347 lines
8.9 KiB
C
347 lines
8.9 KiB
C
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/*-
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Margo Seltzer.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)buf.c 5.7 (Berkeley) 3/12/91";
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#endif /* LIBC_SCCS and not lint */
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/******************************************************************************
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PACKAGE: hash
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DESCRIPTION:
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Contains buffer management
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ROUTINES:
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External
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__buf_init
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__get_buf
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__buf_free
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__reclaim_buf
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Internal
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newbuf
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******************************************************************************/
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#include <sys/param.h>
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#include <assert.h>
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#include <errno.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include "hash.h"
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/* Externals */
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extern HTAB *hashp;
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/* My internals */
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static BUFHEAD *newbuf();
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/* Unlink B from its place in the lru */
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#define BUF_REMOVE(B) \
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{ \
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B->prev->next = B->next; \
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B->next->prev = B->prev; \
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}
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/* Insert B after P */
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#define BUF_INSERT(B,P) \
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{ \
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B->next = P->next; \
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B->prev = P; \
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P->next = B; \
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B->next->prev = B; \
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}
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#define MRU hashp->bufhead.next
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#define LRU hashp->bufhead.prev
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#define MRU_INSERT(B) BUF_INSERT(B,(&hashp->bufhead))
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#define LRU_INSERT(B) BUF_INSERT(B,LRU)
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/*
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We are looking for a buffer with address "addr".
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If prev_bp is NULL, then address is a bucket index.
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If prev_bp is not NULL, then it points to the page previous
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to an overflow page that we are trying to find.
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CAVEAT: The buffer header accessed via prev_bp's ovfl field
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may no longer be valid. Therefore, you must always verify that
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its address matches the address you are seeking.
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*/
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extern BUFHEAD *
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__get_buf ( addr, prev_bp, newpage )
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u_int addr;
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BUFHEAD *prev_bp;
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int newpage; /* If prev_bp is set, indicates that this is
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a new overflow page */
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{
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register int segment_ndx;
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register BUFHEAD *bp;
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register unsigned is_disk = 0;
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register unsigned is_disk_mask = 0;
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SEGMENT segp;
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if ( prev_bp ) {
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bp = prev_bp->ovfl;
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if ( !bp || (bp->addr != addr) ) bp = NULL;
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if ( !newpage ) is_disk = BUF_DISK;
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}
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else {
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/* Grab buffer out of directory */
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segment_ndx = addr & ( hashp->SGSIZE - 1 );
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/*
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* valid segment ensured by __call_hash()
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*/
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segp = hashp->dir[addr >> hashp->SSHIFT];
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#ifdef DEBUG
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assert(segp != NULL);
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#endif
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bp = PTROF(segp[segment_ndx]);
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is_disk_mask = ISDISK(segp[segment_ndx]);
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is_disk = is_disk_mask || !hashp->new_file;
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}
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if ( !bp ) {
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bp = newbuf ( addr, prev_bp );
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if ( !bp || __get_page ( bp->page, addr, !prev_bp, is_disk, 0 )) {
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return(NULL);
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}
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if ( !prev_bp ) {
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segp[segment_ndx] = (BUFHEAD *)((unsigned)bp | is_disk_mask );
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}
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} else {
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BUF_REMOVE ( bp );
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MRU_INSERT ( bp );
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}
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return(bp);
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}
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/*
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We need a buffer for this page. Either allocate one, or
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evict a resident one (if we have as many buffers as we're
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allowed) and put this one in.
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If newbuf finds an error (returning NULL), it also sets errno
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*/
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static BUFHEAD *
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newbuf ( addr, prev_bp )
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u_int addr;
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BUFHEAD *prev_bp;
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{
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register BUFHEAD *bp; /* The buffer we're going to use */
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register BUFHEAD *xbp; /* Temp pointer */
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register BUFHEAD *next_xbp;
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int segment_ndx;
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u_short *shortp;
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u_short oaddr;
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SEGMENT segp;
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oaddr = 0;
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bp = LRU;
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/*
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If LRU buffer is pinned, the buffer pool is too small.
