Merge git://git.kernel.org/pub/scm/linux/kernel/git/wim/linux-2.6-watchdog
[linux-2.6] / 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         /* No point expiring a pending mount */
30         if (dentry->d_flags & DCACHE_AUTOFS_PENDING)
31                 return 0;
32
33         if (!do_now) {
34                 /* Too young to die */
35                 if (!timeout || time_after(ino->last_used + timeout, now))
36                         return 0;
37
38                 /* update last_used here :-
39                    - obviously makes sense if it is in use now
40                    - less obviously, prevents rapid-fire expire
41                      attempts if expire fails the first time */
42                 ino->last_used = now;
43         }
44         return 1;
45 }
46
47 /* Check a mount point for busyness */
48 static int autofs4_mount_busy(struct vfsmount *mnt, struct dentry *dentry)
49 {
50         struct dentry *top = dentry;
51         int status = 1;
52
53         DPRINTK("dentry %p %.*s",
54                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
55
56         mntget(mnt);
57         dget(dentry);
58
59         if (!follow_down(&mnt, &dentry))
60                 goto done;
61
62         if (is_autofs4_dentry(dentry)) {
63                 struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
64
65                 /* This is an autofs submount, we can't expire it */
66                 if (sbi->type == AUTOFS_TYPE_INDIRECT)
67                         goto done;
68
69                 /*
70                  * Otherwise it's an offset mount and we need to check
71                  * if we can umount its mount, if there is one.
72                  */
73                 if (!d_mountpoint(dentry))
74                         goto done;
75         }
76
77         /* Update the expiry counter if fs is busy */
78         if (!may_umount_tree(mnt)) {
79                 struct autofs_info *ino = autofs4_dentry_ino(top);
80                 ino->last_used = jiffies;
81                 goto done;
82         }
83
84         status = 0;
85 done:
86         DPRINTK("returning = %d", status);
87         dput(dentry);
88         mntput(mnt);
89         return status;
90 }
91
92 /*
93  * Calculate next entry in top down tree traversal.
94  * From next_mnt in namespace.c - elegant.
95  */
96 static struct dentry *next_dentry(struct dentry *p, struct dentry *root)
97 {
98         struct list_head *next = p->d_subdirs.next;
99
100         if (next == &p->d_subdirs) {
101                 while (1) {
102                         if (p == root)
103                                 return NULL;
104                         next = p->d_u.d_child.next;
105                         if (next != &p->d_parent->d_subdirs)
106                                 break;
107                         p = p->d_parent;
108                 }
109         }
110         return list_entry(next, struct dentry, d_u.d_child);
111 }
112
113 /*
114  * Check a direct mount point for busyness.
115  * Direct mounts have similar expiry semantics to tree mounts.
116  * The tree is not busy iff no mountpoints are busy and there are no
117  * autofs submounts.
118  */
119 static int autofs4_direct_busy(struct vfsmount *mnt,
120                                 struct dentry *top,
121                                 unsigned long timeout,
122                                 int do_now)
123 {
124         DPRINTK("top %p %.*s",
125                 top, (int) top->d_name.len, top->d_name.name);
126
127         /* If it's busy update the expiry counters */
128         if (!may_umount_tree(mnt)) {
129                 struct autofs_info *ino = autofs4_dentry_ino(top);
130                 if (ino)
131                         ino->last_used = jiffies;
132                 return 1;
133         }
134
135         /* Timeout of a direct mount is determined by its top dentry */
136         if (!autofs4_can_expire(top, timeout, do_now))
137                 return 1;
138
139         return 0;
140 }
141
142 /* Check a directory tree of mount points for busyness
143  * The tree is not busy iff no mountpoints are busy
144  */
145 static int autofs4_tree_busy(struct vfsmount *mnt,
146                              struct dentry *top,
147                              unsigned long timeout,
148                              int do_now)
149 {
150         struct autofs_info *top_ino = autofs4_dentry_ino(top);
151         struct dentry *p;
152
153         DPRINTK("top %p %.*s",
154                 top, (int)top->d_name.len, top->d_name.name);
155
156         /* Negative dentry - give up */
157         if (!simple_positive(top))
158                 return 1;
159
160         spin_lock(&dcache_lock);
161         for (p = top; p; p = next_dentry(p, top)) {
162                 /* Negative dentry - give up */
163                 if (!simple_positive(p))
164                         continue;
165
166                 DPRINTK("dentry %p %.*s",
167                         p, (int) p->d_name.len, p->d_name.name);
168
169                 p = dget(p);
170                 spin_unlock(&dcache_lock);
171
172                 /*
173                  * Is someone visiting anywhere in the subtree ?
