xprtrdma: Fix additional uses of spin_lock_irqsave(rb_lock)

Clean up.

rb_lock critical sections added in rpcrdma_ep_post_extra_recv()
should have first been converted to use normal spin_lock now that
the reply handler is a work queue.

The backchannel set up code should use the appropriate helper
instead of open-coding a rb_recv_bufs list add.

Problem introduced by glib patch re-ordering on my part.

Fixes: f531a5db ('xprtrdma: Pre-allocate backward rpc_rqst')
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Devesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/backchannel.c

@@ -84,9 +84,7 @@ static int rpcrdma_bc_setup_rqst(struct rpcrdma_xprt *r_xprt,
 static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
 				 unsigned int count)
 {
-	struct rpcrdma_buffer *buffers = &r_xprt->rx_buf;
 	struct rpcrdma_rep *rep;
-	unsigned long flags;
 	int rc = 0;
 
 	while (count--) {
@@ -98,9 +96,7 @@ static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
 			break;
 		}
 
-		spin_lock_irqsave(&buffers->rb_lock, flags);
-		list_add(&rep->rr_list, &buffers->rb_recv_bufs);
-		spin_unlock_irqrestore(&buffers->rb_lock, flags);
+		rpcrdma_recv_buffer_put(rep);
 	}
 
 	return rc;

net/sunrpc/xprtrdma/verbs.c

@@ -1338,15 +1338,14 @@ rpcrdma_ep_post_extra_recv(struct rpcrdma_xprt *r_xprt, unsigned int count)
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
 	struct rpcrdma_ep *ep = &r_xprt->rx_ep;
 	struct rpcrdma_rep *rep;
-	unsigned long flags;
 	int rc;
 
 	while (count--) {
-		spin_lock_irqsave(&buffers->rb_lock, flags);
+		spin_lock(&buffers->rb_lock);
 		if (list_empty(&buffers->rb_recv_bufs))
 			goto out_reqbuf;
 		rep = rpcrdma_buffer_get_rep_locked(buffers);
-		spin_unlock_irqrestore(&buffers->rb_lock, flags);
+		spin_unlock(&buffers->rb_lock);
 
 		rc = rpcrdma_ep_post_recv(ia, ep, rep);
 		if (rc)
@@ -1356,7 +1355,7 @@ rpcrdma_ep_post_extra_recv(struct rpcrdma_xprt *r_xprt, unsigned int count)
 	return 0;
 
 out_reqbuf:
-	spin_unlock_irqrestore(&buffers->rb_lock, flags);
+	spin_unlock(&buffers->rb_lock);
 	pr_warn("%s: no extra receive buffers\n", __func__);
 	return -ENOMEM;