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. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * $FreeBSD: src/lib/libc/db/hash/hash_buf.c,v 1.4.8.1 2001/03/05 07:38:05 obrien Exp $ 37 * $DragonFly: src/lib/libc/db/hash/hash_buf.c,v 1.3 2003/11/12 20:21:23 eirikn Exp $ 38 * 39 * @(#)hash_buf.c 8.5 (Berkeley) 7/15/94 40 */ 41 42 /* 43 * PACKAGE: hash 44 * 45 * DESCRIPTION: 46 * Contains buffer management 47 * 48 * ROUTINES: 49 * External 50 * __buf_init 51 * __get_buf 52 * __buf_free 53 * __reclaim_buf 54 * Internal 55 * newbuf 56 */ 57 58 #include <sys/param.h> 59 60 #include <stddef.h> 61 #include <stdio.h> 62 #include <stdlib.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 extern BUFHEAD * 105 __get_buf(hashp, addr, prev_bp, newpage) 106 HTAB *hashp; 107 u_int32_t addr; 108 BUFHEAD *prev_bp; 109 int newpage; /* If prev_bp set, indicates a new overflow page. */ 110 { 111 register BUFHEAD *bp; 112 register u_int32_t is_disk_mask; 113 register int is_disk, segment_ndx; 114 SEGMENT segp; 115 116 is_disk = 0; 117 is_disk_mask = 0; 118 if (prev_bp) { 119 bp = prev_bp->ovfl; 120 if (!bp || (bp->addr != addr)) 121 bp = NULL; 122 if (!newpage) 123 is_disk = BUF_DISK; 124 } else { 125 /* Grab buffer out of directory */ 126 segment_ndx = addr & (hashp->SGSIZE - 1); 127 128 /* valid segment ensured by __call_hash() */ 129 segp = hashp->dir[addr >> hashp->SSHIFT]; 130 #ifdef DEBUG 131 assert(segp != NULL); 132 #endif 133 bp = PTROF(segp[segment_ndx]); 134 is_disk_mask = ISDISK(segp[segment_ndx]); 135 is_disk = is_disk_mask || !hashp->new_file; 136 } 137 138 if (!bp) { 139 bp = newbuf(hashp, addr, prev_bp); 140 if (!bp || 141 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) 142 return (NULL); 143 if (!prev_bp) 144 segp[segment_ndx] = 145 (BUFHEAD *)((ptrdiff_t)bp | is_disk_mask); 146 } else { 147 BUF_REMOVE(bp); 148 MRU_INSERT(bp); 149 } 150 return (bp); 151 } 152 153 /* 154 * We need a buffer for this page. Either allocate one, or evict a resident 155 * one (if we have as many buffers as we're allowed) and put this one in. 156 * 157 * If newbuf finds an error (returning NULL), it also sets errno. 158 */ 159 static BUFHEAD * 160 newbuf(hashp, addr, prev_bp) 161 HTAB *hashp; 162 u_int32_t addr; 163 BUFHEAD *prev_bp; 164 { 165 register BUFHEAD *bp; /* The buffer we're going to use */ 166 register BUFHEAD *xbp; /* Temp pointer */ 167 register BUFHEAD *next_xbp; 168 SEGMENT segp; 169 int segment_ndx; 170 u_int16_t oaddr, *shortp; 171 172 oaddr = 0; 173 bp = LRU; 174 /* 175 * If LRU buffer is pinned, the buffer pool is too small. We need to 176 * allocate more buffers. 177 */ 178 if (hashp->nbufs || (bp->flags & BUF_PIN)) { 179 /* Allocate a new one */ 180 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL) 181 return (NULL); 182 #ifdef PURIFY 183 memset(bp, 0xff, sizeof(BUFHEAD)); 184 #endif 185 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) { 186 free(bp); 187 return (NULL); 188 } 189 #ifdef PURIFY 190 memset(bp->page, 0xff, hashp->BSIZE); 191 #endif 192 if (hashp->nbufs) 193 hashp->nbufs--; 194 } else { 195 /* Kick someone out */ 196 BUF_REMOVE(bp); 197 /* 198 * If this is an overflow page with addr 0, it's already been 199 * flushed back in an overflow chain and initialized. 200 */ 201 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 202 /* 203 * Set oaddr before __put_page so that you get it 204 * before bytes are swapped. 