1feb68ecef9509dd88a4323f3193845af6a84e15
[linux-2.6.git] / fs / autofs4 / expire.c
1 /* -*- c -*- --------------------------------------------------------------- *
2  *
3  * linux/fs/autofs/expire.c
4  *
5  *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
6  *  Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
7  *  Copyright 2001-2006 Ian Kent <raven@themaw.net>
8  *
9  * This file is part of the Linux kernel and is made available under
10  * the terms of the GNU General Public License, version 2, or at your
11  * option, any later version, incorporated herein by reference.
12  *
13  * ------------------------------------------------------------------------- */
14
15 #include "autofs_i.h"
16
17 static unsigned long now;
18
19 /* Check if a dentry can be expired */
20 static inline int autofs4_can_expire(struct dentry *dentry,
21                                         unsigned long timeout, int do_now)
22 {
23         struct autofs_info *ino = autofs4_dentry_ino(dentry);
24
25         /* dentry in the process of being deleted */
26         if (ino == NULL)
27                 return 0;
28
29         if (!do_now) {
30                 /* Too young to die */
31                 if (!timeout || time_after(ino->last_used + timeout, now))
32                         return 0;
33
34                 /* update last_used here :-
35                    - obviously makes sense if it is in use now
36                    - less obviously, prevents rapid-fire expire
37                      attempts if expire fails the first time */
38                 ino->last_used = now;
39         }
40         return 1;
41 }
42
43 /* Check a mount point for busyness */
44 static int autofs4_mount_busy(struct vfsmount *mnt, struct dentry *dentry)
45 {
46         struct dentry *top = dentry;
47         struct path path = {.mnt = mnt, .dentry = dentry};
48         int status = 1;
49
50         DPRINTK("dentry %p %.*s",
51                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
52
53         path_get(&path);
54
55         if (!follow_down_one(&path))
56                 goto done;
57
58         if (is_autofs4_dentry(path.dentry)) {
59                 struct autofs_sb_info *sbi = autofs4_sbi(path.dentry->d_sb);
60
61                 /* This is an autofs submount, we can't expire it */
62                 if (autofs_type_indirect(sbi->type))
63                         goto done;
64
65                 /*
66                  * Otherwise it's an offset mount and we need to check
67                  * if we can umount its mount, if there is one.
68                  */
69                 if (!d_mountpoint(path.dentry)) {
70                         status = 0;
71                         goto done;
72                 }
73         }
74
75         /* Update the expiry counter if fs is busy */
76         if (!may_umount_tree(path.mnt)) {
77                 struct autofs_info *ino = autofs4_dentry_ino(top);
78                 ino->last_used = jiffies;
79                 goto done;
80         }
81
82         status = 0;
83 done:
84         DPRINTK("returning = %d", status);
85         path_put(&path);
86         return status;
87 }
88
89 /*
90  * Calculate and dget next entry in the subdirs list under root.
91  */
92 static struct dentry *get_next_positive_subdir(struct dentry *prev,
93                                                 struct dentry *root)
94 {
95         struct autofs_sb_info *sbi = autofs4_sbi(root->d_sb);
96         struct list_head *next;
97         struct dentry *p, *q;
98
99         spin_lock(&sbi->lookup_lock);
100
101         if (prev == NULL) {
102                 spin_lock(&root->d_lock);
103                 prev = dget_dlock(root);
104                 next = prev->d_subdirs.next;
105                 p = prev;
106                 goto start;
107         }
108
109         p = prev;
110         spin_lock(&p->d_lock);
111 again:
112         next = p->d_u.d_child.next;
113 start:
114         if (next == &root->d_subdirs) {
115                 spin_unlock(&p->d_lock);
116                 spin_unlock(&sbi->lookup_lock);
117                 dput(prev);
118                 return NULL;
119         }
120
121         q = list_entry(next, struct dentry, d_u.d_child);
122
123         spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
124         /* Negative dentry - try next */
125         if (!simple_positive(q)) {
126                 spin_unlock(&p->d_lock);
127                 lock_set_subclass(&q->d_lock.dep_map, 0, _RET_IP_);
128                 p = q;
129                 goto again;
130         }
131         dget_dlock(q);
132         spin_unlock(&q->d_lock);
133         spin_unlock(&p->d_lock);
134         spin_unlock(&sbi->lookup_lock);
135
136         dput(prev);
137
138         return q;
139 }
140
141 /*
142  * Calculate and dget next entry in top down tree traversal.
