1 /*
2 * Copyright (c) 2015 Oracle. All rights reserved.
3 *
4 * Support for backward direction RPCs on RPC/RDMA.
5 */
6
7 #include <linux/module.h>
8 #include <linux/sunrpc/xprt.h>
9 #include <linux/sunrpc/svc.h>
10 #include <linux/sunrpc/svc_xprt.h>
11
12 #include "xprt_rdma.h"
13
14 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
15 # define RPCDBG_FACILITY RPCDBG_TRANS
16 #endif
17
18 #undef RPCRDMA_BACKCHANNEL_DEBUG
19
rpcrdma_bc_free_rqst(struct rpcrdma_xprt * r_xprt,struct rpc_rqst * rqst)20 static void rpcrdma_bc_free_rqst(struct rpcrdma_xprt *r_xprt,
21 struct rpc_rqst *rqst)
22 {
23 struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
24 struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
25
26 spin_lock(&buf->rb_reqslock);
27 list_del(&req->rl_all);
28 spin_unlock(&buf->rb_reqslock);
29
30 rpcrdma_destroy_req(req);
31
32 kfree(rqst);
33 }
34
rpcrdma_bc_setup_rqst(struct rpcrdma_xprt * r_xprt,struct rpc_rqst * rqst)35 static int rpcrdma_bc_setup_rqst(struct rpcrdma_xprt *r_xprt,
36 struct rpc_rqst *rqst)
37 {
38 struct rpcrdma_regbuf *rb;
39 struct rpcrdma_req *req;
40 size_t size;
41
42 req = rpcrdma_create_req(r_xprt);
43 if (IS_ERR(req))
44 return PTR_ERR(req);
45 req->rl_backchannel = true;
46
47 rb = rpcrdma_alloc_regbuf(RPCRDMA_HDRBUF_SIZE,
48 DMA_TO_DEVICE, GFP_KERNEL);
49 if (IS_ERR(rb))
50 goto out_fail;
51 req->rl_rdmabuf = rb;
52
53 size = r_xprt->rx_data.inline_rsize;
54 rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
55 if (IS_ERR(rb))
56 goto out_fail;
57 req->rl_sendbuf = rb;
58 xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base, size);
59 rpcrdma_set_xprtdata(rqst, req);
60 return 0;
61
62 out_fail:
63 rpcrdma_bc_free_rqst(r_xprt, rqst);
64 return -ENOMEM;
65 }
66
67 /* Allocate and add receive buffers to the rpcrdma_buffer's
68 * existing list of rep's. These are released when the
69 * transport is destroyed.
70 */
rpcrdma_bc_setup_reps(struct rpcrdma_xprt * r_xprt,unsigned int count)71 static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
72 unsigned int count)
73 {
74 struct rpcrdma_rep *rep;
75 int rc = 0;
76
77 while (count--) {
78 rep = rpcrdma_create_rep(r_xprt);
79 if (IS_ERR(rep)) {
80 pr_err("RPC: %s: reply buffer alloc failed\n",
81 __func__);
82 rc = PTR_ERR(rep);
83 break;
84 }
85
86 rpcrdma_recv_buffer_put(rep);
87 }
88
89 return rc;
90 }
91
92 /**
93 * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
94 * @xprt: transport associated with these backchannel resources
95 * @reqs: number of concurrent incoming requests to expect
96 *
97 * Returns 0 on success; otherwise a negative errno
98 */
xprt_rdma_bc_setup(struct rpc_xprt * xprt,unsigned int reqs)99 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
100 {
101 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
102 struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
103 struct rpc_rqst *rqst;
104 unsigned int i;
105 int rc;
106
107 /* The backchannel reply path returns each rpc_rqst to the
108 * bc_pa_list _after_ the reply is sent. If the server is
109 * faster than the client, it can send another backward
110 * direction request before the rpc_rqst is returned to the
111 * list. The client rejects the request in this case.
112 *
113 * Twice as many rpc_rqsts are prepared to ensure there is
114 * always an rpc_rqst available as soon as a reply is sent.
