Re: [PATCH 2/3] NFSv4.1 mark layout when already returned

[Boaz Harrosh <bharrosh@panasas.com>]

On 06/11/2012 06:08 PM, Adamson, Andy wrote:

>> You need to wait for in-flight I/Os to either succeed, fail (e.g. time out),
>> or be aborted.  The non-successful cases are going to be reported by the
>> objects layout driver so the MDS can recover from these errors.
> 

> The object layout driver may have this requirement, but the file
> layout driver does not.


I do not see the different texts In that matter. All I see is that
for objects all the core-pnfs wording applies + the error reporting
as part of LAYOUTRETURN.

Specifically I do not see any exemption of files layout about using
layouts (segments) after a LAYOUTRETURN was sent.

And I do not agree with Benny in regard of fencing off. Objects has,
and is specifically specified, a very robust mechanism of "fencing off"
just as files has.

And I do not see anywhere, where it is permitted to the client to
send new RPCs using the same (old) layout_segment after it was returned.
Which what your patch does, because there is a race between pnfs_layout_return()
and paglist_read/write.

What is so wrong with waiting for layout_segment reference to drop
to zero? You still did not explain. What are you trying to solve
by sending a LAYOUTRETURN, before layout_segment is all released?
Please explain?

Thanks
Boaz