1 files changed, 282 insertions, 0 deletions
diff --git a/net/sunrpc/xprtrdma/backchannel.c b/net/sunrpc/xprtrdma/backchannel.c
new file mode 100644
index 000000000..e4d84a13c
--- /dev/null
+++ b/net/sunrpc/xprtrdma/backchannel.c
@@ -0,0 +1,282 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2015-2020, Oracle and/or its affiliates.
+ *
+ * Support for reverse-direction RPCs on RPC/RDMA.
+ */
+
+#include <linux/sunrpc/xprt.h>
+#include <linux/sunrpc/svc.h>
+#include <linux/sunrpc/svc_xprt.h>
+#include <linux/sunrpc/svc_rdma.h>
+
+#include "xprt_rdma.h"
+#include <trace/events/rpcrdma.h>
+
+#undef RPCRDMA_BACKCHANNEL_DEBUG
+
+/**
+ * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
+ * @xprt: transport associated with these backchannel resources
+ * @reqs: number of concurrent incoming requests to expect
+ *
+ * Returns 0 on success; otherwise a negative errno
+ */
+int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
+{
+	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
+
+	r_xprt->rx_buf.rb_bc_srv_max_requests = RPCRDMA_BACKWARD_WRS >> 1;
+	trace_xprtrdma_cb_setup(r_xprt, reqs);
+	return 0;
+}
+
+/**
+ * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
+ * @xprt: transport
+ *
+ * Returns maximum size, in bytes, of a backchannel message
+ */
+size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
+{
+	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
+	struct rpcrdma_ep *ep = r_xprt->rx_ep;
+	size_t maxmsg;
+
+	maxmsg = min_t(unsigned int, ep->re_inline_send, ep->re_inline_recv);
+	maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
+	return maxmsg - RPCRDMA_HDRLEN_MIN;
+}
+
+unsigned int xprt_rdma_bc_max_slots(struct rpc_xprt *xprt)
+{
+	return RPCRDMA_BACKWARD_WRS >> 1;
+}
+
+static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
+{
+	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
+	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
+	__be32 *p;
+
+	rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
+	xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
+			rdmab_data(req->rl_rdmabuf), rqst);
+
+	p = xdr_reserve_space(&req->rl_stream, 28);
+	if (unlikely(!p))
+		return -EIO;
+	*p++ = rqst->rq_xid;
+	*p++ = rpcrdma_version;
+	*p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
+	*p++ = rdma_msg;
+	*p++ = xdr_zero;
+	*p++ = xdr_zero;
+	*p = xdr_zero;
+
+	if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
+				      &rqst->rq_snd_buf, rpcrdma_noch_pullup))
+		return -EIO;
+
+	trace_xprtrdma_cb_reply(r_xprt, rqst);
+	return 0;
+}
+
+/**
+ * xprt_rdma_bc_send_reply - marshal and send a backchannel reply
+ * @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
+ *
+ * Caller holds the transport's write lock.
+ *
+ * Returns:
+ *	%0 if the RPC message has been sent
+ *	%-ENOTCONN if the caller should reconnect and call again
+ *	%-EIO if a permanent error occurred and the request was not
+ *		sent. Do not try to send this message again.
+ */
+int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
+{
+	struct rpc_xprt *xprt = rqst->rq_xprt;
+	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
+	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
+	int rc;
+
+	if (!xprt_connected(xprt))
+		return -ENOTCONN;
+
+	if (!xprt_request_get_cong(xprt, rqst))
+		return -EBADSLT;
+
+	rc = rpcrdma_bc_marshal_reply(rqst);
+	if (rc < 0)
+		goto failed_marshal;
+
+	if (frwr_send(r_xprt, req))
+		goto drop_connection;
+	return 0;
+
+failed_marshal:
+	if (rc != -ENOTCONN)
+		return rc;
+drop_connection:
+	xprt_rdma_close(xprt);
+	return -ENOTCONN;
+}
+
+/**
+ * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
+ * @xprt: transport associated with these backchannel resources
+ * @reqs: number of incoming requests to destroy; ignored
+ */
+void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
+{
+	struct rpc_rqst *rqst, *tmp;
+
+	spin_lock(&xprt->bc_pa_lock);
+	list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
+		list_del(&rqst->rq_bc_pa_list);
+		spin_unlock(&xprt->bc_pa_lock);
+
+		rpcrdma_req_destroy(rpcr_to_rdmar(rqst));
+
+		spin_lock(&xprt->bc_pa_lock);
+	}
+	spin_unlock(&xprt->bc_pa_lock);
+}
+
+/**
+ * xprt_rdma_bc_free_rqst - Release a backchannel rqst
+ * @rqst: request to release
+ */
+void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
+{
+	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
+	struct rpcrdma_rep *rep = req->rl_reply;
+	struct rpc_xprt *xprt = rqst->rq_xprt;
+	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
+
+	rpcrdma_rep_put(&r_xprt->rx_buf, rep);
+	req->rl_reply = NULL;
+
+	spin_lock(&xprt->bc_pa_lock);
+	list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
+	spin_unlock(&xprt->bc_pa_lock);
+	xprt_put(xprt);
+}
+
+static struct rpc_rqst *rpcrdma_bc_rqst_get(struct rpcrdma_xprt *r_xprt)
+{
+	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
+	struct rpcrdma_req *req;
+	struct rpc_rqst *rqst;
+	size_t size;
+
+	spin_lock(&xprt->bc_pa_lock);
+	rqst = list_first_entry_or_null(&xprt->bc_pa_list, struct rpc_rqst,
+					rq_bc_pa_list);
+	if (!rqst)
+		goto create_req;
+	list_del(&rqst->rq_bc_pa_list);
+	spin_unlock(&xprt->bc_pa_lock);
+	return rqst;
+
+create_req:
+	spin_unlock(&xprt->bc_pa_lock);
+
+	/* Set a limit to prevent a remote from overrunning our resources.
