>From scsi driver view, it is a bit troublesome to support both blk-mq
and non-blk-mq at the same time, especially when drivers need to support
multi hw-queue.

This patch introduces 'force_blk_mq' to scsi_host_template so that drivers
can provide blk-mq only support, so driver code can avoid the trouble
for supporting both.

Cc: Omar Sandoval <osan...@fb.com>,
Cc: "Martin K. Petersen" <martin.peter...@oracle.com>,
Cc: James Bottomley <james.bottom...@hansenpartnership.com>,
Cc: Christoph Hellwig <h...@lst.de>,
Cc: Don Brace <don.br...@microsemi.com>
Cc: Kashyap Desai <kashyap.de...@broadcom.com>
Cc: Mike Snitzer <snit...@redhat.com>
Cc: Laurence Oberman <lober...@redhat.com>
Reviewed-by: Hannes Reinecke <h...@suse.de>
Reviewed-by: Christoph Hellwig <h...@lst.de>
Signed-off-by: Ming Lei <ming....@redhat.com>
 drivers/scsi/hosts.c     | 1 +
 include/scsi/scsi_host.h | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 57bf43e34863..cbbc32df7595 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -477,6 +477,7 @@ 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;
        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
index 1a1df0d21ee3..6c6366f0bd15 100644
--- 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.

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