File: /usr/src/linux/fs/autofs/dirhash.c
1 /* -*- linux-c -*- --------------------------------------------------------- *
2 *
3 * linux/fs/autofs/dirhash.c
4 *
5 * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
6 *
7 * This file is part of the Linux kernel and is made available under
8 * the terms of the GNU General Public License, version 2, or at your
9 * option, any later version, incorporated herein by reference.
10 *
11 * ------------------------------------------------------------------------- */
12
13 #include "autofs_i.h"
14
15 /* Functions for maintenance of expiry queue */
16
17 static void autofs_init_usage(struct autofs_dirhash *dh,
18 struct autofs_dir_ent *ent)
19 {
20 list_add_tail(&ent->exp, &dh->expiry_head);
21 ent->last_usage = jiffies;
22 }
23
24 static void autofs_delete_usage(struct autofs_dir_ent *ent)
25 {
26 list_del(&ent->exp);
27 }
28
29 void autofs_update_usage(struct autofs_dirhash *dh,
30 struct autofs_dir_ent *ent)
31 {
32 autofs_delete_usage(ent); /* Unlink from current position */
33 autofs_init_usage(dh,ent); /* Relink at queue tail */
34 }
35
36 struct autofs_dir_ent *autofs_expire(struct super_block *sb,
37 struct autofs_sb_info *sbi,
38 struct vfsmount *mnt)
39 {
40 struct autofs_dirhash *dh = &sbi->dirhash;
41 struct autofs_dir_ent *ent;
42 struct dentry *dentry;
43 unsigned long timeout = sbi->exp_timeout;
44
45 while (1) {
46 if ( list_empty(&dh->expiry_head) || sbi->catatonic )
47 return NULL; /* No entries */
48 /* We keep the list sorted by last_usage and want old stuff */
49 ent = list_entry(dh->expiry_head.next, struct autofs_dir_ent, exp);
50 if (jiffies - ent->last_usage < timeout)
51 break;
52 /* Move to end of list in case expiry isn't desirable */
53 autofs_update_usage(dh, ent);
54
55 /* Check to see that entry is expirable */
56 if ( ent->ino < AUTOFS_FIRST_DIR_INO )
57 return ent; /* Symlinks are always expirable */
58
59 /* Get the dentry for the autofs subdirectory */
60 dentry = ent->dentry;
61
62 if ( !dentry ) {
63 /* Should only happen in catatonic mode */
64 printk("autofs: dentry == NULL but inode range is directory, entry %s\n", ent->name);
65 autofs_delete_usage(ent);
66 continue;
67 }
68
69 if ( !dentry->d_inode ) {
70 dput(dentry);
71 printk("autofs: negative dentry on expiry queue: %s\n",
72 ent->name);
73 autofs_delete_usage(ent);
74 continue;
75 }
76
77 /* Make sure entry is mounted and unused; note that dentry will
78 point to the mounted-on-top root. */
79 if (!S_ISDIR(dentry->d_inode->i_mode)||!d_mountpoint(dentry)) {
80 DPRINTK(("autofs: not expirable (not a mounted directory): %s\n", ent->name));
81 continue;
82 }
83 mntget(mnt);
84 dget(dentry);
85 if (!follow_down(&mnt, &dentry)) {
86 dput(dentry);
87 mntput(mnt);
88 DPRINTK(("autofs: not expirable (not a mounted directory): %s\n", ent->name));
89 continue;
90 }
91 while (d_mountpoint(dentry) && follow_down(&mnt, &dentry))
92 ;
93 dput(dentry);
94
95 if ( may_umount(mnt) == 0 ) {
96 mntput(mnt);
97 DPRINTK(("autofs: signaling expire on %s\n", ent->name));
98 return ent; /* Expirable! */
99 }
100 DPRINTK(("autofs: didn't expire due to may_umount: %s\n", ent->name));
101 mntput(mnt);
102 }
103 return NULL; /* No expirable entries */
104 }
105
106 void autofs_initialize_hash(struct autofs_dirhash *dh) {
107 memset(&dh->h, 0, AUTOFS_HASH_SIZE*sizeof(struct autofs_dir_ent *));
108 INIT_LIST_HEAD(&dh->expiry_head);
109 }
110
111 struct autofs_dir_ent *autofs_hash_lookup(const struct autofs_dirhash *dh, struct qstr *name)
