bd3cde4571
Add primary cache management feature to libminixfs as mfs and ext2
currently do separately, remove cache code from mfs and ext2, and make
them use the libminixfs interface. This makes all fields of the buf
struct private to libminixfs and FS clients aren't supposed to access
them at all. Only the opaque 'void *data' field (the FS block contents,
used to be called bp) is to be accessed by the FS client.
The main purpose is to implement the interface to the 2ndary vm cache
just once, get rid of some code duplication, and add a little
abstraction to reduce the code inertia of the whole caching business.
Some minor sanity checking and prohibition done by mfs in this code
as removed from the generic primary cache code as a result:
- checking all inodes are not in use when allocating/resizing
the cache
- checking readonly filesystems aren't written to
- checking the superblock isn't written to on mounted filesystems
The minixfslib code relies on fs_blockstats() in the client filesystem to
return some FS usage information.
94 lines
3 KiB
C
94 lines
3 KiB
C
/* The file system maintains a buffer cache to reduce the number of disk
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* accesses needed. Whenever a read or write to the disk is done, a check is
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* first made to see if the block is in the cache. This file manages the
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* cache.
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*
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* The entry points into this file are:
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* get_block: request to fetch a block for reading or writing from cache
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* put_block: return a block previously requested with get_block
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* alloc_zone: allocate a new zone (to increase the length of a file)
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* free_zone: release a zone (when a file is removed)
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* invalidate: remove all the cache blocks on some device
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*
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* Private functions:
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* read_block: read or write a block from the disk itself
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*/
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#include "fs.h"
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#include <minix/u64.h>
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#include <minix/bdev.h>
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#include <sys/param.h>
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#include <stdlib.h>
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#include <assert.h>
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#include <minix/libminixfs.h>
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#include <math.h>
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#include "buf.h"
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#include "super.h"
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#include "inode.h"
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/*===========================================================================*
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* alloc_zone *
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*===========================================================================*/
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zone_t alloc_zone(
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dev_t dev, /* device where zone wanted */
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zone_t z /* try to allocate new zone near this one */
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)
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{
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/* Allocate a new zone on the indicated device and return its number. */
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bit_t b, bit;
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struct super_block *sp;
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static int print_oos_msg = 1;
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/* Note that the routine alloc_bit() returns 1 for the lowest possible
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* zone, which corresponds to sp->s_firstdatazone. To convert a value
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* between the bit number, 'b', used by alloc_bit() and the zone number, 'z',
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* stored in the inode, use the formula:
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* z = b + sp->s_firstdatazone - 1
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* Alloc_bit() never returns 0, since this is used for NO_BIT (failure).
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*/
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sp = get_super(dev);
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/* If z is 0, skip initial part of the map known to be fully in use. */
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if (z == sp->s_firstdatazone) {
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bit = sp->s_zsearch;
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} else {
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bit = (bit_t) (z - (sp->s_firstdatazone - 1));
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}
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b = alloc_bit(sp, ZMAP, bit);
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if (b == NO_BIT) {
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err_code = ENOSPC;
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if (print_oos_msg)
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printf("No space on device %d/%d\n", major(sp->s_dev),
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minor(sp->s_dev));
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print_oos_msg = 0; /* Don't repeat message */
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return(NO_ZONE);
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}
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print_oos_msg = 1;
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if (z == sp->s_firstdatazone) sp->s_zsearch = b; /* for next time */
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return( (zone_t) (sp->s_firstdatazone - 1) + (zone_t) b);
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}
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/*===========================================================================*
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* free_zone *
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*===========================================================================*/
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void free_zone(
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dev_t dev, /* device where zone located */
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zone_t numb /* zone to be returned */
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)
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{
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/* Return a zone. */
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register struct super_block *sp;
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bit_t bit;
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/* Locate the appropriate super_block and return bit. */
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sp = get_super(dev);
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if (numb < sp->s_firstdatazone || numb >= sp->s_zones) return;
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bit = (bit_t) (numb - (zone_t) (sp->s_firstdatazone - 1));
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free_bit(sp, ZMAP, bit);
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if (bit < sp->s_zsearch) sp->s_zsearch = bit;
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}
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