On Tuesday August 12, trond.myklebust@xxxxxxxxxx wrote: > On Tue, 2008-08-12 at 12:27 +1000, Neil Brown wrote: > > Hi > > I have a report of a the BUG_ON in rpcb_getport_clnt being > > triggered. This is: > > /* Autobind on cloned rpc clients is discouraged */ > > BUG_ON(clnt->cl_parent != clnt); > > > > It looks to me that while they might be discouraged, they are not > > prevented and so having the BUG_ON is wrong. > > > > When rpc_clone_client creates a clone, it sets cl_autobind to 0, > > and gives the new client a reference to the same cl_xprt as the > > original client. > > > > The only effect of cl_autobind is to prevent rpc_force_rebind from > > clearing the BOUND flag on ->cl_xprt. > > So while a call to rpc_force_rebind on the clone will not clear that > > flag, a call on the original client will clear that flag. > > > > So a cloned client can still end up with a ->cl_xprt with the BOUND > > flag clear. > > > > So call_bind (which is present in the call trace under the oops) can > > find that !xprt_bound, even when the client is a cloned client. > > > > When this happens, ->rpcbind, which is rpcb_getport_clnt, goes BOOM. > > > > What should happen when a clone client finds that its transport is no > > longer bound? Should rpc_getport_async just do > > clnt = task->tk_client->cl_parent; > > ?? > > This shouldn't be a particularly urgent problem, since lockd should > normally be the only thing that needs to use the autobind functionality, > and it does not use cloned clients. > > That said, I think that the answer is that cloned clients may indeed use > rpcbind as long as they share the same program number and version as the > parent. > IOW: we should probably rather BUG_ON() calls to rpc_bind_new_program() > if the parent has xprt->cl_autobind set. Just to confirm, you are saying that the current BUG_ON is indeed wrong, and the fact that it fires does not imply any real bug. It should be removed. Possibly a BUG_ON could be put somewhere else to catch incorrect behaviour. Is that correct? I now have multiple people for whom this BUG_ON has fired. Thanks, NeilBrown -- 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
