net/sunrpc/xprtrdma/backchannel.c

   1 /*
   2  * Copyright (c) 2015 Oracle.  All rights reserved.
   3  *
   4  * Support for backward direction RPCs on RPC/RDMA.
   5  */
   6
   7 #include <linux/module.h>
   8 #include <linux/sunrpc/xprt.h>
   9 #include <linux/sunrpc/svc.h>
  10 #include <linux/sunrpc/svc_xprt.h>
  11
  12 #include "xprt_rdma.h"
  13
  14 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  15 # define RPCDBG_FACILITY        RPCDBG_TRANS
  16 #endif
  17
  18 #undef RPCRDMA_BACKCHANNEL_DEBUG
  19
  20 static void rpcrdma_bc_free_rqst(struct rpcrdma_xprt *r_xprt,
  21                                  struct rpc_rqst *rqst)
  22 {
  23         struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
  24         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
  25
  26         spin_lock(&buf->rb_reqslock);
  27         list_del(&req->rl_all);
  28         spin_unlock(&buf->rb_reqslock);
  29
  30         rpcrdma_destroy_req(req);
  31
  32         kfree(rqst);
  33 }
  34
  35 static int rpcrdma_bc_setup_rqst(struct rpcrdma_xprt *r_xprt,
  36                                  struct rpc_rqst *rqst)
  37 {
  38         struct rpcrdma_regbuf *rb;
  39         struct rpcrdma_req *req;
  40         size_t size;
  41
  42         req = rpcrdma_create_req(r_xprt);
  43         if (IS_ERR(req))
  44                 return PTR_ERR(req);
  45         req->rl_backchannel = true;
  46
  47         rb = rpcrdma_alloc_regbuf(RPCRDMA_HDRBUF_SIZE,
  48                                   DMA_TO_DEVICE, GFP_KERNEL);
  49         if (IS_ERR(rb))
  50                 goto out_fail;
  51         req->rl_rdmabuf = rb;
  52
  53         size = r_xprt->rx_data.inline_rsize;
  54         rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
  55         if (IS_ERR(rb))
  56                 goto out_fail;
  57         req->rl_sendbuf = rb;
  58         xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base, size);
  59         rpcrdma_set_xprtdata(rqst, req);
  60         return 0;
  61
  62 out_fail:
  63         rpcrdma_bc_free_rqst(r_xprt, rqst);
  64         return -ENOMEM;
  65 }
  66
  67 /* Allocate and add receive buffers to the rpcrdma_buffer's
  68  * existing list of rep's. These are released when the
  69  * transport is destroyed.
  70  */
  71 static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
  72                                  unsigned int count)
  73 {
  74         int rc = 0;
  75
  76         while (count--) {
  77                 rc = rpcrdma_create_rep(r_xprt);
  78                 if (rc)
  79                         break;
  80         }
  81         return rc;
  82 }
  83
  84 /**
  85  * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
  86  * @xprt: transport associated with these backchannel resources
  87  * @reqs: number of concurrent incoming requests to expect
  88  *
  89  * Returns 0 on success; otherwise a negative errno
  90  */
  91 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
  92 {
  93         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  94         struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
  95         struct rpc_rqst *rqst;
  96         unsigned int i;
  97         int rc;
  98
  99         /* The backchannel reply path returns each rpc_rqst to the
 100          * bc_pa_list _after_ the reply is sent. If the server is
 101          * faster than the client, it can send another backward
 102          * direction request before the rpc_rqst is returned to the
 103          * list. The client rejects the request in this case.
 104          *
 105          * Twice as many rpc_rqsts are prepared to ensure there is
 106          * always an rpc_rqst available as soon as a reply is sent.
