1 /* $NetBSD: hash_buf.c,v 1.18 2009/04/23 22:09:23 christos 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 #if HAVE_NBTOOL_CONFIG_H
36 #include "nbtool_config.h"
37 #endif
38
39 #include <sys/cdefs.h>
40 __RCSID("$NetBSD: hash_buf.c,v 1.18 2009/04/23 22:09:23 christos Exp $");
41
42 /*
43 * PACKAGE: hash
44 *
45 * DESCRIPTION:
46 * Contains buffer management
47 *
48 * ROUTINES:
49 * External
50 * __buf_init
51 * __get_buf
52 * __buf_free
53 * __reclaim_buf
54 * Internal
55 * newbuf
56 */
57
58 #include <sys/param.h>
59
60 #include <errno.h>
61 #include <stddef.h>
62 #include <stdio.h>
63 #include <stdlib.h>
64 #include <string.h>
65 #include <assert.h>
66
67 #include <db.h>
68 #include "hash.h"
69 #include "page.h"
70 #include "extern.h"
71
72 static BUFHEAD *newbuf(HTAB *, uint32_t, BUFHEAD *);
73
74 /* Unlink B from its place in the lru */
75 #define BUF_REMOVE(B) { \
76 (B)->prev->next = (B)->next; \
77 (B)->next->prev = (B)->prev; \
78 }
79
80 /* Insert B after P */
81 #define BUF_INSERT(B, P) { \
82 (B)->next = (P)->next; \
83 (B)->prev = (P); \
84 (P)->next = (B); \
85 (B)->next->prev = (B); \
86 }
87
88 #define MRU hashp->bufhead.next
89 #define LRU hashp->bufhead.prev
90
91 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead)
92 #define LRU_INSERT(B) BUF_INSERT((B), LRU)
93
94 /*
95 * We are looking for a buffer with address "addr". If prev_bp is NULL, then
96 * address is a bucket index. If prev_bp is not NULL, then it points to the
97 * page previous to an overflow page that we are trying to find.
98 *
99 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
100 * be valid. Therefore, you must always verify that its address matches the
101 * address you are seeking.
102 */
103 BUFHEAD *
__get_buf(HTAB * hashp,uint32_t addr,BUFHEAD * prev_bp,int newpage)104 __get_buf(
105 HTAB *hashp,
106 uint32_t addr,
107 BUFHEAD *prev_bp,
108 int newpage /* If prev_bp set, indicates a new overflow page. */
109 )
110 {
111 BUFHEAD *bp;
112 uint32_t is_disk_mask;
113 int is_disk, segment_ndx = 0; /* pacify gcc */
114 SEGMENT segp = NULL; /* pacify gcc */
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 _DIAGASSERT(segp != NULL);
131 bp = PTROF(segp[segment_ndx]);
132 is_disk_mask = ISDISK(segp[segment_ndx]);
133 is_disk = is_disk_mask || !hashp->new_file;
134 }
135
136 if (!bp) {
137 bp = newbuf(hashp, addr, prev_bp);
138 if (!bp ||
139 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
140 return (NULL);
141 if (!prev_bp)
142 segp[segment_ndx] =
143 (BUFHEAD *)(void *)((u_long)bp | is_disk_mask);
144 } else {
145 BUF_REMOVE(bp);
146 MRU_INSERT(bp);
147 }
148 return (bp);
149 }
150
151 /*
152 * We need a buffer for this page. Either allocate one, or evict a resident
153 * one (if we have as many buffers as we're allowed) and put this one in.
154 *
155 * If newbuf finds an error (returning NULL), it also sets errno.
156 */
157 static BUFHEAD *
newbuf(HTAB * hashp,uint32_t addr,BUFHEAD * prev_bp)158 newbuf(HTAB *hashp, uint32_t addr, BUFHEAD *prev_bp)
159 {
160 BUFHEAD *bp; /* The buffer we're going to use */
161 BUFHEAD *xbp; /* Temp pointer */
162 BUFHEAD *next_xbp;
163 SEGMENT segp;
164 int segment_ndx;
165 uint16_t oaddr, *shortp;
166
167 oaddr = 0;
168 bp = LRU;
169 /*
170 * If LRU buffer is pinned, the buffer pool is too small. We need to
171 * allocate more buffers.
172 */
173 if (hashp->nbufs || (bp->flags & BUF_PIN)) {
174 /* Allocate a new one */
175 if ((bp = calloc(1, sizeof(BUFHEAD))) == NULL)
176 return (NULL);
177 if ((bp->page = calloc(1, (size_t)hashp->BSIZE)) == NULL) {
178 free(bp);
179 return (NULL);
180 }
181 if (hashp->nbufs)
182 hashp->nbufs--;
183 } else {
184 /* Kick someone out */
185 BUF_REMOVE(bp);
186 /*
187 * If this is an overflow page with addr 0, it's already been
188 * flushed back in an overflow chain and initialized.
