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 /* 36 * PACKAGE: hash 37 * 38 * DESCRIPTION: 39 * Contains buffer management 40 * 41 * ROUTINES: 42 * External 43 * __buf_init 44 * __get_buf 45 * __buf_free 46 * __reclaim_buf 47 * Internal 48 * newbuf 49 */ 50 51 #include <sys/param.h> 52 53 #include <stddef.h> 54 #include <stdio.h> 55 #include <stdlib.h> 56 #include <string.h> 57 58 #ifdef DEBUG 59 #include <assert.h> 60 #endif 61 62 #include <db.h> 63 #include "hash.h" 64 #include "page.h" 65 #include "extern.h" 66 67 static BUFHEAD *newbuf(HTAB *, u_int32_t, BUFHEAD *); 68 69 /* Unlink B from its place in the lru */ 70 #define BUF_REMOVE(B) { \ 71 (B)->prev->next = (B)->next; \ 72 (B)->next->prev = (B)->prev; \ 73 } 74 75 /* Insert B after P */ 76 #define BUF_INSERT(B, P) { \ 77 (B)->next = (P)->next; \ 78 (B)->prev = (P); \ 79 (P)->next = (B); \ 80 (B)->next->prev = (B); \ 81 } 82 83 #define MRU hashp->bufhead.next 84 #define LRU hashp->bufhead.prev 85 86 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 87 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 88 89 /* 90 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 91 * address is a bucket index. If prev_bp is not NULL, then it points to the 92 * page previous to an overflow page that we are trying to find. 93 * 94 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 95 * be valid. Therefore, you must always verify that its address matches the 96 * address you are seeking. 97 */ 98 BUFHEAD * 99 __get_buf(HTAB *hashp, u_int32_t addr, 100 BUFHEAD *prev_bp, /* If prev_bp set, indicates a new overflow page. */ 101 int newpage) 102 { 103 BUFHEAD *bp; 104 u_int32_t is_disk_mask; 105 int is_disk, segment_ndx; 106 SEGMENT segp; 107 108 is_disk = 0; 109 is_disk_mask = 0; 110 if (prev_bp) { 111 bp = prev_bp->ovfl; 112 if (!bp || (bp->addr != addr)) 113 bp = NULL; 114 if (!newpage) 115 is_disk = BUF_DISK; 116 } else { 117 /* Grab buffer out of directory */ 118 segment_ndx = addr & (hashp->SGSIZE - 1); 119 120 /* valid segment ensured by __call_hash() */ 121 segp = hashp->dir[addr >> hashp->SSHIFT]; 122 #ifdef DEBUG 123 assert(segp != NULL); 124 #endif 125 bp = PTROF(segp[segment_ndx]); 126 is_disk_mask = ISDISK(segp[segment_ndx]); 127 is_disk = is_disk_mask || !hashp->new_file; 128 } 129 130 if (!bp) { 131 bp = newbuf(hashp, addr, prev_bp); 132 if (!bp || 133 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) 134 return (NULL); 135 if (!prev_bp) 136 segp[segment_ndx] = 137 (BUFHEAD *)((intptr_t)bp | is_disk_mask); 138 } else { 139 BUF_REMOVE(bp); 140 MRU_INSERT(bp); 141 } 142 return (bp); 143 } 144 145 /* 146 * We need a buffer for this page. Either allocate one, or evict a resident 147 * one (if we have as many buffers as we're allowed) and put this one in. 148 * 149 * If newbuf finds an error (returning NULL), it also sets errno. 150 */ 151 static BUFHEAD * 152 newbuf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp) 153 { 154 BUFHEAD *bp; /* The buffer we're going to use */ 155 BUFHEAD *xbp; /* Temp pointer */ 156 BUFHEAD *next_xbp; 157 SEGMENT segp; 158 int segment_ndx; 159 u_int16_t oaddr, *shortp; 160 161 oaddr = 0; 162 bp = LRU; 163 164 /* It is bad to overwrite the page under the cursor. */ 165 if (bp == hashp->cpage) { 166 BUF_REMOVE(bp); 167 MRU_INSERT(bp); 168 bp = LRU; 169 } 170 171 /* If prev_bp is part of bp overflow, create a new buffer. */ 172 if (hashp->nbufs == 0 && prev_bp && bp->ovfl) { 173 BUFHEAD *ovfl; 174 175 for (ovfl = bp->ovfl; ovfl ; ovfl = ovfl->ovfl) { 176 if (ovfl == prev_bp) { 177 hashp->nbufs++; 178 break; 179 } 180 } 181 } 182 183 /* 184 * If LRU buffer is pinned, the buffer pool is too small. We need to 185 * allocate more buffers. 186 */ 187 if (hashp->nbufs || (bp->flags & BUF_PIN) || bp == hashp->cpage) { 188 /* Allocate a new one */ 189 if ((bp = (BUFHEAD *)calloc(1, sizeof(BUFHEAD))) == NULL) 190 return (NULL); 191 if ((bp->page = (char *)calloc(1, hashp->BSIZE)) == NULL) { 192 free(bp); 193 return (NULL); 194 } 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 = (u_int16_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 = NULL; 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 = (u_int16_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 ? prev_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 void 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 int 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 (void)memset(bp->page, 0, hashp->BSIZE); 335 free(bp->page); 336 } 337 BUF_REMOVE(bp); 338 free(bp); 339 bp = LRU; 340 } else 341 bp = bp->prev; 342 } 343 return (0); 344 } 345 346 void 347 __reclaim_buf(HTAB *hashp, BUFHEAD *bp) 348 { 349 bp->ovfl = NULL; 350 bp->addr = 0; 351 bp->flags = 0; 352 BUF_REMOVE(bp); 353 LRU_INSERT(bp); 354 } 355