xref: /openbmc/linux/net/rds/ib_recv.c (revision 43ffe817)
1 /*
2  * Copyright (c) 2006, 2019 Oracle and/or its affiliates. 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_single_path.h"
40 #include "rds.h"
41 #include "ib.h"
42 
43 static struct kmem_cache *rds_ib_incoming_slab;
44 static struct kmem_cache *rds_ib_frag_slab;
45 static atomic_t	rds_ib_allocation = ATOMIC_INIT(0);
46 
47 void rds_ib_recv_init_ring(struct rds_ib_connection *ic)
48 {
49 	struct rds_ib_recv_work *recv;
50 	u32 i;
51 
52 	for (i = 0, recv = ic->i_recvs; i < ic->i_recv_ring.w_nr; i++, recv++) {
53 		struct ib_sge *sge;
54 
55 		recv->r_ibinc = NULL;
56 		recv->r_frag = NULL;
57 
58 		recv->r_wr.next = NULL;
59 		recv->r_wr.wr_id = i;
60 		recv->r_wr.sg_list = recv->r_sge;
61 		recv->r_wr.num_sge = RDS_IB_RECV_SGE;
62 
63 		sge = &recv->r_sge[0];
64 		sge->addr = ic->i_recv_hdrs_dma[i];
65 		sge->length = sizeof(struct rds_header);
66 		sge->lkey = ic->i_pd->local_dma_lkey;
67 
68 		sge = &recv->r_sge[1];
69 		sge->addr = 0;
70 		sge->length = RDS_FRAG_SIZE;
71 		sge->lkey = ic->i_pd->local_dma_lkey;
72 	}
73 }
74 
75 /*
76  * The entire 'from' list, including the from element itself, is put on
77  * to the tail of the 'to' list.
78  */
79 static void list_splice_entire_tail(struct list_head *from,
80 				    struct list_head *to)
81 {
82 	struct list_head *from_last = from->prev;
83 
84 	list_splice_tail(from_last, to);
85 	list_add_tail(from_last, to);
86 }
87 
88 static void rds_ib_cache_xfer_to_ready(struct rds_ib_refill_cache *cache)
89 {
90 	struct list_head *tmp;
91 
92 	tmp = xchg(&cache->xfer, NULL);
93 	if (tmp) {
94 		if (cache->ready)
95 			list_splice_entire_tail(tmp, cache->ready);
96 		else
97 			cache->ready = tmp;
98 	}
99 }
100 
101 static int rds_ib_recv_alloc_cache(struct rds_ib_refill_cache *cache, gfp_t gfp)
102 {
103 	struct rds_ib_cache_head *head;
104 	int cpu;
105 
106 	cache->percpu = alloc_percpu_gfp(struct rds_ib_cache_head, gfp);
107 	if (!cache->percpu)
108 	       return -ENOMEM;
109 
110 	for_each_possible_cpu(cpu) {
111 		head = per_cpu_ptr(cache->percpu, cpu);
112 		head->first = NULL;
113 		head->count = 0;
114 	}
115 	cache->xfer = NULL;
116 	cache->ready = NULL;
117 
118 	return 0;
119 }
120 
121 int rds_ib_recv_alloc_caches(struct rds_ib_connection *ic, gfp_t gfp)
122 {
123 	int ret;
124 
125 	ret = rds_ib_recv_alloc_cache(&ic->i_cache_incs, gfp);
126 	if (!ret) {
127 		ret = rds_ib_recv_alloc_cache(&ic->i_cache_frags, gfp);
128 		if (ret)
129 			free_percpu(ic->i_cache_incs.percpu);
130 	}
131 
132 	return ret;
133 }
134 
135 static void rds_ib_cache_splice_all_lists(struct rds_ib_refill_cache *cache,
136 					  struct list_head *caller_list)
137 {
138 	struct rds_ib_cache_head *head;
139 	int cpu;
140 
141 	for_each_possible_cpu(cpu) {
142 		head = per_cpu_ptr(cache->percpu, cpu);
143 		if (head->first) {
144 			list_splice_entire_tail(head->first, caller_list);
145 			head->first = NULL;
146 		}
147 	}
148 
149 	if (cache->ready) {
150 		list_splice_entire_tail(cache->ready, caller_list);
151 		cache->ready = NULL;
152 	}
153 }
154 
155 void rds_ib_recv_free_caches(struct rds_ib_connection *ic)
156 {
157 	struct rds_ib_incoming *inc;
158 	struct rds_ib_incoming *inc_tmp;
159 	struct rds_page_frag *frag;
160 	struct rds_page_frag *frag_tmp;
161 	LIST_HEAD(list);
162 
163 	rds_ib_cache_xfer_to_ready(&ic->i_cache_incs);
164 	rds_ib_cache_splice_all_lists(&ic->i_cache_incs, &list);
165 	free_percpu(ic->i_cache_incs.percpu);
166 
167 	list_for_each_entry_safe(inc, inc_tmp, &list, ii_cache_entry) {
168 		list_del(&inc->ii_cache_entry);
169 		WARN_ON(!list_empty(&inc->ii_frags));
170 		kmem_cache_free(rds_ib_incoming_slab, inc);
171 		atomic_dec(&rds_ib_allocation);
172 	}
173 
174 	rds_ib_cache_xfer_to_ready(&ic->i_cache_frags);
175 	rds_ib_cache_splice_all_lists(&ic->i_cache_frags, &list);
176 	free_percpu(ic->i_cache_frags.percpu);
177 
178 	list_for_each_entry_safe(frag, frag_tmp, &list, f_cache_entry) {
179 		list_del(&frag->f_cache_entry);
180 		WARN_ON(!list_empty(&frag->f_item));
181 		kmem_cache_free(rds_ib_frag_slab, frag);
182 	}
183 }
184 
185 /* fwd decl */
186 static void rds_ib_recv_cache_put(struct list_head *new_item,
187 				  struct rds_ib_refill_cache *cache);
188 static struct list_head *rds_ib_recv_cache_get(struct rds_ib_refill_cache *cache);
189 
