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         rb = rpcrdma_alloc_regbuf(RPCRDMA_HDRBUF_SIZE,
  48                                   DMA_TO_DEVICE, GFP_KERNEL);
  49         if (IS_ERR(rb))
  50                 goto out_fail;
  51         req->rl_rdmabuf = rb;
  52         xdr_buf_init(&req->rl_hdrbuf, rb->rg_base, rdmab_length(rb));
  53
  54         size = r_xprt->rx_data.inline_rsize;
  55         rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
  56         if (IS_ERR(rb))
  57                 goto out_fail;
  58         req->rl_sendbuf = rb;
  59         xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
  60                      min_t(size_t, size, PAGE_SIZE));
  61         rpcrdma_set_xprtdata(rqst, req);
  62         return 0;
  63
  64 out_fail:
  65         rpcrdma_bc_free_rqst(r_xprt, rqst);
  66         return -ENOMEM;
  67 }
  68
  69 /* Allocate and add receive buffers to the rpcrdma_buffer's
  70  * existing list of rep's. These are released when the
  71  * transport is destroyed.
  72  */
  73 static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
  74                                  unsigned int count)
  75 {
  76         int rc = 0;
  77
  78         while (count--) {
  79                 rc = rpcrdma_create_rep(r_xprt);
  80                 if (rc)
  81                         break;
  82         }
  83         return rc;
  84 }
  85
  86 /**
  87  * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
  88  * @xprt: transport associated with these backchannel resources
  89  * @reqs: number of concurrent incoming requests to expect
  90  *
  91  * Returns 0 on success; otherwise a negative errno
  92  */
  93 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
  94 {
  95         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  96         struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
  97         struct rpc_rqst *rqst;
  98         unsigned int i;
  99         int rc;
 100
 101         /* The backchannel reply path returns each rpc_rqst to the
 102          * bc_pa_list _after_ the reply is sent. If the server is
 103          * faster than the client, it can send another backward
 104          * direction request before the rpc_rqst is returned to the
 105          * list. The client rejects the request in this case.
 106          *
 107          * Twice as many rpc_rqsts are prepared to ensure there is
 108          * always an rpc_rqst available as soon as a reply is sent.
 109          */
 110         if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
 111                 goto out_err;
 112
 113         for (i = 0; i < (reqs << 1); i++) {
 114                 rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
 115                 if (!rqst)
 116                         goto out_free;
 117
 118                 dprintk("RPC:       %s: new rqst %p\n", __func__, rqst);
 119
 120                 rqst->rq_xprt = &r_xprt->rx_xprt;
 121                 INIT_LIST_HEAD(&rqst->rq_list);
 122                 INIT_LIST_HEAD(&rqst->rq_bc_list);
 123                 __set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 124
 125                 if (rpcrdma_bc_setup_rqst(r_xprt, rqst))
 126                         goto out_free;
 127
 128                 spin_lock_bh(&xprt->bc_pa_lock);
 129                 list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 130                 spin_unlock_bh(&xprt->bc_pa_lock);
 131         }
 132
 133         rc = rpcrdma_bc_setup_reps(r_xprt, reqs);
 134         if (rc)
 135                 goto out_free;
 136
 137         rc = rpcrdma_ep_post_extra_recv(r_xprt, reqs);
 138         if (rc)
 139                 goto out_free;
 140
 141         buffer->rb_bc_srv_max_requests = reqs;
 142         request_module("svcrdma");
 143         trace_xprtrdma_cb_setup(r_xprt, reqs);
 144         return 0;
 145
 146 out_free:
 147         xprt_rdma_bc_destroy(xprt, reqs);
 148
 149 out_err:
 150         pr_err("RPC:       %s: setup backchannel transport failed\n", __func__);
 151         return -ENOMEM;
 152 }
 153
 154 /**
 155  * xprt_rdma_bc_up - Create transport endpoint for backchannel service
 156  * @serv: server endpoint
 157  * @net: network namespace
 158  *
 159  * The "xprt" is an implied argument: it supplies the name of the
 160  * backchannel transport class.
 161  *
 162  * Returns zero on success, negative errno on failure
 163  */
 164 int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
 165 {
 166         int ret;
 167
 168         ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
 169         if (ret < 0)
 170                 return ret;
 171         return 0;
 172 }
 173
 174 /**
 175  * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
 176  * @xprt: transport
 177  *
 178  * Returns maximum size, in bytes, of a backchannel message
 179  */
 180 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
 181 {
 182         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 183         struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
 184         size_t maxmsg;
 185
 186         maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
 187         maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
 188         return maxmsg - RPCRDMA_HDRLEN_MIN;
 189 }
 190
 191 static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
 192 {
 193         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
 194         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 195         __be32 *p;
 196
 197         rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
 198         xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
 199                         req->rl_rdmabuf->rg_base);
 200
 201         p = xdr_reserve_space(&req->rl_stream, 28);
 202         if (unlikely(!p))
 203                 return -EIO;
 204         *p++ = rqst->rq_xid;
 205         *p++ = rpcrdma_version;
 206         *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
 207         *p++ = rdma_msg;
 208         *p++ = xdr_zero;
 209         *p++ = xdr_zero;
 210         *p = xdr_zero;
 211
 212         if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
 213                                       &rqst->rq_snd_buf, rpcrdma_noch))
 214                 return -EIO;
 215
 216         trace_xprtrdma_cb_reply(rqst);
 217         return 0;
 218 }
 219
 220 /**
 221  * xprt_rdma_bc_send_reply - marshal and send a backchannel reply
 222  * @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
 223  *
 224  * Caller holds the transport's write lock.