+	 */
+	if (xprt->bc_alloc_count >= RPCRDMA_BACKWARD_WRS)
+		return NULL;
+
+	size = min_t(size_t, r_xprt->rx_ep->re_inline_recv, PAGE_SIZE);
+	req = rpcrdma_req_create(r_xprt, size);
+	if (!req)
+		return NULL;
+	if (rpcrdma_req_setup(r_xprt, req)) {
+		rpcrdma_req_destroy(req);
+		return NULL;
+	}
+
+	xprt->bc_alloc_count++;
+	rqst = &req->rl_slot;
+	rqst->rq_xprt = xprt;
+	__set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
+	xdr_buf_init(&rqst->rq_snd_buf, rdmab_data(req->rl_sendbuf), size);
+	return rqst;
+}
+
+/**
+ * rpcrdma_bc_receive_call - Handle a reverse-direction Call
+ * @r_xprt: transport receiving the call
+ * @rep: receive buffer containing the call
+ *
+ * Operational assumptions:
+ *    o Backchannel credits are ignored, just as the NFS server
+ *      forechannel currently does
+ *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
+ *      No replay detection is done at the transport level
+ */
+void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
+			     struct rpcrdma_rep *rep)
+{
+	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
+	struct svc_serv *bc_serv;
+	struct rpcrdma_req *req;
+	struct rpc_rqst *rqst;
+	struct xdr_buf *buf;
+	size_t size;
+	__be32 *p;
+
+	p = xdr_inline_decode(&rep->rr_stream, 0);
+	size = xdr_stream_remaining(&rep->rr_stream);
+
+#ifdef RPCRDMA_BACKCHANNEL_DEBUG
+	pr_info("RPC:       %s: callback XID %08x, length=%u\n",
+		__func__, be32_to_cpup(p), size);
+	pr_info("RPC:       %s: %*ph\n", __func__, size, p);
+#endif
+
+	rqst = rpcrdma_bc_rqst_get(r_xprt);
+	if (!rqst)
+		goto out_overflow;
+
+	rqst->rq_reply_bytes_recvd = 0;
+	rqst->rq_xid = *p;
+
+	rqst->rq_private_buf.len = size;
+
+	buf = &rqst->rq_rcv_buf;
+	memset(buf, 0, sizeof(*buf));
+	buf->head[0].iov_base = p;
+	buf->head[0].iov_len = size;
+	buf->len = size;
+
+	/* The receive buffer has to be hooked to the rpcrdma_req
+	 * so that it is not released while the req is pointing
+	 * to its buffer, and so that it can be reposted after
+	 * the Upper Layer is done decoding it.
+	 */
+	req = rpcr_to_rdmar(rqst);
+	req->rl_reply = rep;
+	trace_xprtrdma_cb_call(r_xprt, rqst);
+
+	/* Queue rqst for ULP's callback service */
+	bc_serv = xprt->bc_serv;
+	xprt_get(xprt);
+	spin_lock(&bc_serv->sv_cb_lock);
+	list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
+	spin_unlock(&bc_serv->sv_cb_lock);
+
+	wake_up(&bc_serv->sv_cb_waitq);
+
+	r_xprt->rx_stats.bcall_count++;
+	return;
+
+out_overflow:
+	pr_warn("RPC/RDMA backchannel overflow\n");
+	xprt_force_disconnect(xprt);
+	/* This receive buffer gets reposted automatically
+	 * when the connection is re-established.
+	 */
+	return;
+}