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   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         unsigned long timeout = sbi->exp_timeout;
  43
  44         while (1) {
  45                 struct path path;
  46                 int umount_ok;
  47
  48                 if ( list_empty(&dh->expiry_head) || sbi->catatonic )
  49                         return NULL;    /* No entries */
  50                 /* We keep the list sorted by last_usage and want old stuff */
  51                 ent = list_entry(dh->expiry_head.next, struct autofs_dir_ent, exp);
  52                 if (jiffies - ent->last_usage < timeout)
  53                         break;
  54                 /* Move to end of list in case expiry isn't desirable */
  55                 autofs_update_usage(dh, ent);
  56
  57                 /* Check to see that entry is expirable */
  58                 if ( ent->ino < AUTOFS_FIRST_DIR_INO )
  59                         return ent; /* Symlinks are always expirable */
  60
  61                 /* Get the dentry for the autofs subdirectory */
  62                 path.dentry = ent->dentry;
  63
  64                 if (!path.dentry) {
  65                         /* Should only happen in catatonic mode */
  66                         printk("autofs: dentry == NULL but inode range is directory, entry %s\n", ent->name);
  67                         autofs_delete_usage(ent);
  68                         continue;
  69                 }
  70
  71                 if (!path.dentry->d_inode) {
  72                         dput(path.dentry);
  73                         printk("autofs: negative dentry on expiry queue: %s\n",
  74                                ent->name);
  75                         autofs_delete_usage(ent);
  76                         continue;
  77                 }
  78
  79                 /* Make sure entry is mounted and unused; note that dentry will
  80                    point to the mounted-on-top root. */
  81                 if (!S_ISDIR(path.dentry->d_inode->i_mode) ||
  82                     !d_mountpoint(path.dentry)) {
  83                         DPRINTK(("autofs: not expirable (not a mounted directory): %s\n", ent->name));
  84                         continue;
  85                 }
  86                 path.mnt = mnt;
  87                 path_get(&path);
  88                 if (!follow_down(&path.mnt, &path.dentry)) {
  89                         path_put(&path);
  90                         DPRINTK(("autofs: not expirable (not a mounted directory): %s\n", ent->name));
  91                         continue;
  92                 }
  93                 while (d_mountpoint(path.dentry) &&
  94                        follow_down(&path.mnt, &path.dentry))
  95                         ;
  96                 umount_ok = may_umount(path.mnt);
  97                 path_put(&path);
  98
  99                 if (umount_ok) {
 100                         DPRINTK(("autofs: signaling expire on %s\n", ent->name));
 101                         return ent; /* Expirable! */
 102                 }
 103                 DPRINTK(("autofs: didn't expire due to may_umount: %s\n", ent->name));
 104         }
 105         return NULL;            /* No expirable entries */
 106 }
 107
 108 void autofs_initialize_hash(struct autofs_dirhash *dh) {
 109         memset(&dh->h, 0, AUTOFS_HASH_SIZE*sizeof(struct autofs_dir_ent *));
 110         INIT_LIST_HEAD(&dh->expiry_head);
 111 }
 112
 113 struct autofs_dir_ent *autofs_hash_lookup(const struct autofs_dirhash *dh, struct qstr *name)
 114 {
 115         struct autofs_dir_ent *dhn;
 116
 117         DPRINTK(("autofs_hash_lookup: hash = 0x%08x, name = ", name->hash));
 118         autofs_say(name->name,name->len);
 119
 120         for ( dhn = dh->h[(unsigned) name->hash % AUTOFS_HASH_SIZE] ; dhn ; dhn = dhn->next ) {
 121                 if ( name->hash == dhn->hash &&
 122                      name->len == dhn->len &&
 123                      !memcmp(name->name, dhn->name, name->len) )
 124                         break;
 125         }
 126
 127         return dhn;
 128 }
 129
 130 void autofs_hash_insert(struct autofs_dirhash *dh, struct autofs_dir_ent *ent)
 131 {
 132         struct autofs_dir_ent **dhnp;
 133
 134         DPRINTK(("autofs_hash_insert: hash = 0x%08x, name = ", ent->hash));
 135         autofs_say(ent->name,ent->len);
 136
 137         autofs_init_usage(dh,ent);
 138         if (ent->dentry)
 139                 dget(ent->dentry);
 140
 141         dhnp = &dh->h[(unsigned) ent->hash % AUTOFS_HASH_SIZE];
 142         ent->next = *dhnp;
 143         ent->back = dhnp;
 144         *dhnp = ent;
 145         if ( ent->next )
 146                 ent->next->back = &(ent->next);
 147 }
 148
 149 void autofs_hash_delete(struct autofs_dir_ent *ent)
 150 {
 151         *(ent->back) = ent->next;
 152         if ( ent->next )
 153                 ent->next->back = ent->back;
 154
 155         autofs_delete_usage(ent);
 156
 157         if ( ent->dentry )
 158                 dput(ent->dentry);
 159         kfree(ent->name);
 160         kfree(ent);
 161 }
 162
 163 /*
 164  * Used by readdir().  We must validate "ptr", so we can't simply make it
 165  * a pointer.  Values below 0xffff are reserved; calling with any value
 166  * <= 0x10000 will return the first entry found.
