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
  13 #include "xprt_rdma.h"
  14
  15 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  16 # define RPCDBG_FACILITY        RPCDBG_TRANS
  17 #endif
  18
  19 #undef RPCRDMA_BACKCHANNEL_DEBUG
  20
  21 static void rpcrdma_bc_free_rqst(struct rpcrdma_xprt *r_xprt,
  22                                  struct rpc_rqst *rqst)
  23 {
  24         struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
  25         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
  26
  27         spin_lock(&buf->rb_reqslock);
  28         list_del(&req->rl_all);
  29         spin_unlock(&buf->rb_reqslock);
  30
  31         rpcrdma_destroy_req(req);
  32
  33         kfree(rqst);
  34 }
  35
  36 static int rpcrdma_bc_setup_rqst(struct rpcrdma_xprt *r_xprt,
  37                                  struct rpc_rqst *rqst)
  38 {
  39         struct rpcrdma_regbuf *rb;
  40         struct rpcrdma_req *req;
  41         size_t size;
  42
  43         req = rpcrdma_create_req(r_xprt);
  44         if (IS_ERR(req))
  45                 return PTR_ERR(req);
  46
  47         size = r_xprt->rx_data.inline_rsize;
  48         rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
  49         if (IS_ERR(rb))
  50                 goto out_fail;
  51         req->rl_sendbuf = rb;
  52         xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
  53                      min_t(size_t, size, PAGE_SIZE));
  54         rpcrdma_set_xprtdata(rqst, req);
  55         return 0;
  56
  57 out_fail:
  58         rpcrdma_bc_free_rqst(r_xprt, rqst);
  59         return -ENOMEM;
  60 }
  61
  62 /* Allocate and add receive buffers to the rpcrdma_buffer's
  63  * existing list of rep's. These are released when the
  64  * transport is destroyed.
  65  */
  66 static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
  67                                  unsigned int count)
  68 {
  69         int rc = 0;
  70
  71         while (count--) {
  72                 rc = rpcrdma_create_rep(r_xprt);
  73                 if (rc)
  74                         break;
  75         }
  76         return rc;
  77 }
  78
  79 /**
  80  * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
  81  * @xprt: transport associated with these backchannel resources
  82  * @reqs: number of concurrent incoming requests to expect
  83  *
  84  * Returns 0 on success; otherwise a negative errno
  85  */
  86 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
  87 {
  88         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  89         struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
  90         struct rpc_rqst *rqst;
  91         unsigned int i;
  92         int rc;
  93
  94         /* The backchannel reply path returns each rpc_rqst to the
  95          * bc_pa_list _after_ the reply is sent. If the server is
  96          * faster than the client, it can send another backward
  97          * direction request before the rpc_rqst is returned to the
  98          * list. The client rejects the request in this case.
  99          *
 100          * Twice as many rpc_rqsts are prepared to ensure there is
 101          * always an rpc_rqst available as soon as a reply is sent.
 102          */
 103         if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
 104                 goto out_err;
 105
 106         for (i = 0; i < (reqs << 1); i++) {
 107                 rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
 108                 if (!rqst)
 109                         goto out_free;
 110
 111                 dprintk("RPC:       %s: new rqst %p\n", __func__, rqst);
 112
 113                 rqst->rq_xprt = &r_xprt->rx_xprt;
 114                 INIT_LIST_HEAD(&rqst->rq_list);
 115                 INIT_LIST_HEAD(&rqst->rq_bc_list);
 116                 __set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 117
 118                 if (rpcrdma_bc_setup_rqst(r_xprt, rqst))
 119                         goto out_free;
 120
 121                 spin_lock_bh(&xprt->bc_pa_lock);
 122                 list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 123                 spin_unlock_bh(&xprt->bc_pa_lock);
 124         }
 125
 126         rc = rpcrdma_bc_setup_reps(r_xprt, reqs);
 127         if (rc)
 128                 goto out_free;
 129
 130         rc = rpcrdma_ep_post_extra_recv(r_xprt, reqs);
 131         if (rc)
 132                 goto out_free;
 133
 134         buffer->rb_bc_srv_max_requests = reqs;
 135         request_module("svcrdma");
 136         trace_xprtrdma_cb_setup(r_xprt, reqs);
 137         return 0;
 138
 139 out_free:
 140         xprt_rdma_bc_destroy(xprt, reqs);
 141
 142 out_err:
 143         pr_err("RPC:       %s: setup backchannel transport failed\n", __func__);
 144         return -ENOMEM;
 145 }
 146
 147 /**
 148  * xprt_rdma_bc_up - Create transport endpoint for backchannel service
 149  * @serv: server endpoint
 150  * @net: network namespace
 151  *
 152  * The "xprt" is an implied argument: it supplies the name of the
 153  * backchannel transport class.
 154  *
 155  * Returns zero on success, negative errno on failure
 156  */
 157 int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
 158 {
 159         int ret;
 160
 161         ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
 162         if (ret < 0)
 163                 return ret;
 164         return 0;
 165 }
 166
 167 /**
 168  * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
 169  * @xprt: transport
 170  *
 171  * Returns maximum size, in bytes, of a backchannel message
 172  */
 173 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
 174 {
 175         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 176         struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
 177         size_t maxmsg;
 178
 179         maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
 180         maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
 181         return maxmsg - RPCRDMA_HDRLEN_MIN;
 182 }
 183
 184 static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
 185 {
 186         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
 187         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 188         __be32 *p;
 189
 190         rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
 191         xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
 192                         req->rl_rdmabuf->rg_base);
 193
 194         p = xdr_reserve_space(&req->rl_stream, 28);
 195         if (unlikely(!p))
 196                 return -EIO;
 197         *p++ = rqst->rq_xid;
 198         *p++ = rpcrdma_version;
 199         *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
 200         *p++ = rdma_msg;
 201         *p++ = xdr_zero;
 202         *p++ = xdr_zero;
 203         *p = xdr_zero;
 204
 205         if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
 206                                       &rqst->rq_snd_buf, rpcrdma_noch))
 207                 return -EIO;
 208
 209         trace_xprtrdma_cb_reply(rqst);
 210         return 0;
 211 }
 212
 213 /**
 214  * xprt_rdma_bc_send_reply - marshal and send a backchannel reply
 215  * @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
 216  *
 217  * Caller holds the transport's write lock.
