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         int rc = 0;
  78
  79         while (count--) {
  80                 rc = rpcrdma_create_rep(r_xprt);
  81                 if (rc)
  82                         break;
  83         }
  84         return rc;
  85 }
  86
  87 /**
  88  * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
  89  * @xprt: transport associated with these backchannel resources
  90  * @reqs: number of concurrent incoming requests to expect
  91  *
  92  * Returns 0 on success; otherwise a negative errno
  93  */
  94 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
  95 {
  96         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  97         struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
  98         struct rpc_rqst *rqst;
  99         unsigned int i;
 100         int rc;
 101
 102         /* The backchannel reply path returns each rpc_rqst to the
 103          * bc_pa_list _after_ the reply is sent. If the server is
 104          * faster than the client, it can send another backward
 105          * direction request before the rpc_rqst is returned to the
 106          * list. The client rejects the request in this case.
 107          *
 108          * Twice as many rpc_rqsts are prepared to ensure there is
 109          * always an rpc_rqst available as soon as a reply is sent.
 110          */
 111         if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
 112                 goto out_err;
 113
 114         for (i = 0; i < (reqs << 1); i++) {
 115                 rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
 116                 if (!rqst)
 117                         goto out_free;
 118
 119                 dprintk("RPC:       %s: new rqst %p\n", __func__, rqst);
 120
 121                 rqst->rq_xprt = &r_xprt->rx_xprt;
 122                 INIT_LIST_HEAD(&rqst->rq_list);
 123                 INIT_LIST_HEAD(&rqst->rq_bc_list);
 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
 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 /**
 192  * rpcrdma_bc_marshal_reply - Send backwards direction reply
 193  * @rqst: buffer containing RPC reply data
 194  *
 195  * Returns zero on success.
 196  */
 197 int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
 198 {
 199         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
 200         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 201         __be32 *p;
 202
 203         rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
 204         xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
 205                         req->rl_rdmabuf->rg_base);
 206
 207         p = xdr_reserve_space(&req->rl_stream, 28);
 208         if (unlikely(!p))
 209                 return -EIO;
 210         *p++ = rqst->rq_xid;
 211         *p++ = rpcrdma_version;
 212         *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
 213         *p++ = rdma_msg;
 214         *p++ = xdr_zero;
 215         *p++ = xdr_zero;
 216         *p = xdr_zero;
 217
 218         if (!rpcrdma_prepare_send_sges(&r_xprt->rx_ia, req, RPCRDMA_HDRLEN_MIN,
 219                                        &rqst->rq_snd_buf, rpcrdma_noch))
 220                 return -EIO;
 221         return 0;
 222 }
 223
 224 /**
 225  * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
 226  * @xprt: transport associated with these backchannel resources
 227  * @reqs: number of incoming requests to destroy; ignored
 228  */
 229 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
 230 {
 231         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 232         struct rpc_rqst *rqst, *tmp;
 233
 234         spin_lock_bh(&xprt->bc_pa_lock);
 235         list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 236                 list_del(&rqst->rq_bc_pa_list);
 237                 spin_unlock_bh(&xprt->bc_pa_lock);
 238
 239                 rpcrdma_bc_free_rqst(r_xprt, rqst);
 240
 241                 spin_lock_bh(&xprt->bc_pa_lock);
 242         }
 243         spin_unlock_bh(&xprt->bc_pa_lock);
 244 }
 245
 246 /**
 247  * xprt_rdma_bc_free_rqst - Release a backchannel rqst
 248  * @rqst: request to release
 249  */
 250 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
 251 {
 252         struct rpc_xprt *xprt = rqst->rq_xprt;
 253
 254         dprintk("RPC:       %s: freeing rqst %p (req %p)\n",
 255                 __func__, rqst, rpcr_to_rdmar(rqst));
 256
 257         smp_mb__before_atomic();
 258         WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state));
 259         clear_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 260         smp_mb__after_atomic();
 261
 262         spin_lock_bh(&xprt->bc_pa_lock);
 263         list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 264         spin_unlock_bh(&xprt->bc_pa_lock);
 265 }
 266
 267 /**
 268  * rpcrdma_bc_receive_call - Handle a backward direction call
 269  * @xprt: transport receiving the call
 270  * @rep: receive buffer containing the call
 271  *
 272  * Operational assumptions:
 273  *    o Backchannel credits are ignored, just as the NFS server
 274  *      forechannel currently does
 275  *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
 276  *      No replay detection is done at the transport level
 277  */
 278 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
 279                              struct rpcrdma_rep *rep)
 280 {
 281         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
 282         struct svc_serv *bc_serv;
 283         struct rpcrdma_req *req;
 284         struct rpc_rqst *rqst;
 285         struct xdr_buf *buf;
 286         size_t size;
 287         __be32 *p;
 288
 289         p = xdr_inline_decode(&rep->rr_stream, 0);
 290         size = xdr_stream_remaining(&rep->rr_stream);
 291
 292 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
 293         pr_info("RPC:       %s: callback XID %08x, length=%u\n",
 294                 __func__, be32_to_cpup(p), size);
 295         pr_info("RPC:       %s: %*ph\n", __func__, size, p);
 296 #endif
 297
 298         /* Grab a free bc rqst */
 299         spin_lock(&xprt->bc_pa_lock);
 300         if (list_empty(&xprt->bc_pa_list)) {
 301                 spin_unlock(&xprt->bc_pa_lock);
 302                 goto out_overflow;
 303         }
 304         rqst = list_first_entry(&xprt->bc_pa_list,
 305                                 struct rpc_rqst, rq_bc_pa_list);
 306         list_del(&rqst->rq_bc_pa_list);
 307         spin_unlock(&xprt->bc_pa_lock);
 308         dprintk("RPC:       %s: using rqst %p\n", __func__, rqst);
 309
 310         /* Prepare rqst */
 311         rqst->rq_reply_bytes_recvd = 0;
 312         rqst->rq_bytes_sent = 0;
 313         rqst->rq_xid = *p;
 314
 315         rqst->rq_private_buf.len = size;
 316         set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 317
 318         buf = &rqst->rq_rcv_buf;
 319         memset(buf, 0, sizeof(*buf));
 320         buf->head[0].iov_base = p;
 321         buf->head[0].iov_len = size;
 322         buf->len = size;
 323
 324         /* The receive buffer has to be hooked to the rpcrdma_req
 325          * so that it is not released while the req is pointing
 326          * to its buffer, and so that it can be reposted after
 327          * the Upper Layer is done decoding it.
 328          */
 329         req = rpcr_to_rdmar(rqst);
 330         dprintk("RPC:       %s: attaching rep %p to req %p\n",
 331                 __func__, rep, req);
 332         req->rl_reply = rep;
 333
 334         /* Defeat the retransmit detection logic in send_request */
 335         req->rl_connect_cookie = 0;
 336
 337         /* Queue rqst for ULP's callback service */
 338         bc_serv = xprt->bc_serv;
 339         spin_lock(&bc_serv->sv_cb_lock);
 340         list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
 341         spin_unlock(&bc_serv->sv_cb_lock);
 342
 343         wake_up(&bc_serv->sv_cb_waitq);
 344
 345         r_xprt->rx_stats.bcall_count++;
 346         return;
 347
 348 out_overflow:
 349         pr_warn("RPC/RDMA backchannel overflow\n");
 350         xprt_disconnect_done(xprt);
 351         /* This receive buffer gets reposted automatically
 352          * when the connection is re-established.
 353          */
 354         return;
 355 }