hash_buf.c revision 1.10
1 /* $NetBSD: hash_buf.c,v 1.10 2003/08/07 16:42:42 agc 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. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #include <sys/cdefs.h> 36 #if defined(LIBC_SCCS) && !defined(lint) 37 #if 0 38 static char sccsid[] = "@(#)hash_buf.c 8.5 (Berkeley) 7/15/94"; 39 #else 40 __RCSID("$NetBSD: hash_buf.c,v 1.10 2003/08/07 16:42:42 agc Exp $"); 41 #endif 42 #endif /* LIBC_SCCS and not lint */ 43 44 /* 45 * PACKAGE: hash 46 * 47 * DESCRIPTION: 48 * Contains buffer management 49 * 50 * ROUTINES: 51 * External 52 * __buf_init 53 * __get_buf 54 * __buf_free 55 * __reclaim_buf 56 * Internal 57 * newbuf 58 */ 59 60 #include <sys/param.h> 61 62 #include <errno.h> 63 #include <stddef.h> 64 #include <stdio.h> 65 #include <stdlib.h> 66 67 #ifdef DEBUG 68 #include <assert.h> 69 #endif 70 71 #include <db.h> 72 #include "hash.h" 73 #include "page.h" 74 #include "extern.h" 75 76 static BUFHEAD *newbuf __P((HTAB *, u_int32_t, BUFHEAD *)); 77 78 /* Unlink B from its place in the lru */ 79 #define BUF_REMOVE(B) { \ 80 (B)->prev->next = (B)->next; \ 81 (B)->next->prev = (B)->prev; \ 82 } 83 84 /* Insert B after P */ 85 #define BUF_INSERT(B, P) { \ 86 (B)->next = (P)->next; \ 87 (B)->prev = (P); \ 88 (P)->next = (B); \ 89 (B)->next->prev = (B); \ 90 } 91 92 #define MRU hashp->bufhead.next 93 #define LRU hashp->bufhead.prev 94 95 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 96 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 97 98 /* 99 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 100 * address is a bucket index. If prev_bp is not NULL, then it points to the 101 * page previous to an overflow page that we are trying to find. 102 * 103 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 104 * be valid. Therefore, you must always verify that its address matches the 105 * address you are seeking. 106 */ 107 extern BUFHEAD * 108 __get_buf(hashp, addr, prev_bp, newpage) 109 HTAB *hashp; 110 u_int32_t addr; 111 BUFHEAD *prev_bp; 112 int newpage; /* If prev_bp set, indicates a new overflow page. */ 113 { 114 register BUFHEAD *bp; 115 register u_int32_t is_disk_mask; 116 register int is_disk, segment_ndx = 0; /* pacify gcc */ 117 SEGMENT segp = NULL; /* pacify gcc */ 118 119 is_disk = 0; 120 is_disk_mask = 0; 121 if (prev_bp) { 122 bp = prev_bp->ovfl; 123 if (!bp || (bp->addr != addr)) 124 bp = NULL; 125 if (!newpage) 126 is_disk = BUF_DISK; 127 } else { 128 /* Grab buffer out of directory */ 129 segment_ndx = addr & (hashp->SGSIZE - 1); 130 131 /* valid segment ensured by __call_hash() */ 132 segp = hashp->dir[addr >> hashp->SSHIFT]; 133 #ifdef DEBUG 134 assert(segp != NULL); 135 #endif 136 bp = PTROF(segp[segment_ndx]); 137 is_disk_mask = ISDISK(segp[segment_ndx]); 138 is_disk = is_disk_mask || !hashp->new_file; 139 } 140 141 if (!bp) { 142 bp = newbuf(hashp, addr, prev_bp); 143 if (!bp || 144 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) 145 return (NULL); 146 if (!prev_bp) 147 segp[segment_ndx] = 148 (BUFHEAD *)(void *)((u_long)bp | is_disk_mask); 149 } else { 150 BUF_REMOVE(bp); 151 MRU_INSERT(bp); 152 } 153 return (bp); 154 } 155 156 /* 157 * We need a buffer for this page. Either allocate one, or evict a resident 158 * one (if we have as many buffers as we're allowed) and put this one in. 159 * 160 * If newbuf finds an error (returning NULL), it also sets errno. 161 */ 162 static BUFHEAD * 163 newbuf(hashp, addr, prev_bp) 164 HTAB *hashp; 165 u_int32_t addr; 166 BUFHEAD *prev_bp; 167 { 168 register BUFHEAD *bp; /* The buffer we're going to use */ 169 register BUFHEAD *xbp; /* Temp pointer */ 170 register BUFHEAD *next_xbp; 171 SEGMENT segp; 172 int segment_ndx; 173 u_int16_t oaddr, *shortp; 174 175 oaddr = 0; 176 bp = LRU; 177 /* 178 * If LRU buffer is pinned, the buffer pool is too small. We need to 179 * allocate more buffers. 180 */ 181 if (hashp->nbufs || (bp->flags & BUF_PIN)) { 182 /* Allocate a new one */ 183 if ((bp = (BUFHEAD *)calloc(1, sizeof(BUFHEAD))) == NULL) 184 return (NULL); 185 if ((bp->page = calloc(1, (size_t)hashp->BSIZE)) == NULL) { 186 free(bp); 187 return (NULL); 188 } 189 if (hashp->nbufs) 190 hashp->nbufs--; 191 } else { 192 /* Kick someone out */ 193 BUF_REMOVE(bp); 194 /* 195 * If this is an overflow page with addr 0, it's already been 196 * flushed back in an overflow chain and initialized. 