hash_buf.c (12525B)
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. ***REMOVED*** - see 17 * ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change 18 * 4. 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 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 #if !defined(_WIN32) && !defined(_WINDOWS) && !defined(macintosh) 55 #include <sys/param.h> 56 #endif 57 58 #include <errno.h> 59 #include <stddef.h> 60 #include <stdio.h> 61 #include <stdlib.h> 62 #include <string.h> 63 64 #ifdef DEBUG 65 #include <assert.h> 66 #endif 67 68 #include "mcom_db.h" 69 #include "hash.h" 70 #include "page.h" 71 /* #include "extern.h" */ 72 73 static BUFHEAD *newbuf(HTAB *, uint32, BUFHEAD *); 74 75 /* Unlink B from its place in the lru */ 76 #define BUF_REMOVE(B) \ 77 { \ 78 (B)->prev->next = (B)->next; \ 79 (B)->next->prev = (B)->prev; \ 80 } 81 82 /* Insert B after P */ 83 #define BUF_INSERT(B, P) \ 84 { \ 85 (B)->next = (P)->next; \ 86 (B)->prev = (P); \ 87 (P)->next = (B); \ 88 (B)->next->prev = (B); \ 89 } 90 91 #define MRU hashp->bufhead.next 92 #define LRU hashp->bufhead.prev 93 94 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 95 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 96 97 /* 98 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 99 * address is a bucket index. If prev_bp is not NULL, then it points to the 100 * page previous to an overflow page that we are trying to find. 101 * 102 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 103 * be valid. Therefore, you must always verify that its address matches the 104 * address you are seeking. 105 */ 106 extern BUFHEAD * 107 dbm_get_buf(HTAB *hashp, uint32 addr, BUFHEAD *prev_bp, int newpage) 108 /* If prev_bp set, indicates a new overflow page. */ 109 { 110 register BUFHEAD *bp; 111 register uint32 is_disk_mask; 112 register int is_disk, segment_ndx = 0; 113 SEGMENT segp = 0; 114 115 is_disk = 0; 116 is_disk_mask = 0; 117 if (prev_bp) { 118 bp = prev_bp->ovfl; 119 if (!bp || (bp->addr != addr)) 120 bp = NULL; 121 if (!newpage) 122 is_disk = BUF_DISK; 123 } else { 124 /* Grab buffer out of directory */ 125 segment_ndx = addr & (hashp->SGSIZE - 1); 126 127 /* valid segment ensured by dbm_call_hash() */ 128 segp = hashp->dir[addr >> hashp->SSHIFT]; 129 #ifdef DEBUG 130 assert(segp != NULL); 131 #endif 132 133 bp = PTROF(segp[segment_ndx]); 134 135 is_disk_mask = ISDISK(segp[segment_ndx]); 136 is_disk = is_disk_mask || !hashp->new_file; 137 } 138 139 if (!bp) { 140 bp = newbuf(hashp, addr, prev_bp); 141 if (!bp) 142 return (NULL); 143 if (dbm_get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) { 144 /* free bp and its page */ 145 if (prev_bp) { 146 /* if prev_bp is set then the new page that 147 * failed is hooked onto prev_bp as an overflow page. 148 * if we don't remove the pointer to the bad page 149 * we may try and access it later and we will die 150 * horribly because it will have already been 151 * free'd and overwritten with bogus data. 152 */ 153 prev_bp->ovfl = NULL; 154 } 155 BUF_REMOVE(bp); 156 free(bp->page); 157 free(bp); 158 return (NULL); 159 } 160 161 if (!prev_bp) { 162 #if 0 163 /* 16 bit windows and mac can't handle the 164 * oring of the is disk flag. 165 */ 166 segp[segment_ndx] = 167 (BUFHEAD *)((ptrdiff_t)bp | is_disk_mask); 168 #else 169 /* set the is_disk thing inside the structure 170 */ 171 bp->is_disk = is_disk_mask; 172 segp[segment_ndx] = bp; 173 #endif 174 } 175 } else { 176 BUF_REMOVE(bp); 177 MRU_INSERT(bp); 178 } 179 return (bp); 180 } 181 182 /* 183 * We need a buffer for this page. Either allocate one, or evict a resident 184 * one (if we have as many buffers as we're allowed) and put this one in. 185 * 186 * If newbuf finds an error (returning NULL), it also sets errno. 187 */ 188 static BUFHEAD * 189 newbuf(HTAB *hashp, uint32 addr, BUFHEAD *prev_bp) 190 { 191 register BUFHEAD *bp; /* The buffer we're going to use */ 192 register BUFHEAD *xbp; /* Temp pointer */ 193 register BUFHEAD *next_xbp; 194 SEGMENT segp; 195 int segment_ndx; 196 uint16 oaddr, *shortp; 197 198 oaddr = 0; 199 bp = LRU; 200 /* 201 * If LRU buffer is pinned, the buffer pool is too small. We need to 202 * allocate more buffers. 203 */ 204 if (hashp->nbufs || (bp->flags & BUF_PIN)) { 205 /* Allocate a new one */ 206 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL) 207 return (NULL); 208 209 /* this memset is supposedly unnecessary but lets add 210 * it anyways. 211 */ 212 memset(bp, 0xff, sizeof(BUFHEAD)); 213 214 if ((bp->page = (char *)malloc((size_t)hashp->BSIZE)) == NULL) { 215 free(bp); 216 return (NULL); 217 } 218 219 /* this memset is supposedly unnecessary but lets add 220 * it anyways. 