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         req->rl_backchannel = true;
  47
  48         rb = rpcrdma_alloc_regbuf(RPCRDMA_HDRBUF_SIZE,
  49                                   DMA_TO_DEVICE, GFP_KERNEL);
  50         if (IS_ERR(rb))
  51                 goto out_fail;
  52         req->rl_rdmabuf = rb;
  53         xdr_buf_init(&req->rl_hdrbuf, rb->rg_base, rdmab_length(rb));
  54
  55         size = r_xprt->rx_data.inline_rsize;
  56         rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
  57         if (IS_ERR(rb))
  58                 goto out_fail;
  59         req->rl_sendbuf = rb;
  60         xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
  61                      min_t(size_t, size, PAGE_SIZE));
  62         rpcrdma_set_xprtdata(rqst, req);
  63         return 0;
  64
  65 out_fail:
  66         rpcrdma_bc_free_rqst(r_xprt, rqst);
  67         return -ENOMEM;
  68 }
  69
  70 /* Allocate and add receive buffers to the rpcrdma_buffer's
  71  * existing list of rep's. These are released when the
  72  * transport is destroyed.
  73  */
  74 static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
  75                                  unsigned int count)
  76 {
  77         struct rpcrdma_rep *rep;
  78         int rc = 0;
  79
  80         while (count--) {
  81                 rep = rpcrdma_create_rep(r_xprt);
  82                 if (IS_ERR(rep)) {
  83                         pr_err("RPC:       %s: reply buffer alloc failed\n",
  84                                __func__);
  85                         rc = PTR_ERR(rep);
  86                         break;
  87                 }
  88
  89                 rpcrdma_recv_buffer_put(rep);
  90         }
  91
  92         return rc;
  93 }
  94
  95 /**
  96  * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
  97  * @xprt: transport associated with these backchannel resources
  98  * @reqs: number of concurrent incoming requests to expect
  99  *
 100  * Returns 0 on success; otherwise a negative errno
 101  */
 102 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
 103 {
 104         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 105         struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
 106         struct rpc_rqst *rqst;
 107         unsigned int i;
 108         int rc;
 109
 110         /* The backchannel reply path returns each rpc_rqst to the
 111          * bc_pa_list _after_ the reply is sent. If the server is
 112          * faster than the client, it can send another backward
 113          * direction request before the rpc_rqst is returned to the
 114          * list. The client rejects the request in this case.
 115          *
 116          * Twice as many rpc_rqsts are prepared to ensure there is
 117          * always an rpc_rqst available as soon as a reply is sent.
 118          */
 119         if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
 120                 goto out_err;
 121
 122         for (i = 0; i < (reqs << 1); i++) {
 123                 rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
 124                 if (!rqst)
 125                         goto out_free;
 126
 127                 dprintk("RPC:       %s: new rqst %p\n", __func__, rqst);
 128
 129                 rqst->rq_xprt = &r_xprt->rx_xprt;
 130                 INIT_LIST_HEAD(&rqst->rq_list);
 131                 INIT_LIST_HEAD(&rqst->rq_bc_list);
 132
 133                 if (rpcrdma_bc_setup_rqst(r_xprt, rqst))
 134                         goto out_free;
 135
 136                 spin_lock_bh(&xprt->bc_pa_lock);
 137                 list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 138                 spin_unlock_bh(&xprt->bc_pa_lock);
 139         }
 140
 141         rc = rpcrdma_bc_setup_reps(r_xprt, reqs);
 142         if (rc)
 143                 goto out_free;
 144
 145         rc = rpcrdma_ep_post_extra_recv(r_xprt, reqs);
 146         if (rc)
 147                 goto out_free;
 148
 149         buffer->rb_bc_srv_max_requests = reqs;
 150         request_module("svcrdma");
 151
 152         return 0;
 153
 154 out_free:
 155         xprt_rdma_bc_destroy(xprt, reqs);
 156
 157 out_err:
 158         pr_err("RPC:       %s: setup backchannel transport failed\n", __func__);
 159         return -ENOMEM;
 160 }
 161
 162 /**
 163  * xprt_rdma_bc_up - Create transport endpoint for backchannel service
 164  * @serv: server endpoint
 165  * @net: network namespace
 166  *
 167  * The "xprt" is an implied argument: it supplies the name of the
 168  * backchannel transport class.
 169  *
 170  * Returns zero on success, negative errno on failure
 171  */
 172 int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
 173 {
 174         int ret;
 175
 176         ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
 177         if (ret < 0)
 178                 return ret;
 179         return 0;
 180 }
 181
 182 /**
 183  * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
 184  * @xprt: transport
 185  *
 186  * Returns maximum size, in bytes, of a backchannel message
 187  */
 188 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
 189 {
 190         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 191         struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
 192         size_t maxmsg;
 193
 194         maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
 195         maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
 196         return maxmsg - RPCRDMA_HDRLEN_MIN;
 197 }
 198
 199 /**
 200  * rpcrdma_bc_marshal_reply - Send backwards direction reply
 201  * @rqst: buffer containing RPC reply data
 202  *
 203  * Returns zero on success.
