1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Handle vlserver selection and rotation.
3 *
4 * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #include <linux/kernel.h>
9 #include <linux/sched.h>
10 #include <linux/sched/signal.h>
11 #include "internal.h"
12 #include "afs_vl.h"
13
14 /*
15 * Begin an operation on a volume location server.
16 */
17 bool afs_begin_vlserver_operation(struct afs_vl_cursor *vc, struct afs_cell *cell,
18 struct key *key)
19 {
20 static atomic_t debug_ids;
21
22 memset(vc, 0, sizeof(*vc));
23 vc->cell = cell;
24 vc->key = key;
25 vc->cumul_error.error = -EDESTADDRREQ;
26 vc->nr_iterations = -1;
27
28 if (signal_pending(current)) {
29 vc->cumul_error.error = -EINTR;
30 vc->flags |= AFS_VL_CURSOR_STOP;
31 return false;
32 }
33
34 vc->debug_id = atomic_inc_return(&debug_ids);
35 return true;
36 }
37
38 /*
39 * Begin iteration through a server list, starting with the last used server if
40 * possible, or the last recorded good server if not.
41 */
42 static bool afs_start_vl_iteration(struct afs_vl_cursor *vc)
43 {
44 struct afs_cell *cell = vc->cell;
45 unsigned int dns_lookup_count;
46
47 if (cell->dns_source == DNS_RECORD_UNAVAILABLE ||
48 cell->dns_expiry <= ktime_get_real_seconds()) {
49 dns_lookup_count = smp_load_acquire(&cell->dns_lookup_count);
50 set_bit(AFS_CELL_FL_DO_LOOKUP, &cell->flags);
51 afs_queue_cell(cell, afs_cell_trace_get_queue_dns);
52
53 if (cell->dns_source == DNS_RECORD_UNAVAILABLE) {
54 if (wait_var_event_interruptible(
55 &cell->dns_lookup_count,
56 smp_load_acquire(&cell->dns_lookup_count)
57 != dns_lookup_count) < 0) {
58 vc->cumul_error.error = -ERESTARTSYS;
59 return false;
60 }
61 }
62
63 /* Status load is ordered after lookup counter load */
64 if (cell->dns_status == DNS_LOOKUP_GOT_NOT_FOUND) {
65 pr_warn("No record of cell %s\n", cell->name);
66 vc->cumul_error.error = -ENOENT;
67 return false;
68 }
69
70 if (cell->dns_source == DNS_RECORD_UNAVAILABLE) {
71 vc->cumul_error.error = -EDESTADDRREQ;
72 return false;
73 }
74 }
75
76 read_lock(&cell->vl_servers_lock);
77 vc->server_list = afs_get_vlserverlist(
78 rcu_dereference_protected(cell->vl_servers,
79 lockdep_is_held(&cell->vl_servers_lock)));
80 read_unlock(&cell->vl_servers_lock);
81 if (!vc->server_list->nr_servers)
82 return false;
83
84 vc->untried_servers = (1UL << vc->server_list->nr_servers) - 1;
85 vc->server_index = -1;
86 return true;
87 }
88
89 /*
90 * Select the vlserver to use. May be called multiple times to rotate
91 * through the vlservers.
92 */
93 bool afs_select_vlserver(struct afs_vl_cursor *vc)
94 {
95 struct afs_addr_list *alist = vc->alist;
96 struct afs_vlserver *vlserver;
97 unsigned long set, failed;
98 unsigned int rtt;
99 s32 abort_code = vc->call_abort_code;
100 int error = vc->call_error, i;
101
102 vc->nr_iterations++;
103
104 _enter("VC=%x+%x,%d{%lx},%d{%lx},%d,%d",
105 vc->debug_id, vc->nr_iterations, vc->server_index, vc->untried_servers,
106 vc->addr_index, vc->addr_tried,
107 error, abort_code);
108
109 if (vc->flags & AFS_VL_CURSOR_STOP) {
110 _leave(" = f [stopped]");
111 return false;
112 }
113
114 if (vc->nr_iterations == 0)
115 goto start;
116
117 WRITE_ONCE(alist->addrs[vc->addr_index].last_error, error);
118
119 /* Evaluate the result of the previous operation, if there was one. */
120 switch (error) {
121 default:
122 case 0:
123 /* Success or local failure. Stop. */
124 vc->cumul_error.error = error;
125 vc->flags |= AFS_VL_CURSOR_STOP;
126 _leave(" = f [okay/local %d]", vc->cumul_error.error);
127 return false;
128
129 case -ECONNABORTED:
130 /* The far side rejected the operation on some grounds. This
131 * might involve the server being busy or the volume having been moved.
