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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* Handle fileserver selection and rotation.
3 *
4 * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#include <linux/kernel.h>
9#include <linux/slab.h>
10#include <linux/fs.h>
11#include <linux/sched.h>
12#include <linux/delay.h>
13#include <linux/sched/signal.h>
14#include "internal.h"
15#include "afs_fs.h"
16
17/*
18 * Begin iteration through a server list, starting with the vnode's last used
19 * server if possible, or the last recorded good server if not.
20 */
21static bool afs_start_fs_iteration(struct afs_operation *op,
22 struct afs_vnode *vnode)
23{
24 struct afs_server *server;
25 void *cb_server;
26 int i;
27
28 read_lock(&op->volume->servers_lock);
29 op->server_list = afs_get_serverlist(
30 rcu_dereference_protected(op->volume->servers,
31 lockdep_is_held(&op->volume->servers_lock)));
32 read_unlock(&op->volume->servers_lock);
33
34 op->untried = (1UL << op->server_list->nr_servers) - 1;
35 op->index = READ_ONCE(op->server_list->preferred);
36
37 cb_server = vnode->cb_server;
38 if (cb_server) {
39 /* See if the vnode's preferred record is still available */
40 for (i = 0; i < op->server_list->nr_servers; i++) {
41 server = op->server_list->servers[i].server;
42 if (server == cb_server) {
43 op->index = i;
44 goto found_interest;
45 }
46 }
47
48 /* If we have a lock outstanding on a server that's no longer
49 * serving this vnode, then we can't switch to another server
50 * and have to return an error.
51 */
52 if (op->flags & AFS_OPERATION_CUR_ONLY) {
53 op->error = -ESTALE;
54 return false;
55 }
56
57 /* Note that the callback promise is effectively broken */
58 write_seqlock(&vnode->cb_lock);
59 ASSERTCMP(cb_server, ==, vnode->cb_server);
60 vnode->cb_server = NULL;
61 if (test_and_clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags))
62 vnode->cb_break++;
63 write_sequnlock(&vnode->cb_lock);
64 }
65
66found_interest:
67 return true;
68}
69
70/*
71 * Post volume busy note.
72 */
73static void afs_busy(struct afs_volume *volume, u32 abort_code)
74{
75 const char *m;
76
77 switch (abort_code) {
78 case VOFFLINE: m = "offline"; break;
79 case VRESTARTING: m = "restarting"; break;
80 case VSALVAGING: m = "being salvaged"; break;
81 default: m = "busy"; break;
82 }
83
84 pr_notice("kAFS: Volume %llu '%s' is %s\n", volume->vid, volume->name, m);
85}
86
87/*
88 * Sleep and retry the operation to the same fileserver.
89 */
90static bool afs_sleep_and_retry(struct afs_operation *op)
91{
92 if (!(op->flags & AFS_OPERATION_UNINTR)) {
93 msleep_interruptible(1000);
94 if (signal_pending(current)) {
95 op->error = -ERESTARTSYS;
96 return false;
97 }
98 } else {
99 msleep(1000);
100 }
101
102 return true;
103}
104
105/*
106 * Select the fileserver to use. May be called multiple times to rotate
107 * through the fileservers.
108 */
109bool afs_select_fileserver(struct afs_operation *op)
110{
111 struct afs_addr_list *alist;
112 struct afs_server *server;
113 struct afs_vnode *vnode = op->file[0].vnode;
114 struct afs_error e;
115 u32 rtt;
116 int error = op->ac.error, i;
117
118 _enter("%lx[%d],%lx[%d],%d,%d",
119 op->untried, op->index,
120 op->ac.tried, op->ac.index,
121 error, op->ac.abort_code);
122
123 if (op->flags & AFS_OPERATION_STOP) {
124 _leave(" = f [stopped]");
125 return false;
126 }
127
128 op->nr_iterations++;
129
130 /* Evaluate the result of the previous operation, if there was one. */
131 switch (error) {
132 case SHRT_MAX:
133 goto start;
134
135 case 0:
136 default:
137 /* Success or local failure. Stop. */
138 op->error = error;
139 op->flags |= AFS_OPERATION_STOP;
140 _leave(" = f [okay/local %d]", error);
141 return false;
142
143 case -ECONNABORTED:
144 /* The far side rejected the operation on some grounds. This
145 * might involve the server being busy or the volume having been moved.
