mpool.libtp

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/******************************************************************************

VERSION $Id: mpool.libtp,v 1.3 1997/02/22 14:57:55 peter Exp $
PACKAGE: 	User Level Shared Memory Manager

DESCRIPTION: 	
	This package provides a buffer pool interface implemented as
	a collection of file pages mapped into shared memory.

	Based on Mark's buffer manager

ROUTINES: 
    External
	buf_alloc
	buf_flags
	buf_get
	buf_init
	buf_last
	buf_open
	buf_pin
	buf_sync
	buf_unpin
    Internal
	bf_assign_buf
	bf_fid_to_fd
	bf_newbuf
	bf_put_page
	

******************************************************************************/
#include	<sys/types.h>
#include	<assert.h>
#include	<sys/file.h>
#include	<sys/stat.h>
#include	<stdio.h>
#include	<errno.h>
#include	"list.h"
#include	"user.h"
#include	"txn_sys.h"
#include	"buf.h"
#include	"semkeys.h"
#include	"error.h"

/*
    we need to translate between some type of file id that the user 
    process passes and a file descriptor.  For now, it's a nop.
*/
#define GET_MASTER      get_sem ( buf_spinlock )
#define RELEASE_MASTER  release_sem ( buf_spinlock )

#define	LRUID	*buf_lru
#define	LRUP	(bufhdr_table+*buf_lru)
#define	MRU	bufhdr_table[*buf_lru].lru.prev

/* Global indicator that you have started reusing buffers */
int	do_statistics = 0;
/*
    Process Statics (pointers into shared memory)
*/
static	BUF_T	*buf_table = 0;
static	BUFHDR_T	*bufhdr_table;
static	int	*buf_hash_table;
static	int	*buf_lru;		/* LRU is the free list */
static	int	buf_spinlock;
static	FINFO_T	*buf_fids;
static	int	*buf_sp;		/* Pointer to string free space */
static	char	*buf_strings;

/* Process Local FID->FD table */
static	int	fds[NUM_FILE_ENTRIES];

/* Static routines */
static	BUFHDR_T	*bf_assign_buf();
static	int		bf_fid_to_fd();
static	BUFHDR_T	*bf_newbuf();
static	int		bf_put_page();

/*
    Return  0 on success
	    1 on failure
*/
extern int
buf_init ( )
{
    ADDR_T	buf_region;
    BUFHDR_T	*bhp;
    int		i;
    int		ref_count;
    int		*spinlockp;

    /*
	Initialize Process local structures
    */
    for ( i = 0; i < NUM_FILE_ENTRIES; i++ ) {
	fds[i] = -1;
    }

    buf_region = attach_region ( BUF_REGION_NAME, BUF_REGION_NUM,
				 BUF_REGION_SIZE, &ref_count );
    if ( !buf_region ) {
	return (1);
    }
    error_log3 ( "Buf Region: ADDR: %d ID: %d SIZE: %d\n", buf_region,
		    BUF_REGION_NUM, BUF_REGION_SIZE );

    buf_table = (BUF_T *)buf_region;
    bufhdr_table = (BUFHDR_T *)(buf_table + NUM_BUFS);
    buf_hash_table = (int *)(bufhdr_table + NUM_BUFS);
    buf_lru = buf_hash_table + NUMTABLE_ENTRIES;
    spinlockp = buf_lru + 1;
    buf_fids = (FINFO_T *)(spinlockp+1);
    buf_sp = (int *)(buf_fids + NUM_FILE_ENTRIES);
    buf_strings = (char *)(buf_sp + 1);

    /* Create locking spinlock (gets creating holding the lock) */
    buf_spinlock = create_sem ( BUF_SPIN_NAME, BUF_SPIN_NUM, ref_count <= 1 );
    if ( buf_spinlock < 0 )  {
	return(1);
    }
    if ( ref_count <= 1 ) {
	*spinlockp = buf_spinlock;

	/* Now initialize the buffer manager */

	/* 1. Free list */
	*buf_lru = 0;