115 */
116 if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
117 goto out_err;
118
119 for (i = 0; i < (reqs << 1); i++) {
120 rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
121 if (!rqst) {
122 pr_err("RPC: %s: Failed to create bc rpc_rqst\n",
123 __func__);
124 goto out_free;
125 }
126 dprintk("RPC: %s: new rqst %p\n", __func__, rqst);
127
128 rqst->rq_xprt = &r_xprt->rx_xprt;
129 INIT_LIST_HEAD(&rqst->rq_list);
130 INIT_LIST_HEAD(&rqst->rq_bc_list);
131
132 if (rpcrdma_bc_setup_rqst(r_xprt, rqst))
133 goto out_free;
134
135 spin_lock_bh(&xprt->bc_pa_lock);
136 list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
137 spin_unlock_bh(&xprt->bc_pa_lock);
138 }
139
140 rc = rpcrdma_bc_setup_reps(r_xprt, reqs);
141 if (rc)
142 goto out_free;
143
144 rc = rpcrdma_ep_post_extra_recv(r_xprt, reqs);
145 if (rc)
146 goto out_free;
147
148 buffer->rb_bc_srv_max_requests = reqs;
149 request_module("svcrdma");
150
151 return 0;
152
153 out_free:
154 xprt_rdma_bc_destroy(xprt, reqs);
155
156 out_err:
157 pr_err("RPC: %s: setup backchannel transport failed\n", __func__);
158 return -ENOMEM;
159 }
160
161 /**
162 * xprt_rdma_bc_up - Create transport endpoint for backchannel service
163 * @serv: server endpoint
164 * @net: network namespace
165 *
166 * The "xprt" is an implied argument: it supplies the name of the
167 * backchannel transport class.
168 *
169 * Returns zero on success, negative errno on failure
170 */
xprt_rdma_bc_up(struct svc_serv * serv,struct net * net)171 int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
172 {
173 int ret;
174
175 ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
176 if (ret < 0)
177 return ret;
178 return 0;
179 }
180
181 /**
182 * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
183 * @xprt: transport
184 *
185 * Returns maximum size, in bytes, of a backchannel message
186 */
xprt_rdma_bc_maxpayload(struct rpc_xprt * xprt)187 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
188 {
189 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
190 struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
191 size_t maxmsg;
192
193 maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
194 return maxmsg - RPCRDMA_HDRLEN_MIN;
195 }
196
197 /**
198 * rpcrdma_bc_marshal_reply - Send backwards direction reply
199 * @rqst: buffer containing RPC reply data
200 *
201 * Returns zero on success.
202 */
rpcrdma_bc_marshal_reply(struct rpc_rqst * rqst)203 int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
204 {
205 struct rpc_xprt *xprt = rqst->rq_xprt;
206 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
207 struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
208 struct rpcrdma_msg *headerp;
209
210 headerp = rdmab_to_msg(req->rl_rdmabuf);
211 headerp->rm_xid = rqst->rq_xid;
212 headerp->rm_vers = rpcrdma_version;
213 headerp->rm_credit =
214 cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
215 headerp->rm_type = rdma_msg;
216 headerp->rm_body.rm_chunks[0] = xdr_zero;
217 headerp->rm_body.rm_chunks[1] = xdr_zero;
218 headerp->rm_body.rm_chunks[2] = xdr_zero;
219
220 if (!rpcrdma_prepare_send_sges(&r_xprt->rx_ia, req, RPCRDMA_HDRLEN_MIN,
221 &rqst->rq_snd_buf, rpcrdma_noch))
222 return -EIO;
223 return 0;
224 }
225
226 /**
227 * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
228 * @xprt: transport associated with these backchannel resources
229 * @reqs: number of incoming requests to destroy; ignored
230 */
xprt_rdma_bc_destroy(struct rpc_xprt * xprt,unsigned int reqs)231 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
232 {
233 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
234 struct rpc_rqst *rqst, *tmp;
235
236 spin_lock_bh(&xprt->bc_pa_lock);
237 list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
238 list_del(&rqst->rq_bc_pa_list);
239 spin_unlock_bh(&xprt->bc_pa_lock);
240
241 rpcrdma_bc_free_rqst(r_xprt, rqst);
242
243 spin_lock_bh(&xprt->bc_pa_lock);
244 }
245 spin_unlock_bh(&xprt->bc_pa_lock);
246 }
247
248 /**
249 * xprt_rdma_bc_free_rqst - Release a backchannel rqst
250 * @rqst: request to release
251 */
xprt_rdma_bc_free_rqst(struct rpc_rqst * rqst)252 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
253 {
254 struct rpc_xprt *xprt = rqst->rq_xprt;
255
256 dprintk("RPC: %s: freeing rqst %p (req %p)\n",
257 __func__, rqst, rpcr_to_rdmar(rqst));
258
259 smp_mb__before_atomic();
260 WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state));
261 clear_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
262 smp_mb__after_atomic();
263
264 spin_lock_bh(&xprt->bc_pa_lock);
265 list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
266 spin_unlock_bh(&xprt->bc_pa_lock);
267 }
268
269 /**
270 * rpcrdma_bc_receive_call - Handle a backward direction call
271 * @xprt: transport receiving the call
272 * @rep: receive buffer containing the call
273 *
274 * Called in the RPC reply handler, which runs in a tasklet.
