net/sunrpc/xprtrdma/svc_rdma_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 (server-side).
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/sunrpc/svc_rdma.h>
  10 #include "xprt_rdma.h"
  11
  12 #define RPCDBG_FACILITY RPCDBG_SVCXPRT
  13
  14 #undef SVCRDMA_BACKCHANNEL_DEBUG
  15
  16 /**
  17  * svc_rdma_handle_bc_reply - Process incoming backchannel reply
  18  * @xprt: controlling backchannel transport
  19  * @rdma_resp: pointer to incoming transport header
  20  * @rcvbuf: XDR buffer into which to decode the reply
  21  *
  22  * Returns:
  23  *      %0 if @rcvbuf is filled in, xprt_complete_rqst called,
  24  *      %-EAGAIN if server should call ->recvfrom again.
  25  */
  26 int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, __be32 *rdma_resp,
  27                              struct xdr_buf *rcvbuf)
  28 {
  29         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  30         struct kvec *dst, *src = &rcvbuf->head[0];
  31         struct rpc_rqst *req;
  32         unsigned long cwnd;
  33         u32 credits;
  34         size_t len;
  35         __be32 xid;
  36         __be32 *p;
  37         int ret;
  38
  39         p = (__be32 *)src->iov_base;
  40         len = src->iov_len;
  41         xid = *rdma_resp;
  42
  43 #ifdef SVCRDMA_BACKCHANNEL_DEBUG
  44         pr_info("%s: xid=%08x, length=%zu\n",
  45                 __func__, be32_to_cpu(xid), len);
  46         pr_info("%s: RPC/RDMA: %*ph\n",
  47                 __func__, (int)RPCRDMA_HDRLEN_MIN, rdma_resp);
  48         pr_info("%s:      RPC: %*ph\n",
  49                 __func__, (int)len, p);
  50 #endif
  51
  52         ret = -EAGAIN;
  53         if (src->iov_len < 24)
  54                 goto out_shortreply;
  55
  56         spin_lock(&xprt->recv_lock);
  57         req = xprt_lookup_rqst(xprt, xid);
  58         if (!req)
  59                 goto out_notfound;
  60
  61         dst = &req->rq_private_buf.head[0];
  62         memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
  63         if (dst->iov_len < len)
  64                 goto out_unlock;
  65         memcpy(dst->iov_base, p, len);
  66
  67         credits = be32_to_cpup(rdma_resp + 2);
  68         if (credits == 0)
  69                 credits = 1;    /* don't deadlock */
  70         else if (credits > r_xprt->rx_buf.rb_bc_max_requests)
  71                 credits = r_xprt->rx_buf.rb_bc_max_requests;
  72
  73         spin_lock_bh(&xprt->transport_lock);
  74         cwnd = xprt->cwnd;
  75         xprt->cwnd = credits << RPC_CWNDSHIFT;
  76         if (xprt->cwnd > cwnd)
  77                 xprt_release_rqst_cong(req->rq_task);
  78         spin_unlock_bh(&xprt->transport_lock);
  79
  80
  81         ret = 0;
  82         xprt_complete_rqst(req->rq_task, rcvbuf->len);
  83         rcvbuf->len = 0;
  84
  85 out_unlock:
  86         spin_unlock(&xprt->recv_lock);
  87 out:
  88         return ret;
  89
  90 out_shortreply:
  91         dprintk("svcrdma: short bc reply: xprt=%p, len=%zu\n",
  92                 xprt, src->iov_len);
  93         goto out;
  94
  95 out_notfound:
  96         dprintk("svcrdma: unrecognized bc reply: xprt=%p, xid=%08x\n",
  97                 xprt, be32_to_cpu(xid));
  98
  99         goto out_unlock;
 100 }
 101
 102 /* Send a backwards direction RPC call.
 103  *
 104  * Caller holds the connection's mutex and has already marshaled
 105  * the RPC/RDMA request.
 106  *
 107  * This is similar to svc_rdma_send_reply_msg, but takes a struct
 108  * rpc_rqst instead, does not support chunks, and avoids blocking
 109  * memory allocation.
 110  *
 111  * XXX: There is still an opportunity to block in svc_rdma_send()
 112  * if there are no SQ entries to post the Send. This may occur if
 113  * the adapter has a small maximum SQ depth.
 114  */
 115 static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
 116                               struct rpc_rqst *rqst)
 117 {
 118         struct svc_rdma_op_ctxt *ctxt;
 119         int ret;
 120
 121         ctxt = svc_rdma_get_context(rdma);
 122
 123         /* rpcrdma_bc_send_request builds the transport header and
 124          * the backchannel RPC message in the same buffer. Thus only
 125          * one SGE is needed to send both.
