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/* Hurd unionfs
Copyright (C) 2001, 2002 Free Software Foundation, Inc.
Written by Moritz Schulte <moritz@duesseldorf.ccc.de>.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or * (at your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
USA. */
#define _GNU_SOURCE
#include <hurd/netfs.h>
#include <error.h>
#include <stdlib.h>
#include <assert.h>
#include "ncache.h"
#include "lib.h"
#include "unionfs.h"
/* The node cache. */
ncache_t ncache;
/* Cache size, may be overwritten by the user. */
int ncache_size = NCACHE_SIZE;
/* Initialize the node cache, set the maximum number of allowed nodes
in the cache to SIZE_MAX. */
void
ncache_init (int size_max)
{
ncache.mru = NULL;
ncache.lru = NULL;
ncache.size_max = size_max;
ncache.size_current = 0;
mutex_init (&ncache.lock);
}
/* Remove the given node NODE from the cache. */
static void
ncache_node_remove (node_t *node)
{
struct netnode *nn = node->nn;
if (nn->ncache_next)
nn->ncache_next->nn->ncache_prev = nn->ncache_prev;
if (nn->ncache_prev)
nn->ncache_prev->nn->ncache_next = nn->ncache_next;
if (ncache.mru == node)
ncache.mru = nn->ncache_next;
if (ncache.lru == node)
ncache.lru = nn->ncache_prev;
nn->ncache_next = NULL;
nn->ncache_prev = NULL;
ncache.size_current--;
}
void
ncache_reset (void)
{
node_t *node;
mutex_lock (&ncache.lock);
while ((node = ncache.mru))
ncache_node_remove (node);
mutex_unlock (&ncache.lock);
}
/* Lookup the node for the light node LNODE. If it does not exist
anymore in the cache, create a new node. Store the looked up node
in *NODE. */
error_t
ncache_node_lookup (lnode_t *lnode, node_t **node)
{
error_t err = 0;
node_t *n;
if (lnode->node)
{
debug_msg ("ncache_node_lookup for lnode: %s (found in cache)",
lnode->name);
n = lnode->node;
netfs_nref (n);
}
else
{
debug_msg ("ncache_node_lookup for lnode: %s (newly created)",
lnode->name);
err = node_create (lnode, &n);
}
if (! err)
{
mutex_lock (&n->lock);
*node = n;
}
return err;
}
/* Add the given node NODE to the node cache; remove
least-recently-used nodes, if needed. */
void
ncache_node_add (node_t *node)
{
mutex_lock (&ncache.lock);
debug_msg ("adding node to cache: %s", node->nn->lnode->name);
if (ncache.size_max > 0 || ncache.size_current > 0)
{
if (ncache.mru != node)
{
if (node->nn->ncache_next || node->nn->ncache_prev)
/* Node is already in the cache. */
ncache_node_remove (node);
else
/* Add a reference from the cache. */
netfs_nref (node);
node->nn->ncache_next = ncache.mru;
node->nn->ncache_prev = NULL;
if (ncache.mru)
ncache.mru->nn->ncache_prev = node;
if (! ncache.lru)
ncache.lru = node;
ncache.mru = node;
ncache.size_current++;
}
}
/* Forget the least used nodes. */
while (ncache.size_current > ncache.size_max)
{
struct node *lru = ncache.lru;
debug_msg ("removing cached node: %s", lru->nn->lnode->name);
ncache_node_remove (lru);
netfs_nrele (lru);
}
mutex_unlock (&ncache.lock);
}
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