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