1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* |
3 | * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved |
4 | * Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org> |
5 | * Copyright 2001-2006 Ian Kent <raven@themaw.net> |
6 | */ |
7 | |
8 | #include "autofs_i.h" |
9 | |
10 | /* Check if a dentry can be expired */ |
11 | static inline int autofs_can_expire(struct dentry *dentry, |
12 | unsigned long timeout, unsigned int how) |
13 | { |
14 | struct autofs_info *ino = autofs_dentry_ino(dentry); |
15 | |
16 | /* dentry in the process of being deleted */ |
17 | if (ino == NULL) |
18 | return 0; |
19 | |
20 | if (!(how & AUTOFS_EXP_IMMEDIATE)) { |
21 | /* Too young to die */ |
22 | if (!timeout || time_after(ino->last_used + timeout, jiffies)) |
23 | return 0; |
24 | } |
25 | return 1; |
26 | } |
27 | |
28 | /* Check a mount point for busyness */ |
29 | static int autofs_mount_busy(struct vfsmount *mnt, |
30 | struct dentry *dentry, unsigned int how) |
31 | { |
32 | struct dentry *top = dentry; |
33 | struct path path = {.mnt = mnt, .dentry = dentry}; |
34 | int status = 1; |
35 | |
36 | pr_debug("dentry %p %pd\n" , dentry, dentry); |
37 | |
38 | path_get(&path); |
39 | |
40 | if (!follow_down_one(&path)) |
41 | goto done; |
42 | |
43 | if (is_autofs_dentry(path.dentry)) { |
44 | struct autofs_sb_info *sbi = autofs_sbi(sb: path.dentry->d_sb); |
45 | |
46 | /* This is an autofs submount, we can't expire it */ |
47 | if (autofs_type_indirect(type: sbi->type)) |
48 | goto done; |
49 | } |
50 | |
51 | /* Not a submount, has a forced expire been requested */ |
52 | if (how & AUTOFS_EXP_FORCED) { |
53 | status = 0; |
54 | goto done; |
55 | } |
56 | |
57 | /* Update the expiry counter if fs is busy */ |
58 | if (!may_umount_tree(path.mnt)) { |
59 | struct autofs_info *ino; |
60 | |
61 | ino = autofs_dentry_ino(dentry: top); |
62 | ino->last_used = jiffies; |
63 | goto done; |
64 | } |
65 | |
66 | status = 0; |
67 | done: |
68 | pr_debug("returning = %d\n" , status); |
69 | path_put(&path); |
70 | return status; |
71 | } |
72 | |
73 | /* p->d_lock held */ |
74 | static struct dentry *positive_after(struct dentry *p, struct dentry *child) |
75 | { |
76 | if (child) |
77 | child = list_next_entry(child, d_child); |
78 | else |
79 | child = list_first_entry(&p->d_subdirs, struct dentry, d_child); |
80 | |
81 | list_for_each_entry_from(child, &p->d_subdirs, d_child) { |
82 | spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED); |
83 | if (simple_positive(dentry: child)) { |
84 | dget_dlock(dentry: child); |
85 | spin_unlock(lock: &child->d_lock); |
86 | return child; |
87 | } |
88 | spin_unlock(lock: &child->d_lock); |
89 | } |
90 | |
91 | return NULL; |
92 | } |
93 | |
94 | /* |
95 | * Calculate and dget next entry in the subdirs list under root. |
96 | */ |
97 | static struct dentry *get_next_positive_subdir(struct dentry *prev, |
98 | struct dentry *root) |
99 | { |
100 | struct autofs_sb_info *sbi = autofs_sbi(sb: root->d_sb); |
101 | struct dentry *q; |
102 | |
103 | spin_lock(lock: &sbi->lookup_lock); |
104 | spin_lock(lock: &root->d_lock); |
105 | q = positive_after(p: root, child: prev); |
