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         /* Bump page refcnt so Send completion doesn't release
 137          * the rq_buffer before all retransmits are complete.
 138          */
 139         get_page(virt_to_page(rqst->rq_buffer));
 140         ret = svc_rdma_post_send_wr(rdma, ctxt, 1, 0);
 141         if (ret)
 142                 goto out_unmap;
 143
 144 out_err:
 145         dprintk("svcrdma: %s returns %d\n", __func__, ret);
 146         return ret;
 147
 148 out_unmap:
 149         svc_rdma_unmap_dma(ctxt);
 150         svc_rdma_put_context(ctxt, 1);
 151         ret = -EIO;
 152         goto out_err;
 153 }
 154
 155 /* Server-side transport endpoint wants a whole page for its send
 156  * buffer. The client RPC code constructs the RPC header in this
 157  * buffer before it invokes ->send_request.
 158  */
 159 static int
 160 xprt_rdma_bc_allocate(struct rpc_task *task)
 161 {
 162         struct rpc_rqst *rqst = task->tk_rqstp;
 163         size_t size = rqst->rq_callsize;
 164         struct page *page;
 165
 166         if (size > PAGE_SIZE) {
 167                 WARN_ONCE(1, "svcrdma: large bc buffer request (size %zu)\n",
 168                           size);
 169                 return -EINVAL;
 170         }
 171
 172         page = alloc_page(RPCRDMA_DEF_GFP);
 173         if (!page)
 174                 return -ENOMEM;
 175         rqst->rq_buffer = page_address(page);
 176
 177         rqst->rq_rbuffer = kmalloc(rqst->rq_rcvsize, RPCRDMA_DEF_GFP);
 178         if (!rqst->rq_rbuffer) {
 179                 put_page(page);
 180                 return -ENOMEM;
 181         }
 182         return 0;
 183 }
 184
 185 static void
 186 xprt_rdma_bc_free(struct rpc_task *task)
 187 {
 188         struct rpc_rqst *rqst = task->tk_rqstp;
 189
 190         put_page(virt_to_page(rqst->rq_buffer));
 191         kfree(rqst->rq_rbuffer);
 192 }
 193
 194 static int
 195 rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
 196 {
 197         struct rpc_xprt *xprt = rqst->rq_xprt;
 198         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 199         __be32 *p;
 200         int rc;
 201
 202         /* Space in the send buffer for an RPC/RDMA header is reserved
 203          * via xprt->tsh_size.
 204          */
 205         p = rqst->rq_buffer;
 206         *p++ = rqst->rq_xid;
 207         *p++ = rpcrdma_version;
 208         *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
 209         *p++ = rdma_msg;
 210         *p++ = xdr_zero;
 211         *p++ = xdr_zero;
 212         *p   = xdr_zero;
 213
 214 #ifdef SVCRDMA_BACKCHANNEL_DEBUG
 215         pr_info("%s: %*ph\n", __func__, 64, rqst->rq_buffer);
 216 #endif
 217
 218         rc = svc_rdma_bc_sendto(rdma, rqst);
 219         if (rc)
 220                 goto drop_connection;
 221         return rc;
 222
 223 drop_connection:
 224         dprintk("svcrdma: failed to send bc call\n");
 225         xprt_disconnect_done(xprt);
 226         return -ENOTCONN;
 227 }
 228
 229 /* Send an RPC call on the passive end of a transport
 230  * connection.
