Merge acpi-2.6.12 to-akpm
[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 2001-2003 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 return 1 if it can else return 0 */
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 (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
45         return 1;
46 }
47
48 /* Check a mount point for busyness return 1 if not busy, otherwise */
49 static int autofs4_check_mount(struct vfsmount *mnt, struct dentry *dentry)
50 {
51         int status = 0;
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 (!autofs4_follow_mount(&mnt, &dentry))
60                 goto done;
61
62         /* This is an autofs submount, we can't expire it */
63         if (is_autofs4_dentry(dentry))
64                 goto done;
65
66         /* The big question */
67         if (may_umount_tree(mnt) == 0)
68                 status = 1;
69 done:
70         DPRINTK("returning = %d", status);
71         mntput(mnt);
72         dput(dentry);
73         return status;
74 }
75
76 /* Check a directory tree of mount points for busyness
77  * The tree is not busy iff no mountpoints are busy
78  * Return 1 if the tree is busy or 0 otherwise
79  */
80 static int autofs4_check_tree(struct vfsmount *mnt,
81                               struct dentry *top,
82                               unsigned long timeout,
83                               int do_now)
84 {
85         struct dentry *this_parent = top;
86         struct list_head *next;
87
88         DPRINTK("parent %p %.*s",
89                 top, (int)top->d_name.len, top->d_name.name);
90
91         /* Negative dentry - give up */
92         if (!simple_positive(top))
93                 return 0;
94
95         /* Timeout of a tree mount is determined by its top dentry */
96         if (!autofs4_can_expire(top, timeout, do_now))
97                 return 0;
98
99         /* Is someone visiting anywhere in the tree ? */
100         if (may_umount_tree(mnt))
101                 return 0;
102
103         spin_lock(&dcache_lock);
104 repeat:
105         next = this_parent->d_subdirs.next;
106 resume:
107         while (next != &this_parent->d_subdirs) {
108                 struct dentry *dentry = list_entry(next, struct dentry, d_child);
109
110                 /* Negative dentry - give up */
111                 if (!simple_positive(dentry)) {
112                         next = next->next;
113                         continue;
114                 }
115
116                 DPRINTK("dentry %p %.*s",
117                         dentry, (int)dentry->d_name.len, dentry->d_name.name);
118
119                 if (!simple_empty_nolock(dentry)) {
120                         this_parent = dentry;
121                         goto repeat;
122                 }
123
124                 dentry = dget(dentry);
125                 spin_unlock(&dcache_lock);
126
127                 if (d_mountpoint(dentry)) {
128                         /* First busy => tree busy */
129                         if (!autofs4_check_mount(mnt, dentry)) {
130                                 dput(dentry);
131                                 return 0;
132                         }
133                 }
134
135                 dput(dentry);
136                 spin_lock(&dcache_lock);
137                 next = next->next;
138         }
139
140         if (this_parent != top) {
141                 next = this_parent->d_child.next;
142                 this_parent = this_parent->d_parent;
143                 goto resume;
144         }
145         spin_unlock(&dcache_lock);
146
147         return 1;
148 }
149
150 static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
151                                            struct dentry *parent,
152                                            unsigned long timeout,
153                                            int do_now)
154 {
155         struct dentry *this_parent = parent;
156         struct list_head *next;
157
158         DPRINTK("parent %p %.*s",
159                 parent, (int)parent->d_name.len, parent->d_name.name);
160
161         spin_lock(&dcache_lock);
162 repeat:
163         next = this_parent->d_subdirs.next;
164 resume:
165         while (next != &this_parent->d_subdirs) {
166                 struct dentry *dentry = list_entry(next, struct dentry, d_child);
167
168                 /* Negative dentry - give up */
169                 if (!simple_positive(dentry)) {
170                         next = next->next;
171                         continue;
172                 }
173
174                 DPRINTK("dentry %p %.*s",
175                         dentry, (int)dentry->d_name.len, dentry->d_name.name);
176
177                 if (!list_empty(&dentry->d_subdirs)) {
178                         this_parent = dentry;
179                         goto repeat;
180                 }
181
182                 dentry = dget(dentry);
183                 spin_unlock(&dcache_lock);
184
185                 if (d_mountpoint(dentry)) {
186                         /* Can we expire this guy */
187                         if (!autofs4_can_expire(dentry, timeout, do_now))
188                                 goto cont;
189
190                         /* Can we umount this guy */
191                         if (autofs4_check_mount(mnt, dentry))
192                                 return dentry;
193
194                 }
195 cont:
196                 dput(dentry);
197                 spin_lock(&dcache_lock);
198                 next = next->next;
199         }
200
201         if (this_parent != parent) {
202                 next = this_parent->d_child.next;
203                 this_parent = this_parent->d_parent;
204                 goto resume;
205         }
206         spin_unlock(&dcache_lock);
207
208         return NULL;
209 }
210
211 /*
212  * Find an eligible tree to time-out
213  * A tree is eligible if :-
214  *  - it is unused by any user process
215  *  - it has been unused for exp_timeout time
216  */