221 */ 222 memset(bp->page, 0xff, (size_t)hashp->BSIZE); 223 224 if (hashp->nbufs) 225 hashp->nbufs--; 226 } else { 227 /* Kick someone out */ 228 BUF_REMOVE(bp); 229 /* 230 * If this is an overflow page with addr 0, it's already been 231 * flushed back in an overflow chain and initialized. 232 */ 233 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 234 /* 235 * Set oaddr before __put_page so that you get it 236 * before bytes are swapped. 237 */ 238 shortp = (uint16 *)bp->page; 239 if (shortp[0]) { 240 if (shortp[0] > (hashp->BSIZE / sizeof(uint16))) { 241 return (NULL); 242 } 243 oaddr = shortp[shortp[0] - 1]; 244 } 245 if ((bp->flags & BUF_MOD) && dbm_put_page(hashp, bp->page, 246 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 247 return (NULL); 248 /* 249 * Update the pointer to this page (i.e. invalidate it). 250 * 251 * If this is a new file (i.e. we created it at open 252 * time), make sure that we mark pages which have been 253 * written to disk so we retrieve them from disk later, 254 * rather than allocating new pages. 255 */ 256 if (IS_BUCKET(bp->flags)) { 257 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 258 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 259 #ifdef DEBUG 260 assert(segp != NULL); 261 #endif 262 263 if (hashp->new_file && 264 ((bp->flags & BUF_MOD) || 265 ISDISK(segp[segment_ndx]))) 266 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 267 else 268 segp[segment_ndx] = NULL; 269 } 270 /* 271 * Since overflow pages can only be access by means of 272 * their bucket, free overflow pages associated with 273 * this bucket. 274 */ 275 for (xbp = bp; xbp->ovfl;) { 276 next_xbp = xbp->ovfl; 277 xbp->ovfl = 0; 278 xbp = next_xbp; 279 280 /* leave pinned pages alone, we are still using 281 * them. */ 282 if (xbp->flags & BUF_PIN) { 283 continue; 284 } 285 286 /* Check that ovfl pointer is up date. */ 287 if (IS_BUCKET(xbp->flags) || 288 (oaddr != xbp->addr)) 289 break; 290 291 shortp = (uint16 *)xbp->page; 292 if (shortp[0]) { 293 /* LJM is the number of reported 294 * pages way too much? 295 */ 296 if (shortp[0] > hashp->BSIZE / sizeof(uint16)) 297 return NULL; 298 /* set before __put_page */ 299 oaddr = shortp[shortp[0] - 1]; 300 } 301 if ((xbp->flags & BUF_MOD) && dbm_put_page(hashp, 302 xbp->page, xbp->addr, 0, 0)) 303 return (NULL); 304 xbp->addr = 0; 305 xbp->flags = 0; 306 BUF_REMOVE(xbp); 307 LRU_INSERT(xbp); 308 } 309 } 310 } 311 312 /* Now assign this buffer */ 313 bp->addr = addr; 314 #ifdef DEBUG1 315 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 316 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 317 #endif 318 bp->ovfl = NULL; 319 if (prev_bp) { 320 /* 321 * If prev_bp is set, this is an overflow page, hook it in to 322 * the buffer overflow links. 323 */ 324 #ifdef DEBUG1 325 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 326 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0), 327 (bp ? bp->addr : 0)); 328 #endif 329 prev_bp->ovfl = bp; 330 bp->flags = 0; 331 } else 332 bp->flags = BUF_BUCKET; 333 MRU_INSERT(bp); 334 return (bp); 335 } 336 337 extern void 338 dbm_buf_init(HTAB *hashp, int32 nbytes) 339 { 340 BUFHEAD *bfp; 341 int npages; 342 343 bfp = &(hashp->bufhead); 344 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 345 npages = PR_MAX(npages, MIN_BUFFERS); 346 347 hashp->nbufs = npages; 348 bfp->next = bfp; 349 bfp->prev = bfp; 350 /* 351 * This space is calloc'd so these are already null. 352 * 353 * bfp->ovfl = NULL; 354 * bfp->flags = 0; 355 * bfp->page = NULL; 356 * bfp->addr = 0; 357 */ 358 } 359 360 extern int 361 dbm_buf_free(HTAB *hashp, int do_free, int to_disk) 362 { 363 BUFHEAD *bp; 364 int status = -1; 365 366 /* Need to make sure that buffer manager has been initialized */ 367 if (!LRU) 368 return (0); 369 for (bp = LRU; bp != &hashp->bufhead;) { 370 /* Check that the buffer is valid */ 371 if (bp->addr || IS_BUCKET(bp->flags)) { 372 if (to_disk && (bp->flags & BUF_MOD) && 373 (status = dbm_put_page(hashp, bp->page, 374 bp->addr, IS_BUCKET(bp->flags), 0))) { 375 376 if (do_free) { 377 if (bp->page) 378 free(bp->page); 379 BUF_REMOVE(bp); 380 free(bp); 381 } 382 383 return (status); 384 } 385 } 386 /* Check if we are freeing stuff */ 387 if (do_free) { 388 if (bp->page) 389 free(bp->page); 390 BUF_REMOVE(bp); 391 free(bp); 392 bp = LRU; 393 } else 394 bp = bp->prev; 395 } 396 return (0); 397 } 398 399 extern void 400 dbm_reclaim_buf(HTAB *hashp, BUFHEAD *bp) 401 { 402 bp->ovfl = 0; 403 bp->addr = 0; 404 bp->flags = 0; 405 BUF_REMOVE(bp); 406 LRU_INSERT(bp); 407 }