nvme_fc: add module to ops template to allow module references

In nvme-fc: it's possible to have connected active controllers
and as no references are taken on the LLDD, the LLDD can be
unloaded.  The controller would enter a reconnect state and as
long as the LLDD resumed within the reconnect timeout, the
controller would resume.  But if a namespace on the controller
is the root device, allowing the driver to unload can be problematic.
To reload the driver, it may require new io to the boot device,
and as it's no longer connected we get into a catch-22 that
eventually fails, and the system locks up.

Fix this issue by taking a module reference for every connected
controller (which is what the core layer did to the transport
module). Reference is cleared when the controller is removed.

Acked-by: Himanshu Madhani <hmadhani@marvell.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/host/fc.c

@@ -342,7 +342,8 @@ nvme_fc_register_localport(struct nvme_fc_port_info *pinfo,
 	    !template->ls_req || !template->fcp_io ||
 	    !template->ls_abort || !template->fcp_abort ||
 	    !template->max_hw_queues || !template->max_sgl_segments ||
-	    !template->max_dif_sgl_segments || !template->dma_boundary) {
+	    !template->max_dif_sgl_segments || !template->dma_boundary ||
+	    !template->module) {
 		ret = -EINVAL;
 		goto out_reghost_failed;
 	}
@@ -2015,6 +2016,7 @@ nvme_fc_ctrl_free(struct kref *ref)
 {
 	struct nvme_fc_ctrl *ctrl =
 		container_of(ref, struct nvme_fc_ctrl, ref);
+	struct nvme_fc_lport *lport = ctrl->lport;
 	unsigned long flags;
 
 	if (ctrl->ctrl.tagset) {
@@ -2041,6 +2043,7 @@ nvme_fc_ctrl_free(struct kref *ref)
 	if (ctrl->ctrl.opts)
 		nvmf_free_options(ctrl->ctrl.opts);
 	kfree(ctrl);
+	module_put(lport->ops->module);
 }
 
 static void
@@ -3059,10 +3062,15 @@ nvme_fc_init_ctrl(struct device *dev, struct nvmf_ctrl_options *opts,
 		goto out_fail;
 	}
 
+	if (!try_module_get(lport->ops->module)) {
+		ret = -EUNATCH;
+		goto out_free_ctrl;
+	}
+
 	idx = ida_simple_get(&nvme_fc_ctrl_cnt, 0, 0, GFP_KERNEL);
 	if (idx < 0) {
 		ret = -ENOSPC;
-		goto out_free_ctrl;
+		goto out_mod_put;
 	}
 
 	ctrl->ctrl.opts = opts;
@@ -3215,6 +3223,8 @@ out_free_queues:
 out_free_ida:
 	put_device(ctrl->dev);
 	ida_simple_remove(&nvme_fc_ctrl_cnt, ctrl->cnum);
+out_mod_put:
+	module_put(lport->ops->module);
 out_free_ctrl:
 	kfree(ctrl);
 out_fail:

drivers/nvme/target/fcloop.c

@@ -850,6 +850,7 @@ fcloop_targetport_delete(struct nvmet_fc_target_port *targetport)
 #define FCLOOP_DMABOUND_4G		0xFFFFFFFF
 
 static struct nvme_fc_port_template fctemplate = {
+	.module			= THIS_MODULE,
 	.localport_delete	= fcloop_localport_delete,
 	.remoteport_delete	= fcloop_remoteport_delete,
 	.create_queue		= fcloop_create_queue,

drivers/scsi/lpfc/lpfc_nvme.c

@@ -1976,6 +1976,8 @@ out_unlock:
 
 /* Declare and initialization an instance of the FC NVME template. */
 static struct nvme_fc_port_template lpfc_nvme_template = {
+	.module	= THIS_MODULE,
+
 	/* initiator-based functions */
 	.localport_delete  = lpfc_nvme_localport_delete,
 	.remoteport_delete = lpfc_nvme_remoteport_delete,

drivers/scsi/qla2xxx/qla_nvme.c

@@ -610,6 +610,7 @@ static void qla_nvme_remoteport_delete(struct nvme_fc_remote_port *rport)
 }
 
 static struct nvme_fc_port_template qla_nvme_fc_transport = {
+	.module	= THIS_MODULE,
 	.localport_delete = qla_nvme_localport_delete,
 	.remoteport_delete = qla_nvme_remoteport_delete,
 	.create_queue   = qla_nvme_alloc_queue,

include/linux/nvme-fc-driver.h

@@ -270,6 +270,8 @@ struct nvme_fc_remote_port {
  *
  * Host/Initiator Transport Entrypoints/Parameters:
  *
+ * @module:  The LLDD module using the interface
+ *
  * @localport_delete:  The LLDD initiates deletion of a localport via
  *       nvme_fc_deregister_localport(). However, the teardown is
  *       asynchronous. This routine is called upon the completion of the
@@ -383,6 +385,8 @@ struct nvme_fc_remote_port {
  *       Value is Mandatory. Allowed to be zero.
  */
 struct nvme_fc_port_template {
+	struct module	*module;
+
 	/* initiator-based functions */
 	void	(*localport_delete)(struct nvme_fc_local_port *);
 	void	(*remoteport_delete)(struct nvme_fc_remote_port *);