190 
191 /* Recycle frag and attached recv buffer f_sg */
192 static void rds_ib_frag_free(struct rds_ib_connection *ic,
193 			     struct rds_page_frag *frag)
194 {
195 	rdsdebug("frag %p page %p\n", frag, sg_page(&frag->f_sg));
196 
197 	rds_ib_recv_cache_put(&frag->f_cache_entry, &ic->i_cache_frags);
198 	atomic_add(RDS_FRAG_SIZE / SZ_1K, &ic->i_cache_allocs);
199 	rds_ib_stats_add(s_ib_recv_added_to_cache, RDS_FRAG_SIZE);
200 }
201 
202 /* Recycle inc after freeing attached frags */
203 void rds_ib_inc_free(struct rds_incoming *inc)
204 {
205 	struct rds_ib_incoming *ibinc;
206 	struct rds_page_frag *frag;
207 	struct rds_page_frag *pos;
208 	struct rds_ib_connection *ic = inc->i_conn->c_transport_data;
209 
210 	ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);
211 
212 	/* Free attached frags */
213 	list_for_each_entry_safe(frag, pos, &ibinc->ii_frags, f_item) {
214 		list_del_init(&frag->f_item);
215 		rds_ib_frag_free(ic, frag);
216 	}
217 	BUG_ON(!list_empty(&ibinc->ii_frags));
218 
219 	rdsdebug("freeing ibinc %p inc %p\n", ibinc, inc);
220 	rds_ib_recv_cache_put(&ibinc->ii_cache_entry, &ic->i_cache_incs);
221 }
222 
223 static void rds_ib_recv_clear_one(struct rds_ib_connection *ic,
224 				  struct rds_ib_recv_work *recv)
225 {
226 	if (recv->r_ibinc) {
227 		rds_inc_put(&recv->r_ibinc->ii_inc);
228 		recv->r_ibinc = NULL;
229 	}
230 	if (recv->r_frag) {
231 		ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1, DMA_FROM_DEVICE);
232 		rds_ib_frag_free(ic, recv->r_frag);
233 		recv->r_frag = NULL;
234 	}
235 }
236 
237 void rds_ib_recv_clear_ring(struct rds_ib_connection *ic)
238 {
239 	u32 i;
240 
241 	for (i = 0; i < ic->i_recv_ring.w_nr; i++)
242 		rds_ib_recv_clear_one(ic, &ic->i_recvs[i]);
243 }
244 
245 static struct rds_ib_incoming *rds_ib_refill_one_inc(struct rds_ib_connection *ic,
246 						     gfp_t slab_mask)
247 {
248 	struct rds_ib_incoming *ibinc;
249 	struct list_head *cache_item;
250 	int avail_allocs;
251 
252 	cache_item = rds_ib_recv_cache_get(&ic->i_cache_incs);
253 	if (cache_item) {
254 		ibinc = container_of(cache_item, struct rds_ib_incoming, ii_cache_entry);
255 	} else {
256 		avail_allocs = atomic_add_unless(&rds_ib_allocation,
257 						 1, rds_ib_sysctl_max_recv_allocation);
258 		if (!avail_allocs) {
259 			rds_ib_stats_inc(s_ib_rx_alloc_limit);
260 			return NULL;
261 		}
262 		ibinc = kmem_cache_alloc(rds_ib_incoming_slab, slab_mask);
263 		if (!ibinc) {
264 			atomic_dec(&rds_ib_allocation);
265 			return NULL;
266 		}
267 		rds_ib_stats_inc(s_ib_rx_total_incs);
268 	}
269 	INIT_LIST_HEAD(&ibinc->ii_frags);
270 	rds_inc_init(&ibinc->ii_inc, ic->conn, &ic->conn->c_faddr);
271 
272 	return ibinc;
273 }
274 
275 static struct rds_page_frag *rds_ib_refill_one_frag(struct rds_ib_connection *ic,
276 						    gfp_t slab_mask, gfp_t page_mask)
277 {
278 	struct rds_page_frag *frag;
279 	struct list_head *cache_item;
280 	int ret;
281 
282 	cache_item = rds_ib_recv_cache_get(&ic->i_cache_frags);
283 	if (cache_item) {
284 		frag = container_of(cache_item, struct rds_page_frag, f_cache_entry);
285 		atomic_sub(RDS_FRAG_SIZE / SZ_1K, &ic->i_cache_allocs);
286 		rds_ib_stats_add(s_ib_recv_added_to_cache, RDS_FRAG_SIZE);
287 	} else {
288 		frag = kmem_cache_alloc(rds_ib_frag_slab, slab_mask);
289 		if (!frag)
290 			return NULL;
291 
292 		sg_init_table(&frag->f_sg, 1);
293 		ret = rds_page_remainder_alloc(&frag->f_sg,
294 					       RDS_FRAG_SIZE, page_mask);
295 		if (ret) {
296 			kmem_cache_free(rds_ib_frag_slab, frag);
297 			return NULL;
298 		}
299 		rds_ib_stats_inc(s_ib_rx_total_frags);
300 	}
301 
302 	INIT_LIST_HEAD(&frag->f_item);
303 
304 	return frag;
305 }
306 
307 static int rds_ib_recv_refill_one(struct rds_connection *conn,
308 				  struct rds_ib_recv_work *recv, gfp_t gfp)
309 {
310 	struct rds_ib_connection *ic = conn->c_transport_data;
311 	struct ib_sge *sge;
312 	int ret = -ENOMEM;
313 	gfp_t slab_mask = gfp;
314 	gfp_t page_mask = gfp;
315 
316 	if (gfp & __GFP_DIRECT_RECLAIM) {
317 		slab_mask = GFP_KERNEL;
318 		page_mask = GFP_HIGHUSER;
319 	}
320 
321 	if (!ic->i_cache_incs.ready)
322 		rds_ib_cache_xfer_to_ready(&ic->i_cache_incs);
323 	if (!ic->i_cache_frags.ready)
324 		rds_ib_cache_xfer_to_ready(&ic->i_cache_frags);
325 
326 	/*
327 	 * ibinc was taken from recv if recv contained the start of a message.
