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openfs.c

/*
 * openfs.c --- open an ext2 filesystem
 * 
 * Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o.
 * 
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU Public
 * License.
 * %End-Header%
 */

#include <stdio.h>
#include <string.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <fcntl.h>
#include <time.h>
#if HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#if HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif

#include "ext2_fs.h"
#include "ext2fs.h"
#include "e2image.h"

/*
 *  Note: if superblock is non-zero, block-size must also be non-zero.
 *    Superblock and block_size can be zero to use the default size.
 *
 * Valid flags for ext2fs_open()
 * 
 *    EXT2_FLAG_RW      - Open the filesystem for read/write.
 *    EXT2_FLAG_FORCE - Open the filesystem even if some of the
 *                      features aren't supported.
 *    EXT2_FLAG_JOURNAL_DEV_OK - Open an ext3 journal device
 */
errcode_t ext2fs_open(const char *name, int flags, int superblock,
                  int block_size, io_manager manager, ext2_filsys *ret_fs)
{
      ext2_filsys fs;
      errcode_t   retval;
      int         i, j, groups_per_block;
      blk_t       group_block;
      char        *dest;
      struct ext2_group_desc *gdp;
      
      EXT2_CHECK_MAGIC(manager, EXT2_ET_MAGIC_IO_MANAGER);

      retval = ext2fs_get_mem(sizeof(struct struct_ext2_filsys),
                        (void **) &fs);
      if (retval)
            return retval;
      
      memset(fs, 0, sizeof(struct struct_ext2_filsys));
      fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
      fs->flags = flags;
      fs->umask = 022;
      retval = manager->open(name, (flags & EXT2_FLAG_RW) ? IO_FLAG_RW : 0,
                         &fs->io);
      if (retval)
            goto cleanup;
      fs->io->app_data = fs;
      retval = ext2fs_get_mem(strlen(name)+1, (void **) &fs->device_name);
      if (retval)
            goto cleanup;
      strcpy(fs->device_name, name);
      retval = ext2fs_get_mem(SUPERBLOCK_SIZE, (void **) &fs->super);
      if (retval)
            goto cleanup;
      if (flags & EXT2_FLAG_IMAGE_FILE) {
            retval = ext2fs_get_mem(sizeof(struct ext2_image_hdr),
                              (void **) &fs->image_header);
            if (retval)
                  goto cleanup;
            retval = io_channel_read_blk(fs->io, 0,
                                   -sizeof(struct ext2_image_hdr),
                                   fs->image_header);
            if (retval)
                  goto cleanup;
            if (fs->image_header->magic_number != EXT2_ET_MAGIC_E2IMAGE)
                  return EXT2_ET_MAGIC_E2IMAGE;
            superblock = 1;
            block_size = fs->image_header->fs_blocksize;
      }

      /*
       * If the user specifies a specific block # for the
       * superblock, then he/she must also specify the block size!
       * Otherwise, read the master superblock located at offset
       * SUPERBLOCK_OFFSET from the start of the partition.
       *
       * Note: we only save a backup copy of the superblock if we
       * are reading the superblock from the primary superblock location.
       */
      if (superblock) {
            if (!block_size) {
                  retval = EXT2_ET_INVALID_ARGUMENT;
                  goto cleanup;
            }
            io_channel_set_blksize(fs->io, block_size);
            group_block = superblock + 1;
            fs->orig_super = 0;
      } else {
            io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET);
            superblock = 1;
            group_block = 0;
            retval = ext2fs_get_mem(SUPERBLOCK_SIZE,
                              (void **) &fs->orig_super);
            if (retval)
                  goto cleanup;
      }
      retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE,
                             fs->super);
      if (retval)
            goto cleanup;
      if (fs->orig_super)
            memcpy(fs->orig_super, fs->super, SUPERBLOCK_SIZE);

