2 * openfs.c --- open an ext2 filesystem
4 * Copyright (C) 1993, 1994 Theodore Ts'o. This file may be redistributed
5 * under the terms of the GNU Public License.
15 #include <sys/types.h>
17 #include <linux/ext2_fs.h>
22 * Note: if superblock is non-zero, block-size must also be non-zero.
23 * Superblock and block_size can be zero to use the default size.
25 errcode_t ext2fs_open(const char *name, int flags, int superblock,
26 int block_size, io_manager manager, ext2_filsys *ret_fs)
33 EXT2_CHECK_MAGIC(manager, EXT2_ET_MAGIC_IO_MANAGER);
35 fs = (ext2_filsys) malloc(sizeof(struct struct_ext2_filsys));
39 memset(fs, 0, sizeof(struct struct_ext2_filsys));
40 fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
42 retval = manager->open(name, (flags & EXT2_FLAG_RW) ? IO_FLAG_RW : 0,
46 fs->device_name = malloc(strlen(name)+1);
47 if (!fs->device_name) {
51 strcpy(fs->device_name, name);
52 fs->super = malloc(SUPERBLOCK_SIZE);
59 * If the user specifies a specific block # for the
60 * superblock, then he/she must also specify the block size!
61 * Otherwise, read the master superblock located at offset
62 * SUPERBLOCK_OFFSET from the start of the partition.
69 io_channel_set_blksize(fs->io, block_size);
70 group_block = superblock + 1;
72 io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
76 retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
81 if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
82 retval = EXT2_ET_BAD_MAGIC;
85 #ifdef EXT2_CURRENT_REV
86 if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) {
87 retval = EXT2_ET_REV_TOO_HIGH;
91 fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
92 fs->fragsize = EXT2_FRAG_SIZE(fs->super);
93 fs->inode_blocks_per_group = (fs->super->s_inodes_per_group /
94 EXT2_INODES_PER_BLOCK(fs->super));
96 if (block_size != fs->blocksize) {
97 retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
102 * Set the blocksize to the filesystem's blocksize.
104 io_channel_set_blksize(fs->io, fs->blocksize);
107 * Read group descriptors
109 fs->group_desc_count = (fs->super->s_blocks_count -
110 fs->super->s_first_data_block +
111 EXT2_BLOCKS_PER_GROUP(fs->super) - 1)
112 / EXT2_BLOCKS_PER_GROUP(fs->super);
113 fs->desc_blocks = (fs->group_desc_count +
114 EXT2_DESC_PER_BLOCK(fs->super) - 1)
115 / EXT2_DESC_PER_BLOCK(fs->super);
116 fs->group_desc = malloc(fs->desc_blocks * fs->blocksize);
117 if (!fs->group_desc) {
122 group_block = fs->super->s_first_data_block + 1;
123 dest = (char *) fs->group_desc;
124 for (i=0 ; i < fs->desc_blocks; i++) {
125 retval = io_channel_read_blk(fs->io, group_block, 1, dest);
129 dest += fs->blocksize;