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TOMOYO Linux Cross Reference
Linux/net/rds/ib_recv.c

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  1 /*
  2  * Copyright (c) 2006 Oracle.  All rights reserved.
  3  *
  4  * This software is available to you under a choice of one of two
  5  * licenses.  You may choose to be licensed under the terms of the GNU
  6  * General Public License (GPL) Version 2, available from the file
  7  * COPYING in the main directory of this source tree, or the
  8  * OpenIB.org BSD license below:
  9  *
 10  *     Redistribution and use in source and binary forms, with or
 11  *     without modification, are permitted provided that the following
 12  *     conditions are met:
 13  *
 14  *      - Redistributions of source code must retain the above
 15  *        copyright notice, this list of conditions and the following
 16  *        disclaimer.
 17  *
 18  *      - Redistributions in binary form must reproduce the above
 19  *        copyright notice, this list of conditions and the following
 20  *        disclaimer in the documentation and/or other materials
 21  *        provided with the distribution.
 22  *
 23  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 24  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 25  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 26  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 27  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 28  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 29  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 30  * SOFTWARE.
 31  *
 32  */
 33 #include <linux/kernel.h>
 34 #include <linux/slab.h>
 35 #include <linux/pci.h>
 36 #include <linux/dma-mapping.h>
 37 #include <rdma/rdma_cm.h>
 38 
 39 #include "rds.h"
 40 #include "ib.h"
 41 
 42 static struct kmem_cache *rds_ib_incoming_slab;
 43 static struct kmem_cache *rds_ib_frag_slab;
 44 static atomic_t rds_ib_allocation = ATOMIC_INIT(0);
 45 
 46 void rds_ib_recv_init_ring(struct rds_ib_connection *ic)
 47 {
 48         struct rds_ib_recv_work *recv;
 49         u32 i;
 50 
 51         for (i = 0, recv = ic->i_recvs; i < ic->i_recv_ring.w_nr; i++, recv++) {
 52                 struct ib_sge *sge;
 53 
 54                 recv->r_ibinc = NULL;
 55                 recv->r_frag = NULL;
 56 
 57                 recv->r_wr.next = NULL;
 58                 recv->r_wr.wr_id = i;
 59                 recv->r_wr.sg_list = recv->r_sge;
 60                 recv->r_wr.num_sge = RDS_IB_RECV_SGE;
 61 
 62                 sge = &recv->r_sge[0];
 63                 sge->addr = ic->i_recv_hdrs_dma + (i * sizeof(struct rds_header));
 64                 sge->length = sizeof(struct rds_header);
 65                 sge->lkey = ic->i_mr->lkey;
 66 
 67                 sge = &recv->r_sge[1];
 68                 sge->addr = 0;
 69                 sge->length = RDS_FRAG_SIZE;
 70                 sge->lkey = ic->i_mr->lkey;
 71         }
 72 }
 73 
 74 /*
 75  * The entire 'from' list, including the from element itself, is put on
 76  * to the tail of the 'to' list.
 77  */
 78 static void list_splice_entire_tail(struct list_head *from,
 79                                     struct list_head *to)
 80 {
 81         struct list_head *from_last = from->prev;
 82 
 83         list_splice_tail(from_last, to);
 84         list_add_tail(from_last, to);
 85 }
 86 
 87 static void rds_ib_cache_xfer_to_ready(struct rds_ib_refill_cache *cache)
 88 {
 89         struct list_head *tmp;
 90 
 91         tmp = xchg(&cache->xfer, NULL);
 92         if (tmp) {
 93                 if (cache->ready)
 94                         list_splice_entire_tail(tmp, cache->ready);
 95                 else
 96                         cache->ready = tmp;
 97         }
 98 }
 99 
100 static int rds_ib_recv_alloc_cache(struct rds_ib_refill_cache *cache)
101 {
102         struct rds_ib_cache_head *head;
103         int cpu;
104 
105         cache->percpu = alloc_percpu(struct rds_ib_cache_head);
106         if (!cache->percpu)
107                return -ENOMEM;
108 
109         for_each_possible_cpu(cpu) {
110                 head = per_cpu_ptr(cache->percpu, cpu);
111                 head->first = NULL;
112                 head->count = 0;
113         }
114         cache->xfer = NULL;
115         cache->ready = NULL;
116 
117         return 0;
118 }
119 
120 int rds_ib_recv_alloc_caches(struct rds_ib_connection *ic)
121 {
122         int ret;
123 
124         ret = rds_ib_recv_alloc_cache(&ic->i_cache_incs);
125         if (!ret) {
126                 ret = rds_ib_recv_alloc_cache(&ic->i_cache_frags);
127                 if (ret)
128                         free_percpu(ic->i_cache_incs.percpu);
129         }
130 
131         return ret;
132 }
133 
134 static void rds_ib_cache_splice_all_lists(struct rds_ib_refill_cache *cache,
135                                           struct list_head *caller_list)
136 {
137         struct rds_ib_cache_head *head;
138         int cpu;
139 
140         for_each_possible_cpu(cpu) {
141                 head = per_cpu_ptr(cache->percpu, cpu);
142                 if (head->first) {