 167  *
 168  * "last" can be NULL or the value returned by the last search *if* we
 169  * want the next sequential entry.
 170  */
 171 struct autofs_dir_ent *autofs_hash_enum(const struct autofs_dirhash *dh,
 172                                         off_t *ptr, struct autofs_dir_ent *last)
 173 {
 174         int bucket, ecount, i;
 175         struct autofs_dir_ent *ent;
 176
 177         bucket = (*ptr >> 16) - 1;
 178         ecount = *ptr & 0xffff;
 179
 180         if ( bucket < 0 ) {
 181                 bucket = ecount = 0;
 182         }
 183
 184         DPRINTK(("autofs_hash_enum: bucket %d, entry %d\n", bucket, ecount));
 185
 186         ent = last ? last->next : NULL;
 187
 188         if ( ent ) {
 189                 ecount++;
 190         } else {
 191                 while  ( bucket < AUTOFS_HASH_SIZE ) {
 192                         ent = dh->h[bucket];
 193                         for ( i = ecount ; ent && i ; i-- )
 194                                 ent = ent->next;
 195
 196                         if (ent) {
 197                                 ecount++; /* Point to *next* entry */
 198                                 break;
 199                         }
 200
 201                         bucket++; ecount = 0;
 202                 }
 203         }
 204
 205 #ifdef DEBUG
 206         if ( !ent )
 207                 printk("autofs_hash_enum: nothing found\n");
 208         else {
 209                 printk("autofs_hash_enum: found hash %08x, name", ent->hash);
 210                 autofs_say(ent->name,ent->len);
 211         }
 212 #endif
 213
 214         *ptr = ((bucket+1) << 16) + ecount;
 215         return ent;
 216 }
 217
 218 /* Iterate over all the ents, and remove all dentry pointers.  Used on
 219    entering catatonic mode, in order to make the filesystem unmountable. */
 220 void autofs_hash_dputall(struct autofs_dirhash *dh)
 221 {
 222         int i;
 223         struct autofs_dir_ent *ent;
 224
 225         for ( i = 0 ; i < AUTOFS_HASH_SIZE ; i++ ) {
 226                 for ( ent = dh->h[i] ; ent ; ent = ent->next ) {
 227                         if ( ent->dentry ) {
 228                                 dput(ent->dentry);
 229                                 ent->dentry = NULL;
 230                         }
 231                 }
 232         }
 233 }
 234
 235 /* Delete everything.  This is used on filesystem destruction, so we
 236    make no attempt to keep the pointers valid */
 237 void autofs_hash_nuke(struct autofs_sb_info *sbi)
 238 {
 239         int i;
 240         struct autofs_dir_ent *ent, *nent;
 241
 242         for ( i = 0 ; i < AUTOFS_HASH_SIZE ; i++ ) {
 243                 for ( ent = sbi->dirhash.h[i] ; ent ; ent = nent ) {
 244                         nent = ent->next;
 245                         if ( ent->dentry )
 246                                 dput(ent->dentry);
 247                         kfree(ent->name);
 248                         kfree(ent);
 249                 }
 250         }
 251 }