106 | spin_unlock(lock: &root->d_lock); |
107 | spin_unlock(lock: &sbi->lookup_lock); |
108 | dput(prev); |
109 | return q; |
110 | } |
111 | |
112 | /* |
113 | * Calculate and dget next entry in top down tree traversal. |
114 | */ |
115 | static struct dentry *get_next_positive_dentry(struct dentry *prev, |
116 | struct dentry *root) |
117 | { |
118 | struct autofs_sb_info *sbi = autofs_sbi(sb: root->d_sb); |
119 | struct dentry *p = prev, *ret = NULL, *d = NULL; |
120 | |
121 | if (prev == NULL) |
122 | return dget(dentry: root); |
123 | |
124 | spin_lock(lock: &sbi->lookup_lock); |
125 | spin_lock(lock: &p->d_lock); |
126 | while (1) { |
127 | struct dentry *parent; |
128 | |
129 | ret = positive_after(p, child: d); |
130 | if (ret || p == root) |
131 | break; |
132 | parent = p->d_parent; |
133 | spin_unlock(lock: &p->d_lock); |
134 | spin_lock(lock: &parent->d_lock); |
135 | d = p; |
136 | p = parent; |
137 | } |
138 | spin_unlock(lock: &p->d_lock); |
139 | spin_unlock(lock: &sbi->lookup_lock); |
140 | dput(prev); |
141 | return ret; |
142 | } |
143 | |
144 | /* |
145 | * Check a direct mount point for busyness. |
146 | * Direct mounts have similar expiry semantics to tree mounts. |
147 | * The tree is not busy iff no mountpoints are busy and there are no |
148 | * autofs submounts. |
149 | */ |
150 | static int autofs_direct_busy(struct vfsmount *mnt, |
151 | struct dentry *top, |
152 | unsigned long timeout, |
153 | unsigned int how) |
154 | { |
155 | pr_debug("top %p %pd\n" , top, top); |
156 | |
157 | /* Forced expire, user space handles busy mounts */ |
158 | if (how & AUTOFS_EXP_FORCED) |
159 | return 0; |
160 | |
161 | /* If it's busy update the expiry counters */ |
162 | if (!may_umount_tree(mnt)) { |
163 | struct autofs_info *ino; |
164 | |
165 | ino = autofs_dentry_ino(dentry: top); |
166 | if (ino) |
167 | ino->last_used = jiffies; |
168 | return 1; |
169 | } |
170 | |
171 | /* Timeout of a direct mount is determined by its top dentry */ |
172 | if (!autofs_can_expire(dentry: top, timeout, how)) |
173 | return 1; |
174 | |
175 | return 0; |
176 | } |
177 | |
178 | /* |
179 | * Check a directory tree of mount points for busyness |
180 | * The tree is not busy iff no mountpoints are busy |
181 | */ |
182 | static int autofs_tree_busy(struct vfsmount *mnt, |
183 | struct dentry *top, |
184 | unsigned long timeout, |
185 | unsigned int how) |
186 | { |
187 | struct autofs_info *top_ino = autofs_dentry_ino(dentry: top); |
188 | struct dentry *p; |
189 | |
190 | pr_debug("top %p %pd\n" , top, top); |
191 | |
192 | /* Negative dentry - give up */ |
193 | if (!simple_positive(dentry: top)) |
194 | return 1; |
195 | |
196 | p = NULL; |
197 | while ((p = get_next_positive_dentry(prev: p, root: top))) { |
198 | pr_debug("dentry %p %pd\n" , p, p); |
199 | |
200 | /* |
201 | * Is someone visiting anywhere in the subtree ? |
202 | * If there's no mount we need to check the usage |
203 | * count for the autofs dentry. |
204 | * If the fs is busy update the expiry counter. |
205 | */ |
206 | if (d_mountpoint(dentry: p)) { |
207 | if (autofs_mount_busy(mnt, dentry: p, how)) { |
208 | top_ino->last_used = jiffies; |
