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Linux/net/sunrpc/xprtrdma/svc_rdma_backchannel.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Copyright (c) 2015-2018 Oracle.  All rights reserved.
  4  *
  5  * Support for backward direction RPCs on RPC/RDMA (server-side).
  6  */
  7 
  8 #include <linux/sunrpc/svc_rdma.h>
  9 
 10 #include "xprt_rdma.h"
 11 #include <trace/events/rpcrdma.h>
 12 
 13 #define RPCDBG_FACILITY RPCDBG_SVCXPRT
 14 
 15 #undef SVCRDMA_BACKCHANNEL_DEBUG
 16 
 17 /**
 18  * svc_rdma_handle_bc_reply - Process incoming backchannel reply
 19  * @xprt: controlling backchannel transport
 20  * @rdma_resp: pointer to incoming transport header
 21  * @rcvbuf: XDR buffer into which to decode the reply
 22  *
 23  * Returns:
 24  *      %0 if @rcvbuf is filled in, xprt_complete_rqst called,
 25  *      %-EAGAIN if server should call ->recvfrom again.
 26  */
 27 int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, __be32 *rdma_resp,
 28                              struct xdr_buf *rcvbuf)
 29 {
 30         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
 31         struct kvec *dst, *src = &rcvbuf->head[0];
 32         struct rpc_rqst *req;
 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->queue_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         xprt_pin_rqst(req);
 67         spin_unlock(&xprt->queue_lock);
 68 
 69         credits = be32_to_cpup(rdma_resp + 2);
 70         if (credits == 0)
 71                 credits = 1;    /* don't deadlock */
 72         else if (credits > r_xprt->rx_buf.rb_bc_max_requests)
 73                 credits = r_xprt->rx_buf.rb_bc_max_requests;
 74 
 75         spin_lock_bh(&xprt->transport_lock);
 76         xprt->cwnd = credits << RPC_CWNDSHIFT;
 77         spin_unlock_bh(&xprt->transport_lock);
 78 
 79         spin_lock(&xprt->queue_lock);
 80         ret = 0;
 81         xprt_complete_rqst(req->rq_task, rcvbuf->len);
 82         xprt_unpin_rqst(req);
 83         rcvbuf->len = 0;
 84 
 85 out_unlock:
 86         spin_unlock(&xprt->queue_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         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                               struct svc_rdma_send_ctxt *ctxt)
117 {
118         int ret;
119 
120         ret = svc_rdma_map_reply_msg(rdma, ctxt, &rqst->rq_snd_buf, NULL);
121         if (ret < 0)
122                 return -EIO;
123 
124         /* Bump page refcnt so Send completion doesn't release
125          * the rq_buffer before all retransmits are complete.
126          */
127         get_page(virt_to_page(rqst->rq_buffer));
128         ctxt->sc_send_wr.opcode = IB_WR_SEND;
129         return svc_rdma_send(rdma, &ctxt->sc_send_wr);
130 }
131 
132 /* Server-side transport endpoint wants a whole page for its send
133  * buffer. The client RPC code constructs the RPC header in this
134  * buffer before it invokes ->send_request.
135  */
136 static int
137 xprt_rdma_bc_allocate(struct rpc_task *task)
138 {
139         struct rpc_rqst *rqst = task->tk_rqstp;
140         size_t size = rqst->rq_callsize;
141         struct page *page;
142 
143         if (size > PAGE_SIZE) {
144                 WARN_ONCE(1, "svcrdma: large bc buffer request (size %zu)\n",
145                           size);
146                 return -EINVAL;
147         }
148 
149         page = alloc_page(RPCRDMA_DEF_GFP);
150         if (!page)
151                 return -ENOMEM;
152         rqst->rq_buffer = page_address(page);
153 
154         rqst->rq_rbuffer = kmalloc(rqst->rq_rcvsize, RPCRDMA_DEF_GFP);
155         if (!rqst->rq_rbuffer) {
156                 put_page(page);
157                 return -ENOMEM;
158         }
159         return 0;
160 }
161 
162 static void
163 xprt_rdma_bc_free(struct rpc_task *task)
164 {
165         struct rpc_rqst *rqst = task->tk_rqstp;
166 
167         put_page(virt_to_page(rqst->rq_buffer));
168         kfree(rqst->rq_rbuffer);
169 }
170 
171 static int
172 rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
173 {
174         struct rpc_xprt *xprt = rqst->rq_xprt;
175         struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
176         struct svc_rdma_send_ctxt *ctxt;
177         __be32 *p;
178         int rc;
179 
180         ctxt = svc_rdma_send_ctxt_get(rdma);
181         if (!ctxt)
182                 goto drop_connection;
183 
184         p = ctxt->sc_xprt_buf;
185         *p++ = rqst->rq_xid;
186         *p++ = rpcrdma_version;
187         *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
188         *p++ = rdma_msg;
189         *p++ = xdr_zero;
190         *p++ = xdr_zero;
191         *p   = xdr_zero;
192         svc_rdma_sync_reply_hdr(rdma, ctxt, RPCRDMA_HDRLEN_MIN);
193 
194 #ifdef SVCRDMA_BACKCHANNEL_DEBUG
195         pr_info("%s: %*ph\n", __func__, 64, rqst->rq_buffer);
196 #endif
197 
198         rc = svc_rdma_bc_sendto(rdma, rqst, ctxt);
199         if (rc) {
200                 svc_rdma_send_ctxt_put(rdma, ctxt);
201                 goto drop_connection;
202         }
203         return 0;
204 
205 drop_connection:
206         dprintk("svcrdma: failed to send bc call\n");
207         return -ENOTCONN;
208 }
209 
210 /* Send an RPC call on the passive end of a transport
211  * connection.