 107          */
 108         if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
 109                 goto out_err;
 110
 111         for (i = 0; i < (reqs << 1); i++) {
 112                 rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
 113                 if (!rqst) {
 114                         pr_err("RPC:       %s: Failed to create bc rpc_rqst\n",
 115                                __func__);
 116                         goto out_free;
 117                 }
 118                 dprintk("RPC:       %s: new rqst %p\n", __func__, rqst);
 119
 120                 rqst->rq_xprt = &r_xprt->rx_xprt;
 121                 INIT_LIST_HEAD(&rqst->rq_list);
 122                 INIT_LIST_HEAD(&rqst->rq_bc_list);
 123
 124                 if (rpcrdma_bc_setup_rqst(r_xprt, rqst))
 125                         goto out_free;
 126
 127                 spin_lock_bh(&xprt->bc_pa_lock);
 128                 list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 129                 spin_unlock_bh(&xprt->bc_pa_lock);
 130         }
 131
 132         rc = rpcrdma_bc_setup_reps(r_xprt, reqs);
 133         if (rc)
 134                 goto out_free;
 135
 136         rc = rpcrdma_ep_post_extra_recv(r_xprt, reqs);
 137         if (rc)
 138                 goto out_free;
 139
 140         buffer->rb_bc_srv_max_requests = reqs;
 141         request_module("svcrdma");
 142
 143         return 0;
 144
 145 out_free:
 146         xprt_rdma_bc_destroy(xprt, reqs);
 147
 148 out_err:
 149         pr_err("RPC:       %s: setup backchannel transport failed\n", __func__);
 150         return -ENOMEM;
 151 }
 152
 153 /**
 154  * xprt_rdma_bc_up - Create transport endpoint for backchannel service
 155  * @serv: server endpoint
 156  * @net: network namespace
 157  *
 158  * The "xprt" is an implied argument: it supplies the name of the
 159  * backchannel transport class.
 160  *
 161  * Returns zero on success, negative errno on failure
 162  */
 163 int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
 164 {
 165         int ret;
 166
 167         ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
 168         if (ret < 0)
 169                 return ret;
 170         return 0;
 171 }
 172
 173 /**
 174  * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
 175  * @xprt: transport
 176  *
 177  * Returns maximum size, in bytes, of a backchannel message
 178  */
 179 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
 180 {
 181         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 182         struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
 183         size_t maxmsg;
 184
 185         maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
 186         return maxmsg - RPCRDMA_HDRLEN_MIN;
 187 }
 188
 189 /**
 190  * rpcrdma_bc_marshal_reply - Send backwards direction reply
 191  * @rqst: buffer containing RPC reply data
 192  *
 193  * Returns zero on success.
 194  */
 195 int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
 196 {
 197         struct rpc_xprt *xprt = rqst->rq_xprt;
 198         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 199         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 200         struct rpcrdma_msg *headerp;
 201
 202         headerp = rdmab_to_msg(req->rl_rdmabuf);
 203         headerp->rm_xid = rqst->rq_xid;
 204         headerp->rm_vers = rpcrdma_version;
 205         headerp->rm_credit =
 206                         cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
 207         headerp->rm_type = rdma_msg;
 208         headerp->rm_body.rm_chunks[0] = xdr_zero;
 209         headerp->rm_body.rm_chunks[1] = xdr_zero;
 210         headerp->rm_body.rm_chunks[2] = xdr_zero;
 211
 212         if (!rpcrdma_prepare_send_sges(&r_xprt->rx_ia, req, RPCRDMA_HDRLEN_MIN,
 213                                        &rqst->rq_snd_buf, rpcrdma_noch))
 214                 return -EIO;
 215         return 0;
 216 }
 217
 218 /**
 219  * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
 220  * @xprt: transport associated with these backchannel resources
 221  * @reqs: number of incoming requests to destroy; ignored
 222  */
 223 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
 224 {
 225         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 226         struct rpc_rqst *rqst, *tmp;
 227
 228         spin_lock_bh(&xprt->bc_pa_lock);
 229         list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 230                 list_del(&rqst->rq_bc_pa_list);
 231                 spin_unlock_bh(&xprt->bc_pa_lock);
 232
 233                 rpcrdma_bc_free_rqst(r_xprt, rqst);
 234
 235                 spin_lock_bh(&xprt->bc_pa_lock);
 236         }
 237         spin_unlock_bh(&xprt->bc_pa_lock);
 238 }
 239
 240 /**
 241  * xprt_rdma_bc_free_rqst - Release a backchannel rqst
 242  * @rqst: request to release
 243  */
 244 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
 245 {
 246         struct rpc_xprt *xprt = rqst->rq_xprt;
 247
 248         dprintk("RPC:       %s: freeing rqst %p (req %p)\n",
 249                 __func__, rqst, rpcr_to_rdmar(rqst));
 250
 251         smp_mb__before_atomic();
 252         WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state));
 253         clear_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 254         smp_mb__after_atomic();
 255
 256         spin_lock_bh(&xprt->bc_pa_lock);
 257         list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 258         spin_unlock_bh(&xprt->bc_pa_lock);
 259 }
 260
 261 /**
 262  * rpcrdma_bc_receive_call - Handle a backward direction call
 263  * @xprt: transport receiving the call
 264  * @rep: receive buffer containing the call
 265  *
 266  * Called in the RPC reply handler, which runs in a tasklet.
