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/sunrpc/svc_rdma.h>
   8 #include "xprt_rdma.h"
   9
  10 #define RPCDBG_FACILITY RPCDBG_SVCXPRT
  11
  12 #undef SVCRDMA_BACKCHANNEL_DEBUG
  13
  14 int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, struct rpcrdma_msg *rmsgp,
  15                              struct xdr_buf *rcvbuf)
  16 {
  17         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  18         struct kvec *dst, *src = &rcvbuf->head[0];
  19         struct rpc_rqst *req;
  20         unsigned long cwnd;
  21         u32 credits;
  22         size_t len;
  23         __be32 xid;
  24         __be32 *p;
  25         int ret;
  26
  27         p = (__be32 *)src->iov_base;
  28         len = src->iov_len;
  29         xid = rmsgp->rm_xid;
  30
  31 #ifdef SVCRDMA_BACKCHANNEL_DEBUG
  32         pr_info("%s: xid=%08x, length=%zu\n",
  33                 __func__, be32_to_cpu(xid), len);
  34         pr_info("%s: RPC/RDMA: %*ph\n",
  35                 __func__, (int)RPCRDMA_HDRLEN_MIN, rmsgp);
  36         pr_info("%s:      RPC: %*ph\n",
  37                 __func__, (int)len, p);
  38 #endif
  39
  40         ret = -EAGAIN;
  41         if (src->iov_len < 24)
  42                 goto out_shortreply;
  43
  44         spin_lock_bh(&xprt->transport_lock);
  45         req = xprt_lookup_rqst(xprt, xid);
  46         if (!req)
  47                 goto out_notfound;
  48
  49         dst = &req->rq_private_buf.head[0];
  50         memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
  51         if (dst->iov_len < len)
  52                 goto out_unlock;
  53         memcpy(dst->iov_base, p, len);
  54
  55         credits = be32_to_cpu(rmsgp->rm_credit);
  56         if (credits == 0)
  57                 credits = 1;    /* don't deadlock */
  58         else if (credits > r_xprt->rx_buf.rb_bc_max_requests)
  59                 credits = r_xprt->rx_buf.rb_bc_max_requests;
  60
  61         cwnd = xprt->cwnd;
  62         xprt->cwnd = credits << RPC_CWNDSHIFT;
  63         if (xprt->cwnd > cwnd)
  64                 xprt_release_rqst_cong(req->rq_task);
  65
  66         ret = 0;
  67         xprt_complete_rqst(req->rq_task, rcvbuf->len);
  68         rcvbuf->len = 0;
  69
  70 out_unlock:
  71         spin_unlock_bh(&xprt->transport_lock);
  72 out:
  73         return ret;
  74
  75 out_shortreply:
  76         dprintk("svcrdma: short bc reply: xprt=%p, len=%zu\n",
  77                 xprt, src->iov_len);
  78         goto out;
  79
  80 out_notfound:
  81         dprintk("svcrdma: unrecognized bc reply: xprt=%p, xid=%08x\n",
  82                 xprt, be32_to_cpu(xid));
  83
  84         goto out_unlock;
  85 }
  86
  87 /* Send a backwards direction RPC call.
  88  *
  89  * Caller holds the connection's mutex and has already marshaled
  90  * the RPC/RDMA request.
  91  *
  92  * This is similar to svc_rdma_reply, but takes an rpc_rqst
  93  * instead, does not support chunks, and avoids blocking memory
  94  * allocation.
  95  *
  96  * XXX: There is still an opportunity to block in svc_rdma_send()
  97  * if there are no SQ entries to post the Send. This may occur if
  98  * the adapter has a small maximum SQ depth.
