1 /* $OpenBSD: hash_buf.c,v 1.19 2015/01/16 16:48:51 deraadt Exp $ */ 2 3 /*- 4 * Copyright (c) 1990, 1993, 1994 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Margo Seltzer. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 /* 36 * PACKAGE: hash 37 * 38 * DESCRIPTION: 39 * Contains buffer management 40 * 41 * ROUTINES: 42 * External 43 * __buf_init 44 * __get_buf 45 * __buf_free 46 * __reclaim_buf 47 * Internal 48 * newbuf 49 */ 50 51 #include <errno.h> 52 #include <stddef.h> 53 #include <stdio.h> 54 #include <stdlib.h> 55 #include <string.h> 56 57 #ifdef DEBUG 58 #include <assert.h> 59 #endif 60 61 #include <db.h> 62 #include "hash.h" 63 #include "page.h" 64 #include "extern.h" 65 66 #define MAXIMUM(a, b) (((a) > (b)) ? (a) : (b)) 67 68 static BUFHEAD *newbuf(HTAB *, u_int32_t, BUFHEAD *); 69 70 /* Unlink B from its place in the lru */ 71 #define BUF_REMOVE(B) { \ 72 (B)->prev->next = (B)->next; \ 73 (B)->next->prev = (B)->prev; \ 74 } 75 76 /* Insert B after P */ 77 #define BUF_INSERT(B, P) { \ 78 (B)->next = (P)->next; \ 79 (B)->prev = (P); \ 80 (P)->next = (B); \ 81 (B)->next->prev = (B); \ 82 } 83 84 #define MRU hashp->bufhead.next 85 #define LRU hashp->bufhead.prev 86 87 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead) 88 #define LRU_INSERT(B) BUF_INSERT((B), LRU) 89 90 /* 91 * We are looking for a buffer with address "addr". If prev_bp is NULL, then 92 * address is a bucket index. If prev_bp is not NULL, then it points to the 93 * page previous to an overflow page that we are trying to find. 94 * 95 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer 96 * be valid. Therefore, you must always verify that its address matches the 97 * address you are seeking. 98 */ 99 BUFHEAD * 100 __get_buf(HTAB *hashp, u_int32_t addr, 101 BUFHEAD *prev_bp, /* If prev_bp set, indicates a new overflow page. */ 102 int newpage) 103 { 104 BUFHEAD *bp; 105 u_int32_t is_disk_mask; 106 int is_disk, segment_ndx; 107 SEGMENT segp; 108 109 is_disk = 0; 110 is_disk_mask = 0; 111 if (prev_bp) { 112 bp = prev_bp->ovfl; 113 if (!bp || (bp->addr != addr)) 114 bp = NULL; 115 if (!newpage) 116 is_disk = BUF_DISK; 117 } else { 118 /* Grab buffer out of directory */ 119 segment_ndx = addr & (hashp->SGSIZE - 1); 120 121 /* valid segment ensured by __call_hash() */ 122 segp = hashp->dir[addr >> hashp->SSHIFT]; 123 #ifdef DEBUG 124 assert(segp != NULL); 125 #endif 126 bp = PTROF(segp[segment_ndx]); 127 is_disk_mask = ISDISK(segp[segment_ndx]); 128 is_disk = is_disk_mask || !hashp->new_file; 129 } 130 131 if (!bp) { 132 bp = newbuf(hashp, addr, prev_bp); 133 if (!bp || 134 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0)) 135 return (NULL); 136 if (!prev_bp) 137 segp[segment_ndx] = 138 (BUFHEAD *)((ptrdiff_t)bp | is_disk_mask); 139 } else { 140 BUF_REMOVE(bp); 141 MRU_INSERT(bp); 142 } 143 return (bp); 144 } 145 146 /* 147 * We need a buffer for this page. Either allocate one, or evict a resident 148 * one (if we have as many buffers as we're allowed) and put this one in. 149 * 150 * If newbuf finds an error (returning NULL), it also sets errno. 151 */ 152 static BUFHEAD * 153 newbuf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp) 154 { 155 BUFHEAD *bp; /* The buffer we're going to use */ 156 BUFHEAD *xbp; /* Temp pointer */ 157 BUFHEAD *next_xbp; 158 SEGMENT segp; 159 int segment_ndx; 160 u_int16_t oaddr, *shortp; 161 162 oaddr = 0; 163 bp = LRU; 164 165 /* It is bad to overwrite the page under the cursor. */ 166 if (bp == hashp->cpage) { 167 BUF_REMOVE(bp); 168 MRU_INSERT(bp); 169 bp = LRU; 170 } 171 172 /* If prev_bp is part of bp overflow, create a new buffer. */ 173 if (hashp->nbufs == 0 && prev_bp && bp->ovfl) { 174 BUFHEAD *ovfl; 175 176 for (ovfl = bp->ovfl; ovfl ; ovfl = ovfl->ovfl) { 177 if (ovfl == prev_bp) { 178 hashp->nbufs++; 179 break; 180 } 181 } 182 } 183 184 /* 185 * If LRU buffer is pinned, the buffer pool is too small. We need to 186 * allocate more buffers. 