143  */
144 static struct dentry *get_next_positive_dentry(struct dentry *prev,
145                                                 struct dentry *root)
146 {
147         struct autofs_sb_info *sbi = autofs4_sbi(root->d_sb);
148         struct list_head *next;
149         struct dentry *p, *ret;
150
151         if (prev == NULL)
152                 return dget(root);
153
154         spin_lock(&sbi->lookup_lock);
155 relock:
156         p = prev;
157         spin_lock(&p->d_lock);
158 again:
159         next = p->d_subdirs.next;
160         if (next == &p->d_subdirs) {
161                 while (1) {
162                         struct dentry *parent;
163
164                         if (p == root) {
165                                 spin_unlock(&p->d_lock);
166                                 spin_unlock(&sbi->lookup_lock);
167                                 dput(prev);
168                                 return NULL;
169                         }
170
171                         parent = p->d_parent;
172                         if (!spin_trylock(&parent->d_lock)) {
173                                 spin_unlock(&p->d_lock);
174                                 cpu_relax();
175                                 goto relock;
176                         }
177                         spin_unlock(&p->d_lock);
178                         next = p->d_u.d_child.next;
179                         p = parent;
180                         if (next != &parent->d_subdirs)
181                                 break;
182                 }
183         }
184         ret = list_entry(next, struct dentry, d_u.d_child);
185
186         spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
187         /* Negative dentry - try next */
188         if (!simple_positive(ret)) {
189                 spin_unlock(&p->d_lock);
190                 lock_set_subclass(&ret->d_lock.dep_map, 0, _RET_IP_);
191                 p = ret;
192                 goto again;
193         }
194         dget_dlock(ret);
195         spin_unlock(&ret->d_lock);
196         spin_unlock(&p->d_lock);
197         spin_unlock(&sbi->lookup_lock);
198
199         dput(prev);
200
201         return ret;
202 }
203
204 /*
205  * Check a direct mount point for busyness.
206  * Direct mounts have similar expiry semantics to tree mounts.
207  * The tree is not busy iff no mountpoints are busy and there are no
208  * autofs submounts.
209  */
210 static int autofs4_direct_busy(struct vfsmount *mnt,
211                                 struct dentry *top,
212                                 unsigned long timeout,
213                                 int do_now)
214 {
215         DPRINTK("top %p %.*s",
216                 top, (int) top->d_name.len, top->d_name.name);
217
218         /* If it's busy update the expiry counters */
219         if (!may_umount_tree(mnt)) {
220                 struct autofs_info *ino = autofs4_dentry_ino(top);
221                 if (ino)
222                         ino->last_used = jiffies;
223                 return 1;
224         }
225
226         /* Timeout of a direct mount is determined by its top dentry */
227         if (!autofs4_can_expire(top, timeout, do_now))
228                 return 1;
229
230         return 0;
231 }
232
233 /* Check a directory tree of mount points for busyness
234  * The tree is not busy iff no mountpoints are busy
235  */
236 static int autofs4_tree_busy(struct vfsmount *mnt,
237                              struct dentry *top,
238                              unsigned long timeout,
239                              int do_now)
240 {
241         struct autofs_info *top_ino = autofs4_dentry_ino(top);
242         struct dentry *p;
243
244         DPRINTK("top %p %.*s",
245                 top, (int)top->d_name.len, top->d_name.name);
246
247         /* Negative dentry - give up */
248         if (!simple_positive(top))
249                 return 1;
250
251         p = NULL;
252         while ((p = get_next_positive_dentry(p, top))) {
253                 DPRINTK("dentry %p %.*s",
254                         p, (int) p->d_name.len, p->d_name.name);
255
256                 /*
257                  * Is someone visiting anywhere in the subtree ?
258                  * If there's no mount we need to check the usage
259                  * count for the autofs dentry.
260                  * If the fs is busy update the expiry counter.
