Re: [PATCH v2] NFSv4: try lease recovery on NFS4ERR_EXPIRED

[Trond Myklebust <trondmy@hammerspace.com>]

On Wed, 2020-01-22 at 14:20 +0000, Robert Milkowski wrote:
> > -----Original Message-----
> > From: Trond Myklebust <trondmy@hammerspace.com>
> > Sent: 17 January 2020 17:24
> > To: linux-nfs@vger.kernel.org; rmilkowski@gmail.com
> > Cc: anna.schumaker@netapp.com; linux-kernel@vger.kernel.org;
> > chuck.lever@oracle.com
> > Subject: Re: [PATCH v2] NFSv4: try lease recovery on
> > NFS4ERR_EXPIRED
> > 
> > On Fri, 2020-01-17 at 16:12 +0000, Robert Milkowski wrote:
> > > Anyone please?
> > > 
> > > 
> > > -----Original Message-----
> > > From: Robert Milkowski <rmilkowski@gmail.com>
> > > Sent: 08 January 2020 21:48
> > > To: linux-nfs@vger.kernel.org
> > > Cc: 'Trond Myklebust' <trondmy@hammerspace.com>; 'Chuck Lever'
> > > <chuck.lever@oracle.com>; 'Anna Schumaker' <
> > > anna.schumaker@netapp.com
> > > > ;
> > > linux-kernel@vger.kernel.org
> > > Subject: [PATCH v2] NFSv4: try lease recovery on NFS4ERR_EXPIRED
> > > 
> > > From: Robert Milkowski <rmilkowski@gmail.com>
> > > 
> > > Currently, if an nfs server returns NFS4ERR_EXPIRED to open(),
> > > etc.
> > > we return EIO to applications without even trying to recover.
> > > 
> > > Fixes: 272289a3df72 ("NFSv4: nfs4_do_handle_exception() handle
> > > revoke/expiry of a single stateid")
> > > Signed-off-by: Robert Milkowski <rmilkowski@gmail.com>
> > > ---
> > >  fs/nfs/nfs4proc.c | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > > 
> > > diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index
> > > 76d3716..2478405
> > > 100644
> > > --- a/fs/nfs/nfs4proc.c
> > > +++ b/fs/nfs/nfs4proc.c
> > > @@ -481,6 +481,10 @@ static int nfs4_do_handle_exception(struct
> > > nfs_server *server,
> > >  						stateid);
> > >  				goto wait_on_recovery;
> > >  			}
> > > +			if (state == NULL) {
> > > +				nfs4_schedule_lease_recovery(clp);
> > > +				goto wait_on_recovery;
> > > +			}
> > >  			/* Fall through */
> > >  		case -NFS4ERR_OPENMODE:
> > >  			if (inode) {
> > > --
> > > 1.8.3.1
> > > 
> > > 
> > 
> > Does this apply to any case other than NFS4ERR_EXPIRED in the
> > specific
> > case of nfs4_do_open()? I can't see that it does. It looks to me as
> > if
> > the open recovery routines already have their own handling of this
> > case.
> 
> I only observed the issue with open(). After further
> review I think you are right and it only applies to nfs4_do_open().
> 
> 
> > If so, why not just add it as a special case in the nfs4_do_open()
> > error
> > handling? Otherwise this patch will end up overriding other generic
> > cases where we have an inode, but no open state.
> > 
> 
> Fair point.
> So perhaps, few lines further instead of:
> 
> 			if (inode) {
> ...
> 			if (state == NULL) {
> 					break;
> 			}
> 
> There should be:
> 
> 			if (inode) {
> ...
> 			if (state == NULL) {
> 				nfs4_schedule_lease_recovery(clp);
> 				goto wait_on_recovery;
> 			}
> 
> 
> 
> This way we know that inode cannot be null at this point, and it's a
> case where both inode and state are NULL.
> This would be a little bit more general in case we reach this point.
> 
> But if you think it is better to move it to nfs4_do_open() then I've
> just tested the following patch:
> 
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index 76d3716..b7c4044 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -3187,6 +3187,11 @@ static struct nfs4_state *nfs4_do_open(struct
> inode *dir,
>                         exception.retry = 1;
>                         continue;
>                 }
> +               if (status == -NFS4ERR_EXPIRED) {
> +                       nfs4_schedule_lease_recovery(server-
> >nfs_client);
> +                       exception.retry = 1;
> +                       continue;
> +               }
>                 if (status == -EAGAIN) {
>                         /* We must have found a delegation */
>                         exception.retry = 1;
> 

This looks like what I'm asking for, yes. That seems like the minimal
patch that addresses the problem you're describing.


-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com