[PATCH v8 12/18] scsi: Add host and host template flag 'host_tagset'

[John Garry]

From: Hannes Reinecke <hare@xxxxxxxx>

Add Host and host template flag 'host_tagset' so hostwide tagset can be
shared on multiple reply queues after the SCSI device's reply queue is
converted to blk-mq hw queue.

Tested-by: Don Brace<don.brace@xxxxxxxxxxxxx> #SCSI resv cmds patches used
Signed-off-by: Hannes Reinecke <hare@xxxxxxxx>
[jpg: Update comment on .can_queue and add Scsi_Host.host_tagset]
Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
---
 drivers/scsi/hosts.c     | 1 +
 drivers/scsi/scsi_lib.c  | 2 ++
 include/scsi/scsi_host.h | 9 ++++++++-
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 37d1c5565d90..2f162603876f 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -421,6 +421,7 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	shost->cmd_per_lun = sht->cmd_per_lun;
 	shost->unchecked_isa_dma = sht->unchecked_isa_dma;
 	shost->no_write_same = sht->no_write_same;
+	shost->host_tagset = sht->host_tagset;
 
 	if (shost_eh_deadline == -1 || !sht->eh_host_reset_handler)
 		shost->eh_deadline = -1;
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 7c6dd6f75190..cdef5d1777cb 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1891,6 +1891,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
 	tag_set->flags |=
 		BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);
 	tag_set->driver_data = shost;
+	if (shost->host_tagset)
+		tag_set->flags |= BLK_MQ_F_TAG_HCTX_SHARED;
 
 	return blk_mq_alloc_tag_set(tag_set);
 }
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 46ef8cccc982..701f178b20ae 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -436,6 +436,9 @@ struct scsi_host_template {
 	/* True if the controller does not support WRITE SAME */
 	unsigned no_write_same:1;
 
+	/* True if the host uses host-wide tagspace */
+	unsigned host_tagset:1;
+
 	/*
 	 * Countdown for host blocking with no commands outstanding.
 	 */
@@ -603,7 +606,8 @@ struct Scsi_Host {
 	 *
 	 * Note: it is assumed that each hardware queue has a queue depth of
 	 * can_queue. In other words, the total queue depth per host
-	 * is nr_hw_queues * can_queue.
+	 * is nr_hw_queues * can_queue. However, for when host_tagset is set,
+	 * the total queue depth is can_queue.
 	 */
 	unsigned nr_hw_queues;
 	unsigned active_mode:2;
@@ -634,6 +638,9 @@ struct Scsi_Host {
 	/* The controller does not support WRITE SAME */
 	unsigned no_write_same:1;
 
+	/* True if the host uses host-wide tagspace */
+	unsigned host_tagset:1;
+
 	/* Host responded with short (<36 bytes) INQUIRY result */
 	unsigned short_inquiry:1;
 
-- 
2.26.2