 126          */
 127         ret = svc_rdma_map_reply_hdr(rdma, ctxt, rqst->rq_buffer,
 128                                      rqst->rq_snd_buf.len);
 129         if (ret < 0)
 130                 goto out_err;
 131
 132         ret = svc_rdma_repost_recv(rdma, GFP_NOIO);
 133         if (ret)
 134                 goto out_err;
 135
 136         ret = svc_rdma_post_send_wr(rdma, ctxt, 1, 0);
 137         if (ret)
 138                 goto out_unmap;
 139
 140 out_err:
 141         dprintk("svcrdma: %s returns %d\n", __func__, ret);
 142         return ret;
 143
 144 out_unmap:
 145         svc_rdma_unmap_dma(ctxt);
 146         svc_rdma_put_context(ctxt, 1);
 147         ret = -EIO;
 148         goto out_err;
 149 }
 150
 151 /* Server-side transport endpoint wants a whole page for its send
 152  * buffer. The client RPC code constructs the RPC header in this
 153  * buffer before it invokes ->send_request.
 154  */
 155 static int
 156 xprt_rdma_bc_allocate(struct rpc_task *task)
 157 {
 158         struct rpc_rqst *rqst = task->tk_rqstp;
 159         size_t size = rqst->rq_callsize;
 160         struct page *page;
 161
 162         if (size > PAGE_SIZE) {
 163                 WARN_ONCE(1, "svcrdma: large bc buffer request (size %zu)\n",
 164                           size);
 165                 return -EINVAL;
 166         }
 167
 168         /* svc_rdma_sendto releases this page */
 169         page = alloc_page(RPCRDMA_DEF_GFP);
 170         if (!page)
 171                 return -ENOMEM;
 172         rqst->rq_buffer = page_address(page);
 173
 174         rqst->rq_rbuffer = kmalloc(rqst->rq_rcvsize, RPCRDMA_DEF_GFP);
 175         if (!rqst->rq_rbuffer) {
 176                 put_page(page);
 177                 return -ENOMEM;
 178         }
 179         return 0;
 180 }
 181
 182 static void
 183 xprt_rdma_bc_free(struct rpc_task *task)
 184 {
 185         struct rpc_rqst *rqst = task->tk_rqstp;
 186
 187         kfree(rqst->rq_rbuffer);
 188 }
 189
 190 static int
 191 rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
 192 {
 193         struct rpc_xprt *xprt = rqst->rq_xprt;
 194         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 195         __be32 *p;
 196         int rc;
 197
 198         /* Space in the send buffer for an RPC/RDMA header is reserved
 199          * via xprt->tsh_size.
 200          */
 201         p = rqst->rq_buffer;
 202         *p++ = rqst->rq_xid;
 203         *p++ = rpcrdma_version;
 204         *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
 205         *p++ = rdma_msg;
 206         *p++ = xdr_zero;
 207         *p++ = xdr_zero;
 208         *p   = xdr_zero;
 209
 210 #ifdef SVCRDMA_BACKCHANNEL_DEBUG
 211         pr_info("%s: %*ph\n", __func__, 64, rqst->rq_buffer);
 212 #endif
 213
 214         rc = svc_rdma_bc_sendto(rdma, rqst);
 215         if (rc)
 216                 goto drop_connection;
 217         return rc;
 218
 219 drop_connection:
 220         dprintk("svcrdma: failed to send bc call\n");
 221         xprt_disconnect_done(xprt);
 222         return -ENOTCONN;
 223 }
 224
 225 /* Send an RPC call on the passive end of a transport
 226  * connection.
