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(&r_xprt->rx_ia, 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_ia *ia = &r_xprt->rx_ia;
  39         struct rpcrdma_regbuf *rb;
  40         struct rpcrdma_req *req;
  41         struct xdr_buf *buf;
  42         size_t size;
  43
  44         req = rpcrdma_create_req(r_xprt);
  45         if (IS_ERR(req))
  46                 return PTR_ERR(req);
  47         req->rl_backchannel = true;
  48
  49         size = RPCRDMA_INLINE_WRITE_THRESHOLD(rqst);
  50         rb = rpcrdma_alloc_regbuf(ia, size, GFP_KERNEL);
  51         if (IS_ERR(rb))
  52                 goto out_fail;
  53         req->rl_rdmabuf = rb;
  54
  55         size += RPCRDMA_INLINE_READ_THRESHOLD(rqst);
  56         rb = rpcrdma_alloc_regbuf(ia, size, GFP_KERNEL);
  57         if (IS_ERR(rb))
  58                 goto out_fail;
  59         rb->rg_owner = req;
  60         req->rl_sendbuf = rb;
  61         /* so that rpcr_to_rdmar works when receiving a request */
  62         rqst->rq_buffer = (void *)req->rl_sendbuf->rg_base;
  63
  64         buf = &rqst->rq_snd_buf;
  65         buf->head[0].iov_base = rqst->rq_buffer;
  66         buf->head[0].iov_len = 0;
  67         buf->tail[0].iov_base = NULL;
  68         buf->tail[0].iov_len = 0;
  69         buf->page_len = 0;
  70         buf->len = 0;
  71         buf->buflen = size;
  72
  73         return 0;
  74
  75 out_fail:
  76         rpcrdma_bc_free_rqst(r_xprt, rqst);
  77         return -ENOMEM;
  78 }
  79
  80 /* Allocate and add receive buffers to the rpcrdma_buffer's
  81  * existing list of rep's. These are released when the
  82  * transport is destroyed.
  83  */
  84 static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
  85                                  unsigned int count)
  86 {
  87         struct rpcrdma_rep *rep;
  88         int rc = 0;
  89
  90         while (count--) {
  91                 rep = rpcrdma_create_rep(r_xprt);
  92                 if (IS_ERR(rep)) {
  93                         pr_err("RPC:       %s: reply buffer alloc failed\n",
  94                                __func__);
  95                         rc = PTR_ERR(rep);
  96                         break;
  97                 }
  98
  99                 rpcrdma_recv_buffer_put(rep);
 100         }
 101
 102         return rc;
 103 }
 104
 105 /**
 106  * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
 107  * @xprt: transport associated with these backchannel resources
 108  * @reqs: number of concurrent incoming requests to expect
 109  *
 110  * Returns 0 on success; otherwise a negative errno
 111  */
 112 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
 113 {
 114         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 115         struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
 116         struct rpc_rqst *rqst;
 117         unsigned int i;
 118         int rc;
 119
 120         /* The backchannel reply path returns each rpc_rqst to the
 121          * bc_pa_list _after_ the reply is sent. If the server is
 122          * faster than the client, it can send another backward
 123          * direction request before the rpc_rqst is returned to the
 124          * list. The client rejects the request in this case.
 125          *
 126          * Twice as many rpc_rqsts are prepared to ensure there is
 127          * always an rpc_rqst available as soon as a reply is sent.
 128          */
 129         if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
 130                 goto out_err;
 131
 132         for (i = 0; i < (reqs << 1); i++) {
 133                 rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
 134                 if (!rqst) {
 135                         pr_err("RPC:       %s: Failed to create bc rpc_rqst\n",
 136                                __func__);
 137                         goto out_free;
 138                 }
 139                 dprintk("RPC:       %s: new rqst %p\n", __func__, rqst);
 140
 141                 rqst->rq_xprt = &r_xprt->rx_xprt;
 142                 INIT_LIST_HEAD(&rqst->rq_list);
 143                 INIT_LIST_HEAD(&rqst->rq_bc_list);
 144
 145                 if (rpcrdma_bc_setup_rqst(r_xprt, rqst))
 146                         goto out_free;
 147
 148                 spin_lock_bh(&xprt->bc_pa_lock);
 149                 list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 150                 spin_unlock_bh(&xprt->bc_pa_lock);
 151         }
 152
 153         rc = rpcrdma_bc_setup_reps(r_xprt, reqs);
 154         if (rc)
 155                 goto out_free;
 156
 157         rc = rpcrdma_ep_post_extra_recv(r_xprt, reqs);
 158         if (rc)
 159                 goto out_free;
 160
 161         buffer->rb_bc_srv_max_requests = reqs;
 162         request_module("svcrdma");
 163
 164         return 0;
 165
 166 out_free:
 167         xprt_rdma_bc_destroy(xprt, reqs);
 168
 169 out_err:
 170         pr_err("RPC:       %s: setup backchannel transport failed\n", __func__);
 171         return -ENOMEM;
 172 }
 173
 174 /**
 175  * xprt_rdma_bc_up - Create transport endpoint for backchannel service
 176  * @serv: server endpoint
 177  * @net: network namespace
 178  *
 179  * The "xprt" is an implied argument: it supplies the name of the
 180  * backchannel transport class.
