summaryrefslogtreecommitdiffstats
path: root/fs/adfs/map.c
diff options
context:
space:
mode:
Diffstat (limited to 'fs/adfs/map.c')
-rw-r--r--fs/adfs/map.c407
1 files changed, 407 insertions, 0 deletions
diff --git a/fs/adfs/map.c b/fs/adfs/map.c
new file mode 100644
index 0000000000..a81de80c45
--- /dev/null
+++ b/fs/adfs/map.c
@@ -0,0 +1,407 @@
+// 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);
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-27 18:32:31 +0000