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 8.1 (Berkeley) 6/4/93"; 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 bp = malloc(sizeof(struct _bufhead)); 179 if (!bp || !(bp->page = malloc(hashp->BSIZE))) 180 return (NULL); 181 if (hashp->nbufs) 182 hashp->nbufs--; 183 } else { 184 /* Kick someone out */ 185 BUF_REMOVE(bp); 186 /* 187 * If this is an overflow page with addr 0, it's already been 188 * flushed back in an overflow chain and initialized. 189 */ 190 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 191 /* 192 * Set oaddr before __put_page so that you get it 193 * before bytes are swapped. 194 */ 195 shortp = (u_short *)bp->page; 196 if (shortp[0]) 197 oaddr = shortp[shortp[0] - 1]; 198 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 199 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 200 return (NULL); 201 /* 202 * Update the pointer to this page (i.e. invalidate it). 203 * 204 * If this is a new file (i.e. we created it at open 205 * time), make sure that we mark pages which have been 206 * written to disk so we retrieve them from disk later, 207 * rather than allocating new pages. 208 */ 209 if (IS_BUCKET(bp->flags)) { 210 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 211 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 212 #ifdef DEBUG 213 assert(segp != NULL); 214 #endif 215 216 if (hashp->new_file && 217 ((bp->flags & BUF_MOD) || 218 ISDISK(segp[segment_ndx]))) 219 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 220 else 221 segp[segment_ndx] = NULL; 222 } 223 /* 224 * Since overflow pages can only be access by means of 225 * their bucket, free overflow pages associated with 226 * this bucket. 227 */ 228 for (xbp = bp; xbp->ovfl;) { 229 next_xbp = xbp->ovfl; 230 xbp->ovfl = 0; 231 xbp = next_xbp; 232 233 /* Check that ovfl pointer is up date. */ 234 if (IS_BUCKET(xbp->flags) || 235 (oaddr != xbp->addr)) 236 break; 237 238 shortp = (u_short *)xbp->page; 239 if (shortp[0]) 240 /* set before __put_page */ 241 oaddr = shortp[shortp[0] - 1]; 242 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 243 xbp->page, xbp->addr, 0, 0)) 244 return (NULL); 245 xbp->addr = 0; 246 xbp->flags = 0; 247 BUF_REMOVE(xbp); 248 LRU_INSERT(xbp); 249 } 250 } 251 } 252 253 /* Now assign this buffer */ 254 bp->addr = addr; 255 #ifdef DEBUG1 256 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 257 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 258 #endif 259 bp->ovfl = NULL; 260 if (prev_bp) { 261 /* 262 * If prev_bp is set, this is an overflow page, hook it in to 263 * the buffer overflow links. 264 */ 265 #ifdef DEBUG1 266 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 267 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0), 268 (bp ? bp->addr : 0)); 269 #endif 270 prev_bp->ovfl = bp; 271 bp->flags = 0; 272 } else 273 bp->flags = BUF_BUCKET; 274 MRU_INSERT(bp); 275 return (bp); 276 } 277 278 extern void 279 __buf_init(hashp, nbytes) 280 HTAB *hashp; 281 int nbytes; 282 { 283 BUFHEAD *bfp; 284 int npages; 285 286 bfp = &(hashp->bufhead); 287 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 288 npages = MAX(npages, MIN_BUFFERS); 289 290 hashp->nbufs = npages; 291 bfp->next = bfp; 292 bfp->prev = bfp; 293 /* 294 * This space is calloc'd so these are already null. 295 * 296 * bfp->ovfl = NULL; 297 * bfp->flags = 0; 298 * bfp->page = NULL; 299 * bfp->addr = 0; 300 */ 301 } 302 303 extern int 304 __buf_free(hashp, do_free, to_disk) 305 HTAB *hashp; 306 int do_free, to_disk; 307 { 308 BUFHEAD *bp; 309 310 /* Need to make sure that buffer manager has been initialized */ 311 if (!LRU) 312 return (0); 313 for (bp = LRU; bp != &hashp->bufhead;) { 314 /* Check that the buffer is valid */ 315 if (bp->addr || IS_BUCKET(bp->flags)) { 316 if (to_disk && (bp->flags & BUF_MOD) && 317 __put_page(hashp, bp->page, 318 bp->addr, IS_BUCKET(bp->flags), 0)) 319 return (-1); 320 } 321 /* Check if we are freeing stuff */ 322 if (do_free) { 323 if (bp->page) 324 free(bp->page); 325 BUF_REMOVE(bp); 326 free(bp); 327 bp = LRU; 328 } else 329 bp = bp->prev; 330 } 331 return (0); 332 } 333 334 extern void 335 __reclaim_buf(hashp, bp) 336 HTAB *hashp; 337 BUFHEAD *bp; 338 { 339 bp->ovfl = 0; 340 bp->addr = 0; 341 bp->flags = 0; 342 BUF_REMOVE(bp); 343 LRU_INSERT(bp); 344 } 345