1 /* $NetBSD: hash_buf.c,v 1.18 2009/04/23 22:09:23 christos 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 #if HAVE_NBTOOL_CONFIG_H 36 #include "nbtool_config.h" 37 #endif 38 39 #include <sys/cdefs.h> 40 __RCSID("$NetBSD: hash_buf.c,v 1.18 2009/04/23 22:09:23 christos Exp $"); 41 42 /* 43 * PACKAGE: hash 44 * 45 * DESCRIPTION: 46 * Contains buffer management 47 * 48 * ROUTINES: 49 * External 50 * __buf_init 51 * __get_buf 52 * __buf_free 53 * __reclaim_buf 54 * Internal 55 * newbuf 56 */ 57 58 #include <sys/param.h> 59 60 #include <errno.h> 61 #include <stddef.h> 62 #include <stdio.h> 63 #include <stdlib.h> 64 #include <string.h> 65 #include <assert.h> 66 67 #include <db.h> 68 #include "hash.h" 69 #include "page.h" 70 #include "extern.h" 71 72 static BUFHEAD *newbuf(HTAB *, uint32_t, BUFHEAD *); 73 74 /* Unlink B from its place in the lru */ 75 #define BUF_REMOVE(B) { \ 76 (B)->prev->next = (B)->next; \ 77 (B)->next->prev = (B)->prev; \ 78 } 79 80 /* Insert B after P */ 81 #define BUF_INSERT(B, P) { \ 82 (B)->next = (P)->next; \ 83 (B)->prev = (P); \ 84 (P)->next = (B); \ 85 (B)->next->prev = (B); \ 86 } 87 88 #define MRU hashp->bufhead.next 89 #define LRU hashp->bufhead.prev 90 91 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 92 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 93 94 /* 95 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 96 * address is a bucket index. If prev_bp is not NULL, then it points to the 97 * page previous to an overflow page that we are trying to find. 98 * 99 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 100 * be valid. Therefore, you must always verify that its address matches the 101 * address you are seeking. 102 */ 103 BUFHEAD * 104 __get_buf( 105 HTAB *hashp, 106 uint32_t addr, 107 BUFHEAD *prev_bp, 108 int newpage /* If prev_bp set, indicates a new overflow page. */ 109 ) 110 { 111 BUFHEAD *bp; 112 uint32_t is_disk_mask; 113 int is_disk, segment_ndx = 0; /* pacify gcc */ 114 SEGMENT segp = NULL; /* pacify gcc */ 115 116 is_disk = 0; 117 is_disk_mask = 0; 118 if (prev_bp) { 119 bp = prev_bp->ovfl; 120 if (!bp || (bp->addr != addr)) 121 bp = NULL; 122 if (!newpage) 123 is_disk = BUF_DISK; 124 } else { 125 /* Grab buffer out of directory */ 126 segment_ndx = addr & (hashp->SGSIZE - 1); 127 128 /* valid segment ensured by __call_hash() */ 129 segp = hashp->dir[addr >> hashp->SSHIFT]; 130 _DIAGASSERT(segp != NULL); 131 bp = PTROF(segp[segment_ndx]); 132 is_disk_mask = ISDISK(segp[segment_ndx]); 133 is_disk = is_disk_mask || !hashp->new_file; 134 } 135 136 if (!bp) { 137 bp = newbuf(hashp, addr, prev_bp); 138 if (!bp || 139 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) 140 return (NULL); 141 if (!prev_bp) 142 segp[segment_ndx] = 143 (BUFHEAD *)(void *)((u_long)bp | is_disk_mask); 144 } else { 145 BUF_REMOVE(bp); 146 MRU_INSERT(bp); 147 } 148 return (bp); 149 } 150 151 /* 152 * We need a buffer for this page. Either allocate one, or evict a resident 153 * one (if we have as many buffers as we're allowed) and put this one in. 154 * 155 * If newbuf finds an error (returning NULL), it also sets errno. 156 */ 157 static BUFHEAD * 158 newbuf(HTAB *hashp, uint32_t addr, BUFHEAD *prev_bp) 159 { 160 BUFHEAD *bp; /* The buffer we're going to use */ 161 BUFHEAD *xbp; /* Temp pointer */ 162 BUFHEAD *next_xbp; 163 SEGMENT segp; 164 int segment_ndx; 165 uint16_t oaddr, *shortp; 166 167 oaddr = 0; 168 bp = LRU; 169 /* 170 * If LRU buffer is pinned, the buffer pool is too small. We need to 171 * allocate more buffers. 172 */ 173 if (hashp->nbufs || (bp->flags & BUF_PIN)) { 174 /* Allocate a new one */ 175 if ((bp = calloc(1, sizeof(BUFHEAD))) == NULL) 176 return (NULL); 177 if ((bp->page = calloc(1, (size_t)hashp->BSIZE)) == NULL) { 178 free(bp); 179 return (NULL); 180 } 181 if (hashp->nbufs) 182 hashp->nbufs--; 183 } else { 184 /* Kick someone out */ 185 BUF_REMOVE(bp); 186 /* 187 * If this is an overflow page with addr 0, it's already been 188 * flushed back in an overflow chain and initialized. 