SUNRPC: Don't hold the transport lock when receiving backchannel data

The backchannel request has no associated task, so it is going nowhere
until we call xprt_complete_bc_request().
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

net/sunrpc/backchannel_rqst.c

@@ -171,10 +171,10 @@ int xprt_setup_bc(struct rpc_xprt *xprt, unsigned int min_reqs)
 	/*
 	 * Add the temporary list to the backchannel preallocation list
 	 */
-	spin_lock_bh(&xprt->bc_pa_lock);
+	spin_lock(&xprt->bc_pa_lock);
 	list_splice(&tmp_list, &xprt->bc_pa_list);
 	xprt_inc_alloc_count(xprt, min_reqs);
-	spin_unlock_bh(&xprt->bc_pa_lock);
+	spin_unlock(&xprt->bc_pa_lock);
 
 	dprintk("RPC:       setup backchannel transport done\n");
 	return 0;

net/sunrpc/xprtsock.c

@@ -1389,11 +1389,9 @@ static int xs_tcp_read_callback(struct rpc_xprt *xprt,
 				container_of(xprt, struct sock_xprt, xprt);
 	struct rpc_rqst *req;
 
-	/* Look up and lock the request corresponding to the given XID */
-	spin_lock_bh(&xprt->transport_lock);
+	/* Look up the request corresponding to the given XID */
 	req = xprt_lookup_bc_request(xprt, transport->tcp_xid);
 	if (req == NULL) {
-		spin_unlock_bh(&xprt->transport_lock);
 		printk(KERN_WARNING "Callback slot table overflowed\n");
 		xprt_force_disconnect(xprt);
 		return -1;
@@ -1404,7 +1402,6 @@ static int xs_tcp_read_callback(struct rpc_xprt *xprt,
 
 	if (!(transport->tcp_flags & TCP_RCV_COPY_DATA))
 		xprt_complete_bc_request(req, transport->tcp_copied);
-	spin_unlock_bh(&xprt->transport_lock);
 
 	return 0;
 }