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Linux/net/sunrpc/xprtrdma/backchannel.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Copyright (c) 2015 Oracle.  All rights reserved.
  4  *
  5  * Support for backward direction RPCs on RPC/RDMA.
  6  */
  7 
  8 #include <linux/module.h>
  9 #include <linux/sunrpc/xprt.h>
 10 #include <linux/sunrpc/svc.h>
 11 #include <linux/sunrpc/svc_xprt.h>
 12 #include <linux/sunrpc/svc_rdma.h>
 13 
 14 #include "xprt_rdma.h"
 15 #include <trace/events/rpcrdma.h>
 16 
 17 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 18 # define RPCDBG_FACILITY        RPCDBG_TRANS
 19 #endif
 20 
 21 #undef RPCRDMA_BACKCHANNEL_DEBUG
 22 
 23 static void rpcrdma_bc_free_rqst(struct rpcrdma_xprt *r_xprt,
 24                                  struct rpc_rqst *rqst)
 25 {
 26         struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
 27         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 28 
 29         spin_lock(&buf->rb_reqslock);
 30         list_del(&req->rl_all);
 31         spin_unlock(&buf->rb_reqslock);
 32 
 33         rpcrdma_destroy_req(req);
 34 }
 35 
 36 static int rpcrdma_bc_setup_reqs(struct rpcrdma_xprt *r_xprt,
 37                                  unsigned int count)
 38 {
 39         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
 40         struct rpc_rqst *rqst;
 41         unsigned int i;
 42 
 43         for (i = 0; i < (count << 1); i++) {
 44                 struct rpcrdma_regbuf *rb;
 45                 struct rpcrdma_req *req;
 46                 size_t size;
 47 
 48                 req = rpcrdma_create_req(r_xprt);
 49                 if (IS_ERR(req))
 50                         return PTR_ERR(req);
 51                 rqst = &req->rl_slot;
 52 
 53                 rqst->rq_xprt = xprt;
 54                 INIT_LIST_HEAD(&rqst->rq_list);
 55                 INIT_LIST_HEAD(&rqst->rq_bc_list);
 56                 __set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 57                 spin_lock_bh(&xprt->bc_pa_lock);
 58                 list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 59                 spin_unlock_bh(&xprt->bc_pa_lock);
 60 
 61                 size = r_xprt->rx_data.inline_rsize;
 62                 rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
 63                 if (IS_ERR(rb))
 64                         goto out_fail;
 65                 req->rl_sendbuf = rb;
 66                 xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
 67                              min_t(size_t, size, PAGE_SIZE));
 68         }
 69         return 0;
 70 
 71 out_fail:
 72         rpcrdma_bc_free_rqst(r_xprt, rqst);
 73         return -ENOMEM;
 74 }
 75 
 76 /**
 77  * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
 78  * @xprt: transport associated with these backchannel resources
 79  * @reqs: number of concurrent incoming requests to expect
 80  *
 81  * Returns 0 on success; otherwise a negative errno
 82  */
 83 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
 84 {
 85         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 86         int rc;
 87 
 88         /* The backchannel reply path returns each rpc_rqst to the
 89          * bc_pa_list _after_ the reply is sent. If the server is
 90          * faster than the client, it can send another backward
 91          * direction request before the rpc_rqst is returned to the
 92          * list. The client rejects the request in this case.
 93          *
 94          * Twice as many rpc_rqsts are prepared to ensure there is
 95          * always an rpc_rqst available as soon as a reply is sent.
 96          */
 97         if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
 98                 goto out_err;
 99 
100         rc = rpcrdma_bc_setup_reqs(r_xprt, reqs);
101         if (rc)
102                 goto out_free;
103 
104         r_xprt->rx_buf.rb_bc_srv_max_requests = reqs;
105         request_module("svcrdma");
106         trace_xprtrdma_cb_setup(r_xprt, reqs);
107         return 0;
108 
109 out_free:
110         xprt_rdma_bc_destroy(xprt, reqs);
111 
112 out_err:
113         pr_err("RPC:       %s: setup backchannel transport failed\n", __func__);
114         return -ENOMEM;
115 }
116 
117 /**
118  * xprt_rdma_bc_up - Create transport endpoint for backchannel service
119  * @serv: server endpoint
120  * @net: network namespace
121  *
122  * The "xprt" is an implied argument: it supplies the name of the
123  * backchannel transport class.
124  *
125  * Returns zero on success, negative errno on failure
126  */
127 int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
128 {
129         int ret;
130 
131         ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
132         if (ret < 0)
133                 return ret;
134         return 0;
135 }
136 
137 /**
138  * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
139  * @xprt: transport
140  *
141  * Returns maximum size, in bytes, of a backchannel message
142  */
143 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
144 {
145         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
146         struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
147         size_t maxmsg;
148 
149         maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
150         maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
151         return maxmsg - RPCRDMA_HDRLEN_MIN;
152 }
153 
154 static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
155 {
156         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
157         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
158         __be32 *p;
159 
160         rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
161         xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
162                         req->rl_rdmabuf->rg_base);
163 
164         p = xdr_reserve_space(&req->rl_stream, 28);
165         if (unlikely(!p))
166                 return -EIO;
167         *p++ = rqst->rq_xid;
168         *p++ = rpcrdma_version;
169         *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
170         *p++ = rdma_msg;
171         *p++ = xdr_zero;
172         *p++ = xdr_zero;
173         *p = xdr_zero;
174 
175         if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
176                                       &rqst->rq_snd_buf, rpcrdma_noch))
177                 return -EIO;
178 
179         trace_xprtrdma_cb_reply(rqst);
180         return 0;
181 }
182 
183 /**
184  * xprt_rdma_bc_send_reply - marshal and send a backchannel reply
185  * @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
186  *
187  * Caller holds the transport's write lock.