143                         list_splice_entire_tail(head->first, caller_list);
144                         head->first = NULL;
145                 }
146         }
147 
148         if (cache->ready) {
149                 list_splice_entire_tail(cache->ready, caller_list);
150                 cache->ready = NULL;
151         }
152 }
153 
154 void rds_ib_recv_free_caches(struct rds_ib_connection *ic)
155 {
156         struct rds_ib_incoming *inc;
157         struct rds_ib_incoming *inc_tmp;
158         struct rds_page_frag *frag;
159         struct rds_page_frag *frag_tmp;
160         LIST_HEAD(list);
161 
162         rds_ib_cache_xfer_to_ready(&ic->i_cache_incs);
163         rds_ib_cache_splice_all_lists(&ic->i_cache_incs, &list);
164         free_percpu(ic->i_cache_incs.percpu);
165 
166         list_for_each_entry_safe(inc, inc_tmp, &list, ii_cache_entry) {
167                 list_del(&inc->ii_cache_entry);
168                 WARN_ON(!list_empty(&inc->ii_frags));
169                 kmem_cache_free(rds_ib_incoming_slab, inc);
170         }
171 
172         rds_ib_cache_xfer_to_ready(&ic->i_cache_frags);
173         rds_ib_cache_splice_all_lists(&ic->i_cache_frags, &list);
174         free_percpu(ic->i_cache_frags.percpu);
175 
176         list_for_each_entry_safe(frag, frag_tmp, &list, f_cache_entry) {
177                 list_del(&frag->f_cache_entry);
178                 WARN_ON(!list_empty(&frag->f_item));
179                 kmem_cache_free(rds_ib_frag_slab, frag);
180         }
181 }
182 
183 /* fwd decl */
184 static void rds_ib_recv_cache_put(struct list_head *new_item,
185                                   struct rds_ib_refill_cache *cache);
186 static struct list_head *rds_ib_recv_cache_get(struct rds_ib_refill_cache *cache);
187 
188 
189 /* Recycle frag and attached recv buffer f_sg */
190 static void rds_ib_frag_free(struct rds_ib_connection *ic,
191                              struct rds_page_frag *frag)
192 {
193         rdsdebug("frag %p page %p\n", frag, sg_page(&frag->f_sg));
194 
195         rds_ib_recv_cache_put(&frag->f_cache_entry, &ic->i_cache_frags);
196 }
197 
198 /* Recycle inc after freeing attached frags */
199 void rds_ib_inc_free(struct rds_incoming *inc)
200 {
201         struct rds_ib_incoming *ibinc;
202         struct rds_page_frag *frag;
203         struct rds_page_frag *pos;
204         struct rds_ib_connection *ic = inc->i_conn->c_transport_data;
205 
206         ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);
207 
208         /* Free attached frags */
209         list_for_each_entry_safe(frag, pos, &ibinc->ii_frags, f_item) {
210                 list_del_init(&frag->f_item);
211                 rds_ib_frag_free(ic, frag);
212         }
213         BUG_ON(!list_empty(&ibinc->ii_frags));
214 
215         rdsdebug("freeing ibinc %p inc %p\n", ibinc, inc);
216         rds_ib_recv_cache_put(&ibinc->ii_cache_entry, &ic->i_cache_incs);
217 }
218 
219 static void rds_ib_recv_clear_one(struct rds_ib_connection *ic,
220                                   struct rds_ib_recv_work *recv)
221 {
222         if (recv->r_ibinc) {
223                 rds_inc_put(&recv->r_ibinc->ii_inc);
224                 recv->r_ibinc = NULL;
225         }
226         if (recv->r_frag) {
227                 ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1, DMA_FROM_DEVICE);
228                 rds_ib_frag_free(ic, recv->r_frag);
229                 recv->r_frag = NULL;
230         }
231 }
232 
233 void rds_ib_recv_clear_ring(struct rds_ib_connection *ic)
234 {
235         u32 i;
236 
237         for (i = 0; i < ic->i_recv_ring.w_nr; i++)
238                 rds_ib_recv_clear_one(ic, &ic->i_recvs[i]);
239 }
240 
241 static struct rds_ib_incoming *rds_ib_refill_one_inc(struct rds_ib_connection *ic,
242                                                      gfp_t slab_mask)
243 {
244         struct rds_ib_incoming *ibinc;
245         struct list_head *cache_item;
246         int avail_allocs;
247 
248         cache_item = rds_ib_recv_cache_get(&ic->i_cache_incs);
249         if (cache_item) {
250                 ibinc = container_of(cache_item, struct rds_ib_incoming, ii_cache_entry);
251         } else {
252                 avail_allocs = atomic_add_unless(&rds_ib_allocation,
253                                                  1, rds_ib_sysctl_max_recv_allocation);
254                 if (!avail_allocs) {
255                         rds_ib_stats_inc(s_ib_rx_alloc_limit);
256                         return NULL;
257                 }
258                 ibinc = kmem_cache_alloc(rds_ib_incoming_slab, slab_mask);
259                 if (!ibinc) {
260                         atomic_dec(&rds_ib_allocation);
261                         return NULL;
262                 }
263         }
264         INIT_LIST_HEAD(&ibinc->ii_frags);
265         rds_inc_init(&ibinc->ii_inc, ic->conn, ic->conn->c_faddr);
266 
267         return ibinc;
268 }
269 
270 static struct rds_page_frag *rds_ib_refill_one_frag(struct rds_ib_connection *ic,
271                                                     gfp_t slab_mask, gfp_t page_mask)
272 {
273         struct rds_page_frag *frag;
274         struct list_head *cache_item;
275         int ret;
