1 /* $NetBSD: hash_buf.c,v 1.12 2007/02/03 23:46:09 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 #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 1.12 2007/02/03 23:46:09 christos 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 #include <assert.h> 71 72 #include <db.h> 73 #include "hash.h" 74 #include "page.h" 75 #include "extern.h" 76 77 static BUFHEAD *newbuf(HTAB *, u_int32_t, BUFHEAD *); 78 79 /* Unlink B from its place in the lru */ 80 #define BUF_REMOVE(B) { \ 81 (B)->prev->next = (B)->next; \ 82 (B)->next->prev = (B)->prev; \ 83 } 84 85 /* Insert B after P */ 86 #define BUF_INSERT(B, P) { \ 87 (B)->next = (P)->next; \ 88 (B)->prev = (P); \ 89 (P)->next = (B); \ 90 (B)->next->prev = (B); \ 91 } 92 93 #define MRU hashp->bufhead.next 94 #define LRU hashp->bufhead.prev 95 96 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 97 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 98 99 /* 100 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 101 * address is a bucket index. If prev_bp is not NULL, then it points to the 102 * page previous to an overflow page that we are trying to find. 103 * 104 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 105 * be valid. Therefore, you must always verify that its address matches the 106 * address you are seeking. 107 */ 108 BUFHEAD * 109 __get_buf( 110 HTAB *hashp, 111 u_int32_t addr, 112 BUFHEAD *prev_bp, 113 int newpage /* If prev_bp set, indicates a new overflow page. */ 114 ) 115 { 116 BUFHEAD *bp; 117 u_int32_t is_disk_mask; 118 int is_disk, segment_ndx = 0; /* pacify gcc */ 119 SEGMENT segp = NULL; /* pacify gcc */ 120 121 is_disk = 0; 122 is_disk_mask = 0; 123 if (prev_bp) { 124 bp = prev_bp->ovfl; 125 if (!bp || (bp->addr != addr)) 126 bp = NULL; 127 if (!newpage) 128 is_disk = BUF_DISK; 129 } else { 130 /* Grab buffer out of directory */ 131 segment_ndx = addr & (hashp->SGSIZE - 1); 132 133 /* valid segment ensured by __call_hash() */ 134 segp = hashp->dir[addr >> hashp->SSHIFT]; 135 _DIAGASSERT(segp != NULL); 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(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp) 164 { 165 BUFHEAD *bp; /* The buffer we're going to use */ 166 BUFHEAD *xbp; /* Temp pointer */ 167 BUFHEAD *next_xbp; 168 SEGMENT segp; 169 int segment_ndx; 170 u_int16_t oaddr, *shortp; 171 172 oaddr = 0; 173 bp = LRU; 174 /* 175 * If LRU buffer is pinned, the buffer pool is too small. We need to 176 * allocate more buffers. 177 */ 178 if (hashp->nbufs || (bp->flags & BUF_PIN)) { 179 /* Allocate a new one */ 180 if ((bp = calloc(1, sizeof(BUFHEAD))) == NULL) 181 return (NULL); 182 if ((bp->page = calloc(1, (size_t)hashp->BSIZE)) == NULL) { 183 free(bp); 184 return (NULL); 185 } 186 if (hashp->nbufs) 187 hashp->nbufs--; 188 } else { 189 /* Kick someone out */ 190 BUF_REMOVE(bp); 191 /* 192 * If this is an overflow page with addr 0, it's already been 193 * flushed back in an overflow chain and initialized. 194 */ 195 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 196 /* 197 * Set oaddr before __put_page so that you get it 198 * before bytes are swapped. 199 */ 200 shortp = (u_int16_t *)(void *)bp->page; 201 if (shortp[0]) 202 oaddr = shortp[shortp[0] - 1]; 203 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 204 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 205 return (NULL); 206 /* 207 * Update the pointer to this page (i.e. invalidate it). 