209 | dput(p); |
210 | return 1; |
211 | } |
212 | } else { |
213 | struct autofs_info *ino = autofs_dentry_ino(dentry: p); |
214 | unsigned int ino_count = READ_ONCE(ino->count); |
215 | |
216 | /* allow for dget above and top is already dgot */ |
217 | if (p == top) |
218 | ino_count += 2; |
219 | else |
220 | ino_count++; |
221 | |
222 | if (d_count(dentry: p) > ino_count) { |
223 | top_ino->last_used = jiffies; |
224 | dput(p); |
225 | return 1; |
226 | } |
227 | } |
228 | } |
229 | |
230 | /* Forced expire, user space handles busy mounts */ |
231 | if (how & AUTOFS_EXP_FORCED) |
232 | return 0; |
233 | |
234 | /* Timeout of a tree mount is ultimately determined by its top dentry */ |
235 | if (!autofs_can_expire(dentry: top, timeout, how)) |
236 | return 1; |
237 | |
238 | return 0; |
239 | } |
240 | |
241 | static struct dentry *autofs_check_leaves(struct vfsmount *mnt, |
242 | struct dentry *parent, |
243 | unsigned long timeout, |
244 | unsigned int how) |
245 | { |
246 | struct dentry *p; |
247 | |
248 | pr_debug("parent %p %pd\n" , parent, parent); |
249 | |
250 | p = NULL; |
251 | while ((p = get_next_positive_dentry(prev: p, root: parent))) { |
252 | pr_debug("dentry %p %pd\n" , p, p); |
253 | |
254 | if (d_mountpoint(dentry: p)) { |
255 | /* Can we umount this guy */ |
256 | if (autofs_mount_busy(mnt, dentry: p, how)) |
257 | continue; |
258 | |
259 | /* This isn't a submount so if a forced expire |
260 | * has been requested, user space handles busy |
261 | * mounts */ |
262 | if (how & AUTOFS_EXP_FORCED) |
263 | return p; |
264 | |
265 | /* Can we expire this guy */ |
266 | if (autofs_can_expire(dentry: p, timeout, how)) |
267 | return p; |
268 | } |
269 | } |
270 | return NULL; |
271 | } |
272 | |
273 | /* Check if we can expire a direct mount (possibly a tree) */ |
274 | static struct dentry *autofs_expire_direct(struct super_block *sb, |
275 | struct vfsmount *mnt, |
276 | struct autofs_sb_info *sbi, |
277 | unsigned int how) |
278 | { |
279 | struct dentry *root = dget(dentry: sb->s_root); |
280 | struct autofs_info *ino; |
281 | unsigned long timeout; |
282 | |
283 | if (!root) |
284 | return NULL; |
285 | |
286 | timeout = sbi->exp_timeout; |
287 | |
288 | if (!autofs_direct_busy(mnt, top: root, timeout, how)) { |
289 | spin_lock(lock: &sbi->fs_lock); |
290 | ino = autofs_dentry_ino(dentry: root); |
291 | /* No point expiring a pending mount */ |
292 | if (ino->flags & AUTOFS_INF_PENDING) { |
293 | spin_unlock(lock: &sbi->fs_lock); |
294 | goto out; |
295 | } |
296 | ino->flags |= AUTOFS_INF_WANT_EXPIRE; |
297 | spin_unlock(lock: &sbi->fs_lock); |
298 | synchronize_rcu(); |
299 | if (!autofs_direct_busy(mnt, top: root, timeout, how)) { |
300 | spin_lock(lock: &sbi->fs_lock); |
301 | ino->flags |= AUTOFS_INF_EXPIRING; |
302 | init_completion(x: &ino->expire_complete); |
303 | spin_unlock(lock: &sbi->fs_lock); |
304 | return root; |
305 | } |
306 | spin_lock(lock: &sbi->fs_lock); |
307 | ino->flags &= ~AUTOFS_INF_WANT_EXPIRE; |
308 | spin_unlock(lock: &sbi->fs_lock); |
309 | } |
310 | out: |
311 | dput(root); |
312 | |
313 | return NULL; |
314 | } |
315 | |
316 | /* Check if 'dentry' should expire, or return a nearby |