	/* 2. Buffer headers */
	for ( i = 0, bhp = bufhdr_table; i < NUM_BUFS; bhp++, i++ ) {
		bhp->lru.next = i+1;
		bhp->lru.prev = i-1;
		bhp->flags = 0;				/* All Flags off */
		bhp->refcount = 0;
		bhp->wait_proc = -1;			/* No sleepers */
		LISTPE_INIT ( hash, bhp, i );		/* Hash chains */
	}
	bufhdr_table[0].lru.prev = NUM_BUFS-1;
	bufhdr_table[NUM_BUFS-1].lru.next = 0;

	/* 3. Hash Table */
	for ( i = 0; i < NUMTABLE_ENTRIES; i++ ) {
		buf_hash_table[i] = NUM_BUFS;
	}

	/* 4. File ID Table */
	for ( i = 0; i < NUM_FILE_ENTRIES; i++ ) {
		buf_fids[i].offset = -1;
		buf_fids[i].npages = -1;
		buf_fids[i].refcount = 0;
	}

	/* 5. Free String Pointer */
	*buf_sp = (FILE_NAME_LEN*NUM_FILE_ENTRIES);
	if (RELEASE_MASTER) {
		return(1);
	}
	error_log0 ( "Initialized buffer region\n" );
    } 
    return (0);
}

extern	void
buf_exit()
{
    int	ref;
    int	i;

    /* Flush Buffer Pool on Exit */
    for ( i = 0; i < NUM_FILE_ENTRIES; i++ ) {
	if ( fds[i] != -1 ) {
		close ( fds[i] );
	}
    }
    if ( buf_table ) {
	detach_region ( buf_table, BUF_REGION_NUM, BUF_REGION_SIZE, &ref );
    }
    return;
}

/*
	We need an empty buffer.  Find the LRU unpinned NON-Dirty page.
*/
static BUFHDR_T	*
bf_newbuf()
{
    int		fd;
    int		lruid;
    int		nbytes;
    int		ndx;
    BUFHDR_T	*bhp;

    lruid = LRUID;
    for ( bhp = LRUP; 
	  bhp->flags & (BUF_PINNED|BUF_IO_IN_PROGRESS); 
	  bhp = LISTP_NEXTP (bufhdr_table, lru, bhp ) ) {

	if ( bhp->lru.next == lruid ) {
		/* OUT OF BUFFERS */
		error_log1 ( "All buffers are pinned.  %s\n",
				"Unable to grant buffer request" );
		return(NULL);
	}
    }
    /* BHP can be used */
    if ( bhp->flags & BUF_DIRTY ) {
	do_statistics = 1;
	/* 
	    MIS  Check for log flushed appropriately
	*/
	fd = bf_fid_to_fd(bhp->id.file_id);
	if ( fd == -1 ) {
	    error_log1 ("Invalid fid %d\n", bhp->id.file_id);
	    return(NULL);
	}
	if ( bf_put_page(fd, bhp) < 0 ) {
	    return(NULL);
	}
    }
    /* Update Hash Pointers */
    ndx = BUF_HASH ( bhp->id.file_id, bhp->id.obj_id );
    LISTP_REMOVE(bufhdr_table, hash, bhp);
    if ( buf_hash_table[ndx] == (bhp-bufhdr_table) ) {
	if ( bhp->hash.next != (bhp-bufhdr_table) ) {
		buf_hash_table[ndx] = bhp->hash.next;
	} else {
		buf_hash_table[ndx] = NUM_BUFS;
	}
    }
    INIT_BUF(bhp); 

    return(bhp);
}
/*
    buf_alloc

    Add a page to a file and return a buffer for it.

