1 /*- 2 * Copyright (c) 1990, 1993, 1994 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Margo Seltzer. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * $FreeBSD: src/lib/libc/db/hash/hash_buf.c,v 1.4.8.1 2001/03/05 07:38:05 obrien Exp $ 33 * $DragonFly: src/lib/libc/db/hash/hash_buf.c,v 1.7 2005/11/19 20:46:32 swildner Exp $ 34 * 35 * @(#)hash_buf.c 8.5 (Berkeley) 7/15/94 36 */ 37 38 /* 39 * PACKAGE: hash 40 * 41 * DESCRIPTION: 42 * Contains buffer management 43 * 44 * ROUTINES: 45 * External 46 * __buf_init 47 * __get_buf 48 * __buf_free 49 * __reclaim_buf 50 * Internal 51 * newbuf 52 */ 53 54 #include <sys/param.h> 55 56 #include <stddef.h> 57 #include <stdio.h> 58 #include <stdlib.h> 59 #include <string.h> 60 61 #ifdef DEBUG 62 #include <assert.h> 63 #endif 64 65 #include <db.h> 66 #include "hash.h" 67 #include "page.h" 68 #include "extern.h" 69 70 static BUFHEAD *newbuf (HTAB *, u_int32_t, BUFHEAD *); 71 72 /* Unlink B from its place in the lru */ 73 #define BUF_REMOVE(B) { \ 74 (B)->prev->next = (B)->next; \ 75 (B)->next->prev = (B)->prev; \ 76 } 77 78 /* Insert B after P */ 79 #define BUF_INSERT(B, P) { \ 80 (B)->next = (P)->next; \ 81 (B)->prev = (P); \ 82 (P)->next = (B); \ 83 (B)->next->prev = (B); \ 84 } 85 86 #define MRU hashp->bufhead.next 87 #define LRU hashp->bufhead.prev 88 89 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 90 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 91 92 /* 93 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 94 * address is a bucket index. If prev_bp is not NULL, then it points to the 95 * page previous to an overflow page that we are trying to find. 96 * 97 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 98 * be valid. Therefore, you must always verify that its address matches the 99 * address you are seeking. 100 * 101 * Parameters: 102 * newpage: If prev_bp set, indicates a new overflow page 103 */ 104 extern BUFHEAD * 105 __get_buf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp, int newpage) 106 { 107 BUFHEAD *bp; 108 u_int32_t is_disk_mask; 109 int is_disk, segment_ndx; 110 SEGMENT segp; 111 112 is_disk = 0; 113 is_disk_mask = 0; 114 segment_ndx = 0; 115 segp = NULL; 116 if (prev_bp) { 117 bp = prev_bp->ovfl; 118 if (!bp || (bp->addr != addr)) 119 bp = NULL; 120 if (!newpage) 121 is_disk = BUF_DISK; 122 } else { 123 /* Grab buffer out of directory */ 124 segment_ndx = addr & (hashp->SGSIZE - 1); 125 126 /* valid segment ensured by __call_hash() */ 127 segp = hashp->dir[addr >> hashp->SSHIFT]; 128 #ifdef DEBUG 129 assert(segp != NULL); 130 #endif 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 *)((ptrdiff_t)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, u_int32_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 u_int16_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 = (BUFHEAD *)calloc(1, sizeof(BUFHEAD))) == NULL) 176 return (NULL); 177 #ifdef PURIFY 178 memset(bp, 0xff, sizeof(BUFHEAD)); 179 #endif 180 if ((bp->page = (char *)calloc(1, hashp->BSIZE)) == NULL) { 181 free(bp); 182 return (NULL); 183 } 184 #ifdef PURIFY 185 memset(bp->page, 0xff, hashp->BSIZE); 186 #endif 187 if (hashp->nbufs) 188 hashp->nbufs--; 189 } else { 190 /* Kick someone out */ 191 BUF_REMOVE(bp); 192 /* 193 * If this is an overflow page with addr 0, it's already been 194 * flushed back in an overflow chain and initialized. 195 */ 196 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 197 /* 198 * Set oaddr before __put_page so that you get it 199 * before bytes are swapped. 