1/*
2 * Copyright (c) 2007, 2017 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/slab.h>
34#include <linux/types.h>
35#include <linux/rbtree.h>
36#include <linux/bitops.h>
37#include <linux/export.h>
38
39#include "rds.h"
40
41/*
42 * This file implements the receive side of the unconventional congestion
43 * management in RDS.
44 *
45 * Messages waiting in the receive queue on the receiving socket are accounted
46 * against the sockets SO_RCVBUF option value.  Only the payload bytes in the
47 * message are accounted for.  If the number of bytes queued equals or exceeds
48 * rcvbuf then the socket is congested.  All sends attempted to this socket's
49 * address should return block or return -EWOULDBLOCK.
50 *
51 * Applications are expected to be reasonably tuned such that this situation
52 * very rarely occurs.  An application encountering this "back-pressure" is
53 * considered a bug.
54 *
55 * This is implemented by having each node maintain bitmaps which indicate
56 * which ports on bound addresses are congested.  As the bitmap changes it is
57 * sent through all the connections which terminate in the local address of the
58 * bitmap which changed.
59 *
60 * The bitmaps are allocated as connections are brought up.  This avoids
61 * allocation in the interrupt handling path which queues messages on sockets.
62 * The dense bitmaps let transports send the entire bitmap on any bitmap change
63 * reasonably efficiently.  This is much easier to implement than some
64 * finer-grained communication of per-port congestion.  The sender does a very
65 * inexpensive bit test to test if the port it's about to send to is congested
66 * or not.
67 */
68
69/*
70 * Interaction with poll is a tad tricky. We want all processes stuck in
71 * poll to wake up and check whether a congested destination became uncongested.
72 * The really sad thing is we have no idea which destinations the application
73 * wants to send to - we don't even know which rds_connections are involved.
74 * So until we implement a more flexible rds poll interface, we have to make
75 * do with this:
76 * We maintain a global counter that is incremented each time a congestion map
77 * update is received. Each rds socket tracks this value, and if rds_poll
78 * finds that the saved generation number is smaller than the global generation
79 * number, it wakes up the process.
80 */
81static atomic_t		rds_cong_generation = ATOMIC_INIT(0);
82
83/*
84 * Congestion monitoring
85 */
86static LIST_HEAD(rds_cong_monitor);
87static DEFINE_RWLOCK(rds_cong_monitor_lock);
88
89/*
90 * Yes, a global lock.  It's used so infrequently that it's worth keeping it
91 * global to simplify the locking.  It's only used in the following
92 * circumstances:
93 *
94 *  - on connection buildup to associate a conn with its maps
95 *  - on map changes to inform conns of a new map to send
96 *
97 *  It's sadly ordered under the socket callback lock and the connection lock.
98 *  Receive paths can mark ports congested from interrupt context so the
99 *  lock masks interrupts.
100 */
101static DEFINE_SPINLOCK(rds_cong_lock);
102static struct rb_root rds_cong_tree = RB_ROOT;
103
104static struct rds_cong_map *rds_cong_tree_walk(const struct in6_addr *addr,
105					       struct rds_cong_map *insert)
106{
107	struct rb_node **p = &rds_cong_tree.rb_node;
108	struct rb_node *parent = NULL;
109	struct rds_cong_map *map;
110
111	while (*p) {
112		int diff;
113
114		parent = *p;
115		map = rb_entry(parent, struct rds_cong_map, m_rb_node);
116
117		diff = rds_addr_cmp(addr, &map->m_addr);
118		if (diff < 0)
119			p = &(*p)->rb_left;
120		else if (diff > 0)
121			p = &(*p)->rb_right;
122		else
123			return map;
124	}
125
126	if (insert) {
127		rb_link_node(&insert->m_rb_node, parent, p);
128		rb_insert_color(&insert->m_rb_node, &rds_cong_tree);
129	}
130	return NULL;
131}
132
133/*
134 * There is only ever one bitmap for any address.  Connections try and allocate
135 * these bitmaps in the process getting pointers to them.  The bitmaps are only
136 * ever freed as the module is removed after all connections have been freed.
137 */
138static struct rds_cong_map *rds_cong_from_addr(const struct in6_addr *addr)
139{
140	struct rds_cong_map *map;
141	struct rds_cong_map *ret = NULL;
142	unsigned long zp;
143	unsigned long i;
144	unsigned long flags;
145
146	map = kzalloc(sizeof(struct rds_cong_map), GFP_KERNEL);
147	if (!map)
148		return NULL;
149
150	map->m_addr = *addr;
151	init_waitqueue_head(&map->m_waitq);
152	INIT_LIST_HEAD(&map->m_conn_list);
153
154	for (i = 0; i < RDS_CONG_MAP_PAGES; i++) {
155		zp = get_zeroed_page(GFP_KERNEL);
156		if (zp == 0)
157			goto out;
158		map->m_page_addrs[i] = zp;
159	}
160
161	spin_lock_irqsave(&rds_cong_lock, flags);
162	ret = rds_cong_tree_walk(addr, map);
163	spin_unlock_irqrestore(&rds_cong_lock, flags);
164
165	if (!ret) {
166		ret = map;
167		map = NULL;
168	}
169
170out:
171	if (map) {
172		for (i = 0; i < RDS_CONG_MAP_PAGES && map->m_page_addrs[i]; i++)
173			free_page(map->m_page_addrs[i]);
174		kfree(map);
175	}
176
177	rdsdebug("map %p for addr %pI6c\n", ret, addr);
178
179	return ret;
180}
181
182/*
183 * Put the conn on its local map's list.  This is called when the conn is
184 * really added to the hash.  It's nested under the rds_conn_lock, sadly.
