1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (c) 2015, 2017 Oracle. All rights reserved.
4 * Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
5 */
6
7/* Lightweight memory registration using Fast Registration Work
8 * Requests (FRWR).
9 *
10 * FRWR features ordered asynchronous registration and invalidation
11 * of arbitrarily-sized memory regions. This is the fastest and safest
12 * but most complex memory registration mode.
13 */
14
15/* Normal operation
16 *
17 * A Memory Region is prepared for RDMA Read or Write using a FAST_REG
18 * Work Request (frwr_map). When the RDMA operation is finished, this
19 * Memory Region is invalidated using a LOCAL_INV Work Request
20 * (frwr_unmap_async and frwr_unmap_sync).
21 *
22 * Typically FAST_REG Work Requests are not signaled, and neither are
23 * RDMA Send Work Requests (with the exception of signaling occasionally
24 * to prevent provider work queue overflows). This greatly reduces HCA
25 * interrupt workload.
26 */
27
28/* Transport recovery
29 *
30 * frwr_map and frwr_unmap_* cannot run at the same time the transport
31 * connect worker is running. The connect worker holds the transport
32 * send lock, just as ->send_request does. This prevents frwr_map and
33 * the connect worker from running concurrently. When a connection is
34 * closed, the Receive completion queue is drained before the allowing
35 * the connect worker to get control. This prevents frwr_unmap and the
36 * connect worker from running concurrently.
37 *
38 * When the underlying transport disconnects, MRs that are in flight
39 * are flushed and are likely unusable. Thus all MRs are destroyed.
40 * New MRs are created on demand.
41 */
42
43#include <linux/sunrpc/svc_rdma.h>
44
45#include "xprt_rdma.h"
46#include <trace/events/rpcrdma.h>
47
48static void frwr_cid_init(struct rpcrdma_ep *ep,
49 struct rpcrdma_mr *mr)
50{
51 struct rpc_rdma_cid *cid = &mr->mr_cid;
52
53 cid->ci_queue_id = ep->re_attr.send_cq->res.id;
54 cid->ci_completion_id = mr->mr_ibmr->res.id;
55}
56
57static void frwr_mr_unmap(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr *mr)
58{
59 if (mr->mr_device) {
60 trace_xprtrdma_mr_unmap(mr);
61 ib_dma_unmap_sg(dev: mr->mr_device, sg: mr->mr_sg, nents: mr->mr_nents,
62 direction: mr->mr_dir);
63 mr->mr_device = NULL;
64 }
65}
66
67/**
68 * frwr_mr_release - Destroy one MR
69 * @mr: MR allocated by frwr_mr_init
70 *
71 */
72void frwr_mr_release(struct rpcrdma_mr *mr)
73{
74 int rc;
75
76 frwr_mr_unmap(r_xprt: mr->mr_xprt, mr);
77
78 rc = ib_dereg_mr(mr: mr->mr_ibmr);
79 if (rc)
80 trace_xprtrdma_frwr_dereg(mr, rc);
81 kfree(objp: mr->mr_sg);
82 kfree(objp: mr);
83}
84
85static void frwr_mr_put(struct rpcrdma_mr *mr)
86{
87 frwr_mr_unmap(r_xprt: mr->mr_xprt, mr);
88
89 /* The MR is returned to the req's MR free list instead
90 * of to the xprt's MR free list. No spinlock is needed.
91 */
92 rpcrdma_mr_push(mr, list: &mr->mr_req->rl_free_mrs);
93}
94
95/* frwr_reset - Place MRs back on the free list
96 * @req: request to reset
97 *
98 * Used after a failed marshal. For FRWR, this means the MRs
99 * don't have to be fully released and recreated.
100 *
101 * NB: This is safe only as long as none of @req's MRs are
102 * involved with an ongoing asynchronous FAST_REG or LOCAL_INV
103 * Work Request.
104 */
105void frwr_reset(struct rpcrdma_req *req)
106{
107 struct rpcrdma_mr *mr;
108
109 while ((mr = rpcrdma_mr_pop(list: &req->rl_registered)))
110 frwr_mr_put(mr);
111}
112
113/**
114 * frwr_mr_init - Initialize one MR
115 * @r_xprt: controlling transport instance
116 * @mr: generic MR to prepare for FRWR
117 *
118 * Returns zero if successful. Otherwise a negative errno
119 * is returned.
