On Wed, Jul 20, 2022 at 10:38:31AM -0400, Jeff Layton wrote: > On Wed, 2022-07-20 at 16:15 +0200, Lukas Czerner wrote: --snip-- > > How would we approach making iversion a default? libmount is passing > > this option to the kernel as just a MS_I_VERSION flag that is set when > > -o iversion is used and left empty when the -o noiversion is used. This > > means that while we could make it a default in ext4, we don't have any > > way of knowing whether the user asked for -o noiversion. So that's not > > really an option. > > > > Updating the mke2fs/tune2fs to allow setting iversion as a default mount > > option I think has the same problem. > > > > So the only way I can see ATM would be to introduce another mountflag > > for libmount to indicate -o noiversion. This way we can make iversion a > > default on ext4 without loosing the information about user provided -o > > noiversion option. > > > > Is there a different way I am not seeing? > > > > Right, implementing this is the difficult bit actually since this uses a > MS_* flag. If we do make this the default, we'd definitely want to > continue allowing "-o noiversion" to disable it. > > Could we just reverse the default in libmount? It might cause this to > suddenly be enabled in some deployments, but in most cases, people > wouldn't even notice and they could still specify -o noiversion to turn > it off. Can be done, but that would change the default for everyone. Not sure if that desirable. Also I can image this being a bit confusing. I still think the best approach would be to introduce another MS_ flag for noiversion case. I think there is precedence in the case of MS_STRICTATIME - not exactly the same but similar enough. > Another idea would be to introduce new mount options for this, but > that's kind of nasty from a UI standpoint. > > > > > If we can do reasonably extensive testing that will indeed show > > negligible impact when nothing is querying i_version, then I would be in > > favor of the change. > > > > Excellent! I think that would be best if we can get away with it. A lot > of people are currently running ext4-backed nfs servers and aren't using > that mount option. Could you provide some performance numbers for iversion case? Thanks! -Lukas > -- > Jeff Layton <jlayton@xxxxxxxxxx> >
