net/sunrpc/xprtrdma/backchannel.c

   1 /*
   2  * Copyright (c) 2015 Oracle.  All rights reserved.
   3  *
   4  * Support for backward direction RPCs on RPC/RDMA.
   5  */
   6
   7 #include <linux/module.h>
   8 #include <linux/sunrpc/xprt.h>
   9 #include <linux/sunrpc/svc.h>
  10 #include <linux/sunrpc/svc_xprt.h>
  11
  12 #include "xprt_rdma.h"
  13
  14 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  15 # define RPCDBG_FACILITY        RPCDBG_TRANS
  16 #endif
  17
  18 #undef RPCRDMA_BACKCHANNEL_DEBUG
  19
  20 static void rpcrdma_bc_free_rqst(struct rpcrdma_xprt *r_xprt,
  21                                  struct rpc_rqst *rqst)
  22 {
  23         struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
  24         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
  25
  26         spin_lock(&buf->rb_reqslock);
  27         list_del(&req->rl_all);
  28         spin_unlock(&buf->rb_reqslock);
  29
  30         rpcrdma_destroy_req(req);
  31
  32         kfree(rqst);
  33 }
  34
  35 static int rpcrdma_bc_setup_rqst(struct rpcrdma_xprt *r_xprt,
  36                                  struct rpc_rqst *rqst)
  37 {
  38         struct rpcrdma_regbuf *rb;
  39         struct rpcrdma_req *req;
  40         size_t size;
  41
  42         req = rpcrdma_create_req(r_xprt);
  43         if (IS_ERR(req))
  44                 return PTR_ERR(req);
  45         req->rl_backchannel = true;
  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
  53         size = r_xprt->rx_data.inline_rsize;
  54         rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
  55         if (IS_ERR(rb))
  56                 goto out_fail;
  57         req->rl_sendbuf = rb;
  58         xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
  59                      min_t(size_t, size, PAGE_SIZE));
  60         rpcrdma_set_xprtdata(rqst, req);
  61         return 0;
  62
  63 out_fail:
  64         rpcrdma_bc_free_rqst(r_xprt, rqst);
  65         return -ENOMEM;
  66 }
  67
  68 /* Allocate and add receive buffers to the rpcrdma_buffer's
  69  * existing list of rep's. These are released when the
  70  * transport is destroyed.
  71  */
  72 static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
  73                                  unsigned int count)
  74 {
  75         struct rpcrdma_rep *rep;
  76         int rc = 0;
  77
  78         while (count--) {
  79                 rep = rpcrdma_create_rep(r_xprt);
  80                 if (IS_ERR(rep)) {
  81                         pr_err("RPC:       %s: reply buffer alloc failed\n",
  82                                __func__);
  83                         rc = PTR_ERR(rep);
  84                         break;
  85                 }
  86
  87                 rpcrdma_recv_buffer_put(rep);
  88         }
  89
  90         return rc;
  91 }
  92
  93 /**
  94  * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
  95  * @xprt: transport associated with these backchannel resources
  96  * @reqs: number of concurrent incoming requests to expect
  97  *
  98  * Returns 0 on success; otherwise a negative errno
  99  */
 100 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
 101 {
 102         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 103         struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
 104         struct rpc_rqst *rqst;
 105         unsigned int i;
 106         int rc;
 107
 108         /* The backchannel reply path returns each rpc_rqst to the
 109          * bc_pa_list _after_ the reply is sent. If the server is
 110          * faster than the client, it can send another backward
 111          * direction request before the rpc_rqst is returned to the
 112          * list. The client rejects the request in this case.
 113          *
 114          * Twice as many rpc_rqsts are prepared to ensure there is
 115          * always an rpc_rqst available as soon as a reply is sent.
 116          */
 117         if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
 118                 goto out_err;
 119
 120         for (i = 0; i < (reqs << 1); i++) {
 121                 rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
 122                 if (!rqst) {
 123                         pr_err("RPC:       %s: Failed to create bc rpc_rqst\n",
 124                                __func__);
 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 rpc_xprt *xprt = rqst->rq_xprt;
 208         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 209         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 210         struct rpcrdma_msg *headerp;
 211
 212         headerp = rdmab_to_msg(req->rl_rdmabuf);
 213         headerp->rm_xid = rqst->rq_xid;
 214         headerp->rm_vers = rpcrdma_version;
 215         headerp->rm_credit =
 216                         cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
 217         headerp->rm_type = rdma_msg;
 218         headerp->rm_body.rm_chunks[0] = xdr_zero;
 219         headerp->rm_body.rm_chunks[1] = xdr_zero;
 220         headerp->rm_body.rm_chunks[2] = xdr_zero;
 221
 222         if (!rpcrdma_prepare_send_sges(&r_xprt->rx_ia, req, RPCRDMA_HDRLEN_MIN,
 223                                        &rqst->rq_snd_buf, rpcrdma_noch))
 224                 return -EIO;
 225         return 0;
 226 }
 227
 228 /**
 229  * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
 230  * @xprt: transport associated with these backchannel resources
 231  * @reqs: number of incoming requests to destroy; ignored
 232  */
 233 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
 234 {
 235         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 236         struct rpc_rqst *rqst, *tmp;
 237
 238         spin_lock_bh(&xprt->bc_pa_lock);
 239         list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 240                 list_del(&rqst->rq_bc_pa_list);
 241                 spin_unlock_bh(&xprt->bc_pa_lock);
 242
 243                 rpcrdma_bc_free_rqst(r_xprt, rqst);
 244
 245                 spin_lock_bh(&xprt->bc_pa_lock);
 246         }
 247         spin_unlock_bh(&xprt->bc_pa_lock);
 248 }
 249
 250 /**
 251  * xprt_rdma_bc_free_rqst - Release a backchannel rqst
 252  * @rqst: request to release
 253  */
 254 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
 255 {
 256         struct rpc_xprt *xprt = rqst->rq_xprt;
 257
 258         dprintk("RPC:       %s: freeing rqst %p (req %p)\n",
 259                 __func__, rqst, rpcr_to_rdmar(rqst));
 260
 261         smp_mb__before_atomic();
 262         WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state));
 263         clear_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 264         smp_mb__after_atomic();
 265
 266         spin_lock_bh(&xprt->bc_pa_lock);
 267         list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 268         spin_unlock_bh(&xprt->bc_pa_lock);
 269 }
 270
 271 /**
 272  * rpcrdma_bc_receive_call - Handle a backward direction call
 273  * @xprt: transport receiving the call
 274  * @rep: receive buffer containing the call
 275  *
 276  * Called in the RPC reply handler, which runs in a tasklet.
