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