net/sunrpc/xprtrdma/backchannel.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (c) 2015-2020, Oracle and/or its affiliates.
   4  *
   5  * Support for reverse-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 #undef RPCRDMA_BACKCHANNEL_DEBUG
  17
  18 /**
  19  * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
  20  * @xprt: transport associated with these backchannel resources
  21  * @reqs: number of concurrent incoming requests to expect
  22  *
  23  * Returns 0 on success; otherwise a negative errno
  24  */
  25 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
  26 {
  27         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  28
  29         r_xprt->rx_buf.rb_bc_srv_max_requests = RPCRDMA_BACKWARD_WRS >> 1;
  30         trace_xprtrdma_cb_setup(r_xprt, reqs);
  31         return 0;
  32 }
  33
  34 /**
  35  * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
  36  * @xprt: transport
  37  *
  38  * Returns maximum size, in bytes, of a backchannel message
  39  */
  40 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
  41 {
  42         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  43         struct rpcrdma_ep *ep = r_xprt->rx_ep;
  44         size_t maxmsg;
  45
  46         maxmsg = min_t(unsigned int, ep->re_inline_send, ep->re_inline_recv);
  47         maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
  48         return maxmsg - RPCRDMA_HDRLEN_MIN;
  49 }
  50
  51 unsigned int xprt_rdma_bc_max_slots(struct rpc_xprt *xprt)
  52 {
  53         return RPCRDMA_BACKWARD_WRS >> 1;
  54 }
  55
  56 static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
  57 {
  58         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
  59         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
  60         __be32 *p;
  61
  62         rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
  63         xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
  64                         rdmab_data(req->rl_rdmabuf), rqst);
  65
  66         p = xdr_reserve_space(&req->rl_stream, 28);
  67         if (unlikely(!p))
  68                 return -EIO;
  69         *p++ = rqst->rq_xid;
  70         *p++ = rpcrdma_version;
  71         *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
  72         *p++ = rdma_msg;
  73         *p++ = xdr_zero;
  74         *p++ = xdr_zero;
  75         *p = xdr_zero;
  76
  77         if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
  78                                       &rqst->rq_snd_buf, rpcrdma_noch_pullup))
  79                 return -EIO;
  80
  81         trace_xprtrdma_cb_reply(r_xprt, rqst);
  82         return 0;
  83 }
  84
  85 /**
  86  * xprt_rdma_bc_send_reply - marshal and send a backchannel reply
  87  * @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
  88  *
  89  * Caller holds the transport's write lock.
  90  *
  91  * Returns:
  92  *      %0 if the RPC message has been sent
  93  *      %-ENOTCONN if the caller should reconnect and call again
  94  *      %-EIO if a permanent error occurred and the request was not
  95  *              sent. Do not try to send this message again.
  96  */
  97 int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
  98 {
  99         struct rpc_xprt *xprt = rqst->rq_xprt;
 100         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 101         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 102         int rc;
 103
 104         if (!xprt_connected(xprt))
 105                 return -ENOTCONN;
 106
 107         if (!xprt_request_get_cong(xprt, rqst))
 108                 return -EBADSLT;
 109
 110         rc = rpcrdma_bc_marshal_reply(rqst);
 111         if (rc < 0)
 112                 goto failed_marshal;
 113
 114         if (frwr_send(r_xprt, req))
 115                 goto drop_connection;
 116         return 0;
 117
 118 failed_marshal:
 119         if (rc != -ENOTCONN)
 120                 return rc;
 121 drop_connection:
 122         xprt_rdma_close(xprt);
 123         return -ENOTCONN;
 124 }
 125
 126 /**
 127  * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
 128  * @xprt: transport associated with these backchannel resources
 129  * @reqs: number of incoming requests to destroy; ignored
 130  */
 131 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
 132 {
 133         struct rpc_rqst *rqst, *tmp;
 134
 135         spin_lock(&xprt->bc_pa_lock);
 136         list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 137                 list_del(&rqst->rq_bc_pa_list);
 138                 spin_unlock(&xprt->bc_pa_lock);
 139
 140                 rpcrdma_req_destroy(rpcr_to_rdmar(rqst));
 141
 142                 spin_lock(&xprt->bc_pa_lock);
 143         }
 144         spin_unlock(&xprt->bc_pa_lock);
 145 }
 146
 147 /**
 148  * xprt_rdma_bc_free_rqst - Release a backchannel rqst
 149  * @rqst: request to release
 150  */
 151 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
 152 {
 153         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 154         struct rpcrdma_rep *rep = req->rl_reply;
 155         struct rpc_xprt *xprt = rqst->rq_xprt;
 156         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 157
 158         rpcrdma_rep_put(&r_xprt->rx_buf, rep);
 159         req->rl_reply = NULL;
 160
 161         spin_lock(&xprt->bc_pa_lock);
 162         list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 163         spin_unlock(&xprt->bc_pa_lock);
 164         xprt_put(xprt);
 165 }
 166
 167 static struct rpc_rqst *rpcrdma_bc_rqst_get(struct rpcrdma_xprt *r_xprt)
 168 {
 169         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
 170         struct rpcrdma_req *req;
 171         struct rpc_rqst *rqst;
 172         size_t size;
 173
 174         spin_lock(&xprt->bc_pa_lock);
 175         rqst = list_first_entry_or_null(&xprt->bc_pa_list, struct rpc_rqst,
 176                                         rq_bc_pa_list);
 177         if (!rqst)
 178                 goto create_req;
 179         list_del(&rqst->rq_bc_pa_list);
 180         spin_unlock(&xprt->bc_pa_lock);
 181         return rqst;
 182
 183 create_req:
 184         spin_unlock(&xprt->bc_pa_lock);
 185
 186         /* Set a limit to prevent a remote from overrunning our resources.
