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_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 }