  99  */
 100 static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
 101                               struct rpc_rqst *rqst)
 102 {
 103         struct xdr_buf *sndbuf = &rqst->rq_snd_buf;
 104         struct svc_rdma_op_ctxt *ctxt;
 105         struct svc_rdma_req_map *vec;
 106         struct ib_send_wr send_wr;
 107         int ret;
 108
 109         vec = svc_rdma_get_req_map(rdma);
 110         ret = svc_rdma_map_xdr(rdma, sndbuf, vec, false);
 111         if (ret)
 112                 goto out_err;
 113
 114         ret = svc_rdma_repost_recv(rdma, GFP_NOIO);
 115         if (ret)
 116                 goto out_err;
 117
 118         ctxt = svc_rdma_get_context(rdma);
 119         ctxt->pages[0] = virt_to_page(rqst->rq_buffer);
 120         ctxt->count = 1;
 121
 122         ctxt->direction = DMA_TO_DEVICE;
 123         ctxt->sge[0].lkey = rdma->sc_pd->local_dma_lkey;
 124         ctxt->sge[0].length = sndbuf->len;
 125         ctxt->sge[0].addr =
 126             ib_dma_map_page(rdma->sc_cm_id->device, ctxt->pages[0], 0,
 127                             sndbuf->len, DMA_TO_DEVICE);
 128         if (ib_dma_mapping_error(rdma->sc_cm_id->device, ctxt->sge[0].addr)) {
 129                 ret = -EIO;
 130                 goto out_unmap;
 131         }
 132         atomic_inc(&rdma->sc_dma_used);
 133
 134         memset(&send_wr, 0, sizeof(send_wr));
 135         ctxt->cqe.done = svc_rdma_wc_send;
 136         send_wr.wr_cqe = &ctxt->cqe;
 137         send_wr.sg_list = ctxt->sge;
 138         send_wr.num_sge = 1;
 139         send_wr.opcode = IB_WR_SEND;
 140         send_wr.send_flags = IB_SEND_SIGNALED;
 141
 142         ret = svc_rdma_send(rdma, &send_wr);
 143         if (ret) {
 144                 ret = -EIO;
 145                 goto out_unmap;
 146         }
 147
 148 out_err:
 149         svc_rdma_put_req_map(rdma, vec);
 150         dprintk("svcrdma: %s returns %d\n", __func__, ret);
 151         return ret;
 152
 153 out_unmap:
 154         svc_rdma_unmap_dma(ctxt);
 155         svc_rdma_put_context(ctxt, 1);
 156         goto out_err;
 157 }
 158
 159 /* Server-side transport endpoint wants a whole page for its send
 160  * buffer. The client RPC code constructs the RPC header in this
 161  * buffer before it invokes ->send_request.
 162  *
 163  * Returns NULL if there was a temporary allocation failure.
 164  */
 165 static void *
 166 xprt_rdma_bc_allocate(struct rpc_task *task, size_t size)
 167 {
 168         struct rpc_rqst *rqst = task->tk_rqstp;
 169         struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
 170         struct svcxprt_rdma *rdma;
 171         struct page *page;
 172
 173         rdma = container_of(sxprt, struct svcxprt_rdma, sc_xprt);
 174
 175         /* Prevent an infinite loop: try to make this case work */
 176         if (size > PAGE_SIZE)
 177                 WARN_ONCE(1, "svcrdma: large bc buffer request (size %zu)\n",
 178                           size);
 179
 180         page = alloc_page(RPCRDMA_DEF_GFP);
 181         if (!page)
 182                 return NULL;
 183
 184         return page_address(page);
 185 }
 186
 187 static void
 188 xprt_rdma_bc_free(void *buffer)
 189 {
 190         /* No-op: ctxt and page have already been freed. */
 191 }
 192
 193 static int
 194 rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
 195 {
 196         struct rpc_xprt *xprt = rqst->rq_xprt;
 197         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 198         struct rpcrdma_msg *headerp = (struct rpcrdma_msg *)rqst->rq_buffer;
 199         int rc;
 200
 201         /* Space in the send buffer for an RPC/RDMA header is reserved
 202          * via xprt->tsh_size.
 203          */
 204         headerp->rm_xid = rqst->rq_xid;
 205         headerp->rm_vers = rpcrdma_version;
 206         headerp->rm_credit = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
 207         headerp->rm_type = rdma_msg;
 208         headerp->rm_body.rm_chunks[0] = xdr_zero;
 209         headerp->rm_body.rm_chunks[1] = xdr_zero;
 210         headerp->rm_body.rm_chunks[2] = xdr_zero;
 211
 212 #ifdef SVCRDMA_BACKCHANNEL_DEBUG
 213         pr_info("%s: %*ph\n", __func__, 64, rqst->rq_buffer);
 214 #endif
 215
 216         rc = svc_rdma_bc_sendto(rdma, rqst);
 217         if (rc)
 218                 goto drop_connection;
 219         return rc;
 220
 221 drop_connection:
 222         dprintk("svcrdma: failed to send bc call\n");
 223         xprt_disconnect_done(xprt);
 224         return -ENOTCONN;
 225 }
 226
 227 /* Send an RPC call on the passive end of a transport
 228  * connection.