132 */
133 switch (abort_code) {
134 case AFSVL_IO:
135 case AFSVL_BADVOLOPER:
136 case AFSVL_NOMEM:
137 /* The server went weird. */
138 afs_prioritise_error(&vc->cumul_error, -EREMOTEIO, abort_code);
139 //write_lock(&vc->cell->vl_servers_lock);
140 //vc->server_list->weird_mask |= 1 << vc->server_index;
141 //write_unlock(&vc->cell->vl_servers_lock);
142 goto next_server;
143
144 default:
145 afs_prioritise_error(&vc->cumul_error, error, abort_code);
146 goto failed;
147 }
148
149 case -ERFKILL:
150 case -EADDRNOTAVAIL:
151 case -ENETUNREACH:
152 case -EHOSTUNREACH:
153 case -EHOSTDOWN:
154 case -ECONNREFUSED:
155 case -ETIMEDOUT:
156 case -ETIME:
157 _debug("no conn %d", error);
158 afs_prioritise_error(&vc->cumul_error, error, 0);
159 goto iterate_address;
160
161 case -ECONNRESET:
162 _debug("call reset");
163 afs_prioritise_error(&vc->cumul_error, error, 0);
164 vc->flags |= AFS_VL_CURSOR_RETRY;
165 goto next_server;
166
167 case -EOPNOTSUPP:
168 _debug("notsupp");
169 goto next_server;
170 }
171
172 restart_from_beginning:
173 _debug("restart");
174 if (vc->call_responded &&
175 vc->addr_index != vc->alist->preferred &&
176 test_bit(alist->preferred, &vc->addr_tried))
177 WRITE_ONCE(alist->preferred, vc->addr_index);
178 afs_put_addrlist(alist, afs_alist_trace_put_vlrotate_restart);
179 alist = vc->alist = NULL;
180
181 afs_put_vlserverlist(vc->cell->net, vc->server_list);
182 vc->server_list = NULL;
183 if (vc->flags & AFS_VL_CURSOR_RETRIED)
184 goto failed;
185 vc->flags |= AFS_VL_CURSOR_RETRIED;
186 start:
187 _debug("start");
188 ASSERTCMP(alist, ==, NULL);
189
190 if (!afs_start_vl_iteration(vc))
191 goto failed;
192
193 error = afs_send_vl_probes(vc->cell->net, vc->key, vc->server_list);
194 if (error < 0) {
195 afs_prioritise_error(&vc->cumul_error, error, 0);
196 goto failed;
197 }
198
199 pick_server:
200 _debug("pick [%lx]", vc->untried_servers);
201 ASSERTCMP(alist, ==, NULL);
202
203 error = afs_wait_for_vl_probes(vc->server_list, vc->untried_servers);
204 if (error < 0) {
205 afs_prioritise_error(&vc->cumul_error, error, 0);
206 goto failed;
207 }
208
209 /* Pick the untried server with the lowest RTT. */
210 vc->server_index = vc->server_list->preferred;
211 if (test_bit(vc->server_index, &vc->untried_servers))
212 goto selected_server;
213
214 vc->server_index = -1;
215 rtt = UINT_MAX;
216 for (i = 0; i < vc->server_list->nr_servers; i++) {
217 struct afs_vlserver *s = vc->server_list->servers[i].server;
218
219 if (!test_bit(i, &vc->untried_servers) ||
220 !test_bit(AFS_VLSERVER_FL_RESPONDING, &s->flags))
221 continue;
222 if (s->probe.rtt <= rtt) {
223 vc->server_index = i;
224 rtt = s->probe.rtt;
225 }
226 }
227
228 if (vc->server_index == -1)
229 goto no_more_servers;
230
231 selected_server:
232 _debug("use %d", vc->server_index);
233 __clear_bit(vc->server_index, &vc->untried_servers);
234
235 /* We're starting on a different vlserver from the list. We need to
236 * check it, find its address list and probe its capabilities before we
237 * use it.
238 */
239 vlserver = vc->server_list->servers[vc->server_index].server;
240 vc->server = vlserver;
241
242 _debug("USING VLSERVER: %s", vlserver->name);
243
244 read_lock(&vlserver->lock);
245 alist = rcu_dereference_protected(vlserver->addresses,
246 lockdep_is_held(&vlserver->lock));
247 vc->alist = afs_get_addrlist(alist, afs_alist_trace_get_vlrotate_set);
248 read_unlock(&vlserver->lock);
249
250 vc->addr_tried = 0;
251 vc->addr_index = -1;
252
253 iterate_address:
254 /* Iterate over the current server's address list to try and find an
255 * address on which it will respond to us.
256 */
257 set = READ_ONCE(alist->responded);
258 failed = READ_ONCE(alist->probe_failed);
259 vc->addr_index = READ_ONCE(alist->preferred);
260
261 _debug("%lx-%lx-%lx,%d", set, failed, vc->addr_tried, vc->addr_index);
262
263 set &= ~(failed | vc->addr_tried);
264
265 if (!set)
266 goto next_server;
267
268 if (!test_bit(vc->addr_index, &set))
269 vc->addr_index = __ffs(set);
270
271 set_bit(vc->addr_index, &vc->addr_tried);
272 vc->alist = alist;
273
274 _debug("VL address %d/%d", vc->addr_index, alist->nr_addrs);
275
276 vc->call_responded = false;
277 _leave(" = t %pISpc", rxrpc_kernel_remote_addr(alist->addrs[vc->addr_index].peer));
278 return true;
279
280 next_server:
281 _debug("next");
282 ASSERT(alist);
283 if (vc->call_responded &&
284 vc->addr_index != alist->preferred &&
285 test_bit(alist->preferred, &vc->addr_tried))
286 WRITE_ONCE(alist->preferred, vc->addr_index);
287 afs_put_addrlist(alist, afs_alist_trace_put_vlrotate_next);
288 alist = vc->alist = NULL;
289 goto pick_server;
290
291 no_more_servers:
292 /* That's all the servers poked to no good effect. Try again if some
293 * of them were busy.
