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/* -*- linux-c -*- --------------------------------------------------------- *
*
* linux/fs/autofs/dirhash.c
*
* Copyright 1997 Transmeta Corporation -- All Rights Reserved
*
* This file is part of the Linux kernel and is made available under
* the terms of the GNU General Public License, version 2, or at your
* option, any later version, incorporated herein by reference.
*
* ------------------------------------------------------------------------- */
#include "autofs_i.h"
/* Functions for maintenance of expiry queue */
static void autofs_init_usage(struct autofs_dirhash *dh,
struct autofs_dir_ent *ent)
{
ent->exp_next = &dh->expiry_head;
ent->exp_prev = dh->expiry_head.exp_prev;
dh->expiry_head.exp_prev->exp_next = ent;
dh->expiry_head.exp_prev = ent;
ent->last_usage = jiffies;
}
static void autofs_delete_usage(struct autofs_dir_ent *ent)
{
ent->exp_prev->exp_next = ent->exp_next;
ent->exp_next->exp_prev = ent->exp_prev;
}
void autofs_update_usage(struct autofs_dirhash *dh,
struct autofs_dir_ent *ent)
{
autofs_delete_usage(ent); /* Unlink from current position */
autofs_init_usage(dh,ent); /* Relink at queue tail */
}
struct autofs_dir_ent *autofs_expire(struct autofs_dirhash *dh,
unsigned long timeout)
{
struct autofs_dir_ent *ent;
ent = dh->expiry_head.exp_next;
if ( ent == &(dh->expiry_head) ) return NULL;
return (jiffies - ent->last_usage >= timeout) ? ent : NULL;
}
/* Adapted from the Dragon Book, page 436 */
/* This particular hashing algorithm requires autofs_hash_t == u32 */
autofs_hash_t autofs_hash(const char *name, int len)
{
autofs_hash_t h = 0;
while ( len-- ) {
h = (h << 4) + (unsigned char) (*name++);
h ^= ((h & 0xf0000000) >> 24);
}
return h;
}
void autofs_initialize_hash(struct autofs_dirhash *dh) {
memset(&dh->h, 0, AUTOFS_HASH_SIZE*sizeof(struct autofs_dir_ent *));
dh->expiry_head.exp_next = dh->expiry_head.exp_prev =
&dh->expiry_head;
}
struct autofs_dir_ent *autofs_hash_lookup(const struct autofs_dirhash *dh, autofs_hash_t hash, const char *name, int len)
{
struct autofs_dir_ent *dhn;
DPRINTK(("autofs_hash_lookup: hash = 0x%08x, name = ", hash));
autofs_say(name,len);
for ( dhn = dh->h[hash % AUTOFS_HASH_SIZE] ; dhn ; dhn = dhn->next ) {
if ( hash == dhn->hash &&
len == dhn->len &&
!memcmp(name, dhn->name, len) )
break;
}
return dhn;
}
void autofs_hash_insert(struct autofs_dirhash *dh, struct autofs_dir_ent *ent)
{
struct autofs_dir_ent **dhnp;
DPRINTK(("autofs_hash_insert: hash = 0x%08x, name = ", ent->hash));
autofs_say(ent->name,ent->len);
autofs_init_usage(dh,ent);
dhnp = &dh->h[ent->hash % AUTOFS_HASH_SIZE];
ent->next = *dhnp;
ent->back = dhnp;
*dhnp = ent;
}
void autofs_hash_delete(struct autofs_dir_ent *ent)
{
*(ent->back) = ent->next;
autofs_delete_usage(ent);
kfree(ent->name);
kfree(ent);
}
/*
* Used by readdir(). We must validate "ptr", so we can't simply make it
* a pointer. Values below 0xffff are reserved; calling with any value
* <= 0x10000 will return the first entry found.
*/
struct autofs_dir_ent *autofs_hash_enum(const struct autofs_dirhash *dh, off_t *ptr)
{
int bucket, ecount, i;
struct autofs_dir_ent *ent;
bucket = (*ptr >> 16) - 1;
ecount = *ptr & 0xffff;
if ( bucket < 0 ) {
bucket = ecount = 0;
}
DPRINTK(("autofs_hash_enum: bucket %d, entry %d\n", bucket, ecount));
ent = NULL;
while ( bucket < AUTOFS_HASH_SIZE ) {
ent = dh->h[bucket];
for ( i = ecount ; ent && i ; i-- )
ent = ent->next;
if (ent) {
ecount++; /* Point to *next* entry */
break;
}
bucket++; ecount = 0;
}
#ifdef DEBUG
if ( !ent )
printk("autofs_hash_enum: nothing found\n");
else {
printk("autofs_hash_enum: found hash %08x, name", ent->hash);
autofs_say(ent->name,ent->len);
}
#endif
*ptr = ((bucket+1) << 16) + ecount;
return ent;
}
/* Delete everything. This is used on filesystem destruction, so we
make no attempt to keep the pointers valid */
void autofs_hash_nuke(struct autofs_dirhash *dh)
{
int i;
struct autofs_dir_ent *ent, *nent;
for ( i = 0 ; i < AUTOFS_HASH_SIZE ; i++ ) {
for ( ent = dh->h[i] ; ent ; ent = nent ) {
nent = ent->next;
kfree(ent->name);
kfree(ent);
}
}
}
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