Re: [PATCH 3/9] IB: add a helper to safely drain a QP

[Sagi Grimberg <sagig-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>]

> That won't work for iWARP.  Is this code new?  I didn't see any errors that would result from this code when I tested iSER over
> cxgb4 with the old iwarp support patches.

It's there since ~3.17 I think...

>
> Perhaps we need another way to do this?  Like a completion object in the QP that gets triggered when the SQ and RQ become empty
> after a transition to ERROR (and CLOSING for iwarp).  Then a core service that just waits until the QP is empty.  Implementation of
> this design would hit the providers though since only they know when the flush is completed.

ULPs need a drain functionality, so ib_drain_qp() is the way to go...

How about we add a drain_qp() callout and have:

	if (qp->device->drain_qp) {
		qp->device->drain_qp();
		return;
	}

	IB drain qp logic...

This way iWARP devices can have their own magic on how to implement this
functionality.

Thoughts?
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