*/
ADDR_T
buf_alloc ( fid, new_pageno )
int	fid;
int	*new_pageno;
{
	BUFHDR_T	*bhp;
	int	fd;
	int	len;
	int	ndx;
	OBJ_T	fobj;

	if (GET_MASTER) {
		return(NULL);
	}
	if ( buf_fids[fid].npages == -1 ) {
	    /* initialize npages field */
	    fd = bf_fid_to_fd ( fid );
	}
	assert (fid < NUM_FILE_ENTRIES);

	*new_pageno = buf_fids[fid].npages;
	if ( *new_pageno == -1 ) {
	    RELEASE_MASTER;
	    return ( NULL );
	}
	buf_fids[fid].npages++;
	ndx = BUF_HASH ( fid, *new_pageno );
	fobj.file_id = fid;
	fobj.obj_id  = *new_pageno;
	bhp = bf_assign_buf ( ndx, &fobj, BF_PIN|BF_DIRTY|BF_EMPTY, &len );
	if ( RELEASE_MASTER ) {
		/* Memory leak */
		return(NULL);
	}
	if ( bhp ) {
	    return ((ADDR_T)(buf_table+(bhp-bufhdr_table)));
	} else {
	    return ( NULL );
	}
}


/*
	Buffer Flags
	BF_DIRTY		Mark page as dirty
	BF_EMPTY		Don't initialize page, just get buffer
	BF_PIN			Retrieve with pin 

MIS
Might want to add a flag that sets an LSN for this buffer is the
DIRTY flag is set

Eventually, you may want a flag that indicates the I/O and lock
request should be shipped off together, but not for now.
*/
extern ADDR_T
buf_get ( file_id, page_id, flags, len )
int	file_id;
int	page_id;
u_long	flags;
int	*len;		/* Number of bytes read into buffer */
{
	BUFHDR_T	*bhp;
	int		bufid;
	int		fd;
	int		ndx;
	int		next_bufid;
	int		stat;
	OBJ_T		fobj;	

	ndx = BUF_HASH ( file_id, page_id );
	fobj.file_id = (long) file_id;
	fobj.obj_id = (long) page_id;
	if ( GET_MASTER ) {
		return(NULL);
	}
	/*
		This could be a for loop, but we lose speed
		by making all the cases general purpose so we
		optimize for the no-collision case. 
	*/
	bufid = buf_hash_table[ndx]; 
	if ( bufid < NUM_BUFS ) {
	    for ( bhp = bufhdr_table+bufid; 
		  !OBJ_EQ (bhp->id, fobj) || !(bhp->flags & BUF_VALID);
		  bhp = LISTP_NEXTP ( bufhdr_table, hash, bhp ) ) {

		if ( bhp->hash.next == bufid ) {
		    goto not_found;
		}
	    }
/* found */
	    if ( flags & BF_PIN ) {
		    bhp->flags |= BUF_PINNED;
		    bhp->refcount++;
#ifdef PIN_DEBUG
	fprintf(stderr, "buf_get: %X PINNED (%d)\n", 
			buf_table + (bhp-bufhdr_table), bhp->refcount);
#endif
	    }
	    if ( flags & BF_DIRTY ) {
		    bhp->flags |= BUF_DIRTY;
	    }

	    while ( bhp->flags & BUF_IO_IN_PROGRESS ) {
		/* MIS -- eventually err check here */
#ifdef DEBUG
		printf("About to sleep on %d (me: %d\n)\n", bhp->wait_proc,
			my_txnp - txn_table);
#endif
#ifdef WAIT_STATS
		buf_waits++;
#endif
		stat = proc_sleep_on ( &(bhp->wait_proc), buf_spinlock );
		if ( stat ) {
			/* Memory leak */
			return(NULL);
		}
		if (!( bhp->flags & BUF_IO_IN_PROGRESS) &&
		    (!OBJ_EQ (bhp->id, fobj) || !(bhp->flags & BUF_VALID))) {
			if (RELEASE_MASTER)
				return(NULL);
			return(buf_get ( file_id, page_id, flags, len ));
		}
	    }
	    MAKE_MRU( bhp );
	    *len = BUFSIZE;
	} else {
not_found:
	    /* If you get here, the page isn't in the hash table */
	    bhp = bf_assign_buf ( ndx, &fobj, flags, len );
	}
	/* Common code between found and not found */

	if ( bhp && bhp->flags & BUF_NEWPAGE ) {
	    *len = 0;