 218  *
 219  * Returns:
 220  *      %0 if the RPC message has been sent
 221  *      %-ENOTCONN if the caller should reconnect and call again
 222  *      %-EIO if a permanent error occurred and the request was not
 223  *              sent. Do not try to send this message again.
 224  */
 225 int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
 226 {
 227         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
 228         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 229         int rc;
 230
 231         if (!xprt_connected(rqst->rq_xprt))
 232                 goto drop_connection;
 233
 234         rc = rpcrdma_bc_marshal_reply(rqst);
 235         if (rc < 0)
 236                 goto failed_marshal;
 237
 238         if (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, req))
 239                 goto drop_connection;
 240         return 0;
 241
 242 failed_marshal:
 243         if (rc != -ENOTCONN)
 244                 return rc;
 245 drop_connection:
 246         xprt_disconnect_done(rqst->rq_xprt);
 247         return -ENOTCONN;
 248 }
 249
 250 /**
 251  * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
 252  * @xprt: transport associated with these backchannel resources
 253  * @reqs: number of incoming requests to destroy; ignored
 254  */
 255 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
 256 {
 257         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 258         struct rpc_rqst *rqst, *tmp;
 259
 260         spin_lock_bh(&xprt->bc_pa_lock);
 261         list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 262                 list_del(&rqst->rq_bc_pa_list);
 263                 spin_unlock_bh(&xprt->bc_pa_lock);
 264
 265                 rpcrdma_bc_free_rqst(r_xprt, rqst);
 266
 267                 spin_lock_bh(&xprt->bc_pa_lock);
 268         }
 269         spin_unlock_bh(&xprt->bc_pa_lock);
 270 }
 271
 272 /**
 273  * xprt_rdma_bc_free_rqst - Release a backchannel rqst
 274  * @rqst: request to release
 275  */
 276 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
 277 {
 278         struct rpc_xprt *xprt = rqst->rq_xprt;
 279
 280         dprintk("RPC:       %s: freeing rqst %p (req %p)\n",
 281                 __func__, rqst, rpcr_to_rdmar(rqst));
 282
 283         spin_lock_bh(&xprt->bc_pa_lock);
 284         list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 285         spin_unlock_bh(&xprt->bc_pa_lock);
 286 }
 287
 288 /**
 289  * rpcrdma_bc_receive_call - Handle a backward direction call
 290  * @r_xprt: transport receiving the call
 291  * @rep: receive buffer containing the call
 292  *
 293  * Operational assumptions:
 294  *    o Backchannel credits are ignored, just as the NFS server
 295  *      forechannel currently does
 296  *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
 297  *      No replay detection is done at the transport level
 298  */
 299 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
 300                              struct rpcrdma_rep *rep)
 301 {
 302         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
 303         struct svc_serv *bc_serv;
 304         struct rpcrdma_req *req;
 305         struct rpc_rqst *rqst;
 306         struct xdr_buf *buf;
 307         size_t size;
 308         __be32 *p;
 309
 310         p = xdr_inline_decode(&rep->rr_stream, 0);
 311         size = xdr_stream_remaining(&rep->rr_stream);
 312
 313 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
 314         pr_info("RPC:       %s: callback XID %08x, length=%u\n",
 315                 __func__, be32_to_cpup(p), size);
 316         pr_info("RPC:       %s: %*ph\n", __func__, size, p);
 317 #endif
 318
 319         /* Grab a free bc rqst */
 320         spin_lock(&xprt->bc_pa_lock);
 321         if (list_empty(&xprt->bc_pa_list)) {
 322                 spin_unlock(&xprt->bc_pa_lock);
 323                 goto out_overflow;
 324         }
 325         rqst = list_first_entry(&xprt->bc_pa_list,
 326                                 struct rpc_rqst, rq_bc_pa_list);
 327         list_del(&rqst->rq_bc_pa_list);
 328         spin_unlock(&xprt->bc_pa_lock);
 329
 330         /* Prepare rqst */
 331         rqst->rq_reply_bytes_recvd = 0;
 332         rqst->rq_bytes_sent = 0;
 333         rqst->rq_xid = *p;
 334
 335         rqst->rq_private_buf.len = size;
 336
 337         buf = &rqst->rq_rcv_buf;
 338         memset(buf, 0, sizeof(*buf));
 339         buf->head[0].iov_base = p;
 340         buf->head[0].iov_len = size;
 341         buf->len = size;
 342
 343         /* The receive buffer has to be hooked to the rpcrdma_req
 344          * so that it is not released while the req is pointing
 345          * to its buffer, and so that it can be reposted after
 346          * the Upper Layer is done decoding it.
 347          */
 348         req = rpcr_to_rdmar(rqst);
 349         req->rl_reply = rep;
 350         trace_xprtrdma_cb_call(rqst);
 351
 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);
 357
 358         wake_up(&bc_serv->sv_cb_waitq);
 359
 360         r_xprt->rx_stats.bcall_count++;
 361         return;
 362
 363 out_overflow:
 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.
 368          */
 369         return;
 370 }