333 lines
11 KiB
C
333 lines
11 KiB
C
/* This file manages the super block table and the related data structures,
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* namely, the bit maps that keep track of which zones and which inodes are
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* allocated and which are free. When a new inode or zone is needed, the
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* appropriate bit map is searched for a free entry.
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*
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* The entry points into this file are
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* alloc_bit: somebody wants to allocate a zone or inode; find one
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* free_bit: indicate that a zone or inode is available for allocation
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* get_super: search the 'superblock' table for a device
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* mounted: tells if file inode is on mounted (or ROOT) file system
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* read_super: read a superblock
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*/
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#include "fs.h"
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#include <string.h>
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#include <minix/com.h>
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#include <minix/u64.h>
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#include "buf.h"
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#include "inode.h"
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#include "super.h"
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#include "const.h"
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/*===========================================================================*
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* alloc_bit *
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*===========================================================================*/
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PUBLIC bit_t alloc_bit(sp, map, origin)
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struct super_block *sp; /* the filesystem to allocate from */
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int map; /* IMAP (inode map) or ZMAP (zone map) */
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bit_t origin; /* number of bit to start searching at */
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{
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/* Allocate a bit from a bit map and return its bit number. */
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block_t start_block; /* first bit block */
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bit_t map_bits; /* how many bits are there in the bit map? */
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unsigned bit_blocks; /* how many blocks are there in the bit map? */
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unsigned block, word, bcount;
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struct buf *bp;
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bitchunk_t *wptr, *wlim, k;
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bit_t i, b;
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if (sp->s_rd_only)
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panic(__FILE__,"can't allocate bit on read-only filesys.", NO_NUM);
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if (map == IMAP) {
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start_block = START_BLOCK;
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map_bits = sp->s_ninodes + 1;
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bit_blocks = sp->s_imap_blocks;
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} else {
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start_block = START_BLOCK + sp->s_imap_blocks;
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map_bits = sp->s_zones - (sp->s_firstdatazone - 1);
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bit_blocks = sp->s_zmap_blocks;
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}
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/* Figure out where to start the bit search (depends on 'origin'). */
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if (origin >= map_bits) origin = 0; /* for robustness */
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/* Locate the starting place. */
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block = origin / FS_BITS_PER_BLOCK(sp->s_block_size);
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word = (origin % FS_BITS_PER_BLOCK(sp->s_block_size)) / FS_BITCHUNK_BITS;
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/* Iterate over all blocks plus one, because we start in the middle. */
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bcount = bit_blocks + 1;
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do {
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bp = get_block(sp->s_dev, start_block + block, NORMAL);
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wlim = &bp->b_bitmap[FS_BITMAP_CHUNKS(sp->s_block_size)];
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/* Iterate over the words in block. */
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for (wptr = &bp->b_bitmap[word]; wptr < wlim; wptr++) {
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/* Does this word contain a free bit? */
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if (*wptr == (bitchunk_t) ~0) continue;
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/* Find and allocate the free bit. */
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k = conv2(sp->s_native, (int) *wptr);
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for (i = 0; (k & (1 << i)) != 0; ++i) {}
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/* Bit number from the start of the bit map. */
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b = ((bit_t) block * FS_BITS_PER_BLOCK(sp->s_block_size))
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+ (wptr - &bp->b_bitmap[0]) * FS_BITCHUNK_BITS
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+ i;
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/* Don't allocate bits beyond the end of the map. */
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if (b >= map_bits) break;
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/* Allocate and return bit number. */
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k |= 1 << i;
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*wptr = conv2(sp->s_native, (int) k);
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bp->b_dirt = DIRTY;
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put_block(bp, MAP_BLOCK);
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return(b);
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}
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put_block(bp, MAP_BLOCK);
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if (++block >= bit_blocks) block = 0; /* last block, wrap around */
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word = 0;
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} while (--bcount > 0);
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return(NO_BIT); /* no bit could be allocated */
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}
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/*===========================================================================*
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* free_bit *
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*===========================================================================*/
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PUBLIC void free_bit(sp, map, bit_returned)
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struct super_block *sp; /* the filesystem to operate on */
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int map; /* IMAP (inode map) or ZMAP (zone map) */
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bit_t bit_returned; /* number of bit to insert into the map */
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{
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/* Return a zone or inode by turning off its bitmap bit. */
