drivers/staging/autofs/dirhash.c

   1 /* -*- linux-c -*- --------------------------------------------------------- *
   2  *
   3  * drivers/staging/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)) {
  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) && follow_down(&path))
  94                         ;
  95                 umount_ok = may_umount(path.mnt);
  96                 path_put(&path);
  97
  98                 if (umount_ok) {
  99                         DPRINTK(("autofs: signaling expire on %s\n", ent->name));
 100                         return ent; /* Expirable! */
 101                 }
 102                 DPRINTK(("autofs: didn't expire due to may_umount: %s\n", ent->name));
 103         }
 104         return NULL;            /* No expirable entries */
 105 }
 106
 107 void autofs_initialize_hash(struct autofs_dirhash *dh) {
 108         memset(&dh->h, 0, AUTOFS_HASH_SIZE*sizeof(struct autofs_dir_ent *));
 109         INIT_LIST_HEAD(&dh->expiry_head);
 110 }
 111
 112 struct autofs_dir_ent *autofs_hash_lookup(const struct autofs_dirhash *dh, struct qstr *name)
 113 {
 114         struct autofs_dir_ent *dhn;
 115
 116         DPRINTK(("autofs_hash_lookup: hash = 0x%08x, name = ", name->hash));
 117         autofs_say(name->name,name->len);
 118
 119         for ( dhn = dh->h[(unsigned) name->hash % AUTOFS_HASH_SIZE] ; dhn ; dhn = dhn->next ) {
 120                 if ( name->hash == dhn->hash &&
 121                      name->len == dhn->len &&
 122                      !memcmp(name->name, dhn->name, name->len) )
 123                         break;
 124         }
 125
 126         return dhn;
 127 }
 128
 129 void autofs_hash_insert(struct autofs_dirhash *dh, struct autofs_dir_ent *ent)
 130 {
 131         struct autofs_dir_ent **dhnp;
 132
 133         DPRINTK(("autofs_hash_insert: hash = 0x%08x, name = ", ent->hash));
 134         autofs_say(ent->name,ent->len);
 135
 136         autofs_init_usage(dh,ent);
 137         if (ent->dentry)
 138                 dget(ent->dentry);
 139
 140         dhnp = &dh->h[(unsigned) ent->hash % AUTOFS_HASH_SIZE];
 141         ent->next = *dhnp;
 142         ent->back = dhnp;
 143         *dhnp = ent;
 144         if ( ent->next )
 145                 ent->next->back = &(ent->next);
 146 }
 147
 148 void autofs_hash_delete(struct autofs_dir_ent *ent)
 149 {
 150         *(ent->back) = ent->next;
 151         if ( ent->next )
 152                 ent->next->back = ent->back;
 153
 154         autofs_delete_usage(ent);
 155
 156         if ( ent->dentry )
 157                 dput(ent->dentry);
 158         kfree(ent->name);
 159         kfree(ent);
 160 }
 161
 162 /*
 163  * Used by readdir().  We must validate "ptr", so we can't simply make it
 164  * a pointer.  Values below 0xffff are reserved; calling with any value
 165  * <= 0x10000 will return the first entry found.
 166  *
 167  * "last" can be NULL or the value returned by the last search *if* we
 168  * want the next sequential entry.
 169  */
 170 struct autofs_dir_ent *autofs_hash_enum(const struct autofs_dirhash *dh,
 171                                         off_t *ptr, struct autofs_dir_ent *last)
 172 {
 173         int bucket, ecount, i;
 174         struct autofs_dir_ent *ent;
 175
 176         bucket = (*ptr >> 16) - 1;
 177         ecount = *ptr & 0xffff;
 178
 179         if ( bucket < 0 ) {
 180                 bucket = ecount = 0;
 181         }
 182
 183         DPRINTK(("autofs_hash_enum: bucket %d, entry %d\n", bucket, ecount));
 184
 185         ent = last ? last->next : NULL;
 186
 187         if ( ent ) {
 188                 ecount++;
 189         } else {
 190                 while  ( bucket < AUTOFS_HASH_SIZE ) {
 191                         ent = dh->h[bucket];
 192                         for ( i = ecount ; ent && i ; i-- )
 193                                 ent = ent->next;
 194
 195                         if (ent) {
 196                                 ecount++; /* Point to *next* entry */
 197                                 break;
 198                         }
 199
 200                         bucket++; ecount = 0;
 201                 }
 202         }
 203
 204 #ifdef DEBUG
 205         if ( !ent )
 206                 printk("autofs_hash_enum: nothing found\n");
 207         else {
 208                 printk("autofs_hash_enum: found hash %08x, name", ent->hash);
 209                 autofs_say(ent->name,ent->len);
 210         }
 211 #endif
 212
 213         *ptr = ((bucket+1) << 16) + ecount;
 214         return ent;
 215 }
 216
 217 /* Iterate over all the ents, and remove all dentry pointers.  Used on
 218    entering catatonic mode, in order to make the filesystem unmountable. */
 219 void autofs_hash_dputall(struct autofs_dirhash *dh)
 220 {
 221         int i;
 222         struct autofs_dir_ent *ent;
 223
 224         for ( i = 0 ; i < AUTOFS_HASH_SIZE ; i++ ) {
 225                 for ( ent = dh->h[i] ; ent ; ent = ent->next ) {
 226                         if ( ent->dentry ) {
 227                                 dput(ent->dentry);
 228                                 ent->dentry = NULL;
 229                         }
 230                 }
 231         }
 232 }
 233
 234 /* Delete everything.  This is used on filesystem destruction, so we
 235    make no attempt to keep the pointers valid */
 236 void autofs_hash_nuke(struct autofs_sb_info *sbi)
 237 {
 238         int i;
 239         struct autofs_dir_ent *ent, *nent;
 240
 241         for ( i = 0 ; i < AUTOFS_HASH_SIZE ; i++ ) {
 242                 for ( ent = sbi->dirhash.h[i] ; ent ; ent = nent ) {
 243                         nent = ent->next;
 244                         if ( ent->dentry )
 245                                 dput(ent->dentry);
 246                         kfree(ent->name);
 247                         kfree(ent);
 248                 }
 249         }
 250 }