diff options
author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 22:20:36 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 22:20:36 (GMT) |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /fs/adfs/map.c | |
download | linux-fsl-qoriq-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.xz |
Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'fs/adfs/map.c')
-rw-r--r-- | fs/adfs/map.c | 296 |
1 files changed, 296 insertions, 0 deletions
diff --git a/fs/adfs/map.c b/fs/adfs/map.c new file mode 100644 index 0000000..92ab4fb --- /dev/null +++ b/fs/adfs/map.c @@ -0,0 +1,296 @@ +/* + * 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; +} |