2 * Copyright (c) 2015 Oracle. All rights reserved.
4 * Support for backward direction RPCs on RPC/RDMA.
7 #include <linux/module.h>
8 #include <linux/sunrpc/xprt.h>
9 #include <linux/sunrpc/svc.h>
10 #include <linux/sunrpc/svc_xprt.h>
12 #include "xprt_rdma.h"
14 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
15 # define RPCDBG_FACILITY RPCDBG_TRANS
18 #undef RPCRDMA_BACKCHANNEL_DEBUG
20 static void rpcrdma_bc_free_rqst(struct rpcrdma_xprt *r_xprt,
21 struct rpc_rqst *rqst)
23 struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
24 struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
26 spin_lock(&buf->rb_reqslock);
27 list_del(&req->rl_all);
28 spin_unlock(&buf->rb_reqslock);
30 rpcrdma_destroy_req(req);
35 static int rpcrdma_bc_setup_rqst(struct rpcrdma_xprt *r_xprt,
36 struct rpc_rqst *rqst)
38 struct rpcrdma_regbuf *rb;
39 struct rpcrdma_req *req;
42 req = rpcrdma_create_req(r_xprt);
45 req->rl_backchannel = true;
47 rb = rpcrdma_alloc_regbuf(RPCRDMA_HDRBUF_SIZE,
48 DMA_TO_DEVICE, GFP_KERNEL);
53 size = r_xprt->rx_data.inline_rsize;
54 rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
58 xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
59 min_t(size_t, size, PAGE_SIZE));
60 rpcrdma_set_xprtdata(rqst, req);
64 rpcrdma_bc_free_rqst(r_xprt, rqst);
68 /* Allocate and add receive buffers to the rpcrdma_buffer's
69 * existing list of rep's. These are released when the
70 * transport is destroyed.
72 static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
75 struct rpcrdma_rep *rep;
79 rep = rpcrdma_create_rep(r_xprt);
81 pr_err("RPC: %s: reply buffer alloc failed\n",
87 rpcrdma_recv_buffer_put(rep);
94 * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
95 * @xprt: transport associated with these backchannel resources
96 * @reqs: number of concurrent incoming requests to expect
98 * Returns 0 on success; otherwise a negative errno
100 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
102 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
103 struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
104 struct rpc_rqst *rqst;
108 /* The backchannel reply path returns each rpc_rqst to the
109 * bc_pa_list _after_ the reply is sent. If the server is
110 * faster than the client, it can send another backward
111 * direction request before the rpc_rqst is returned to the
112 * list. The client rejects the request in this case.
114 * Twice as many rpc_rqsts are prepared to ensure there is
115 * always an rpc_rqst available as soon as a reply is sent.
117 if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
120 for (i = 0; i < (reqs << 1); i++) {
121 rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
125 dprintk("RPC: %s: new rqst %p\n", __func__, rqst);
127 rqst->rq_xprt = &r_xprt->rx_xprt;
128 INIT_LIST_HEAD(&rqst->rq_list);
129 INIT_LIST_HEAD(&rqst->rq_bc_list);
131 if (rpcrdma_bc_setup_rqst(r_xprt, rqst))
134 spin_lock_bh(&xprt->bc_pa_lock);
135 list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
136 spin_unlock_bh(&xprt->bc_pa_lock);
139 rc = rpcrdma_bc_setup_reps(r_xprt, reqs);
143 rc = rpcrdma_ep_post_extra_recv(r_xprt, reqs);
147 buffer->rb_bc_srv_max_requests = reqs;
148 request_module("svcrdma");
153 xprt_rdma_bc_destroy(xprt, reqs);
156 pr_err("RPC: %s: setup backchannel transport failed\n", __func__);
161 * xprt_rdma_bc_up - Create transport endpoint for backchannel service
162 * @serv: server endpoint
163 * @net: network namespace
165 * The "xprt" is an implied argument: it supplies the name of the
166 * backchannel transport class.
168 * Returns zero on success, negative errno on failure
170 int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
174 ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
181 * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
184 * Returns maximum size, in bytes, of a backchannel message
186 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
188 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
189 struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
192 maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
193 maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
194 return maxmsg - RPCRDMA_HDRLEN_MIN;
198 * rpcrdma_bc_marshal_reply - Send backwards direction reply
199 * @rqst: buffer containing RPC reply data
201 * Returns zero on success.
203 int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
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;
210 headerp = rdmab_to_msg(req->rl_rdmabuf);
211 headerp->rm_xid = rqst->rq_xid;
212 headerp->rm_vers = rpcrdma_version;
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;
220 if (!rpcrdma_prepare_send_sges(&r_xprt->rx_ia, req, RPCRDMA_HDRLEN_MIN,
221 &rqst->rq_snd_buf, rpcrdma_noch))
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
231 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
233 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
234 struct rpc_rqst *rqst, *tmp;
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);
241 rpcrdma_bc_free_rqst(r_xprt, rqst);
243 spin_lock_bh(&xprt->bc_pa_lock);
245 spin_unlock_bh(&xprt->bc_pa_lock);
249 * xprt_rdma_bc_free_rqst - Release a backchannel rqst
250 * @rqst: request to release
252 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
254 struct rpc_xprt *xprt = rqst->rq_xprt;
256 dprintk("RPC: %s: freeing rqst %p (req %p)\n",
257 __func__, rqst, rpcr_to_rdmar(rqst));
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();
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);
270 * rpcrdma_bc_receive_call - Handle a backward direction call
271 * @xprt: transport receiving the call
272 * @rep: receive buffer containing the call
274 * Called in the RPC reply handler, which runs in a tasklet.
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
283 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
284 struct rpcrdma_rep *rep)
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;
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);
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.
308 if (rep->rr_len < RPCRDMA_HDRLEN_MIN + 24)
310 p = (__be32 *)((unsigned char *)headerp + RPCRDMA_HDRLEN_MIN);
311 size = rep->rr_len - RPCRDMA_HDRLEN_MIN;
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);
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);
326 rqst->rq_reply_bytes_recvd = 0;
327 rqst->rq_bytes_sent = 0;
328 rqst->rq_xid = headerp->rm_xid;
330 rqst->rq_private_buf.len = size;
331 set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
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;
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
344 req = rpcr_to_rdmar(rqst);
345 dprintk("RPC: %s: attaching rep %p to req %p\n",
349 /* Defeat the retransmit detection logic in send_request */
350 req->rl_connect_cookie = 0;
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);
358 wake_up(&bc_serv->sv_cb_waitq);
360 r_xprt->rx_stats.bcall_count++;
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.
372 pr_warn("RPC/RDMA short backward direction call\n");
374 if (rpcrdma_ep_post_recv(&r_xprt->rx_ia, rep))
375 xprt_disconnect_done(xprt);
377 pr_warn("RPC: %s: reposting rep %p\n",