smb: server: let smb_direct_cm_handler() call ib_drain_qp() after smb_direct_disconnect_rdma_work()

All handlers triggered by ib_drain_qp() should already see the
broken connection.

smb_direct_cm_handler() is called under a mutex of the rdma_cm,
we should make sure ib_drain_qp() and all rdma layer logic completes
and unlocks the mutex.

It means free_transport() will also already see the connection
as SMBDIRECT_SOCKET_DISCONNECTED, so we need to call
crdma_[un]lock_handler(sc->rdma.cm_id) around
ib_drain_qp(), rdma_destroy_qp(), ib_free_cq() and ib_dealloc_pd().

Otherwise we free resources while the ib_drain_qp() within
smb_direct_cm_handler() is still running.

We have to unlock before rdma_destroy_id() as it locks again.

Fixes: 141fa98 ("ksmbd: call ib_drain_qp when disconnected")
Fixes: 4c564f0 ("smb: server: make use of common smbdirect_socket")
Cc: Namjae Jeon <[email protected]>
Cc: Steve French <[email protected]>
Cc: Tom Talpey <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Stefan Metzmacher <[email protected]>
Acked-by: Namjae Jeon <[email protected]>
Signed-off-by: Steve French <[email protected]>

Author: metze-samba

fs/smb/server/transport_rdma.c

@@ -466,6 +466,9 @@ static void free_transport(struct smb_direct_transport *t)
 	disable_delayed_work_sync(&sc->idle.timer_work);
 	disable_work_sync(&sc->idle.immediate_work);
 
+	if (sc->rdma.cm_id)
+		rdma_lock_handler(sc->rdma.cm_id);
+
 	if (sc->ib.qp) {
 		ib_drain_qp(sc->ib.qp);
 		sc->ib.qp = NULL;
@@ -494,8 +497,10 @@ static void free_transport(struct smb_direct_transport *t)
 		ib_free_cq(sc->ib.recv_cq);
 	if (sc->ib.pd)
 		ib_dealloc_pd(sc->ib.pd);
-	if (sc->rdma.cm_id)
+	if (sc->rdma.cm_id) {
+		rdma_unlock_handler(sc->rdma.cm_id);
 		rdma_destroy_id(sc->rdma.cm_id);
+	}
 
 	smb_direct_destroy_pools(sc);
 	ksmbd_conn_free(KSMBD_TRANS(t)->conn);
@@ -1724,10 +1729,10 @@ static int smb_direct_cm_handler(struct rdma_cm_id *cm_id,
 	}
 	case RDMA_CM_EVENT_DEVICE_REMOVAL:
 	case RDMA_CM_EVENT_DISCONNECTED: {
-		ib_drain_qp(sc->ib.qp);
-
 		sc->status = SMBDIRECT_SOCKET_DISCONNECTED;
 		smb_direct_disconnect_rdma_work(&sc->disconnect_work);
+		if (sc->ib.qp)
+			ib_drain_qp(sc->ib.qp);
 		break;
 	}
 	case RDMA_CM_EVENT_CONNECT_ERROR: {