RDMA/device: Expose ib_device_try_get(()

It turns out future patches need this capability quite widely now, not
just for netlink, so provide two global functions to manage the
registration lock refcount.

This also moves the point the lock becomes 1 to within
ib_register_device() so that the semantics of the public API are very sane
and clear. Calling ib_device_try_get() will fail on devices that are only
allocated but not yet registered.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
index 8872453e26c0..238ec42778ef 100644
--- a/drivers/infiniband/core/device.c
+++ b/drivers/infiniband/core/device.c
@@ -156,19 +156,26 @@ struct ib_device *ib_device_get_by_index(u32 index)
 	down_read(&lists_rwsem);
 	device = __ib_device_get_by_index(index);
 	if (device) {
-		/* Do not return a device if unregistration has started. */
-		if (!refcount_inc_not_zero(&device->refcount))
+		if (!ib_device_try_get(device))
 			device = NULL;
 	}
 	up_read(&lists_rwsem);
 	return device;
 }
 
+/**
+ * ib_device_put - Release IB device reference
+ * @device: device whose reference to be released
+ *
+ * ib_device_put() releases reference to the IB device to allow it to be
+ * unregistered and eventually free.
+ */
 void ib_device_put(struct ib_device *device)
 {
 	if (refcount_dec_and_test(&device->refcount))
 		complete(&device->unreg_completion);
 }
+EXPORT_SYMBOL(ib_device_put);
 
 static struct ib_device *__ib_device_get_by_name(const char *name)
 {
@@ -303,7 +310,6 @@ struct ib_device *ib_alloc_device(size_t size)
 	rwlock_init(&device->client_data_lock);
 	INIT_LIST_HEAD(&device->client_data_list);
 	INIT_LIST_HEAD(&device->port_list);
-	refcount_set(&device->refcount, 1);
 	init_completion(&device->unreg_completion);
 
 	return device;
@@ -620,6 +626,7 @@ int ib_register_device(struct ib_device *device, const char *name,
 		goto cg_cleanup;
 	}
 
+	refcount_set(&device->refcount, 1);
 	device->reg_state = IB_DEV_REGISTERED;
 
 	list_for_each_entry(client, &client_list, list)