212  */
213 static int
214 xprt_rdma_bc_send_request(struct rpc_rqst *rqst)
215 {
216         struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
217         struct svcxprt_rdma *rdma;
218         int ret;
219 
220         dprintk("svcrdma: sending bc call with xid: %08x\n",
221                 be32_to_cpu(rqst->rq_xid));
222 
223         mutex_lock(&sxprt->xpt_mutex);
224 
225         ret = -ENOTCONN;
226         rdma = container_of(sxprt, struct svcxprt_rdma, sc_xprt);
227         if (!test_bit(XPT_DEAD, &sxprt->xpt_flags)) {
228                 ret = rpcrdma_bc_send_request(rdma, rqst);
229                 if (ret == -ENOTCONN)
230                         svc_close_xprt(sxprt);
231         }
232 
233         mutex_unlock(&sxprt->xpt_mutex);
234 
235         if (ret < 0)
236                 return ret;
237         return 0;
238 }
239 
240 static void
241 xprt_rdma_bc_close(struct rpc_xprt *xprt)
242 {
243         dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
244         xprt->cwnd = RPC_CWNDSHIFT;
245 }
246 
247 static void
248 xprt_rdma_bc_put(struct rpc_xprt *xprt)
249 {
250         dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
251 
252         xprt_free(xprt);
253 }
254 
255 static const struct rpc_xprt_ops xprt_rdma_bc_procs = {
256         .reserve_xprt           = xprt_reserve_xprt_cong,
257         .release_xprt           = xprt_release_xprt_cong,
258         .alloc_slot             = xprt_alloc_slot,
259         .free_slot              = xprt_free_slot,
260         .release_request        = xprt_release_rqst_cong,
261         .buf_alloc              = xprt_rdma_bc_allocate,
262         .buf_free               = xprt_rdma_bc_free,
263         .send_request           = xprt_rdma_bc_send_request,
264         .set_retrans_timeout    = xprt_set_retrans_timeout_def,
265         .close                  = xprt_rdma_bc_close,
266         .destroy                = xprt_rdma_bc_put,
267         .print_stats            = xprt_rdma_print_stats
268 };
269 
270 static const struct rpc_timeout xprt_rdma_bc_timeout = {
271         .to_initval = 60 * HZ,
272         .to_maxval = 60 * HZ,
273 };
274 
275 /* It shouldn't matter if the number of backchannel session slots
276  * doesn't match the number of RPC/RDMA credits. That just means
277  * one or the other will have extra slots that aren't used.
278  */
279 static struct rpc_xprt *
280 xprt_setup_rdma_bc(struct xprt_create *args)
281 {
282         struct rpc_xprt *xprt;
283         struct rpcrdma_xprt *new_xprt;
284 
285         if (args->addrlen > sizeof(xprt->addr)) {
286                 dprintk("RPC:       %s: address too large\n", __func__);
287                 return ERR_PTR(-EBADF);
288         }
289 
290         xprt = xprt_alloc(args->net, sizeof(*new_xprt),
291                           RPCRDMA_MAX_BC_REQUESTS,
292                           RPCRDMA_MAX_BC_REQUESTS);
293         if (!xprt) {
294                 dprintk("RPC:       %s: couldn't allocate rpc_xprt\n",
295                         __func__);
296                 return ERR_PTR(-ENOMEM);
297         }
298 
299         xprt->timeout = &xprt_rdma_bc_timeout;
300         xprt_set_bound(xprt);
301         xprt_set_connected(xprt);
302         xprt->bind_timeout = RPCRDMA_BIND_TO;
303         xprt->reestablish_timeout = RPCRDMA_INIT_REEST_TO;
304         xprt->idle_timeout = RPCRDMA_IDLE_DISC_TO;
305 
306         xprt->prot = XPRT_TRANSPORT_BC_RDMA;
307         xprt->tsh_size = 0;
308         xprt->ops = &xprt_rdma_bc_procs;
309 
310         memcpy(&xprt->addr, args->dstaddr, args->addrlen);
311         xprt->addrlen = args->addrlen;
312         xprt_rdma_format_addresses(xprt, (struct sockaddr *)&xprt->addr);
313         xprt->resvport = 0;
314 
315         xprt->max_payload = xprt_rdma_max_inline_read;
316 
317         new_xprt = rpcx_to_rdmax(xprt);
318         new_xprt->rx_buf.rb_bc_max_requests = xprt->max_reqs;
319 
320         xprt_get(xprt);
321         args->bc_xprt->xpt_bc_xprt = xprt;
322         xprt->bc_xprt = args->bc_xprt;
323 
324         /* Final put for backchannel xprt is in __svc_rdma_free */
325         xprt_get(xprt);
326         return xprt;
327 }
328 
329 struct xprt_class xprt_rdma_bc = {
330         .list                   = LIST_HEAD_INIT(xprt_rdma_bc.list),
331         .name                   = "rdma backchannel",
332         .owner                  = THIS_MODULE,
333         .ident                  = XPRT_TRANSPORT_BC_RDMA,
334         .setup                  = xprt_setup_rdma_bc,
335 };
336 

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