174                  * If there's no mount we need to check the usage
175                  * count for the autofs dentry.
176                  * If the fs is busy update the expiry counter.
177                  */
178                 if (d_mountpoint(p)) {
179                         if (autofs4_mount_busy(mnt, p)) {
180                                 top_ino->last_used = jiffies;
181                                 dput(p);
182                                 return 1;
183                         }
184                 } else {
185                         struct autofs_info *ino = autofs4_dentry_ino(p);
186                         unsigned int ino_count = atomic_read(&ino->count);
187
188                         /*
189                          * Clean stale dentries below that have not been
190                          * invalidated after a mount fail during lookup
191                          */
192                         d_invalidate(p);
193
194                         /* allow for dget above and top is already dgot */
195                         if (p == top)
196                                 ino_count += 2;
197                         else
198                                 ino_count++;
199
200                         if (atomic_read(&p->d_count) > ino_count) {
201                                 top_ino->last_used = jiffies;
202                                 dput(p);
203                                 return 1;
204                         }
205                 }
206                 dput(p);
207                 spin_lock(&dcache_lock);
208         }
209         spin_unlock(&dcache_lock);
210
211         /* Timeout of a tree mount is ultimately determined by its top dentry */
212         if (!autofs4_can_expire(top, timeout, do_now))
213                 return 1;
214
215         return 0;
216 }
217
218 static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
219                                            struct dentry *parent,
220                                            unsigned long timeout,
221                                            int do_now)
222 {
223         struct dentry *p;
224
225         DPRINTK("parent %p %.*s",
226                 parent, (int)parent->d_name.len, parent->d_name.name);
227
228         spin_lock(&dcache_lock);
229         for (p = parent; p; p = next_dentry(p, parent)) {
230                 /* Negative dentry - give up */
231                 if (!simple_positive(p))
232                         continue;
233
234                 DPRINTK("dentry %p %.*s",
235                         p, (int) p->d_name.len, p->d_name.name);
236
237                 p = dget(p);
238                 spin_unlock(&dcache_lock);
239
240                 if (d_mountpoint(p)) {
241                         /* Can we umount this guy */
242                         if (autofs4_mount_busy(mnt, p))
243                                 goto cont;
244
245                         /* Can we expire this guy */
246                         if (autofs4_can_expire(p, timeout, do_now))
247                                 return p;
248                 }
249 cont:
250                 dput(p);
251                 spin_lock(&dcache_lock);
252         }
253         spin_unlock(&dcache_lock);
254         return NULL;
255 }
256
257 /* Check if we can expire a direct mount (possibly a tree) */
258 struct dentry *autofs4_expire_direct(struct super_block *sb,
259                                      struct vfsmount *mnt,
260                                      struct autofs_sb_info *sbi,
261                                      int how)
262 {
263         unsigned long timeout;
264         struct dentry *root = dget(sb->s_root);
265         int do_now = how & AUTOFS_EXP_IMMEDIATE;
266
267         if (!root)
268                 return NULL;
269
270         now = jiffies;
271         timeout = sbi->exp_timeout;
272
273         spin_lock(&sbi->fs_lock);
274         if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
275                 struct autofs_info *ino = autofs4_dentry_ino(root);
276                 if (d_mountpoint(root)) {
277                         ino->flags |= AUTOFS_INF_MOUNTPOINT;
