super.c

elinux jffs初始版本 具体了解JFFS的文件系统！

	unsigned short resgid = EXT2_DEF_RESGID;
	unsigned long logic_sb_block = 1;
	kdev_t dev = sb->s_dev;
	int db_count;
	int i, j;

	sb->u.ext2_sb.s_mount_opt = 0;
	set_opt (sb->u.ext2_sb.s_mount_opt, CHECK_NORMAL);
	if (!parse_options ((char *) data, &sb_block, &resuid, &resgid,
	    &sb->u.ext2_sb.s_mount_opt)) {
		sb->s_dev = 0;
		return NULL;
	}

	MOD_INC_USE_COUNT;
	lock_super (sb);
	set_blocksize (dev, BLOCK_SIZE);
	if (!(bh = bread (dev, sb_block, BLOCK_SIZE))) {
		sb->s_dev = 0;
		unlock_super (sb);
		printk ("EXT2-fs: unable to read superblock\n");
		MOD_DEC_USE_COUNT;
		return NULL;
	}
	/*
	 * Note: s_es must be initialized s_es as soon as possible because
	 * some ext2 macro-instructions depend on its value
	 */
	es = (struct ext2_super_block *) bh->b_data;
	sb->u.ext2_sb.s_es = es;
	sb->s_magic = es->s_magic;
	if (sb->s_magic != EXT2_SUPER_MAGIC) {
		if (!silent)
			printk ("VFS: Can't find an ext2 filesystem on dev "
				"%s.\n", kdevname(dev));
	failed_mount:
		sb->s_dev = 0;
		unlock_super (sb);
		if (bh)
			brelse(bh);
		MOD_DEC_USE_COUNT;
		return NULL;
	}
	if (es->s_rev_level > EXT2_GOOD_OLD_REV) {
		if (es->s_feature_incompat & ~EXT2_FEATURE_INCOMPAT_SUPP) {
			printk("EXT2-fs: %s: couldn't mount because of "
			       "unsupported optional features.\n", 
			       kdevname(dev));
			goto failed_mount;
		}
		if (!(sb->s_flags & MS_RDONLY) &&
		    (es->s_feature_ro_compat & ~EXT2_FEATURE_RO_COMPAT_SUPP)) {
			printk("EXT2-fs: %s: couldn't mount RDWR because of "
			       "unsupported optional features.\n", 
			       kdevname(dev));
			goto failed_mount;
		}
	}
	sb->s_blocksize_bits = sb->u.ext2_sb.s_es->s_log_block_size + 10;
	sb->s_blocksize = 1 << sb->s_blocksize_bits;
	if (sb->s_blocksize != BLOCK_SIZE && 
	    (sb->s_blocksize == 1024 || sb->s_blocksize == 2048 ||  
	     sb->s_blocksize == 4096)) {
		unsigned long offset;