 187          */
 188         if (xprt->bc_alloc_count >= RPCRDMA_BACKWARD_WRS)
 189                 return NULL;
 190
 191         size = min_t(size_t, r_xprt->rx_ep->re_inline_recv, PAGE_SIZE);
 192         req = rpcrdma_req_create(r_xprt, size);
 193         if (!req)
 194                 return NULL;
 195         if (rpcrdma_req_setup(r_xprt, req)) {
 196                 rpcrdma_req_destroy(req);
 197                 return NULL;
 198         }
 199
 200         xprt->bc_alloc_count++;
 201         rqst = &req->rl_slot;
 202         rqst->rq_xprt = xprt;
 203         __set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 204         xdr_buf_init(&rqst->rq_snd_buf, rdmab_data(req->rl_sendbuf), size);
 205         return rqst;
 206 }
 207
 208 /**
 209  * rpcrdma_bc_receive_call - Handle a reverse-direction Call
 210  * @r_xprt: transport receiving the call
 211  * @rep: receive buffer containing the call
 212  *
 213  * Operational assumptions:
 214  *    o Backchannel credits are ignored, just as the NFS server
 215  *      forechannel currently does
 216  *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
 217  *      No replay detection is done at the transport level
 218  */
 219 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
 220                              struct rpcrdma_rep *rep)
 221 {
 222         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
 223         struct svc_serv *bc_serv;
 224         struct rpcrdma_req *req;
 225         struct rpc_rqst *rqst;
 226         struct xdr_buf *buf;
 227         size_t size;
 228         __be32 *p;
 229
 230         p = xdr_inline_decode(&rep->rr_stream, 0);
 231         size = xdr_stream_remaining(&rep->rr_stream);
 232
 233 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
 234         pr_info("RPC:       %s: callback XID %08x, length=%u\n",
 235                 __func__, be32_to_cpup(p), size);
 236         pr_info("RPC:       %s: %*ph\n", __func__, size, p);
 237 #endif
 238
 239         rqst = rpcrdma_bc_rqst_get(r_xprt);
 240         if (!rqst)
 241                 goto out_overflow;
 242
 243         rqst->rq_reply_bytes_recvd = 0;
 244         rqst->rq_xid = *p;
 245
 246         rqst->rq_private_buf.len = size;
 247
 248         buf = &rqst->rq_rcv_buf;
 249         memset(buf, 0, sizeof(*buf));
 250         buf->head[0].iov_base = p;
 251         buf->head[0].iov_len = size;
 252         buf->len = size;
 253
 254         /* The receive buffer has to be hooked to the rpcrdma_req
 255          * so that it is not released while the req is pointing
 256          * to its buffer, and so that it can be reposted after
 257          * the Upper Layer is done decoding it.
 258          */
 259         req = rpcr_to_rdmar(rqst);
 260         req->rl_reply = rep;
 261         trace_xprtrdma_cb_call(r_xprt, rqst);
 262
 263         /* Queue rqst for ULP's callback service */
 264         bc_serv = xprt->bc_serv;
 265         xprt_get(xprt);
 266         lwq_enqueue(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
 267
 268         svc_pool_wake_idle_thread(&bc_serv->sv_pools[0]);
 269
 270         r_xprt->rx_stats.bcall_count++;
 271         return;
 272
 273 out_overflow:
 274         pr_warn("RPC/RDMA backchannel overflow\n");
 275         xprt_force_disconnect(xprt);
 276         /* This receive buffer gets reposted automatically
 277          * when the connection is re-established.
 278          */
 279         return;
 280 }