278                         root->d_mounted--;
279                 }
280                 ino->flags |= AUTOFS_INF_EXPIRING;
281                 init_completion(&ino->expire_complete);
282                 spin_unlock(&sbi->fs_lock);
283                 return root;
284         }
285         spin_unlock(&sbi->fs_lock);
286         dput(root);
287
288         return NULL;
289 }
290
291 /*
292  * Find an eligible tree to time-out
293  * A tree is eligible if :-
294  *  - it is unused by any user process
295  *  - it has been unused for exp_timeout time
296  */
297 struct dentry *autofs4_expire_indirect(struct super_block *sb,
298                                        struct vfsmount *mnt,
299                                        struct autofs_sb_info *sbi,
300                                        int how)
301 {
302         unsigned long timeout;
303         struct dentry *root = sb->s_root;
304         struct dentry *expired = NULL;
305         struct list_head *next;
306         int do_now = how & AUTOFS_EXP_IMMEDIATE;
307         int exp_leaves = how & AUTOFS_EXP_LEAVES;
308         struct autofs_info *ino;
309         unsigned int ino_count;
310
311         if (!root)
312                 return NULL;
313
314         now = jiffies;
315         timeout = sbi->exp_timeout;
316
317         spin_lock(&dcache_lock);
318         next = root->d_subdirs.next;
319
320         /* On exit from the loop expire is set to a dgot dentry
321          * to expire or it's NULL */
322         while ( next != &root->d_subdirs ) {
323                 struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);
324
325                 /* Negative dentry - give up */
326                 if (!simple_positive(dentry)) {
327                         next = next->next;
328                         continue;
329                 }
330
331                 dentry = dget(dentry);
332                 spin_unlock(&dcache_lock);
333
334                 spin_lock(&sbi->fs_lock);
335                 ino = autofs4_dentry_ino(dentry);
336
337                 /*
338                  * Case 1: (i) indirect mount or top level pseudo direct mount
339                  *         (autofs-4.1).
340                  *         (ii) indirect mount with offset mount, check the "/"
341                  *         offset (autofs-5.0+).
342                  */
343                 if (d_mountpoint(dentry)) {
344                         DPRINTK("checking mountpoint %p %.*s",
345                                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
346
347                         /* Path walk currently on this dentry? */
348                         ino_count = atomic_read(&ino->count) + 2;
349                         if (atomic_read(&dentry->d_count) > ino_count)
350                                 goto next;
351
352                         /* Can we umount this guy */
353                         if (autofs4_mount_busy(mnt, dentry))
354                                 goto next;
355
356                         /* Can we expire this guy */
357                         if (autofs4_can_expire(dentry, timeout, do_now)) {
358                                 expired = dentry;
359                                 goto found;
360                         }
361                         goto next;
362                 }
363
364                 if (simple_empty(dentry))
365                         goto next;
366
367                 /* Case 2: tree mount, expire iff entire tree is not busy */
368                 if (!exp_leaves) {
369                         /* Path walk currently on this dentry? */
370                         ino_count = atomic_read(&ino->count) + 1;
371                         if (atomic_read(&dentry->d_count) > ino_count)
372                                 goto next;
373
374                         if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
375                                 expired = dentry;
376                                 goto found;
377                         }
378                 /*
379                  * Case 3: pseudo direct mount, expire individual leaves
380                  *         (autofs-4.1).