188  *
189  * Returns:
190  *      %0 if the RPC message has been sent
191  *      %-ENOTCONN if the caller should reconnect and call again
192  *      %-EIO if a permanent error occurred and the request was not
193  *              sent. Do not try to send this message again.
194  */
195 int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
196 {
197         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
198         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
199         int rc;
200 
201         if (!xprt_connected(rqst->rq_xprt))
202                 goto drop_connection;
203 
204         rc = rpcrdma_bc_marshal_reply(rqst);
205         if (rc < 0)
206                 goto failed_marshal;
207 
208         rpcrdma_post_recvs(r_xprt, true);
209         if (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, req))
210                 goto drop_connection;
211         return 0;
212 
213 failed_marshal:
214         if (rc != -ENOTCONN)
215                 return rc;
216 drop_connection:
217         xprt_disconnect_done(rqst->rq_xprt);
218         return -ENOTCONN;
219 }
220 
221 /**
222  * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
223  * @xprt: transport associated with these backchannel resources
224  * @reqs: number of incoming requests to destroy; ignored
225  */
226 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
227 {
228         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
229         struct rpc_rqst *rqst, *tmp;
230 
231         spin_lock_bh(&xprt->bc_pa_lock);
232         list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
233                 list_del(&rqst->rq_bc_pa_list);
234                 spin_unlock_bh(&xprt->bc_pa_lock);
235 
236                 rpcrdma_bc_free_rqst(r_xprt, rqst);
237 
238                 spin_lock_bh(&xprt->bc_pa_lock);
239         }
240         spin_unlock_bh(&xprt->bc_pa_lock);
241 }
242 
243 /**
244  * xprt_rdma_bc_free_rqst - Release a backchannel rqst
245  * @rqst: request to release
246  */
247 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
248 {
249         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
250         struct rpc_xprt *xprt = rqst->rq_xprt;
251 
252         dprintk("RPC:       %s: freeing rqst %p (req %p)\n",
253                 __func__, rqst, req);
254 
255         rpcrdma_recv_buffer_put(req->rl_reply);
256         req->rl_reply = NULL;
257 
258         spin_lock_bh(&xprt->bc_pa_lock);
259         list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
260         spin_unlock_bh(&xprt->bc_pa_lock);
261 }
262 
263 /**
264  * rpcrdma_bc_receive_call - Handle a backward direction call
265  * @r_xprt: transport receiving the call
266  * @rep: receive buffer containing the call
267  *
268  * Operational assumptions:
269  *    o Backchannel credits are ignored, just as the NFS server
270  *      forechannel currently does
271  *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
272  *      No replay detection is done at the transport level
273  */
274 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
275                              struct rpcrdma_rep *rep)
276 {
277         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
278         struct svc_serv *bc_serv;
279         struct rpcrdma_req *req;
280         struct rpc_rqst *rqst;
281         struct xdr_buf *buf;
282         size_t size;
283         __be32 *p;
284 
285         p = xdr_inline_decode(&rep->rr_stream, 0);
286         size = xdr_stream_remaining(&rep->rr_stream);
287 
288 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
289         pr_info("RPC:       %s: callback XID %08x, length=%u\n",
290                 __func__, be32_to_cpup(p), size);
291         pr_info("RPC:       %s: %*ph\n", __func__, size, p);
292 #endif
293 
294         /* Grab a free bc rqst */
295         spin_lock(&xprt->bc_pa_lock);
296         if (list_empty(&xprt->bc_pa_list)) {
297                 spin_unlock(&xprt->bc_pa_lock);
298                 goto out_overflow;
299         }
300         rqst = list_first_entry(&xprt->bc_pa_list,
301                                 struct rpc_rqst, rq_bc_pa_list);
302         list_del(&rqst->rq_bc_pa_list);
303         spin_unlock(&xprt->bc_pa_lock);
304 
305         /* Prepare rqst */
306         rqst->rq_reply_bytes_recvd = 0;
307         rqst->rq_bytes_sent = 0;
308         rqst->rq_xid = *p;
309 
310         rqst->rq_private_buf.len = size;
311 
312         buf = &rqst->rq_rcv_buf;
313         memset(buf, 0, sizeof(*buf));
314         buf->head[0].iov_base = p;
315         buf->head[0].iov_len = size;
316         buf->len = size;
317 
318         /* The receive buffer has to be hooked to the rpcrdma_req
319          * so that it is not released while the req is pointing
320          * to its buffer, and so that it can be reposted after
321          * the Upper Layer is done decoding it.
322          */
323         req = rpcr_to_rdmar(rqst);
324         req->rl_reply = rep;
325         trace_xprtrdma_cb_call(rqst);
326 
327         /* Queue rqst for ULP's callback service */
328         bc_serv = xprt->bc_serv;
329         spin_lock(&bc_serv->sv_cb_lock);
330         list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
331         spin_unlock(&bc_serv->sv_cb_lock);
332 
333         wake_up(&bc_serv->sv_cb_waitq);
334 
335         r_xprt->rx_stats.bcall_count++;
336         return;
337 
338 out_overflow:
339         pr_warn("RPC/RDMA backchannel overflow\n");
340         xprt_disconnect_done(xprt);
341         /* This receive buffer gets reposted automatically
342          * when the connection is re-established.
343          */
344         return;
345 }
346 

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