xref: /linux/net/sunrpc/xprtrdma/svc_rdma_backchannel.c (revision 0b8061c340b643e01da431dd60c75a41bb1d31ec)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (c) 2015-2018 Oracle.  All rights reserved.
4  *
5  * Support for reverse-direction RPCs on RPC/RDMA (server-side).
6  */
7 
8 #include <linux/sunrpc/svc_rdma.h>
9 
10 #include "xprt_rdma.h"
11 #include <trace/events/rpcrdma.h>
12 
13 /**
14  * svc_rdma_handle_bc_reply - Process incoming backchannel Reply
15  * @rqstp: resources for handling the Reply
16  * @rctxt: Received message
17  *
18  */
19 void svc_rdma_handle_bc_reply(struct svc_rqst *rqstp,
20 			      struct svc_rdma_recv_ctxt *rctxt)
21 {
22 	struct svc_xprt *sxprt = rqstp->rq_xprt;
23 	struct rpc_xprt *xprt = sxprt->xpt_bc_xprt;
24 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
25 	struct xdr_buf *rcvbuf = &rqstp->rq_arg;
26 	struct kvec *dst, *src = &rcvbuf->head[0];
27 	__be32 *rdma_resp = rctxt->rc_recv_buf;
28 	struct rpc_rqst *req;
29 	u32 credits;
30 
31 	spin_lock(&xprt->queue_lock);
32 	req = xprt_lookup_rqst(xprt, *rdma_resp);
33 	if (!req)
34 		goto out_unlock;
35 
36 	dst = &req->rq_private_buf.head[0];
37 	memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
38 	if (dst->iov_len < src->iov_len)
39 		goto out_unlock;
40 	memcpy(dst->iov_base, src->iov_base, src->iov_len);
41 	xprt_pin_rqst(req);
42 	spin_unlock(&xprt->queue_lock);
43 
44 	credits = be32_to_cpup(rdma_resp + 2);
45 	if (credits == 0)
46 		credits = 1;	/* don't deadlock */
47 	else if (credits > r_xprt->rx_buf.rb_bc_max_requests)
48 		credits = r_xprt->rx_buf.rb_bc_max_requests;
49 	spin_lock(&xprt->transport_lock);
50 	xprt->cwnd = credits << RPC_CWNDSHIFT;
51 	spin_unlock(&xprt->transport_lock);
52 
53 	spin_lock(&xprt->queue_lock);
54 	xprt_complete_rqst(req->rq_task, rcvbuf->len);
55 	xprt_unpin_rqst(req);
56 	rcvbuf->len = 0;
57 
58 out_unlock:
59 	spin_unlock(&xprt->queue_lock);
60 }
61 
62 /* Send a reverse-direction RPC Call.
63  *
64  * Caller holds the connection's mutex and has already marshaled
65  * the RPC/RDMA request.
66  *
67  * This is similar to svc_rdma_send_reply_msg, but takes a struct
68  * rpc_rqst instead, does not support chunks, and avoids blocking
69  * memory allocation.
70  *
71  * XXX: There is still an opportunity to block in svc_rdma_send()
72  * if there are no SQ entries to post the Send. This may occur if
73  * the adapter has a small maximum SQ depth.
74  */
75 static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
76 			      struct rpc_rqst *rqst,
77 			      struct svc_rdma_send_ctxt *sctxt)
78 {
79 	struct svc_rdma_recv_ctxt *rctxt;
80 	int ret;
81 
82 	rctxt = svc_rdma_recv_ctxt_get(rdma);
83 	if (!rctxt)
84 		return -EIO;
85 
86 	ret = svc_rdma_map_reply_msg(rdma, sctxt, rctxt, &rqst->rq_snd_buf);
87 	svc_rdma_recv_ctxt_put(rdma, rctxt);
88 	if (ret < 0)
89 		return -EIO;
90 
91 	/* Bump page refcnt so Send completion doesn't release
92 	 * the rq_buffer before all retransmits are complete.