381                  */
382                 } else {
383                         /* Path walk currently on this dentry? */
384                         ino_count = atomic_read(&ino->count) + 1;
385                         if (atomic_read(&dentry->d_count) > ino_count)
386                                 goto next;
387
388                         expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
389                         if (expired) {
390                                 dput(dentry);
391                                 goto found;
392                         }
393                 }
394 next:
395                 spin_unlock(&sbi->fs_lock);
396                 dput(dentry);
397                 spin_lock(&dcache_lock);
398                 next = next->next;
399         }
400         spin_unlock(&dcache_lock);
401         return NULL;
402
403 found:
404         DPRINTK("returning %p %.*s",
405                 expired, (int)expired->d_name.len, expired->d_name.name);
406         ino = autofs4_dentry_ino(expired);
407         ino->flags |= AUTOFS_INF_EXPIRING;
408         init_completion(&ino->expire_complete);
409         spin_unlock(&sbi->fs_lock);
410         spin_lock(&dcache_lock);
411         list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
412         spin_unlock(&dcache_lock);
413         return expired;
414 }
415
416 int autofs4_expire_wait(struct dentry *dentry)
417 {
418         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
419         struct autofs_info *ino = autofs4_dentry_ino(dentry);
420         int status;
421
422         /* Block on any pending expire */
423         spin_lock(&sbi->fs_lock);
424         if (ino->flags & AUTOFS_INF_EXPIRING) {
425                 spin_unlock(&sbi->fs_lock);
426
427                 DPRINTK("waiting for expire %p name=%.*s",
428                          dentry, dentry->d_name.len, dentry->d_name.name);
429
430                 status = autofs4_wait(sbi, dentry, NFY_NONE);
431                 wait_for_completion(&ino->expire_complete);
432
433                 DPRINTK("expire done status=%d", status);
434
435                 if (d_unhashed(dentry))
436                         return -EAGAIN;
437
438                 return status;
439         }
440         spin_unlock(&sbi->fs_lock);
441
442         return 0;
443 }
444
445 /* Perform an expiry operation */
446 int autofs4_expire_run(struct super_block *sb,
447                       struct vfsmount *mnt,
448                       struct autofs_sb_info *sbi,
449                       struct autofs_packet_expire __user *pkt_p)
450 {
451         struct autofs_packet_expire pkt;
452         struct autofs_info *ino;
453         struct dentry *dentry;
454         int ret = 0;
455
456         memset(&pkt,0,sizeof pkt);
457
458         pkt.hdr.proto_version = sbi->version;
459         pkt.hdr.type = autofs_ptype_expire;
460
461         if ((dentry = autofs4_expire_indirect(sb, mnt, sbi, 0)) == NULL)
462                 return -EAGAIN;
463
464         pkt.len = dentry->d_name.len;
465         memcpy(pkt.name, dentry->d_name.name, pkt.len);
466         pkt.name[pkt.len] = '\0';
467         dput(dentry);
468
469         if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
470                 ret = -EFAULT;
471
472         spin_lock(&sbi->fs_lock);
473         ino = autofs4_dentry_ino(dentry);
474         ino->flags &= ~AUTOFS_INF_EXPIRING;
475         complete_all(&ino->expire_complete);
476         spin_unlock(&sbi->fs_lock);
477
478         return ret;
479 }
480
481 /* Call repeatedly until it returns -EAGAIN, meaning there's nothing
482    more to be done */
483 int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
484                         struct autofs_sb_info *sbi, int __user *arg)
485 {
486         struct dentry *dentry;
487         int ret = -EAGAIN;
488         int do_now = 0;
489
490         if (arg && get_user(do_now, arg))
491                 return -EFAULT;
492
493         if (sbi->type & AUTOFS_TYPE_TRIGGER)
494                 dentry = autofs4_expire_direct(sb, mnt, sbi, do_now);
495         else
496                 dentry = autofs4_expire_indirect(sb, mnt, sbi, do_now);
497
498         if (dentry) {
499                 struct autofs_info *ino = autofs4_dentry_ino(dentry);
500
501                 /* This is synchronous because it makes the daemon a
502                    little easier */
503                 ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
504
505                 spin_lock(&sbi->fs_lock);
506                 if (ino->flags & AUTOFS_INF_MOUNTPOINT) {
507                         sb->s_root->d_mounted++;
508                         ino->flags &= ~AUTOFS_INF_MOUNTPOINT;
509                 }
510                 ino->flags &= ~AUTOFS_INF_EXPIRING;
511                 complete_all(&ino->expire_complete);
512                 spin_unlock(&sbi->fs_lock);
513                 dput(dentry);
514         }
515
516         return ret;
517 }
518