[linux.git] / fs / adfs / map.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/fs/adfs/map.c
 *
 *  Copyright (C) 1997-2002 Russell King
 */
#include <linux/slab.h>
#include <linux/statfs.h>
#include <asm/unaligned.h>
#include "adfs.h"

/*
 * The ADFS map is basically a set of sectors.  Each sector is called a
 * zone which contains a bitstream made up of variable sized fragments.
 * Each bit refers to a set of bytes in the filesystem, defined by
 * log2bpmb.  This may be larger or smaller than the sector size, but
 * the overall size it describes will always be a round number of
 * sectors.  A fragment id is always idlen bits long.
 *
 *  < idlen > <       n        > <1>
 * +---------+-------//---------+---+
 * | frag id |  0000....000000  | 1 |
 * +---------+-------//---------+---+
 *
 * The physical disk space used by a fragment is taken from the start of
 * the fragment id up to and including the '1' bit - ie, idlen + n + 1
 * bits.
 *
 * A fragment id can be repeated multiple times in the whole map for
 * large or fragmented files.  The first map zone a fragment starts in
 * is given by fragment id / ids_per_zone - this allows objects to start
 * from any zone on the disk.
 *
 * Free space is described by a linked list of fragments.  Each free
 * fragment describes free space in the same way as the other fragments,
 * however, the frag id specifies an offset (in map bits) from the end
 * of this fragment to the start of the next free fragment.
 *
 * Objects stored on the disk are allocated object ids (we use these as
 * our inode numbers.)  Object ids contain a fragment id and an optional
 * offset.  This allows a directory fragment to contain small files
 * associated with that directory.
 */

/*
 * For the future...
 */
static DEFINE_RWLOCK(adfs_map_lock);

/*
 * This is fun.  We need to load up to 19 bits from the map at an
 * arbitrary bit alignment.  (We're limited to 19 bits by F+ version 2).
 */
#define GET_FRAG_ID(_map,_start,_idmask)				\
	({								\
		unsigned char *_m = _map + (_start >> 3);		\
		u32 _frag = get_unaligned_le32(_m);			\
		_frag >>= (_start & 7);					\
		_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 u32 frag_id, unsigned int *offset)
{
	const unsigned int endbit = dm->dm_endbit;
	const u32 idmask = (1 << idlen) - 1;
	unsigned char *map = dm->dm_bh->b_data;
	unsigned int start = dm->dm_startbit;
	unsigned int freelink, fragend;
	u32 frag;

	frag = GET_FRAG_ID(map, 8, idmask & 0x7fff);
	freelink = frag ? 8 + frag : 0;

	do {
		frag = GET_FRAG_ID(map, start, idmask);

		fragend = find_next_bit_le(map, endbit, start + idlen);
		if (fragend >= endbit)
			goto error;

		if (start == freelink) {
			freelink += frag & 0x7fff;
		} else if (frag == frag_id) {
			unsigned int length = fragend + 1 - start;

			if (*offset < length)
				return start + *offset;
			*offset -= length;
		}

		start = fragend + 1;
	} while (start < endbit);
	return -1;

error:
	printk(KERN_ERR "adfs: oversized fragment 0x%x at 0x%x-0x%x\n",
		frag, start, fragend);
	return -1;
}

/*
 * 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 endbit = dm->dm_endbit;
	const unsigned int idlen  = asb->s_idlen;
	const unsigned int frag_idlen = idlen <= 15 ? idlen : 15;
	const u32 idmask = (1 << frag_idlen) - 1;
	unsigned char *map = dm->dm_bh->b_data;
	unsigned int start = 8, fragend;
	u32 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;

		frag = GET_FRAG_ID(map, start, idmask);

		fragend = find_next_bit_le(map, endbit, start + idlen);
		if (fragend >= endbit)
			goto error;

		total += fragend + 1 - 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 u32 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
 */
void adfs_map_statfs(struct super_block *sb, struct kstatfs *buf)
{
	struct adfs_sb_info *asb = ADFS_SB(sb);
	struct adfs_discrecord *dr = adfs_map_discrecord(asb->s_map);
	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);

	buf->f_blocks  = adfs_disc_size(dr) >> sb->s_blocksize_bits;
	buf->f_files   = asb->s_ids_per_zone * asb->s_map_size;
	buf->f_bavail  =
	buf->f_bfree   = signed_asl(total, asb->s_map2blk);
}

