Re: [PATCH, RFC 2/2] dm: support REQ_FLUSH directly

Hi Mike,

(08/27/10 23:13), Mike Snitzer wrote:

quoted

If there will be no need for supporting a request-based target
with num_flush_requests > 1, the special handling of flush
can be removed.

And since there is no such target in the current tree,
I don't object if you remove that part of code for good reason.

OK, certainly something to keep in mind.  But _really_ knowing the
multipath FLUSH+FUA performance difference (extra special-case code vs
none) requires a full FLUSH conversion of request-based DM anyway.

In general, request-based DM's barrier/flush code does carry a certain
maintenance overhead.  It is quite a bit of distracting code in the core
DM which isn't buying us anything.. so we _could_ just remove it and
never look back (until we have some specific need for num_flush_requests

quoted

1 in rq-based DM).

So, I'm not objecting to your idea.
Could you please create a patch to remove that?

Thanks,
-- 
Jun'ichi Nomura, NEC Corporation