Re: [PATCH 1/1] NFSD: fix error handling in callbacks

["J. Bruce Fields" <bfields@redhat.com>]

On Tue, Mar 09, 2021 at 08:59:51PM +0000, Trond Myklebust wrote:
> On Tue, 2021-03-09 at 15:41 -0500, Olga Kornievskaia wrote:
> > On Tue, Mar 9, 2021 at 3:22 PM Trond Myklebust <
> > trondmy@hammerspace.com> wrote:
> > > 
> > > On Tue, 2021-03-09 at 10:37 -0500, J. Bruce Fields wrote:
> > > > On Tue, Mar 09, 2021 at 09:41:27AM -0500, Olga Kornievskaia
> > > > wrote:
> > > > > From: Olga Kornievskaia <kolga@netapp.com>
> > > > > 
> > > > > When the server tries to do a callback and a client fails it
> > > > > due to
> > > > > authentication problems, we need the server to set callback
> > > > > down
> > > > > flag in RENEW so that client can recover.
> > > > 
> > > > I was looking at this.  It looks to me like this should really be
> > > > just:
> > > > 
> > > >         case 1:
> > > >                 if (task->tk_status)
> > > >                         nfsd4_mark_cb_down(clp, task->tk_status);
> > > > 
> > > > If tk_status showed an error, and the ->done method doesn't
> > > > return 0
> > > > to
> > > > tell us it something worth retrying, then the callback failed
> > > > permanently, so we should mark the callback path down, regardless
> > > > of
> > > > the
> > > > exact error.
> > > 
> > > I disagree. task->tk_status could be an unhandled NFSv4 error (see
> > > nfsd4_cb_recall_done()). The client might, for instance, be in the
> > > process of returning the delegation being recalled. Why should that
> > > result in the callback channel being marked as down?
> > > 
> > 
> > Are you talking about say the connection going down and server should
> > just reconnect instead of recovering the callback channel. I assumed
> > that connection break is something that's not  recoverable by the
> > callback but perhaps I'm wrong.
> 
> No. I'm saying that nfsd4_cb_recall_done() will return a value of '1'
> for both task->tk_status == -EBADHANDLE and -NFS4ERR_BAD_STATEID. I'm
> not seeing why either of those errors should be handled by marking the
> callback channel as being down.
> 
> Looking further, it seems that the same function will also return '1'
> without checking the value of task->tk_status if the delegation has
> been revoked or returned. So that would mean that even NFS4ERR_DELAY
> could trigger the call to nfsd4_mark_cb_down() with the above change.

Yeah, OK, that's wrong, apologies.

I'm just a little worried about the attempt to enumerate transport level
errors in nfsd4_cb_done().  Are we sure that EIO, ETIMEDOUT, EACCESS is
the right list?

--b.

> 
> > 
> > > > 
> > > > --b.
> > > > 
> > > > > 
> > > > > Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
> > > > > ---
> > > > >  fs/nfsd/nfs4callback.c | 1 +
> > > > >  1 file changed, 1 insertion(+)
> > > > > 
> > > > > diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
> > > > > index 052be5bf9ef5..7325592b456e 100644
> > > > > --- a/fs/nfsd/nfs4callback.c
> > > > > +++ b/fs/nfsd/nfs4callback.c
> > > > > @@ -1189,6 +1189,7 @@ static void nfsd4_cb_done(struct rpc_task
> > > > > *task, void *calldata)
> > > > >                 switch (task->tk_status) {
> > > > >                 case -EIO:
> > > > >                 case -ETIMEDOUT:
> > > > > +               case -EACCES:
> > > > >                         nfsd4_mark_cb_down(clp, task-
> > > > > >tk_status);
> > > > >                 }
> > > > >                 break;
> > > > > --
> > > > > 2.27.0
> > > > > 
> > > > 
> > > 
> > > --
> > > Trond Myklebust
> > > Linux NFS client maintainer, Hammerspace
> > > trond.myklebust@hammerspace.com
> > > 
> > > 
> 
> -- 
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@hammerspace.com
> 
>