SUNRPC: Refactor rpc_xdr_buf_init()

Clean up: there is some XDR initialization logic that is common
to the forward channel and backchannel. Move it to an XDR header
so it can be shared.

rpc_rqst::rq_buffer points to a buffer containing big-endian data.
Update its annotation as part of the clean up.

Signed-off-by: Chuck Lever <[e-mail]>
Signed-off-by: Anna Schumaker <[e-mail]>

include/linux/sunrpc/xdr.h

···
 			len;		/* Length of XDR encoded message */
 };
 
+static inline void
+xdr_buf_init(struct xdr_buf *buf, void *start, size_t len)
+{
+	buf->head[0].iov_base = start;
+	buf->head[0].iov_len = len;
+	buf->tail[0].iov_len = 0;
+	buf->page_len = 0;
+	buf->flags = 0;
+	buf->len = 0;
+	buf->buflen = len;
+}
+
 /*
  * pre-xdr'ed macros.
  */

include/linux/sunrpc/xprt.h

···
 	void (*rq_release_snd_buf)(struct rpc_rqst *); /* release rq_enc_pages */
 	struct list_head	rq_list;
 
-	__u32 *			rq_buffer;	/* XDR encode buffer */
+	void			*rq_buffer;	/* Call XDR encode buffer */
 	size_t			rq_callsize,
 				rq_rcvsize;
 	size_t			rq_xmit_bytes_sent;	/* total bytes sent */

net/sunrpc/backchannel_rqst.c

···
 	page = alloc_page(gfp_flags);
 	if (page == NULL)
 		return -ENOMEM;
-	buf->head[0].iov_base = page_address(page);
-	buf->head[0].iov_len = PAGE_SIZE;
-	buf->tail[0].iov_base = NULL;
-	buf->tail[0].iov_len = 0;
-	buf->page_len = 0;
-	buf->len = 0;
-	buf->buflen = PAGE_SIZE;
+	xdr_buf_init(buf, page_address(page), PAGE_SIZE);
 	return 0;
 }
 

net/sunrpc/clnt.c

···
 	task->tk_rqstp->rq_bytes_sent = 0;
 }
 
-static inline void
-rpc_xdr_buf_init(struct xdr_buf *buf, void *start, size_t len)
-{
-	buf->head[0].iov_base = start;
-	buf->head[0].iov_len = len;
-	buf->tail[0].iov_len = 0;
-	buf->page_len = 0;
-	buf->flags = 0;
-	buf->len = 0;
-	buf->buflen = len;
-}
-
 /*
  * 3.	Encode arguments of an RPC call
  */
···
 
 	dprint_status(task);
 
-	rpc_xdr_buf_init(&req->rq_snd_buf,
-			 req->rq_buffer,
-			 req->rq_callsize);
-	rpc_xdr_buf_init(&req->rq_rcv_buf,
-			 (char *)req->rq_buffer + req->rq_callsize,
-			 req->rq_rcvsize);
+	xdr_buf_init(&req->rq_snd_buf,
+		     req->rq_buffer,
+		     req->rq_callsize);
+	xdr_buf_init(&req->rq_rcv_buf,
+		     (char *)req->rq_buffer + req->rq_callsize,
+		     req->rq_rcvsize);
 
 	p = rpc_encode_header(task);
 	if (p == NULL) {

net/sunrpc/xprtrdma/backchannel.c

···
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
 	struct rpcrdma_regbuf *rb;
 	struct rpcrdma_req *req;
-	struct xdr_buf *buf;
 	size_t size;
 
 	req = rpcrdma_create_req(r_xprt);
···
 	req->rl_sendbuf = rb;
 	/* so that rpcr_to_rdmar works when receiving a request */
 	rqst->rq_buffer = (void *)req->rl_sendbuf->rg_base;
-
-	buf = &rqst->rq_snd_buf;
-	buf->head[0].iov_base = rqst->rq_buffer;
-	buf->head[0].iov_len = 0;
-	buf->tail[0].iov_base = NULL;
-	buf->tail[0].iov_len = 0;
-	buf->page_len = 0;
-	buf->len = 0;
-	buf->buflen = size;
-
+	xdr_buf_init(&rqst->rq_snd_buf, rqst->rq_buffer, size);
 	return 0;
 
 out_fail: