From: <tao.peng@emc.com>
To: <benny@tonian.com>, <rees@umich.edu>
CC: <bergwolf@gmail.com>, <linux-nfs@vger.kernel.org>, <honey@citi.umich.edu>
Date: Fri, 10 Jun 2011 01:36:05 -0400
Subject: RE: [PATCH 87/88] Add configurable prefetch size for layoutget
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Hi, Benny,

-----Original Message-----
From: linux-nfs-owner@vger.kernel.org [mailto:linux-nfs-owner@vger.kernel.org] On Behalf Of Benny Halevy
Sent: Friday, June 10, 2011 5:23 AM
To: Jim Rees
Cc: Peng Tao; linux-nfs@vger.kernel.org; peter honeyman
Subject: Re: [PATCH 87/88] Add configurable prefetch size for layoutget

On 2011-06-09 06:58, Jim Rees wrote:
> Benny Halevy wrote:
> 
>   > My understanding is that layoutget specifies a min and max, and the server
>   
>   There's a min.  What do you consider the max?
>   Whatever gets into csa_fore_chan_attrs.ca_maxresponsesize?
> 
> The spec doesn't say max, it says "desired."  I guess I assumed the server
> wouldn't normally return more than desired.

No, the server may freely upgrade the returned layout segment by returning
a layout for a larger byte range or even returning a RW layout where a READ
layout was asked for.
[PT] It is true that server can upgrade the layout segment freely. But there is always a price to pay. Server has to be dealing with all kind of clients.
If server returns more than being asked for, it may hurt other clients.