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From:   Benjamin Coddington <bcodding@redhat.com>
To:     trond.myklebust@hammerspace.com, anna@kernel.org
Cc:     linux-nfs@vger.kernel.org
Subject: Re: [PATCH v2] NFSv4: fairly test all delegations on a SEQ4_
 revocation
Date:   Thu, 14 Sep 2023 09:18:09 -0400
Message-ID: <D8B1F20B-E08D-4ED1-A0F5-0C2C763FEC88@redhat.com>
In-Reply-To: <6c85bc9cc6bd8d70fe0e74b096c72944f61874a7.1692903063.git.bcodding@redhat.com>
References: <426fa7ac71b4c9496039cc16169029a5abcb6dc5.1692902495.git.bcodding@redhat.com>
 <6c85bc9cc6bd8d70fe0e74b096c72944f61874a7.1692903063.git.bcodding@redhat.com>
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On 24 Aug 2023, at 14:52, Benjamin Coddington wrote:

> When the client is required to use TEST_STATEID to discover which
> delegation(s) have been revoked, it may continually test delegations at the
> head of the list if the server continues to be unsatisfied and send
> SEQ4_STATUS_RECALLABLE_STATE_REVOKED.  For a large number of delegations
> this behavior is prone to live-lock because the client may never be able to
> test and free revoked state at the end of the list since the
> SEQ4_STATUS_RECALLABLE_STATE_REVOKED will cause us to flag delegations at
> the head of the list to be tested.  This problem is further exacerbated by
> the state manager's willingness to be scheduled out on a busy system while
> testing the list of delegations.
>
> Keep a generation counter for each attempt to test all delegations, and
> skip delegations that have already been tested in the current pass.
>
> Signed-off-by: Benjamin Coddington <bcodding@redhat.com>

This one went through the ringer in an environment that saw multiple clients
live-locking, and resolves the problem for them.  They asked me to add:

Tested-by: Torkil Svensgaard <torkil@drcmr.dk>
Tested-by: Ruben Vestergaard <rubenv@drcmr.dk>

Ben