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 #include "ext2_fs.h"
  27
  28
  29 #include "ext2fs.h"
  30 #include "e2image.h"
  31
  32 blk_t ext2fs_descriptor_block_loc(ext2_filsys fs, blk_t group_block, dgrp_t i)
  33 {
  34         int     bg;
  35         int     has_super = 0;
  36         int     ret_blk;
  37
  38         if (!(fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG) ||
  39             (i < fs->super->s_first_meta_bg))
  40                 return (group_block + i + 1);
  41
  42         bg = (fs->blocksize / sizeof (struct ext2_group_desc)) * i;
  43         if (ext2fs_bg_has_super(fs, bg))
  44                 has_super = 1;
  45         ret_blk = (fs->super->s_first_data_block + has_super +
  46                    (bg * fs->super->s_blocks_per_group));
  47         /*
  48          * If group_block is not the normal value, we're trying to use
  49          * the backup group descriptors and superblock --- so use the
  50          * alternate location of the second block group in the
  51          * metablock group.  Ideally we should be testing each bg
  52          * descriptor block individually for correctness, but we don't
  53          * have the infrastructure in place to do that.
  54          */
  55         if (group_block != fs->super->s_first_data_block &&
  56             ((ret_blk + fs->super->s_blocks_per_group) <
  57              fs->super->s_blocks_count))
  58                 ret_blk += fs->super->s_blocks_per_group;
  59         return ret_blk;
  60 }
  61
  62 /*
  63  *  Note: if superblock is non-zero, block-size must also be non-zero.
  64  *      Superblock and block_size can be zero to use the default size.
  65  *
  66  * Valid flags for ext2fs_open()
  67  *
  68  *      EXT2_FLAG_RW    - Open the filesystem for read/write.
  69  *      EXT2_FLAG_FORCE - Open the filesystem even if some of the
  70  *                              features aren't supported.
  71  *      EXT2_FLAG_JOURNAL_DEV_OK - Open an ext3 journal device
  72  */
  73 errcode_t ext2fs_open(const char *name, int flags, int superblock,
  74                       unsigned int block_size, io_manager manager,
  75                       ext2_filsys *ret_fs)
  76 {
  77         ext2_filsys     fs;
  78         errcode_t       retval;
  79         unsigned long   i;
  80         int             j, groups_per_block, blocks_per_group;
  81         blk_t           group_block, blk;
  82         char            *dest;
  83         struct ext2_group_desc *gdp;
  84
  85         EXT2_CHECK_MAGIC(manager, EXT2_ET_MAGIC_IO_MANAGER);
  86
  87         retval = ext2fs_get_mem(sizeof(struct struct_ext2_filsys), &fs);
  88         if (retval)
  89                 return retval;
  90
  91         memset(fs, 0, sizeof(struct struct_ext2_filsys));
  92         fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
  93         fs->flags = flags;
  94         fs->umask = 022;
  95         retval = manager->open(name, (flags & EXT2_FLAG_RW) ? IO_FLAG_RW : 0,
  96                                &fs->io);
  97         if (retval)
  98                 goto cleanup;
  99         fs->image_io = fs->io;
 100         fs->io->app_data = fs;
 101         retval = ext2fs_get_mem(strlen(name)+1, &fs->device_name);
 102         if (retval)
 103                 goto cleanup;
 104         strcpy(fs->device_name, name);
 105         retval = ext2fs_get_mem(SUPERBLOCK_SIZE, &fs->super);
 106         if (retval)
 107                 goto cleanup;
 108         if (flags & EXT2_FLAG_IMAGE_FILE) {
 109                 retval = ext2fs_get_mem(sizeof(struct ext2_image_hdr),
 110                                         &fs->image_header);
 111                 if (retval)
 112                         goto cleanup;
 113                 retval = io_channel_read_blk(fs->io, 0,
 114                                              -sizeof(struct ext2_image_hdr),
 115                                              fs->image_header);
 116                 if (retval)
 117                         goto cleanup;
 118                 if (fs->image_header->magic_number != EXT2_ET_MAGIC_E2IMAGE)
 119                         return EXT2_ET_MAGIC_E2IMAGE;
 120                 superblock = 1;
 121                 block_size = fs->image_header->fs_blocksize;
 122         }
 123
 124         /*
 125          * If the user specifies a specific block # for the
 126          * superblock, then he/she must also specify the block size!