 267  * Be quick about it.
 268  *
 269  * Operational assumptions:
 270  *    o Backchannel credits are ignored, just as the NFS server
 271  *      forechannel currently does
 272  *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
 273  *      No replay detection is done at the transport level
 274  */
 275 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
 276                              struct rpcrdma_rep *rep)
 277 {
 278         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
 279         struct rpcrdma_msg *headerp;
 280         struct svc_serv *bc_serv;
 281         struct rpcrdma_req *req;
 282         struct rpc_rqst *rqst;
 283         struct xdr_buf *buf;
 284         size_t size;
 285         __be32 *p;
 286
 287         headerp = rdmab_to_msg(rep->rr_rdmabuf);
 288 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
 289         pr_info("RPC:       %s: callback XID %08x, length=%u\n",
 290                 __func__, be32_to_cpu(headerp->rm_xid), rep->rr_len);
 291         pr_info("RPC:       %s: %*ph\n", __func__, rep->rr_len, headerp);
 292 #endif
 293
 294         /* Sanity check:
 295          * Need at least enough bytes for RPC/RDMA header, as code
 296          * here references the header fields by array offset. Also,
 297          * backward calls are always inline, so ensure there
 298          * are some bytes beyond the RPC/RDMA header.
 299          */
 300         if (rep->rr_len < RPCRDMA_HDRLEN_MIN + 24)
 301                 goto out_short;
 302         p = (__be32 *)((unsigned char *)headerp + RPCRDMA_HDRLEN_MIN);
 303         size = rep->rr_len - RPCRDMA_HDRLEN_MIN;
 304
 305         /* Grab a free bc rqst */
 306         spin_lock(&xprt->bc_pa_lock);
 307         if (list_empty(&xprt->bc_pa_list)) {
 308                 spin_unlock(&xprt->bc_pa_lock);
 309                 goto out_overflow;
 310         }
 311         rqst = list_first_entry(&xprt->bc_pa_list,
 312                                 struct rpc_rqst, rq_bc_pa_list);
 313         list_del(&rqst->rq_bc_pa_list);
 314         spin_unlock(&xprt->bc_pa_lock);
 315         dprintk("RPC:       %s: using rqst %p\n", __func__, rqst);
 316
 317         /* Prepare rqst */
 318         rqst->rq_reply_bytes_recvd = 0;
 319         rqst->rq_bytes_sent = 0;
 320         rqst->rq_xid = headerp->rm_xid;
 321
 322         rqst->rq_private_buf.len = size;
 323         set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 324
 325         buf = &rqst->rq_rcv_buf;
 326         memset(buf, 0, sizeof(*buf));
 327         buf->head[0].iov_base = p;
 328         buf->head[0].iov_len = size;
 329         buf->len = size;
 330
 331         /* The receive buffer has to be hooked to the rpcrdma_req
 332          * so that it can be reposted after the server is done
 333          * parsing it but just before sending the backward
 334          * direction reply.
 335          */
 336         req = rpcr_to_rdmar(rqst);
 337         dprintk("RPC:       %s: attaching rep %p to req %p\n",
 338                 __func__, rep, req);
 339         req->rl_reply = rep;
 340
 341         /* Defeat the retransmit detection logic in send_request */
 342         req->rl_connect_cookie = 0;
 343
 344         /* Queue rqst for ULP's callback service */
 345         bc_serv = xprt->bc_serv;
 346         spin_lock(&bc_serv->sv_cb_lock);
 347         list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
 348         spin_unlock(&bc_serv->sv_cb_lock);
 349
 350         wake_up(&bc_serv->sv_cb_waitq);
 351
 352         r_xprt->rx_stats.bcall_count++;
 353         return;
 354
 355 out_overflow:
 356         pr_warn("RPC/RDMA backchannel overflow\n");
 357         xprt_disconnect_done(xprt);
 358         /* This receive buffer gets reposted automatically
 359          * when the connection is re-established.
 360          */
 361         return;
 362
 363 out_short:
 364         pr_warn("RPC/RDMA short backward direction call\n");
 365
 366         if (rpcrdma_ep_post_recv(&r_xprt->rx_ia, rep))
 367                 xprt_disconnect_done(xprt);
 368         else
 369                 pr_warn("RPC:       %s: reposting rep %p\n",
 370                         __func__, rep);
 371 }