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 * 4. 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 33 #if defined(LIBC_SCCS) && !defined(lint) 34 static char sccsid[] = "@(#)hash_buf.c 8.5 (Berkeley) 7/15/94"; 35 #endif /* LIBC_SCCS and not lint */ 36 #include <sys/cdefs.h> 37 __FBSDID("$FreeBSD$"); 38 39 /* 40 * PACKAGE: hash 41 * 42 * DESCRIPTION: 43 * Contains buffer management 44 * 45 * ROUTINES: 46 * External 47 * __buf_init 48 * __get_buf 49 * __buf_free 50 * __reclaim_buf 51 * Internal 52 * newbuf 53 */ 54 55 #include <sys/param.h> 56 57 #include <stddef.h> 58 #include <stdio.h> 59 #include <stdlib.h> 60 61 #ifdef DEBUG 62 #include <assert.h> 63 #endif 64 65 #include <db.h> 66 #include "hash.h" 67 #include "page.h" 68 #include "extern.h" 69 70 static BUFHEAD *newbuf(HTAB *, u_int32_t, BUFHEAD *); 71 72 /* Unlink B from its place in the lru */ 73 #define BUF_REMOVE(B) { \ 74 (B)->prev->next = (B)->next; \ 75 (B)->next->prev = (B)->prev; \ 76 } 77 78 /* Insert B after P */ 79 #define BUF_INSERT(B, P) { \ 80 (B)->next = (P)->next; \ 81 (B)->prev = (P); \ 82 (P)->next = (B); \ 83 (B)->next->prev = (B); \ 84 } 85 86 #define MRU hashp->bufhead.next 87 #define LRU hashp->bufhead.prev 88 89 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 90 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 91 92 /* 93 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 94 * address is a bucket index. If prev_bp is not NULL, then it points to the 95 * page previous to an overflow page that we are trying to find. 96 * 97 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 98 * be valid. Therefore, you must always verify that its address matches the 99 * address you are seeking. 100 */ 101 BUFHEAD * 102 __get_buf(HTAB *hashp, u_int32_t addr, 103 BUFHEAD *prev_bp, /* If prev_bp set, indicates a new overflow page. */ 104 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 if (prev_bp) { 114 bp = prev_bp->ovfl; 115 if (!bp || (bp->addr != addr)) 116 bp = NULL; 117 if (!newpage) 118 is_disk = BUF_DISK; 119 } else { 120 /* Grab buffer out of directory */ 121 segment_ndx = addr & (hashp->SGSIZE - 1); 122 123 /* valid segment ensured by __call_hash() */ 124 segp = hashp->dir[addr >> hashp->SSHIFT]; 125 #ifdef DEBUG 126 assert(segp != NULL); 127 #endif 128 bp = PTROF(segp[segment_ndx]); 129 is_disk_mask = ISDISK(segp[segment_ndx]); 130 is_disk = is_disk_mask || !hashp->new_file; 131 } 132 133 if (!bp) { 134 bp = newbuf(hashp, addr, prev_bp); 135 if (!bp || 136 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) 137 return (NULL); 138 if (!prev_bp) 139 segp[segment_ndx] = 140 (BUFHEAD *)((ptrdiff_t)bp | is_disk_mask); 141 } else { 142 BUF_REMOVE(bp); 143 MRU_INSERT(bp); 144 } 145 return (bp); 146 } 147 148 /* 149 * We need a buffer for this page. Either allocate one, or evict a resident 150 * one (if we have as many buffers as we're allowed) and put this one in. 151 * 152 * If newbuf finds an error (returning NULL), it also sets errno. 153 */ 154 static BUFHEAD * 155 newbuf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp) 156 { 157 BUFHEAD *bp; /* The buffer we're going to use */ 158 BUFHEAD *xbp; /* Temp pointer */ 159 BUFHEAD *next_xbp; 160 SEGMENT segp; 161 int segment_ndx; 162 u_int16_t oaddr, *shortp; 163 164 oaddr = 0; 165 bp = LRU; 166 /* 167 * If LRU buffer is pinned, the buffer pool is too small. We need to 168 * allocate more buffers. 169 */ 170 if (hashp->nbufs || (bp->flags & BUF_PIN)) { 171 /* Allocate a new one */ 172 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL) 173 return (NULL); 174 #ifdef PURIFY 175 memset(bp, 0xff, sizeof(BUFHEAD)); 176 #endif 177 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) { 178 free(bp); 179 return (NULL); 180 } 181 #ifdef PURIFY 182 memset(bp->page, 0xff, hashp->BSIZE); 183 #endif 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_int16_t *)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_int16_t *)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 void 282 __buf_init(HTAB *hashp, int nbytes) 283 { 284 BUFHEAD *bfp; 285 int npages; 286 287 bfp = &(hashp->bufhead); 288 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 289 npages = MAX(npages, MIN_BUFFERS); 290 291 hashp->nbufs = npages; 292 bfp->next = bfp; 293 bfp->prev = bfp; 294 /* 295 * This space is calloc'd so these are already null. 296 * 297 * bfp->ovfl = NULL; 298 * bfp->flags = 0; 299 * bfp->page = NULL; 300 * bfp->addr = 0; 301 */ 302 } 303 304 int 305 __buf_free(HTAB *hashp, int do_free, int to_disk) 306 { 307 BUFHEAD *bp; 308 309 /* Need to make sure that buffer manager has been initialized */ 310 if (!LRU) 311 return (0); 312 for (bp = LRU; bp != &hashp->bufhead;) { 313 /* Check that the buffer is valid */ 314 if (bp->addr || IS_BUCKET(bp->flags)) { 315 if (to_disk && (bp->flags & BUF_MOD) && 316 __put_page(hashp, bp->page, 317 bp->addr, IS_BUCKET(bp->flags), 0)) 318 return (-1); 319 } 320 /* Check if we are freeing stuff */ 321 if (do_free) { 322 if (bp->page) 323 free(bp->page); 324 BUF_REMOVE(bp); 325 free(bp); 326 bp = LRU; 327 } else 328 bp = bp->prev; 329 } 330 return (0); 331 } 332 333 void 334 __reclaim_buf(HTAB *hashp, BUFHEAD *bp) 335 { 336 bp->ovfl = 0; 337 bp->addr = 0; 338 bp->flags = 0; 339 BUF_REMOVE(bp); 340 LRU_INSERT(bp); 341 } 342