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