rpcrdma: fix handling for RDMA_CM_EVENT_DEVICE_REMOVAL

Under the scenario of IB device bonding, when bringing down one of the
ports, or all ports, we saw xprtrdma entering a non-recoverable state
where it is not even possible to complete the disconnect and shut it
down the mount, requiring a reboot. Following debug, we saw that
transport connect never ended after receiving the
RDMA_CM_EVENT_DEVICE_REMOVAL callback.

The DEVICE_REMOVAL callback is irrespective of whether the CM_ID is
connected, and ESTABLISHED may not have happened. So need to work with
each of these states accordingly.

Fixes: 2acc5cae ('xprtrdma: Prevent dereferencing r_xprt->rx_ep after it is freed')
Cc: Sagi Grimberg <sagi.grimberg@vastdata.com>
Signed-off-by: Dan Aloni <dan.aloni@vastdata.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

net/sunrpc/xprtrdma/verbs.c

@@ -244,7 +244,11 @@ rpcrdma_cm_event_handler(struct rdma_cm_id *id, struct rdma_cm_event *event)
 	case RDMA_CM_EVENT_DEVICE_REMOVAL:
 		pr_info("rpcrdma: removing device %s for %pISpc\n",
 			ep->re_id->device->name, sap);
-		fallthrough;
+		switch (xchg(&ep->re_connect_status, -ENODEV)) {
+		case 0: goto wake_connect_worker;
+		case 1: goto disconnected;
+		}
+		return 0;
 	case RDMA_CM_EVENT_ADDR_CHANGE:
 		ep->re_connect_status = -ENODEV;
 		goto disconnected;