[sheepdog] Preview - patch convertconfig part 1

[Christoph Hellwig]

> +#define CONFIGFILE_SIGNATURE   0x0000aaaa00000000

Does this mean anything? :)

> +/***** remove in > v0.5.0 *****/
> +/* configfile version 2 */
> +struct sheepdog_config_2 {
> +	uint64_t ctime;
> +	uint64_t space;
> +	uint16_t flags;
> +	uint8_t copies;
> +	uint8_t store[STORE_LEN];
> +};

Do we really need to keep this one around?

> +/***** remove in > v0.5.0 *****/
> +/* configfile version 1 */

A more useful comment would be what versions used it.

> +	/*
> +	 * read and convert config
> +	 *  new config has a version in the first 8 bytes
> +	 *  4 bytes version number
> +	 *  4 bytes fix version signature
> +	 */

A safer check might simply be by file size?

> +	fd = open(config_path, O_RDONLY);
> +	if (fd < 0)
> +	{

Please try to run the checkpath.pl script over the code and fix it's
warnings.

> +		/* new config file */
> +		mknod(config_path, def_fmode, S_IFREG);

mknod errors should be handled.