205 */ 206 shortp = (u_int16_t *)bp->page; 207 if (shortp[0]) 208 oaddr = shortp[shortp[0] - 1]; 209 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 210 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 211 return (NULL); 212 /* 213 * Update the pointer to this page (i.e. invalidate it). 214 * 215 * If this is a new file (i.e. we created it at open 216 * time), make sure that we mark pages which have been 217 * written to disk so we retrieve them from disk later, 218 * rather than allocating new pages. 219 */ 220 if (IS_BUCKET(bp->flags)) { 221 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 222 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 223 #ifdef DEBUG 224 assert(segp != NULL); 225 #endif 226 227 if (hashp->new_file && 228 ((bp->flags & BUF_MOD) || 229 ISDISK(segp[segment_ndx]))) 230 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 231 else 232 segp[segment_ndx] = NULL; 233 } 234 /* 235 * Since overflow pages can only be access by means of 236 * their bucket, free overflow pages associated with 237 * this bucket. 238 */ 239 for (xbp = bp; xbp->ovfl;) { 240 next_xbp = xbp->ovfl; 241 xbp->ovfl = 0; 242 xbp = next_xbp; 243 244 /* Check that ovfl pointer is up date. */ 245 if (IS_BUCKET(xbp->flags) || 246 (oaddr != xbp->addr)) 247 break; 248 249 shortp = (u_int16_t *)xbp->page; 250 if (shortp[0]) 251 /* set before __put_page */ 252 oaddr = shortp[shortp[0] - 1]; 253 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 254 xbp->page, xbp->addr, 0, 0)) 255 return (NULL); 256 xbp->addr = 0; 257 xbp->flags = 0; 258 BUF_REMOVE(xbp); 259 LRU_INSERT(xbp); 260 } 261 } 262 } 263 264 /* Now assign this buffer */ 265 bp->addr = addr; 266 #ifdef DEBUG1 267 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 268 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 269 #endif 270 bp->ovfl = NULL; 271 if (prev_bp) { 272 /* 273 * If prev_bp is set, this is an overflow page, hook it in to 274 * the buffer overflow links. 275 */ 276 #ifdef DEBUG1 277 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 278 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0), 279 (bp ? bp->addr : 0)); 280 #endif 281 prev_bp->ovfl = bp; 282 bp->flags = 0; 283 } else 284 bp->flags = BUF_BUCKET; 285 MRU_INSERT(bp); 286 return (bp); 287 } 288 289 extern void 290 __buf_init(hashp, nbytes) 291 HTAB *hashp; 292 int nbytes; 293 { 294 BUFHEAD *bfp; 295 int npages; 296 297 bfp = &(hashp->bufhead); 298 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 299 npages = MAX(npages, MIN_BUFFERS); 300 301 hashp->nbufs = npages; 302 bfp->next = bfp; 303 bfp->prev = bfp; 304 /* 305 * This space is calloc'd so these are already null. 306 * 307 * bfp->ovfl = NULL; 308 * bfp->flags = 0; 309 * bfp->page = NULL; 310 * bfp->addr = 0; 311 */ 312 } 313 314 extern int 315 __buf_free(hashp, do_free, to_disk) 316 HTAB *hashp; 317 int do_free, to_disk; 318 { 319 BUFHEAD *bp; 320 321 /* Need to make sure that buffer manager has been initialized */ 322 if (!LRU) 323 return (0); 324 for (bp = LRU; bp != &hashp->bufhead;) { 325 /* Check that the buffer is valid */ 326 if (bp->addr || IS_BUCKET(bp->flags)) { 327 if (to_disk && (bp->flags & BUF_MOD) && 328 __put_page(hashp, bp->page, 329 bp->addr, IS_BUCKET(bp->flags), 0)) 330 return (-1); 331 } 332 /* Check if we are freeing stuff */ 333 if (do_free) { 334 if (bp->page) 335 free(bp->page); 336 BUF_REMOVE(bp); 337 free(bp); 338 bp = LRU; 339 } else 340 bp = bp->prev; 341 } 342 return (0); 343 } 344 345 extern void 346 __reclaim_buf(hashp, bp) 347 HTAB *hashp; 348 BUFHEAD *bp; 349 { 350 bp->ovfl = 0; 351 bp->addr = 0; 352 bp->flags = 0; 353 BUF_REMOVE(bp); 354 LRU_INSERT(bp); 355 } 356