146 */
147 switch (op->ac.abort_code) {
148 case VNOVOL:
149 /* This fileserver doesn't know about the volume.
150 * - May indicate that the VL is wrong - retry once and compare
151 * the results.
152 * - May indicate that the fileserver couldn't attach to the vol.
153 */
154 if (op->flags & AFS_OPERATION_VNOVOL) {
155 op->error = -EREMOTEIO;
156 goto next_server;
157 }
158
159 write_lock(&op->volume->servers_lock);
160 op->server_list->vnovol_mask |= 1 << op->index;
161 write_unlock(&op->volume->servers_lock);
162
163 set_bit(AFS_VOLUME_NEEDS_UPDATE, &op->volume->flags);
164 error = afs_check_volume_status(op->volume, op);
165 if (error < 0)
166 goto failed_set_error;
167
168 if (test_bit(AFS_VOLUME_DELETED, &op->volume->flags)) {
169 op->error = -ENOMEDIUM;
170 goto failed;
171 }
172
173 /* If the server list didn't change, then assume that
174 * it's the fileserver having trouble.
175 */
176 if (rcu_access_pointer(op->volume->servers) == op->server_list) {
177 op->error = -EREMOTEIO;
178 goto next_server;
179 }
180
181 /* Try again */
182 op->flags |= AFS_OPERATION_VNOVOL;
183 _leave(" = t [vnovol]");
184 return true;
185
186 case VSALVAGE: /* TODO: Should this return an error or iterate? */
187 case VVOLEXISTS:
188 case VNOSERVICE:
189 case VONLINE:
190 case VDISKFULL:
191 case VOVERQUOTA:
192 op->error = afs_abort_to_error(op->ac.abort_code);
193 goto next_server;
194
195 case VOFFLINE:
196 if (!test_and_set_bit(AFS_VOLUME_OFFLINE, &op->volume->flags)) {
197 afs_busy(op->volume, op->ac.abort_code);
198 clear_bit(AFS_VOLUME_BUSY, &op->volume->flags);
199 }
200 if (op->flags & AFS_OPERATION_NO_VSLEEP) {
201 op->error = -EADV;
202 goto failed;
203 }
204 if (op->flags & AFS_OPERATION_CUR_ONLY) {
205 op->error = -ESTALE;
206 goto failed;
207 }
208 goto busy;
209
210 case VSALVAGING:
211 case VRESTARTING:
212 case VBUSY:
213 /* Retry after going round all the servers unless we
214 * have a file lock we need to maintain.
215 */
216 if (op->flags & AFS_OPERATION_NO_VSLEEP) {
217 op->error = -EBUSY;
218 goto failed;
219 }
220 if (!test_and_set_bit(AFS_VOLUME_BUSY, &op->volume->flags)) {
221 afs_busy(op->volume, op->ac.abort_code);
222 clear_bit(AFS_VOLUME_OFFLINE, &op->volume->flags);
223 }
224 busy:
225 if (op->flags & AFS_OPERATION_CUR_ONLY) {
226 if (!afs_sleep_and_retry(op))
227 goto failed;
228
229 /* Retry with same server & address */
230 _leave(" = t [vbusy]");
231 return true;
232 }
233
234 op->flags |= AFS_OPERATION_VBUSY;
235 goto next_server;
236
237 case VMOVED:
238 /* The volume migrated to another server. We consider
239 * consider all locks and callbacks broken and request
240 * an update from the VLDB.
241 *
242 * We also limit the number of VMOVED hops we will
243 * honour, just in case someone sets up a loop.
244 */
245 if (op->flags & AFS_OPERATION_VMOVED) {
246 op->error = -EREMOTEIO;
247 goto failed;
248 }
249 op->flags |= AFS_OPERATION_VMOVED;
250
251 set_bit(AFS_VOLUME_WAIT, &op->volume->flags);
252 set_bit(AFS_VOLUME_NEEDS_UPDATE, &op->volume->flags);
253 error = afs_check_volume_status(op->volume, op);
254 if (error < 0)
255 goto failed_set_error;
256
257 /* If the server list didn't change, then the VLDB is
258 * out of sync with the fileservers. This is hopefully
259 * a temporary condition, however, so we don't want to
260 * permanently block access to the file.
261 *
262 * TODO: Try other fileservers if we can.
263 *
264 * TODO: Retry a few times with sleeps.
