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/module.h>
9 #include <linux/sunrpc/xprt.h>
10 #include <linux/sunrpc/svc.h>
11 #include <linux/sunrpc/svc_xprt.h>
13 #include "xprt_rdma.h"
15 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
16 # define RPCDBG_FACILITY RPCDBG_TRANS
19 #undef RPCRDMA_BACKCHANNEL_DEBUG
21 static void rpcrdma_bc_free_rqst(struct rpcrdma_xprt *r_xprt,
22 struct rpc_rqst *rqst)
24 struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
25 struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
27 spin_lock(&buf->rb_reqslock);
28 list_del(&req->rl_all);
29 spin_unlock(&buf->rb_reqslock);
31 rpcrdma_destroy_req(req);
36 static int rpcrdma_bc_setup_rqst(struct rpcrdma_xprt *r_xprt,
37 struct rpc_rqst *rqst)
39 struct rpcrdma_regbuf *rb;
40 struct rpcrdma_req *req;
43 req = rpcrdma_create_req(r_xprt);
47 size = r_xprt->rx_data.inline_rsize;
48 rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
52 xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
53 min_t(size_t, size, PAGE_SIZE));
54 rpcrdma_set_xprtdata(rqst, req);
58 rpcrdma_bc_free_rqst(r_xprt, rqst);
62 /* Allocate and add receive buffers to the rpcrdma_buffer's
63 * existing list of rep's. These are released when the
64 * transport is destroyed.
66 static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
72 rc = rpcrdma_create_rep(r_xprt);
80 * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
81 * @xprt: transport associated with these backchannel resources
82 * @reqs: number of concurrent incoming requests to expect
84 * Returns 0 on success; otherwise a negative errno
86 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
88 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
89 struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
90 struct rpc_rqst *rqst;
94 /* The backchannel reply path returns each rpc_rqst to the
95 * bc_pa_list _after_ the reply is sent. If the server is
96 * faster than the client, it can send another backward
97 * direction request before the rpc_rqst is returned to the
98 * list. The client rejects the request in this case.
100 * Twice as many rpc_rqsts are prepared to ensure there is
101 * always an rpc_rqst available as soon as a reply is sent.
103 if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
106 for (i = 0; i < (reqs << 1); i++) {
107 rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
111 dprintk("RPC: %s: new rqst %p\n", __func__, rqst);
113 rqst->rq_xprt = &r_xprt->rx_xprt;
114 INIT_LIST_HEAD(&rqst->rq_list);
115 INIT_LIST_HEAD(&rqst->rq_bc_list);
116 __set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
118 if (rpcrdma_bc_setup_rqst(r_xprt, rqst))
121 spin_lock_bh(&xprt->bc_pa_lock);
122 list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
123 spin_unlock_bh(&xprt->bc_pa_lock);
126 rc = rpcrdma_bc_setup_reps(r_xprt, reqs);
130 rc = rpcrdma_ep_post_extra_recv(r_xprt, reqs);
134 buffer->rb_bc_srv_max_requests = reqs;
135 request_module("svcrdma");
136 trace_xprtrdma_cb_setup(r_xprt, reqs);
140 xprt_rdma_bc_destroy(xprt, reqs);
143 pr_err("RPC: %s: setup backchannel transport failed\n", __func__);
148 * xprt_rdma_bc_up - Create transport endpoint for backchannel service
149 * @serv: server endpoint
150 * @net: network namespace
152 * The "xprt" is an implied argument: it supplies the name of the
153 * backchannel transport class.
155 * Returns zero on success, negative errno on failure
157 int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
161 ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
168 * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
171 * Returns maximum size, in bytes, of a backchannel message
173 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
175 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
176 struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
179 maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
180 maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
181 return maxmsg - RPCRDMA_HDRLEN_MIN;
184 static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
186 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
187 struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
190 rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
191 xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
192 req->rl_rdmabuf->rg_base);
194 p = xdr_reserve_space(&req->rl_stream, 28);
198 *p++ = rpcrdma_version;
199 *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
205 if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
206 &rqst->rq_snd_buf, rpcrdma_noch))
209 trace_xprtrdma_cb_reply(rqst);
214 * xprt_rdma_bc_send_reply - marshal and send a backchannel reply
215 * @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
217 * Caller holds the transport's write lock.