int adfs_map_lookup(struct super_block *sb, u32 frag_id, unsigned int offset)
{
	struct adfs_sb_info *asb = ADFS_SB(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 0x%04x at offset %d not found in map",
		   frag_id, offset);
	return 0;

bad_fragment:
	adfs_error(sb, "invalid fragment 0x%04x (zone = %d, max = %d)",
		   frag_id, zone, asb->s_map_size);
	return 0;
}

static unsigned char adfs_calczonecheck(struct super_block *sb, unsigned char *map)
{
	unsigned int v0, v1, v2, v3;
	int i;

	v0 = v1 = v2 = v3 = 0;
	for (i = sb->s_blocksize - 4; i; i -= 4) {
		v0 += map[i]     + (v3 >> 8);
		v3 &= 0xff;
		v1 += map[i + 1] + (v0 >> 8);
		v0 &= 0xff;
		v2 += map[i + 2] + (v1 >> 8);
		v1 &= 0xff;
		v3 += map[i + 3] + (v2 >> 8);
		v2 &= 0xff;
	}
	v0 +=           v3 >> 8;
	v1 += map[1] + (v0 >> 8);
	v2 += map[2] + (v1 >> 8);
	v3 += map[3] + (v2 >> 8);

	return v0 ^ v1 ^ v2 ^ v3;
}

static int adfs_checkmap(struct super_block *sb, struct adfs_discmap *dm)
{
	unsigned char crosscheck = 0, zonecheck = 1;
	int i;

	for (i = 0; i < ADFS_SB(sb)->s_map_size; i++) {
		unsigned char *map;

		map = dm[i].dm_bh->b_data;

		if (adfs_calczonecheck(sb, map) != map[0]) {
			adfs_error(sb, "zone %d fails zonecheck", i);
			zonecheck = 0;
		}
		crosscheck ^= map[3];
	}
	if (crosscheck != 0xff)
		adfs_error(sb, "crosscheck != 0xff");
	return crosscheck == 0xff && zonecheck;
}

/*
 * Layout the map - the first zone contains a copy of the disc record,
 * and the last zone must be limited to the size of the filesystem.
 */
static void adfs_map_layout(struct adfs_discmap *dm, unsigned int nzones,
			    struct adfs_discrecord *dr)
{
	unsigned int zone, zone_size;
	u64 size;

	zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare);

	dm[0].dm_bh       = NULL;
	dm[0].dm_startblk = 0;
	dm[0].dm_startbit = 32 + ADFS_DR_SIZE_BITS;
	dm[0].dm_endbit   = 32 + zone_size;

	for (zone = 1; zone < nzones; zone++) {
		dm[zone].dm_bh       = NULL;
		dm[zone].dm_startblk = zone * zone_size - ADFS_DR_SIZE_BITS;
		dm[zone].dm_startbit = 32;
		dm[zone].dm_endbit   = 32 + zone_size;
	}

	size = adfs_disc_size(dr) >> dr->log2bpmb;
	size -= (nzones - 1) * zone_size - ADFS_DR_SIZE_BITS;
	dm[nzones - 1].dm_endbit = 32 + size;
}

static int adfs_map_read(struct adfs_discmap *dm, struct super_block *sb,
			 unsigned int map_addr, unsigned int nzones)
{
	unsigned int zone;

	for (zone = 0; zone < nzones; zone++) {
		dm[zone].dm_bh = sb_bread(sb, map_addr + zone);
		if (!dm[zone].dm_bh)
			return -EIO;
	}

	return 0;
}

static void adfs_map_relse(struct adfs_discmap *dm, unsigned int nzones)
{
	unsigned int zone;

	for (zone = 0; zone < nzones; zone++)
		brelse(dm[zone].dm_bh);
}

struct adfs_discmap *adfs_read_map(struct super_block *sb, struct adfs_discrecord *dr)
{
	struct adfs_sb_info *asb = ADFS_SB(sb);
	struct adfs_discmap *dm;
	unsigned int map_addr, zone_size, nzones;
	int ret;

	nzones    = dr->nzones | dr->nzones_high << 8;
	zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare);

	asb->s_idlen = dr->idlen;
	asb->s_map_size = nzones;
	asb->s_map2blk = dr->log2bpmb - dr->log2secsize;
	asb->s_log2sharesize = dr->log2sharesize;
	asb->s_ids_per_zone = zone_size / (asb->s_idlen + 1);

	map_addr = (nzones >> 1) * zone_size -
		     ((nzones > 1) ? ADFS_DR_SIZE_BITS : 0);
	map_addr = signed_asl(map_addr, asb->s_map2blk);

