1 /** $MirOS: src/lib/libc/db/hash/hash_buf.c,v 1.4 2009/01/15 22:23:27 ahoka Exp $ */
2 /* $OpenBSD: hash_buf.c,v 1.16 2005/08/05 13:03:00 espie Exp $ */
3
4 /*-
5 * Copyright (c) 1990, 1993, 1994
6 * The Regents of the University of California. All rights reserved.
7 *
8 * This code is derived from software contributed to Berkeley by
9 * Margo Seltzer.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. Neither the name of the University nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36 /*
37 * PACKAGE: hash
38 *
39 * DESCRIPTION:
40 * Contains buffer management
41 *
42 * ROUTINES:
43 * External
44 * __buf_init
45 * __get_buf
46 * __buf_free
47 * __reclaim_buf
48 * Internal
49 * newbuf
50 */
51
52 #include <sys/param.h>
53
54 #include <errno.h>
55 #include <stddef.h>
56 #include <stdio.h>
57 #include <stdlib.h>
58 #include <string.h>
59
60 #ifdef DEBUG
61 #include <assert.h>
62 #endif
63
64 #include <db.h>
65 #include "hash.h"
66 #include "page.h"
67 #include "extern.h"
68
69 __SCCSID("@(#)hash_buf.c 8.5 (Berkeley) 7/15/94");
70 __RCSID("$MirOS: src/lib/libc/db/hash/hash_buf.c,v 1.4 2009/01/15 22:23:27 ahoka Exp $");
71
72 static BUFHEAD *newbuf(HTAB *, u_int32_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,u_int32_t addr,BUFHEAD * prev_bp,int newpage)104 __get_buf(HTAB *hashp, u_int32_t addr,
105 BUFHEAD *prev_bp, /* If prev_bp set, indicates a new overflow page. */
106 int newpage)
107 {
108 BUFHEAD *bp;
109 u_int32_t is_disk_mask = 0;
110 int is_disk, segment_ndx = 0;
111 SEGMENT segp = 0;
112
113 is_disk = 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 *)((ptrdiff_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 *
newbuf(HTAB * hashp,u_int32_t addr,BUFHEAD * prev_bp)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 /*
176 * If LRU buffer is pinned, the buffer pool is too small. We need to
177 * allocate more buffers.
178 */
179 if (hashp->nbufs || (bp->flags & BUF_PIN) || bp == hashp->cpage) {
180 /* Allocate a new one */
181 if ((bp = (BUFHEAD *)calloc(1, sizeof(BUFHEAD))) == NULL)
182 return (NULL);
183 if ((bp->page = (char *)calloc(1, hashp->BSIZE)) == NULL) {
184 free(bp);
185 return (NULL);
186 }
187 if (hashp->nbufs)
188 hashp->nbufs--;
189 } else {
190 /* Kick someone out */
191 BUF_REMOVE(bp);
192 /*
193 * If this is an overflow page with addr 0, it's already been
194 * flushed back in an overflow chain and initialized.
195 */
196 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
197 /*
198 * Set oaddr before __put_page so that you get it
199 * before bytes are swapped.
200 */
201 shortp = (u_int16_t *)bp->page;
202 if (shortp[0])
203 oaddr = shortp[shortp[0] - 1];
204 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
205 bp->addr, (int)IS_BUCKET(bp->flags), 0))
206 return (NULL);
207 /*
208 * Update the pointer to this page (i.e. invalidate it).
209 *
210 * If this is a new file (i.e. we created it at open
211 * time), make sure that we mark pages which have been
212 * written to disk so we retrieve them from disk later,
213 * rather than allocating new pages.
214 */
215 if (IS_BUCKET(bp->flags)) {
216 segment_ndx = bp->addr & (hashp->SGSIZE - 1);
217 segp = hashp->dir[bp->addr >> hashp->SSHIFT];
218 #ifdef DEBUG
219 assert(segp != NULL);
220 #endif
221
222 if (hashp->new_file &&
223 ((bp->flags & BUF_MOD) ||
224 ISDISK(segp[segment_ndx])))
225 segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
226 else
227 segp[segment_ndx] = NULL;
228 }
229 /*
230 * Since overflow pages can only be access by means of
231 * their bucket, free overflow pages associated with
232 * this bucket.