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We need to allocate more buffers
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*/
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if ( hashp->nbufs || (bp->flags & BUF_PIN) ) {
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/* Allocate a new one */
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bp = (BUFHEAD *)malloc ( sizeof (struct _bufhead) );
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if ( !bp || !(bp->page = (char *)malloc ( hashp->BSIZE )) ) {
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return (NULL);
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}
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hashp->nbufs--;
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} else {
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/* Kick someone out */
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BUF_REMOVE( bp );
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/*
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If this is an overflow page with addr 0, it's already
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been flushed back in an overflow chain and initialized
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*/
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if ( (bp->addr != 0) || (bp->flags & BUF_BUCKET) ) {
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/*
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Set oaddr before __put_page so that you get it
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before bytes are swapped
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*/
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shortp = (u_short *)bp->page;
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if ( shortp[0] ) {
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oaddr = shortp[shortp[0]-1];
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}
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if ( (bp->flags & BUF_MOD) &&
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__put_page(bp->page, bp->addr, (int)IS_BUCKET(bp->flags), 0) ) {
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return(NULL);
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}
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/*
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Update the pointer to this page (i.e. invalidate it).
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If this is a new file (i.e. we created it at open time),
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make sure that we mark pages which have been written to
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disk so we retrieve them from disk later, rather than
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allocating new pages.
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*/
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if ( IS_BUCKET(bp->flags)) {
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segment_ndx = bp->addr & ( hashp->SGSIZE - 1 );
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segp = hashp->dir[bp->addr >> hashp->SSHIFT];
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assert(segp != NULL);
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if ( hashp->new_file &&
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((bp->flags & BUF_MOD) || ISDISK(segp[segment_ndx])) ) {
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segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
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} else segp[segment_ndx] = NULL;
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}
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/*
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Since overflow pages can only be access by means of
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their bucket, free overflow pages associated with this
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bucket.
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*/
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for ( xbp = bp; xbp->ovfl; ) {
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next_xbp = xbp->ovfl;
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xbp->ovfl = 0;
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xbp = next_xbp;
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/* Check that ovfl pointer is up date */
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if ( IS_BUCKET(xbp->flags) || (oaddr != xbp->addr) ) break;
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shortp = (u_short *)xbp->page;
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if ( shortp[0] ) {
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oaddr = shortp[shortp[0]-1]; /* set before __put_page */
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}
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if ( (xbp->flags & BUF_MOD) &&
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__put_page ( xbp->page, xbp->addr, 0, 0 ) ) {
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return(NULL);
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}
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xbp->addr = 0;
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xbp->flags = 0;
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BUF_REMOVE ( xbp );
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LRU_INSERT ( xbp );
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}
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}
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}
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/* Now assign this buffer */
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bp->addr = addr;
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#ifdef DEBUG1
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fprintf ( stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", bp->addr,
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(bp->ovfl?bp->ovfl->addr:0), 0);
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#endif
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bp->ovfl = NULL;
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if ( prev_bp ) {
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/*
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If prev_bp is set, this is an overflow page, hook it in to the
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buffer overflow links
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*/
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#ifdef DEBUG1
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fprintf ( stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", prev_bp->addr,
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(prev_bp->ovfl?bp->ovfl->addr:0),
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(bp?bp->addr: 0));
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#endif
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prev_bp->ovfl = bp;
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bp->flags = 0;
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} else bp->flags = BUF_BUCKET;
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MRU_INSERT ( bp );
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return ( bp );
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}
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extern void
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__buf_init ( nbytes )
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int nbytes;
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{
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int npages;
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BUFHEAD *bfp = &(hashp->bufhead);
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npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
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npages = MAX ( npages, MIN_BUFFERS );
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hashp->nbufs = npages;
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bfp->next = bfp;
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bfp->prev = bfp;
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/*
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This space is calloc'd so these are already null
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bfp->ovfl = NULL;
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bfp->flags = 0;
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bfp->page = NULL;
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bfp->addr = 0;
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*/
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}
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extern int
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__buf_free ( do_free, to_disk )
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int do_free;
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int to_disk;
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{
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BUFHEAD *bp;
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/* Need to make sure that buffer manager has been initialized */
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if ( !LRU ) {
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return(0);
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}
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for ( bp = LRU; bp != &hashp->bufhead; ) {
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/* Check that the buffer is valid */
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if ( bp->addr || IS_BUCKET(bp->flags) ) {
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if ( to_disk && (bp->flags & BUF_MOD) &&
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__put_page (bp->page, bp->addr, IS_BUCKET(bp->flags), 0 )) {
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return (-1);
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}
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}
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/* Check if we are freeing stuff */
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if ( do_free ) {
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if ( bp->page ) free ( bp->page );
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BUF_REMOVE(bp);
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(void)free ( bp );
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bp = LRU;
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} else bp = bp->prev;
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}
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return(0);
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}
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extern void
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__reclaim_buf ( bp )
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BUFHEAD *bp;
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{
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bp->ovfl = 0;
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bp->addr = 0;
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bp->flags = 0;
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BUF_REMOVE ( bp );
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LRU_INSERT ( bp );
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}
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