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