317 | * dentry that is suitable. |
318 | * If returned dentry is different from arg dentry, |
319 | * then a dget() reference was taken, else not. |
320 | */ |
321 | static struct dentry *should_expire(struct dentry *dentry, |
322 | struct vfsmount *mnt, |
323 | unsigned long timeout, |
324 | unsigned int how) |
325 | { |
326 | struct autofs_info *ino = autofs_dentry_ino(dentry); |
327 | unsigned int ino_count; |
328 | |
329 | /* No point expiring a pending mount */ |
330 | if (ino->flags & AUTOFS_INF_PENDING) |
331 | return NULL; |
332 | |
333 | /* |
334 | * Case 1: (i) indirect mount or top level pseudo direct mount |
335 | * (autofs-4.1). |
336 | * (ii) indirect mount with offset mount, check the "/" |
337 | * offset (autofs-5.0+). |
338 | */ |
339 | if (d_mountpoint(dentry)) { |
340 | pr_debug("checking mountpoint %p %pd\n" , dentry, dentry); |
341 | |
342 | /* Can we umount this guy */ |
343 | if (autofs_mount_busy(mnt, dentry, how)) |
344 | return NULL; |
345 | |
346 | /* This isn't a submount so if a forced expire |
347 | * has been requested, user space handles busy |
348 | * mounts */ |
349 | if (how & AUTOFS_EXP_FORCED) |
350 | return dentry; |
351 | |
352 | /* Can we expire this guy */ |
353 | if (autofs_can_expire(dentry, timeout, how)) |
354 | return dentry; |
355 | return NULL; |
356 | } |
357 | |
358 | if (d_is_symlink(dentry)) { |
359 | pr_debug("checking symlink %p %pd\n" , dentry, dentry); |
360 | |
361 | /* Forced expire, user space handles busy mounts */ |
362 | if (how & AUTOFS_EXP_FORCED) |
363 | return dentry; |
364 | |
365 | /* |
366 | * A symlink can't be "busy" in the usual sense so |
367 | * just check last used for expire timeout. |
368 | */ |
369 | if (autofs_can_expire(dentry, timeout, how)) |
370 | return dentry; |
371 | return NULL; |
372 | } |
373 | |
374 | if (autofs_empty(ino)) |
375 | return NULL; |
376 | |
377 | /* Case 2: tree mount, expire iff entire tree is not busy */ |
378 | if (!(how & AUTOFS_EXP_LEAVES)) { |
379 | /* Not a forced expire? */ |
380 | if (!(how & AUTOFS_EXP_FORCED)) { |
381 | /* ref-walk currently on this dentry? */ |
382 | ino_count = READ_ONCE(ino->count) + 1; |
383 | if (d_count(dentry) > ino_count) |
384 | return NULL; |
385 | } |
386 | |
387 | if (!autofs_tree_busy(mnt, top: dentry, timeout, how)) |
388 | return dentry; |
389 | /* |
390 | * Case 3: pseudo direct mount, expire individual leaves |
391 | * (autofs-4.1). |
392 | */ |
393 | } else { |
394 | struct dentry *expired; |
395 | |
396 | /* Not a forced expire? */ |
397 | if (!(how & AUTOFS_EXP_FORCED)) { |
398 | /* ref-walk currently on this dentry? */ |
399 | ino_count = READ_ONCE(ino->count) + 1; |
400 | if (d_count(dentry) > ino_count) |
401 | return NULL; |
402 | } |
403 | |
404 | expired = autofs_check_leaves(mnt, parent: dentry, timeout, how); |
405 | if (expired) { |
406 | if (expired == dentry) |
407 | dput(dentry); |
408 | return expired; |
409 | } |
410 | } |
411 | return NULL; |
412 | } |
413 | |
414 | /* |
415 | * Find an eligible tree to time-out |
416 | * A tree is eligible if :- |
417 | * - it is unused by any user process |
418 | * - it has been unused for exp_timeout time |
