block: switch polling to be bio based

Replace the blk_poll interface that requires the caller to keep a queue
and cookie from the submissions with polling based on the bio.

Polling for the bio itself leads to a few advantages:

 - the cookie construction can made entirely private in blk-mq.c
 - the caller does not need to remember the request_queue and cookie
   separately and thus sidesteps their lifetime issues
 - keeping the device and the cookie inside the bio allows to trivially
   support polling BIOs remapping by stacking drivers
 - a lot of code to propagate the cookie back up the submission path can
   be removed entirely.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Link: https://lore.kernel.org/r/20211012111226.760968-15-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 8 insertions, 2 deletions

diff --git a/block/blk-exec.c b/block/blk-exec.c
index 1fa7f25e5726..55f0cd34b37b 100644
--- a/block/blk-exec.c
+++ b/block/blk-exec.c
@@ -65,13 +65,19 @@ EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
 
 static bool blk_rq_is_poll(struct request *rq)
 {
-	return rq->mq_hctx && rq->mq_hctx->type == HCTX_TYPE_POLL;
+	if (!rq->mq_hctx)
+		return false;
+	if (rq->mq_hctx->type != HCTX_TYPE_POLL)
+		return false;
+	if (WARN_ON_ONCE(!rq->bio))
+		return false;
+	return true;
 }
 
 static void blk_rq_poll_completion(struct request *rq, struct completion *wait)
 {
 	do {
-		blk_poll(rq->q, request_to_qc_t(rq->mq_hctx, rq), 0);
+		bio_poll(rq->bio, 0);
 		cond_resched();
 	} while (!completion_done(wait));
 }