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 33 #define _DEFAULT_SOURCE 34 #include <sys/param.h> 35 #if defined(LIBC_SCCS) && !defined(lint) 36 static char sccsid[] = "@(#)hash_buf.c 8.5 (Berkeley) 7/15/94"; 37 #endif /* LIBC_SCCS and not lint */ 38 39 /* 40 * PACKAGE: hash 41 * 42 * DESCRIPTION: 43 * Contains buffer management 44 * 45 * ROUTINES: 46 * External 47 * __buf_init 48 * __get_buf 49 * __buf_free 50 * __reclaim_buf 51 * Internal 52 * newbuf 53 */ 54 55 #include <sys/param.h> 56 57 #include <stddef.h> 58 #include <stdio.h> 59 #include <stdlib.h> 60 61 #ifdef DEBUG 62 #include <assert.h> 63 #endif 64 65 #include "db_local.h" 66 #include "hash.h" 67 #include "page.h" 68 #include "extern.h" 69 70 static BUFHEAD *newbuf(HTAB *, __uint32_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 /* Macros for min/max. */ 93 #ifndef MIN 94 #define MIN(a,b) (((a)<(b))?(a):(b)) 95 #endif 96 #ifndef MAX 97 #define MAX(a,b) (((a)>(b))?(a):(b)) 98 #endif 99 100 /* 101 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 102 * address is a bucket index. If prev_bp is not NULL, then it points to the 103 * page previous to an overflow page that we are trying to find. 104 * 105 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 106 * be valid. Therefore, you must always verify that its address matches the 107 * address you are seeking. 108 */ 109 extern BUFHEAD * __get_buf(HTAB * hashp,__uint32_t addr,BUFHEAD * prev_bp,int newpage)110 __get_buf(HTAB *hashp, 111 __uint32_t addr, 112 BUFHEAD *prev_bp, 113 int newpage) /* If prev_bp set, indicates a new overflow page. */ 114 { 115 BUFHEAD *bp; 116 __uint32_t is_disk_mask; 117 int is_disk, segment_ndx = 0; 118 SEGMENT segp = NULL; 119 120 is_disk = 0; 121 is_disk_mask = 0; 122 if (prev_bp) { 123 bp = prev_bp->ovfl; 124 if (!bp || (bp->addr != addr)) 125 bp = NULL; 126 if (!newpage) 127 is_disk = BUF_DISK; 128 } else { 129 /* Grab buffer out of directory */ 130 segment_ndx = addr & (hashp->SGSIZE - 1); 131 132 /* valid segment ensured by __call_hash() */ 133 segp = hashp->dir[addr >> hashp->SSHIFT]; 134 #ifdef DEBUG 135 assert(segp != NULL); 136 #endif 137 bp = PTROF(segp[segment_ndx]); 138 is_disk_mask = ISDISK(segp[segment_ndx]); 139 is_disk = is_disk_mask || !hashp->new_file; 140 } 141 142 if (!bp) { 143 bp = newbuf(hashp, addr, prev_bp); 144 if (!bp || 145 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) 146 return (NULL); 147 if (!prev_bp) 148 segp[segment_ndx] = 149 (BUFHEAD *)((ptrdiff_t)bp | (intptr_t)is_disk_mask); 150 } else { 151 BUF_REMOVE(bp); 152 MRU_INSERT(bp); 153 } 154 return (bp); 155 } 156 157 /* 158 * We need a buffer for this page. Either allocate one, or evict a resident 159 * one (if we have as many buffers as we're allowed) and put this one in. 160 * 161 * If newbuf finds an error (returning NULL), it also sets errno. 162 */ 163 static BUFHEAD * newbuf(HTAB * hashp,__uint32_t addr,BUFHEAD * prev_bp)164 newbuf(HTAB *hashp, 165 __uint32_t addr, 166 BUFHEAD *prev_bp) 167 { 168 BUFHEAD *bp; /* The buffer we're going to use */ 169 BUFHEAD *xbp; /* Temp pointer */ 170 BUFHEAD *next_xbp; 171 SEGMENT segp; 172 int segment_ndx; 173 __uint16_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 *)malloc(sizeof(BUFHEAD))) == NULL) 184 return (NULL); 185 #ifdef PURIFY 186 memset(bp, 0xff, sizeof(BUFHEAD)); 187 #endif 188 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) { 189 free(bp); 190 return (NULL); 191 } 192 #ifdef PURIFY 193 memset(bp->page, 0xff, hashp->BSIZE); 194 #endif 195 if (hashp->nbufs) 196 hashp->nbufs--; 197 } else { 198 /* Kick someone out */ 199 BUF_REMOVE(bp); 200 /* 201 * If this is an overflow page with addr 0, it's already been 202 * flushed back in an overflow chain and initialized. 