276 
277         cache_item = rds_ib_recv_cache_get(&ic->i_cache_frags);
278         if (cache_item) {
279                 frag = container_of(cache_item, struct rds_page_frag, f_cache_entry);
280         } else {
281                 frag = kmem_cache_alloc(rds_ib_frag_slab, slab_mask);
282                 if (!frag)
283                         return NULL;
284 
285                 sg_init_table(&frag->f_sg, 1);
286                 ret = rds_page_remainder_alloc(&frag->f_sg,
287                                                RDS_FRAG_SIZE, page_mask);
288                 if (ret) {
289                         kmem_cache_free(rds_ib_frag_slab, frag);
290                         return NULL;
291                 }
292         }
293 
294         INIT_LIST_HEAD(&frag->f_item);
295 
296         return frag;
297 }
298 
299 static int rds_ib_recv_refill_one(struct rds_connection *conn,
300                                   struct rds_ib_recv_work *recv, int prefill)
301 {
302         struct rds_ib_connection *ic = conn->c_transport_data;
303         struct ib_sge *sge;
304         int ret = -ENOMEM;
305         gfp_t slab_mask = GFP_NOWAIT;
306         gfp_t page_mask = GFP_NOWAIT;
307 
308         if (prefill) {
309                 slab_mask = GFP_KERNEL;
310                 page_mask = GFP_HIGHUSER;
311         }
312 
313         if (!ic->i_cache_incs.ready)
314                 rds_ib_cache_xfer_to_ready(&ic->i_cache_incs);
315         if (!ic->i_cache_frags.ready)
316                 rds_ib_cache_xfer_to_ready(&ic->i_cache_frags);
317 
318         /*
319          * ibinc was taken from recv if recv contained the start of a message.
320          * recvs that were continuations will still have this allocated.
321          */
322         if (!recv->r_ibinc) {
323                 recv->r_ibinc = rds_ib_refill_one_inc(ic, slab_mask);
324                 if (!recv->r_ibinc)
325                         goto out;
326         }
327 
328         WARN_ON(recv->r_frag); /* leak! */
329         recv->r_frag = rds_ib_refill_one_frag(ic, slab_mask, page_mask);
330         if (!recv->r_frag)
331                 goto out;
332 
333         ret = ib_dma_map_sg(ic->i_cm_id->device, &recv->r_frag->f_sg,
334                             1, DMA_FROM_DEVICE);
335         WARN_ON(ret != 1);
336 
337         sge = &recv->r_sge[0];
338         sge->addr = ic->i_recv_hdrs_dma + (recv - ic->i_recvs) * sizeof(struct rds_header);
339         sge->length = sizeof(struct rds_header);
340 
341         sge = &recv->r_sge[1];
342         sge->addr = ib_sg_dma_address(ic->i_cm_id->device, &recv->r_frag->f_sg);
343         sge->length = ib_sg_dma_len(ic->i_cm_id->device, &recv->r_frag->f_sg);
344 
345         ret = 0;
346 out:
347         return ret;
348 }
349 
350 /*
351  * This tries to allocate and post unused work requests after making sure that
352  * they have all the allocations they need to queue received fragments into
353  * sockets.
354  *
355  * -1 is returned if posting fails due to temporary resource exhaustion.
356  */
357 void rds_ib_recv_refill(struct rds_connection *conn, int prefill)
358 {
359         struct rds_ib_connection *ic = conn->c_transport_data;
360         struct rds_ib_recv_work *recv;
361         struct ib_recv_wr *failed_wr;
362         unsigned int posted = 0;
363         int ret = 0;
364         u32 pos;
365 
366         while ((prefill || rds_conn_up(conn)) &&
367                rds_ib_ring_alloc(&ic->i_recv_ring, 1, &pos)) {
368                 if (pos >= ic->i_recv_ring.w_nr) {
369                         printk(KERN_NOTICE "Argh - ring alloc returned pos=%u\n",
370                                         pos);
371                         break;
372                 }
373 
374                 recv = &ic->i_recvs[pos];
375                 ret = rds_ib_recv_refill_one(conn, recv, prefill);
376                 if (ret) {
377                         break;
378                 }
379 
380                 /* XXX when can this fail? */
381                 ret = ib_post_recv(ic->i_cm_id->qp, &recv->r_wr, &failed_wr);
382                 rdsdebug("recv %p ibinc %p page %p addr %lu ret %d\n", recv,
383                          recv->r_ibinc, sg_page(&recv->r_frag->f_sg),
384                          (long) ib_sg_dma_address(
385                                 ic->i_cm_id->device,
386                                 &recv->r_frag->f_sg),
387                         ret);
388                 if (ret) {
389                         rds_ib_conn_error(conn, "recv post on "
390                                "%pI4 returned %d, disconnecting and "
391                                "reconnecting\n", &conn->c_faddr,
392                                ret);
393                         break;
394                 }
395 
396                 posted++;
397         }
398 
399         /* We're doing flow control - update the window. */
400         if (ic->i_flowctl && posted)
401                 rds_ib_advertise_credits(conn, posted);
402 
403         if (ret)
404                 rds_ib_ring_unalloc(&ic->i_recv_ring, 1);
405 }
406 
407 /*
408  * We want to recycle several types of recv allocations, like incs and frags.
