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         fs = (ext2_filsys) malloc(sizeof(struct struct_ext2_filsys));
  57         if (!fs)
  58                 return EXT2_NO_MEMORY;
  59
  60         memset(fs, 0, sizeof(struct struct_ext2_filsys));
  61         fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
  62         fs->flags = flags;
  63         retval = manager->open(name, (flags & EXT2_FLAG_RW) ? IO_FLAG_RW : 0,
  64                                &fs->io);
  65         if (retval)
  66                 goto cleanup;
  67         fs->io->app_data = fs;
  68         fs->device_name = malloc(strlen(name)+1);
  69         if (!fs->device_name) {
  70                 retval = EXT2_NO_MEMORY;
  71                 goto cleanup;
  72         }
  73         strcpy(fs->device_name, name);
  74         fs->super = malloc(SUPERBLOCK_SIZE);
  75         if (!fs->super) {
  76                 retval = EXT2_NO_MEMORY;
  77                 goto cleanup;
  78         }
  79
  80         /*
  81          * If the user specifies a specific block # for the
  82          * superblock, then he/she must also specify the block size!
  83          * Otherwise, read the master superblock located at offset
  84          * SUPERBLOCK_OFFSET from the start of the partition.
  85          */
  86         if (superblock) {
  87                 if (!block_size) {
  88                         retval = EXT2_INVALID_ARGUMENT;
  89                         goto cleanup;
  90                 }
  91                 io_channel_set_blksize(fs->io, block_size);
  92                 group_block = superblock + 1;
  93         } else {
  94                 io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
  95                 superblock = 1;
  96                 group_block = 0;
  97         }
  98         retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
  99                                      fs->super);
 100         if (retval)
 101                 goto cleanup;
 102
 103         if ((fs->super->s_magic == ext2fs_swab16(EXT2_SUPER_MAGIC)) ||
 104             (fs->flags & EXT2_FLAG_SWAP_BYTES)) {
 105                 fs->flags |= EXT2_FLAG_SWAP_BYTES;
 106
 107                 ext2fs_swap_super(fs->super);
 108         }
 109
 110         if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
 111                 retval = EXT2_ET_BAD_MAGIC;
 112                 goto cleanup;
 113         }
 114 #ifdef EXT2_DYNAMIC_REV
 115         if (fs->super->s_rev_level > EXT2_DYNAMIC_REV) {
 116                 retval = EXT2_ET_REV_TOO_HIGH;
 117                 goto cleanup;
 118         }
 119 #else
 120 #ifdef  EXT2_CURRENT_REV
 121         if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) {
 122                 retval = EXT2_ET_REV_TOO_HIGH;
 123                 goto cleanup;
 124         }
 125 #endif
 126 #endif
 127         /*
 128          * Check for feature set incompatibility
 129          */
 130         if (!(flags & EXT2_FLAG_FORCE)) {
 131                 s = (struct ext2fs_sb *) fs->super;
 132                 if (s->s_feature_incompat & ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {
 133                         retval = EXT2_ET_UNSUPP_FEATURE;
 134                         goto cleanup;
 135                 }
 136                 if ((flags & EXT2_FLAG_RW) &&
 137                     (s->s_feature_ro_compat &
 138                      ~EXT2_LIB_FEATURE_RO_COMPAT_SUPP)) {
 139                         retval = EXT2_ET_RO_UNSUPP_FEATURE;
 140                         goto cleanup;
 141                 }
 142         }
 143
 144         fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
 145         if (fs->blocksize == 0) {
 146                 retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 147                 goto cleanup;
 148         }
 149         fs->fragsize = EXT2_FRAG_SIZE(fs->super);
 150         fs->inode_blocks_per_group = ((fs->super->s_inodes_per_group *
 151                                        EXT2_INODE_SIZE(fs->super) +
 152                                        EXT2_BLOCK_SIZE(fs->super) - 1) /
 153                                       EXT2_BLOCK_SIZE(fs->super));
 154         if (block_size) {
 155                 if (block_size != fs->blocksize) {
 156                         retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
 157                         goto cleanup;
 158                 }
 159         }
 160         /*
 161          * Set the blocksize to the filesystem's blocksize.
 162          */
 163         io_channel_set_blksize(fs->io, fs->blocksize);
 164
 165         /*
 166          * Read group descriptors
 167          */
 168         fs->group_desc_count = (fs->super->s_blocks_count -
 169                                 fs->super->s_first_data_block +
 170                                 EXT2_BLOCKS_PER_GROUP(fs->super) - 1)
 171                 / EXT2_BLOCKS_PER_GROUP(fs->super);
 172         fs->desc_blocks = (fs->group_desc_count +
 173                            EXT2_DESC_PER_BLOCK(fs->super) - 1)
 174                 / EXT2_DESC_PER_BLOCK(fs->super);
 175         fs->group_desc = malloc((size_t) (fs->desc_blocks * fs->blocksize));
 176         if (!fs->group_desc) {
 177                 retval = EXT2_NO_MEMORY;
 178                 goto cleanup;
 179         }
 180         if (!group_block)
 181                 group_block = fs->super->s_first_data_block + 1;
 182         dest = (char *) fs->group_desc;
 183         for (i=0 ; i < fs->desc_blocks; i++) {
 184                 retval = io_channel_read_blk(fs->io, group_block, 1, dest);
 185                 if (retval)
 186                         goto cleanup;
 187                 group_block++;
 188                 if (fs->flags & EXT2_FLAG_SWAP_BYTES) {
 189                         gdp = (struct ext2_group_desc *) dest;
 190                         groups_per_block = fs->blocksize /
 191                                 sizeof(struct ext2_group_desc);
 192                         for (j=0; j < groups_per_block; j++)
 193                                 ext2fs_swap_group_desc(gdp++);
 194                 }
 195                 dest += fs->blocksize;
 196         }
 197
 198         *ret_fs = fs;
 199         return 0;
 200 cleanup:
 201         ext2fs_free(fs);
 202         return retval;
 203 }
 204