openfs.c

busybox最新版的源码:学习和应用的好东东,多的不说了,大家看后再说吧

/* vi: set sw=4 ts=4: */
/*
 * 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 Public
 * License.
 * %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

#include "ext2_fs.h"


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

blk_t ext2fs_descriptor_block_loc(ext2_filsys fs, blk_t group_block, dgrp_t i)
{
	int	bg;
	int	has_super = 0;
	int	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 = (fs->blocksize / sizeof (struct ext2_group_desc)) * i;
	if (ext2fs_bg_has_super(fs, bg))
		has_super = 1;
	ret_blk = (fs->super->s_first_data_block + has_super +
		   (bg * fs->super->s_blocks_per_group));
	/*
	 * 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) <
	     fs->super->s_blocks_count))
		ret_blk += fs->super->s_blocks_per_group;
	return ret_blk;
}

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
 */
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;
	int		groups_per_block, blocks_per_group;
	blk_t		group_block, blk;
	char		*dest, *cp;
#if BB_BIG_ENDIAN
	int j;
	struct ext2_group_desc *gdp;
#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;
	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;
	}

	retval = manager->open(fs->device_name,
			       (flags & EXT2_FLAG_RW) ? IO_FLAG_RW : 0,
			       &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 = ext2fs_get_mem(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);

#if BB_BIG_ENDIAN
	if ((fs->super->s_magic == ext2fs_swab16(EXT2_SUPER_MAGIC)) ||
	    (fs->flags & EXT2_FLAG_SWAP_BYTES)) {
		fs->flags |= EXT2_FLAG_SWAP_BYTES;

		ext2fs_swap_super(fs->super);
	}
#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)) {
		if (fs->super->s_feature_incompat &
		    ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {
			retval = EXT2_ET_UNSUPP_FEATURE;
			goto cleanup;
		}
		if ((flags & EXT2_FLAG_RW) &&
		    (fs->super->s_feature_ro_compat &
		     ~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;
		}
	}

	fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
	if (fs->blocksize == 0) {
		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
		goto cleanup;
	}
	fs->fragsize = EXT2_FRAG_SIZE(fs->super);
	fs->inode_blocks_per_group = ((fs->super->s_inodes_per_group *
				       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;
	}

	/*
	 * 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)) {
		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
		goto cleanup;
	}
	fs->group_desc_count = (fs->super->s_blocks_count -
				fs->super->s_first_data_block +
				blocks_per_group - 1) / blocks_per_group;
	fs->desc_blocks = (fs->group_desc_count +
			   EXT2_DESC_PER_BLOCK(fs->super) - 1)
		/ EXT2_DESC_PER_BLOCK(fs->super);
	retval = ext2fs_get_mem(fs->desc_blocks * fs->blocksize,
				&fs->group_desc);
	if (retval)
		goto cleanup;
	if (!group_block)
		group_block = fs->super->s_first_data_block;
	dest = (char *) fs->group_desc;
	groups_per_block = fs->blocksize / sizeof(struct ext2_group_desc);
	for (i = 0; i < fs->desc_blocks; i++) {
		blk = ext2fs_descriptor_block_loc(fs, group_block, i);
		retval = io_channel_read_blk(fs->io, blk, 1, dest);
		if (retval)
			goto cleanup;
#if BB_BIG_ENDIAN
		if (fs->flags & EXT2_FLAG_SWAP_BYTES) {
			gdp = (struct ext2_group_desc *) dest;
			for (j=0; j < groups_per_block; j++)
				ext2fs_swap_group_desc(gdp++);
		}
#endif
		dest += fs->blocksize;
	}

	*ret_fs = fs;
	return 0;
cleanup:
	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)
{
	if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
		return EXT2_ET_NOT_IMAGE_FILE;
	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;
}