328 	 * recvs that were continuations will still have this allocated.
329 	 */
330 	if (!recv->r_ibinc) {
331 		recv->r_ibinc = rds_ib_refill_one_inc(ic, slab_mask);
332 		if (!recv->r_ibinc)
333 			goto out;
334 	}
335 
336 	WARN_ON(recv->r_frag); /* leak! */
337 	recv->r_frag = rds_ib_refill_one_frag(ic, slab_mask, page_mask);
338 	if (!recv->r_frag)
339 		goto out;
340 
341 	ret = ib_dma_map_sg(ic->i_cm_id->device, &recv->r_frag->f_sg,
342 			    1, DMA_FROM_DEVICE);
343 	WARN_ON(ret != 1);
344 
345 	sge = &recv->r_sge[0];
346 	sge->addr = ic->i_recv_hdrs_dma[recv - ic->i_recvs];
347 	sge->length = sizeof(struct rds_header);
348 
349 	sge = &recv->r_sge[1];
350 	sge->addr = sg_dma_address(&recv->r_frag->f_sg);
351 	sge->length = sg_dma_len(&recv->r_frag->f_sg);
352 
353 	ret = 0;
354 out:
355 	return ret;
356 }
357 
358 static int acquire_refill(struct rds_connection *conn)
359 {
360 	return test_and_set_bit(RDS_RECV_REFILL, &conn->c_flags) == 0;
361 }
362 
363 static void release_refill(struct rds_connection *conn)
364 {
365 	clear_bit(RDS_RECV_REFILL, &conn->c_flags);
366 
367 	/* We don't use wait_on_bit()/wake_up_bit() because our waking is in a
368 	 * hot path and finding waiters is very rare.  We don't want to walk
369 	 * the system-wide hashed waitqueue buckets in the fast path only to
370 	 * almost never find waiters.
371 	 */
372 	if (waitqueue_active(&conn->c_waitq))
373 		wake_up_all(&conn->c_waitq);
374 }
375 
376 /*
377  * This tries to allocate and post unused work requests after making sure that
378  * they have all the allocations they need to queue received fragments into
379  * sockets.
380  */
381 void rds_ib_recv_refill(struct rds_connection *conn, int prefill, gfp_t gfp)
382 {
383 	struct rds_ib_connection *ic = conn->c_transport_data;
384 	struct rds_ib_recv_work *recv;
385 	unsigned int posted = 0;
386 	int ret = 0;
387 	bool can_wait = !!(gfp & __GFP_DIRECT_RECLAIM);
388 	bool must_wake = false;
389 	u32 pos;
390 
391 	/* the goal here is to just make sure that someone, somewhere
392 	 * is posting buffers.  If we can't get the refill lock,
393 	 * let them do their thing
394 	 */
395 	if (!acquire_refill(conn))
396 		return;
397 
398 	while ((prefill || rds_conn_up(conn)) &&
399 	       rds_ib_ring_alloc(&ic->i_recv_ring, 1, &pos)) {
400 		if (pos >= ic->i_recv_ring.w_nr) {
401 			printk(KERN_NOTICE "Argh - ring alloc returned pos=%u\n",
402 					pos);
403 			break;
404 		}
405 
406 		recv = &ic->i_recvs[pos];
407 		ret = rds_ib_recv_refill_one(conn, recv, gfp);
408 		if (ret) {
409 			must_wake = true;
410 			break;
411 		}
412 
413 		rdsdebug("recv %p ibinc %p page %p addr %lu\n", recv,
414 			 recv->r_ibinc, sg_page(&recv->r_frag->f_sg),
415 			 (long)sg_dma_address(&recv->r_frag->f_sg));
416 
417 		/* XXX when can this fail? */
418 		ret = ib_post_recv(ic->i_cm_id->qp, &recv->r_wr, NULL);
419 		if (ret) {
420 			rds_ib_conn_error(conn, "recv post on "
421 			       "%pI6c returned %d, disconnecting and "
422 			       "reconnecting\n", &conn->c_faddr,
423 			       ret);
424 			break;
425 		}
426 
427 		posted++;
428 
429 		if ((posted > 128 && need_resched()) || posted > 8192) {
430 			must_wake = true;
431 			break;
432 		}
433 	}
434 
435 	/* We're doing flow control - update the window. */
436 	if (ic->i_flowctl && posted)
437 		rds_ib_advertise_credits(conn, posted);
438 
439 	if (ret)
440 		rds_ib_ring_unalloc(&ic->i_recv_ring, 1);
441 
442 	release_refill(conn);
443 
444 	/* if we're called from the softirq handler, we'll be GFP_NOWAIT.
