1 /* $NetBSD: hash_buf.c,v 1.11 2004/06/20 22:20:14 jmc 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 #if defined(LIBC_SCCS) && !defined(lint) 41 #if 0 42 static char sccsid[] = "@(#)hash_buf.c 8.5 (Berkeley) 7/15/94"; 43 #else 44 __RCSID("$NetBSD: hash_buf.c,v 1.11 2004/06/20 22:20:14 jmc Exp $"); 45 #endif 46 #endif /* LIBC_SCCS and not lint */ 47 48 /* 49 * PACKAGE: hash 50 * 51 * DESCRIPTION: 52 * Contains buffer management 53 * 54 * ROUTINES: 55 * External 56 * __buf_init 57 * __get_buf 58 * __buf_free 59 * __reclaim_buf 60 * Internal 61 * newbuf 62 */ 63 64 #include <sys/param.h> 65 66 #include <errno.h> 67 #include <stddef.h> 68 #include <stdio.h> 69 #include <stdlib.h> 70 71 #ifdef DEBUG 72 #include <assert.h> 73 #endif 74 75 #include <db.h> 76 #include "hash.h" 77 #include "page.h" 78 #include "extern.h" 79 80 static BUFHEAD *newbuf __P((HTAB *, u_int32_t, BUFHEAD *)); 81 82 /* Unlink B from its place in the lru */ 83 #define BUF_REMOVE(B) { \ 84 (B)->prev->next = (B)->next; \ 85 (B)->next->prev = (B)->prev; \ 86 } 87 88 /* Insert B after P */ 89 #define BUF_INSERT(B, P) { \ 90 (B)->next = (P)->next; \ 91 (B)->prev = (P); \ 92 (P)->next = (B); \ 93 (B)->next->prev = (B); \ 94 } 95 96 #define MRU hashp->bufhead.next 97 #define LRU hashp->bufhead.prev 98 99 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 100 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 101 102 /* 103 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 104 * address is a bucket index. If prev_bp is not NULL, then it points to the 105 * page previous to an overflow page that we are trying to find. 106 * 107 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 108 * be valid. Therefore, you must always verify that its address matches the 109 * address you are seeking. 110 */ 111 extern BUFHEAD * 112 __get_buf(hashp, addr, prev_bp, newpage) 113 HTAB *hashp; 114 u_int32_t addr; 115 BUFHEAD *prev_bp; 116 int newpage; /* If prev_bp set, indicates a new overflow page. */ 117 { 118 register BUFHEAD *bp; 119 register u_int32_t is_disk_mask; 120 register int is_disk, segment_ndx = 0; /* pacify gcc */ 121 SEGMENT segp = NULL; /* pacify gcc */ 122 123 is_disk = 0; 124 is_disk_mask = 0; 125 if (prev_bp) { 126 bp = prev_bp->ovfl; 127 if (!bp || (bp->addr != addr)) 128 bp = NULL; 129 if (!newpage) 130 is_disk = BUF_DISK; 131 } else { 132 /* Grab buffer out of directory */ 133 segment_ndx = addr & (hashp->SGSIZE - 1); 134 135 /* valid segment ensured by __call_hash() */ 136 segp = hashp->dir[addr >> hashp->SSHIFT]; 137 #ifdef DEBUG 138 assert(segp != NULL); 139 #endif 140 bp = PTROF(segp[segment_ndx]); 141 is_disk_mask = ISDISK(segp[segment_ndx]); 142 is_disk = is_disk_mask || !hashp->new_file; 143 } 144 145 if (!bp) { 146 bp = newbuf(hashp, addr, prev_bp); 147 if (!bp || 148 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) 149 return (NULL); 150 if (!prev_bp) 151 segp[segment_ndx] = 152 (BUFHEAD *)(void *)((u_long)bp | is_disk_mask); 153 } else { 154 BUF_REMOVE(bp); 155 MRU_INSERT(bp); 156 } 157 return (bp); 158 } 159 160 /* 161 * We need a buffer for this page. Either allocate one, or evict a resident 162 * one (if we have as many buffers as we're allowed) and put this one in. 163 * 164 * If newbuf finds an error (returning NULL), it also sets errno. 165 */ 166 static BUFHEAD * 167 newbuf(hashp, addr, prev_bp) 168 HTAB *hashp; 169 u_int32_t addr; 170 BUFHEAD *prev_bp; 171 { 172 register BUFHEAD *bp; /* The buffer we're going to use */ 173 register BUFHEAD *xbp; /* Temp pointer */ 174 register BUFHEAD *next_xbp; 175 SEGMENT segp; 176 int segment_ndx; 177 u_int16_t oaddr, *shortp; 178 179 oaddr = 0; 180 bp = LRU; 181 /* 182 * If LRU buffer is pinned, the buffer pool is too small. We need to 183 * allocate more buffers. 184 */ 185 if (hashp->nbufs || (bp->flags & BUF_PIN)) { 186 /* Allocate a new one */ 187 if ((bp = (BUFHEAD *)calloc(1, sizeof(BUFHEAD))) == NULL) 188 return (NULL); 189 if ((bp->page = calloc(1, (size_t)hashp->BSIZE)) == NULL) { 190 free(bp); 191 return (NULL); 192 } 193 if (hashp->nbufs) 194 hashp->nbufs--; 195 } else { 196 /* Kick someone out */ 197 BUF_REMOVE(bp); 198 /* 199 * If this is an overflow page with addr 0, it's already been 200 * flushed back in an overflow chain and initialized. 