On 12/11/13 08:00, Jeff Layton wrote: > We've gotten a lot of complaints recently about the 15s delay when > doing a sec=sys mount without gssd running. > > A large part of the problem is that the kernel isn't able to reliably > detect when rpc.gssd is running. What we currently have is a > gssd_running flag that is initially set to 1. When an upcall times out, > that gets set to 0, and subsequent upcalls get a much shorter timeout > (1/4s instead of 15s). It's reset back to '1' when a pipe is reopened. > > The approach of using a flag like this is pretty inadequate. First, it > doesn't eliminate the long delay on the initial upcall attempt. Also, > if gssd spontaneously dies, then the flag will still be set to 1 until > the next upcall attempt times out. Finally, it currently requires that > the pipe be reopened in order to reset the flag back to true. > > This patchset replaces that flag with a more reliable mechanism for > detecting when gssd is running. When rpc_pipefs is mounted, it creates a > new "dummy" pipe that gssd will naturally find and hold open. We'll > never send an upcall down this pipe, and writing to it always fails. > But, since we can detect when something is holding it open, we can use > that to determine whether gssd is running. > > The current patch just uses this mechanism to replace the gssd_running > flag with this new mechanism. This shortens the long delay when mounting > without gssd running, but does not silence these warnings: > > RPC: AUTH_GSS upcall timed out. > Please check user daemon is running. > > I'm willing to add a patch to do that, but I'm a little unclear on the > best way to do so. Those messages are generated by the auth_gss code. We > probably do want to print them if someone mounted with sec=krb5, but > suppress them when mounting with sec=sys. > > Do we need to somehow pass down that intent to auth_gss? Another idea > would be to call gssd_running() from the nfs mount code and use that to > determine whether to try and use krb5 at all... > > Discuss! I've just verified that a mount, with these patches, takes about 1.2 seconds when rpc.gssd is not running.... With rpc.gssd it take about .2 seconds. Tested-by: Steve Dickson <steved@xxxxxxxxxx> 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
