summaryrefslogtreecommitdiffstats
path: root/net/sunrpc/xprtrdma/backchannel.c
blob: 03f6b5840764dcc2c486015edd8dc7de4cd84b26 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
/*
 * Copyright (c) 2015 Oracle.  All rights reserved.
 *
 * Support for backward direction RPCs on RPC/RDMA.
 */

#include <linux/module.h>
#include <linux/sunrpc/xprt.h>
#include <linux/sunrpc/svc.h>
#include <linux/sunrpc/svc_xprt.h>

#include "xprt_rdma.h"

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
# define RPCDBG_FACILITY	RPCDBG_TRANS
#endif

#undef RPCRDMA_BACKCHANNEL_DEBUG

static void rpcrdma_bc_free_rqst(struct rpcrdma_xprt *r_xprt,
				 struct rpc_rqst *rqst)
{
	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);

	spin_lock(&buf->rb_reqslock);
	list_del(&req->rl_all);
	spin_unlock(&buf->rb_reqslock);

	rpcrdma_destroy_req(req);

	kfree(rqst);
}

static int rpcrdma_bc_setup_rqst(struct rpcrdma_xprt *r_xprt,
				 struct rpc_rqst *rqst)
{
	struct rpcrdma_regbuf *rb;
	struct rpcrdma_req *req;
	size_t size;

	req = rpcrdma_create_req(r_xprt);
	if (IS_ERR(req))
		return PTR_ERR(req);
	req->rl_backchannel = true;

	rb = rpcrdma_alloc_regbuf(RPCRDMA_HDRBUF_SIZE,
				  DMA_TO_DEVICE, GFP_KERNEL);
	if (IS_ERR(rb))
		goto out_fail;
	req->rl_rdmabuf = rb;

	size = r_xprt->rx_data.inline_rsize;
	rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
	if (IS_ERR(rb))
		goto out_fail;
	req->rl_sendbuf = rb;
	xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
		     min_t(size_t, size, PAGE_SIZE));
	rpcrdma_set_xprtdata(rqst, req);
	return 0;

out_fail:
	rpcrdma_bc_free_rqst(r_xprt, rqst);
	return -ENOMEM;
}

/* Allocate and add receive buffers to the rpcrdma_buffer's
 * existing list of rep's. These are released when the
 * transport is destroyed.
 */
static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
				 unsigned int count)
{
	struct rpcrdma_rep *rep;
	int rc = 0;

	while (count--) {
		rep = rpcrdma_create_rep(r_xprt);
		if (IS_ERR(rep)) {
			pr_err("RPC:       %s: reply buffer alloc failed\n",
			       __func__);
			rc = PTR_ERR(rep);
			break;
		}

		rpcrdma_recv_buffer_put(rep);
	}

	return rc;
}

/**
 * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
 * @xprt: transport associated with these backchannel resources
 * @reqs: number of concurrent incoming requests to expect
 *
 * Returns 0 on success; otherwise a negative errno
 */
int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
{
	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
	struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
	struct rpc_rqst *rqst;
	unsigned int i;
	int rc;

	/* The backchannel reply path returns each rpc_rqst to the
	 * bc_pa_list _after_ the reply is sent. If the server is
	 * faster than the client, it can send another backward
	 * direction request before the rpc_rqst is returned to the
	 * list. The client rejects the request in this case.
	 *
	 * Twice as many rpc_rqsts are prepared to ensure there is
	 * always an rpc_rqst available as soon as a reply is sent.
	 */
	if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
		goto out_err;

	for (i = 0; i < (reqs << 1); i++) {
		rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
		if (!rqst)
			goto out_free;

		dprintk("RPC:       %s: new rqst %p\n", __func__, rqst);

		rqst->rq_xprt = &r_xprt->rx_xprt;
		INIT_LIST_HEAD(&rqst->rq_list);
		INIT_LIST_HEAD(&rqst->rq_bc_list);