445 	 * in this case the ring being low is going to lead to more interrupts
446 	 * and we can safely let the softirq code take care of it unless the
447 	 * ring is completely empty.
448 	 *
449 	 * if we're called from krdsd, we'll be GFP_KERNEL.  In this case
450 	 * we might have raced with the softirq code while we had the refill
451 	 * lock held.  Use rds_ib_ring_low() instead of ring_empty to decide
452 	 * if we should requeue.
453 	 */
454 	if (rds_conn_up(conn) &&
455 	    (must_wake ||
456 	    (can_wait && rds_ib_ring_low(&ic->i_recv_ring)) ||
457 	    rds_ib_ring_empty(&ic->i_recv_ring))) {
458 		queue_delayed_work(rds_wq, &conn->c_recv_w, 1);
459 	}
460 	if (can_wait)
461 		cond_resched();
462 }
463 
464 /*
465  * We want to recycle several types of recv allocations, like incs and frags.
466  * To use this, the *_free() function passes in the ptr to a list_head within
467  * the recyclee, as well as the cache to put it on.
468  *
469  * First, we put the memory on a percpu list. When this reaches a certain size,
470  * We move it to an intermediate non-percpu list in a lockless manner, with some
471  * xchg/compxchg wizardry.
472  *
473  * N.B. Instead of a list_head as the anchor, we use a single pointer, which can
474  * be NULL and xchg'd. The list is actually empty when the pointer is NULL, and
475  * list_empty() will return true with one element is actually present.
476  */
477 static void rds_ib_recv_cache_put(struct list_head *new_item,
478 				 struct rds_ib_refill_cache *cache)
479 {
480 	unsigned long flags;
481 	struct list_head *old, *chpfirst;
482 
483 	local_irq_save(flags);
484 
485 	chpfirst = __this_cpu_read(cache->percpu->first);
486 	if (!chpfirst)
487 		INIT_LIST_HEAD(new_item);
488 	else /* put on front */
489 		list_add_tail(new_item, chpfirst);
490 
491 	__this_cpu_write(cache->percpu->first, new_item);
492 	__this_cpu_inc(cache->percpu->count);
493 
494 	if (__this_cpu_read(cache->percpu->count) < RDS_IB_RECYCLE_BATCH_COUNT)
495 		goto end;
496 
497 	/*
498 	 * Return our per-cpu first list to the cache's xfer by atomically
499 	 * grabbing the current xfer list, appending it to our per-cpu list,
500 	 * and then atomically returning that entire list back to the
501 	 * cache's xfer list as long as it's still empty.
502 	 */
503 	do {
504 		old = xchg(&cache->xfer, NULL);
505 		if (old)
506 			list_splice_entire_tail(old, chpfirst);
507 		old = cmpxchg(&cache->xfer, NULL, chpfirst);
508 	} while (old);
509 
510 
511 	__this_cpu_write(cache->percpu->first, NULL);
512 	__this_cpu_write(cache->percpu->count, 0);
513 end:
514 	local_irq_restore(flags);
515 }
516 
517 static struct list_head *rds_ib_recv_cache_get(struct rds_ib_refill_cache *cache)
518 {
519 	struct list_head *head = cache->ready;
520 
521 	if (head) {
522 		if (!list_empty(head)) {
523 			cache->ready = head->next;
524 			list_del_init(head);
525 		} else
526 			cache->ready = NULL;
527 	}
528 
529 	return head;
530 }
531 
532 int rds_ib_inc_copy_to_user(struct rds_incoming *inc, struct iov_iter *to)
533 {
534 	struct rds_ib_incoming *ibinc;
535 	struct rds_page_frag *frag;
536 	unsigned long to_copy;
537 	unsigned long frag_off = 0;
538 	int copied = 0;
539 	int ret;
540 	u32 len;
541 
542 	ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);
543 	frag = list_entry(ibinc->ii_frags.next, struct rds_page_frag, f_item);
544 	len = be32_to_cpu(inc->i_hdr.h_len);
545 
546 	while (iov_iter_count(to) && copied < len) {
547 		if (frag_off == RDS_FRAG_SIZE) {
548 			frag = list_entry(frag->f_item.next,
549 					  struct rds_page_frag, f_item);
550 			frag_off = 0;
551 		}
552 		to_copy = min_t(unsigned long, iov_iter_count(to),
553 				RDS_FRAG_SIZE - frag_off);
554 		to_copy = min_t(unsigned long, to_copy, len - copied);
555 
556 		/* XXX needs + offset for multiple recvs per page */
557 		rds_stats_add(s_copy_to_user, to_copy);
558 		ret = copy_page_to_iter(sg_page(&frag->f_sg),
559 					frag->f_sg.offset + frag_off,
560 					to_copy,
561 					to);
562 		if (ret != to_copy)
563 			return -EFAULT;
564 
565 		frag_off += to_copy;
566 		copied += to_copy;
567 	}
568 
569 	return copied;
570 }
571 
572 /* ic starts out kzalloc()ed */
573 void rds_ib_recv_init_ack(struct rds_ib_connection *ic)
574 {
575 	struct ib_send_wr *wr = &ic->i_ack_wr;
576 	struct ib_sge *sge = &ic->i_ack_sge;
577 
578 	sge->addr = ic->i_ack_dma;
579 	sge->length = sizeof(struct rds_header);
580 	sge->lkey = ic->i_pd->local_dma_lkey;
581 
582 	wr->sg_list = sge;
583 	wr->num_sge = 1;
584 	wr->opcode = IB_WR_SEND;
585 	wr->wr_id = RDS_IB_ACK_WR_ID;
586 	wr->send_flags = IB_SEND_SIGNALED | IB_SEND_SOLICITED;
587 }
588 
589 /*
590  * You'd think that with reliable IB connections you wouldn't need to ack
591  * messages that have been received.  The problem is that IB hardware generates
592  * an ack message before it has DMAed the message into memory.  This creates a
593  * potential message loss if the HCA is disabled for any reason between when it
594  * sends the ack and before the message is DMAed and processed.  This is only a
595  * potential issue if another HCA is available for fail-over.