419 | */ |
420 | static struct dentry *autofs_expire_indirect(struct super_block *sb, |
421 | struct vfsmount *mnt, |
422 | struct autofs_sb_info *sbi, |
423 | unsigned int how) |
424 | { |
425 | unsigned long timeout; |
426 | struct dentry *root = sb->s_root; |
427 | struct dentry *dentry; |
428 | struct dentry *expired; |
429 | struct dentry *found; |
430 | struct autofs_info *ino; |
431 | |
432 | if (!root) |
433 | return NULL; |
434 | |
435 | timeout = sbi->exp_timeout; |
436 | |
437 | dentry = NULL; |
438 | while ((dentry = get_next_positive_subdir(prev: dentry, root))) { |
439 | spin_lock(lock: &sbi->fs_lock); |
440 | ino = autofs_dentry_ino(dentry); |
441 | if (ino->flags & AUTOFS_INF_WANT_EXPIRE) { |
442 | spin_unlock(lock: &sbi->fs_lock); |
443 | continue; |
444 | } |
445 | spin_unlock(lock: &sbi->fs_lock); |
446 | |
447 | expired = should_expire(dentry, mnt, timeout, how); |
448 | if (!expired) |
449 | continue; |
450 | |
451 | spin_lock(lock: &sbi->fs_lock); |
452 | ino = autofs_dentry_ino(dentry: expired); |
453 | ino->flags |= AUTOFS_INF_WANT_EXPIRE; |
454 | spin_unlock(lock: &sbi->fs_lock); |
455 | synchronize_rcu(); |
456 | |
457 | /* Make sure a reference is not taken on found if |
458 | * things have changed. |
459 | */ |
460 | how &= ~AUTOFS_EXP_LEAVES; |
461 | found = should_expire(dentry: expired, mnt, timeout, how); |
462 | if (found != expired) { // something has changed, continue |
463 | dput(found); |
464 | goto next; |
465 | } |
466 | |
467 | if (expired != dentry) |
468 | dput(dentry); |
469 | |
470 | spin_lock(lock: &sbi->fs_lock); |
471 | goto found; |
472 | next: |
473 | spin_lock(lock: &sbi->fs_lock); |
474 | ino->flags &= ~AUTOFS_INF_WANT_EXPIRE; |
475 | spin_unlock(lock: &sbi->fs_lock); |
476 | if (expired != dentry) |
477 | dput(expired); |
478 | } |
479 | return NULL; |
480 | |
481 | found: |
482 | pr_debug("returning %p %pd\n" , expired, expired); |
483 | ino->flags |= AUTOFS_INF_EXPIRING; |
484 | init_completion(x: &ino->expire_complete); |
485 | spin_unlock(lock: &sbi->fs_lock); |
486 | return expired; |
487 | } |
488 | |
489 | int autofs_expire_wait(const struct path *path, int rcu_walk) |
490 | { |
491 | struct dentry *dentry = path->dentry; |
492 | struct autofs_sb_info *sbi = autofs_sbi(sb: dentry->d_sb); |
493 | struct autofs_info *ino = autofs_dentry_ino(dentry); |
494 | int status; |
495 | int state; |
496 | |
497 | /* Block on any pending expire */ |
498 | if (!(ino->flags & AUTOFS_INF_WANT_EXPIRE)) |
499 | return 0; |
500 | if (rcu_walk) |
501 | return -ECHILD; |
502 | |
503 | retry: |
504 | spin_lock(lock: &sbi->fs_lock); |
505 | state = ino->flags & (AUTOFS_INF_WANT_EXPIRE | AUTOFS_INF_EXPIRING); |
506 | if (state == AUTOFS_INF_WANT_EXPIRE) { |
507 | spin_unlock(lock: &sbi->fs_lock); |
508 | /* |
509 | * Possibly being selected for expire, wait until |
510 | * it's selected or not. |
511 | */ |
512 | schedule_timeout_uninterruptible(HZ/10); |
513 | goto retry; |
514 | } |
515 | if (state & AUTOFS_INF_EXPIRING) { |
516 | spin_unlock(lock: &sbi->fs_lock); |
517 | |
518 | pr_debug("waiting for expire %p name=%pd\n" , dentry, dentry); |
519 | |
