On Thu 15-01-15 01:40:34, Christoph Hellwig wrote: > On Wed, Jan 14, 2015 at 07:27:08PM +0100, Jan Kara wrote: > > Currently, v2 quota format blindly stored flags from in-memory dqinfo on > > disk, although there are no flags supported. Since it is stupid to store > > flags which have no effect, just store 0 unconditionally and don't > > bother loading it from disk. > > > > Note that userspace could have stored some flags there via Q_SETINFO > > quotactl and then later read them (although flags have no effect) but > > I'm pretty sure noone does that (most definitely quota-tools don't and > > quota interface doesn't have too much other users). > > What about future proofing? Current kernels can store flags on disk, > so the best is to reserve the currently (and possibly previously) > assigned values, and mask them out when reading from disk. Hum, I'm not sure I follow you. Current kernels will store any 32-bit number user sets in flags field. So if we wanted to be 100% safe, we'd have to just ignore that field. Which isn't currently a problem since quota code doesn't use the field for anything (it was added just for future extensions). But since I'm pretty certain noone actually relies on values of that field, I though we could just get away with forcibly zeroing the field now and if there's a need to use the field in a few years, we could start using it. 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
