hash_buf.c revision 1.6
1 /* $NetBSD: hash_buf.c,v 1.6 1996/05/03 21:43:51 cgd Exp $ */ 2 3 /*- 4 * Copyright (c) 1990, 1993, 1994 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Margo Seltzer. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #if defined(LIBC_SCCS) && !defined(lint) 40 #if 0 41 static char sccsid[] = "@(#)hash_buf.c 8.5 (Berkeley) 7/15/94"; 42 #else 43 static char rcsid[] = "$NetBSD: hash_buf.c,v 1.6 1996/05/03 21:43:51 cgd Exp $"; 44 #endif 45 #endif /* LIBC_SCCS and not lint */ 46 47 /* 48 * PACKAGE: hash 49 * 50 * DESCRIPTION: 51 * Contains buffer management 52 * 53 * ROUTINES: 54 * External 55 * __buf_init 56 * __get_buf 57 * __buf_free 58 * __reclaim_buf 59 * Internal 60 * newbuf 61 */ 62 63 #include <sys/param.h> 64 65 #include <errno.h> 66 #include <stddef.h> 67 #include <stdio.h> 68 #include <stdlib.h> 69 70 #ifdef DEBUG 71 #include <assert.h> 72 #endif 73 74 #include <db.h> 75 #include "hash.h" 76 #include "page.h" 77 #include "extern.h" 78 79 static BUFHEAD *newbuf __P((HTAB *, u_int32_t, BUFHEAD *)); 80 81 /* Unlink B from its place in the lru */ 82 #define BUF_REMOVE(B) { \ 83 (B)->prev->next = (B)->next; \ 84 (B)->next->prev = (B)->prev; \ 85 } 86 87 /* Insert B after P */ 88 #define BUF_INSERT(B, P) { \ 89 (B)->next = (P)->next; \ 90 (B)->prev = (P); \ 91 (P)->next = (B); \ 92 (B)->next->prev = (B); \ 93 } 94 95 #define MRU hashp->bufhead.next 96 #define LRU hashp->bufhead.prev 97 98 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 99 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 100 101 /* 102 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 103 * address is a bucket index. If prev_bp is not NULL, then it points to the 104 * page previous to an overflow page that we are trying to find. 105 * 106 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 107 * be valid. Therefore, you must always verify that its address matches the 108 * address you are seeking. 109 */ 110 extern BUFHEAD * 111 __get_buf(hashp, addr, prev_bp, newpage) 112 HTAB *hashp; 113 u_int32_t addr; 114 BUFHEAD *prev_bp; 115 int newpage; /* If prev_bp set, indicates a new overflow page. */ 116 { 117 register BUFHEAD *bp; 118 register u_int32_t is_disk_mask; 119 register int is_disk, segment_ndx; 120 SEGMENT segp; 121 122 is_disk = 0; 123 is_disk_mask = 0; 124 if (prev_bp) { 125 bp = prev_bp->ovfl; 126 if (!bp || (bp->addr != addr)) 127 bp = NULL; 128 if (!newpage) 129 is_disk = BUF_DISK; 130 } else { 131 /* Grab buffer out of directory */ 132 segment_ndx = addr & (hashp->SGSIZE - 1); 133 134 /* valid segment ensured by __call_hash() */ 135 segp = hashp->dir[addr >> hashp->SSHIFT]; 136 #ifdef DEBUG 137 assert(segp != NULL); 138 #endif 139 bp = PTROF(segp[segment_ndx]); 140 is_disk_mask = ISDISK(segp[segment_ndx]); 141 is_disk = is_disk_mask || !hashp->new_file; 142 } 143 144 if (!bp) { 145 bp = newbuf(hashp, addr, prev_bp); 146 if (!bp || 147 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) 148 return (NULL); 149 if (!prev_bp) 150 segp[segment_ndx] = 151 (BUFHEAD *)((ptrdiff_t)bp | is_disk_mask); 152 } else { 153 BUF_REMOVE(bp); 154 MRU_INSERT(bp); 155 } 156 return (bp); 157 } 158 159 /* 160 * We need a buffer for this page. Either allocate one, or evict a resident 161 * one (if we have as many buffers as we're allowed) and put this one in. 162 * 163 * If newbuf finds an error (returning NULL), it also sets errno. 164 */ 165 static BUFHEAD * 166 newbuf(hashp, addr, prev_bp) 167 HTAB *hashp; 168 u_int32_t addr; 169 BUFHEAD *prev_bp; 170 { 171 register BUFHEAD *bp; /* The buffer we're going to use */ 172 register BUFHEAD *xbp; /* Temp pointer */ 173 register BUFHEAD *next_xbp; 174 SEGMENT segp; 175 int segment_ndx; 176 u_int16_t oaddr, *shortp; 177 178 oaddr = 0; 179 bp = LRU; 180 /* 181 * If LRU buffer is pinned, the buffer pool is too small. We need to 182 * allocate more buffers. 