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 #include <string.h> 61 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(HTAB *, u_int32_t, 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 BUFHEAD * 103 __get_buf(HTAB *hashp, u_int32_t addr, 104 BUFHEAD *prev_bp, /* If prev_bp set, indicates a new overflow page. */ 105 int newpage) 106 { 107 BUFHEAD *bp; 108 u_int32_t is_disk_mask; 109 int is_disk, segment_ndx; 110 SEGMENT segp; 111 112 is_disk = 0; 113 is_disk_mask = 0; 114 if (prev_bp) { 115 bp = prev_bp->ovfl; 116 if (!bp || (bp->addr != addr)) 117 bp = NULL; 118 if (!newpage) 119 is_disk = BUF_DISK; 120 } else { 121 /* Grab buffer out of directory */ 122 segment_ndx = addr & (hashp->SGSIZE - 1); 123 124 /* valid segment ensured by __call_hash() */ 125 segp = hashp->dir[addr >> hashp->SSHIFT]; 126 #ifdef DEBUG 127 assert(segp != NULL); 128 #endif 129 bp = PTROF(segp[segment_ndx]); 130 is_disk_mask = ISDISK(segp[segment_ndx]); 131 is_disk = is_disk_mask || !hashp->new_file; 132 } 133 134 if (!bp) { 135 bp = newbuf(hashp, addr, prev_bp); 136 if (!bp || 137 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) 138 return (NULL); 139 if (!prev_bp) 140 segp[segment_ndx] = 141 (BUFHEAD *)((intptr_t)bp | is_disk_mask); 142 } else { 143 BUF_REMOVE(bp); 144 MRU_INSERT(bp); 145 } 146 return (bp); 147 } 148 149 /* 150 * We need a buffer for this page. Either allocate one, or evict a resident 151 * one (if we have as many buffers as we're allowed) and put this one in. 152 * 153 * If newbuf finds an error (returning NULL), it also sets errno. 154 */ 155 static BUFHEAD * 156 newbuf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp) 157 { 158 BUFHEAD *bp; /* The buffer we're going to use */ 159 BUFHEAD *xbp; /* Temp pointer */ 160 BUFHEAD *next_xbp; 161 SEGMENT segp; 162 int segment_ndx; 163 u_int16_t oaddr, *shortp; 164 165 oaddr = 0; 166 bp = LRU; 167 168 /* It is bad to overwrite the page under the cursor. */ 169 if (bp == hashp->cpage) { 170 BUF_REMOVE(bp); 171 MRU_INSERT(bp); 172 bp = LRU; 173 } 174 175 /* If prev_bp is part of bp overflow, create a new buffer. */ 176 if (hashp->nbufs == 0 && prev_bp && bp->ovfl) { 177 BUFHEAD *ovfl; 178 179 for (ovfl = bp->ovfl; ovfl ; ovfl = ovfl->ovfl) { 180 if (ovfl == prev_bp) { 181 hashp->nbufs++; 182 break; 183 } 184 } 185 } 186 187 /* 188 * If LRU buffer is pinned, the buffer pool is too small. We need to 189 * allocate more buffers. 190 */ 191 if (hashp->nbufs || (bp->flags & BUF_PIN) || bp == hashp->cpage) { 192 /* Allocate a new one */ 193 if ((bp = (BUFHEAD *)calloc(1, sizeof(BUFHEAD))) == NULL) 194 return (NULL); 195 if ((bp->page = (char *)calloc(1, hashp->BSIZE)) == NULL) { 196 free(bp); 197 return (NULL); 198 } 199 if (hashp->nbufs) 200 hashp->nbufs--; 201 } else { 202 /* Kick someone out */ 203 BUF_REMOVE(bp); 204 /* 205 * If this is an overflow page with addr 0, it's already been 206 * flushed back in an overflow chain and initialized. 207 */ 208 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 209 /* 210 * Set oaddr before __put_page so that you get it 211 * before bytes are swapped. 212 */ 213 shortp = (u_int16_t *)bp->page; 214 if (shortp[0]) 215 oaddr = shortp[shortp[0] - 1]; 216 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 217 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 218 return (NULL); 219 /* 220 * Update the pointer to this page (i.e. invalidate it). 