409  * To use this, the *_free() function passes in the ptr to a list_head within
410  * the recyclee, as well as the cache to put it on.
411  *
412  * First, we put the memory on a percpu list. When this reaches a certain size,
413  * We move it to an intermediate non-percpu list in a lockless manner, with some
414  * xchg/compxchg wizardry.
415  *
416  * N.B. Instead of a list_head as the anchor, we use a single pointer, which can
417  * be NULL and xchg'd. The list is actually empty when the pointer is NULL, and
418  * list_empty() will return true with one element is actually present.
419  */
420 static void rds_ib_recv_cache_put(struct list_head *new_item,
421                                  struct rds_ib_refill_cache *cache)
422 {
423         unsigned long flags;
424         struct list_head *old, *chpfirst;
425 
426         local_irq_save(flags);
427 
428         chpfirst = __this_cpu_read(cache->percpu->first);
429         if (!chpfirst)
430                 INIT_LIST_HEAD(new_item);
431         else /* put on front */
432                 list_add_tail(new_item, chpfirst);
433 
434         __this_cpu_write(cache->percpu->first, new_item);
435         __this_cpu_inc(cache->percpu->count);
436 
437         if (__this_cpu_read(cache->percpu->count) < RDS_IB_RECYCLE_BATCH_COUNT)
438                 goto end;
439 
440         /*
441          * Return our per-cpu first list to the cache's xfer by atomically
442          * grabbing the current xfer list, appending it to our per-cpu list,
443          * and then atomically returning that entire list back to the
444          * cache's xfer list as long as it's still empty.
445          */
446         do {
447                 old = xchg(&cache->xfer, NULL);
448                 if (old)
449                         list_splice_entire_tail(old, chpfirst);
450                 old = cmpxchg(&cache->xfer, NULL, chpfirst);
451         } while (old);
452 
453 
454         __this_cpu_write(cache->percpu->first, NULL);
455         __this_cpu_write(cache->percpu->count, 0);
456 end:
457         local_irq_restore(flags);
458 }
459 
460 static struct list_head *rds_ib_recv_cache_get(struct rds_ib_refill_cache *cache)
461 {
462         struct list_head *head = cache->ready;
463 
464         if (head) {
465                 if (!list_empty(head)) {
466                         cache->ready = head->next;
467                         list_del_init(head);
468                 } else
469                         cache->ready = NULL;
470         }
471 
472         return head;
473 }
474 
475 int rds_ib_inc_copy_to_user(struct rds_incoming *inc, struct iovec *first_iov,
476                             size_t size)
477 {
478         struct rds_ib_incoming *ibinc;
479         struct rds_page_frag *frag;
480         struct iovec *iov = first_iov;
481         unsigned long to_copy;
482         unsigned long frag_off = 0;
483         unsigned long iov_off = 0;
484         int copied = 0;
485         int ret;
486         u32 len;
487 
488         ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);
489         frag = list_entry(ibinc->ii_frags.next, struct rds_page_frag, f_item);
490         len = be32_to_cpu(inc->i_hdr.h_len);
491 
492         while (copied < size && copied < len) {
493                 if (frag_off == RDS_FRAG_SIZE) {
494                         frag = list_entry(frag->f_item.next,
495                                           struct rds_page_frag, f_item);
496                         frag_off = 0;
497                 }
498                 while (iov_off == iov->iov_len) {
499                         iov_off = 0;
500                         iov++;
501                 }
502 
503                 to_copy = min(iov->iov_len - iov_off, RDS_FRAG_SIZE - frag_off);
504                 to_copy = min_t(size_t, to_copy, size - copied);
505                 to_copy = min_t(unsigned long, to_copy, len - copied);
506 
507                 rdsdebug("%lu bytes to user [%p, %zu] + %lu from frag "
508                          "[%p, %u] + %lu\n",
509                          to_copy, iov->iov_base, iov->iov_len, iov_off,
510                          sg_page(&frag->f_sg), frag->f_sg.offset, frag_off);
511 
512                 /* XXX needs + offset for multiple recvs per page */
513                 ret = rds_page_copy_to_user(sg_page(&frag->f_sg),
514                                             frag->f_sg.offset + frag_off,
515                                             iov->iov_base + iov_off,
516                                             to_copy);
517                 if (ret) {
518                         copied = ret;
519                         break;
520                 }
521 
522                 iov_off += to_copy;
523                 frag_off += to_copy;
524                 copied += to_copy;
525         }
526 
527         return copied;
528 }
529 
530 /* ic starts out kzalloc()ed */
531 void rds_ib_recv_init_ack(struct rds_ib_connection *ic)
532 {
533         struct ib_send_wr *wr = &ic->i_ack_wr;
534         struct ib_sge *sge = &ic->i_ack_sge;
535 
536         sge->addr = ic->i_ack_dma;
537         sge->length = sizeof(struct rds_header);
538         sge->lkey = ic->i_mr->lkey;
539 
540         wr->sg_list = sge;
541         wr->num_sge = 1;
542         wr->opcode = IB_WR_SEND;
543         wr->wr_id = RDS_IB_ACK_WR_ID;
544         wr->send_flags = IB_SEND_SIGNALED | IB_SEND_SOLICITED;
545 }
546 
547 /*
548  * You'd think that with reliable IB connections you wouldn't need to ack
549  * messages that have been received.  The problem is that IB hardware generates
550  * an ack message before it has DMAed the message into memory.  This creates a
551  * potential message loss if the HCA is disabled for any reason between when it
552  * sends the ack and before the message is DMAed and processed.  This is only a
553  * potential issue if another HCA is available for fail-over.
