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Subject: Re: [PATCH v3] NFSv4.1: new layout stateid can not be overwrite by one out of date
From: Trond Myklebust <trond.myklebust@primarydata.com>
In-Reply-To: <1392620881-26561-1-git-send-email-shaobingqing@bwstor.com.cn>
Date: Mon, 17 Feb 2014 11:46:53 -0500
Cc: linuxnfs <linux-nfs@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Message-Id: <DEE24522-5DD2-4C42-9DD9-EC18F0FF05D8@primarydata.com>
References: <N> <1392620881-26561-1-git-send-email-shaobingqing@bwstor.com.cn>
To: shaobingqing <shaobingqing@bwstor.com.cn>
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On Feb 17, 2014, at 2:08, shaobingqing <shaobingqing@bwstor.com.cn> wrote:

> If initiate_file_draining returned NFS4ERR_DELAY, all the lsegs of
> a file might be released before the retrying cb_layout request arriving
> at the client. In this situation,the list lo->plh_segs is empty, 
> layoutget request of the file will use open stateid to obtain a new 
> layout stateid. And if the retrying cb_layout request arrived at the 
> client after the layoutget reply, new layout stateid would be overwrite 
> by one out of date.

I have very serious doubts about adding layout state to represent what the server is _trying_ to do. What if the server decides not to retry the recall? What if it reboots?

Let?s start with looking at the motivations: Have you ever run into the above problem in practice? If so, what was the effect on overall performance?

_________________________________
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@primarydata.com