 277  * Be quick about it.
 278  *
 279  * Operational assumptions:
 280  *    o Backchannel credits are ignored, just as the NFS server
 281  *      forechannel currently does
 282  *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
 283  *      No replay detection is done at the transport level
 284  */
 285 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
 286                              struct rpcrdma_rep *rep)
 287 {
 288         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
 289         struct rpcrdma_msg *headerp;
 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         headerp = rdmab_to_msg(rep->rr_rdmabuf);
 298 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
 299         pr_info("RPC:       %s: callback XID %08x, length=%u\n",
 300                 __func__, be32_to_cpu(headerp->rm_xid), rep->rr_len);
 301         pr_info("RPC:       %s: %*ph\n", __func__, rep->rr_len, headerp);
 302 #endif
 303
 304         /* Sanity check:
 305          * Need at least enough bytes for RPC/RDMA header, as code
 306          * here references the header fields by array offset. Also,
 307          * backward calls are always inline, so ensure there
 308          * are some bytes beyond the RPC/RDMA header.
 309          */
 310         if (rep->rr_len < RPCRDMA_HDRLEN_MIN + 24)
 311                 goto out_short;
 312         p = (__be32 *)((unsigned char *)headerp + RPCRDMA_HDRLEN_MIN);
 313         size = rep->rr_len - RPCRDMA_HDRLEN_MIN;
 314
 315         /* Grab a free bc rqst */
 316         spin_lock(&xprt->bc_pa_lock);
 317         if (list_empty(&xprt->bc_pa_list)) {
 318                 spin_unlock(&xprt->bc_pa_lock);
 319                 goto out_overflow;
 320         }
 321         rqst = list_first_entry(&xprt->bc_pa_list,
 322                                 struct rpc_rqst, rq_bc_pa_list);
 323         list_del(&rqst->rq_bc_pa_list);
 324         spin_unlock(&xprt->bc_pa_lock);
 325         dprintk("RPC:       %s: using rqst %p\n", __func__, rqst);
 326
 327         /* Prepare rqst */
 328         rqst->rq_reply_bytes_recvd = 0;
 329         rqst->rq_bytes_sent = 0;
 330         rqst->rq_xid = headerp->rm_xid;
 331
 332         rqst->rq_private_buf.len = size;
 333         set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 334
 335         buf = &rqst->rq_rcv_buf;
 336         memset(buf, 0, sizeof(*buf));
 337         buf->head[0].iov_base = p;
 338         buf->head[0].iov_len = size;
 339         buf->len = size;
 340
 341         /* The receive buffer has to be hooked to the rpcrdma_req
 342          * so that it can be reposted after the server is done
 343          * parsing it but just before sending the backward
 344          * direction reply.
 345          */
 346         req = rpcr_to_rdmar(rqst);
 347         dprintk("RPC:       %s: attaching rep %p to req %p\n",
 348                 __func__, rep, req);
 349         req->rl_reply = rep;
 350
 351         /* Defeat the retransmit detection logic in send_request */
 352         req->rl_connect_cookie = 0;
 353
 354         /* Queue rqst for ULP's callback service */
 355         bc_serv = xprt->bc_serv;
 356         spin_lock(&bc_serv->sv_cb_lock);
 357         list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
 358         spin_unlock(&bc_serv->sv_cb_lock);
 359
 360         wake_up(&bc_serv->sv_cb_waitq);
 361
 362         r_xprt->rx_stats.bcall_count++;
 363         return;
 364
 365 out_overflow:
 366         pr_warn("RPC/RDMA backchannel overflow\n");
 367         xprt_disconnect_done(xprt);
 368         /* This receive buffer gets reposted automatically
 369          * when the connection is re-established.
 370          */
 371         return;
 372
 373 out_short:
 374         pr_warn("RPC/RDMA short backward direction call\n");
 375
 376         if (rpcrdma_ep_post_recv(&r_xprt->rx_ia, rep))
 377                 xprt_disconnect_done(xprt);
 378         else
 379                 pr_warn("RPC:       %s: reposting rep %p\n",
 380                         __func__, rep);
 381 }