554  *
555  * When the remote host receives our ack they'll free the sent message from
556  * their send queue.  To decrease the latency of this we always send an ack
557  * immediately after we've received messages.
558  *
559  * For simplicity, we only have one ack in flight at a time.  This puts
560  * pressure on senders to have deep enough send queues to absorb the latency of
561  * a single ack frame being in flight.  This might not be good enough.
562  *
563  * This is implemented by have a long-lived send_wr and sge which point to a
564  * statically allocated ack frame.  This ack wr does not fall under the ring
565  * accounting that the tx and rx wrs do.  The QP attribute specifically makes
566  * room for it beyond the ring size.  Send completion notices its special
567  * wr_id and avoids working with the ring in that case.
568  */
569 #ifndef KERNEL_HAS_ATOMIC64
570 static void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq,
571                                 int ack_required)
572 {
573         unsigned long flags;
574 
575         spin_lock_irqsave(&ic->i_ack_lock, flags);
576         ic->i_ack_next = seq;
577         if (ack_required)
578                 set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
579         spin_unlock_irqrestore(&ic->i_ack_lock, flags);
580 }
581 
582 static u64 rds_ib_get_ack(struct rds_ib_connection *ic)
583 {
584         unsigned long flags;
585         u64 seq;
586 
587         clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
588 
589         spin_lock_irqsave(&ic->i_ack_lock, flags);
590         seq = ic->i_ack_next;
591         spin_unlock_irqrestore(&ic->i_ack_lock, flags);
592 
593         return seq;
594 }
595 #else
596 static void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq,
597                                 int ack_required)
598 {
599         atomic64_set(&ic->i_ack_next, seq);
600         if (ack_required) {
601                 smp_mb__before_clear_bit();
602                 set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
603         }
604 }
605 
606 static u64 rds_ib_get_ack(struct rds_ib_connection *ic)
607 {
608         clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
609         smp_mb__after_clear_bit();
610 
611         return atomic64_read(&ic->i_ack_next);
612 }
613 #endif
614 
615 
616 static void rds_ib_send_ack(struct rds_ib_connection *ic, unsigned int adv_credits)
617 {
618         struct rds_header *hdr = ic->i_ack;
619         struct ib_send_wr *failed_wr;
620         u64 seq;
621         int ret;
622 
623         seq = rds_ib_get_ack(ic);
624 
625         rdsdebug("send_ack: ic %p ack %llu\n", ic, (unsigned long long) seq);
626         rds_message_populate_header(hdr, 0, 0, 0);
627         hdr->h_ack = cpu_to_be64(seq);
628         hdr->h_credit = adv_credits;
629         rds_message_make_checksum(hdr);
630         ic->i_ack_queued = jiffies;
631 
632         ret = ib_post_send(ic->i_cm_id->qp, &ic->i_ack_wr, &failed_wr);
633         if (unlikely(ret)) {
634                 /* Failed to send. Release the WR, and
635                  * force another ACK.
636                  */
637                 clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
638                 set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
639 
640                 rds_ib_stats_inc(s_ib_ack_send_failure);
641 
642                 rds_ib_conn_error(ic->conn, "sending ack failed\n");
643         } else
644                 rds_ib_stats_inc(s_ib_ack_sent);
645 }
646 
647 /*
648  * There are 3 ways of getting acknowledgements to the peer:
649  *  1.  We call rds_ib_attempt_ack from the recv completion handler
650  *      to send an ACK-only frame.
651  *      However, there can be only one such frame in the send queue
652  *      at any time, so we may have to postpone it.
653  *  2.  When another (data) packet is transmitted while there's
654  *      an ACK in the queue, we piggyback the ACK sequence number
655  *      on the data packet.
656  *  3.  If the ACK WR is done sending, we get called from the
657  *      send queue completion handler, and check whether there's
658  *      another ACK pending (postponed because the WR was on the
659  *      queue). If so, we transmit it.
660  *
661  * We maintain 2 variables:
662  *  -   i_ack_flags, which keeps track of whether the ACK WR
663  *      is currently in the send queue or not (IB_ACK_IN_FLIGHT)
664  *  -   i_ack_next, which is the last sequence number we received
665  *
666  * Potentially, send queue and receive queue handlers can run concurrently.
667  * It would be nice to not have to use a spinlock to synchronize things,
668  * but the one problem that rules this out is that 64bit updates are
669  * not atomic on all platforms. Things would be a lot simpler if
670  * we had atomic64 or maybe cmpxchg64 everywhere.
671  *
672  * Reconnecting complicates this picture just slightly. When we
673  * reconnect, we may be seeing duplicate packets. The peer
674  * is retransmitting them, because it hasn't seen an ACK for
675  * them. It is important that we ACK these.
676  *
677  * ACK mitigation adds a header flag "ACK_REQUIRED"; any packet with
678  * this flag set *MUST* be acknowledged immediately.
679  */
680 
681 /*
682  * When we get here, we're called from the recv queue handler.
683  * Check whether we ought to transmit an ACK.
