dm: requeue from blk-mq dm_mq_queue_rq() using BLK_MQ_RQ_QUEUE_BUSY (45714fbe) · Commits · 戴 / test

Use BLK_MQ_RQ_QUEUE_BUSY to requeue a blk-mq request directly from the DM blk-mq device's .queue_rq. This cleans up the previous convoluted handling of request requeueing that would return BLK_MQ_RQ_QUEUE_OK (even though it wasn't) and then run blk_mq_requeue_request() followed by blk_mq_kick_requeue_list(). Also, document that DM blk-mq ontop of old request_fn devices cannot fail in clone_rq() since the clone request is preallocated as part of the pdu. Reported-by:

Christoph Hellwig <hch@lst.de> Signed-off-by:

Mike Snitzer <snitzer@redhat.com>

drivers/md/dm.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -2754,13 +2754,15 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
		if (dm_table_get_type(map) == DM_TYPE_REQUEST_BASED) {
		/* clone request is allocated at the end of the pdu */
		tio->clone = (void *)blk_mq_rq_to_pdu(rq) + sizeof(struct dm_rq_target_io);
		if (!clone_rq(rq, md, tio, GFP_ATOMIC))
		return BLK_MQ_RQ_QUEUE_BUSY;
		(void) clone_rq(rq, md, tio, GFP_ATOMIC);
		queue_kthread_work(&md->kworker, &tio->work);
		} else {
		/* Direct call is fine since .queue_rq allows allocations */
		if (map_request(tio, rq, md) == DM_MAPIO_REQUEUE)
		dm_requeue_unmapped_original_request(md, rq);
		if (map_request(tio, rq, md) == DM_MAPIO_REQUEUE) {
		/* Undo dm_start_request() before requeuing */
		rq_completed(md, rq_data_dir(rq), false);
		return BLK_MQ_RQ_QUEUE_BUSY;
		}
		}

		return BLK_MQ_RQ_QUEUE_OK;

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