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-rw-r--r--fs/adfs/map.c296
1 files changed, 296 insertions, 0 deletions
diff --git a/fs/adfs/map.c b/fs/adfs/map.c
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+++ b/fs/adfs/map.c
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+/*
+ * linux/fs/adfs/map.c
+ *
+ * Copyright (C) 1997-2002 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/errno.h>
+#include <linux/fs.h>
+#include <linux/adfs_fs.h>
+#include <linux/spinlock.h>
+#include <linux/buffer_head.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
+ * arbitary 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((u32 *)_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 unsigned int frag_id, unsigned int *offset)
+{
+ const unsigned int mapsize = dm->dm_endbit;
+ const u32 idmask = (1 << idlen) - 1;
+ unsigned char *map = dm->dm_bh->b_data + 4;
+ unsigned int start = dm->dm_startbit;
+ unsigned int mapptr;
+ u32 frag;
+
+ do {
+ frag = GET_FRAG_ID(map, start, idmask);
+ mapptr = start + idlen;
+
+ /*
+ * find end of fragment
+ */
+ {
+ __le32 *_map = (__le32 *)map;
+ u32 v = le32_to_cpu(_map[mapptr >> 5]) >> (mapptr & 31);
+ while (v == 0) {
+ mapptr = (mapptr & ~31) + 32;
+ if (mapptr >= mapsize)
+ goto error;
+ v = le32_to_cpu(_map[mapptr >> 5]);
+ }
+
+ mapptr += 1 + ffz(~v);
+ }
+
+ if (frag == frag_id)
+ goto found;
+again:
+ start = mapptr;
+ } while (mapptr < mapsize);
+ return -1;
+
+error:
+ printk(KERN_ERR "adfs: oversized fragment 0x%x at 0x%x-0x%x\n",
+ frag, start, mapptr);
+ 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 u32 idmask = (1 << frag_idlen) - 1;
+ unsigned char *map = dm->dm_bh->b_data;
+ unsigned int start = 8, mapptr;
+ 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;
+
+ /*
+ * get fragment id
+ */
+ frag = GET_FRAG_ID(map, start, idmask);
+ mapptr = start + idlen;
+
+ /*
+ * find end of fragment
+ */
+ {
+ __le32 *_map = (__le32 *)map;
+ u32 v = le32_to_cpu(_map[mapptr >> 5]) >> (mapptr & 31);
+ while (v == 0) {
+ mapptr = (mapptr & ~31) + 32;
+ if (mapptr >= mapsize)
+ goto error;
+ v = le32_to_cpu(_map[mapptr >> 5]);
+ }
+
+ mapptr += 1 + ffz(~v);
+ }
+
+ 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 = ADFS_SB(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, unsigned int 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;
+}
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