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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 */
5a0e3ad6 33#include <linux/slab.h>
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34#include <linux/types.h>
35#include <linux/rbtree.h>
12ce2242 36#include <linux/bitops.h>
bc3b2d7f 37#include <linux/export.h>
c3b32404 38
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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);
8690bfa1 144 if (!map)
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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
8690bfa1 162 if (!ret) {
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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
8690bfa1 208 if (!(conn->c_lcong && conn->c_fcong))
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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);
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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 */
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238 queue_delayed_work(rds_wq,
239 &conn->c_path[0].cp_send_w, 0);
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240 }
241 }
242
243 spin_unlock_irqrestore(&rds_cong_lock, flags);
244}
245
246void rds_cong_map_updated(struct rds_cong_map *map, uint64_t portmask)
247{
248 rdsdebug("waking map %p for %pI4\n",
249 map, &map->m_addr);
250 rds_stats_inc(s_cong_update_received);
251 atomic_inc(&rds_cong_generation);
252 if (waitqueue_active(&map->m_waitq))
253 wake_up(&map->m_waitq);
254 if (waitqueue_active(&rds_poll_waitq))
255 wake_up_all(&rds_poll_waitq);
256
257 if (portmask && !list_empty(&rds_cong_monitor)) {
258 unsigned long flags;
259 struct rds_sock *rs;
260
261 read_lock_irqsave(&rds_cong_monitor_lock, flags);
262 list_for_each_entry(rs, &rds_cong_monitor, rs_cong_list) {
263 spin_lock(&rs->rs_lock);
264 rs->rs_cong_notify |= (rs->rs_cong_mask & portmask);
265 rs->rs_cong_mask &= ~portmask;
266 spin_unlock(&rs->rs_lock);
267 if (rs->rs_cong_notify)
268 rds_wake_sk_sleep(rs);
269 }
270 read_unlock_irqrestore(&rds_cong_monitor_lock, flags);
271 }
272}
616b757a 273EXPORT_SYMBOL_GPL(rds_cong_map_updated);
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274
275int rds_cong_updated_since(unsigned long *recent)
276{
277 unsigned long gen = atomic_read(&rds_cong_generation);
278
279 if (likely(*recent == gen))
280 return 0;
281 *recent = gen;
282 return 1;
283}
284
285/*
286 * We're called under the locking that protects the sockets receive buffer
287 * consumption. This makes it a lot easier for the caller to only call us
288 * when it knows that an existing set bit needs to be cleared, and vice versa.
289 * We can't block and we need to deal with concurrent sockets working against
290 * the same per-address map.
291 */
292void rds_cong_set_bit(struct rds_cong_map *map, __be16 port)
293{
294 unsigned long i;
295 unsigned long off;
296
297 rdsdebug("setting congestion for %pI4:%u in map %p\n",
298 &map->m_addr, ntohs(port), map);
299
300 i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
301 off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
302
e47db94e 303 set_bit_le(off, (void *)map->m_page_addrs[i]);
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304}
305
306void rds_cong_clear_bit(struct rds_cong_map *map, __be16 port)
307{
308 unsigned long i;
309 unsigned long off;
310
311 rdsdebug("clearing congestion for %pI4:%u in map %p\n",
312 &map->m_addr, ntohs(port), map);
313
314 i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
315 off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
316
e47db94e 317 clear_bit_le(off, (void *)map->m_page_addrs[i]);
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318}
319
320static int rds_cong_test_bit(struct rds_cong_map *map, __be16 port)
321{
322 unsigned long i;
323 unsigned long off;
324
325 i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
326 off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
327
e1dc1c81 328 return test_bit_le(off, (void *)map->m_page_addrs[i]);
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329}
330
331void rds_cong_add_socket(struct rds_sock *rs)
332{
333 unsigned long flags;
334
335 write_lock_irqsave(&rds_cong_monitor_lock, flags);
336 if (list_empty(&rs->rs_cong_list))
337 list_add(&rs->rs_cong_list, &rds_cong_monitor);
338 write_unlock_irqrestore(&rds_cong_monitor_lock, flags);
339}
340
341void rds_cong_remove_socket(struct rds_sock *rs)
342{
343 unsigned long flags;
344 struct rds_cong_map *map;
345
346 write_lock_irqsave(&rds_cong_monitor_lock, flags);
347 list_del_init(&rs->rs_cong_list);
348 write_unlock_irqrestore(&rds_cong_monitor_lock, flags);
349
350 /* update congestion map for now-closed port */
351 spin_lock_irqsave(&rds_cong_lock, flags);
352 map = rds_cong_tree_walk(rs->rs_bound_addr, NULL);
353 spin_unlock_irqrestore(&rds_cong_lock, flags);
354
355 if (map && rds_cong_test_bit(map, rs->rs_bound_port)) {
356 rds_cong_clear_bit(map, rs->rs_bound_port);
357 rds_cong_queue_updates(map);
358 }
359}
360
361int rds_cong_wait(struct rds_cong_map *map, __be16 port, int nonblock,
362 struct rds_sock *rs)
363{
364 if (!rds_cong_test_bit(map, port))
365 return 0;
366 if (nonblock) {
367 if (rs && rs->rs_cong_monitor) {
368 unsigned long flags;
369
370 /* It would have been nice to have an atomic set_bit on
371 * a uint64_t. */
372 spin_lock_irqsave(&rs->rs_lock, flags);
373 rs->rs_cong_mask |= RDS_CONG_MONITOR_MASK(ntohs(port));
374 spin_unlock_irqrestore(&rs->rs_lock, flags);
375
376 /* Test again - a congestion update may have arrived in
377 * the meantime. */
378 if (!rds_cong_test_bit(map, port))
379 return 0;
380 }
381 rds_stats_inc(s_cong_send_error);
382 return -ENOBUFS;
383 }
384
385 rds_stats_inc(s_cong_send_blocked);
386 rdsdebug("waiting on map %p for port %u\n", map, be16_to_cpu(port));
387
388 return wait_event_interruptible(map->m_waitq,
389 !rds_cong_test_bit(map, port));
390}
391
392void rds_cong_exit(void)
393{
394 struct rb_node *node;
395 struct rds_cong_map *map;
396 unsigned long i;
397
398 while ((node = rb_first(&rds_cong_tree))) {
399 map = rb_entry(node, struct rds_cong_map, m_rb_node);
400 rdsdebug("freeing map %p\n", map);
401 rb_erase(&map->m_rb_node, &rds_cong_tree);
402 for (i = 0; i < RDS_CONG_MAP_PAGES && map->m_page_addrs[i]; i++)
403 free_page(map->m_page_addrs[i]);
404 kfree(map);
405 }
406}
407
408/*
409 * Allocate a RDS message containing a congestion update.
410 */
411struct rds_message *rds_cong_update_alloc(struct rds_connection *conn)
412{
413 struct rds_cong_map *map = conn->c_lcong;
414 struct rds_message *rm;
415
416 rm = rds_message_map_pages(map->m_page_addrs, RDS_CONG_MAP_BYTES);
417 if (!IS_ERR(rm))
418 rm->m_inc.i_hdr.h_flags = RDS_FLAG_CONG_BITMAP;
419
420 return rm;
421}