xprtrdma: buf_free not called for CB replies

Since commit 5a6d1db455 ("SUNRPC: Add a transport-specific private
field in rpc_rqst"), the rpc_rqst's for RPC-over-RDMA backchannel
operations leave rq_buffer set to NULL.

xprt_release does not invoke ->op->buf_free when rq_buffer is NULL.
The RPCRDMA_REQ_F_BACKCHANNEL check in xprt_rdma_free is therefore
redundant because xprt_rdma_free is not invoked for backchannel
requests.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/backchannel.c

@@ -43,7 +43,6 @@ static int rpcrdma_bc_setup_rqst(struct rpcrdma_xprt *r_xprt,
 	req = rpcrdma_create_req(r_xprt);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
-	__set_bit(RPCRDMA_REQ_F_BACKCHANNEL, &req->rl_flags);
 
 	rb = rpcrdma_alloc_regbuf(RPCRDMA_HDRBUF_SIZE,
 				  DMA_TO_DEVICE, GFP_KERNEL);

net/sunrpc/xprtrdma/transport.c

@@ -686,9 +686,6 @@ xprt_rdma_free(struct rpc_task *task)
 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
 	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 
-	if (test_bit(RPCRDMA_REQ_F_BACKCHANNEL, &req->rl_flags))
-		return;
-
 	dprintk("RPC:       %s: called on 0x%p\n", __func__, req->rl_reply);
 
 	if (test_bit(RPCRDMA_REQ_F_PENDING, &req->rl_flags))

net/sunrpc/xprtrdma/xprt_rdma.h

@@ -354,8 +354,7 @@ struct rpcrdma_req {
 
 /* rl_flags */
 enum {
-	RPCRDMA_REQ_F_BACKCHANNEL = 0,
-	RPCRDMA_REQ_F_PENDING,
+	RPCRDMA_REQ_F_PENDING = 0,
 	RPCRDMA_REQ_F_TX_RESOURCES,
 };