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1/* Handle fileserver selection and rotation.
2 *
3 * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#include <linux/kernel.h>
13#include <linux/slab.h>
14#include <linux/fs.h>
15#include <linux/sched.h>
16#include <linux/delay.h>
17#include <linux/sched/signal.h>
18#include "internal.h"
19#include "afs_fs.h"
20
21/*
22 * Initialise a filesystem server cursor for iterating over FS servers.
23 */
24static void afs_init_fs_cursor(struct afs_fs_cursor *fc, struct afs_vnode *vnode)
25{
26 memset(fc, 0, sizeof(*fc));
27}
28
29/*
30 * Begin an operation on the fileserver.
31 *
32 * Fileserver operations are serialised on the server by vnode, so we serialise
33 * them here also using the io_lock.
34 */
35bool afs_begin_vnode_operation(struct afs_fs_cursor *fc, struct afs_vnode *vnode,
36 struct key *key)
37{
38 afs_init_fs_cursor(fc, vnode);
39 fc->vnode = vnode;
40 fc->key = key;
41 fc->ac.error = SHRT_MAX;
42
43 if (mutex_lock_interruptible(&vnode->io_lock) < 0) {
44 fc->ac.error = -EINTR;
45 fc->flags |= AFS_FS_CURSOR_STOP;
46 return false;
47 }
48
49 if (vnode->lock_state != AFS_VNODE_LOCK_NONE)
50 fc->flags |= AFS_FS_CURSOR_CUR_ONLY;
51 return true;
52}
53
54/*
55 * Begin iteration through a server list, starting with the vnode's last used
56 * server if possible, or the last recorded good server if not.
57 */
58static bool afs_start_fs_iteration(struct afs_fs_cursor *fc,
59 struct afs_vnode *vnode)
60{
61 struct afs_cb_interest *cbi;
62 int i;
63
64 read_lock(&vnode->volume->servers_lock);
65 fc->server_list = afs_get_serverlist(vnode->volume->servers);
66 read_unlock(&vnode->volume->servers_lock);
67
68 cbi = vnode->cb_interest;
69 if (cbi) {
70 /* See if the vnode's preferred record is still available */
71 for (i = 0; i < fc->server_list->nr_servers; i++) {
72 if (fc->server_list->servers[i].cb_interest == cbi) {
73 fc->start = i;
74 goto found_interest;
75 }
76 }
77
78 /* If we have a lock outstanding on a server that's no longer
79 * serving this vnode, then we can't switch to another server
80 * and have to return an error.
81 */
82 if (fc->flags & AFS_FS_CURSOR_CUR_ONLY) {
83 fc->ac.error = -ESTALE;
84 return false;
85 }
86
87 /* Note that the callback promise is effectively broken */
88 write_seqlock(&vnode->cb_lock);
89 ASSERTCMP(cbi, ==, vnode->cb_interest);
90 vnode->cb_interest = NULL;
91 if (test_and_clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags))
92 vnode->cb_break++;
93 write_sequnlock(&vnode->cb_lock);
94
95 afs_put_cb_interest(afs_v2net(vnode), cbi);
96 cbi = NULL;
97 } else {
98 fc->start = READ_ONCE(fc->server_list->index);
99 }
100
101found_interest:
102 fc->index = fc->start;
103 return true;
104}
105
106/*
107 * Post volume busy note.
108 */
109static void afs_busy(struct afs_volume *volume, u32 abort_code)
110{
111 const char *m;
112
113 switch (abort_code) {
114 case VOFFLINE: m = "offline"; break;
115 case VRESTARTING: m = "restarting"; break;
116 case VSALVAGING: m = "being salvaged"; break;
117 default: m = "busy"; break;
118 }
119
120 pr_notice("kAFS: Volume %u '%s' is %s\n", volume->vid, volume->name, m);
121}
122
123/*
124 * Sleep and retry the operation to the same fileserver.
125 */
126static bool afs_sleep_and_retry(struct afs_fs_cursor *fc)
127{
128 msleep_interruptible(1000);
129 if (signal_pending(current)) {
130 fc->ac.error = -ERESTARTSYS;
131 return false;
132 }
133
134 return true;
135}
136
137/*
138 * Select the fileserver to use. May be called multiple times to rotate
139 * through the fileservers.