187 */ 188 if (hashp->nbufs || (bp->flags & BUF_PIN) || bp == hashp->cpage) { 189 /* Allocate a new one */ 190 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL) 191 return (NULL); 192 memset(bp, 0xff, sizeof(BUFHEAD)); 193 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) { 194 free(bp); 195 return (NULL); 196 } 197 memset(bp->page, 0xff, hashp->BSIZE); 198 if (hashp->nbufs) 199 hashp->nbufs--; 200 } else { 201 /* Kick someone out */ 202 BUF_REMOVE(bp); 203 /* 204 * If this is an overflow page with addr 0, it's already been 205 * flushed back in an overflow chain and initialized. 206 */ 207 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) { 208 /* 209 * Set oaddr before __put_page so that you get it 210 * before bytes are swapped. 211 */ 212 shortp = (u_int16_t *)bp->page; 213 if (shortp[0]) 214 oaddr = shortp[shortp[0] - 1]; 215 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page, 216 bp->addr, (int)IS_BUCKET(bp->flags), 0)) 217 return (NULL); 218 /* 219 * Update the pointer to this page (i.e. invalidate it). 220 * 221 * If this is a new file (i.e. we created it at open 222 * time), make sure that we mark pages which have been 223 * written to disk so we retrieve them from disk later, 224 * rather than allocating new pages. 225 */ 226 if (IS_BUCKET(bp->flags)) { 227 segment_ndx = bp->addr & (hashp->SGSIZE - 1); 228 segp = hashp->dir[bp->addr >> hashp->SSHIFT]; 229 #ifdef DEBUG 230 assert(segp != NULL); 231 #endif 232 233 if (hashp->new_file && 234 ((bp->flags & BUF_MOD) || 235 ISDISK(segp[segment_ndx]))) 236 segp[segment_ndx] = (BUFHEAD *)BUF_DISK; 237 else 238 segp[segment_ndx] = NULL; 239 } 240 /* 241 * Since overflow pages can only be access by means of 242 * their bucket, free overflow pages associated with 243 * this bucket. 244 */ 245 for (xbp = bp; xbp->ovfl;) { 246 next_xbp = xbp->ovfl; 247 xbp->ovfl = 0; 248 xbp = next_xbp; 249 250 /* Check that ovfl pointer is up date. */ 251 if (IS_BUCKET(xbp->flags) || 252 (oaddr != xbp->addr)) 253 break; 254 255 shortp = (u_int16_t *)xbp->page; 256 if (shortp[0]) 257 /* set before __put_page */ 258 oaddr = shortp[shortp[0] - 1]; 259 if ((xbp->flags & BUF_MOD) && __put_page(hashp, 260 xbp->page, xbp->addr, 0, 0)) 261 return (NULL); 262 xbp->addr = 0; 263 xbp->flags = 0; 264 BUF_REMOVE(xbp); 265 LRU_INSERT(xbp); 266 } 267 } 268 } 269 270 /* Now assign this buffer */ 271 bp->addr = addr; 272 #ifdef DEBUG1 273 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n", 274 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0); 275 #endif 276 bp->ovfl = NULL; 277 if (prev_bp) { 278 /* 279 * If prev_bp is set, this is an overflow page, hook it in to 280 * the buffer overflow links. 281 */ 282 #ifdef DEBUG1 283 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n", 284 prev_bp->addr, (prev_bp->ovfl ? prev_bp->ovfl->addr : 0), 285 (bp ? bp->addr : 0)); 286 #endif 287 prev_bp->ovfl = bp; 288 bp->flags = 0; 289 } else 290 bp->flags = BUF_BUCKET; 291 MRU_INSERT(bp); 292 return (bp); 293 } 294 295 void 296 __buf_init(HTAB *hashp, int nbytes) 297 { 298 BUFHEAD *bfp; 299 int npages; 300 301 bfp = &(hashp->bufhead); 302 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT; 303 npages = MAXIMUM(npages, MIN_BUFFERS); 304 305 hashp->nbufs = npages; 306 bfp->next = bfp; 307 bfp->prev = bfp; 308 /* 309 * This space is calloc'd so these are already null. 310 * 311 * bfp->ovfl = NULL; 312 * bfp->flags = 0; 313 * bfp->page = NULL; 314 * bfp->addr = 0; 315 */ 316 } 317 318 int 319 __buf_free(HTAB *hashp, int do_free, int to_disk) 320 { 321 BUFHEAD *bp; 322 323 /* Need to make sure that buffer manager has been initialized */ 324 if (!LRU) 325 return (0); 326 for (bp = LRU; bp != &hashp->bufhead;) { 327 /* Check that the buffer is valid */ 328 if (bp->addr || IS_BUCKET(bp->flags)) { 329 if (to_disk && (bp->flags & BUF_MOD) && 330 __put_page(hashp, bp->page, 331 bp->addr, IS_BUCKET(bp->flags), 0)) 332 return (-1); 333 } 334 /* Check if we are freeing stuff */ 335 if (do_free) { 336 if (bp->page) { 337 (void)memset(bp->page, 0, hashp->BSIZE); 338 free(bp->page); 339 } 340 BUF_REMOVE(bp); 341 free(bp); 342 bp = LRU; 343 } else 344 bp = bp->prev; 345 } 346 return (0); 347 } 348 349 void 350 __reclaim_buf(HTAB *hashp, BUFHEAD *bp) 351 { 352 bp->ovfl = 0; 353 bp->addr = 0; 354 bp->flags = 0; 355 BUF_REMOVE(bp); 356 LRU_INSERT(bp); 357 } 358