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 #include <fcntl.h>
  18 #include <time.h>
  19 #if HAVE_SYS_STAT_H
  20 #include <sys/stat.h>
  21 #endif
  22 #if HAVE_SYS_TYPES_H
  23 #include <sys/types.h>
  24 #endif
  25
  26 #if EXT2_FLAT_INCLUDES
  27 #include "ext2_fs.h"
  28 #else
  29 #include <linux/ext2_fs.h>
  30 #endif
  31
  32 #include "ext2fs.h"
  33
  34 /*
  35  *  Note: if superblock is non-zero, block-size must also be non-zero.
  36  *      Superblock and block_size can be zero to use the default size.
  37  *
  38  * Valid flags for ext2fs_open()
  39  *
  40  *      EXT2_FLAG_RW    - Open the filesystem for read/write.
  41  *      EXT2_FLAG_FORCE - Open the filesystem even if some of the
  42  *                              features aren't supported.
  43  */
  44 errcode_t ext2fs_open(const char *name, int flags, int superblock,
  45                       int block_size, io_manager manager, ext2_filsys *ret_fs)
  46 {
  47         ext2_filsys     fs;
  48         errcode_t       retval;
  49         int             i, j, groups_per_block;
  50         blk_t           group_block;
  51         char            *dest;
  52         struct ext2_group_desc *gdp;
  53         struct ext2fs_sb        *s;
  54
  55         EXT2_CHECK_MAGIC(manager, EXT2_ET_MAGIC_IO_MANAGER);
  56
  57         retval = ext2fs_get_mem(sizeof(struct struct_ext2_filsys),
  58                                 (void **) &fs);
  59         if (retval)
  60                 return retval;
  61
  62         memset(fs, 0, sizeof(struct struct_ext2_filsys));
  63         fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
  64         fs->flags = flags;
  65         retval = manager->open(name, (flags & EXT2_FLAG_RW) ? IO_FLAG_RW : 0,
  66                                &fs->io);
  67         if (retval)
  68                 goto cleanup;
  69         fs->io->app_data = fs;
  70         retval = ext2fs_get_mem(strlen(name)+1, (void **) &fs->device_name);
  71         if (retval)
  72                 goto cleanup;
  73         strcpy(fs->device_name, name);
  74         retval = ext2fs_get_mem(SUPERBLOCK_SIZE, (void **) &fs->super);
  75         if (retval)
  76                 goto cleanup;
  77
  78         /*
  79          * If the user specifies a specific block # for the
  80          * superblock, then he/she must also specify the block size!
  81          * Otherwise, read the master superblock located at offset
  82          * SUPERBLOCK_OFFSET from the start of the partition.
  83          */
  84         if (superblock) {
  85                 if (!block_size) {
  86                         retval = EXT2_ET_INVALID_ARGUMENT;
  87                         goto cleanup;
  88                 }
  89                 io_channel_set_blksize(fs->io, block_size);
  90                 group_block = superblock + 1;
  91         } else {
  92                 io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
  93                 superblock = 1;
  94                 group_block = 0;
  95         }
  96         retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
  97                                      fs->super);
  98         if (retval)
  99                 goto cleanup;
 100
 101         if ((fs->super->s_magic == ext2fs_swab16(EXT2_SUPER_MAGIC)) ||
 102             (fs->flags & EXT2_FLAG_SWAP_BYTES)) {
 103                 fs->flags |= EXT2_FLAG_SWAP_BYTES;
 104
 105                 ext2fs_swap_super(fs->super);
 106         }
 107
 108         if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
 109                 retval = EXT2_ET_BAD_MAGIC;
 110                 goto cleanup;
 111         }
 112 #ifdef EXT2_DYNAMIC_REV
 113         if (fs->super->s_rev_level > EXT2_DYNAMIC_REV) {
 114                 retval = EXT2_ET_REV_TOO_HIGH;
 115                 goto cleanup;
 116         }
 117 #else
 118 #ifdef  EXT2_CURRENT_REV
 119         if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) {
 120                 retval = EXT2_ET_REV_TOO_HIGH;
 121                 goto cleanup;
 122         }
 123 #endif
 124 #endif
 125         /*
 126          * Check for feature set incompatibility
 127          */
 128         if (!(flags & EXT2_FLAG_FORCE)) {
 129                 s = (struct ext2fs_sb *) fs->super;
 130                 if (s->s_feature_incompat & ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {
 131                         retval = EXT2_ET_UNSUPP_FEATURE;
 132                         goto cleanup;
 133                 }
 134                 if ((flags & EXT2_FLAG_RW) &&
 135                     (s->s_feature_ro_compat &
 136                      ~EXT2_LIB_FEATURE_RO_COMPAT_SUPP)) {
 137                         retval = EXT2_ET_RO_UNSUPP_FEATURE;
 138                         goto cleanup;
 139                 }
 140         }
 141
 142         fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
 143         if (fs->blocksize == 0) {
 144                 retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 145                 goto cleanup;
 146         }
 147         fs->fragsize = EXT2_FRAG_SIZE(fs->super);
 148         fs->inode_blocks_per_group = ((fs->super->s_inodes_per_group *
 149                                        EXT2_INODE_SIZE(fs->super) +
 150                                        EXT2_BLOCK_SIZE(fs->super) - 1) /
 151                                       EXT2_BLOCK_SIZE(fs->super));
 152         if (block_size) {
 153                 if (block_size != fs->blocksize) {
 154                         retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
 155                         goto cleanup;
 156                 }
 157         }
 158         /*
 159          * Set the blocksize to the filesystem's blocksize.
 160          */
 161         io_channel_set_blksize(fs->io, fs->blocksize);
 162
 163         /*
 164          * Read group descriptors
 165          */
 166         if ((EXT2_BLOCKS_PER_GROUP(fs->super)) == 0) {
 167                 retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 168                 goto cleanup;
 169         }
 170         fs->group_desc_count = (fs->super->s_blocks_count -
 171                                 fs->super->s_first_data_block +
 172                                 EXT2_BLOCKS_PER_GROUP(fs->super) - 1)
 173                 / EXT2_BLOCKS_PER_GROUP(fs->super);
 174         fs->desc_blocks = (fs->group_desc_count +
 175                            EXT2_DESC_PER_BLOCK(fs->super) - 1)
 176                 / EXT2_DESC_PER_BLOCK(fs->super);
 177         retval = ext2fs_get_mem(fs->desc_blocks * fs->blocksize,
 178                                 (void **) &fs->group_desc);
 179         if (retval)
 180                 goto cleanup;
 181         if (!group_block)
 182                 group_block = fs->super->s_first_data_block + 1;
 183         dest = (char *) fs->group_desc;
 184         for (i=0 ; i < fs->desc_blocks; i++) {
 185                 retval = io_channel_read_blk(fs->io, group_block, 1, dest);
 186                 if (retval)
 187                         goto cleanup;
 188                 group_block++;
 189                 if (fs->flags & EXT2_FLAG_SWAP_BYTES) {
 190                         gdp = (struct ext2_group_desc *) dest;
 191                         groups_per_block = fs->blocksize /
 192                                 sizeof(struct ext2_group_desc);
 193                         for (j=0; j < groups_per_block; j++)
 194                                 ext2fs_swap_group_desc(gdp++);
 195                 }
 196                 dest += fs->blocksize;
 197         }
 198
 199         *ret_fs = fs;
 200         return 0;
 201 cleanup:
 202         ext2fs_free(fs);
 203         return retval;
 204 }
 205