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 * 3. 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 #define _DEFAULT_SOURCE
34 #include <sys/param.h>
35 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)hash_buf.c 8.5 (Berkeley) 7/15/94";
37 #endif /* LIBC_SCCS and not lint */
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_local.h"
66 #include "hash.h"
67 #include "page.h"
68 #include "extern.h"
69
70 static BUFHEAD *newbuf(HTAB *, __uint32_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 /* Macros for min/max. */
93 #ifndef MIN
94 #define MIN(a,b) (((a)<(b))?(a):(b))
95 #endif
96 #ifndef MAX
97 #define MAX(a,b) (((a)>(b))?(a):(b))
98 #endif
99
100 /*
101 * We are looking for a buffer with address "addr". If prev_bp is NULL, then
102 * address is a bucket index. If prev_bp is not NULL, then it points to the
103 * page previous to an overflow page that we are trying to find.
104 *
105 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
106 * be valid. Therefore, you must always verify that its address matches the
107 * address you are seeking.
108 */
109 extern BUFHEAD *
__get_buf(HTAB * hashp,__uint32_t addr,BUFHEAD * prev_bp,int newpage)110 __get_buf(HTAB *hashp,
111 __uint32_t addr,
112 BUFHEAD *prev_bp,
113 int newpage) /* If prev_bp set, indicates a new overflow page. */
114 {
115 BUFHEAD *bp;
116 __uint32_t is_disk_mask;
117 int is_disk, segment_ndx = 0;
118 SEGMENT segp = NULL;
119
120 is_disk = 0;
121 is_disk_mask = 0;
122 if (prev_bp) {
123 bp = prev_bp->ovfl;
124 if (!bp || (bp->addr != addr))
125 bp = NULL;
126 if (!newpage)
127 is_disk = BUF_DISK;
128 } else {
129 /* Grab buffer out of directory */
130 segment_ndx = addr & (hashp->SGSIZE - 1);
131
132 /* valid segment ensured by __call_hash() */
133 segp = hashp->dir[addr >> hashp->SSHIFT];
134 #ifdef DEBUG
135 assert(segp != NULL);
136 #endif
137 bp = PTROF(segp[segment_ndx]);
138 is_disk_mask = ISDISK(segp[segment_ndx]);
139 is_disk = is_disk_mask || !hashp->new_file;
140 }
141
142 if (!bp) {
143 bp = newbuf(hashp, addr, prev_bp);
144 if (!bp ||
145 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
146 return (NULL);
147 if (!prev_bp)
148 segp[segment_ndx] =
149 (BUFHEAD *)((ptrdiff_t)bp | (intptr_t)is_disk_mask);
150 } else {
151 BUF_REMOVE(bp);
152 MRU_INSERT(bp);
153 }
154 return (bp);
155 }
156
157 /*
158 * We need a buffer for this page. Either allocate one, or evict a resident
159 * one (if we have as many buffers as we're allowed) and put this one in.
160 *
161 * If newbuf finds an error (returning NULL), it also sets errno.
162 */
163 static BUFHEAD *
newbuf(HTAB * hashp,__uint32_t addr,BUFHEAD * prev_bp)164 newbuf(HTAB *hashp,
165 __uint32_t addr,
166 BUFHEAD *prev_bp)
167 {
168 BUFHEAD *bp; /* The buffer we're going to use */
169 BUFHEAD *xbp; /* Temp pointer */
170 BUFHEAD *next_xbp;
171 SEGMENT segp;
172 int segment_ndx;
173 __uint16_t oaddr, *shortp;
174
175 oaddr = 0;
176 bp = LRU;
177 /*
178 * If LRU buffer is pinned, the buffer pool is too small. We need to
179 * allocate more buffers.
180 */
181 if (hashp->nbufs || (bp->flags & BUF_PIN)) {
182 /* Allocate a new one */
183 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL)
184 return (NULL);
185 #ifdef PURIFY
186 memset(bp, 0xff, sizeof(BUFHEAD));
187 #endif
188 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) {
189 free(bp);
190 return (NULL);
191 }
192 #ifdef PURIFY
193 memset(bp->page, 0xff, hashp->BSIZE);
194 #endif
195 if (hashp->nbufs)
196 hashp->nbufs--;
197 } else {
198 /* Kick someone out */
199 BUF_REMOVE(bp);
200 /*
201 * If this is an overflow page with addr 0, it's already been
202 * flushed back in an overflow chain and initialized.
203 */
204 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
205 /*
206 * Set oaddr before __put_page so that you get it
207 * before bytes are swapped.
