Subject: Re: [nfsv4] Some XDR for SEEK

From: Dean <[email-masked]>
Date: Thu, 06 Oct 2011 10:06:07 -0700

On 9/26/11 3:11 PM, Thomas Haynes wrote:
> On Sep 26, 2011, at 5:07 PM, Trond Myklebust wrote:
>
>> Yes, but it requires the client to estimate the size of the hole/data in
>> the seek() case. Otherwise, the server is liable to return too much or
>> too little data.
>>
>> IOW: I'm fine with having options to generate space maps should there be
>> a demand for it, but it would be useful to also have equivalents of
>> 'find the next', since that is what will be implemented in clients.
> SEEK 4k, 1
>
> States to find the next boundary at offset 4k.

I guess I don't understand the need to go beyond what is currently being 
defined via SEEK_DATA/SEEK_HOLE.  A major reason (according to 
http://lwn.net/Articles/440255/) that linux is moving away from the 
ioctl FIEMAP and towards SEEK_DATA/SEEK_HOLE is all the problems that a 
powerful interface that can return a map of all the extends can cause 
(please see article for details).

Let's keep things simple and just implement a SEEK operation that looks 
for the next hole or data based on the offset.

Dean