185 */
186void rds_cong_add_conn(struct rds_connection *conn)
187{
188	unsigned long flags;
189
190	rdsdebug("conn %p now on map %p\n", conn, conn->c_lcong);
191	spin_lock_irqsave(&rds_cong_lock, flags);
192	list_add_tail(&conn->c_map_item, &conn->c_lcong->m_conn_list);
193	spin_unlock_irqrestore(&rds_cong_lock, flags);
194}
195
196void rds_cong_remove_conn(struct rds_connection *conn)
197{
198	unsigned long flags;
199
200	rdsdebug("removing conn %p from map %p\n", conn, conn->c_lcong);
201	spin_lock_irqsave(&rds_cong_lock, flags);
202	list_del_init(&conn->c_map_item);
203	spin_unlock_irqrestore(&rds_cong_lock, flags);
204}
205
206int rds_cong_get_maps(struct rds_connection *conn)
207{
208	conn->c_lcong = rds_cong_from_addr(&conn->c_laddr);
209	conn->c_fcong = rds_cong_from_addr(&conn->c_faddr);
210
211	if (!(conn->c_lcong && conn->c_fcong))
212		return -ENOMEM;
213
214	return 0;
215}
216
217void rds_cong_queue_updates(struct rds_cong_map *map)
218{
219	struct rds_connection *conn;
220	unsigned long flags;
221
222	spin_lock_irqsave(&rds_cong_lock, flags);
223
224	list_for_each_entry(conn, &map->m_conn_list, c_map_item) {
225		struct rds_conn_path *cp = &conn->c_path[0];
226
227		rcu_read_lock();
228		if (!test_and_set_bit(0, &conn->c_map_queued) &&
229		    !rds_destroy_pending(cp->cp_conn)) {
230			rds_stats_inc(s_cong_update_queued);
231			/* We cannot inline the call to rds_send_xmit() here
232			 * for two reasons (both pertaining to a TCP transport):
233			 * 1. When we get here from the receive path, we
234			 *    are already holding the sock_lock (held by
235			 *    tcp_v4_rcv()). So inlining calls to
236			 *    tcp_setsockopt and/or tcp_sendmsg will deadlock
237			 *    when it tries to get the sock_lock())
238			 * 2. Interrupts are masked so that we can mark the
239			 *    port congested from both send and recv paths.
240			 *    (See comment around declaration of rdc_cong_lock).
241			 *    An attempt to get the sock_lock() here will
242			 *    therefore trigger warnings.
243			 * Defer the xmit to rds_send_worker() instead.
244			 */
245			queue_delayed_work(rds_wq, &cp->cp_send_w, 0);
246		}
247		rcu_read_unlock();
248	}
249
250	spin_unlock_irqrestore(&rds_cong_lock, flags);
251}
252
253void rds_cong_map_updated(struct rds_cong_map *map, uint64_t portmask)
254{
255	rdsdebug("waking map %p for %pI4\n",
256	  map, &map->m_addr);
257	rds_stats_inc(s_cong_update_received);
258	atomic_inc(&rds_cong_generation);
259	if (waitqueue_active(&map->m_waitq))
260		wake_up(&map->m_waitq);
261	if (waitqueue_active(&rds_poll_waitq))
262		wake_up_all(&rds_poll_waitq);
263
264	if (portmask && !list_empty(&rds_cong_monitor)) {
265		unsigned long flags;
266		struct rds_sock *rs;
267
268		read_lock_irqsave(&rds_cong_monitor_lock, flags);
269		list_for_each_entry(rs, &rds_cong_monitor, rs_cong_list) {
270			spin_lock(&rs->rs_lock);
271			rs->rs_cong_notify |= (rs->rs_cong_mask & portmask);
272			rs->rs_cong_mask &= ~portmask;
273			spin_unlock(&rs->rs_lock);
274			if (rs->rs_cong_notify)
275				rds_wake_sk_sleep(rs);
276		}
277		read_unlock_irqrestore(&rds_cong_monitor_lock, flags);
278	}
279}
280EXPORT_SYMBOL_GPL(rds_cong_map_updated);
281
282int rds_cong_updated_since(unsigned long *recent)
283{
284	unsigned long gen = atomic_read(&rds_cong_generation);
285
286	if (likely(*recent == gen))
287		return 0;
288	*recent = gen;
289	return 1;
290}
291
292/*
293 * We're called under the locking that protects the sockets receive buffer
294 * consumption.  This makes it a lot easier for the caller to only call us
295 * when it knows that an existing set bit needs to be cleared, and vice versa.
