/*- * Copyright (c) 1990, 1993, 1994 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * Margo Seltzer. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ /* * PACKAGE: hash * * DESCRIPTION: * Contains buffer management * * ROUTINES: * External * __buf_init * __get_buf * __buf_free * __reclaim_buf * Internal * newbuf */ #ifdef WIN32 #include <io.h> #endif #include <errno.h> #include <stddef.h> #include <stdio.h> #include <stdlib.h> #ifdef DEBUG #include <assert.h> #endif #include "db.h" #include "hash.h" #include "page.h" #include "extern.h" static BUFHEAD *newbuf (HTAB *, uint32_t, BUFHEAD *); /* Unlink B from its place in the lru */ #define BUF_REMOVE(B) { \ (B)->prev->next = (B)->next; \ (B)->next->prev = (B)->prev; \ } /* Insert B after P */ #define BUF_INSERT(B, P) { \ (B)->next = (P)->next; \ (B)->prev = (P); \ (P)->next = (B); \ (B)->next->prev = (B); \ } #define MRU hashp->bufhead.next #define LRU hashp->bufhead.prev #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) #define LRU_INSERT(B) BUF_INSERT((B), LRU) /* * We are looking for a buffer with address "addr". If prev_bp is NULL, then * address is a bucket index. If prev_bp is not NULL, then it points to the * page previous to an overflow page that we are trying to find. * * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer * be valid. Therefore, you must always verify that its address matches the * address you are seeking. */ extern BUFHEAD * __get_buf(HTAB *hashp, uint32_t addr, BUFHEAD *prev_bp, int newpage) /* newpage - If prev_bp set, indicates a new overflow page. */ { register BUFHEAD *bp; register uint32_t is_disk_mask; register int is_disk, segment_ndx = 0; SEGMENT segp = NULL; is_disk = 0; is_disk_mask = 0; if (prev_bp) { bp = prev_bp->ovfl; if (!bp || (bp->addr != addr)) bp = NULL; if (!newpage) is_disk = BUF_DISK; } else { /* Grab buffer out of directory */ segment_ndx = addr & (hashp->SGSIZE - 1); /* valid segment ensured by __call_hash() */ segp = hashp->dir[addr >> hashp->SSHIFT]; #ifdef DEBUG assert(segp != NULL); #endif bp = PTROF(segp[segment_ndx]); is_disk_mask = ISDISK(segp[segment_ndx]); is_disk = is_disk_mask || !hashp->new_file; } if (!bp) { bp = newbuf(hashp, addr, prev_bp); if (!bp || __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) return (NULL); if (!prev_bp) segp[segment_ndx] = (BUFHEAD *)((ptrdiff_t)bp | is_disk_mask); } else { BUF_REMOVE(bp); MRU_INSERT(bp); } return (bp); } /* * We need a buffer for this page. Either allocate one, or evict a resident * one (if we have as many buffers as we're allowed) and put this one in. * * If newbuf finds an error (returning NULL), it also sets errno. */ static BUFHEAD * newbuf(HTAB *hashp, uint32_t addr, BUFHEAD *prev_bp) { register BUFHEAD *bp; /* The buffer we're going to use */ register BUFHEAD *xbp; /* Temp pointer */ register BUFHEAD *next_xbp; SEGMENT segp; int segment_ndx; uint16_t oaddr, *shortp; oaddr = 0; bp = LRU; /* * If LRU buffer is pinned, the buffer pool is too small. We need to * allocate more buffers. */ if (hashp->nbufs || (bp->flags & BUF_PIN)) { /* Allocate a new one */ if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL) return (NULL); #ifdef PURIFY memset(bp, 0xff, sizeof(BUFHEAD)); #endif if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) { free(bp); return (NULL); } #ifdef