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);
46 req->rl_backchannel = true;
48 rb = rpcrdma_alloc_regbuf(RPCRDMA_HDRBUF_SIZE,
49 DMA_TO_DEVICE, GFP_KERNEL);
53 xdr_buf_init(&req->rl_hdrbuf, rb->rg_base, rdmab_length(rb));
55 size = r_xprt->rx_data.inline_rsize;
56 rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
60 xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
61 min_t(size_t, size, PAGE_SIZE));
62 rpcrdma_set_xprtdata(rqst, req);
66 rpcrdma_bc_free_rqst(r_xprt, rqst);
70 /* Allocate and add receive buffers to the rpcrdma_buffer's
71 * existing list of rep's. These are released when the
72 * transport is destroyed.
74 static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
80 rc = rpcrdma_create_rep(r_xprt);
88 * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
89 * @xprt: transport associated with these backchannel resources
90 * @reqs: number of concurrent incoming requests to expect
92 * Returns 0 on success; otherwise a negative errno
94 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
96 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
97 struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
98 struct rpc_rqst *rqst;
102 /* The backchannel reply path returns each rpc_rqst to the
103 * bc_pa_list _after_ the reply is sent. If the server is
104 * faster than the client, it can send another backward
105 * direction request before the rpc_rqst is returned to the
106 * list. The client rejects the request in this case.
108 * Twice as many rpc_rqsts are prepared to ensure there is
109 * always an rpc_rqst available as soon as a reply is sent.
111 if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
114 for (i = 0; i < (reqs << 1); i++) {
115 rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
119 dprintk("RPC: %s: new rqst %p\n", __func__, rqst);
121 rqst->rq_xprt = &r_xprt->rx_xprt;
122 INIT_LIST_HEAD(&rqst->rq_list);
123 INIT_LIST_HEAD(&rqst->rq_bc_list);
125 if (rpcrdma_bc_setup_rqst(r_xprt, rqst))
128 spin_lock_bh(&xprt->bc_pa_lock);
129 list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
130 spin_unlock_bh(&xprt->bc_pa_lock);
133 rc = rpcrdma_bc_setup_reps(r_xprt, reqs);
137 rc = rpcrdma_ep_post_extra_recv(r_xprt, reqs);
141 buffer->rb_bc_srv_max_requests = reqs;
142 request_module("svcrdma");
147 xprt_rdma_bc_destroy(xprt, reqs);
150 pr_err("RPC: %s: setup backchannel transport failed\n", __func__);
155 * xprt_rdma_bc_up - Create transport endpoint for backchannel service
156 * @serv: server endpoint
157 * @net: network namespace
159 * The "xprt" is an implied argument: it supplies the name of the
160 * backchannel transport class.
162 * Returns zero on success, negative errno on failure
164 int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
168 ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
175 * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
178 * Returns maximum size, in bytes, of a backchannel message
180 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
182 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
183 struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
186 maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
187 maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
188 return maxmsg - RPCRDMA_HDRLEN_MIN;
192 * rpcrdma_bc_marshal_reply - Send backwards direction reply
193 * @rqst: buffer containing RPC reply data
195 * Returns zero on success.
197 int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
199 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
200 struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
203 rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
204 xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
205 req->rl_rdmabuf->rg_base);
207 p = xdr_reserve_space(&req->rl_stream, 28);
211 *p++ = rpcrdma_version;
212 *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
218 if (!rpcrdma_prepare_send_sges(&r_xprt->rx_ia, req, RPCRDMA_HDRLEN_MIN,
219 &rqst->rq_snd_buf, rpcrdma_noch))
225 * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
226 * @xprt: transport associated with these backchannel resources
227 * @reqs: number of incoming requests to destroy; ignored
229 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
231 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
232 struct rpc_rqst *rqst, *tmp;
234 spin_lock_bh(&xprt->bc_pa_lock);
235 list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
236 list_del(&rqst->rq_bc_pa_list);
237 spin_unlock_bh(&xprt->bc_pa_lock);
239 rpcrdma_bc_free_rqst(r_xprt, rqst);
241 spin_lock_bh(&xprt->bc_pa_lock);
243 spin_unlock_bh(&xprt->bc_pa_lock);
247 * xprt_rdma_bc_free_rqst - Release a backchannel rqst
248 * @rqst: request to release
250 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
252 struct rpc_xprt *xprt = rqst->rq_xprt;
254 dprintk("RPC: %s: freeing rqst %p (req %p)\n",
255 __func__, rqst, rpcr_to_rdmar(rqst));
257 smp_mb__before_atomic();
258 WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state));
259 clear_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
260 smp_mb__after_atomic();
262 spin_lock_bh(&xprt->bc_pa_lock);
263 list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
264 spin_unlock_bh(&xprt->bc_pa_lock);
268 * rpcrdma_bc_receive_call - Handle a backward direction call
269 * @xprt: transport receiving the call
270 * @rep: receive buffer containing the call
272 * Operational assumptions:
273 * o Backchannel credits are ignored, just as the NFS server
274 * forechannel currently does
275 * o The ULP manages a replay cache (eg, NFSv4.1 sessions).
276 * No replay detection is done at the transport level
278 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
279 struct rpcrdma_rep *rep)
281 struct rpc_xprt *xprt = &r_xprt->rx_xprt;
282 struct svc_serv *bc_serv;
283 struct rpcrdma_req *req;
284 struct rpc_rqst *rqst;
289 p = xdr_inline_decode(&rep->rr_stream, 0);
290 size = xdr_stream_remaining(&rep->rr_stream);
292 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
293 pr_info("RPC: %s: callback XID %08x, length=%u\n",
294 __func__, be32_to_cpup(p), size);
295 pr_info("RPC: %s: %*ph\n", __func__, size, p);
298 /* Grab a free bc rqst */
299 spin_lock(&xprt->bc_pa_lock);
300 if (list_empty(&xprt->bc_pa_list)) {
301 spin_unlock(&xprt->bc_pa_lock);
304 rqst = list_first_entry(&xprt->bc_pa_list,
305 struct rpc_rqst, rq_bc_pa_list);
306 list_del(&rqst->rq_bc_pa_list);
307 spin_unlock(&xprt->bc_pa_lock);
308 dprintk("RPC: %s: using rqst %p\n", __func__, rqst);
311 rqst->rq_reply_bytes_recvd = 0;
312 rqst->rq_bytes_sent = 0;
315 rqst->rq_private_buf.len = size;
316 set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
318 buf = &rqst->rq_rcv_buf;
319 memset(buf, 0, sizeof(*buf));
320 buf->head[0].iov_base = p;
321 buf->head[0].iov_len = size;
324 /* The receive buffer has to be hooked to the rpcrdma_req
325 * so that it is not released while the req is pointing
326 * to its buffer, and so that it can be reposted after
327 * the Upper Layer is done decoding it.
329 req = rpcr_to_rdmar(rqst);
330 dprintk("RPC: %s: attaching rep %p to req %p\n",
334 /* Defeat the retransmit detection logic in send_request */
335 req->rl_connect_cookie = 0;
337 /* Queue rqst for ULP's callback service */
338 bc_serv = xprt->bc_serv;
339 spin_lock(&bc_serv->sv_cb_lock);
340 list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
341 spin_unlock(&bc_serv->sv_cb_lock);
343 wake_up(&bc_serv->sv_cb_waitq);
345 r_xprt->rx_stats.bcall_count++;
349 pr_warn("RPC/RDMA backchannel overflow\n");
350 xprt_disconnect_done(xprt);
351 /* This receive buffer gets reposted automatically
352 * when the connection is re-established.