 181  *
 182  * Returns zero on success, negative errno on failure
 183  */
 184 int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
 185 {
 186         int ret;
 187
 188         ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
 189         if (ret < 0)
 190                 return ret;
 191         return 0;
 192 }
 193
 194 /**
 195  * rpcrdma_bc_marshal_reply - Send backwards direction reply
 196  * @rqst: buffer containing RPC reply data
 197  *
 198  * Returns zero on success.
 199  */
 200 int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
 201 {
 202         struct rpc_xprt *xprt = rqst->rq_xprt;
 203         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 204         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
 205         struct rpcrdma_msg *headerp;
 206         size_t rpclen;
 207
 208         headerp = rdmab_to_msg(req->rl_rdmabuf);
 209         headerp->rm_xid = rqst->rq_xid;
 210         headerp->rm_vers = rpcrdma_version;
 211         headerp->rm_credit =
 212                         cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
 213         headerp->rm_type = rdma_msg;
 214         headerp->rm_body.rm_chunks[0] = xdr_zero;
 215         headerp->rm_body.rm_chunks[1] = xdr_zero;
 216         headerp->rm_body.rm_chunks[2] = xdr_zero;
 217
 218         rpclen = rqst->rq_svec[0].iov_len;
 219
 220 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
 221         pr_info("RPC:       %s: rpclen %zd headerp 0x%p lkey 0x%x\n",
 222                 __func__, rpclen, headerp, rdmab_lkey(req->rl_rdmabuf));
 223         pr_info("RPC:       %s: RPC/RDMA: %*ph\n",
 224                 __func__, (int)RPCRDMA_HDRLEN_MIN, headerp);
 225         pr_info("RPC:       %s:      RPC: %*ph\n",
 226                 __func__, (int)rpclen, rqst->rq_svec[0].iov_base);
 227 #endif
 228
 229         req->rl_send_iov[0].addr = rdmab_addr(req->rl_rdmabuf);
 230         req->rl_send_iov[0].length = RPCRDMA_HDRLEN_MIN;
 231         req->rl_send_iov[0].lkey = rdmab_lkey(req->rl_rdmabuf);
 232
 233         req->rl_send_iov[1].addr = rdmab_addr(req->rl_sendbuf);
 234         req->rl_send_iov[1].length = rpclen;
 235         req->rl_send_iov[1].lkey = rdmab_lkey(req->rl_sendbuf);
 236
 237         req->rl_niovs = 2;
 238         return 0;
 239 }
 240
 241 /**
 242  * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
 243  * @xprt: transport associated with these backchannel resources
 244  * @reqs: number of incoming requests to destroy; ignored
 245  */
 246 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
 247 {
 248         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 249         struct rpc_rqst *rqst, *tmp;
 250
 251         spin_lock_bh(&xprt->bc_pa_lock);
 252         list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
 253                 list_del(&rqst->rq_bc_pa_list);
 254                 spin_unlock_bh(&xprt->bc_pa_lock);
 255
 256                 rpcrdma_bc_free_rqst(r_xprt, rqst);
 257
 258                 spin_lock_bh(&xprt->bc_pa_lock);
 259         }
 260         spin_unlock_bh(&xprt->bc_pa_lock);
 261 }
 262
 263 /**
 264  * xprt_rdma_bc_free_rqst - Release a backchannel rqst
 265  * @rqst: request to release
 266  */
 267 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
 268 {
 269         struct rpc_xprt *xprt = rqst->rq_xprt;
 270
 271         dprintk("RPC:       %s: freeing rqst %p (req %p)\n",
 272                 __func__, rqst, rpcr_to_rdmar(rqst));
 273
 274         smp_mb__before_atomic();
 275         WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state));
 276         clear_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 277         smp_mb__after_atomic();
 278
 279         spin_lock_bh(&xprt->bc_pa_lock);
 280         list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
 281         spin_unlock_bh(&xprt->bc_pa_lock);
 282 }
 283
 284 /**
 285  * rpcrdma_bc_receive_call - Handle a backward direction call
 286  * @xprt: transport receiving the call
 287  * @rep: receive buffer containing the call
 288  *
 289  * Called in the RPC reply handler, which runs in a tasklet.
