On Wed 13-02-19 11:40:39, Theodore Y. Ts'o wrote: > There's been a long-term disagreement about how the per-file DAX flag > should work. > > * Should it exist at all? > * What happens when the DAX flag is cleared? > * Should it be not allowed and return an error? > (Or maybe only if the file is otherwise opened anywhere in the system?) > * Should it only takes effect when the file system is unmounted, > or when the inode drops out of the inode cache? > * Should we remove the flag entirely and make it be something the > system automagically infers? > > I had hoped consensus would be achieved before the ext4 per-file DAX > flag lands, but it hasn't for a *long* time. Technically the DAX flag > is "experimental", which technically means it could be removed --- > although I suspect at this point, it would break some userspace, so > our options about how to adjust the semantics of the flag are probably > constrained. Well, there's no filesystem that would really support the DAX flag currently (XFS accepts it, stores it, but does nothing with it). So I think we are reasonably free in defining the semantics. Also I think this is closely related to Dan's topic "What should be done to remove experimental tag from DAX" (or however it was called). Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