208 * 209 * If this is a new file (i.e. we created it at open 210 * time), make sure that we mark pages which have been 211 * written to disk so we retrieve them from disk later, 212 * rather than allocating new pages. 213 */ 214 if (IS_BUCKET(bp->flags)) { 215 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 216 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 217 _DIAGASSERT(segp != NULL); 218 219 if (hashp->new_file && 220 ((bp->flags & BUF_MOD) || 221 ISDISK(segp[segment_ndx]))) 222 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 223 else 224 segp[segment_ndx] = NULL; 225 } 226 /* 227 * Since overflow pages can only be access by means of 228 * their bucket, free overflow pages associated with 229 * this bucket. 230 */ 231 for (xbp = bp; xbp->ovfl;) { 232 next_xbp = xbp->ovfl; 233 xbp->ovfl = 0; 234 xbp = next_xbp; 235 236 /* Check that ovfl pointer is up date. */ 237 if (IS_BUCKET(xbp->flags) || 238 (oaddr != xbp->addr)) 239 break; 240 241 shortp = (u_int16_t *)(void *)xbp->page; 242 if (shortp[0]) 243 /* set before __put_page */ 244 oaddr = shortp[shortp[0] - 1]; 245 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 246 xbp->page, xbp->addr, 0, 0)) 247 return (NULL); 248 xbp->addr = 0; 249 xbp->flags = 0; 250 BUF_REMOVE(xbp); 251 LRU_INSERT(xbp); 252 } 253 } 254 } 255 256 /* Now assign this buffer */ 257 bp->addr = addr; 258 #ifdef DEBUG1 259 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 260 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 261 #endif 262 bp->ovfl = NULL; 263 if (prev_bp) { 264 /* 265 * If prev_bp is set, this is an overflow page, hook it in to 266 * the buffer overflow links. 267 */ 268 #ifdef DEBUG1 269 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 270 prev_bp->addr, (prev_bp->ovfl ? prev_bp->ovfl->addr : 0), 271 (bp ? bp->addr : 0)); 272 #endif 273 prev_bp->ovfl = bp; 274 bp->flags = 0; 275 } else 276 bp->flags = BUF_BUCKET; 277 MRU_INSERT(bp); 278 return (bp); 279 } 280 281 void 282 __buf_init(HTAB *hashp, u_int nbytes) 283 { 284 BUFHEAD *bfp; 285 int npages; 286 287 bfp = &(hashp->bufhead); 288 npages = (unsigned int)(nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 289 npages = MAX(npages, MIN_BUFFERS); 290 291 hashp->nbufs = npages; 292 bfp->next = bfp; 293 bfp->prev = bfp; 294 /* 295 * This space is calloc'd so these are already null. 296 * 297 * bfp->ovfl = NULL; 298 * bfp->flags = 0; 299 * bfp->page = NULL; 300 * bfp->addr = 0; 301 */ 302 } 303 304 int 305 __buf_free(HTAB *hashp, int do_free, int to_disk) 306 { 307 BUFHEAD *bp; 308 309 /* Need to make sure that buffer manager has been initialized */ 310 if (!LRU) 311 return (0); 312 for (bp = LRU; bp != &hashp->bufhead;) { 313 /* Check that the buffer is valid */ 314 if (bp->addr || IS_BUCKET(bp->flags)) { 315 if (to_disk && (bp->flags & BUF_MOD) && 316 __put_page(hashp, bp->page, 317 bp->addr, IS_BUCKET(bp->flags), 0)) 318 return (-1); 319 } 320 /* Check if we are freeing stuff */ 321 if (do_free) { 322 if (bp->page) 323 free(bp->page); 324 BUF_REMOVE(bp); 325 free(bp); 326 bp = LRU; 327 } else 328 bp = bp->prev; 329 } 330 return (0); 331 } 332 333 void 334 __reclaim_buf(HTAB *hashp, BUFHEAD *bp) 335 { 336 bp->ovfl = 0; 337 bp->addr = 0; 338 bp->flags = 0; 339 BUF_REMOVE(bp); 340 LRU_INSERT(bp); 341 } 342