=
 	    fs->super->s_inodes_count) {
 		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 		goto cleanup;
 	}
 	fs->desc_blocks = ext2fs_div_ceil(fs->group_desc_count,
 					  EXT2_DESC_PER_BLOCK(fs->super));
 	retval = ext2fs_get_array(fs->desc_blocks, fs->blocksize,
 				&fs->group_desc);
 	if (retval)
 		goto cleanup;
 	if (!group_block)
 		group_block = fs->super->s_first_data_block;
 	if (group_block == 0 && fs->blocksize == 1024)
 		group_block = 1; /* Deal with 1024 blocksize && bigalloc */
 	dest = (char *) fs->group_desc;
 #ifdef WORDS_BIGENDIAN
 	groups_per_block = EXT2_DESC_PER_BLOCK(fs->super);
 #endif
 	if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)
 		first_meta_bg = fs->super->s_first_meta_bg;
 	else
 		first_meta_bg = fs->desc_blocks;
 	if (first_meta_bg) {
 		retval = io_channel_read_blk(fs->io, group_block+1,
 					     first_meta_bg, dest);
 		if (retval)
 			goto cleanup;
 #ifdef WORDS_BIGENDIAN
 		gdp = (struct ext2_group_desc *) dest;
 		for (j=0; j < groups_per_block*first_meta_bg; j++) {
 			gdp = ext2fs_group_desc(fs, fs->group_desc, j);
 			ext2fs_swap_group_desc2(fs, gdp);
 		}
 #endif
 		dest += fs->blocksize*first_meta_bg;
 	}
 	for (i=first_meta_bg ; i < fs->desc_blocks; i++) {
 		blk = ext2fs_descriptor_block_loc2(fs, group_block, i);
 		retval = io_channel_read_blk64(fs->io, blk, 1, dest);
 		if (retval)
 			goto cleanup;
 #ifdef WORDS_BIGENDIAN
 		for (j=0; j < groups_per_block; j++) {
 			gdp = ext2fs_group_desc(fs, fs->group_desc,
 						i * groups_per_block + j);
 			ext2fs_swap_group_desc2(fs, gdp);
 		}
 #endif
 		dest += fs->blocksize;
 	}

 	fs->stride = fs->super->s_raid_stride;

 	/*
 	 * If recovery is from backup superblock, Clear _UNININT flags &
 	 * reset bg_itable_unused to zero
 	 */
 	if (superblock > 1 && EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
 					EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
 		dgrp_t group;

 		for (group = 0; group < fs->group_desc_count; group++) {
 			ext2fs_bg_flags_clear(fs, group, EXT2_BG_BLOCK_UNINIT);
 			ext2fs_bg_flags_clear(fs, group, EXT2_BG_INODE_UNINIT);
 			ext2fs_bg_itable_unused_set(fs, group, 0);
 			/* The checksum will be reset later, but fix it here
 			 * anyway to avoid printing a lot of spurious errors. */
 			ext2fs_group_desc_csum_set(fs, group);
 		}
 		if (fs->flags & EXT2_FLAG_RW)
 			ext2fs_mark_super_dirty(fs);
 	}

 	if ((fs->super->s_feature_incompat & EXT4_FEATURE_INCOMPAT_MMP) &&
 	    !(flags & EXT2_FLAG_SKIP_MMP) &&
 	    (flags & (EXT2_FLAG_RW | EXT2_FLAG_EXCLUSIVE))) {
 		retval = ext2fs_mmp_start(fs);
 		if (retval) {
 			fs->flags |= EXT2_FLAG_SKIP_MMP; /* just do cleanup */
 			ext2fs_mmp_stop(fs);
 			goto cleanup;
 		}
 	}

 	fs->flags &= ~EXT2_FLAG_NOFREE_ON_ERROR;
 	*ret_fs = fs;

 	return 0;
 cleanup:
 	if (flags & EXT2_FLAG_NOFREE_ON_ERROR)
 		*ret_fs = fs;
 	else
 		ext2fs_free(fs);
 	return retval;
 }

