[Lustre-devel] Query to understand the Lustre request/reply message

[Nicolas Williams]

On Wed, Oct 13, 2010 at 09:25:00AM +0300, Alexey Lyashkov wrote:
> 
> On Oct 13, 2010, at 08:42, Nicolas Williams wrote:
> > 
> > 
> > - add handlers for the new RPC to mdt_handler.c (for the MDS) or
> >   ost_handler.c (for the OST), and so on
> > 
> >   The handlers are responsible for knowing which buffers contain what,
> >   and for swabbing them.  You have to make sure that you don't swab a
> >   buffer more than once.
> > 
> BTW.
> That not enough.
> Some of operations wants to have own recostructors for replay/resend.

I glossed over replay/resend, mostly because I know little about them,
but also because they are completely orthogonal to the message format
details.  If you want to add an RPC then the first step should be to get
the RPC format designed and surrounding code up and running, then you
can take care of replay/resend.

> Some of operations want to have a return lock - as example MDS_GETATTR
> and MDS_REINT commands.

That too is orthogonal to the message formats.  The message format has
to have a buffer (field) declared to carry lock (or capability, or
whatever) bits, and some function has to be invoked to populate the
buffer in the reply.

Nico
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