4472b590c7
This patch changes the prefetch API so that file systems must now provide a set of block numbers, rather than a set of buffers. The result is a leaner and more well-defined API; linear computation of the range of blocks to prefetch; duplicates no longer interfering with the prefetch process; guaranteed inclusion of the block needed next into the prefetch range; and, limits and policy decisions better established by libminixfs now actually being moved into libminixfs. Change-Id: I7e44daf2d2d164bc5e2f1473ad717f3ff0f0a77f
110 lines
3.7 KiB
C
110 lines
3.7 KiB
C
/* 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 contains some
|
|
* related routines, but the cache is now in libminixfs.
|
|
*/
|
|
|
|
#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>
|
|
#include "buf.h"
|
|
#include "super.h"
|
|
#include "inode.h"
|
|
|
|
/*===========================================================================*
|
|
* get_block *
|
|
*===========================================================================*/
|
|
struct buf *get_block(dev_t dev, block_t block, int how)
|
|
{
|
|
/* Wrapper routine for lmfs_get_block(). This MFS implementation does not deal
|
|
* well with block read errors pretty much anywhere. To prevent corruption due
|
|
* to unchecked error conditions, we panic upon an I/O failure here.
|
|
*/
|
|
struct buf *bp;
|
|
int r;
|
|
|
|
if ((r = lmfs_get_block(&bp, dev, block, how)) != OK && r != ENOENT)
|
|
panic("MFS: error getting block (%llu,%u): %d", dev, block, r);
|
|
|
|
assert(r == OK || how == PEEK);
|
|
|
|
return (r == OK) ? bp : NULL;
|
|
}
|
|
|
|
/*===========================================================================*
|
|
* alloc_zone *
|
|
*===========================================================================*/
|
|
zone_t alloc_zone(
|
|
dev_t dev, /* device where zone wanted */
|
|
zone_t z /* try to allocate new zone near this one */
|
|
)
|
|
{
|
|
/* 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;
|
|
|
|
/* 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 = &superblock;
|
|
|
|
/* 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));
|
|
}
|
|
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 */
|
|
return(NO_ZONE);
|
|
}
|
|
print_oos_msg = 1;
|
|
if (z == sp->s_firstdatazone) sp->s_zsearch = b; /* for next time */
|
|
return( (zone_t) (sp->s_firstdatazone - 1) + (zone_t) b);
|
|
}
|
|
|
|
/*===========================================================================*
|
|
* free_zone *
|
|
*===========================================================================*/
|
|
void free_zone(
|
|
dev_t dev, /* device where zone located */
|
|
zone_t numb /* zone to be returned */
|
|
)
|
|
{
|
|
/* Return a zone. */
|
|
|
|
register struct super_block *sp;
|
|
bit_t bit;
|
|
|
|
/* Locate the appropriate super_block and return bit. */
|
|
sp = &superblock;
|
|
if (numb < sp->s_firstdatazone || numb >= sp->s_zones) return;
|
|
bit = (bit_t) (numb - (zone_t) (sp->s_firstdatazone - 1));
|
|
free_bit(sp, ZMAP, bit);
|
|
if (bit < sp->s_zsearch) sp->s_zsearch = bit;
|
|
|
|
/* Also tell libminixfs, so that 1) if it has a block for this bit, it can
|
|
* mark it as clean, thus reducing useless writes, and 2) it can tell VM that
|
|
* any previous inode association is to be broken for this block, so that the
|
|
* block will not be mapped in erroneously later on.
|
|
*/
|
|
assert(sp->s_log_zone_size == 0); /* otherwise we need a loop here.. */
|
|
lmfs_free_block(dev, (block_t)numb);
|
|
}
|