208 */
209 shortp = (__uint16_t *)bp->page;
210 if (shortp[0])
211 oaddr = shortp[shortp[0] - 1];
212 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
213 bp->addr, (int)IS_BUCKET(bp->flags), 0))
214 return (NULL);
215 /*
216 * Update the pointer to this page (i.e. invalidate it).
217 *
218 * If this is a new file (i.e. we created it at open
219 * time), make sure that we mark pages which have been
220 * written to disk so we retrieve them from disk later,
221 * rather than allocating new pages.
222 */
223 if (IS_BUCKET(bp->flags)) {
224 segment_ndx = bp->addr & (hashp->SGSIZE - 1);
225 segp = hashp->dir[bp->addr >> hashp->SSHIFT];
226 #ifdef DEBUG
227 assert(segp != NULL);
228 #endif
229
230 if (hashp->new_file &&
231 ((bp->flags & BUF_MOD) ||
232 ISDISK(segp[segment_ndx])))
233 segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
234 else
235 segp[segment_ndx] = NULL;
236 }
237 /*
238 * Since overflow pages can only be access by means of
239 * their bucket, free overflow pages associated with
240 * this bucket.
241 */
242 for (xbp = bp; xbp->ovfl;) {
243 next_xbp = xbp->ovfl;
244 xbp->ovfl = 0;
245 xbp = next_xbp;
246
247 /* Check that ovfl pointer is up date. */
248 if (IS_BUCKET(xbp->flags) ||
249 (oaddr != xbp->addr))
250 break;
251
252 shortp = (__uint16_t *)xbp->page;
253 if (shortp[0])
254 /* set before __put_page */
255 oaddr = shortp[shortp[0] - 1];
256 if ((xbp->flags & BUF_MOD) && __put_page(hashp,
257 xbp->page, xbp->addr, 0, 0))
258 return (NULL);
259 xbp->addr = 0;
260 xbp->flags = 0;
261 BUF_REMOVE(xbp);
262 LRU_INSERT(xbp);
263 }
264 }
265 }
266
267 /* Now assign this buffer */
268 bp->addr = addr;
269 #ifdef DEBUG1
270 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
271 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
272 #endif
273 bp->ovfl = NULL;
274 if (prev_bp) {
275 /*
276 * If prev_bp is set, this is an overflow page, hook it in to
277 * the buffer overflow links.
278 */
279 #ifdef DEBUG1
280 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
281 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0),
282 (bp ? bp->addr : 0));
283 #endif
284 prev_bp->ovfl = bp;
285 bp->flags = 0;
286 } else
287 bp->flags = BUF_BUCKET;
288 MRU_INSERT(bp);
289 return (bp);
290 }
291
292 extern void
__buf_init(HTAB * hashp,int nbytes)293 __buf_init(HTAB *hashp, int nbytes)
294 {
295 BUFHEAD *bfp;
296 int npages;
297
298 bfp = &(hashp->bufhead);
299 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
300 npages = MAX(npages, MIN_BUFFERS);
301
302 hashp->nbufs = npages;
303 bfp->next = bfp;
304 bfp->prev = bfp;
305 /*
306 * This space is calloc'd so these are already null.
307 *
308 * bfp->ovfl = NULL;
309 * bfp->flags = 0;
310 * bfp->page = NULL;
311 * bfp->addr = 0;
312 */
313 }
314
315 extern int
__buf_free(HTAB * hashp,int do_free,int to_disk)316 __buf_free(HTAB *hashp, int do_free, int to_disk)
317 {
318 BUFHEAD *bp;
319
320 /* Need to make sure that buffer manager has been initialized */
321 if (!LRU)
322 return (0);
323 for (bp = LRU; bp != &hashp->bufhead;) {
324 /* Check that the buffer is valid */
325 if (bp->addr || IS_BUCKET(bp->flags)) {
326 if (to_disk && (bp->flags & BUF_MOD) &&
327 __put_page(hashp, bp->page,
328 bp->addr, IS_BUCKET(bp->flags), 0))
329 return (-1);
330 }
331 /* Check if we are freeing stuff */
332 if (do_free) {
333 if (bp->page)
334 free(bp->page);
335 BUF_REMOVE(bp);
336 free(bp);
337 bp = LRU;
338 } else
339 bp = bp->prev;
340 }
341 return (0);
342 }
343
344 extern void
__reclaim_buf(HTAB * hashp,BUFHEAD * bp)345 __reclaim_buf(HTAB *hashp, 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