265 */
266 if (rcu_access_pointer(op->volume->servers) == op->server_list) {
267 op->error = -ENOMEDIUM;
268 goto failed;
269 }
270
271 goto restart_from_beginning;
272
273 default:
274 clear_bit(AFS_VOLUME_OFFLINE, &op->volume->flags);
275 clear_bit(AFS_VOLUME_BUSY, &op->volume->flags);
276 op->error = afs_abort_to_error(op->ac.abort_code);
277 goto failed;
278 }
279
280 case -ETIMEDOUT:
281 case -ETIME:
282 if (op->error != -EDESTADDRREQ)
283 goto iterate_address;
284 fallthrough;
285 case -ERFKILL:
286 case -EADDRNOTAVAIL:
287 case -ENETUNREACH:
288 case -EHOSTUNREACH:
289 case -EHOSTDOWN:
290 case -ECONNREFUSED:
291 _debug("no conn");
292 op->error = error;
293 goto iterate_address;
294
295 case -ENETRESET:
296 pr_warn("kAFS: Peer reset %s (op=%x)\n",
297 op->type ? op->type->name : "???", op->debug_id);
298 fallthrough;
299 case -ECONNRESET:
300 _debug("call reset");
301 op->error = error;
302 goto failed;
303 }
304
305restart_from_beginning:
306 _debug("restart");
307 afs_end_cursor(&op->ac);
308 op->server = NULL;
309 afs_put_serverlist(op->net, op->server_list);
310 op->server_list = NULL;
311start:
312 _debug("start");
313 /* See if we need to do an update of the volume record. Note that the
314 * volume may have moved or even have been deleted.
315 */
316 error = afs_check_volume_status(op->volume, op);
317 if (error < 0)
318 goto failed_set_error;
319
320 if (!afs_start_fs_iteration(op, vnode))
321 goto failed;
322
323 _debug("__ VOL %llx __", op->volume->vid);
324
325pick_server:
326 _debug("pick [%lx]", op->untried);
327
328 error = afs_wait_for_fs_probes(op->server_list, op->untried);
329 if (error < 0)
330 goto failed_set_error;
331
332 /* Pick the untried server with the lowest RTT. If we have outstanding
333 * callbacks, we stick with the server we're already using if we can.
334 */
335 if (op->server) {
336 _debug("server %u", op->index);
337 if (test_bit(op->index, &op->untried))
338 goto selected_server;
339 op->server = NULL;
340 _debug("no server");
341 }
342
343 op->index = -1;
344 rtt = U32_MAX;
345 for (i = 0; i < op->server_list->nr_servers; i++) {
346 struct afs_server *s = op->server_list->servers[i].server;
347
348 if (!test_bit(i, &op->untried) ||
349 !test_bit(AFS_SERVER_FL_RESPONDING, &s->flags))
350 continue;
351 if (s->probe.rtt < rtt) {
352 op->index = i;
353 rtt = s->probe.rtt;
354 }
355 }
356
357 if (op->index == -1)
358 goto no_more_servers;
359
360selected_server:
361 _debug("use %d", op->index);
362 __clear_bit(op->index, &op->untried);
363
364 /* We're starting on a different fileserver from the list. We need to
365 * check it, create a callback intercept, find its address list and
366 * probe its capabilities before we use it.
367 */
368 ASSERTCMP(op->ac.alist, ==, NULL);
369 server = op->server_list->servers[op->index].server;
370
371 if (!afs_check_server_record(op, server))
372 goto failed;
373
374 _debug("USING SERVER: %pU", &server->uuid);
375
376 op->flags |= AFS_OPERATION_RETRY_SERVER;
377 op->server = server;
378 if (vnode->cb_server != server) {
379 vnode->cb_server = server;
380 vnode->cb_s_break = server->cb_s_break;
381 vnode->cb_fs_s_break = atomic_read(&server->cell->fs_s_break);
382 vnode->cb_v_break = vnode->volume->cb_v_break;
383 clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
384 }
385
386 read_lock(&server->fs_lock);
387 alist = rcu_dereference_protected(server->addresses,
388 lockdep_is_held(&server->fs_lock));
389 afs_get_addrlist(alist);
390 read_unlock(&server->fs_lock);
391
392retry_server:
393 memset(&op->ac, 0, sizeof(op->ac));
394
395 if (!op->ac.alist)
396 op->ac.alist = alist;
397 else
398 afs_put_addrlist(alist);
399
400 op->ac.index = -1;
401
402iterate_address:
403 ASSERT(op->ac.alist);
404 /* Iterate over the current server's address list to try and find an
405 * address on which it will respond to us.
