minix/servers/fs/super.c

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