 204  */
 205 int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
 206 {
 207         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
 208         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 209         __be32 *p;
 210
 211         rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
 212         xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
 213                         req->rl_rdmabuf->rg_base);
 214
 215         p = xdr_reserve_space(&req->rl_stream, 28);
 216         if (unlikely(!p))
 217                 return -EIO;
 218         *p++ = rqst->rq_xid;
 219         *p++ = rpcrdma_version;
 220         *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
 221         *p++ = rdma_msg;
 222         *p++ = xdr_zero;
 223         *p++ = xdr_zero;
 224         *p = xdr_zero;
 225
 226         if (!rpcrdma_prepare_send_sges(&r_xprt->rx_ia, req, RPCRDMA_HDRLEN_MIN,
 227                                        &rqst->rq_snd_buf, rpcrdma_noch))
 228                 return -EIO;
 229         return 0;
 230 }
 231
 232 /**
 233  * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
 234  * @xprt: transport associated with these backchannel resources
 235  * @reqs: number of incoming requests to destroy; ignored
 236  */
 237 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
 238 {
 239         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 240         struct rpc_rqst *rqst, *tmp;
 241
 242         spin_lock_bh(&xprt->bc_pa_lock);
 243         list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 244                 list_del(&rqst->rq_bc_pa_list);
 245                 spin_unlock_bh(&xprt->bc_pa_lock);
 246
 247                 rpcrdma_bc_free_rqst(r_xprt, rqst);
 248
 249                 spin_lock_bh(&xprt->bc_pa_lock);
 250         }
 251         spin_unlock_bh(&xprt->bc_pa_lock);
 252 }
 253
 254 /**
 255  * xprt_rdma_bc_free_rqst - Release a backchannel rqst
 256  * @rqst: request to release
 257  */
 258 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
 259 {
 260         struct rpc_xprt *xprt = rqst->rq_xprt;
 261
 262         dprintk("RPC:       %s: freeing rqst %p (req %p)\n",
 263                 __func__, rqst, rpcr_to_rdmar(rqst));
 264
 265         smp_mb__before_atomic();
 266         WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state));
 267         clear_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 268         smp_mb__after_atomic();
 269
 270         spin_lock_bh(&xprt->bc_pa_lock);
 271         list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 272         spin_unlock_bh(&xprt->bc_pa_lock);
 273 }
 274
 275 /**
 276  * rpcrdma_bc_receive_call - Handle a backward direction call
 277  * @xprt: transport receiving the call
 278  * @rep: receive buffer containing the call
 279  *
 280  * Operational assumptions:
 281  *    o Backchannel credits are ignored, just as the NFS server
 282  *      forechannel currently does
 283  *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
 284  *      No replay detection is done at the transport level
 285  */
 286 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
 287                              struct rpcrdma_rep *rep)
 288 {
 289         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
 290         struct svc_serv *bc_serv;
 291         struct rpcrdma_req *req;
 292         struct rpc_rqst *rqst;
 293         struct xdr_buf *buf;
 294         size_t size;
 295         __be32 *p;
 296
 297         p = xdr_inline_decode(&rep->rr_stream, 0);
 298         size = xdr_stream_remaining(&rep->rr_stream);
 299
 300 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
 301         pr_info("RPC:       %s: callback XID %08x, length=%u\n",
 302                 __func__, be32_to_cpup(p), size);
 303         pr_info("RPC:       %s: %*ph\n", __func__, size, p);
 304 #endif
 305
 306         /* Grab a free bc rqst */
 307         spin_lock(&xprt->bc_pa_lock);
 308         if (list_empty(&xprt->bc_pa_list)) {
 309                 spin_unlock(&xprt->bc_pa_lock);
 310                 goto out_overflow;
 311         }
 312         rqst = list_first_entry(&xprt->bc_pa_list,
 313                                 struct rpc_rqst, rq_bc_pa_list);
 314         list_del(&rqst->rq_bc_pa_list);
 315         spin_unlock(&xprt->bc_pa_lock);
 316         dprintk("RPC:       %s: using rqst %p\n", __func__, rqst);
 317
 318         /* Prepare rqst */
 319         rqst->rq_reply_bytes_recvd = 0;
 320         rqst->rq_bytes_sent = 0;
 321         rqst->rq_xid = *p;
 322
 323         rqst->rq_private_buf.len = size;
 324         set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 325
 326         buf = &rqst->rq_rcv_buf;
 327         memset(buf, 0, sizeof(*buf));
 328         buf->head[0].iov_base = p;
 329         buf->head[0].iov_len = size;
 330         buf->len = size;
 331
 332         /* The receive buffer has to be hooked to the rpcrdma_req
 333          * so that it is not released while the req is pointing
 334          * to its buffer, and so that it can be reposted after
 335          * the Upper Layer is done decoding it.
 336          */
 337         req = rpcr_to_rdmar(rqst);
 338         dprintk("RPC:       %s: attaching rep %p to req %p\n",
 339                 __func__, rep, req);
 340         req->rl_reply = rep;
 341
 342         /* Defeat the retransmit detection logic in send_request */
 343         req->rl_connect_cookie = 0;
 344
 345         /* Queue rqst for ULP's callback service */
 346         bc_serv = xprt->bc_serv;
 347         spin_lock(&bc_serv->sv_cb_lock);
 348         list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
 349         spin_unlock(&bc_serv->sv_cb_lock);
 350
 351         wake_up(&bc_serv->sv_cb_waitq);
 352
 353         r_xprt->rx_stats.bcall_count++;
 354         return;
 355
 356 out_overflow:
 357         pr_warn("RPC/RDMA backchannel overflow\n");
 358         xprt_disconnect_done(xprt);
 359         /* This receive buffer gets reposted automatically
 360          * when the connection is re-established.
 361          */
 362         return;
 363 }