scsi: core: introduce force_blk_mq

Ming Lei · martinkpetersen · commit 2f31115e940c · 2018-03-14T23:31:13.000-04:00
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 &lt;osandov@fb.com&gt;,
Cc: "Martin K. Petersen" &lt;martin.petersen@oracle.com&gt;,
Cc: James Bottomley &lt;james.bottomley@hansenpartnership.com&gt;,
Cc: Christoph Hellwig &lt;hch@lst.de&gt;,
Cc: Don Brace &lt;don.brace@microsemi.com&gt;
Cc: Kashyap Desai &lt;kashyap.desai@broadcom.com&gt;
Cc: Mike Snitzer &lt;snitzer@redhat.com&gt;
Cc: Laurence Oberman &lt;loberman@redhat.com&gt;
Signed-off-by: Ming Lei &lt;ming.lei@redhat.com&gt;
Reviewed-by: Hannes Reinecke &lt;hare@suse.de&gt;
Reviewed-by: Christoph Hellwig &lt;hch@lst.de&gt;
Signed-off-by: Martin K. Petersen &lt;martin.petersen@oracle.com&gt;
diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
@@ -474,6 +474,7 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 		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);
diff --git 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.
 	 */