 290  * Be quick about it.
 291  *
 292  * Operational assumptions:
 293  *    o Backchannel credits are ignored, just as the NFS server
 294  *      forechannel currently does
 295  *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
 296  *      No replay detection is done at the transport level
 297  */
 298 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
 299                              struct rpcrdma_rep *rep)
 300 {
 301         struct rpc_xprt *xprt = &r_xprt->rx_xprt;
 302         struct rpcrdma_msg *headerp;
 303         struct svc_serv *bc_serv;
 304         struct rpcrdma_req *req;
 305         struct rpc_rqst *rqst;
 306         struct xdr_buf *buf;
 307         size_t size;
 308         __be32 *p;
 309
 310         headerp = rdmab_to_msg(rep->rr_rdmabuf);
 311 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
 312         pr_info("RPC:       %s: callback XID %08x, length=%u\n",
 313                 __func__, be32_to_cpu(headerp->rm_xid), rep->rr_len);
 314         pr_info("RPC:       %s: %*ph\n", __func__, rep->rr_len, headerp);
 315 #endif
 316
 317         /* Sanity check:
 318          * Need at least enough bytes for RPC/RDMA header, as code
 319          * here references the header fields by array offset. Also,
 320          * backward calls are always inline, so ensure there
 321          * are some bytes beyond the RPC/RDMA header.
 322          */
 323         if (rep->rr_len < RPCRDMA_HDRLEN_MIN + 24)
 324                 goto out_short;
 325         p = (__be32 *)((unsigned char *)headerp + RPCRDMA_HDRLEN_MIN);
 326         size = rep->rr_len - RPCRDMA_HDRLEN_MIN;
 327
 328         /* Grab a free bc rqst */
 329         spin_lock(&xprt->bc_pa_lock);
 330         if (list_empty(&xprt->bc_pa_list)) {
 331                 spin_unlock(&xprt->bc_pa_lock);
 332                 goto out_overflow;
 333         }
 334         rqst = list_first_entry(&xprt->bc_pa_list,
 335                                 struct rpc_rqst, rq_bc_pa_list);
 336         list_del(&rqst->rq_bc_pa_list);
 337         spin_unlock(&xprt->bc_pa_lock);
 338         dprintk("RPC:       %s: using rqst %p\n", __func__, rqst);
 339
 340         /* Prepare rqst */
 341         rqst->rq_reply_bytes_recvd = 0;
 342         rqst->rq_bytes_sent = 0;
 343         rqst->rq_xid = headerp->rm_xid;
 344
 345         rqst->rq_private_buf.len = size;
 346         set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
 347
 348         buf = &rqst->rq_rcv_buf;
 349         memset(buf, 0, sizeof(*buf));
 350         buf->head[0].iov_base = p;
 351         buf->head[0].iov_len = size;
 352         buf->len = size;
 353
 354         /* The receive buffer has to be hooked to the rpcrdma_req
 355          * so that it can be reposted after the server is done
 356          * parsing it but just before sending the backward
 357          * direction reply.
 358          */
 359         req = rpcr_to_rdmar(rqst);
 360         dprintk("RPC:       %s: attaching rep %p to req %p\n",
 361                 __func__, rep, req);
 362         req->rl_reply = rep;
 363
 364         /* Defeat the retransmit detection logic in send_request */
 365         req->rl_connect_cookie = 0;
 366
 367         /* Queue rqst for ULP's callback service */
 368         bc_serv = xprt->bc_serv;
 369         spin_lock(&bc_serv->sv_cb_lock);
 370         list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
 371         spin_unlock(&bc_serv->sv_cb_lock);
 372
 373         wake_up(&bc_serv->sv_cb_waitq);
 374
 375         r_xprt->rx_stats.bcall_count++;
 376         return;
 377
 378 out_overflow:
 379         pr_warn("RPC/RDMA backchannel overflow\n");
 380         xprt_disconnect_done(xprt);
 381         /* This receive buffer gets reposted automatically
 382          * when the connection is re-established.
 383          */
 384         return;
 385
 386 out_short:
 387         pr_warn("RPC/RDMA short backward direction call\n");
 388
 389         if (rpcrdma_ep_post_recv(&r_xprt->rx_ia, &r_xprt->rx_ep, rep))
 390                 xprt_disconnect_done(xprt);
 391         else
 392                 pr_warn("RPC:       %s: reposting rep %p\n",
 393                         __func__, rep);
 394 }