Re: [PATCH 1/3] NFSv4: Ensure we do not reuse open owner names

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On Apr 23, 2012, at 5:32 PM, Myklebust, Trond wrote:

> On Mon, 2012-04-23 at 16:57 -0400, Chuck Lever wrote:
>> On Apr 23, 2012, at 4:48 PM, Myklebust, Trond wrote:
>> 
>>> On Mon, 2012-04-23 at 16:44 -0400, Chuck Lever wrote:
>>>> Hi-
>>>> 
>>>> I wish you had told me you were going to fix this too.  I've been testing a fix for this for a couple weeks.  Was going to post this afternoon.  Shall I toss mine?
>>> 
>>> I was hitting that BAD_SEQID storm during testing of the other open
>>> fixes last week.
>> 
>> Fair enough, but I announced I had a fix in my April 15 status report.  Oh well.
>> 
>> So, I decided that a timestamp would leak information about the client, so I'm using a simple counter instead.  Would you consider that for your patch?
> 
> How would a timestamp leak useful information? The server and anyone
> monitoring the NFS traffic already knows at what time the open owner was
> created to within a few milliseconds.

It leaks the exact time as the client sees it.  This is why time-based UUIDs are no longer considered safe.

But also, is it possible that a state_owner could be destroyed and created so quickly on a system with inadequate timestamp resolution, such that the new owner ID would not actually be different than the previous one?

-- 
Chuck Lever
chuck[dot]lever[at]oracle[dot]com




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