On Thu, Feb 20, 2014 at 12:50:15PM -0500, Steve Dickson wrote: > > > On 02/17/2014 06:43 PM, NeilBrown wrote: > > > > Protocol negotiation in mount.nfs does not correctly negotiate with a > > server which only support NFSv3 and UDP. > > > > When mount.nfs attempts an NFSv4 mount and fails with ECONNREFUSED > > it does not fall back to NFSv3, as this is not recognised as a > > "does not support NFSv4" error. > > However ECONNREFUSED is a clear indication that the server doesn't > > support TCP, and ipso facto does not support NFSv4. > > So ECONNREFUSED should trigger a fallback from v4 to v2/3. > I'm also pretty this is the error returned when the server is > down or more pointy when server is rebooting... Probably worth checking that. > Do we really want to fallback at this point? >From a bz comment (#984901, not sure why it's private): Any NFS server has to support either tcp or rpcbind. But it's OK for a server to support only of those two. So the only way to handle both cases while continuing to retry after ECONNREFUSED is to alternate between trying nfs4/tcp and rpcbind until you can connect to one or the other. If it's the rpcbind call that succeeds first then I think we want to do one more try of nfs4/tcp just to make sure it didn't just come up, before falling back to v3. The rpcbind call is done in userspace, if I understand right, so I think this is doable. Looking at utils/mount/ I don't understand the mount process well enough to understand exactly how to do it. Maybe everything but the final nfs_sys_mount needs to be moved out of nfs_do_mount_v3v2 into a new nfs_do_probe_v3v2 and nfs_autonegotiate should alternate between nfs_try_mount_v4 and nfs_do_probe_v3v2 as long as both return ECONNREFUSED, calling nfs_try_mount_v3v2 only if nfs_try_mount_v4 has failed after a succesful nfs_do_probe_v3v2? Except the v3v2 mount logic seems to actually modify the mount_options, so probably that doesn't quite work. ? --b. -- 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