296 * We can't block and we need to deal with concurrent sockets working against
297 * the same per-address map.
298 */
299void rds_cong_set_bit(struct rds_cong_map *map, __be16 port)
300{
301	unsigned long i;
302	unsigned long off;
303
304	rdsdebug("setting congestion for %pI4:%u in map %p\n",
305	  &map->m_addr, ntohs(port), map);
306
307	i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
308	off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
309
310	set_bit_le(off, (void *)map->m_page_addrs[i]);
311}
312
313void rds_cong_clear_bit(struct rds_cong_map *map, __be16 port)
314{
315	unsigned long i;
316	unsigned long off;
317
318	rdsdebug("clearing congestion for %pI4:%u in map %p\n",
319	  &map->m_addr, ntohs(port), map);
320
321	i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
322	off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
323
324	clear_bit_le(off, (void *)map->m_page_addrs[i]);
325}
326
327static int rds_cong_test_bit(struct rds_cong_map *map, __be16 port)
328{
329	unsigned long i;
330	unsigned long off;
331
332	i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
333	off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
334
335	return test_bit_le(off, (void *)map->m_page_addrs[i]);
336}
337
338void rds_cong_add_socket(struct rds_sock *rs)
339{
340	unsigned long flags;
341
342	write_lock_irqsave(&rds_cong_monitor_lock, flags);
343	if (list_empty(&rs->rs_cong_list))
344		list_add(&rs->rs_cong_list, &rds_cong_monitor);
345	write_unlock_irqrestore(&rds_cong_monitor_lock, flags);
346}
347
348void rds_cong_remove_socket(struct rds_sock *rs)
349{
350	unsigned long flags;
351	struct rds_cong_map *map;
352
353	write_lock_irqsave(&rds_cong_monitor_lock, flags);
354	list_del_init(&rs->rs_cong_list);
355	write_unlock_irqrestore(&rds_cong_monitor_lock, flags);
356
357	/* update congestion map for now-closed port */
358	spin_lock_irqsave(&rds_cong_lock, flags);
359	map = rds_cong_tree_walk(&rs->rs_bound_addr, NULL);
360	spin_unlock_irqrestore(&rds_cong_lock, flags);
361
362	if (map && rds_cong_test_bit(map, rs->rs_bound_port)) {
363		rds_cong_clear_bit(map, rs->rs_bound_port);
364		rds_cong_queue_updates(map);
365	}
366}
367
368int rds_cong_wait(struct rds_cong_map *map, __be16 port, int nonblock,
369		  struct rds_sock *rs)
370{
371	if (!rds_cong_test_bit(map, port))
372		return 0;
373	if (nonblock) {
374		if (rs && rs->rs_cong_monitor) {
375			unsigned long flags;
376
377			/* It would have been nice to have an atomic set_bit on
378			 * a uint64_t. */
379			spin_lock_irqsave(&rs->rs_lock, flags);
380			rs->rs_cong_mask |= RDS_CONG_MONITOR_MASK(ntohs(port));
381			spin_unlock_irqrestore(&rs->rs_lock, flags);
382
383			/* Test again - a congestion update may have arrived in
384			 * the meantime. */
385			if (!rds_cong_test_bit(map, port))
386				return 0;
387		}
388		rds_stats_inc(s_cong_send_error);
389		return -ENOBUFS;
390	}
391
392	rds_stats_inc(s_cong_send_blocked);
393	rdsdebug("waiting on map %p for port %u\n", map, be16_to_cpu(port));
394
395	return wait_event_interruptible(map->m_waitq,
396					!rds_cong_test_bit(map, port));
397}
398
399void rds_cong_exit(void)
400{
401	struct rb_node *node;
402	struct rds_cong_map *map;
403	unsigned long i;
404
405	while ((node = rb_first(&rds_cong_tree))) {
406		map = rb_entry(node, struct rds_cong_map, m_rb_node);
407		rdsdebug("freeing map %p\n", map);
408		rb_erase(&map->m_rb_node, &rds_cong_tree);
409		for (i = 0; i < RDS_CONG_MAP_PAGES && map->m_page_addrs[i]; i++)
410			free_page(map->m_page_addrs[i]);
411		kfree(map);
412	}
413}
414
415/*
416 * Allocate a RDS message containing a congestion update.
417 */
418struct rds_message *rds_cong_update_alloc(struct rds_connection *conn)
419{
420	struct rds_cong_map *map = conn->c_lcong;
421	struct rds_message *rm;
422
423	rm = rds_message_map_pages(map->m_page_addrs, RDS_CONG_MAP_BYTES);
424	if (!IS_ERR(rm))
425		rm->m_inc.i_hdr.h_flags = RDS_FLAG_CONG_BITMAP;
426
427	return rm;
428}
429