PURIFY memset(bp->page, 0xff, hashp->BSIZE); #endif if (hashp->nbufs) hashp->nbufs--; } else { /* Kick someone out */ BUF_REMOVE(bp); /* * If this is an overflow page with addr 0, it's already been * flushed back in an overflow chain and initialized. */ if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { /* * Set oaddr before __put_page so that you get it * before bytes are swapped. */ shortp = (uint16_t *)bp->page; if (shortp[0]) oaddr = shortp[shortp[0] - 1]; if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, bp->addr, (int)IS_BUCKET(bp->flags), 0)) return (NULL); /* * Update the pointer to this page (i.e. invalidate it). * * If this is a new file (i.e. we created it at open * time), make sure that we mark pages which have been * written to disk so we retrieve them from disk later, * rather than allocating new pages. */ if (IS_BUCKET(bp->flags)) { segment_ndx = bp->addr & (hashp->SGSIZE - 1); segp = hashp->dir[bp->addr >> hashp->SSHIFT]; #ifdef DEBUG assert(segp != NULL); #endif if (hashp->new_file && ((bp->flags & BUF_MOD) || ISDISK(segp[segment_ndx]))) segp[segment_ndx] = (BUFHEAD *)BUF_DISK; else segp[segment_ndx] = NULL; } /* * Since overflow pages can only be access by means of * their bucket, free overflow pages associated with * this bucket. */ for (xbp = bp; xbp->ovfl;) { next_xbp = xbp->ovfl; xbp->ovfl = 0; xbp = next_xbp; /* Check that ovfl pointer is up date. */ if (IS_BUCKET(xbp->flags) || (oaddr != xbp->addr)) break; shortp = (uint16_t *)xbp->page; if (shortp[0]) /* set before __put_page */ oaddr = shortp[shortp[0] - 1]; if ((xbp->flags & BUF_MOD) && __put_page(hashp, xbp->page, xbp->addr, 0, 0)) return (NULL); xbp->addr = 0; xbp->flags = 0; BUF_REMOVE(xbp); LRU_INSERT(xbp); } } } /* Now assign this buffer */ bp->addr = addr; #ifdef DEBUG1 fprintf(stderr,"NEWBUF1: %d->ovfl was %d is now %d\n", bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); #endif bp->ovfl = NULL; if (prev_bp) { /* * If prev_bp is set, this is an overflow page, hook it in to * the buffer overflow links. */ #ifdef DEBUG1 fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0), (bp ? bp->addr : 0)); #endif prev_bp->ovfl = bp; bp->flags = 0; } else bp->flags = BUF_BUCKET; MRU_INSERT(bp); return (bp); } extern void __buf_init(HTAB *hashp, int nbytes) { BUFHEAD *bfp; int npages; bfp = &(hashp->bufhead); npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; npages = MAX(npages, MIN_BUFFERS); hashp->nbufs = npages; bfp->next = bfp; bfp->prev = bfp; /* * This space is calloc'd so these are already null. * * bfp->ovfl = NULL; * bfp->flags = 0; * bfp->page = NULL; * bfp->addr = 0; */ } extern int __buf_free(HTAB *hashp, int do_free, int to_disk) { BUFHEAD *bp; /* Need to make sure that buffer manager has been initialized */ if (!LRU) return (0); for (bp = LRU; bp != &hashp->bufhead;) { /* Check that the buffer is valid */ if (bp->addr || IS_BUCKET(bp->flags)) { if (to_disk && (bp->flags & BUF_MOD) && __put_page(hashp, bp->page, bp->addr, IS_BUCKET(bp->flags), 0)) return (-1); } /* Check if we are freeing stuff */ if (do_free) { if (bp->page) free(bp->page); BUF_REMOVE(bp); free(bp); bp = LRU; } else bp = bp->prev; } return (0); } extern void __reclaim_buf(HTAB *hashp, BUFHEAD *bp) { bp->ovfl = 0; bp->addr = 0; bp->flags = 0; BUF_REMOVE(bp); LRU_INSERT(bp); }