linux-kernel - Re: [Question]nfs: never returned delegation

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Message-ID: <4a2a349225757422f2b0102a2517ba343e32465a.camel@kernel.org>
Date: Mon, 11 Aug 2025 06:06:25 -0700
From: Trond Myklebust <trondmy@...nel.org>
To: Jeff Layton <jlayton@...nel.org>, "zhangjian (CG)"
 <zhangjian496@...wei.com>, 	anna@...nel.org
Cc: linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Question]nfs: never returned delegation

On Mon, 2025-08-11 at 09:03 -0400, Jeff Layton wrote:
> On Mon, 2025-08-11 at 20:48 +0800, zhangjian (CG) wrote:
> > Recently, we meet a NFS problem in 5.10. There are so many
> > test_state_id request after a non-privilaged request in tcpdump
> > result. There are 40w+ delegations in client (I read the delegation
> > list from /proc/kcore).
> > Firstly, I think state manager cost a lot in
> > nfs_server_reap_expired_delegations. But I see they are all in
> > NFS_DELEGATION_REVOKED state except 6 in NFS_DELEGATION_REFERENCED
> > (I read this from /proc/kcore too). 
> > I analyze NFS code and find if NFSPROC4_CLNT_DELEGRETURN procedure
> > meet ETIMEOUT, delegation will be marked as NFS4ERR_DELEG_REVOKED
> > and never return it again. NFS server will keep the revoked
> > delegation in clp->cl_revoked forever. This will result in
> > following sequence response with RECALLABLE_STATE_REVOKED flag.
> > Client will send test_state_id request for all non-revoked
> > delegation.
> > This can only be solved by restarting NFS server.
> > I think ETIMEOUT in NFSPROC4_CLNT_DELEGRETURN procedure may be not
> > the only case that cause lots of non-terminable test_state_id
> > requests after any non-privilaged request. 
> > Wish NFS experts give some advices on this problem.
> > 
> 
> What should happen is that the client should issue a TEST_STATEID and
> then follow up with a FREE_STATEID once it's clear that it has been
> revoked. Alternately, if the client expires then the server will
> purge
> any state it held at that point. The server is required to keep a
> record of these objects until one of those events occurs.
> 
> v5.10 is pretty old, and there have been a number of fixes in this
> area
> in both the client and server over the last several years. You may
> want
> to try a newer kernel (or look at doing some backporting).
> 
> Cheers,

No. If you get an ETIMEDOUT, then it means you are doing soft mounts or
softerr. The client will not follow up with TEST_STATEID or
FREE_STATEID.

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trondmy@...nel.org, trond.myklebust@...merspace.com