1// SPDX-License-Identifier: GPL-2.0 2/* 3 * Copyright (c) 2015-2020, Oracle and/or its affiliates. 4 * 5 * Support for reverse-direction RPCs on RPC/RDMA. 6 */ 7 8#include <linux/sunrpc/xprt.h> 9#include <linux/sunrpc/svc.h> 10#include <linux/sunrpc/svc_xprt.h> 11#include <linux/sunrpc/svc_rdma.h> 12 13#include "xprt_rdma.h" 14#include <trace/events/rpcrdma.h> 15 16#undef RPCRDMA_BACKCHANNEL_DEBUG 17 18/** 19 * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests 20 * @xprt: transport associated with these backchannel resources 21 * @reqs: number of concurrent incoming requests to expect 22 * 23 * Returns 0 on success; otherwise a negative errno 24 */ 25int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs) 26{ 27 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt); 28 29 r_xprt->rx_buf.rb_bc_srv_max_requests = RPCRDMA_BACKWARD_WRS >> 1; 30 trace_xprtrdma_cb_setup(r_xprt, reqs); 31 return 0; 32} 33 34/** 35 * xprt_rdma_bc_maxpayload - Return maximum backchannel message size 36 * @xprt: transport 37 * 38 * Returns maximum size, in bytes, of a backchannel message 39 */ 40size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt) 41{ 42 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt); 43 struct rpcrdma_ep *ep = r_xprt->rx_ep; 44 size_t maxmsg; 45 46 maxmsg = min_t(unsigned int, ep->re_inline_send, ep->re_inline_recv); 47 maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE); 48 return maxmsg - RPCRDMA_HDRLEN_MIN; 49} 50 51unsigned int xprt_rdma_bc_max_slots(struct rpc_xprt *xprt) 52{ 53 return RPCRDMA_BACKWARD_WRS >> 1; 54} 55 56static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst) 57{ 58 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt); 59 struct rpcrdma_req *req = rpcr_to_rdmar(rqst); 60 __be32 *p; 61 62 rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0); 63 xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf, 64 rdmab_data(req->rl_rdmabuf), rqst); 65 66 p = xdr_reserve_space(&req->rl_stream, 28); 67 if (unlikely(!p)) 68 return -EIO; 69 *p++ = rqst->rq_xid; 70 *p++ = rpcrdma_version; 71 *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests); 72 *p++ = rdma_msg; 73 *p++ = xdr_zero; 74 *p++ = xdr_zero; 75 *p = xdr_zero; 76 77 if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN, 78 &rqst->rq_snd_buf, rpcrdma_noch_pullup)) 79 return -EIO; 80 81 trace_xprtrdma_cb_reply(r_xprt, rqst); 82 return 0; 83} 84 85/** 86 * xprt_rdma_bc_send_reply - marshal and send a backchannel reply 87 * @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf 88 * 89 * Caller holds the transport's write lock. 90 * 91 * Returns: 92 * %0 if the RPC message has been sent 93 * %-ENOTCONN if the caller should reconnect and call again 94 * %-EIO if a permanent error occurred and the request was not 95 * sent. Do not try to send this message again. 96 */ 97int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst) 98{ 99 struct rpc_xprt *xprt = rqst->rq_xprt; 100 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt); 101 struct rpcrdma_req *req = rpcr_to_rdmar(rqst); 102 int rc; 103 104 if (!xprt_connected(xprt)) 105 return -ENOTCONN; 106 107 if (!xprt_request_get_cong(xprt, rqst)) 108 return -EBADSLT; 109 110 rc = rpcrdma_bc_marshal_reply(rqst); 111 if (rc < 0) 112 goto failed_marshal; 113 114 if (frwr_send(r_xprt, req)) 115 goto drop_connection; 116 return 0; 117 118failed_marshal: 119 if (rc != -ENOTCONN) 120 return rc; 121drop_connection: 122 xprt_rdma_close(xprt); 123 return -ENOTCONN; 124} 125 126/** 127 * xprt_rdma_bc_destroy - Release resources for handling backchannel requests 128 * @xprt: transport associated with these backchannel resources 129 * @reqs: number of incoming requests to destroy; ignored 130 */ 131void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs) 132{ 133 struct rpc_rqst *rqst, *tmp; 134 135 spin_lock(&xprt->bc_pa_lock); 136 list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) { 137 list_del(&rqst->rq_bc_pa_list); 138 spin_unlock(&xprt->bc_pa_lock); 139 140 rpcrdma_req_destroy(rpcr_to_rdmar(rqst)); 