 127          * Otherwise, read the master superblock located at offset
 128          * SUPERBLOCK_OFFSET from the start of the partition.
 129          *
 130          * Note: we only save a backup copy of the superblock if we
 131          * are reading the superblock from the primary superblock location.
 132          */
 133         if (superblock) {
 134                 if (!block_size) {
 135                         retval = EXT2_ET_INVALID_ARGUMENT;
 136                         goto cleanup;
 137                 }
 138                 io_channel_set_blksize(fs->io, block_size);
 139                 group_block = superblock;
 140                 fs->orig_super = 0;
 141         } else {
 142                 io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
 143                 superblock = 1;
 144                 group_block = 0;
 145                 retval = ext2fs_get_mem(SUPERBLOCK_SIZE, &fs->orig_super);
 146                 if (retval)
 147                         goto cleanup;
 148         }
 149         retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
 150                                      fs->super);
 151         if (retval)
 152                 goto cleanup;
 153         if (fs->orig_super)
 154                 memcpy(fs->orig_super, fs->super, SUPERBLOCK_SIZE);
 155
 156 #ifdef EXT2FS_ENABLE_SWAPFS
 157         if ((fs->super->s_magic == ext2fs_swab16(EXT2_SUPER_MAGIC)) ||
 158             (fs->flags & EXT2_FLAG_SWAP_BYTES)) {
 159                 fs->flags |= EXT2_FLAG_SWAP_BYTES;
 160
 161                 ext2fs_swap_super(fs->super);
 162         }
 163 #endif
 164
 165         if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
 166                 retval = EXT2_ET_BAD_MAGIC;
 167                 goto cleanup;
 168         }
 169         if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) {
 170                 retval = EXT2_ET_REV_TOO_HIGH;
 171                 goto cleanup;
 172         }
 173
 174         /*
 175          * Check for feature set incompatibility
 176          */
 177         if (!(flags & EXT2_FLAG_FORCE)) {
 178                 if (fs->super->s_feature_incompat &
 179                     ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {
 180                         retval = EXT2_ET_UNSUPP_FEATURE;
 181                         goto cleanup;
 182                 }
 183                 if ((flags & EXT2_FLAG_RW) &&
 184                     (fs->super->s_feature_ro_compat &
 185                      ~EXT2_LIB_FEATURE_RO_COMPAT_SUPP)) {
 186                         retval = EXT2_ET_RO_UNSUPP_FEATURE;
 187                         goto cleanup;
 188                 }
 189                 if (!(flags & EXT2_FLAG_JOURNAL_DEV_OK) &&
 190                     (fs->super->s_feature_incompat &
 191                      EXT3_FEATURE_INCOMPAT_JOURNAL_DEV)) {
 192                         retval = EXT2_ET_UNSUPP_FEATURE;
 193                         goto cleanup;
 194                 }
 195         }
 196
 197         fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
 198         if (fs->blocksize == 0) {
 199                 retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 200                 goto cleanup;
 201         }
 202         fs->fragsize = EXT2_FRAG_SIZE(fs->super);
 203         fs->inode_blocks_per_group = ((fs->super->s_inodes_per_group *
 204                                        EXT2_INODE_SIZE(fs->super) +
 205                                        EXT2_BLOCK_SIZE(fs->super) - 1) /
 206                                       EXT2_BLOCK_SIZE(fs->super));
 207         if (block_size) {
 208                 if (block_size != fs->blocksize) {
 209                         retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
 210                         goto cleanup;
 211                 }
 212         }
 213         /*
 214          * Set the blocksize to the filesystem's blocksize.
 215          */
 216         io_channel_set_blksize(fs->io, fs->blocksize);
 217
 218         /*
 219          * If this is an external journal device, don't try to read
 220          * the group descriptors, because they're not there.
