1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (c) 2015 Oracle. All rights reserved.
5 * Support for backward direction RPCs on RPC/RDMA.
8 #include <linux/sunrpc/xprt.h>
9 #include <linux/sunrpc/svc.h>
10 #include <linux/sunrpc/svc_xprt.h>
11 #include <linux/sunrpc/svc_rdma.h>
13 #include "xprt_rdma.h"
14 #include <trace/events/rpcrdma.h>
16 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
17 # define RPCDBG_FACILITY RPCDBG_TRANS
20 #undef RPCRDMA_BACKCHANNEL_DEBUG
23 * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
24 * @xprt: transport associated with these backchannel resources
25 * @reqs: number of concurrent incoming requests to expect
27 * Returns 0 on success; otherwise a negative errno
29 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
31 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
33 r_xprt->rx_buf.rb_bc_srv_max_requests = RPCRDMA_BACKWARD_WRS >> 1;
34 trace_xprtrdma_cb_setup(r_xprt, reqs);
39 * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
42 * Returns maximum size, in bytes, of a backchannel message
44 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
46 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
47 struct rpcrdma_ep *ep = &r_xprt->rx_ep;
50 maxmsg = min_t(unsigned int, ep->rep_inline_send, ep->rep_inline_recv);
51 maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
52 return maxmsg - RPCRDMA_HDRLEN_MIN;
55 static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
57 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
58 struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
61 rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
62 xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
63 rdmab_data(req->rl_rdmabuf), rqst);
65 p = xdr_reserve_space(&req->rl_stream, 28);
69 *p++ = rpcrdma_version;
70 *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
76 if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
77 &rqst->rq_snd_buf, rpcrdma_noch))
80 trace_xprtrdma_cb_reply(rqst);
85 * xprt_rdma_bc_send_reply - marshal and send a backchannel reply
86 * @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
88 * Caller holds the transport's write lock.
91 * %0 if the RPC message has been sent
92 * %-ENOTCONN if the caller should reconnect and call again
93 * %-EIO if a permanent error occurred and the request was not
94 * sent. Do not try to send this message again.
96 int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
98 struct rpc_xprt *xprt = rqst->rq_xprt;
99 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
100 struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
103 if (!xprt_connected(xprt))
106 if (!xprt_request_get_cong(xprt, rqst))
109 rc = rpcrdma_bc_marshal_reply(rqst);
113 if (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, req))
114 goto drop_connection;
121 xprt_rdma_close(xprt);
126 * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
127 * @xprt: transport associated with these backchannel resources
128 * @reqs: number of incoming requests to destroy; ignored
130 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
132 struct rpc_rqst *rqst, *tmp;
134 spin_lock(&xprt->bc_pa_lock);
135 list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
136 list_del(&rqst->rq_bc_pa_list);
137 spin_unlock(&xprt->bc_pa_lock);
139 rpcrdma_req_destroy(rpcr_to_rdmar(rqst));
141 spin_lock(&xprt->bc_pa_lock);
143 spin_unlock(&xprt->bc_pa_lock);
147 * xprt_rdma_bc_free_rqst - Release a backchannel rqst
148 * @rqst: request to release
150 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
152 struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
153 struct rpc_xprt *xprt = rqst->rq_xprt;
155 rpcrdma_recv_buffer_put(req->rl_reply);
156 req->rl_reply = NULL;
158 spin_lock(&xprt->bc_pa_lock);
159 list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
160 spin_unlock(&xprt->bc_pa_lock);
163 static struct rpc_rqst *rpcrdma_bc_rqst_get(struct rpcrdma_xprt *r_xprt)
165 struct rpc_xprt *xprt = &r_xprt->rx_xprt;
166 struct rpcrdma_req *req;
167 struct rpc_rqst *rqst;
170 spin_lock(&xprt->bc_pa_lock);
171 rqst = list_first_entry_or_null(&xprt->bc_pa_list, struct rpc_rqst,
175 list_del(&rqst->rq_bc_pa_list);
176 spin_unlock(&xprt->bc_pa_lock);
180 spin_unlock(&xprt->bc_pa_lock);
182 /* Set a limit to prevent a remote from overrunning our resources.
184 if (xprt->bc_alloc_count >= RPCRDMA_BACKWARD_WRS)
187 size = min_t(size_t, r_xprt->rx_ep.rep_inline_recv, PAGE_SIZE);
188 req = rpcrdma_req_create(r_xprt, size, GFP_KERNEL);
192 xprt->bc_alloc_count++;
193 rqst = &req->rl_slot;
194 rqst->rq_xprt = xprt;
195 __set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
196 xdr_buf_init(&rqst->rq_snd_buf, rdmab_data(req->rl_sendbuf), size);
201 * rpcrdma_bc_receive_call - Handle a backward direction call
202 * @r_xprt: transport receiving the call
203 * @rep: receive buffer containing the call
205 * Operational assumptions:
206 * o Backchannel credits are ignored, just as the NFS server
207 * forechannel currently does
208 * o The ULP manages a replay cache (eg, NFSv4.1 sessions).
209 * No replay detection is done at the transport level
211 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
212 struct rpcrdma_rep *rep)
214 struct rpc_xprt *xprt = &r_xprt->rx_xprt;
215 struct svc_serv *bc_serv;
216 struct rpcrdma_req *req;
217 struct rpc_rqst *rqst;
222 p = xdr_inline_decode(&rep->rr_stream, 0);
223 size = xdr_stream_remaining(&rep->rr_stream);
225 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
226 pr_info("RPC: %s: callback XID %08x, length=%u\n",
227 __func__, be32_to_cpup(p), size);
228 pr_info("RPC: %s: %*ph\n", __func__, size, p);
231 rqst = rpcrdma_bc_rqst_get(r_xprt);
235 rqst->rq_reply_bytes_recvd = 0;
238 rqst->rq_private_buf.len = size;
240 buf = &rqst->rq_rcv_buf;
241 memset(buf, 0, sizeof(*buf));
242 buf->head[0].iov_base = p;
243 buf->head[0].iov_len = size;
246 /* The receive buffer has to be hooked to the rpcrdma_req
247 * so that it is not released while the req is pointing
248 * to its buffer, and so that it can be reposted after
249 * the Upper Layer is done decoding it.
251 req = rpcr_to_rdmar(rqst);
253 trace_xprtrdma_cb_call(rqst);
255 /* Queue rqst for ULP's callback service */
256 bc_serv = xprt->bc_serv;
257 spin_lock(&bc_serv->sv_cb_lock);
258 list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
259 spin_unlock(&bc_serv->sv_cb_lock);
261 wake_up(&bc_serv->sv_cb_waitq);
263 r_xprt->rx_stats.bcall_count++;
267 pr_warn("RPC/RDMA backchannel overflow\n");
268 xprt_force_disconnect(xprt);
269 /* This receive buffer gets reposted automatically
270 * when the connection is re-established.