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,
  52                                                 struct autofs_dir_ent, exp);
  53                 if (jiffies - ent->last_usage < timeout)
  54                         break;
  55                 /* Move to end of list in case expiry isn't desirable */
  56                 autofs_update_usage(dh, ent);
  57
  58                 /* Check to see that entry is expirable */
  59                 if (ent->ino < AUTOFS_FIRST_DIR_INO)
  60                         return ent; /* Symlinks are always expirable */
  61
  62                 /* Get the dentry for the autofs subdirectory */
  63                 path.dentry = ent->dentry;
  64
  65                 if (!path.dentry) {
  66                         /* Should only happen in catatonic mode */
  67                         printk(KERN_DEBUG "autofs: dentry == NULL but inode \
  68                                 range is directory, entry %s\n", ent->name);
  69                         autofs_delete_usage(ent);
  70                         continue;
  71                 }
  72
  73                 if (!path.dentry->d_inode) {
  74                         dput(path.dentry);
  75                         printk(KERN_DEBUG "autofs: negative dentry on expiry queue: %s\n",
  76                                ent->name);
  77                         autofs_delete_usage(ent);
  78                         continue;
  79                 }
  80
  81                 /* Make sure entry is mounted and unused; note that dentry will
  82                    point to the mounted-on-top root. */
  83                 if (!S_ISDIR(path.dentry->d_inode->i_mode) ||
  84                     !d_mountpoint(path.dentry)) {
  85                         DPRINTK(("autofs: not expirable \
  86                                 (not a mounted directory): %s\n", ent->name));
  87                         continue;
  88                 }
  89                 path.mnt = mnt;
  90                 path_get(&path);
  91                 if (!follow_down_one(&path)) {
  92                         path_put(&path);
  93                         DPRINTK(("autofs: not expirable\
  94                         (not a mounted directory): %s\n", ent->name));
  95                         continue;
  96                 }
  97                 follow_down(&path, false);  // TODO: need to check error
  98                 umount_ok = may_umount(path.mnt);
  99                 path_put(&path);
 100
 101                 if (umount_ok) {
 102                         DPRINTK(("autofs: signaling expire on %s\n",
 103                                                                 ent->name));
 104                         return ent; /* Expirable! */
 105                 }
 106
 107                 DPRINTK(("autofs: didn't expire due to may_umount: %s\n",
 108                                                                 ent->name));
 109         }
 110         return NULL;            /* No expirable entries */
 111 }
 112
 113 void autofs_initialize_hash(struct autofs_dirhash *dh)
 114 {
 115         memset(&dh->h, 0, AUTOFS_HASH_SIZE*sizeof(struct autofs_dir_ent *));
 116         INIT_LIST_HEAD(&dh->expiry_head);
 117 }
 118
 119 struct autofs_dir_ent *autofs_hash_lookup(const struct autofs_dirhash *dh,
 120                                                 struct qstr *name)
 121 {
 122         struct autofs_dir_ent *dhn;
 123
 124         DPRINTK(("autofs_hash_lookup: hash = 0x%08x, name = ", name->hash));
 125         autofs_say(name->name, name->len);
 126
 127         for (dhn = dh->h[(unsigned) name->hash % AUTOFS_HASH_SIZE];
 128                 dhn;
 129                 dhn = dhn->next) {
 130                 if (name->hash == dhn->hash &&
 131                      name->len == dhn->len &&
 132                      !memcmp(name->name, dhn->name, name->len))
 133                         break;
 134         }
 135
 136         return dhn;
 137 }
 138
 139 void autofs_hash_insert(struct autofs_dirhash *dh, struct autofs_dir_ent *ent)
 140 {
 141         struct autofs_dir_ent **dhnp;
 142
 143         DPRINTK(("autofs_hash_insert: hash = 0x%08x, name = ", ent->hash));
 144         autofs_say(ent->name, ent->len);
 145
 146         autofs_init_usage(dh, ent);
 147         if (ent->dentry)
 148                 dget(ent->dentry);
 149
 150         dhnp = &dh->h[(unsigned) ent->hash % AUTOFS_HASH_SIZE];
 151         ent->next = *dhnp;
 152         ent->back = dhnp;
 153         *dhnp = ent;
 154         if (ent->next)
 155                 ent->next->back = &(ent->next);
 156 }
 157
 158 void autofs_hash_delete(struct autofs_dir_ent *ent)
 159 {
 160         *(ent->back) = ent->next;
 161         if (ent->next)
 162                 ent->next->back = ent->back;
 163
 164         autofs_delete_usage(ent);
 165
 166         if (ent->dentry)
 167                 dput(ent->dentry);
 168         kfree(ent->name);
 169         kfree(ent);
 170 }
 171
 172 /*
 173  * Used by readdir().  We must validate "ptr", so we can't simply make it
 174  * a pointer.  Values below 0xffff are reserved; calling with any value
 175  * <= 0x10000 will return the first entry found.
