On Thu, 2017-03-09 at 15:16 +0200, Sagi Grimberg wrote:

+int blk_mq_poll_batch(struct request_queue *q, unsigned int batch)
+{
+	struct blk_mq_hw_ctx *hctx;
+
+	if (!q->mq_ops || !q->mq_ops->poll_batch)
+		return 0;
+
+	hctx =3D blk_mq_map_queue(q, smp_processor_id());
+	return q->mq_ops->poll_batch(hctx, batch);
+}
+EXPORT_SYMBOL_GPL(blk_mq_poll_batch);

A new exported function without any documentation? Wow. Please add a header
above this function that documents at least which other completion processi=
ng
code can execute concurrently with this function and from which contexts th=
e
other completion processing code can be called (e.g. blk_mq_poll() and
.complete()).

Why to return if (!q->mq_ops || !q->mq_ops->poll_batch)? Shouldn't that be =
a
WARN_ON_ONCE() instead? I think it is an error to calling blk_mq_poll_batch=
()
against a queue that does not define .poll_batch().

Additionally, I think making the hardware context an argument of this funct=
ion
instead of using blk_mq_map_queue(q, smp_processor_id()) would make this
function much more versatile.

Bart.=