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Linux/net/sunrpc/xprtrdma/svc_rdma_backchannel.c

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  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);
111         if (ret)
112                 goto out_err;
113 
114         /* Post a recv buffer to handle the reply for this request. */
115         ret = svc_rdma_post_recv(rdma, GFP_NOIO);
116         if (ret) {
117                 pr_err("svcrdma: Failed to post bc receive buffer, err=%d.\n",
118                        ret);
119                 pr_err("svcrdma: closing transport %p.\n", rdma);
120                 set_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags);
121                 ret = -ENOTCONN;
122                 goto out_err;
123         }
124 
125         ctxt = svc_rdma_get_context(rdma);
126         ctxt->pages[0] = virt_to_page(rqst->rq_buffer);
127         ctxt->count = 1;
128 
129         ctxt->wr_op = IB_WR_SEND;
130         ctxt->direction = DMA_TO_DEVICE;
131         ctxt->sge[0].lkey = rdma->sc_pd->local_dma_lkey;
132         ctxt->sge[0].length = sndbuf->len;
133         ctxt->sge[0].addr =
134             ib_dma_map_page(rdma->sc_cm_id->device, ctxt->pages[0], 0,
135                             sndbuf->len, DMA_TO_DEVICE);
136         if (ib_dma_mapping_error(rdma->sc_cm_id->device, ctxt->sge[0].addr)) {
137                 ret = -EIO;
138                 goto out_unmap;
139         }
140         atomic_inc(&rdma->sc_dma_used);
141 
142         memset(&send_wr, 0, sizeof(send_wr));
143         send_wr.wr_id = (unsigned long)ctxt;
144         send_wr.sg_list = ctxt->sge;
145         send_wr.num_sge = 1;
146         send_wr.opcode = IB_WR_SEND;
147         send_wr.send_flags = IB_SEND_SIGNALED;
148 
149         ret = svc_rdma_send(rdma, &send_wr);
150         if (ret) {
151                 ret = -EIO;
152                 goto out_unmap;
153         }
154 
155 out_err:
156         svc_rdma_put_req_map(rdma, vec);
157         dprintk("svcrdma: %s returns %d\n", __func__, ret);
158         return ret;
159 
160 out_unmap:
161         svc_rdma_unmap_dma(ctxt);
162         svc_rdma_put_context(ctxt, 1);
163         goto out_err;
164 }
165 
166 /* Server-side transport endpoint wants a whole page for its send
167  * buffer. The client RPC code constructs the RPC header in this
168  * buffer before it invokes ->send_request.
169  *
170  * Returns NULL if there was a temporary allocation failure.
171  */
172 static void *
173 xprt_rdma_bc_allocate(struct rpc_task *task, size_t size)
174 {
175         struct rpc_rqst *rqst = task->tk_rqstp;
176         struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
177         struct svcxprt_rdma *rdma;
178         struct page *page;
179 
180         rdma = container_of(sxprt, struct svcxprt_rdma, sc_xprt);
181 
182         /* Prevent an infinite loop: try to make this case work */
183         if (size > PAGE_SIZE)
184                 WARN_ONCE(1, "svcrdma: large bc buffer request (size %zu)\n",
185                           size);
186 
187         page = alloc_page(RPCRDMA_DEF_GFP);
188         if (!page)
189                 return NULL;
190 
191         return page_address(page);
192 }
193 
194 static void
195 xprt_rdma_bc_free(void *buffer)
196 {
197         /* No-op: ctxt and page have already been freed. */
198 }
199 
200 static int
201 rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
202 {
203         struct rpc_xprt *xprt = rqst->rq_xprt;
204         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
205         struct rpcrdma_msg *headerp = (struct rpcrdma_msg *)rqst->rq_buffer;
206         int rc;
207 
208         /* Space in the send buffer for an RPC/RDMA header is reserved
209          * via xprt->tsh_size.
210          */
211         headerp->rm_xid = rqst->rq_xid;
212         headerp->rm_vers = rpcrdma_version;
213         headerp->rm_credit = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
214         headerp->rm_type = rdma_msg;
215         headerp->rm_body.rm_chunks[0] = xdr_zero;
216         headerp->rm_body.rm_chunks[1] = xdr_zero;
217         headerp->rm_body.rm_chunks[2] = xdr_zero;
218 
219 #ifdef SVCRDMA_BACKCHANNEL_DEBUG
220         pr_info("%s: %*ph\n", __func__, 64, rqst->rq_buffer);
221 #endif
222 
223         rc = svc_rdma_bc_sendto(rdma, rqst);
224         if (rc)
225                 goto drop_connection;
226         return rc;
227 
228 drop_connection:
229         dprintk("svcrdma: failed to send bc call\n");
230         xprt_disconnect_done(xprt);
231         return -ENOTCONN;
232 }
233 
234 /* Send an RPC call on the passive end of a transport
235  * connection.