 /*
  * Set/get the filesystem data I/O channel.
  *
  * These functions are only valid if EXT2_FLAG_IMAGE_FILE is true.
  */
 errcode_t ext2fs_get_data_io(ext2_filsys fs, io_channel *old_io)
 {
 	if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
 		return EXT2_ET_NOT_IMAGE_FILE;
 	if (old_io) {
 		*old_io = (fs->image_io == fs->io) ? 0 : fs->io;
 	}
 	return 0;
 }

 errcode_t ext2fs_set_data_io(ext2_filsys fs, io_channel new_io)
 {
 	if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
 		return EXT2_ET_NOT_IMAGE_FILE;
 	fs->io = new_io ? new_io : fs->image_io;
 	return 0;
 }

 errcode_t ext2fs_rewrite_to_io(ext2_filsys fs, io_channel new_io)
 {
 	errcode_t err;

 	if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
 		return EXT2_ET_NOT_IMAGE_FILE;
 	err = io_channel_set_blksize(new_io, fs->blocksize);
 	if (err)
 		return err;
 	if ((new_io == fs->image_io) || (new_io == fs->io))
 		return 0;
 	if ((fs->image_io != fs->io) &&
 	    fs->image_io)
 		io_channel_close(fs->image_io);
 	if (fs->io)
 		io_channel_close(fs->io);
 	fs->io = fs->image_io = new_io;
 	fs->flags |= EXT2_FLAG_DIRTY | EXT2_FLAG_RW |
 		EXT2_FLAG_BB_DIRTY | EXT2_FLAG_IB_DIRTY;
 	fs->flags &= ~EXT2_FLAG_IMAGE_FILE;
 	return 0;
 }
	/*
	* openfs.c --- open an ext2 filesystem
	*
	* Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o.
	*
	* %Begin-Header%
	* This file may be redistributed under the terms of the GNU Library
	* General Public License, version 2.
	* %End-Header%
	*/

	#include <stdio.h>
	#include <string.h>
	#if HAVE_UNISTD_H
	#include <unistd.h>
	#endif
	#include <fcntl.h>
	#include <time.h>
	#if HAVE_SYS_STAT_H
	#include <sys/stat.h>
	#endif
	#if HAVE_SYS_TYPES_H
	#include <sys/types.h>
	#endif
	#ifdef HAVE_ERRNO_H
	#include <errno.h>
	#endif

	#include "ext2_fs.h"


	#include "ext2fs.h"
	#include "e2image.h"

	blk64_t ext2fs_descriptor_block_loc2(ext2_filsys fs, blk64_t group_block,
	dgrp_t i)
	{
	int bg;
	int has_super = 0;
	blk64_t ret_blk;

	if (!(fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG) \|\|
	(i < fs->super->s_first_meta_bg))
	return (group_block + i + 1);

	bg = EXT2_DESC_PER_BLOCK(fs->super) * i;
	if (ext2fs_bg_has_super(fs, bg))
	has_super = 1;
	ret_blk = ext2fs_group_first_block2(fs, bg) + has_super;
	/*
	* If group_block is not the normal value, we're trying to use
	* the backup group descriptors and superblock --- so use the
	* alternate location of the second block group in the
	* metablock group. Ideally we should be testing each bg
	* descriptor block individually for correctness, but we don't
	* have the infrastructure in place to do that.
	*/
	if (group_block != fs->super->s_first_data_block &&
	((ret_blk + fs->super->s_blocks_per_group) <
	ext2fs_blocks_count(fs->super)))
	ret_blk += fs->super->s_blocks_per_group;
	return ret_blk;
	}

	blk_t ext2fs_descriptor_block_loc(ext2_filsys fs, blk_t group_block, dgrp_t i)
	{
	return ext2fs_descriptor_block_loc2(fs, group_block, i);
	}

	errcode_t ext2fs_open(const char *name, int flags, int superblock,
	unsigned int block_size, io_manager manager,
	ext2_filsys *ret_fs)
	{
	return ext2fs_open2(name, 0, flags, superblock, block_size,
	manager, ret_fs);
	}

