[pnfs] [nfs41] 10 patches for async session reset

[William A. (Andy) Adamson]

On Thu, Jun 12, 2008 at 7:40 AM, Benny Halevy <bhalevy at panasas.com> wrote:

> Andy, sorry but after reading the patchset I think the method
> you implemented can be simplified if the destroy session path
> wouldn't spawn a kthread for session_destroyer().
>
> nfs41_destroy_session could just mark the session for destroy
> and as expired and that will function as a barrier.
> That should be the only thing to do on the various cleanup paths.
> (including nfs41_sequence_call_done which starts session recovery
> today)
>
> Recovery should be done only on the setup_sequence path and it should
> wait until the slot table is drained, otherwise it should sleep
> on the slot_tbl_waitq.  When all slots are done, recovery can start.
> For the reset case it should just start with sending a destroy_session
> before recovering it.
>
> Can this work?


I see what you mean, the code could be simplified. Don't free the session on
reset, just re-initialize it and therefore use the slot_tlb_waitq instead of
the destroy_waitq. Combine the destroy thread with the recover thread which
will now have three tasks:

1) just call create_session (NFS41_SESSION_EXPIRED) - set in the exchange_id
path
2) call destroy session (wait for completion) call create session.
NFS41_SESSION_RESET - a new state set by the error handlers
3) just call destroy session. (NFS41_SESSION_DESTROY) set in the kill_super
path

It should work. I'll try it. Thanks for the review. I'll pay more attention
to indent......

-->Andy

>
>
> Benny
>
> On Jun. 11, 2008, 21:18 +0300, "Adamson, Andy" <William.Adamson at netapp.com>
> wrote:
> > The first patch in this series fixes a bug in create session. All of the
> rest implement asynchronous session reset, where a session gets an
> op_sequence operation error. This code places any new rpc_task that would
> look for a slot on a new queue moves any rpc_tasks waiting for a slot on the
> forward channel to the same queue, waits for the current outstanding rpc's
> (e.g. slots to clear), destroys the session, initializes a new session, and
> wakes
> > up all the tasks on the new queue. the session recovery code is then
> called by the next rpc_task - create session is then called,
> > and voila! the session is reset.
> >
> > I wrote a simple add-on to the pynfs server that returned
> NFS4ERR_MISORDERED every 50th OP_SEQUENCE call. This code passes basic and
> general connectathon tests against this server. I'll work on adding the
> pynfs changes to the python distro.
> >
> > -->Andy
> >
> >
> >
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> >
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