520 | status = autofs_wait(sbi, path, NFY_NONE); |
521 | wait_for_completion(&ino->expire_complete); |
522 | |
523 | pr_debug("expire done status=%d\n" , status); |
524 | |
525 | if (d_unhashed(dentry)) |
526 | return -EAGAIN; |
527 | |
528 | return status; |
529 | } |
530 | spin_unlock(lock: &sbi->fs_lock); |
531 | |
532 | return 0; |
533 | } |
534 | |
535 | /* Perform an expiry operation */ |
536 | int autofs_expire_run(struct super_block *sb, |
537 | struct vfsmount *mnt, |
538 | struct autofs_sb_info *sbi, |
539 | struct autofs_packet_expire __user *pkt_p) |
540 | { |
541 | struct autofs_packet_expire pkt; |
542 | struct autofs_info *ino; |
543 | struct dentry *dentry; |
544 | int ret = 0; |
545 | |
546 | memset(&pkt, 0, sizeof(pkt)); |
547 | |
548 | pkt.hdr.proto_version = sbi->version; |
549 | pkt.hdr.type = autofs_ptype_expire; |
550 | |
551 | dentry = autofs_expire_indirect(sb, mnt, sbi, how: 0); |
552 | if (!dentry) |
553 | return -EAGAIN; |
554 | |
555 | pkt.len = dentry->d_name.len; |
556 | memcpy(pkt.name, dentry->d_name.name, pkt.len); |
557 | pkt.name[pkt.len] = '\0'; |
558 | |
559 | if (copy_to_user(to: pkt_p, from: &pkt, n: sizeof(struct autofs_packet_expire))) |
560 | ret = -EFAULT; |
561 | |
562 | spin_lock(lock: &sbi->fs_lock); |
563 | ino = autofs_dentry_ino(dentry); |
564 | /* avoid rapid-fire expire attempts if expiry fails */ |
565 | ino->last_used = jiffies; |
566 | ino->flags &= ~(AUTOFS_INF_EXPIRING|AUTOFS_INF_WANT_EXPIRE); |
567 | complete_all(&ino->expire_complete); |
568 | spin_unlock(lock: &sbi->fs_lock); |
569 | |
570 | dput(dentry); |
571 | |
572 | return ret; |
573 | } |
574 | |
575 | int autofs_do_expire_multi(struct super_block *sb, struct vfsmount *mnt, |
576 | struct autofs_sb_info *sbi, unsigned int how) |
577 | { |
578 | struct dentry *dentry; |
579 | int ret = -EAGAIN; |
580 | |
581 | if (autofs_type_trigger(type: sbi->type)) |
582 | dentry = autofs_expire_direct(sb, mnt, sbi, how); |
583 | else |
584 | dentry = autofs_expire_indirect(sb, mnt, sbi, how); |
585 | |
586 | if (dentry) { |
587 | struct autofs_info *ino = autofs_dentry_ino(dentry); |
588 | const struct path path = { .mnt = mnt, .dentry = dentry }; |
589 | |
590 | /* This is synchronous because it makes the daemon a |
591 | * little easier |
592 | */ |
593 | ret = autofs_wait(sbi, &path, NFY_EXPIRE); |
594 | |
595 | spin_lock(lock: &sbi->fs_lock); |
596 | /* avoid rapid-fire expire attempts if expiry fails */ |
597 | ino->last_used = jiffies; |
598 | ino->flags &= ~(AUTOFS_INF_EXPIRING|AUTOFS_INF_WANT_EXPIRE); |
599 | complete_all(&ino->expire_complete); |
600 | spin_unlock(lock: &sbi->fs_lock); |
601 | dput(dentry); |
602 | } |
603 | |
604 | return ret; |
605 | } |
606 | |
607 | /* |
608 | * Call repeatedly until it returns -EAGAIN, meaning there's nothing |
609 | * more to be done. |
610 | */ |
611 | int autofs_expire_multi(struct super_block *sb, struct vfsmount *mnt, |
612 | struct autofs_sb_info *sbi, int __user *arg) |
613 | { |
614 | unsigned int how = 0; |
615 | |
616 | if (arg && get_user(how, arg)) |
617 | return -EFAULT; |
618 | |
619 | return autofs_do_expire_multi(sb, mnt, sbi, how); |
620 | } |
621 | |