net/sunrpc/xprtrdma/svc_rdma_backchannel.c

   1 /*
   2  * Copyright (c) 2015 Oracle.  All rights reserved.
   3  *
   4  * Support for backward direction RPCs on RPC/RDMA (server-side).
   5  */
   6
   7 #include <linux/module.h>
   8 #include <linux/sunrpc/svc_rdma.h>
   9 #include "xprt_rdma.h"
  10
  11 #define RPCDBG_FACILITY RPCDBG_SVCXPRT
  12
  13 #undef SVCRDMA_BACKCHANNEL_DEBUG
  14
  15 /**
  16  * svc_rdma_handle_bc_reply - Process incoming backchannel reply
  17  * @xprt: controlling backchannel transport
  18  * @rdma_resp: pointer to incoming transport header
  19  * @rcvbuf: XDR buffer into which to decode the reply
  20  *
  21  * Returns:
  22  *      %0 if @rcvbuf is filled in, xprt_complete_rqst called,
  23  *      %-EAGAIN if server should call ->recvfrom again.
  24  */
  25 int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, __be32 *rdma_resp,
  26                              struct xdr_buf *rcvbuf)
  27 {
  28         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  29         struct kvec *dst, *src = &rcvbuf->head[0];
  30         struct rpc_rqst *req;
  31         unsigned long cwnd;
  32         u32 credits;
  33         size_t len;
  34         __be32 xid;
  35         __be32 *p;
  36         int ret;
  37
  38         p = (__be32 *)src->iov_base;
  39         len = src->iov_len;
  40         xid = *rdma_resp;
  41
  42 #ifdef SVCRDMA_BACKCHANNEL_DEBUG
  43         pr_info("%s: xid=%08x, length=%zu\n",
  44                 __func__, be32_to_cpu(xid), len);
  45         pr_info("%s: RPC/RDMA: %*ph\n",
  46                 __func__, (int)RPCRDMA_HDRLEN_MIN, rdma_resp);
  47         pr_info("%s:      RPC: %*ph\n",
  48                 __func__, (int)len, p);
  49 #endif
  50
  51         ret = -EAGAIN;
  52         if (src->iov_len < 24)
  53                 goto out_shortreply;
  54
  55         spin_lock(&xprt->recv_lock);
  56         req = xprt_lookup_rqst(xprt, xid);
  57         if (!req)
  58                 goto out_notfound;
  59
  60         dst = &req->rq_private_buf.head[0];
  61         memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
  62         if (dst->iov_len < len)
  63                 goto out_unlock;
  64         memcpy(dst->iov_base, p, len);
  65
  66         credits = be32_to_cpup(rdma_resp + 2);
  67         if (credits == 0)
  68                 credits = 1;    /* don't deadlock */
  69         else if (credits > r_xprt->rx_buf.rb_bc_max_requests)
  70                 credits = r_xprt->rx_buf.rb_bc_max_requests;
  71
  72         spin_lock_bh(&xprt->transport_lock);
  73         cwnd = xprt->cwnd;
  74         xprt->cwnd = credits << RPC_CWNDSHIFT;
  75         if (xprt->cwnd > cwnd)
  76                 xprt_release_rqst_cong(req->rq_task);
  77         spin_unlock_bh(&xprt->transport_lock);
  78
  79
  80         ret = 0;
  81         xprt_complete_rqst(req->rq_task, rcvbuf->len);
  82         rcvbuf->len = 0;
  83
  84 out_unlock:
  85         spin_unlock(&xprt->recv_lock);
  86 out:
  87         return ret;
  88
  89 out_shortreply:
  90         dprintk("svcrdma: short bc reply: xprt=%p, len=%zu\n",
  91                 xprt, src->iov_len);
  92         goto out;
  93
  94 out_notfound:
  95         dprintk("svcrdma: unrecognized bc reply: xprt=%p, xid=%08x\n",
  96                 xprt, be32_to_cpu(xid));
  97
  98         goto out_unlock;
  99 }
 100
 101 /* Send a backwards direction RPC call.
 102  *
 103  * Caller holds the connection's mutex and has already marshaled
 104  * the RPC/RDMA request.
 105  *
 106  * This is similar to svc_rdma_send_reply_msg, but takes a struct
 107  * rpc_rqst instead, does not support chunks, and avoids blocking
 108  * memory allocation.
 109  *
 110  * XXX: There is still an opportunity to block in svc_rdma_send()
 111  * if there are no SQ entries to post the Send. This may occur if
 112  * the adapter has a small maximum SQ depth.
 113  */
 114 static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
 115                               struct rpc_rqst *rqst)
 116 {
 117         struct svc_rdma_op_ctxt *ctxt;
 118         int ret;
 119
 120         ctxt = svc_rdma_get_context(rdma);
 121
 122         /* rpcrdma_bc_send_request builds the transport header and
 123          * the backchannel RPC message in the same buffer. Thus only
 124          * one SGE is needed to send both.
