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. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * $FreeBSD: src/lib/libc/db/hash/hash_buf.c,v 1.4.8.1 2001/03/05 07:38:05 obrien Exp $ 33 * $DragonFly: src/lib/libc/db/hash/hash_buf.c,v 1.7 2005/11/19 20:46:32 swildner Exp $ 34 * 35 * @(#)hash_buf.c 8.5 (Berkeley) 7/15/94 36 */ 37 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 60 #ifdef DEBUG 61 #include <assert.h> 62 #endif 63 64 #include <db.h> 65 #include "hash.h" 66 #include "page.h" 67 #include "extern.h" 68 69 static BUFHEAD *newbuf (HTAB *, u_int32_t, BUFHEAD *); 70 71 /* Unlink B from its place in the lru */ 72 #define BUF_REMOVE(B) { \ 73 (B)->prev->next = (B)->next; \ 74 (B)->next->prev = (B)->prev; \ 75 } 76 77 /* Insert B after P */ 78 #define BUF_INSERT(B, P) { \ 79 (B)->next = (P)->next; \ 80 (B)->prev = (P); \ 81 (P)->next = (B); \ 82 (B)->next->prev = (B); \ 83 } 84 85 #define MRU hashp->bufhead.next 86 #define LRU hashp->bufhead.prev 87 88 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 89 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 90 91 /* 92 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 93 * address is a bucket index. If prev_bp is not NULL, then it points to the 94 * page previous to an overflow page that we are trying to find. 95 * 96 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 97 * be valid. Therefore, you must always verify that its address matches the 98 * address you are seeking. 99 * 100 * Parameters: 101 * newpage: If prev_bp set, indicates a new overflow page 102 */ 103 extern BUFHEAD * 104 __get_buf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp, 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 segment_ndx = 0; 114 segp = NULL; 115 if (prev_bp) { 116 bp = prev_bp->ovfl; 117 if (!bp || (bp->addr != addr)) 118 bp = NULL; 119 if (!newpage) 120 is_disk = BUF_DISK; 121 } else { 122 /* Grab buffer out of directory */ 123 segment_ndx = addr & (hashp->SGSIZE - 1); 124 125 /* valid segment ensured by __call_hash() */ 126 segp = hashp->dir[addr >> hashp->SSHIFT]; 127 #ifdef DEBUG 128 assert(segp != NULL); 129 #endif 130 bp = PTROF(segp[segment_ndx]); 131 is_disk_mask = ISDISK(segp[segment_ndx]); 132 is_disk = is_disk_mask || !hashp->new_file; 133 } 134 135 if (!bp) { 136 bp = newbuf(hashp, addr, prev_bp); 137 if (!bp || 138 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) 139 return (NULL); 140 if (!prev_bp) 141 segp[segment_ndx] = 142 (BUFHEAD *)((ptrdiff_t)bp | is_disk_mask); 143 } else { 144 BUF_REMOVE(bp); 145 MRU_INSERT(bp); 146 } 147 return (bp); 148 } 149 150 /* 151 * We need a buffer for this page. Either allocate one, or evict a resident 152 * one (if we have as many buffers as we're allowed) and put this one in. 153 * 154 * If newbuf finds an error (returning NULL), it also sets errno. 155 */ 156 static BUFHEAD * 157 newbuf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp) 158 { 159 BUFHEAD *bp; /* The buffer we're going to use */ 160 BUFHEAD *xbp; /* Temp pointer */ 161 BUFHEAD *next_xbp; 162 SEGMENT segp; 163 int segment_ndx; 164 u_int16_t oaddr, *shortp; 165 166 oaddr = 0; 167 bp = LRU; 168 /* 169 * If LRU buffer is pinned, the buffer pool is too small. We need to 170 * allocate more buffers. 171 */ 172 if (hashp->nbufs || (bp->flags & BUF_PIN)) { 173 /* Allocate a new one */ 174 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL) 175 return (NULL); 176 #ifdef PURIFY 177 memset(bp, 0xff, sizeof(BUFHEAD)); 178 #endif 179 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) { 180 free(bp); 181 return (NULL); 182 } 183 #ifdef PURIFY 184 memset(bp->page, 0xff, hashp->BSIZE); 185 #endif 186 if (hashp->nbufs) 187 hashp->nbufs--; 188 } else { 189 /* Kick someone out */ 190 BUF_REMOVE(bp); 191 /* 192 * If this is an overflow page with addr 0, it's already been 193 * flushed back in an overflow chain and initialized. 