141 142 spin_lock(&xprt->bc_pa_lock); 143 } 144 spin_unlock(&xprt->bc_pa_lock); 145} 146 147/** 148 * xprt_rdma_bc_free_rqst - Release a backchannel rqst 149 * @rqst: request to release 150 */ 151void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst) 152{ 153 struct rpcrdma_req *req = rpcr_to_rdmar(rqst); 154 struct rpcrdma_rep *rep = req->rl_reply; 155 struct rpc_xprt *xprt = rqst->rq_xprt; 156 struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt); 157 158 rpcrdma_rep_put(&r_xprt->rx_buf, rep); 159 req->rl_reply = NULL; 160 161 spin_lock(&xprt->bc_pa_lock); 162 list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list); 163 spin_unlock(&xprt->bc_pa_lock); 164 xprt_put(xprt); 165} 166 167static struct rpc_rqst *rpcrdma_bc_rqst_get(struct rpcrdma_xprt *r_xprt) 168{ 169 struct rpc_xprt *xprt = &r_xprt->rx_xprt; 170 struct rpcrdma_req *req; 171 struct rpc_rqst *rqst; 172 size_t size; 173 174 spin_lock(&xprt->bc_pa_lock); 175 rqst = list_first_entry_or_null(&xprt->bc_pa_list, struct rpc_rqst, 176 rq_bc_pa_list); 177 if (!rqst) 178 goto create_req; 179 list_del(&rqst->rq_bc_pa_list); 180 spin_unlock(&xprt->bc_pa_lock); 181 return rqst; 182 183create_req: 184 spin_unlock(&xprt->bc_pa_lock); 185 186 /* Set a limit to prevent a remote from overrunning our resources. 187 */ 188 if (xprt->bc_alloc_count >= RPCRDMA_BACKWARD_WRS) 189 return NULL; 190 191 size = min_t(size_t, r_xprt->rx_ep->re_inline_recv, PAGE_SIZE); 192 req = rpcrdma_req_create(r_xprt, size); 193 if (!req) 194 return NULL; 195 if (rpcrdma_req_setup(r_xprt, req)) { 196 rpcrdma_req_destroy(req); 197 return NULL; 198 } 199 200 xprt->bc_alloc_count++; 201 rqst = &req->rl_slot; 202 rqst->rq_xprt = xprt; 203 __set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state); 204 xdr_buf_init(&rqst->rq_snd_buf, rdmab_data(req->rl_sendbuf), size); 205 return rqst; 206} 207 208/** 209 * rpcrdma_bc_receive_call - Handle a reverse-direction Call 210 * @r_xprt: transport receiving the call 211 * @rep: receive buffer containing the call 212 * 213 * Operational assumptions: 214 * o Backchannel credits are ignored, just as the NFS server 215 * forechannel currently does 216 * o The ULP manages a replay cache (eg, NFSv4.1 sessions). 217 * No replay detection is done at the transport level 218 */ 219void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt, 220 struct rpcrdma_rep *rep) 221{ 222 struct rpc_xprt *xprt = &r_xprt->rx_xprt; 223 struct svc_serv *bc_serv; 224 struct rpcrdma_req *req; 225 struct rpc_rqst *rqst; 226 struct xdr_buf *buf; 227 size_t size; 228 __be32 *p; 229 230 p = xdr_inline_decode(&rep->rr_stream, 0); 231 size = xdr_stream_remaining(&rep->rr_stream); 232 233#ifdef RPCRDMA_BACKCHANNEL_DEBUG 234 pr_info("RPC: %s: callback XID %08x, length=%u\n", 235 __func__, be32_to_cpup(p), size); 236 pr_info("RPC: %s: %*ph\n", __func__, size, p); 237#endif 238 239 rqst = rpcrdma_bc_rqst_get(r_xprt); 240 if (!rqst) 241 goto out_overflow; 242 243 rqst->rq_reply_bytes_recvd = 0; 244 rqst->rq_xid = *p; 245 246 rqst->rq_private_buf.len = size; 247 248 buf = &rqst->rq_rcv_buf; 249 memset(buf, 0, sizeof(*buf)); 250 buf->head[0].iov_base = p; 251 buf->head[0].iov_len = size; 252 buf->len = size; 253 254 /* The receive buffer has to be hooked to the rpcrdma_req 255 * so that it is not released while the req is pointing 256 * to its buffer, and so that it can be reposted after 257 * the Upper Layer is done decoding it. 258 */ 259 req = rpcr_to_rdmar(rqst); 260 req->rl_reply = rep; 261 trace_xprtrdma_cb_call(r_xprt, rqst); 262 263 /* Queue rqst for ULP's callback service */ 264 bc_serv = xprt->bc_serv; 265 xprt_get(xprt); 266 lwq_enqueue(&rqst->rq_bc_list, &bc_serv->sv_cb_list); 267 268 svc_pool_wake_idle_thread(&bc_serv->sv_pools[0]); 269 270 r_xprt->rx_stats.bcall_count++; 271 return; 272 273out_overflow: 274 pr_warn("RPC/RDMA backchannel overflow\n"); 275 xprt_force_disconnect(xprt); 276 /* This receive buffer gets reposted automatically 277 * when the connection is re-established. 278 */ 279 return; 280} 281