	dm = kmalloc_array(nzones, sizeof(*dm), GFP_KERNEL);
	if (dm == NULL) {
		adfs_error(sb, "not enough memory");
		return ERR_PTR(-ENOMEM);
	}

	adfs_map_layout(dm, nzones, dr);

	ret = adfs_map_read(dm, sb, map_addr, nzones);
	if (ret) {
		adfs_error(sb, "unable to read map");
		goto error_free;
	}

	if (adfs_checkmap(sb, dm))
		return dm;

	adfs_error(sb, "map corrupted");

error_free:
	adfs_map_relse(dm, nzones);
	kfree(dm);
	return ERR_PTR(-EIO);
}

void adfs_free_map(struct super_block *sb)
{
	struct adfs_sb_info *asb = ADFS_SB(sb);

	adfs_map_relse(asb->s_map, asb->s_map_size);
	kfree(asb->s_map);
}
Commit	Line	Data
d2912cb1	1	// SPDX-License-Identifier: GPL-2.0-only
1da177e4 LT	2	/*
	3	* linux/fs/adfs/map.c
	4	*
	5	* Copyright (C) 1997-2002 Russell King
1da177e4	6	*/
f75d398d	7	#include <linux/slab.h>
e6160e46	8	#include <linux/statfs.h>
1da177e4	9	#include <asm/unaligned.h>
1da177e4 LT	10	#include "adfs.h"
	11
	12	/*
	13	* The ADFS map is basically a set of sectors. Each sector is called a
	14	* zone which contains a bitstream made up of variable sized fragments.
	15	* Each bit refers to a set of bytes in the filesystem, defined by
	16	* log2bpmb. This may be larger or smaller than the sector size, but
	17	* the overall size it describes will always be a round number of
	18	* sectors. A fragment id is always idlen bits long.
	19	*
	20	* < idlen > < n > <1>
	21	* +---------+-------//---------+---+
	22	* \| frag id \| 0000....000000 \| 1 \|
	23	* +---------+-------//---------+---+
	24	*
	25	* The physical disk space used by a fragment is taken from the start of
	26	* the fragment id up to and including the '1' bit - ie, idlen + n + 1
	27	* bits.
	28	*
	29	* A fragment id can be repeated multiple times in the whole map for
	30	* large or fragmented files. The first map zone a fragment starts in
	31	* is given by fragment id / ids_per_zone - this allows objects to start
	32	* from any zone on the disk.
	33	*
	34	* Free space is described by a linked list of fragments. Each free
	35	* fragment describes free space in the same way as the other fragments,
	36	* however, the frag id specifies an offset (in map bits) from the end
	37	* of this fragment to the start of the next free fragment.
	38	*
	39	* Objects stored on the disk are allocated object ids (we use these as
	40	* our inode numbers.) Object ids contain a fragment id and an optional
	41	* offset. This allows a directory fragment to contain small files
	42	* associated with that directory.
	43	*/
	44
	45	/*
	46	* For the future...
	47	*/
	48	static DEFINE_RWLOCK(adfs_map_lock);
	49
	50	/*
	51	* This is fun. We need to load up to 19 bits from the map at an
25985edc	52	* arbitrary bit alignment. (We're limited to 19 bits by F+ version 2).
1da177e4 LT	53	*/
	54	#define GET_FRAG_ID(_map,_start,_idmask) \
	55	({ \
	56	unsigned char *_m = _map + (_start >> 3); \
224c8866	57	u32 _frag = get_unaligned_le32(_m); \
1da177e4 LT	58	_frag >>= (_start & 7); \
	59	_frag & _idmask; \
	60	})
	61
	62	/*
	63	* return the map bit offset of the fragment frag_id in the zone dm.
	64	* Note that the loop is optimised for best asm code - look at the
	65	* output of:
	66	* gcc -D__KERNEL__ -O2 -I../../include -o - -S map.c
	67	*/
5ed70bb4 RK	68	static int lookup_zone(const struct adfs_discmap *dm, const unsigned int idlen,
