scsi: Add host and host template flag 'host_tagset'

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.

[jpg: Update comment on .can_queue and add Scsi_Host.host_tagset]

Signed-off-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Tested-by: Don Brace<don.brace@microsemi.com> #SCSI resv cmds patches used
Tested-by: Douglas Gilbert <dgilbert@interlog.com>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 37d1c55..2f16260 100644 (file)
--- 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 7affaaf..a89478a 100644 (file)
--- 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 46ef8cc..701f178 100644 (file)
--- 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;