140 */
141bool afs_select_fileserver(struct afs_fs_cursor *fc)
142{
143 struct afs_addr_list *alist;
144 struct afs_server *server;
145 struct afs_vnode *vnode = fc->vnode;
146
147 _enter("%u/%u,%u/%u,%d,%d",
148 fc->index, fc->start,
149 fc->ac.index, fc->ac.start,
150 fc->ac.error, fc->ac.abort_code);
151
152 if (fc->flags & AFS_FS_CURSOR_STOP) {
153 _leave(" = f [stopped]");
154 return false;
155 }
156
157 /* Evaluate the result of the previous operation, if there was one. */
158 switch (fc->ac.error) {
159 case SHRT_MAX:
160 goto start;
161
162 case 0:
163 default:
164 /* Success or local failure. Stop. */
165 fc->flags |= AFS_FS_CURSOR_STOP;
166 _leave(" = f [okay/local %d]", fc->ac.error);
167 return false;
168
169 case -ECONNABORTED:
170 /* The far side rejected the operation on some grounds. This
171 * might involve the server being busy or the volume having been moved.
172 */
173 switch (fc->ac.abort_code) {
174 case VNOVOL:
175 /* This fileserver doesn't know about the volume.
176 * - May indicate that the VL is wrong - retry once and compare
177 * the results.
178 * - May indicate that the fileserver couldn't attach to the vol.
179 */
180 if (fc->flags & AFS_FS_CURSOR_VNOVOL) {
181 fc->ac.error = -EREMOTEIO;
182 goto next_server;
183 }
184
185 write_lock(&vnode->volume->servers_lock);
186 fc->server_list->vnovol_mask |= 1 << fc->index;
187 write_unlock(&vnode->volume->servers_lock);
188
189 set_bit(AFS_VOLUME_NEEDS_UPDATE, &vnode->volume->flags);
190 fc->ac.error = afs_check_volume_status(vnode->volume, fc->key);
191 if (fc->ac.error < 0)
192 goto failed;
193
194 if (test_bit(AFS_VOLUME_DELETED, &vnode->volume->flags)) {
195 fc->ac.error = -ENOMEDIUM;
196 goto failed;
197 }
198
199 /* If the server list didn't change, then assume that
200 * it's the fileserver having trouble.
201 */
202 if (vnode->volume->servers == fc->server_list) {
203 fc->ac.error = -EREMOTEIO;
204 goto next_server;
205 }
206
207 /* Try again */
208 fc->flags |= AFS_FS_CURSOR_VNOVOL;
209 _leave(" = t [vnovol]");
210 return true;
211
212 case VSALVAGE: /* TODO: Should this return an error or iterate? */
213 case VVOLEXISTS:
214 case VNOSERVICE:
215 case VONLINE:
216 case VDISKFULL:
217 case VOVERQUOTA:
218 fc->ac.error = afs_abort_to_error(fc->ac.abort_code);
219 goto next_server;
220
221 case VOFFLINE:
222 if (!test_and_set_bit(AFS_VOLUME_OFFLINE, &vnode->volume->flags)) {
223 afs_busy(vnode->volume, fc->ac.abort_code);
224 clear_bit(AFS_VOLUME_BUSY, &vnode->volume->flags);
225 }
226 if (fc->flags & AFS_FS_CURSOR_NO_VSLEEP) {
227 fc->ac.error = -EADV;
228 goto failed;
229 }
230 if (fc->flags & AFS_FS_CURSOR_CUR_ONLY) {
231 fc->ac.error = -ESTALE;
232 goto failed;
233 }
234 goto busy;
235
236 case VSALVAGING:
237 case VRESTARTING:
238 case VBUSY:
239 /* Retry after going round all the servers unless we
240 * have a file lock we need to maintain.
241 */
242 if (fc->flags & AFS_FS_CURSOR_NO_VSLEEP) {
243 fc->ac.error = -EBUSY;
244 goto failed;
245 }
246 if (!test_and_set_bit(AFS_VOLUME_BUSY, &vnode->volume->flags)) {
247 afs_busy(vnode->volume, fc->ac.abort_code);
248 clear_bit(AFS_VOLUME_OFFLINE, &vnode->volume->flags);
249 }
250 busy:
251 if (fc->flags & AFS_FS_CURSOR_CUR_ONLY) {
252 if (!afs_sleep_and_retry(fc))
253 goto failed;
254
255 /* Retry with same server & address */
256 _leave(" = t [vbusy]");
257 return true;
258 }
259
260 fc->flags |= AFS_FS_CURSOR_VBUSY;
261 goto next_server;
262
263 case VMOVED:
264 /* The volume migrated to another server. We consider
265 * consider all locks and callbacks broken and request
266 * an update from the VLDB.
