vhost-scsi: Drop vhost_scsi_mutex use in port callouts

We are using the vhost_scsi_mutex to make sure vhost_scsi_port_link and
vhost_scsi_port_unlink see if vhost_scsi_clear_endpoint has cleared
tpg->vhost_scsi and it can't be freed while they are using.

However, we currently set the tpg->vhost_scsi pointer while holding
tv_tpg_mutex. So, we can just hold that while calling
vhost_scsi_hotplug/hotunplug. We then don't need to hold the
vhost_scsi_mutex while vhost_scsi_clear_endpoint is holding it and doing
a flush which could cause the LUN map/unmap to have to wait on another
device's flush.
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20230321020624.13323-7-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/scsi.c

@@ -2040,15 +2040,10 @@ static int vhost_scsi_port_link(struct se_portal_group *se_tpg,
 	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
 				struct vhost_scsi_tpg, se_tpg);
 
-	mutex_lock(&vhost_scsi_mutex);
-
 	mutex_lock(&tpg->tv_tpg_mutex);
 	tpg->tv_tpg_port_count++;
-	mutex_unlock(&tpg->tv_tpg_mutex);
-
 	vhost_scsi_hotplug(tpg, lun);
-
-	mutex_unlock(&vhost_scsi_mutex);
+	mutex_unlock(&tpg->tv_tpg_mutex);
 
 	return 0;
 }
@@ -2059,15 +2054,10 @@ static void vhost_scsi_port_unlink(struct se_portal_group *se_tpg,
 	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
 				struct vhost_scsi_tpg, se_tpg);
 
-	mutex_lock(&vhost_scsi_mutex);
-
 	mutex_lock(&tpg->tv_tpg_mutex);
 	tpg->tv_tpg_port_count--;
-	mutex_unlock(&tpg->tv_tpg_mutex);
-
 	vhost_scsi_hotunplug(tpg, lun);
-
-	mutex_unlock(&vhost_scsi_mutex);
+	mutex_unlock(&tpg->tv_tpg_mutex);
 }
 
 static ssize_t vhost_scsi_tpg_attrib_fabric_prot_type_store(