 125          */
 126         ret = svc_rdma_map_reply_hdr(rdma, ctxt, rqst->rq_buffer,
 127                                      rqst->rq_snd_buf.len);
 128         if (ret < 0)
 129                 goto out_err;
 130
 131         ret = svc_rdma_repost_recv(rdma, GFP_NOIO);
 132         if (ret)
 133                 goto out_err;
 134
 135         ret = svc_rdma_post_send_wr(rdma, ctxt, 1, 0);
 136         if (ret)
 137                 goto out_unmap;
 138
 139 out_err:
 140         dprintk("svcrdma: %s returns %d\n", __func__, ret);
 141         return ret;
 142
 143 out_unmap:
 144         svc_rdma_unmap_dma(ctxt);
 145         svc_rdma_put_context(ctxt, 1);
 146         ret = -EIO;
 147         goto out_err;
 148 }
 149
 150 /* Server-side transport endpoint wants a whole page for its send
 151  * buffer. The client RPC code constructs the RPC header in this
 152  * buffer before it invokes ->send_request.
 153  */
 154 static int
 155 xprt_rdma_bc_allocate(struct rpc_task *task)
 156 {
 157         struct rpc_rqst *rqst = task->tk_rqstp;
 158         size_t size = rqst->rq_callsize;
 159         struct page *page;
 160
 161         if (size > PAGE_SIZE) {
 162                 WARN_ONCE(1, "svcrdma: large bc buffer request (size %zu)\n",
 163                           size);
 164                 return -EINVAL;
 165         }
 166
 167         /* svc_rdma_sendto releases this page */
 168         page = alloc_page(RPCRDMA_DEF_GFP);
 169         if (!page)
 170                 return -ENOMEM;
 171         rqst->rq_buffer = page_address(page);
 172
 173         rqst->rq_rbuffer = kmalloc(rqst->rq_rcvsize, RPCRDMA_DEF_GFP);
 174         if (!rqst->rq_rbuffer) {
 175                 put_page(page);
 176                 return -ENOMEM;
 177         }
 178         return 0;
 179 }
 180
 181 static void
 182 xprt_rdma_bc_free(struct rpc_task *task)
 183 {
 184         struct rpc_rqst *rqst = task->tk_rqstp;
 185
 186         kfree(rqst->rq_rbuffer);
 187 }
 188
 189 static int
 190 rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
 191 {
 192         struct rpc_xprt *xprt = rqst->rq_xprt;
 193         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 194         __be32 *p;
 195         int rc;
 196
 197         /* Space in the send buffer for an RPC/RDMA header is reserved
 198          * via xprt->tsh_size.
 199          */
 200         p = rqst->rq_buffer;
 201         *p++ = rqst->rq_xid;
 202         *p++ = rpcrdma_version;
 203         *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
 204         *p++ = rdma_msg;
 205         *p++ = xdr_zero;
 206         *p++ = xdr_zero;
 207         *p   = xdr_zero;
 208
 209 #ifdef SVCRDMA_BACKCHANNEL_DEBUG
 210         pr_info("%s: %*ph\n", __func__, 64, rqst->rq_buffer);
 211 #endif
 212
 213         rc = svc_rdma_bc_sendto(rdma, rqst);
 214         if (rc)
 215                 goto drop_connection;
 216         return rc;
 217
 218 drop_connection:
 219         dprintk("svcrdma: failed to send bc call\n");
 220         xprt_disconnect_done(xprt);
 221         return -ENOTCONN;
 222 }
 223
 224 /* Send an RPC call on the passive end of a transport
 225  * connection.
