1 /*- 2 * Copyright (c) 1990, 1993 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 37 #if defined(LIBC_SCCS) && !defined(lint) 38 static char sccsid[] = "@(#)hash_buf.c 8.2 (Berkeley) 2/21/94"; 39 #endif /* LIBC_SCCS and not lint */ 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 <errno.h> 60 #include <stdio.h> 61 #include <stdlib.h> 62 #ifdef DEBUG 63 #include <assert.h> 64 #endif 65 66 #include <db.h> 67 #include "hash.h" 68 #include "page.h" 69 #include "extern.h" 70 71 static BUFHEAD *newbuf __P((HTAB *, u_int, BUFHEAD *)); 72 73 /* Unlink B from its place in the lru */ 74 #define BUF_REMOVE(B) { \ 75 (B)->prev->next = (B)->next; \ 76 (B)->next->prev = (B)->prev; \ 77 } 78 79 /* Insert B after P */ 80 #define BUF_INSERT(B, P) { \ 81 (B)->next = (P)->next; \ 82 (B)->prev = (P); \ 83 (P)->next = (B); \ 84 (B)->next->prev = (B); \ 85 } 86 87 #define MRU hashp->bufhead.next 88 #define LRU hashp->bufhead.prev 89 90 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 91 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 92 93 /* 94 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 95 * address is a bucket index. If prev_bp is not NULL, then it points to the 96 * page previous to an overflow page that we are trying to find. 97 * 98 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 99 * be valid. Therefore, you must always verify that its address matches the 100 * address you are seeking. 101 */ 102 extern BUFHEAD * 103 __get_buf(hashp, addr, prev_bp, newpage) 104 HTAB *hashp; 105 u_int addr; 106 BUFHEAD *prev_bp; 107 int newpage; /* If prev_bp set, indicates a new overflow page. */ 108 { 109 register BUFHEAD *bp; 110 register u_int is_disk_mask; 111 register 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 *)((u_int)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(hashp, addr, prev_bp) 159 HTAB *hashp; 160 u_int addr; 161 BUFHEAD *prev_bp; 162 { 163 register BUFHEAD *bp; /* The buffer we're going to use */ 164 register BUFHEAD *xbp; /* Temp pointer */ 165 register BUFHEAD *next_xbp; 166 SEGMENT segp; 167 int segment_ndx; 168 u_short oaddr, *shortp; 169 170 oaddr = 0; 171 bp = LRU; 172 /* 173 * If LRU buffer is pinned, the buffer pool is too small. We need to 174 * allocate more buffers. 175 */ 176 if (hashp->nbufs || (bp->flags & BUF_PIN)) { 177 /* Allocate a new one */ 178 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL) 179 return (NULL); 180 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) { 181 free(bp); 182 return (NULL); 183 } 184 if (hashp->nbufs) 185 hashp->nbufs--; 186 } else { 187 /* Kick someone out */ 188 BUF_REMOVE(bp); 189 /* 190 * If this is an overflow page with addr 0, it's already been 191 * flushed back in an overflow chain and initialized. 192 */ 193 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 194 /* 195 * Set oaddr before __put_page so that you get it 196 * before bytes are swapped. 197 */ 198 shortp = (u_short *)bp->page; 199 if (shortp[0]) 200 oaddr = shortp[shortp[0] - 1]; 201 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 202 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 203 return (NULL); 204 /* 205 * Update the pointer to this page (i.e. invalidate it). 206 * 207 * If this is a new file (i.e. we created it at open 208 * time), make sure that we mark pages which have been 209 * written to disk so we retrieve them from disk later, 210 * rather than allocating new pages. 211 */ 212 if (IS_BUCKET(bp->flags)) { 213 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 214 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 215 #ifdef DEBUG 216 assert(segp != NULL); 217 #endif 218 219 if (hashp->new_file && 220 ((bp->flags & BUF_MOD) || 221 ISDISK(segp[segment_ndx]))) 222 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 223 else 224 segp[segment_ndx] = NULL; 225 } 226 /* 227 * Since overflow pages can only be access by means of 228 * their bucket, free overflow pages associated with 229 * this bucket. 230 */ 231 for (xbp = bp; xbp->ovfl;) { 232 next_xbp = xbp->ovfl; 233 xbp->ovfl = 0; 234 xbp = next_xbp; 235 236 /* Check that ovfl pointer is up date. */ 237 if (IS_BUCKET(xbp->flags) || 238 (oaddr != xbp->addr)) 239 break; 240 241 shortp = (u_short *)xbp->page; 242 if (shortp[0]) 243 /* set before __put_page */ 244 oaddr = shortp[shortp[0] - 1]; 245 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 246 xbp->page, xbp->addr, 0, 0)) 247 return (NULL); 248 xbp->addr = 0; 249 xbp->flags = 0; 250 BUF_REMOVE(xbp); 251 LRU_INSERT(xbp); 252 } 253 } 254 } 255 256 /* Now assign this buffer */ 257 bp->addr = addr; 258 #ifdef DEBUG1 259 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 260 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 261 #endif 262 bp->ovfl = NULL; 263 if (prev_bp) { 264 /* 265 * If prev_bp is set, this is an overflow page, hook it in to 266 * the buffer overflow links. 267 */ 268 #ifdef DEBUG1 269 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 270 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0), 271 (bp ? bp->addr : 0)); 272 #endif 273 prev_bp->ovfl = bp; 274 bp->flags = 0; 275 } else 276 bp->flags = BUF_BUCKET; 277 MRU_INSERT(bp); 278 return (bp); 279 } 280 281 extern void 282 __buf_init(hashp, nbytes) 283 HTAB *hashp; 284 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(hashp, do_free, to_disk) 308 HTAB *hashp; 309 int do_free, to_disk; 310 { 311 BUFHEAD *bp; 312 313 /* Need to make sure that buffer manager has been initialized */ 314 if (!LRU) 315 return (0); 316 for (bp = LRU; bp != &hashp->bufhead;) { 317 /* Check that the buffer is valid */ 318 if (bp->addr || IS_BUCKET(bp->flags)) { 319 if (to_disk && (bp->flags & BUF_MOD) && 320 __put_page(hashp, bp->page, 321 bp->addr, IS_BUCKET(bp->flags), 0)) 322 return (-1); 323 } 324 /* Check if we are freeing stuff */ 325 if (do_free) { 326 if (bp->page) 327 free(bp->page); 328 BUF_REMOVE(bp); 329 free(bp); 330 bp = LRU; 331 } else 332 bp = bp->prev; 333 } 334 return (0); 335 } 336 337 extern void 338 __reclaim_buf(hashp, bp) 339 HTAB *hashp; 340 BUFHEAD *bp; 341 { 342 bp->ovfl = 0; 343 bp->addr = 0; 344 bp->flags = 0; 345 BUF_REMOVE(bp); 346 LRU_INSERT(bp); 347 } 348