Re: [PATCH] nfsd: remove long-standing revoked delegations by force

["zhangjian (CG)" <zhangjian496@huawei.com>]

Hello every experts.

If we can see all delegations on hard-mounted nfs client, which are also
on server cl_revoked list, changed from
NFS_DELEGATION_RETURN_IF_CLOSED|NFS_DELEGATION_REVOKED|NFS_DELEGATION_TEST_EXPIRED
to NFS_DELEGATION_RETURN_IF_CLOSED|NFS_DELEGATION_REVOKED, can we give
some hypothesis on this problem ?

By the way, this problem can be cover over by decreasing file count on
server.

Thanks,
zhangjian

On 2025/9/2 20:43, Benjamin Coddington wrote:
> On 2 Sep 2025, at 8:10, Li Lingfeng wrote:
> 
>> Our expected outcome was that the client would release the abnormal
>> delegation via TEST_STATEID/FREE_STATEID upon detecting its invalidity.
>> However, this problematic delegation is no longer present in the
>> client's server->delegations list—whether due to client-side timeouts or
>> the server-side bug [1].
> 
> How does the client timeout TEST_STATEID - are you mounting with 'soft'?
> 
> We should find the server-side bug and fix it rather than write code to
> paper over it.  I do think the synchronization of state here is a bit
> fragile and wish the protocol had a generation, sequence, or marker for
> setting SEQ4_STATUS_ bits..
> 
>>>
>>> Should we instead just administratively evict the client since it's
>>> clearly not behaving right in this case?
>> Thanks for the suggestion. While administratively evicting the client would
>> certainly resolve the immediate delegation issue, I'm concerned that approach
>> might be a bit heavy-handed.
>> The problematic behavior seems isolated to a single delegation. Meanwhile,
>> the client itself likely has numerous other open files and active state on
>> the server. Forcing a complete client reconnect would tear down all that
>> state, which could cause significant application disruption and be perceived
>> as a service outage from the client's perspective.
>>
>> [1] https://lore.kernel.org/all/de669327-c93a-49e5-a53b-bda9e67d34a2@huawei.com/
> 
> ^^ in this thread you reference v5.10 - there was a knfsd fix for a
> cl_revoked leak "3b816601e279", and there have been 3 or 4 fixes to fix
> problems and optimize the client walk of delegations since then.  Jeff
> pointed out that there have been fixes in these areas.  Are you finding this
> problem still with all those fixes included?
> 
> Ben
> 
>