 226  */
 227 static int
 228 xprt_rdma_bc_send_request(struct rpc_task *task)
 229 {
 230         struct rpc_rqst *rqst = task->tk_rqstp;
 231         struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
 232         struct svcxprt_rdma *rdma;
 233         int ret;
 234
 235         dprintk("svcrdma: sending bc call with xid: %08x\n",
 236                 be32_to_cpu(rqst->rq_xid));
 237
 238         if (!mutex_trylock(&sxprt->xpt_mutex)) {
 239                 rpc_sleep_on(&sxprt->xpt_bc_pending, task, NULL);
 240                 if (!mutex_trylock(&sxprt->xpt_mutex))
 241                         return -EAGAIN;
 242                 rpc_wake_up_queued_task(&sxprt->xpt_bc_pending, task);
 243         }
 244
 245         ret = -ENOTCONN;
 246         rdma = container_of(sxprt, struct svcxprt_rdma, sc_xprt);
 247         if (!test_bit(XPT_DEAD, &sxprt->xpt_flags))
 248                 ret = rpcrdma_bc_send_request(rdma, rqst);
 249
 250         mutex_unlock(&sxprt->xpt_mutex);
 251
 252         if (ret < 0)
 253                 return ret;
 254         return 0;
 255 }
 256
 257 static void
 258 xprt_rdma_bc_close(struct rpc_xprt *xprt)
 259 {
 260         dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
 261 }
 262
 263 static void
 264 xprt_rdma_bc_put(struct rpc_xprt *xprt)
 265 {
 266         dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
 267
 268         xprt_free(xprt);
 269         module_put(THIS_MODULE);
 270 }
 271
 272 static const struct rpc_xprt_ops xprt_rdma_bc_procs = {
 273         .reserve_xprt           = xprt_reserve_xprt_cong,
 274         .release_xprt           = xprt_release_xprt_cong,
 275         .alloc_slot             = xprt_alloc_slot,
 276         .release_request        = xprt_release_rqst_cong,
 277         .buf_alloc              = xprt_rdma_bc_allocate,
 278         .buf_free               = xprt_rdma_bc_free,
 279         .send_request           = xprt_rdma_bc_send_request,
 280         .set_retrans_timeout    = xprt_set_retrans_timeout_def,
 281         .close                  = xprt_rdma_bc_close,
 282         .destroy                = xprt_rdma_bc_put,
 283         .print_stats            = xprt_rdma_print_stats
 284 };
 285
 286 static const struct rpc_timeout xprt_rdma_bc_timeout = {
 287         .to_initval = 60 * HZ,
 288         .to_maxval = 60 * HZ,
 289 };
 290
 291 /* It shouldn't matter if the number of backchannel session slots
 292  * doesn't match the number of RPC/RDMA credits. That just means
 293  * one or the other will have extra slots that aren't used.
 294  */
 295 static struct rpc_xprt *
 296 xprt_setup_rdma_bc(struct xprt_create *args)
 297 {
 298         struct rpc_xprt *xprt;
 299         struct rpcrdma_xprt *new_xprt;
 300
 301         if (args->addrlen > sizeof(xprt->addr)) {
 302                 dprintk("RPC:       %s: address too large\n", __func__);
 303                 return ERR_PTR(-EBADF);
 304         }
 305
 306         xprt = xprt_alloc(args->net, sizeof(*new_xprt),
 307                           RPCRDMA_MAX_BC_REQUESTS,
 308                           RPCRDMA_MAX_BC_REQUESTS);
 309         if (!xprt) {
 310                 dprintk("RPC:       %s: couldn't allocate rpc_xprt\n",
 311                         __func__);
 312                 return ERR_PTR(-ENOMEM);
 313         }
 314
 315         xprt->timeout = &xprt_rdma_bc_timeout;
 316         xprt_set_bound(xprt);
 317         xprt_set_connected(xprt);
 318         xprt->bind_timeout = RPCRDMA_BIND_TO;
 319         xprt->reestablish_timeout = RPCRDMA_INIT_REEST_TO;
 320         xprt->idle_timeout = RPCRDMA_IDLE_DISC_TO;
 321
 322         xprt->prot = XPRT_TRANSPORT_BC_RDMA;
 323         xprt->tsh_size = RPCRDMA_HDRLEN_MIN / sizeof(__be32);
 324         xprt->ops = &xprt_rdma_bc_procs;
 325
 326         memcpy(&xprt->addr, args->dstaddr, args->addrlen);
 327         xprt->addrlen = args->addrlen;
 328         xprt_rdma_format_addresses(xprt, (struct sockaddr *)&xprt->addr);
 329         xprt->resvport = 0;
 330
 331         xprt->max_payload = xprt_rdma_max_inline_read;
 332
 333         new_xprt = rpcx_to_rdmax(xprt);
 334         new_xprt->rx_buf.rb_bc_max_requests = xprt->max_reqs;
 335
 336         xprt_get(xprt);
 337         args->bc_xprt->xpt_bc_xprt = xprt;
 338         xprt->bc_xprt = args->bc_xprt;
 339
 340         if (!try_module_get(THIS_MODULE))
 341                 goto out_fail;
 342
 343         /* Final put for backchannel xprt is in __svc_rdma_free */
 344         xprt_get(xprt);
 345         return xprt;
 346
 347 out_fail:
 348         xprt_rdma_free_addresses(xprt);
 349         args->bc_xprt->xpt_bc_xprt = NULL;
 350         args->bc_xprt->xpt_bc_xps = NULL;
 351         xprt_put(xprt);
 352         xprt_free(xprt);
 353         return ERR_PTR(-EINVAL);
 354 }
 355
 356 struct xprt_class xprt_rdma_bc = {
 357         .list                   = LIST_HEAD_INIT(xprt_rdma_bc.list),
 358         .name                   = "rdma backchannel",
 359         .owner                  = THIS_MODULE,
 360         .ident                  = XPRT_TRANSPORT_BC_RDMA,
 361         .setup                  = xprt_setup_rdma_bc,
 362 };