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/*
* linux/fs/adfs/map.c
*
* Copyright (C) 1997-1999 Russell King
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/version.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/adfs_fs.h>
#include <linux/spinlock.h>
#include "adfs.h"
/*
* For the future...
*/
static rwlock_t adfs_map_lock;
#define GET_FRAG_ID(_map,_start,_idmask) \
({ \
unsigned long _v2, _frag; \
unsigned int _tmp; \
_tmp = _start >> 5; \
_frag = le32_to_cpu(_map[_tmp]); \
_v2 = le32_to_cpu(_map[_tmp + 1]); \
_tmp = start & 31; \
_frag = (_frag >> _tmp) | (_v2 << (32 - _tmp)); \
_frag & _idmask; \
})
/*
* return the map bit offset of the fragment frag_id in
* the zone dm.
* Note that the loop is optimised for best asm code -
* look at the output of:
* gcc -D__KERNEL__ -O2 -I../../include -o - -S map.c
*/
static int
lookup_zone(const struct adfs_discmap *dm, const unsigned int idlen,
const unsigned int frag_id, unsigned int *offset)
{
const unsigned int mapsize = dm->dm_endbit;
const unsigned int idmask = (1 << idlen) - 1;
unsigned long *map = ((unsigned long *)dm->dm_bh->b_data) + 1;
unsigned int start = dm->dm_startbit;
unsigned int mapptr;
do {
unsigned long frag;
frag = GET_FRAG_ID(map, start, idmask);
mapptr = start + idlen;
/*
* find end of fragment
*/
{
unsigned long v2;
while ((v2 = map[mapptr >> 5] >> (mapptr & 31)) == 0) {
mapptr = (mapptr & ~31) + 32;
if (mapptr >= mapsize)
goto error;
}
mapptr += 1 + ffz(~v2);
}
if (frag == frag_id)
goto found;
again:
start = mapptr;
} while (mapptr < mapsize);
error:
return -1;
found:
{
int length = mapptr - start;
if (*offset >= length) {
*offset -= length;
goto again;
}
}
return start + *offset;
}
/*
* Scan the free space map, for this zone, calculating the total
* number of map bits in each free space fragment.
*
* Note: idmask is limited to 15 bits [3.2]
*/
static unsigned int
scan_free_map(struct adfs_sb_info *asb, struct adfs_discmap *dm)
{
const unsigned int mapsize = dm->dm_endbit + 32;
const unsigned int idlen = asb->s_idlen;
const unsigned int frag_idlen = idlen <= 15 ? idlen : 15;
const unsigned int idmask = (1 << frag_idlen) - 1;
unsigned long *map = (unsigned long *)dm->dm_bh->b_data;
unsigned int start = 8, mapptr;
unsigned long frag;
unsigned long total = 0;
/*
* get fragment id
*/
frag = GET_FRAG_ID(map, start, idmask);
/*
* If the freelink is null, then no free fragments
* exist in this zone.
*/
if (frag == 0)
return 0;
do {
start += frag;
/*
* get fragment id
*/
frag = GET_FRAG_ID(map, start, idmask);
mapptr = start + idlen;
/*
* find end of fragment
*/
{
unsigned long v2;
while ((v2 = map[mapptr >> 5] >> (mapptr & 31)) == 0) {
mapptr = (mapptr & ~31) + 32;
if (mapptr >= mapsize)
goto error;
}
mapptr += 1 + ffz(~v2);
}
total += mapptr - start;
} while (frag >= idlen + 1);
if (frag != 0)
printk(KERN_ERR "adfs: undersized free fragment\n");
return total;
error:
printk(KERN_ERR "adfs: oversized free fragment\n");
return 0;
}
static int
scan_map(struct adfs_sb_info *asb, unsigned int zone,
const unsigned int frag_id, unsigned int mapoff)
{
const unsigned int idlen = asb->s_idlen;
struct adfs_discmap *dm, *dm_end;
int result;
dm = asb->s_map + zone;
zone = asb->s_map_size;
dm_end = asb->s_map + zone;
do {
result = lookup_zone(dm, idlen, frag_id, &mapoff);
if (result != -1)
goto found;
dm ++;
if (dm == dm_end)
dm = asb->s_map;
} while (--zone > 0);
return -1;
found:
result -= dm->dm_startbit;
result += dm->dm_startblk;
return result;
}
/*
* calculate the amount of free blocks in the map.
*
* n=1
* total_free = E(free_in_zone_n)
* nzones
*/
unsigned int
adfs_map_free(struct super_block *sb)
{
struct adfs_sb_info *asb = &sb->u.adfs_sb;
struct adfs_discmap *dm;
unsigned int total = 0;
unsigned int zone;
dm = asb->s_map;
zone = asb->s_map_size;
do {
total += scan_free_map(asb, dm++);
} while (--zone > 0);
return signed_asl(total, asb->s_map2blk);
}
int adfs_map_lookup (struct super_block *sb, int frag_id, int offset)
{
struct adfs_sb_info *asb = &sb->u.adfs_sb;
unsigned int zone, mapoff;
int result;
/*
* map & root fragment is special - it starts in the center of the
* disk. The other fragments start at zone (frag / ids_per_zone)
*/
if (frag_id == ADFS_ROOT_FRAG)
zone = asb->s_map_size >> 1;
else
zone = frag_id / asb->s_ids_per_zone;
if (zone >= asb->s_map_size)
goto bad_fragment;
/* Convert sector offset to map offset */
mapoff = signed_asl(offset, -asb->s_map2blk);
read_lock(&adfs_map_lock);
result = scan_map(asb, zone, frag_id, mapoff);
read_unlock(&adfs_map_lock);
if (result > 0) {
unsigned int secoff;
/* Calculate sector offset into map block */
secoff = offset - signed_asl(mapoff, asb->s_map2blk);
return secoff + signed_asl(result, asb->s_map2blk);
}
adfs_error(sb, "fragment %04X at offset %d not found in map",
frag_id, offset);
return 0;
bad_fragment:
adfs_error(sb, "fragment %X is invalid (zone = %d, max = %d)",
frag_id, zone, asb->s_map_size);
return 0;
}
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