On Tue 13-11-12 01:50:48, OGAWA Hirofumi wrote: > Jan Kara <jack@xxxxxxx> writes: > > > On Mon 12-11-12 01:06:41, OGAWA Hirofumi wrote: > >> Jan Kara <jack@xxxxxxx> writes: > >> > >> > 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 tz= which allows user to specify offset in minutes > >> > that should be applied to time stamps on the filesystem. > >> > >> What is in some cases? tz_minuteswest style timezone is known as it > >> doesn't work. E.g. summer time. > > Yes, DST is one problem. Another problem (which is more annoying to the > > user reporting this) is that he has HW clock set to UTC but system time is > > in CET. Somewhat surprisingly (at least to me before I read the code) this > > means sys_tz.minuteswest == 0. So when he connects say his camera, which > > has time in CET, to the computer he sees timestamps off by one hour. With > > tz= mount option he could mount the filesystem with tz=60 and be mostly > > happy (modulo DST). > > > >> And tz= is reserved for true solution. E.g. load timezone database to > >> kernel and use it for time conversion. So, if we really want this hack, > >> it should be different option name. > > Yes, knowing about time zones in kernel is the only way to properly > > handle fat timestamps in the presence of DST. But time zones are such a > > mess (DST being determined by a law separately each year) I don't see this > > happening - the annoyance by bad timestamps simply isn't big enough. > > > > If you feel strongly about reserving 'tz' mount option, I can rename the > > mount option to something else... Would 'time_offset' be OK with you? > > OK. It should be exclusive with "tz", and the option should be > documented to > > Documentation/filesystems/vfat.txt > > as it doesn't work sometimes. That's a good idea. Thanks for reminding me. I'll send you an updated patch in a moment. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
