net/sunrpc/xprtrdma/backchannel.c

   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_bc_list);
  55                 __set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
  56                 spin_lock(&xprt->bc_pa_lock);
  57                 list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
  58                 spin_unlock(&xprt->bc_pa_lock);
  59
  60                 size = r_xprt->rx_data.inline_rsize;
  61                 rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
  62                 if (IS_ERR(rb))
  63                         goto out_fail;
  64                 req->rl_sendbuf = rb;
  65                 xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
  66                              min_t(size_t, size, PAGE_SIZE));
  67         }
  68         return 0;
  69
  70 out_fail:
  71         rpcrdma_bc_free_rqst(r_xprt, rqst);
  72         return -ENOMEM;
  73 }
  74
  75 /**
  76  * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
  77  * @xprt: transport associated with these backchannel resources
  78  * @reqs: number of concurrent incoming requests to expect
  79  *
  80  * Returns 0 on success; otherwise a negative errno
  81  */
  82 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
  83 {
  84         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  85         int rc;
  86
  87         /* The backchannel reply path returns each rpc_rqst to the
  88          * bc_pa_list _after_ the reply is sent. If the server is
  89          * faster than the client, it can send another backward
  90          * direction request before the rpc_rqst is returned to the
  91          * list. The client rejects the request in this case.
  92          *
  93          * Twice as many rpc_rqsts are prepared to ensure there is
  94          * always an rpc_rqst available as soon as a reply is sent.
  95          */
  96         if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
  97                 goto out_err;
  98
  99         rc = rpcrdma_bc_setup_reqs(r_xprt, reqs);
 100         if (rc)
 101                 goto out_free;
 102
 103         r_xprt->rx_buf.rb_bc_srv_max_requests = reqs;
 104         request_module("svcrdma");
 105         trace_xprtrdma_cb_setup(r_xprt, reqs);
 106         return 0;
 107
 108 out_free:
 109         xprt_rdma_bc_destroy(xprt, reqs);
 110
 111 out_err:
 112         pr_err("RPC:       %s: setup backchannel transport failed\n", __func__);
 113         return -ENOMEM;
 114 }
 115
 116 /**
 117  * xprt_rdma_bc_up - Create transport endpoint for backchannel service
 118  * @serv: server endpoint
 119  * @net: network namespace
 120  *
 121  * The "xprt" is an implied argument: it supplies the name of the
 122  * backchannel transport class.
 123  *
 124  * Returns zero on success, negative errno on failure
 125  */
 126 int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
 127 {
 128         int ret;
 129
 130         ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
 131         if (ret < 0)
 132                 return ret;
 133         return 0;
 134 }
 135
 136 /**
 137  * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
 138  * @xprt: transport
 139  *
 140  * Returns maximum size, in bytes, of a backchannel message
 141  */
 142 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
 143 {
 144         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 145         struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
 146         size_t maxmsg;
 147
 148         maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
 149         maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
 150         return maxmsg - RPCRDMA_HDRLEN_MIN;
 151 }
 152
 153 static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
 154 {
 155         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
 156         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 157         __be32 *p;
 158
 159         rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
 160         xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
 161                         req->rl_rdmabuf->rg_base);
 162
 163         p = xdr_reserve_space(&req->rl_stream, 28);
 164         if (unlikely(!p))
 165                 return -EIO;
 166         *p++ = rqst->rq_xid;
 167         *p++ = rpcrdma_version;
 168         *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
 169         *p++ = rdma_msg;
 170         *p++ = xdr_zero;
 171         *p++ = xdr_zero;
 172         *p = xdr_zero;
 173
 174         if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
 175                                       &rqst->rq_snd_buf, rpcrdma_noch))
 176                 return -EIO;
 177
 178         trace_xprtrdma_cb_reply(rqst);
 179         return 0;
 180 }
 181
 182 /**
 183  * xprt_rdma_bc_send_reply - marshal and send a backchannel reply
 184  * @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
 185  *
 186  * Caller holds the transport's write lock.
 187  *
 188  * Returns:
 189  *      %0 if the RPC message has been sent
 190  *      %-ENOTCONN if the caller should reconnect and call again
 191  *      %-EIO if a permanent error occurred and the request was not
 192  *              sent. Do not try to send this message again.