684  */
685 void rds_ib_attempt_ack(struct rds_ib_connection *ic)
686 {
687         unsigned int adv_credits;
688 
689         if (!test_bit(IB_ACK_REQUESTED, &ic->i_ack_flags))
690                 return;
691 
692         if (test_and_set_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags)) {
693                 rds_ib_stats_inc(s_ib_ack_send_delayed);
694                 return;
695         }
696 
697         /* Can we get a send credit? */
698         if (!rds_ib_send_grab_credits(ic, 1, &adv_credits, 0, RDS_MAX_ADV_CREDIT)) {
699                 rds_ib_stats_inc(s_ib_tx_throttle);
700                 clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
701                 return;
702         }
703 
704         clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
705         rds_ib_send_ack(ic, adv_credits);
706 }
707 
708 /*
709  * We get here from the send completion handler, when the
710  * adapter tells us the ACK frame was sent.
711  */
712 void rds_ib_ack_send_complete(struct rds_ib_connection *ic)
713 {
714         clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
715         rds_ib_attempt_ack(ic);
716 }
717 
718 /*
719  * This is called by the regular xmit code when it wants to piggyback
720  * an ACK on an outgoing frame.
721  */
722 u64 rds_ib_piggyb_ack(struct rds_ib_connection *ic)
723 {
724         if (test_and_clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags))
725                 rds_ib_stats_inc(s_ib_ack_send_piggybacked);
726         return rds_ib_get_ack(ic);
727 }
728 
729 /*
730  * It's kind of lame that we're copying from the posted receive pages into
731  * long-lived bitmaps.  We could have posted the bitmaps and rdma written into
732  * them.  But receiving new congestion bitmaps should be a *rare* event, so
733  * hopefully we won't need to invest that complexity in making it more
734  * efficient.  By copying we can share a simpler core with TCP which has to
735  * copy.
736  */
737 static void rds_ib_cong_recv(struct rds_connection *conn,
738                               struct rds_ib_incoming *ibinc)
739 {
740         struct rds_cong_map *map;
741         unsigned int map_off;
742         unsigned int map_page;
743         struct rds_page_frag *frag;
744         unsigned long frag_off;
745         unsigned long to_copy;
746         unsigned long copied;
747         uint64_t uncongested = 0;
748         void *addr;
749 
750         /* catch completely corrupt packets */
751         if (be32_to_cpu(ibinc->ii_inc.i_hdr.h_len) != RDS_CONG_MAP_BYTES)
752                 return;
753 
754         map = conn->c_fcong;
755         map_page = 0;
756         map_off = 0;
757 
758         frag = list_entry(ibinc->ii_frags.next, struct rds_page_frag, f_item);
759         frag_off = 0;
760 
761         copied = 0;
762 
763         while (copied < RDS_CONG_MAP_BYTES) {
764                 uint64_t *src, *dst;
765                 unsigned int k;
766 
767                 to_copy = min(RDS_FRAG_SIZE - frag_off, PAGE_SIZE - map_off);
768                 BUG_ON(to_copy & 7); /* Must be 64bit aligned. */
769 
770                 addr = kmap_atomic(sg_page(&frag->f_sg));
771 
772                 src = addr + frag_off;
773                 dst = (void *)map->m_page_addrs[map_page] + map_off;
774                 for (k = 0; k < to_copy; k += 8) {
775                         /* Record ports that became uncongested, ie
776                          * bits that changed from 0 to 1. */
777                         uncongested |= ~(*src) & *dst;
778                         *dst++ = *src++;
779                 }
780                 kunmap_atomic(addr);
781 
782                 copied += to_copy;
783 
784                 map_off += to_copy;
785                 if (map_off == PAGE_SIZE) {
786                         map_off = 0;
787                         map_page++;
788                 }
789 
790                 frag_off += to_copy;
791                 if (frag_off == RDS_FRAG_SIZE) {
792                         frag = list_entry(frag->f_item.next,
793                                           struct rds_page_frag, f_item);
794                         frag_off = 0;
795                 }
796         }
797 
798         /* the congestion map is in little endian order */
799         uncongested = le64_to_cpu(uncongested);
800 
801         rds_cong_map_updated(map, uncongested);
802 }
803 
804 /*
805  * Rings are posted with all the allocations they'll need to queue the
806  * incoming message to the receiving socket so this can't fail.
807  * All fragments start with a header, so we can make sure we're not receiving
808  * garbage, and we can tell a small 8 byte fragment from an ACK frame.