		if (rpcrdma_bc_setup_rqst(r_xprt, rqst))
			goto out_free;

		spin_lock_bh(&xprt->bc_pa_lock);
		list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
		spin_unlock_bh(&xprt->bc_pa_lock);
	}

	rc = rpcrdma_bc_setup_reps(r_xprt, reqs);
	if (rc)
		goto out_free;

	rc = rpcrdma_ep_post_extra_recv(r_xprt, reqs);
	if (rc)
		goto out_free;

	buffer->rb_bc_srv_max_requests = reqs;
	request_module("svcrdma");

	return 0;

out_free:
	xprt_rdma_bc_destroy(xprt, reqs);

out_err:
	pr_err("RPC:       %s: setup backchannel transport failed\n", __func__);
	return -ENOMEM;
}

/**
 * xprt_rdma_bc_up - Create transport endpoint for backchannel service
 * @serv: server endpoint
 * @net: network namespace
 *
 * The "xprt" is an implied argument: it supplies the name of the
 * backchannel transport class.
 *
 * Returns zero on success, negative errno on failure
 */
int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
{
	int ret;

	ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
	if (ret < 0)
		return ret;
	return 0;
}

/**
 * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
 * @xprt: transport
 *
 * Returns maximum size, in bytes, of a backchannel message
 */
size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
{
	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
	struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
	size_t maxmsg;

	maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
	maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
	return maxmsg - RPCRDMA_HDRLEN_MIN;
}

/**
 * rpcrdma_bc_marshal_reply - Send backwards direction reply
 * @rqst: buffer containing RPC reply data
 *
 * Returns zero on success.
 */
int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
{
	struct rpc_xprt *xprt = rqst->rq_xprt;
	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
	struct rpcrdma_msg *headerp;

	headerp = rdmab_to_msg(req->rl_rdmabuf);
	headerp->rm_xid = rqst->rq_xid;
	headerp->rm_vers = rpcrdma_version;
	headerp->rm_credit =
			cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
	headerp->rm_type = rdma_msg;
	headerp->rm_body.rm_chunks[0] = xdr_zero;
	headerp->rm_body.rm_chunks[1] = xdr_zero;
	headerp->rm_body.rm_chunks[2] = xdr_zero;

	if (!rpcrdma_prepare_send_sges(&r_xprt->rx_ia, req, RPCRDMA_HDRLEN_MIN,
				       &rqst->rq_snd_buf, rpcrdma_noch))
		return -EIO;
	return 0;
}

/**
 * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
 * @xprt: transport associated with these backchannel resources
 * @reqs: number of incoming requests to destroy; ignored
 */
void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
{
	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
	struct rpc_rqst *rqst, *tmp;

	spin_lock_bh(&xprt->bc_pa_lock);
	list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
		list_del(&rqst->rq_bc_pa_list);
		spin_unlock_bh(&xprt->bc_pa_lock);

		rpcrdma_bc_free_rqst(r_xprt, rqst);

		spin_lock_bh(&xprt->bc_pa_lock);
	}
	spin_unlock_bh(&xprt->bc_pa_lock);
}

/**
 * xprt_rdma_bc_free_rqst - Release a backchannel rqst
 * @rqst: request to release
 */
void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
{
	struct rpc_xprt *xprt = rqst->rq_xprt;

	dprintk("RPC:       %s: freeing rqst %p (req %p)\n",
		__func__, rqst, rpcr_to_rdmar(rqst));

	smp_mb__before_atomic();
	WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state));
	clear_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
	smp_mb__after_atomic();

	spin_lock_bh(&xprt->bc_pa_lock);
	list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
	spin_unlock_bh(&xprt->bc_pa_lock);
}