203 */ 204 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 205 /* 206 * Set oaddr before __put_page so that you get it 207 * before bytes are swapped. 208 */ 209 shortp = (__uint16_t *)bp->page; 210 if (shortp[0]) 211 oaddr = shortp[shortp[0] - 1]; 212 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 213 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 214 return (NULL); 215 /* 216 * Update the pointer to this page (i.e. invalidate it). 217 * 218 * If this is a new file (i.e. we created it at open 219 * time), make sure that we mark pages which have been 220 * written to disk so we retrieve them from disk later, 221 * rather than allocating new pages. 222 */ 223 if (IS_BUCKET(bp->flags)) { 224 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 225 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 226 #ifdef DEBUG 227 assert(segp != NULL); 228 #endif 229 230 if (hashp->new_file && 231 ((bp->flags & BUF_MOD) || 232 ISDISK(segp[segment_ndx]))) 233 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 234 else 235 segp[segment_ndx] = NULL; 236 } 237 /* 238 * Since overflow pages can only be access by means of 239 * their bucket, free overflow pages associated with 240 * this bucket. 241 */ 242 for (xbp = bp; xbp->ovfl;) { 243 next_xbp = xbp->ovfl; 244 xbp->ovfl = 0; 245 xbp = next_xbp; 246 247 /* Check that ovfl pointer is up date. */ 248 if (IS_BUCKET(xbp->flags) || 249 (oaddr != xbp->addr)) 250 break; 251 252 shortp = (__uint16_t *)xbp->page; 253 if (shortp[0]) 254 /* set before __put_page */ 255 oaddr = shortp[shortp[0] - 1]; 256 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 257 xbp->page, xbp->addr, 0, 0)) 258 return (NULL); 259 xbp->addr = 0; 260 xbp->flags = 0; 261 BUF_REMOVE(xbp); 262 LRU_INSERT(xbp); 263 } 264 } 265 } 266 267 /* Now assign this buffer */ 268 bp->addr = addr; 269 #ifdef DEBUG1 270 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 271 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 272 #endif 273 bp->ovfl = NULL; 274 if (prev_bp) { 275 /* 276 * If prev_bp is set, this is an overflow page, hook it in to 277 * the buffer overflow links. 278 */ 279 #ifdef DEBUG1 280 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 281 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0), 282 (bp ? bp->addr : 0)); 283 #endif 284 prev_bp->ovfl = bp; 285 bp->flags = 0; 286 } else 287 bp->flags = BUF_BUCKET; 288 MRU_INSERT(bp); 289 return (bp); 290 } 291 292 extern void __buf_init(HTAB * hashp,int nbytes)293 __buf_init(HTAB *hashp, int nbytes) 294 { 295 BUFHEAD *bfp; 296 int npages; 297 298 bfp = &(hashp->bufhead); 299 npages = (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 __buf_free(HTAB * hashp,int do_free,int to_disk)316 __buf_free(HTAB *hashp, int do_free, int to_disk) 317 { 318 BUFHEAD *bp; 319 320 /* Need to make sure that buffer manager has been initialized */ 321 if (!LRU) 322 return (0); 323 for (bp = LRU; bp != &hashp->bufhead;) { 324 /* Check that the buffer is valid */ 325 if (bp->addr || IS_BUCKET(bp->flags)) { 326 if (to_disk && (bp->flags & BUF_MOD) && 327 __put_page(hashp, bp->page, 328 bp->addr, IS_BUCKET(bp->flags), 0)) 329 return (-1); 330 } 331 /* Check if we are freeing stuff */ 332 if (do_free) { 333 if (bp->page) 334 free(bp->page); 335 BUF_REMOVE(bp); 336 free(bp); 337 bp = LRU; 338 } else 339 bp = bp->prev; 340 } 341 return (0); 342 } 343 344 extern void __reclaim_buf(HTAB * hashp,BUFHEAD * bp)345 __reclaim_buf(HTAB *hashp, 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
