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 	ret = svc_rdma_send(rdma, sctxt);
97 	if (ret < 0)
98 		return ret;
99 
100 	ret = wait_for_completion_killable(&sctxt->sc_done);
101 	svc_rdma_send_ctxt_put(rdma, sctxt);
102 	return ret;
103 }
104 
105 /* Server-side transport endpoint wants a whole page for its send
106  * buffer. The client RPC code constructs the RPC header in this
107  * buffer before it invokes ->send_request.
108  */
109 static int
110 xprt_rdma_bc_allocate(struct rpc_task *task)
111 {
112 	struct rpc_rqst *rqst = task->tk_rqstp;
113 	size_t size = rqst->rq_callsize;
114 	struct page *page;
115 
116 	if (size > PAGE_SIZE) {
117 		WARN_ONCE(1, "svcrdma: large bc buffer request (size %zu)\n",
118 			  size);
119 		return -EINVAL;
120 	}
121 
122 	page = alloc_page(RPCRDMA_DEF_GFP);
123 	if (!page)
124 		return -ENOMEM;
125 	rqst->rq_buffer = page_address(page);
126 
127 	rqst->rq_rbuffer = kmalloc(rqst->rq_rcvsize, RPCRDMA_DEF_GFP);
128 	if (!rqst->rq_rbuffer) {
129 		put_page(page);
130 		return -ENOMEM;
131 	}
132 	return 0;
133 }
134 
135 static void
136 xprt_rdma_bc_free(struct rpc_task *task)
137 {
138 	struct rpc_rqst *rqst = task->tk_rqstp;
139 
140 	put_page(virt_to_page(rqst->rq_buffer));
141 	kfree(rqst->rq_rbuffer);
142 }
143 
144 static int
145 rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
146 {
147 	struct rpc_xprt *xprt = rqst->rq_xprt;
148 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
149 	struct svc_rdma_send_ctxt *ctxt;
150 	__be32 *p;
151 	int rc;
152 
153 	ctxt = svc_rdma_send_ctxt_get(rdma);
154 	if (!ctxt)
155 		goto drop_connection;
156 
157 	p = xdr_reserve_space(&ctxt->sc_stream, RPCRDMA_HDRLEN_MIN);
158 	if (!p)
159 		goto put_ctxt;
160 	*p++ = rqst->rq_xid;
161 	*p++ = rpcrdma_version;
162 	*p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
163 	*p++ = rdma_msg;
164 	*p++ = xdr_zero;
165 	*p++ = xdr_zero;
166 	*p   = xdr_zero;
167 
168 	rqst->rq_xtime = ktime_get();
169 	rc = svc_rdma_bc_sendto(rdma, rqst, ctxt);
170 	if (rc)
171 		goto put_ctxt;
172 	return 0;
173 
174 put_ctxt:
175 	svc_rdma_send_ctxt_put(rdma, ctxt);
176 
177 drop_connection:
178 	return -ENOTCONN;
179 }
180 
181 /**
182  * xprt_rdma_bc_send_request - Send a reverse-direction Call
183  * @rqst: rpc_rqst containing Call message to be sent
184  *
185  * Return values:
186  *   %0 if the message was sent successfully
187  *   %ENOTCONN if the message was not sent
188  */
189 static int xprt_rdma_bc_send_request(struct rpc_rqst *rqst)
190 {
191 	struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
192 	struct svcxprt_rdma *rdma =
193 		container_of(sxprt, struct svcxprt_rdma, sc_xprt);
194 	int ret;
195 
196 	if (test_bit(XPT_DEAD, &sxprt->xpt_flags))
197 		return -ENOTCONN;
198 
199 	ret = rpcrdma_bc_send_request(rdma, rqst);
