1/*
2 * Copyright (c) 2007 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/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(__be32 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		parent = *p;
113		map = rb_entry(parent, struct rds_cong_map, m_rb_node);
114
115		if (addr < map->m_addr)
116			p = &(*p)->rb_left;
117		else if (addr > map->m_addr)
118			p = &(*p)->rb_right;
119		else
120			return map;
121	}
122
123	if (insert) {
124		rb_link_node(&insert->m_rb_node, parent, p);
125		rb_insert_color(&insert->m_rb_node, &rds_cong_tree);
126	}
127	return NULL;
128}
129
130/*
131 * There is only ever one bitmap for any address.  Connections try and allocate
132 * these bitmaps in the process getting pointers to them.  The bitmaps are only
133 * ever freed as the module is removed after all connections have been freed.
134 */
135static struct rds_cong_map *rds_cong_from_addr(__be32 addr)
136{
137	struct rds_cong_map *map;
138	struct rds_cong_map *ret = NULL;
139	unsigned long zp;
140	unsigned long i;
141	unsigned long flags;
142
143	map = kzalloc(sizeof(struct rds_cong_map), GFP_KERNEL);
144	if (!map)
145		return NULL;
146
147	map->m_addr = addr;
148	init_waitqueue_head(&map->m_waitq);
149	INIT_LIST_HEAD(&map->m_conn_list);
150
151	for (i = 0; i < RDS_CONG_MAP_PAGES; i++) {
152		zp = get_zeroed_page(GFP_KERNEL);
153		if (zp == 0)
154			goto out;
155		map->m_page_addrs[i] = zp;
156	}
157
158	spin_lock_irqsave(&rds_cong_lock, flags);
159	ret = rds_cong_tree_walk(addr, map);
160	spin_unlock_irqrestore(&rds_cong_lock, flags);
161
162	if (!ret) {
163		ret = map;
164		map = NULL;
165	}
166
167out:
168	if (map) {
169		for (i = 0; i < RDS_CONG_MAP_PAGES && map->m_page_addrs[i]; i++)
170			free_page(map->m_page_addrs[i]);
171		kfree(map);
172	}
173
174	rdsdebug("map %p for addr %x\n", ret, be32_to_cpu(addr));
175
176	return ret;
177}
178
179/*
180 * Put the conn on its local map's list.  This is called when the conn is
181 * really added to the hash.  It's nested under the rds_conn_lock, sadly.
182 */
183void rds_cong_add_conn(struct rds_connection *conn)
184{
185	unsigned long flags;
186
187	rdsdebug("conn %p now on map %p\n", conn, conn->c_lcong);
188	spin_lock_irqsave(&rds_cong_lock, flags);
189	list_add_tail(&conn->c_map_item, &conn->c_lcong->m_conn_list);
190	spin_unlock_irqrestore(&rds_cong_lock, flags);
191}
192
193void rds_cong_remove_conn(struct rds_connection *conn)
194{
195	unsigned long flags;
196
197	rdsdebug("removing conn %p from map %p\n", conn, conn->c_lcong);
198	spin_lock_irqsave(&rds_cong_lock, flags);
199	list_del_init(&conn->c_map_item);
200	spin_unlock_irqrestore(&rds_cong_lock, flags);
201}
202
203int rds_cong_get_maps(struct rds_connection *conn)
204{
205	conn->c_lcong = rds_cong_from_addr(conn->c_laddr);
206	conn->c_fcong = rds_cong_from_addr(conn->c_faddr);
207
208	if (!(conn->c_lcong && conn->c_fcong))
209		return -ENOMEM;
210
211	return 0;
212}
213
214void rds_cong_queue_updates(struct rds_cong_map *map)
215{
216	struct rds_connection *conn;
217	unsigned long flags;
218
219	spin_lock_irqsave(&rds_cong_lock, flags);
220
221	list_for_each_entry(conn, &map->m_conn_list, c_map_item) {
222		if (!test_and_set_bit(0, &conn->c_map_queued)) {
223			rds_stats_inc(s_cong_update_queued);
224			/* We cannot inline the call to rds_send_xmit() here
225			 * for two reasons (both pertaining to a TCP transport):
226			 * 1. When we get here from the receive path, we
227			 *    are already holding the sock_lock (held by
228			 *    tcp_v4_rcv()). So inlining calls to
229			 *    tcp_setsockopt and/or tcp_sendmsg will deadlock
230			 *    when it tries to get the sock_lock())
231			 * 2. Interrupts are masked so that we can mark the
232			 *    the port congested from both send and recv paths.
233			 *    (See comment around declaration of rdc_cong_lock).
234			 *    An attempt to get the sock_lock() here will
235			 *    therefore trigger warnings.
236			 * Defer the xmit to rds_send_worker() instead.
