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/sunrpc/xprt.h>
   9 #include <linux/sunrpc/svc.h>
  10 #include <linux/sunrpc/svc_xprt.h>
  11 #include <linux/sunrpc/svc_rdma.h>
  12
  13 #include "xprt_rdma.h"
  14 #include <trace/events/rpcrdma.h>
  15
  16 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  17 # define RPCDBG_FACILITY        RPCDBG_TRANS
  18 #endif
  19
  20 #undef RPCRDMA_BACKCHANNEL_DEBUG
  21
  22 static int rpcrdma_bc_setup_reqs(struct rpcrdma_xprt *r_xprt,
  23                                  unsigned int count)
  24 {
  25         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
  26         struct rpcrdma_req *req;
  27         struct rpc_rqst *rqst;
  28         unsigned int i;
  29
  30         for (i = 0; i < (count << 1); i++) {
  31                 struct rpcrdma_regbuf *rb;
  32                 size_t size;
  33
  34                 req = rpcrdma_create_req(r_xprt);
  35                 if (IS_ERR(req))
  36                         return PTR_ERR(req);
  37                 rqst = &req->rl_slot;
  38
  39                 rqst->rq_xprt = xprt;
  40                 INIT_LIST_HEAD(&rqst->rq_bc_list);
  41                 __set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
  42                 spin_lock(&xprt->bc_pa_lock);
  43                 list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
  44                 spin_unlock(&xprt->bc_pa_lock);
  45
  46                 size = r_xprt->rx_data.inline_rsize;
  47                 rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
  48                 if (IS_ERR(rb))
  49                         goto out_fail;
  50                 req->rl_sendbuf = rb;
  51                 xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
  52                              min_t(size_t, size, PAGE_SIZE));
  53         }
  54         return 0;
  55
  56 out_fail:
  57         rpcrdma_req_destroy(req);
  58         return -ENOMEM;
  59 }
  60
  61 /**
  62  * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
  63  * @xprt: transport associated with these backchannel resources
  64  * @reqs: number of concurrent incoming requests to expect
  65  *
  66  * Returns 0 on success; otherwise a negative errno
  67  */
  68 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
  69 {
  70         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  71         int rc;
  72
  73         /* The backchannel reply path returns each rpc_rqst to the
  74          * bc_pa_list _after_ the reply is sent. If the server is
  75          * faster than the client, it can send another backward
  76          * direction request before the rpc_rqst is returned to the
  77          * list. The client rejects the request in this case.
  78          *
  79          * Twice as many rpc_rqsts are prepared to ensure there is
  80          * always an rpc_rqst available as soon as a reply is sent.
  81          */
  82         if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
  83                 goto out_err;
  84
  85         rc = rpcrdma_bc_setup_reqs(r_xprt, reqs);
  86         if (rc)
  87                 goto out_free;
  88
  89         r_xprt->rx_buf.rb_bc_srv_max_requests = reqs;
  90         trace_xprtrdma_cb_setup(r_xprt, reqs);
  91         return 0;
  92
  93 out_free:
  94         xprt_rdma_bc_destroy(xprt, reqs);
  95
  96 out_err:
  97         pr_err("RPC:       %s: setup backchannel transport failed\n", __func__);
  98         return -ENOMEM;
  99 }
 100
 101 /**
 102  * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
 103  * @xprt: transport
 104  *
 105  * Returns maximum size, in bytes, of a backchannel message
 106  */
 107 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
 108 {
 109         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 110         struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
 111         size_t maxmsg;
 112
 113         maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
 114         maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
 115         return maxmsg - RPCRDMA_HDRLEN_MIN;
 116 }
 117
 118 static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
 119 {
 120         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
 121         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 122         __be32 *p;
 123
 124         rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
 125         xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
 126                         req->rl_rdmabuf->rg_base);
 127
 128         p = xdr_reserve_space(&req->rl_stream, 28);
 129         if (unlikely(!p))
 130                 return -EIO;
 131         *p++ = rqst->rq_xid;
 132         *p++ = rpcrdma_version;
 133         *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
 134         *p++ = rdma_msg;
 135         *p++ = xdr_zero;
 136         *p++ = xdr_zero;
 137         *p = xdr_zero;
 138
 139         if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
 140                                       &rqst->rq_snd_buf, rpcrdma_noch))
 141                 return -EIO;
 142
 143         trace_xprtrdma_cb_reply(rqst);
 144         return 0;
 145 }
 146
 147 /**
 148  * xprt_rdma_bc_send_reply - marshal and send a backchannel reply
 149  * @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
 150  *
 151  * Caller holds the transport's write lock.
 152  *
 153  * Returns:
 154  *      %0 if the RPC message has been sent
 155  *      %-ENOTCONN if the caller should reconnect and call again
 156  *      %-EIO if a permanent error occurred and the request was not
 157  *              sent. Do not try to send this message again.