294 */
295 if (vc->flags & AFS_VL_CURSOR_RETRY)
296 goto restart_from_beginning;
297
298 for (i = 0; i < vc->server_list->nr_servers; i++) {
299 struct afs_vlserver *s = vc->server_list->servers[i].server;
300
301 if (test_bit(AFS_VLSERVER_FL_RESPONDING, &s->flags))
302 vc->cumul_error.responded = true;
303 afs_prioritise_error(&vc->cumul_error, READ_ONCE(s->probe.error),
304 s->probe.abort_code);
305 }
306
307 failed:
308 if (alist) {
309 if (vc->call_responded &&
310 vc->addr_index != alist->preferred &&
311 test_bit(alist->preferred, &vc->addr_tried))
312 WRITE_ONCE(alist->preferred, vc->addr_index);
313 afs_put_addrlist(alist, afs_alist_trace_put_vlrotate_fail);
314 alist = vc->alist = NULL;
315 }
316 vc->flags |= AFS_VL_CURSOR_STOP;
317 _leave(" = f [failed %d]", vc->cumul_error.error);
318 return false;
319 }
320
321 /*
322 * Dump cursor state in the case of the error being EDESTADDRREQ.
323 */
324 static void afs_vl_dump_edestaddrreq(const struct afs_vl_cursor *vc)
325 {
326 struct afs_cell *cell = vc->cell;
327 static int count;
328 int i;
329
330 if (!IS_ENABLED(CONFIG_AFS_DEBUG_CURSOR) || count > 3)
331 return;
332 count++;
333
334 rcu_read_lock();
335 pr_notice("EDESTADDR occurred\n");
336 pr_notice("CELL: %s err=%d\n", cell->name, cell->error);
337 pr_notice("DNS: src=%u st=%u lc=%x\n",
338 cell->dns_source, cell->dns_status, cell->dns_lookup_count);
339 pr_notice("VC: ut=%lx ix=%u ni=%hu fl=%hx err=%hd\n",
340 vc->untried_servers, vc->server_index, vc->nr_iterations,
341 vc->flags, vc->cumul_error.error);
342 pr_notice("VC: call er=%d ac=%d r=%u\n",
343 vc->call_error, vc->call_abort_code, vc->call_responded);
344
345 if (vc->server_list) {
346 const struct afs_vlserver_list *sl = vc->server_list;
347 pr_notice("VC: SL nr=%u ix=%u\n",
348 sl->nr_servers, sl->index);
349 for (i = 0; i < sl->nr_servers; i++) {
350 const struct afs_vlserver *s = sl->servers[i].server;
351 pr_notice("VC: server %s+%hu fl=%lx E=%hd\n",
352 s->name, s->port, s->flags, s->probe.error);
353 if (s->addresses) {
354 const struct afs_addr_list *a =
355 rcu_dereference(s->addresses);
356 pr_notice("VC: - nr=%u/%u/%u pf=%u\n",
357 a->nr_ipv4, a->nr_addrs, a->max_addrs,
358 a->preferred);
359 pr_notice("VC: - R=%lx F=%lx\n",
360 a->responded, a->probe_failed);
361 if (a == vc->alist)
362 pr_notice("VC: - current\n");
363 }
364 }
365 }
366
367 pr_notice("AC: t=%lx ax=%u\n", vc->addr_tried, vc->addr_index);
368 rcu_read_unlock();
369 }
370
371 /*
372 * Tidy up a volume location server cursor and unlock the vnode.
373 */
374 int afs_end_vlserver_operation(struct afs_vl_cursor *vc)
375 {
376 struct afs_net *net = vc->cell->net;
377
378 _enter("VC=%x+%x", vc->debug_id, vc->nr_iterations);
379
380 switch (vc->cumul_error.error) {
381 case -EDESTADDRREQ:
382 case -EADDRNOTAVAIL:
383 case -ENETUNREACH:
384 case -EHOSTUNREACH:
385 afs_vl_dump_edestaddrreq(vc);
386 break;
387 }
388
389 if (vc->alist) {
390 if (vc->call_responded &&
391 vc->addr_index != vc->alist->preferred &&
392 test_bit(vc->alist->preferred, &vc->addr_tried))
393 WRITE_ONCE(vc->alist->preferred, vc->addr_index);
394 afs_put_addrlist(vc->alist, afs_alist_trace_put_vlrotate_end);
395 vc->alist = NULL;
396 }
397 afs_put_vlserverlist(net, vc->server_list);
398 return vc->cumul_error.error;
399 }
400
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