596  *
597  * When the remote host receives our ack they'll free the sent message from
598  * their send queue.  To decrease the latency of this we always send an ack
599  * immediately after we've received messages.
600  *
601  * For simplicity, we only have one ack in flight at a time.  This puts
602  * pressure on senders to have deep enough send queues to absorb the latency of
603  * a single ack frame being in flight.  This might not be good enough.
604  *
605  * This is implemented by have a long-lived send_wr and sge which point to a
606  * statically allocated ack frame.  This ack wr does not fall under the ring
607  * accounting that the tx and rx wrs do.  The QP attribute specifically makes
608  * room for it beyond the ring size.  Send completion notices its special
609  * wr_id and avoids working with the ring in that case.
610  */
611 #ifndef KERNEL_HAS_ATOMIC64
612 void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq, int ack_required)
613 {
614 	unsigned long flags;
615 
616 	spin_lock_irqsave(&ic->i_ack_lock, flags);
617 	ic->i_ack_next = seq;
618 	if (ack_required)
619 		set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
620 	spin_unlock_irqrestore(&ic->i_ack_lock, flags);
621 }
622 
623 static u64 rds_ib_get_ack(struct rds_ib_connection *ic)
624 {
625 	unsigned long flags;
626 	u64 seq;
627 
628 	clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
629 
630 	spin_lock_irqsave(&ic->i_ack_lock, flags);
631 	seq = ic->i_ack_next;
632 	spin_unlock_irqrestore(&ic->i_ack_lock, flags);
633 
634 	return seq;
635 }
636 #else
637 void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq, int ack_required)
638 {
639 	atomic64_set(&ic->i_ack_next, seq);
640 	if (ack_required) {
641 		smp_mb__before_atomic();
642 		set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
643 	}
644 }
645 
646 static u64 rds_ib_get_ack(struct rds_ib_connection *ic)
647 {
648 	clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
649 	smp_mb__after_atomic();
650 
651 	return atomic64_read(&ic->i_ack_next);
652 }
653 #endif
654 
655 
656 static void rds_ib_send_ack(struct rds_ib_connection *ic, unsigned int adv_credits)
657 {
658 	struct rds_header *hdr = ic->i_ack;
659 	u64 seq;
660 	int ret;
661 
662 	seq = rds_ib_get_ack(ic);
663 
664 	rdsdebug("send_ack: ic %p ack %llu\n", ic, (unsigned long long) seq);
665 	rds_message_populate_header(hdr, 0, 0, 0);
666 	hdr->h_ack = cpu_to_be64(seq);
667 	hdr->h_credit = adv_credits;
668 	rds_message_make_checksum(hdr);
669 	ic->i_ack_queued = jiffies;
670 
671 	ret = ib_post_send(ic->i_cm_id->qp, &ic->i_ack_wr, NULL);
672 	if (unlikely(ret)) {
673 		/* Failed to send. Release the WR, and
674 		 * force another ACK.
675 		 */
676 		clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
677 		set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
678 
679 		rds_ib_stats_inc(s_ib_ack_send_failure);
680 
681 		rds_ib_conn_error(ic->conn, "sending ack failed\n");
682 	} else
683 		rds_ib_stats_inc(s_ib_ack_sent);
684 }
685 
686 /*
687  * There are 3 ways of getting acknowledgements to the peer:
688  *  1.	We call rds_ib_attempt_ack from the recv completion handler
689  *	to send an ACK-only frame.
690  *	However, there can be only one such frame in the send queue
691  *	at any time, so we may have to postpone it.
692  *  2.	When another (data) packet is transmitted while there's
693  *	an ACK in the queue, we piggyback the ACK sequence number
694  *	on the data packet.
695  *  3.	If the ACK WR is done sending, we get called from the
696  *	send queue completion handler, and check whether there's
697  *	another ACK pending (postponed because the WR was on the
698  *	queue). If so, we transmit it.
699  *
700  * We maintain 2 variables:
701  *  -	i_ack_flags, which keeps track of whether the ACK WR
702  *	is currently in the send queue or not (IB_ACK_IN_FLIGHT)
703  *  -	i_ack_next, which is the last sequence number we received
704  *
705  * Potentially, send queue and receive queue handlers can run concurrently.