5ed70bb4 RK	69	const u32 frag_id, unsigned int *offset)
1da177e4	70	{
197ba3c5	71	const unsigned int endbit = dm->dm_endbit;
1da177e4	72	const u32 idmask = (1 << idlen) - 1;
197ba3c5	73	unsigned char *map = dm->dm_bh->b_data;
1da177e4	74	unsigned int start = dm->dm_startbit;
f93793fd	75	unsigned int freelink, fragend;
1da177e4 LT	76	u32 frag;
1da177e4 LT	77
f93793fd RK	78	frag = GET_FRAG_ID(map, 8, idmask & 0x7fff);
	79	freelink = frag ? 8 + frag : 0;
	80
1da177e4 LT	81	do {
1da177e4 LT	82	frag = GET_FRAG_ID(map, start, idmask);
792314f8 RK	83
	84	fragend = find_next_bit_le(map, endbit, start + idlen);
	85	if (fragend >= endbit)
	86	goto error;
	87
f93793fd RK	88	if (start == freelink) {
	89	freelink += frag & 0x7fff;
	90	} else if (frag == frag_id) {
792314f8 RK	91	unsigned int length = fragend + 1 - start;
	92
	93	if (*offset < length)
	94	return start + *offset;
	95	*offset -= length;
1da177e4 LT	96	}
1da177e4 LT	97
792314f8 RK	98	start = fragend + 1;
792314f8 RK	99	} while (start < endbit);
1da177e4 LT	100	return -1;
	101
	102	error:
	103	printk(KERN_ERR "adfs: oversized fragment 0x%x at 0x%x-0x%x\n",
792314f8	104	frag, start, fragend);
1da177e4	105	return -1;
1da177e4 LT	106	}
	107
	108	/*
	109	* Scan the free space map, for this zone, calculating the total
	110	* number of map bits in each free space fragment.
	111	*
	112	* Note: idmask is limited to 15 bits [3.2]
	113	*/
	114	static unsigned int
	115	scan_free_map(struct adfs_sb_info asb, struct adfs_discmap dm)
	116	{
197ba3c5	117	const unsigned int endbit = dm->dm_endbit;
1da177e4 LT	118	const unsigned int idlen = asb->s_idlen;
	119	const unsigned int frag_idlen = idlen <= 15 ? idlen : 15;
	120	const u32 idmask = (1 << frag_idlen) - 1;
	121	unsigned char *map = dm->dm_bh->b_data;
792314f8	122	unsigned int start = 8, fragend;
1da177e4 LT	123	u32 frag;
	124	unsigned long total = 0;
	125
	126	/*
	127	* get fragment id
	128	*/
	129	frag = GET_FRAG_ID(map, start, idmask);
	130
	131	/*
	132	* If the freelink is null, then no free fragments
	133	* exist in this zone.
	134	*/
	135	if (frag == 0)
	136	return 0;
	137
	138	do {
	139	start += frag;
	140
1da177e4	141	frag = GET_FRAG_ID(map, start, idmask);
1da177e4	142
792314f8 RK	143	fragend = find_next_bit_le(map, endbit, start + idlen);
	144	if (fragend >= endbit)
	145	goto error;
	146
	147	total += fragend + 1 - start;
1da177e4 LT	148	} while (frag >= idlen + 1);
	149
	150	if (frag != 0)
	151	printk(KERN_ERR "adfs: undersized free fragment\n");
	152
	153	return total;
	154	error:
	155	printk(KERN_ERR "adfs: oversized free fragment\n");
	156	return 0;
	157	}
	158
5ed70bb4 RK	159	static int scan_map(struct adfs_sb_info *asb, unsigned int zone,
5ed70bb4 RK	160	const u32 frag_id, unsigned int mapoff)
1da177e4 LT	161	{
	162	const unsigned int idlen = asb->s_idlen;
	163	struct adfs_discmap dm, dm_end;
	164	int result;
	165
	166	dm = asb->s_map + zone;
	167	zone = asb->s_map_size;
	168	dm_end = asb->s_map + zone;
	169
	170	do {
	171	result = lookup_zone(dm, idlen, frag_id, &mapoff);
	172
	173	if (result != -1)
	174	goto found;
	175
	176	dm ++;
	177	if (dm == dm_end)
	178	dm = asb->s_map;
	179	} while (--zone > 0);
	180
	181	return -1;
	182	found:
	183	result -= dm->dm_startbit;
	184	result += dm->dm_startblk;
	185
	186	return result;
