1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (c) 2015-2020, Oracle and/or its affiliates.
4 *
5 * Support for reverse-direction RPCs on RPC/RDMA.
6 */
7
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>
12
13 #include "xprt_rdma.h"
14 #include <trace/events/rpcrdma.h>
15
16 #undef RPCRDMA_BACKCHANNEL_DEBUG
17
18 /**
19 * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
20 * @xprt: transport associated with these backchannel resources
21 * @reqs: number of concurrent incoming requests to expect
22 *
23 * Returns 0 on success; otherwise a negative errno
24 */
xprt_rdma_bc_setup(struct rpc_xprt * xprt,unsigned int reqs)25 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
26 {
27 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
28
29 r_xprt->rx_buf.rb_bc_srv_max_requests = RPCRDMA_BACKWARD_WRS >> 1;
30 trace_xprtrdma_cb_setup(r_xprt, reqs);
31 return 0;
32 }
33
34 /**
35 * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
36 * @xprt: transport
37 *
38 * Returns maximum size, in bytes, of a backchannel message
39 */
xprt_rdma_bc_maxpayload(struct rpc_xprt * xprt)40 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
41 {
42 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
43 struct rpcrdma_ep *ep = r_xprt->rx_ep;
44 size_t maxmsg;
45
46 maxmsg = min_t(unsigned int, ep->re_inline_send, ep->re_inline_recv);
47 maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
48 return maxmsg - RPCRDMA_HDRLEN_MIN;
49 }
50
xprt_rdma_bc_max_slots(struct rpc_xprt * xprt)51 unsigned int xprt_rdma_bc_max_slots(struct rpc_xprt *xprt)
52 {
53 return RPCRDMA_BACKWARD_WRS >> 1;
54 }
55
rpcrdma_bc_marshal_reply(struct rpc_rqst * rqst)56 static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
57 {
58 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
59 struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
60 __be32 *p;
61
62 rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
63 xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
64 rdmab_data(req->rl_rdmabuf), rqst);
65
66 p = xdr_reserve_space(&req->rl_stream, 28);
67 if (unlikely(!p))
68 return -EIO;
69 *p++ = rqst->rq_xid;
70 *p++ = rpcrdma_version;
71 *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
72 *p++ = rdma_msg;
73 *p++ = xdr_zero;
74 *p++ = xdr_zero;
75 *p = xdr_zero;
76
77 if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
78 &rqst->rq_snd_buf, rpcrdma_noch_pullup))
79 return -EIO;
80
81 trace_xprtrdma_cb_reply(r_xprt, rqst);
82 return 0;
83 }
84
85 /**
86 * xprt_rdma_bc_send_reply - marshal and send a backchannel reply
87 * @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
88 *
89 * Caller holds the transport's write lock.
90 *
91 * Returns:
92 * %0 if the RPC message has been sent
93 * %-ENOTCONN if the caller should reconnect and call again
94 * %-EIO if a permanent error occurred and the request was not
95 * sent. Do not try to send this message again.
96 */
xprt_rdma_bc_send_reply(struct rpc_rqst * rqst)97 int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
98 {
99 struct rpc_xprt *xprt = rqst->rq_xprt;
100 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
101 struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
102 int rc;
103
104 if (!xprt_connected(xprt))
105 return -ENOTCONN;
106
107 if (!xprt_request_get_cong(xprt, rqst))
108 return -EBADSLT;
109
110 rc = rpcrdma_bc_marshal_reply(rqst);
111 if (rc < 0)
112 goto failed_marshal;
113
114 if (frwr_send(r_xprt, req))
115 goto drop_connection;
116 return 0;
117
118 failed_marshal:
119 if (rc != -ENOTCONN)
120 return rc;
121 drop_connection:
122 xprt_rdma_close(xprt);
123 return -ENOTCONN;
124 }
125
126 /**
127 * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
128 * @xprt: transport associated with these backchannel resources
129 * @reqs: number of incoming requests to destroy; ignored
130 */
xprt_rdma_bc_destroy(struct rpc_xprt * xprt,unsigned int reqs)131 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
132 {
133 struct rpc_rqst *rqst, *tmp;
134
135 spin_lock(&xprt->bc_pa_lock);
136 list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
137 list_del(&rqst->rq_bc_pa_list);
138 spin_unlock(&xprt->bc_pa_lock);
139
140 rpcrdma_req_destroy(rpcr_to_rdmar(rqst));
141
142 spin_lock(&xprt->bc_pa_lock);
143 }
144 spin_unlock(&xprt->bc_pa_lock);
145 }
146
147 /**
148 * xprt_rdma_bc_free_rqst - Release a backchannel rqst
149 * @rqst: request to release
150 */
xprt_rdma_bc_free_rqst(struct rpc_rqst * rqst)151 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
152 {
153 struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
154 struct rpcrdma_rep *rep = req->rl_reply;
155 struct rpc_xprt *xprt = rqst->rq_xprt;
156 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
157
158 rpcrdma_rep_put(&r_xprt->rx_buf, rep);
159 req->rl_reply = NULL;
160
161 spin_lock(&xprt->bc_pa_lock);
162 list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
163 spin_unlock(&xprt->bc_pa_lock);
164 xprt_put(xprt);
165 }
166
rpcrdma_bc_rqst_get(struct rpcrdma_xprt * r_xprt)167 static struct rpc_rqst *rpcrdma_bc_rqst_get(struct rpcrdma_xprt *r_xprt)
168 {
169 struct rpc_xprt *xprt = &r_xprt->rx_xprt;
170 struct rpcrdma_req *req;
171 struct rpc_rqst *rqst;
172 size_t size;
173
174 spin_lock(&xprt->bc_pa_lock);
175 rqst = list_first_entry_or_null(&xprt->bc_pa_list, struct rpc_rqst,
176 rq_bc_pa_list);
177 if (!rqst)
178 goto create_req;
179 list_del(&rqst->rq_bc_pa_list);
180 spin_unlock(&xprt->bc_pa_lock);
181 return rqst;
182
183 create_req:
184 spin_unlock(&xprt->bc_pa_lock);
185
186 /* Set a limit to prevent a remote from overrunning our resources.
