Re: Write delegation

[Yudong Gao <stgyd@umich.edu>]

Thanks for the reply, Andy!

So the write delegation can only reduce the unnecessary open/close and
lock/locku. But if a client modify the same page for multiple times,
e.g. editing the file in a editor, is there any optimization to
prevent the client from sending the half-updated pages? Ideally only
the final update need to be put on the wire.

Thanks!

best,

Yudong

On Wed, Aug 4, 2010 at 1:59 PM, Andy Adamson <andros@netapp.com> wrote:
>
> On Aug 4, 2010, at 3:21 PM, Yudong Gao wrote:
>
>> Hi,
>>
>> I am not able to find the implementation of directory delegation,
>> either. Similarly, the callback functions CB_NOTIFY is not
>> implemented, either. I find that in preprocss_nfs41_op() in
>> callback_xdr.c, whenever a CB_NOTIFY is encountered, an
>> NFS4ERR_NOTSUPP is returned directly.
>
> CB_NOTIFY is not currently supported on the Linux NFS client.
>
>>
>> Am I missing something? Or they are just not supported in the current version?
>>
>> Thanks a lot!
>>
>> best,
>>
>> Yudong
>>
>> On Mon, Aug 2, 2010 at 5:17 PM, Yudong Gao <stgyd@umich.edu> wrote:
>>> Hi,
>>>
>>> I am looking at the delegation implementation in the source code of
>>> NFS 4.1 in kernel 2.6.32.15. I can find the code for read delegation,
>>> which is working and can serve the read requests locally. But I can
>>> never find the code about write delegation, which is supposed to cache
>>> the write update locally. I try to look at the functions including
>>> nfs_writepage(s), nfs_file_flush() but none of them checks or uses the
>>> write delegation.
>>>
>>> Is write delegation currently implemented in NFS 4.1?
>
> Write delegation is supported but I don't think write behavior changes - writes are still cached and flushed as without a write delegation. The write delegation does prevent open/close and lock/locku from being put on the wire.
>
> -->Andy
>
>>>
>>> Thanks!
>>>
>>> best,
>>>
>>> Yudong
>>>
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>