93 	 */
94 	get_page(virt_to_page(rqst->rq_buffer));
95 	sctxt->sc_send_wr.opcode = IB_WR_SEND;
96 	return svc_rdma_send(rdma, sctxt);
97 }
98 
99 /* Server-side transport endpoint wants a whole page for its send
100  * buffer. The client RPC code constructs the RPC header in this
101  * buffer before it invokes ->send_request.
102  */
103 static int
104 xprt_rdma_bc_allocate(struct rpc_task *task)
105 {
106 	struct rpc_rqst *rqst = task->tk_rqstp;
107 	size_t size = rqst->rq_callsize;
108 	struct page *page;
109 
110 	if (size > PAGE_SIZE) {
111 		WARN_ONCE(1, "svcrdma: large bc buffer request (size %zu)\n",
112 			  size);
113 		return -EINVAL;
114 	}
115 
116 	page = alloc_page(RPCRDMA_DEF_GFP);
117 	if (!page)
118 		return -ENOMEM;
119 	rqst->rq_buffer = page_address(page);
120 
121 	rqst->rq_rbuffer = kmalloc(rqst->rq_rcvsize, RPCRDMA_DEF_GFP);
122 	if (!rqst->rq_rbuffer) {
123 		put_page(page);
124 		return -ENOMEM;
125 	}
126 	return 0;
127 }
128 
129 static void
130 xprt_rdma_bc_free(struct rpc_task *task)
131 {
132 	struct rpc_rqst *rqst = task->tk_rqstp;
133 
134 	put_page(virt_to_page(rqst->rq_buffer));
135 	kfree(rqst->rq_rbuffer);
136 }
137 
138 static int
139 rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
140 {
141 	struct rpc_xprt *xprt = rqst->rq_xprt;
142 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
143 	struct svc_rdma_send_ctxt *ctxt;
144 	__be32 *p;
145 	int rc;
146 
147 	ctxt = svc_rdma_send_ctxt_get(rdma);
148 	if (!ctxt)
149 		goto drop_connection;
150 
151 	p = xdr_reserve_space(&ctxt->sc_stream, RPCRDMA_HDRLEN_MIN);
152 	if (!p)
153 		goto put_ctxt;
154 	*p++ = rqst->rq_xid;
155 	*p++ = rpcrdma_version;
156 	*p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
157 	*p++ = rdma_msg;
158 	*p++ = xdr_zero;
159 	*p++ = xdr_zero;
160 	*p   = xdr_zero;
161 
162 	rqst->rq_xtime = ktime_get();
163 	rc = svc_rdma_bc_sendto(rdma, rqst, ctxt);
164 	if (rc)
165 		goto put_ctxt;
166 	return 0;
167 
168 put_ctxt:
169 	svc_rdma_send_ctxt_put(rdma, ctxt);
170 
171 drop_connection:
172 	return -ENOTCONN;
173 }
174 
175 /**
176  * xprt_rdma_bc_send_request - Send a reverse-direction Call
177  * @rqst: rpc_rqst containing Call message to be sent
178  *
179  * Return values:
180  *   %0 if the message was sent successfully
181  *   %ENOTCONN if the message was not sent
182  */
183 static int xprt_rdma_bc_send_request(struct rpc_rqst *rqst)
184 {
185 	struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
186 	struct svcxprt_rdma *rdma =
187 		container_of(sxprt, struct svcxprt_rdma, sc_xprt);
188 	int ret;
189 
190 	if (test_bit(XPT_DEAD, &sxprt->xpt_flags))
191 		return -ENOTCONN;
192 
193 	ret = rpcrdma_bc_send_request(rdma, rqst);
194 	if (ret == -ENOTCONN)
195 		svc_close_xprt(sxprt);
196 	return ret;