 158  */
 159 int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
 160 {
 161         struct rpc_xprt *xprt = rqst->rq_xprt;
 162         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 163         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 164         int rc;
 165
 166         if (!xprt_connected(xprt))
 167                 return -ENOTCONN;
 168
 169         if (!xprt_request_get_cong(xprt, rqst))
 170                 return -EBADSLT;
 171
 172         rc = rpcrdma_bc_marshal_reply(rqst);
 173         if (rc < 0)
 174                 goto failed_marshal;
 175
 176         if (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, req))
 177                 goto drop_connection;
 178         return 0;
 179
 180 failed_marshal:
 181         if (rc != -ENOTCONN)
 182                 return rc;
 183 drop_connection:
 184         xprt_rdma_close(xprt);
 185         return -ENOTCONN;
 186 }
 187
 188 /**
 189  * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
 190  * @xprt: transport associated with these backchannel resources
 191  * @reqs: number of incoming requests to destroy; ignored
 192  */
 193 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
 194 {
 195         struct rpc_rqst *rqst, *tmp;
 196
 197         spin_lock(&xprt->bc_pa_lock);
 198         list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 199                 list_del(&rqst->rq_bc_pa_list);
 200                 spin_unlock(&xprt->bc_pa_lock);
 201
 202                 rpcrdma_req_destroy(rpcr_to_rdmar(rqst));
 203
 204                 spin_lock(&xprt->bc_pa_lock);
 205         }
 206         spin_unlock(&xprt->bc_pa_lock);
 207 }
 208
 209 /**
 210  * xprt_rdma_bc_free_rqst - Release a backchannel rqst
 211  * @rqst: request to release
 212  */
 213 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
 214 {
 215         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 216         struct rpc_xprt *xprt = rqst->rq_xprt;
 217
 218         rpcrdma_recv_buffer_put(req->rl_reply);
 219         req->rl_reply = NULL;
 220
 221         spin_lock(&xprt->bc_pa_lock);
 222         list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 223         spin_unlock(&xprt->bc_pa_lock);
 224 }
 225
 226 /**
 227  * rpcrdma_bc_receive_call - Handle a backward direction call
 228  * @r_xprt: transport receiving the call
 229  * @rep: receive buffer containing the call
 230  *
 231  * Operational assumptions:
 232  *    o Backchannel credits are ignored, just as the NFS server
 233  *      forechannel currently does
 234  *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
 235  *      No replay detection is done at the transport level
 236  */
 237 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
 238                              struct rpcrdma_rep *rep)
 239 {
 240         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
 241         struct svc_serv *bc_serv;
 242         struct rpcrdma_req *req;
 243         struct rpc_rqst *rqst;
 244         struct xdr_buf *buf;
 245         size_t size;
 246         __be32 *p;
 247
 248         p = xdr_inline_decode(&rep->rr_stream, 0);
 249         size = xdr_stream_remaining(&rep->rr_stream);
 250
 251 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
 252         pr_info("RPC:       %s: callback XID %08x, length=%u\n",
 253                 __func__, be32_to_cpup(p), size);
 254         pr_info("RPC:       %s: %*ph\n", __func__, size, p);
 255 #endif
 256
 257         /* Grab a free bc rqst */
 258         spin_lock(&xprt->bc_pa_lock);
 259         if (list_empty(&xprt->bc_pa_list)) {
 260                 spin_unlock(&xprt->bc_pa_lock);
 261                 goto out_overflow;
 262         }
 263         rqst = list_first_entry(&xprt->bc_pa_list,
 264                                 struct rpc_rqst, rq_bc_pa_list);
 265         list_del(&rqst->rq_bc_pa_list);
 266         spin_unlock(&xprt->bc_pa_lock);
 267
 268         /* Prepare rqst */
 269         rqst->rq_reply_bytes_recvd = 0;
 270         rqst->rq_bytes_sent = 0;
 271         rqst->rq_xid = *p;
 272
 273         rqst->rq_private_buf.len = size;
 274
 275         buf = &rqst->rq_rcv_buf;
 276         memset(buf, 0, sizeof(*buf));
 277         buf->head[0].iov_base = p;
 278         buf->head[0].iov_len = size;
 279         buf->len = size;
 280
 281         /* The receive buffer has to be hooked to the rpcrdma_req
 282          * so that it is not released while the req is pointing
 283          * to its buffer, and so that it can be reposted after
 284          * the Upper Layer is done decoding it.
 285          */
 286         req = rpcr_to_rdmar(rqst);
 287         req->rl_reply = rep;
 288         trace_xprtrdma_cb_call(rqst);
 289
 290         /* Queue rqst for ULP's callback service */
 291         bc_serv = xprt->bc_serv;
 292         spin_lock(&bc_serv->sv_cb_lock);
 293         list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
 294         spin_unlock(&bc_serv->sv_cb_lock);
 295
 296         wake_up(&bc_serv->sv_cb_waitq);
 297
 298         r_xprt->rx_stats.bcall_count++;
 299         return;
 300
 301 out_overflow:
 302         pr_warn("RPC/RDMA backchannel overflow\n");
 303         xprt_force_disconnect(xprt);
 304         /* This receive buffer gets reposted automatically
 305          * when the connection is re-established.
 306          */
 307         return;
 308 }