	/*
	* Note: if superblock is non-zero, block-size must also be non-zero.
	* Superblock and block_size can be zero to use the default size.
	*
	* Valid flags for ext2fs_open()
	*
	* EXT2_FLAG_RW - Open the filesystem for read/write.
	* EXT2_FLAG_FORCE - Open the filesystem even if some of the
	* features aren't supported.
	* EXT2_FLAG_JOURNAL_DEV_OK - Open an ext3 journal device
	* EXT2_FLAG_SKIP_MMP - Open without multi-mount protection check.
	* EXT2_FLAG_64BITS - Allow 64-bit bitfields (needed for large
	* filesystems)
	*/
	errcode_t ext2fs_open2(const char name, const char io_options,
	int flags, int superblock,
	unsigned int block_size, io_manager manager,
	ext2_filsys *ret_fs)
	{
	ext2_filsys fs;
	errcode_t retval;
	unsigned long i, first_meta_bg;
	__u32 features;
	unsigned int blocks_per_group, io_flags;
	blk64_t group_block, blk;
	char dest, cp;
	#ifdef WORDS_BIGENDIAN
	unsigned int groups_per_block;
	struct ext2_group_desc *gdp;
	int j;
	#endif

	EXT2_CHECK_MAGIC(manager, EXT2_ET_MAGIC_IO_MANAGER);

	retval = ext2fs_get_mem(sizeof(struct struct_ext2_filsys), &fs);
	if (retval)
	return retval;

	memset(fs, 0, sizeof(struct struct_ext2_filsys));
	fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
	fs->flags = flags;
	/* don't overwrite sb backups unless flag is explicitly cleared */
	fs->flags \|= EXT2_FLAG_MASTER_SB_ONLY;
	fs->umask = 022;
	retval = ext2fs_get_mem(strlen(name)+1, &fs->device_name);
	if (retval)
	goto cleanup;
	strcpy(fs->device_name, name);
	cp = strchr(fs->device_name, '?');
	if (!io_options && cp) {
	*cp++ = 0;
	io_options = cp;
	}

	io_flags = 0;
	if (flags & EXT2_FLAG_RW)
	io_flags \|= IO_FLAG_RW;
	if (flags & EXT2_FLAG_EXCLUSIVE)
	io_flags \|= IO_FLAG_EXCLUSIVE;
	if (flags & EXT2_FLAG_DIRECT_IO)
	io_flags \|= IO_FLAG_DIRECT_IO;
	retval = manager->open(fs->device_name, io_flags, &fs->io);
	if (retval)
	goto cleanup;
	if (io_options &&
	(retval = io_channel_set_options(fs->io, io_options)))
	goto cleanup;
	fs->image_io = fs->io;
	fs->io->app_data = fs;
	retval = io_channel_alloc_buf(fs->io, -SUPERBLOCK_SIZE, &fs->super);
	if (retval)
	goto cleanup;
	if (flags & EXT2_FLAG_IMAGE_FILE) {
	retval = ext2fs_get_mem(sizeof(struct ext2_image_hdr),
	&fs->image_header);
	if (retval)
	goto cleanup;
	retval = io_channel_read_blk(fs->io, 0,
	-(int)sizeof(struct ext2_image_hdr),
	fs->image_header);
	if (retval)
	goto cleanup;
	if (fs->image_header->magic_number != EXT2_ET_MAGIC_E2IMAGE)
	return EXT2_ET_MAGIC_E2IMAGE;
	superblock = 1;
	block_size = fs->image_header->fs_blocksize;
	}