	187	}
	188
	189	/*
	190	* calculate the amount of free blocks in the map.
	191	*
	192	* n=1
	193	* total_free = E(free_in_zone_n)
	194	* nzones
	195	*/
e6160e46	196	void adfs_map_statfs(struct super_block sb, struct kstatfs buf)
1da177e4 LT	197	{
1da177e4 LT	198	struct adfs_sb_info *asb = ADFS_SB(sb);
e6160e46	199	struct adfs_discrecord *dr = adfs_map_discrecord(asb->s_map);
1da177e4 LT	200	struct adfs_discmap *dm;
	201	unsigned int total = 0;
	202	unsigned int zone;
	203
	204	dm = asb->s_map;
	205	zone = asb->s_map_size;
	206
	207	do {
	208	total += scan_free_map(asb, dm++);
	209	} while (--zone > 0);
	210
e6160e46 RK	211	buf->f_blocks = adfs_disc_size(dr) >> sb->s_blocksize_bits;
	212	buf->f_files = asb->s_ids_per_zone * asb->s_map_size;
	213	buf->f_bavail =
	214	buf->f_bfree = signed_asl(total, asb->s_map2blk);
1da177e4 LT	215	}
1da177e4 LT	216
5ed70bb4	217	int adfs_map_lookup(struct super_block *sb, u32 frag_id, unsigned int offset)
1da177e4 LT	218	{
	219	struct adfs_sb_info *asb = ADFS_SB(sb);
	220	unsigned int zone, mapoff;
	221	int result;
	222
	223	/*
	224	* map & root fragment is special - it starts in the center of the
	225	* disk. The other fragments start at zone (frag / ids_per_zone)
	226	*/
	227	if (frag_id == ADFS_ROOT_FRAG)
	228	zone = asb->s_map_size >> 1;
	229	else
	230	zone = frag_id / asb->s_ids_per_zone;
	231
	232	if (zone >= asb->s_map_size)
	233	goto bad_fragment;
	234
	235	/* Convert sector offset to map offset */
	236	mapoff = signed_asl(offset, -asb->s_map2blk);
	237
	238	read_lock(&adfs_map_lock);
	239	result = scan_map(asb, zone, frag_id, mapoff);
	240	read_unlock(&adfs_map_lock);
	241
	242	if (result > 0) {
	243	unsigned int secoff;
	244
	245	/* Calculate sector offset into map block */
	246	secoff = offset - signed_asl(mapoff, asb->s_map2blk);
	247	return secoff + signed_asl(result, asb->s_map2blk);
	248	}
	249
	250	adfs_error(sb, "fragment 0x%04x at offset %d not found in map",
	251	frag_id, offset);
	252	return 0;
	253
	254	bad_fragment:
	255	adfs_error(sb, "invalid fragment 0x%04x (zone = %d, max = %d)",
	256	frag_id, zone, asb->s_map_size);
	257	return 0;
	258	}
f75d398d RK	259
	260	static unsigned char adfs_calczonecheck(struct super_block sb, unsigned char map)
	261	{
	262	unsigned int v0, v1, v2, v3;
	263	int i;
	264
	265	v0 = v1 = v2 = v3 = 0;
	266	for (i = sb->s_blocksize - 4; i; i -= 4) {
	267	v0 += map[i] + (v3 >> 8);
	268	v3 &= 0xff;
	269	v1 += map[i + 1] + (v0 >> 8);
	270	v0 &= 0xff;
	271	v2 += map[i + 2] + (v1 >> 8);
	272	v1 &= 0xff;
	273	v3 += map[i + 3] + (v2 >> 8);
	274	v2 &= 0xff;
	275	}
	276	v0 += v3 >> 8;
	277	v1 += map[1] + (v0 >> 8);
	278	v2 += map[2] + (v1 >> 8);
	279	v3 += map[3] + (v2 >> 8);
	280
	281	return v0 ^ v1 ^ v2 ^ v3;
	282	}
	283
	284	static int adfs_checkmap(struct super_block sb, struct adfs_discmap dm)
	285	{
	286	unsigned char crosscheck = 0, zonecheck = 1;
	287	int i;
	288
	289	for (i = 0; i < ADFS_SB(sb)->s_map_size; i++) {
	290	unsigned char *map;
	291
	292	map = dm[i].dm_bh->b_data;
	293
	294	if (adfs_calczonecheck(sb, map) != map[0]) {
	295	adfs_error(sb, "zone %d fails zonecheck", i);
	296	zonecheck = 0;
	297	}
	298	crosscheck ^= map[3];
	299	}
	300	if (crosscheck != 0xff)
	301	adfs_error(sb, "crosscheck != 0xff");
	302	return crosscheck == 0xff && zonecheck;
