minix/servers/mfs/cache.c

94 lines
3 KiB
C
Raw Normal View History

2005-04-21 16:53:53 +02:00
/* The file system maintains a buffer cache to reduce the number of disk
* accesses needed. Whenever a read or write to the disk is done, a check is
* first made to see if the block is in the cache. This file manages the
* cache.
*
* The entry points into this file are:
* get_block: request to fetch a block for reading or writing from cache
* put_block: return a block previously requested with get_block
* alloc_zone: allocate a new zone (to increase the length of a file)
* free_zone: release a zone (when a file is removed)
* invalidate: remove all the cache blocks on some device
2005-10-12 17:06:47 +02:00
*
* Private functions:
* read_block: read or write a block from the disk itself
2005-04-21 16:53:53 +02:00
*/
#include "fs.h"
#include <minix/u64.h>
#include <minix/bdev.h>
#include <sys/param.h>
#include <stdlib.h>
#include <assert.h>
#include <minix/libminixfs.h>
#include <math.h>
2005-04-21 16:53:53 +02:00
#include "buf.h"
#include "super.h"
#include "inode.h"
2005-04-21 16:53:53 +02:00
/*===========================================================================*
* alloc_zone *
*===========================================================================*/
2012-03-25 20:25:53 +02:00
zone_t alloc_zone(
dev_t dev, /* device where zone wanted */
zone_t z /* try to allocate new zone near this one */
)
2005-04-21 16:53:53 +02:00
{
/* Allocate a new zone on the indicated device and return its number. */
bit_t b, bit;
struct super_block *sp;
static int print_oos_msg = 1;
2005-04-21 16:53:53 +02:00
/* Note that the routine alloc_bit() returns 1 for the lowest possible
* zone, which corresponds to sp->s_firstdatazone. To convert a value
* between the bit number, 'b', used by alloc_bit() and the zone number, 'z',
* stored in the inode, use the formula:
* z = b + sp->s_firstdatazone - 1
* Alloc_bit() never returns 0, since this is used for NO_BIT (failure).
*/
sp = get_super(dev);
/* If z is 0, skip initial part of the map known to be fully in use. */
if (z == sp->s_firstdatazone) {
bit = sp->s_zsearch;
} else {
bit = (bit_t) (z - (sp->s_firstdatazone - 1));
2005-04-21 16:53:53 +02:00
}
b = alloc_bit(sp, ZMAP, bit);
if (b == NO_BIT) {
err_code = ENOSPC;
if (print_oos_msg)
printf("No space on device %d/%d\n", major(sp->s_dev),
minor(sp->s_dev));
print_oos_msg = 0; /* Don't repeat message */
2005-04-21 16:53:53 +02:00
return(NO_ZONE);
}
print_oos_msg = 1;
2005-04-21 16:53:53 +02:00
if (z == sp->s_firstdatazone) sp->s_zsearch = b; /* for next time */
return( (zone_t) (sp->s_firstdatazone - 1) + (zone_t) b);
2005-04-21 16:53:53 +02:00
}
/*===========================================================================*
* free_zone *
*===========================================================================*/
2012-03-25 20:25:53 +02:00
void free_zone(
dev_t dev, /* device where zone located */
zone_t numb /* zone to be returned */
)
2005-04-21 16:53:53 +02:00
{
/* Return a zone. */
register struct super_block *sp;
bit_t bit;
/* Locate the appropriate super_block and return bit. */
sp = get_super(dev);
if (numb < sp->s_firstdatazone || numb >= sp->s_zones) return;
bit = (bit_t) (numb - (zone_t) (sp->s_firstdatazone - 1));
2005-04-21 16:53:53 +02:00
free_bit(sp, ZMAP, bit);
if (bit < sp->s_zsearch) sp->s_zsearch = bit;
}