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) ) {
  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_sb_info *sbi)
 236 {
 237         int i;
 238         struct autofs_dir_ent *ent, *nent;
 239
 240         for ( i = 0 ; i < AUTOFS_HASH_SIZE ; i++ ) {
 241                 for ( ent = sbi->dirhash.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 }