minix3/fs/mfs/super.c

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2020-02-21 00:59:27 +05:30
/* 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
* 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 <assert.h>
#include <minix/com.h>
#include <minix/u64.h>
#include <minix/bdev.h>
#include <machine/param.h>
#include <machine/vmparam.h>
#include "buf.h"
#include "inode.h"
#include "super.h"
#include "const.h"
static u32_t used_blocks = 0;
/*===========================================================================*
* alloc_bit *
*===========================================================================*/
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 */
block_t block;
bit_t map_bits; /* how many bits are there in the bit map? */
short bit_blocks; /* how many blocks are there in the bit map? */
unsigned word, bcount;
struct buf *bp;
bitchunk_t *wptr, *wlim, k;
bit_t i, b;
if (sp->s_rd_only)
panic("can't allocate bit on read-only filesys");
if (map == IMAP) {
start_block = START_BLOCK;
map_bits = (bit_t) (sp->s_ninodes + 1);
bit_blocks = sp->s_imap_blocks;
} else {
start_block = START_BLOCK + sp->s_imap_blocks;
map_bits = (bit_t) (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 = (block_t) (origin / FS_BITS_PER_BLOCK(sp->s_block_size));
word = (origin % FS_BITS_PER_BLOCK(sp->s_block_size)) / FS_BITCHUNK_BITS;
/* 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 = &b_bitmap(bp)[FS_BITMAP_CHUNKS(sp->s_block_size)];
/* Iterate over the words in block. */
for (wptr = &b_bitmap(bp)[word]; wptr < wlim; wptr++) {
/* Does this word contain a free bit? */
if (*wptr == (bitchunk_t) ~0) continue;
/* Find and allocate the free bit. */
k = (bitchunk_t) conv4(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 - &b_bitmap(bp)[0]) * FS_BITCHUNK_BITS
+ 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 = (bitchunk_t) conv4(sp->s_native, (int) k);
MARKDIRTY(bp);
put_block(bp, MAP_BLOCK);
if(map == ZMAP) {
used_blocks++;
lmfs_blockschange(sp->s_dev, 1);
}
return(b);
}
put_block(bp, MAP_BLOCK);
if (++block >= (unsigned int) bit_blocks) /* last block, wrap around */
block = 0;
word = 0;
} while (--bcount > 0);
return(NO_BIT); /* no bit could be allocated */
}
/*===========================================================================*
* free_bit *
*===========================================================================*/
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("can't free bit on read-only filesys");
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);
word = (bit_returned % FS_BITS_PER_BLOCK(sp->s_block_size))
/ FS_BITCHUNK_BITS;
bit = bit_returned % FS_BITCHUNK_BITS;
mask = 1 << bit;
bp = get_block(sp->s_dev, start_block + block, NORMAL);
k = (bitchunk_t) conv4(sp->s_native, (int) b_bitmap(bp)[word]);
if (!(k & mask)) {
if (map == IMAP) panic("tried to free unused inode");
else panic("tried to free unused block: %u", bit_returned);
}
k &= ~mask;
b_bitmap(bp)[word] = (bitchunk_t) conv4(sp->s_native, (int) k);
MARKDIRTY(bp);
put_block(bp, MAP_BLOCK);
if(map == ZMAP) {
used_blocks--;
lmfs_blockschange(sp->s_dev, -1);
}
}
/*===========================================================================*
* get_super *
*===========================================================================*/
struct super_block *get_super(
dev_t dev /* device number whose super_block is sought */
)
{
if (dev == NO_DEV)
panic("request for super_block of NO_DEV");
if(superblock.s_dev != dev)
panic("wrong superblock: 0x%x", (int) dev);
return(&superblock);
}
/*===========================================================================*
* get_block_size *
*===========================================================================*/
unsigned int get_block_size(dev_t dev)
{
if (dev == NO_DEV)
panic("request for block size of NO_DEV");
return(lmfs_fs_block_size());
}
/*===========================================================================*
* rw_super *
*===========================================================================*/
static int rw_super(struct super_block *sp, int writing)
{
/* Read/write a superblock. */
int r;
dev_t save_dev = sp->s_dev;
struct buf *bp;
char *sbbuf;
/* To keep the 1kb on disk clean, only read/write up to and including
* this field.
*/
#define LAST_ONDISK_FIELD s_disk_version
int ondisk_bytes = (int) ((char *) &sp->LAST_ONDISK_FIELD - (char *) sp)
+ sizeof(sp->LAST_ONDISK_FIELD);
assert(ondisk_bytes > 0);
assert(ondisk_bytes < PAGE_SIZE);
assert(ondisk_bytes < sizeof(struct super_block));
if (sp->s_dev == NO_DEV)
panic("request for super_block of NO_DEV");
/* we rely on the cache blocksize, before reading the
* superblock, being big enough that our complete superblock
* is in block 0.
*
* copy between the disk block and the superblock buffer (depending
* on direction). mark the disk block dirty if the copy is into the
* disk block.