		brelse (bh);
		set_blocksize (dev, sb->s_blocksize);
		logic_sb_block = (sb_block*BLOCK_SIZE) / sb->s_blocksize;
		offset = (sb_block*BLOCK_SIZE) % sb->s_blocksize;
		bh = bread (dev, logic_sb_block, sb->s_blocksize);
		if(!bh) {
			printk("EXT2-fs: Couldn't read superblock on "
			       "2nd try.\n");
			goto failed_mount;
		}
		es = (struct ext2_super_block *) (((char *)bh->b_data) + offset);
		sb->u.ext2_sb.s_es = es;
		if (es->s_magic != EXT2_SUPER_MAGIC) {
			printk ("EXT2-fs: Magic mismatch, very weird !\n");
			goto failed_mount;
		}
	}
	if (es->s_rev_level == EXT2_GOOD_OLD_REV) {
		sb->u.ext2_sb.s_inode_size = EXT2_GOOD_OLD_INODE_SIZE;
		sb->u.ext2_sb.s_first_ino = EXT2_GOOD_OLD_FIRST_INO;
	} else {
		sb->u.ext2_sb.s_inode_size = es->s_inode_size;
		sb->u.ext2_sb.s_first_ino = es->s_first_ino;
		if (sb->u.ext2_sb.s_inode_size != EXT2_GOOD_OLD_INODE_SIZE) {
			printk ("EXT2-fs: unsupported inode size: %d\n",
				sb->u.ext2_sb.s_inode_size);
			goto failed_mount;
		}
	}
	sb->u.ext2_sb.s_frag_size = EXT2_MIN_FRAG_SIZE <<
				   es->s_log_frag_size;
	if (sb->u.ext2_sb.s_frag_size)
		sb->u.ext2_sb.s_frags_per_block = sb->s_blocksize /
						  sb->u.ext2_sb.s_frag_size;
	else
		sb->s_magic = 0;
	sb->u.ext2_sb.s_blocks_per_group = es->s_blocks_per_group;
	sb->u.ext2_sb.s_frags_per_group = es->s_frags_per_group;
	sb->u.ext2_sb.s_inodes_per_group = es->s_inodes_per_group;
	sb->u.ext2_sb.s_inodes_per_block = sb->s_blocksize /
					   EXT2_INODE_SIZE(sb);
	sb->u.ext2_sb.s_itb_per_group = sb->u.ext2_sb.s_inodes_per_group /
				        sb->u.ext2_sb.s_inodes_per_block;
	sb->u.ext2_sb.s_desc_per_block = sb->s_blocksize /
					 sizeof (struct ext2_group_desc);
	sb->u.ext2_sb.s_sbh = bh;
	if (resuid != EXT2_DEF_RESUID)
		sb->u.ext2_sb.s_resuid = resuid;
	else
		sb->u.ext2_sb.s_resuid = es->s_def_resuid;
	if (resgid != EXT2_DEF_RESGID)
		sb->u.ext2_sb.s_resgid = resgid;
	else
		sb->u.ext2_sb.s_resgid = es->s_def_resgid;
	sb->u.ext2_sb.s_mount_state = es->s_state;
	sb->u.ext2_sb.s_rename_lock = 0;
	sb->u.ext2_sb.s_rename_wait = NULL;
	sb->u.ext2_sb.s_addr_per_block_bits =
		log2 (EXT2_ADDR_PER_BLOCK(sb));
	sb->u.ext2_sb.s_desc_per_block_bits =
		log2 (EXT2_DESC_PER_BLOCK(sb));
	if (sb->s_magic != EXT2_SUPER_MAGIC) {
		if (!silent)
			printk ("VFS: Can't find an ext2 filesystem on dev "
				"%s.\n",
				kdevname(dev));
		goto failed_mount;
	}
	if (sb->s_blocksize != bh->b_size) {
		if (!silent)
			printk ("VFS: Unsupported blocksize on dev "
				"%s.\n", kdevname(dev));
		goto failed_mount;
	}

	if (sb->s_blocksize != sb->u.ext2_sb.s_frag_size) {
		printk ("EXT2-fs: fragsize %lu != blocksize %lu (not supported yet)\n",
			sb->u.ext2_sb.s_frag_size, sb->s_blocksize);
		goto failed_mount;
	}

	if (sb->u.ext2_sb.s_blocks_per_group > sb->s_blocksize * 8) {
		printk ("EXT2-fs: #blocks per group too big: %lu\n",
			sb->u.ext2_sb.s_blocks_per_group);
		goto failed_mount;
	}
	if (sb->u.ext2_sb.s_frags_per_group > sb->s_blocksize * 8) {
		printk ("EXT2-fs: #fragments per group too big: %lu\n",
			sb->u.ext2_sb.s_frags_per_group);
		goto failed_mount;
	}
	if (sb->u.ext2_sb.s_inodes_per_group > sb->s_blocksize * 8) {
		printk ("EXT2-fs: #inodes per group too big: %lu\n",
			sb->u.ext2_sb.s_inodes_per_group);
		goto failed_mount;
	}