197 }
198 
199 static void
200 xprt_rdma_bc_close(struct rpc_xprt *xprt)
201 {
202 	xprt_disconnect_done(xprt);
203 	xprt->cwnd = RPC_CWNDSHIFT;
204 }
205 
206 static void
207 xprt_rdma_bc_put(struct rpc_xprt *xprt)
208 {
209 	xprt_rdma_free_addresses(xprt);
210 	xprt_free(xprt);
211 }
212 
213 static const struct rpc_xprt_ops xprt_rdma_bc_procs = {
214 	.reserve_xprt		= xprt_reserve_xprt_cong,
215 	.release_xprt		= xprt_release_xprt_cong,
216 	.alloc_slot		= xprt_alloc_slot,
217 	.free_slot		= xprt_free_slot,
218 	.release_request	= xprt_release_rqst_cong,
219 	.buf_alloc		= xprt_rdma_bc_allocate,
220 	.buf_free		= xprt_rdma_bc_free,
221 	.send_request		= xprt_rdma_bc_send_request,
222 	.wait_for_reply_request	= xprt_wait_for_reply_request_def,
223 	.close			= xprt_rdma_bc_close,
224 	.destroy		= xprt_rdma_bc_put,
225 	.print_stats		= xprt_rdma_print_stats
226 };
227 
228 static const struct rpc_timeout xprt_rdma_bc_timeout = {
229 	.to_initval = 60 * HZ,
230 	.to_maxval = 60 * HZ,
231 };
232 
233 /* It shouldn't matter if the number of backchannel session slots
234  * doesn't match the number of RPC/RDMA credits. That just means
235  * one or the other will have extra slots that aren't used.
236  */
237 static struct rpc_xprt *
238 xprt_setup_rdma_bc(struct xprt_create *args)
239 {
240 	struct rpc_xprt *xprt;
241 	struct rpcrdma_xprt *new_xprt;
242 
243 	if (args->addrlen > sizeof(xprt->addr))
244 		return ERR_PTR(-EBADF);
245 
246 	xprt = xprt_alloc(args->net, sizeof(*new_xprt),
247 			  RPCRDMA_MAX_BC_REQUESTS,
248 			  RPCRDMA_MAX_BC_REQUESTS);
249 	if (!xprt)
250 		return ERR_PTR(-ENOMEM);
251 
252 	xprt->timeout = &xprt_rdma_bc_timeout;
253 	xprt_set_bound(xprt);
254 	xprt_set_connected(xprt);
255 	xprt->bind_timeout = RPCRDMA_BIND_TO;
256 	xprt->reestablish_timeout = RPCRDMA_INIT_REEST_TO;
257 	xprt->idle_timeout = RPCRDMA_IDLE_DISC_TO;
258 
259 	xprt->prot = XPRT_TRANSPORT_BC_RDMA;
260 	xprt->ops = &xprt_rdma_bc_procs;
261 
262 	memcpy(&xprt->addr, args->dstaddr, args->addrlen);
263 	xprt->addrlen = args->addrlen;
264 	xprt_rdma_format_addresses(xprt, (struct sockaddr *)&xprt->addr);
265 	xprt->resvport = 0;
266 
267 	xprt->max_payload = xprt_rdma_max_inline_read;
268 
269 	new_xprt = rpcx_to_rdmax(xprt);
270 	new_xprt->rx_buf.rb_bc_max_requests = xprt->max_reqs;
271 
272 	xprt_get(xprt);
273 	args->bc_xprt->xpt_bc_xprt = xprt;
274 	xprt->bc_xprt = args->bc_xprt;
275 
276 	/* Final put for backchannel xprt is in __svc_rdma_free */
277 	xprt_get(xprt);
278 	return xprt;
279 }
280 
281 struct xprt_class xprt_rdma_bc = {
282 	.list			= LIST_HEAD_INIT(xprt_rdma_bc.list),
283 	.name			= "rdma backchannel",
284 	.owner			= THIS_MODULE,
285 	.ident			= XPRT_TRANSPORT_BC_RDMA,
286 	.setup			= xprt_setup_rdma_bc,
287 };
288