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SubjectRe: problem with nfs4: rpciod seems to loop in rpc_shutdown_client forever
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Am Dienstag, 22. März 2011 schrieb J. Bruce Fields:
> On Tue, Mar 22, 2011 at 03:52:21PM +0100, Wolfgang Walter wrote:
> > Am Dienstag, 22. März 2011 schrieb J. Bruce Fields:
> > > On Fri, Mar 18, 2011 at 11:49:21PM +0100, Wolfgang Walter wrote:
> > > > Hello,
> > > >
> > > > I have a problem with our nfs-server (stable 2.6.32.33 but also with
> > > > .31 or .32 and probably older ones): sometimes
> > > > one or more rpciod get stuck. I used
> > > >
> > > > rpcdebug -m rpc -s all
> > > >
> > > > I get messages as the following one about every second:
> > > >
> > > > Mar 18 11:15:37 au kernel: [44640.906793] RPC: killing all
> > > > tasks for client ffff88041c51de00 Mar 18 11:15:38 au kernel:
> > > > [44641.906793] RPC: killing all tasks for client
> > > > ffff88041c51de00 Mar 18 11:15:39 au kernel: [44642.906795] RPC:
> > > > killing all tasks for client ffff88041c51de00 Mar 18 11:15:40 au
> > > > kernel: [44643.906793] RPC: killing all tasks for client
> > > > ffff88041c51de00 Mar 18 11:15:41 au kernel: [44644.906795] RPC:
> > > > killing all tasks for client ffff88041c51de00 Mar 18 11:15:42 au
> > > > kernel: [44645.906794] RPC: killing all tasks for client
> > > > ffff88041c51de00
> > > >
> > > > and I get this messages:
> > > >
> > > > Mar 18 22:45:57 au kernel: [86061.779008] 174 0381 -5
> > > > ffff88041c51de00 (null) 0 ffffffff817211a0 nfs4_cbv1 CB_NULL
> > > > a:rpc_exit_task q:none
> > > >
> > > > My theorie is this one:
> > > >
> > > > * this async task is runnable but does not progress (calling
> > > > rpc_exit_task). * this is because the same rpciod which handles this
> > > > task loops in rpc_shutdown_client waiting for this task to go away. *
> > > > because rpc_shutdown_client is called from an async rpc, too
> > >
> > > Off hand I don't see any place where rpc_shutdown_client() is called
> > > from rpciod; do you?
> >
> > I'm not familiar with the code.
> >
> > But could it be that this is in fs/nfsd/nfs4state.c ?
> >
> > Just a guess because 2.6.38 does not have this problem and in 2.6.38 it
> > seems to have a workqueue of its own.
>
> Well, spotted, yes it's true that 2.6.32 had called put_nfs4_client()
> from an rpc_call_done callback, that put_nfs4_client() can end up
> calling rpc_shutdown_client, and that that's since been fixed....
>
> If someone wants to backport the fix to 2.6.32.y....
>
> Actually I think it might be sufficient just to apply
> 147efd0dd702ce2f1ab44449bd70369405ef68fd ? But I haven't tried.
>
> --b.
>
> commit 147efd0dd702ce2f1ab44449bd70369405ef68fd
> Author: J. Bruce Fields <bfields@citi.umich.edu>
> Date: Sun Feb 21 17:41:19 2010 -0800
>
> nfsd4: shutdown callbacks on expiry
>
> Once we've expired the client, there's no further purpose to the
> callbacks; go ahead and shut down the callback client rather than
> waiting for the last reference to go.
>
> Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
>
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index efef7f2..9ce5831 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -697,9 +697,6 @@ shutdown_callback_client(struct nfs4_client *clp)
> static inline void
> free_client(struct nfs4_client *clp)
> {
> - shutdown_callback_client(clp);
> - if (clp->cl_cb_xprt)
> - svc_xprt_put(clp->cl_cb_xprt);
> if (clp->cl_cred.cr_group_info)
> put_group_info(clp->cl_cred.cr_group_info);
> kfree(clp->cl_principal);
> @@ -752,6 +749,9 @@ expire_client(struct nfs4_client *clp)
> se_perclnt);
> release_session(ses);
> }
> + shutdown_callback_client(clp);
> + if (clp->cl_cb_xprt)
> + svc_xprt_put(clp->cl_cb_xprt);
> put_nfs4_client(clp);
> }

I'll test it this weekend.

I use 2.6.38 on this server for now and probably will stay with it. But having
a working longterm-kernel to fall back is important for me :-).

Regards,
--
Wolfgang Walter
Studentenwerk München
Anstalt des öffentlichen Rechts
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