 229  */
 230 static int
 231 xprt_rdma_bc_send_request(struct rpc_task *task)
 232 {
 233         struct rpc_rqst *rqst = task->tk_rqstp;
 234         struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
 235         struct svcxprt_rdma *rdma;
 236         int ret;
 237
 238         dprintk("svcrdma: sending bc call with xid: %08x\n",
 239                 be32_to_cpu(rqst->rq_xid));
 240
 241         if (!mutex_trylock(&sxprt->xpt_mutex)) {
 242                 rpc_sleep_on(&sxprt->xpt_bc_pending, task, NULL);
 243                 if (!mutex_trylock(&sxprt->xpt_mutex))
 244                         return -EAGAIN;
 245                 rpc_wake_up_queued_task(&sxprt->xpt_bc_pending, task);
 246         }
 247
 248         ret = -ENOTCONN;
 249         rdma = container_of(sxprt, struct svcxprt_rdma, sc_xprt);
 250         if (!test_bit(XPT_DEAD, &sxprt->xpt_flags))
 251                 ret = rpcrdma_bc_send_request(rdma, rqst);
 252
 253         mutex_unlock(&sxprt->xpt_mutex);
 254
 255         if (ret < 0)
 256                 return ret;
 257         return 0;
 258 }
 259
 260 static void
 261 xprt_rdma_bc_close(struct rpc_xprt *xprt)
 262 {
 263         dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
 264 }
 265
 266 static void
 267 xprt_rdma_bc_put(struct rpc_xprt *xprt)
 268 {
 269         dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
 270
 271         xprt_free(xprt);
 272         module_put(THIS_MODULE);
 273 }
 274
 275 static struct rpc_xprt_ops xprt_rdma_bc_procs = {
 276         .reserve_xprt           = xprt_reserve_xprt_cong,
 277         .release_xprt           = xprt_release_xprt_cong,
 278         .alloc_slot             = xprt_alloc_slot,
 279         .release_request        = xprt_release_rqst_cong,
 280         .buf_alloc              = xprt_rdma_bc_allocate,
 281         .buf_free               = xprt_rdma_bc_free,
 282         .send_request           = xprt_rdma_bc_send_request,
 283         .set_retrans_timeout    = xprt_set_retrans_timeout_def,
 284         .close                  = xprt_rdma_bc_close,
 285         .destroy                = xprt_rdma_bc_put,
 286         .print_stats            = xprt_rdma_print_stats
 287 };
 288
 289 static const struct rpc_timeout xprt_rdma_bc_timeout = {
 290         .to_initval = 60 * HZ,
 291         .to_maxval = 60 * HZ,
 292 };
 293
 294 /* It shouldn't matter if the number of backchannel session slots
 295  * doesn't match the number of RPC/RDMA credits. That just means
 296  * one or the other will have extra slots that aren't used.
 297  */
 298 static struct rpc_xprt *
 299 xprt_setup_rdma_bc(struct xprt_create *args)
 300 {
 301         struct rpc_xprt *xprt;
 302         struct rpcrdma_xprt *new_xprt;
 303
 304         if (args->addrlen > sizeof(xprt->addr)) {
 305                 dprintk("RPC:       %s: address too large\n", __func__);
 306                 return ERR_PTR(-EBADF);
 307         }
 308
 309         xprt = xprt_alloc(args->net, sizeof(*new_xprt),
 310                           RPCRDMA_MAX_BC_REQUESTS,
 311                           RPCRDMA_MAX_BC_REQUESTS);
 312         if (!xprt) {
 313                 dprintk("RPC:       %s: couldn't allocate rpc_xprt\n",
 314                         __func__);
 315                 return ERR_PTR(-ENOMEM);
 316         }
 317
 318         xprt->timeout = &xprt_rdma_bc_timeout;
 319         xprt_set_bound(xprt);
 320         xprt_set_connected(xprt);
 321         xprt->bind_timeout = RPCRDMA_BIND_TO;
 322         xprt->reestablish_timeout = RPCRDMA_INIT_REEST_TO;
 323         xprt->idle_timeout = RPCRDMA_IDLE_DISC_TO;
 324
 325         xprt->prot = XPRT_TRANSPORT_BC_RDMA;
 326         xprt->tsh_size = RPCRDMA_HDRLEN_MIN / sizeof(__be32);
 327         xprt->ops = &xprt_rdma_bc_procs;
 328
 329         memcpy(&xprt->addr, args->dstaddr, args->addrlen);
 330         xprt->addrlen = args->addrlen;
 331         xprt_rdma_format_addresses(xprt, (struct sockaddr *)&xprt->addr);
 332         xprt->resvport = 0;
 333
 334         xprt->max_payload = xprt_rdma_max_inline_read;
 335
 336         new_xprt = rpcx_to_rdmax(xprt);
 337         new_xprt->rx_buf.rb_bc_max_requests = xprt->max_reqs;
 338
 339         xprt_get(xprt);
 340         args->bc_xprt->xpt_bc_xprt = xprt;
 341         xprt->bc_xprt = args->bc_xprt;
 342
 343         if (!try_module_get(THIS_MODULE))
 344                 goto out_fail;
 345
 346         /* Final put for backchannel xprt is in __svc_rdma_free */
 347         xprt_get(xprt);
 348         return xprt;
 349
 350 out_fail:
 351         xprt_rdma_free_addresses(xprt);
 352         args->bc_xprt->xpt_bc_xprt = NULL;
 353         xprt_put(xprt);
 354         xprt_free(xprt);
 355         return ERR_PTR(-EINVAL);
 356 }
 357
 358 struct xprt_class xprt_rdma_bc = {
 359         .list                   = LIST_HEAD_INIT(xprt_rdma_bc.list),
 360         .name                   = "rdma backchannel",
 361         .owner                  = THIS_MODULE,
 362         .ident                  = XPRT_TRANSPORT_BC_RDMA,
 363         .setup                  = xprt_setup_rdma_bc,
 364 };