1 files changed, 290 insertions, 0 deletions
diff --git a/fs/adfs/map.c b/fs/adfs/map.c
new file mode 100644
index 000000000..6935f0520
--- /dev/null
+++ b/fs/adfs/map.c
@@ -0,0 +1,290 @@
+/*
+ *  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/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
+ * 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 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;
+}