 193  */
 194 int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
 195 {
 196         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
 197         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 198         int rc;
 199
 200         if (!xprt_connected(rqst->rq_xprt))
 201                 goto drop_connection;
 202
 203         if (!xprt_request_get_cong(rqst->rq_xprt, rqst))
 204                 return -EBADSLT;
 205
 206         rc = rpcrdma_bc_marshal_reply(rqst);
 207         if (rc < 0)
 208                 goto failed_marshal;
 209
 210         rpcrdma_post_recvs(r_xprt, true);
 211         if (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, req))
 212                 goto drop_connection;
 213         return 0;
 214
 215 failed_marshal:
 216         if (rc != -ENOTCONN)
 217                 return rc;
 218 drop_connection:
 219         xprt_disconnect_done(rqst->rq_xprt);
 220         return -ENOTCONN;
 221 }
 222
 223 /**
 224  * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
 225  * @xprt: transport associated with these backchannel resources
 226  * @reqs: number of incoming requests to destroy; ignored
 227  */
 228 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
 229 {
 230         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 231         struct rpc_rqst *rqst, *tmp;
 232
 233         spin_lock(&xprt->bc_pa_lock);
 234         list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 235                 list_del(&rqst->rq_bc_pa_list);
 236                 spin_unlock(&xprt->bc_pa_lock);
 237
 238                 rpcrdma_bc_free_rqst(r_xprt, rqst);
 239
 240                 spin_lock(&xprt->bc_pa_lock);
 241         }
 242         spin_unlock(&xprt->bc_pa_lock);
 243 }
 244
 245 /**
 246  * xprt_rdma_bc_free_rqst - Release a backchannel rqst
 247  * @rqst: request to release
 248  */
 249 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
 250 {
 251         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 252         struct rpc_xprt *xprt = rqst->rq_xprt;
 253
 254         dprintk("RPC:       %s: freeing rqst %p (req %p)\n",
 255                 __func__, rqst, req);
 256
 257         rpcrdma_recv_buffer_put(req->rl_reply);
 258         req->rl_reply = NULL;
 259
 260         spin_lock(&xprt->bc_pa_lock);
 261         list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 262         spin_unlock(&xprt->bc_pa_lock);
 263 }
 264
 265 /**
 266  * rpcrdma_bc_receive_call - Handle a backward direction call
 267  * @r_xprt: transport receiving the call
 268  * @rep: receive buffer containing the call
 269  *
 270  * Operational assumptions:
 271  *    o Backchannel credits are ignored, just as the NFS server
 272  *      forechannel currently does
 273  *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
 274  *      No replay detection is done at the transport level
 275  */
 276 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
 277                              struct rpcrdma_rep *rep)
 278 {
 279         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
 280         struct svc_serv *bc_serv;
 281         struct rpcrdma_req *req;
 282         struct rpc_rqst *rqst;
 283         struct xdr_buf *buf;
 284         size_t size;
 285         __be32 *p;
 286
 287         p = xdr_inline_decode(&rep->rr_stream, 0);
 288         size = xdr_stream_remaining(&rep->rr_stream);
 289
 290 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
 291         pr_info("RPC:       %s: callback XID %08x, length=%u\n",
 292                 __func__, be32_to_cpup(p), size);
 293         pr_info("RPC:       %s: %*ph\n", __func__, size, p);
 294 #endif
 295
 296         /* Grab a free bc rqst */
 297         spin_lock(&xprt->bc_pa_lock);
 298         if (list_empty(&xprt->bc_pa_list)) {
 299                 spin_unlock(&xprt->bc_pa_lock);
 300                 goto out_overflow;
 301         }
 302         rqst = list_first_entry(&xprt->bc_pa_list,
 303                                 struct rpc_rqst, rq_bc_pa_list);
 304         list_del(&rqst->rq_bc_pa_list);
 305         spin_unlock(&xprt->bc_pa_lock);
 306
 307         /* Prepare rqst */
 308         rqst->rq_reply_bytes_recvd = 0;
 309         rqst->rq_bytes_sent = 0;
 310         rqst->rq_xid = *p;
 311
 312         rqst->rq_private_buf.len = size;
 313
 314         buf = &rqst->rq_rcv_buf;
 315         memset(buf, 0, sizeof(*buf));
 316         buf->head[0].iov_base = p;
 317         buf->head[0].iov_len = size;
 318         buf->len = size;
 319
 320         /* The receive buffer has to be hooked to the rpcrdma_req
 321          * so that it is not released while the req is pointing
 322          * to its buffer, and so that it can be reposted after
 323          * the Upper Layer is done decoding it.
 324          */
 325         req = rpcr_to_rdmar(rqst);
 326         req->rl_reply = rep;
 327         trace_xprtrdma_cb_call(rqst);
 328
 329         /* Queue rqst for ULP's callback service */
 330         bc_serv = xprt->bc_serv;
 331         spin_lock(&bc_serv->sv_cb_lock);
 332         list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
 333         spin_unlock(&bc_serv->sv_cb_lock);
 334
 335         wake_up(&bc_serv->sv_cb_waitq);
 336
 337         r_xprt->rx_stats.bcall_count++;
 338         return;
 339
 340 out_overflow:
 341         pr_warn("RPC/RDMA backchannel overflow\n");
 342         xprt_disconnect_done(xprt);
 343         /* This receive buffer gets reposted automatically
 344          * when the connection is re-established.
 345          */
 346         return;
 347 }