200 */ 201 shortp = (u_int16_t *)bp->page; 202 if (shortp[0]) 203 oaddr = shortp[shortp[0] - 1]; 204 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 205 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 206 return (NULL); 207 /* 208 * Update the pointer to this page (i.e. invalidate it). 209 * 210 * If this is a new file (i.e. we created it at open 211 * time), make sure that we mark pages which have been 212 * written to disk so we retrieve them from disk later, 213 * rather than allocating new pages. 214 */ 215 if (IS_BUCKET(bp->flags)) { 216 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 217 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 218 #ifdef DEBUG 219 assert(segp != NULL); 220 #endif 221 222 if (hashp->new_file && 223 ((bp->flags & BUF_MOD) || 224 ISDISK(segp[segment_ndx]))) 225 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 226 else 227 segp[segment_ndx] = NULL; 228 } 229 /* 230 * Since overflow pages can only be access by means of 231 * their bucket, free overflow pages associated with 232 * this bucket. 233 */ 234 for (xbp = bp; xbp->ovfl;) { 235 next_xbp = xbp->ovfl; 236 xbp->ovfl = 0; 237 xbp = next_xbp; 238 239 /* Check that ovfl pointer is up date. */ 240 if (IS_BUCKET(xbp->flags) || 241 (oaddr != xbp->addr)) 242 break; 243 244 shortp = (u_int16_t *)xbp->page; 245 if (shortp[0]) 246 /* set before __put_page */ 247 oaddr = shortp[shortp[0] - 1]; 248 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 249 xbp->page, xbp->addr, 0, 0)) 250 return (NULL); 251 xbp->addr = 0; 252 xbp->flags = 0; 253 BUF_REMOVE(xbp); 254 LRU_INSERT(xbp); 255 } 256 } 257 } 258 259 /* Now assign this buffer */ 260 bp->addr = addr; 261 #ifdef DEBUG1 262 fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 263 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 264 #endif 265 bp->ovfl = NULL; 266 if (prev_bp) { 267 /* 268 * If prev_bp is set, this is an overflow page, hook it in to 269 * the buffer overflow links. 270 */ 271 #ifdef DEBUG1 272 fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 273 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0), 274 (bp ? bp->addr : 0)); 275 #endif 276 prev_bp->ovfl = bp; 277 bp->flags = 0; 278 } else 279 bp->flags = BUF_BUCKET; 280 MRU_INSERT(bp); 281 return (bp); 282 } 283 284 extern void 285 __buf_init(HTAB *hashp, int nbytes) 286 { 287 BUFHEAD *bfp; 288 int npages; 289 290 bfp = &(hashp->bufhead); 291 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 292 npages = MAX(npages, MIN_BUFFERS); 293 294 hashp->nbufs = npages; 295 bfp->next = bfp; 296 bfp->prev = bfp; 297 /* 298 * This space is calloc'd so these are already null. 299 * 300 * bfp->ovfl = NULL; 301 * bfp->flags = 0; 302 * bfp->page = NULL; 303 * bfp->addr = 0; 304 */ 305 } 306 307 extern int 308 __buf_free(HTAB *hashp, int do_free, int to_disk) 309 { 310 BUFHEAD *bp; 311 312 /* Need to make sure that buffer manager has been initialized */ 313 if (!LRU) 314 return (0); 315 for (bp = LRU; bp != &hashp->bufhead;) { 316 /* Check that the buffer is valid */ 317 if (bp->addr || IS_BUCKET(bp->flags)) { 318 if (to_disk && (bp->flags & BUF_MOD) && 319 __put_page(hashp, bp->page, 320 bp->addr, IS_BUCKET(bp->flags), 0)) 321 return (-1); 322 } 323 /* Check if we are freeing stuff */ 324 if (do_free) { 325 if (bp->page) { 326 memset(bp->page, 0, hashp->BSIZE); 327 free(bp->page); 328 } 329 BUF_REMOVE(bp); 330 free(bp); 331 bp = LRU; 332 } else 333 bp = bp->prev; 334 } 335 return (0); 336 } 337 338 extern void 339 __reclaim_buf(HTAB *hashp, BUFHEAD *bp) 340 { 341 bp->ovfl = 0; 342 bp->addr = 0; 343 bp->flags = 0; 344 BUF_REMOVE(bp); 345 LRU_INSERT(bp); 346 } 347