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/* Backing store management for GNU Hurd.
Copyright (C) 1996 Free Software Foundation, Inc.
Written by Thomas Bushnell, n/BSG.
This file is part of the GNU Hurd.
The GNU Hurd 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, or (at
your option) any later version.
The GNU Hurd 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., 675 Mass Ave, Cambridge, MA 02139, USA. */
#include <hurd/store.h>
const struct store_class *const permitted_classes[] =
{
&store_device_class, &store_ileave_class, &store_concat_class, 0
};
/* Allocation map, by PAGE. */
/* If a bit is SET the corresponding PAGE is free. */
char *bmap;
/* Number of bytes in bmap */
size_t bmap_len;
/* Allocation rotor */
char *bmap_rotor;
pthread_mutex_t bmap_lock = PTHREAD_MUTEX_INITIALIZER;
error_t
init_backing (char *name)
{
error_t err;
int i;
err = store_open (name, STORE_NO_FILEIO, &permitted_classes, &backing_store);
if (err)
return err;
bmap_len = backing_store->size / vm_page_size / NBBY;
bmap = malloc (bmap_len);
for (i = 0; i < bmap_len; i++)
bmap[i] = 0xff;
bmap_rotor = bmap;
/* Mark the very first page as occupied. This makes sure we never
return zero offsets from allocate_backing_page (which
conventionally means that there is no space left. It also makes
sure we don't tromp on the misfeature in Linux of using the first
page for permanent data. */
*bmap_rotor |= 1;
}
int
allocate_backing_page ()
{
int wrapped;
int bit;
int pfn;
pthread_mutex_lock (&bmap_lock);
wrapped = (bmap_rotor == bmap);
while (!wrapped || bmap_rotor < bmap + bmap_len)
{
if (bmap[bmap_rotor])
break;
bmap_rotor++;
if (bmap_rotor >= bmap + bmap_len)
wrapped++;
}
if (wrapped == 2)
{
/* Didn't find one... */
pthread_mutex_unlock (&bmap_lock);
printf ("WARNING: Out of paging space; pageout failing.");
return 0;
}
/* Find which bit */
bit = ffs (*bmap_rotor);
assert (bit);
bit--;
/* Mark it */
*bmap_rotor |= 1 << bit;
/* Return the correct offset */
pfn = (bmap_rotor - bmap) * 8 + bit;
pthread_mutex_unlock (&bmap_lock);
return pfn * (vm_page_size / store->block_size);
}
void
return_backing_pages (off_t *map, int maplen)
{
int i;
pthread_mutex_lock (&bmap_lock);
for (i = 0; i < maplen; i++)
{
int pfn;
char *b;
int bit;
pfn = map[i] / (vm_page_size / store->block_size);
b = bmap + pfn & ~7;
bit = pfn & 7;
assert ((*b & (1 << bit)) == 0);
*b |= 1 << bit;
}
pthread_mutex_unlock (&bmap_lock);
}
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