183 */ 184 if (hashp->nbufs || (bp->flags & BUF_PIN)) { 185 /* Allocate a new one */ 186 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL) 187 return (NULL); 188 #ifdef PURIFY 189 memset(bp, 0xff, sizeof(BUFHEAD)); 190 #endif 191 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) { 192 free(bp); 193 return (NULL); 194 } 195 #ifdef PURIFY 196 memset(bp->page, 0xff, hashp->BSIZE); 197 #endif 198 if (hashp->nbufs) 199 hashp->nbufs--; 200 } else { 201 /* Kick someone out */ 202 BUF_REMOVE(bp); 203 /* 204 * If this is an overflow page with addr 0, it's already been 205 * flushed back in an overflow chain and initialized. 206 */ 207 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 208 /* 209 * Set oaddr before __put_page so that you get it 210 * before bytes are swapped. 211 */ 212 shortp = (u_int16_t *)bp->page; 213 if (shortp[0]) 214 oaddr = shortp[shortp[0] - 1]; 215 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 216 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 217 return (NULL); 218 /* 219 * Update the pointer to this page (i.e. invalidate it). 220 * 221 * If this is a new file (i.e. we created it at open 222 * time), make sure that we mark pages which have been 223 * written to disk so we retrieve them from disk later, 224 * rather than allocating new pages. 225 */ 226 if (IS_BUCKET(bp->flags)) { 227 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 228 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 229 #ifdef DEBUG 230 assert(segp != NULL); 231 #endif 232 233 if (hashp->new_file && 234 ((bp->flags & BUF_MOD) || 235 ISDISK(segp[segment_ndx]))) 236 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 237 else 238 segp[segment_ndx] = NULL; 239 } 240 /* 241 * Since overflow pages can only be access by means of 242 * their bucket, free overflow pages associated with 243 * this bucket. 244 */ 245 for (xbp = bp; xbp->ovfl;) { 246 next_xbp = xbp->ovfl; 247 xbp->ovfl = 0; 248 xbp = next_xbp; 249 250 /* Check that ovfl pointer is up date. */ 251 if (IS_BUCKET(xbp->flags) || 252 (oaddr != xbp->addr)) 253 break; 254 255 shortp = (u_int16_t *)xbp->page; 256 if (shortp[0]) 257 /* set before __put_page */ 258 oaddr = shortp[shortp[0] - 1]; 259 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 260 xbp->page, xbp->addr, 0, 0)) 261 return (NULL); 262 xbp->addr = 0; 263 xbp->flags = 0; 264 BUF_REMOVE(xbp); 265 LRU_INSERT(xbp); 266 } 267 } 268 } 269 270 /* Now assign this buffer */ 271 bp->addr = addr; 272 #ifdef DEBUG1 273 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 274 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 275 #endif 276 bp->ovfl = NULL; 277 if (prev_bp) { 278 /* 279 * If prev_bp is set, this is an overflow page, hook it in to 280 * the buffer overflow links. 281 */ 282 #ifdef DEBUG1 283 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 284 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0), 285 (bp ? bp->addr : 0)); 286 #endif 287 prev_bp->ovfl = bp; 288 bp->flags = 0; 289 } else 290 bp->flags = BUF_BUCKET; 291 MRU_INSERT(bp); 292 return (bp); 293 } 294 295 extern void 296 __buf_init(hashp, nbytes) 297 HTAB *hashp; 298 int nbytes; 299 { 300 BUFHEAD *bfp; 301 int npages; 302 303 bfp = &(hashp->bufhead); 304 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 305 npages = MAX(npages, MIN_BUFFERS); 306 307 hashp->nbufs = npages; 308 bfp->next = bfp; 309 bfp->prev = bfp; 310 /* 311 * This space is calloc'd so these are already null. 312 * 313 * bfp->ovfl = NULL; 314 * bfp->flags = 0; 315 * bfp->page = NULL; 316 * bfp->addr = 0; 317 */ 318 } 319 320 extern int 321 __buf_free(hashp, do_free, to_disk) 322 HTAB *hashp; 323 int do_free, to_disk; 324 { 325 BUFHEAD *bp; 326 327 /* Need to make sure that buffer manager has been initialized */ 328 if (!LRU) 329 return (0); 330 for (bp = LRU; bp != &hashp->bufhead;) { 331 /* Check that the buffer is valid */ 332 if (bp->addr || IS_BUCKET(bp->flags)) { 333 if (to_disk && (bp->flags & BUF_MOD) && 334 __put_page(hashp, bp->page, 335 bp->addr, IS_BUCKET(bp->flags), 0)) 336 return (-1); 337 } 338 /* Check if we are freeing stuff */ 339 if (do_free) { 340 if (bp->page) 341 free(bp->page); 342 BUF_REMOVE(bp); 343 free(bp); 344 bp = LRU; 345 } else 346 bp = bp->prev; 347 } 348 return (0); 349 } 350 351 extern void 352 __reclaim_buf(hashp, bp) 353 HTAB *hashp; 354 BUFHEAD *bp; 355 { 356 bp->ovfl = 0; 357 bp->addr = 0; 358 bp->flags = 0; 359 BUF_REMOVE(bp); 360 LRU_INSERT(bp); 361 } 362
Indexes created Tue Sep 23 14:10:03 GMT 2025