201 */ 202 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 203 /* 204 * Set oaddr before __put_page so that you get it 205 * before bytes are swapped. 206 */ 207 shortp = (u_int16_t *)(void *)bp->page; 208 if (shortp[0]) 209 oaddr = shortp[shortp[0] - 1]; 210 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 211 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 212 return (NULL); 213 /* 214 * Update the pointer to this page (i.e. invalidate it). 215 * 216 * If this is a new file (i.e. we created it at open 217 * time), make sure that we mark pages which have been 218 * written to disk so we retrieve them from disk later, 219 * rather than allocating new pages. 220 */ 221 if (IS_BUCKET(bp->flags)) { 222 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 223 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 224 #ifdef DEBUG 225 assert(segp != NULL); 226 #endif 227 228 if (hashp->new_file && 229 ((bp->flags & BUF_MOD) || 230 ISDISK(segp[segment_ndx]))) 231 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 232 else 233 segp[segment_ndx] = NULL; 234 } 235 /* 236 * Since overflow pages can only be access by means of 237 * their bucket, free overflow pages associated with 238 * this bucket. 239 */ 240 for (xbp = bp; xbp->ovfl;) { 241 next_xbp = xbp->ovfl; 242 xbp->ovfl = 0; 243 xbp = next_xbp; 244 245 /* Check that ovfl pointer is up date. */ 246 if (IS_BUCKET(xbp->flags) || 247 (oaddr != xbp->addr)) 248 break; 249 250 shortp = (u_int16_t *)(void *)xbp->page; 251 if (shortp[0]) 252 /* set before __put_page */ 253 oaddr = shortp[shortp[0] - 1]; 254 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 255 xbp->page, xbp->addr, 0, 0)) 256 return (NULL); 257 xbp->addr = 0; 258 xbp->flags = 0; 259 BUF_REMOVE(xbp); 260 LRU_INSERT(xbp); 261 } 262 } 263 } 264 265 /* Now assign this buffer */ 266 bp->addr = addr; 267 #ifdef DEBUG1 268 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 269 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 270 #endif 271 bp->ovfl = NULL; 272 if (prev_bp) { 273 /* 274 * If prev_bp is set, this is an overflow page, hook it in to 275 * the buffer overflow links. 276 */ 277 #ifdef DEBUG1 278 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 279 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0), 280 (bp ? bp->addr : 0)); 281 #endif 282 prev_bp->ovfl = bp; 283 bp->flags = 0; 284 } else 285 bp->flags = BUF_BUCKET; 286 MRU_INSERT(bp); 287 return (bp); 288 } 289 290 extern void 291 __buf_init(hashp, nbytes) 292 HTAB *hashp; 293 u_int nbytes; 294 { 295 BUFHEAD *bfp; 296 int npages; 297 298 bfp = &(hashp->bufhead); 299 npages = (unsigned int)(nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 300 npages = MAX(npages, MIN_BUFFERS); 301 302 hashp->nbufs = npages; 303 bfp->next = bfp; 304 bfp->prev = bfp; 305 /* 306 * This space is calloc'd so these are already null. 307 * 308 * bfp->ovfl = NULL; 309 * bfp->flags = 0; 310 * bfp->page = NULL; 311 * bfp->addr = 0; 312 */ 313 } 314 315 extern int 316 __buf_free(hashp, do_free, to_disk) 317 HTAB *hashp; 318 int do_free, to_disk; 319 { 320 BUFHEAD *bp; 321 322 /* Need to make sure that buffer manager has been initialized */ 323 if (!LRU) 324 return (0); 325 for (bp = LRU; bp != &hashp->bufhead;) { 326 /* Check that the buffer is valid */ 327 if (bp->addr || IS_BUCKET(bp->flags)) { 328 if (to_disk && (bp->flags & BUF_MOD) && 329 __put_page(hashp, bp->page, 330 bp->addr, IS_BUCKET(bp->flags), 0)) 331 return (-1); 332 } 333 /* Check if we are freeing stuff */ 334 if (do_free) { 335 if (bp->page) 336 free(bp->page); 337 BUF_REMOVE(bp); 338 free(bp); 339 bp = LRU; 340 } else 341 bp = bp->prev; 342 } 343 return (0); 344 } 345 346 extern void 347 __reclaim_buf(hashp, bp) 348 HTAB *hashp; 349 BUFHEAD *bp; 350 { 351 bp->ovfl = 0; 352 bp->addr = 0; 353 bp->flags = 0; 354 BUF_REMOVE(bp); 355 LRU_INSERT(bp); 356 } 357