120 */
121int frwr_mr_init(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr *mr)
122{
123 struct rpcrdma_ep *ep = r_xprt->rx_ep;
124 unsigned int depth = ep->re_max_fr_depth;
125 struct scatterlist *sg;
126 struct ib_mr *frmr;
127
128 sg = kcalloc_node(n: depth, size: sizeof(*sg), XPRTRDMA_GFP_FLAGS,
129 node: ibdev_to_node(ibdev: ep->re_id->device));
130 if (!sg)
131 return -ENOMEM;
132
133 frmr = ib_alloc_mr(pd: ep->re_pd, mr_type: ep->re_mrtype, max_num_sg: depth);
134 if (IS_ERR(ptr: frmr))
135 goto out_mr_err;
136
137 mr->mr_xprt = r_xprt;
138 mr->mr_ibmr = frmr;
139 mr->mr_device = NULL;
140 INIT_LIST_HEAD(list: &mr->mr_list);
141 init_completion(x: &mr->mr_linv_done);
142 frwr_cid_init(ep, mr);
143
144 sg_init_table(sg, depth);
145 mr->mr_sg = sg;
146 return 0;
147
148out_mr_err:
149 kfree(objp: sg);
150 trace_xprtrdma_frwr_alloc(mr, rc: PTR_ERR(ptr: frmr));
151 return PTR_ERR(ptr: frmr);
152}
153
154/**
155 * frwr_query_device - Prepare a transport for use with FRWR
156 * @ep: endpoint to fill in
157 * @device: RDMA device to query
158 *
159 * On success, sets:
160 * ep->re_attr
161 * ep->re_max_requests
162 * ep->re_max_rdma_segs
163 * ep->re_max_fr_depth
164 * ep->re_mrtype
165 *
166 * Return values:
167 * On success, returns zero.
168 * %-EINVAL - the device does not support FRWR memory registration
169 * %-ENOMEM - the device is not sufficiently capable for NFS/RDMA
170 */
171int frwr_query_device(struct rpcrdma_ep *ep, const struct ib_device *device)
172{
173 const struct ib_device_attr *attrs = &device->attrs;
174 int max_qp_wr, depth, delta;
175 unsigned int max_sge;
176
177 if (!(attrs->device_cap_flags & IB_DEVICE_MEM_MGT_EXTENSIONS) ||
178 attrs->max_fast_reg_page_list_len == 0) {
179 pr_err("rpcrdma: 'frwr' mode is not supported by device %s\n",
180 device->name);
181 return -EINVAL;
182 }
183
184 max_sge = min_t(unsigned int, attrs->max_send_sge,
185 RPCRDMA_MAX_SEND_SGES);
186 if (max_sge < RPCRDMA_MIN_SEND_SGES) {
187 pr_err("rpcrdma: HCA provides only %u send SGEs\n", max_sge);
188 return -ENOMEM;
189 }
190 ep->re_attr.cap.max_send_sge = max_sge;
191 ep->re_attr.cap.max_recv_sge = 1;
192
193 ep->re_mrtype = IB_MR_TYPE_MEM_REG;
194 if (attrs->kernel_cap_flags & IBK_SG_GAPS_REG)
195 ep->re_mrtype = IB_MR_TYPE_SG_GAPS;
196
197 /* Quirk: Some devices advertise a large max_fast_reg_page_list_len
198 * capability, but perform optimally when the MRs are not larger
199 * than a page.
200 */
201 if (attrs->max_sge_rd > RPCRDMA_MAX_HDR_SEGS)
202 ep->re_max_fr_depth = attrs->max_sge_rd;
203 else
204 ep->re_max_fr_depth = attrs->max_fast_reg_page_list_len;
205 if (ep->re_max_fr_depth > RPCRDMA_MAX_DATA_SEGS)
206 ep->re_max_fr_depth = RPCRDMA_MAX_DATA_SEGS;
207
208 /* Add room for frwr register and invalidate WRs.
