lib/ext2fs/openfs.c

   1 /*
   2  * openfs.c --- open an ext2 filesystem
   3  *
   4  * Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o.
   5  *
   6  * %Begin-Header%
   7  * This file may be redistributed under the terms of the GNU Public
   8  * License.
   9  * %End-Header%
  10  */
  11
  12 #include <stdio.h>
  13 #include <string.h>
  14 #if HAVE_UNISTD_H
  15 #include <unistd.h>
  16 #endif
  17 #if HAVE_STDLIB_H
  18 #include <stdlib.h>
  19 #endif
  20 #include <fcntl.h>
  21 #include <time.h>
  22 #if HAVE_SYS_STAT_H
  23 #include <sys/stat.h>
  24 #endif
  25 #if HAVE_SYS_TYPES_H
  26 #include <sys/types.h>
  27 #endif
  28
  29 #include <linux/ext2_fs.h>
  30
  31 #include "ext2fs.h"
  32
  33 /*
  34  *  Note: if superblock is non-zero, block-size must also be non-zero.
  35  *      Superblock and block_size can be zero to use the default size.
  36  *
  37  * Valid flags for ext2fs_open()
  38  *
  39  *      EXT2_FLAG_RW    - Open the filesystem for read/write.
  40  *      EXT2_FLAG_FORCE - Open the filesystem even if some of the
  41  *                              features aren't supported.
  42  */
  43 errcode_t ext2fs_open(const char *name, int flags, int superblock,
  44                       int block_size, io_manager manager, ext2_filsys *ret_fs)
  45 {
  46         ext2_filsys     fs;
  47         errcode_t       retval;
  48         int             i, j, groups_per_block;
  49         blk_t           group_block;
  50         char            *dest;
  51         struct ext2_group_desc *gdp;
  52         struct ext2fs_sb        *s;
  53
  54         EXT2_CHECK_MAGIC(manager, EXT2_ET_MAGIC_IO_MANAGER);
  55
  56         retval = ext2fs_get_mem(sizeof(struct struct_ext2_filsys),
  57                                 (void **) &fs);
  58         if (retval)
  59                 return retval;
  60
  61         memset(fs, 0, sizeof(struct struct_ext2_filsys));
  62         fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
  63         fs->flags = flags;
  64         retval = manager->open(name, (flags & EXT2_FLAG_RW) ? IO_FLAG_RW : 0,
  65                                &fs->io);
  66         if (retval)
  67                 goto cleanup;
  68         fs->io->app_data = fs;
  69         retval = ext2fs_get_mem(strlen(name)+1, (void **) &fs->device_name);
  70         if (retval)
  71                 goto cleanup;
  72         strcpy(fs->device_name, name);
  73         retval = ext2fs_get_mem(SUPERBLOCK_SIZE, (void **) &fs->super);
  74         if (retval)
  75                 goto cleanup;
  76
  77         /*
  78          * If the user specifies a specific block # for the
  79          * superblock, then he/she must also specify the block size!
  80          * Otherwise, read the master superblock located at offset
  81          * SUPERBLOCK_OFFSET from the start of the partition.