706  * It would be nice to not have to use a spinlock to synchronize things,
707  * but the one problem that rules this out is that 64bit updates are
708  * not atomic on all platforms. Things would be a lot simpler if
709  * we had atomic64 or maybe cmpxchg64 everywhere.
710  *
711  * Reconnecting complicates this picture just slightly. When we
712  * reconnect, we may be seeing duplicate packets. The peer
713  * is retransmitting them, because it hasn't seen an ACK for
714  * them. It is important that we ACK these.
715  *
716  * ACK mitigation adds a header flag "ACK_REQUIRED"; any packet with
717  * this flag set *MUST* be acknowledged immediately.
718  */
719 
720 /*
721  * When we get here, we're called from the recv queue handler.
722  * Check whether we ought to transmit an ACK.
723  */
724 void rds_ib_attempt_ack(struct rds_ib_connection *ic)
725 {
726 	unsigned int adv_credits;
727 
728 	if (!test_bit(IB_ACK_REQUESTED, &ic->i_ack_flags))
729 		return;
730 
731 	if (test_and_set_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags)) {
732 		rds_ib_stats_inc(s_ib_ack_send_delayed);
733 		return;
734 	}
735 
736 	/* Can we get a send credit? */
737 	if (!rds_ib_send_grab_credits(ic, 1, &adv_credits, 0, RDS_MAX_ADV_CREDIT)) {
738 		rds_ib_stats_inc(s_ib_tx_throttle);
739 		clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
740 		return;
741 	}
742 
743 	clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
744 	rds_ib_send_ack(ic, adv_credits);
745 }
746 
747 /*
748  * We get here from the send completion handler, when the
749  * adapter tells us the ACK frame was sent.
750  */
751 void rds_ib_ack_send_complete(struct rds_ib_connection *ic)
752 {
753 	clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
754 	rds_ib_attempt_ack(ic);
755 }
756 
757 /*
758  * This is called by the regular xmit code when it wants to piggyback
759  * an ACK on an outgoing frame.
760  */
761 u64 rds_ib_piggyb_ack(struct rds_ib_connection *ic)
762 {
763 	if (test_and_clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags))
764 		rds_ib_stats_inc(s_ib_ack_send_piggybacked);
765 	return rds_ib_get_ack(ic);
766 }
767 
768 /*
769  * It's kind of lame that we're copying from the posted receive pages into
770  * long-lived bitmaps.  We could have posted the bitmaps and rdma written into
771  * them.  But receiving new congestion bitmaps should be a *rare* event, so
772  * hopefully we won't need to invest that complexity in making it more
773  * efficient.  By copying we can share a simpler core with TCP which has to
774  * copy.
775  */
776 static void rds_ib_cong_recv(struct rds_connection *conn,
777 			      struct rds_ib_incoming *ibinc)
778 {
779 	struct rds_cong_map *map;
780 	unsigned int map_off;
781 	unsigned int map_page;
782 	struct rds_page_frag *frag;
783 	unsigned long frag_off;
784 	unsigned long to_copy;
785 	unsigned long copied;
786 	__le64 uncongested = 0;
787 	void *addr;
788 
789 	/* catch completely corrupt packets */
790 	if (be32_to_cpu(ibinc->ii_inc.i_hdr.h_len) != RDS_CONG_MAP_BYTES)
791 		return;
792 
793 	map = conn->c_fcong;
794 	map_page = 0;
795 	map_off = 0;
796 
797 	frag = list_entry(ibinc->ii_frags.next, struct rds_page_frag, f_item);
798 	frag_off = 0;
799 
800 	copied = 0;
801 
802 	while (copied < RDS_CONG_MAP_BYTES) {
803 		__le64 *src, *dst;
804 		unsigned int k;
805 
806 		to_copy = min(RDS_FRAG_SIZE - frag_off, PAGE_SIZE - map_off);
807 		BUG_ON(to_copy & 7); /* Must be 64bit aligned. */
808 
809 		addr = kmap_atomic(sg_page(&frag->f_sg));
810 
811 		src = addr + frag->f_sg.offset + frag_off;
812 		dst = (void *)map->m_page_addrs[map_page] + map_off;
813 		for (k = 0; k < to_copy; k += 8) {
814 			/* Record ports that became uncongested, ie
815 			 * bits that changed from 0 to 1. */
816 			uncongested |= ~(*src) & *dst;
817 			*dst++ = *src++;
818 		}
819 		kunmap_atomic(addr);
820 
821 		copied += to_copy;
822 
823 		map_off += to_copy;
824 		if (map_off == PAGE_SIZE) {
825 			map_off = 0;
826 			map_page++;
827 		}
828 
829 		frag_off += to_copy;
830 		if (frag_off == RDS_FRAG_SIZE) {
831 			frag = list_entry(frag->f_item.next,
832 					  struct rds_page_frag, f_item);
833 			frag_off = 0;
834 		}
835 	}
836 
837 	/* the congestion map is in little endian order */
838 	rds_cong_map_updated(map, le64_to_cpu(uncongested));
839 }
840 
841 static void rds_ib_process_recv(struct rds_connection *conn,
842 				struct rds_ib_recv_work *recv, u32 data_len,
843 				struct rds_ib_ack_state *state)
844 {
845 	struct rds_ib_connection *ic = conn->c_transport_data;
846 	struct rds_ib_incoming *ibinc = ic->i_ibinc;
847 	struct rds_header *ihdr, *hdr;
848 
849 	/* XXX shut down the connection if port 0,0 are seen? */
850 