209 * 1. FRWR reg WR for head
210 * 2. FRWR invalidate WR for head
211 * 3. N FRWR reg WRs for pagelist
212 * 4. N FRWR invalidate WRs for pagelist
213 * 5. FRWR reg WR for tail
214 * 6. FRWR invalidate WR for tail
215 * 7. The RDMA_SEND WR
216 */
217 depth = 7;
218
219 /* Calculate N if the device max FRWR depth is smaller than
220 * RPCRDMA_MAX_DATA_SEGS.
221 */
222 if (ep->re_max_fr_depth < RPCRDMA_MAX_DATA_SEGS) {
223 delta = RPCRDMA_MAX_DATA_SEGS - ep->re_max_fr_depth;
224 do {
225 depth += 2; /* FRWR reg + invalidate */
226 delta -= ep->re_max_fr_depth;
227 } while (delta > 0);
228 }
229
230 max_qp_wr = attrs->max_qp_wr;
231 max_qp_wr -= RPCRDMA_BACKWARD_WRS;
232 max_qp_wr -= 1;
233 if (max_qp_wr < RPCRDMA_MIN_SLOT_TABLE)
234 return -ENOMEM;
235 if (ep->re_max_requests > max_qp_wr)
236 ep->re_max_requests = max_qp_wr;
237 ep->re_attr.cap.max_send_wr = ep->re_max_requests * depth;
238 if (ep->re_attr.cap.max_send_wr > max_qp_wr) {
239 ep->re_max_requests = max_qp_wr / depth;
240 if (!ep->re_max_requests)
241 return -ENOMEM;
242 ep->re_attr.cap.max_send_wr = ep->re_max_requests * depth;
243 }
244 ep->re_attr.cap.max_send_wr += RPCRDMA_BACKWARD_WRS;
245 ep->re_attr.cap.max_send_wr += 1; /* for ib_drain_sq */
246 ep->re_attr.cap.max_recv_wr = ep->re_max_requests;
247 ep->re_attr.cap.max_recv_wr += RPCRDMA_BACKWARD_WRS;
248 ep->re_attr.cap.max_recv_wr += RPCRDMA_MAX_RECV_BATCH;
249 ep->re_attr.cap.max_recv_wr += 1; /* for ib_drain_rq */
250
251 ep->re_max_rdma_segs =
252 DIV_ROUND_UP(RPCRDMA_MAX_DATA_SEGS, ep->re_max_fr_depth);
253 /* Reply chunks require segments for head and tail buffers */
254 ep->re_max_rdma_segs += 2;
255 if (ep->re_max_rdma_segs > RPCRDMA_MAX_HDR_SEGS)
256 ep->re_max_rdma_segs = RPCRDMA_MAX_HDR_SEGS;
257
258 /* Ensure the underlying device is capable of conveying the
259 * largest r/wsize NFS will ask for. This guarantees that
260 * failing over from one RDMA device to another will not
261 * break NFS I/O.
262 */
263 if ((ep->re_max_rdma_segs * ep->re_max_fr_depth) < RPCRDMA_MAX_SEGS)
264 return -ENOMEM;
265
266 return 0;
267}
268
269/**
270 * frwr_map - Register a memory region
271 * @r_xprt: controlling transport
272 * @seg: memory region co-ordinates
273 * @nsegs: number of segments remaining
274 * @writing: true when RDMA Write will be used
275 * @xid: XID of RPC using the registered memory
276 * @mr: MR to fill in
277 *
278 * Prepare a REG_MR Work Request to register a memory region
279 * for remote access via RDMA READ or RDMA WRITE.
280 *
281 * Returns the next segment or a negative errno pointer.
282 * On success, @mr is filled in.
