Re: [PATCH v2] fat: Provide option for setting timezone offset

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 12 Nov 2012 23:27:28 +0100
Jan Kara <jack@suse.cz> wrote:

> So far FAT either offsets time stamps by sys_tz.minuteswest or leaves them
> as they are (when tz=UTC mount option is used). However in some cases it
> is useful if one can specify time stamp offset on his own (e.g. when time
> zone of the camera connected is different from time zone of the computer,
> or when HW clock is in UTC and thus sys_tz.minuteswest == 0).
> 
> So provide a mount option time_offset= which allows user to specify offset in
> minutes that should be applied to time stamps on the filesystem.


Did you test "mount -o remount"?

I suspect it won't work correctly - inodes which are already in
cache at remount time will not reflect the updated offset?

If so, a quick fix would be to disallow the ability to set time_offset
via remount (dunno how?) and document it.

>
> ...
>
> @@ -1005,8 +1011,17 @@ static int parse_options(struct super_block *sb, char *options, int is_vfat,
>  		case Opt_flush:
>  			opts->flush = 1;
>  			break;
> +		case Opt_time_offset:
> +			if (match_int(&args[0], &option))
> +				return 0;
> +			if (option < -12 * 60 || option > 12 * 60)
> +				return 0;

Is it correct to return 0 here?  0 means "success"?

> +			opts->tz_set = 1;
> +			opts->time_offset = option;
> +			break;
>  		case Opt_tz_utc:
> -			opts->tz_utc = 1;
> +			opts->tz_set = 1;
> +			opts->time_offset = 0;
>  			break;
>  		case Opt_err_cont:
>  			opts->errors = FAT_ERRORS_CONT;
>
> ...
>