187 */
188 if (xprt->bc_alloc_count >= RPCRDMA_BACKWARD_WRS)
189 return NULL;
190
191 size = min_t(size_t, r_xprt->rx_ep->re_inline_recv, PAGE_SIZE);
192 req = rpcrdma_req_create(r_xprt, size);
193 if (!req)
194 return NULL;
195 if (rpcrdma_req_setup(r_xprt, req)) {
196 rpcrdma_req_destroy(req);
197 return NULL;
198 }
199
200 xprt->bc_alloc_count++;
201 rqst = &req->rl_slot;
202 rqst->rq_xprt = xprt;
203 __set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
204 xdr_buf_init(&rqst->rq_snd_buf, rdmab_data(req->rl_sendbuf), size);
205 return rqst;
206 }
207
208 /**
209 * rpcrdma_bc_receive_call - Handle a reverse-direction Call
210 * @r_xprt: transport receiving the call
211 * @rep: receive buffer containing the call
212 *
213 * Operational assumptions:
214 * o Backchannel credits are ignored, just as the NFS server
215 * forechannel currently does
216 * o The ULP manages a replay cache (eg, NFSv4.1 sessions).
217 * No replay detection is done at the transport level
218 */
rpcrdma_bc_receive_call(struct rpcrdma_xprt * r_xprt,struct rpcrdma_rep * rep)219 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
220 struct rpcrdma_rep *rep)
221 {
222 struct rpc_xprt *xprt = &r_xprt->rx_xprt;
223 struct svc_serv *bc_serv;
224 struct rpcrdma_req *req;
225 struct rpc_rqst *rqst;
226 struct xdr_buf *buf;
227 size_t size;
228 __be32 *p;
229
230 p = xdr_inline_decode(&rep->rr_stream, 0);
231 size = xdr_stream_remaining(&rep->rr_stream);
232
233 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
234 pr_info("RPC: %s: callback XID %08x, length=%u\n",
235 __func__, be32_to_cpup(p), size);
236 pr_info("RPC: %s: %*ph\n", __func__, size, p);
237 #endif
238
239 rqst = rpcrdma_bc_rqst_get(r_xprt);
240 if (!rqst)
241 goto out_overflow;
242
243 rqst->rq_reply_bytes_recvd = 0;
244 rqst->rq_xid = *p;
245
246 rqst->rq_private_buf.len = size;
247
248 buf = &rqst->rq_rcv_buf;
249 memset(buf, 0, sizeof(*buf));
250 buf->head[0].iov_base = p;
251 buf->head[0].iov_len = size;
252 buf->len = size;
253
254 /* The receive buffer has to be hooked to the rpcrdma_req
255 * so that it is not released while the req is pointing
256 * to its buffer, and so that it can be reposted after
257 * the Upper Layer is done decoding it.
258 */
259 req = rpcr_to_rdmar(rqst);
260 req->rl_reply = rep;
261 trace_xprtrdma_cb_call(r_xprt, rqst);
262
263 /* Queue rqst for ULP's callback service */
264 bc_serv = xprt->bc_serv;
265 xprt_get(xprt);
266 spin_lock(&bc_serv->sv_cb_lock);
267 list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
268 spin_unlock(&bc_serv->sv_cb_lock);
269
270 wake_up(&bc_serv->sv_cb_waitq);
271
272 r_xprt->rx_stats.bcall_count++;
273 return;
274
275 out_overflow:
276 pr_warn("RPC/RDMA backchannel overflow\n");
277 xprt_force_disconnect(xprt);
278 /* This receive buffer gets reposted automatically
279 * when the connection is re-established.
280 */
281 return;
282 }
283