220 * %0 if the RPC message has been sent
221 * %-ENOTCONN if the caller should reconnect and call again
222 * %-EIO if a permanent error occurred and the request was not
223 * sent. Do not try to send this message again.
225 int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
227 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
228 struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
231 if (!xprt_connected(rqst->rq_xprt))
232 goto drop_connection;
234 rc = rpcrdma_bc_marshal_reply(rqst);
238 if (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, req))
239 goto drop_connection;
246 xprt_disconnect_done(rqst->rq_xprt);
251 * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
252 * @xprt: transport associated with these backchannel resources
253 * @reqs: number of incoming requests to destroy; ignored
255 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
257 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
258 struct rpc_rqst *rqst, *tmp;
260 spin_lock_bh(&xprt->bc_pa_lock);
261 list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
262 list_del(&rqst->rq_bc_pa_list);
263 spin_unlock_bh(&xprt->bc_pa_lock);
265 rpcrdma_bc_free_rqst(r_xprt, rqst);
267 spin_lock_bh(&xprt->bc_pa_lock);
269 spin_unlock_bh(&xprt->bc_pa_lock);
273 * xprt_rdma_bc_free_rqst - Release a backchannel rqst
274 * @rqst: request to release
276 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
278 struct rpc_xprt *xprt = rqst->rq_xprt;
280 dprintk("RPC: %s: freeing rqst %p (req %p)\n",
281 __func__, rqst, rpcr_to_rdmar(rqst));
283 spin_lock_bh(&xprt->bc_pa_lock);
284 list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
285 spin_unlock_bh(&xprt->bc_pa_lock);
289 * rpcrdma_bc_receive_call - Handle a backward direction call
290 * @r_xprt: transport receiving the call
291 * @rep: receive buffer containing the call
293 * Operational assumptions:
294 * o Backchannel credits are ignored, just as the NFS server
295 * forechannel currently does
296 * o The ULP manages a replay cache (eg, NFSv4.1 sessions).
297 * No replay detection is done at the transport level
299 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
300 struct rpcrdma_rep *rep)
302 struct rpc_xprt *xprt = &r_xprt->rx_xprt;
303 struct svc_serv *bc_serv;
304 struct rpcrdma_req *req;
305 struct rpc_rqst *rqst;
310 p = xdr_inline_decode(&rep->rr_stream, 0);
311 size = xdr_stream_remaining(&rep->rr_stream);
313 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
314 pr_info("RPC: %s: callback XID %08x, length=%u\n",
315 __func__, be32_to_cpup(p), size);
316 pr_info("RPC: %s: %*ph\n", __func__, size, p);
319 /* Grab a free bc rqst */
320 spin_lock(&xprt->bc_pa_lock);
321 if (list_empty(&xprt->bc_pa_list)) {
322 spin_unlock(&xprt->bc_pa_lock);
325 rqst = list_first_entry(&xprt->bc_pa_list,
326 struct rpc_rqst, rq_bc_pa_list);
327 list_del(&rqst->rq_bc_pa_list);
328 spin_unlock(&xprt->bc_pa_lock);
331 rqst->rq_reply_bytes_recvd = 0;
332 rqst->rq_bytes_sent = 0;
335 rqst->rq_private_buf.len = size;
337 buf = &rqst->rq_rcv_buf;
338 memset(buf, 0, sizeof(*buf));
339 buf->head[0].iov_base = p;
340 buf->head[0].iov_len = size;
343 /* The receive buffer has to be hooked to the rpcrdma_req
344 * so that it is not released while the req is pointing
345 * to its buffer, and so that it can be reposted after
346 * the Upper Layer is done decoding it.
348 req = rpcr_to_rdmar(rqst);
350 trace_xprtrdma_cb_call(rqst);
352 /* Queue rqst for ULP's callback service */
353 bc_serv = xprt->bc_serv;
354 spin_lock(&bc_serv->sv_cb_lock);
355 list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
356 spin_unlock(&bc_serv->sv_cb_lock);
358 wake_up(&bc_serv->sv_cb_waitq);
360 r_xprt->rx_stats.bcall_count++;
364 pr_warn("RPC/RDMA backchannel overflow\n");
365 xprt_disconnect_done(xprt);
366 /* This receive buffer gets reposted automatically
367 * when the connection is re-established.