Chuck Lever wrote: > On Mar 19, 2009, at Mar 19, 2009, 12:34 PM, Muntz, Daniel wrote: >>> -----Original Message----- >>> From: Steve Dickson [mailto:SteveD@xxxxxxxxxx] >>> Sent: Thursday, March 19, 2009 9:18 AM >>> To: linux NFS Mailing list >>> Subject: The next step: nfsvers=4 >>> >>> As I see it, the next step to seamlessly move to V4 as the >>> default is to make 'mount -o nfsvers=4' actually do a v4 mount... >>> >>> There are two obvious place we can make this change. >>> In the kernel and/or in the mount command... >>> >>> Looking at the kernel, since v3 and v4 truly two different >>> file systems its seems a bit late for the nfs_get_sb() to all >>> of sudden have to change file system type. Meaning when >>> nfs_get_sb() sees the "nfsvers=4" somehow it would have to >>> back out and call nfs4_get_sb(), which obviously is a bit hacky.... >>> >>> Now I guess we could have one nfs_get_sb() for both v3 and v4. >>> Where the nfs_get_sb() could peek into the options data to >>> see which version is needed. This would also mean the mount >>> command would always have to set a version so when the "nfsvers=" >>> options is not set, the kernel would know which version to use. >>> Again, this feels a bit hacky as well but doable... >>> >>> At least to me, what seems like the best option is to have >>> the mount.nfs binary early on intercept "nfsvers=4" option >>> and then change the fs_type to "nfs4", which would allow >>> everything to "trickle down" as it does today... Again to me, >>> that seem like the least intrusive way to do it... >>> >>> Comments? Is there other ways? > > Having the mount.nfs command translate sounds like a pretty easy thing > to prototype. Yes.. I agree... > >> Whichever way it's done, if v4 becomes the default, don't forget to also >> make the default behavior be that the system will fall back and try a v3 >> mount if v4 isn't available. Otherwise you'll break a huge percentage >> of your user base. Of course then you also have to deal with the >> semantics of how to specifify "only v4" vs. "try v4 first and fall >> back". > > Today, specifying vers=3 means "I want vers=3 or nothing". Not > specifying any version means the mount command can choose which version > to use based on what both sides support. > > If no vers= option is specified, I don't think it would be difficult for > the text-based mount command to try a "nfs4" mount first, and if that > fails try an "nfs" mount. > > Steve, would you like me to provide a prototype mount.nfs command that > handles this? Well I was thinking more of lets walk before we run... meaning... lets just get the 'nfsvers=4' working and accepted. Then deal with the v4/v3/v2 fall back in the next patch set... As you say... the prototype looks to be pretty easy... so let me take a crack at it... besides... you are making some good progress with IPV6 code... I don't think this should get in the way of that... steved. steved. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
