projects/linux·blob master · refs

428 lines · 12.8 KiB

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_obj(struct rds_cong_map);
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(cp->cp_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 (wq_has_sleeper(&map->m_waitq))
260 wake_up(&map->m_waitq);
261 if (wq_has_sleeper(&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}