lib/ext2fs/openfs.c

   1 /*
   2  * openfs.c --- open an ext2 filesystem
   3  *
   4  * Copyright (C) 1993, 1994, 1995 Theodore Ts'o.
   5  *
   6  * This file may be redistributed under the terms of the GNU Public
   7  * License.
   8  */
   9
  10 #include <stdio.h>
  11 #include <string.h>
  12 #if HAVE_UNISTD_H
  13 #include <unistd.h>
  14 #endif
  15 #if HAVE_STDLIB_H
  16 #include <stdlib.h>
  17 #endif
  18 #include <fcntl.h>
  19 #include <time.h>
  20 #if HAVE_ERRNO_H
  21 #include <errno.h>
  22 #endif
  23 #include <sys/stat.h>
  24 #include <sys/types.h>
  25
  26 #include <linux/ext2_fs.h>
  27
  28 #include "ext2fs.h"
  29
  30 /*
  31  *  Note: if superblock is non-zero, block-size must also be non-zero.
  32  *      Superblock and block_size can be zero to use the default size.
  33  */
  34 errcode_t ext2fs_open(const char *name, int flags, int superblock,
  35                       int block_size, io_manager manager, ext2_filsys *ret_fs)
  36 {
  37         ext2_filsys     fs;
  38         errcode_t       retval;
  39         int             i, j, group_block, groups_per_block;
  40         char            *dest;
  41         struct ext2_group_desc *gdp;
  42
  43         EXT2_CHECK_MAGIC(manager, EXT2_ET_MAGIC_IO_MANAGER);
  44
  45         fs = (ext2_filsys) malloc(sizeof(struct struct_ext2_filsys));
  46         if (!fs)
  47                 return ENOMEM;
  48
  49         memset(fs, 0, sizeof(struct struct_ext2_filsys));
  50         fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
  51         fs->flags = flags;
  52         retval = manager->open(name, (flags & EXT2_FLAG_RW) ? IO_FLAG_RW : 0,
  53                                &fs->io);
  54         if (retval)
  55                 goto cleanup;
  56         fs->device_name = malloc(strlen(name)+1);
  57         if (!fs->device_name) {
  58                 retval = ENOMEM;
  59                 goto cleanup;
  60         }
  61         strcpy(fs->device_name, name);
  62         fs->super = malloc(SUPERBLOCK_SIZE);
  63         if (!fs->super) {
  64                 retval = ENOMEM;
  65                 goto cleanup;
  66         }
  67
  68         /*
  69          * If the user specifies a specific block # for the
  70          * superblock, then he/she must also specify the block size!
  71          * Otherwise, read the master superblock located at offset
  72          * SUPERBLOCK_OFFSET from the start of the partition.
  73          */
  74         if (superblock) {
  75                 if (!block_size) {
  76                         retval = EINVAL;
  77                         goto cleanup;
  78                 }
  79                 io_channel_set_blksize(fs->io, block_size);
  80                 group_block = superblock + 1;
  81         } else {
  82                 io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
  83                 superblock = 1;
  84                 group_block = 0;
  85         }
  86         retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
  87                                      fs->super);
  88         if (retval)
  89                 goto cleanup;
  90
  91         if ((fs->super->s_magic == ext2fs_swab16(EXT2_SUPER_MAGIC)) ||
  92             (fs->flags & EXT2_SWAP_BYTES)) {
  93                 fs->flags |= EXT2_SWAP_BYTES;
  94
  95                 ext2fs_swap_super(fs->super);
  96         }
  97
  98         if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
  99                 retval = EXT2_ET_BAD_MAGIC;
 100                 goto cleanup;
 101         }
 102 #ifdef  EXT2_CURRENT_REV
 103         if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) {
 104                 retval = EXT2_ET_REV_TOO_HIGH;
 105                 goto cleanup;
 106         }
 107 #endif
 108         fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
 109         fs->fragsize = EXT2_FRAG_SIZE(fs->super);
 110         fs->inode_blocks_per_group = (fs->super->s_inodes_per_group /
 111                                       EXT2_INODES_PER_BLOCK(fs->super));
 112         if (block_size) {
 113                 if (block_size != fs->blocksize) {
 114                         retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
 115                         goto cleanup;
 116                 }
 117         }
 118         /*
 119          * Set the blocksize to the filesystem's blocksize.
 120          */
 121         io_channel_set_blksize(fs->io, fs->blocksize);
 122
 123         /*
 124          * Read group descriptors
 125          */
 126         fs->group_desc_count = (fs->super->s_blocks_count -
 127                                 fs->super->s_first_data_block +
 128                                 EXT2_BLOCKS_PER_GROUP(fs->super) - 1)
 129                 / EXT2_BLOCKS_PER_GROUP(fs->super);
 130         fs->desc_blocks = (fs->group_desc_count +
 131                            EXT2_DESC_PER_BLOCK(fs->super) - 1)
 132                 / EXT2_DESC_PER_BLOCK(fs->super);
 133         fs->group_desc = malloc(fs->desc_blocks * fs->blocksize);
 134         if (!fs->group_desc) {
 135                 retval = ENOMEM;
 136                 goto cleanup;
 137         }
 138         if (!group_block)
 139                 group_block = fs->super->s_first_data_block + 1;
 140         dest = (char *) fs->group_desc;
 141         for (i=0 ; i < fs->desc_blocks; i++) {
 142                 retval = io_channel_read_blk(fs->io, group_block, 1, dest);
 143                 if (retval)
 144                         goto cleanup;
 145                 group_block++;
 146                 if (fs->flags & EXT2_SWAP_BYTES) {
 147                         gdp = (struct ext2_group_desc *) dest;
 148                         groups_per_block = fs->blocksize /
 149                                 sizeof(struct ext2_group_desc);
 150                         for (j=0; j < groups_per_block; j++)
 151                                 ext2fs_swap_group_desc(gdp++);
 152                 }
 153                 dest += fs->blocksize;
 154         }
 155
 156         *ret_fs = fs;
 157         return 0;
 158 cleanup:
 159         ext2fs_free(fs);
 160         return retval;
 161 }
 162