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 37 #if defined(LIBC_SCCS) && !defined(lint) 38 static char sccsid[] = "@(#)hash_buf.c 8.4 (Berkeley) 6/4/94"; 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 <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 __P((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 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) { 183 free(bp); 184 return (NULL); 185 } 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 (void)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 (void)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(hashp, nbytes) 285 HTAB *hashp; 286 int nbytes; 287 { 288 BUFHEAD *bfp; 289 int npages; 290 291 bfp = &(hashp->bufhead); 292 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 293 npages = MAX(npages, MIN_BUFFERS); 294 295 hashp->nbufs = npages; 296 bfp->next = bfp; 297 bfp->prev = bfp; 298 /* 299 * This space is calloc'd so these are already null. 300 * 301 * bfp->ovfl = NULL; 302 * bfp->flags = 0; 303 * bfp->page = NULL; 304 * bfp->addr = 0; 305 */ 306 } 307 308 extern int 309 __buf_free(hashp, do_free, to_disk) 310 HTAB *hashp; 311 int do_free, to_disk; 312 { 313 BUFHEAD *bp; 314 315 /* Need to make sure that buffer manager has been initialized */ 316 if (!LRU) 317 return (0); 318 for (bp = LRU; bp != &hashp->bufhead;) { 319 /* Check that the buffer is valid */ 320 if (bp->addr || IS_BUCKET(bp->flags)) { 321 if (to_disk && (bp->flags & BUF_MOD) && 322 __put_page(hashp, bp->page, 323 bp->addr, IS_BUCKET(bp->flags), 0)) 324 return (-1); 325 } 326 /* Check if we are freeing stuff */ 327 if (do_free) { 328 if (bp->page) 329 free(bp->page); 330 BUF_REMOVE(bp); 331 free(bp); 332 bp = LRU; 333 } else 334 bp = bp->prev; 335 } 336 return (0); 337 } 338 339 extern void 340 __reclaim_buf(hashp, bp) 341 HTAB *hashp; 342 BUFHEAD *bp; 343 { 344 bp->ovfl = 0; 345 bp->addr = 0; 346 bp->flags = 0; 347 BUF_REMOVE(bp); 348 LRU_INSERT(bp); 349 } 350