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unsigned block, word, bit;
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struct buf *bp;
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bitchunk_t k, mask;
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block_t start_block;
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if (sp->s_rd_only)
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panic(__FILE__,"can't free bit on read-only filesys.", NO_NUM);
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if (map == IMAP) {
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start_block = START_BLOCK;
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} else {
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start_block = START_BLOCK + sp->s_imap_blocks;
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}
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block = bit_returned / FS_BITS_PER_BLOCK(sp->s_block_size);
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word = (bit_returned % FS_BITS_PER_BLOCK(sp->s_block_size))
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/ FS_BITCHUNK_BITS;
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bit = bit_returned % FS_BITCHUNK_BITS;
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mask = 1 << bit;
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bp = get_block(sp->s_dev, start_block + block, NORMAL);
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k = conv2(sp->s_native, (int) bp->b_bitmap[word]);
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if (!(k & mask)) {
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panic(__FILE__,map == IMAP ? "tried to free unused inode" :
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"tried to free unused block", bit_returned);
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}
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k &= ~mask;
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bp->b_bitmap[word] = conv2(sp->s_native, (int) k);
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bp->b_dirt = DIRTY;
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put_block(bp, MAP_BLOCK);
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}
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/*===========================================================================*
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* get_super *
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*===========================================================================*/
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PUBLIC struct super_block *get_super(dev)
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dev_t dev; /* device number whose super_block is sought */
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{
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/* Search the superblock table for this device. It is supposed to be there. */
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register struct super_block *sp;
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if (dev == NO_DEV)
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panic(__FILE__,"request for super_block of NO_DEV", NO_NUM);
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for (sp = &super_block[0]; sp < &super_block[NR_SUPERS]; sp++)
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if (sp->s_dev == dev) return(sp);
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printf("MFS(%d)get_super: sp->s_dev: %d, dev: %d\n", SELF_E, sp->s_dev, dev);
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/* Search failed. Something wrong. */
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panic(__FILE__,"can't find superblock for device (in decimal)", (int) dev);
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return(NIL_SUPER); /* to keep the compiler and lint quiet */
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}
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/*===========================================================================*
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* get_block_size *
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*===========================================================================*/
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PUBLIC int get_block_size(dev_t dev)
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{
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/* Search the superblock table for this device. */
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register struct super_block *sp;
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if (dev == NO_DEV)
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panic(__FILE__,"request for block size of NO_DEV", NO_NUM);
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for (sp = &super_block[0]; sp < &super_block[NR_SUPERS]; sp++) {
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if (sp->s_dev == dev) {
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return(sp->s_block_size);
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}
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}
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/* no mounted filesystem? use this block size then. */
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return _MIN_BLOCK_SIZE;
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}
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/*===========================================================================*
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* mounted *
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*===========================================================================*/
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/* Report on whether the given inode is on a mounted (or ROOT) file system. */
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/*
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PUBLIC int mounted(rip)
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register struct inode *rip;
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{
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register struct super_block *sp;
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register dev_t dev;
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dev = (dev_t) rip->i_zone[0];
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if (dev == root_dev) return(TRUE);
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for (sp = &super_block[0]; sp < &super_block[NR_SUPERS]; sp++)
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if (sp->s_dev == dev) return(TRUE);
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return(FALSE);
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}
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*/
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/*===========================================================================*
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* read_super *
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*===========================================================================*/
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PUBLIC int read_super(sp)
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register struct super_block *sp; /* pointer to a superblock */
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{
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/* Read a superblock. */
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dev_t dev;
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int magic;
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int version, native, r;
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static char sbbuf[_MIN_BLOCK_SIZE];
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dev = sp->s_dev; /* save device (will be overwritten by copy) */
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if (dev == NO_DEV)
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panic(__FILE__,"request for super_block of NO_DEV", NO_NUM);
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r = block_dev_io(MFS_DEV_READ, dev, SELF_E,
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sbbuf, cvu64(SUPER_BLOCK_BYTES), _MIN_BLOCK_SIZE, 0);
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if (r != _MIN_BLOCK_SIZE) {
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return EINVAL;
