1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 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 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 * 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 BUFHEAD * 102 __get_buf(HTAB *hashp, u_int32_t addr, 103 BUFHEAD *prev_bp, /* If prev_bp set, indicates a new overflow page. */ 104 int newpage) 105 { 106 BUFHEAD *bp; 107 u_int32_t is_disk_mask; 108 int is_disk, segment_ndx; 109 SEGMENT segp; 110 111 is_disk = 0; 112 is_disk_mask = 0; 113 if (prev_bp) { 114 bp = prev_bp->ovfl; 115 if (!bp || (bp->addr != addr)) 116 bp = NULL; 117 if (!newpage) 118 is_disk = BUF_DISK; 119 } else { 120 /* Grab buffer out of directory */ 121 segment_ndx = addr & (hashp->SGSIZE - 1); 122 123 /* valid segment ensured by __call_hash() */ 124 segp = hashp->dir[addr >> hashp->SSHIFT]; 125 #ifdef DEBUG 126 assert(segp != NULL); 127 #endif 128 bp = PTROF(segp[segment_ndx]); 129 is_disk_mask = ISDISK(segp[segment_ndx]); 130 is_disk = is_disk_mask || !hashp->new_file; 131 } 132 133 if (!bp) { 134 bp = newbuf(hashp, addr, prev_bp); 135 if (!bp || 136 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) 137 return (NULL); 138 if (!prev_bp) 139 segp[segment_ndx] = 140 (BUFHEAD *)((intptr_t)bp | is_disk_mask); 141 } else { 142 BUF_REMOVE(bp); 143 MRU_INSERT(bp); 144 } 145 return (bp); 146 } 147 148 /* 149 * We need a buffer for this page. Either allocate one, or evict a resident 150 * one (if we have as many buffers as we're allowed) and put this one in. 151 * 152 * If newbuf finds an error (returning NULL), it also sets errno. 153 */ 154 static BUFHEAD * 155 newbuf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp) 156 { 157 BUFHEAD *bp; /* The buffer we're going to use */ 158 BUFHEAD *xbp; /* Temp pointer */ 159 BUFHEAD *next_xbp; 160 SEGMENT segp; 161 int segment_ndx; 162 u_int16_t oaddr, *shortp; 163 164 oaddr = 0; 165 bp = LRU; 166 167 /* It is bad to overwrite the page under the cursor. */ 168 if (bp == hashp->cpage) { 169 BUF_REMOVE(bp); 170 MRU_INSERT(bp); 171 bp = LRU; 172 } 173 174 /* If prev_bp is part of bp overflow, create a new buffer. */ 175 if (hashp->nbufs == 0 && prev_bp && bp->ovfl) { 176 BUFHEAD *ovfl; 177 178 for (ovfl = bp->ovfl; ovfl ; ovfl = ovfl->ovfl) { 179 if (ovfl == prev_bp) { 180 hashp->nbufs++; 181 break; 182 } 183 } 184 } 185 186 /* 187 * If LRU buffer is pinned, the buffer pool is too small. We need to 188 * allocate more buffers. 189 */ 190 if (hashp->nbufs || (bp->flags & BUF_PIN) || bp == hashp->cpage) { 191 /* Allocate a new one */ 192 if ((bp = (BUFHEAD *)calloc(1, sizeof(BUFHEAD))) == NULL) 193 return (NULL); 194 if ((bp->page = (char *)calloc(1, hashp->BSIZE)) == NULL) { 195 free(bp); 196 return (NULL); 197 } 198 if (hashp->nbufs) 199 hashp->nbufs--; 200 } else { 201 /* Kick someone out */ 202 BUF_REMOVE(bp); 203 /* 204 * If this is an overflow page with addr 0, it's already been 205 * flushed back in an overflow chain and initialized. 206 */ 207 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 208 /* 209 * Set oaddr before __put_page so that you get it 210 * before bytes are swapped. 211 */ 212 shortp = (u_int16_t *)bp->page; 213 if (shortp[0]) 214 oaddr = shortp[shortp[0] - 1]; 215 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 216 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 217 return (NULL); 218 /* 219 * Update the pointer to this page (i.e. invalidate it). 