 176  *
 177  * "last" can be NULL or the value returned by the last search *if* we
 178  * want the next sequential entry.
 179  */
 180 struct autofs_dir_ent *autofs_hash_enum(const struct autofs_dirhash *dh,
 181                                         off_t *ptr, struct autofs_dir_ent *last)
 182 {
 183         int bucket, ecount, i;
 184         struct autofs_dir_ent *ent;
 185
 186         bucket = (*ptr >> 16) - 1;
 187         ecount = *ptr & 0xffff;
 188
 189         if (bucket < 0)
 190                 bucket = ecount = 0;
 191
 192         DPRINTK(("autofs_hash_enum: bucket %d, entry %d\n", bucket, ecount));
 193
 194         ent = last ? last->next : NULL;
 195
 196         if (ent) {
 197                 ecount++;
 198         } else {
 199                 while  (bucket < AUTOFS_HASH_SIZE) {
 200                         ent = dh->h[bucket];
 201                         for (i = ecount ; ent && i ; i--)
 202                                 ent = ent->next;
 203
 204                         if (ent) {
 205                                 ecount++; /* Point to *next* entry */
 206                                 break;
 207                         }
 208
 209                         bucket++; ecount = 0;
 210                 }
 211         }
 212
 213 #ifdef DEBUG
 214         if (!ent)
 215                 printk(KERN_DEBUG "autofs_hash_enum: nothing found\n");
 216         else {
 217                 printk(KERN_DEBUG "autofs_hash_enum: found hash %08x, name",
 218                                                                 ent->hash);
 219                 autofs_say(ent->name, ent->len);
 220         }
 221 #endif
 222
 223         *ptr = ((bucket+1) << 16) + ecount;
 224         return ent;
 225 }
 226
 227 /* Iterate over all the ents, and remove all dentry pointers.  Used on
 228    entering catatonic mode, in order to make the filesystem unmountable. */
 229 void autofs_hash_dputall(struct autofs_dirhash *dh)
 230 {
 231         int i;
 232         struct autofs_dir_ent *ent;
 233
 234         for (i = 0 ; i < AUTOFS_HASH_SIZE ; i++) {
 235                 for (ent = dh->h[i] ; ent ; ent = ent->next) {
 236                         if (ent->dentry) {
 237                                 dput(ent->dentry);
 238                                 ent->dentry = NULL;
 239                         }
 240                 }
 241         }
 242 }
 243
 244 /* Delete everything.  This is used on filesystem destruction, so we
 245    make no attempt to keep the pointers valid */
 246 void autofs_hash_nuke(struct autofs_sb_info *sbi)
 247 {
 248         int i;
 249         struct autofs_dir_ent *ent, *nent;
 250
 251         for (i = 0 ; i < AUTOFS_HASH_SIZE ; i++) {
 252                 for (ent = sbi->dirhash.h[i] ; ent ; ent = nent) {
 253                         nent = ent->next;
 254                         if (ent->dentry)
 255                                 dput(ent->dentry);
 256                         kfree(ent->name);
 257                         kfree(ent);
 258                 }
 259         }
 260 }