 225  *
 226  * Returns:
 227  *      %0 if the RPC message has been sent
 228  *      %-ENOTCONN if the caller should reconnect and call again
 229  *      %-EIO if a permanent error occurred and the request was not
 230  *              sent. Do not try to send this message again.
 231  */
 232 int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
 233 {
 234         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
 235         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 236         int rc;
 237
 238         if (!xprt_connected(rqst->rq_xprt))
 239                 goto drop_connection;
 240
 241         rc = rpcrdma_bc_marshal_reply(rqst);
 242         if (rc < 0)
 243                 goto failed_marshal;
 244
 245         if (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, req))
 246                 goto drop_connection;
 247         return 0;
 248
 249 failed_marshal:
 250         if (rc != -ENOTCONN)
 251                 return rc;
 252 drop_connection:
 253         xprt_disconnect_done(rqst->rq_xprt);
 254         return -ENOTCONN;
 255 }
 256
 257 /**
 258  * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
 259  * @xprt: transport associated with these backchannel resources
 260  * @reqs: number of incoming requests to destroy; ignored
 261  */
 262 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
 263 {
 264         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 265         struct rpc_rqst *rqst, *tmp;
 266
 267         spin_lock_bh(&xprt->bc_pa_lock);
 268         list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 269                 list_del(&rqst->rq_bc_pa_list);
 270                 spin_unlock_bh(&xprt->bc_pa_lock);
 271
 272                 rpcrdma_bc_free_rqst(r_xprt, rqst);
 273
 274                 spin_lock_bh(&xprt->bc_pa_lock);
 275         }
 276         spin_unlock_bh(&xprt->bc_pa_lock);
 277 }
 278
 279 /**
 280  * xprt_rdma_bc_free_rqst - Release a backchannel rqst
 281  * @rqst: request to release
 282  */
 283 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
 284 {
 285         struct rpc_xprt *xprt = rqst->rq_xprt;
 286
 287         dprintk("RPC:       %s: freeing rqst %p (req %p)\n",
 288                 __func__, rqst, rpcr_to_rdmar(rqst));
 289
 290         spin_lock_bh(&xprt->bc_pa_lock);
 291         list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 292         spin_unlock_bh(&xprt->bc_pa_lock);
 293 }
 294
 295 /**
 296  * rpcrdma_bc_receive_call - Handle a backward direction call
 297  * @r_xprt: transport receiving the call
 298  * @rep: receive buffer containing the call
 299  *
 300  * Operational assumptions:
 301  *    o Backchannel credits are ignored, just as the NFS server
 302  *      forechannel currently does
 303  *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
 304  *      No replay detection is done at the transport level
 305  */
 306 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
 307                              struct rpcrdma_rep *rep)
 308 {
 309         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
 310         struct svc_serv *bc_serv;
 311         struct rpcrdma_req *req;
 312         struct rpc_rqst *rqst;
 313         struct xdr_buf *buf;
 314         size_t size;
 315         __be32 *p;
 316
 317         p = xdr_inline_decode(&rep->rr_stream, 0);
 318         size = xdr_stream_remaining(&rep->rr_stream);
 319
 320 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
 321         pr_info("RPC:       %s: callback XID %08x, length=%u\n",
 322                 __func__, be32_to_cpup(p), size);
 323         pr_info("RPC:       %s: %*ph\n", __func__, size, p);
 324 #endif
 325
 326         /* Grab a free bc rqst */
 327         spin_lock(&xprt->bc_pa_lock);
 328         if (list_empty(&xprt->bc_pa_list)) {
 329                 spin_unlock(&xprt->bc_pa_lock);
 330                 goto out_overflow;
 331         }
 332         rqst = list_first_entry(&xprt->bc_pa_list,
 333                                 struct rpc_rqst, rq_bc_pa_list);
 334         list_del(&rqst->rq_bc_pa_list);
 335         spin_unlock(&xprt->bc_pa_lock);
 336
 337         /* Prepare rqst */
 338         rqst->rq_reply_bytes_recvd = 0;
 339         rqst->rq_bytes_sent = 0;
 340         rqst->rq_xid = *p;
 341
 342         rqst->rq_private_buf.len = size;
 343
 344         buf = &rqst->rq_rcv_buf;
 345         memset(buf, 0, sizeof(*buf));
 346         buf->head[0].iov_base = p;
 347         buf->head[0].iov_len = size;
 348         buf->len = size;
 349
 350         /* The receive buffer has to be hooked to the rpcrdma_req
 351          * so that it is not released while the req is pointing
 352          * to its buffer, and so that it can be reposted after
 353          * the Upper Layer is done decoding it.
 354          */
 355         req = rpcr_to_rdmar(rqst);
 356         req->rl_reply = rep;
 357         trace_xprtrdma_cb_call(rqst);
 358
 359         /* Queue rqst for ULP's callback service */
 360         bc_serv = xprt->bc_serv;
 361         spin_lock(&bc_serv->sv_cb_lock);
 362         list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
 363         spin_unlock(&bc_serv->sv_cb_lock);
 364
 365         wake_up(&bc_serv->sv_cb_waitq);
 366
 367         r_xprt->rx_stats.bcall_count++;
 368         return;
 369
 370 out_overflow:
 371         pr_warn("RPC/RDMA backchannel overflow\n");
 372         xprt_disconnect_done(xprt);
 373         /* This receive buffer gets reposted automatically
 374          * when the connection is re-established.
 375          */
 376         return;
 377 }