261                  */
262                 if (d_mountpoint(p)) {
263                         if (autofs4_mount_busy(mnt, p)) {
264                                 top_ino->last_used = jiffies;
265                                 dput(p);
266                                 return 1;
267                         }
268                 } else {
269                         struct autofs_info *ino = autofs4_dentry_ino(p);
270                         unsigned int ino_count = atomic_read(&ino->count);
271
272                         /*
273                          * Clean stale dentries below that have not been
274                          * invalidated after a mount fail during lookup
275                          */
276                         d_invalidate(p);
277
278                         /* allow for dget above and top is already dgot */
279                         if (p == top)
280                                 ino_count += 2;
281                         else
282                                 ino_count++;
283
284                         if (p->d_count > ino_count) {
285                                 top_ino->last_used = jiffies;
286                                 dput(p);
287                                 return 1;
288                         }
289                 }
290         }
291
292         /* Timeout of a tree mount is ultimately determined by its top dentry */
293         if (!autofs4_can_expire(top, timeout, do_now))
294                 return 1;
295
296         return 0;
297 }
298
299 static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
300                                            struct dentry *parent,
301                                            unsigned long timeout,
302                                            int do_now)
303 {
304         struct dentry *p;
305
306         DPRINTK("parent %p %.*s",
307                 parent, (int)parent->d_name.len, parent->d_name.name);
308
309         p = NULL;
310         while ((p = get_next_positive_dentry(p, parent))) {
311                 DPRINTK("dentry %p %.*s",
312                         p, (int) p->d_name.len, p->d_name.name);
313
314                 if (d_mountpoint(p)) {
315                         /* Can we umount this guy */
316                         if (autofs4_mount_busy(mnt, p))
317                                 continue;
318
319                         /* Can we expire this guy */
320                         if (autofs4_can_expire(p, timeout, do_now))
321                                 return p;
322                 }
323         }
324         return NULL;
325 }
326
327 /* Check if we can expire a direct mount (possibly a tree) */
328 struct dentry *autofs4_expire_direct(struct super_block *sb,
329                                      struct vfsmount *mnt,
330                                      struct autofs_sb_info *sbi,
331                                      int how)
332 {
333         unsigned long timeout;
334         struct dentry *root = dget(sb->s_root);
335         int do_now = how & AUTOFS_EXP_IMMEDIATE;
336         struct autofs_info *ino;
337
338         if (!root)
339                 return NULL;
340
341         now = jiffies;
342         timeout = sbi->exp_timeout;
343
344         spin_lock(&sbi->fs_lock);
345         ino = autofs4_dentry_ino(root);
346         /* No point expiring a pending mount */
347         if (ino->flags & AUTOFS_INF_PENDING)
348                 goto out;
349         if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
350                 struct autofs_info *ino = autofs4_dentry_ino(root);
351                 ino->flags |= AUTOFS_INF_EXPIRING;
352                 init_completion(&ino->expire_complete);
353                 spin_unlock(&sbi->fs_lock);
354                 return root;
355         }
356 out:
357         spin_unlock(&sbi->fs_lock);
358         dput(root);
359
360         return NULL;
361 }
362
363 /*
364  * Find an eligible tree to time-out
365  * A tree is eligible if :-
366  *  - it is unused by any user process
367  *  - it has been unused for exp_timeout time
368  */
369 struct dentry *autofs4_expire_indirect(struct super_block *sb,
370                                        struct vfsmount *mnt,
371                                        struct autofs_sb_info *sbi,
372                                        int how)
373 {
374         unsigned long timeout;
375         struct dentry *root = sb->s_root;
376         struct dentry *dentry;
377         struct dentry *expired = NULL;
378         int do_now = how & AUTOFS_EXP_IMMEDIATE;
379         int exp_leaves = how & AUTOFS_EXP_LEAVES;
380         struct autofs_info *ino;
381         unsigned int ino_count;
382
383         if (!root)
384                 return NULL;
385
386         now = jiffies;
387         timeout = sbi->exp_timeout;
388
389         dentry = NULL;
390         while ((dentry = get_next_positive_subdir(dentry, root))) {
391                 spin_lock(&sbi->fs_lock);
392                 ino = autofs4_dentry_ino(dentry);
393                 /* No point expiring a pending mount */
394                 if (ino->flags & AUTOFS_INF_PENDING)
395                         goto next;
396
397                 /*
398                  * Case 1: (i) indirect mount or top level pseudo direct mount
399                  *         (autofs-4.1).
400                  *         (ii) indirect mount with offset mount, check the "/"
401                  *         offset (autofs-5.0+).
402                  */
403                 if (d_mountpoint(dentry)) {
404                         DPRINTK("checking mountpoint %p %.*s",
405                                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
406
407                         /* Path walk currently on this dentry? */
408                         ino_count = atomic_read(&ino->count) + 2;
409                         if (dentry->d_count > ino_count)
410                                 goto next;
411
412                         /* Can we umount this guy */
413                         if (autofs4_mount_busy(mnt, dentry))
414                                 goto next;
415
416                         /* Can we expire this guy */
417                         if (autofs4_can_expire(dentry, timeout, do_now)) {
418                                 expired = dentry;
419                                 goto found;
420                         }
421                         goto next;
422                 }
423
424                 if (simple_empty(dentry))
425                         goto next;
426
427                 /* Case 2: tree mount, expire iff entire tree is not busy */
428                 if (!exp_leaves) {
429                         /* Path walk currently on this dentry? */
430                         ino_count = atomic_read(&ino->count) + 1;
431                         if (dentry->d_count > ino_count)
432                                 goto next;
433
434                         if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
435                                 expired = dentry;
436                                 goto found;
437                         }
438                 /*
439                  * Case 3: pseudo direct mount, expire individual leaves
440                  *         (autofs-4.1).