851 	rdsdebug("ic %p ibinc %p recv %p byte len %u\n", ic, ibinc, recv,
852 		 data_len);
853 
854 	if (data_len < sizeof(struct rds_header)) {
855 		rds_ib_conn_error(conn, "incoming message "
856 		       "from %pI6c didn't include a "
857 		       "header, disconnecting and "
858 		       "reconnecting\n",
859 		       &conn->c_faddr);
860 		return;
861 	}
862 	data_len -= sizeof(struct rds_header);
863 
864 	ihdr = ic->i_recv_hdrs[recv - ic->i_recvs];
865 
866 	/* Validate the checksum. */
867 	if (!rds_message_verify_checksum(ihdr)) {
868 		rds_ib_conn_error(conn, "incoming message "
869 		       "from %pI6c has corrupted header - "
870 		       "forcing a reconnect\n",
871 		       &conn->c_faddr);
872 		rds_stats_inc(s_recv_drop_bad_checksum);
873 		return;
874 	}
875 
876 	/* Process the ACK sequence which comes with every packet */
877 	state->ack_recv = be64_to_cpu(ihdr->h_ack);
878 	state->ack_recv_valid = 1;
879 
880 	/* Process the credits update if there was one */
881 	if (ihdr->h_credit)
882 		rds_ib_send_add_credits(conn, ihdr->h_credit);
883 
884 	if (ihdr->h_sport == 0 && ihdr->h_dport == 0 && data_len == 0) {
885 		/* This is an ACK-only packet. The fact that it gets
886 		 * special treatment here is that historically, ACKs
887 		 * were rather special beasts.
888 		 */
889 		rds_ib_stats_inc(s_ib_ack_received);
890 
891 		/*
892 		 * Usually the frags make their way on to incs and are then freed as
893 		 * the inc is freed.  We don't go that route, so we have to drop the
894 		 * page ref ourselves.  We can't just leave the page on the recv
895 		 * because that confuses the dma mapping of pages and each recv's use
896 		 * of a partial page.
897 		 *
898 		 * FIXME: Fold this into the code path below.
899 		 */
900 		rds_ib_frag_free(ic, recv->r_frag);
901 		recv->r_frag = NULL;
902 		return;
903 	}
904 
905 	/*
906 	 * If we don't already have an inc on the connection then this
907 	 * fragment has a header and starts a message.. copy its header
908 	 * into the inc and save the inc so we can hang upcoming fragments
909 	 * off its list.
910 	 */
911 	if (!ibinc) {
912 		ibinc = recv->r_ibinc;
913 		recv->r_ibinc = NULL;
914 		ic->i_ibinc = ibinc;
915 
916 		hdr = &ibinc->ii_inc.i_hdr;
917 		ibinc->ii_inc.i_rx_lat_trace[RDS_MSG_RX_HDR] =
918 				local_clock();
919 		memcpy(hdr, ihdr, sizeof(*hdr));
920 		ic->i_recv_data_rem = be32_to_cpu(hdr->h_len);
921 		ibinc->ii_inc.i_rx_lat_trace[RDS_MSG_RX_START] =
922 				local_clock();
923 
924 		rdsdebug("ic %p ibinc %p rem %u flag 0x%x\n", ic, ibinc,
925 			 ic->i_recv_data_rem, hdr->h_flags);
926 	} else {
927 		hdr = &ibinc->ii_inc.i_hdr;
928 		/* We can't just use memcmp here; fragments of a
929 		 * single message may carry different ACKs */
930 		if (hdr->h_sequence != ihdr->h_sequence ||
931 		    hdr->h_len != ihdr->h_len ||
932 		    hdr->h_sport != ihdr->h_sport ||
933 		    hdr->h_dport != ihdr->h_dport) {
934 			rds_ib_conn_error(conn,
935 				"fragment header mismatch; forcing reconnect\n");
936 			return;
937 		}
938 	}
939 
940 	list_add_tail(&recv->r_frag->f_item, &ibinc->ii_frags);
941 	recv->r_frag = NULL;
942 
943 	if (ic->i_recv_data_rem > RDS_FRAG_SIZE)
944 		ic->i_recv_data_rem -= RDS_FRAG_SIZE;
945 	else {
946 		ic->i_recv_data_rem = 0;
947 		ic->i_ibinc = NULL;
948 
949 		if (ibinc->ii_inc.i_hdr.h_flags == RDS_FLAG_CONG_BITMAP) {
950 			rds_ib_cong_recv(conn, ibinc);
951 		} else {
952 			rds_recv_incoming(conn, &conn->c_faddr, &conn->c_laddr,
953 					  &ibinc->ii_inc, GFP_ATOMIC);
954 			state->ack_next = be64_to_cpu(hdr->h_sequence);
955 			state->ack_next_valid = 1;
956 		}
957 
958 		/* Evaluate the ACK_REQUIRED flag *after* we received
959 		 * the complete frame, and after bumping the next_rx
960 		 * sequence. */
961 		if (hdr->h_flags & RDS_FLAG_ACK_REQUIRED) {
962 			rds_stats_inc(s_recv_ack_required);
963 			state->ack_required = 1;
964 		}
965 
966 		rds_inc_put(&ibinc->ii_inc);
967 	}
968 }
969 
970 void rds_ib_recv_cqe_handler(struct rds_ib_connection *ic,
971 			     struct ib_wc *wc,
972 			     struct rds_ib_ack_state *state)
973 {
974 	struct rds_connection *conn = ic->conn;
975 	struct rds_ib_recv_work *recv;
976 
977 	rdsdebug("wc wr_id 0x%llx status %u (%s) byte_len %u imm_data %u\n",
978 		 (unsigned long long)wc->wr_id, wc->status,
979 		 ib_wc_status_msg(wc->status), wc->byte_len,
980 		 be32_to_cpu(wc->ex.imm_data));
981 
982 	rds_ib_stats_inc(s_ib_rx_cq_event);
983 	recv = &ic->i_recvs[rds_ib_ring_oldest(&ic->i_recv_ring)];
984 	ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1,
985 			DMA_FROM_DEVICE);
986 
987 	/* Also process recvs in connecting state because it is possible
988 	 * to get a recv completion _before_ the rdmacm ESTABLISHED
989 	 * event is processed.