	/*
	* If the user specifies a specific block # for the
	* superblock, then he/she must also specify the block size!
	* Otherwise, read the master superblock located at offset
	* SUPERBLOCK_OFFSET from the start of the partition.
	*
	* Note: we only save a backup copy of the superblock if we
	* are reading the superblock from the primary superblock location.
	*/
	if (superblock) {
	if (!block_size) {
	retval = EXT2_ET_INVALID_ARGUMENT;
	goto cleanup;
	}
	io_channel_set_blksize(fs->io, block_size);
	group_block = superblock;
	fs->orig_super = 0;
	} else {
	io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
	superblock = 1;
	group_block = 0;
	retval = ext2fs_get_mem(SUPERBLOCK_SIZE, &fs->orig_super);
	if (retval)
	goto cleanup;
	}
	retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
	fs->super);
	if (retval)
	goto cleanup;
	if (fs->orig_super)
	memcpy(fs->orig_super, fs->super, SUPERBLOCK_SIZE);

	#ifdef WORDS_BIGENDIAN
	fs->flags \|= EXT2_FLAG_SWAP_BYTES;
	ext2fs_swap_super(fs->super);
	#else
	if (fs->flags & EXT2_FLAG_SWAP_BYTES) {
	retval = EXT2_ET_UNIMPLEMENTED;
	goto cleanup;
	}
	#endif

	if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
	retval = EXT2_ET_BAD_MAGIC;
	goto cleanup;
	}
	if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) {
	retval = EXT2_ET_REV_TOO_HIGH;
	goto cleanup;
	}

	/*
	* Check for feature set incompatibility
	*/
	if (!(flags & EXT2_FLAG_FORCE)) {
	features = fs->super->s_feature_incompat;
	#ifdef EXT2_LIB_SOFTSUPP_INCOMPAT
	if (flags & EXT2_FLAG_SOFTSUPP_FEATURES)
	features &= ~EXT2_LIB_SOFTSUPP_INCOMPAT;
	#endif
	if (features & ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {
	retval = EXT2_ET_UNSUPP_FEATURE;
	goto cleanup;
	}

	features = fs->super->s_feature_ro_compat;
	#ifdef EXT2_LIB_SOFTSUPP_RO_COMPAT
	if (flags & EXT2_FLAG_SOFTSUPP_FEATURES)
	features &= ~EXT2_LIB_SOFTSUPP_RO_COMPAT;
	#endif
	if ((flags & EXT2_FLAG_RW) &&
	(features & ~EXT2_LIB_FEATURE_RO_COMPAT_SUPP)) {
	retval = EXT2_ET_RO_UNSUPP_FEATURE;
	goto cleanup;
	}

	if (!(flags & EXT2_FLAG_JOURNAL_DEV_OK) &&
	(fs->super->s_feature_incompat &
	EXT3_FEATURE_INCOMPAT_JOURNAL_DEV)) {
	retval = EXT2_ET_UNSUPP_FEATURE;
	goto cleanup;
	}
	}

	if ((fs->super->s_log_block_size + EXT2_MIN_BLOCK_LOG_SIZE) >
	EXT2_MAX_BLOCK_LOG_SIZE) {
	retval = EXT2_ET_CORRUPT_SUPERBLOCK;
	goto cleanup;
	}

	/*
	* bigalloc requires cluster-aware bitfield operations, which at the
	* moment means we need EXT2_FLAG_64BITS.
	*/
	if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
	EXT4_FEATURE_RO_COMPAT_BIGALLOC) &&
	!(flags & EXT2_FLAG_64BITS)) {
	retval = EXT2_ET_CANT_USE_LEGACY_BITMAPS;
	goto cleanup;
	}