237			 */
238			queue_delayed_work(rds_wq, &conn->c_send_w, 0);
239		}
240	}
241
242	spin_unlock_irqrestore(&rds_cong_lock, flags);
243}
244
245void rds_cong_map_updated(struct rds_cong_map *map, uint64_t portmask)
246{
247	rdsdebug("waking map %p for %pI4\n",
248	  map, &map->m_addr);
249	rds_stats_inc(s_cong_update_received);
250	atomic_inc(&rds_cong_generation);
251	if (waitqueue_active(&map->m_waitq))
252		wake_up(&map->m_waitq);
253	if (waitqueue_active(&rds_poll_waitq))
254		wake_up_all(&rds_poll_waitq);
255
256	if (portmask && !list_empty(&rds_cong_monitor)) {
257		unsigned long flags;
258		struct rds_sock *rs;
259
260		read_lock_irqsave(&rds_cong_monitor_lock, flags);
261		list_for_each_entry(rs, &rds_cong_monitor, rs_cong_list) {
262			spin_lock(&rs->rs_lock);
263			rs->rs_cong_notify |= (rs->rs_cong_mask & portmask);
264			rs->rs_cong_mask &= ~portmask;
265			spin_unlock(&rs->rs_lock);
266			if (rs->rs_cong_notify)
267				rds_wake_sk_sleep(rs);
268		}
269		read_unlock_irqrestore(&rds_cong_monitor_lock, flags);
270	}
271}
272EXPORT_SYMBOL_GPL(rds_cong_map_updated);
273
274int rds_cong_updated_since(unsigned long *recent)
275{
276	unsigned long gen = atomic_read(&rds_cong_generation);
277
278	if (likely(*recent == gen))
279		return 0;
280	*recent = gen;
281	return 1;
282}
283
284/*
285 * We're called under the locking that protects the sockets receive buffer
286 * consumption.  This makes it a lot easier for the caller to only call us
287 * when it knows that an existing set bit needs to be cleared, and vice versa.
288 * We can't block and we need to deal with concurrent sockets working against
289 * the same per-address map.
290 */
291void rds_cong_set_bit(struct rds_cong_map *map, __be16 port)
292{
293	unsigned long i;
294	unsigned long off;
295
296	rdsdebug("setting congestion for %pI4:%u in map %p\n",
297	  &map->m_addr, ntohs(port), map);
298
299	i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
300	off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
301
302	__set_bit_le(off, (void *)map->m_page_addrs[i]);
303}
304
305void rds_cong_clear_bit(struct rds_cong_map *map, __be16 port)
306{
307	unsigned long i;
308	unsigned long off;
309
310	rdsdebug("clearing congestion for %pI4:%u in map %p\n",
311	  &map->m_addr, ntohs(port), map);
312
313	i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
314	off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
315
316	__clear_bit_le(off, (void *)map->m_page_addrs[i]);
317}
318
319static int rds_cong_test_bit(struct rds_cong_map *map, __be16 port)
320{
321	unsigned long i;
322	unsigned long off;
323
324	i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
325	off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
326
327	return test_bit_le(off, (void *)map->m_page_addrs[i]);
328}
329
330void rds_cong_add_socket(struct rds_sock *rs)
331{
332	unsigned long flags;
333
334	write_lock_irqsave(&rds_cong_monitor_lock, flags);
335	if (list_empty(&rs->rs_cong_list))
336		list_add(&rs->rs_cong_list, &rds_cong_monitor);
337	write_unlock_irqrestore(&rds_cong_monitor_lock, flags);
338}
339
340void rds_cong_remove_socket(struct rds_sock *rs)
341{
342	unsigned long flags;
343	struct rds_cong_map *map;
344
345	write_lock_irqsave(&rds_cong_monitor_lock, flags);
346	list_del_init(&rs->rs_cong_list);
347	write_unlock_irqrestore(&rds_cong_monitor_lock, flags);
348
349	/* update congestion map for now-closed port */
350	spin_lock_irqsave(&rds_cong_lock, flags);
351	map = rds_cong_tree_walk(rs->rs_bound_addr, NULL);
352	spin_unlock_irqrestore(&rds_cong_lock, flags);
353
354	if (map && rds_cong_test_bit(map, rs->rs_bound_port)) {
355		rds_cong_clear_bit(map, rs->rs_bound_port);
356		rds_cong_queue_updates(map);
357	}
358}
359
360int rds_cong_wait(struct rds_cong_map *map, __be16 port, int nonblock,
361		  struct rds_sock *rs)
362{
363	if (!rds_cong_test_bit(map, port))
364		return 0;
365	if (nonblock) {
366		if (rs && rs->rs_cong_monitor) {
367			unsigned long flags;
368
369			/* It would have been nice to have an atomic set_bit on
370			 * a uint64_t. */
371			spin_lock_irqsave(&rs->rs_lock, flags);
372			rs->rs_cong_mask |= RDS_CONG_MONITOR_MASK(ntohs(port));
373			spin_unlock_irqrestore(&rs->rs_lock, flags);
374
375			/* Test again - a congestion update may have arrived in
376			 * the meantime. */
377			if (!rds_cong_test_bit(map, port))
378				return 0;
379		}
380		rds_stats_inc(s_cong_send_error);
381		return -ENOBUFS;
382	}
383
384	rds_stats_inc(s_cong_send_blocked);
385	rdsdebug("waiting on map %p for port %u\n", map, be16_to_cpu(port));
386
387	return wait_event_interruptible(map->m_waitq,
388					!rds_cong_test_bit(map, port));
389}
390
391void rds_cong_exit(void)
392{
393	struct rb_node *node;
394	struct rds_cong_map *map;
395	unsigned long i;
396
397	while ((node = rb_first(&rds_cong_tree))) {
398		map = rb_entry(node, struct rds_cong_map, m_rb_node);
399		rdsdebug("freeing map %p\n", map);
400		rb_erase(&map->m_rb_node, &rds_cong_tree);
401		for (i = 0; i < RDS_CONG_MAP_PAGES && map->m_page_addrs[i]; i++)
402			free_page(map->m_page_addrs[i]);
403		kfree(map);
404	}
405}
406
407/*
408 * Allocate a RDS message containing a congestion update.
409 */
410struct rds_message *rds_cong_update_alloc(struct rds_connection *conn)
411{
412	struct rds_cong_map *map = conn->c_lcong;
413	struct rds_message *rm;
414
415	rm = rds_message_map_pages(map->m_page_addrs, RDS_CONG_MAP_BYTES);
416	if (!IS_ERR(rm))
417		rm->m_inc.i_hdr.h_flags = RDS_FLAG_CONG_BITMAP;
418
419	return rm;
420}
421