267 *
268 * We also limit the number of VMOVED hops we will
269 * honour, just in case someone sets up a loop.
270 */
271 if (fc->flags & AFS_FS_CURSOR_VMOVED) {
272 fc->ac.error = -EREMOTEIO;
273 goto failed;
274 }
275 fc->flags |= AFS_FS_CURSOR_VMOVED;
276
277 set_bit(AFS_VOLUME_WAIT, &vnode->volume->flags);
278 set_bit(AFS_VOLUME_NEEDS_UPDATE, &vnode->volume->flags);
279 fc->ac.error = afs_check_volume_status(vnode->volume, fc->key);
280 if (fc->ac.error < 0)
281 goto failed;
282
283 /* If the server list didn't change, then the VLDB is
284 * out of sync with the fileservers. This is hopefully
285 * a temporary condition, however, so we don't want to
286 * permanently block access to the file.
287 *
288 * TODO: Try other fileservers if we can.
289 *
290 * TODO: Retry a few times with sleeps.
291 */
292 if (vnode->volume->servers == fc->server_list) {
293 fc->ac.error = -ENOMEDIUM;
294 goto failed;
295 }
296
297 goto restart_from_beginning;
298
299 default:
300 clear_bit(AFS_VOLUME_OFFLINE, &vnode->volume->flags);
301 clear_bit(AFS_VOLUME_BUSY, &vnode->volume->flags);
302 fc->ac.error = afs_abort_to_error(fc->ac.abort_code);
303 goto failed;
304 }
305
306 case -ENETUNREACH:
307 case -EHOSTUNREACH:
308 case -ECONNREFUSED:
309 case -ETIMEDOUT:
310 case -ETIME:
311 _debug("no conn");
312 goto iterate_address;
313 }
314
315restart_from_beginning:
316 _debug("restart");
317 afs_end_cursor(&fc->ac);
318 afs_put_cb_interest(afs_v2net(vnode), fc->cbi);
319 fc->cbi = NULL;
320 afs_put_serverlist(afs_v2net(vnode), fc->server_list);
321 fc->server_list = NULL;
322start:
323 _debug("start");
324 /* See if we need to do an update of the volume record. Note that the
325 * volume may have moved or even have been deleted.
326 */
327 fc->ac.error = afs_check_volume_status(vnode->volume, fc->key);
328 if (fc->ac.error < 0)
329 goto failed;
330
331 if (!afs_start_fs_iteration(fc, vnode))
332 goto failed;
333
334use_server:
335 _debug("use");
336 /* We're starting on a different fileserver from the list. We need to
337 * check it, create a callback intercept, find its address list and
338 * probe its capabilities before we use it.
339 */
340 ASSERTCMP(fc->ac.alist, ==, NULL);
341 server = fc->server_list->servers[fc->index].server;
342
343 if (!afs_check_server_record(fc, server))
344 goto failed;
345
346 _debug("USING SERVER: %pU", &server->uuid);
347
348 /* Make sure we've got a callback interest record for this server. We
349 * have to link it in before we send the request as we can be sent a
350 * break request before we've finished decoding the reply and
351 * installing the vnode.
352 */
353 fc->ac.error = afs_register_server_cb_interest(vnode, fc->server_list,
354 fc->index);
355 if (fc->ac.error < 0)
356 goto failed;
357
358 fc->cbi = afs_get_cb_interest(vnode->cb_interest);
359
360 read_lock(&server->fs_lock);
361 alist = rcu_dereference_protected(server->addresses,
362 lockdep_is_held(&server->fs_lock));
363 afs_get_addrlist(alist);
364 read_unlock(&server->fs_lock);
365
366 memset(&fc->ac, 0, sizeof(fc->ac));
367
368 /* Probe the current fileserver if we haven't done so yet. */
369 if (!test_bit(AFS_SERVER_FL_PROBED, &server->flags)) {
370 fc->ac.alist = afs_get_addrlist(alist);
371
372 if (!afs_probe_fileserver(fc)) {
373 switch (fc->ac.error) {
374 case -ENOMEM:
375 case -ERESTARTSYS:
376 case -EINTR:
377 goto failed;
378 default:
379 goto next_server;
380 }
381 }
382 }
383
384 if (!fc->ac.alist)
385 fc->ac.alist = alist;
386 else
387 afs_put_addrlist(alist);
388
389 fc->ac.start = READ_ONCE(alist->index);
390 fc->ac.index = fc->ac.start;
391
392iterate_address:
393 ASSERT(fc->ac.alist);
394 _debug("iterate %d/%d", fc->ac.index, fc->ac.alist->nr_addrs);
395 /* Iterate over the current server's address list to try and find an
396 * address on which it will respond to us.