217 static struct dentry *autofs4_expire(struct super_block *sb,
218                                      struct vfsmount *mnt,
219                                      struct autofs_sb_info *sbi,
220                                      int how)
221 {
222         unsigned long timeout;
223         struct dentry *root = sb->s_root;
224         struct dentry *expired = NULL;
225         struct list_head *next;
226         int do_now = how & AUTOFS_EXP_IMMEDIATE;
227         int exp_leaves = how & AUTOFS_EXP_LEAVES;
228
229         if ( !sbi->exp_timeout || !root )
230                 return NULL;
231
232         now = jiffies;
233         timeout = sbi->exp_timeout;
234
235         spin_lock(&dcache_lock);
236         next = root->d_subdirs.next;
237
238         /* On exit from the loop expire is set to a dgot dentry
239          * to expire or it's NULL */
240         while ( next != &root->d_subdirs ) {
241                 struct dentry *dentry = list_entry(next, struct dentry, d_child);
242
243                 /* Negative dentry - give up */
244                 if ( !simple_positive(dentry) ) {
245                         next = next->next;
246                         continue;
247                 }
248
249                 dentry = dget(dentry);
250                 spin_unlock(&dcache_lock);
251
252                 /* Case 1: indirect mount or top level direct mount */
253                 if (d_mountpoint(dentry)) {
254                         DPRINTK("checking mountpoint %p %.*s",
255                                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
256
257                         /* Can we expire this guy */
258                         if (!autofs4_can_expire(dentry, timeout, do_now))
259                                 goto next;
260
261                         /* Can we umount this guy */
262                         if (autofs4_check_mount(mnt, dentry)) {
263                                 expired = dentry;
264                                 break;
265                         }
266                         goto next;
267                 }
268
269                 if ( simple_empty(dentry) )
270                         goto next;
271
272                 /* Case 2: tree mount, expire iff entire tree is not busy */
273                 if (!exp_leaves) {
274                         /* Lock the tree as we must expire as a whole */
275                         spin_lock(&sbi->fs_lock);
276                         if (autofs4_check_tree(mnt, dentry, timeout, do_now)) {
277                                 struct autofs_info *inf = autofs4_dentry_ino(dentry);
278
279                                 /* Set this flag early to catch sys_chdir and the like */
280                                 inf->flags |= AUTOFS_INF_EXPIRING;
281                                 spin_unlock(&sbi->fs_lock);
282                                 expired = dentry;
283                                 break;
284                         }
285                         spin_unlock(&sbi->fs_lock);
286                 /* Case 3: direct mount, expire individual leaves */
287                 } else {
288                         expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
289                         if (expired) {
290                                 dput(dentry);
291                                 break;
292                         }
293                 }
294 next:
295                 dput(dentry);
296                 spin_lock(&dcache_lock);
297                 next = next->next;
298         }
299
300         if ( expired ) {
301                 DPRINTK("returning %p %.*s",
302                         expired, (int)expired->d_name.len, expired->d_name.name);
303                 spin_lock(&dcache_lock);
304                 list_del(&expired->d_parent->d_subdirs);
305                 list_add(&expired->d_parent->d_subdirs, &expired->d_child);
306                 spin_unlock(&dcache_lock);
307                 return expired;
308         }
309         spin_unlock(&dcache_lock);
310
311         return NULL;
312 }
313
314 /* Perform an expiry operation */
315 int autofs4_expire_run(struct super_block *sb,
316                       struct vfsmount *mnt,
317                       struct autofs_sb_info *sbi,
318                       struct autofs_packet_expire __user *pkt_p)
319 {
320         struct autofs_packet_expire pkt;
321         struct dentry *dentry;
322
323         memset(&pkt,0,sizeof pkt);
324
325         pkt.hdr.proto_version = sbi->version;
326         pkt.hdr.type = autofs_ptype_expire;
327
328         if ((dentry = autofs4_expire(sb, mnt, sbi, 0)) == NULL)
329                 return -EAGAIN;
330
331         pkt.len = dentry->d_name.len;
332         memcpy(pkt.name, dentry->d_name.name, pkt.len);
333         pkt.name[pkt.len] = '\0';
334         dput(dentry);
335
336         if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
337                 return -EFAULT;
338
339         return 0;
340 }
341
342 /* Call repeatedly until it returns -EAGAIN, meaning there's nothing
343    more to be done */
344 int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
345                         struct autofs_sb_info *sbi, int __user *arg)
346 {
347         struct dentry *dentry;
348         int ret = -EAGAIN;
349         int do_now = 0;
350
351         if (arg && get_user(do_now, arg))
352                 return -EFAULT;
353
354         if ((dentry = autofs4_expire(sb, mnt, sbi, do_now)) != NULL) {
355                 struct autofs_info *de_info = autofs4_dentry_ino(dentry);
356
357                 /* This is synchronous because it makes the daemon a
358                    little easier */
359                 de_info->flags |= AUTOFS_INF_EXPIRING;
360                 ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
361                 de_info->flags &= ~AUTOFS_INF_EXPIRING;
362                 dput(dentry);
363         }
364                 
365         return ret;
366 }
367