283 */
284struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
285 struct rpcrdma_mr_seg *seg,
286 int nsegs, bool writing, __be32 xid,
287 struct rpcrdma_mr *mr)
288{
289 struct rpcrdma_ep *ep = r_xprt->rx_ep;
290 struct ib_reg_wr *reg_wr;
291 int i, n, dma_nents;
292 struct ib_mr *ibmr;
293 u8 key;
294
295 if (nsegs > ep->re_max_fr_depth)
296 nsegs = ep->re_max_fr_depth;
297 for (i = 0; i < nsegs;) {
298 sg_set_page(sg: &mr->mr_sg[i], page: seg->mr_page,
299 len: seg->mr_len, offset: seg->mr_offset);
300
301 ++seg;
302 ++i;
303 if (ep->re_mrtype == IB_MR_TYPE_SG_GAPS)
304 continue;
305 if ((i < nsegs && seg->mr_offset) ||
306 offset_in_page((seg-1)->mr_offset + (seg-1)->mr_len))
307 break;
308 }
309 mr->mr_dir = rpcrdma_data_dir(writing);
310 mr->mr_nents = i;
311
312 dma_nents = ib_dma_map_sg(dev: ep->re_id->device, sg: mr->mr_sg, nents: mr->mr_nents,
313 direction: mr->mr_dir);
314 if (!dma_nents)
315 goto out_dmamap_err;
316 mr->mr_device = ep->re_id->device;
317
318 ibmr = mr->mr_ibmr;
319 n = ib_map_mr_sg(mr: ibmr, sg: mr->mr_sg, sg_nents: dma_nents, NULL, PAGE_SIZE);
320 if (n != dma_nents)
321 goto out_mapmr_err;
322
323 ibmr->iova &= 0x00000000ffffffff;
324 ibmr->iova |= ((u64)be32_to_cpu(xid)) << 32;
325 key = (u8)(ibmr->rkey & 0x000000FF);
326 ib_update_fast_reg_key(mr: ibmr, newkey: ++key);
327
328 reg_wr = &mr->mr_regwr;
329 reg_wr->mr = ibmr;
330 reg_wr->key = ibmr->rkey;
331 reg_wr->access = writing ?
332 IB_ACCESS_REMOTE_WRITE | IB_ACCESS_LOCAL_WRITE :
333 IB_ACCESS_REMOTE_READ;
334
335 mr->mr_handle = ibmr->rkey;
336 mr->mr_length = ibmr->length;
337 mr->mr_offset = ibmr->iova;
338 trace_xprtrdma_mr_map(mr);
339
340 return seg;
341
342out_dmamap_err:
343 trace_xprtrdma_frwr_sgerr(mr, sg_nents: i);
344 return ERR_PTR(error: -EIO);
345
346out_mapmr_err:
347 trace_xprtrdma_frwr_maperr(mr, num_mapped: n);
348 return ERR_PTR(error: -EIO);
349}
350
351/**
352 * frwr_wc_fastreg - Invoked by RDMA provider for a flushed FastReg WC
353 * @cq: completion queue
354 * @wc: WCE for a completed FastReg WR
355 *
356 * Each flushed MR gets destroyed after the QP has drained.
357 */
358static void frwr_wc_fastreg(struct ib_cq *cq, struct ib_wc *wc)
359{
360 struct ib_cqe *cqe = wc->wr_cqe;
361 struct rpcrdma_mr *mr = container_of(cqe, struct rpcrdma_mr, mr_cqe);
362
363 /* WARNING: Only wr_cqe and status are reliable at this point */
364 trace_xprtrdma_wc_fastreg(wc, cid: &mr->mr_cid);
365
366 rpcrdma_flush_disconnect(r_xprt: cq->cq_context, wc);
367}
368
369/**
370 * frwr_send - post Send WRs containing the RPC Call message
371 * @r_xprt: controlling transport instance
372 * @req: prepared RPC Call
373 *
374 * For FRWR, chain any FastReg WRs to the Send WR. Only a
375 * single ib_post_send call is needed to register memory
376 * and then post the Send WR.
377 *
378 * Returns the return code from ib_post_send.
379 *
380 * Caller must hold the transport send lock to ensure that the
381 * pointers to the transport's rdma_cm_id and QP are stable.