236  */
237 static int
238 xprt_rdma_bc_send_request(struct rpc_task *task)
239 {
240         struct rpc_rqst *rqst = task->tk_rqstp;
241         struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
242         struct svcxprt_rdma *rdma;
243         int ret;
244 
245         dprintk("svcrdma: sending bc call with xid: %08x\n",
246                 be32_to_cpu(rqst->rq_xid));
247 
248         if (!mutex_trylock(&sxprt->xpt_mutex)) {
249                 rpc_sleep_on(&sxprt->xpt_bc_pending, task, NULL);
250                 if (!mutex_trylock(&sxprt->xpt_mutex))
251                         return -EAGAIN;
252                 rpc_wake_up_queued_task(&sxprt->xpt_bc_pending, task);
253         }
254 
255         ret = -ENOTCONN;
256         rdma = container_of(sxprt, struct svcxprt_rdma, sc_xprt);
257         if (!test_bit(XPT_DEAD, &sxprt->xpt_flags))
258                 ret = rpcrdma_bc_send_request(rdma, rqst);
259 
260         mutex_unlock(&sxprt->xpt_mutex);
261 
262         if (ret < 0)
263                 return ret;
264         return 0;
265 }
266 
267 static void
268 xprt_rdma_bc_close(struct rpc_xprt *xprt)
269 {
270         dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
271 }
272 
273 static void
274 xprt_rdma_bc_put(struct rpc_xprt *xprt)
275 {
276         dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
277 
278         xprt_free(xprt);
279         module_put(THIS_MODULE);
280 }
281 
282 static struct rpc_xprt_ops xprt_rdma_bc_procs = {
283         .reserve_xprt           = xprt_reserve_xprt_cong,
284         .release_xprt           = xprt_release_xprt_cong,
285         .alloc_slot             = xprt_alloc_slot,
286         .release_request        = xprt_release_rqst_cong,
287         .buf_alloc              = xprt_rdma_bc_allocate,
288         .buf_free               = xprt_rdma_bc_free,
289         .send_request           = xprt_rdma_bc_send_request,
290         .set_retrans_timeout    = xprt_set_retrans_timeout_def,
291         .close                  = xprt_rdma_bc_close,
292         .destroy                = xprt_rdma_bc_put,
293         .print_stats            = xprt_rdma_print_stats
294 };
295 
296 static const struct rpc_timeout xprt_rdma_bc_timeout = {
297         .to_initval = 60 * HZ,
298         .to_maxval = 60 * HZ,
299 };
300 
301 /* It shouldn't matter if the number of backchannel session slots
302  * doesn't match the number of RPC/RDMA credits. That just means
303  * one or the other will have extra slots that aren't used.
304  */
305 static struct rpc_xprt *
306 xprt_setup_rdma_bc(struct xprt_create *args)
307 {
308         struct rpc_xprt *xprt;
309         struct rpcrdma_xprt *new_xprt;
310 
311         if (args->addrlen > sizeof(xprt->addr)) {
312                 dprintk("RPC:       %s: address too large\n", __func__);
313                 return ERR_PTR(-EBADF);
314         }
315 
316         xprt = xprt_alloc(args->net, sizeof(*new_xprt),
317                           RPCRDMA_MAX_BC_REQUESTS,
318                           RPCRDMA_MAX_BC_REQUESTS);
319         if (!xprt) {
320                 dprintk("RPC:       %s: couldn't allocate rpc_xprt\n",
321                         __func__);
322                 return ERR_PTR(-ENOMEM);
323         }
324 
325         xprt->timeout = &xprt_rdma_bc_timeout;
326         xprt_set_bound(xprt);
327         xprt_set_connected(xprt);
328         xprt->bind_timeout = RPCRDMA_BIND_TO;
329         xprt->reestablish_timeout = RPCRDMA_INIT_REEST_TO;
330         xprt->idle_timeout = RPCRDMA_IDLE_DISC_TO;
331 
332         xprt->prot = XPRT_TRANSPORT_BC_RDMA;
333         xprt->tsh_size = RPCRDMA_HDRLEN_MIN / sizeof(__be32);
334         xprt->ops = &xprt_rdma_bc_procs;
335 
336         memcpy(&xprt->addr, args->dstaddr, args->addrlen);
337         xprt->addrlen = args->addrlen;
338         xprt_rdma_format_addresses(xprt, (struct sockaddr *)&xprt->addr);
339         xprt->resvport = 0;
340 
341         xprt->max_payload = xprt_rdma_max_inline_read;
342 
343         new_xprt = rpcx_to_rdmax(xprt);
344         new_xprt->rx_buf.rb_bc_max_requests = xprt->max_reqs;
345 
346         xprt_get(xprt);
347         args->bc_xprt->xpt_bc_xprt = xprt;
348         xprt->bc_xprt = args->bc_xprt;
349 
350         if (!try_module_get(THIS_MODULE))
351                 goto out_fail;
352 
353         /* Final put for backchannel xprt is in __svc_rdma_free */
354         xprt_get(xprt);
355         return xprt;
356 
357 out_fail:
358         xprt_rdma_free_addresses(xprt);
359         args->bc_xprt->xpt_bc_xprt = NULL;
360         xprt_put(xprt);
361         xprt_free(xprt);
362         return ERR_PTR(-EINVAL);
363 }
364 
365 struct xprt_class xprt_rdma_bc = {
366         .list                   = LIST_HEAD_INIT(xprt_rdma_bc.list),
367         .name                   = "rdma backchannel",
368         .owner                  = THIS_MODULE,
369         .ident                  = XPRT_TRANSPORT_BC_RDMA,
370         .setup                  = xprt_setup_rdma_bc,
371 };
372 

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