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