[Lustre-devel] client-side reply handling

Andreas Dilger adilger at sun.com
Thu Dec 3 13:17:51 PST 2009

On 2009-12-03, at 08:00, Eric Barton wrote:
> Edited from IRC...
>> <Liang> eeb_: do you mean, we can be 100% sure it's safe to unpack
>>        in-place only when the buffer is unlinked? so it is better
>>        to unregister reply buffer before calling into
>>        after_reply()->unpack_reply()?
> Yes, I think so.  While the reply buffer remains attached, it's
> possible to overwrite it at any time.  This could happen if...
> a) The server is buggy or malign

Let's hope we never have to worry about malicious server nodes...

> b) The request is re-sent and the same reply matchbits are used,
>   which is what I think happens currently for non-bulk reqs.

In theory, the reply to the re-sent request should be identical due
to reply reconstruction, so it shouldn't matter if it happens to
overwrite the same buffer.

> ...so unlikely, but possible.

Cheers, Andreas
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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