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- // 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);
- }
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