382 */
383int frwr_send(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
384{
385 struct ib_send_wr *post_wr, *send_wr = &req->rl_wr;
386 struct rpcrdma_ep *ep = r_xprt->rx_ep;
387 struct rpcrdma_mr *mr;
388 unsigned int num_wrs;
389 int ret;
390
391 num_wrs = 1;
392 post_wr = send_wr;
393 list_for_each_entry(mr, &req->rl_registered, mr_list) {
394 trace_xprtrdma_mr_fastreg(mr);
395
396 mr->mr_cqe.done = frwr_wc_fastreg;
397 mr->mr_regwr.wr.next = post_wr;
398 mr->mr_regwr.wr.wr_cqe = &mr->mr_cqe;
399 mr->mr_regwr.wr.num_sge = 0;
400 mr->mr_regwr.wr.opcode = IB_WR_REG_MR;
401 mr->mr_regwr.wr.send_flags = 0;
402 post_wr = &mr->mr_regwr.wr;
403 ++num_wrs;
404 }
405
406 if ((kref_read(kref: &req->rl_kref) > 1) || num_wrs > ep->re_send_count) {
407 send_wr->send_flags |= IB_SEND_SIGNALED;
408 ep->re_send_count = min_t(unsigned int, ep->re_send_batch,
409 num_wrs - ep->re_send_count);
410 } else {
411 send_wr->send_flags &= ~IB_SEND_SIGNALED;
412 ep->re_send_count -= num_wrs;
413 }
414
415 trace_xprtrdma_post_send(req);
416 ret = ib_post_send(qp: ep->re_id->qp, send_wr: post_wr, NULL);
417 if (ret)
418 trace_xprtrdma_post_send_err(r_xprt, req, rc: ret);
419 return ret;
420}
421
422/**
423 * frwr_reminv - handle a remotely invalidated mr on the @mrs list
424 * @rep: Received reply
425 * @mrs: list of MRs to check
426 *
427 */
428void frwr_reminv(struct rpcrdma_rep *rep, struct list_head *mrs)
429{
430 struct rpcrdma_mr *mr;
431
432 list_for_each_entry(mr, mrs, mr_list)
433 if (mr->mr_handle == rep->rr_inv_rkey) {
434 list_del_init(entry: &mr->mr_list);
435 trace_xprtrdma_mr_reminv(mr);
436 frwr_mr_put(mr);
437 break; /* only one invalidated MR per RPC */
438 }
439}
440
441static void frwr_mr_done(struct ib_wc *wc, struct rpcrdma_mr *mr)
442{
443 if (likely(wc->status == IB_WC_SUCCESS))
444 frwr_mr_put(mr);
445}
446
447/**
448 * frwr_wc_localinv - Invoked by RDMA provider for a LOCAL_INV WC
449 * @cq: completion queue
450 * @wc: WCE for a completed LocalInv WR
451 *
452 */
453static void frwr_wc_localinv(struct ib_cq *cq, struct ib_wc *wc)
454{
455 struct ib_cqe *cqe = wc->wr_cqe;
456 struct rpcrdma_mr *mr = container_of(cqe, struct rpcrdma_mr, mr_cqe);
457
458 /* WARNING: Only wr_cqe and status are reliable at this point */
459 trace_xprtrdma_wc_li(wc, cid: &mr->mr_cid);
460 frwr_mr_done(wc, mr);
461
462 rpcrdma_flush_disconnect(r_xprt: cq->cq_context, wc);
463}
464
465/**
466 * frwr_wc_localinv_wake - Invoked by RDMA provider for a LOCAL_INV WC
467 * @cq: completion queue
468 * @wc: WCE for a completed LocalInv WR
469 *
470 * Awaken anyone waiting for an MR to finish being fenced.
471 */
472static void frwr_wc_localinv_wake(struct ib_cq *cq, struct ib_wc *wc)
473{
474 struct ib_cqe *cqe = wc->wr_cqe;
475 struct rpcrdma_mr *mr = container_of(cqe, struct rpcrdma_mr, mr_cqe);
476
477 /* WARNING: Only wr_cqe and status are reliable at this point */
478 trace_xprtrdma_wc_li_wake(wc, cid: &mr->mr_cid);
479 frwr_mr_done(wc, mr);
480 complete(&mr->mr_linv_done);
481
482 rpcrdma_flush_disconnect(r_xprt: cq->cq_context, wc);
483}
484
485/**
486 * frwr_unmap_sync - invalidate memory regions that were registered for @req
487 * @r_xprt: controlling transport instance
488 * @req: rpcrdma_req with a non-empty list of MRs to process
489 *
490 * Sleeps until it is safe for the host CPU to access the previously mapped
491 * memory regions. This guarantees that registered MRs are properly fenced
492 * from the server before the RPC consumer accesses the data in them. It
493 * also ensures proper Send flow control: waking the next RPC waits until
494 * this RPC has relinquished all its Send Queue entries.