  82          */
  83         if (superblock) {
  84                 if (!block_size) {
  85                         retval = EXT2_ET_INVALID_ARGUMENT;
  86                         goto cleanup;
  87                 }
  88                 io_channel_set_blksize(fs->io, block_size);
  89                 group_block = superblock + 1;
  90         } else {
  91                 io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
  92                 superblock = 1;
  93                 group_block = 0;
  94         }
  95         retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
  96                                      fs->super);
  97         if (retval)
  98                 goto cleanup;
  99
 100         if ((fs->super->s_magic == ext2fs_swab16(EXT2_SUPER_MAGIC)) ||
 101             (fs->flags & EXT2_FLAG_SWAP_BYTES)) {
 102                 fs->flags |= EXT2_FLAG_SWAP_BYTES;
 103
 104                 ext2fs_swap_super(fs->super);
 105         }
 106
 107         if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
 108                 retval = EXT2_ET_BAD_MAGIC;
 109                 goto cleanup;
 110         }
 111 #ifdef EXT2_DYNAMIC_REV
 112         if (fs->super->s_rev_level > EXT2_DYNAMIC_REV) {
 113                 retval = EXT2_ET_REV_TOO_HIGH;
 114                 goto cleanup;
 115         }
 116 #else
 117 #ifdef  EXT2_CURRENT_REV
 118         if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) {
 119                 retval = EXT2_ET_REV_TOO_HIGH;
 120                 goto cleanup;
 121         }
 122 #endif
 123 #endif
 124         /*
 125          * Check for feature set incompatibility
 126          */
 127         if (!(flags & EXT2_FLAG_FORCE)) {
 128                 s = (struct ext2fs_sb *) fs->super;
 129                 if (s->s_feature_incompat & ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {
 130                         retval = EXT2_ET_UNSUPP_FEATURE;
 131                         goto cleanup;
 132                 }
 133                 if ((flags & EXT2_FLAG_RW) &&
 134                     (s->s_feature_ro_compat &
 135                      ~EXT2_LIB_FEATURE_RO_COMPAT_SUPP)) {
 136                         retval = EXT2_ET_RO_UNSUPP_FEATURE;
 137                         goto cleanup;
 138                 }
 139         }
 140
 141         fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
 142         if (fs->blocksize == 0) {
 143                 retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 144                 goto cleanup;
 145         }
 146         fs->fragsize = EXT2_FRAG_SIZE(fs->super);
 147         fs->inode_blocks_per_group = ((fs->super->s_inodes_per_group *
 148                                        EXT2_INODE_SIZE(fs->super) +
 149                                        EXT2_BLOCK_SIZE(fs->super) - 1) /
 150                                       EXT2_BLOCK_SIZE(fs->super));
 151         if (block_size) {
 152                 if (block_size != fs->blocksize) {
 153                         retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
 154                         goto cleanup;
 155                 }
 156         }
 157         /*
 158          * Set the blocksize to the filesystem's blocksize.
 159          */
 160         io_channel_set_blksize(fs->io, fs->blocksize);
 161
 162         /*
 163          * Read group descriptors
 164          */
 165         fs->group_desc_count = (fs->super->s_blocks_count -
 166                                 fs->super->s_first_data_block +
 167                                 EXT2_BLOCKS_PER_GROUP(fs->super) - 1)
 168                 / EXT2_BLOCKS_PER_GROUP(fs->super);
 169         fs->desc_blocks = (fs->group_desc_count +
 170                            EXT2_DESC_PER_BLOCK(fs->super) - 1)
 171                 / EXT2_DESC_PER_BLOCK(fs->super);
 172         retval = ext2fs_get_mem(fs->desc_blocks * fs->blocksize,
 173                                 (void **) &fs->group_desc);
 174         if (retval)
 175                 goto cleanup;
 176         if (!group_block)
 177                 group_block = fs->super->s_first_data_block + 1;
 178         dest = (char *) fs->group_desc;
 179         for (i=0 ; i < fs->desc_blocks; i++) {
 180                 retval = io_channel_read_blk(fs->io, group_block, 1, dest);
 181                 if (retval)
 182                         goto cleanup;
 183                 group_block++;
 184                 if (fs->flags & EXT2_FLAG_SWAP_BYTES) {
 185                         gdp = (struct ext2_group_desc *) dest;
 186                         groups_per_block = fs->blocksize /
 187                                 sizeof(struct ext2_group_desc);
 188                         for (j=0; j < groups_per_block; j++)
 189                                 ext2fs_swap_group_desc(gdp++);
 190                 }
 191                 dest += fs->blocksize;
 192         }
 193
 194         *ret_fs = fs;
 195         return 0;
 196 cleanup:
 197         ext2fs_free(fs);
 198         return retval;
 199 }
 200