 227  */
 228 static int
 229 xprt_rdma_bc_send_request(struct rpc_task *task)
 230 {
 231         struct rpc_rqst *rqst = task->tk_rqstp;
 232         struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
 233         struct svcxprt_rdma *rdma;
 234         int ret;
 235
 236         dprintk("svcrdma: sending bc call with xid: %08x\n",
 237                 be32_to_cpu(rqst->rq_xid));
 238
 239         if (!mutex_trylock(&sxprt->xpt_mutex)) {
 240                 rpc_sleep_on(&sxprt->xpt_bc_pending, task, NULL);
 241                 if (!mutex_trylock(&sxprt->xpt_mutex))
 242                         return -EAGAIN;
 243                 rpc_wake_up_queued_task(&sxprt->xpt_bc_pending, task);
 244         }
 245
 246         ret = -ENOTCONN;
 247         rdma = container_of(sxprt, struct svcxprt_rdma, sc_xprt);
 248         if (!test_bit(XPT_DEAD, &sxprt->xpt_flags))
 249                 ret = rpcrdma_bc_send_request(rdma, rqst);
 250
 251         mutex_unlock(&sxprt->xpt_mutex);
 252
 253         if (ret < 0)
 254                 return ret;
 255         return 0;
 256 }
 257
 258 static void
 259 xprt_rdma_bc_close(struct rpc_xprt *xprt)
 260 {
 261         dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
 262 }
 263
 264 static void
 265 xprt_rdma_bc_put(struct rpc_xprt *xprt)
 266 {
 267         dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
 268
 269         xprt_free(xprt);
 270         module_put(THIS_MODULE);
 271 }
 272
 273 static const struct rpc_xprt_ops xprt_rdma_bc_procs = {
 274         .reserve_xprt           = xprt_reserve_xprt_cong,
 275         .release_xprt           = xprt_release_xprt_cong,
 276         .alloc_slot             = xprt_alloc_slot,
 277         .release_request        = xprt_release_rqst_cong,
 278         .buf_alloc              = xprt_rdma_bc_allocate,
 279         .buf_free               = xprt_rdma_bc_free,
 280         .send_request           = xprt_rdma_bc_send_request,
 281         .set_retrans_timeout    = xprt_set_retrans_timeout_def,
 282         .close                  = xprt_rdma_bc_close,
 283         .destroy                = xprt_rdma_bc_put,
 284         .print_stats            = xprt_rdma_print_stats
 285 };
 286
 287 static const struct rpc_timeout xprt_rdma_bc_timeout = {
 288         .to_initval = 60 * HZ,
 289         .to_maxval = 60 * HZ,
 290 };
 291
 292 /* It shouldn't matter if the number of backchannel session slots
 293  * doesn't match the number of RPC/RDMA credits. That just means
 294  * one or the other will have extra slots that aren't used.
 295  */
 296 static struct rpc_xprt *
 297 xprt_setup_rdma_bc(struct xprt_create *args)
 298 {
 299         struct rpc_xprt *xprt;
 300         struct rpcrdma_xprt *new_xprt;
 301
 302         if (args->addrlen > sizeof(xprt->addr)) {
 303                 dprintk("RPC:       %s: address too large\n", __func__);
 304                 return ERR_PTR(-EBADF);
 305         }
 306
 307         xprt = xprt_alloc(args->net, sizeof(*new_xprt),
 308                           RPCRDMA_MAX_BC_REQUESTS,
 309                           RPCRDMA_MAX_BC_REQUESTS);
 310         if (!xprt) {
 311                 dprintk("RPC:       %s: couldn't allocate rpc_xprt\n",
 312                         __func__);
 313                 return ERR_PTR(-ENOMEM);
 314         }
 315
 316         xprt->timeout = &xprt_rdma_bc_timeout;
 317         xprt_set_bound(xprt);
 318         xprt_set_connected(xprt);
 319         xprt->bind_timeout = RPCRDMA_BIND_TO;
 320         xprt->reestablish_timeout = RPCRDMA_INIT_REEST_TO;
 321         xprt->idle_timeout = RPCRDMA_IDLE_DISC_TO;
 322
 323         xprt->prot = XPRT_TRANSPORT_BC_RDMA;
 324         xprt->tsh_size = RPCRDMA_HDRLEN_MIN / sizeof(__be32);
 325         xprt->ops = &xprt_rdma_bc_procs;
 326
 327         memcpy(&xprt->addr, args->dstaddr, args->addrlen);
 328         xprt->addrlen = args->addrlen;
 329         xprt_rdma_format_addresses(xprt, (struct sockaddr *)&xprt->addr);
 330         xprt->resvport = 0;
 331
 332         xprt->max_payload = xprt_rdma_max_inline_read;
 333
 334         new_xprt = rpcx_to_rdmax(xprt);
 335         new_xprt->rx_buf.rb_bc_max_requests = xprt->max_reqs;
 336
 337         xprt_get(xprt);
 338         args->bc_xprt->xpt_bc_xprt = xprt;
 339         xprt->bc_xprt = args->bc_xprt;
 340
 341         if (!try_module_get(THIS_MODULE))
 342                 goto out_fail;
 343
 344         /* Final put for backchannel xprt is in __svc_rdma_free */
 345         xprt_get(xprt);
 346         return xprt;
 347
 348 out_fail:
 349         xprt_rdma_free_addresses(xprt);
 350         args->bc_xprt->xpt_bc_xprt = NULL;
 351         args->bc_xprt->xpt_bc_xps = NULL;
 352         xprt_put(xprt);
 353         xprt_free(xprt);
 354         return ERR_PTR(-EINVAL);
 355 }
 356
 357 struct xprt_class xprt_rdma_bc = {
 358         .list                   = LIST_HEAD_INIT(xprt_rdma_bc.list),
 359         .name                   = "rdma backchannel",
 360         .owner                  = THIS_MODULE,
 361         .ident                  = XPRT_TRANSPORT_BC_RDMA,
 362         .setup                  = xprt_setup_rdma_bc,
 363 };