RDMA/srpt: Introduce a reference count in struct srpt_device

This will be used to keep struct srpt_device around as long as either the
RDMA port exists or a LIO target port is associated with the struct
srpt_device.

Link: https://lore.kernel.org/r/20220727193415.1583860-3-bvanassche@acm.org
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Author: bvanassche

drivers/infiniband/ulp/srpt/ib_srpt.c

@@ -3104,6 +3104,18 @@ static int srpt_use_srq(struct srpt_device *sdev, bool use_srq)
 	return ret;
 }
 
+static void srpt_free_sdev(struct kref *refcnt)
+{
+	struct srpt_device *sdev = container_of(refcnt, typeof(*sdev), refcnt);
+
+	kfree(sdev);
+}
+
+static void srpt_sdev_put(struct srpt_device *sdev)
+{
+	kref_put(&sdev->refcnt, srpt_free_sdev);
+}
+
 /**
  * srpt_add_one - InfiniBand device addition callback function
  * @device: Describes a HCA.
@@ -3122,6 +3134,7 @@ static int srpt_add_one(struct ib_device *device)
 	if (!sdev)
 		return -ENOMEM;
 
+	kref_init(&sdev->refcnt);
 	sdev->device = device;
 	mutex_init(&sdev->sdev_mutex);
 
@@ -3217,7 +3230,7 @@ static int srpt_add_one(struct ib_device *device)
 	srpt_free_srq(sdev);
 	ib_dealloc_pd(sdev->pd);
 free_dev:
-	kfree(sdev);
+	srpt_sdev_put(sdev);
 	pr_info("%s(%s) failed.\n", __func__, dev_name(&device->dev));
 	return ret;
 }
@@ -3261,7 +3274,7 @@ static void srpt_remove_one(struct ib_device *device, void *client_data)
 
 	ib_dealloc_pd(sdev->pd);
 
-	kfree(sdev);
+	srpt_sdev_put(sdev);
 }
 
 static struct ib_client srpt_client = {

drivers/infiniband/ulp/srpt/ib_srpt.h

@@ -434,6 +434,7 @@ struct srpt_port {
 
 /**
  * struct srpt_device - information associated by SRPT with a single HCA
+ * @refcnt:	   Reference count for this device.
  * @device:        Backpointer to the struct ib_device managed by the IB core.
  * @pd:            IB protection domain.
  * @lkey:          L_Key (local key) with write access to all local memory.
@@ -449,6 +450,7 @@ struct srpt_port {
  * @port:          Information about the ports owned by this HCA.
  */
 struct srpt_device {
+	struct kref		refcnt;
 	struct ib_device	*device;
 	struct ib_pd		*pd;
 	u32			lkey;