990 	 */
991 	if (wc->status == IB_WC_SUCCESS) {
992 		rds_ib_process_recv(conn, recv, wc->byte_len, state);
993 	} else {
994 		/* We expect errors as the qp is drained during shutdown */
995 		if (rds_conn_up(conn) || rds_conn_connecting(conn))
996 			rds_ib_conn_error(conn, "recv completion on <%pI6c,%pI6c, %d> had status %u (%s), vendor err 0x%x, disconnecting and reconnecting\n",
997 					  &conn->c_laddr, &conn->c_faddr,
998 					  conn->c_tos, wc->status,
999 					  ib_wc_status_msg(wc->status),
1000 					  wc->vendor_err);
1001 	}
1002 
1003 	/* rds_ib_process_recv() doesn't always consume the frag, and
1004 	 * we might not have called it at all if the wc didn't indicate
1005 	 * success. We already unmapped the frag's pages, though, and
1006 	 * the following rds_ib_ring_free() call tells the refill path
1007 	 * that it will not find an allocated frag here. Make sure we
1008 	 * keep that promise by freeing a frag that's still on the ring.
1009 	 */
1010 	if (recv->r_frag) {
1011 		rds_ib_frag_free(ic, recv->r_frag);
1012 		recv->r_frag = NULL;
1013 	}
1014 	rds_ib_ring_free(&ic->i_recv_ring, 1);
1015 
1016 	/* If we ever end up with a really empty receive ring, we're
1017 	 * in deep trouble, as the sender will definitely see RNR
1018 	 * timeouts. */
1019 	if (rds_ib_ring_empty(&ic->i_recv_ring))
1020 		rds_ib_stats_inc(s_ib_rx_ring_empty);
1021 
1022 	if (rds_ib_ring_low(&ic->i_recv_ring)) {
1023 		rds_ib_recv_refill(conn, 0, GFP_NOWAIT | __GFP_NOWARN);
1024 		rds_ib_stats_inc(s_ib_rx_refill_from_cq);
1025 	}
1026 }
1027 
1028 int rds_ib_recv_path(struct rds_conn_path *cp)
1029 {
1030 	struct rds_connection *conn = cp->cp_conn;
1031 	struct rds_ib_connection *ic = conn->c_transport_data;
1032 
1033 	rdsdebug("conn %p\n", conn);
1034 	if (rds_conn_up(conn)) {
1035 		rds_ib_attempt_ack(ic);
1036 		rds_ib_recv_refill(conn, 0, GFP_KERNEL);
1037 		rds_ib_stats_inc(s_ib_rx_refill_from_thread);
1038 	}
1039 
1040 	return 0;
1041 }
1042 
1043 int rds_ib_recv_init(void)
1044 {
1045 	struct sysinfo si;
1046 	int ret = -ENOMEM;
1047 
1048 	/* Default to 30% of all available RAM for recv memory */
1049 	si_meminfo(&si);
1050 	rds_ib_sysctl_max_recv_allocation = si.totalram / 3 * PAGE_SIZE / RDS_FRAG_SIZE;
1051 
1052 	rds_ib_incoming_slab =
1053 		kmem_cache_create_usercopy("rds_ib_incoming",
1054 					   sizeof(struct rds_ib_incoming),
1055 					   0, SLAB_HWCACHE_ALIGN,
1056 					   offsetof(struct rds_ib_incoming,
1057 						    ii_inc.i_usercopy),
1058 					   sizeof(struct rds_inc_usercopy),
1059 					   NULL);
1060 	if (!rds_ib_incoming_slab)
1061 		goto out;
1062 
1063 	rds_ib_frag_slab = kmem_cache_create("rds_ib_frag",
1064 					sizeof(struct rds_page_frag),
1065 					0, SLAB_HWCACHE_ALIGN, NULL);
1066 	if (!rds_ib_frag_slab) {
1067 		kmem_cache_destroy(rds_ib_incoming_slab);
1068 		rds_ib_incoming_slab = NULL;
1069 	} else
1070 		ret = 0;
1071 out:
1072 	return ret;
1073 }
1074 
1075 void rds_ib_recv_exit(void)
1076 {
1077 	WARN_ON(atomic_read(&rds_ib_allocation));
1078 
1079 	kmem_cache_destroy(rds_ib_incoming_slab);
1080 	kmem_cache_destroy(rds_ib_frag_slab);
1081 }
1082