221 * 222 * If this is a new file (i.e. we created it at open 223 * time), make sure that we mark pages which have been 224 * written to disk so we retrieve them from disk later, 225 * rather than allocating new pages. 226 */ 227 if (IS_BUCKET(bp->flags)) { 228 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 229 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 230 #ifdef DEBUG 231 assert(segp != NULL); 232 #endif 233 234 if (hashp->new_file && 235 ((bp->flags & BUF_MOD) || 236 ISDISK(segp[segment_ndx]))) 237 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 238 else 239 segp[segment_ndx] = NULL; 240 } 241 /* 242 * Since overflow pages can only be access by means of 243 * their bucket, free overflow pages associated with 244 * this bucket. 245 */ 246 for (xbp = bp; xbp->ovfl;) { 247 next_xbp = xbp->ovfl; 248 xbp->ovfl = NULL; 249 xbp = next_xbp; 250 251 /* Check that ovfl pointer is up date. */ 252 if (IS_BUCKET(xbp->flags) || 253 (oaddr != xbp->addr)) 254 break; 255 256 shortp = (u_int16_t *)xbp->page; 257 if (shortp[0]) 258 /* set before __put_page */ 259 oaddr = shortp[shortp[0] - 1]; 260 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 261 xbp->page, xbp->addr, 0, 0)) 262 return (NULL); 263 xbp->addr = 0; 264 xbp->flags = 0; 265 BUF_REMOVE(xbp); 266 LRU_INSERT(xbp); 267 } 268 } 269 } 270 271 /* Now assign this buffer */ 272 bp->addr = addr; 273 #ifdef DEBUG1 274 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 275 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 276 #endif 277 bp->ovfl = NULL; 278 if (prev_bp) { 279 /* 280 * If prev_bp is set, this is an overflow page, hook it in to 281 * the buffer overflow links. 282 */ 283 #ifdef DEBUG1 284 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 285 prev_bp->addr, (prev_bp->ovfl ? prev_bp->ovfl->addr : 0), 286 (bp ? bp->addr : 0)); 287 #endif 288 prev_bp->ovfl = bp; 289 bp->flags = 0; 290 } else 291 bp->flags = BUF_BUCKET; 292 MRU_INSERT(bp); 293 return (bp); 294 } 295 296 void 297 __buf_init(HTAB *hashp, int nbytes) 298 { 299 BUFHEAD *bfp; 300 int npages; 301 302 bfp = &(hashp->bufhead); 303 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 304 npages = MAX(npages, MIN_BUFFERS); 305 306 hashp->nbufs = npages; 307 bfp->next = bfp; 308 bfp->prev = bfp; 309 /* 310 * This space is calloc'd so these are already null. 311 * 312 * bfp->ovfl = NULL; 313 * bfp->flags = 0; 314 * bfp->page = NULL; 315 * bfp->addr = 0; 316 */ 317 } 318 319 int 320 __buf_free(HTAB *hashp, int do_free, int to_disk) 321 { 322 BUFHEAD *bp; 323 324 /* Need to make sure that buffer manager has been initialized */ 325 if (!LRU) 326 return (0); 327 for (bp = LRU; bp != &hashp->bufhead;) { 328 /* Check that the buffer is valid */ 329 if (bp->addr || IS_BUCKET(bp->flags)) { 330 if (to_disk && (bp->flags & BUF_MOD) && 331 __put_page(hashp, bp->page, 332 bp->addr, IS_BUCKET(bp->flags), 0)) 333 return (-1); 334 } 335 /* Check if we are freeing stuff */ 336 if (do_free) { 337 if (bp->page) { 338 (void)memset(bp->page, 0, hashp->BSIZE); 339 free(bp->page); 340 } 341 BUF_REMOVE(bp); 342 free(bp); 343 bp = LRU; 344 } else 345 bp = bp->prev; 346 } 347 return (0); 348 } 349 350 void 351 __reclaim_buf(HTAB *hashp, BUFHEAD *bp) 352 { 353 bp->ovfl = NULL; 354 bp->addr = 0; 355 bp->flags = 0; 356 BUF_REMOVE(bp); 357 LRU_INSERT(bp); 358 } 359