197 */ 198 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 199 /* 200 * Set oaddr before __put_page so that you get it 201 * before bytes are swapped. 202 */ 203 shortp = (u_int16_t *)(void *)bp->page; 204 if (shortp[0]) 205 oaddr = shortp[shortp[0] - 1]; 206 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 207 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 208 return (NULL); 209 /* 210 * Update the pointer to this page (i.e. invalidate it). 211 * 212 * If this is a new file (i.e. we created it at open 213 * time), make sure that we mark pages which have been 214 * written to disk so we retrieve them from disk later, 215 * rather than allocating new pages. 216 */ 217 if (IS_BUCKET(bp->flags)) { 218 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 219 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 220 #ifdef DEBUG 221 assert(segp != NULL); 222 #endif 223 224 if (hashp->new_file && 225 ((bp->flags & BUF_MOD) || 226 ISDISK(segp[segment_ndx]))) 227 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 228 else 229 segp[segment_ndx] = NULL; 230 } 231 /* 232 * Since overflow pages can only be access by means of 233 * their bucket, free overflow pages associated with 234 * this bucket. 235 */ 236 for (xbp = bp; xbp->ovfl;) { 237 next_xbp = xbp->ovfl; 238 xbp->ovfl = 0; 239 xbp = next_xbp; 240 241 /* Check that ovfl pointer is up date. */ 242 if (IS_BUCKET(xbp->flags) || 243 (oaddr != xbp->addr)) 244 break; 245 246 shortp = (u_int16_t *)(void *)xbp->page; 247 if (shortp[0]) 248 /* set before __put_page */ 249 oaddr = shortp[shortp[0] - 1]; 250 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 251 xbp->page, xbp->addr, 0, 0)) 252 return (NULL); 253 xbp->addr = 0; 254 xbp->flags = 0; 255 BUF_REMOVE(xbp); 256 LRU_INSERT(xbp); 257 } 258 } 259 } 260 261 /* Now assign this buffer */ 262 bp->addr = addr; 263 #ifdef DEBUG1 264 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 265 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 266 #endif 267 bp->ovfl = NULL; 268 if (prev_bp) { 269 /* 270 * If prev_bp is set, this is an overflow page, hook it in to 271 * the buffer overflow links. 272 */ 273 #ifdef DEBUG1 274 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 275 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0), 276 (bp ? bp->addr : 0)); 277 #endif 278 prev_bp->ovfl = bp; 279 bp->flags = 0; 280 } else 281 bp->flags = BUF_BUCKET; 282 MRU_INSERT(bp); 283 return (bp); 284 } 285 286 extern void 287 __buf_init(hashp, nbytes) 288 HTAB *hashp; 289 u_int nbytes; 290 { 291 BUFHEAD *bfp; 292 int npages; 293 294 bfp = &(hashp->bufhead); 295 npages = (unsigned int)(nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 296 npages = MAX(npages, MIN_BUFFERS); 297 298 hashp->nbufs = npages; 299 bfp->next = bfp; 300 bfp->prev = bfp; 301 /* 302 * This space is calloc'd so these are already null. 303 * 304 * bfp->ovfl = NULL; 305 * bfp->flags = 0; 306 * bfp->page = NULL; 307 * bfp->addr = 0; 308 */ 309 } 310 311 extern int 312 __buf_free(hashp, do_free, to_disk) 313 HTAB *hashp; 314 int do_free, to_disk; 315 { 316 BUFHEAD *bp; 317 318 /* Need to make sure that buffer manager has been initialized */ 319 if (!LRU) 320 return (0); 321 for (bp = LRU; bp != &hashp->bufhead;) { 322 /* Check that the buffer is valid */ 323 if (bp->addr || IS_BUCKET(bp->flags)) { 324 if (to_disk && (bp->flags & BUF_MOD) && 325 __put_page(hashp, bp->page, 326 bp->addr, IS_BUCKET(bp->flags), 0)) 327 return (-1); 328 } 329 /* Check if we are freeing stuff */ 330 if (do_free) { 331 if (bp->page) 332 free(bp->page); 333 BUF_REMOVE(bp); 334 free(bp); 335 bp = LRU; 336 } else 337 bp = bp->prev; 338 } 339 return (0); 340 } 341 342 extern void 343 __reclaim_buf(hashp, bp) 344 HTAB *hashp; 345 BUFHEAD *bp; 346 { 347 bp->ovfl = 0; 348 bp->addr = 0; 349 bp->flags = 0; 350 BUF_REMOVE(bp); 351 LRU_INSERT(bp); 352 } 353
Indexes created Fri Sep 26 08:10:20 GMT 2025