	303	}
	304
6092b6be RK	305	/*
	306	* Layout the map - the first zone contains a copy of the disc record,
	307	* and the last zone must be limited to the size of the filesystem.
	308	*/
	309	static void adfs_map_layout(struct adfs_discmap *dm, unsigned int nzones,
	310	struct adfs_discrecord *dr)
	311	{
	312	unsigned int zone, zone_size;
	313	u64 size;
	314
	315	zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare);
	316
	317	dm[0].dm_bh = NULL;
	318	dm[0].dm_startblk = 0;
197ba3c5 RK	319	dm[0].dm_startbit = 32 + ADFS_DR_SIZE_BITS;
197ba3c5 RK	320	dm[0].dm_endbit = 32 + zone_size;
6092b6be RK	321
	322	for (zone = 1; zone < nzones; zone++) {
	323	dm[zone].dm_bh = NULL;
	324	dm[zone].dm_startblk = zone * zone_size - ADFS_DR_SIZE_BITS;
197ba3c5 RK	325	dm[zone].dm_startbit = 32;
197ba3c5 RK	326	dm[zone].dm_endbit = 32 + zone_size;
6092b6be RK	327	}
	328
	329	size = adfs_disc_size(dr) >> dr->log2bpmb;
	330	size -= (nzones - 1) * zone_size - ADFS_DR_SIZE_BITS;
197ba3c5	331	dm[nzones - 1].dm_endbit = 32 + size;
6092b6be RK	332	}
	333
	334	static int adfs_map_read(struct adfs_discmap dm, struct super_block sb,
	335	unsigned int map_addr, unsigned int nzones)
	336	{
	337	unsigned int zone;
	338
	339	for (zone = 0; zone < nzones; zone++) {
	340	dm[zone].dm_bh = sb_bread(sb, map_addr + zone);
	341	if (!dm[zone].dm_bh)
	342	return -EIO;
	343	}
	344
	345	return 0;
	346	}
	347
	348	static void adfs_map_relse(struct adfs_discmap *dm, unsigned int nzones)
	349	{
	350	unsigned int zone;
	351
	352	for (zone = 0; zone < nzones; zone++)
	353	brelse(dm[zone].dm_bh);
	354	}
	355
f75d398d RK	356	struct adfs_discmap adfs_read_map(struct super_block sb, struct adfs_discrecord *dr)
f75d398d RK	357	{
6092b6be	358	struct adfs_sb_info *asb = ADFS_SB(sb);
f75d398d RK	359	struct adfs_discmap *dm;
f75d398d RK	360	unsigned int map_addr, zone_size, nzones;
6092b6be	361	int ret;
f75d398d	362
f6f14a0d	363	nzones = dr->nzones \| dr->nzones_high << 8;
f75d398d	364	zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare);
f75d398d	365
f6f14a0d RK	366	asb->s_idlen = dr->idlen;
	367	asb->s_map_size = nzones;
	368	asb->s_map2blk = dr->log2bpmb - dr->log2secsize;
	369	asb->s_log2sharesize = dr->log2sharesize;
f75d398d RK	370	asb->s_ids_per_zone = zone_size / (asb->s_idlen + 1);
f75d398d RK	371
f6f14a0d RK	372	map_addr = (nzones >> 1) * zone_size -
	373	((nzones > 1) ? ADFS_DR_SIZE_BITS : 0);
	374	map_addr = signed_asl(map_addr, asb->s_map2blk);
	375
f75d398d RK	376	dm = kmalloc_array(nzones, sizeof(*dm), GFP_KERNEL);
	377	if (dm == NULL) {
	378	adfs_error(sb, "not enough memory");
	379	return ERR_PTR(-ENOMEM);
	380	}
	381
6092b6be	382	adfs_map_layout(dm, nzones, dr);
f75d398d	383
6092b6be RK	384	ret = adfs_map_read(dm, sb, map_addr, nzones);
	385	if (ret) {
	386	adfs_error(sb, "unable to read map");
	387	goto error_free;
f75d398d RK	388	}
f75d398d RK	389
f75d398d RK	390	if (adfs_checkmap(sb, dm))
	391	return dm;
	392
	393	adfs_error(sb, "map corrupted");
	394
	395	error_free:
6092b6be	396	adfs_map_relse(dm, nzones);
f75d398d RK	397	kfree(dm);
	398	return ERR_PTR(-EIO);
	399	}
7b195267 RK	400
	401	void adfs_free_map(struct super_block *sb)
	402	{
	403	struct adfs_sb_info *asb = ADFS_SB(sb);
	404
	405	adfs_map_relse(asb->s_map, asb->s_map_size);
	406	kfree(asb->s_map);
	407	}