// SPDX-License-Identifier: GPL-2.0-only /* * linux/fs/adfs/map.c * * Copyright (C) 1997-2002 Russell King */ #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 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 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 */ 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, 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; }