809  */
810 struct rds_ib_ack_state {
811         u64             ack_next;
812         u64             ack_recv;
813         unsigned int    ack_required:1;
814         unsigned int    ack_next_valid:1;
815         unsigned int    ack_recv_valid:1;
816 };
817 
818 static void rds_ib_process_recv(struct rds_connection *conn,
819                                 struct rds_ib_recv_work *recv, u32 data_len,
820                                 struct rds_ib_ack_state *state)
821 {
822         struct rds_ib_connection *ic = conn->c_transport_data;
823         struct rds_ib_incoming *ibinc = ic->i_ibinc;
824         struct rds_header *ihdr, *hdr;
825 
826         /* XXX shut down the connection if port 0,0 are seen? */
827 
828         rdsdebug("ic %p ibinc %p recv %p byte len %u\n", ic, ibinc, recv,
829                  data_len);
830 
831         if (data_len < sizeof(struct rds_header)) {
832                 rds_ib_conn_error(conn, "incoming message "
833                        "from %pI4 didn't include a "
834                        "header, disconnecting and "
835                        "reconnecting\n",
836                        &conn->c_faddr);
837                 return;
838         }
839         data_len -= sizeof(struct rds_header);
840 
841         ihdr = &ic->i_recv_hdrs[recv - ic->i_recvs];
842 
843         /* Validate the checksum. */
844         if (!rds_message_verify_checksum(ihdr)) {
845                 rds_ib_conn_error(conn, "incoming message "
846                        "from %pI4 has corrupted header - "
847                        "forcing a reconnect\n",
848                        &conn->c_faddr);
849                 rds_stats_inc(s_recv_drop_bad_checksum);
850                 return;
851         }
852 
853         /* Process the ACK sequence which comes with every packet */
854         state->ack_recv = be64_to_cpu(ihdr->h_ack);
855         state->ack_recv_valid = 1;
856 
857         /* Process the credits update if there was one */
858         if (ihdr->h_credit)
859                 rds_ib_send_add_credits(conn, ihdr->h_credit);
860 
861         if (ihdr->h_sport == 0 && ihdr->h_dport == 0 && data_len == 0) {
862                 /* This is an ACK-only packet. The fact that it gets
863                  * special treatment here is that historically, ACKs
864                  * were rather special beasts.
865                  */
866                 rds_ib_stats_inc(s_ib_ack_received);
867 
868                 /*
869                  * Usually the frags make their way on to incs and are then freed as
870                  * the inc is freed.  We don't go that route, so we have to drop the
871                  * page ref ourselves.  We can't just leave the page on the recv
872                  * because that confuses the dma mapping of pages and each recv's use
873                  * of a partial page.
874                  *
875                  * FIXME: Fold this into the code path below.
876                  */
877                 rds_ib_frag_free(ic, recv->r_frag);
878                 recv->r_frag = NULL;
879                 return;
880         }
881 
882         /*
883          * If we don't already have an inc on the connection then this
884          * fragment has a header and starts a message.. copy its header
885          * into the inc and save the inc so we can hang upcoming fragments
886          * off its list.
887          */
888         if (!ibinc) {
889                 ibinc = recv->r_ibinc;
890                 recv->r_ibinc = NULL;
891                 ic->i_ibinc = ibinc;
892 
893                 hdr = &ibinc->ii_inc.i_hdr;
894                 memcpy(hdr, ihdr, sizeof(*hdr));
895                 ic->i_recv_data_rem = be32_to_cpu(hdr->h_len);
896 
897                 rdsdebug("ic %p ibinc %p rem %u flag 0x%x\n", ic, ibinc,
898                          ic->i_recv_data_rem, hdr->h_flags);
899         } else {
900                 hdr = &ibinc->ii_inc.i_hdr;
901                 /* We can't just use memcmp here; fragments of a
902                  * single message may carry different ACKs */
903                 if (hdr->h_sequence != ihdr->h_sequence ||
904                     hdr->h_len != ihdr->h_len ||
905                     hdr->h_sport != ihdr->h_sport ||
906                     hdr->h_dport != ihdr->h_dport) {
907                         rds_ib_conn_error(conn,
908                                 "fragment header mismatch; forcing reconnect\n");
909                         return;
910                 }
911         }
912 
913         list_add_tail(&recv->r_frag->f_item, &ibinc->ii_frags);
914         recv->r_frag = NULL;
915 
916         if (ic->i_recv_data_rem > RDS_FRAG_SIZE)
917                 ic->i_recv_data_rem -= RDS_FRAG_SIZE;
918         else {
919                 ic->i_recv_data_rem = 0;
920                 ic->i_ibinc = NULL;
921 
922                 if (ibinc->ii_inc.i_hdr.h_flags == RDS_FLAG_CONG_BITMAP)
923                         rds_ib_cong_recv(conn, ibinc);
924                 else {
925                         rds_recv_incoming(conn, conn->c_faddr, conn->c_laddr,
926                                           &ibinc->ii_inc, GFP_ATOMIC);
927                         state->ack_next = be64_to_cpu(hdr->h_sequence);
928                         state->ack_next_valid = 1;
929                 }
930 
931                 /* Evaluate the ACK_REQUIRED flag *after* we received
932                  * the complete frame, and after bumping the next_rx
933                  * sequence. */
934                 if (hdr->h_flags & RDS_FLAG_ACK_REQUIRED) {
935                         rds_stats_inc(s_recv_ack_required);
936                         state->ack_required = 1;
937                 }
938 
939                 rds_inc_put(&ibinc->ii_inc);
940         }
941 }
942 
943 /*
944  * Plucking the oldest entry from the ring can be done concurrently with
945  * the thread refilling the ring.  Each ring operation is protected by
946  * spinlocks and the transient state of refilling doesn't change the
947  * recording of which entry is oldest.
948  *
949  * This relies on IB only calling one cq comp_handler for each cq so that
950  * there will only be one caller of rds_recv_incoming() per RDS connection.
