84 lines
3.1 KiB
C
84 lines
3.1 KiB
C
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// NEW CODE implementing a simple disk i/o multiplexing layer
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#ifndef _DISKIO_H
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#define _DISKIO_H
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#include "sched.h"
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// TODO: Replace BSIZE references in old code with this and/or make it flexible
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#define DISKIO_BLOCK_SIZE 4096
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typedef struct diskio_buffer diskio_buffer_t;
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typedef struct diskio_cache diskio_cache_t;
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// NOTE: This still resembles the old structure but will probably be changed
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// as different options/backends/etc. are added.
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struct diskio_buffer {
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diskio_cache_t* owner;
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unsigned int referencecount;
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int padding;
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int isvalid;
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int isdisk; // Is this a buffer owned by the disk (rather than the fs code??)
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unsigned int device;
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unsigned int blocknumber;
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sched_sleeplock_t lock;
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// Least-recently-used list:
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diskio_buffer_t* previous;
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diskio_buffer_t* next;
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// Block data
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unsigned char* data; // TODO: Flexible buffers
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};
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// The diskio_cache structure should fit in a page, so it must be limited in
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// to a few hundred buffer references for now:
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#define DISKIO_CACHE_MAXBUFFERS 500
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struct diskio_cache {
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sched_spinlock_t spin;
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diskio_buffer_t* leastrecentlist;
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unsigned long long buffercount;
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unsigned long long blocksize;
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diskio_buffer_t* buffers[DISKIO_CACHE_MAXBUFFERS];
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};
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// These are the internal allocation functions, a cache pre-allocates a number
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// of buffer structures (each representing 1 disk block) then re-allocates them
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// on demand from it's internal list.
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diskio_buffer_t* diskio_buffer_alloc(diskio_cache_t* owner, unsigned long long blocksize);
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void diskio_buffer_free(diskio_buffer_t* buffer);
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diskio_cache_t* diskio_cache_alloc(unsigned long long buffercount, unsigned long long blocksize);
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void diskio_cache_free(diskio_cache_t* cache);
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// These are the internal read/write functions which link to any I/O multiplexing
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void diskio_performread(diskio_buffer_t* buffer);
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void diskio_performwrite(diskio_buffer_t* buffer);
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// Performs a logical write of a buffered block through it's associated cache,
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// checks that the buffer is already locked and writes it to the disk.
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void diskio_buffer_write(diskio_buffer_t* buffer);
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// Performs a logical read of a buffered block through a cache, returning it in
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// locked form with the given block.
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diskio_buffer_t* diskio_buffer_read(diskio_cache_t* cache, unsigned int device, unsigned int blocknumber);
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// (Re-)allocates a buffer from the cache for a given device and block number
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// combination, but does NOT attempt to read the block from disk. Returns an
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// existing or newly repurposed buffer from the cache in a locked state.
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diskio_buffer_t* diskio_buffer_get_noread(diskio_cache_t* cache, unsigned int device, unsigned int blocknumber);
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void diskio_buffer_release(diskio_buffer_t* buffer);
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void diskio_buffer_reference(diskio_buffer_t* buffer);
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void diskio_buffer_dereference(diskio_buffer_t* buffer);
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// Used internally for reads/writes to ramdisk devices
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void diskio_ramdisk_rw(diskio_buffer_t* buffer, int wr);
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struct drives; // Defined properly in drives.h
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// Called to mount any available ramdisk images on the given drives structure.
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void diskio_mountallramdisks(struct drives* drives);
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// From ifndef at top of file:
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#endif
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