189 */
190 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
191 /*
192 * Set oaddr before __put_page so that you get it
193 * before bytes are swapped.
194 */
195 shortp = (uint16_t *)(void *)bp->page;
196 if (shortp[0])
197 oaddr = shortp[shortp[0] - 1];
198 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
199 bp->addr, (int)IS_BUCKET(bp->flags), 0))
200 return (NULL);
201 /*
202 * Update the pointer to this page (i.e. invalidate it).
203 *
204 * If this is a new file (i.e. we created it at open
205 * time), make sure that we mark pages which have been
206 * written to disk so we retrieve them from disk later,
207 * rather than allocating new pages.
208 */
209 if (IS_BUCKET(bp->flags)) {
210 segment_ndx = bp->addr & (hashp->SGSIZE - 1);
211 segp = hashp->dir[bp->addr >> hashp->SSHIFT];
212 _DIAGASSERT(segp != NULL);
213
214 if (hashp->new_file &&
215 ((bp->flags & BUF_MOD) ||
216 ISDISK(segp[segment_ndx])))
217 segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
218 else
219 segp[segment_ndx] = NULL;
220 }
221 /*
222 * Since overflow pages can only be access by means of
223 * their bucket, free overflow pages associated with
224 * this bucket.
225 */
226 for (xbp = bp; xbp->ovfl;) {
227 next_xbp = xbp->ovfl;
228 xbp->ovfl = 0;
229 xbp = next_xbp;
230
231 /* Check that ovfl pointer is up date. */
232 if (IS_BUCKET(xbp->flags) ||
233 (oaddr != xbp->addr))
234 break;
235
236 shortp = (uint16_t *)(void *)xbp->page;
237 if (shortp[0])
238 /* set before __put_page */
239 oaddr = shortp[shortp[0] - 1];
240 if ((xbp->flags & BUF_MOD) && __put_page(hashp,
241 xbp->page, xbp->addr, 0, 0))
242 return (NULL);
243 xbp->addr = 0;
244 xbp->flags = 0;
245 BUF_REMOVE(xbp);
246 LRU_INSERT(xbp);
247 }
248 }
249 }
250
251 /* Now assign this buffer */
252 bp->addr = addr;
253 #ifdef DEBUG1
254 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
255 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
256 #endif
257 bp->ovfl = NULL;
258 if (prev_bp) {
259 /*
260 * If prev_bp is set, this is an overflow page, hook it in to
261 * the buffer overflow links.
262 */
263 #ifdef DEBUG1
264 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
265 prev_bp->addr, (prev_bp->ovfl ? prev_bp->ovfl->addr : 0),
266 (bp ? bp->addr : 0));
267 #endif
268 prev_bp->ovfl = bp;
269 bp->flags = 0;
270 } else
271 bp->flags = BUF_BUCKET;
272 MRU_INSERT(bp);
273 return (bp);
274 }
275
276 void
__buf_init(HTAB * hashp,u_int nbytes)277 __buf_init(HTAB *hashp, u_int nbytes)
278 {
279 BUFHEAD *bfp;
280 int npages;
281
282 bfp = &(hashp->bufhead);
283 npages = (unsigned int)(nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
284 npages = MAX(npages, MIN_BUFFERS);
285
286 hashp->nbufs = npages;
287 bfp->next = bfp;
288 bfp->prev = bfp;
289 /*
290 * This space is calloc'd so these are already null.
291 *
292 * bfp->ovfl = NULL;
293 * bfp->flags = 0;
294 * bfp->page = NULL;
295 * bfp->addr = 0;
296 */
297 }
298
299 int
__buf_free(HTAB * hashp,int do_free,int to_disk)300 __buf_free(HTAB *hashp, int do_free, int to_disk)
301 {
302 BUFHEAD *bp;
303
304 /* Need to make sure that buffer manager has been initialized */
305 if (!LRU)
306 return (0);
307 for (bp = LRU; bp != &hashp->bufhead;) {
308 /* Check that the buffer is valid */
309 if (bp->addr || IS_BUCKET(bp->flags)) {
310 if (to_disk && (bp->flags & BUF_MOD) &&
311 __put_page(hashp, bp->page,
312 bp->addr, IS_BUCKET(bp->flags), 0))
313 return (-1);
314 }
315 /* Check if we are freeing stuff */
316 if (do_free) {
317 if (bp->page) {
318 (void)memset(bp->page, 0, (size_t)hashp->BSIZE);
319 free(bp->page);
320 }
321 BUF_REMOVE(bp);
322 free(bp);
323 bp = LRU;
324 } else
325 bp = bp->prev;
326 }
327 return (0);
328 }
329
330 void
__reclaim_buf(HTAB * hashp,BUFHEAD * bp)331 __reclaim_buf(HTAB *hashp, BUFHEAD *bp)
332 {
333 bp->ovfl = 0;
334 bp->addr = 0;
335 bp->flags = 0;
336 BUF_REMOVE(bp);
337 LRU_INSERT(bp);
338 }
339