 221          */
 222         if (fs->super->s_feature_incompat &
 223             EXT3_FEATURE_INCOMPAT_JOURNAL_DEV) {
 224                 fs->group_desc_count = 0;
 225                 *ret_fs = fs;
 226                 return 0;
 227         }
 228
 229         /*
 230          * Read group descriptors
 231          */
 232         blocks_per_group = EXT2_BLOCKS_PER_GROUP(fs->super);
 233         if (blocks_per_group == 0 ||
 234             blocks_per_group > EXT2_MAX_BLOCKS_PER_GROUP(fs->super) ||
 235             fs->inode_blocks_per_group > EXT2_MAX_INODES_PER_GROUP(fs->super)) {
 236                 retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 237                 goto cleanup;
 238         }
 239         fs->group_desc_count = (fs->super->s_blocks_count -
 240                                 fs->super->s_first_data_block +
 241                                 blocks_per_group - 1) / blocks_per_group;
 242         fs->desc_blocks = (fs->group_desc_count +
 243                            EXT2_DESC_PER_BLOCK(fs->super) - 1)
 244                 / EXT2_DESC_PER_BLOCK(fs->super);
 245         retval = ext2fs_get_mem(fs->desc_blocks * fs->blocksize,
 246                                 &fs->group_desc);
 247         if (retval)
 248                 goto cleanup;
 249         if (!group_block)
 250                 group_block = fs->super->s_first_data_block;
 251         dest = (char *) fs->group_desc;
 252         groups_per_block = fs->blocksize / sizeof(struct ext2_group_desc);
 253         for (i=0 ; i < fs->desc_blocks; i++) {
 254                 blk = ext2fs_descriptor_block_loc(fs, group_block, i);
 255                 retval = io_channel_read_blk(fs->io, blk, 1, dest);
 256                 if (retval)
 257                         goto cleanup;
 258 #ifdef EXT2FS_ENABLE_SWAPFS
 259                 if (fs->flags & EXT2_FLAG_SWAP_BYTES) {
 260                         gdp = (struct ext2_group_desc *) dest;
 261                         for (j=0; j < groups_per_block; j++)
 262                                 ext2fs_swap_group_desc(gdp++);
 263                 }
 264 #endif
 265                 dest += fs->blocksize;
 266         }
 267
 268         *ret_fs = fs;
 269         return 0;
 270 cleanup:
 271         ext2fs_free(fs);
 272         return retval;
 273 }
 274
 275 /*
 276  * Set/get the filesystem data I/O channel.
 277  *
 278  * These functions are only valid if EXT2_FLAG_IMAGE_FILE is true.
 279  */
 280 errcode_t ext2fs_get_data_io(ext2_filsys fs, io_channel *old_io)
 281 {
 282         if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
 283                 return EXT2_ET_NOT_IMAGE_FILE;
 284         if (old_io) {
 285                 *old_io = (fs->image_io == fs->io) ? 0 : fs->io;
 286         }
 287         return 0;
 288 }
 289
 290 errcode_t ext2fs_set_data_io(ext2_filsys fs, io_channel new_io)
 291 {
 292         if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
 293                 return EXT2_ET_NOT_IMAGE_FILE;
 294         fs->io = new_io ? new_io : fs->image_io;
 295         return 0;
 296 }
 297
 298 errcode_t ext2fs_rewrite_to_io(ext2_filsys fs, io_channel new_io)
 299 {
 300         if ((fs->flags & EXT2_FLAG_IMAGE_FILE) == 0)
 301                 return EXT2_ET_NOT_IMAGE_FILE;
 302         fs->io = fs->image_io = new_io;
 303         fs->flags |= EXT2_FLAG_DIRTY | EXT2_FLAG_RW |
 304                 EXT2_FLAG_BB_DIRTY | EXT2_FLAG_IB_DIRTY;
 305         fs->flags &= ~EXT2_FLAG_IMAGE_FILE;
 306         return 0;
 307 }