*/
assert(lmfs_fs_block_size() >= sizeof(struct super_block) + SUPER_BLOCK_BYTES);
assert(SUPER_BLOCK_BYTES >= sizeof(struct super_block));
assert(SUPER_BLOCK_BYTES >= ondisk_bytes);
if(!(bp = get_block(sp->s_dev, 0, NORMAL)))
panic("get_block of superblock failed");
/* sbbuf points to the disk block at the superblock offset */
sbbuf = (char *) b_data(bp) + SUPER_BLOCK_BYTES;
if(writing) {
memset(b_data(bp), 0, lmfs_fs_block_size());
memcpy(sbbuf, sp, ondisk_bytes);
lmfs_markdirty(bp);
} else {
memset(sp, 0, sizeof(*sp));
memcpy(sp, sbbuf, ondisk_bytes);
sp->s_dev = save_dev;
}
put_block(bp, FULL_DATA_BLOCK);
lmfs_flushall();
return OK;
}
/*===========================================================================*
* read_super *
*===========================================================================*/
int read_super(struct super_block *sp)
{
unsigned int magic;
block_t offset;
int version, native, r;
if((r=rw_super(sp, 0)) != OK)
return r;
magic = sp->s_magic; /* determines file system type */
if(magic == SUPER_V2 || magic == SUPER_MAGIC) {
printf("MFS: only supports V3 filesystems.\n");
return EINVAL;
}
/* Get file system version and type - only support v3. */
if(magic != SUPER_V3) {
return EINVAL;
}
version = V3;
native = 1;
/* If the super block has the wrong byte order, swap the fields; the magic
* number doesn't need conversion. */
sp->s_ninodes = (ino_t) conv4(native, (int) sp->s_ninodes);
sp->s_nzones = (zone1_t) conv2(native, (int) sp->s_nzones);
sp->s_imap_blocks = (short) conv2(native, (int) sp->s_imap_blocks);
sp->s_zmap_blocks = (short) conv2(native, (int) sp->s_zmap_blocks);
sp->s_firstdatazone_old =(zone1_t)conv2(native,(int)sp->s_firstdatazone_old);
sp->s_log_zone_size = (short) conv2(native, (int) sp->s_log_zone_size);
sp->s_max_size = (off_t) conv4(native, sp->s_max_size);
sp->s_zones = (zone_t)conv4(native, sp->s_zones);
/* Calculate some other numbers that depend on the version here too, to
* hide some of the differences.
*/
assert(version == V3);
sp->s_block_size = (unsigned short) conv2(native,(int) sp->s_block_size);
if (sp->s_block_size < PAGE_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);
/* For even larger disks, a similar problem occurs with s_firstdatazone.
* If the on-disk field contains zero, we assume that the value was too
* large to fit, and compute it on the fly.
*/
if (sp->s_firstdatazone_old == 0) {
offset = START_BLOCK + sp->s_imap_blocks + sp->s_zmap_blocks;
offset += (sp->s_ninodes + sp->s_inodes_per_block - 1) /
sp->s_inodes_per_block;
sp->s_firstdatazone = (offset + (1 << sp->s_log_zone_size) - 1) >>
sp->s_log_zone_size;
} else {
sp->s_firstdatazone = (zone_t) sp->s_firstdatazone_old;
}
if (sp->s_block_size < PAGE_SIZE)
return(EINVAL);
if ((sp->s_block_size % 512) != 0)
return(EINVAL);
if (SUPER_SIZE > sp->s_block_size)
return(EINVAL);
if ((sp->s_block_size % V2_INODE_SIZE) != 0) {
return(EINVAL);
}
/* Limit s_max_size to LONG_MAX */
if ((unsigned long)sp->s_max_size > LONG_MAX)
sp->s_max_size = LONG_MAX;
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
|| sp->s_firstdatazone <= 4
|| sp->s_firstdatazone >= sp->s_zones
|| (unsigned) sp->s_log_zone_size > 4) {
printf("not enough imap or zone map blocks, \n");
printf("or not enough inodes, or not enough zones, \n"
"or invalid first data zone, or zone size too large\n");
return(EINVAL);
}
/* Check any flags we don't understand but are required to. Currently
* these don't exist so all such unknown bits are fatal.
*/
if(sp->s_flags & MFSFLAG_MANDATORY_MASK) {
printf("MFS: unsupported feature flags on this FS.\n"
"Please use a newer MFS to mount it.\n");
return(EINVAL);
}
return(OK);
}
/*===========================================================================*
* write_super *
*===========================================================================*/
int write_super(struct super_block *sp)
{
if(sp->s_rd_only)
panic("can't write superblock of readonly filesystem");
return rw_super(sp, 1);
}
static int blocks_known = 0;
u32_t get_used_blocks(struct super_block *sp)
{
if(!blocks_known) {
/* how many blocks are in use? */
used_blocks = sp->s_zones - count_free_bits(sp, ZMAP);
blocks_known = 1;
}
return used_blocks;
}