951  */
952 void rds_ib_recv_cq_comp_handler(struct ib_cq *cq, void *context)
953 {
954         struct rds_connection *conn = context;
955         struct rds_ib_connection *ic = conn->c_transport_data;
956 
957         rdsdebug("conn %p cq %p\n", conn, cq);
958 
959         rds_ib_stats_inc(s_ib_rx_cq_call);
960 
961         tasklet_schedule(&ic->i_recv_tasklet);
962 }
963 
964 static inline void rds_poll_cq(struct rds_ib_connection *ic,
965                                struct rds_ib_ack_state *state)
966 {
967         struct rds_connection *conn = ic->conn;
968         struct ib_wc wc;
969         struct rds_ib_recv_work *recv;
970 
971         while (ib_poll_cq(ic->i_recv_cq, 1, &wc) > 0) {
972                 rdsdebug("wc wr_id 0x%llx status %u (%s) byte_len %u imm_data %u\n",
973                          (unsigned long long)wc.wr_id, wc.status,
974                          rds_ib_wc_status_str(wc.status), wc.byte_len,
975                          be32_to_cpu(wc.ex.imm_data));
976                 rds_ib_stats_inc(s_ib_rx_cq_event);
977 
978                 recv = &ic->i_recvs[rds_ib_ring_oldest(&ic->i_recv_ring)];
979 
980                 ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1, DMA_FROM_DEVICE);
981 
982                 /*
983                  * Also process recvs in connecting state because it is possible
984                  * to get a recv completion _before_ the rdmacm ESTABLISHED
985                  * event is processed.
986                  */
987                 if (wc.status == IB_WC_SUCCESS) {
988                         rds_ib_process_recv(conn, recv, wc.byte_len, state);
989                 } else {
990                         /* We expect errors as the qp is drained during shutdown */
991                         if (rds_conn_up(conn) || rds_conn_connecting(conn))
992                                 rds_ib_conn_error(conn, "recv completion on %pI4 had "
993                                                   "status %u (%s), disconnecting and "
994                                                   "reconnecting\n", &conn->c_faddr,
995                                                   wc.status,
996                                                   rds_ib_wc_status_str(wc.status));
997                 }
998 
999                 /*
1000                  * It's very important that we only free this ring entry if we've truly
1001                  * freed the resources allocated to the entry.  The refilling path can
1002                  * leak if we don't.
1003                  */
1004                 rds_ib_ring_free(&ic->i_recv_ring, 1);
1005         }
1006 }
1007 
1008 void rds_ib_recv_tasklet_fn(unsigned long data)
1009 {
1010         struct rds_ib_connection *ic = (struct rds_ib_connection *) data;
1011         struct rds_connection *conn = ic->conn;
1012         struct rds_ib_ack_state state = { 0, };
1013 
1014         rds_poll_cq(ic, &state);
1015         ib_req_notify_cq(ic->i_recv_cq, IB_CQ_SOLICITED);
1016         rds_poll_cq(ic, &state);
1017 
1018         if (state.ack_next_valid)
1019                 rds_ib_set_ack(ic, state.ack_next, state.ack_required);
1020         if (state.ack_recv_valid && state.ack_recv > ic->i_ack_recv) {
1021                 rds_send_drop_acked(conn, state.ack_recv, NULL);
1022                 ic->i_ack_recv = state.ack_recv;
1023         }
1024         if (rds_conn_up(conn))
1025                 rds_ib_attempt_ack(ic);
1026 
1027         /* If we ever end up with a really empty receive ring, we're
1028          * in deep trouble, as the sender will definitely see RNR
1029          * timeouts. */
1030         if (rds_ib_ring_empty(&ic->i_recv_ring))
1031                 rds_ib_stats_inc(s_ib_rx_ring_empty);
1032 
1033         if (rds_ib_ring_low(&ic->i_recv_ring))
1034                 rds_ib_recv_refill(conn, 0);
1035 }
1036 
1037 int rds_ib_recv(struct rds_connection *conn)
1038 {
1039         struct rds_ib_connection *ic = conn->c_transport_data;
1040         int ret = 0;
1041 
1042         rdsdebug("conn %p\n", conn);
1043         if (rds_conn_up(conn))
1044                 rds_ib_attempt_ack(ic);
1045 
1046         return ret;
1047 }
1048 
1049 int rds_ib_recv_init(void)
1050 {
1051         struct sysinfo si;
1052         int ret = -ENOMEM;
1053 
1054         /* Default to 30% of all available RAM for recv memory */
1055         si_meminfo(&si);
1056         rds_ib_sysctl_max_recv_allocation = si.totalram / 3 * PAGE_SIZE / RDS_FRAG_SIZE;
1057 
1058         rds_ib_incoming_slab = kmem_cache_create("rds_ib_incoming",
1059                                         sizeof(struct rds_ib_incoming),
1060                                         0, SLAB_HWCACHE_ALIGN, NULL);
1061         if (!rds_ib_incoming_slab)
1062                 goto out;
1063 
1064         rds_ib_frag_slab = kmem_cache_create("rds_ib_frag",
1065                                         sizeof(struct rds_page_frag),
1066                                         0, SLAB_HWCACHE_ALIGN, NULL);
1067         if (!rds_ib_frag_slab)
1068                 kmem_cache_destroy(rds_ib_incoming_slab);
1069         else
1070                 ret = 0;
1071 out:
1072         return ret;
1073 }
1074 
1075 void rds_ib_recv_exit(void)
1076 {
1077         kmem_cache_destroy(rds_ib_incoming_slab);
1078         kmem_cache_destroy(rds_ib_frag_slab);
1079 }
1080 

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