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 extern BUFHEAD * 102 __get_buf(hashp, addr, prev_bp, newpage) 103 HTAB *hashp; 104 u_int32_t addr; 105 BUFHEAD *prev_bp; 106 int newpage; /* If prev_bp set, indicates a new overflow page. */ 107 { 108 BUFHEAD *bp; 109 u_int32_t is_disk_mask; 110 int is_disk, segment_ndx; 111 SEGMENT segp; 112 113 is_disk = 0; 114 is_disk_mask = 0; 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(hashp, addr, prev_bp) 158 HTAB *hashp; 159 u_int32_t addr; 160 BUFHEAD *prev_bp; 161 { 162 BUFHEAD *bp; /* The buffer we're going to use */ 163 BUFHEAD *xbp; /* Temp pointer */ 164 BUFHEAD *next_xbp; 165 SEGMENT segp; 166 int segment_ndx; 167 u_int16_t oaddr, *shortp; 168 169 oaddr = 0; 170 bp = LRU; 171 /* 172 * If LRU buffer is pinned, the buffer pool is too small. We need to 173 * allocate more buffers. 174 */ 175 if (hashp->nbufs || (bp->flags & BUF_PIN)) { 176 /* Allocate a new one */ 177 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL) 178 return (NULL); 179 #ifdef PURIFY 180 memset(bp, 0xff, sizeof(BUFHEAD)); 181 #endif 182 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) { 183 free(bp); 184 return (NULL); 185 } 186 #ifdef PURIFY 187 memset(bp->page, 0xff, hashp->BSIZE); 188 #endif 189 if (hashp->nbufs) 190 hashp->nbufs--; 191 } else { 192 /* Kick someone out */ 193 BUF_REMOVE(bp); 194 /* 195 * If this is an overflow page with addr 0, it's already been 196 * flushed back in an overflow chain and initialized. 197 */ 198 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 199 /* 200 * Set oaddr before __put_page so that you get it 201 * before bytes are swapped. 202 */ 203 shortp = (u_int16_t *)bp->page; 204 if (shortp[0]) 205 oaddr = shortp[shortp[0] - 1]; 206 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 207 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 208 return (NULL); 209 /* 210 * Update the pointer to this page (i.e. invalidate it). 211 * 212 * If this is a new file (i.e. we created it at open 213 * time), make sure that we mark pages which have been 214 * written to disk so we retrieve them from disk later, 215 * rather than allocating new pages. 216 */ 217 if (IS_BUCKET(bp->flags)) { 218 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 219 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 220 #ifdef DEBUG 221 assert(segp != NULL); 222 #endif 223 224 if (hashp->new_file && 225 ((bp->flags & BUF_MOD) || 226 ISDISK(segp[segment_ndx]))) 227 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 228 else 229 segp[segment_ndx] = NULL; 230 } 231 /* 232 * Since overflow pages can only be access by means of 233 * their bucket, free overflow pages associated with 234 * this bucket. 235 */ 236 for (xbp = bp; xbp->ovfl;) { 237 next_xbp = xbp->ovfl; 238 xbp->ovfl = 0; 239 xbp = next_xbp; 240 241 /* Check that ovfl pointer is up date. */ 242 if (IS_BUCKET(xbp->flags) || 243 (oaddr != xbp->addr)) 244 break; 245 246 shortp = (u_int16_t *)xbp->page; 247 if (shortp[0]) 248 /* set before __put_page */ 249 oaddr = shortp[shortp[0] - 1]; 250 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 251 xbp->page, xbp->addr, 0, 0)) 252 return (NULL); 253 xbp->addr = 0; 254 xbp->flags = 0; 255 BUF_REMOVE(xbp); 256 LRU_INSERT(xbp); 257 } 258 } 259 } 260 261 /* Now assign this buffer */ 262 bp->addr = addr; 263 #ifdef DEBUG1 264 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 265 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 266 #endif 267 bp->ovfl = NULL; 268 if (prev_bp) { 269 /* 270 * If prev_bp is set, this is an overflow page, hook it in to 271 * the buffer overflow links. 272 */ 273 #ifdef DEBUG1 274 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 275 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0), 276 (bp ? bp->addr : 0)); 277 #endif 278 prev_bp->ovfl = bp; 279 bp->flags = 0; 280 } else 281 bp->flags = BUF_BUCKET; 282 MRU_INSERT(bp); 283 return (bp); 284 } 285 286 extern void 287 __buf_init(hashp, nbytes) 288 HTAB *hashp; 289 int nbytes; 290 { 291 BUFHEAD *bfp; 292 int npages; 293 294 bfp = &(hashp->bufhead); 295 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 296 npages = MAX(npages, MIN_BUFFERS); 297 298 hashp->nbufs = npages; 299 bfp->next = bfp; 300 bfp->prev = bfp; 301 /* 302 * This space is calloc'd so these are already null. 303 * 304 * bfp->ovfl = NULL; 305 * bfp->flags = 0; 306 * bfp->page = NULL; 307 * bfp->addr = 0; 308 */ 309 } 310 311 extern int 312 __buf_free(hashp, do_free, to_disk) 313 HTAB *hashp; 314 int do_free, to_disk; 315 { 316 BUFHEAD *bp; 317 318 /* Need to make sure that buffer manager has been initialized */ 319 if (!LRU) 320 return (0); 321 for (bp = LRU; bp != &hashp->bufhead;) { 322 /* Check that the buffer is valid */ 323 if (bp->addr || IS_BUCKET(bp->flags)) { 324 if (to_disk && (bp->flags & BUF_MOD) && 325 __put_page(hashp, bp->page, 326 bp->addr, IS_BUCKET(bp->flags), 0)) 327 return (-1); 328 } 329 /* Check if we are freeing stuff */ 330 if (do_free) { 331 if (bp->page) 332 free(bp->page); 333 BUF_REMOVE(bp); 334 free(bp); 335 bp = LRU; 336 } else 337 bp = bp->prev; 338 } 339 return (0); 340 } 341 342 extern void 343 __reclaim_buf(hashp, bp) 344 HTAB *hashp; 345 BUFHEAD *bp; 346 { 347 bp->ovfl = 0; 348 bp->addr = 0; 349 bp->flags = 0; 350 BUF_REMOVE(bp); 351 LRU_INSERT(bp); 352 } 353