441                  */
442                 } else {
443                         /* Path walk currently on this dentry? */
444                         ino_count = atomic_read(&ino->count) + 1;
445                         if (dentry->d_count > ino_count)
446                                 goto next;
447
448                         expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
449                         if (expired) {
450                                 dput(dentry);
451                                 goto found;
452                         }
453                 }
454 next:
455                 spin_unlock(&sbi->fs_lock);
456         }
457         return NULL;
458
459 found:
460         DPRINTK("returning %p %.*s",
461                 expired, (int)expired->d_name.len, expired->d_name.name);
462         ino = autofs4_dentry_ino(expired);
463         ino->flags |= AUTOFS_INF_EXPIRING;
464         init_completion(&ino->expire_complete);
465         spin_unlock(&sbi->fs_lock);
466         spin_lock(&sbi->lookup_lock);
467         spin_lock(&expired->d_parent->d_lock);
468         spin_lock_nested(&expired->d_lock, DENTRY_D_LOCK_NESTED);
469         list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
470         spin_unlock(&expired->d_lock);
471         spin_unlock(&expired->d_parent->d_lock);
472         spin_unlock(&sbi->lookup_lock);
473         return expired;
474 }
475
476 int autofs4_expire_wait(struct dentry *dentry)
477 {
478         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
479         struct autofs_info *ino = autofs4_dentry_ino(dentry);
480         int status;
481
482         /* Block on any pending expire */
483         spin_lock(&sbi->fs_lock);
484         if (ino->flags & AUTOFS_INF_EXPIRING) {
485                 spin_unlock(&sbi->fs_lock);
486
487                 DPRINTK("waiting for expire %p name=%.*s",
488                          dentry, dentry->d_name.len, dentry->d_name.name);
489
490                 status = autofs4_wait(sbi, dentry, NFY_NONE);
491                 wait_for_completion(&ino->expire_complete);
492
493                 DPRINTK("expire done status=%d", status);
494
495                 if (d_unhashed(dentry))
496                         return -EAGAIN;
497
498                 return status;
499         }
500         spin_unlock(&sbi->fs_lock);
501
502         return 0;
503 }
504
505 /* Perform an expiry operation */
506 int autofs4_expire_run(struct super_block *sb,
507                       struct vfsmount *mnt,
508                       struct autofs_sb_info *sbi,
509                       struct autofs_packet_expire __user *pkt_p)
510 {
511         struct autofs_packet_expire pkt;
512         struct autofs_info *ino;
513         struct dentry *dentry;
514         int ret = 0;
515
516         memset(&pkt,0,sizeof pkt);
517
518         pkt.hdr.proto_version = sbi->version;
519         pkt.hdr.type = autofs_ptype_expire;
520
521         if ((dentry = autofs4_expire_indirect(sb, mnt, sbi, 0)) == NULL)
522                 return -EAGAIN;
523
524         pkt.len = dentry->d_name.len;
525         memcpy(pkt.name, dentry->d_name.name, pkt.len);
526         pkt.name[pkt.len] = '\0';
527         dput(dentry);
528
529         if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
530                 ret = -EFAULT;
531
532         spin_lock(&sbi->fs_lock);
533         ino = autofs4_dentry_ino(dentry);
534         ino->flags &= ~AUTOFS_INF_EXPIRING;
535         complete_all(&ino->expire_complete);
536         spin_unlock(&sbi->fs_lock);
537
538         return ret;
539 }
540
541 int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
542                             struct autofs_sb_info *sbi, int when)
543 {
544         struct dentry *dentry;
545         int ret = -EAGAIN;
546
547         if (autofs_type_trigger(sbi->type))
548                 dentry = autofs4_expire_direct(sb, mnt, sbi, when);
549         else
550                 dentry = autofs4_expire_indirect(sb, mnt, sbi, when);
551
552         if (dentry) {
553                 struct autofs_info *ino = autofs4_dentry_ino(dentry);
554
555                 /* This is synchronous because it makes the daemon a
556                    little easier */
557                 ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
558
559                 spin_lock(&sbi->fs_lock);
560                 ino->flags &= ~AUTOFS_INF_EXPIRING;
561                 spin_lock(&dentry->d_lock);
562                 if (!ret) {
563                         if ((IS_ROOT(dentry) ||
564                             (autofs_type_indirect(sbi->type) &&
565                              IS_ROOT(dentry->d_parent))) &&
566                             !(dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
567                                 __managed_dentry_set_automount(dentry);
568                 }
569                 spin_unlock(&dentry->d_lock);
570                 complete_all(&ino->expire_complete);
571                 spin_unlock(&sbi->fs_lock);
572                 dput(dentry);
573         }
574
575         return ret;
576 }
577
578 /* Call repeatedly until it returns -EAGAIN, meaning there's nothing
579    more to be done */
580 int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
581                         struct autofs_sb_info *sbi, int __user *arg)
582 {
583         int do_now = 0;
584
585         if (arg && get_user(do_now, arg))
586                 return -EFAULT;
587
588         return autofs4_do_expire_multi(sb, mnt, sbi, do_now);
589 }
590