 231  */
 232 static int
 233 xprt_rdma_bc_send_request(struct rpc_task *task)
 234 {
 235         struct rpc_rqst *rqst = task->tk_rqstp;
 236         struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
 237         struct svcxprt_rdma *rdma;
 238         int ret;
 239
 240         dprintk("svcrdma: sending bc call with xid: %08x\n",
 241                 be32_to_cpu(rqst->rq_xid));
 242
 243         if (!mutex_trylock(&sxprt->xpt_mutex)) {
 244                 rpc_sleep_on(&sxprt->xpt_bc_pending, task, NULL);
 245                 if (!mutex_trylock(&sxprt->xpt_mutex))
 246                         return -EAGAIN;
 247                 rpc_wake_up_queued_task(&sxprt->xpt_bc_pending, task);
 248         }
 249
 250         ret = -ENOTCONN;
 251         rdma = container_of(sxprt, struct svcxprt_rdma, sc_xprt);
 252         if (!test_bit(XPT_DEAD, &sxprt->xpt_flags))
 253                 ret = rpcrdma_bc_send_request(rdma, rqst);
 254
 255         mutex_unlock(&sxprt->xpt_mutex);
 256
 257         if (ret < 0)
 258                 return ret;
 259         return 0;
 260 }
 261
 262 static void
 263 xprt_rdma_bc_close(struct rpc_xprt *xprt)
 264 {
 265         dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
 266 }
 267
 268 static void
 269 xprt_rdma_bc_put(struct rpc_xprt *xprt)
 270 {
 271         dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
 272
 273         xprt_free(xprt);
 274         module_put(THIS_MODULE);
 275 }
 276
 277 static const struct rpc_xprt_ops xprt_rdma_bc_procs = {
 278         .reserve_xprt           = xprt_reserve_xprt_cong,
 279         .release_xprt           = xprt_release_xprt_cong,
 280         .alloc_slot             = xprt_alloc_slot,
 281         .release_request        = xprt_release_rqst_cong,
 282         .buf_alloc              = xprt_rdma_bc_allocate,
 283         .buf_free               = xprt_rdma_bc_free,
 284         .send_request           = xprt_rdma_bc_send_request,
 285         .set_retrans_timeout    = xprt_set_retrans_timeout_def,
 286         .close                  = xprt_rdma_bc_close,
 287         .destroy                = xprt_rdma_bc_put,
 288         .print_stats            = xprt_rdma_print_stats
 289 };
 290
 291 static const struct rpc_timeout xprt_rdma_bc_timeout = {
 292         .to_initval = 60 * HZ,
 293         .to_maxval = 60 * HZ,
 294 };
 295
 296 /* It shouldn't matter if the number of backchannel session slots
 297  * doesn't match the number of RPC/RDMA credits. That just means
 298  * one or the other will have extra slots that aren't used.
 299  */
 300 static struct rpc_xprt *
 301 xprt_setup_rdma_bc(struct xprt_create *args)
 302 {
 303         struct rpc_xprt *xprt;
 304         struct rpcrdma_xprt *new_xprt;
 305
 306         if (args->addrlen > sizeof(xprt->addr)) {
 307                 dprintk("RPC:       %s: address too large\n", __func__);
 308                 return ERR_PTR(-EBADF);
 309         }
 310
 311         xprt = xprt_alloc(args->net, sizeof(*new_xprt),
 312                           RPCRDMA_MAX_BC_REQUESTS,
 313                           RPCRDMA_MAX_BC_REQUESTS);
 314         if (!xprt) {
 315                 dprintk("RPC:       %s: couldn't allocate rpc_xprt\n",
 316                         __func__);
 317                 return ERR_PTR(-ENOMEM);
 318         }
 319
 320         xprt->timeout = &xprt_rdma_bc_timeout;
 321         xprt_set_bound(xprt);
 322         xprt_set_connected(xprt);
 323         xprt->bind_timeout = RPCRDMA_BIND_TO;
 324         xprt->reestablish_timeout = RPCRDMA_INIT_REEST_TO;
 325         xprt->idle_timeout = RPCRDMA_IDLE_DISC_TO;
 326
 327         xprt->prot = XPRT_TRANSPORT_BC_RDMA;
 328         xprt->tsh_size = RPCRDMA_HDRLEN_MIN / sizeof(__be32);
 329         xprt->ops = &xprt_rdma_bc_procs;
 330
 331         memcpy(&xprt->addr, args->dstaddr, args->addrlen);
 332         xprt->addrlen = args->addrlen;
 333         xprt_rdma_format_addresses(xprt, (struct sockaddr *)&xprt->addr);
 334         xprt->resvport = 0;
 335
 336         xprt->max_payload = xprt_rdma_max_inline_read;
 337
 338         new_xprt = rpcx_to_rdmax(xprt);
 339         new_xprt->rx_buf.rb_bc_max_requests = xprt->max_reqs;
 340
 341         xprt_get(xprt);
 342         args->bc_xprt->xpt_bc_xprt = xprt;
 343         xprt->bc_xprt = args->bc_xprt;
 344
 345         if (!try_module_get(THIS_MODULE))
 346                 goto out_fail;
 347
 348         /* Final put for backchannel xprt is in __svc_rdma_free */
 349         xprt_get(xprt);
 350         return xprt;
 351
 352 out_fail:
 353         xprt_rdma_free_addresses(xprt);
 354         args->bc_xprt->xpt_bc_xprt = NULL;
 355         args->bc_xprt->xpt_bc_xps = NULL;
 356         xprt_put(xprt);
 357         xprt_free(xprt);
 358         return ERR_PTR(-EINVAL);
 359 }
 360
 361 struct xprt_class xprt_rdma_bc = {
 362         .list                   = LIST_HEAD_INIT(xprt_rdma_bc.list),
 363         .name                   = "rdma backchannel",
 364         .owner                  = THIS_MODULE,
 365         .ident                  = XPRT_TRANSPORT_BC_RDMA,
 366         .setup                  = xprt_setup_rdma_bc,
 367 };