SUNRPC: Add a bvec array to struct xdr_buf for use with iovec_iter()

Add a bvec array to struct xdr_buf, and have the client allocate it
when we need to receive data into pages.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

include/linux/sunrpc/xdr.h

@@ -18,6 +18,7 @@
 #include <asm/unaligned.h>
 #include <linux/scatterlist.h>
 
+struct bio_vec;
 struct rpc_rqst;
 
 /*
@@ -52,6 +53,7 @@ struct xdr_buf {
 	struct kvec	head[1],	/* RPC header + non-page data */
 			tail[1];	/* Appended after page data */
 
+	struct bio_vec	*bvec;
 	struct page **	pages;		/* Array of pages */
 	unsigned int	page_base,	/* Start of page data */
 			page_len,	/* Length of page data */
@@ -70,6 +72,8 @@ 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->bvec = NULL;
+	buf->pages = NULL;
 	buf->page_len = 0;
 	buf->flags = 0;
 	buf->len = 0;
@@ -116,6 +120,9 @@ __be32 *xdr_decode_netobj(__be32 *p, struct xdr_netobj *);
 void	xdr_inline_pages(struct xdr_buf *, unsigned int,
 			 struct page **, unsigned int, unsigned int);
 void	xdr_terminate_string(struct xdr_buf *, const u32);
+size_t	xdr_buf_pagecount(struct xdr_buf *buf);
+int	xdr_alloc_bvec(struct xdr_buf *buf, gfp_t gfp);
+void	xdr_free_bvec(struct xdr_buf *buf);
 
 static inline __be32 *xdr_encode_array(__be32 *p, const void *s, unsigned int len)
 {

include/linux/sunrpc/xprt.h

@@ -141,6 +141,7 @@ struct rpc_xprt_ops {
 	void		(*connect)(struct rpc_xprt *xprt, struct rpc_task *task);
 	int		(*buf_alloc)(struct rpc_task *task);
 	void		(*buf_free)(struct rpc_task *task);
+	void		(*prepare_request)(struct rpc_rqst *req);
 	int		(*send_request)(struct rpc_rqst *req);
 	void		(*set_retrans_timeout)(struct rpc_task *task);
 	void		(*timer)(struct rpc_xprt *xprt, struct rpc_task *task);
@@ -343,6 +344,7 @@ int			xprt_reserve_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task);
 void			xprt_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task);
 void			xprt_free_slot(struct rpc_xprt *xprt,
 				       struct rpc_rqst *req);
+void			xprt_request_prepare(struct rpc_rqst *req);
 bool			xprt_prepare_transmit(struct rpc_task *task);
 void			xprt_request_enqueue_transmit(struct rpc_task *task);
 void			xprt_request_enqueue_receive(struct rpc_task *task);

net/sunrpc/clnt.c

@@ -1753,6 +1753,8 @@ rpc_xdr_encode(struct rpc_task *task)
 
 	task->tk_status = rpcauth_wrap_req(task, encode, req, p,
 			task->tk_msg.rpc_argp);
+	if (task->tk_status == 0)
+		xprt_request_prepare(req);
 }
 
 /*
@@ -1768,7 +1770,7 @@ call_encode(struct rpc_task *task)
 	/* Did the encode result in an error condition? */
 	if (task->tk_status != 0) {
 		/* Was the error nonfatal? */
-		if (task->tk_status == -EAGAIN)
+		if (task->tk_status == -EAGAIN || task->tk_status == -ENOMEM)
 			rpc_delay(task, HZ >> 4);
 		else
 			rpc_exit(task, task->tk_status);

net/sunrpc/xdr.c

@@ -15,6 +15,7 @@
 #include <linux/errno.h>
 #include <linux/sunrpc/xdr.h>
 #include <linux/sunrpc/msg_prot.h>
+#include <linux/bvec.h>
 
 /*
  * XDR functions for basic NFS types
@@ -128,6 +129,39 @@ xdr_terminate_string(struct xdr_buf *buf, const u32 len)
 }
 EXPORT_SYMBOL_GPL(xdr_terminate_string);
 
+size_t
+xdr_buf_pagecount(struct xdr_buf *buf)
+{
+	if (!buf->page_len)
+		return 0;
+	return (buf->page_base + buf->page_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+}
+
+int
+xdr_alloc_bvec(struct xdr_buf *buf, gfp_t gfp)
+{
+	size_t i, n = xdr_buf_pagecount(buf);
+
+	if (n != 0 && buf->bvec == NULL) {
+		buf->bvec = kmalloc_array(n, sizeof(buf->bvec[0]), gfp);
+		if (!buf->bvec)
+			return -ENOMEM;
+		for (i = 0; i < n; i++) {
+			buf->bvec[i].bv_page = buf->pages[i];
+			buf->bvec[i].bv_len = PAGE_SIZE;
+			buf->bvec[i].bv_offset = 0;
+		}
+	}
+	return 0;
+}
+
+void
+xdr_free_bvec(struct xdr_buf *buf)
+{
+	kfree(buf->bvec);
+	buf->bvec = NULL;
+}
+
 void
 xdr_inline_pages(struct xdr_buf *xdr, unsigned int offset,
 		 struct page **pages, unsigned int base, unsigned int len)

net/sunrpc/xprt.c

@@ -1263,6 +1263,22 @@ xprt_request_dequeue_transmit(struct rpc_task *task)
 	spin_unlock(&xprt->queue_lock);
 }
 
+/**
+ * xprt_request_prepare - prepare an encoded request for transport
+ * @req: pointer to rpc_rqst
+ *
+ * Calls into the transport layer to do whatever is needed to prepare
+ * the request for transmission or receive.
+ */
+void
+xprt_request_prepare(struct rpc_rqst *req)
+{
+	struct rpc_xprt *xprt = req->rq_xprt;
+
+	if (xprt->ops->prepare_request)
+		xprt->ops->prepare_request(req);
+}
+
 /**
  * xprt_request_need_retransmit - Test if a task needs retransmission
  * @task: pointer to rpc_task
@@ -1727,6 +1743,7 @@ void xprt_release(struct rpc_task *task)
 	if (req->rq_buffer)
 		xprt->ops->buf_free(task);
 	xprt_inject_disconnect(xprt);
+	xdr_free_bvec(&req->rq_rcv_buf);
 	if (req->rq_cred != NULL)
 		put_rpccred(req->rq_cred);
 	task->tk_rqstp = NULL;