	sb->u.ext2_sb.s_groups_count = (es->s_blocks_count -
				        es->s_first_data_block +
				       EXT2_BLOCKS_PER_GROUP(sb) - 1) /
				       EXT2_BLOCKS_PER_GROUP(sb);
	db_count = (sb->u.ext2_sb.s_groups_count + EXT2_DESC_PER_BLOCK(sb) - 1) /
		   EXT2_DESC_PER_BLOCK(sb);
	sb->u.ext2_sb.s_group_desc = kmalloc (db_count * sizeof (struct buffer_head *), GFP_KERNEL);
	if (sb->u.ext2_sb.s_group_desc == NULL) {
		printk ("EXT2-fs: not enough memory\n");
		goto failed_mount;
	}
	for (i = 0; i < db_count; i++) {
		sb->u.ext2_sb.s_group_desc[i] = bread (dev, logic_sb_block + i + 1,
						       sb->s_blocksize);
		if (!sb->u.ext2_sb.s_group_desc[i]) {
			for (j = 0; j < i; j++)
				brelse (sb->u.ext2_sb.s_group_desc[j]);
			kfree_s (sb->u.ext2_sb.s_group_desc,
				 db_count * sizeof (struct buffer_head *));
			printk ("EXT2-fs: unable to read group descriptors\n");
			goto failed_mount;
		}
	}
	if (!ext2_check_descriptors (sb)) {
		for (j = 0; j < db_count; j++)
			brelse (sb->u.ext2_sb.s_group_desc[j]);
		kfree_s (sb->u.ext2_sb.s_group_desc,
			 db_count * sizeof (struct buffer_head *));
		printk ("EXT2-fs: group descriptors corrupted !\n");
		goto failed_mount;
	}
	for (i = 0; i < EXT2_MAX_GROUP_LOADED; i++) {
		sb->u.ext2_sb.s_inode_bitmap_number[i] = 0;
		sb->u.ext2_sb.s_inode_bitmap[i] = NULL;
		sb->u.ext2_sb.s_block_bitmap_number[i] = 0;
		sb->u.ext2_sb.s_block_bitmap[i] = NULL;
	}
	sb->u.ext2_sb.s_loaded_inode_bitmaps = 0;
	sb->u.ext2_sb.s_loaded_block_bitmaps = 0;
	sb->u.ext2_sb.s_db_per_group = db_count;
	unlock_super (sb);
	/*
	 * set up enough so that it can read an inode
	 */
	sb->s_dev = dev;
	sb->s_op = &ext2_sops;
	if (!(sb->s_mounted = iget (sb, EXT2_ROOT_INO))) {
		sb->s_dev = 0;
		for (i = 0; i < db_count; i++)
			if (sb->u.ext2_sb.s_group_desc[i])
				brelse (sb->u.ext2_sb.s_group_desc[i]);
		kfree_s (sb->u.ext2_sb.s_group_desc,
			 db_count * sizeof (struct buffer_head *));
		brelse (bh);
		printk ("EXT2-fs: get root inode failed\n");
		MOD_DEC_USE_COUNT;
		return NULL;
	}
	ext2_setup_super (sb, es);
	return sb;
}

static void ext2_commit_super (struct super_block * sb,
			       struct ext2_super_block * es)
{
	es->s_wtime = CURRENT_TIME;
	mark_buffer_dirty(sb->u.ext2_sb.s_sbh, 1);
	sb->s_dirt = 0;
}

/*
 * In the second extended file system, it is not necessary to
 * write the super block since we use a mapping of the
 * disk super block in a buffer.
 *
 * However, this function is still used to set the fs valid
 * flags to 0.  We need to set this flag to 0 since the fs
 * may have been checked while mounted and e2fsck may have
 * set s_state to EXT2_VALID_FS after some corrections.
 */

void ext2_write_super (struct super_block * sb)
{
	struct ext2_super_block * es;

	if (!(sb->s_flags & MS_RDONLY)) {
		es = sb->u.ext2_sb.s_es;

		ext2_debug ("setting valid to 0\n");

		if (es->s_state & EXT2_VALID_FS) {
			es->s_state &= ~EXT2_VALID_FS;
			es->s_mtime = CURRENT_TIME;
		}
		ext2_commit_super (sb, es);
	}
	sb->s_dirt = 0;
}

int ext2_remount (struct super_block * sb, int * flags, char * data)
{
	struct ext2_super_block * es;
	unsigned short resuid = sb->u.ext2_sb.s_resuid;
	unsigned short resgid = sb->u.ext2_sb.s_resgid;
	unsigned long new_mount_opt;
	unsigned long tmp;

	/*
	 * Allow the "check" option to be passed as a remount option.
	 */
	new_mount_opt = EXT2_MOUNT_CHECK_NORMAL;
	if (!parse_options (data, &tmp, &resuid, &resgid,
			    &new_mount_opt))
		return -EINVAL;

	sb->u.ext2_sb.s_mount_opt = new_mount_opt;
	sb->u.ext2_sb.s_resuid = resuid;
	sb->u.ext2_sb.s_resgid = resgid;
	es = sb->u.ext2_sb.s_es;
	if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
		return 0;
	if (*flags & MS_RDONLY) {
		if (es->s_state & EXT2_VALID_FS ||
		    !(sb->u.ext2_sb.s_mount_state & EXT2_VALID_FS))
			return 0;
		/*
		 * OK, we are remounting a valid rw partition rdonly, so set
		 * the rdonly flag and then mark the partition as valid again.
		 */
		es->s_state = sb->u.ext2_sb.s_mount_state;
		es->s_mtime = CURRENT_TIME;
		mark_buffer_dirty(sb->u.ext2_sb.s_sbh, 1);
		sb->s_dirt = 1;
		ext2_commit_super (sb, es);
	}
	else {
		/*
		 * Mounting a RDONLY partition read-write, so reread and
		 * store the current valid flag.  (It may have been changed 
		 * by e2fsck since we originally mounted the partition.)
		 */
		sb->u.ext2_sb.s_mount_state = es->s_state;
		sb->s_flags &= ~MS_RDONLY;
		ext2_setup_super (sb, es);
	}
	return 0;
}

static struct file_system_type ext2_fs_type = {
        ext2_read_super, "ext2", 1, NULL
};

int init_ext2_fs(void)
{
        return register_filesystem(&ext2_fs_type);
}

#ifdef MODULE
int init_module(void)
{
	int status;

	if ((status = init_ext2_fs()) == 0)
		register_symtab(0);
	return status;
}

void cleanup_module(void)
{
        unregister_filesystem(&ext2_fs_type);
}

#endif

void ext2_statfs (struct super_block * sb, struct statfs * buf, int bufsiz)
{
	unsigned long overhead;
	unsigned long overhead_per_group;
	struct statfs tmp;

	if (test_opt (sb, MINIX_DF))
		overhead = 0;
	else {
		/*
		 * Compute the overhead (FS structures)
		 */
		overhead_per_group = 1 /* super block */ +
				     sb->u.ext2_sb.s_db_per_group /* descriptors */ +
				     1 /* block bitmap */ +
				     1 /* inode bitmap */ +
				     sb->u.ext2_sb.s_itb_per_group /* inode table */;
		overhead = sb->u.ext2_sb.s_es->s_first_data_block +
			   sb->u.ext2_sb.s_groups_count * overhead_per_group;
	}

	tmp.f_type = EXT2_SUPER_MAGIC;
	tmp.f_bsize = sb->s_blocksize;
	tmp.f_blocks = sb->u.ext2_sb.s_es->s_blocks_count - overhead;
	tmp.f_bfree = ext2_count_free_blocks (sb);
	tmp.f_bavail = tmp.f_bfree - sb->u.ext2_sb.s_es->s_r_blocks_count;
	if (tmp.f_bfree < sb->u.ext2_sb.s_es->s_r_blocks_count)
		tmp.f_bavail = 0;
	tmp.f_files = sb->u.ext2_sb.s_es->s_inodes_count;
	tmp.f_ffree = ext2_count_free_inodes (sb);
	tmp.f_namelen = EXT2_NAME_LEN;
	memcpy_tofs(buf, &tmp, bufsiz);
}