220 * 221 * If this is a new file (i.e. we created it at open 222 * time), make sure that we mark pages which have been 223 * written to disk so we retrieve them from disk later, 224 * rather than allocating new pages. 225 */ 226 if (IS_BUCKET(bp->flags)) { 227 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 228 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 229 #ifdef DEBUG 230 assert(segp != NULL); 231 #endif 232 233 if (hashp->new_file && 234 ((bp->flags & BUF_MOD) || 235 ISDISK(segp[segment_ndx]))) 236 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 237 else 238 segp[segment_ndx] = NULL; 239 } 240 /* 241 * Since overflow pages can only be access by means of 242 * their bucket, free overflow pages associated with 243 * this bucket. 244 */ 245 for (xbp = bp; xbp->ovfl;) { 246 next_xbp = xbp->ovfl; 247 xbp->ovfl = NULL; 248 xbp = next_xbp; 249 250 /* Check that ovfl pointer is up date. */ 251 if (IS_BUCKET(xbp->flags) || 252 (oaddr != xbp->addr)) 253 break; 254 255 shortp = (u_int16_t *)xbp->page; 256 if (shortp[0]) 257 /* set before __put_page */ 258 oaddr = shortp[shortp[0] - 1]; 259 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 260 xbp->page, xbp->addr, 0, 0)) 261 return (NULL); 262 xbp->addr = 0; 263 xbp->flags = 0; 264 BUF_REMOVE(xbp); 265 LRU_INSERT(xbp); 266 } 267 } 268 } 269 270 /* Now assign this buffer */ 271 bp->addr = addr; 272 #ifdef DEBUG1 273 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 274 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 275 #endif 276 bp->ovfl = NULL; 277 if (prev_bp) { 278 /* 279 * If prev_bp is set, this is an overflow page, hook it in to 280 * the buffer overflow links. 281 */ 282 #ifdef DEBUG1 283 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 284 prev_bp->addr, (prev_bp->ovfl ? prev_bp->ovfl->addr : 0), 285 (bp ? bp->addr : 0)); 286 #endif 287 prev_bp->ovfl = bp; 288 bp->flags = 0; 289 } else 290 bp->flags = BUF_BUCKET; 291 MRU_INSERT(bp); 292 return (bp); 293 } 294 295 void 296 __buf_init(HTAB *hashp, int nbytes) 297 { 298 BUFHEAD *bfp; 299 int npages; 300 301 bfp = &(hashp->bufhead); 302 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 303 npages = MAX(npages, MIN_BUFFERS); 304 305 hashp->nbufs = npages; 306 bfp->next = bfp; 307 bfp->prev = bfp; 308 /* 309 * This space is calloc'd so these are already null. 310 * 311 * bfp->ovfl = NULL; 312 * bfp->flags = 0; 313 * bfp->page = NULL; 314 * bfp->addr = 0; 315 */ 316 } 317 318 int 319 __buf_free(HTAB *hashp, int do_free, int to_disk) 320 { 321 BUFHEAD *bp; 322 323 /* Need to make sure that buffer manager has been initialized */ 324 if (!LRU) 325 return (0); 326 for (bp = LRU; bp != &hashp->bufhead;) { 327 /* Check that the buffer is valid */ 328 if (bp->addr || IS_BUCKET(bp->flags)) { 329 if (to_disk && (bp->flags & BUF_MOD) && 330 __put_page(hashp, bp->page, 331 bp->addr, IS_BUCKET(bp->flags), 0)) 332 return (-1); 333 } 334 /* Check if we are freeing stuff */ 335 if (do_free) { 336 if (bp->page) { 337 (void)memset(bp->page, 0, hashp->BSIZE); 338 free(bp->page); 339 } 340 BUF_REMOVE(bp); 341 free(bp); 342 bp = LRU; 343 } else 344 bp = bp->prev; 345 } 346 return (0); 347 } 348 349 void 350 __reclaim_buf(HTAB *hashp, BUFHEAD *bp) 351 { 352 bp->ovfl = NULL; 353 bp->addr = 0; 354 bp->flags = 0; 355 BUF_REMOVE(bp); 356 LRU_INSERT(bp); 357 } 358