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 #include <sys/cdefs.h> 39 __FBSDID("$FreeBSD$"); 40 41 /* 42 * PACKAGE: hash 43 * 44 * DESCRIPTION: 45 * Contains buffer management 46 * 47 * ROUTINES: 48 * External 49 * __buf_init 50 * __get_buf 51 * __buf_free 52 * __reclaim_buf 53 * Internal 54 * newbuf 55 */ 56 57 #include <sys/param.h> 58 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 <db.h> 69 #include "hash.h" 70 #include "page.h" 71 #include "extern.h" 72 73 static BUFHEAD *newbuf(HTAB *, u_int32_t, BUFHEAD *); 74 75 /* Unlink B from its place in the lru */ 76 #define BUF_REMOVE(B) { \ 77 (B)->prev->next = (B)->next; \ 78 (B)->next->prev = (B)->prev; \ 79 } 80 81 /* Insert B after P */ 82 #define BUF_INSERT(B, P) { \ 83 (B)->next = (P)->next; \ 84 (B)->prev = (P); \ 85 (P)->next = (B); \ 86 (B)->next->prev = (B); \ 87 } 88 89 #define MRU hashp->bufhead.next 90 #define LRU hashp->bufhead.prev 91 92 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 93 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 94 95 /* 96 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 97 * address is a bucket index. If prev_bp is not NULL, then it points to the 98 * page previous to an overflow page that we are trying to find. 99 * 100 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 101 * be valid. Therefore, you must always verify that its address matches the 102 * address you are seeking. 103 */ 104 BUFHEAD * 105 __get_buf(HTAB *hashp, u_int32_t addr, 106 BUFHEAD *prev_bp, /* If prev_bp set, indicates a new overflow page. */ 107 int newpage) 108 { 109 BUFHEAD *bp; 110 u_int32_t is_disk_mask; 111 int is_disk, segment_ndx; 112 SEGMENT segp; 113 114 is_disk = 0; 115 is_disk_mask = 0; 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 *)((intptr_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 /* It is bad to overwrite the page under the cursor. */ 171 if (bp == hashp->cpage) { 172 BUF_REMOVE(bp); 173 MRU_INSERT(bp); 174 bp = LRU; 175 } 176 177 /* If prev_bp is part of bp overflow, create a new buffer. */ 178 if (hashp->nbufs == 0 && prev_bp && bp->ovfl) { 179 BUFHEAD *ovfl; 180 181 for (ovfl = bp->ovfl; ovfl ; ovfl = ovfl->ovfl) { 182 if (ovfl == prev_bp) { 183 hashp->nbufs++; 184 break; 185 } 186 } 187 } 188 189 /* 190 * If LRU buffer is pinned, the buffer pool is too small. We need to 191 * allocate more buffers. 192 */ 193 if (hashp->nbufs || (bp->flags & BUF_PIN) || bp == hashp->cpage) { 194 /* Allocate a new one */ 195 if ((bp = (BUFHEAD *)calloc(1, sizeof(BUFHEAD))) == NULL) 196 return (NULL); 197 if ((bp->page = (char *)calloc(1, hashp->BSIZE)) == NULL) { 198 free(bp); 199 return (NULL); 200 } 201 if (hashp->nbufs) 202 hashp->nbufs--; 203 } else { 204 /* Kick someone out */ 205 BUF_REMOVE(bp); 206 /* 207 * If this is an overflow page with addr 0, it's already been 208 * flushed back in an overflow chain and initialized. 209 */ 210 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 211 /* 212 * Set oaddr before __put_page so that you get it 213 * before bytes are swapped. 214 */ 215 shortp = (u_int16_t *)bp->page; 216 if (shortp[0]) 217 oaddr = shortp[shortp[0] - 1]; 218 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 219 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 220 return (NULL); 221 /* 222 * Update the pointer to this page (i.e. invalidate it). 