495 */
496void frwr_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
497{
498 struct ib_send_wr *first, **prev, *last;
499 struct rpcrdma_ep *ep = r_xprt->rx_ep;
500 const struct ib_send_wr *bad_wr;
501 struct rpcrdma_mr *mr;
502 int rc;
503
504 /* ORDER: Invalidate all of the MRs first
505 *
506 * Chain the LOCAL_INV Work Requests and post them with
507 * a single ib_post_send() call.
508 */
509 prev = &first;
510 mr = rpcrdma_mr_pop(list: &req->rl_registered);
511 do {
512 trace_xprtrdma_mr_localinv(mr);
513 r_xprt->rx_stats.local_inv_needed++;
514
515 last = &mr->mr_invwr;
516 last->next = NULL;
517 last->wr_cqe = &mr->mr_cqe;
518 last->sg_list = NULL;
519 last->num_sge = 0;
520 last->opcode = IB_WR_LOCAL_INV;
521 last->send_flags = IB_SEND_SIGNALED;
522 last->ex.invalidate_rkey = mr->mr_handle;
523
524 last->wr_cqe->done = frwr_wc_localinv;
525
526 *prev = last;
527 prev = &last->next;
528 } while ((mr = rpcrdma_mr_pop(list: &req->rl_registered)));
529
530 mr = container_of(last, struct rpcrdma_mr, mr_invwr);
531
532 /* Strong send queue ordering guarantees that when the
533 * last WR in the chain completes, all WRs in the chain
534 * are complete.
535 */
536 last->wr_cqe->done = frwr_wc_localinv_wake;
537 reinit_completion(x: &mr->mr_linv_done);
538
539 /* Transport disconnect drains the receive CQ before it
540 * replaces the QP. The RPC reply handler won't call us
541 * unless re_id->qp is a valid pointer.
542 */
543 bad_wr = NULL;
544 rc = ib_post_send(qp: ep->re_id->qp, send_wr: first, bad_send_wr: &bad_wr);
545
546 /* The final LOCAL_INV WR in the chain is supposed to
547 * do the wake. If it was never posted, the wake will
548 * not happen, so don't wait in that case.
549 */
550 if (bad_wr != first)
551 wait_for_completion(&mr->mr_linv_done);
552 if (!rc)
553 return;
554
555 /* On error, the MRs get destroyed once the QP has drained. */
556 trace_xprtrdma_post_linv_err(req, status: rc);
557
558 /* Force a connection loss to ensure complete recovery.
559 */
560 rpcrdma_force_disconnect(ep);
561}
562
563/**
564 * frwr_wc_localinv_done - Invoked by RDMA provider for a signaled LOCAL_INV WC
565 * @cq: completion queue
566 * @wc: WCE for a completed LocalInv WR
567 *
568 */
569static void frwr_wc_localinv_done(struct ib_cq *cq, struct ib_wc *wc)
570{
571 struct ib_cqe *cqe = wc->wr_cqe;
572 struct rpcrdma_mr *mr = container_of(cqe, struct rpcrdma_mr, mr_cqe);
573 struct rpcrdma_rep *rep;
574
575 /* WARNING: Only wr_cqe and status are reliable at this point */
576 trace_xprtrdma_wc_li_done(wc, cid: &mr->mr_cid);
577
578 /* Ensure that @rep is generated before the MR is released */
579 rep = mr->mr_req->rl_reply;
580 smp_rmb();
581
582 if (wc->status != IB_WC_SUCCESS) {
583 if (rep)
584 rpcrdma_unpin_rqst(rep);
585 rpcrdma_flush_disconnect(r_xprt: cq->cq_context, wc);
586 return;
587 }
588 frwr_mr_put(mr);
589 rpcrdma_complete_rqst(rep);
590}
591
592/**
593 * frwr_unmap_async - invalidate memory regions that were registered for @req
594 * @r_xprt: controlling transport instance
595 * @req: rpcrdma_req with a non-empty list of MRs to process
596 *
597 * This guarantees that registered MRs are properly fenced from the
598 * server before the RPC consumer accesses the data in them. It also
599 * ensures proper Send flow control: waking the next RPC waits until
600 * this RPC has relinquished all its Send Queue entries.
