[bug report] RDMA/devices: Re-organize device.c locking

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Jason Gunthorpe,

The patch 921eab1143aa: "RDMA/devices: Re-organize device.c locking"
from Feb 6, 2019, leads to the following static checker warning:

	drivers/infiniband/core/device.c:712 add_client_context()
	warn: missing error code 'ret'

drivers/infiniband/core/device.c
    689 static int add_client_context(struct ib_device *device,
    690 			      struct ib_client *client)
    691 {
    692 	int ret = 0;
    693 
    694 	if (!device->kverbs_provider && !client->no_kverbs_req)
    695 		return 0;
    696 
    697 	down_write(&device->client_data_rwsem);
    698 	/*
    699 	 * So long as the client is registered hold both the client and device
    700 	 * unregistration locks.
    701 	 */
    702 	if (!refcount_inc_not_zero(&client->uses))
    703 		goto out_unlock;
    704 	refcount_inc(&device->refcount);
    705 
    706 	/*
    707 	 * Another caller to add_client_context got here first and has already
    708 	 * completely initialized context.
    709 	 */
    710 	if (xa_get_mark(&device->client_data, client->client_id,
    711 		    CLIENT_DATA_REGISTERED))
--> 712 		goto out;

Hard to tell if ret should be zero or negative.

    713 
    714 	ret = xa_err(xa_store(&device->client_data, client->client_id, NULL,
    715 			      GFP_KERNEL));
    716 	if (ret)
    717 		goto out;
    718 	downgrade_write(&device->client_data_rwsem);
    719 	if (client->add) {
    720 		if (client->add(device)) {
    721 			/*
    722 			 * If a client fails to add then the error code is
    723 			 * ignored, but we won't call any more ops on this
    724 			 * client.
    725 			 */
    726 			xa_erase(&device->client_data, client->client_id);
    727 			up_read(&device->client_data_rwsem);
    728 			ib_device_put(device);
    729 			ib_client_put(client);
    730 			return 0;
    731 		}
    732 	}
    733 
    734 	/* Readers shall not see a client until add has been completed */
    735 	xa_set_mark(&device->client_data, client->client_id,
    736 		    CLIENT_DATA_REGISTERED);
    737 	up_read(&device->client_data_rwsem);
    738 	return 0;
    739 
    740 out:
    741 	ib_device_put(device);
    742 	ib_client_put(client);
    743 out_unlock:
    744 	up_write(&device->client_data_rwsem);
    745 	return ret;
    746 }

regards,
dan carpenter