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}
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memcpy(sp, sbbuf, sizeof(*sp));
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sp->s_dev = NO_DEV; /* restore later */
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magic = sp->s_magic; /* determines file system type */
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/* Get file system version and type. */
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if (magic == SUPER_MAGIC || magic == conv2(BYTE_SWAP, SUPER_MAGIC)) {
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version = V1;
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native = (magic == SUPER_MAGIC);
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} else if (magic == SUPER_V2 || magic == conv2(BYTE_SWAP, SUPER_V2)) {
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version = V2;
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native = (magic == SUPER_V2);
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} else if (magic == SUPER_V3) {
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version = V3;
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native = 1;
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} else {
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return(EINVAL);
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}
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/* If the super block has the wrong byte order, swap the fields; the magic
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* number doesn't need conversion. */
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sp->s_ninodes = conv4(native, sp->s_ninodes);
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sp->s_nzones = conv2(native, (int) sp->s_nzones);
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sp->s_imap_blocks = conv2(native, (int) sp->s_imap_blocks);
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sp->s_zmap_blocks = conv2(native, (int) sp->s_zmap_blocks);
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sp->s_firstdatazone = conv2(native, (int) sp->s_firstdatazone);
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sp->s_log_zone_size = conv2(native, (int) sp->s_log_zone_size);
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sp->s_max_size = conv4(native, sp->s_max_size);
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sp->s_zones = conv4(native, sp->s_zones);
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/* In V1, the device size was kept in a short, s_nzones, which limited
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* devices to 32K zones. For V2, it was decided to keep the size as a
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* long. However, just changing s_nzones to a long would not work, since
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* then the position of s_magic in the super block would not be the same
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* in V1 and V2 file systems, and there would be no way to tell whether
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* a newly mounted file system was V1 or V2. The solution was to introduce
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* a new variable, s_zones, and copy the size there.
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*
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* Calculate some other numbers that depend on the version here too, to
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* hide some of the differences.
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*/
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if (version == V1) {
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sp->s_block_size = _STATIC_BLOCK_SIZE;
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sp->s_zones = sp->s_nzones; /* only V1 needs this copy */
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sp->s_inodes_per_block = V1_INODES_PER_BLOCK;
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sp->s_ndzones = V1_NR_DZONES;
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sp->s_nindirs = V1_INDIRECTS;
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} else {
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if (version == V2)
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sp->s_block_size = _STATIC_BLOCK_SIZE;
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if (sp->s_block_size < _MIN_BLOCK_SIZE) {
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return EINVAL;
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}
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sp->s_inodes_per_block = V2_INODES_PER_BLOCK(sp->s_block_size);
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sp->s_ndzones = V2_NR_DZONES;
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sp->s_nindirs = V2_INDIRECTS(sp->s_block_size);
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}
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if (sp->s_block_size < _MIN_BLOCK_SIZE) {
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return EINVAL;
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}
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if (sp->s_block_size > _MAX_BLOCK_SIZE) {
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printf("Filesystem block size is %d kB; maximum filesystem\n"
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"block size is %d kB. This limit can be increased by recompiling.\n",
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sp->s_block_size/1024, _MAX_BLOCK_SIZE/1024);
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return EINVAL;
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}
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if ((sp->s_block_size % 512) != 0) {
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return EINVAL;
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}
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if (SUPER_SIZE > sp->s_block_size) {
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return EINVAL;
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}
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if ((sp->s_block_size % V2_INODE_SIZE) != 0 ||
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(sp->s_block_size % V1_INODE_SIZE) != 0) {
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return EINVAL;
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}
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/* Limit s_max_size to LONG_MAX */
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if ((unsigned long)sp->s_max_size > LONG_MAX)
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{
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printf("read_super: reducing s_max_size to LONG_MAX\n");
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sp->s_max_size= LONG_MAX;
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}
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sp->s_isearch = 0; /* inode searches initially start at 0 */
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sp->s_zsearch = 0; /* zone searches initially start at 0 */
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sp->s_version = version;
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sp->s_native = native;
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/* Make a few basic checks to see if super block looks reasonable. */
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if (sp->s_imap_blocks < 1 || sp->s_zmap_blocks < 1
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|| sp->s_ninodes < 1 || sp->s_zones < 1
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|| (unsigned) sp->s_log_zone_size > 4) {
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printf("not enough imap or zone map blocks, \n");
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printf("or not enough inodes, or not enough zones, "
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"or zone size too large\n");
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return(EINVAL);
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}
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sp->s_dev = dev; /* restore device number */
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return(OK);
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}
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