blk-mq: split out a __blk_mq_get_driver_tag helper

Allocation of the driver tag in the case of using a scheduler shares very
little code with the "normal" tag allocation.  Split out a new helper to
streamline this path, and untangle it from the complex normal tag
allocation.

This way also avoids to fail driver tag allocation because of inactive hctx
during cpu hotplug, and fixes potential hang risk.

Fixes: bf0beec0607d ("blk-mq: drain I/O when all CPUs in a hctx are offline")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: John Garry <john.garry@huawei.com>
Cc: Dongli Zhang <dongli.zhang@oracle.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 0 insertions, 29 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9a36ac1c1fa1..4f57d27bfa73 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1052,35 +1052,6 @@ static inline unsigned int queued_to_index(unsigned int queued)
 	return min(BLK_MQ_MAX_DISPATCH_ORDER - 1, ilog2(queued) + 1);
 }
 
-bool blk_mq_get_driver_tag(struct request *rq)
-{
-	struct blk_mq_alloc_data data = {
-		.q = rq->q,
-		.hctx = rq->mq_hctx,
-		.flags = BLK_MQ_REQ_NOWAIT,
-		.cmd_flags = rq->cmd_flags,
-	};
-	bool shared;
-
-	if (rq->tag != BLK_MQ_NO_TAG)
-		return true;
-
-	if (blk_mq_tag_is_reserved(data.hctx->sched_tags, rq->internal_tag))
-		data.flags |= BLK_MQ_REQ_RESERVED;
-
-	shared = blk_mq_tag_busy(data.hctx);
-	rq->tag = blk_mq_get_tag(&data);
-	if (rq->tag >= 0) {
-		if (shared) {
-			rq->rq_flags |= RQF_MQ_INFLIGHT;
-			atomic_inc(&data.hctx->nr_active);
-		}
-		data.hctx->tags->rqs[rq->tag] = rq;
-	}
-
-	return rq->tag != BLK_MQ_NO_TAG;
-}
-
 static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
 				int flags, void *key)
 {