233 */
234 for (xbp = bp; xbp->ovfl;) {
235 next_xbp = xbp->ovfl;
236 xbp->ovfl = 0;
237 xbp = next_xbp;
238
239 /* Check that ovfl pointer is up date. */
240 if (IS_BUCKET(xbp->flags) ||
241 (oaddr != xbp->addr))
242 break;
243
244 shortp = (u_int16_t *)xbp->page;
245 if (shortp[0])
246 /* set before __put_page */
247 oaddr = shortp[shortp[0] - 1];
248 if ((xbp->flags & BUF_MOD) && __put_page(hashp,
249 xbp->page, xbp->addr, 0, 0))
250 return (NULL);
251 xbp->addr = 0;
252 xbp->flags = 0;
253 BUF_REMOVE(xbp);
254 LRU_INSERT(xbp);
255 }
256 }
257 }
258
259 /* Now assign this buffer */
260 bp->addr = addr;
261 #ifdef DEBUG1
262 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
263 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
264 #endif
265 bp->ovfl = NULL;
266 if (prev_bp) {
267 /*
268 * If prev_bp is set, this is an overflow page, hook it in to
269 * the buffer overflow links.
270 */
271 #ifdef DEBUG1
272 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
273 prev_bp->addr, (prev_bp->ovfl ? prev_bp->ovfl->addr : 0),
274 (bp ? bp->addr : 0));
275 #endif
276 prev_bp->ovfl = bp;
277 bp->flags = 0;
278 } else
279 bp->flags = BUF_BUCKET;
280 MRU_INSERT(bp);
281 return (bp);
282 }
283
284 void
__buf_init(HTAB * hashp,int nbytes)285 __buf_init(HTAB *hashp, int nbytes)
286 {
287 BUFHEAD *bfp;
288 int npages;
289
290 bfp = &(hashp->bufhead);
291 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
292 npages = MAX(npages, MIN_BUFFERS);
293
294 hashp->nbufs = npages;
295 bfp->next = bfp;
296 bfp->prev = bfp;
297 /*
298 * This space is calloc'd so these are already null.
299 *
300 * bfp->ovfl = NULL;
301 * bfp->flags = 0;
302 * bfp->page = NULL;
303 * bfp->addr = 0;
304 */
305 }
306
307 int
__buf_free(HTAB * hashp,int do_free,int to_disk)308 __buf_free(HTAB *hashp, int do_free, int to_disk)
309 {
310 BUFHEAD *bp;
311
312 /* Need to make sure that buffer manager has been initialized */
313 if (!LRU)
314 return (0);
315 for (bp = LRU; bp != &hashp->bufhead;) {
316 /* Check that the buffer is valid */
317 if (bp->addr || IS_BUCKET(bp->flags)) {
318 if (to_disk && (bp->flags & BUF_MOD) &&
319 __put_page(hashp, bp->page,
320 bp->addr, IS_BUCKET(bp->flags), 0))
321 return (-1);
322 }
323 /* Check if we are freeing stuff */
324 if (do_free) {
325 if (bp->page) {
326 (void)memset(bp->page, 0, hashp->BSIZE);
327 free(bp->page);
328 }
329 BUF_REMOVE(bp);
330 free(bp);
331 bp = LRU;
332 } else
333 bp = bp->prev;
334 }
335 return (0);
336 }
337
338 void
__reclaim_buf(HTAB * hashp,BUFHEAD * bp)339 __reclaim_buf(HTAB *hashp, BUFHEAD *bp)
340 {
341 bp->ovfl = 0;
342 bp->addr = 0;
343 bp->flags = 0;
344 BUF_REMOVE(bp);
345 LRU_INSERT(bp);
346 }
347