194 */ 195 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 196 /* 197 * Set oaddr before __put_page so that you get it 198 * before bytes are swapped. 199 */ 200 shortp = (u_int16_t *)bp->page; 201 if (shortp[0]) 202 oaddr = shortp[shortp[0] - 1]; 203 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 204 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 205 return (NULL); 206 /* 207 * Update the pointer to this page (i.e. invalidate it). 208 * 209 * If this is a new file (i.e. we created it at open 210 * time), make sure that we mark pages which have been 211 * written to disk so we retrieve them from disk later, 212 * rather than allocating new pages. 213 */ 214 if (IS_BUCKET(bp->flags)) { 215 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 216 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 217 #ifdef DEBUG 218 assert(segp != NULL); 219 #endif 220 221 if (hashp->new_file && 222 ((bp->flags & BUF_MOD) || 223 ISDISK(segp[segment_ndx]))) 224 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 225 else 226 segp[segment_ndx] = NULL; 227 } 228 /* 229 * Since overflow pages can only be access by means of 230 * their bucket, free overflow pages associated with 231 * this bucket. 232 */ 233 for (xbp = bp; xbp->ovfl;) { 234 next_xbp = xbp->ovfl; 235 xbp->ovfl = 0; 236 xbp = next_xbp; 237 238 /* Check that ovfl pointer is up date. */ 239 if (IS_BUCKET(xbp->flags) || 240 (oaddr != xbp->addr)) 241 break; 242 243 shortp = (u_int16_t *)xbp->page; 244 if (shortp[0]) 245 /* set before __put_page */ 246 oaddr = shortp[shortp[0] - 1]; 247 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 248 xbp->page, xbp->addr, 0, 0)) 249 return (NULL); 250 xbp->addr = 0; 251 xbp->flags = 0; 252 BUF_REMOVE(xbp); 253 LRU_INSERT(xbp); 254 } 255 } 256 } 257 258 /* Now assign this buffer */ 259 bp->addr = addr; 260 #ifdef DEBUG1 261 fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 262 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 263 #endif 264 bp->ovfl = NULL; 265 if (prev_bp) { 266 /* 267 * If prev_bp is set, this is an overflow page, hook it in to 268 * the buffer overflow links. 269 */ 270 #ifdef DEBUG1 271 fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 272 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0), 273 (bp ? bp->addr : 0)); 274 #endif 275 prev_bp->ovfl = bp; 276 bp->flags = 0; 277 } else 278 bp->flags = BUF_BUCKET; 279 MRU_INSERT(bp); 280 return (bp); 281 } 282 283 extern void 284 __buf_init(HTAB *hashp, int nbytes) 285 { 286 BUFHEAD *bfp; 287 int npages; 288 289 bfp = &(hashp->bufhead); 290 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 291 npages = MAX(npages, MIN_BUFFERS); 292 293 hashp->nbufs = npages; 294 bfp->next = bfp; 295 bfp->prev = bfp; 296 /* 297 * This space is calloc'd so these are already null. 298 * 299 * bfp->ovfl = NULL; 300 * bfp->flags = 0; 301 * bfp->page = NULL; 302 * bfp->addr = 0; 303 */ 304 } 305 306 extern int 307 __buf_free(HTAB *hashp, int do_free, int to_disk) 308 { 309 BUFHEAD *bp; 310 311 /* Need to make sure that buffer manager has been initialized */ 312 if (!LRU) 313 return (0); 314 for (bp = LRU; bp != &hashp->bufhead;) { 315 /* Check that the buffer is valid */ 316 if (bp->addr || IS_BUCKET(bp->flags)) { 317 if (to_disk && (bp->flags & BUF_MOD) && 318 __put_page(hashp, bp->page, 319 bp->addr, IS_BUCKET(bp->flags), 0)) 320 return (-1); 321 } 322 /* Check if we are freeing stuff */ 323 if (do_free) { 324 if (bp->page) 325 free(bp->page); 326 BUF_REMOVE(bp); 327 free(bp); 328 bp = LRU; 329 } else 330 bp = bp->prev; 331 } 332 return (0); 333 } 334 335 extern void 336 __reclaim_buf(HTAB *hashp, BUFHEAD *bp) 337 { 338 bp->ovfl = 0; 339 bp->addr = 0; 340 bp->flags = 0; 341 BUF_REMOVE(bp); 342 LRU_INSERT(bp); 343 } 344