/**
 * rpcrdma_bc_receive_call - Handle a backward direction call
 * @xprt: transport receiving the call
 * @rep: receive buffer containing the call
 *
 * Called in the RPC reply handler, which runs in a tasklet.
 * Be quick about it.
 *
 * Operational assumptions:
 *    o Backchannel credits are ignored, just as the NFS server
 *      forechannel currently does
 *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
 *      No replay detection is done at the transport level
 */
void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
			     struct rpcrdma_rep *rep)
{
	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
	struct rpcrdma_msg *headerp;
	struct svc_serv *bc_serv;
	struct rpcrdma_req *req;
	struct rpc_rqst *rqst;
	struct xdr_buf *buf;
	size_t size;
	__be32 *p;

	headerp = rdmab_to_msg(rep->rr_rdmabuf);
#ifdef RPCRDMA_BACKCHANNEL_DEBUG
	pr_info("RPC:       %s: callback XID %08x, length=%u\n",
		__func__, be32_to_cpu(headerp->rm_xid), rep->rr_len);
	pr_info("RPC:       %s: %*ph\n", __func__, rep->rr_len, headerp);
#endif

	/* Sanity check:
	 * Need at least enough bytes for RPC/RDMA header, as code
	 * here references the header fields by array offset. Also,
	 * backward calls are always inline, so ensure there
	 * are some bytes beyond the RPC/RDMA header.
	 */
	if (rep->rr_len < RPCRDMA_HDRLEN_MIN + 24)
		goto out_short;
	p = (__be32 *)((unsigned char *)headerp + RPCRDMA_HDRLEN_MIN);
	size = rep->rr_len - RPCRDMA_HDRLEN_MIN;

	/* Grab a free bc rqst */
	spin_lock(&xprt->bc_pa_lock);
	if (list_empty(&xprt->bc_pa_list)) {
		spin_unlock(&xprt->bc_pa_lock);
		goto out_overflow;
	}
	rqst = list_first_entry(&xprt->bc_pa_list,
				struct rpc_rqst, rq_bc_pa_list);
	list_del(&rqst->rq_bc_pa_list);
	spin_unlock(&xprt->bc_pa_lock);
	dprintk("RPC:       %s: using rqst %p\n", __func__, rqst);

	/* Prepare rqst */
	rqst->rq_reply_bytes_recvd = 0;
	rqst->rq_bytes_sent = 0;
	rqst->rq_xid = headerp->rm_xid;

	rqst->rq_private_buf.len = size;
	set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);

	buf = &rqst->rq_rcv_buf;
	memset(buf, 0, sizeof(*buf));
	buf->head[0].iov_base = p;
	buf->head[0].iov_len = size;
	buf->len = size;

	/* The receive buffer has to be hooked to the rpcrdma_req
	 * so that it can be reposted after the server is done
	 * parsing it but just before sending the backward
	 * direction reply.
	 */
	req = rpcr_to_rdmar(rqst);
	dprintk("RPC:       %s: attaching rep %p to req %p\n",
		__func__, rep, req);
	req->rl_reply = rep;

	/* Defeat the retransmit detection logic in send_request */
	req->rl_connect_cookie = 0;

	/* Queue rqst for ULP's callback service */
	bc_serv = xprt->bc_serv;
	spin_lock(&bc_serv->sv_cb_lock);
	list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
	spin_unlock(&bc_serv->sv_cb_lock);

	wake_up(&bc_serv->sv_cb_waitq);

	r_xprt->rx_stats.bcall_count++;
	return;

out_overflow:
	pr_warn("RPC/RDMA backchannel overflow\n");
	xprt_disconnect_done(xprt);
	/* This receive buffer gets reposted automatically
	 * when the connection is re-established.
	 */
	return;

out_short:
	pr_warn("RPC/RDMA short backward direction call\n");

	if (rpcrdma_ep_post_recv(&r_xprt->rx_ia, rep))
		xprt_disconnect_done(xprt);
	else
		pr_warn("RPC:       %s: reposting rep %p\n",
			__func__, rep);
}