601 */
602void frwr_unmap_async(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
603{
604 struct ib_send_wr *first, *last, **prev;
605 struct rpcrdma_ep *ep = r_xprt->rx_ep;
606 struct rpcrdma_mr *mr;
607 int rc;
608
609 /* Chain the LOCAL_INV Work Requests and post them with
610 * a single ib_post_send() call.
611 */
612 prev = &first;
613 mr = rpcrdma_mr_pop(list: &req->rl_registered);
614 do {
615 trace_xprtrdma_mr_localinv(mr);
616 r_xprt->rx_stats.local_inv_needed++;
617
618 last = &mr->mr_invwr;
619 last->next = NULL;
620 last->wr_cqe = &mr->mr_cqe;
621 last->sg_list = NULL;
622 last->num_sge = 0;
623 last->opcode = IB_WR_LOCAL_INV;
624 last->send_flags = IB_SEND_SIGNALED;
625 last->ex.invalidate_rkey = mr->mr_handle;
626
627 last->wr_cqe->done = frwr_wc_localinv;
628
629 *prev = last;
630 prev = &last->next;
631 } while ((mr = rpcrdma_mr_pop(list: &req->rl_registered)));
632
633 /* Strong send queue ordering guarantees that when the
634 * last WR in the chain completes, all WRs in the chain
635 * are complete. The last completion will wake up the
636 * RPC waiter.
637 */
638 last->wr_cqe->done = frwr_wc_localinv_done;
639
640 /* Transport disconnect drains the receive CQ before it
641 * replaces the QP. The RPC reply handler won't call us
642 * unless re_id->qp is a valid pointer.
643 */
644 rc = ib_post_send(qp: ep->re_id->qp, send_wr: first, NULL);
645 if (!rc)
646 return;
647
648 /* On error, the MRs get destroyed once the QP has drained. */
649 trace_xprtrdma_post_linv_err(req, status: rc);
650
651 /* The final LOCAL_INV WR in the chain is supposed to
652 * do the wake. If it was never posted, the wake does
653 * not happen. Unpin the rqst in preparation for its
654 * retransmission.
655 */
656 rpcrdma_unpin_rqst(rep: req->rl_reply);
657
658 /* Force a connection loss to ensure complete recovery.
659 */
660 rpcrdma_force_disconnect(ep);
661}
662
663/**
664 * frwr_wp_create - Create an MR for padding Write chunks
665 * @r_xprt: transport resources to use
666 *
667 * Return 0 on success, negative errno on failure.
668 */
669int frwr_wp_create(struct rpcrdma_xprt *r_xprt)
670{
671 struct rpcrdma_ep *ep = r_xprt->rx_ep;
672 struct rpcrdma_mr_seg seg;
673 struct rpcrdma_mr *mr;
674
675 mr = rpcrdma_mr_get(r_xprt);
676 if (!mr)
677 return -EAGAIN;
678 mr->mr_req = NULL;
679 ep->re_write_pad_mr = mr;
680
681 seg.mr_len = XDR_UNIT;
682 seg.mr_page = virt_to_page(ep->re_write_pad);
683 seg.mr_offset = offset_in_page(ep->re_write_pad);
684 if (IS_ERR(ptr: frwr_map(r_xprt, seg: &seg, nsegs: 1, writing: true, xdr_zero, mr)))
685 return -EIO;
686 trace_xprtrdma_mr_fastreg(mr);
687
688 mr->mr_cqe.done = frwr_wc_fastreg;
689 mr->mr_regwr.wr.next = NULL;
690 mr->mr_regwr.wr.wr_cqe = &mr->mr_cqe;
691 mr->mr_regwr.wr.num_sge = 0;
692 mr->mr_regwr.wr.opcode = IB_WR_REG_MR;
693 mr->mr_regwr.wr.send_flags = 0;
694
695 return ib_post_send(qp: ep->re_id->qp, send_wr: &mr->mr_regwr.wr, NULL);
696}
697

source code of linux/net/sunrpc/xprtrdma/frwr_ops.c