406 */
407 if (!afs_iterate_addresses(&op->ac))
408 goto out_of_addresses;
409
410 _debug("address [%u] %u/%u %pISp",
411 op->index, op->ac.index, op->ac.alist->nr_addrs,
412 &op->ac.alist->addrs[op->ac.index].transport);
413
414 _leave(" = t");
415 return true;
416
417out_of_addresses:
418 /* We've now had a failure to respond on all of a server's addresses -
419 * immediately probe them again and consider retrying the server.
420 */
421 afs_probe_fileserver(op->net, op->server);
422 if (op->flags & AFS_OPERATION_RETRY_SERVER) {
423 alist = op->ac.alist;
424 error = afs_wait_for_one_fs_probe(
425 op->server, !(op->flags & AFS_OPERATION_UNINTR));
426 switch (error) {
427 case 0:
428 op->flags &= ~AFS_OPERATION_RETRY_SERVER;
429 goto retry_server;
430 case -ERESTARTSYS:
431 goto failed_set_error;
432 case -ETIME:
433 case -EDESTADDRREQ:
434 goto next_server;
435 }
436 }
437
438next_server:
439 _debug("next");
440 afs_end_cursor(&op->ac);
441 goto pick_server;
442
443no_more_servers:
444 /* That's all the servers poked to no good effect. Try again if some
445 * of them were busy.
446 */
447 if (op->flags & AFS_OPERATION_VBUSY)
448 goto restart_from_beginning;
449
450 e.error = -EDESTADDRREQ;
451 e.responded = false;
452 for (i = 0; i < op->server_list->nr_servers; i++) {
453 struct afs_server *s = op->server_list->servers[i].server;
454
455 afs_prioritise_error(&e, READ_ONCE(s->probe.error),
456 s->probe.abort_code);
457 }
458
459 error = e.error;
460
461failed_set_error:
462 op->error = error;
463failed:
464 op->flags |= AFS_OPERATION_STOP;
465 afs_end_cursor(&op->ac);
466 _leave(" = f [failed %d]", op->error);
467 return false;
468}
469
470/*
471 * Dump cursor state in the case of the error being EDESTADDRREQ.
472 */
473void afs_dump_edestaddrreq(const struct afs_operation *op)
474{
475 static int count;
476 int i;
477
478 if (!IS_ENABLED(CONFIG_AFS_DEBUG_CURSOR) || count > 3)
479 return;
480 count++;
481
482 rcu_read_lock();
483
484 pr_notice("EDESTADDR occurred\n");
485 pr_notice("FC: cbb=%x cbb2=%x fl=%x err=%hd\n",
486 op->file[0].cb_break_before,
487 op->file[1].cb_break_before, op->flags, op->error);
488 pr_notice("FC: ut=%lx ix=%d ni=%u\n",
489 op->untried, op->index, op->nr_iterations);
490
491 if (op->server_list) {
492 const struct afs_server_list *sl = op->server_list;
493 pr_notice("FC: SL nr=%u pr=%u vnov=%hx\n",
494 sl->nr_servers, sl->preferred, sl->vnovol_mask);
495 for (i = 0; i < sl->nr_servers; i++) {
496 const struct afs_server *s = sl->servers[i].server;
497 pr_notice("FC: server fl=%lx av=%u %pU\n",
498 s->flags, s->addr_version, &s->uuid);
499 if (s->addresses) {
500 const struct afs_addr_list *a =
501 rcu_dereference(s->addresses);
502 pr_notice("FC: - av=%u nr=%u/%u/%u pr=%u\n",
503 a->version,
504 a->nr_ipv4, a->nr_addrs, a->max_addrs,
505 a->preferred);
506 pr_notice("FC: - R=%lx F=%lx\n",
507 a->responded, a->failed);
508 if (a == op->ac.alist)
509 pr_notice("FC: - current\n");
510 }
511 }
512 }
513
514 pr_notice("AC: t=%lx ax=%u ac=%d er=%d r=%u ni=%u\n",
515 op->ac.tried, op->ac.index, op->ac.abort_code, op->ac.error,
516 op->ac.responded, op->ac.nr_iterations);
517 rcu_read_unlock();
518}