275 * Be quick about it.
276 *
277 * Operational assumptions:
278 * o Backchannel credits are ignored, just as the NFS server
279 * forechannel currently does
280 * o The ULP manages a replay cache (eg, NFSv4.1 sessions).
281 * No replay detection is done at the transport level
282 */
rpcrdma_bc_receive_call(struct rpcrdma_xprt * r_xprt,struct rpcrdma_rep * rep)283 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
284 struct rpcrdma_rep *rep)
285 {
286 struct rpc_xprt *xprt = &r_xprt->rx_xprt;
287 struct rpcrdma_msg *headerp;
288 struct svc_serv *bc_serv;
289 struct rpcrdma_req *req;
290 struct rpc_rqst *rqst;
291 struct xdr_buf *buf;
292 size_t size;
293 __be32 *p;
294
295 headerp = rdmab_to_msg(rep->rr_rdmabuf);
296 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
297 pr_info("RPC: %s: callback XID %08x, length=%u\n",
298 __func__, be32_to_cpu(headerp->rm_xid), rep->rr_len);
299 pr_info("RPC: %s: %*ph\n", __func__, rep->rr_len, headerp);
300 #endif
301
302 /* Sanity check:
303 * Need at least enough bytes for RPC/RDMA header, as code
304 * here references the header fields by array offset. Also,
305 * backward calls are always inline, so ensure there
306 * are some bytes beyond the RPC/RDMA header.
307 */
308 if (rep->rr_len < RPCRDMA_HDRLEN_MIN + 24)
309 goto out_short;
310 p = (__be32 *)((unsigned char *)headerp + RPCRDMA_HDRLEN_MIN);
311 size = rep->rr_len - RPCRDMA_HDRLEN_MIN;
312
313 /* Grab a free bc rqst */
314 spin_lock(&xprt->bc_pa_lock);
315 if (list_empty(&xprt->bc_pa_list)) {
316 spin_unlock(&xprt->bc_pa_lock);
317 goto out_overflow;
318 }
319 rqst = list_first_entry(&xprt->bc_pa_list,
320 struct rpc_rqst, rq_bc_pa_list);
321 list_del(&rqst->rq_bc_pa_list);
322 spin_unlock(&xprt->bc_pa_lock);
323 dprintk("RPC: %s: using rqst %p\n", __func__, rqst);
324
325 /* Prepare rqst */
326 rqst->rq_reply_bytes_recvd = 0;
327 rqst->rq_bytes_sent = 0;
328 rqst->rq_xid = headerp->rm_xid;
329
330 rqst->rq_private_buf.len = size;
331 set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
332
333 buf = &rqst->rq_rcv_buf;
334 memset(buf, 0, sizeof(*buf));
335 buf->head[0].iov_base = p;
336 buf->head[0].iov_len = size;
337 buf->len = size;
338
339 /* The receive buffer has to be hooked to the rpcrdma_req
340 * so that it can be reposted after the server is done
341 * parsing it but just before sending the backward
342 * direction reply.
343 */
344 req = rpcr_to_rdmar(rqst);
345 dprintk("RPC: %s: attaching rep %p to req %p\n",
346 __func__, rep, req);
347 req->rl_reply = rep;
348
349 /* Defeat the retransmit detection logic in send_request */
350 req->rl_connect_cookie = 0;
351
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);
357
358 wake_up(&bc_serv->sv_cb_waitq);
359
360 r_xprt->rx_stats.bcall_count++;
361 return;
362
363 out_overflow:
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.
368 */
369 return;
370
371 out_short:
372 pr_warn("RPC/RDMA short backward direction call\n");
373
374 if (rpcrdma_ep_post_recv(&r_xprt->rx_ia, rep))
375 xprt_disconnect_done(xprt);
376 else
377 pr_warn("RPC: %s: reposting rep %p\n",
378 __func__, rep);
379 }
380