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