#ifdef EXT2FS_ENABLE_SWAPFS
      if ((fs->super->s_magic == ext2fs_swab16(EXT2_SUPER_MAGIC)) ||
          (fs->flags & EXT2_FLAG_SWAP_BYTES)) {
            fs->flags |= EXT2_FLAG_SWAP_BYTES;

            ext2fs_swap_super(fs->super);
      }
#endif
      
      if (fs->super->s_magic != EXT2_SUPER_MAGIC) {
            retval = EXT2_ET_BAD_MAGIC;
            goto cleanup;
      }
      if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) {
            retval = EXT2_ET_REV_TOO_HIGH;
            goto cleanup;
      }

      /*
       * Check for feature set incompatibility
       */
      if (!(flags & EXT2_FLAG_FORCE)) {
            if (fs->super->s_feature_incompat &
                ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {
                  retval = EXT2_ET_UNSUPP_FEATURE;
                  goto cleanup;
            }
            if ((flags & EXT2_FLAG_RW) &&
                (fs->super->s_feature_ro_compat &
                 ~EXT2_LIB_FEATURE_RO_COMPAT_SUPP)) {
                  retval = EXT2_ET_RO_UNSUPP_FEATURE;
                  goto cleanup;
            }
            if (!(flags & EXT2_FLAG_JOURNAL_DEV_OK) &&
                (fs->super->s_feature_incompat &
                 EXT3_FEATURE_INCOMPAT_JOURNAL_DEV)) {
                  retval = EXT2_ET_UNSUPP_FEATURE;
                  goto cleanup;
            }
      }
      
      fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
      if (fs->blocksize == 0) {
            retval = EXT2_ET_CORRUPT_SUPERBLOCK;
            goto cleanup;
      }
      fs->fragsize = EXT2_FRAG_SIZE(fs->super);
      fs->inode_blocks_per_group = ((fs->super->s_inodes_per_group *
                               EXT2_INODE_SIZE(fs->super) +
                               EXT2_BLOCK_SIZE(fs->super) - 1) /
                              EXT2_BLOCK_SIZE(fs->super));
      if (block_size) {
            if (block_size != fs->blocksize) {
                  retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;
                  goto cleanup;
            }
      }
      /*
       * Set the blocksize to the filesystem's blocksize.
       */
      io_channel_set_blksize(fs->io, fs->blocksize);

      /*
       * If this is an external journal device, don't try to read
       * the group descriptors, because they're not there.
       */
      if (fs->super->s_feature_incompat &
          EXT3_FEATURE_INCOMPAT_JOURNAL_DEV) {
            fs->group_desc_count = 0;
            *ret_fs = fs;
            return 0;
      }
      
      /*
       * Read group descriptors
       */
      if ((EXT2_BLOCKS_PER_GROUP(fs->super)) == 0) {
            retval = EXT2_ET_CORRUPT_SUPERBLOCK;
            goto cleanup;
      }
      fs->group_desc_count = (fs->super->s_blocks_count -
                        fs->super->s_first_data_block +
                        EXT2_BLOCKS_PER_GROUP(fs->super) - 1)
            / EXT2_BLOCKS_PER_GROUP(fs->super);
      fs->desc_blocks = (fs->group_desc_count +
                     EXT2_DESC_PER_BLOCK(fs->super) - 1)
            / EXT2_DESC_PER_BLOCK(fs->super);
      retval = ext2fs_get_mem(fs->desc_blocks * fs->blocksize,
                        (void **) &fs->group_desc);
      if (retval)
            goto cleanup;
      if (!group_block)
            group_block = fs->super->s_first_data_block + 1;
      dest = (char *) fs->group_desc;
      for (i=0 ; i < fs->desc_blocks; i++) {
            retval = io_channel_read_blk(fs->io, group_block, 1, dest);
            if (retval)
                  goto cleanup;
            group_block++;
#ifdef EXT2FS_ENABLE_SWAPFS
            if (fs->flags & EXT2_FLAG_SWAP_BYTES) {
                  gdp = (struct ext2_group_desc *) dest;
                  groups_per_block = fs->blocksize /
                        sizeof(struct ext2_group_desc);
                  for (j=0; j < groups_per_block; j++)
                        ext2fs_swap_group_desc(gdp++);
            }
#endif
            dest += fs->blocksize;
      }

      *ret_fs = fs;
      return 0;
cleanup:
      ext2fs_free(fs);
      return retval;
}


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