xprtrdma: De-duplicate "allocate new, free old regbuf"

Clean up by providing an API to do this common task.

At this point, the difference between rpcrdma_get_sendbuf and
rpcrdma_get_recvbuf has become tiny. These can be collapsed into a
single helper.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/transport.c

@@ -585,52 +585,15 @@ xprt_rdma_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *rqst)
 	rpc_wake_up_next(&xprt->backlog);
 }
 
-static bool
-rpcrdma_get_sendbuf(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
-		    size_t size, gfp_t flags)
+static bool rpcrdma_check_regbuf(struct rpcrdma_xprt *r_xprt,
+				 struct rpcrdma_regbuf *rb, size_t size,
+				 gfp_t flags)
 {
-	struct rpcrdma_regbuf *rb;
-
-	if (likely(rdmab_length(req->rl_sendbuf) >= size))
-		return true;
-
-	rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, flags);
-	if (!rb)
-		return false;
-
-	rpcrdma_free_regbuf(req->rl_sendbuf);
-	r_xprt->rx_stats.hardway_register_count += size;
-	req->rl_sendbuf = rb;
-	return true;
-}
-
-/* The rq_rcv_buf is used only if a Reply chunk is necessary.
- * The decision to use a Reply chunk is made later in
- * rpcrdma_marshal_req. This buffer is registered at that time.
- *
- * Otherwise, the associated RPC Reply arrives in a separate
- * Receive buffer, arbitrarily chosen by the HCA. The buffer
- * allocated here for the RPC Reply is not utilized in that
- * case. See rpcrdma_inline_fixup.
- *
- * A regbuf is used here to remember the buffer size.
- */
-static bool
-rpcrdma_get_recvbuf(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
-		    size_t size, gfp_t flags)
-{
-	struct rpcrdma_regbuf *rb;
-
-	if (likely(rdmab_length(req->rl_recvbuf) >= size))
-		return true;
-
-	rb = rpcrdma_alloc_regbuf(size, DMA_NONE, flags);
-	if (!rb)
+	if (unlikely(rdmab_length(rb) < size)) {
+		if (!rpcrdma_regbuf_realloc(rb, size, flags))
 			return false;
-
-	rpcrdma_free_regbuf(req->rl_recvbuf);
 		r_xprt->rx_stats.hardway_register_count += size;
-	req->rl_recvbuf = rb;
+	}
 	return true;
 }
 
@@ -655,9 +618,11 @@ xprt_rdma_allocate(struct rpc_task *task)
 	if (RPC_IS_SWAPPER(task))
 		flags = __GFP_MEMALLOC | GFP_NOWAIT | __GFP_NOWARN;
 
-	if (!rpcrdma_get_sendbuf(r_xprt, req, rqst->rq_callsize, flags))
+	if (!rpcrdma_check_regbuf(r_xprt, req->rl_sendbuf, rqst->rq_callsize,
+				  flags))
 		goto out_fail;
-	if (!rpcrdma_get_recvbuf(r_xprt, req, rqst->rq_rcvsize, flags))
+	if (!rpcrdma_check_regbuf(r_xprt, req->rl_recvbuf, rqst->rq_rcvsize,
+				  flags))
 		goto out_fail;
 
 	rqst->rq_buffer = rdmab_data(req->rl_sendbuf);

net/sunrpc/xprtrdma/verbs.c

@@ -1399,6 +1399,31 @@ rpcrdma_alloc_regbuf(size_t size, enum dma_data_direction direction,
 	return rb;
 }
 
+/**
+ * rpcrdma_regbuf_realloc - re-allocate a SEND/RECV buffer
+ * @rb: regbuf to reallocate
+ * @size: size of buffer to be allocated, in bytes
+ * @flags: GFP flags
+ *
+ * Returns true if reallocation was successful. If false is
+ * returned, @rb is left untouched.
+ */
+bool rpcrdma_regbuf_realloc(struct rpcrdma_regbuf *rb, size_t size, gfp_t flags)
+{
+	void *buf;
+
+	buf = kmalloc(size, flags);
+	if (!buf)
+		return false;
+
+	rpcrdma_dma_unmap_regbuf(rb);
+	kfree(rb->rg_data);
+
+	rb->rg_data = buf;
+	rb->rg_iov.length = size;
+	return true;
+}
+
 /**
  * __rpcrdma_map_regbuf - DMA-map a regbuf
  * @ia: controlling rpcrdma_ia

net/sunrpc/xprtrdma/xprt_rdma.h

@@ -552,6 +552,8 @@ void rpcrdma_recv_buffer_put(struct rpcrdma_rep *);
 
 struct rpcrdma_regbuf *rpcrdma_alloc_regbuf(size_t, enum dma_data_direction,
 					    gfp_t);
+bool rpcrdma_regbuf_realloc(struct rpcrdma_regbuf *rb, size_t size,
+			    gfp_t flags);
 bool __rpcrdma_dma_map_regbuf(struct rpcrdma_ia *, struct rpcrdma_regbuf *);
 void rpcrdma_free_regbuf(struct rpcrdma_regbuf *);