Re: [RFC][PATCH] client cannot get lock after other client got lock occur network partition.

[Mi Jinlong <mijinlong@cn.fujitsu.com>]

Hi Trond

Trond Myklebust =8E=CA=93=B9:
> On Mon, 2009-11-09 at 17:19 +0800, Mi Jinlong wrote:
>> Hi Trond et all
>>
>> There is a bug, when i test NFSv3 file's lock as followed:
>>
>> Step1: ClientA and ClientB open a same nfs file;
>> Step2: ClientA locks file with write lock, it's ok;
>> Step3: Cut off the network between ClientA and Server;
>> Step4: ClientB can not acquire for write lock successful forever, ev=
en though
>>        the network partition larger than NLM_HOST_EXPIRE.
>>
>> As i know, If use NFSv4, step4 can success after LEASE_TIME.
>>
>> Is it necessary to fix NFSv3 ?=20
>>
>> The attached patch can make this case OK, but i am not sure it's goo=
d.
>=20
> Unfortunately, NLM (the NFSv2 and v3 locking protocol) is not lease
> based, so the above scenario is truly an unfixable one.
>=20
> The problem with applying your patch is, in essence, that we risk
> breaking another scenario where a client grabs a lock, and then holds=
 it
> for a while.
> The reason this breaks is that there is no equivalent in the NLM
> protocol of the NFSv4 RENEW operation to tell the server that "This
> client is still alive and wants you to keep its state".

Thanks for your answer!

This bug seems serious, shouldn't we fix it?

thanks,
Mi Jinlong