	if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
	EXT4_FEATURE_RO_COMPAT_BIGALLOC) &&
	(fs->super->s_log_block_size != fs->super->s_log_cluster_size)) {
	retval = EXT2_ET_CORRUPT_SUPERBLOCK;
	goto cleanup;
	}
	fs->fragsize = fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
	if (EXT2_INODE_SIZE(fs->super) < EXT2_GOOD_OLD_INODE_SIZE) {
	retval = EXT2_ET_CORRUPT_SUPERBLOCK;
	goto cleanup;
	}
	fs->cluster_ratio_bits = fs->super->s_log_cluster_size -
	fs->super->s_log_block_size;
	if (EXT2_BLOCKS_PER_GROUP(fs->super) !=
	EXT2_CLUSTERS_PER_GROUP(fs->super) << fs->cluster_ratio_bits) {
	retval = EXT2_ET_CORRUPT_SUPERBLOCK;
	goto cleanup;
	}
	fs->inode_blocks_per_group = ((EXT2_INODES_PER_GROUP(fs->super) *
	EXT2_INODE_SIZE(fs->super) +
	EXT2_BLOCK_SIZE(fs->super) - 1) /
	EXT2_BLOCK_SIZE(fs->super));
	if (block_size) {
	if (block_size != fs->blocksize) {
	retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
	goto cleanup;
	}
	}
	/*
	* Set the blocksize to the filesystem's blocksize.
	*/
	io_channel_set_blksize(fs->io, fs->blocksize);

	/*
	* If this is an external journal device, don't try to read
	* the group descriptors, because they're not there.
	*/
	if (fs->super->s_feature_incompat &
	EXT3_FEATURE_INCOMPAT_JOURNAL_DEV) {
	fs->group_desc_count = 0;
	*ret_fs = fs;
	return 0;
	}

	if (EXT2_INODES_PER_GROUP(fs->super) == 0) {
	retval = EXT2_ET_CORRUPT_SUPERBLOCK;
	goto cleanup;
	}

	/*
	* Read group descriptors
	*/
	blocks_per_group = EXT2_BLOCKS_PER_GROUP(fs->super);
	if (blocks_per_group == 0 \|\|
	blocks_per_group > EXT2_MAX_BLOCKS_PER_GROUP(fs->super) \|\|
	fs->inode_blocks_per_group > EXT2_MAX_INODES_PER_GROUP(fs->super) \|\|
	EXT2_DESC_PER_BLOCK(fs->super) == 0 \|\|
	fs->super->s_first_data_block >= ext2fs_blocks_count(fs->super)) {
	retval = EXT2_ET_CORRUPT_SUPERBLOCK;
	goto cleanup;
	}
	fs->group_desc_count = ext2fs_div64_ceil(ext2fs_blocks_count(fs->super) -
	fs->super->s_first_data_block,
	blocks_per_group);
	if (fs->group_desc_count * EXT2_INODES_PER_GROUP(fs->super) !=
	fs->super->s_inodes_count) {
	retval = EXT2_ET_CORRUPT_SUPERBLOCK;
	goto cleanup;
	}
	fs->desc_blocks = ext2fs_div_ceil(fs->group_desc_count,
	EXT2_DESC_PER_BLOCK(fs->super));
	retval = ext2fs_get_array(fs->desc_blocks, fs->blocksize,
	&fs->group_desc);
	if (retval)
	goto cleanup;
	if (!group_block)
	group_block = fs->super->s_first_data_block;
	if (group_block == 0 && fs->blocksize == 1024)
	group_block = 1; /* Deal with 1024 blocksize && bigalloc */
	dest = (char *) fs->group_desc;
	#ifdef WORDS_BIGENDIAN
	groups_per_block = EXT2_DESC_PER_BLOCK(fs->super);
	#endif
	if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)
	first_meta_bg = fs->super->s_first_meta_bg;
	else
	first_meta_bg = fs->desc_blocks;
	if (first_meta_bg) {
	retval = io_channel_read_blk(fs->io, group_block+1,
	first_meta_bg, dest);
	if (retval)
	goto cleanup;
	#ifdef WORDS_BIGENDIAN
	gdp = (struct ext2_group_desc *) dest;
	for (j=0; j < groups_per_block*first_meta_bg; j++) {
	gdp = ext2fs_group_desc(fs, fs->group_desc, j);
	ext2fs_swap_group_desc2(fs, gdp);
	}
	#endif
	dest += fs->blocksize*first_meta_bg;
	}
	for (i=first_meta_bg ; i < fs->desc_blocks; i++) {
	blk = ext2fs_descriptor_block_loc2(fs, group_block, i);
	retval = io_channel_read_blk64(fs->io, blk, 1, dest);
	if (retval)
	goto cleanup;
	#ifdef WORDS_BIGENDIAN
	for (j=0; j < groups_per_block; j++) {
	gdp = ext2fs_group_desc(fs, fs->group_desc,
	i * groups_per_block + j);
	ext2fs_swap_group_desc2(fs, gdp);
	}
	#endif
	dest += fs->blocksize;
	}

