Re: [PATCH] nfsd: always handle RPC_SIGNALLED earlier in nfsd4_cb_sequence_done()

[Chuck Lever <chuck.lever@oracle.com>]

On 1/22/25 10:44 AM, Jeff Layton wrote:
> On Wed, 2025-01-22 at 10:20 -0500, Chuck Lever wrote:
>> On 1/22/25 10:10 AM, Jeff Layton wrote:
>>> The v4.0 client always restarts the callback when the connection is shut
>>> down (which is indicated by RPC_SIGNALLED()). The RPC is then requeued
>>> and the result eventually should complete (or be aborted).
>>>
>>> The v4.1 code instead processes the result and only later decides to
>>> restart the call. Even more problematic is the fact that it releases the
>>> slot beforehand. The restarted call may get a new slot, which would
>>> could break DRC handling.
>>
>> "break DRC handling" -- I'd like to understand this.
>>
>> NFSD always sets cachethis to false in CB_SEQUENCE, so there is no DRC
>> for these operations. The only thing the client saves is the slot
>> sequence number IIUC.
>>
>> Is retrying an uncached operation via a different slot a problem?
>>
> 
> Ahh, I missed that we always set cachethis to false. So, there is
> probably now a problem with the DRC after all. Still, I don't see a
> good argument for processing the CB_SEQUENCE result, when we intend to
> retransmit the call anyway.

I expect that the rationale is that the slot sequence number needs to be
advanced appropriately before the slot can be used again.


-- 
Chuck Lever