112 {
113 struct autofs_dir_ent *dhn;
114
115 DPRINTK(("autofs_hash_lookup: hash = 0x%08x, name = ", name->hash));
116 autofs_say(name->name,name->len);
117
118 for ( dhn = dh->h[(unsigned) name->hash % AUTOFS_HASH_SIZE] ; dhn ; dhn = dhn->next ) {
119 if ( name->hash == dhn->hash &&
120 name->len == dhn->len &&
121 !memcmp(name->name, dhn->name, name->len) )
122 break;
123 }
124
125 return dhn;
126 }
127
128 void autofs_hash_insert(struct autofs_dirhash *dh, struct autofs_dir_ent *ent)
129 {
130 struct autofs_dir_ent **dhnp;
131
132 DPRINTK(("autofs_hash_insert: hash = 0x%08x, name = ", ent->hash));
133 autofs_say(ent->name,ent->len);
134
135 autofs_init_usage(dh,ent);
136 if (ent->dentry)
137 dget(ent->dentry);
138
139 dhnp = &dh->h[(unsigned) ent->hash % AUTOFS_HASH_SIZE];
140 ent->next = *dhnp;
141 ent->back = dhnp;
142 *dhnp = ent;
143 if ( ent->next )
144 ent->next->back = &(ent->next);
145 }
146
147 void autofs_hash_delete(struct autofs_dir_ent *ent)
148 {
149 *(ent->back) = ent->next;
150 if ( ent->next )
151 ent->next->back = ent->back;
152
153 autofs_delete_usage(ent);
154
155 if ( ent->dentry )
156 dput(ent->dentry);
157 kfree(ent->name);
158 kfree(ent);
159 }
160
161 /*
162 * Used by readdir(). We must validate "ptr", so we can't simply make it
163 * a pointer. Values below 0xffff are reserved; calling with any value
164 * <= 0x10000 will return the first entry found.
165 *
166 * "last" can be NULL or the value returned by the last search *if* we
167 * want the next sequential entry.
168 */
169 struct autofs_dir_ent *autofs_hash_enum(const struct autofs_dirhash *dh,
170 off_t *ptr, struct autofs_dir_ent *last)
171 {
172 int bucket, ecount, i;
173 struct autofs_dir_ent *ent;
174
175 bucket = (*ptr >> 16) - 1;
176 ecount = *ptr & 0xffff;
177
178 if ( bucket < 0 ) {
179 bucket = ecount = 0;
180 }
181
182 DPRINTK(("autofs_hash_enum: bucket %d, entry %d\n", bucket, ecount));
183
184 ent = last ? last->next : NULL;
185
186 if ( ent ) {
187 ecount++;
188 } else {
189 while ( bucket < AUTOFS_HASH_SIZE ) {
190 ent = dh->h[bucket];
191 for ( i = ecount ; ent && i ; i-- )
192 ent = ent->next;
193
194 if (ent) {
195 ecount++; /* Point to *next* entry */
196 break;
197 }
198
199 bucket++; ecount = 0;
200 }
201 }
202
203 #ifdef DEBUG
204 if ( !ent )
205 printk("autofs_hash_enum: nothing found\n");
206 else {
207 printk("autofs_hash_enum: found hash %08x, name", ent->hash);
208 autofs_say(ent->name,ent->len);
209 }
210 #endif
211
212 *ptr = ((bucket+1) << 16) + ecount;
213 return ent;
214 }
215
216 /* Iterate over all the ents, and remove all dentry pointers. Used on
217 entering catatonic mode, in order to make the filesystem unmountable. */
218 void autofs_hash_dputall(struct autofs_dirhash *dh)
219 {
220 int i;
221 struct autofs_dir_ent *ent;
222
223 for ( i = 0 ; i < AUTOFS_HASH_SIZE ; i++ ) {
224 for ( ent = dh->h[i] ; ent ; ent = ent->next ) {
225 if ( ent->dentry ) {
226 dput(ent->dentry);
227 ent->dentry = NULL;
228 }
229 }
230 }
231 }
232
233 /* Delete everything. This is used on filesystem destruction, so we
234 make no attempt to keep the pointers valid */
235 void autofs_hash_nuke(struct autofs_dirhash *dh)
236 {
237 int i;
238 struct autofs_dir_ent *ent, *nent;
239
240 for ( i = 0 ; i < AUTOFS_HASH_SIZE ; i++ ) {
241 for ( ent = dh->h[i] ; ent ; ent = nent ) {
242 nent = ent->next;
243 if ( ent->dentry )
244 dput(ent->dentry);
245 kfree(ent->name);
246 kfree(ent);
247 }
248 }
249 }
250