189 */ 190 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 191 /* 192 * Set oaddr before __put_page so that you get it 193 * before bytes are swapped. 194 */ 195 shortp = (uint16_t *)(void *)bp->page; 196 if (shortp[0]) 197 oaddr = shortp[shortp[0] - 1]; 198 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 199 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 200 return (NULL); 201 /* 202 * Update the pointer to this page (i.e. invalidate it). 203 * 204 * If this is a new file (i.e. we created it at open 205 * time), make sure that we mark pages which have been 206 * written to disk so we retrieve them from disk later, 207 * rather than allocating new pages. 208 */ 209 if (IS_BUCKET(bp->flags)) { 210 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 211 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 212 _DIAGASSERT(segp != NULL); 213 214 if (hashp->new_file && 215 ((bp->flags & BUF_MOD) || 216 ISDISK(segp[segment_ndx]))) 217 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 218 else 219 segp[segment_ndx] = NULL; 220 } 221 /* 222 * Since overflow pages can only be access by means of 223 * their bucket, free overflow pages associated with 224 * this bucket. 225 */ 226 for (xbp = bp; xbp->ovfl;) { 227 next_xbp = xbp->ovfl; 228 xbp->ovfl = 0; 229 xbp = next_xbp; 230 231 /* Check that ovfl pointer is up date. */ 232 if (IS_BUCKET(xbp->flags) || 233 (oaddr != xbp->addr)) 234 break; 235 236 shortp = (uint16_t *)(void *)xbp->page; 237 if (shortp[0]) 238 /* set before __put_page */ 239 oaddr = shortp[shortp[0] - 1]; 240 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 241 xbp->page, xbp->addr, 0, 0)) 242 return (NULL); 243 xbp->addr = 0; 244 xbp->flags = 0; 245 BUF_REMOVE(xbp); 246 LRU_INSERT(xbp); 247 } 248 } 249 } 250 251 /* Now assign this buffer */ 252 bp->addr = addr; 253 #ifdef DEBUG1 254 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 255 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 256 #endif 257 bp->ovfl = NULL; 258 if (prev_bp) { 259 /* 260 * If prev_bp is set, this is an overflow page, hook it in to 261 * the buffer overflow links. 262 */ 263 #ifdef DEBUG1 264 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 265 prev_bp->addr, (prev_bp->ovfl ? prev_bp->ovfl->addr : 0), 266 (bp ? bp->addr : 0)); 267 #endif 268 prev_bp->ovfl = bp; 269 bp->flags = 0; 270 } else 271 bp->flags = BUF_BUCKET; 272 MRU_INSERT(bp); 273 return (bp); 274 } 275 276 void 277 __buf_init(HTAB *hashp, u_int nbytes) 278 { 279 BUFHEAD *bfp; 280 int npages; 281 282 bfp = &(hashp->bufhead); 283 npages = (unsigned int)(nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 284 npages = MAX(npages, MIN_BUFFERS); 285 286 hashp->nbufs = npages; 287 bfp->next = bfp; 288 bfp->prev = bfp; 289 /* 290 * This space is calloc'd so these are already null. 291 * 292 * bfp->ovfl = NULL; 293 * bfp->flags = 0; 294 * bfp->page = NULL; 295 * bfp->addr = 0; 296 */ 297 } 298 299 int 300 __buf_free(HTAB *hashp, int do_free, int to_disk) 301 { 302 BUFHEAD *bp; 303 304 /* Need to make sure that buffer manager has been initialized */ 305 if (!LRU) 306 return (0); 307 for (bp = LRU; bp != &hashp->bufhead;) { 308 /* Check that the buffer is valid */ 309 if (bp->addr || IS_BUCKET(bp->flags)) { 310 if (to_disk && (bp->flags & BUF_MOD) && 311 __put_page(hashp, bp->page, 312 bp->addr, IS_BUCKET(bp->flags), 0)) 313 return (-1); 314 } 315 /* Check if we are freeing stuff */ 316 if (do_free) { 317 if (bp->page) { 318 (void)memset(bp->page, 0, (size_t)hashp->BSIZE); 319 free(bp->page); 320 } 321 BUF_REMOVE(bp); 322 free(bp); 323 bp = LRU; 324 } else 325 bp = bp->prev; 326 } 327 return (0); 328 } 329 330 void 331 __reclaim_buf(HTAB *hashp, BUFHEAD *bp) 332 { 333 bp->ovfl = 0; 334 bp->addr = 0; 335 bp->flags = 0; 336 BUF_REMOVE(bp); 337 LRU_INSERT(bp); 338 } 339
Indexes created Sun Sep 21 20:09:37 GMT 2025