397 */
398 if (!afs_iterate_addresses(&fc->ac))
399 goto next_server;
400
401 _leave(" = t");
402 return true;
403
404next_server:
405 _debug("next");
406 afs_end_cursor(&fc->ac);
407 afs_put_cb_interest(afs_v2net(vnode), fc->cbi);
408 fc->cbi = NULL;
409 fc->index++;
410 if (fc->index >= fc->server_list->nr_servers)
411 fc->index = 0;
412 if (fc->index != fc->start)
413 goto use_server;
414
415 /* That's all the servers poked to no good effect. Try again if some
416 * of them were busy.
417 */
418 if (fc->flags & AFS_FS_CURSOR_VBUSY)
419 goto restart_from_beginning;
420
421 fc->ac.error = -EDESTADDRREQ;
422 goto failed;
423
424failed:
425 fc->flags |= AFS_FS_CURSOR_STOP;
426 afs_end_cursor(&fc->ac);
427 _leave(" = f [failed %d]", fc->ac.error);
428 return false;
429}
430
431/*
432 * Select the same fileserver we used for a vnode before and only that
433 * fileserver. We use this when we have a lock on that file, which is backed
434 * only by the fileserver we obtained it from.
435 */
436bool afs_select_current_fileserver(struct afs_fs_cursor *fc)
437{
438 struct afs_vnode *vnode = fc->vnode;
439 struct afs_cb_interest *cbi = vnode->cb_interest;
440 struct afs_addr_list *alist;
441
442 _enter("");
443
444 switch (fc->ac.error) {
445 case SHRT_MAX:
446 if (!cbi) {
447 fc->ac.error = -ESTALE;
448 fc->flags |= AFS_FS_CURSOR_STOP;
449 return false;
450 }
451
452 fc->cbi = afs_get_cb_interest(vnode->cb_interest);
453
454 read_lock(&cbi->server->fs_lock);
455 alist = rcu_dereference_protected(cbi->server->addresses,
456 lockdep_is_held(&cbi->server->fs_lock));
457 afs_get_addrlist(alist);
458 read_unlock(&cbi->server->fs_lock);
459 if (!alist) {
460 fc->ac.error = -ESTALE;
461 fc->flags |= AFS_FS_CURSOR_STOP;
462 return false;
463 }
464
465 memset(&fc->ac, 0, sizeof(fc->ac));
466 fc->ac.alist = alist;
467 fc->ac.start = READ_ONCE(alist->index);
468 fc->ac.index = fc->ac.start;
469 goto iterate_address;
470
471 case 0:
472 default:
473 /* Success or local failure. Stop. */
474 fc->flags |= AFS_FS_CURSOR_STOP;
475 _leave(" = f [okay/local %d]", fc->ac.error);
476 return false;
477
478 case -ECONNABORTED:
479 fc->flags |= AFS_FS_CURSOR_STOP;
480 _leave(" = f [abort]");
481 return false;
482
483 case -ENETUNREACH:
484 case -EHOSTUNREACH:
485 case -ECONNREFUSED:
486 case -ETIMEDOUT:
487 case -ETIME:
488 _debug("no conn");
489 goto iterate_address;
490 }
491
492iterate_address:
493 /* Iterate over the current server's address list to try and find an
494 * address on which it will respond to us.
495 */
496 if (afs_iterate_addresses(&fc->ac)) {
497 _leave(" = t");
498 return true;
499 }
500
501 afs_end_cursor(&fc->ac);
502 return false;
503}
504
505/*
506 * Tidy up a filesystem cursor and unlock the vnode.
507 */
508int afs_end_vnode_operation(struct afs_fs_cursor *fc)
509{
510 struct afs_net *net = afs_v2net(fc->vnode);
511 int ret;
512
513 mutex_unlock(&fc->vnode->io_lock);
514
515 afs_end_cursor(&fc->ac);
516 afs_put_cb_interest(net, fc->cbi);
517 afs_put_serverlist(net, fc->server_list);
518
519 ret = fc->ac.error;
520 if (ret == -ECONNABORTED)
521 afs_abort_to_error(fc->ac.abort_code);
522
523 return fc->ac.error;
524}