blk-mq: directly poll requests

Polling needs a bio with a valid bi_bdev, but neither of those are
guaranteed for polled driver requests. Make request based polling
directly use blk-mq's polling function instead.

When executing a request from a polled hctx, we know the request's
cookie, and that it's from a live blk-mq queue that supports polling, so
we can safely skip everything that bio_poll provides.

Cc: [email protected]
Reported-by: Martin Belanger <[email protected]>
Reported-by: Daniel Wagner <[email protected]>
Signed-off-by: Keith Busch <[email protected]>
Tested-by: Daniel Wagner <[email protected]>
Revieded-by: Daniel Wagner <[email protected]>
Reviewed-by: Chaitanya Kulkarni <[email protected]>
Reviewed-by: Sagi Grimberg <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Tested-by: Shin'ichiro Kawasaki <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: keithbusch

block/blk-mq.c

@@ -1359,16 +1359,14 @@ bool blk_rq_is_poll(struct request *rq)
 		return false;
 	if (rq->mq_hctx->type != HCTX_TYPE_POLL)
 		return false;
-	if (WARN_ON_ONCE(!rq->bio))
-		return false;
 	return true;
 }
 EXPORT_SYMBOL_GPL(blk_rq_is_poll);
 
 static void blk_rq_poll_completion(struct request *rq, struct completion *wait)
 {
 	do {
-		bio_poll(rq->bio, NULL, 0);
+		blk_mq_poll(rq->q, blk_rq_to_qc(rq), NULL, 0);
 		cond_resched();
 	} while (!completion_done(wait));
 }