200 	if (ret == -ENOTCONN)
201 		svc_close_xprt(sxprt);
202 	return ret;
203 }
204 
205 static void
206 xprt_rdma_bc_close(struct rpc_xprt *xprt)
207 {
208 	xprt_disconnect_done(xprt);
209 	xprt->cwnd = RPC_CWNDSHIFT;
210 }
211 
212 static void
213 xprt_rdma_bc_put(struct rpc_xprt *xprt)
214 {
215 	xprt_rdma_free_addresses(xprt);
216 	xprt_free(xprt);
217 }
218 
219 static const struct rpc_xprt_ops xprt_rdma_bc_procs = {
220 	.reserve_xprt		= xprt_reserve_xprt_cong,
221 	.release_xprt		= xprt_release_xprt_cong,
222 	.alloc_slot		= xprt_alloc_slot,
223 	.free_slot		= xprt_free_slot,
224 	.release_request	= xprt_release_rqst_cong,
225 	.buf_alloc		= xprt_rdma_bc_allocate,
226 	.buf_free		= xprt_rdma_bc_free,
227 	.send_request		= xprt_rdma_bc_send_request,
228 	.wait_for_reply_request	= xprt_wait_for_reply_request_def,
229 	.close			= xprt_rdma_bc_close,
230 	.destroy		= xprt_rdma_bc_put,
231 	.print_stats		= xprt_rdma_print_stats
232 };
233 
234 static const struct rpc_timeout xprt_rdma_bc_timeout = {
235 	.to_initval = 60 * HZ,
236 	.to_maxval = 60 * HZ,
237 };
238 
239 /* It shouldn't matter if the number of backchannel session slots
240  * doesn't match the number of RPC/RDMA credits. That just means
241  * one or the other will have extra slots that aren't used.
242  */
243 static struct rpc_xprt *
244 xprt_setup_rdma_bc(struct xprt_create *args)
245 {
246 	struct rpc_xprt *xprt;
247 	struct rpcrdma_xprt *new_xprt;
248 
249 	if (args->addrlen > sizeof(xprt->addr))
250 		return ERR_PTR(-EBADF);
251 
252 	xprt = xprt_alloc(args->net, sizeof(*new_xprt),
253 			  RPCRDMA_MAX_BC_REQUESTS,
254 			  RPCRDMA_MAX_BC_REQUESTS);
255 	if (!xprt)
256 		return ERR_PTR(-ENOMEM);
257 
258 	xprt->timeout = &xprt_rdma_bc_timeout;
259 	xprt_set_bound(xprt);
260 	xprt_set_connected(xprt);
261 	xprt->bind_timeout = 0;
262 	xprt->reestablish_timeout = 0;
263 	xprt->idle_timeout = 0;
264 
265 	xprt->prot = XPRT_TRANSPORT_BC_RDMA;
266 	xprt->ops = &xprt_rdma_bc_procs;
267 
268 	memcpy(&xprt->addr, args->dstaddr, args->addrlen);
269 	xprt->addrlen = args->addrlen;
270 	xprt_rdma_format_addresses(xprt, (struct sockaddr *)&xprt->addr);
271 	xprt->resvport = 0;
272 
273 	xprt->max_payload = xprt_rdma_max_inline_read;
274 
275 	new_xprt = rpcx_to_rdmax(xprt);
276 	new_xprt->rx_buf.rb_bc_max_requests = xprt->max_reqs;
277 
278 	xprt_get(xprt);
279 	args->bc_xprt->xpt_bc_xprt = xprt;
280 	xprt->bc_xprt = args->bc_xprt;
281 
282 	/* Final put for backchannel xprt is in __svc_rdma_free */
283 	xprt_get(xprt);
284 	return xprt;
285 }
286 
287 struct xprt_class xprt_rdma_bc = {
288 	.list			= LIST_HEAD_INIT(xprt_rdma_bc.list),
289 	.name			= "rdma backchannel",
290 	.owner			= THIS_MODULE,
291 	.ident			= XPRT_TRANSPORT_BC_RDMA,
292 	.setup			= xprt_setup_rdma_bc,
293 };
294