[PATCH 4.14 004/104] scsi: core: introduce force_blk_mq

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ming Lei <ming.lei@xxxxxxxxxx>

commit 2f31115e940c4afd49b99c33123534e2ac924ffb upstream.

This patch introduces 'force_blk_mq' to the scsi_host_template so that
drivers that have no desire to support the legacy I/O path can signal
blk-mq only support.

[mkp: commit desc]

Cc: Omar Sandoval <osandov@xxxxxx>,
Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>,
Cc: James Bottomley <james.bottomley@xxxxxxxxxxxxxxxxxxxxx>,
Cc: Christoph Hellwig <hch@xxxxxx>,
Cc: Don Brace <don.brace@xxxxxxxxxxxxx>
Cc: Kashyap Desai <kashyap.desai@xxxxxxxxxxxx>
Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
Cc: Laurence Oberman <loberman@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/scsi/hosts.c     |    1 +
 include/scsi/scsi_host.h |    3 +++
 2 files changed, 4 insertions(+)

--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -474,6 +474,7 @@ struct Scsi_Host *scsi_host_alloc(struct
 		shost->dma_boundary = 0xffffffff;
 
 	shost->use_blk_mq = scsi_use_blk_mq;
+	shost->use_blk_mq = scsi_use_blk_mq || shost->hostt->force_blk_mq;
 
 	device_initialize(&shost->shost_gendev);
 	dev_set_name(&shost->shost_gendev, "host%d", shost->host_no);
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -452,6 +452,9 @@ struct scsi_host_template {
 	/* True if the controller does not support WRITE SAME */
 	unsigned no_write_same:1;
 
+	/* True if the low-level driver supports blk-mq only */
+	unsigned force_blk_mq:1;
+
 	/*
 	 * Countdown for host blocking with no commands outstanding.
 	 */