223 * 224 * If this is a new file (i.e. we created it at open 225 * time), make sure that we mark pages which have been 226 * written to disk so we retrieve them from disk later, 227 * rather than allocating new pages. 228 */ 229 if (IS_BUCKET(bp->flags)) { 230 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 231 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 232 #ifdef DEBUG 233 assert(segp != NULL); 234 #endif 235 236 if (hashp->new_file && 237 ((bp->flags & BUF_MOD) || 238 ISDISK(segp[segment_ndx]))) 239 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 240 else 241 segp[segment_ndx] = NULL; 242 } 243 /* 244 * Since overflow pages can only be access by means of 245 * their bucket, free overflow pages associated with 246 * this bucket. 247 */ 248 for (xbp = bp; xbp->ovfl;) { 249 next_xbp = xbp->ovfl; 250 xbp->ovfl = NULL; 251 xbp = next_xbp; 252 253 /* Check that ovfl pointer is up date. */ 254 if (IS_BUCKET(xbp->flags) || 255 (oaddr != xbp->addr)) 256 break; 257 258 shortp = (u_int16_t *)xbp->page; 259 if (shortp[0]) 260 /* set before __put_page */ 261 oaddr = shortp[shortp[0] - 1]; 262 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 263 xbp->page, xbp->addr, 0, 0)) 264 return (NULL); 265 xbp->addr = 0; 266 xbp->flags = 0; 267 BUF_REMOVE(xbp); 268 LRU_INSERT(xbp); 269 } 270 } 271 } 272 273 /* Now assign this buffer */ 274 bp->addr = addr; 275 #ifdef DEBUG1 276 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 277 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 278 #endif 279 bp->ovfl = NULL; 280 if (prev_bp) { 281 /* 282 * If prev_bp is set, this is an overflow page, hook it in to 283 * the buffer overflow links. 284 */ 285 #ifdef DEBUG1 286 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 287 prev_bp->addr, (prev_bp->ovfl ? prev_bp->ovfl->addr : 0), 288 (bp ? bp->addr : 0)); 289 #endif 290 prev_bp->ovfl = bp; 291 bp->flags = 0; 292 } else 293 bp->flags = BUF_BUCKET; 294 MRU_INSERT(bp); 295 return (bp); 296 } 297 298 void 299 __buf_init(HTAB *hashp, int nbytes) 300 { 301 BUFHEAD *bfp; 302 int npages; 303 304 bfp = &(hashp->bufhead); 305 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 306 npages = MAX(npages, MIN_BUFFERS); 307 308 hashp->nbufs = npages; 309 bfp->next = bfp; 310 bfp->prev = bfp; 311 /* 312 * This space is calloc'd so these are already null. 313 * 314 * bfp->ovfl = NULL; 315 * bfp->flags = 0; 316 * bfp->page = NULL; 317 * bfp->addr = 0; 318 */ 319 } 320 321 int 322 __buf_free(HTAB *hashp, int do_free, int to_disk) 323 { 324 BUFHEAD *bp; 325 326 /* Need to make sure that buffer manager has been initialized */ 327 if (!LRU) 328 return (0); 329 for (bp = LRU; bp != &hashp->bufhead;) { 330 /* Check that the buffer is valid */ 331 if (bp->addr || IS_BUCKET(bp->flags)) { 332 if (to_disk && (bp->flags & BUF_MOD) && 333 __put_page(hashp, bp->page, 334 bp->addr, IS_BUCKET(bp->flags), 0)) 335 return (-1); 336 } 337 /* Check if we are freeing stuff */ 338 if (do_free) { 339 if (bp->page) { 340 (void)memset(bp->page, 0, hashp->BSIZE); 341 free(bp->page); 342 } 343 BUF_REMOVE(bp); 344 free(bp); 345 bp = LRU; 346 } else 347 bp = bp->prev; 348 } 349 return (0); 350 } 351 352 void 353 __reclaim_buf(HTAB *hashp, BUFHEAD *bp) 354 { 355 bp->ovfl = NULL; 356 bp->addr = 0; 357 bp->flags = 0; 358 BUF_REMOVE(bp); 359 LRU_INSERT(bp); 360 } 361