	fs->stride = fs->super->s_raid_stride;

	/*
	* If recovery is from backup superblock, Clear _UNININT flags &
	* reset bg_itable_unused to zero
	*/
	if (superblock > 1 && EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
	EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
	dgrp_t group;

	for (group = 0; group < fs->group_desc_count; group++) {
	ext2fs_bg_flags_clear(fs, group, EXT2_BG_BLOCK_UNINIT);
	ext2fs_bg_flags_clear(fs, group, EXT2_BG_INODE_UNINIT);
	ext2fs_bg_itable_unused_set(fs, group, 0);
	/* The checksum will be reset later, but fix it here
	* anyway to avoid printing a lot of spurious errors. */
	ext2fs_group_desc_csum_set(fs, group);
	}
	if (fs->flags & EXT2_FLAG_RW)
	ext2fs_mark_super_dirty(fs);
	}

	if ((fs->super->s_feature_incompat & EXT4_FEATURE_INCOMPAT_MMP) &&
	!(flags & EXT2_FLAG_SKIP_MMP) &&
	(flags & (EXT2_FLAG_RW \| EXT2_FLAG_EXCLUSIVE))) {
	retval = ext2fs_mmp_start(fs);
	if (retval) {
	fs->flags \|= EXT2_FLAG_SKIP_MMP; /* just do cleanup */
	ext2fs_mmp_stop(fs);
	goto cleanup;
	}
	}

	fs->flags &= ~EXT2_FLAG_NOFREE_ON_ERROR;
	*ret_fs = fs;

	return 0;
	cleanup:
	if (flags & EXT2_FLAG_NOFREE_ON_ERROR)
	*ret_fs = fs;
	else
	ext2fs_free(fs);
	return retval;
	}

	/*
	* Set/get the filesystem data I/O channel.
	*
	* These functions are only valid if EXT2_FLAG_IMAGE_FILE is true.
	*/
	errcode_t ext2fs_get_data_io(ext2_filsys fs, io_channel *old_io)
	{
	if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
	return EXT2_ET_NOT_IMAGE_FILE;
	if (old_io) {
	*old_io = (fs->image_io == fs->io) ? 0 : fs->io;
	}
	return 0;
	}

	errcode_t ext2fs_set_data_io(ext2_filsys fs, io_channel new_io)
	{
	if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
	return EXT2_ET_NOT_IMAGE_FILE;
	fs->io = new_io ? new_io : fs->image_io;
	return 0;
	}

	errcode_t ext2fs_rewrite_to_io(ext2_filsys fs, io_channel new_io)
	{
	errcode_t err;

	if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
	return EXT2_ET_NOT_IMAGE_FILE;
	err = io_channel_set_blksize(new_io, fs->blocksize);
	if (err)
	return err;
	if ((new_io == fs->image_io) \|\| (new_io == fs->io))
	return 0;
	if ((fs->image_io != fs->io) &&
	fs->image_io)
	io_channel_close(fs->image_io);
	if (fs->io)
	io_channel_close(fs->io);
	fs->io = fs->image_io = new_io;
	fs->flags \|= EXT2_FLAG_DIRTY \| EXT2_FLAG_RW \|
	EXT2_FLAG_BB_DIRTY \| EXT2_FLAG_IB_DIRTY;
	fs->flags &= ~EXT2_FLAG_IMAGE_FILE;
	return 0;
	}