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